US2040104A - Tar treatment - Google Patents

Description

3 Sheets-Sheet l A. H. RADASCH TAR vTREATMENT Filed Feb. 2'?, 1931 May 12, 1936,

ATTORNEYS ay 12, 19364 A,.H. RADASCH TAR TREATMENT FiledFeb. 27, 1931 3 sheets-sneek 2 ATTORN EYE:

3 SheetVs-Shet C5 A. H. RADASCH TAR TREATMENT Filed Feb. 27, 1951 ATTORNEYS Patented May 12, 1936 UNITEDy STATES PATENT OFFICE TAR TREATMENT Arthur H. Radasch, Bloomfield, N. J., assignor to The ,Barrett Company, New York, N. Y., a corporation of New Jersey Application February 27, 1931, Serial No. 518,606

21 Claims.

tar acids and neutral oil therefrom. The invention includes both the method of treatment and apparatus therefor. It will be described more particularly as applied to the treatment of coal tar.

Tar acids may be selectively removed from tar,

by heating the tar and circulating through and in intimate contact with it inert gases containing neutral oil vapors. In this way tar acids are evaporated from the tar With less than the usual amount of accompanying neutral oil. Tar acids may be removed from the vapors by treatment with caustic soda, and part of. the neutral oils may be removed by cooling the vapors to a desired temperature after the caustic. treatment. Tar acid oil may be alternatively condensed from the vapors before they enter the caustic extractor. The vapors remaining after the caustic treatment and cooling, either before or after this treatment, and still containing some neutral oil vapors may then be recirculated through fresh tar and the process repeated.

To operate such a system on tars or like material containing, for example, 3-4% tar acids, so as to effect a commercially desirable recovery (60% to 80% of the tar acids), with recirculation of a moderate amount of vapors and gases (say 250-350 cu. ft. per gallon of tar), cooled to a temperature of about 105110 C. and below 125 C. to condense neutral oil before recycling, it has been considered necessary to preheat the tar to a temperature of about 210-225 C. in order that the vapors leaving the tar may be at sufciently high temperature, say 150 C., to carry the tar acids and neutral oils. This requirement has made it impossible to use steam to heat the tar for this process in a steam heater at a pressure of about 175 lbs. per square inch (gage pressure) corresponding to a temperature of approximately 195 C., the pressure available at most plants. The use of steam for heating tar is otherwise very desirable, especially because of the relatitive cheapness-Of the apparatus required.

I have discovered how these difficulties may 50 be overcome, i. e., how a satisfactory recovery of tar acids and production of neutral oil or tar acid oil from tar may be effected without kthe use of temperatures in excess of those obtainable from readily available high-pressure steam or other 55 lowTtemperature hatingmedum,ji. e., .at tem 'the same amount of neutral oils.

peratures not over 200 C., and without the recirculation of excessive amounts of inert vapors.

While my method is particularly advantageous Where steam is used as the source of heat, it is not limited to such conditions. The heat may be 5 supplied by the latent or sensible heat of other hot circulating fluids, such as hot gases, vapors, oil, etc., at a temperature not over 200 C., which may be readily obtainable vor cheaper or for some other reason may be more desirable than hotter 10.

mediums.

According to my invention a large amount of heat is introduced into the tar at relatively low temperatures by stepwise heating and by applying heat to the tar during the distillation. In what follows the invention is described more particularly in connection with the use of high-pressure steam at a temperature of about 195 C.

According to this invention the tar is first preheated preferably by indirect contact with steam 20 in a steam preheater. The heated tar is then introduced into a vaporizer through which a current of inert gases, including neutral oil vapors, is circulated while heat is supplied to the tar by indirect interchange with high-pressure steam to 25 vaporize tar acids and neutral oil from the heated tar. Before entering the vaporizer the tar may be heated to a temperature above its initial boiling point so that on entering the vaporizer lower boiling oils and moisture, if wet tar is used, are 30,

volatilized and a hot residue is produced. Heat is then supplied to the residue by indirect interchange with high-pressure steam and tar acids and neutral oil are vaporized in the current of inert gases including neutral oil vapors which is 35 maintained in the vaporizer.

The inert gases which enter the vaporizer contain vapors of neutral oils so that the vaporization or distillation which takes place within the vaporizer is a selective distillation in which both 40 tar acids and neutral oil are vaporized, but more tar acids are vaporized than usually accompany The neutral oils present in the gases entering the vaporizer repress the vaporization of neutral oil from the 45 hot tar while the substantial absence of tar acid vapors from the entering gases permits unrestricted, vaporization of tar acids. Although complete removal of tar acids from the tar will not ordinarily be effected in the vaporizer, the residue will contain a lower percentage of tar acids than the product obtained by the removal of the same per cent of volatile matter from the tar by ordinary distillation methods.

According to one method of operation the gases and vapors pass from the vaporizer to a caustic extractor in which tar acids are extracted and then the gases and remaining neutral oil vapors pass to a condenser in which they are partially cooled and part but not all of the neutral oil separates from the gases. At least a portion of the resulting gases and neutral oil vapors are re-cycled through the vaporizer and the neutral oil vapors repress the Vaporization of neutral oils so that selective distillation occurs. As an alternative method the condensation of the neutral oil may take place in the caustic extractor simultaneously with the extraction of the tar acids.

