CN205461091U - Modified underpressure distillation tower and acetonitrile system of refining - Google Patents
Modified underpressure distillation tower and acetonitrile system of refining Download PDFInfo
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- CN205461091U CN205461091U CN201520688119.2U CN201520688119U CN205461091U CN 205461091 U CN205461091 U CN 205461091U CN 201520688119 U CN201520688119 U CN 201520688119U CN 205461091 U CN205461091 U CN 205461091U
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Abstract
The utility model relates to an underpressure distillation tower of the refined system of acetonitrile, this underpressure distillation tower include rectifying section and stripping section, its characterized in that set up the regular packing in the rectifying section as component in the rectifying section. According to the utility model discloses an underpressure distillation tower when obtaining higher separation efficiency, can also effectively reduce the tower height, save the equipment investment.
Description
Technical field
This utility model relates to the vacuum distillation tower of a kind of improvement and uses the acetonitrile refining system of this vacuum distillation tower.
Background technology
In ammoxidation of propylene acrylonitrile production production technology, acetonitrile, hydrocyanic acid are as by-product recovery.Generally use by decyanation tower, chemical treatment, reduce pressure, the group technology of the azeotropic distillation that pressurizes, acetonitrile is reclaimed continuously, can effectively remove the impurity such as water and hydrocyanic acid, acrylonitrile, propionitrile, propenyl in acetonitrile.
Such as, the technique that EP055920 discloses a kind of continuous recovery acetonitrile.This technique uses the rectification removing Light ends such as hydrocyanic acid, adds alkali and add formaldehyde chemical treatment and remove hydrocyanic acid, rectification under vacuum and the method for compression rectification combined dehydration further, improves the refined recovery rate of acetonitrile, the acetonitrile product of available higher degree.But the process adds and add formaldehyde chemical treatment step, operation complexity.The technique that CN1328993A also reports a kind of continuous recovery acetonitrile.By setting up an alkali metal hydroxide or the charging aperture of alkaline earth metal hydroxide at the rectifying section of traditional vacuum rectification tower and compression rectification tower, alkali compounds is added in local, utilize cyanalcohol can decomposite free HCN under conditions of alkalescence heats, and the compound that HCN is easy and alkaline metal cpds generation is stable decomposited, thus the characteristic removed by rectification, make the HCN decomposing out in distillation process successfully to discharge from tower bottom of rectifying tower, reach to remove the purpose of trace HCN in acetonitrile.
In the prior art, for the vacuum distillation tower in acetonitrile refining system, in the case of scale is less, in tower, employing filler is as inner member, and in the case of larger, in tower, the board-like tower tray of many employings is as inner member.
Owing to having, specific surface area is big, pressure drop is little, fluid divides uniformly, mass-and heat-transfer efficiency advantages of higher in structured packing, is therefore widely used.Particularly screen waviness packings, has the advantage efficient, pressure drop is low and flux is big, is more suitable for the rectification under vacuum for difficult separation mixture.But containing heavy constituent and polymeric impurities in the charging of native system vacuum distillation tower, easily cause the blocking of structured packing at charging aperture with lower part, thus affect the long-term operation of equipment.Therefore, reasonably combined column inner member, is this tower height effect, the key of stable operation.
Utility model content
The present inventor finds through long-term research, uses different inner members by the different tower section at vacuum distillation tower, it is possible to realize reducing tower height and tower pressure drop, making the effects such as plant running is more stable, equipment investment is lower.
[1] first aspect of the present utility model provides the vacuum distillation tower for acetonitrile refining system of a kind of improvement, and this vacuum distillation tower includes rectifying section and stripping section, wherein, arranges structured packing as rectifying section inner member in described rectifying section.
[2] in the vacuum distillation tower described in [1], it is preferable that described structured packing is ripple packing.
[3] in the vacuum distillation tower described in [2], it is preferable that described ripple packing is screen waviness packings.
[4] in the vacuum distillation tower described in [1], it is preferable that board-like tower tray is set in described stripping section as stripping section inner member.
[5] in the vacuum distillation tower described in [1], it is preferable that random packing is set in described stripping section as stripping section inner member.
