CN1161327C - Quench process for recovery of acrylonitrile - Google Patents
Quench process for recovery of acrylonitrile Download PDFInfo
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- CN1161327C CN1161327C CNB011319550A CN01131955A CN1161327C CN 1161327 C CN1161327 C CN 1161327C CN B011319550 A CNB011319550 A CN B011319550A CN 01131955 A CN01131955 A CN 01131955A CN 1161327 C CN1161327 C CN 1161327C
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Abstract
The present invention relates to a method of quenching acrylonitrile, which mainly solves the problems in the prior art: the recovery rate of acrylonitrile can not be increased unless the acidic ammonium salt waste liquid is deeply buried, or the recovery rate of acrylonitrile is low because the quench tower shows partially strong basicity because of uneven spray due to the problem of inner components of the quench tower. The present invention solves the problems better by adopting the technical scheme that staying time of the quenching liquid in lower segment tower kettle of the quench tower is controlled, acids are directly added to the tower kettle at the lower segment of the quench tower so that pH number of the liquid in the tower kettle is controlled at 7 to 7.5, and water is added at the lower segment so that restructuring concentration in the tower kettle is controlled. The present invention can be used for industrial production devices of acrylonitrile.
Description
Technical field
The present invention relates to a kind of recover acrylonitrile quick cooling method.
Background technology
The production of ammoxidation of hydrocarbons system unsaturated nitrile is a key areas of petrochemical industry, wherein propylene or isobutene ammonia oxidizing acrylonitrile production or methacrylonitrile industrialization already, but have a common issue with, promptly unsaturated nitrile is unsettled under alkaline condition, and polymerization very easily takes place.Therefore no matter which kind of oxidative ammonolysis, the unreacted ammonia in the reactant gases all need be removed, and all adopts the sulfuric acid chilling to remove unreacted ammonia at present.
With the ammoxidating propylene to prepare acrylonitrile is example: propylene, ammonia and air generate major product vinyl cyanide and byproduct acetonitrile, prussic acid, propenal, vinylformic acid, carbon monoxide and carbonic acid gas by the fluidized-bed reactor ammonia oxidation, also have a small amount of unreacted propylene and ammonia.After reactant gases leaves reactor, enter quench tower, absorb unreacted ammonia with aqueous sulfuric acid and generate sulphur ammonium generation sulphur ammonium sewage through cooling.Remove gas behind the unreacted ammonia absorption tower of anhydrating, with water at low temperature with in the gas all organism absorb.Absorption liquid goes vinyl cyanide to reclaim refining step and isolates the high-purity propylene nitrile, prussic acid and crude acetonitrile.
In aforesaid propylene nitrile production technique, very important with the unreacted ammonia that sulfuric acid is removed in the reactant gases at quench tower.Because vinyl cyanide and prussic acid all are easy polymeric materials, easier polymerization under alkaline condition especially.Cause the loss of vinyl cyanide and hydrogen cyanide product like this, promptly the refining rate of recovery of vinyl cyanide is lower, generally about 90%, wherein in the loss of quench tower place vinyl cyanide just up to 8%.
Document US 3885928 has been introduced a kind of recovery and refining system of alkene nitrile, wherein the purpose of emergency cooling process is on the one hand reactor effluent to be cooled to certain temperature, is on the other hand to remove unreacted ammonia and the polymkeric substance and the heavy impurity that react generation in the reactor effluent.The technical scheme that is adopted in the document be water and sulfuric acid as quench liquid, the tower base stream of moisture, sour, polymkeric substance and other impurity is discharged from quenching system.Contain 10% ammonium sulfate, 16% heavy organism, a small amount of lightweight organism and water (about 74%) in these tower base streams by weight percentage approximately.Because the ammonia transformation efficiency is not controlled, make the easy and alkene nitrile generation side reaction of unreacted ammonia, reduced the refining rate of recovery of alkene nitrile.The clear 55-104 of document JP, 246 have introduced a kind of quench tower quick cooling method that has multistage outer circulation water coolant, and its quench tower bottom is a filler, and top is the two-section type structure of void tower.Reactor outlet gas enters quench tower lower portion about 230 ℃, (wherein acid is sulfuric acid with unreacted ammonia in acid fully herein, add in the outer circulation liquid a part as spray liquid, do not indicate the regulation range of pH value), behind the washing reaction gas, import epimere, be cooled to derive from the top about 40 ℃ through outer circulation water coolant (10～60 ℃).One material is extracted at maximum plate place out in epimere tower inner propene nitrile concentration, without the absorption tower, directly in subsequent treatment process.Wherein to require be 10～25 times of extraction amount to the