According to another method of operation the gases and vapors pass from the Vaporizer to a condenser in which they are partially cooled and part, but not all of the oil vapors condense from the gases. The oil condensate is a tar acid oil, i. e., it contains both neutral oils and tar acids. By employing a fractional condenser two or more tar acid oil fractions may be obtained. At least a portion of the gases and remaining oil vapors then pass to a caustic extractor in which tar acids are extracted and the resulting gases and neutral oil vapors are re-cycled through the vaporizer to effe-ct further selective distillation of tar.

The apparatus of this invention includes a vaporizer in which there is a steam coil or other heating means connected with a source of highpressure ste-am or other heating fluid of relatively low temperature. It has a large heating surface With which the tar or other material being selectively distilled is brought into contact as it passes through the vaporizer. Suiiicient steam is supplied under regulated pressure to the heating coil to maintain the tar at the tern` perature necessary to effect the desired vaporization of tar acids and neutral oil and to supply the heat necessary for the vaporization. The pressure at which it is necessary to supply the steam is determined by the temperature at which the gases and vapors are to leave the vaporizer. Vapors are carried oft from the vaporizer as soon as they form by the inert gases which are circulated through the vaporizer.

At most tar producing plants steam is available under a pressure of about 150 to 17.75 pounds. With steam at this pressure the inert gases passing through the vaporizer may be heated to 150 C. or higher and with the gases and vapors leaving the vaporizer at this temperature, 60 to 65% of the tar acids can be recovered from ordinary coke-oven tar. If the heating medium which may be steam or other suitable heating fluid has a lower temperature a lower percentage of the tar acids will be recovered. For example, at a gas temperature of C. the recovery may be only 30 or 40% or more, and this may be all that is required, as where a high percentage of phenol and cresol: and a lower percentage of xylenols and higher boiling tar acids is desired.

It is advantageous to provide a heat interchanger to function in co-operation with the vaporizer so that at least a part of the heat of the hot residue resulting from the selective distillation is recovered by the gases and neutral oil vapors before they enter the vaporizer. By bringing the hot residue and the gases into direct contact with one another, preferably on the counter-current principle the residue may be cooled so that it leaves the system at a relatively low temperature and considerable economy of heat will thus be effected.

By the process of this invention hydrocarbon material is heated and selectively distilled so as to separately recover tar acids and neutral oils in an amount independent of each other and the heat required for the vaporization of the tar acids and neutral oil is supplied solely by highpressure steam or other heating medium of relatively loW temperature during the vaporization. High-pressure steam is a particularly advantageous heating medium but without the particular means which this invention provides for heating the hydrocarbon material Within the vaporizer during the selective distillation, the desired results could not be obtained within the temperature range attainable with commonly available steam pressures. However, by supplying heat (most of which is consumed as the` latent heat of vaporization of the neutral oils and tar acids distilled) to the hydrocarbon material during the selective distillation and by introducing the hydrocarbon material into the vaporizer in a heated condition, preferably heated by indirect contact with steam, the required vaporization of the tar acids and neutral oils is eiected. If the neutral oils are condensed from the vapors prior to the extraction with caustic they will be blended with tar acids and the condensate will be an acid oil. If they are condensed after the caustic extraction the condensate Will be a neutral oil, relatively free from tar acids.

By employing a heat interchanger for condensing the neutral oils or acid oils from the gases and vapors it is possible to preheat the tar or other hydrocarbon material to some extent by heat interchange with these hot gases and vapors. This eiects a substantial economy of heat.

The inert gas employed in the vaporization of the tar acids from the tar or other hydrocarbon material may comprise steam and may be composed almost entirely of condensible vapors, as where wet tar or other wet tar-acid containing material is treated, and at least a part of the steam generated from the moisture present is recycled through the system to effect the inert gas vaporization of the tar acids and neutral oils. The inert gas used is one chemically inert to tar acids and Which may be employed as a carrier for tar acid vapors and includes neutral oil vapors.

A portion of the gases is bled from the cycle, preferably continuously, to compensate for steam or other gases generated during the treatment of the hydrocarbon material and so keep the system under constant pressure. The gases and vapors bled from the cycle may be vented to the atmosphere although they are preferably cooled to eff ect total condensation of the vapors carried by them. If the bleed-01T is placed after the caustic extractor the oils which are condensed in the bleed condenser are neutral oils from which the tar acids have been separated from the oil vapors passing through the extractor. They may be blended with the neutral oil condensed in the line condenser. If the bleed-off is located ahead of the caustic extractor the oils which are con- -densed will be acid oils. If the condenser which cools the recirculated gas is placed in the cycle before the caustic extractor to condense acid oils, these two acid-oil condensates may be combined.

