CN1161328C - Quench process for raising recovery of acrylonitrile - Google Patents
Quench process for raising recovery of acrylonitrile Download PDFInfo
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- CN1161328C CN1161328C CNB011319577A CN01131957A CN1161328C CN 1161328 C CN1161328 C CN 1161328C CN B011319577 A CNB011319577 A CN B011319577A CN 01131957 A CN01131957 A CN 01131957A CN 1161328 C CN1161328 C CN 1161328C
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Abstract
The present invention relates to a quenching method for raising the recovery rate of acrylonitrile, and mainly solves the problems in the prior art: the recovery rate of acrylonitrile can not be increased unless the waste liquid of acidic ammonium salt is directly and deeply buried to be treated, or the recovery rate of acrylonitrile is low because parts of a quench tower show strong basicity because of uneven spray caused by the problem of the components in the quench tower, and the temperature of outer circulating liquid is too high so that acrylonitrile is easily polymerized, etc. The present invention favorably solves the problems by adopting a technical scheme that water is supplemented into the lower segment of the quench tower to control the concentration of the heavy components of the liquid in a tower still, and acid is directly added to the tower still at the lower segment of the quench tower to control the pH value of the liquid in the tower still and reduce the temperature of the outer circulating spraying liquid. The present invention can be used in industrial acrylonitrile production devices.
Description
Technical field
The present invention relates to a kind of quick cooling method that improves recovery of acrylonitrile.
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, vinyl cyanide is all higher in the rate of recovery of quench tower, 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.Outer circulation liquid temp height can increase the residence time of gas-phase propene nitrile experience polymerization temperature scope, thereby increases the polymerization losses of vinyl cyanide.
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 vinyl cyanide 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 that improves recovery of acrylonitrile may further comprise the steps successively:
A) quench tower is made up of for two sections epimere and hypomere at least, between epimere and the hypomere catch tray is arranged, and riser is arranged on the catch tray;
B) temperature is that the hypomere temperature is that 40～85 ℃ aqueous quench liquid contacts in quench tower lower portion in 180～280 ℃ the reactor effluent that contains ammonia and vinyl cyanide and the quenching system, quench tower lower portion is added water, 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, more preferably scope is 7～7.3, the sour preferred version that quench tower lower portion adds is at least a or its miscellany that is selected from 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.In the operation of quench tower lower portion, add water, heavy constituent concentration is 0.1～5% to the additional amount preferable range 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 quench tower lower portion tower bottoms heavy constituent concentration by weight percentage preferable range be 0.5～4.0%, more preferably scope is 0.5～2.0%.The quench tower lower portion temperature is that 40～85 ℃ aqueous quench liquid realizes that by circulated sprinkling liquid is cooled off with water cooler quench tower lower portion aqueous quench liquid temp preferable range is 50～75 ℃, and more preferably scope is 60～70 ℃.
The present invention is because therefore capable of circulation, the recovery of ammonium salt in the epimere circulation fluid 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 avoid 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 acrylic acid preferred version, can regulate quench tower 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 amount of makeup water, can reduce the concentration that generates heavy constituent in the tower bottoms body, reduce the polymerization losses of vinyl cyanide.The spray temperature that reduces outer circulation liquid can reduce the residence time of gas-phase propene nitrile experience polymerization temperature scope in quenching process, thereby reduces the loss 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 4.8%, 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 for adding water (can be pure water or recycling waste water), 16 is water cooler, and 17 for adding water, 18 acid solutions for adding.
Among Fig. 3, reactant gases 2 after precooling enters quench tower lower portion, is extracted out from the tower still and sprays through water cooler 16 cooled circulation fluids 7, is 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 18 directly joins in the tower still, to regulate the pH value of still liquid.The amount of amount of makeup water 17 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 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, is 70 ℃ with water cooler cooling back spray liquid temperature, and to make the weight concentration of the polymkeric substance and composition thereof of vinyl cyanide, prussic acid or propenal in the tower still be 2.0% by increasing amount of makeup water, and still liquid pH value is 7.5.Contain vinyl cyanide 39.4 Grams Per Hours in the tower top outlet gas, the quench tower recovery of acrylonitrile is 93.8%.