epimere quantity of circulating water.Claim that according to this patent this measure can reduce the load on absorption tower, and the energy expenditure of systemic circulation (poor-water that relates in extraction in the finger device, absorption, the evaporation of propylene ammonia and the FF reboiler system).But because it only adds acid at hypomere, it is not high to remove the ammonia effect.And the pressure-controlling in the tower requires high, and pressure is higher a little, and the polymerization losses of vinyl cyanide just increases.Therefore, this design recovery of acrylonitrile is not high.Introduced a kind of quick cooling method in the document WO 96/23765, its quench tower is the two-section type structure, and its middle and upper part is a filler, and the bottom is a void tower.Reactor outlet gas enters hypomere at 260～280 ℃, and (wherein acid is sulfuric acid, as the part of spray liquid, hypomere tower bottoms pH value is 5.5 in the adding outer circulation liquid, and hypomere tower bottoms temperature is 85 ℃), in acid and behind the unreacted ammonia, washing reaction gas, import epimere herein.After epimere is cooled to 37～39 ℃, derive from the top.Also can add further neutralization of ammonia of acid at epimere.Behind the linear speed of spray, quantity of circulating water and the pH value of controlling hypomere recirculated water, reactor outlet gas, claim that according to the document removing the ammonia effect can be more than 90%.That is to say, also have about 10% ammonia will with acrylonitrile polymerization.Therefore, the loss of vinyl cyanide is bigger in the quench tower.
Above-mentioned document all is that the hypomere at quench tower adds sulfuric acid and removes ammonia, reduce unreacted ammonia at the chance of loss of hypomere and acrylonitrile polymerization or all add acid at two sections and remove unreacted ammonia fully, the process for production of acrylonitrile of sulphur ammonium is not reclaimed in this employing, because quench tower is to operate under acidic conditions, the polymerization losses that has suppressed vinyl cyanide, the rate of recovery of vinyl cyanide in quench tower is all higher, but do the condition that must possess like this, otherwise can produce a large amount of sulfide and contaminate environment behind the ammonium salt liquid waste incineration the direct buried processing of acid ammonium salt waste liquid.In the process for production of acrylonitrile that reclaims the sulphur ammonium, must at first wash and remove the impurity such as catalyst dust, high boiling material and polymkeric substance that reactant gases is carried secretly, and in epimere adding sulfuric acid, also be reclaimed to obtain clean sulphur ammonium with unreacted ammonia at quench tower lower portion.In quenching process, if because arranging of nozzle is unreasonable, or a small amount of nozzle stops up, can cause the quench tower lower portion non-uniform spraying, the hypomere part is than strong basicity, and vinyl cyanide with polymerization reaction take place, causes the loss of quench tower vinyl cyanide to increase under alkaline condition.If enter follow-up tower in the unreacted ammonia and not exclusively in the quench tower, will have a strong impact on the operation of follow-up tower, also will increase the loss of vinyl cyanide greatly simultaneously.
Summary of the invention
Technical problem to be solved by this invention be overcome in the past that document exists must be with the direct buried processing of acid ammonium salt waste liquid, could improve recovery of acrylonitrile or since quench tower inner member problem cause non-uniform spraying, the hypomere part is than strong basicity, cause the low defective of recovery of acrylonitrile, a kind of quick cooling method of new recover acrylonitrile is provided.This method has not will the direct buried processing of ammonium salt waste liquid, can reclaim the sulphur ammonium, and can improve the characteristics of recovery of acrylonitrile.
For solving the problems of the technologies described above, the technical solution used in the present invention is as follows: a kind of quick cooling method of recover acrylonitrile may further comprise the steps successively:
A) quench tower is made up of for two sections epimere and hypomere at least, in the middle of epimere and the hypomere catch tray is arranged, and riser is arranged on the catch tray;
B) to be 180～280 ℃ the reactor effluent that contains ammonia and vinyl cyanide contact in quench tower lower portion with aqueous quench liquid in the quenching system temperature, wherein aqueous quench liquid is 5～180 seconds in the residence time of quench tower lower portion tower still, directly add acid in the quench tower lower portion tower still, the pH value that makes the quench tower lower portion tower bottoms is below 7.5;
C) the gaseous state chilling effluent after the quench tower lower portion contact enters the quench tower epimere by riser;
D) the gaseous state chilling effluent that enters the quench tower epimere with contain vitriolic epimere circulated sprinkling liquid and contact after, part sulphur ammonium sewage desulfuration ammonium retrieving arrangement, the gaseous state chilling effluent of quench tower epimere goes to the absorption tower.