[6] in the vacuum distillation tower described in [1]～[5] any one, it is preferable that described vacuum distillation tower is configured with 1～60 piece of theoretical plate.
[7] in the vacuum distillation tower described in [6], it is preferable that described stripping section is configured with 1～30 piece of theoretical plate.
[8] in the vacuum distillation tower described in [6], it is preferable that described rectifying section is configured with 1～30 piece of theoretical plate.
[9] another aspect of the present utility model provides a kind of acetonitrile refining system, including:
Decyanation tower, this decyanation tower is used for separating raw material crude acetonitrile, to remove light component, part water and the weight Organic substance in described raw material crude acetonitrile, and extracts out containing water-acetonitrile from the stripping section bottom side line gas phase of this decyanation tower；
Chemical treatment still, described enters this chemical treatment still containing water-acetonitrile, and is carried out adding alkali chemical treatment by this chemical treatment still, with obtain be stripped of free HCN containing water-acetonitrile；
[1] vacuum distillation tower～described in [8] any one, described in be stripped of free HCN enter this vacuum distillation tower containing water-acetonitrile, to steam the acetonitrile being stripped of major part water from the tower top of this vacuum distillation tower；And
Distillation under pressure tower, described in be stripped of the acetonitrile of major part water and enter this distillation under pressure tower, steam aqueous acetonitrile material with the tower top from this distillation under pressure tower and return vacuum distillation tower charging, and extracting high-purity acetonitrile out in the stripping section bottom gas phase of this distillation under pressure tower.
Utility model effect
Use vacuum distillation tower of the present utility model, tower height and tower pressure drop can not only be reduced, additionally it is possible to the equipment that realizes runs the feature more stable, equipment investment is lower.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of vacuum distillation tower of the present utility model.
List of reference signs
1: vacuum distillation tower
2: vacuum distillation tower condenser
3: vacuum distillation tower return tank
Detailed description of the invention
Below with reference to accompanying drawing, detailed description of the invention of the present utility model is described.
Acetonitrile refining process of the present utility model, comprises the following steps:
The Light ends such as a) raw material crude acetonitrile separates through decyanation tower, major part HCN are discharged by tower top, and part water and weight Organic substance are discharged by tower reactor；
B) be stripped of Light ends adds alkali chemical treatment through chemical treatment still containing water-acetonitrile after decyanation tower stripping section bottom side line gas phase is extracted out；
C) after adding the alkali chemical treatment free HCN of removing, vacuum distillation tower is entered containing water-acetonitrile, at tower reactor removing weight Organic substance；
D) steaming from vacuum distillation tower tower top and be stripped of the acetonitrile of major part water and enter distillation under pressure tower, tower top steams aqueous acetonitrile material and returns vacuum distillation tower charging, extracts high-purity acetonitrile out in stripping section bottom gas phase.
In step a), raw material crude acetonitrile can come from any applicable source, such as from acrylonitrile installation acetonitrile desorbing tower top, by weight percentage, its composition can include 20～80% acetonitrile, 1～4%HCN, 0.1～0.3% acrylonitrile, 0.3～0.7% propionitrile, 20～79% water.Raw material crude acetonitrile is extracted out from stripping section bottom side line gas phase after decyanation column distillation and is removed chemical treatment still containing about the acetonitrile material of acetonitrile 75%.The actual conditions of decyanation tower is as follows: tower top pressure is 0.10～0.125Mpa, and feeding temperature is 30～80 DEG C, and tower top drop temperature is 35～60 DEG C, and stripping section lateral line withdrawal function temperature is 85～100 DEG C, and bottom temperature is 105～120 DEG C.
The acetonitrile material containing about acetonitrile 75% from decyanation tower side line enters chemical reaction kettle and carries out chemical treatment, removes the impurity such as free hydrogen cyanic acid and a small amount of acrylonitrile, and the reactant liquor after chemical treatment enters vacuum distillation tower 1.In terms of chemical treatment still, the alkali added is alkali metal hydroxide or alkaline earth metal hydroxide；It is preferably sodium hydroxide or potassium hydroxide；More preferably sodium hydroxide.
