CA1178025A - Method for producing a pressurized oxide of sulfur - Google Patents
Method for producing a pressurized oxide of sulfurInfo
- Publication number
- CA1178025A CA1178025A CA000389605A CA389605A CA1178025A CA 1178025 A CA1178025 A CA 1178025A CA 000389605 A CA000389605 A CA 000389605A CA 389605 A CA389605 A CA 389605A CA 1178025 A CA1178025 A CA 1178025A
- Authority
- CA
- Canada
- Prior art keywords
- sulfur
- air
- pressurized
- zone
- cooling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 title claims abstract description 157
- 229910052717 sulfur Inorganic materials 0.000 title claims abstract description 157
- 239000011593 sulfur Substances 0.000 title claims abstract description 157
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 5
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims abstract description 98
- AKEJUJNQAAGONA-UHFFFAOYSA-N sulfur trioxide Chemical compound O=S(=O)=O AKEJUJNQAAGONA-UHFFFAOYSA-N 0.000 claims abstract description 80
- 230000003197 catalytic effect Effects 0.000 claims abstract description 27
- 238000002485 combustion reaction Methods 0.000 claims abstract description 25
- 239000011541 reaction mixture Substances 0.000 claims abstract description 15
- 238000011144 upstream manufacturing Methods 0.000 claims abstract description 5
- 239000000203 mixture Substances 0.000 claims description 49
- 238000001816 cooling Methods 0.000 claims description 42
- 238000000034 method Methods 0.000 claims description 42
- 238000006243 chemical reaction Methods 0.000 claims description 37
- 238000001035 drying Methods 0.000 claims description 22
- 238000010438 heat treatment Methods 0.000 claims description 12
- 239000007789 gas Substances 0.000 claims description 10
- 230000000694 effects Effects 0.000 claims description 9
- 230000002411 adverse Effects 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 8
- 229910052760 oxygen Inorganic materials 0.000 claims description 8
- 239000001301 oxygen Substances 0.000 claims description 8
- 230000015572 biosynthetic process Effects 0.000 claims description 5
- 230000001172 regenerating effect Effects 0.000 claims description 5
- 230000008929 regeneration Effects 0.000 claims description 4
- 238000011069 regeneration method Methods 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 3
- 208000036366 Sensation of pressure Diseases 0.000 claims 1
- 230000000977 initiatory effect Effects 0.000 claims 1
- 239000008246 gaseous mixture Substances 0.000 abstract description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 229910001220 stainless steel Inorganic materials 0.000 description 6
- 239000010935 stainless steel Substances 0.000 description 6
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 239000003546 flue gas Substances 0.000 description 3
- 239000002808 molecular sieve Substances 0.000 description 3
- 239000000741 silica gel Substances 0.000 description 3
- 229910002027 silica gel Inorganic materials 0.000 description 3
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 3
- 238000007664 blowing Methods 0.000 description 2
- 239000011449 brick Substances 0.000 description 2
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical group O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 description 2
- 239000010881 fly ash Substances 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 150000003871 sulfonates Chemical class 0.000 description 2
- 238000006277 sulfonation reaction Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000000889 atomisation Methods 0.000 description 1
- 230000000740 bleeding effect Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000003750 conditioning effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000003599 detergent Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011017 operating method Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/74—Preparation
- C01B17/76—Preparation by contact processes
- C01B17/78—Preparation by contact processes characterised by the catalyst used
- C01B17/79—Preparation by contact processes characterised by the catalyst used containing vanadium
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/48—Sulfur dioxide; Sulfurous acid
- C01B17/50—Preparation of sulfur dioxide
- C01B17/54—Preparation of sulfur dioxide by burning elemental sulfur
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
- Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
Abstract
ABSTRACT OF THE DISCLOSURE
A method for producing an oxide of sulfur using pressurized air. The pressurized air is mixed with molten sulfur at a sulfur burner to ignite and combust the molten sulfur and form a reaction mixture. The molten sulfur may be atomized. The pressurized air may be divided into two portions, one of which is preheated. The unheated pressurized air is mixed with the reaction mixture in the sulfur burner downstream of the location where the preheated pressurized air is mixed with the molten sulfur. Combustion of all the sulfur to sulfur dioxide is essentially completed within the sulfur burner, and the temperature of the gaseous mixture leaving the sulfur burner is controlled. The sulfur dioxide may then be cooled and converted to sulfur trioxide in a catalytic converter. The Moisture content of the pressurized air is reduced in a pressurized dryer upstream of the sulfur burner.
A method for producing an oxide of sulfur using pressurized air. The pressurized air is mixed with molten sulfur at a sulfur burner to ignite and combust the molten sulfur and form a reaction mixture. The molten sulfur may be atomized. The pressurized air may be divided into two portions, one of which is preheated. The unheated pressurized air is mixed with the reaction mixture in the sulfur burner downstream of the location where the preheated pressurized air is mixed with the molten sulfur. Combustion of all the sulfur to sulfur dioxide is essentially completed within the sulfur burner, and the temperature of the gaseous mixture leaving the sulfur burner is controlled. The sulfur dioxide may then be cooled and converted to sulfur trioxide in a catalytic converter. The Moisture content of the pressurized air is reduced in a pressurized dryer upstream of the sulfur burner.
Description
~ACKGROUND OF THE INV~NTION
The present invention relates generally to methods for producing an oxide of sulfur~ such as sulfur dioxide or sulfur trioxide, and more particularly to a method for producing a pressurized oxide of sulfur employing a sulfur burner.
Typically, sulfur dioxide is formed by reacting molten sulfur with a quantity of air containing oxygen in excess of that required to stoichiometrically react with the sulfur, thereby to produce a reaction mixture comprising sulfur dioxide and air. Because this reaction is exothermic, it is performed in a sulfur-burning zone which is thermally insulated because of the high temperatures produced by the exothermic reaction.
It is desirable that all the sulfur be combusted before it leaves the sulfur-burning zone. Typically, this is accomplished by maximizing the surface area of the molten sulfur exposed to the oxidizing air. Techniques for maximizing the surface area of the molten sulfur include dripping the molten sulfur over a brick checkerwork or atomizing the molten sulfur (e.g., atomizing with pressurized air).
The reaction mixture leaving the sulfur-burning zone comprises sulfur dioxide and air. The concentration of sulfur dioxide reflects the amount of combustion which has occurred in the sulfur-burning zone. Therefore, the greater the concentration of sulfur dioxide in the reaction mixture, the hiqher the temperature of the mixture as it leaves the sulfur-burning zone.
Sulfur dioxide may be an end material in itself or it may be converted to sulfur trioxide in a catalytic converter wherein the sulfur dioxide is reacted with additional -1- ~
~'7~25 or carryover air. There is an optimum temperature at which sulfur dioxide may be converted to sulfur trioxide in a catalytic converting zone, and, if the reaction mixture from the sulfur burner is at a temperature exceeding this optimum conversion temperature, the reaction mixture must be cooled before it enters the catalytic converting zone.
Usually, the reaction mixture from the sulfur burner contains sufficient excess air to provide the oxygen necessary to form sulfur trioxide out of the sulfur dioxide, but, if sufficient oxygen is not contained in the reaction mixture from the sulfur-burning zone, additional air will have to be added to this reaction mixture at or before the beginning of the catalytic converting step for producing sulfur trioxide.
Pressurized air may be employed in the sulfur-burning and catalytic converting steps, and this has a number of advantages. It increases the intensity of combustion, and this allows the combustion of a given quantity of sulfur to occur in a shorter time, thereby reducing the period of time the reaction ingredients are required to spend in the sulfur-burning zone. This, in turn, allows a reduction in the size of the sulfur-burning zone through which the reaction ingredients flow while they react.
Pressurized air also causes an increase in conversion efficiency in the catalytic converting zone which conventionally employs three or four stages to complete the conversion of the sulfur dioxide to sulfur trioxide. The use of pressurized air also reduces the size requirements for the entire processing plant.
However, the use of the pressurized air also requires an increase in the strength of the various components of the plant, including the conduits downstream of the sulfur-burning O~S
zone and which connect that zone with the catalytic converting zone. These components are usually made of stainless steel which has the corrosion resistant properties required when highly reactive ~aterials such as hot sulfur dioxide flow through the conduits and the like.
As previously noted, the use of pressurized air at the sulfur-burning zone increases the intensity of combustion which in turn can increase the temperature of the reaction mixture leaving the sulfur-burning zone. This temperature can be so high as to heat the stainless steel components to a temperature at which the stainless steel loses its strength. As noted above, high strength properties are particularly necessary when pressurized air is employed in the reaction process.
Sulfur trioxide is employed, among other uses, for conditioning fly ash particles from flue gas and as a reactant in a process for producing sulfonates which in turn are used for making detergents. When used in making sulfonates, the sulfur trioxide must be cooled to a temperature well below the temperature thereof when it leaves the catalytic converting zone. When the sulfur trioxide is cooled to a temperature suitable for use as a reactant in a sulfonating process, it is possible that, if the reaction mixture containing the sulfur trioxide also contains water vapor, oleum may form due to a reaction between water vapor which precipitates during cooling and the sulfur trioxide. The formation of oleum is undesirable if the sulfur trioxide-containing mixture is to be used in a sulfonating operation. Accordingly, it is desirable to remove moisture from the air which is used in oxidizing the sulfur to sulfur dioxide and to sulfur trioxide, before the air is introduced into the sulfur-burning zone. Moisture removal is also desirable in most cases 1~'7~ 5 where the temperature of the sulfur trioxide-containing mixture is cooled to a temperature below its dew point because this causes the formation of oleum with its undesirable highly corrosive properties.
One conventional technique for removing moisture from air employs driers wherein the moisture is removed by absorption from the gas into water-absorbing media such as silica gel or molecular sieves. Eventually, these media absorb so much water that they lose their moisture-absorbing ability, and the media must be regenerated in order further to perform a water-removing function. This regeneration usually involves blowing hot air through the water-saturated medium to remove the water therefrom and then blowing cool air therethrough to cool the dryer. This, of course, requires a capital expenditure for hot air and cool air blowers and conduits as well as an energy expenditure to operate these blowers. In addition, the cooling air is usually atmospheric air which contains moisture that is absorbed by the water-absorbing medium in the dryer during cooling of the latter, thereby reducing its subsequent drying ability.
