CN1117603C

CN1117603C - Pressure variable adsorptive method for separating hydrogen nitrogen and pure carbon dioxide from exchange air

Info

Publication number: CN1117603C
Application number: CN 99115109
Authority: CN
Inventors: 伍仁兴
Original assignee: Chengdu Research Institute Of New Chemical Industry
Current assignee: Chengdu Research Institute Of New Chemical Industry
Priority date: 1999-08-30
Filing date: 1999-08-30
Publication date: 2003-08-13
Anticipated expiration: 2019-08-30
Also published as: CN1248482A

Abstract

The present invention relates to a pressure-variable adsorption method for separating hydrogen, nitrogen and pure CO2 from conversion gas, which has the technical scheme that the conversion gas is the conversion gas of coal gas; a first adsorption tower and a second adsorption tower are connected in series; the first adsorption tower is used for preparing CO2, and the outlet of the first adsorption tower is a hydrogen and nitrogen mixing gas containing CO2; the outlet gas of the first adsorption tower enters the second adsorption tower for preparing hydrogen and nitrogen; the first adsorption tower and the second adsorption tower sequentially comprise the steps of adsorption A, equalized pressure reduction ED, vacuum pumping VC, equalized pressure rise ED and final pressure rise FR in one cycle period; the first adsorption tower has the step of pure CO2 conversion P after the equalized pressure reduction ED and before the vacuum pumping VC.

Description

The pressure swing absorption process of separation of hydrogen, nitrogen and pure carbon dioxide from conversion gas

Technical field:

The present invention with from being raw material with the coal, import separation of hydrogen nitrogen and pure CO in the conversion gas of coal generating gas of air or oxygen enrichment in the gas-making process ₂, replace the pressure swing absorption process of wet method decarburization in the urea production relevant.

Background technology:

Remove CO in the conversion gas in the synthesis process of urea ₂Usually adopt Physical Absorption method and chemical absorption method.These methods are used a large amount of solvents, are called wet method usually again.The waste that these solvents have is big, and the toxicity that has is big, the regeneration energy consumption height that has, and the instability that has, what have has shortcomings such as burn into leakage pollution environment, decarburization troublesome poeration.

As everyone knows, PSA has been successfully applied to all gases separating technology, also has patent to relate to purified ammonia synthesis gas and the pure CO of system ₂, as U.S. Pat P5,133,785, as Chinese patent ZL91107278.0, Chinese patent application numbers 97107517.4, Chinese patent application numbers 88105938.2 etc.But,, in 133,785, almost do not have N in the separated conversion gas at U.S. Pat P5 ₂Gas, separating resulting are pure CO ₂With pure H ₂Gas, because in this technology, H ₂The general PSA system H that the part that purifies gas adopts ₂Technology is used pure H ₂The flushing bed, the hydrogen yield is low.If this technology is used for separation of hydrogen, nitrogen from the coal generating gas conversion gas that adds air at gas-making process, not only hydrogen, nitrogen yield are low, and hydrogen, nitrogen lacks of proper care than ratio, have a strong impact on the efficient of synthetic ammonia.In Chinese patent ZL91107278.0 and Chinese patent application numbers 97107517.4, introduced a kind of CO that from conversion gas, directly removes ₂Method, but the wet method decarburization of these methods in can not the substituted ureas synthesis technique proposed a kind of from containing CO in Chinese patent application numbers 88105938.2 ₂CO purifies in the gas ₂Pressure swing absorption process, the wet method decarburization during this method is can not substituted ureas synthetic.Be raw material with the coal, importing in the conversion gas urea synthesis technology of air in the gas making process that decarbonization process has its particularity, at first requires hydrogen, nitrogen yield height.The yield of nitrogen particularly is because N ₂Certain adsorptivity is arranged, and the relative wet method of PSA method is more easily lost nitrogen, on the other hand the CO in the coal generating gas conversion gas ₂It is synthetic excessive to be used for urea, therefore, requires the pure CO that extracts ₂Amount satisfy that urea is synthetic get final product, if the CO of purification ₂Measure too greatly, will cause the increase of equipment investment and energy consumption.Can not overcome these problems with prior art.

Summary of the invention:

Purpose of the present invention just provides a kind of from the coal being separation of hydrogen nitrogen and pure CO the conversion gas of raw material ₂Gas is used for the synthetic pressure swing absorption process of urea, this method reduced investment and operating cost is low especially.

