CA2182641A1 - Process for the absorption of nitrogen from gas mixtures using pressure-swing adsorption with zeolites - Google Patents
Process for the absorption of nitrogen from gas mixtures using pressure-swing adsorption with zeolitesInfo
- Publication number
- CA2182641A1 CA2182641A1 CA002182641A CA2182641A CA2182641A1 CA 2182641 A1 CA2182641 A1 CA 2182641A1 CA 002182641 A CA002182641 A CA 002182641A CA 2182641 A CA2182641 A CA 2182641A CA 2182641 A1 CA2182641 A1 CA 2182641A1
- Authority
- CA
- Canada
- Prior art keywords
- zeolite
- adsorber
- pressure
- adsorption
- air
- 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.)
- Abandoned
Links
- 239000010457 zeolite Substances 0.000 title claims abstract description 75
- 238000001179 sorption measurement Methods 0.000 title claims abstract description 38
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 24
- 239000007789 gas Substances 0.000 title claims abstract description 23
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 12
- 239000000203 mixture Substances 0.000 title claims abstract description 10
- 238000000034 method Methods 0.000 title claims description 31
- 238000010521 absorption reaction Methods 0.000 title 1
- 229910021536 Zeolite Inorganic materials 0.000 claims abstract description 65
- 238000012856 packing Methods 0.000 claims abstract description 25
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000008187 granular material Substances 0.000 claims abstract description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 17
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 11
- 229910052593 corundum Inorganic materials 0.000 claims description 10
- 229910001845 yogo sapphire Inorganic materials 0.000 claims description 10
- 229910052681 coesite Inorganic materials 0.000 claims description 8
- 229910052906 cristobalite Inorganic materials 0.000 claims description 8
- 239000000377 silicon dioxide Substances 0.000 claims description 8
- 235000012239 silicon dioxide Nutrition 0.000 claims description 8
- 229910052682 stishovite Inorganic materials 0.000 claims description 8
- 229910052905 tridymite Inorganic materials 0.000 claims description 8
- FUJCRWPEOMXPAD-UHFFFAOYSA-N Li2O Inorganic materials [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 claims description 3
- XUCJHNOBJLKZNU-UHFFFAOYSA-M dilithium;hydroxide Chemical compound [Li+].[Li+].[OH-] XUCJHNOBJLKZNU-UHFFFAOYSA-M 0.000 claims description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 10
- 239000001301 oxygen Substances 0.000 description 10
- 229910052760 oxygen Inorganic materials 0.000 description 10
- 238000000926 separation method Methods 0.000 description 6
- 238000012360 testing method Methods 0.000 description 5
- 238000003795 desorption Methods 0.000 description 3
- 238000005342 ion exchange Methods 0.000 description 3
- 238000011068 loading method Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000002274 desiccant Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- -1 lithium cations Chemical class 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 125000000449 nitro group Chemical group [O-][N+](*)=O 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 239000000741 silica gel Substances 0.000 description 1
- 229910002027 silica gel Inorganic materials 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000035899 viability Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
- B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
- B01D53/047—Pressure swing adsorption
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
- B01J20/16—Alumino-silicates
- B01J20/18—Synthetic zeolitic molecular sieves
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
- B01D2253/10—Inorganic adsorbents
- B01D2253/106—Silica or silicates
- B01D2253/108—Zeolites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
- B01D2253/10—Inorganic adsorbents
- B01D2253/106—Silica or silicates
- B01D2253/108—Zeolites
- B01D2253/1085—Zeolites characterized by a silicon-aluminium ratio
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
- B01D2253/30—Physical properties of adsorbents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/10—Single element gases other than halogens
- B01D2257/102—Nitrogen
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2259/00—Type of treatment
- B01D2259/40—Further details for adsorption processes and devices
- B01D2259/403—Further details for adsorption processes and devices using three beds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2259/00—Type of treatment
- B01D2259/40—Further details for adsorption processes and devices
- B01D2259/41—Further details for adsorption processes and devices using plural beds of the same adsorbent in series
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
- B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
- B01D53/047—Pressure swing adsorption
- B01D53/0476—Vacuum pressure swing adsorption
Abstract
In the selective adsorption of nitrogen from gas mixtures with less polar gas components at temperatures of 20 to 50°C using pressure-swing adsorption, in which the gas mixture is passed through an adsorber which is filled with a packing of zeolite granules, the improvement which comprises providing at least two packings in the adsorber, a Na-zeolite X being provided in the inlet zone ofthe adsorber and a Li-zeolite X being provided in the outlet zone of the adsorber.
Description
Le A 31 227-Foreign Countries / Le/m/S-P
Process for adsorption of nitro~en from ~as mixtures usin~ pressure-swin~
adsorption with zeolites 5 The present invention relates to an improved pressure-swing adsorption process for adsorbing nitrogen from gas mixtures using zeolite granules.