In treating raw coke-oven tar, with a content tar acids present in the tar may be separately recovered by the process of this invention. The' amount of neutral oil distilled from the tar is not dependent upon the amount of tar acids recovered but depends on the extent to which the gases are cooled and also on the amount of gases bled from the cycle. Some 15 or more per cent of neutral oil (based on the volume of the tar) may be recovered from the tar according to the process of this invention. The neutral oils vaporized have approximately the same upper boiling limit as the tar acids vaporized. The amount of neutral oil which may be separately recovered or which may be recovered with tar acids as acid oil may be so regulated as to yield condensate of a particular boiling range or so as to produce a residue of desired properties. For example, if coke-oven tar is being treated the operation may be controlled so as to produce a residue having a melting point of 105 to 110 F. and suitable for use as a binder for making roads, or by removing less neutral oil a lighter tar suitable for road surfacing material or as a base for making road surfacing material, or as a iiux for making binders for tar roads, etc., may be produced as desired.

When tar is used to condense oils by bringing it into indirect Contact with the oil vapors in the circulating gas stream the heat recovered from the condensation of oil vapors permits the recovery of additional percentages of neutral oil without greatly increasing the quantity of steam required for the vaporization.

Any taracid-containing tar may be treated according to the process of this invention, such as coke-oven tars, gas-house tars, vertical-retort tars. low-temperature tars, and other coal tars. The tar may be dehydrated or Wet tar. It may be a heavy or a light tar. Other tar acid and neutral-oil containing hydrocarbon material, such as coal-tar distillate oils, etc., may also be treated according to this invention.

The invention will be further described with reference to the drawings, more particularly as applied to the treatment of tar by the use of highpressure steam, but the scope of the invention is not limited to the particular apparatus shown nor to the particular operating conditions referred to for illustration or to the particular materials treated. In the drawings- Fig. 1 shows more or less diagrammatically, apparatus for carrying out the invention in a Inanner to make carbolate and neutral oils;

Fig. 2 shows a modied apparatus; and

Fig. 3 shows apparatus for carrying out the invention in a manner to make acid oils and carbolate.

Referring t-o Fig. 1 of the drawings, the tar preferably preheated somewhat to facilitate pumping, is forced by the pump I through the line 2 into the tar cooled condenser 3 in which it is heated indirectly to approximately to 125 C. by the hot gas leaving the caustic extractor I3 and then passes through the line 4 to the heater 5 in which its temperature is raised to about 175 C. Y At this temperature its water content and more or less of its lower boiling constituents (generally up to about 5%) will be vaporized, depending upon the pressure employed at this point in the system. The heater 5 is shown as a tubular heater and is heated indirectly by steam at about pounds pressure.

The tar heated to a temperature of, for example, C. leaves the heater 5 through the pipe 6 and is sprayed through the nozzles 'I over coils 8 in the vaporizer 9. Any water and lower boiling constituents in the tar, volatile at this temperature, are ashed from the tar as it enters the vaporizer. The coils 8 are heated -by steam also or in part in the carbolate.

at a pressure of about 150 pounds and the heat necessary for vaporization of the oils distilled from the tar in the vaporizer and Whatever heat is necessary to bring the gas used for distillation up to the temperature at which the gas leaves the vaporizer through the pipe I2 is supplied to the tar by the steam condensing within the coils.

Instead of passing the tar through a heater such as the heater 5 before entering the vaporizer, the tar may be passed directly from the4 condenser 3 to the vaporizer and be introduced therein with or without flashing and the necessary additional heat may be supplied to the tar entirely by heat interchange with high-pressure steam in the vaporizer 9 instead of partially in the heater 5 and partially in the vaporizer. According to the preferred method, however, the tar is heated in a steam preheater such as the heater 5 and then flashed and then further heated by steam in the vaporizer.

The gases from the vaporizer which include vapors of both tar acids and neutral oils are treated with an alkaline reagent such as caustic soda in the caustic extractor I3 and this treatment eiects substantially complete removal of tar acids from the mixture of gas and vapors.

This caustic extractor is shown as a double tower,

each section of which is lled with baflling means. The gases and vapors first flow downward through one section and then upward through the other section, but the order of direction of flow may be reversed or a single tower or any other suitable type of extractor which will produce a large surface of contact between the gas and the extracting liquid may be used. Fresh caustic is fed to the extractor through the inlet at 26. A portion of the mixed caustic and carbolate solution formed by `interaction of caustic with the tar acid vapors is withdrawn through the line I4 to the pump I5 and then recirculated through the line I6. From this line it is sprayed through the nozzles I'I and produces a `heavy wash which effectively wets the surfaces of the battles in the caustic extractor. The caustic reacts with the tar acids in the gases and is converted to carbolate. An amount of carbolate equal to the production is withdrawn through theV overflow at 21 to a collector not shown.