The present invention is achieved in that

A kind of from conversion gas the pressure swing adsorption method of separation of hydrogen, nitrogen and pure carbon dioxide gas, conversion gas imports the coal generating gas of air or oxygen enrichment for being raw material with the coal in the gas-making process, use first, second group adsorption tower serial operation, first group is high concentration CO ₂Adsorption zone, conversion gas enter the adsorbent bed that first group of adsorption tower be in adsorption step and adsorb, and adsorbent optionally adsorbs the CO in the conversion gas in the bed ₂, H ₂Components such as O, adsorbent bed stripping gas are pure CO ₂Product gas is difficult for the component hydrogen, nitrogen and the part CO that adsorb ₂Discharge from the port of export and send into the adsorption tower adsorbent bed that is in adsorption step second group of adsorption tower and adsorb Deng (thick hydrogen, nitrogen), adsorbent is selected CO absorption ₂The component hydrogen, nitrogen that is difficult for absorption from the product end discharge product gas hydrogen, nitrogen, the adsorption tower of first and second group comprises absorption A successively in a cycle period, drop pressure ED vacuumizes VC, boost pressure ER, the FR step of finally boosting, first group of adsorption tower behind drop pressure ED, find time before useful pure carbon dioxide product gas displacement P step, the pure carbon dioxide product displaces other component the bed from the entrance point direction under displacement pressure, work off one's feeling vent one's spleen emptying or its are used.CO in thick hydrogen, the nitrogen ₂Concentration is 1-8% (V), and the best is 3-5% (V).

First group of adsorption tower has forward to put between drop pressure ED and displacement P presses the PP step.

Second group of adsorption tower is step-down PP step after all pressing after drop pressure ED step, second group of drop pressure gas can be used as the boost pressure gas of the equal voltage rise ER of first group of adsorption tower.

Inhale the drop pressure ED of tower and vacuumize to have between the VC step forward to put for second group and press or the reverse pressure PP step of putting.

First and second group adsorption tower has isolation step I between boost pressure ER or drop pressure ED step.

The number of every group of adsorption tower is 2-24, two groups of adsorption tower numbers can be unequal, and the tower number that is in adsorbed state simultaneously can be two or more, and vacuum lines is more than one or one, many vacuum pipelines can increase the pumpdown time, strengthen desorption effect.

The adsorbent of adsorption tower is activated alumina, active carbon, silica gel, a kind of in the zeolite molecular sieve or constitute the layering combination cot by wherein several.

The pressure of displacement step P is 0-0.3MPa.

The pressure of absorption A step is 0.1-3.0MPa, and two groups adsorptive pressure can be unequal.

After can pressurizeing, the thick hydrogen of first group of adsorption tower port of export, nitrogen enters second group of adsorption tower.

The present invention is according to CO ₂Constantly boost in adsorption process in the absorption forward position, after absorption finishes, and CO ₂Between forward position and outlet the one section unsaturation adsorption zone and the principle of adsorption zone are not arranged, adsorption tower are divided into upper and lower two groups of serial operations, below one group be first group, above one group be second group.First group is high concentration CO ₂Adsorption zone, second group is low concentration CO ₂Adsorption zone and adsorption zone not.First group of adsorption tower has pure CO ₂Displacement step and vacuum desorption step, its effect are the CO that purifies from conversion gas ₂, first group of adsorption tower outlet is for containing finite concentration CO ₂Thick hydrogen and nitrogen gas.Second group of adsorption tower has the vacuum regeneration step, and its effect is the CO that removes in the thick hydrogen and nitrogen gas ₂, make CO in the hydrogen and nitrogen gas ₂Less than 0.2%.Control the CO in the thick hydrogen and nitrogen gas ₂Be 1-8% (V) that the best is 3-5% (V), the pure CO that this moment, first group of adsorption tower produced ₂Amount can satisfy the synthetic needs of urea and unlikely excessive in a large number.Simple purification CO relatively ₂PSA technology because after the grouping, first group of adsorption tower middle CO that works off one's feeling vent one's spleen ₂Concentration is higher, adsorbent bed CO absorption ₂Saturation degree also higher, therefore in displacement step, replace CO ₂Consumption significantly reduce, thereby improved bed efficient, reduced energy consumption.Owing to after the grouping, can realize the pure CO of control ₂Yield be our needed level, therefore the equipment investment of first group of adsorption tower is less, energy consumption also reduces greatly; Because after the grouping, the displacement gas of first group of adsorption tower is worked off one's feeling vent one's spleen and is not entered second group of bed, has guaranteed the cleannes of second group of bed, to purifying CO in thick hydrogen, the nitrogen ₂Highly beneficial; Owing to dividing into groups the back in second group of adsorption tower, CO in the thick hydrogen and nitrogen gas ₂Low with respect to conversion gas concentration, therefore easier being removed only, plant investment is with respect to direct decarburization from conversion gas also much less, and hydrogen nitrogen yield is also higher simultaneously.Method of the present invention is the synthetic middle wet method decarburization of substituted ureas fully not only, and mutual investment and operating cost are all low.