The production of oxygen from air at ambient temperature is performed industrially on a large scale using molecular sieve zeolites (see, e.g. Gas Review Nippon, page 13, no. 5 1985). Here, the preferential adsorption of nitrogen as 10 compared with oxygen is utilized, i.e. oxygen and argon are collected as product, after passing the current of air through a zeolite packing, at the discharge point from the packing. Desorption of the adsorbed nitrogen may then be performed, forinstance, by evacuation of the packing. In this case, the process is called vacuum-swing adsorption (VSA), in contrast to the also well-known pressure-swing 15 adsorption process (PSA). A continuous VSA process is characterized by the following process steps: a) passage of air through the zeolite packing (at, for instance, 1 atmosphere) and withdrawal of O2-rich gas in the discharge zone; b) evacuation of the packing to a reduced pressure (for example of about 100 to 400 mbar in counterflow to the current of air, using a vacuum pump; c) filling the 20 packing with O2-rich gas (for example at 1 bar in counterflow to the current of air (see e.g. Fig. 1)). In the PSA process, step b) is performed at about 1 bar while flushing out with some of the O2-rich gas. In the so-called PVSA process (a combination of VSA and PSA), separation is performed at 1.1 to 2 bar and de-sorption at about 200 to 500 mbar (minimum pressure). The purpose of this 25 process is to obtain a high product concentration, with respect to the amount of zeolite used, and to achieve a high 2 yield (ratio of amount f 2 in the product to amount f 2 in the air introduced). A high 2 yield means there is a low energy demand for the vacuum pump and air compressor.
As a result of the three steps mentioned above, three zeolite packings are generally 30 used, i.e. three adsorbers, which are operated in a cycle. Adsorption may also be performed with 2 adsorbers in the case of the VSA process (GB-A 1,559,325).
The economic viability of this type of adsorption plant is affected by the capital outlay on, for example, amounts of adsorption agent, the size of the vacuum pumps and in particular by operating costs such as the power consumption of the 35 vacuum pumps. Zeolites have therefore been developed with which it is possible Le A 31 227-Forei~n Countries ~18 ~ 6 ~ 1 to achieve as high an adsorption of nitrogen as possible, so that the amount of zeolite used can be kept low, or can even be reduced. Zeolites of the Ca-A type are used for this purpose, as described in EP-A-128 545.
Further developments in this area are aimed at increasing the selectivity for S nitrogen as compared with oxygen.
Higher selectivity is achieved by using lithium-zeolite X (EP-A 297 542). A
higher separation factor is obtained as well as a higher N2-loading as compared with Na-zeolite X.
A better energy value is also obtained using Li-zeolite X as compared with Na-zeolite X (EP-A 461 478).
To further optimize the adsorption process in the area of air separation, adsorption agents have been suggested which consist of a variety of zones with different types of zeolite.
JP 87/148 304 discloses an oxygen enrichment process in which, instead of an ad-15 sorber with one zeolite packing, an adsorber with special arrangements of differenttypes of zeolite is used. The adsorber contains, on the air inlet side, zeolites of the Na-X, Na-Y or Ca-X type, and on the air outlet side, zeolites of the Ca-A type.
In EP-A-374 631, a Ca-zeolite A with low N2-adsorption is used on the inlet sideand a Ca-zeolite A with high N2-adsorption is used on the outlet side, wherein the 20 CaO/Al2O3 content in both zeolites is of about the same magnitude. The different N2-loadings are due to different activation procedures.
EP-A 0 546 542 describes a bed arrangement in which Li-zeolite X is used in the air inlet zones and Na-zeolite X is used in the air outlet zones. An arrangement in which Na-zeolite X is used in the inlet zones and Li-zeolite X and Na-zeolite X
25 are used in the outlet zones is, according to the specification, poorer and not preferred.
The object of the present invention is to provide an energy-favourable pressure-swing adsorption process for the adsorption of nitrogen from gas mixtures with less polar gas components, also to achieve improved 2 yields as compared with Le A 31 227-Forei~n Countries ~ 1 8 2 6 41 the prior art, to lower the manufacturing costs of oxygen from air separation and to keep the energy costs low.
This object is achieved, surprisingly, by combinations of special types of zeolites in the pressure-swing adsorption process.
5 The invention provides a process for the adsorption of nitrogen from gas mixtures with less polar components, in particular from air, at temperatures between 20 and 50C using pressure-swing adsorption, in which the gas mixture is passed throughan adsorber which is filled with packings of zeolite granules, which is characterized in that at least two, preferably two, packings are present in the 10 adsorber, wherein a packing of Na-zeolite X is present in the inlet zone of the adsorber and a packing of Li-zeolite X is present in the outlet zone of the adsorber.
In the case of pressure-swing adsorption processes, a distinction has to be made in particular between VSA processes (in this process variant the evacuation pressure is between 100 and 400 mbar and the adsorption pressure is between 1 bar and 1.1 bar), PSA processes (here, a desorption pressure of 1 to 1.1 bar and an adsorption pressure of 2 to 6 bar are used) and PVSA (here an evacuation pressure between 200 and 700 mbar and an adsorption pressure between 1.1 and 2 bar are used).
