CN1268413C - Two-stage pressure-variable adsorption process for decarbonizing raw gas in production of urea - Google Patents

Abstract

The present invention discloses a pressure-swing adsorption decarburising method for raw gas in the process of carbamide production. A first-stage pressure-swing adsorption device sequentially has the processing steps of adsorption A, equalizing pressure reduction ED, product carbon dioxide replacement P, product carbon dioxide pressure reduction D, vacuum pumping VC, equalizing pressure rise ER and final pressure rise FR in one cycle period; a second-stage pressure-swing adsorption device sequentially has the processing steps of adsorption A, equalizing pressure reduction ED, backward discharging BD, vacuum pumping VC, equalizing pressure rise ER and final pressure rise FR in one cycle period; when the equalizing pressure reduction ED of the first-stage pressure-swing adsorption device ends, the concentration of carbon dioxide in the instant flowing gas of an adsorption tower is from 50 to 96%(V); a specific adsorbent combination is filled in the adsorption tower of the first-stage pressure-swing adsorption device from the bottom to the top. Compared with the prior art, the present invention has the advantages of high recovery rate of nitrogen of devices, large investment saving, low operating cost, high adsorbent pressure and obvious technical economy benefit.

Description

Two sections transformation absorption of unstripped gas decarbonizing urea method in the urea production

The present invention relates to urea production process, relate in particular to and adopt two sections transformations absorption decarbonizing urea methods from gas-making process with the coal is the synthetic-ammonia transformation gas of raw material, to carry out the method for decarbonizing urea.

We know, in the synthetic ammonia urea production process, carbon dioxide in the conversion gas need be purified to more than 98.5% (V), also need simultaneously the hydrogen in the conversion gas, nitrogen separation origin, carbon dioxide in hydrogen, the nitrogen generally requires less than 0.2% (V), therefore, in fact decarbonizing urea is exactly purifying carbon dioxide and separation of hydrogen, nitrogen from conversion gas.Adopt two-stage pressure swing adsorption to carry out the method for decarbonizing urea from conversion gas, existing disclosed abroad patent documentation report is as United States Patent (USP): U.S.Pat.Nos.4,171,207; 4,790,858; 5,133,785.In United States Patent (USP) (U.S.Pat.Nos.4,171,207; 4,790,858; 5,133,785) in, adopted two-stage pressure swing adsorption apparatus, but its conversion gas is to be that raw material obtains through transforming with the natural gas, carbon dioxide content is lower in the conversion gas, have only about 20% (V), be used for the synthetic carbon dioxide quantity not sufficient of urea, recovery rate of CO 2 generally requires more than 95～99%, and adding the product that requires to obtain is pure carbon dioxide and pure hydrogen, so, thereafter a stage pressure swing adsorption apparatus adopts general transformation absorption process for making hydrogen, washes reproducing adsorbent with hydrogen, and hydrogen recovery rate is low.If above-mentioned patent is used for synthetic-ammonia transformation gas purifying carbon dioxide that gas-making process is raw material with the coal and separation of hydrogen, nitrogen, then not only hydrogen, rate of recovery of nitrogen are very low, and power consumption and investment are also very high, increased the cost of synthetic nitrogen, therefore external above-mentioned being used for the natural gas is the synthetic ammonia decarbonizing urea patented technology of raw material and to be not suitable for domestic be the synthetic ammonia decarbonizing urea of raw material with the coal.

Be in the synthetic ammonia decarbonizing urea technology of raw material at home with the coal, mostly adopt Physical Absorption method and chemical absorption method several years ago, wet method decarbonization process such as improvement hot potash method, improvement MDEA method, carbon third method and NHD method are more typically arranged, shortcoming such as these methods have the operation and maintenance costs height, solvent toxicity is big, technological process is complicated and labour intensity is big.Because domestic is the particularity that the synthetic ammonia urea production decarburization of raw material requires with the coal, require hydrogen nitrogen recovery height in the conversion gas on the one hand, on the other hand, carbon dioxide content is higher in the conversion gas, about about 27～29% (V), it is excessive to be used for the synthetic carbon dioxide of urea, the general requirement of product recovery rate of CO 2 gets final product greater than 68～70%, so nearest 2 years, domestic-developed has gone out new employing two-stage pressure swing adsorption carries out decarbonizing urea from conversion gas method, as Chinese patent publication number: CN1235862A (the open date: on November 24th, 1999); CN1248482A (the open date: on March 29th, 2000), above-mentioned two technology are compared with the wet method decarbonization process, technological process is simple, labour intensity is little, maintenance cost is low and eliminated solvent toxicity, the integrated operation expense is lower than wet method decarburization when low pressure is adsorbed, but, when adsorptive pressure was higher, its investment and integrated operation expense did not totally relatively have advantage than carbon third method and NHD method decarburization height.

(the open date: on November 24th, 1999), adopted two-stage pressure swing adsorption apparatus, the product of Huo Deing is pure carbon dioxide and hydrogen, nitrogen simultaneously at Chinese patent publication number: CN1235862A.From specification as can be seen, the purpose of its invention is, in first stage pressure swing adsorption apparatus, use before the product carbon dioxide replacement, allow the interior gas concentration lwevel of adsorption tower improve as far as possible, to reduce displacement tolerance, energy efficient, for this reason, increased pre-absorption FA and adsorb LA again and all press to finish after forward put to steps such as normal pressures, product carbon dioxide replacement pressure is normal pressure, the highest equal pressure drop number of times of adsorption tower is 6 times, after the equal pressure drop end of adsorption tower, being recycled to pressurizes in the unstripped gas again enters pressure-swing absorption apparatus to last portion gas along putting in the adsorption tower, and the suitable emptying of a part of gas in back is to normal pressure.If adopt this patent disclosure with some carbon dioxide and the pressurization of other gas circulation, then increase pressure swing adsorption decarbonization device and compressor load on the one hand and increased investment, increased the power consumption of pressure swing adsorption decarbonization device vavuum pump and compressor on the other hand again, adsorptive pressure is high more, circulating flow rate is many more, and investment that pressure swing adsorption decarbonization device and compressor increase and power consumption are just many more.For example when adsorptive pressure is 2.1MPa, adsorption column pressure drops to 0.12～0.15MPa after adopting 6 equal pressure drops, its carbon dioxide circulating flow rate will account for 35～40% of total carbon dioxide capacity in the raw material conversion gas, with adsorptive pressure is that 0.7MPa compares pressure swing adsorption decarbonization plant investment increase about 45～50% (comprising the investment that compressor increases), and the pressure swing adsorption decarbonization power consumption increases (be mainly compressor and increase power consumption) 50～60%.When adsorptive pressure was less than or equal to 0.8MPa (G), this method can be reduced investment outlay and energy consumption, compared with the wet method decarburization to have greater advantage.But, when adsorptive pressure during, adopt this method investment and energy consumption but will increase, and adsorptive pressure is high more more than or equal to 0.8MPa (G), investment and energy consumption increase are many more.

Equally, (the open date: on March 29th, 2000), also adopted two-stage pressure swing adsorption apparatus, the product of Huo Deing is pure carbon dioxide and hydrogen, nitrogen simultaneously at Chinese patent publication number: CN1248482A.In accessory rights claim and the specification as can be seen, first, in two sections pressure swing adsorption decarbonization technology of its independent claims record, adsorption column pressure may also may be higher than normal pressure for normal pressure before vacuumizing after the equal pressure drop ED of the displacement pressure that the first stage pressure swing adsorption apparatus product carbon dioxide replacement step adopts and second stage pressure swing adsorption apparatus finishes, when all the pressure drop number of times is abundant after adsorption tower absorption finishes, adsorption column pressure can be normal pressure before vacuumizing after the equal pressure drop ED of the first stage pressure swing adsorption apparatus product carbon dioxide replacement pressure and second stage pressure swing adsorption apparatus finishes, but this will increase plant investment, the high more number of times of all pressing of adsorptive pressure is many more, the plant investment increase is big more, for example when adsorptive pressure is 2.1MPa, adopt 13～15 equal pressure drops adsorption column pressure could be dropped near normal pressure, with adsorptive pressure is that 0.7MPa compares first section and second stage pressure swing adsorption apparatus investment increase about 40～50%, and power consumption increases about 10%; Equal pressure drop number of times more after a little while after adsorption tower absorption finishes, adsorption column pressure is higher than normal pressure before vacuumizing after the equal pressure drop ED of the first stage pressure swing adsorption apparatus product carbon dioxide replacement pressure and second stage pressure swing adsorption apparatus finishes, because adsorption column pressure is not decompressed to close with gas holder pressure and the equal pressure drop ED of second stage pressure swing adsorption apparatus does not drop to normal pressure before vacuumizing after finishing and just directly vacuumizes after the first stage pressure swing adsorption apparatus product carbon dioxide replacement P step, not only wasted vacuum capability, increase the vavuum pump power consumption, and gases at high pressure periodically enter vavuum pump, influence the life-span of vavuum pump and the formation of water ring, and then influence vacuumizes efficient, can damage the important spare part of vavuum pump when serious, vavuum pump can't be moved, the product amount of carbon dioxide of pressurized displacement is more approximately than the normal pressure displacement simultaneously, therefore, the used power consumption of the carbon dioxide of compression pressurized displacement is replaced many than normal pressure, all the pressure drop number of times is few more, adsorption column pressure is high more before vacuumizing after the equal pressure drop ED of the first stage pressure swing adsorption apparatus product carbon dioxide replacement pressure and second stage pressure swing adsorption apparatus finishes, the vavuum pump power consumption increases manyly more, and is just serious more to the damage of vavuum pump important spare part.Second, problem that two sections pressure swing adsorption decarbonization technology of its dependent claims 3 and 4 records exist and shortcoming are except increasing the vavuum pump power consumption, influence the life-span of vavuum pump and the formation of water ring, the important spare part of badly damaged vavuum pump, make outside vavuum pump can't move, when along adsorption column pressure after putting PP when low, the product carbon dioxide of recovery can not satisfy urea production, adsorptive pressure is high more, and the problems referred to above and shortcoming that Chinese patent publication number: CN1248482A exists are serious more.When adsorptive pressure was less than or equal to 0.8MPa (G), this method can be reduced investment outlay and energy consumption, compared with the wet method decarburization to have greater advantage.But, when adsorptive pressure during, adopt this method investment and energy consumption but will increase, even the product carbon dioxide that recovery occurs can not satisfy the situation of urea production, and the high more the problems referred to above of adsorptive pressure are serious more more than or equal to 0.8MPa (G).In addition, on Chinese patent publication number: CN1248482A (the open date: on March 29th, 2000), the adsorbent of filling has used zeolite molecular sieve in its adsorption tower, the loss of nitrogen will be increased, this be because carbon dioxide and nitrogen the separation on the zeolite molecular sieve much smaller than carbon dioxide and nitrogen the separation on silica gel, if adopt zeolite molecular sieve, then the loss of nitrogen will increase greatly in the conversion gas, can not satisfy urea production like this.