Description of drawings:

Fig. 1 is first group of adsorption tower process chart.

Fig. 2 is second group of adsorption tower process chart.

Fig. 3 is first group of adsorption tower processing step working procedure table.

Fig. 4 is second group of adsorption tower processing step working procedure table.

Fig. 5 is two group of six tower (A group and B group) series process flow figure.

Fig. 6 is two group of six tower (A group and B group) processing step working procedure table.

The specific embodiment:

With the coal is raw material, introduces the conversion gas that air or oxygen enrichment are made in the gas-making process, and its typical case forms as shown in the table:

Form	H ₂	N ₂	CO	CH ₄	O ₂+Ar	CO ₂	H ₂S	H ₂O
Form	H ₂	N ₂	CO	CH ₄	O ₂+Ar	CO ₂	H ₂S	H ₂O	Concentration (%) (V)	40-60	10-24	0.3-3	0.5-4	＜1	18-31	-200mg/m ³	Saturated

The present invention is divided into two groups of adsorption tower serial operations with adsorption tower, and first group is extracted pure CO ₂, extract CO ₂CO in the thick hydrogen and nitrogen gas of back outlet ₂Concentration is 1-8% (V), and the best is 3-5% (V), and second group removes CO in thick hydrogen, the nitrogen ₂, make it less than 0.2%.Each adsorption tower is once experiencing following steps in the circulation successively in the adsorption towers at different levels.

First group:

1, absorption A: unstripped gas (conversion gas) is sent into the adsorbent bed charging aperture that is in adsorption step adsorb, adsorbent optionally adsorbs easy adsorbent component CO in the bed ₂, H ₂O etc., and in bed, set up easy adsorbent component adsorption zone, be difficult for the component (as hydrogen, nitrogen, carbon monoxide, methane etc.) and a part of CO of absorption relatively ₂Discharge by whole adsorbent bed and from the port of export, easily adsorbent component adsorption zone continuous port of export to bed in adsorption process moves, and when gas concentration lwevel reaches certain value in working off one's feeling vent one's spleen, ends unstripped gas, stops absorption.

2, equal pressure drop ED: after absorption finished, dead space gaseous hydrogen in the adsorbent bed, nitrogen concentration were very high, and this part gas need be recycled, when this part gas is discharged from the bed outlet, and CO ₂Concentration will increase gradually.Other bed of having finished evacuation step that this part gas can be used for this group boosts, and according to adsorptive pressure, bed number, the bed number average pressure drop pressure that is in adsorbed state simultaneously can be divided into repeatedly carries out.Each drop pressure gas carries out boost pressure to other different beds.

3, forward put pressure PP: when the adsorptive pressure height, all press number of times less, after all pressure finished, the tower internal pressure was higher than displacement pressure, and this moment can be along the further step-down of absorption direction, and pressure is reduced to displacement pressure.

4, displacement P: utilize the pure CO of a part of product ₂, along the absorption direction, under displacement pressure, the adsorption tower of just finishing above-mentioned steps to be replaced, displacement gas is replaced other component to port of export direction by adsorbent bed from entrance point, displaces implication and is exporting emptying or using it for anything else.

5, vacuumize VC: from tower bottom or middle part with CO the tower ₂Extract out, promptly obtain CO ₂Product gas.

6, equal voltage rise ER: the gas that utilizes the adsorbent bed of equal pressure drop ED step to discharge, enter from the port of export and to finish the adsorbent bed that vacuumizes step, make its pressure that progressively raises, all voltage rise can be carried out repeatedly.Each gas of accepting is from the equal pressure drop gas of different beds.

7, the FR that finally boosts: utilize adsorption step to work off one's feeling vent one's spleen and bed is boosted, be raised to adsorptive pressure from the outlet side.

Second group:

1, absorption A: thick hydrogen, the nitrogen of first group of adsorption tower outlet are sent into the adsorption tower feed end that is in adsorption step in second group of adsorption tower adsorb, adsorbent optionally adsorbs easy adsorbent component CO ₂, this part CO ₂Be impurity CO ₂, and in bed, set up the adsorption zone of easy adsorbent component, the components such as hydrogen, nitrogen that are difficult for absorption are discharged impurity CO from the product end by adsorption bed ₂Adsorption zone continuous product end to bed in adsorption process moves, and when the absorption forward position moves to the certain position of bed, stops absorption.

2, equal pressure drop ED: after absorption finishes, bed dead space gas needs further to reclaim, to several times gas be discharged in the bed from adsorbent bed product end, this part gas can be used for other of second group have been finished the bed that vacuumizes step and has boosted, and other bed that also can be used for first group of adsorption tower boosts.All pressure drop can be carried out several times, and each all pressure drop gas is all calmed the anger to other different beds and boosted.