20 Using the combination of special zeolites according to the invention, not only can the 2 yield be increased but also, surprisingly, the energy consumption can be reduced.
The Li-zeolite X used is preferably a zeolite which has a SiO2/AI2O3 molar ratioof 2.0 to 2.5 and 80-100 % of whose AIO2 tetrahedral units are associated with 25 lithium cations.
The proportion of Li-zeolite X in the total amount of packing material in the adsorber is preferably 20 to 80 %. The proportion depends on the air inlet tempe-rature and on the pressure ratio between the maximum adsorption pressure and theminimum desorption pressure.
2182fi~1 -For an adsorption pressure of 1 to 1.5 bar, the minimum suction pressure should preferably be between 100 and 500 mbar.
The Na-zeolite X preferably has a SiO2/A12O3 molar ratio of 2.0 to 3Ø
Preferably, the Na-zeolite X has a SiO2/A12O3 molar ratio of 2.0 to 3.0 and the Li-zeolite X is present in an amount of 20 to 85 wt.%, with respect to the total amount of packing in the adsorber.
The technical procedures involved in the process according to the invention are described in detail in, for instance "Gas Separation and Purification" 1991, vol. 5, June, pages 89 to 90.
The gas stream can advantageously be dried before passage through the zeolite packing, for instance by means of a drying layer of silica gel.
The invention is explained in more detail in the accompanying drawings along with the examples which follow.
In the drawings Fig. 1 is a plot of N2 loading against pressure for the Na-zeolite X and Li-zeolite X of the examples:
Fig. 2 is a flow sheet of the instant process; and Figs. 3 and 4 are charts showing the poorer perform-ance with regard to energy consumption when operating outside the present invention.
Le A 31 227-Forei~n Countries 2 ~ 8 2 6 4 1 Examples The types of zeolite tested were prepared by ion exchange from the correspondingNa-zeolite X granules.
Sample A (Na-zeolite X) The Na-zeolite X granules were prepared in accordance with DE-A 1 203 238, example 2, wherein the granules prepared in this way contained about 18 %
Na-zeolite A and 82 % Na-zeolite X. The SiO2/Al2O3 ratio was 2.3, the particle size was 1 - 2 mm and the bulk density was about 650 g/l. Activation was performed at 600C using dry nitrogen.
Sample B (Li-zeolite X) 12 liters of binder-free Na-zeolite X granules, prepared as in DE-A 1 203 238, were placed in a suitable column with a heatable jacket. Then 690 liters of 1 M
lithium chloride solution were pumped through the granular packing over the D course of 15 hours. The temperature was 85C. After completing the ion exchange procedure, the granules were washed with water which had been adjusted to a pH
of 9 with LiOH. The degree of exchange (Li2O/Al2O3) in the zeolite was 96 %
after the ion exchange procedure.
The adsorption capacities for nitrogen of the samples are given in Fig. 1 and Table 1.
Table 1 Adsorption properties of the samples:
Sample A B
N2 adsorption at 1 bar, 25C in 9 25 22 [Nl/kg]
N2/O2 adsorption ratio at I bar, 25C 2.65 4.55 Le A 31 227-Forei~n Countries 2 ~ ~ 2 6 4 1 Performin~ the tests The following parameters were kept constant in the test unit and when performingthe tests:
Diameter of the bed 500 mm Depth of Al2O3 layer at air inlet 10 % of MS
depth Air inlet temperature 40C
Air outlet temperature 40C
Pressure of air at inlet 1.150 bar (max) Depth of zeolite layer 1.600 mm Minimum evacuation pressure, inlet 250 mbar Pressure at the start of evacuation 900 mbar Evacuation time 30 seconds Refilling step (BFP time) 6 seconds The adsorbers were provided with insulation in order to exclude heat transfer to15 the surroundings. The wall thickness of the container was about I mm.
Performing the tests with an adsorber cycle in accordance with Fig. 2:
C 10 - air blower H 10- cooling/heating G 10 - product blower V 10 - vacuum pump A, B, C - adsorber Time 0 sec:
Adsorber A has completed adsorption.
Le A 31 227-Forei~n Countries ~ 18 2 6 ~ 1 Time 0-6 sec= BFP time:
On adsorber A, only valve 15A is open. On adsorber C, only valves 12C and 13C
are open. As a result, O2-rich gas flows from adsorber A via valve 15A, control valve 17ABC and valve 13C into adsorber C. In adsorber C, the evacuation step is5 thus terminated, wherein the pressure rises from the minimum value (250 bar) to a higher value. In adsorber A the pressure falls from the maximum value (1,150 mbar) to the starting level (initial suction pressure) of 900 mbar.
Adsorber B starts air separation, i.e. air passes through valve I IB into adsorber B, O2-rich product gas leaves the adsorber via valve 14B and is taken to compressor10 G10.