In the technique scheme, quench tower epimere preferred version is the column plate type structure or the filler of 1～10 block of theoretical tray, and the pH value preferred version of quench tower epimere spray liquid is 2～5.The pH value preferable range of quench tower lower portion tower bottoms is 7～7.5, and more preferably scope is 7～7.3.The sour preferred version that quench tower lower portion adds is selected from least a or its miscellany in acetic acid, oxalic acid, vinylformic acid, phosphoric acid, sulfuric acid, boric acid or the formic acid, and the more preferably scheme of the acid that quench tower lower portion adds is selected from least a or its miscellany in acetic acid, oxalic acid or the vinylformic acid.Preferred version is for adding water in the operation of quench tower lower portion, heavy constituent concentration is 0.1～5% to the additional amount of water by weight percentage in the quench tower lower portion tower bottoms in order to make, wherein reorganization is divided into polymkeric substance of vinyl cyanide, prussic acid or propenal and composition thereof, in the hypomere tower bottoms heavy constituent concentration by weight percentage preferable range be 0.5～4.0%, more preferably scope is 0.5～2.0%.Aqueous quench liquid is 10～100 seconds in the residence time preferable range of quench tower lower portion tower still, and more preferably scope is 20～50 seconds.
Therefore capable of circulation owing to ammonium salt in the epimere circulation fluid among the present invention, recovery can avoid the direct buried processing of ammonium salt waste liquid.Acid is directly added in the quench tower lower portion tower still, quench tower lower portion tower bottoms pH value is reduced to below 7.5, avoided to reduce the autohemagglutination and the addition polymerization loss of vinyl cyanide in addition because of hypomere spray poor effect causes the part to be more alkaline situation.Above the epimere catch tray, set up the column plate type structure or the filler of 1～10 block of theoretical tray, improved mass transfer and heat transfer between gas-liquid two-phase, improved and removed the ammonia effect, in having strengthened and efficient, improved the rate of recovery of vinyl cyanide in quench tower.Because quench tower lower portion does not reclaim with the ammonium salt that sour neutralization of ammonia produces, only doing reaction is the sewage burn processing, acid is selected from acetic acid, oxalic acid or vinylformic acid, can regulate quench tower lower portion still liquid pH value on the one hand, produce sulfurous gas after can avoiding on the other hand burning, atmosphere is caused secondary pollution problem, a large amount of combustions heat that simultaneously recyclable sewage roasting kiln produces.In the quench tower lower portion make up water, can reduce the concentration that generates heavy constituent in the tower bottoms body, reduce the polymerization losses of vinyl cyanide, control aqueous quench liquid is in the residence time of quench tower lower portion tower still, can reduce the time of acrylonitrile polymerization reaction, reduce the polymerization losses of vinyl cyanide.Confirm that through test adopt technical scheme of the present invention, the rate of recovery of vinyl cyanide is the highest to improve 5.0%, has obtained better technical effect.
Description of drawings
Fig. 1 is the quench tower emergency cooling process flow process of the clear 55-104246 of JP.
Fig. 2 is the quench tower emergency cooling process flow process of WO96/23765.
Fig. 3 is a quench tower emergency cooling process flow process of the present invention.
1 is quench tower among Fig. 1, Fig. 2 and Fig. 3, and 2 is reactor outlet gas, and 3 is riser, 4 is column plate, and 5 is filler, and 6 is water cooler, 7 are outer circulation liquid, and 8 is Extract, and 9 is acid solution, 10 for working off one's feeling vent one's spleen, and 11 is epimere still liquid, and 12 is hypomere still liquid, 13 is gas flowfield, and 14 is nozzle, and 15 is the water of adding (can be pure water or recycling waste water), 16 for adding water, 17 acid solutions for adding.
Among Fig. 3, reactant gases 2 after precooling enters quench tower lower portion, and circulation fluid 7 sprays of being extracted out from the tower still are quenched to 40～85 ℃ from 180～280 ℃, washing simultaneously removes catalyzer, high boiling material, the polymkeric substance of deentrainment, and 12 blowdowns of part still liquid are done to burn but and handled.Acid solution such as oxalic acid or acetic acid or vinylformic acid 17 directly joins in the tower still, to regulate the pH value of still liquid.In the residence time of quench tower lower portion tower still, reach the purpose that reduces loss in acrylonitrile by control aqueous quench liquid.The amount of amount of makeup water 16 and circulated sprinkling liquid 7 is regulated by corresponding pump and pipeline valve.In epimere circulation fluid 7, add the unreacted ammonia in the sulfuric acid 9 neutralization reaction gases, to obtain clean sulphur ammonium 11 for reclaiming.Reactant gases 10 behind the chilling enters the absorption tower, with water at low temperature condensability organism is wherein absorbed.