Ordinarily a commercially concentrated solution of caustic soda containing about 50% sodium hydroxide is used for the extraction, although other suitable alkaline solutions may be employed. The fresh caustic supplied to the cycle through pipe 26 is preferably heated to the temperature of the caustic in the extractor to prevent any cooling effect on the gases with resulting condensation of neutral oils in the caustic extractor. However, the temperature in the caustic extractor, which may be 140 C. or over, may be above the boiling point of even this concentrated caustic solution and more or less water may evaporate from the caustic-carbolate solution. If no special provision is made for supplying the latent heat of the water evaporated, the heat will-be furnished by the hot gas stream. The gases will be. cooled and some neutral oil vapors will be con-v densed. The neutral oils will dissolve in whole If condensation of neutral oils in the extractor is undesirable, a heat interchanger I6a is provided in the line I6 to heat the circulated caustic-carbolate solution and it is preferably maintained at a temperature slightly higher than that of the gas entering the caustic extractor. In this way the condensationV of neutral oil may be reduced to a. minimum..-

Cir

IfA desirable. thezcaustic extractionmay be carried out-in suoli a manner as to eifect condensation, of neutral oils simultaneously with the exgases.y Such condensation may supplement the traction of the tar acids from the recirculated condensation in the condenser 3 or all of the neutral oils condensed in the system may be condensed in the extractor simultaneously with'. the extraction of tar acids from the mixture of gases and vapors.

Irrespective of whether'the operation is regulated so as to effect no substantial condensation of neutral oils in the extractor but only in the separate condenser 3, or whether condensation of `neutral oils in the extractor is permitted and supplements the. condensation of oils in the separate condenser, the mixture of gases and neutraloils from the caustic extractor passes through the line I 8 to the condenser@ in Which it is cooled to a temperature preferably below 125 C. and usually to 105 C., more or less, the exact temperature depending upon the amount of oils to be condensed. If there is no substantial condensation of oils in they extractor and tar is used as the sole cooling medium in the condenser, the tar may be heated from about 50 C. to as high as 100 C. and the gases may be cooled 30 or 40 C. or more. The oil condensate is drawn off through the outlet I9. This oil is substantially free from Water. The oil amounts to about 6-12% of neutral oils, based on the volume of the tar treated, although the percentage will vary depending upon the particular type of tar treated.

The tar acids may be extracted in several steps from the gases and vapors thereby separately collecting fractions rich in phenol, cresols, or xylenols, and the neutral oil may be collected in two or more fractions, or all of the tar acids recovered may be recovered in a single step and all of the neutral oil may be condensed as a total neutral oil fraction.

The resulting, inert gas which comprises a substantial percentage of neutral oil vapors but not more than a small amount of tar acid vapors, leaves the condenser through the line 20. Part of it is circulated by the gas blower 2l through the line 22 and returned to the heat interchanger l) where it is further heated by the hot nonvolatilized -residue from the tar and the residue is cooled. The heated gas is then used for further distillation of' tar acids and neutral oils from the tar.

That portion of the gas not recirculated through the blower is vented oif through the line 23 into the vent condenser 24 for recovery of neutral oil. With this neutral oil will condense an amount of water approximately equal to that ordinarily present in the` tar together with an amount equal to that evaporated from the caustic solution in the caustic extractor (including Water produced by neutralization of the tar acids by the caustic) and whatever additional water vapor may have been added to the cycle. If this oil vapor and the water vapor from the tar and the water evaporated from the caustic solution, etc., were not bled 01T from the system the vapors Would soon build up a very high back pressure. The entire system is open to the atmosphere through the vent condenser and therefore operates at substantially atmospheric pressure. By providing suitable regulating valves and means for removal of the products formed pressures above or below atmospheric pressure may be. maintained.

The heat interchanger for heating the recirculated gas and cooling the ta-r residue may be.,

constructed as a single unit with the vaporizer so that the heated tar flows directly from the surface of the heating coil into the zone of direct. Or the heat interchanger and vaporizer may be constructed as separate unitsA heat interchange.

with means forA collecting the residue as it flows from the heating coil and introducing it into the.

vaporizer 50, an extractor and condenser 5|, a

separate heat interchanger 52 for cooling the dephenolized tar residue and heating the gases and neutral oil vapors before they enter the vaporizer 50, a decanter 53, a heat interchanger 54 for regulating the temperature of the recirculated carbolate and a bleed condenser 55.

The tar enters the vaporizer through the line 55vat a temperature which may be below its initial boiling point, for example, in the neighborhood of 50 C. Heat is supplied to the tar in the vaporizer by the heating coil 1| which is heated by steam. The tar is heated and tar acids and neutral oils are vaporized in a current of inert gases and neutral oil vapors which enters the vaporizer 50 from the heat interchanger 52 through the line 51'.

The resulting gaseous mixture which comprises vapors of both neutral oils and tar acids passes from the vaporizer to the caustic extractor 5I, which may be of any suitable construction, and is shown as an extractor of the same type as that shown in Fig. 1. However, according to the method illustrated in Fig. 2 condensation of neutral oils is effected simultaneously with the extraction of the tar acids in the extractor 5l. The amount of neutral oils condensed is regulated by controlling the temperature of the caustic solution sprayed intothe gases. lThe heat interchanger 54 is provided for this purpose. The mixture of the neutral oils condensed and the carbolate formed is drawn olf through the line 58 into the decanter 53. The neutral oils are drawn off to the storage tank 59. The carbolate is in part drawn off through the line 60 into the tank 6I and the balance is recirculated through the line 62 by means of the pump 63 through the heat interchanger 54 and sprayed through the nozzles 64 into the gases and vapors in the extractor 5I. Fresh caustic is supplied through the line 65 to compensate for that drawn off through the'line 60. The amount and temperature of the caustic-carbolate solution sprayed into the extractor and the concentration of NaOH in this caustic-carbolate solution are so regulated as to effect the desired extraction of tar acid vapors and to condense the desired amount of neutral oils. The tar acid neutralization may be substantially complete and from 6-12% or more of neutral oils may be condensed.