Time 6-30 sec:
On adsorber A, only valve 12A is open. Adsorber A is pumped out from, for example, 900 mbar, via vacuum pump V 10 to, for example, 250 mbar. Adsorber B is on adsorption (see under "time 0-6 sec"), and at the same time O2-rich gas passes via valve 13C into adsorber C via 18ABC and 16ABC. On adsorber C only valve 13C is open. The amount admitted is such that at the end of this period the pressure in adsorber C is 1,080 to 1,090 mbar.
In the next cycle, adsorber C separates the air, then adsorber A, i.e. the two time intervals "0-6 sec" and "6-30 sec" are appropriately repeated.
20 While the tests were performed, the following parameters were also measured:
the amount of O2-rich product, the change in pressure at the adsorption inlet during the evacuation period, the amount of gas pumped out.
The amount of gas pumped out and the amount f 2 product is used to calculate 25 the amount of air admitted and thus the 2 yield (= amount f 2 in the product to the amount of 2 in the air).
All values refer to an 2 concentration in the product of 93 vol.%. All values (such as amount of oxygen) were converted to an amount of 2 of 1,000 m3/h Le A 31 227-Forei~n Countries 2 1 8 2 6 41 The energy demand of the vacuum pump was calculated from the change in pressure during evacuation detected at the suction end of the packing, by utili~in~
the characteristic curve (= energy demand as a function of suction pressure) of a known Roots cycloidal blower with a suction capacity of 20,000 m3/h at 1.03 bar.S The energy demand of the air blower was calculated using the following formula.
(3,060 x Pm-286 x Vo) Pm = 1045 mbar 10,621 x ',1 Vo = amount of air at 1.03 bar.
Il = Efficiency = 0.95 10 ExamPle 1 (Comparison: Na-zeolite X) Na-zeolite X corresponding to sample A was used in the adsorbers. The residual amount of H2O in the activated zeolite was less than 0.5 wt.% (according to DIN
8948; P2Os method). The amount of zeolite per adsorber was 190 kg. Oxygen enrichment took place in accordance with the details given above. The following 15 data were determined:
Temperature of air at inlet [C] 40 Amount of product [Nm3/h] 15.9 2 yield [%] 45 5 Calculated total energy demand [KWh/Nm3O2] 0.46 20 Example 2 (Comparison; Li-zeolite X) Li-zeolite corresponding to sample B was used in the adsorbers (190 kg/adsorber).
The residual amount of H2O in the activated zeolite was less than 0.5 %. The following data were determined:
Le A 31 227-Foreign Countries 21 8 2 6 41 g Temperature of air at inlet [C] 40 Amount of product [Nm3/h] 23 2 yield [%] 54 Calculated total energy demand [KWh/Nm302] 0 375 Example 3 (Comparison; Li-zeolite X in the inlet zones and Na-zeolite X in theoutlet zones) Above the zones of drying agent in the adsorbers were introduced 95 kg of sampleB and above that 95 kg of sample A. The following data were determined:
Temperature of air at inlet [C] 40 Amount of product [Nm3/h] 18 2 yield [%] 44.5 Calculated total energy demand [KWh/Nm3O2] 0.46 Example 4 (according to the invention; Na-zeolite X in the inlet zones and Li-zeolite X in the outlet zones) 15 Above the drying zones in the adsorbers were introduced 95 kg of sample A and above that 95 kg of sample B.
Temperature of air at inlet [C] 40 Amount of product [Nm3/h] 20.6 2 yield [%] 51.5 Calculated total energy demand [KWh/Nm3O2] 0.378 Example 3 provides very poor energy values for the oxygen produced (see Fig. 3 and Fig. 4). The inverted sequence of packings (example 4), however, produces good values. The energy demand is almost identical to the energy demand with Le A 31 227-Forei~n Countries 2 I 8 2 6 4 1 pure Li-zeolite packings (example 2). Since lithium-zeolite X is much more expensive to manufacture than Na-zeolite X, oxygen can be produced much more cheaply using the packings according to the invention.
It will be understood that the specification and examples are illustrative but not 5 limitative of the present invention and that other embodiments within the spirit and scope of the invention will suggest themselves to those skilled in the art.
Process for adsorption of nitro~en from ~as mixtures usin~ pressure-swin~
adsorption with zeolites 5 The present invention relates to an improved pressure-swing adsorption process for adsorbing nitrogen from gas mixtures using zeolite granules.
The production of oxygen from air at ambient temperature is performed industrially on a large scale using molecular sieve zeolites (see, e.g. Gas Review Nippon, page 13, no. 5 1985). Here, the preferential adsorption of nitrogen as 10 compared with oxygen is utilized, i.e. oxygen and argon are collected as product, after passing the current of air through a zeolite packing, at the discharge point from the packing. Desorption of the adsorbed nitrogen may then be performed, forinstance, by evacuation of the packing. In this case, the process is called vacuum-swing adsorption (VSA), in contrast to the also well-known pressure-swing 15 adsorption process (PSA). A continuous VSA process is characterized by the following process steps: a) passage of air through the zeolite packing (at, for instance, 1 atmosphere) and withdrawal of O2-rich gas in the discharge zone; b) evacuation of the packing to a reduced pressure (for example of about 100 to 400 mbar in counterflow to the current of air, using a vacuum pump; c) filling the 20 packing with O2-rich gas (for example at 1 bar in counterflow to the current of air (see e.g. Fig. 1)). In the PSA process, step b) is performed at about 1 bar while flushing out with some of the O2-rich gas. In the so-called PVSA process (a combination of VSA and PSA), separation is performed at 1.1 to 2 bar and de-sorption at about 200 to 500 mbar (minimum pressure). The purpose of this 25 process is to obtain a high product concentration, with respect to the amount of zeolite used, and to achieve a high 2 yield (ratio of amount f 2 in the product to amount f 2 in the air introduced). A high 2 yield means there is a low energy demand for the vacuum pump and air compressor.
