CN219636938U - Recovery device for polyvinyl alcohol waste liquid - Google Patents
Recovery device for polyvinyl alcohol waste liquid Download PDFInfo
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- CN219636938U CN219636938U CN202320474659.5U CN202320474659U CN219636938U CN 219636938 U CN219636938 U CN 219636938U CN 202320474659 U CN202320474659 U CN 202320474659U CN 219636938 U CN219636938 U CN 219636938U
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- acetaldehyde
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- 239000007788 liquid Substances 0.000 title claims abstract description 62
- 239000002699 waste material Substances 0.000 title claims abstract description 35
- 239000004372 Polyvinyl alcohol Substances 0.000 title claims abstract description 29
- 229920002451 polyvinyl alcohol Polymers 0.000 title claims abstract description 29
- 238000011084 recovery Methods 0.000 title claims abstract description 22
- IKHGUXGNUITLKF-UHFFFAOYSA-N Acetaldehyde Chemical compound CC=O IKHGUXGNUITLKF-UHFFFAOYSA-N 0.000 claims abstract description 230
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 claims abstract description 136
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 claims abstract description 136
- 238000000926 separation method Methods 0.000 claims abstract description 128
- 238000000746 purification Methods 0.000 claims abstract description 72
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 138
- 239000007789 gas Substances 0.000 claims description 116
- 238000004821 distillation Methods 0.000 claims description 112
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 87
- 239000012071 phase Substances 0.000 claims description 71
- 238000003421 catalytic decomposition reaction Methods 0.000 claims description 43
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 32
- 238000007670 refining Methods 0.000 claims description 22
- 239000007791 liquid phase Substances 0.000 claims description 15
- 238000004064 recycling Methods 0.000 claims description 12
- 238000006136 alcoholysis reaction Methods 0.000 claims description 9
- 238000009833 condensation Methods 0.000 claims description 8
- 230000005494 condensation Effects 0.000 claims description 8
- 238000010992 reflux Methods 0.000 claims description 4
- 230000003197 catalytic effect Effects 0.000 claims 1
- 239000007792 gaseous phase Substances 0.000 claims 1
- 239000012808 vapor phase Substances 0.000 claims 1
- 230000001105 regulatory effect Effects 0.000 abstract description 16
- 238000004519 manufacturing process Methods 0.000 abstract description 15
- 230000000694 effects Effects 0.000 description 10
- DKPFZGUDAPQIHT-UHFFFAOYSA-N butyl acetate Chemical compound CCCCOC(C)=O DKPFZGUDAPQIHT-UHFFFAOYSA-N 0.000 description 8
- 230000001276 controlling effect Effects 0.000 description 7
- 230000006872 improvement Effects 0.000 description 5
- 239000002994 raw material Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000005265 energy consumption Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000007710 freezing Methods 0.000 description 2
- 230000008014 freezing Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000013067 intermediate product Substances 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000002918 waste heat Substances 0.000 description 2
- IKHGUXGNUITLKF-XPULMUKRSA-N acetaldehyde Chemical compound [14CH]([14CH3])=O IKHGUXGNUITLKF-XPULMUKRSA-N 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The utility model relates to a recovery device of polyvinyl alcohol waste liquid, which comprises a methyl acetate purification tower and an acetaldehyde crude separation tower, wherein a distilled gas phase of the methyl acetate purification tower is sent to the acetaldehyde crude separation tower, a first distilled condenser and a second distilled condenser are arranged between the methyl acetate purification tower and the acetaldehyde crude separation tower, the first distilled condenser and the second distilled condenser are connected in series or in parallel, and an acetaldehyde crude separation tower reboiler is also connected to the acetaldehyde crude separation tower. The feeding and the stable tower pressure of the acetaldehyde crude separation tower can be ensured, so that the purity of refined acetaldehyde produced by the device is ensured, and meanwhile, the device adopts an automatic regulating system and can adapt to low-load and high-load production requirements.
Description
Technical Field
The utility model relates to the technical field of chemical industry, in particular to a recycling device of polyvinyl alcohol waste liquid.