SUMMARY OF THE _NVENTION
The present invention comprises a method for producing an oxide of sulfur using pressurized air and in which all the advantages previously obtained by the use of pressurized air are retained while avoiding the drawbacks and disadvantages which have previously arisen with the use of pressurized air. The present invention also enables the removal of moisture from the air, upstream of the sulfur-burning zone, while substantially reducing the energy required to remove the moisture.
In accordance with the present invention, combustion of the sulfur in ~he sulfur-burning zone is essentially completed even without maximizing the surface area of the molten sulfur exposed to the pressurized air (as by atomizing or trickling over a brick checkerwork). The resulting pres-surized mixture of sulfur dioxide and air may contain up to about 18 vol.% sulfur dioxide. The volume of the sulfur burner, of the sulfur dioxide coolers and of the conduits for transporting the pressurized mixture from the sulfur burner to the coolers and then to a catalytic converter i5 reduced to less than 50% (e.g., to one-third) of the volume required to combust the same weight amounts of sulfur and air and to handle the same weight amounts of sulfur dioxide and air, in a given time period, at atmospheric pressure. Similarly, the volume of catalytic converting beds re~uired to obtain essentially complete conversion (e.g., 99% or more) of sulfur dioxide to sulfur trioxide is reduced to less than 60% (e.g., to one-half) of the volume required to convert the same weight amount of sulfur trioxide, in a given time period, at atmospheric pressure. Conversion of about 99% can be obtained with only two conversion stages (with a cooling stage in between), and conversion greater than 99% is obtained with three converting stages. A pressure in excess of about 30 psig should be maintained, up to about 120 psig or to a pressure within the practical strength and thickness limits economically feasible for the equipment.
50 to 70 psig is a desirable and practical pressure range.
In accordance with one embodiment of the present invention, the pressurized air is divided into two portions before it enters the sulfur-burning zone. One of these two portions is preheated to a temperature above the ignition temperature of the sulfur, while the other portion remains unpreheated. Combustion of the sulfur is initiated by mixing the sulfur with the preheated portion of air, as the sulfur enters the sulfur-burning zone, to produce a reaction mixture ~lt7~
containing sulfur dioxide. Then the unpreheated portion of air is introduced into the sulfur-burning zone downstream of the location therein where the preheated air portion was mixed with the sulfur.
The proportion of pressurized air which is preheated and the temperature to which it is preheated are controlled.
As a result, it is possible not only to completely combust the sulfur within the sulfur-burning zone in a relatively short time (thereby reducing the length of the sulfur-burning zone through which the gases must flow during the combustion process) but, also, it is possible to control the temperature of the pressurized mixture of sulfur dioxide and air leaving the sulfur-burning zone so as not to affect adversely the stainless steel components of the processing system downstream of the sulfur-burning zone.
The preheated one portion of air is heated in a heat exchanger through which is flowed the hot pressurized mixture of sulfur dioxide and air leaving the sulfur-burning zone. In this heat exchanger, the sulfur dioxide is indirectly cooled while the one portion of pressurized air is indirectly preheated. Because the temperature to which the one portion of pressurized air is heated must be controlled to avoid an excessive temperature in the gases leaving the sulfur-burning zone, it is not possible to completely cool the hot pressurized mixture of sulfur dioxide and air in this heat exchanger or to cool this mixture to an optimum temperature for conversion of the sulfur dioxide into sulfur trioxide; and, in such a case, an additional cooling step must be provided between this heat exchanger and the catalytic converting zone.
When a sulfur trioxide-air mixture produced by a method in accordance with the present invention is to iL7~ S
be cooled to a temperature for use in a sulfonation operation or to any temperature below the dew point of undried air in the sulfur trioxide-containing mixture, then, in order to avoid the formation of significant amounts of oleum during such a cooling step, it is necessary to remove moisture from the pressurized air before it is introduced into the sulfur-burning zone. This is accomplished in accordance with the present invention by flowing the pressurized air through a drier which employs a chemical, such as silica gel, or molecular sieves to remove the moisture from the air. The higher the pressure of the air, the less moisture it will hold, and the precipi~ating moisture in the pres-surized air is absorbed in the drier. Thus, pressurization facilitates drying of the air.
When the drier has absorbed sufficient moisture to become saturated, it must be regenerated. Regeneration is accomplished in accordance with one embodiment of the present invention by bleeding off a small fraction of previ-ously dried, pressurized air from a companion pressurized dryer, depressurizing the bled-off air and flowing it through the depleted drier to absorb from that drier sufficient moisture to regenerate it. The method of this embodiment of the present invention avoids employing heating and cooling air to regenerate the driers, thereby eliminating two large fans and the associated conduits. In addition it does not deplete the drying capacity of the drier during regeneration.
Moreover, the energy expended in compressing the air to pressurize it prior to introduction into the heatless pressure driers is less than the energy expended in operating fans for regenerating unpressurized driers.
Other features and advantages are inherent in the method claimed and disclosed or will become apparent 11'7~Z5 to those skilled in 'he art from the following detailed description in conjunction with the accompanying diagrammatic drawing.
BRIEF DESCRIPTION OF T~E DRAWING
Fig. 1 is a schematic flow diagram of an embodiment of a method in accordance with the present ihvention; and Fig. 2 is an elevational view, partially cut away and par~ially in section, of a sulfur-burning zone employed in a method in accordance with the present invention.
DE~AILED DESCRIPTION
Referring initially to Fig. 1, air is compressed at 10 and then dried in one of a pair of driers 15, 16 following which the pressurized air is divided into two portions.
One portion flows through a line 34 to a heat exchanger at 36 for preheating the one portion of pressurized air, following which the preheated air is introduced into a sul-fur-burning zone 39 along with sulfur and atomizing air.
The other portion of pressurized air remains unheated and is introduced through a line 35 into sulfur burner 39 down-stream of the location where the preheated air portion was mixed with the sulfur.
The sulfur is combusted in the sulfur-burning zone to produce a first-pressurized mixture of sulfur dioxide and air which leaves the sulfur burner through a conduit 58. Downstream of the sulfur burner, the first-pressurized mixture of sulfur dioxide and air is cooled in heat exchanger 36 by the one portion of pressurized air which undergoes preheating at heat exchanger 36. Downstream of heat exchanger 36 the first pressurized mixture of sulfur dioxide and air is further cooled at a radiant cooler 60 following which the mixture of sulfur dioxide and air is introduced into a cata-lytic converter 62 wherein the sulfur dioxide is converted to sulfur trioxide to produce a second pressurized mixture containing sulfur trioxide and air. This mixture is subse-quently cooled at one or more cooling steps comprising a radiant cooler 70 and a cascade cooler 71, following which the cooled sulfur trioxide is withdrawn through a conduit 75 which conducts the sulfur trioxicle for use in a sulfonating process or for treating flue gas, for example.
~ he method and apparatus illustrated in Fig. 1 will now be described in greater detail. Air is compressed at compressor 10 to a pressure in the range 35-70 psig, preferably 50-70 psig. The pressurized air is then flowed through a water separator 11 for removing some of the moisture precipitated during the compression operation and through an oil separator 12 for removing oil mists which may be present in the pressurized air after the compressing operation.
The pressurized air is then flowed through a conduit 13 to one of two unheated, pressurized driers 15, 16.
In the course of being dried, pressurized air from conduit 13 initially passes through a swing valve 14 which alternates the flow of pressurized air, every five minutes or so, back and forth between a branch line 23 leading to drier 15 and a branch line 24 leading to drier 16. Driers 15, 16 employ silica gel or molecular sieves as a drying medium, each being a stationary drying mediumO At the pressure under which the air is maintained when it flows through a drier 15 or 16 (50-70 psig), moisture is removed from the air sufficient to provide the pressurized air with a dewpoint below -40F (-40C).
Dried pressurized air is withdrawn from dryer 15 through a conduit 17 communicating with conduit 30 leading to sulfur burner 39. A portion of the dried air in conduit 17 (e.g., about 10 vol.%) is bled off through a line 26 communicating with a line 19 which leads through a conduit _g_ 11'7~Z5 18 into drier 16. The pressurized air bled off through line 26 is depressurized to atmospheric pressure before it is introduced into drier 16. The depressurized air flowing through drier 16 absorbs moisture from the drying medium in drier 16 to regenerate the latter. Moisture-laden air is drawn off from drier 16 through conduit 24 and from there hrough swing valve 14 into a vent line 25. A similar arrange-ment is utilized to regenerate drier 15 with dry air removed from drier 16.
More particularly, dried, pressurized air is with-drawn from drier 16 through conduit 18 communi~ating with conduit 30 leading to sulfur burner 39. A portion of the dried air in conduit 18 is bled off from line 18 through line 26 into a line 20 communicating with conduit 17 from drier 15. The pressurized air bled off from conduit 18 is depressurized to atmospheric pressure, before it is intro-duced into drier 15. As the depressurized air flows through drier 15 it absorbs the moisture from the drying medium in drier 1~ to regenerate the latter. ~oisture-laden air is withdrawn from drier 15 through conduit 23, swing valve 14 and vent line 25.
The drying and regenerating technique discussed above is employed in a preferred embodiment of the present invention. In a broader aspect of the present invention, pressurized drying can be employed without regenerating the drier with depressurized air in the manner described above. In such a case, the reduction of moisture to the extent possible with pressurized air is still available as an advantage, and a drier satuated with moisture can be regenerated in another fashion, e.g., with hot air.
Communicating with conduit 30 is a by-pass line 31 having a by-pass heater 32 for heating the pressurized air during standby sperating conditions or during startup.
The present invention relates generally to methods for producing an oxide of sulfur~ such as sulfur dioxide or sulfur trioxide, and more particularly to a method for producing a pressurized oxide of sulfur employing a sulfur burner.
Typically, sulfur dioxide is formed by reacting molten sulfur with a quantity of air containing oxygen in excess of that required to stoichiometrically react with the sulfur, thereby to produce a reaction mixture comprising sulfur dioxide and air. Because this reaction is exothermic, it is performed in a sulfur-burning zone which is thermally insulated because of the high temperatures produced by the exothermic reaction.
It is desirable that all the sulfur be combusted before it leaves the sulfur-burning zone. Typically, this is accomplished by maximizing the surface area of the molten sulfur exposed to the oxidizing air. Techniques for maximizing the surface area of the molten sulfur include dripping the molten sulfur over a brick checkerwork or atomizing the molten sulfur (e.g., atomizing with pressurized air).