[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, is 60 ℃ with water cooler cooling back spray liquid temperature, and 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 adding water, and still liquid pH value is 7.5.Contain vinyl cyanide 39.7 Grams Per Hours in the tower top outlet gas, the quench tower recovery of acrylonitrile is 94.5%.
[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, with water cooler cooling back spray liquid temperature is 50 ℃, 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, directly add in the tower still with acetic acid, regulating still liquid pH value 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 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, is 60 ℃ with water cooler cooling back spray liquid temperature, and adding the water yield by increase, to make the weight concentration of the polymkeric substance and composition thereof of vinyl cyanide, prussic acid or propenal in the tower still be 2%.Add oxalic acid in the tower still, still liquid pH value is 7.3.Contain vinyl cyanide 40.0 Grams Per Hours in the tower top outlet gas, the quench tower recovery of acrylonitrile is 95.2%.
Claims (10)
1, a kind of quick cooling method that improves recovery of acrylonitrile may further comprise the steps successively:
A) quench tower is made up of for two sections epimere and hypomere at least, between epimere and the hypomere catch tray is arranged, and riser is arranged on the catch tray;
B) temperature is that the hypomere temperature is that 40～85 ℃ aqueous quench liquid contacts in quench tower lower portion in 180～280 ℃ the reactor effluent that contains ammonia and vinyl cyanide and the quenching system, quench tower lower portion is added water, 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 quick cooling method of the described raising recovery of acrylonitrile 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 spray liquid is 2～5.
3,, it is characterized in that the hypomere temperature is that 40～85 ℃ aqueous quench liquid is by realizing circulated sprinkling liquid with water cooler cooling according to the quick cooling method of the described raising recovery of acrylonitrile of claim 1.
4,, it is characterized in that hypomere aqueous quench liquid temp is 50～75 ℃ according to the quick cooling method of the described raising recovery of acrylonitrile of claim 1.
5,, it is characterized in that hypomere aqueous quench liquid temp is 60～70 ℃ according to the quick cooling method of the described raising recovery of acrylonitrile of claim 4.
6, according to the quick cooling method of the described raising recovery of acrylonitrile of claim 1, it is characterized in that adding water at 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, and wherein reorganization is divided into polymkeric substance of vinyl cyanide, prussic acid or propenal and composition thereof.
7,, it is characterized in that heavy constituent concentration is 0.5～4.0% by weight percentage in the quench tower lower portion tower bottoms according to the quick cooling method of the described raising recovery of acrylonitrile of claim 6.
8,, it is characterized in that heavy constituent concentration is 0.5～2.0% by weight percentage in the quench tower lower portion tower bottoms according to the quick cooling method of the described raising recovery of acrylonitrile of claim 7.
9,, it is characterized in that quench tower lower portion tower bottoms pH value is 7～7.5 according to the quick cooling method of the described raising recovery of acrylonitrile of claim 1.
10,, it is characterized in that quench tower lower portion tower bottoms pH value is 7～7.3 according to the quick cooling method of the described raising recovery of acrylonitrile of claim 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB011319577A CN1161328C (en) | 2001-10-22 | 2001-10-22 | Quench process for raising recovery of acrylonitrile |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB011319577A CN1161328C (en) | 2001-10-22 | 2001-10-22 | Quench process for raising recovery of acrylonitrile |
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| CN1413983A CN1413983A (en) | 2003-04-30 |
| CN1161328C true CN1161328C (en) | 2004-08-11 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNB011319577A Expired - Lifetime CN1161328C (en) | 2001-10-22 | 2001-10-22 | Quench process for raising recovery of acrylonitrile |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106474900A (en) * | 2015-08-26 | 2017-03-08 | 中国石油化工股份有限公司 | Improve recovery of acrylonitrile the chilling tower apparatus of reduces cost and quick cooling method |
| CN116531929B (en) * | 2023-07-06 | 2023-09-19 | 潍坊奥瑞环保科技有限公司 | Quenching tower device for improving acrylonitrile recovery rate |
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- 2001-10-22 CN CNB011319577A patent/CN1161328C/en not_active Expired - Lifetime
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