Vacuum distillation tower 1 aspect, tower top pressure is 0.013～0.04Mpa, and feeding temperature is 30～50 DEG C, and tower top temperature is 30～50 DEG C, and bottom temperature is 50～75 DEG C.
Part from the return tank of top of the tower 3 of vacuum distillation tower 1 contains the acetonitrile of less moisture content and enters distillation under pressure column distillation, and obtains acetonitrile of high purity product from distillation under pressure tower side line.In terms of distillation under pressure tower, tower top pressure is 0.1～0.5Mpa, and feeding temperature is 30～90 DEG C, and tower top temperature is 90～140 DEG C, and stripping section lateral line withdrawal function temperature is 100～135 DEG C, and bottom temperature is 110～145 DEG C.
Vacuum distillation tower of the present utility model is described in detail below with reference to Fig. 1.
As it is shown in figure 1, the acetonitrile material 7 coming from the aqueous of the chemical treatment still of acetonitrile refining system of the present utility model and heavy constituent impurity enters in the middle part of vacuum distillation tower 1.Vacuum distillation tower 1 is configured with pipeline connection port 8, for accepting to enter the raw material of this tower.Tower interior conduit connector less than 8 is configured with the board-like tower tray of polylith or random packing 5, is used for separating water and heavy constituent impurity；Tower interior conduit connector 8 configuration as above has structured packing 6, for concentrating and can obtain the acetonitrile material 9 containing acetonitrile about 90%.
Vacuum distillation tower system is configured with overhead condenser 2 and return tank 3, and after vacuum distillation tower distills, top gaseous phase material 9 sends into return tank 3 after sending into overhead condenser 2 condensation cooling.Return tank 3 is configured with pipe joint 4, and pipe joint 4 is arranged to connect pumped vacuum systems, so that the vacuum needed for the acquisition of vacuum tower system.The overhead condensation liquid part 10 entering return tank is admitted to vacuum distillation tower overhead reflux mouth as backflow, and another part 14 sends to distillation under pressure tower as charging.Distilling through vacuum distillation tower, aqueous and heavy constituent impurity still liquid 11 discharges waste water from tower reactor and processes.
Vacuum distillation tower of the present utility model is configured with 1～60 piece of theoretical plate；Preferably, 10～50 pieces of theoretical plates of configuration；It is highly preferred that 24～36 pieces of theoretical plates of configuration.
As it has been described above, stripping section inner member uses board-like tower tray or random packing；Preferably, vacuum distillation tower stripping section inner member uses high-efficient tower plate or efficiently random packing.Vacuum distillation tower stripping section of the present utility model is configured with 1～30 piece of theoretical plate；Preferably, 10～20 pieces of theoretical plates of configuration；It is highly preferred that 12～18 pieces of theoretical plates of configuration.
As it has been described above, rectifying section inner member uses structured packing；Preferably, vacuum distillation tower rectifying section inner member uses ripple packing；It is highly preferred that vacuum distillation tower rectifying section inner member uses screen waviness packings.Vacuum distillation tower rectifying section of the present utility model is configured with 1～30 piece of theoretical plate；It is highly preferred that 10～20 pieces of theoretical plates of configuration；It is highly preferred that 12～18 pieces of theoretical plates of configuration.
Embodiment
Below by way of specific embodiment, this utility model is further elaborated.
[embodiment 1]
With weight, containing acetonitrile 50%, the raw material crude acetonitrile of hydrocyanic acid 1.5%, adding from the middle part of dehydrogenation cyanic acid tower, operation pressure is normal pressure, and tower top temperature is 50 DEG C, and bottom temperature is 115 DEG C, and stripping section lateral line withdrawal function temperature is 92 DEG C.Removed overhead hydrocyanic acid, stripping section lateral line withdrawal function concentration be 75% acetonitrile go chemical treatment.Add enough 40%NaOH solution reactions 4～6 hours.Vacuum distillation tower decompression dehydration and distillation under pressure tower pressurizing and dehydrating is entered after chemical treatment.