3, all press back step-down PP: all press finish after, as the adsorptive pressure height, all press number of times more after a little while, all press and finish back bed internal pressure and be higher than atmospheric pressure, need further bed step-down this moment, step-down can be carried out along the absorption direction, also can be against the operation of absorption direction.Hydrogen, nitrogen concentration are very high in this part gas, recyclable utilization.Usually it is returned raw material system.

4, vacuumize VC: to regenerate in order making in the bed, to adopt the way that vacuumizes the CO of absorption ₂Release from the feed end of tower, make bed obtain regeneration.

5, equal voltage rise ER: after finding time to finish, utilize the equal pressure drop gas of other bed to enter this adsorption tower, it is boosted from the product end.Equally, all voltage rise can repeatedly be carried out, and is used for the equal pressure drop gas of the gas of equal voltage rise from different bed different phases at every turn.

6, the FR that finally boosts: all rise finish after, bed layer pressure does not also reach the requirement of adsorptive pressure, a part of product gas that discharge with a part of adsorbent bed that is in adsorption step this moment boosts until adsorptive pressure to this adsorbent bed.

Every adsorption tower all moves in proper order by the program step of its place group, just staggers mutually on the time.The professional and technical personnel knows, the method according to this invention, every group of adsorption tower can be made up of several towers, and the tower number that is in adsorbed state simultaneously can be two or more, and two groups of adsorption towers be in the tower number of adsorbed state can be identical also can be inequality.The increase and decrease of tower number all presses number of times to change, and what of isolation step all do not exceed scope of the present invention.

Embodiment 1:

With the coal is raw material, and the conversion gas that imports the coal generating gas of air in the gas-making process is unstripped gas, separates pure CO ₂With hydrogen, nitrogen product gas.

Fig. 1, Fig. 2 are the technological process of present embodiment, and Fig. 3, Fig. 4 are the working procedure table of present embodiment.

With the coal is the conversion gas typical case composition of raw material system gas: component C O ₂CO H ₂N ₂CH ₄H ₂S H ₂O concentration V% 25-30 0.3-3 45-55 18-22 1-2＜25-40 ℃ of pressure 0.6～0.8MPa of 150PRm saturation temperature

Fig. 1 and Fig. 2 are respectively two groups of adsorption tower process charts, and Fig. 1 is first group, and Fig. 2 is second group, two groups of serial operations, and first group of effect is with CO in the conversion gas ₂Purify to more than 98%, reach the urea synthesis requirement, second group of effect is with the partly CO that purified ₂After thick hydrogen, nitrogen promptly work off one's feeling vent one's spleen and further purify in first group of adsorption tower upper end, make CO in the hydrogen, nitrogen of second group of adsorption tower upper end outlet ₂Concentration is less than 0.2% (V), to satisfy the needs of next step operation of synthetic ammonia.

Adsorption tower A-L12 platform is arranged in Fig. 1, and P1-P2 is a vavuum pump, and P3 is an air blast, and V1 is CO ₂The product surge tank.Load activated alumina, activated carbon, three kinds of adsorbents of silica gel in the adsorption tower, form combination cot successively from bottom to up.All the time there are 4 towers to be in adsorbed state, carry out four times and all press.Article two, vacuum pipeline G8a, G8b vacuumizes adsorption tower respectively, to increase the pumpdown time.Be example now, first group of adsorption tower purification of the present invention CO is described with the A tower ₂Method.

1, adsorption step A

At this moment, the A tower has been finished the clothes step of finally boosting that first group of adsorption tower worked off one's feeling vent one's spleen.Open sequencing valve 1A, 2A, conversion gas enters adsorption tower A through pipeline G1, in adsorption tower A, and CO ₂Selected absorption, the hydrogen that is not adsorbed, nitrogen and contain portion C O, CH ₄And CO ₂Thick hydrogen, nitrogen flow out from 2A.As the middle CO that works off one's feeling vent one's spleen ₂When mean concentration reaches 4% (V), close 1A, 2A and stop absorption.

Adsorption tower is worked off one's feeling vent one's spleen and is gone into orotracheal tube G21 through what pipeline G2 directly removed second group of adsorption tower.

2, drop pressure step for the first time is called for short one and all falls E ₁D

Open sequencing valve 3A, 3F, the equal gas of one in the A tower enters the F tower through pipeline G3 the F tower is carried out equal liter, treats to close 3A, 3F after the two pressure tower balances.

3, two all fall E ₂D:

Open sequencing valve 4A, 4G, gas enters the G tower through valve 4A, pipeline G4, valve 4G the G tower is carried out two equal gas lifts pressures in the A tower, treats shut off valve 4G after the two pressure tower balances.

4, three all fall E ₃D:

Open sequencing valve 4H, A tower gas enters the H tower through valve 4A, pipe G4, valve 4H the H tower is carried out three equal gas lifts pressures, treats to close 4A, 4H after the two pressure tower balances.

