CN1508122A

CN1508122A - Acrylonitrile quench tower

Info

Publication number: CN1508122A
Application number: CNA021551170A
Authority: CN
Inventors: 辉张; 张辉; 甘永胜; 何志
Original assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Current assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Priority date: 2002-12-17
Filing date: 2002-12-17
Publication date: 2004-06-30
Anticipated expiration: 2022-12-17
Also published as: CN1199940C

Abstract

The present invention relates to a quenching tower of acrylonitrile. Said quenching tower is characterized by that an internal member formed from 1-12 filling material units whose exterior is made into the form of cylinder and interior channel is made into the regular or irregular geometric form can be added in the lower section of quenching tower interior. Said invention can reduce loss of acrylonitrile in the quenching tower by about 50%, and can raise its recovery rate by 3.9-5.0%.

Description

Acrylonitrile quench tower

Technical field

The present invention relates to a kind of acrylonitrile quench tower.

Background technology

Vinyl cyanide is one of important Organic Chemicals, throughput in the existing considerable scale of China, the level of relevant vinyl cyanide technology is equivalent to foreign technology on the whole, but aspect the emergency cooling process and the refining rate of recovery of raising vinyl cyanide of reactor tail gas, no matter be imported unit or domestic design apparatus voluntarily, effect is all undesirable.According to demarcation analysis repeatedly, to produce at home in the device of vinyl cyanide, the refining rate of recovery of vinyl cyanide generally has only about 90%, and wherein the loss at quench tower inner propene nitrile just accounts for about 8%.

Vinyl cyanide transforms for making propylene mainly by the preparation of ammoxidation of propylene method as far as possible at present, generally all adopts the excessive processing method of ammonia, therefore, contains a certain amount of unreacted ammonia in the reactor tail gas.Because ammonia is easy and acrylonitrile polymerization, and vinyl cyanide also is easy to autohemagglutination with another primary product prussic acid under alkaline condition, therefore, the unreacted ammonia of removing in quenching process in the reactor tail gas is just very important.Abroad in the device, general directly add in the acid and unreacted ammonia, reduce the chance that unreacted ammonia loses at hypomere and acrylonitrile polymerization at hypomere.

Introduced a kind of quench tower equipment and quick cooling method of vinyl cyanide in the document JP 80104246, the hypomere of its quench tower is the Raschig ring filler, and each section of top is the structure of sieve-tray tower.The hypomere of this invention is a sour environment, and filler is used to increase the gas-to-liquid contact surface; Epimere is a neutral environment, and plank frame is convenient to side line extraction material.This invention only adds acid at hypomere, and it is not high to remove the ammonia effect; Claim that according to this patent the pressure-controlling in the tower requires high, pressure is higher a little, and the polymerization losses of vinyl cyanide just increases.Therefore, the loss in acrylonitrile of this quench tower equipment is bigger, and the rate of recovery of vinyl cyanide is not high.

A kind of emergency cooling process of vinyl cyanide and used quench tower equipment have been introduced in the document WO 96/23765.The hypomere of its tower is a void tower, and all the other each sections are magnetic Raschig ring filler.The hypomere of this patent is a sour environment, can add acid at epimere in case of necessity.Claim that according to the document ammonia effect of removing of this quench tower equipment can be more than 90%.But because the hypomere of equipment does not have any inner member, gas-liquid herein distributes very unreasonable, and it is incomplete to remove ammonia, and the loss of vinyl cyanide is still very big.

Above-mentioned document all directly adds in the acid and unreacted ammonia at the hypomere of quench tower equipment, causes containing ammonium salt in the hypomere sewage, has increased the sewage disposal difficulty.Hypomere at fast cooling device increases filler, because the hypomere material is dirtier, contains some catalyst dusts that bring from reactor, and impurity such as some high boiling material and polymkeric substance result in blockage easily.And if the hypomere of fast cooling device does not have any inner member, form the gas-liquid skewness easily herein, in causing and unreacted ammonia effect undesirable, increased the loss of vinyl cyanide greatly.

Summary of the invention

Technical problem to be solved by this invention is to overcome to produce in the past that hypomere sewage contains ammonium salt in the acrylonitrile process technology, ammonium salt can't reclaim, sewage must be handled by deep-well, and tower be easy to blocking problem or since the tower hypomere do not have any inner member, cause the gas-liquid irrational distribution, the hypomere part is than strong basicity, and vinyl cyanide provides a kind of new acrylonitrile quench tower in the problem that this loss increases.This quench tower can avoid forming ammonium salt sewage, needn't handle ammonium salt sewage by deep-well, and increase inner member, and the gas-liquid of having improved device interior distributes, and has reduced the polymerization losses of vinyl cyanide under alkaline environment, has improved the rate of recovery of vinyl cyanide.