The purpose of this invention is to provide two sections pressure swing adsorption decarbonization methods of a kind of urea unstripped gas, solve the above-mentioned problems in the prior art, and improved the rate of recovery of nitrogen of device.Reduce investment outlay significantly and operating cost,, obtain than the more and more obvious technology economy advantage of prior art along with increasing of adsorptive pressure.

The objective of the invention is to realize by following technological means.

Unstripped gas pressure swing adsorption decarbonization method in the urea production, unstripped gas is that gas-making process is the synthetic-ammonia transformation gas of raw material with the coal, the method adopts two stage pressure swing adsorption apparatus serial operations, first stage pressure swing adsorption apparatus is used for the purifying carbon dioxide product, and second stage pressure swing adsorption apparatus is used for separation of hydrogen, nitrogen product.Conversion gas enters the adsorption tower that first stage pressure swing adsorption apparatus is in adsorption step, adsorbent in the adsorption tower optionally adsorbs the water in the conversion gas successively, organic sulfur, component such as inorganic sulfur and carbon dioxide, Xi Fu partial CO 2 and be difficult for the carbon monoxide of absorption not, methane, nitrogen, components such as hydrogen flow out from the port of export and enter the adsorption tower that second stage pressure swing adsorption apparatus is in adsorption step, adsorbent in the adsorption tower is absorbing carbon dioxide optionally, is difficult for the carbon monoxide of absorption, methane, nitrogen, components such as hydrogen are discharged the compression section that enters synthetic ammonia from the port of export.The adsorption tower of first stage pressure swing adsorption apparatus experiences absorption A successively in a cycle period, equal pressure drop ED, product carbon dioxide replacement P, product carbon dioxide step-down D, vacuumize VC, equal voltage rise ER, the FR pressure swing adsorption technique step of finally boosting, the gas that the first stage pressure swing adsorption apparatus adsorption tower is emitted in product carbon dioxide step-down D step and be the product carbon dioxide vacuumizing the gas that the VC step extracts out, the adsorption tower of second stage pressure swing adsorption apparatus experiences absorption A successively in a cycle period, equal pressure drop ED, the contrary BD of putting, vacuumize VC, equal voltage rise ER, the FR pressure swing adsorption technique step of finally boosting, the gaseous mixture that second stage pressure swing adsorption apparatus is in the adsorption tower outlet outflow of adsorption step is mainly nitrogen, hydrogen is at nitrogen, also contain a spot of carbon monoxide and methane in the hydrogen product.After the equal pressure drop ED of first stage pressure swing adsorption apparatus finished, adsorption tower outlet gas concentration lwevel was 50～95% (V), and the best is 75～90% (V).

After the means as above, the present invention compared with prior art reduces investment outlay and operating cost significantly, and has improved the rate of recovery of nitrogen of device.

When reality is implemented, reach service condition preferably for making system, can do following the adjustment to concrete processing step.

The adsorbent that loads from down to up in the first stage pressure swing adsorption apparatus adsorption tower is followed successively by activated alumina, active carbon and Kiselgel A; Or activated alumina and active carbon; Or activated alumina and Kiselgel A, the adsorbent of filling only is a Kiselgel A in the second stage pressure swing adsorption apparatus adsorption tower, adopt above-mentioned specific adsorbent to make up the saturation water that can remove on the one hand in the conversion gas, organic sulfur and inorganic sulfur, the main on the other hand rate of recovery of nitrogen that can make is very high, the Kiselgel A that loads in the first stage pressure swing adsorption apparatus adsorption tower is a large amount of, account for 50～80% of the interior three kinds of adsorbent total amounts of adsorption tower, activated alumina wherein and active carbon are mainly used in the saturation water that removes respectively in the conversion gas, organic sulfur and inorganic sulfur, what of consumption are by the saturation water in the conversion gas, organic sulfur and rate and inorganic sulphur content decision.

After the first stage pressure swing adsorption apparatus product carbon dioxide replacement P step finishes, earlier the product carbon dioxide in the adsorption tower is put into and all pressed surge tank, when adsorption tower and after all pressing surge tank pressure in a basic balance, again the product carbon dioxide in the adsorption tower is put into gas holder, it mainly is to prevent after product carbon dioxide replacement P step finishes that this purpose of all pressing surge tank is set, directly the product carbon dioxide in the adsorption tower is put into gas holder, in order to avoid cause gas holder height moment too fast gas holder is dashed of rising to turn over or the excessive emptying of product carbon dioxide can not be satisfied urea production.

The mean concentration of carbon dioxide was 2～9% (V) during first stage pressure swing adsorption apparatus was worked off one's feeling vent one's spleen, and in this scope, the high more effect of the mean concentration of carbon dioxide is good more.

When the equal pressure drop ED of first stage pressure swing adsorption apparatus finishes, gas concentration lwevel was 50～96% (V) during the adsorption tower transient flow was given vent to anger, the best is 75～90% (V), and the pressure after all pressure drop ED finishes is product carbon dioxide replacement pressure, and its number range is generally 0.02～0.9MPa.

The pressure of two-stage pressure swing adsorption apparatus adsorption step A is 0.6～3.6MPa, and the adsorptive pressure of two-stage pressure swing adsorption apparatus can be unequal.

Description of drawings is as follows:

Fig. 1 is the process chart of the embodiment of the invention 1.

Fig. 2 is the processing step working procedure table of the embodiment of the invention 1 first stage pressure swing adsorption apparatus adsorption tower.

Fig. 3 is the processing step working procedure table of the embodiment of the invention 1 second stage pressure swing adsorption apparatus adsorption tower.

Fig. 4 is the process chart of the embodiment of the invention 2.

Fig. 5 is the processing step working procedure table of the embodiment of the invention 2 first stage pressure swing adsorption apparatus adsorption towers.

Fig. 6 is the processing step working procedure table of the embodiment of the invention 2 second stage pressure swing adsorption apparatus adsorption towers.

Fig. 7 is the process chart of the embodiment of the invention 3.

Fig. 8 is the processing step working procedure table of the embodiment of the invention 3 first stage pressure swing adsorption apparatus adsorption towers.

Fig. 9 is the processing step working procedure table of the embodiment of the invention 3 second stage pressure swing adsorption apparatus adsorption towers.

Embodiments of the present invention:

Unstripped gas of the present invention is that gas-making process is the synthetic-ammonia transformation gas of raw material with the coal, its typical table composed as follows:

Component	H 2	N 2	CO 2	CO	CH 4	O 2+Ar	Total sulfur	H 2O (vapour)
									Concentration (%) (V)	46～ 55	15～ 18	22～ 32	0.3～8	1～2	≤0.8	≤ 300mg/Nm 3	Saturated

The present invention adopts two-stage pressure swing adsorption to carry out the essence decarburization from conversion gas, first stage pressure swing adsorption apparatus is used for the purifying carbon dioxide product, the mean concentration of carbon dioxide was 2～9% (V) during its adsorption tower was worked off one's feeling vent one's spleen, the adsorbent that loads from down to up in the adsorption tower is an activated alumina, active carbon and Kiselgel A, or be activated alumina and active carbon, or be activated alumina and Kiselgel A, the carbon dioxide (mean concentration is 2～9% (V)) that second stage pressure swing adsorption apparatus is used for first stage pressure swing adsorption apparatus is worked off one's feeling vent one's spleen is removed to below 0.2%, and the adsorbent of filling is a Kiselgel A in the adsorption tower.Each adsorption tower of two-stage pressure swing adsorption apparatus experiences following steps successively in a circulation.

First stage pressure swing adsorption apparatus:

(1) absorption A

The conversion pneumatic transmission is gone into to be in the adsorption tower charging aperture of adsorption step, adsorbent in the adsorption tower optionally adsorbs the water in the conversion gas successively, component such as organic sulfur and inorganic sulfur and carbon dioxide, Xi Fu partial CO 2 and be difficult for the carbon monoxide of absorption not, methane, nitrogen, components such as hydrogen flow out from the port of export and enter the adsorption tower that second stage pressure swing adsorption apparatus is in adsorption step, As time goes on, adsorbent water, the total amount of component such as organic sulfur and inorganic sulfur and carbon dioxide constantly increases, when the adsorbents adsorb said components is saturated, stop air inlet, this moment, absorption finished.Gas concentration lwevel can be controlled at 2～9% (V) in working off one's feeling vent one's spleen.

(2) equal pressure drop ED

After absorption finishes, hydrogen in the dead space gas in the adsorption tower, nitrogen gas concn is higher and gas concentration lwevel is lower, this part hydrogen, nitrogen need be recycled on the one hand, gas concentration lwevel needs to improve in the adsorption tower on the other hand, for this reason, must be the gas in the adsorption tower along adsorbing direction from the step-down of adsorption tower exit.The gradation of dead space gas is discharged from adsorption tower outlet and is entered this section and finished the corresponding adsorption tower of evacuation step and boost, gas of every row is just all pressed once, along with the increase of all pressing number of times, the gas concentration lwevel in adsorption tower exit constantly increases, and hydrogen, nitrogen obtain recycling simultaneously.All press number of times to finish the gas concentration lwevel decision in adsorption tower exit, back by adsorptive pressure and absorption.Promptly all press number of times to satisfy and all press the gas concentration lwevel that finishes adsorption tower exit, back in 50～96% (V) scope, best in 75～90% (V) scope.