5, four all fall E ₄D:

Open sequencing valve 5A, 5I, A tower gas enters the I tower through valve 5A, pipeline G5, valve 5I the I tower is carried out four equal gas lifts pressures, treats to close 4H after the two pressure tower balances.

6, along putting step-down PP

When all pressure drop is four times, after all falling end, have certain pressure to open sequencing valve KV-2 at this moment in the tower, gas is emitted outside the tower along the absorption direction through valve 5A, pipeline G5, sequencing valve KV-2 in the tower, shut off valve 5A, KV-2 when the approaching displacement of tower internal pressure pressure 0-0.03MPa.

7, products C O ₂Displacement P

Open sequencing valve 7A, 6A, at this moment products C O ₂Through air blast P3, pipeline G7, valve 7A enters adsorption tower A, the A tower is replaced, by substitution gas through valve 6A, pipeline G6 emptying.As the middle CO that drops a hint ₂When reaching the regulation requirement, shut off valve 7A, 6A.

8, vacuumize

Open sequencing valve 8A, CO ₂Product gas is through valve 8A, pipeline G8, and vavuum pump P1 is evacuated to CO ₂In the product surge tank V1, evacuation pressure-0.06 in the tower～-0.09MPa.8A finds time to finish to close.

9, isolation step I for the first time ₁

All sequencing valves of A tower are in closed condition, wait pending next step.

10, the 4th E that boosts that all calms the anger ₄R (being called for short four all rises)

Open sequencing valve 5E, 5A, gas enters the A tower through valve 5E, pipeline G5, valve 5A in the E tower, closes valve 5A after two pressure tower balances.

11, isolate 1 for the second time ₂

12, three all rise E ₃R

Open sequencing valve 4F, 4A, the gas in the F tower enters the A tower A tower is boosted through valve 4F, pipeline G4, valve 4A, closes sequencing valve 4A, 4F when two pressure towers reach balance.

13, isolate I for the third time ₃

14, two all rise E ₂R

Open sequencing valve 4A, 4G, gas enters the A tower through valve 4G, pipeline G4, valve 4A in the G tower, the A tower is carried out two equal gas lifts press, and when two pressure tower balances, closes sequencing valve 4A, 4G.

15, isolate 1 the 4th time ₄

A tower sequencing valve all is in closed condition, waits pending next step.

16, one all rise E ₁R

Open sequencing valve 3A, 3H, the interior gas of H tower enters the A tower through valve 3H, pipeline G3, valve 3A the A tower is carried out an equal gas lift pressure, when two pressure tower balances, closes sequencing valve 3A, 3H.

17, finally boost

Open among sequencing valve KV-1,3A, the pipeline G2 adsorption tower and work off one's feeling vent one's spleen and enter the A tower A tower is finally boosted through valve KV-1, pipeline G3, valve 3A, when pressure rises to adsorptive pressure, shut off valve KV-1,3A.

So far, the A tower has been finished a circulation, can enter next circulation again.Other tower is the same with the circulation step of A tower in first group, just staggers mutually on the time, sees Fig. 3.

Second group:

The unstripped gas of second group of adsorption tower is worked off one's feeling vent one's spleen from first group of adsorption tower.Enter the unstripped gas pipeline G21 of the second group of adsorption tower that is attached thereto through pipeline G2.

Second group of adsorption tower has adsorption tower M-V10 platform, filling gel adsorbent in the adsorption tower.All the time there are 3 adsorption towers to be in adsorbed state, can carry out 5 times and all press.See Fig. 2, Fig. 4.

Be that example illustrates that second group of adsorption tower purifies the method for thick hydrogen, nitrogen now with the M tower.

1, adsorption step A

Open sequencing valve 1M, 2M, thick hydrogen, nitrogen enter adsorption tower M through pipe G21, valve 1M.In adsorption tower M, CO in the gaseous mixture ₂Be adsorbed agent in the bottom and select absorption, the product hydrogen that the end is adsorbed, nitrogen remove the synthetic ammonia subsequent processing through valve 2M, pipeline G22.Along with the carrying out of absorption, CO ₂Mass-transfer zone continues to push ahead, and when the absorption forward position reaches certain position, stops absorption.Close sequencing valve 1M, 2M this moment.

2, an equal step-down E ₁D

Open sequencing valve 3M, 3Q, gas enters the Q tower through valve 3M, pipeline G23, valve 3Q in the M tower, after two pressure tower balances, closes valve 3M, 3Q.

3, two all fall E ₂D

Open sequencing valve 4M, 4R, gas enters the R tower through valve 4M, pipeline G24, valve 4R in the M tower, after two pressure tower balances, closes valve 4R.