The reaction mixture leaving the sulfur-burning zone comprises sulfur dioxide and air. The concentration of sulfur dioxide reflects the amount of combustion which has occurred in the sulfur-burning zone. Therefore, the greater the concentration of sulfur dioxide in the reaction mixture, the hiqher the temperature of the mixture as it leaves the sulfur-burning zone.
Sulfur dioxide may be an end material in itself or it may be converted to sulfur trioxide in a catalytic converter wherein the sulfur dioxide is reacted with additional -1- ~
~'7~25 or carryover air. There is an optimum temperature at which sulfur dioxide may be converted to sulfur trioxide in a catalytic converting zone, and, if the reaction mixture from the sulfur burner is at a temperature exceeding this optimum conversion temperature, the reaction mixture must be cooled before it enters the catalytic converting zone.
Usually, the reaction mixture from the sulfur burner contains sufficient excess air to provide the oxygen necessary to form sulfur trioxide out of the sulfur dioxide, but, if sufficient oxygen is not contained in the reaction mixture from the sulfur-burning zone, additional air will have to be added to this reaction mixture at or before the beginning of the catalytic converting step for producing sulfur trioxide.
Pressurized air may be employed in the sulfur-burning and catalytic converting steps, and this has a number of advantages. It increases the intensity of combustion, and this allows the combustion of a given quantity of sulfur to occur in a shorter time, thereby reducing the period of time the reaction ingredients are required to spend in the sulfur-burning zone. This, in turn, allows a reduction in the size of the sulfur-burning zone through which the reaction ingredients flow while they react.
Pressurized air also causes an increase in conversion efficiency in the catalytic converting zone which conventionally employs three or four stages to complete the conversion of the sulfur dioxide to sulfur trioxide. The use of pressurized air also reduces the size requirements for the entire processing plant.
However, the use of the pressurized air also requires an increase in the strength of the various components of the plant, including the conduits downstream of the sulfur-burning O~S
zone and which connect that zone with the catalytic converting zone. These components are usually made of stainless steel which has the corrosion resistant properties required when highly reactive ~aterials such as hot sulfur dioxide flow through the conduits and the like.
As previously noted, the use of pressurized air at the sulfur-burning zone increases the intensity of combustion which in turn can increase the temperature of the reaction mixture leaving the sulfur-burning zone. This temperature can be so high as to heat the stainless steel components to a temperature at which the stainless steel loses its strength. As noted above, high strength properties are particularly necessary when pressurized air is employed in the reaction process.
Sulfur trioxide is employed, among other uses, for conditioning fly ash particles from flue gas and as a reactant in a process for producing sulfonates which in turn are used for making detergents. When used in making sulfonates, the sulfur trioxide must be cooled to a temperature well below the temperature thereof when it leaves the catalytic converting zone. When the sulfur trioxide is cooled to a temperature suitable for use as a reactant in a sulfonating process, it is possible that, if the reaction mixture containing the sulfur trioxide also contains water vapor, oleum may form due to a reaction between water vapor which precipitates during cooling and the sulfur trioxide. The formation of oleum is undesirable if the sulfur trioxide-containing mixture is to be used in a sulfonating operation. Accordingly, it is desirable to remove moisture from the air which is used in oxidizing the sulfur to sulfur dioxide and to sulfur trioxide, before the air is introduced into the sulfur-burning zone. Moisture removal is also desirable in most cases 1~'7~ 5 where the temperature of the sulfur trioxide-containing mixture is cooled to a temperature below its dew point because this causes the formation of oleum with its undesirable highly corrosive properties.
One conventional technique for removing moisture from air employs driers wherein the moisture is removed by absorption from the gas into water-absorbing media such as silica gel or molecular sieves. Eventually, these media absorb so much water that they lose their moisture-absorbing ability, and the media must be regenerated in order further to perform a water-removing function. This regeneration usually involves blowing hot air through the water-saturated medium to remove the water therefrom and then blowing cool air therethrough to cool the dryer. This, of course, requires a capital expenditure for hot air and cool air blowers and conduits as well as an energy expenditure to operate these blowers. In addition, the cooling air is usually atmospheric air which contains moisture that is absorbed by the water-absorbing medium in the dryer during cooling of the latter, thereby reducing its subsequent drying ability.
SUMMARY OF THE _NVENTION
The present invention comprises a method for producing an oxide of sulfur using pressurized air and in which all the advantages previously obtained by the use of pressurized air are retained while avoiding the drawbacks and disadvantages which have previously arisen with the use of pressurized air. The present invention also enables the removal of moisture from the air, upstream of the sulfur-burning zone, while substantially reducing the energy required to remove the moisture.
In accordance with the present invention, combustion of the sulfur in ~he sulfur-burning zone is essentially completed even without maximizing the surface area of the molten sulfur exposed to the pressurized air (as by atomizing or trickling over a brick checkerwork). The resulting pres-surized mixture of sulfur dioxide and air may contain up to about 18 vol.% sulfur dioxide. The volume of the sulfur burner, of the sulfur dioxide coolers and of the conduits for transporting the pressurized mixture from the sulfur burner to the coolers and then to a catalytic converter i5 reduced to less than 50% (e.g., to one-third) of the volume required to combust the same weight amounts of sulfur and air and to handle the same weight amounts of sulfur dioxide and air, in a given time period, at atmospheric pressure. Similarly, the volume of catalytic converting beds re~uired to obtain essentially complete conversion (e.g., 99% or more) of sulfur dioxide to sulfur trioxide is reduced to less than 60% (e.g., to one-half) of the volume required to convert the same weight amount of sulfur trioxide, in a given time period, at atmospheric pressure. Conversion of about 99% can be obtained with only two conversion stages (with a cooling stage in between), and conversion greater than 99% is obtained with three converting stages. A pressure in excess of about 30 psig should be maintained, up to about 120 psig or to a pressure within the practical strength and thickness limits economically feasible for the equipment.
50 to 70 psig is a desirable and practical pressure range.
In accordance with one embodiment of the present invention, the pressurized air is divided into two portions before it enters the sulfur-burning zone. One of these two portions is preheated to a temperature above the ignition temperature of the sulfur, while the other portion remains unpreheated. Combustion of the sulfur is initiated by mixing the sulfur with the preheated portion of air, as the sulfur enters the sulfur-burning zone, to produce a reaction mixture ~lt7~
containing sulfur dioxide. Then the unpreheated portion of air is introduced into the sulfur-burning zone downstream of the location therein where the preheated air portion was mixed with the sulfur.
The proportion of pressurized air which is preheated and the temperature to which it is preheated are controlled.
As a result, it is possible not only to completely combust the sulfur within the sulfur-burning zone in a relatively short time (thereby reducing the length of the sulfur-burning zone through which the gases must flow during the combustion process) but, also, it is possible to control the temperature of the pressurized mixture of sulfur dioxide and air leaving the sulfur-burning zone so as not to affect adversely the stainless steel components of the processing system downstream of the sulfur-burning zone.
The preheated one portion of air is heated in a heat exchanger through which is flowed the hot pressurized mixture of sulfur dioxide and air leaving the sulfur-burning zone. In this heat exchanger, the sulfur dioxide is indirectly cooled while the one portion of pressurized air is indirectly preheated. Because the temperature to which the one portion of pressurized air is heated must be controlled to avoid an excessive temperature in the gases leaving the sulfur-burning zone, it is not possible to completely cool the hot pressurized mixture of sulfur dioxide and air in this heat exchanger or to cool this mixture to an optimum temperature for conversion of the sulfur dioxide into sulfur trioxide; and, in such a case, an additional cooling step must be provided between this heat exchanger and the catalytic converting zone.
When a sulfur trioxide-air mixture produced by a method in accordance with the present invention is to iL7~ S
be cooled to a temperature for use in a sulfonation operation or to any temperature below the dew point of undried air in the sulfur trioxide-containing mixture, then, in order to avoid the formation of significant amounts of oleum during such a cooling step, it is necessary to remove moisture from the pressurized air before it is introduced into the sulfur-burning zone. This is accomplished in accordance with the present invention by flowing the pressurized air through a drier which employs a chemical, such as silica gel, or molecular sieves to remove the moisture from the air. The higher the pressure of the air, the less moisture it will hold, and the precipi~ating moisture in the pres-surized air is absorbed in the drier. Thus, pressurization facilitates drying of the air.
When the drier has absorbed sufficient moisture to become saturated, it must be regenerated. Regeneration is accomplished in accordance with one embodiment of the present invention by bleeding off a small fraction of previ-ously dried, pressurized air from a companion pressurized dryer, depressurizing the bled-off air and flowing it through the depleted drier to absorb from that drier sufficient moisture to regenerate it. The method of this embodiment of the present invention avoids employing heating and cooling air to regenerate the driers, thereby eliminating two large fans and the associated conduits. In addition it does not deplete the drying capacity of the drier during regeneration.
Moreover, the energy expended in compressing the air to pressurize it prior to introduction into the heatless pressure driers is less than the energy expended in operating fans for regenerating unpressurized driers.
Other features and advantages are inherent in the method claimed and disclosed or will become apparent 11'7~Z5 to those skilled in 'he art from the following detailed description in conjunction with the accompanying diagrammatic drawing.
BRIEF DESCRIPTION OF T~E DRAWING
Fig. 1 is a schematic flow diagram of an embodiment of a method in accordance with the present ihvention; and Fig. 2 is an elevational view, partially cut away and par~ially in section, of a sulfur-burning zone employed in a method in accordance with the present invention.
DE~AILED DESCRIPTION
Referring initially to Fig. 1, air is compressed at 10 and then dried in one of a pair of driers 15, 16 following which the pressurized air is divided into two portions.
One portion flows through a line 34 to a heat exchanger at 36 for preheating the one portion of pressurized air, following which the preheated air is introduced into a sul-fur-burning zone 39 along with sulfur and atomizing air.
The other portion of pressurized air remains unheated and is introduced through a line 35 into sulfur burner 39 down-stream of the location where the preheated air portion was mixed with the sulfur.
The sulfur is combusted in the sulfur-burning zone to produce a first-pressurized mixture of sulfur dioxide and air which leaves the sulfur burner through a conduit 58. Downstream of the sulfur burner, the first-pressurized mixture of sulfur dioxide and air is cooled in heat exchanger 36 by the one portion of pressurized air which undergoes preheating at heat exchanger 36. Downstream of heat exchanger 36 the first pressurized mixture of sulfur dioxide and air is further cooled at a radiant cooler 60 following which the mixture of sulfur dioxide and air is introduced into a cata-lytic converter 62 wherein the sulfur dioxide is converted to sulfur trioxide to produce a second pressurized mixture containing sulfur trioxide and air. This mixture is subse-quently cooled at one or more cooling steps comprising a radiant cooler 70 and a cascade cooler 71, following which the cooled sulfur trioxide is withdrawn through a conduit 75 which conducts the sulfur trioxicle for use in a sulfonating process or for treating flue gas, for example.