Background
The gas phase of a condenser distilled from a methyl acetate purifying tower of the prior polyvinyl alcohol waste liquid recovery device is used as an acetaldehyde crude separation tower for feeding, the distillate of the acetaldehyde crude separation tower is sent to an acetaldehyde refining tower for feeding, and the refined acetaldehyde distilled from the acetaldehyde refining tower is sent to a tank area for being sold. In the process, the feeding amount and the tower pressure of the acetaldehyde crude separation tower are controlled by controlling the opening of the cold medium circulating water inlet valve of the distillation condenser of the methyl acetate purification tower, and the feeding amount and the tower pressure of the acetaldehyde crude separation tower are unstable in operation and large in fluctuation of the tower pressure and the feeding amount, so that the feeding component of the acetaldehyde refining tower is greatly changed, the operation of the acetaldehyde refining tower is unstable, and the purity of refined acetaldehyde is influenced.
Disclosure of Invention
In view of the above, the utility model aims to provide a recovery device for polyvinyl alcohol waste liquid, which ensures the feeding and the stable tower pressure of an acetaldehyde crude separation tower. Meanwhile, the device adopts an automatic regulating system, and can adapt to low-load and high-load production requirements.
The utility model provides a recovery device of polyvinyl alcohol waste liquid, which comprises a methyl acetate purification tower and an acetaldehyde crude separation tower, wherein a distilled gas phase of the methyl acetate purification tower is sent to the acetaldehyde crude separation tower, a first distilled condenser and a second distilled condenser are arranged between the methyl acetate purification tower and the acetaldehyde crude separation tower, the first distilled condenser and the second distilled condenser are connected in series or in parallel, and an acetaldehyde crude separation tower reboiler is also connected to the acetaldehyde crude separation tower.
Preferably, the recovery device of the polyvinyl alcohol waste liquid further comprises a methyl acetate rough separation tower, a methanol purification tower, a catalytic decomposition tower, an acetic acid rough separation tower and an acetic acid purification tower; and after the alcoholysis waste liquid enters the methyl acetate coarse separation tower, the distillate phase is conveyed to the methyl acetate purification tower and the kettle liquid is conveyed to the methanol purification tower, the methyl acetate purification tower kettle liquid is conveyed to the methanol purification tower, one part of the methyl acetate purification tower distillate condenser liquid phase is conveyed to the catalytic decomposition tower, the other part of the methyl acetate purification tower distillate condenser liquid phase is conveyed to the upper part of the methyl acetate purification tower for reflux, the distillate condenser gas phase is conveyed to the acetaldehyde coarse separation tower, the catalytic decomposition tower kettle liquid is conveyed to the acetic acid coarse separation tower, and the acetic acid coarse separation tower kettle liquid is conveyed to the acetic acid purification tower.
Preferably, a heat source inlet of the reboiler of the crude acetaldehyde separation tower is connected with a hot water outlet of the methanol purification tower.
Preferably, a methyl acetate crude separation tower reboiler is connected to the methyl acetate crude separation tower, a heat source inlet of the methyl acetate crude separation tower reboiler is connected to a distillation gas phase outlet of the acetic acid purification tower, and a heat source outlet of the methyl acetate crude separation tower reboiler is connected to a distillation condenser inlet of the acetic acid purification tower.
Preferably, the recovery device of the polyvinyl alcohol waste liquid further comprises an acetaldehyde refining tower, wherein the effluent of the acetaldehyde crude separation tower is sent to a methyl acetate purifying tower distillation tank, the effluent of the acetaldehyde crude separation tower is sent to an acetaldehyde refining tower for feeding, the effluent of the acetaldehyde refining tower is sent to a tank area, the effluent of the acetaldehyde refining tower is sent to the methyl acetate purifying tower distillation tank, and one part of the acetic acid crude separation tower distillation gas phase is sent to the methyl acetate purifying tower, and the other part of the acetic acid crude separation tower distillation gas phase is sent to an acetic acid crude separation tower distillation condenser.
Preferably, the catalytic decomposition tower is connected with a catalytic decomposition tower tail gas condenser.
Preferably, the lower liquid outlet of the tail gas condenser of the catalytic decomposition tower is connected with the feeding tank of the acetaldehyde refining tower.
Preferably, the catalytic decomposition tower is connected with a catalytic decomposition tower distillation condenser, condensate of the catalytic decomposition tower distillation condenser is sent to a methyl acetate purifying tower, and non-condensed gas phase distilled and condensed by the catalytic decomposition tower is sent to a catalytic decomposition tower tail gas condenser for condensation.
Preferably, the non-condensed gas phase of the methyl acetate crude separation tower distillation condenser is connected with the gas phase inlet of the methyl acetate tail gas condenser through a pipeline, and the methyl acetate tail gas condenser condensate enters the methyl acetate purification tower distillation tank.
