CN2432211Y - Acrylonitrile quench tower - Google Patents

Abstract

The utility model relates to an acrylonitrile quench tower, which mainly solves the problem that in the existing literature, a quench technology needs to process a deep well of waste water of ammonium salt or that acrylonitrile is polymerized with ammonium on the position of a quench tower with serious loss to cause low recovery rate of the acrylonitrile of the quench tower. The utility model better solves the problem by that two segments of quench towers are adopted, the lower segments of the quench towers are hollow towers, the upper segments of the quench towers are provided with one to ten tower boards, and the middles of the quench towers are provided with air ascension pipes. The utility model can be used for industrial production.

Description

Acrylonitrile quench tower

The utility model relates to acrylonitrile quench tower.

The production of ammoxidation of hydrocarbons system unsaturated nitrile is a key areas of petrochemical industry, wherein propylene or isobutene ammonia oxidizing acrylonitrile production and 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 neutralizing 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 neutralizing tower.Because vinyl cyanide and prussic acid all are easy polymeric materials, easier polymerization under neutral and slight alkalinity 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 nearby about 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 ℃, in acid fully and unreacted ammonia, behind the washing reaction gas, import epimere herein, is 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 the requirement of epimere quantity of circulating water is more than 10 times of extraction amount.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 ℃, in acid and behind the unreacted ammonia, washing reaction gas, imports 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 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, improve the rate of recovery of vinyl cyanide at quench tower, must possess the technology that the direct deep-well of ammonium salt waste liquid is handled but do like this, otherwise the contaminated meeting of ammonium salt causes reclaiming difficulty.

The purpose of this utility model is that document exists and the direct deep-well of ammonium salt waste liquid must be handled in order to overcome in the past, could improve the shortcoming of recovery of acrylonitrile, and a kind of new acrylonitrile quench tower is provided.This quench tower does not have and will handle by the direct deep-well of ammonium salt waste liquid, can improve the characteristics of recovery of acrylonitrile simultaneously.

The purpose of this utility model is to realize by following technical scheme: a kind of acrylonitrile quench tower, form for two sections by epimere and hypomere, and wherein hypomere is a void tower, epimere is the column plate type structure of 1～10 block of column plate, is riser between epimere and the hypomere.

In the technique scheme aisle spare of riser be tower section long-pending 15～30%; Quench tower epimere stage number preferable range is 1～5.

The utility model makes reactor outlet gas reduce in the residence time of quench tower lower portion by regulating the aisle spare of going up riser between the hypomere, has reduced the chance of vinyl cyanide and unreacted ammonia react loss.Simultaneously, the column plate type structure of quench tower epimere has been improved mass transfer and the heat transfer between gas-liquid two-phase, has improved and has removed the ammonia effect, has improved the rate of recovery of vinyl cyanide at quench tower, simultaneously because therefore capable of circulation, the recovery of ammonium salt in the epimere circulation fluid can avoid the direct deep-well of ammonium salt waste liquid to handle.Confirm that through test the rate of recovery of vinyl cyanide has improved more than 4%, has obtained effect preferably.

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, and 4 is column plate, and 5 is filler, 6 is water cooler, and 7 are outer circulation liquid, and 8 is Extract, and 9 is acid solution, and 10 for working off one's feeling vent one's spleen, 11 is epimere still liquid, and 12 is hypomere still liquid, and 13 is gas flowfield, and 14 is nozzle.

Below by embodiment the utility model is further elaborated: [embodiment 1]

The weight percent of reactor outlet gas consists of: vinyl cyanide 12.1%, and acetonitrile 0.5%, prussic acid 1.5%, propenal 0.1%, vinylformic acid 0.3%, ammonia 0.4%, other are 85.1% years old.The reactor outlet airshed is 43.87 tons/hour, 220 ℃ of feeding temperatures, adopt the quench tower design cycle of Fig. 3: epimere stage number 2, riser duct area 18%, it is 3.2 that epimere adds sulfuric acid control pH value, and hypomere does not add acid, and the quench tower recovery of acrylonitrile is 94%, tower epimere height is 6.6 meters, and tower diameter is 3.4 meters.[embodiment 2]

Adopt Fig. 3 quench tower design cycle, just the epimere stage number is 10, riser duct area 22%, and other condition is with embodiment 1, evidence, the quench tower recovery of acrylonitrile is 93.5%, and tower epimere height is 7.1 meters, and tower diameter is 3.4 meters.[embodiment 3]

Adopt Fig. 3 quench tower design cycle, just the epimere stage number is 5, and the epimere pH value is controlled to be 5.0, riser duct area 28%, and other condition is with embodiment 1.Evidence, quench tower recovery of acrylonitrile are 93.0%, and tower epimere height is 6.9 meters, and tower diameter is 3.4 meters.[comparative example 1]

Reactor outlet gas is formed with embodiment 1,15 kilograms/hour of flows, and 220 ℃ of feeding temperatures adopt quench tower design cycle shown in Figure 1, and filler is a Raschig ring, epimere stage number 5, hypomere does not add acid, epimere pH value 3.2.Evidence: the quench tower recovery of acrylonitrile is 86%.[comparative example 2]

Reactor outlet gas is formed with embodiment 1,15 kilograms/hour of flows, and 220 ℃ of feeding temperatures adopt quench tower design cycle shown in Figure 2, and the epimere filler is the magnetic Raschig ring, and hypomere does not add acid, epimere pH value 5.0.Evidence: the quench tower recovery of acrylonitrile is 89%.

Claims (3)

1, a kind of acrylonitrile quench tower is made up of for two sections epimere and hypomere, and wherein hypomere is a void tower, and epimere is the column plate type structure of 1～10 block of column plate, is riser between epimere and the hypomere.

2, acrylonitrile quench tower according to claim 1, the aisle spare that it is characterized in that riser be tower section long-pending 15～30%.

3, acrylonitrile quench tower according to claim 1 is characterized in that the epimere stage number is 1～5.

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