Instead. of separating the mixture from the extractor into carbolate and neutral oil and spraying back into the extractor only the carbolate, which contains suicient caustic to effect the desired neutralization, a part of the mixture of carbolate and neutral oils may bev sprayed back 'i the bleed-"off gases will, in this case, be acid-coninto the extractor and the carbolate 'and neutral oils in the remainder will then be separated.

A portion of the gases and neutral oil vapors from the caustic extractor `is bled oif from the system and is preferably cooled in the bleed condenser to condense neutral oils and steam, which are drawn off through the line 66. The balance of the gases and vapors are recirculated by the pump 61 to the heat exchanger 52 where they are reheated by spraying them with the hot dephenolized tar which is pumped from the vaporizer 50 through the line 68 and the spray nozzles 10 by means ofthe pump S9. The reheated gases then enter the vaporizer where vaporization of tar acids and neutral oils takes place with the aid of heat supplied by the steam in the coil 'll in the vaporizer.

When the invention is carried out according to the method shown diagrammatically in Fig. 3, the gases leaving the Vaporizer and containing both tar acids and neutral 'oils pass rst to the condenser 3 in which the gases are cooled for separation of oils. The oil condensate will contain both neutral oils and tar acids. The condensation of the acid oil is preferably effected by employing as a cooling medium the tar to be treated. 'I'he extent of cooling the gas is regulated according to the amount of neutral cil it is desired to condense or according to the amount of tar acids that are to be condensed with' the neutral oil or according to the nature of tar residue desired to be produced in the vaporizer. When the invention is operated in the preferred manner, the tar may be heated from about 50 C. to C. or higher and the' gas at a temperature of C. to 145 C. may be cooled down to about 105 C. Under these conditions from 12 to 15% of acid oil may condense in the condenser 3' and the acids in this oil may comprise from 30 to 50% of the acids originally present in the tar being treated.

'After leaving the condenser '3' at least a portion of the gases, containing vapors of both neutral oils and tar acids, enter the caustic extractor I3', in which the remaining tar acid vapors are substantially completely removed from the inert gas and neutral oil vapors by chemical reaction with an alkaline reagent. The operation of this caustic extractor is substantially the same as that of the caustic extractor `|3 described in connection with Fig. l, although the carbolate produced will contain a somewhat lower percentage of tar acids owing to the lower temperature of operation. On the other hand, however, the earbolat'e produced inv the extractor I3' will contain a larger proportion of the lower boiling tar acids such as phenols and cresols than the acid oil separated in the condenser 3'.

After the alkaline extraction at least a portion of the remaining inert gases, including neutraloil vapors but substantially free from tar-acid vapors, is recirculated in contact with a fresh batch of tar for further selective distillation of tar acids and neutral oils. The operation of the vaporizer 9 and the heat interchanger l0 is substantially the same as that described in connection with Fig. l.

A portion of the circulating gases is bled from the system to enable the operation to take place at substantially atmospheric pressure and these gases are preferably cooled to condense the oils contained therein. In Fig. 3 the Vent condenser 24' is shown connected to the line I 8" entering Vthe caustic extractor. The oils condensed from taining oils andare advantageously blended with the acid oils removed from the cycle by condensation in the condenser 3. If the condenser 24 is connected to the line 20', the oil condensate 5 will be substantially acid free and may be separately collected.

Other details and modifications of the operation are readily inferred from the description in connection with Figs. 1 and 2. l0

The amount of gas circulated through the system has an important bearing on the yield of tar acids by this process. If the gas leaves the vaporizer at a temperature of C. as' indicated in the illustration, it has been found that the gas 15 circulated should be from Z50-350 cu. ft. per gallon of coke-oven tar of normal tar acid content (34%) in order to obtain a satisfactory recovery as carbolate of 60 to 80% of the tar acids in the tar.

The amount of tar acids in the tar has a bearing on the percentage recovery of tar acids and on the amount of gas to be circulated. For example, if the tar contains 6-8% of tar acids of approximately the same qualityas those of a tar of 34% tar acid content the gas circulation should be approximately doubled to yield 'the same tar acid recovery.

At the temperature employed in the vaporization, the tar acids, as a class, have a certain vapor pressure. Since the gases circulated through the vaporizer contain substantially no tar acids, tar acids `in the tar vaporize freely and tend to build up a concentration in the gas equal to their vapor pressure at the temperature employed. Since fresh gas is continually being supplied to the vapcrizer the tar acid and other vapors are continuously swept from contact with the tar and vaporization of the tar acids proceeds.