4, three all fall E ₃D

Open sequencing valve 4S, gas enters the S tower through valve 4M, pipeline G24, valve 4S in the M tower, after two pressure tower balances, closes valve 4M, 4S.

5, four all fall E ₄D

Open sequencing valve 5M, 5T, gas flows into the T tower through valve 5M, pipeline G25, valve 5T in the M tower, closes valve 5T after two pressure tower balances.

6, five all fall E ₅D

Open sequencing valve 5U, gas enters the U tower through valve 5M, pipeline G25, valve 5U in the M tower, closes valve 5M, 5U after two pressure tower balances.

7, step-down PP forward

Open sequencing valve 3M, KV4, gas is emitted outside the tower through 3M, pipeline G23, valve KV4 in the M tower, near atmospheric pressure, closes 3M, KV4 until the tower internal pressure then.

After can pressurizeing, suitable venting returns the unstripped gas system recoveries.

Forward the also available reverse step-down of step-down replaces; Open sequencing valve 6M, gas is emitted outside the tower through 6M, pipeline G26 in the M tower.

8, vacuumize VC

Open sequencing valve 7M, the CO that is adsorbed in the tower ₂And dead space gas is through valve 7M, pipeline G27, vavuum pump P ₄Extract out, evacuation step finishes, and the tower internal pressure is-0.07～-0.9MPa.Close 7M.

9, five all rise E ₅R

Open sequencing valve 5M, 50, the 5th equal pressure drop gas enters the M tower through valve 50, pipeline G25, valve 5M in the O tower, after the two pressure tower balances, and shut off valve 50.

10, all rise E on ₄R

Open sequencing valve 5P, the 4th equal pressure drop gas enters the M tower through valve 5P, pipeline G25, valve 5M in the P tower.After the two pressure tower balances, close valve 5M, 5P.

11, three all rise E ₃R

Open sequencing valve 4M, 4Q, Q tower drop pressure gas for the third time enters the M tower through valve 4Q, pipeline G24, valve 4M, as two pressure tower balances, shut off valve 4Q.

12, two all rise E ₂R

Open sequencing valve 4R, R tower drop pressure gas for the second time enters the M tower through valve 4R, pipeline G24, valve 4M, as two pressure tower balances, shut off valve 4M, 4R.

13, one all rise E ₁R

Open sequencing valve 3M, 3S, S tower drop pressure gas for the first time enters the M tower through valve 3S, pipeline G23, valve 3M, after two pressure tower balances, and shut off valve 3S.

14, finally boost

Open sequencing valve KV3, allow part hydrogen, nitrogen product enter the M tower, make the M pressure tower reach adsorptive pressure, shut off valve KV3,3M through pipeline G22, valve KV3, pipeline G23, valve 3M.

So far, the M tower has been finished a circulation, can enter next sorption cycle again, and the circulation step of other tower of second group is the same with the M tower, just staggers mutually on the time.

The present embodiment result is products C O ₂Purity 99.5%, CO ₂Yield is greater than 70%, no matter be that output or purity all reach and surpasses the needs that urea synthesizes; CO in product hydrogen, the nitrogen ₂Concentration is less than 0.2% (V), hydrogen total recovery 98.5%, nitrogen total recovery 96%.

Embodiment 2:

Fig. 5 is the process chart of present embodiment, and Fig. 6 is the processing step working procedure table of present embodiment.Have A group and B to organize two groups of adsorption towers in this enforcement, the A group has six adsorption towers of A1～A6, and the B group has six adsorption towers of B1～B6.A group B group serial operation, the A group is used to the CO that purifies ₂, the B group is used for removing thick hydrogen, nitrogen CO ₂Difference from Example 1 is a pairing tower serial operation during each tower is organized with B in the A group in the present embodiment.

The conversion atmospheric pressure, composition, the temperature that are used for present embodiment are identical with embodiment 1.

The adsorbent that loads in the A group adsorption tower is activated alumina, activated carbon, three kinds of adsorbents of silica gel, forms combination cot successively from bottom to up, loads silica gel absorber in the B group adsorption tower.

Be example now, present embodiment is described with A1 tower B1 tower.

1, adsorption step A

Open sequencing valve 1A1,2A1,2B1, conversion gas enters tower A1 through pipeline G31, valve 1A1, CO in A1 ₂Selected absorption, hydrogen, nitrogen and a small amount of CO ₂Gaseous mixture, enter among the adsorption tower B1 CO in hydrogen, the nitrogen in B1 through valve 2A1 ₂Be adsorbed, product hydrogen, nitrogen remove the subsequent processing of ammonia synthesis process through valve 2B1, pipeline G42.

CO in tower B1 ₂When the absorption forward position arrives in the bed certain position, stop absorption, close valve 1A1,2A1,2B1.