(3) product carbon dioxide replacement P

After all pressure drop finishes, with a part of product carbon dioxide pressurization, enter adsorption tower from the adsorption tower bottom inlet, replace other component along the absorption direction by adsorption tower, displace implication emptying or use it for anything else, displacement pressure is necessary for equal pressure drop and finishes back adsorption tower internal pressure.

(4) product carbon dioxide step-down D

After the replacement completion, the product carbon dioxide in the adsorption tower is put into all pressed surge tank earlier, after adsorption tower and the pressure of all pressing surge tank are in a basic balance, again the product carbon dioxide in the adsorption tower is put into gas holder until near gas holder pressure.

(5) vacuumize VC

After the step-down of product carbon dioxide finished, adsorbent carbon dioxide being released with vavuum pump from the adsorption tower bottom entered product carbon dioxide gas holder, promptly obtains carbon dioxide product.

(6) equal voltage rise ER

Vacuumize after VC finishes, the gas that utilizes the equal voltage drop step of this section to discharge enters adsorption tower from the port of export, makes the adsorption tower pressure that progressively raises, and all voltage rise equates with the number of times of equal pressure drop.The gas of each all voltage rises is from the equal pressure drop gas of different adsorption towers.

(7) FR that finally boosts

After all voltage rise finishes, utilize the adsorption tower that is in adsorption step to work off one's feeling vent one's spleen and adsorption tower is boosted, until being raised to adsorptive pressure from the top.

Second stage pressure swing adsorption apparatus

(1) absorption A

The adsorption tower that first stage pressure swing adsorption apparatus is in adsorption step is worked off one's feeling vent one's spleen and is sent into the adsorption tower that second stage pressure swing adsorption apparatus is in adsorption step, adsorbent in the adsorption tower is absorbing carbon dioxide optionally, and components such as the carbon monoxide of difficult absorption, methane, nitrogen, hydrogen are discharged the compression section that enters synthetic ammonia from the port of export.As time goes on, adsorbent total carbon dioxide capacity constantly increases, and when the adsorbents adsorb carbon dioxide is saturated, stops air inlet, and this moment, absorption finished, and gas concentration lwevel must be controlled at below 0.2% (V) in working off one's feeling vent one's spleen.

(2) equal pressure drop ED

After absorption finished, hydrogen in the dead space gas in the adsorption tower, nitrogen gas concn were higher, and this part hydrogen, nitrogen need be recycled.The gradation of dead space gas is discharged from adsorption tower outlet and is entered this section and finished the corresponding adsorption tower of evacuation step and boost, and gas of every row is just all pressed once, and along with the increase of all pressing number of times, the gas concentration lwevel in adsorption tower exit constantly increases.All press number of times to finish the gas concentration lwevel decision in adsorption tower exit, back by adsorptive pressure and absorption.

(3) the contrary BD of putting

After all pressure drop ED finished, gas pressure also was higher than atmospheric pressure in the adsorption tower, and gas concentration lwevel is higher, in order to save the vavuum pump power consumption, with the reverse emptying of this part gas or return raw material system.

(4) vacuumize VC

Contrary put end after, from the adsorption tower bottom with vavuum pump with the emptying of releasing of adsorbent carbon dioxide and other component, make adsorbent obtain regeneration.

(5) equal voltage rise ER

After vacuumizing end, the gas that utilizes equal voltage drop step to discharge enters from the port of export and to finish the adsorption tower that vacuumizes step, makes the adsorption tower pressure that progressively raises, and all voltage rise equates with the number of times of equal pressure drop.The gas of each all voltage rises is from the equal pressure drop gas of different adsorption towers

(6) FR that finally boosts

After all voltage rise finishes, utilize the adsorption tower that is in adsorption step to work off one's feeling vent one's spleen and adsorption tower is boosted, until being raised to adsorptive pressure from the top.

Embodiments of the invention 1:

This routine unstripped gas adopts the synthetic-ammonia transformation gas of gap method gas making acquisition for being raw material with the anthracite.Adopt the present invention the carbon dioxide in this synthetic-ammonia transformation gas to be purified and separation hydrogen, nitrogen wherein.

Fig. 1 is the process chart of present embodiment.

Fig. 2 is the processing step working procedure table of present embodiment first stage pressure swing adsorption apparatus.

Fig. 3 is the processing step working procedure table of present embodiment second stage pressure swing adsorption apparatus.

The synthetic-ammonia transformation gas of present embodiment is composed as follows:

Component H ₂N ₂CO ₂CO CH ₄O ₂+ Ar total sulfur water (vapour)

Concentration V% 52～53 17～18 28≤0.8 1～2≤0.8 150mg/Nm ³Saturated

Temperature :≤40 ℃

Pressure: 0.7MPa (G)

As shown in Figure 1, adsorption tower A～H is totally 8 composition first stage pressure swing adsorption apparatus, the adsorbent that loads from down to up in the adsorption tower is followed successively by activated alumina, active carbon and Kiselgel A, moves single tower absorption and all presses program four times, utilizes vacuum pipeline G19 that adsorption tower is vacuumized by vavuum pump P1; Adsorption tower a～g is totally 7 composition second stage pressure swing adsorption apparatus, and the adsorbent of filling is a Kiselgel A in the adsorption tower, moves single tower absorption and all presses program four times, utilizes vacuum pipeline G27 that adsorption tower is vacuumized by vavuum pump P2.P1, C, V1, V are respectively the first stage pressure swing adsorption apparatus vavuum pump, compressor, product carbon dioxide intermediate buffering jar and product carbon dioxide gas holder, and P2 is the second stage pressure swing adsorption apparatus vavuum pump.Present embodiment is with above-mentioned two stage pressure swing adsorption apparatus serial operations, first stage pressure swing adsorption apparatus is purified to carbon dioxide more than 98.5% (V), be used for urea synthesis, the second stage pressure swing adsorption apparatus effect is that working off one's feeling vent one's spleen of first stage pressure swing adsorption apparatus further purified, make in the hydrogen, nitrogen of the second stage pressure swing adsorption apparatus adsorption tower a～g upper end outlet gas concentration lwevel less than 0.2% (V), to satisfy the needs of next step operation of synthetic ammonia.

Conversion gas enters the adsorption tower that first stage pressure swing adsorption apparatus is in adsorption step, adsorbent in the adsorption tower optionally adsorbs the components such as water, organic sulfur, inorganic sulfur and carbon dioxide in the conversion gas successively, components such as the carbon monoxide of Xi Fu partial CO 2 and difficult absorption, methane, nitrogen, hydrogen are not discharged from the port of export and are entered the adsorption tower that second stage pressure swing adsorption apparatus is in adsorption step, adsorbent in the adsorption tower is absorbing carbon dioxide optionally, and components such as the carbon monoxide of difficult absorption, methane, nitrogen, hydrogen are discharged from the port of export and entered compression section.The adsorption tower of first stage pressure swing adsorption apparatus experiences absorption A successively in a cycle period, one all falls E1D, two all fall E2D, three all fall E3D, four all fall E4D, product carbon dioxide replacement P, product carbon dioxide step-down D, vacuumize VC, four all rise E4R, three all rise E3R, two all rise E2R, one all rises E1R, the FR pressure swing adsorption technique step of finally boosting, first stage pressure swing adsorption apparatus is the product carbon dioxide at product carbon dioxide step-down D with the gas that vacuumizes the acquisition of VC step, the adsorption tower of second stage pressure swing adsorption apparatus experiences absorption A successively in a cycle period, one all falls E1D, two all fall E2D, three all fall E3D, four all fall E4D, the contrary BD of putting, vacuumize VC, four all rise E4R, three all rise E3R, two all rise E2R, one all rises E1R, the FR pressure swing adsorption technique step of finally boosting, the gaseous mixture that second stage pressure swing adsorption apparatus is in the adsorption tower outlet discharge of adsorption step is mainly nitrogen, hydrogen product wherein also contains a spot of carbon monoxide and methane.Be example with the A tower now, contrast Fig. 2 illustrates the processing step of the present embodiment first stage pressure swing adsorption apparatus adsorption tower in a cyclic process:

(1) absorption A

At this moment, the A tower has been finished the FR step of finally boosting, open sequencing valve 1A, 2A, conversion gas enters adsorption tower A through pipeline G11, in the A adsorption tower, adsorbent optionally adsorbs the water in the conversion gas successively, organic sulfur, component such as inorganic sulfur and carbon dioxide, Xi Fu partial CO 2 and be difficult for the carbon monoxide of absorption not, methane, nitrogen, components such as hydrogen flow out through sequencing valve 2A from the port of export and enter the adsorption tower that second stage pressure swing adsorption apparatus is in adsorption step, As time goes on, adsorbent water, the total amount of component such as organic sulfur and inorganic sulfur and carbon dioxide constantly increases, when the adsorbents adsorb said components is saturated, stop air inlet, this moment, absorption finished, and gas concentration lwevel is controlled at 9% (V) in working off one's feeling vent one's spleen.

(2) for the first time equal voltage drop step is called for short one and all falls E1D

After absorption finishes, open sequencing valve 3A, 3C, the gas in the A tower enters the C tower through pipeline G13 to carry out one to the C tower and all rises, and after A and C pressure tower are in a basic balance, closes sequencing valve 3A.

(3) for the second time equal voltage drop step is called for short two and all falls E2D

One all end is fallen and after, open sequencing valve 4A, 4D, the gas in the A tower enters the D tower through pipeline G14 to carry out two to the D tower and all rises, and after A and D pressure tower are in a basic balance, closes sequencing valve 4D.

(4) equal for the third time voltage drop step is called for short three and all falls E3D

Two all end is fallen and after, open sequencing valve 4E, the gas in the A tower enters the E tower through pipeline G14 to carry out three to the E tower and all rises, and after A and E pressure tower are in a basic balance, closes sequencing valve 4A.