As a result of the three steps mentioned above, three zeolite packings are generally 30 used, i.e. three adsorbers, which are operated in a cycle. Adsorption may also be performed with 2 adsorbers in the case of the VSA process (GB-A 1,559,325).
The economic viability of this type of adsorption plant is affected by the capital outlay on, for example, amounts of adsorption agent, the size of the vacuum pumps and in particular by operating costs such as the power consumption of the 35 vacuum pumps. Zeolites have therefore been developed with which it is possible Le A 31 227-Forei~n Countries ~18 ~ 6 ~ 1 to achieve as high an adsorption of nitrogen as possible, so that the amount of zeolite used can be kept low, or can even be reduced. Zeolites of the Ca-A type are used for this purpose, as described in EP-A-128 545.
Further developments in this area are aimed at increasing the selectivity for S nitrogen as compared with oxygen.
Higher selectivity is achieved by using lithium-zeolite X (EP-A 297 542). A
higher separation factor is obtained as well as a higher N2-loading as compared with Na-zeolite X.
A better energy value is also obtained using Li-zeolite X as compared with Na-zeolite X (EP-A 461 478).
To further optimize the adsorption process in the area of air separation, adsorption agents have been suggested which consist of a variety of zones with different types of zeolite.
JP 87/148 304 discloses an oxygen enrichment process in which, instead of an ad-15 sorber with one zeolite packing, an adsorber with special arrangements of differenttypes of zeolite is used. The adsorber contains, on the air inlet side, zeolites of the Na-X, Na-Y or Ca-X type, and on the air outlet side, zeolites of the Ca-A type.
In EP-A-374 631, a Ca-zeolite A with low N2-adsorption is used on the inlet sideand a Ca-zeolite A with high N2-adsorption is used on the outlet side, wherein the 20 CaO/Al2O3 content in both zeolites is of about the same magnitude. The different N2-loadings are due to different activation procedures.
EP-A 0 546 542 describes a bed arrangement in which Li-zeolite X is used in the air inlet zones and Na-zeolite X is used in the air outlet zones. An arrangement in which Na-zeolite X is used in the inlet zones and Li-zeolite X and Na-zeolite X
25 are used in the outlet zones is, according to the specification, poorer and not preferred.
The object of the present invention is to provide an energy-favourable pressure-swing adsorption process for the adsorption of nitrogen from gas mixtures with less polar gas components, also to achieve improved 2 yields as compared with Le A 31 227-Forei~n Countries ~ 1 8 2 6 41 the prior art, to lower the manufacturing costs of oxygen from air separation and to keep the energy costs low.
This object is achieved, surprisingly, by combinations of special types of zeolites in the pressure-swing adsorption process.
5 The invention provides a process for the adsorption of nitrogen from gas mixtures with less polar components, in particular from air, at temperatures between 20 and 50C using pressure-swing adsorption, in which the gas mixture is passed throughan adsorber which is filled with packings of zeolite granules, which is characterized in that at least two, preferably two, packings are present in the 10 adsorber, wherein a packing of Na-zeolite X is present in the inlet zone of the adsorber and a packing of Li-zeolite X is present in the outlet zone of the adsorber.
In the case of pressure-swing adsorption processes, a distinction has to be made in particular between VSA processes (in this process variant the evacuation pressure is between 100 and 400 mbar and the adsorption pressure is between 1 bar and 1.1 bar), PSA processes (here, a desorption pressure of 1 to 1.1 bar and an adsorption pressure of 2 to 6 bar are used) and PVSA (here an evacuation pressure between 200 and 700 mbar and an adsorption pressure between 1.1 and 2 bar are used).
20 Using the combination of special zeolites according to the invention, not only can the 2 yield be increased but also, surprisingly, the energy consumption can be reduced.
The Li-zeolite X used is preferably a zeolite which has a SiO2/AI2O3 molar ratioof 2.0 to 2.5 and 80-100 % of whose AIO2 tetrahedral units are associated with 25 lithium cations.
The proportion of Li-zeolite X in the total amount of packing material in the adsorber is preferably 20 to 80 %. The proportion depends on the air inlet tempe-rature and on the pressure ratio between the maximum adsorption pressure and theminimum desorption pressure.
2182fi~1 -For an adsorption pressure of 1 to 1.5 bar, the minimum suction pressure should preferably be between 100 and 500 mbar.