Preferably, the non-condensed gas phase of the tail gas condenser of the catalytic decomposition tower is connected with the gas phase inlet of the methyl acetate tail gas condenser.
According to the utility model, the first distillation condenser and the second distillation condenser are arranged between the methyl acetate purifying tower and the acetaldehyde crude separation tower, when the first distillation condenser and the second distillation condenser are connected in series, the distilled gas phase of the methyl acetate purifying tower firstly enters the first distillation condenser, the gas phase and the liquid phase condensed by the first distillation condenser both enter the second distillation condenser, the distilled gas phase of the second distillation condenser enters the acetaldehyde crude separation tower, the feeding quantity of the acetaldehyde crude separation tower is controlled by adjusting the opening of the circulating water inlet regulating valves of the first distillation condenser and the second distillation condenser, the regulating valve of the first distillation condenser is used for controlling the gas phase quantity entering the second distillation condenser, the regulating valve of the second distillation condenser is used for controlling the gas phase quantity entering the acetaldehyde crude separation tower, so that the feeding stability of the acetaldehyde crude separation tower is ensured, and meanwhile, the acetaldehyde crude separation tower is provided with the acetaldehyde crude separation tower so that the feeding stability and the tower pressure stability of the acetaldehyde crude separation tower are ensured, and the feeding component stability of the acetaldehyde crude separation tower is ensured, and the refined purity is ensured. When the first distillation condenser and the second distillation condenser are connected in parallel, the distilled gas phase of the methyl acetate purification tower simultaneously enters the first distillation condenser and the second distillation condenser, the distilled gas phase of the first distillation condenser and the distilled gas phase of the second distillation condenser simultaneously enter the acetaldehyde crude separation tower, the distilled liquid phase of the first distillation condenser and the distilled liquid phase of the second distillation condenser simultaneously enter the distilled tank of the methyl acetate purification tower, the first distillation condenser can be used as a main distillation condenser at the moment, the second distillation condenser is used as an auxiliary condenser, the opening of the circulating water inlet regulating valve of the first distillation condenser is set to be a fixed opening, the circulating water inlet regulating valve of the second distillation condenser is used for controlling the gas phase amount entering the acetaldehyde crude separation tower, and when the distilled gas phase of the second distillation condenser is insufficient for meeting the feeding requirement of the acetaldehyde crude separation tower, the opening of the circulating water inlet regulating valve of the first distillation condenser is regulated, and the gas phase amount of the distilled gas phase of the first distillation condenser entering the acetaldehyde crude separation tower is increased, so that stable feeding of the acetaldehyde crude separation tower is ensured.
Drawings
In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present utility model, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a recovery apparatus for polyvinyl alcohol waste liquid according to an embodiment of the utility model;
fig. 2 is a schematic structural diagram of a device for recycling waste polyvinyl alcohol liquid according to an embodiment of the utility model.
Detailed Description
The description of the embodiments of this specification should be taken in conjunction with the accompanying drawings, which are a complete description of the embodiments. In the drawings, the shape or thickness of the embodiments may be enlarged and indicated simply or conveniently. Furthermore, portions of the structures in the drawings will be described in terms of separate descriptions, and it should be noted that elements not shown or described in the drawings are in a form known to those of ordinary skill in the art.
Any references to directions and orientations in the description of the embodiments herein are for convenience only and should not be construed as limiting the scope of the utility model in any way. The following description of the preferred embodiments will refer to combinations of features, which may be present alone or in combination, and the utility model is not particularly limited to the preferred embodiments. The scope of the utility model is defined by the claims.
At present, the polyvinyl alcohol waste liquid recovery device has the following problems:
energy consumption aspect
In the production device, the distilled gas phase of the acetic acid purifying tower is totally condensed by circulating water, the waste heat is not fully utilized, and the methyl acetate rough separation tower is heated by steam, so that the energy is wasted.