(5) the 4th equal voltage drop step are called for short four and all fall E4D

Three all end is fallen and after, open sequencing valve 5A, 5F, the gas in the A tower enters the F tower through pipeline G15 to carry out four to the F tower and all rises, when the gas concentration lwevel in A tower exit during greater than 85% (V), close sequencing valve 5A, 5F, the interior pressure of A tower this moment is 0.07MPa (G).

(6) product carbon dioxide replacement P

Four all end is fallen and after, open sequencing valve 7A, 6A, the compressed machine C of product carbon dioxide this moment, pipeline G17 enter adsorption tower A from the import of A tower bottom, along the absorption direction adsorption tower A is replaced, be displaced the gas emptying that comes or use it for anything else, when carbon dioxide reaches the regulation requirement in displacement is dropped a hint, close sequencing valve 7A, 6A, displacement pressure is 0.07MPa (G).

(7) product carbon dioxide step-down D

After the product carbon dioxide replacement finishes, open sequencing valve 8A earlier, KV11a, V1 is communicated with product carbon dioxide intermediate buffering jar, when the A pressure tower equals the pressure of product carbon dioxide intermediate buffering jar V1 substantially, close sequencing valve KV11a, open sequencing valve KV11b, product carbon dioxide gas holder V is put in product carbon dioxide step-down in the A tower, when the pressure of A tower during near gas holder V pressure, close sequencing valve 8A, KV11b opens sequencing valve KV11c at last, and V1 is communicated with gas holder V with product carbon dioxide intermediate buffering jar, when product carbon dioxide intermediate buffering jar V1 pressure during, close sequencing valve KV11c near gas holder V pressure.

(8) vacuumize VC

After the step-down of product carbon dioxide finishes, open sequencing valve 9A, the carbon dioxide in the tower being released from the A tower bottom through pipeline G19, vavuum pump P1 enters product carbon dioxide gas holder V, vacuumize end after, close sequencing valve 9A.

(9) the 4th equal voltage rise steps are called for short four and all rise E4R

Vacuumize after VC finishes, open sequencing valve 5A, 5D, the gas in the D tower enters the A tower through pipeline G15 to carry out four to the A tower and all rises, four all end is fallen and after, close sequencing valve 5A, 5D.

(10) equal for the third time voltage rise step is called for short three and all rises E3R

Four all rise to finish after, open sequencing valve 4A, the gas in the E tower enters the A tower through pipeline G14 to carry out three to the A tower and all rises, and after E and A pressure tower are in a basic balance, closes sequencing valve 4E.

(11) for the second time equal voltage rise step is called for short two and all rises E2R

Three all rise to finish after, open sequencing valve 4F, the gas in the F tower enters the A tower through pipeline G14 to carry out two to the A tower and all rises, and after F and A pressure tower are in a basic balance, closes sequencing valve 4F, 4A.

(12) for the first time equal voltage rise step is called for short one and all rises E1R

Two all rise to finish after, open sequencing valve 3A, 3G, the gas in the G tower enters the A tower through pipeline G13 to carry out one to the A tower and all rises, and after G and A pressure tower are in a basic balance, closes sequencing valve 3G.

(13) FR that finally boosts

One all rise to finish after, open sequencing valve KV10, utilize the adsorption tower that is in adsorption step to work off one's feeling vent one's spleen and boost from the top to the A tower, when the A pressure tower rises to adsorptive pressure, close sequencing valve KV10,3A.

So far, the A tower has been finished a circulation, can enter next circulation again.B～H adsorption tower is the same with the circulation step of A tower, just staggers mutually on the time, sees Fig. 2.

Be example with a tower now, contrast Fig. 3 illustrates the processing step of the present embodiment second stage pressure swing adsorption apparatus adsorption tower in a cyclic process:

(1) absorption A

At this moment, the a tower has been finished the FR step of finally boosting, open sequencing valve 1a, 2a, conversion gas enters adsorption tower a through pipeline G21, in a adsorption tower, adsorbent optionally adsorbs the components such as carbon dioxide of first stage pressure swing adsorption apparatus in working off one's feeling vent one's spleen, Xi Fu amounts of carbon dioxide and be difficult for the carbon monoxide of absorption not, methane, nitrogen, components such as hydrogen flow out the compression section that enters synthetic ammonia from the port of export through sequencing valve 2a, As time goes on, adsorbent total carbon dioxide capacity constantly increases, when the adsorbents adsorb carbon dioxide is saturated, the gas concentration lwevel of working off one's feeling vent one's spleen is controlled at below 0.2% (V), closes sequencing valve 1a, 2a stops air inlet, this moment, absorption finished, and gas concentration lwevel is controlled at below 0.2% (V) in working off one's feeling vent one's spleen.

(2) for the first time equal voltage drop step is called for short one and all falls E1D

After absorption finishes, open sequencing valve 3a, 3c, the gas in a tower enters the c tower through pipeline G23 to carry out one to the c tower and all rises, and after a and c pressure tower are in a basic balance, closes sequencing valve 3a.

(3) for the second time equal voltage drop step is called for short two and all falls E2D

One all end is fallen and after, open sequencing valve 4a, 4d, the gas in a tower enters the d tower through pipeline G24 to carry out two to the d tower and all rises, and after a and d pressure tower are in a basic balance, closes sequencing valve 4d.

(4) equal for the third time voltage drop step is called for short three and all falls E3D

Two all end is fallen and after, open sequencing valve 4e, the gas in a tower enters the e tower through pipeline G24 to carry out three to the e tower and all rises, and after a and e pressure tower are in a basic balance, closes sequencing valve 4a.

(5) the 4th equal voltage drop step are called for short four and all fall E4D

Three all end is fallen and after, open sequencing valve 5a, 5f, the gas in a tower enters the f tower through pipeline G25 to carry out four to the f tower and all rises, and after a and f pressure tower are in a basic balance, closes sequencing valve 5a, 5f.

(6) the contrary BD of putting

Four all end is fallen and after, open sequencing valve KV13c, with the reverse emptying of the gas in a tower, when the gas in a tower drops to normal pressure, close sequencing valve 6a, KV13c.

(7) vacuumize VC

Contrary put end after, open sequencing valve 7a, through pipeline G27, vavuum pump P2 from a tower bottom the emptying of releasing of the gas in the tower, vacuumize end after, close sequencing valve 7a.

(8) the 4th equal voltage rise steps are called for short four and all rise E4R

After vacuumizing end, open sequencing valve 5a, 5c, the gas in the c tower enters a tower through pipeline G25 to carry out four to a tower and all rises, and after c and a pressure tower are in a basic balance, closes sequencing valve 5a, 5c.

(9) equal for the third time voltage rise step is called for short three and all rises E3R

Four all rise to finish after, open sequencing valve 4a, 4d, the gas in the d tower enters a tower through pipeline G24 to carry out three to a tower and all rises, and after d and a pressure tower are in a basic balance, closes sequencing valve 4d.

(10) for the second time equal voltage rise step is called for short two and all rises E2R

Three all rise to finish after, open sequencing valve 4e, the gas in the e tower enters a tower through pipeline G24 to carry out two to a tower and all rises, and after e and a pressure tower are in a basic balance, closes sequencing valve 4e, 4a.

(11) for the first time equal voltage rise step is called for short one and all rises E1R

Two all rise to finish after, open sequencing valve 3a, 3f, the gas in the f tower enters a tower through pipeline G23 to carry out one to a tower and all rises, and after f and a pressure tower are in a basic balance, closes sequencing valve 3f.

(12) FR that finally boosts

One all rise to finish after, open sequencing valve KV12, utilize the adsorption tower that is in adsorption step to work off one's feeling vent one's spleen and boost from the top to a tower, when a pressure tower rises to adsorptive pressure, close sequencing valve KV12,3a.

So far, a tower has been finished a circulation, can enter next circulation again.B～g adsorption tower is the same with the circulation step of A tower, just staggers mutually on the time, sees Fig. 3.

The present embodiment result is 99% (V) for the product carbon dioxide purity, and recovery rate of CO 2 is greater than 70% (V), and gas concentration lwevel is less than 0.1% (V) in product hydrogen, the nitrogen.

For present embodiment, adopt process of the present invention to compare with the prior art that with documents (CN1248482A) is representative, consider by producing 120000 tons of synthetic ammonia scales per year, (adsorptive pressure is 0.7MPa (G) in other condition, conversion gas is formed and temperature, the sorption cycle time, adsorbent kind and ratio, the power-equipment performance, instrument and meter and control function, special-purpose sequencing valve and hydraulic system structure and life-span) under the identical situation, synthetic ammonia decarburization power consumption decline 25% per ton (about 35 degree), the investment of decarburization original equipment can be saved about 10% (about 2,200,000 yuan).

After the equal pressure drop of present embodiment finishes, when the gas concentration lwevel in adsorption tower exit is 50% (V), adsorption tower displacement pressure is 0.16～0.18MPa (G), at this moment, compare with above-mentioned prior art, consider by producing 120000 tons of synthetic ammonia scales per year, (adsorptive pressure is 0.7MPa (G) in other condition, conversion gas is formed and temperature, the sorption cycle time, adsorbent kind and ratio, the power-equipment performance, instrument and meter and control function, special-purpose sequencing valve and hydraulic system structure and life-span) under the identical situation, synthetic ammonia decarburization power consumption decline 10% per ton (about 15 degree), the investment of decarburization original equipment can be saved about 10% (about 1,800,000 yuan).