The Na-zeolite X preferably has a SiO2/A12O3 molar ratio of 2.0 to 3Ø
Preferably, the Na-zeolite X has a SiO2/A12O3 molar ratio of 2.0 to 3.0 and the Li-zeolite X is present in an amount of 20 to 85 wt.%, with respect to the total amount of packing in the adsorber.
The technical procedures involved in the process according to the invention are described in detail in, for instance "Gas Separation and Purification" 1991, vol. 5, June, pages 89 to 90.
The gas stream can advantageously be dried before passage through the zeolite packing, for instance by means of a drying layer of silica gel.
The invention is explained in more detail in the accompanying drawings along with the examples which follow.
In the drawings Fig. 1 is a plot of N2 loading against pressure for the Na-zeolite X and Li-zeolite X of the examples:
Fig. 2 is a flow sheet of the instant process; and Figs. 3 and 4 are charts showing the poorer perform-ance with regard to energy consumption when operating outside the present invention.
Le A 31 227-Forei~n Countries 2 ~ 8 2 6 4 1 Examples The types of zeolite tested were prepared by ion exchange from the correspondingNa-zeolite X granules.
Sample A (Na-zeolite X) The Na-zeolite X granules were prepared in accordance with DE-A 1 203 238, example 2, wherein the granules prepared in this way contained about 18 %
Na-zeolite A and 82 % Na-zeolite X. The SiO2/Al2O3 ratio was 2.3, the particle size was 1 - 2 mm and the bulk density was about 650 g/l. Activation was performed at 600C using dry nitrogen.
Sample B (Li-zeolite X) 12 liters of binder-free Na-zeolite X granules, prepared as in DE-A 1 203 238, were placed in a suitable column with a heatable jacket. Then 690 liters of 1 M
lithium chloride solution were pumped through the granular packing over the D course of 15 hours. The temperature was 85C. After completing the ion exchange procedure, the granules were washed with water which had been adjusted to a pH
of 9 with LiOH. The degree of exchange (Li2O/Al2O3) in the zeolite was 96 %
after the ion exchange procedure.
The adsorption capacities for nitrogen of the samples are given in Fig. 1 and Table 1.
Table 1 Adsorption properties of the samples:
Sample A B
N2 adsorption at 1 bar, 25C in 9 25 22 [Nl/kg]
N2/O2 adsorption ratio at I bar, 25C 2.65 4.55 Le A 31 227-Forei~n Countries 2 ~ ~ 2 6 4 1 Performin~ the tests The following parameters were kept constant in the test unit and when performingthe tests:
Diameter of the bed 500 mm Depth of Al2O3 layer at air inlet 10 % of MS
depth Air inlet temperature 40C
Air outlet temperature 40C
Pressure of air at inlet 1.150 bar (max) Depth of zeolite layer 1.600 mm Minimum evacuation pressure, inlet 250 mbar Pressure at the start of evacuation 900 mbar Evacuation time 30 seconds Refilling step (BFP time) 6 seconds The adsorbers were provided with insulation in order to exclude heat transfer to15 the surroundings. The wall thickness of the container was about I mm.
Performing the tests with an adsorber cycle in accordance with Fig. 2:
C 10 - air blower H 10- cooling/heating G 10 - product blower V 10 - vacuum pump A, B, C - adsorber Time 0 sec:
Adsorber A has completed adsorption.
Le A 31 227-Forei~n Countries ~ 18 2 6 ~ 1 Time 0-6 sec= BFP time:
On adsorber A, only valve 15A is open. On adsorber C, only valves 12C and 13C
are open. As a result, O2-rich gas flows from adsorber A via valve 15A, control valve 17ABC and valve 13C into adsorber C. In adsorber C, the evacuation step is5 thus terminated, wherein the pressure rises from the minimum value (250 bar) to a higher value. In adsorber A the pressure falls from the maximum value (1,150 mbar) to the starting level (initial suction pressure) of 900 mbar.
Adsorber B starts air separation, i.e. air passes through valve I IB into adsorber B, O2-rich product gas leaves the adsorber via valve 14B and is taken to compressor10 G10.
Time 6-30 sec:
On adsorber A, only valve 12A is open. Adsorber A is pumped out from, for example, 900 mbar, via vacuum pump V 10 to, for example, 250 mbar. Adsorber B is on adsorption (see under "time 0-6 sec"), and at the same time O2-rich gas passes via valve 13C into adsorber C via 18ABC and 16ABC. On adsorber C only valve 13C is open. The amount admitted is such that at the end of this period the pressure in adsorber C is 1,080 to 1,090 mbar.
In the next cycle, adsorber C separates the air, then adsorber A, i.e. the two time intervals "0-6 sec" and "6-30 sec" are appropriately repeated.
20 While the tests were performed, the following parameters were also measured:
the amount of O2-rich product, the change in pressure at the adsorption inlet during the evacuation period, the amount of gas pumped out.