(II) aspect of processing Capacity
Along with the improvement of the productivity of the polyvinyl alcohol front-end production device, part of equipment cannot meet the production requirements under the condition of no production expansion in the recovery process, such as a methyl acetate purification tower, a catalytic decomposition tower and the like. The gas phase of the distillation condenser of the methyl acetate purification tower is used as the raw material of the acetaldehyde coarse separation tower, the feeding quantity and the tower pressure of the raw material of the acetaldehyde coarse separation tower are controlled by controlling the opening of a cold medium circulating water inlet valve of the distillation condenser of the methyl acetate purification tower, and the raw material pressure and the feeding quantity of the raw material of the acetaldehyde coarse separation tower are unstable in operation and relatively large in fluctuation, so that the feeding components of the acetaldehyde refining tower are greatly changed, the operation of the acetaldehyde refining tower is unstable, and the purity of refined acetaldehyde is influenced.
At present, the tail gas of the catalytic decomposition tower and the tail gas of methyl acetate share a tail gas condenser (namely the methyl acetate tail gas condenser), and as the original methyl acetate tail gas condenser is limited in condensation area, the distilled acetaldehyde content of the catalytic decomposition tower exceeds the standard along with the increase of production load, the methyl acetate tail gas condenser cannot be condensed, the air discharge amount is large, the tail gas emission does not reach the standard, the acetaldehyde content in the system is high, and the quality of methanol and methyl acetate is influenced.
With the increase of front-end productivity, the partial equipment of the original alcoholysis waste liquid recovery device has limited treatment capacity and operates under the condition of long-term high load, and the quality and purity of intermediate products (methanol and methyl acetate) cannot meet the process requirements.
In view of the above problems, the following measures are currently taken, and there are the following problems:
aiming at the problem that the condensation area of a tail gas condenser shared by the catalytic decomposition tower and the methyl acetate tail gas (namely the methyl acetate tail gas condenser) is small, (1) under the condition of not making any transformation, only the back flushing condenser and the full opening of a freezing water valve can be adopted, so that the condensation effect is ensured; (2) secondly, a distillation condenser is newly added for parallel use with the original condenser, the effect is quick, the treatment capacity of the rectifying tower can be improved, but the investment is larger, and new equipment can be possibly placed without space for the established project under the influence of the layout of field equipment; (3) the U-shaped pipe is newly added on the liquid discharging pipeline of the condenser, so that the liquid level in the condenser is increased, the heat exchange effect is improved, the investment is low, and the effect of treating capacity when the capacity is increased is not obvious.
Aiming at the problem of unstable operation of the tower pressure and the feeding amount of the acetaldehyde crude separation tower, (1) only the distillation condenser of the backflushing methyl acetate purification tower can be adopted to improve the heat exchange effect, and the treatment capacity of the rectifying tower cannot be improved; (2) a U-shaped pipe is newly added on a liquid outlet pipeline of a distilled condenser of the methyl acetate purifying tower, so that the height of the liquid level in the condenser is increased, the heat exchange effect is improved, but the effect of treating capacity when the capacity is increased is not obvious. (3) The methyl acetate purifying tower with larger heat exchange area is replaced to distillate the condenser, but the larger the heat exchange area is, the condensation effect is limited by the size of the existing circulating water inlet and outlet pipeline, and the expected target cannot be achieved.
Along with the increase of front-end productivity, the problems are increasingly prominent, the treatment capacity of the methyl acetate crude separation tower is severely limited, a new set of alcoholysis waste liquid treatment device is newly built, the investment cost is high, the use area of the existing land is limited, partial equipment cannot be newly increased in order to ensure safety, and the production load of the rectifying tower is too small, the energy consumption is high, and the operation cost is high.