For solving the problems of the technologies described above, the technical solution used in the present invention is as follows: a kind of acrylonitrile quench tower, at least form for two sections by epimere and hypomere, catch tray is arranged in the middle of epimere and the hypomere, riser is arranged on the catch tray, epimere is the column plate type structure of 1～10 block of column plate, hypomere is the spray structure that contains inner member, wherein spray structure is positioned at below the catch tray, above the inner member, inner member is circular by 1～12 outside, and the internal passages is that the filler unit of rule or random geometry is formed, the height of filler unit equals the height of inner member, and is vertical arrangement side by side.

In the technique scheme, the column plate preferred version of epimere is reverse-flow double overflow column plate.The inner member bottom is positioned at the bottom of the chilling Tata, and the inner member top is identical with liquid level on the on-the-spot liquid level meter of chilling Tata still.The geometrical shape preferred version of filler unit internal passages is circle, equilateral triangle, rectangle or regular polygon, the upper bottom surface of filler unit is more than or equal to the bottom surface of filler unit, the internal passages arithmetical mean sectional area of all filler units is 10～80% of a quench tower sectional area, and preferable range is 25～75%.

Hypomere did not add acid when acrylonitrile quench tower of the present invention used, be alkaline environment, after gas enters hypomere, because the effect of inner member has produced a new gas distribution, this distribution can contact with circulated sprinkling liquid is reverse targetedly, reduce gas phenomenon such as laterally inhomogeneous and back-mixing in tower, under the prerequisite that does not influence chilling, washing effect, reduced the polymerization chance of unreacted ammonia and vinyl cyanide.Circulated sprinkling liquid is contacting with gas after newly-increased inner member is gone out from the tower still.Because vinyl cyanide has certain solubleness in water, therefore, must reduce the solution loss and because the polymerization losses of dissolving back in liquid phase of vinyl cyanide.Newly-increased inner member has limited the flow direction of tower still internal recycle spray liquid, reduced still liquid in the tower still because diffusion and the horizontal back-mixing that concentration gradient forms, reduce the residence time and vinyl cyanide the dissolving in liquid phase of still liquid in tower, therefore reduced the loss of vinyl cyanide.Simultaneously, because newly-increased inner member has the certain amount of fluid passage, therefore be difficult for being stopped up by catalyst fines or other polymeric impurities.

Because riser has certain height, all there is gas-liquid phase problem of uneven distribution between riser and riser top, mass transfer and heat-transfer effect in this space between gas-liquid two-phase are undesirable, in and the effect of unreacted ammonia bad, strengthened the polymerization losses of vinyl cyanide.Behind the newly-increased column plate of each section of top, gas-liquid obtains redistribution, and more even, gas-to-liquid contact is more abundant, and two alternate mass transfer and heat-transfer effects have clear improvement, and the loss of vinyl cyanide is reduced.Full scale plant is used proof: use acrylonitrile quench tower of the present invention, the recovery of acrylonitrile of whole device can improve 3.9～5.0%, and it is about 50% that the loss in acrylonitrile of quench tower has reduced, and obtained better technical effect.

Description of drawings

Fig. 1 is the quench tower equipment and the emergency cooling process flow process of document JP 80104246.

Fig. 2 is the quench tower equipment and the emergency cooling process flow process of document WO 9623765.

Fig. 3 A is acrylonitrile quenching tower of the present invention and emergency cooling process flow process.

Fig. 3 B, Fig. 3 C are respectively the filler unit that constitutes inner member.

1 is quench tower among Fig. 1, Fig. 2, Fig. 3, and 2 is reactor tail gas, and 3 is the riser on the catch tray, 4 is column plate, and 5 is filler, and 6 is water cooler, 7 is hypomere outer circulation liquid, and 8 is Extract, and 9 is acid solution, 10 is quench tower tail gas, 11 is epimere still liquid, and 12 is hypomere still liquid, 13 nozzles, 14 are inner member of the present invention, and 15 is epimere outer circulation liquid.D1, D2 are the outer surface diameter up and down of filler unit, and d1, d2 are the upper and lower surface calculated diameter of filler unit internal passages, and H is the height of filler unit.

Among Fig. 3, the reactor tail gas 2 after precooling enters quench tower lower portion, produces a new gas distribution field under the effect of inner member 14.Be chilled to 65～85 ℃ after gas and hypomere outer circulation liquid 7 reverse the contacts.Circulation fluid 7 is contacting with reactor tail gas 2 after inner member 14 is discharged from the tower still, and 2 of reactor tail gas are contacting after riser rises to the quench tower epimere.Gas is redistributed after by epimere column plate 4 again, ejects from quench tower with the epimere outer circulation liquid 15 reverse backs that contact, and enters the subsequent technique flow process.

The present invention is further elaborated below by embodiment.