The invention will be further elaborated below by embodiment.
Embodiment
[comparative example 1]
Enter in the reactant gases of quench tower and contain vinyl cyanide 42 Grams Per Hours, temperature is 210 ℃, epimere is 5 blocks of theoretical trays, hypomere is the chilling cat head working pressure 0.036MPa of void tower, 82 ℃ of top temperature, 82 ℃ of still temperature, epimere circulated sprinkling amount is 123.6 ml/min, it is 3.5 that sulfuric acid adds in the epimere circulation fluid with control epimere circulation fluid pH value.Hypomere circulated sprinkling amount is 31.9 ml/min, and temperature is 82 ℃, blowdown flow rate 0.4 ml/min, and aqueous quench liquid is 320 seconds in the residence time of quench tower lower portion tower still, hypomere still liquid pH value is 7.8.Contain vinyl cyanide 38.6 Grams Per Hours in the tower top outlet gas, the quench tower recovery of acrylonitrile is 91.9%.
[embodiment 1]
Enter in the reactant gases of quench tower and contain vinyl cyanide 42 Grams Per Hours, temperature is 210 ℃, epimere is 5 blocks of theoretical trays, hypomere is the chilling cat head working pressure 0.036MPa of void tower, 82 ℃ of top temperature, 82 ℃ of still temperature, epimere circulated sprinkling amount is 123.6 ml/min, it is 3.5 that sulfuric acid adds in the epimere circulation fluid with control epimere circulation fluid pH value.Hypomere circulated sprinkling amount is 31.9 ml/min, and temperature is 82 ℃, blowdown flow rate 0.4 ml/min, and aqueous quench liquid is 20 seconds in the residence time of quench tower lower portion tower still, hypomere still liquid pH value is 7.5.Contain vinyl cyanide 40.7 Grams Per Hours in the tower top outlet gas, the quench tower recovery of acrylonitrile is 96.9%.
[embodiment 2]
Enter in the reactant gases of quench tower and contain vinyl cyanide 42 Grams Per Hours, temperature is 210 ℃, epimere is 5 blocks of theoretical trays, hypomere is the chilling cat head working pressure 0.036MPa of void tower, 82 ℃ of top temperature, 82 ℃ of still temperature, epimere circulated sprinkling amount is 123.6 ml/min, it is 3.5 that sulfuric acid adds in the epimere circulation fluid with control epimere circulation fluid pH value.Hypomere circulated sprinkling amount is 31.9 ml/min, blowdown flow rate 0.4 ml/min, and aqueous quench liquid is 50 seconds in the residence time of quench tower lower portion tower still, directly adding acetic acid adjusting hypomere still liquid pH value in the tower still is 7.0.Contain vinyl cyanide 40.6 Grams Per Hours in the tower top outlet gas, the quench tower recovery of acrylonitrile is 96.7%.
[embodiment 3]
Enter in the reactant gases of quench tower and contain vinyl cyanide 42 Grams Per Hours, temperature is 210 ℃, epimere is 5 blocks of theoretical trays, hypomere is the chilling cat head working pressure 0.036MPa of void tower, 82 ℃ of top temperature, 82 ℃ of still temperature, epimere circulated sprinkling amount is 123.6 ml/min, it is 3.5 that sulfuric acid adds in the epimere circulation fluid with control epimere circulation fluid pH value.Hypomere circulated sprinkling amount is 31.9 ml/min, to make the weight concentration of the polymkeric substance and composition thereof of vinyl cyanide, prussic acid or propenal in the tower still be 0.5% by increasing amount of makeup water, aqueous quench liquid is 150 seconds in the residence time of quench tower lower portion tower still, and directly adding oxalic acid adjusting hypomere still liquid pH value in the tower still is 7.0.Contain vinyl cyanide 40.3 Grams Per Hours in the tower top outlet gas, the quench tower recovery of acrylonitrile is 96.0%.