For present embodiment, adopt particular adsorbent combination of the present invention to compare with the prior art that with documents (CN1248482A) is representative, consider by producing 120000 tons of synthetic nitrogen scales per year, (adsorptive pressure is 0.7MPa (G) in other condition, conversion gas is formed and temperature, the sorption cycle time, the power-equipment performance, instrument and meter and control function, special-purpose sequencing valve and hydraulic system structure and life-span) under the identical situation, (nitrogen loss reduction changes with the ratio that molecular sieve and activated carbon account for nitrogen loss reduction average out to 55% of the present invention, 55% reduction is the mean value under the various ratios), synthetic ammonia decarburization power consumption per ton on average descends 12% (about 18 degree), decarburization original equipment investment can be saved 2.5% (about 500,000 yuan), annually increases about 1,900,000 yuan (comprising the benefit that reduces the synthetic ammonia ability to be increased produce because of the nitrogen loss and the electricity charge of saving).。

For present embodiment, adopt the surge tank of all pressing of the present invention can prevent after product carbon dioxide replacement P step finishes, directly the product carbon dioxide in the adsorption tower is put into gas holder, make the excessive emptying of product carbon dioxide can not satisfy urea production in order to avoid cause gas holder height to rise too fast.

Embodiments of the invention 2:

Condition such as the conversion gas composition of present embodiment and temperature, adsorbent kind and ratio, power-equipment performance, instrument and meter and control function, special-purpose sequencing valve and hydraulic system structure and life-span and embodiment 1 are in full accord, and the adsorptive pressure of present embodiment is 2.1MPa (G).

As shown in Figure 4, adsorption tower A～I is totally 9 composition first stage pressure swing adsorption apparatus, the adsorbent that loads from down to up in the adsorption tower is followed successively by activated alumina, active carbon and Kiselgel A, moves single tower absorption and all presses program five times, utilizes vacuum pipeline G19 that adsorption tower is vacuumized by vavuum pump P1; Adsorption tower a～i is totally 9 composition second stage pressure swing adsorption apparatus, and the adsorbent of filling is a Kiselgel A in the adsorption tower, moves single tower absorption and all presses program six times, utilizes vacuum pipeline G27 that adsorption tower is vacuumized by vavuum pump P2.P1, C, V1, V are respectively the first stage pressure swing adsorption apparatus vavuum pump, compressor, product carbon dioxide and all press surge tank and product carbon dioxide gas holder, and P2 is the second stage pressure swing adsorption apparatus vavuum pump.Present embodiment is with above-mentioned two stage pressure swing adsorption apparatus serial operations, first stage pressure swing adsorption apparatus is purified to carbon dioxide more than 98.5% (V), be used for urea synthesis, the second stage pressure swing adsorption apparatus effect is that working off one's feeling vent one's spleen of first stage pressure swing adsorption apparatus further purified, make in the hydrogen, nitrogen of the second stage pressure swing adsorption apparatus adsorption tower a～i upper end outlet gas concentration lwevel less than 0.2% (V), to satisfy the needs of next step operation of synthetic ammonia.

Conversion gas enters the adsorption tower that first stage pressure swing adsorption apparatus is in adsorption step, adsorbent in the adsorption tower optionally adsorbs the components such as water, organic sulfur, inorganic sulfur and carbon dioxide in the conversion gas successively, components such as the carbon monoxide of Xi Fu partial CO 2 and difficult absorption, methane, nitrogen, hydrogen are not discharged from the port of export and are entered the adsorption tower that second stage pressure swing adsorption apparatus is in adsorption step, adsorbent in the adsorption tower is absorbing carbon dioxide optionally, and components such as the carbon monoxide of difficult absorption, methane, nitrogen, hydrogen are discharged from the port of export and entered compression section.The adsorption tower of first stage pressure swing adsorption apparatus experiences absorption A successively in a cycle period, one all falls E1D, two all fall E2D, three all fall E3D, four all fall E4D, five all fall E5D, product carbon dioxide replacement P, product carbon dioxide step-down D, vacuumize VC, five all rise E5R, four all rise E4R, three all rise E3R, two all rise E2R, one all rises E1R, the FR pressure swing adsorption technique step of finally boosting, first stage pressure swing adsorption apparatus is the product carbon dioxide at product carbon dioxide step-down D with the gas that vacuumizes the acquisition of VC step, the adsorption tower of second stage pressure swing adsorption apparatus experiences absorption A successively in a cycle period, one all falls E1D, two all fall E2D, three all fall E3D, four all fall E4D, five all fall E5D, six all fall E6D, the contrary BD of putting, vacuumize VC, six all rise E6R, five all rise E5R, four all rise E4R, three all rise E3R, two all rise E2R, one all rises E1R, the FR pressure swing adsorption technique step of finally boosting, the gaseous mixture that second stage pressure swing adsorption apparatus is in the adsorption tower outlet discharge of adsorption step is mainly nitrogen, hydrogen product wherein also contains a spot of carbon monoxide and methane.Be example with the A tower now, contrast Fig. 5 illustrates the processing step of the present embodiment first stage pressure swing adsorption apparatus adsorption tower in a cyclic process:

(1) absorption A

At this moment, the A tower has been finished the FR step of finally boosting, open sequencing valve 1A, 2A, conversion gas enters adsorption tower A through pipeline G11, in the A adsorption tower, adsorbent optionally adsorbs the water in the conversion gas successively, organic sulfur, component such as inorganic sulfur and carbon dioxide, Xi Fu partial CO 2 and be difficult for the carbon monoxide of absorption not, methane, nitrogen, components such as hydrogen flow out through sequencing valve 2A from the port of export and enter the adsorption tower that second stage pressure swing adsorption apparatus is in adsorption step, As time goes on, adsorbent water, the total amount of component such as organic sulfur and inorganic sulfur and carbon dioxide constantly increases, when the adsorbents adsorb said components is saturated, stop air inlet, this moment, absorption finished, and gas concentration lwevel is controlled at 9% (V) in working off one's feeling vent one's spleen.

(2) for the first time equal voltage drop step is called for short one and all falls E1D

After absorption finishes, open sequencing valve 3A, 3C, the gas in the A tower enters the C tower through pipeline G13 to carry out one to the C tower and all rises, and after A and C pressure tower are in a basic balance, closes sequencing valve 3A.

(3) for the second time equal voltage drop step is called for short two and all falls E2D

One all end is fallen and after, open sequencing valve 4A, 4D, the gas in the A tower enters the D tower through pipeline G14 to carry out two to the D tower and all rises, and after A and D pressure tower are in a basic balance, closes sequencing valve 4D.

(4) equal for the third time voltage drop step is called for short three and all falls E3D

Two all end is fallen and after, open sequencing valve 4E, the gas in the A tower enters the E tower through pipeline G14 to carry out three to the E tower and all rises, and after A and E pressure tower are in a basic balance, closes sequencing valve 4A.

(5) the 4th equal voltage drop step are called for short four and all fall E4D

Three all end is fallen and after, open sequencing valve 5A, 5F, the gas in the A tower enters the F tower through pipeline G15 to carry out four to the F tower and all rises, and after A and F pressure tower are in a basic balance, closes sequencing valve 5F.

(6) the 5th equal voltage drop step are called for short five and all fall E5D

Four all end is fallen and after, open sequencing valve 5G, the gas in the A tower enters the G tower through pipeline G15 to carry out five to the G tower and all rises, and when the gas concentration lwevel in A tower exit during greater than 90% (V), closes sequencing valve 5A, 5G, the pressure in this moment A tower is 0.25MPa (G).

(7) product carbon dioxide replacement P

Five all end is fallen and after, open sequencing valve 7A, 6A, the compressed machine C of product carbon dioxide this moment, pipeline G17 enter adsorption tower A from the import of A tower bottom, along the absorption direction adsorption tower A is replaced, be displaced the gas emptying that comes or use it for anything else, when carbon dioxide reaches the regulation requirement in displacement is dropped a hint, close sequencing valve 7A, 6A, displacement pressure is 0.25MPa (G).

(8) product carbon dioxide step-down D

After the product carbon dioxide replacement finishes, open sequencing valve 8A earlier, KV11a, all press surge tank V1 to be communicated with the product carbon dioxide, when the A pressure tower equals the product carbon dioxide substantially and all presses the pressure of surge tank V1, close sequencing valve KV11a, open sequencing valve KV11b, product carbon dioxide gas holder V is put in product carbon dioxide step-down in the A tower, when the pressure of A tower during near gas holder V pressure, close sequencing valve 8A, KV11b opens sequencing valve KV11c at last, all presses surge tank V1 to be communicated with gas holder V the product carbon dioxide, when the product carbon dioxide is all pressed surge tank V1 pressure near gas holder V pressure, close sequencing valve KV11c.

(9) vacuumize VC

After the step-down of product carbon dioxide finishes, open sequencing valve 9A, the carbon dioxide in the tower being released from the A tower bottom through pipeline G19, vavuum pump P1 enters product carbon dioxide gas holder V, vacuumize end after, close sequencing valve 9A.

(10) the 5th equal voltage rise steps are called for short five and all rise E5R

Vacuumize after VC finishes, open sequencing valve 5A, 5D, the gas in the D tower enters the A tower through pipeline G15 to carry out five to the A tower and all rises, and after D and A pressure tower are in a basic balance, closes sequencing valve 5D.

(11) the 4th equal voltage rise steps are called for short four and all rise E4R

Five all rise E5R finish after, open sequencing valve 5A, 5E, the gas in the E tower enters the A tower through pipeline G15 to carry out four to the A tower and all rises, and after E and A pressure tower are in a basic balance, closes sequencing valve 5A, 5E.

(12) equal for the third time voltage rise step is called for short three and all rises E3R

Four all rise to finish after, open sequencing valve 4A, 4F, the gas in the F tower enters the A tower through pipeline G14 to carry out three to the A tower and all rises, and after F and A pressure tower are in a basic balance, closes sequencing valve 4F.

(13) for the second time equal voltage rise step is called for short two and all rises E2R

Three all rise to finish after, open sequencing valve 4G, the gas in the G tower enters the A tower through pipeline G14 to carry out two to the A tower and all rises, and after G and A pressure tower are in a basic balance, closes sequencing valve 4G, 4A.

(14) for the first time equal voltage rise step is called for short one and all rises E1R

Two all rise to finish after, open sequencing valve 3A, 3H, the gas in the H tower enters the A tower through pipeline G13 to carry out one to the A tower and all rises, and after H and A pressure tower are in a basic balance, closes sequencing valve 3H.