Vacuum distillation tower uses 30 pieces of theoretical plates, the acetonitrile that concentration is 75% from chemical treatment still enters in the middle of 15～16 pieces of theoretical plates in the middle part of tower, 28 pieces of light-duty float valves that stripping section uses plate spacing to be 500mm, rectifying section is designed with BX type screen waviness packings, packed height 7 meters, tower top pressure is 0.026Mpa, tower top temperature 40 DEG C, bottom temperature 64 DEG C, getting rid of the impurity such as water and propionitrile from vacuum distillation tower tower reactor, tower top obtains the acetonitrile material that concentration is 90%.A vacuum distillation tower tower top material part passes back into tower top, and another part removes distillation under pressure tower.
Distillation under pressure column overhead pressure is 0.3MPa, tower top temperature 108 DEG C, bottom temperature 125 DEG C, obtains finished product acetonitrile from distillation under pressure tower side line.Refining through above flow process, acetonitrile 99.95%, propionitrile 148ppm, water 345ppm in finished product acetonitrile.
[comparative example 1]
In addition to 28 pieces of light-duty float valves that rectifying section uses spacing to be 450mm, use equipment same as in Example 1 and condition, raw material crude acetonitrile is refined.As a result, acetonitrile 99.95%, propionitrile 150ppm, water 350ppm in the finished product acetonitrile obtained.
By using vacuum distillation tower of the present utility model, in the case of obtaining the acetonitrile product that quality is essentially identical, making total tower height reduce by 5 meters, tower rectifying section equipment investment reduces 25%.
Claims (9)
1., for a vacuum distillation tower for acetonitrile refining system, this vacuum distillation tower includes rectifying section and stripping section, it is characterised in that arrange structured packing in described rectifying section as rectifying section inner member.
Vacuum distillation tower the most according to claim 1, it is characterised in that described structured packing is ripple packing.
Vacuum distillation tower the most according to claim 2, it is characterised in that described ripple packing is screen waviness packings.
Vacuum distillation tower the most according to claim 1, it is characterised in that board-like tower tray is set in described stripping section as stripping section inner member.
Vacuum distillation tower the most according to claim 1, it is characterised in that random packing is set in described stripping section as stripping section inner member.
6. according to the vacuum distillation tower described in Claims 1 to 5 any one, it is characterised in that described vacuum distillation tower is configured with 1～60 piece of theoretical plate.
Vacuum distillation tower the most according to claim 6, it is characterised in that described stripping section is configured with 1～30 piece of theoretical plate.
Vacuum distillation tower the most according to claim 6, it is characterised in that described rectifying section is configured with 1～30 piece of theoretical plate.
9. an acetonitrile refining system, it is characterised in that including:
Decyanation tower, this decyanation tower is used for separating raw material crude acetonitrile, to remove light component, part water and the weight Organic substance in described raw material crude acetonitrile, and extracts out containing water-acetonitrile from the stripping section bottom side line gas phase of this decyanation tower；
Chemical treatment still, described enters this chemical treatment still containing water-acetonitrile, and is carried out adding alkali chemical treatment by this chemical treatment still, with obtain be stripped of free HCN containing water-acetonitrile；
Vacuum distillation tower described in claim 1～8 any one, described in be stripped of free HCN enter this vacuum distillation tower containing water-acetonitrile, to steam the acetonitrile being stripped of major part water from the tower top of this vacuum distillation tower；And
Distillation under pressure tower, described in be stripped of the acetonitrile of major part water and enter this distillation under pressure tower, steam aqueous acetonitrile material with the tower top from this distillation under pressure tower and return vacuum distillation tower charging, and extracting high-purity acetonitrile out in the stripping section bottom gas phase of this distillation under pressure tower.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106492495A (en) * | 2015-09-07 | 2017-03-15 | 中国石油化工股份有限公司 | Improved vacuum distillation tower and acetonitrile refining system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106492495A (en) * | 2015-09-07 | 2017-03-15 | 中国石油化工股份有限公司 | Improved vacuum distillation tower and acetonitrile refining system |
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