[embodiment 4]
Enter in the reactant gases of quench tower and contain vinyl cyanide 42 Grams Per Hours, temperature is 210 ℃, epimere is 5 blocks of theoretical trays, hypomere is the chilling cat head working pressure 0.036MPa of void tower, 82 ℃ of top temperature, 82 ℃ of still temperature, epimere circulated sprinkling amount is 123.6 ml/min, it is 3.5 that sulfuric acid adds in the epimere circulation fluid with control epimere circulation fluid pH value.Hypomere circulated sprinkling amount is 31.9 ml/min, and to make the weight concentration of the polymkeric substance and composition thereof of vinyl cyanide, prussic acid or propenal in the hypomere tower still be 2.0% by increasing amount of makeup water, and aqueous quench liquid is 150 seconds in the residence time of quench tower lower portion tower still.Directly add acetic acid in the tower still, hypomere still liquid pH value is 7.3.Contain vinyl cyanide 39.8 Grams Per Hours in the tower top outlet gas, the quench tower recovery of acrylonitrile is 94.8%.
Claims (8)
1, a kind of recover acrylonitrile quick cooling method may further comprise the steps successively:
A) quench tower is made up of for two sections epimere and hypomere at least, in the middle of epimere and the hypomere catch tray is arranged, and riser is arranged on the catch tray;
B) temperature is that 180～280 ℃ the reactor effluent that contains ammonia and vinyl cyanide contacts in quench tower lower portion with the aqueous quench liquid of quenching system, wherein aqueous quench liquid is 5～180 seconds in the residence time of quench tower lower portion tower still, directly add acid in the quench tower lower portion tower still, the pH value that makes the quench tower lower portion tower bottoms is below 7.5;
C) the gaseous state chilling effluent after the quench tower lower portion contact enters the quench tower epimere by riser;
D) the gaseous state chilling effluent that enters the quench tower epimere with contain vitriolic epimere circulated sprinkling liquid and contact after, part sulphur ammonium sewage desulfuration ammonium retrieving arrangement, the gaseous state chilling effluent of quench tower epimere goes to the absorption tower.
2, according to the described recover acrylonitrile quick cooling method of claim 1, it is characterized in that the quench tower epimere is the column plate type structure or the filler of 1～10 block of theoretical tray, the pH value of quench tower epimere circulated sprinkling liquid is 2～5.
3,, it is characterized in that aqueous quench liquid is 10～100 seconds in the residence time of quench tower lower portion tower still according to the described recover acrylonitrile quick cooling method of claim 1.
4,, it is characterized in that aqueous quench liquid is 20～50 seconds in the residence time of quench tower lower portion tower still according to the described recover acrylonitrile quick cooling method of claim 3.
5, according to the described recover acrylonitrile quick cooling method of claim 1, it is characterized in that quench tower lower portion tower bottoms pH value is 7～7.5, heavy constituent concentration is 0.1～5% by weight percentage in the hypomere tower bottoms, and wherein reorganization is divided into polymkeric substance of vinyl cyanide, prussic acid or propenal and composition thereof.
6,, it is characterized in that quench tower lower portion tower bottoms pH value is 7～7.3 according to the described recover acrylonitrile quick cooling method of claim 5.
7,, it is characterized in that heavy constituent concentration is 0.5～4.0% by weight percentage in the hypomere tower bottoms according to the described recover acrylonitrile quick cooling method of claim 5.
8,, it is characterized in that heavy constituent concentration is 0.5～2.0% by weight percentage in the hypomere tower bottoms according to the described recover acrylonitrile quick cooling method of claim 7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB011319550A CN1161327C (en) | 2001-10-22 | 2001-10-22 | Quench process for recovery of acrylonitrile |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB011319550A CN1161327C (en) | 2001-10-22 | 2001-10-22 | Quench process for recovery of acrylonitrile |
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| CN1413981A CN1413981A (en) | 2003-04-30 |
| CN1161327C true CN1161327C (en) | 2004-08-11 |
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| CNB011319550A Expired - Lifetime CN1161327C (en) | 2001-10-22 | 2001-10-22 | Quench process for recovery of acrylonitrile |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105983314A (en) * | 2015-01-31 | 2016-10-05 | 中国石油化工股份有限公司 | Automatic control device and method for amount of acid added into neutralization tower |
| CN112444139A (en) * | 2019-09-05 | 2021-03-05 | 中石油吉林化工工程有限公司 | Tower top condensing system of dehydrocyanic acid tower |
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- 2001-10-22 CN CNB011319550A patent/CN1161327C/en not_active Expired - Lifetime
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