The amount of gas pumped out and the amount f 2 product is used to calculate 25 the amount of air admitted and thus the 2 yield (= amount f 2 in the product to the amount of 2 in the air).
All values refer to an 2 concentration in the product of 93 vol.%. All values (such as amount of oxygen) were converted to an amount of 2 of 1,000 m3/h Le A 31 227-Forei~n Countries 2 1 8 2 6 41 The energy demand of the vacuum pump was calculated from the change in pressure during evacuation detected at the suction end of the packing, by utili~in~
the characteristic curve (= energy demand as a function of suction pressure) of a known Roots cycloidal blower with a suction capacity of 20,000 m3/h at 1.03 bar.S The energy demand of the air blower was calculated using the following formula.
(3,060 x Pm-286 x Vo) Pm = 1045 mbar 10,621 x ',1 Vo = amount of air at 1.03 bar.
Il = Efficiency = 0.95 10 ExamPle 1 (Comparison: Na-zeolite X) Na-zeolite X corresponding to sample A was used in the adsorbers. The residual amount of H2O in the activated zeolite was less than 0.5 wt.% (according to DIN
8948; P2Os method). The amount of zeolite per adsorber was 190 kg. Oxygen enrichment took place in accordance with the details given above. The following 15 data were determined:
Temperature of air at inlet [C] 40 Amount of product [Nm3/h] 15.9 2 yield [%] 45 5 Calculated total energy demand [KWh/Nm3O2] 0.46 20 Example 2 (Comparison; Li-zeolite X) Li-zeolite corresponding to sample B was used in the adsorbers (190 kg/adsorber).
The residual amount of H2O in the activated zeolite was less than 0.5 %. The following data were determined:
Le A 31 227-Foreign Countries 21 8 2 6 41 g Temperature of air at inlet [C] 40 Amount of product [Nm3/h] 23 2 yield [%] 54 Calculated total energy demand [KWh/Nm302] 0 375 Example 3 (Comparison; Li-zeolite X in the inlet zones and Na-zeolite X in theoutlet zones) Above the zones of drying agent in the adsorbers were introduced 95 kg of sampleB and above that 95 kg of sample A. The following data were determined:
Temperature of air at inlet [C] 40 Amount of product [Nm3/h] 18 2 yield [%] 44.5 Calculated total energy demand [KWh/Nm3O2] 0.46 Example 4 (according to the invention; Na-zeolite X in the inlet zones and Li-zeolite X in the outlet zones) 15 Above the drying zones in the adsorbers were introduced 95 kg of sample A and above that 95 kg of sample B.
Temperature of air at inlet [C] 40 Amount of product [Nm3/h] 20.6 2 yield [%] 51.5 Calculated total energy demand [KWh/Nm3O2] 0.378 Example 3 provides very poor energy values for the oxygen produced (see Fig. 3 and Fig. 4). The inverted sequence of packings (example 4), however, produces good values. The energy demand is almost identical to the energy demand with Le A 31 227-Forei~n Countries 2 I 8 2 6 4 1 pure Li-zeolite packings (example 2). Since lithium-zeolite X is much more expensive to manufacture than Na-zeolite X, oxygen can be produced much more cheaply using the packings according to the invention.
It will be understood that the specification and examples are illustrative but not 5 limitative of the present invention and that other embodiments within the spirit and scope of the invention will suggest themselves to those skilled in the art.
Claims (5)
1. In the selective adsorption of nitrogen from gas mixtures with less polar gas components at temperatures of 20 to 50°C using pressure-swing adsorption, in which the gas mixture is passed through an adsorber which is filled with a packing of zeolite granules, the improvement which comprises providing at least two packings in the adsorber, a Na-zeolite X
being provided in the inlet zone of the adsorber and a Li-zeolite X being provided in the outlet zone of the adsorber.
being provided in the inlet zone of the adsorber and a Li-zeolite X being provided in the outlet zone of the adsorber.
2. The process according to Claim 1, wherein the Li-zeolite X has a Li2O/Al2O3 molar ratio of 0.80 to 1.0 and a SiO2/Al2O3 molar ratio of 2.0 to 2.5.
3. The process according to Claim 1, wherein the Na-zeolite X has a SiO2/Al2O3 molar ratio of 2.0 to 3Ø
4. The process according to Claim 1, wherein the Li-zeolite X is present in an amount of 20 to 85 wt.%, with respect to the total amount of packing in the adsorber.