The neutral oils, as a class, have a denite vapor pressure at the temperature employed in the vaporizer, but the gas supplied to the vaporizer already contains an appreciable amount of neutral oils that have not been condensed in the cycle. The tendency in the vaporizer is to produce a gas saturated with both neutral oil and tar acid vapors at the temperature at which the gases leave the vaporizer. However, the presence of neutral oil vapors and the substantial absence of tar acid vapors in the recirculated gas causes selective distillation to take place and relatively less neutral oil is vaporized with the tar acids than lin the production of carbolic oil by the usual methods.

The removal of tar acids and neutral oils from the system is also selective. In the caustic extractor the tar acids are selectively extracted by chemical reaction with caustic soda. When the invention is carried out as described in connection with Fig. 1 or Fig. 2 the amount of neutral oil condensed bears no relation to the amount of tar acids extracted. When the invention is carried out according to the method described in Fig. 3, the tar acids condensed in the acid oil 65 fraction bear a more or less fixed relation to the amount of neutral oils which condense simultaneously but an additional amount of tar acids is recovered by the extraction step which follows the condensation and the total tar acids recovered (which includes the tar acids in the acid oil fraction and the tar acids recovered as carbolate) is independent of the total amount of neutral oil recovered.

Although according to the preferred method of 75 Aing hydrocarbon material,

generated by vaporization of moisture in the tar, additional steam maybe added to the system as in the Vaporizer, if desirable, `in which case the amount of gas bled from the systems through the bleed condensers will be increased to compensate for this added gas. Other inert gas may also -be added to the system if desired.

The system may be operated under conditions other than those disclosed in the examples. For instance, it may be desirable to preheat a portion only of the fresh tar before admitting it to the vaporizer, or a part of the tar may be preheated in one manner as by indirect'heat exchange with ,steam and the balance of the tar may be preheated in a different manner as `in a nre-heated tar heater. In any case, part or all of the tar Vmay be preheated to some degree by bringing it tially less than the 60 to 80% of contained tar acids usually 'desired from coke-oventar. 'Ihe conditions of operation such as temperatures, amount'of gas recirculated and the like are so regulated as-to produce the amount and quality of tar acids and oils desired.

I claim:

1.V 'Ihe method of-distilling tar acids and neutral oils from hydrocarbon material by heat interchange with a heating medium no hotter than 200 C. in a current of inert gases which comprises heating liquid Ytar-acid and neutral-oil containing hydrocarbon material, then passing inert-gases including neutral yoil vapors in intimate contact With the heatedmaterial and maintaining the gasesand vapors leaving contact with the material at a temperature Yof C. or higher .by passing said heatingmedium in indirect heat interchange with said heated material While the inert-gases are being'passed in intimate contact therewith, cooling the resulting vapors to con- .dense acid oils and extracting the vapors with caustic rto form carbolate and recirculating at lleast a portion of the resulting neutral oil vapors in admixture with inertrgases into renewed contact .with said heated hydrocarbon material to further distill it.

2. The method of Vdistilling tar acids and neutral oils from hydrocarbon material by heat interch-angevvith aheating medium no hotter than 200.,C. in a current ofinert gases which comprises heating liquid tar-acid and neutral-oil containthen bringing the heated material into intimate Contact with inert -gases including neutral oil vapors while heating .the material by indirect heat interchange with the heating medium, extracting the resulting 4Vgaseswith caustic to form carbolate and cooling the-extractedgases to condense neutral oilsI and recirculating at least a portion of the resulting n.neutral oil vapors in admixture With'inert gases Afor further use in the distillation ofthe 'hydro- .carbon material.

3. The-method of treating hydrocarbon material Which :comprises heating liquid tar-acid and neutral-oil containing hydrocarbon material, introducing the heated material into a vaporizer, passing inert gases including neutral-oil vapors through the .vaporizer in intimate contact with operation 4the steam recirculated as inert gas is `saidthydrocarbon materiarwhile maintaining the gases tand vapors.V leavingthe vaporizer at a Ytemperature of 120 C. or higher by heating the materials in `said vaporizer by indirect heat inter- -change With high-pressure steam, bringing an valkaline reagent into direct contact with Y the gases and vapors `coming'from the vaporizer `to lrecover tar lacids therefrom in the form of carbolate and passing at least a portion of theresulting neutral-oil vapors in admixture with inert gases through the vaporizer to effect selective distillation of the hydrocarbon material.

4. The method of treating hydrocarbonmateri-al which comprises heating liquid tar-acid and neutral-oil containing hydrocarbon material, irltroducing the Aheated material into a vaporizer, introducing inert gases and neutral-,oil vapors into the vaporize-r and bringing 'them into intimate Contact With lthe hydrocarbon material therein while supplying heat to the material tby indirect heat interchange with high-pressure steam, removing tar acids from the resulting gases and-vapors by direct contact with an alkaline reagent and cooling them to condense part but not all of the neutral oils and then returning at least a part "of the resulting mixture of gases andtneutral oils to the vaporizer to effect selective distillation ofthe hydrocarbon Vmaterial therein.