2, an equal step-down E ₁D

Open sequencing valve 3A1,3A3, gas enters tower A3 through valve 3A1, pipeline G33, valve 3A3 in the A1 tower, closes valve 3A1,3A3 after tower A1 and tower A3 two pressure tower balances.

In open valve 3A1,3A3, open sequencing valve 3B1,3B3, gas enters tower B3 through valve 3B1, pipeline C43, valve 3B3, shut off valve 3B1,3B3 after two pressure tower balances in the B1 tower.

3, two equal step-down E ₂D

Open sequencing valve 4A1,4A4, gas after two pressure tower balances, closes valve 4A4 to the pressurising of A4 tower in the A1 tower.

Open sequencing valve 4B1,4B4 simultaneously, gas is closed 4B4 to the pressurising of B4 tower in the B1 tower after two pressure tower balances.

4, three equal step-down E ₃D

Open sequencing valve 4A5, the gas in the A1 tower after the two pressure tower balances, closes valve 4A1,4A5 to the A5 pressurising.

Open sequencing valve 4B5 simultaneously, the gas in the B1 tower after the two pressure tower balances, closes valve 4B1,4B5 to tower B5 pressurising.

5, along putting step-down PP

Open sequencing valve 4A1, KV31, gas is not emitted outside the tower through valve 4A1, pipeline G34, valve KV31 in the A1 tower, when the A1 pressure tower reaches displacement pressure, closes valve 4A1, KV31.Present embodiment displacement pressure 0.0-0.03MPa.

Open sequencing valve 4B1, KV42 simultaneously, emit outside the tower through valve 4B1, pipeline G44, valve KV42 in the B1 tower, when the tower internal pressure reaches atmospheric pressure, close valve 4B1, KV42.

B1 tower forward step-down also can be replaced the reverse pressure of putting by reverse step-down: open sequencing valve 5B1, gas is emitted outside the tower through pipeline G45.

6, products C O ₂Displacement P

Open sequencing valve 6A1,5A1, portioned product CO ₂Enter the A1 tower bed is replaced through air blast P32, pipeline G36, valve 6A1, substitution gas is through valve 5A1, pipeline G35 emptying, CO in displacing implication ₂When reaching finite concentration, close valve 6A1,5A1.

The B1 tower does not have displacement step, and all sequencing valves of B1 tower cut out and are in isolation step I1 at this moment, wait pending next step.

7, evacuation step CV

Open sequencing valve 7A1, the pure CO in the A1 tower ₂Be drawn to products C O through valve 7A1, pipeline G37, vacuum P31 ₂Surge tank V2, A1 tower internal pressure is evacuated to-0.07～-0.09MPa, valve 7A1 finds time to finish to close.

Open sequencing valve 6B1 simultaneously, the gas in the B1 tower is extracted out outside the tower through valve 6B1, pipeline G46, vavuum pump P41, when the tower internal pressure be evacuated to-0.06～-during 0.09MPa, close valve 6B1.

8, three all rise E ₃R

Open sequencing valve 4A1,4A3, equal for the third time pressure drop gas is all calmed the anger to the A1 tower through valve 4A3, pipeline G34,4A1 and is boosted in the tower A3, after two pressure tower balances, closes valve 4A1,4A3.

Open high sequencing valve 4B1,4B3 simultaneously.Equal for the third time pressure drop gas is all calmed the anger to the B1 tower through valve 4B3, pipeline G44, valve 4B1 and is boosted in the tower B3, after two pressure tower balances, closes valve 4B1,4B3.

9, isolate I for the second time ₂

A1 tower and all sequencing valves of B1 tower are in closed condition, wait pending next step.

10, two all rise E ₂R

Open sequencing valve 4A1,4A4, for the second time equal pressure drop gas is all calmed the anger to the A1 tower through valve 4A4, pipeline G34, valve 4A1 and is boosted in the tower A4, after two pressure tower balances, closes 4A1,4A4.

Open sequencing valve 4B1,4B4 simultaneously, for the second time equal pressure drop gas is all calmed the anger to the B1 tower through valve 4B4, pipeline G44, valve 4B1 and is boosted in the tower B4, after two pressure tower balances, closes 4B1,4B4.

12, isolate I for the third time ₃

A1, all sequencing valves of B1 tower are in closed condition, wait pending next step.

13, one all rise E ₁R

Open sequencing valve 3A1,3A5, the interior drop pressure gas for the first time of tower A5 is all calmed the anger to the A1 tower through valve 3A5, pipeline G33, valve 3A1 and is boosted, after two pressure tower balances, and shut off valve 3A1,3A5.