(15) FR that finally boosts

One all rise to finish after, open sequencing valve KV10, utilize the adsorption tower that is in adsorption step to work off one's feeling vent one's spleen and boost from the top to the A tower, when the A pressure tower rises to adsorptive pressure, close sequencing valve KV10,3A.

So far, the A tower has been finished a circulation, can enter next circulation again.B～I adsorption tower is the same with the circulation step of A tower, just staggers mutually on the time, sees Fig. 5.

Be example with a tower now, contrast Fig. 6 illustrates the processing step of the present embodiment second stage pressure swing adsorption apparatus adsorption tower in a cyclic process:

(1) absorption A

At this moment, the a tower has been finished the FR step of finally boosting, open sequencing valve 1a, 2a, conversion gas enters adsorption tower a through pipeline G21, in a adsorption tower, adsorbent optionally adsorbs the components such as carbon dioxide of first stage pressure swing adsorption apparatus in working off one's feeling vent one's spleen, Xi Fu amounts of carbon dioxide and be difficult for the carbon monoxide of absorption not, methane, nitrogen, components such as hydrogen flow out the compression section that enters synthetic ammonia from the port of export through sequencing valve 2a, As time goes on, adsorbent total carbon dioxide capacity constantly increases, when the adsorbents adsorb carbon dioxide is saturated, close sequencing valve 1a, 2a, stop air inlet, this moment, absorption finished, and gas concentration lwevel is controlled at below 0.2% (V) in working off one's feeling vent one's spleen.

(2) for the first time equal voltage drop step is called for short one and all falls E1D

After absorption finishes, open sequencing valve 3a, 3c, the gas in a tower enters the c tower through pipeline G23 to carry out one to the c tower and all rises, and after a and c pressure tower are in a basic balance, closes sequencing valve 3a.

(3) for the second time equal voltage drop step is called for short two and all falls E2D

One all end is fallen and after, open sequencing valve 4a, 4d, the gas in a tower enters the d tower through pipeline G24 to carry out two to the d tower and all rises, and after a and d pressure tower are in a basic balance, closes sequencing valve 4d.

(4) equal for the third time voltage drop step is called for short three and all falls E3D

Two all end is fallen and after, open sequencing valve 4e, the gas in a tower enters the e tower through pipeline G24 to carry out three to the e tower and all rises, and after a and e pressure tower are in a basic balance, closes sequencing valve 4a.

(5) the 4th equal voltage drop step are called for short four and all fall E4D

Three all end is fallen and after, open sequencing valve 5a, 5f, the gas in a tower enters the f tower through pipeline G25 to carry out four to the f tower and all rises, and after a and f pressure tower are in a basic balance, closes sequencing valve 5f.

(6) the 5th equal voltage drop step are called for short five and all fall E5D

Four all end is fallen and after, open sequencing valve 5g, the gas in a tower enters the g tower through pipeline G25 to carry out five to the g tower and all rises, and after a and g pressure tower are in a basic balance, closes sequencing valve 5a, 5g.

(7) the 6th equal voltage drop step are called for short six and all fall E6D

Five all end is fallen and after, open sequencing valve 6a, 6h, the gas in a tower enters the h tower through pipeline G28 to carry out six to the h tower and all rises, and after a and h pressure tower are in a basic balance, closes sequencing valve 6a, 6h.

(8) the contrary BD of putting

Six all end is fallen and after, open sequencing valve 7a, with the reverse emptying of the gas in a tower, when the gas in a tower drops to normal pressure, close sequencing valve 7a.

(9) vacuumize VC

Contrary put end after, open sequencing valve 8a, through pipeline G27, vavuum pump P2 from a tower bottom the emptying of releasing of the gas in the tower, vacuumize end after, close sequencing valve 8a.

(10) the 6th equal voltage rise steps are called for short six and all rise E6R

After vacuumizing end, open sequencing valve 6a, 6c, the gas in the c tower enters a tower through pipeline G28 to carry out six to a tower and all rises, and after c and a pressure tower are in a basic balance, closes sequencing valve 6a, 6c.

(11) the 5th equal voltage rise steps are called for short five and all rise E5R

Six all rise to finish after, open sequencing valve 5a, 5d, the gas in the d tower enters a tower through pipeline G25 to carry out five to a tower and all rises, and after d and a pressure tower are in a basic balance, closes sequencing valve 5d.

(12) the 4th equal voltage rise steps are called for short four and all rise E4R

Five all rise to finish after, open sequencing valve 5e, the gas in the e tower enters a tower through pipeline G25 to carry out four to a tower and all rises, and after e and a pressure tower are in a basic balance, closes sequencing valve 5a, 5e.

(13) equal for the third time voltage rise step is called for short three and all rises E3R

Four all rise to finish after, open sequencing valve 4a, 4f, the gas in the f tower enters a tower through pipeline G24 to carry out three to a tower and all rises, and after f and a pressure tower are in a basic balance, closes sequencing valve 4f.

(14) for the second time equal voltage rise step is called for short two and all rises E2R

Three all rise to finish after, open sequencing valve 4g, the gas in the g tower enters a tower through pipeline G24 to carry out two to a tower and all rises, and after g and a pressure tower are in a basic balance, closes sequencing valve 4g, 4a.

(15) for the first time equal voltage rise step is called for short one and all rises E1R

Two all rise to finish after, open sequencing valve 3a, 3h, the gas in the h tower enters a tower through pipeline G23 to carry out one to a tower and all rises, and after h and a pressure tower are in a basic balance, closes sequencing valve 3h.

(16) FR that finally boosts

One all rise to finish after, open sequencing valve KV12, utilize the adsorption tower that is in adsorption step to work off one's feeling vent one's spleen and boost from the top to a tower, when a pressure tower rises to adsorptive pressure, close sequencing valve KV12,3a.

So far, a tower has been finished a circulation, can enter next circulation again.B～i adsorption tower is the same with the circulation step of A tower, just staggers mutually on the time, sees Fig. 6.

The present embodiment result is 99% (V) for the product carbon dioxide purity, and recovery rate of CO 2 is greater than 70% (V), and gas concentration lwevel is less than 0.1% (V) in product hydrogen, the nitrogen.

For present embodiment, adopt process of the present invention to compare with the prior art that with documents (CN1248482A) is representative, consider by producing 120000 tons of synthetic ammonia scales per year, (adsorptive pressure is 2.1MPa (G) in other condition, conversion gas is formed and temperature, the sorption cycle time, adsorbent kind and ratio, the power-equipment performance, instrument and meter and control function, special-purpose sequencing valve and hydraulic system structure and life-span) under the identical situation, synthetic ammonia decarburization power consumption per ton on average descends 53% (about 67 degree), and the investment of decarburization original equipment on average can be saved about 27% (about 5,600,000 yuan).

After the equal pressure drop of present embodiment finishes, when the gas concentration lwevel in adsorption tower exit is 50% (V), adsorption tower displacement pressure is 0.53～0.55MPa (G), at this moment, compare with above-mentioned prior art, consider by producing 120000 tons of synthetic ammonia scales per year, (adsorptive pressure is 2.1MPa (G) in other condition, conversion gas is formed and temperature, the sorption cycle time, adsorbent kind and ratio, the power-equipment performance, instrument and meter and control function, special-purpose sequencing valve and hydraulic system structure and life-span) under the identical situation, synthetic ammonia decarburization power consumption per ton on average descends 13% (about 16 degree), and the investment of decarburization original equipment on average can be saved about 15% (about 3,200,000 yuan).

For present embodiment, adopt particular adsorbent combination of the present invention to compare with the prior art that with documents (CN1248482A) is representative, consider by producing 120000 tons of synthetic ammonia scales per year, (adsorptive pressure is 2.1MPa (G) in other condition, conversion gas is formed and temperature, the sorption cycle time, the power-equipment performance, instrument and meter and control function, special-purpose sequencing valve and hydraulic system structure and life-span) under the identical situation, (nitrogen loss reduction changes with the ratio that molecular sieve and activated carbon account for nitrogen loss reduction average out to 45% of the present invention, 45% reduction is the mean value under the various ratios), synthetic ammonia decarburization power consumption per ton on average descends 10% (about 13 degree), average 1.9% (about 400,000 yuan) of saving of decarburization original equipment investment annually increase about 1,500,000 yuan (comprising the benefit that reduces the synthetic ammonia ability to be increased produce because of the nitrogen loss and the electricity charge of saving).

For present embodiment, adopt the surge tank of all pressing of the present invention can prevent after product carbon dioxide replacement P step finishes, directly (pressure is that 0.25～0.55MPa) product carbon dioxide is put into gas holder, in order to avoid device is stopped the high pressure in the adsorption tower.

Embodiments of the invention 3:

Condition such as the conversion gas composition of present embodiment and temperature, adsorbent kind and ratio, power-equipment performance, instrument and meter and control function, special-purpose sequencing valve and hydraulic system structure and life-span and embodiment 1 and embodiment 2 are in full accord, and the adsorptive pressure of present embodiment is 3.6MPa (G).

As shown in Figure 7, adsorption tower A～J is totally 10 composition first stage pressure swing adsorption apparatus, the adsorbent that loads from down to up in the adsorption tower is followed successively by activated alumina, active carbon and Kiselgel A, move single tower absorption and all press program six times, utilize vacuum pipeline G19 that adsorption tower is vacuumized by vavuum pump P1; Adsorption tower a～j is totally 10 composition second stage pressure swing adsorption apparatus, and the adsorbent of filling is a Kiselgel A in the adsorption tower, moves single tower absorption and all presses program seven times, utilizes vacuum pipeline G27 that adsorption tower is vacuumized by vavuum pump P2.P1, C, V1, V are respectively the first stage pressure swing adsorption apparatus vavuum pump, compressor, product carbon dioxide and all press surge tank and product carbon dioxide gas holder, and P2 is the second stage pressure swing adsorption apparatus vavuum pump.Present embodiment is with above-mentioned two stage pressure swing adsorption apparatus serial operations, first stage pressure swing adsorption apparatus is purified to carbon dioxide more than 98.5% (V), be used for urea synthesis, the second stage pressure swing adsorption apparatus effect is that working off one's feeling vent one's spleen of first stage pressure swing adsorption apparatus further purified, make in the hydrogen, nitrogen of the second stage pressure swing adsorption apparatus adsorption tower a～j upper end outlet gas concentration lwevel less than 0.2% (V), to satisfy the needs of next step operation of synthetic ammonia.