~ he method and apparatus illustrated in Fig. 1 will now be described in greater detail. Air is compressed at compressor 10 to a pressure in the range 35-70 psig, preferably 50-70 psig. The pressurized air is then flowed through a water separator 11 for removing some of the moisture precipitated during the compression operation and through an oil separator 12 for removing oil mists which may be present in the pressurized air after the compressing operation.
The pressurized air is then flowed through a conduit 13 to one of two unheated, pressurized driers 15, 16.
In the course of being dried, pressurized air from conduit 13 initially passes through a swing valve 14 which alternates the flow of pressurized air, every five minutes or so, back and forth between a branch line 23 leading to drier 15 and a branch line 24 leading to drier 16. Driers 15, 16 employ silica gel or molecular sieves as a drying medium, each being a stationary drying mediumO At the pressure under which the air is maintained when it flows through a drier 15 or 16 (50-70 psig), moisture is removed from the air sufficient to provide the pressurized air with a dewpoint below -40F (-40C).
Dried pressurized air is withdrawn from dryer 15 through a conduit 17 communicating with conduit 30 leading to sulfur burner 39. A portion of the dried air in conduit 17 (e.g., about 10 vol.%) is bled off through a line 26 communicating with a line 19 which leads through a conduit _g_ 11'7~Z5 18 into drier 16. The pressurized air bled off through line 26 is depressurized to atmospheric pressure before it is introduced into drier 16. The depressurized air flowing through drier 16 absorbs moisture from the drying medium in drier 16 to regenerate the latter. Moisture-laden air is drawn off from drier 16 through conduit 24 and from there hrough swing valve 14 into a vent line 25. A similar arrange-ment is utilized to regenerate drier 15 with dry air removed from drier 16.
More particularly, dried, pressurized air is with-drawn from drier 16 through conduit 18 communi~ating with conduit 30 leading to sulfur burner 39. A portion of the dried air in conduit 18 is bled off from line 18 through line 26 into a line 20 communicating with conduit 17 from drier 15. The pressurized air bled off from conduit 18 is depressurized to atmospheric pressure, before it is intro-duced into drier 15. As the depressurized air flows through drier 15 it absorbs the moisture from the drying medium in drier 1~ to regenerate the latter. ~oisture-laden air is withdrawn from drier 15 through conduit 23, swing valve 14 and vent line 25.
The drying and regenerating technique discussed above is employed in a preferred embodiment of the present invention. In a broader aspect of the present invention, pressurized drying can be employed without regenerating the drier with depressurized air in the manner described above. In such a case, the reduction of moisture to the extent possible with pressurized air is still available as an advantage, and a drier satuated with moisture can be regenerated in another fashion, e.g., with hot air.
Communicating with conduit 30 is a by-pass line 31 having a by-pass heater 32 for heating the pressurized air during standby sperating conditions or during startup.
2') Referring now to the one portion of pressurized air which has been preheated in heat exchanger 36, the amount of this preheated air should be at least that required to react stoichiometrically with the sulur fed into the sulfur burner. The maximum amount of preheated air is dependent upon the temperature of the first pressurized mixture of sulfur dioxide and air leaving sulfur burner 39 through conduit 58. The temperature of this mixture should not exceed 1500F (815C) in order to avoid an adverse effect upon the strength of the stainless steel of which the equipment components downstream of sulfur burner 39 are composed.
If the temperature of this mixture is too high, it can be reduced by reducing the amount of air subjected to preheating, by reducing the temperature to which this air is preheated and by reducing the amount of sulfur which is introduced into the sulfur burner for combustion into sulfur dioxide.
Generally, the amount of sulfur and the amount and temperature of the preheated air are controlled to provide the ~irst pressurized mixture leaving sulfur burner 39 with a temperature in the range 800-1500F (426-815C) and a sulfur dioxide content of 3-18 vol.~.
The minimum temperature of the preheated portion of air withdrawn from heat exchanger 36 is 475F (246C), the ignition temperature for the sulfur. As previously noted, the other portion of pressurized air, not preheated, is introduced into sulfur burner 39 through a conduit 35.
This portion of the pressurized air is at essentially the same temperature as the pressurized ~ir in conduit 30 (e.g., 60-~0F (16-27C)).
The portion of pressurized air subjected to pre-heating is introduced into heat exchanger 36 through line 34 and is withdrawn from the heat exchanger through a line 37.
Communicating with the bottom of sulfur burner 39, through a conduit 55, is a startup heater 40 which is used during startup of the equipment and process, before combustion of any sulfur has occurred.
Sulfur for combustion at burner 39 is melted in a sulfur melter 41, utilizing, as a heating medium, steam introduced into sulfur melter 41 through a conduit 42.
Condensate is removed from sulfur melter 41 through a line 43. The molten sulfur from sulfur melter 41 is pumped by a sulfur pump 46 through filters 44, 45 and into a line 47 communicating with sulfur burner 39. The molten sulfur in line 47 is at a temperature of minimum sulfur viscosity, e.g., 270F (132C). For molten sulfur, the viscosity increases above 300F (149C). A preferred temperature range for the molten sulfur is 260-300F (127-149C).
To facilitate the combustion of the molten sulfur in sulfur burner 39, it is desirable, in one embodiment of the invention, to maximize the surfa~e area of the molten sulfur exposed to the pressurized air. This is accomplished by atomizing the molten sulfur with atomizing air obtained by withdrawing from conduit 30 through branch line 49 a portion of the pressurized air and compressing it further in a compressor 48. A line 50 leads from compressor 48 to a heater 51 for the atomizing air. The atomizing air is indirectly heated in heater 51 by steam introduced through an inlet line 52. Condensate is removed from heater 51 through a condensate line 53. Heated atomizing air is with-drawn from heater 51 through a line 54.
The pressure of the atomizing air is about 30 psi greater than that of the pressurized air fed into sulfur burner 39 through conduits 35 and 37, and that pressure is preferably about 50-70 psig (e.g., 65-70 psig). Thus, the atomizing air has a pressure up to 100 psig.
~1~7~S
Referring now to Fig. 2, the molten sulfur and the atomizing air are fed into the top of sulfur burner 39 through a pair of coaxial conduits 47 and 54, respectively.
Molten sulfur exits from conduit ~7 through a nozzle 77 in which the sulfur is combined with high-pressure air from conduit 54 and is immediately atomized. The atomized globules of molten sulfur have a size in the range 20-50 microns.
The mixture of atomized molten sulfur and atomizing air exits into a conical shaped portion 80 in the top of sulfur burner 39. Conical portion 80 constitutes the entry to the sulfur-burning zone.
The atomizing air is heated at heater 51 to a temperature greater than 243F (117C), the freeæing temperature of sulfur, and less than 300F, above which there is a large increase in the viscosity of molten sulfur. A preferred temperature for the atomizing air is 270F (132C). The sulfur, upon being atomized by the atomizing air, is at a temperature less than 300F (149C) and preferably no less than 260F (127C).
As the atomized molten sulfur enters conical portion 80 at the top of sulfur burner 3g, it is enveloped and mixed with preheated air entering conical portion 80 through a conduit 38 (Fig. 2) communicating with line 37 from heat exchanger 36 and concentric with atomizing air conduit 54.
As previously noted, the preheated pressurized air introduced into the sulfur burner through conduits 37, 38 has a temperature which is at least the ignition temperature of the sulfur (475F (246C)).
As the atomized molten sulfur is mixed with the preheated pressurized air, the minute globules of molten sulfur are vaporized and then ignited to combust the sulfur and the oxygen in the preheated air to form sulfur dioxide.
s As previousl~ noted, there is sufficient preheated pressurized air to provide enough oxygen to stoichiometrically react with the amount of sulfur being introduced into sulfur burner 39.
The unheated, pressurized portion of the pressurized air entering sulfur burner 39 through conduit 35 is typically at a temperature in the range 60-80F (16-27C) when it enters the sulfur burner. This unheated pressurized air flows from conduit 35 into a manifold 81 (Fig. 2) which introduces the unheated pressurized air into the suLfur burning zone downstream of the location therein where the preheated portion of air was mixed with the sulfur.
It is desirable that combustion of the sulfur with oxygen to form sulfur dioxide be completed within the sulfur burner, which is lined with insulation 82. Completion therein is facilitated by introducing the air into the sulfur burner in a pressurized condition. Pressurized air causes a more intense combustion thereby reducing the length of the sulfur-burning zone through which the reacting gases must pass before combustion is completed. Typically, utilizing the pressure and preheated temperature conditions noted above, combustion can be completed in about 2.1 seconds.
When sulfur is combusted in the presence of pres-surized air, the completion of combustion is so enhanced as to provide essentially complete combustion within the sulfur burner without maximizing the surface area of the molten sulfur exposed to the combusting air. Thus, although in the illustrated embodiment the surface area of the molten sulfur is maximized by atomizing, in a broader aspect of the invention, both atomizing nozzle 77 and atomizing air conduit 54 can be eliminated and essentially complete com-bustion of the sulfur in sulfur burner 39 will still be obtained.
~ `s~ 5 If the combustion of sulfur were not completed within the sulfur burner 39, sulfur burning would continue in conduit 58 downstream of sulfur burner 39, an occurrence which would be undesirable.
Completion of combustion within the sulfur burner is also enhanced by preheating that portion of the air which is initially mixed with the molten sulfur at the entry 80 to the sulfur-burning zone.
The unheated portion of pressurized air is introduced into the sulfur burner downstream of the location where the preheated pressurized air ignites the sulfur so as to enable combustion to proceed to a substantial extent before the unheated pressurized air imparts to the gaseous reaction mixture a diluting and cooling effect. Maintaining the air introduced through conduit 35 in an unpreheated condition helps to control, to a temperature no greater than 1500F
(816C), the pressurized mixture leaving sulfur burner 39 through conduit 58. As previously noted, this temperature limitation in conduit 58 is necessary in order to avoid an adverse effect upon the strength of the stainless steel components of the apparatus located downstream of sulfur burner 39.