5. The method of treating tar which comprises heating tar, introducing it into-a vaporizer, passing a. current of inert gases including neutral- Voil vapors therethrough in intimatecontact with the. heated tar While supplying sufcient heat to the tar by indirect heat interch-ange With highpressure steam to vaporize neutral o-il and tar "i acids from the tar, extracting tar acids from the resulting gases `and vapors b-y direct contact with an ralkaline reagent, bringing the resulting gases and lvapors into indirect heat interchange relaition Withthe tar to be treated, whereby the tar is heated and the gases and vapors'are cooled and part but not all of the neutral oil is-separatedv therefrom as condensate and then returning-part of the resulting gases and neutral-oil vapors to the vaporizer.

6. The method of treating tar which comprises heating coal t-ar, introducing it into a vaporizer, vpassing a current of inert gases including neutraloil vapors therethrough in intimate contact With the heated-tar While supplying suilicient heat to an alkaline reagent, bringing the resulting Vgases i" s rand vapors into indirect heat interchange relationwith the tar to be treated-whereby the tar is heated and the gases and vapors are-cooledand part but not -allof the neutral oils separated Ytherefromas condensate, returning part of the 'remaining neutral-oil vapors to the vaporizer and supplying heat to the partially heated tar by indirect heat interchange with high-pressure steam to raise the tar above its initial boiling point before introducing it into the vaporizer.

7. The method of treating tar which comprises heating coal tar, introducing the heated tar into a vaporizer, introducing inert gases including vapors of neutral oils into the vaporizer and bringing them into intimate contact With the tar therein While supplying suflicientheat to the tar 'by indirect heat interchange with high-pressure steam to effect selective distillation of the tar in the inert gases and neutral-oil vapors, thereby producing a hot residue, extracting tar acids from .75

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the resulting gases and vapors and cooling them to condense part but not all of the neutral oils therefrom, heating at least part of the resulting neutral-oil vapors and inert gases by bringing them intodirect contact with the hot residue and then introducing the gases and neutral-oil vapors thus heated into the vaporizer.

8. The method of treating liquid hydrocarbon material containing neutral oil and not less than 3% tar acids, which comprises continuously heating the said material by indirect heat exchange with a fluid heating medium, the temperature of which does `not exceed 200 C., flashing off vapors of volatile constituents, blending these vapors with gases and vapors coming from the treatment of. the flashing residue, passing the `blended gases and vapors at a temperature not less than about 140 C. in intimate contact with hot concentrated caustic-carbolate solution whereby at least of the tar acids contained in the material being treated are removed, cooling the resulting gases and vapors to C., or lower, whereby neutral oils are condensed, removing suflicient of the resulting gases and vapors to maintain approximately atmospheric pressure in the lgases and vapors at the point of removal, and recirculating the balance of the gases and vapors continuously into intimate contact with the residue from the flashing operation while simultaneously heating the said residue and the vrecirculated gases and vapors by indirect heat exchange with a uid heating medium the temperature of which does not exceed 200 C., the continuous feed of the liquid material and the recirculation of the gases and vapors being so regulated that the gases are recirculated at a rate not greater than 350 cu. ft. per gallon of material treated.

9. The method of treating tar, which comprises heating coal tar, introducing it into a vaporizer, passing a current of inert gases including neutral oil vapors therethrough in intimate contact with the heated tar while supplying sufcient heat to the 'tar and inert gases by indirect heat interchange with high-pressure steam to vaporize neutral oil and tar acids from the tar and to maintain the gases and vapors leaving contact with the tar at a temperature of about C. orl

higher. passing the resulting gases and vapors to a condenser. subjecting them to cooling to a temperature below about 125 C. to condense oils therefrom while leaving both neutral oil and tar acids in the vapor phase, bringing the resulting gases into direct Contact with an alkaline reagent to remove tar acids in vapor form and recycling atleast a portion of the resulting neutraloil vapors through the vaporizer in direct contact with tar therein.

10. The method of vaporizing tar acids and neutral oil from coal tar in a Vaporizer in a current of inert gases including neutral-oil vapo-rs and extracting tar acids from the resulting gases and vapors and cooling them to condense neutral oils and recycling at least a portion of the resulting neutral oil vapors to the vaporizer, which comprises heating the tar above its initial boiling point and flashing it in the vaporizer, introducing vthe gases into the vaporizer at a temperature not rent of inert gases including neutral-oil vapors and extracting tar acids from the resulting gases and vapors and cooling them to condense neutral oils and recycling at least a portion of the resulting neutral-oil vapors tol the vaporizer, which comprises heating the tar above its initial boiling point and flashing it into the vaporizer, introducing the inert gases into the vaporizer at a temperature not greater than 125 C., and heating the residue from the hashing operation in the vaporizerV to a temperature of at least 150" C. by indirect heat interchange with high-pressure steam.