5. The process according to Claim 4, wherein the Li-zeolite X has a Li2O/Al2O3 molar ratio of 0.80 to 1.0 and a SiO2/Al2O3 molar ratio of 2.0 to 2.5, and the Na-zeolite X has a SiO2/Al2O3 molar ratio of 2.0 to 3Ø
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19529094A DE19529094A1 (en) | 1995-08-08 | 1995-08-08 | Process for the adsorption of nitrogen from gas mixtures by means of pressure swing adsorption with zeolites |
| DE19529094.1 | 1995-08-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2182641A1 true CA2182641A1 (en) | 1997-02-09 |
Family
ID=7768966
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002182641A Abandoned CA2182641A1 (en) | 1995-08-08 | 1996-08-02 | Process for the absorption of nitrogen from gas mixtures using pressure-swing adsorption with zeolites |
Country Status (11)
| Country | Link |
|---|---|
| EP (1) | EP0757919A1 (en) |
| JP (1) | JPH0952703A (en) |
| KR (1) | KR970009858A (en) |
| CN (1) | CN1151330A (en) |
| BR (1) | BR9603342A (en) |
| CA (1) | CA2182641A1 (en) |
| CZ (1) | CZ234396A3 (en) |
| DE (1) | DE19529094A1 (en) |
| HU (1) | HUP9602189A2 (en) |
| PL (1) | PL315539A1 (en) |
| TR (1) | TR199600606A2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6824590B2 (en) | 2000-11-07 | 2004-11-30 | Air Products And Chemicals, Inc. | Use of lithium-containing fau in air separation processes including water and/or carbon dioxide removal |
| US20180229212A1 (en) * | 2017-02-13 | 2018-08-16 | Won Hi Tech Corp. | Adsorption tower for oxygen generating system containing two kinds of adsorbing agents filled therein |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6152991A (en) * | 1997-04-17 | 2000-11-28 | Praxair Technology, Inc. | Multilayer adsorbent beds for PSA gas separation |
| FR2792210B1 (en) * | 1999-04-13 | 2001-09-14 | Air Liquide Sante Int | PORTABLE MEDICAL EQUIPMENT FOR OXYGEN THERAPY AT HOME |
| FR2809329B1 (en) * | 2000-05-25 | 2002-08-16 | Air Liquide | PORTABLE OXYGEN CONCENTRATOR |
| US6651658B1 (en) | 2000-08-03 | 2003-11-25 | Sequal Technologies, Inc. | Portable oxygen concentration system and method of using the same |
| US6691702B2 (en) | 2000-08-03 | 2004-02-17 | Sequal Technologies, Inc. | Portable oxygen concentration system and method of using the same |
| US6544318B2 (en) * | 2001-02-13 | 2003-04-08 | Air Products And Chemicals, Inc. | High purity oxygen production by pressure swing adsorption |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0621006B2 (en) * | 1985-12-23 | 1994-03-23 | 日本酸素株式会社 | High-concentration oxygen gas production equipment by pressure fluctuation adsorption method |
| JPS634824A (en) * | 1986-06-24 | 1988-01-09 | Tosoh Corp | Impure gas adsorption bed |
| US5169413A (en) * | 1991-10-07 | 1992-12-08 | Praxair Technology Inc. | Low temperature pressure swing adsorption with refrigeration |
| US5203887A (en) * | 1991-12-11 | 1993-04-20 | Praxair Technology, Inc. | Adsorbent beds for pressure swing adsorption operations |
| US5529610A (en) * | 1993-09-07 | 1996-06-25 | Air Products And Chemicals, Inc. | Multiple zeolite adsorbent layers in oxygen separation |
-
1995
- 1995-08-08 DE DE19529094A patent/DE19529094A1/en not_active Withdrawn
-
1996
- 1996-07-24 TR TR96/00606A patent/TR199600606A2/en unknown
- 1996-07-26 EP EP96112062A patent/EP0757919A1/en not_active Withdrawn
- 1996-08-02 JP JP8219037A patent/JPH0952703A/en active Pending
- 1996-08-02 CA CA002182641A patent/CA2182641A1/en not_active Abandoned
- 1996-08-06 PL PL96315539A patent/PL315539A1/en unknown
- 1996-08-07 KR KR1019960032846A patent/KR970009858A/en not_active Application Discontinuation
- 1996-08-07 BR BR9603342A patent/BR9603342A/en not_active Application Discontinuation
- 1996-08-07 CZ CZ962343A patent/CZ234396A3/en unknown
- 1996-08-08 HU HU9602189A patent/HUP9602189A2/en unknown
- 1996-08-08 CN CN96111512A patent/CN1151330A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6824590B2 (en) | 2000-11-07 | 2004-11-30 | Air Products And Chemicals, Inc. | Use of lithium-containing fau in air separation processes including water and/or carbon dioxide removal |
| US20180229212A1 (en) * | 2017-02-13 | 2018-08-16 | Won Hi Tech Corp. | Adsorption tower for oxygen generating system containing two kinds of adsorbing agents filled therein |
Also Published As
| Publication number | Publication date |
|---|---|
| HU9602189D0 (en) | 1996-09-30 |
| CZ234396A3 (en) | 1997-03-12 |
| HUP9602189A2 (en) | 1997-06-30 |
| BR9603342A (en) | 1998-05-05 |
| TR199600606A2 (en) | 1997-02-21 |
| DE19529094A1 (en) | 1997-02-13 |
| CN1151330A (en) | 1997-06-11 |
| PL315539A1 (en) | 1997-02-17 |
| JPH0952703A (en) | 1997-02-25 |
| EP0757919A1 (en) | 1997-02-12 |
| KR970009858A (en) | 1997-03-27 |
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