Conversion gas enters the adsorption tower that first stage pressure swing adsorption apparatus is in adsorption step, adsorbent in the adsorption tower optionally adsorbs the components such as water, organic sulfur, inorganic sulfur and carbon dioxide in the conversion gas successively, components such as the carbon monoxide of Xi Fu partial CO 2 and difficult absorption, methane, nitrogen, hydrogen are not discharged from the port of export and are entered the adsorption tower that second stage pressure swing adsorption apparatus is in adsorption step, adsorbent in the adsorption tower is absorbing carbon dioxide optionally, and components such as the carbon monoxide of difficult absorption, methane, nitrogen, hydrogen are discharged from the port of export and entered compression section.The adsorption tower of first stage pressure swing adsorption apparatus experiences absorption A successively in a cycle period, one all falls E1D, two all fall E2D, three all fall E3D, four all fall E4D, five all fall E5D, six all fall E6D, product carbon dioxide replacement P, product carbon dioxide step-down D, vacuumize VC, six all rise E6R, five all rise E5R, four all rise E4R, three all rise E3R, two all rise E2R, one all rises E1R, the FR pressure swing adsorption technique step of finally boosting, first stage pressure swing adsorption apparatus is the product carbon dioxide at product carbon dioxide step-down D with the gas that vacuumizes the acquisition of VC step, the adsorption tower of second stage pressure swing adsorption apparatus experiences absorption A successively in a cycle period, one all falls E1D, two all fall E2D, three all fall E3D, four all fall E4D, five all fall E5D, six all fall E6D, seven all fall E7D, the contrary BD of putting, vacuumize VC, seven all rise E7R, six all rise E6R, five all rise E5R, four all rise E4R, three all rise E3R, two all rise E2R, one all rises E1R, the FR pressure swing adsorption technique step of finally boosting, the gaseous mixture that second stage pressure swing adsorption apparatus is in the adsorption tower outlet discharge of adsorption step is mainly nitrogen, hydrogen product wherein also contains a spot of carbon monoxide and methane.Be example with the A tower now, contrast Fig. 8 illustrates the processing step of the present embodiment first stage pressure swing adsorption apparatus adsorption tower in a cyclic process:

(1) absorption A

At this moment, the A tower has been finished the FR step of finally boosting, open sequencing valve 1A, 2A, conversion gas enters adsorption tower A through pipeline G11, in the A adsorption tower, adsorbent optionally adsorbs the water in the conversion gas successively, organic sulfur, component such as inorganic sulfur and carbon dioxide, Xi Fu partial CO 2 and be difficult for the carbon monoxide of absorption not, methane, nitrogen, components such as hydrogen flow out through sequencing valve 2A from the port of export and enter the adsorption tower that second stage pressure swing adsorption apparatus is in adsorption step, As time goes on, adsorbent water, the total amount of component such as organic sulfur and inorganic sulfur and carbon dioxide constantly increases, when the adsorbents adsorb said components is saturated, stop air inlet, this moment, absorption finished, and gas concentration lwevel is controlled at 9% (V) in working off one's feeling vent one's spleen.

(2) for the first time equal voltage drop step is called for short one and all falls E1D

After absorption finishes, open sequencing valve 3A, 3C, the gas in the A tower enters the C tower through pipeline G13 to carry out one to the C tower and all rises, and after A and C pressure tower are in a basic balance, closes sequencing valve 3A.

(3) for the second time equal voltage drop step is called for short two and all falls E2D

One all end is fallen and after, open sequencing valve 4A, 4D, the gas in the A tower enters the D tower through pipeline G14 to carry out two to the D tower and all rises, and after A and D pressure tower are in a basic balance, closes sequencing valve 4D.

(4) equal for the third time voltage drop step is called for short three and all falls E3D

Two all end is fallen and after, open sequencing valve 4E, the gas in the A tower enters the E tower through pipeline G14 to carry out three to the E tower and all rises, and after A and E pressure tower are in a basic balance, closes sequencing valve 4A.

(5) the 4th equal voltage drop step are called for short four and all fall E4D

Three all end is fallen and after, open sequencing valve 5A, 5F, the gas in the A tower enters the F tower through pipeline G15 to carry out four to the F tower and all rises, and after A and F pressure tower are in a basic balance, closes sequencing valve 5F.

(6) the 5th equal voltage drop step are called for short five and all fall E5D

Four all end is fallen and after, open sequencing valve 5G, the gas in the A tower enters the G tower through pipeline G15 to carry out five to the G tower and all rises, and after A and G pressure tower are in a basic balance, closes sequencing valve 5A, 5G.

(7) the 6th equal voltage drop step are called for short six and all fall E6D

Five all end is fallen and after, open sequencing valve 6A, 6H, the gas in the A tower enters the H tower through pipeline G16 to carry out six to the H tower and all rises, when the gas concentration lwevel in A tower exit during greater than 90% (V), close sequencing valve 6A, 6H, the interior pressure of A tower this moment is 0.42MPa (G).

(8) product carbon dioxide replacement P

Six all end is fallen and after, open sequencing valve 7A, 10A, the compressed machine C of product carbon dioxide this moment, pipeline G17 enter adsorption tower A from the import of A tower bottom, along the absorption direction adsorption tower A is replaced, be displaced the gas emptying that comes or use it for anything else, when carbon dioxide reaches the regulation requirement in displacement is dropped a hint, close sequencing valve 7A, 10A, displacement pressure is 0.42MPa (G).

(9) product carbon dioxide step-down D

After the product carbon dioxide replacement finishes, open sequencing valve 8A earlier, KV11a, all press surge tank V1 to be communicated with the product carbon dioxide, when the A pressure tower equals the product carbon dioxide substantially and all presses the pressure of surge tank V1, close sequencing valve KV11a, open sequencing valve KV11b, product carbon dioxide gas holder V is put in product carbon dioxide step-down in the A tower, when the pressure of A tower during near gas holder V pressure, close sequencing valve 8A, KV11b opens sequencing valve KV11c at last, all presses surge tank V1 to be communicated with gas holder V the product carbon dioxide, when product carbon dioxide intermediate buffering jar V1 pressure during, close sequencing valve KV11c near gas holder V pressure.

(10) vacuumize VC

After the step-down of product carbon dioxide finishes, open sequencing valve 9A, the carbon dioxide in the tower being released from the A tower bottom through pipeline G19, vavuum pump P1 enters product carbon dioxide gas holder V, vacuumize end after, close sequencing valve 9A.

(11) the 6th equal voltage rise steps are called for short six and all rise E6R

Vacuumize after VC finishes, open sequencing valve 6A, 6D, the gas in the D tower enters the A tower through pipeline G16 to carry out six to the A tower and all rises, six all end is fallen and after, close sequencing valve 6A, 6D.

(12) the 5th equal voltage rise steps are called for short five and all rise E5R

Six all rise E6R finish after, open sequencing valve 5A, 5E, the gas in the E tower enters the A tower through pipeline G15 to carry out five to the A tower and all rises, five all end is fallen and after, close sequencing valve 5E.

(13) the 4th equal voltage rise steps are called for short four and all rise E4R

Five all rise E5R finish after, open sequencing valve 5F, the gas in the F tower enters the A tower through pipeline G15 to carry out four to the A tower and all rises, four all end is fallen and after, close sequencing valve 5A, 5F.

(14) equal for the third time voltage rise step is called for short three and all rises E3R

Four all rise to finish after, open sequencing valve 4A, 4G, the gas in the G tower enters the A tower through pipeline G14 to carry out three to the A tower and all rises, and after G and A pressure tower are in a basic balance, closes sequencing valve 4G.

(15) for the second time equal voltage rise step is called for short two and all rises E2R

Three all rise to finish after, open sequencing valve 4H, the gas in the H tower enters the A tower through pipeline G14 to carry out two to the A tower and all rises, and after H and A pressure tower are in a basic balance, closes sequencing valve 4H, 4A.

(16) for the first time equal voltage rise step is called for short one and all rises E1R

Two all rise to finish after, open sequencing valve 3A, 3I, the gas in 1 tower enters the A tower through pipeline G13 to carry out one to the A tower and all rises, and after I and A pressure tower are in a basic balance, closes sequencing valve 3I.

(17) FR that finally boosts

One all rise to finish after, open sequencing valve KV13, utilize the adsorption tower that is in adsorption step to work off one's feeling vent one's spleen and boost from the top to the A tower, when the A pressure tower rises to adsorptive pressure, close sequencing valve KV13,3A.

So far, the A tower has been finished a circulation, can enter next circulation again.B～J adsorption tower is the same with the circulation step of A tower, just staggers mutually on the time, sees Fig. 2.

Be example contrast Fig. 9 now, the processing step of the present embodiment second stage pressure swing adsorption apparatus adsorption tower in a cyclic process be described with a tower:

(1) absorption A

At this moment, the a tower has been finished the FR step of finally boosting, open sequencing valve 1a, 2a, conversion gas enters adsorption tower a through pipeline G21, in a adsorption tower, adsorbent optionally adsorbs the components such as carbon dioxide of first stage pressure swing adsorption apparatus in working off one's feeling vent one's spleen, Xi Fu amounts of carbon dioxide and be difficult for the carbon monoxide of absorption not, methane, nitrogen, components such as hydrogen flow out the compression section that enters synthetic ammonia from the port of export through sequencing valve 2a, As time goes on, adsorbent total carbon dioxide capacity constantly increases, when the adsorbents adsorb carbon dioxide is saturated, close sequencing valve 1a, 2a, stop air inlet, this moment, absorption finished, and gas concentration lwevel is controlled at below 0.2% (V) in working off one's feeling vent one's spleen.