12. The method of vaporizing tar acids and neutral oil from coal tar in a vaporizer in a current of inert gases including neutral-oil vapors and extracting tar acids from the resulting gases and vapors and cooling them to condense neutral oils and recycling at least a portion of the resulting neutral oil vapors to the vaporizer, which comprises introducing the inert gases into the vaporizer at a temperature of not more than 50 C. and heating the tar in the vaporizer by indirect heat interchange with high-pressure steam so as to distill it. l

13. The method of vaporizing tar acids and neutral oil from coal tar in a vaporizer in a current of inert gases including neutral-oil vapors and extracting tar acids from the resulting gases and vapors and cooling them to condense neutral oils and recycling at least a portion of the resulting neutral-oil vapors to the vapo-rizer, which comprises heating the tar above its initial boiling point, ashing it in the vaporizer and heating the residue from the flashing operation by indirect heat interchange with high-pressure steam in the vaporizer so as to distill it.

14. The method of vaporizing tar acids and neutral oil from coal tar in a vaporizer in a current of inert gases including neutral-oil vapors and extracting tar acids from the resulting gases and vapors and cooling them to condense neutral oils and recycling at least a portion of the resulting neutral-oil vapors to the vaporizer, which comprises heating the tar by indirect heat interchange with the gases during the cooling step, introducing the tar into the vaporizer in a heated state and supplying heat to the tar in the vaporizer by indirect heat interchange with highpressure steam so as to distill it.

15. The method of vaporizing tar acids and neutral oil from coal tar in a vaporizer in a current of inert gases including neutral-oil vapors, cooling the resulting gases and vapors to condense neutral oils and extracting tar acids from them and recycling at least a portion of the resulting neutral-oil vapors to the vaporizer, which comprises cooling the gases and vapors from the vaporizer to a temperature of about 105 C., then extracting tar acids from the partially cooled vapors, introducing the recycled gases into the vaporizer at a temperature below that at which the tar is distilled and maintaining the gases and vapors leaving contact with said coal tar in the vaporizer at a temperature of about 150 C. or higher by heating the tar in the vaporizer by indirect contact with high-pressure steam.

16. The method of vaporizing tar acids and neutral oil from tar in a vaporizer in a current of inert gases including neutral-oil vapors and extracting tar acids from the resulting gases and vapors and cooling them to condense neutral oils and recycling at least a portion of the resulting neutral-oil vapors to the vaporizer, which comprises distilling the tar in the vaporizer by the addition of heat thereto by indirect heat interchange with high-pressurexsteam and heating the recycled gases by direct contact with the residue from this distilling operation.

17. The method of vaporizing tar acids and neutral oil from tar in a vaporizer ina current of inert gases including neutral-oil vapors and extracting tar acids from the resulting gases and vapors and cooling them to condense neutral oils and recycling at least a portion of the resulting neutral-oil vapors to the vaporizer, which comprises heating the tar by indirect heat interchange with the gases inf/the cooling step, further heating the tar by indirect heat interchange with high-pressure steam, introducing the tar into the vaporizer and heating it therein by indirect heat interchange with high-pressure steam While tar acid and neutral oil are vaporized therefrom.

18. The method of vaporizing tar acids and neutral oil from coal tar in a vaporizer in a current of inert gases including neutral-oil vapors and extracting tar-acids from4 the resulting gases and vapors and cooling them to condense neutral oils and recycling at least a portion of the resulting neutral-oil vapors to the vaporizer, which comprises heating the tar in the vaporizer to a temperature of at least 150 C. by indirect heat interchange with high-pressure steam.

19. The method of distilling tar acids from hydrocarbon material in a current of inert gas which comprises treating said material in the sequence of (1) passing a heating medium in indirect heatv exchange with the hydrocarbon material, (2) passing an inert gas in direct contact with the heated material While passing a heating medium in indirect heat exchange with said heated material, and (3) directly contacting the material after the foregoing treatment and while out of heat exchange relation with the said last mentioned heating medium with said inert gas prior to utilizing the same in step 2.

20. In a process for distilling tar acids and oils from hydrocarbon material containing the same wherein an inert gas is recirculated in a cyclic system in direct contact with the hydrocarbon material and is then treated for the separate removal of tar acids and of oils by extracting the gas with caustic and by cooling the gas to condense oils therefrom, that improvement which comprises heating the hydrocarbon material, then passing the inert gas in direct contact with the heated material While passing a heating medium no hotter than 200 C. in indirect heat exchange with the heated hydrocarbon material to maintain said material and the inert gas and vapors passing out of contact therewith at a temperature of 120 C. or higher.

21. The method of distilling Atar acids and neutral oils from hydrocarbon material by heat interchange with a heating medium no hotter than 200 C. in a current of inert gases which comprises heating liquid tar-acidand'neutral-oilcontaining hydrocarbon material, then.bringing the heated material into intimate contact with inert gases including neutral oil vapors while heating the material by indirect heat interchange ARTHUR H. RADASCH.

CERTIFICATE OF CORRECTION.

Patent NO. 2,040, 104. May l2, 1956.

ARTHUR H. RADASCH.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: PageA, first column, line 4, strike out the Words "gases, Such condensation may supplement the" and insert the same in the same column after line 5; page '7,

first column, line 18, claim 8, for "in" read into; and that the said Letters Patent should be read with these corrections therein thatJ the same may conform to the record of the oase in the Patent Office.

Signed and sealed this 25th day of August, A. D. 1936.

Leslie Frazer Seal) Acting Commissioner of .Patents-v

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