The preheated portion of pressurized air introduced into the sulfur burner through conduits 37, 38 causes an immediate ignition of the molten sulfur when atomized globules of the latter enter the sulfur burner at conical entry portion 80. Moreover, because there is no contact between the pre-heated air and the molten sulfur until the latter has entered the sulfur-burning zone at entry 80, premature ignition of the molten sulfur, upstream of the sulfur burner, is avoided. The molten sulfur is not subjected at all to the heating influence of the preheated pressurized air until the sulfur has entered the sulfur-burning zone and has left ~:~'7~J25 the conduits which transport it there. It would be unde-sirable to subject the molten sulfur to the heating influence of the preheated air while the sulfur was still in the conduit conducting it to the sulfur-heating zone because to do so could heat the sulfur above the maximum temperature at which its viscosity is a minimum (300F (149C)). Had the sulfur been subjected to the heating influence of the preheated air while the sulfur was still in conduit 47 or 38 (Fig.
2), the increased viscosity would have interfered with the flow of the sulfur through these conduits and with the atomi-zation of the molten sulfur.
As previously noted, the ratio of preheated to unpreheated air introduced into the sulfur burner is con-trolled to maintain the pressurized gaseous mixture leaving the sulfur burner at a temperature below 1500F (815C).
This ratio can be controlled with a valve (not shown) located at the junction of conduit 30 and branch lines 34, 35.
The technique described above, wherein the pres-surized air is introduced into the sulfur burner as preheated and unpreheated portions, is one embodiment of the present invention. In another embodiment, no portion of the pres-surized air is preheated, and the pressurization is relied upon to promote completion of combustion in the sulfur-burning zone.
The first pressurized mixture of sulfur dioxide and air is cooled in two steps between sulfur burner 39 and catalytic converter 62. One of these cooling steps is at heat exchanger 36 wherein cooling is accomplished through indirect cooling by the preheat air as the latter undergoes heating, and the second cooling step is at radiant cooler 60. The temperature of the pressurized gaseous mixture in condui~ 58 upstream of heat exchanger 36 is less than 11 7~0~.5 1500F (816C), and the temperature of this gaseous mixture is cooled, in steps, down to about 800F (427C) when it enters catalytic converter 62. Typically, the temperature of the gaseous mixture in conduit 58 is about 1450F, the temperature in conduit 59 between heat exchanger 36 and radiant cooler 60 is about 1300F (704C), and the temperature in line 61 between radiant cooler 60 and catalytic converter 62 is about 800F (427C). The pressurized gaseous mixture in conduit 58 cannot be entirely indirectly cooled at heat exchanger 36, to the desired catalytic converting temperature of about 800F (427C), because to do so would cause an increase in the temperature of the preheated pressurized air entering sulfur burner 39 in turn causing an increase to a temperature above 1500F (816C) of the gaseous mixture exiting the sulfur burner through conduit 5~, which is un-desirable.
The gaseous mixture of sulfur dioxide and air enters catalytic converter 62 through line 61. In the cata-lytic converter, the sulfur dioxide reacts with oxygen in the air of that mixture to produce sulfur trioxide. Conver-sion from sulfur dioxide to sulfur trioxide occurs in each of the three stages, 63, 64, 65 of catalytic converter 62.
However, in a method in accordance with the present invention conversion is about 99% complete after second stage 64 and over 99% complete after third stage 65. Between first con-version stage 63 and second conversion stage 64 the gaseous mixture passes through a first cooling line 66, and between second conversion stage 64 and third conversion stage 65 the gaseous mixture passes through a second cooling line 67. The function of cooling lines 66, 67 is to cool the mixture as the sulfur dioxide therein undergoes conversion to sulfur trioxide, .hereby to maintain the temperature .11~78QZS
of the mixture at essentially the same temperature as when it was introduced into first conversion stage 63, or lower.
The gaseous mixture leaving catalytic converter 62 through conduit 68 comprises sulfur trioxide and pres~
surized air at a temperature of about 800F (427C) or lower.
This second pressurized mixture is subjected to cooling in a radiant cooler 70 to lower the temperature of the second pressurized mixture to about 350-600F (177-316C~. The gaseous mixture lea~ing radiant cooler 70 may be further cooled at a cascade cooler 71 to which cooling water is supplied through an inlet line 72 and from which water is withdrawn through a line 73.
The cooled gaseous mixture of sulfur trioxide and air is removed from the cascade cooler through a conduit 75, and the temperature of the gaseous mixture in conduit 75 is typically in the range 85-120F (29-49C). The sulfur trioxide concentration in conduit 75 is about 3-18 vol.%.
Because the pressurized air was dried to a dewpoint below -40F (-40C), cooling of the mixture in conduit 75 to a temperature below 120F does not precipitate enough water to form significant amounts of oleum in conduit 75, an occur-rence which would be undesirable if the gaseous mixture containing the sulfur trioxide was subsequently to be used in a sulfonating operation or where the highly corrosive properties of oleum may be objectionable. A significant amount of oleum is an amount which produces an undesirable or adverse effect.
If the gaseous mixture containing the sulfur tri-oxide is to be used for flue gas treatment, cooling in cas-cade cooler 71 may be eliminated.
In a typical operation employing the method il-lustrated in Fig. 1, the following amounts of material are 2s handled at pressures of about 55-60 psig.
sulfur into 225 lbs/hr sulfur burner (108 kg/hr.) air into 2887 lbs/hr.
sulfur burner (1311 kg/hr.) SO plus air 3112 lbs/hr.
in~o catalytic (1413 kg/hr.) converter S0 plus air 3112 lbs/hr.
ou~ of catalytic (1413 kg/hr.) converter The sulfur burner has interior dimensions, below entry 80, as follows: diameter 21 inches (53 cm) and height 77 inches (196 cm). The conduit from sulfur burner 39 has a diameter of 4" (10 cm). The catalytic bed in each of the three stages of the catalytic converter has a diameter of 23 inches (58 cm) and a height of 21 inches (53 cm). The catalyst is vanadium pentoxide.
The embodimen~ of the present invention illustrated in Fig. 1 employs three stages of conversion from S02 to SO3 with a first cooling step at 66 between stages 63 and 64 and a second cooling step at 67 between stages 64 and 65. However, when the gas is pressurized in accordance with the present invention, conversion is so complete in the first two stages (e.g., about 99%)~ that the conversion operating procedures normally employed downstream of second stage 64 may be dispensed with.
Thus, if the SO3 is intended for use in fly ash treatment, where an SO3 conversion from S02 of about 99%
is adequate in the treating gas, a third stage of conversion (such as stage 65) is not needed.
If the SO3 is intended for use in a sulfonation operation where an SO3 conversion greater than 99% is desirable, the third stage is employed to increase the conversion from about 99% (e.g., 98.8%) at the outlet of second stage 64 to greater than 99% from the outlet of third stage 65.
However, if third conversion stage 65 is employed, the gas from second stage 64 need not be cooled at 67 before intro-duction into third stage 65. This is because most of the 99% conversion occurring in the first two stages occurs at first conversion stage 63, with the conversion occurring at second conversion stage 64 being relatively so small that it does not generate an increase in temperature suffi-c;.ent to warrant cooling between stages 64 and 55~ Cooling is required between stages 63 and 64, at 66.
Preferably, the gas is subjected to mixing between stages 64 and 65 (as well as between stages 63 and 64), and this can be performed within converter 62 by running the gas through a layer of pebbles between conversion stages, a conventional procedure in converting processes.
The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.
If the temperature of this mixture is too high, it can be reduced by reducing the amount of air subjected to preheating, by reducing the temperature to which this air is preheated and by reducing the amount of sulfur which is introduced into the sulfur burner for combustion into sulfur dioxide.
Generally, the amount of sulfur and the amount and temperature of the preheated air are controlled to provide the ~irst pressurized mixture leaving sulfur burner 39 with a temperature in the range 800-1500F (426-815C) and a sulfur dioxide content of 3-18 vol.~.
The minimum temperature of the preheated portion of air withdrawn from heat exchanger 36 is 475F (246C), the ignition temperature for the sulfur. As previously noted, the other portion of pressurized air, not preheated, is introduced into sulfur burner 39 through a conduit 35.
This portion of the pressurized air is at essentially the same temperature as the pressurized ~ir in conduit 30 (e.g., 60-~0F (16-27C)).
The portion of pressurized air subjected to pre-heating is introduced into heat exchanger 36 through line 34 and is withdrawn from the heat exchanger through a line 37.
Communicating with the bottom of sulfur burner 39, through a conduit 55, is a startup heater 40 which is used during startup of the equipment and process, before combustion of any sulfur has occurred.
Sulfur for combustion at burner 39 is melted in a sulfur melter 41, utilizing, as a heating medium, steam introduced into sulfur melter 41 through a conduit 42.
Condensate is removed from sulfur melter 41 through a line 43. The molten sulfur from sulfur melter 41 is pumped by a sulfur pump 46 through filters 44, 45 and into a line 47 communicating with sulfur burner 39. The molten sulfur in line 47 is at a temperature of minimum sulfur viscosity, e.g., 270F (132C). For molten sulfur, the viscosity increases above 300F (149C). A preferred temperature range for the molten sulfur is 260-300F (127-149C).
To facilitate the combustion of the molten sulfur in sulfur burner 39, it is desirable, in one embodiment of the invention, to maximize the surfa~e area of the molten sulfur exposed to the pressurized air. This is accomplished by atomizing the molten sulfur with atomizing air obtained by withdrawing from conduit 30 through branch line 49 a portion of the pressurized air and compressing it further in a compressor 48. A line 50 leads from compressor 48 to a heater 51 for the atomizing air. The atomizing air is indirectly heated in heater 51 by steam introduced through an inlet line 52. Condensate is removed from heater 51 through a condensate line 53. Heated atomizing air is with-drawn from heater 51 through a line 54.
The pressure of the atomizing air is about 30 psi greater than that of the pressurized air fed into sulfur burner 39 through conduits 35 and 37, and that pressure is preferably about 50-70 psig (e.g., 65-70 psig). Thus, the atomizing air has a pressure up to 100 psig.
~1~7~S
Referring now to Fig. 2, the molten sulfur and the atomizing air are fed into the top of sulfur burner 39 through a pair of coaxial conduits 47 and 54, respectively.
Molten sulfur exits from conduit ~7 through a nozzle 77 in which the sulfur is combined with high-pressure air from conduit 54 and is immediately atomized. The atomized globules of molten sulfur have a size in the range 20-50 microns.