(2) for the first time equal voltage drop step is called for short one and all falls E1D

After absorption finishes, open sequencing valve 3a, 3c, the gas in a tower enters the c tower through pipeline G23 to carry out one to the c tower and all rises, and after a and c pressure tower are in a basic balance, closes sequencing valve 3a.

(3) for the second time equal voltage drop step is called for short two and all falls E2D

One all end is fallen and after, open sequencing valve 4a, 4d, the gas in a tower enters the d tower through pipeline G24 to carry out two to the d tower and all rises, and after a and d pressure tower are in a basic balance, closes sequencing valve 4d.

(4) equal for the third time voltage drop step is called for short three and all falls E3D

Two all end is fallen and after, open sequencing valve 4e, the gas in a tower enters the e tower through pipeline G24 to carry out three to the e tower and all rises, and after a and e pressure tower are in a basic balance, closes sequencing valve 4a.

(5) the 4th equal voltage drop step are called for short four and all fall E4D

Three all end is fallen and after, open sequencing valve 5a, 5f, the gas in a tower enters the f tower through pipeline G25 to carry out four to the f tower and all rises, and after a and f pressure tower are in a basic balance, closes sequencing valve 5f.

(6) the 5th equal voltage drop step are called for short five and all fall E5D

Four all end is fallen and after, open sequencing valve 5a, 5g, the gas in a tower enters the g tower through pipeline G25 to carry out five to the g tower and all rises, and after a and g pressure tower are in a basic balance, closes sequencing valve 5a, 5g.

(7) the 6th equal voltage drop step are called for short six and all fall E6D

Five all end is fallen and after, open sequencing valve 6a, 6h, the gas in a tower enters the h tower through pipeline G28 to carry out six to the h tower and all rises, and after a and h pressure tower are in a basic balance, closes sequencing valve 6h.

(8) the 7th equal voltage drop step are called for short seven and all fall E7D

Six all end is fallen and after, open sequencing valve 6a, 6i, the gas in a tower enters the i tower through pipeline G28 to carry out seven to the i tower and all rises, and after a and i pressure tower are in a basic balance, closes sequencing valve 6a, 6i.

(9) the contrary BD of putting

Seven all end is fallen and after, open sequencing valve 7a, with the reverse emptying of the gas in a tower, when the gas in a tower drops to normal pressure, close sequencing valve 7a.

(10) vacuumize VC

Contrary put end after, open sequencing valve 8a, through pipeline G27, vavuum pump P2 from a tower bottom the emptying of releasing of the gas in the tower, vacuumize end after, close sequencing valve 8a.

(11) the 7th equal voltage rise steps are called for short seven and all rise E7R

After vacuumizing end, open sequencing valve 6a, 6c, the gas in the c tower enters a tower through pipeline G28 to carry out seven to a tower and all rises, and after c and a pressure tower are in a basic balance, closes sequencing valve 6c.

(12) the 6th equal voltage rise steps are called for short six and all rise E6R

Seven all rise to finish after, open sequencing valve 6d, the gas in the d tower enters a tower through pipeline G28 to carry out six to a tower and all rises, and after d and a pressure tower are in a basic balance, closes sequencing valve 6a, 6d.

(13) the 5th equal voltage rise steps are called for short five and all rise E5R

Six all rise to finish after, open sequencing valve 5a, 5e, the gas in the e tower enters a tower through pipeline G25 to carry out five to a tower and all rises, and after e and a pressure tower are in a basic balance, closes sequencing valve 5e.

(14) the 4th equal voltage rise steps are called for short four and all rise E4R

Five all rise to finish after, open sequencing valve 5f, the gas in the f tower enters a tower through pipeline G25 to carry out four to a tower and all rises, and after f and a pressure tower are in a basic balance, closes sequencing valve 5a, 5f.

(15) equal for the third time voltage rise step is called for short three and all rises E3R

Four all rise to finish after, open sequencing valve 4a, 4g, the gas in the g tower enters a tower through pipeline G24 to carry out three to a tower and all rises, and after g and a pressure tower are in a basic balance, closes sequencing valve 4g.

(16) for the second time equal voltage rise step is called for short two and all rises E2R

Three all rise to finish after, open sequencing valve 4h, the gas in the h tower enters a tower through pipeline G24 to carry out two to a tower and all rises, and after h and a pressure tower are in a basic balance, closes sequencing valve 4h, 4a.

(17) for the first time equal voltage rise step is called for short one and all rises E1R

Two all rise to finish after, open sequencing valve 3a, 3i, the gas in the i tower enters a tower through pipeline G23 to carry out one to a tower and all rises, and after i and a pressure tower are in a basic balance, closes sequencing valve 3i.

(18) FR that finally boosts

One all rise to finish after, open sequencing valve KV12, utilize the adsorption tower that is in adsorption step to work off one's feeling vent one's spleen and boost from the top to a tower, when a pressure tower rises to adsorptive pressure, close sequencing valve KV12,3a.

So far, a tower has been finished a circulation, can enter next circulation again.B～j adsorption tower is the same with the circulation step of A tower, just staggers mutually on the time, sees Fig. 9.

The present embodiment result is 99% (V) for the product carbon dioxide purity, and recovery rate of CO 2 is greater than 70% (V), and gas concentration lwevel is less than 0.1% (V) in product hydrogen, the nitrogen.

For present embodiment, adopt process of the present invention to compare with the prior art that with documents (CN1248482A) is representative, consider by producing 120000 tons of synthetic ammonia scales per year, (adsorptive pressure is 3.6MPa (G) in other condition, conversion gas is formed and temperature, the sorption cycle time, adsorbent kind and ratio, the power-equipment performance, instrument and meter and control function, special-purpose sequencing valve and hydraulic system structure and life-span) under the identical situation, synthetic ammonia decarburization power consumption per ton on average descends 65% (about 85 degree), and the investment of decarburization original equipment on average can be saved about 32% (about 6,800,000 yuan).

After the equal pressure drop of present embodiment finishes, when the gas concentration lwevel in adsorption tower exit is 50% (V), adsorption tower displacement pressure is 0.88～0.90MPa (G), at this moment, compare with above-mentioned prior art, consider by producing 120000 tons of synthetic ammonia scales per year, (adsorptive pressure is 3.6MPa (G) in other condition, conversion gas is formed and temperature, the sorption cycle time, adsorbent kind and ratio, the power-equipment performance, instrument and meter and control function, special-purpose sequencing valve and hydraulic system structure and life-span) under the identical situation, synthetic ammonia decarburization power consumption per ton on average descends 3% (about 4 degree), and the investment of decarburization original equipment on average can be saved about 17% (about 3,600,000 yuan).

For present embodiment, adopt particular adsorbent combination of the present invention to compare with the prior art that with documents (CN1248482A) is representative, consider by producing 120000 tons of synthetic ammonia scales per year, (adsorptive pressure is 2.1MPa (G) in other condition, conversion gas is formed and temperature, the sorption cycle time, the power-equipment performance, instrument and meter and control function, special-purpose sequencing valve and hydraulic system structure and life-span) under the identical situation, (nitrogen loss reduction changes with the ratio that molecular sieve and activated carbon account for nitrogen loss reduction average out to 35% of the present invention, 35% reduction is the mean value under the various ratios), synthetic ammonia decarburization power consumption per ton on average descends 8% (about 10 degree), average 1.9% (about 400,000 yuan) of saving of decarburization original equipment investment annually increase about 1,100,000 yuan (comprising the benefit that reduces the synthetic ammonia ability to be increased produce because of the nitrogen loss and the electricity charge of saving).

For present embodiment, adopt the surge tank of all pressing of the present invention can prevent after product carbon dioxide replacement P step finishes, directly (pressure is that 0.42～0.90MPa) product carbon dioxide is put into gas holder, in order to avoid device is stopped the high pressure in the adsorption tower.

Claims (4)

1, unstripped gas pressure swing adsorption decarbonization method in the urea production, two stage pressure swing adsorption apparatus serial operations, unstripped gas is the synthetic-ammonia transformation gas of raw material with the coal, and first stage pressure swing adsorption apparatus is used for purifying carbon dioxide, and second stage pressure swing adsorption apparatus is used for separation of hydrogen, nitrogen; First stage pressure swing adsorption apparatus in a cycle period successively experience absorption A, all pressure drop ED, product carbon dioxide replacement P, product carbon dioxide step-down D, vacuumize VC, all voltage rise ER, the final FR pressure swing adsorption technique step of boosting; Second stage pressure swing adsorption apparatus in a cycle period successively experience absorption A, all pressure drop ED, contraryly put BD, vacuumize VC, all voltage rise ER, the final FR pressure swing adsorption technique step of boosting; The mean concentration of carbon dioxide was 9V% during first stage pressure swing adsorption apparatus was worked off one's feeling vent one's spleen; When the first stage pressure swing adsorption apparatus drop pressure ED finished, gas concentration lwevel was 50～96V% during the adsorption tower transient flow was given vent to anger.

2, unstripped gas pressure swing adsorption decarbonization method in the urea production according to claim 1, it is characterized in that the adsorbent that loads from down to up in the first stage pressure swing adsorption apparatus adsorption tower is activated alumina, active carbon and Kiselgel A, or activated alumina and active carbon, or activated alumina and Kiselgel A, the adsorbent of filling only is a Kiselgel A in the second stage pressure swing adsorption apparatus adsorption tower.

3, unstripped gas pressure swing adsorption decarbonization method in the urea production according to claim 1, when it is characterized in that the equal pressure drop ED of first stage pressure swing adsorption apparatus finishes, gas concentration lwevel was 75～90V% during the adsorption tower transient flow was given vent to anger, pressure after all pressure drop ED finishes is product carbon dioxide replacement pressure, and its number range is 0.02～0.9MPa.

4, unstripped gas pressure swing adsorption decarbonization method in the urea production according to claim 1, the pressure that it is characterized in that two-stage pressure swing adsorption apparatus adsorption step A is 0.6～3.6MPa, the adsorptive pressure of two-stage pressure swing adsorption apparatus can be unequal.

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