Embodiment

[comparative example 1]

Reactor tail gas is formed (weight %): vinyl cyanide 12.3, and acetonitrile 0.5, prussic acid 1.5, propenal 0.1, vinylformic acid 0.2, ammonia 0.4, other are 85.0 years old.Flow is 9.25 tons/hour, 230 ℃ of feeding temperatures, and the quench tower two sections of employing are all for void tower designs, and hypomere does not add acid.The recovery of acrylonitrile of full scale plant is 89.1%, and the recovery of acrylonitrile of quench tower is 90.7%.

[comparative example 2]

Reactor tail gas is formed (weight %): vinyl cyanide 12.3, and acetonitrile 0.5, prussic acid 1.5, propenal 0.1, vinylformic acid 0.2, ammonia 0.4, other are 85.0 years old.Flow is 49 kilograms/hour, and 230 ℃ of feeding temperatures, the quench tower lower portion of employing are the Raschig ring filler, and epimere is a column plate, and stage number is 5, and hypomere does not add acid.Experimental results show that: the recovery of acrylonitrile of quench tower is 91.5%.

[embodiment 1]

Reactor tail gas is formed (weight %): vinyl cyanide 12.1, and acetonitrile 0.5, prussic acid 1.4, propenal 0.1, vinylformic acid 0.4, ammonia 0.4, other are 85.1 years old.Flow is 9.25 tons/hour, 230 ℃ of feeding temperatures, adopt quench tower of the present invention, the filler unit number of inner member 14 is 7, and the internal passages of filler unit is an equilateral triangle, D2=0.5D1, d2=0.5dl, the internal passages arithmetical mean sectional area of all filler units be tower section long-pending 75%, the epimere stage number is 7, hypomere does not add acid.The recovery of acrylonitrile of quench tower is 95.8%, and the full scale plant recovery of acrylonitrile is 94.4%.

[embodiment 2]

Reactor tail gas is formed (weight %): vinyl cyanide 12.1, and acetonitrile 0.5, prussic acid 1.4, propenal 0.1, vinylformic acid 0.4, ammonia 0.4, other are 85.1 years old.Flow is 9.25 tons/hour, 230 ℃ of feeding temperatures, adopt quench tower of the present invention, the filler unit number of inner member 14 is 4, and the internal passages of filler unit is a regular pentagon, D2=0.75D1, d2=0.75dl, the internal passages arithmetical mean sectional area of all filler units be tower section long-pending 45%, the epimere stage number is 5, hypomere does not add acid.The recovery of acrylonitrile of quench tower is 96.6%, and the recovery of acrylonitrile of full scale plant is 95.1%.

[embodiment 3]

Reactor tail gas is formed (weight %): vinyl cyanide 12.1, and acetonitrile 0.5, prussic acid 1.4, propenal 0.1, vinylformic acid 0.4, ammonia 0.4, other are 85.1 years old.Flow is 9.25 tons/hour, 230 ℃ of feeding temperatures, adopt quench tower of the present invention, the filler unit number of inner member 14 is 6, the internal passages of filler unit is circular, D2=D1, the internal passages arithmetical mean sectional area of all filler units of d2=d1 be tower section long-pending 25%, the epimere stage number is 3, and hypomere does not add acid.The recovery of acrylonitrile of quench tower is 96.2%, and the recovery of acrylonitrile of full scale plant is 94.7%.

Claims

1, a kind of acrylonitrile quench tower, at least form for two sections by epimere and hypomere, catch tray is arranged in the middle of epimere and the hypomere, riser is arranged on the catch tray, epimere is the column plate type structure of 1～10 block of column plate, hypomere is the spray structure that contains inner member, wherein spray structure is positioned at below the catch tray, above the inner member, it is characterized in that inner member is circular by 1～12 outside, the internal passages is that the filler unit of rule or random geometry is formed, and the height of filler unit equals the height of inner member, and is vertical arrangement side by side.

2, according to the described acrylonitrile quench tower of claim 1, the column plate that it is characterized in that epimere is reverse-flow double overflow column plate.

3, according to the described acrylonitrile quench tower of claim 1, it is characterized in that the inner member bottom is positioned at the bottom of the chilling Tata, the inner member top is identical with liquid level on the on-the-spot liquid level meter of chilling Tata still.

4, according to the described acrylonitrile quench tower of claim 1, the geometrical shape that it is characterized in that the filler unit internal passages is circle, equilateral triangle, rectangle or regular polygon, the upper bottom surface of filler unit is more than or equal to the bottom surface of filler unit, and the internal passages arithmetical mean sectional area of all filler units is 10～80% of a quench tower sectional area.

5,, it is characterized in that the internal passages arithmetical mean sectional area of all filler units is 25～75% of a quench tower sectional area according to the described acrylonitrile quench tower of claim 4.