The mixture of atomized molten sulfur and atomizing air exits into a conical shaped portion 80 in the top of sulfur burner 39. Conical portion 80 constitutes the entry to the sulfur-burning zone.
The atomizing air is heated at heater 51 to a temperature greater than 243F (117C), the freeæing temperature of sulfur, and less than 300F, above which there is a large increase in the viscosity of molten sulfur. A preferred temperature for the atomizing air is 270F (132C). The sulfur, upon being atomized by the atomizing air, is at a temperature less than 300F (149C) and preferably no less than 260F (127C).
As the atomized molten sulfur enters conical portion 80 at the top of sulfur burner 3g, it is enveloped and mixed with preheated air entering conical portion 80 through a conduit 38 (Fig. 2) communicating with line 37 from heat exchanger 36 and concentric with atomizing air conduit 54.
As previously noted, the preheated pressurized air introduced into the sulfur burner through conduits 37, 38 has a temperature which is at least the ignition temperature of the sulfur (475F (246C)).
As the atomized molten sulfur is mixed with the preheated pressurized air, the minute globules of molten sulfur are vaporized and then ignited to combust the sulfur and the oxygen in the preheated air to form sulfur dioxide.
s As previousl~ noted, there is sufficient preheated pressurized air to provide enough oxygen to stoichiometrically react with the amount of sulfur being introduced into sulfur burner 39.
The unheated, pressurized portion of the pressurized air entering sulfur burner 39 through conduit 35 is typically at a temperature in the range 60-80F (16-27C) when it enters the sulfur burner. This unheated pressurized air flows from conduit 35 into a manifold 81 (Fig. 2) which introduces the unheated pressurized air into the suLfur burning zone downstream of the location therein where the preheated portion of air was mixed with the sulfur.
It is desirable that combustion of the sulfur with oxygen to form sulfur dioxide be completed within the sulfur burner, which is lined with insulation 82. Completion therein is facilitated by introducing the air into the sulfur burner in a pressurized condition. Pressurized air causes a more intense combustion thereby reducing the length of the sulfur-burning zone through which the reacting gases must pass before combustion is completed. Typically, utilizing the pressure and preheated temperature conditions noted above, combustion can be completed in about 2.1 seconds.
When sulfur is combusted in the presence of pres-surized air, the completion of combustion is so enhanced as to provide essentially complete combustion within the sulfur burner without maximizing the surface area of the molten sulfur exposed to the combusting air. Thus, although in the illustrated embodiment the surface area of the molten sulfur is maximized by atomizing, in a broader aspect of the invention, both atomizing nozzle 77 and atomizing air conduit 54 can be eliminated and essentially complete com-bustion of the sulfur in sulfur burner 39 will still be obtained.
~ `s~ 5 If the combustion of sulfur were not completed within the sulfur burner 39, sulfur burning would continue in conduit 58 downstream of sulfur burner 39, an occurrence which would be undesirable.
Completion of combustion within the sulfur burner is also enhanced by preheating that portion of the air which is initially mixed with the molten sulfur at the entry 80 to the sulfur-burning zone.
The unheated portion of pressurized air is introduced into the sulfur burner downstream of the location where the preheated pressurized air ignites the sulfur so as to enable combustion to proceed to a substantial extent before the unheated pressurized air imparts to the gaseous reaction mixture a diluting and cooling effect. Maintaining the air introduced through conduit 35 in an unpreheated condition helps to control, to a temperature no greater than 1500F
(816C), the pressurized mixture leaving sulfur burner 39 through conduit 58. As previously noted, this temperature limitation in conduit 58 is necessary in order to avoid an adverse effect upon the strength of the stainless steel components of the apparatus located downstream of sulfur burner 39.
The preheated portion of pressurized air introduced into the sulfur burner through conduits 37, 38 causes an immediate ignition of the molten sulfur when atomized globules of the latter enter the sulfur burner at conical entry portion 80. Moreover, because there is no contact between the pre-heated air and the molten sulfur until the latter has entered the sulfur-burning zone at entry 80, premature ignition of the molten sulfur, upstream of the sulfur burner, is avoided. The molten sulfur is not subjected at all to the heating influence of the preheated pressurized air until the sulfur has entered the sulfur-burning zone and has left ~:~'7~J25 the conduits which transport it there. It would be unde-sirable to subject the molten sulfur to the heating influence of the preheated air while the sulfur was still in the conduit conducting it to the sulfur-heating zone because to do so could heat the sulfur above the maximum temperature at which its viscosity is a minimum (300F (149C)). Had the sulfur been subjected to the heating influence of the preheated air while the sulfur was still in conduit 47 or 38 (Fig.
2), the increased viscosity would have interfered with the flow of the sulfur through these conduits and with the atomi-zation of the molten sulfur.
As previously noted, the ratio of preheated to unpreheated air introduced into the sulfur burner is con-trolled to maintain the pressurized gaseous mixture leaving the sulfur burner at a temperature below 1500F (815C).
This ratio can be controlled with a valve (not shown) located at the junction of conduit 30 and branch lines 34, 35.
The technique described above, wherein the pres-surized air is introduced into the sulfur burner as preheated and unpreheated portions, is one embodiment of the present invention. In another embodiment, no portion of the pres-surized air is preheated, and the pressurization is relied upon to promote completion of combustion in the sulfur-burning zone.
The first pressurized mixture of sulfur dioxide and air is cooled in two steps between sulfur burner 39 and catalytic converter 62. One of these cooling steps is at heat exchanger 36 wherein cooling is accomplished through indirect cooling by the preheat air as the latter undergoes heating, and the second cooling step is at radiant cooler 60. The temperature of the pressurized gaseous mixture in condui~ 58 upstream of heat exchanger 36 is less than 11 7~0~.5 1500F (816C), and the temperature of this gaseous mixture is cooled, in steps, down to about 800F (427C) when it enters catalytic converter 62. Typically, the temperature of the gaseous mixture in conduit 58 is about 1450F, the temperature in conduit 59 between heat exchanger 36 and radiant cooler 60 is about 1300F (704C), and the temperature in line 61 between radiant cooler 60 and catalytic converter 62 is about 800F (427C). The pressurized gaseous mixture in conduit 58 cannot be entirely indirectly cooled at heat exchanger 36, to the desired catalytic converting temperature of about 800F (427C), because to do so would cause an increase in the temperature of the preheated pressurized air entering sulfur burner 39 in turn causing an increase to a temperature above 1500F (816C) of the gaseous mixture exiting the sulfur burner through conduit 5~, which is un-desirable.
The gaseous mixture of sulfur dioxide and air enters catalytic converter 62 through line 61. In the cata-lytic converter, the sulfur dioxide reacts with oxygen in the air of that mixture to produce sulfur trioxide. Conver-sion from sulfur dioxide to sulfur trioxide occurs in each of the three stages, 63, 64, 65 of catalytic converter 62.
However, in a method in accordance with the present invention conversion is about 99% complete after second stage 64 and over 99% complete after third stage 65. Between first con-version stage 63 and second conversion stage 64 the gaseous mixture passes through a first cooling line 66, and between second conversion stage 64 and third conversion stage 65 the gaseous mixture passes through a second cooling line 67. The function of cooling lines 66, 67 is to cool the mixture as the sulfur dioxide therein undergoes conversion to sulfur trioxide, .hereby to maintain the temperature .11~78QZS
of the mixture at essentially the same temperature as when it was introduced into first conversion stage 63, or lower.
The gaseous mixture leaving catalytic converter 62 through conduit 68 comprises sulfur trioxide and pres~
surized air at a temperature of about 800F (427C) or lower.
This second pressurized mixture is subjected to cooling in a radiant cooler 70 to lower the temperature of the second pressurized mixture to about 350-600F (177-316C~. The gaseous mixture lea~ing radiant cooler 70 may be further cooled at a cascade cooler 71 to which cooling water is supplied through an inlet line 72 and from which water is withdrawn through a line 73.
The cooled gaseous mixture of sulfur trioxide and air is removed from the cascade cooler through a conduit 75, and the temperature of the gaseous mixture in conduit 75 is typically in the range 85-120F (29-49C). The sulfur trioxide concentration in conduit 75 is about 3-18 vol.%.
Because the pressurized air was dried to a dewpoint below -40F (-40C), cooling of the mixture in conduit 75 to a temperature below 120F does not precipitate enough water to form significant amounts of oleum in conduit 75, an occur-rence which would be undesirable if the gaseous mixture containing the sulfur trioxide was subsequently to be used in a sulfonating operation or where the highly corrosive properties of oleum may be objectionable. A significant amount of oleum is an amount which produces an undesirable or adverse effect.
If the gaseous mixture containing the sulfur tri-oxide is to be used for flue gas treatment, cooling in cas-cade cooler 71 may be eliminated.
In a typical operation employing the method il-lustrated in Fig. 1, the following amounts of material are 2s handled at pressures of about 55-60 psig.
sulfur into 225 lbs/hr sulfur burner (108 kg/hr.) air into 2887 lbs/hr.
sulfur burner (1311 kg/hr.) SO plus air 3112 lbs/hr.
in~o catalytic (1413 kg/hr.) converter S0 plus air 3112 lbs/hr.
ou~ of catalytic (1413 kg/hr.) converter The sulfur burner has interior dimensions, below entry 80, as follows: diameter 21 inches (53 cm) and height 77 inches (196 cm). The conduit from sulfur burner 39 has a diameter of 4" (10 cm). The catalytic bed in each of the three stages of the catalytic converter has a diameter of 23 inches (58 cm) and a height of 21 inches (53 cm). The catalyst is vanadium pentoxide.
The embodimen~ of the present invention illustrated in Fig. 1 employs three stages of conversion from S02 to SO3 with a first cooling step at 66 between stages 63 and 64 and a second cooling step at 67 between stages 64 and 65. However, when the gas is pressurized in accordance with the present invention, conversion is so complete in the first two stages (e.g., about 99%)~ that the conversion operating procedures normally employed downstream of second stage 64 may be dispensed with.
Thus, if the SO3 is intended for use in fly ash treatment, where an SO3 conversion from S02 of about 99%
is adequate in the treating gas, a third stage of conversion (such as stage 65) is not needed.
If the SO3 is intended for use in a sulfonation operation where an SO3 conversion greater than 99% is desirable, the third stage is employed to increase the conversion from about 99% (e.g., 98.8%) at the outlet of second stage 64 to greater than 99% from the outlet of third stage 65.