Open sequencing valve 3B1,3B5 simultaneously, the interior drop pressure gas for the first time of tower B5 is all calmed the anger to A1 through valve 3B5, pipeline G43, valve 3A1 and is boosted, after two pressure tower balances, and shut off valve 3B1,3B5.

14, the FR that finally boosts

Open sequencing valve 3A1,3A6, the A6 tower section that is in adsorption step is worked off one's feeling vent one's spleen and through valve 3A6, pipeline G33 valve 3A1 the A1 tower is finally boosted, and closes valve 3A1,3A6 after the A1 pressure tower reaches absorption affinity.

Open sequencing valve KV41,3B1 simultaneously, hydrogen, nitrogen product gas finally boost to the B1 tower through pipeline G42, pipeline G42, valve KV41, valve 3B1, when the B1 pressure tower rises to adsorptive pressure, close valve KV41,3B1.

So far, A1 tower and B1 tower have been finished a circulation, can enter next sorption cycle again.The circulation step of the adsorption tower of A2 and B2 to B6 is the same with A1 and B1, just staggers mutually on the time.

The present embodiment result is products C O ₂Purity 99.5%, CO ₂Yield is greater than 70%.CO in product hydrogen, the nitrogen ₂Concentration is less than 0.2% (V), hydrogen yield 98% (V), and the nitrogen yield is greater than 94% (V).

Embodiment 3:

Other condition is identical with embodiment 1, and difference is thick hydrogen, ammonia to be forced into 1.8Mpa enter second group of adsorption tower because second group of increased pressure, second group of adsorption tower volume be decreased to first group 2/3rds.Operation result is CO ₂Purity 99.5 (V), yield is greater than 70%, CO in hydrogen, the nitrogen ₂Less than 0.2% (V), hydrogen yield 98.5%, nitrogen yield 94%.

Claims

1, a kind of from conversion gas separation of hydrogen, nitrogen and pure CO ₂Pressure swing adsorption method, conversion gas imports the conversion gas of the coal generating gas of air or oxygen enrichment for being raw material with the coal in the gas-making process, use first, second group adsorption tower serial operation, first group of adsorption tower is used to the CO that purifies ₂Product, second group of adsorption tower is used for purified hydrogen, nitrogen product, and conversion gas at first enters the adsorption tower that is in adsorption step in first group of adsorption tower and adsorbs, and adsorbent is selected the easy adsorbent component CO of absorption in bed ₂Deng component, be difficult for adsorbent component hydrogen, nitrogen and a part of CO ₂Discharge from the port of export and send into the adsorption tower that is in adsorption step second group of adsorption tower and adsorb Deng gas, adsorbent is selected CO absorption in the bed ₂, being difficult for adsorbent component hydrogen, nitrogen and discharging from the port of export and obtain product hydrogen, nitrogen, the stripping gas of first group of adsorption tower is products C O ₂, first group of adsorption tower comprises absorption A, drop pressure ED, CO successively in a cycle period ₂Gas displacement P vacuumizes VC, the ER that boosts that all calms the anger, and the FR pressure swing adsorption technique step of finally boosting, second group of adsorption tower comprises absorption A successively in a cycle period, drop pressure ED vacuumizes VC, boost pressure ER, the FR pressure swing adsorption technique step of finally boosting.

2, according to the pressure swing adsorption method of claim 1, CO in work off one's feeling vent one's spleen (thick hydrogen, the nitrogen) of first group of adsorption tower ₂The mean concentration percent by volume is 1-8%.

3, method according to claim 1 is characterized in that first group of adsorption tower has between the P in drop pressure ED and displacement forward to put the pressure step.

4, method according to claim 1 and 2 is characterized in that the drop pressure ED of second group of adsorption tower and vacuumizes to have between the VC step forward to put pressing or the reverse pressure PP step of putting.

5,, it is characterized in that first and second group adsorption tower has isolation step I between boost pressure ER or drop pressure ED step according to claim 1,2 or 3 described methods.

6, method according to claim 1, the number that it is characterized in that every group of adsorption tower are 2-24, and two groups of adsorption tower numbers can be unequal, and the tower number that is in adsorbed state simultaneously can be two or more, and vacuum lines is more than one or one.

7, method according to claim 1, the adsorbent that it is characterized in that adsorption tower are a kind of in activated alumina, active carbon, silica gel, the zeolite molecular sieve or constitute the layering combination cot by wherein several.

8, according to claim 1,2 or 3 described methods, the pressure that it is characterized in that replacing the P step is 0-0.3MPa.

9, according to claim 1,2 or 3 described methods, the pressure that it is characterized in that adsorbing the A step is 0.1--3.0MPa, and two groups adsorptive pressure can be unequal.

10,, it is characterized in that entering second group of adsorption tower behind the thick hydrogen, nitrogen pressure of first group of adsorption tower port of export according to claim 1,2 or 3 described methods.