However, if third conversion stage 65 is employed, the gas from second stage 64 need not be cooled at 67 before intro-duction into third stage 65. This is because most of the 99% conversion occurring in the first two stages occurs at first conversion stage 63, with the conversion occurring at second conversion stage 64 being relatively so small that it does not generate an increase in temperature suffi-c;.ent to warrant cooling between stages 64 and 55~ Cooling is required between stages 63 and 64, at 66.
Preferably, the gas is subjected to mixing between stages 64 and 65 (as well as between stages 63 and 64), and this can be performed within converter 62 by running the gas through a layer of pebbles between conversion stages, a conventional procedure in converting processes.
The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.
Claims (21)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for producing sulfur trioxide gas, said method comprising:
introducing molten sulfur into a confined sulfur-burning zone;
introducing pressurized air having a pressure greater than about 30 psig up to about 120 psig into said confined sulfur-burning zone;
combusting said sulfur and said pressurized air in said sulfur-burning zone to produce a first pres-surized mixture of pressurized sulfur dioxide and air;
converting said pressurized sulfur dioxide into pressurized sulfur trioxide in a confined converting zone downstream of said sulfur-burning zone to produce a second pressurized mixture of sulfur trioxide and air;
performing said converting step in three cata-lytic converting stages;
cooling said pressurized mixture between the first and second of said converting stages;
obtaining at least about 99% conversion in the first two of said converting stages;
and obtaining greater than 99% conversion in said three converting stages without cooling between the second and third stages.
introducing molten sulfur into a confined sulfur-burning zone;
introducing pressurized air having a pressure greater than about 30 psig up to about 120 psig into said confined sulfur-burning zone;
combusting said sulfur and said pressurized air in said sulfur-burning zone to produce a first pres-surized mixture of pressurized sulfur dioxide and air;
converting said pressurized sulfur dioxide into pressurized sulfur trioxide in a confined converting zone downstream of said sulfur-burning zone to produce a second pressurized mixture of sulfur trioxide and air;
performing said converting step in three cata-lytic converting stages;
cooling said pressurized mixture between the first and second of said converting stages;
obtaining at least about 99% conversion in the first two of said converting stages;
and obtaining greater than 99% conversion in said three converting stages without cooling between the second and third stages.
2. A method as recited in Claim 1 and com-prising:
cooling said second pressurized mixture of sulfur trioxide and air downstream of said converting zone;
and introducing said pressurized air into an unheated, pressurized, moisture-absorbing, drying zone containing a stationary drying medium, and before said air is introduced into said sulfur-burning zone, to pro-duce dried, pressurized air having a dew point sufficient-ly low substantially to prevent, during the coolng of said second pressurized mixture, the formation of oleum in amounts having an adverse corrosive effect or an ad-verse effect in a sulfonating operation.
cooling said second pressurized mixture of sulfur trioxide and air downstream of said converting zone;
and introducing said pressurized air into an unheated, pressurized, moisture-absorbing, drying zone containing a stationary drying medium, and before said air is introduced into said sulfur-burning zone, to pro-duce dried, pressurized air having a dew point sufficient-ly low substantially to prevent, during the coolng of said second pressurized mixture, the formation of oleum in amounts having an adverse corrosive effect or an ad-verse effect in a sulfonating operation.
3. A method as recited in Claim 1 and com-prising:
restricting the volume of said catalytic convert-ing stages to less than 60% of the volume required to convert the same weight amount of sulfur dioxide and handle the same weight amount of air at atmospheric pres-sure.
restricting the volume of said catalytic convert-ing stages to less than 60% of the volume required to convert the same weight amount of sulfur dioxide and handle the same weight amount of air at atmospheric pres-sure.
4. A method as recited in Claim 1 and com-prising:
cooling said first pressurized mixture in a confined cooling zone located between said sulfur-burning zone and said converting zone;
transporting said first pressurized mixture from said confined sulfur-burning zone to said confined cooling zone and then to said confined converting zone in transporting conduits;
and restricting the volume of said transporting conduits and of said cooling zone to less than about 50%
of the volume required to transport the same weight amounts of sulfur dioxide and air at atmospheric pressure.
cooling said first pressurized mixture in a confined cooling zone located between said sulfur-burning zone and said converting zone;
transporting said first pressurized mixture from said confined sulfur-burning zone to said confined cooling zone and then to said confined converting zone in transporting conduits;
and restricting the volume of said transporting conduits and of said cooling zone to less than about 50%
of the volume required to transport the same weight amounts of sulfur dioxide and air at atmospheric pressure.
5. A method as recited in Claim 4 and com-prising:
restricting the volume of said transporting conduits and of said cooling zone to about one-third of the volume required at atmospheric pressure.
restricting the volume of said transporting conduits and of said cooling zone to about one-third of the volume required at atmospheric pressure.
6. A method as recited in Claim 1 and comprising:
preheating at least a portion of said pressurized air to a temperature above the ignition temperature of sulfur;
and restricting the length of said sulfur-burning zone, and restricting the volume of said sulfur-burning zone by at least about 50%, compared to a sulfur-burning zone required to combust the same weight amounts of sulfur and air at atmospheric pressure without pre-heating.
preheating at least a portion of said pressurized air to a temperature above the ignition temperature of sulfur;
and restricting the length of said sulfur-burning zone, and restricting the volume of said sulfur-burning zone by at least about 50%, compared to a sulfur-burning zone required to combust the same weight amounts of sulfur and air at atmospheric pressure without pre-heating.
7. A method as recited in Claim 6 and com-prising:
restricting the volume of said sulfur-burning zone to about one-third of the volume required at atmos-pheric pressure.
restricting the volume of said sulfur-burning zone to about one-third of the volume required at atmos-pheric pressure.
8. A method as recited in Claim 6 and com-prising:
initiating combustion of the sulfur by mixing the sulfur with said preheated portion of pressurized air, as the sulfur enters said sulfur-burning zone, to produce a reaction mixture containing sulfur dioxide;
essentially completing the combustion of said molten sulfur in said sulfur-burning zone;
and withdrawing said first pressurized mixture from said sulfur-burning zone into apparatus downstream of said sulfur-burning zone.
initiating combustion of the sulfur by mixing the sulfur with said preheated portion of pressurized air, as the sulfur enters said sulfur-burning zone, to produce a reaction mixture containing sulfur dioxide;
essentially completing the combustion of said molten sulfur in said sulfur-burning zone;
and withdrawing said first pressurized mixture from said sulfur-burning zone into apparatus downstream of said sulfur-burning zone.
9. A method as recited in Claim 8 and com-prising:
controlling the temperature of said first pres-surized mixture as it leaves the sulfur-burning zone to avoid an adverse effect upon the strength of said down-stream apparatus.
controlling the temperature of said first pres-surized mixture as it leaves the sulfur-burning zone to avoid an adverse effect upon the strength of said down-stream apparatus.
10. A method as recited in Claim 9 wherein said controlling step comprises:
controlling the amounts and temperature of air and sulfur introduced into said sulfur-burning zone to provide said first pressurized mixture with a temperature in the range 800° to 1500°F (426° to 815°C).
controlling the amounts and temperature of air and sulfur introduced into said sulfur-burning zone to provide said first pressurized mixture with a temperature in the range 800° to 1500°F (426° to 815°C).
11. A method as recited in Claim 8 wherein:
said first pressurized mixture has a sulfur dioxide content in the range 3-18 vol.%.
said first pressurized mixture has a sulfur dioxide content in the range 3-18 vol.%.
12. A method as recited in Claim 8 and com-prising:
avoiding subjecting the sulfur to the heating influence of said preheated air portion upstream of the entry to said sulfur-burning zone.
avoiding subjecting the sulfur to the heating influence of said preheated air portion upstream of the entry to said sulfur-burning zone.
13. A method as recited in Claim 8 and com-prising:
dividing said pressurized air into two portions;
said preheating step being performed on one of said portions, the other of said portions remaining un-preheated;
and introducing said unpreheated portion of air into said sulfur-burning zone downstream of the loca-tion therein where said preheated air portion was mixed with the sulfur.
dividing said pressurized air into two portions;
said preheating step being performed on one of said portions, the other of said portions remaining un-preheated;
and introducing said unpreheated portion of air into said sulfur-burning zone downstream of the loca-tion therein where said preheated air portion was mixed with the sulfur.
14. A method as recited in Claim 13 wherein:
said preheated air portion comprises at least the stoichiometric amount of oxygen required to convert all of said molten sulfur to sulfur dioxide and has a temperature above 475°F and below 1500°F (246° and 815°C);
and said method comprises controlling the ratio of preheated to unpreheated air and the amount of sulfur to maintain said first pressurized mixture at a tempera-ture no greater than 1500°F (815°C) as it leaves said sulfur-burning zone.
said preheated air portion comprises at least the stoichiometric amount of oxygen required to convert all of said molten sulfur to sulfur dioxide and has a temperature above 475°F and below 1500°F (246° and 815°C);
and said method comprises controlling the ratio of preheated to unpreheated air and the amount of sulfur to maintain said first pressurized mixture at a tempera-ture no greater than 1500°F (815°C) as it leaves said sulfur-burning zone.
15. A method as recited in Claim 8 wherein said preheating step comprises:
indirectly cooling said first pressurized mix-ture with said portion of pressurized air, at a first heat exchanging zone downstream of said sulfur-burning zone, to preheat said portion.
indirectly cooling said first pressurized mix-ture with said portion of pressurized air, at a first heat exchanging zone downstream of said sulfur-burning zone, to preheat said portion.
16. A method as recited in Claim 8 and com-prising:
cooling said first pressurized mixture to a predetermined temperature range at a location downstream of said sulfur-burning zone, said cooling being performed in two separate, discrete steps;
one of said two steps comprising indirectly cooling said first pressurized mixture with said portion of pressurized air to preheat said portion of pressurized air and to partially cool said first pressurized mixture;
and controlling the extent of said indirect cooling at said one cooling step to limit the temperature to which said portion of pressurized air is preheated so as to maintain a temperature in said first pressurized mixture at the outlet of said sulfur-burning zone no greater than 1500°F (815°C).
cooling said first pressurized mixture to a predetermined temperature range at a location downstream of said sulfur-burning zone, said cooling being performed in two separate, discrete steps;
one of said two steps comprising indirectly cooling said first pressurized mixture with said portion of pressurized air to preheat said portion of pressurized air and to partially cool said first pressurized mixture;
and controlling the extent of said indirect cooling at said one cooling step to limit the temperature to which said portion of pressurized air is preheated so as to maintain a temperature in said first pressurized mixture at the outlet of said sulfur-burning zone no greater than 1500°F (815°C).
17. A method as recited in Claim 1 and comprising:
cooling said second pressurized mixture of sulfur trioxide and air downstream of said converting zone to a temperature below about 120°F (49°C);
drying said pressurized air by flowing it through an unheated, pressurized, moisture-absorbing, drying zone, containing a stationary drying medium, and before said air is introduced into said sulfur-burning zone;
and pressurizing said air, before it is flowed through said drying zone, to a pressure which, as a result of said drying step produces dried, pressurized air having a dew point sufficiently low substantially to prevent, during said cooling of said second pressurized mixture below about 120°F (49°C), the formation of oleum in amounts which have an adverse corrosive effect or an adverse effect in a sulfonating operation.
cooling said second pressurized mixture of sulfur trioxide and air downstream of said converting zone to a temperature below about 120°F (49°C);
drying said pressurized air by flowing it through an unheated, pressurized, moisture-absorbing, drying zone, containing a stationary drying medium, and before said air is introduced into said sulfur-burning zone;
and pressurizing said air, before it is flowed through said drying zone, to a pressure which, as a result of said drying step produces dried, pressurized air having a dew point sufficiently low substantially to prevent, during said cooling of said second pressurized mixture below about 120°F (49°C), the formation of oleum in amounts which have an adverse corrosive effect or an adverse effect in a sulfonating operation.
18. A method as recited in Claim 17 wherein said pressurizing step comprises:
pressurizing said air to a pressure which, in said drying zone, reduces the dew point of said air below -40°F (-40°C).
pressurizing said air to a pressure which, in said drying zone, reduces the dew point of said air below -40°F (-40°C).
19. A method as recited in Claim 18 wherein said pressurizing step comprises:
pressurizing said air to a pressure in the range 50 to 70 psig.
pressurizing said air to a pressure in the range 50 to 70 psig.
20. A method as recited in Claim 18 wherein said drying zone is of the type which, after the removal of moisture from air in said drying zone, may be regen-erated to deplete it of moisture by passing heated air and cooling air sequentially through said zone, said method further comprising:
regenerating said zone by depressurizing a fraction of the pressurized air dried by said method and diverting said depressurized fraction of dry air thorugh said zone;
said regenerating step being performed without heating or cooling said depressurized fraction of dry air and without employing a separate blower for said depressurized fraction of air;
and maintaining (1) the energy expended to pressurize said air at less than (2) the energy required to obtain said dew point below -40°F (-40°C) when said drying zone is regenerated by passing heated air and cooling air therethrough and employing separate blowers to do so.
regenerating said zone by depressurizing a fraction of the pressurized air dried by said method and diverting said depressurized fraction of dry air thorugh said zone;
said regenerating step being performed without heating or cooling said depressurized fraction of dry air and without employing a separate blower for said depressurized fraction of air;
and maintaining (1) the energy expended to pressurize said air at less than (2) the energy required to obtain said dew point below -40°F (-40°C) when said drying zone is regenerated by passing heated air and cooling air therethrough and employing separate blowers to do so.
21. A method as recited in Claim 20 and com-prising:
obtaining said fraction of dry air from another drying zone arranged in tandem with the drying zone under-going regeneration.
obtaining said fraction of dry air from another drying zone arranged in tandem with the drying zone under-going regeneration.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US21105380A | 1980-11-28 | 1980-11-28 | |
| US211,053 | 1980-11-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1178025A true CA1178025A (en) | 1984-11-20 |
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ID=22785415
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000389605A Expired CA1178025A (en) | 1980-11-28 | 1981-11-06 | Method for producing a pressurized oxide of sulfur |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS57111210A (en) |
| AR (1) | AR226384A1 (en) |
| BR (1) | BR8107701A (en) |
| CA (1) | CA1178025A (en) |
| DE (1) | DE3146798A1 (en) |
| FR (1) | FR2495125B1 (en) |
| GB (1) | GB2088350B (en) |
| IT (1) | IT1201033B (en) |
| MX (1) | MX156581A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5196038A (en) * | 1990-03-15 | 1993-03-23 | Wright Robert A | Flue gas conditioning system |
| US5240470A (en) * | 1992-04-07 | 1993-08-31 | Wilhelm Environmental Technologies, Inc. | In-duct flue gas conditioning system |
| WO1993019852A1 (en) * | 1992-04-07 | 1993-10-14 | Wilhelm Environmental Technologies, Inc. | Flue gas conditioning system |
| US5261931A (en) * | 1990-03-15 | 1993-11-16 | Wilhelm Environmental Technologies, Inc. | Flue gas conditioning system |
| US5288309A (en) * | 1992-04-07 | 1994-02-22 | Wilhelm Environmental Technologies, Inc. | Flue gas conditioning agent demand control apparatus |
| US5350441A (en) * | 1990-03-15 | 1994-09-27 | Wilhelm Environmental Technologies, Inc. | Flue gas conditioning system |
| US5356597A (en) * | 1992-04-07 | 1994-10-18 | Wilhelm Environmental Technologies, Inc. | In-duct flue gas conditioning system |
| US5370720A (en) * | 1993-07-23 | 1994-12-06 | Welhelm Environmental Technologies, Inc. | Flue gas conditioning system |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5244642A (en) * | 1992-06-18 | 1993-09-14 | The Chemithon Corporation | Method for conditioning flue gas |
| US6572835B1 (en) | 1997-01-24 | 2003-06-03 | The Chemithon Corporation | Method and apparatus for producing gaseous sulfur trioxide |
| CN108558708A (en) | 2012-08-20 | 2018-09-21 | 索尔维特殊聚合物美国有限责任公司 | Using the method for SO 3 sulfonated halogenated benzene derivative |
| CN105036087A (en) * | 2015-06-30 | 2015-11-11 | 广西农垦糖业集团红河制糖有限公司 | Sulfur burning apparatus |
| ITUA20162644A1 (en) * | 2016-04-15 | 2017-10-15 | Iit S R L | METHOD AND SYSTEM OF IGNITION OF THE SULFUR IN COMBUSTION OVEN |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1005836A (en) * | 1947-10-03 | 1952-04-16 | Saint Gobain | Process for recovering the energy of hot gases from the combustion of sulphide bodies |
| US3432263A (en) * | 1966-03-28 | 1969-03-11 | Chemical Construction Corp | High pressure sulfuric acid process |
| US3455652A (en) * | 1966-05-31 | 1969-07-15 | Chemical Construction Corp | Process for the production of sulfur trioxide and sulfuric acid |
| DE1667702B2 (en) * | 1967-03-15 | 1975-02-27 | Metallgesellschaft Ag, 6000 Frankfurt | Process for the production of sulfur trioxide and / or sulfuric acid by the contact process |
| FR2007886A1 (en) * | 1968-05-06 | 1970-01-16 | Humphreys Et Glasgow Ltd | Sulphuric acid production |
| FR2128992A5 (en) * | 1971-03-10 | 1972-10-27 | Ugine Kuhlmann | |
| DE2264878A1 (en) * | 1972-11-23 | 1975-05-15 | Uhde Gmbh Friedrich | Sulphur dioxide contg gases prepn - at temp for conversion to trioxide, by burning sulphur stoichiometrically and removing excess heat |
| US4213958A (en) * | 1977-11-14 | 1980-07-22 | Canadian Industries Limited | Production of sulphur trioxide, sulphuric acid and oleum |
-
1981
- 1981-10-22 AR AR287191A patent/AR226384A1/en active
- 1981-10-27 IT IT68393/81A patent/IT1201033B/en active
- 1981-10-30 FR FR8120422A patent/FR2495125B1/en not_active Expired
- 1981-11-05 JP JP56177766A patent/JPS57111210A/en active Granted
- 1981-11-06 CA CA000389605A patent/CA1178025A/en not_active Expired
- 1981-11-19 MX MX190215A patent/MX156581A/en unknown
- 1981-11-26 DE DE19813146798 patent/DE3146798A1/en not_active Ceased
- 1981-11-26 BR BR8107701A patent/BR8107701A/en unknown
- 1981-11-26 GB GB8135737A patent/GB2088350B/en not_active Expired
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5196038A (en) * | 1990-03-15 | 1993-03-23 | Wright Robert A | Flue gas conditioning system |
| US5261931A (en) * | 1990-03-15 | 1993-11-16 | Wilhelm Environmental Technologies, Inc. | Flue gas conditioning system |
| US5350441A (en) * | 1990-03-15 | 1994-09-27 | Wilhelm Environmental Technologies, Inc. | Flue gas conditioning system |
| US5240470A (en) * | 1992-04-07 | 1993-08-31 | Wilhelm Environmental Technologies, Inc. | In-duct flue gas conditioning system |
| WO1993019852A1 (en) * | 1992-04-07 | 1993-10-14 | Wilhelm Environmental Technologies, Inc. | Flue gas conditioning system |
| US5288309A (en) * | 1992-04-07 | 1994-02-22 | Wilhelm Environmental Technologies, Inc. | Flue gas conditioning agent demand control apparatus |
| US5288303A (en) * | 1992-04-07 | 1994-02-22 | Wilhelm Environmental Technologies, Inc. | Flue gas conditioning system |
| US5356597A (en) * | 1992-04-07 | 1994-10-18 | Wilhelm Environmental Technologies, Inc. | In-duct flue gas conditioning system |
| US5547495A (en) * | 1992-04-07 | 1996-08-20 | Wilhelm Environmental Technologies, Inc. | Flue gas conditioning system |
| US5370720A (en) * | 1993-07-23 | 1994-12-06 | Welhelm Environmental Technologies, Inc. | Flue gas conditioning system |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2495125A1 (en) | 1982-06-04 |
| BR8107701A (en) | 1982-08-24 |
| JPH0359001B2 (en) | 1991-09-09 |
| IT1201033B (en) | 1989-01-27 |
| IT8168393A0 (en) | 1981-10-27 |
| AR226384A1 (en) | 1982-06-30 |
| FR2495125B1 (en) | 1986-07-11 |
| GB2088350B (en) | 1984-09-26 |
| DE3146798A1 (en) | 1982-06-16 |
| JPS57111210A (en) | 1982-07-10 |
| GB2088350A (en) | 1982-06-09 |
| MX156581A (en) | 1988-09-14 |
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