As shown in fig. 1 and 2, the apparatus for recycling polyvinyl alcohol waste liquid according to the embodiment of the utility model is schematically shown in the structure and the schematic diagram. The recovery device of the polyvinyl alcohol waste liquid comprises a methyl acetate rough separation tower 1, a methyl acetate purification tower 2, a methanol purification tower 3, a catalytic decomposition tower 4, an acetic acid rough separation tower 5, an acetic acid purification tower 6, an acetaldehyde rough separation tower 8 and an acetaldehyde refining tower 9. Alcoholysis waste liquid (main component: methanol, methyl acetate) into a methyl acetate crude separation column 1, and the distillate phase of the methyl acetate crude separation column 1 is sent to a methyl acetate purification column 2 (main component: 70-80wt% of methyl acetate, 19-29wt% of methanol, 0.5-0.8wt% of acetaldehyde and other components), and the effluent of the methyl acetate crude separation tower 1 kettle (main components: 90-95wt% of methanol, 5-10wt% of water and 2 kettle liquid (main components: 65-80wt% of methyl acetate and 20-35wt% of methanol) of the methyl acetate purification tower are sent to the methanol purification tower 3, high-temperature hot water discharged from the kettle of the methanol purification tower 3 can heat materials in an acetaldehyde crude separation tower reboiler c, the distilled liquid of the methanol purification tower 3 is refined methanol and sent to a middle tank area, a liquid phase (main components: 85-95wt% of methyl acetate and 5-15wt% of methanol) of a distillation condenser of the methyl acetate purification tower 2 is sent to a catalytic decomposition tower 4, a gas phase (main components: 90-95wt% of methyl acetate and 5-8wt% of acetaldehyde) of the methyl acetate purification tower 2 is sent to an acetaldehyde crude separation tower 8, a kettle liquid (main components: 90-95wt% of methyl acetate) of the methyl acetate crude separation tower 8 is sent to an acetaldehyde purification tower distillation tank f, a distilled liquid (main components: 10-20wt% of methyl acetate, 80-90wt% of acetaldehyde is sent to a distillation tower 9 of acetaldehyde crude acetaldehyde, a distilled liquid (main components: 9-40 wt% of methyl acetate, a distilled liquid of the main components: 90-40 wt% of the methyl acetate distillation tower) of the methyl acetate crude separation tower is sent to the acetaldehyde crude separation tower 9, and a distilled liquid (main components: 90-40 wt% of methyl acetate is sent to the distillation tower) of the methyl acetate crude separation tower is sent to the methyl acetate distillation tower 8 25-35wt% of acetic acid is sent to an acetic acid crude separation tower 5, and the acetic acid crude separation tower 5 distills off gas phase (main component: 65-75wt% of methyl acetate and 25-35wt% of methanol are sent to a methyl acetate purification tower 2, wherein one part (about 80-95wt%) is used for further separating and recovering methyl acetate and methanol in the gas phase distilled from the acetic acid crude separation tower 5, and the other part (5-15wt%) is sent to an acetic acid crude separation tower distillation condenser (not shown in figures 1 and 2), and the distillation condenser liquid phase is used for reflux of the acetic acid crude separation tower 5, so that reflux quantity is ensured. The acetic acid is discharged from the bottom of the coarse acetic acid separating tower 5 (the main components are 55-65wt% of acetic acid and 35-45wt% of water) and is sent to an acetic acid purifying tower 6, and the gas phase (the main components are n-butyl acetate and water) distilled from the acetic acid purifying tower 6 is condensed by a condenser and then is discharged.
In this embodiment, a new condenser (i.e., a first distillation condenser a) is connected in series in front of a distillation condenser (i.e., a second distillation condenser b) of the original methyl acetate purification tower 2, a distillation gas phase of the methyl acetate purification tower 2 enters the first distillation condenser a, a gas phase and a liquid phase condensed by the first distillation condenser a enter the second distillation condenser b, the gas phase of the second distillation condenser b enters the acetaldehyde crude separation tower 8, and the feeding amount of the acetaldehyde crude separation tower 8 is controlled by adjusting the opening of a circulating water inlet adjusting valve of the newly added distillation condenser in front, wherein the circulating water adjusting valve of the first distillation condenser a mainly controls the gas phase amount entering the second distillation condenser b, and the circulating water adjusting valve of the second distillation condenser b mainly controls the gas phase amount entering the acetaldehyde crude separation tower 8. In addition, the first distillation condenser a may be connected in parallel to the front of the second distillation condenser b (such a connection mode is not shown in fig. 1 and 2), the distilled gas phase of the methyl acetate purifying column 2 simultaneously enters two condensers, the gas phase outlets of the two condensers enter the acetaldehyde roughing column 8 after entering the same pipeline, the liquid phase outlets of the two condensers enter the methyl acetate purifying column distillation tank f after entering the same pipeline, and the feeding amount of the acetaldehyde roughing column 8 is controlled by adjusting the opening of the circulating water inlet adjusting valve of the two condensers. Meanwhile, in this embodiment, an acetaldehyde crude separation tower reboiler c is newly added on the acetaldehyde crude separation tower 8, and the heat required by the acetaldehyde crude separation tower 8 is considered to be less, in order to save steam, the heat source of the acetaldehyde crude separation tower reboiler c adopts hot water circulation of about 95 ℃ generated in the recovery device, specifically, the inlet of the acetaldehyde crude separation tower reboiler c is connected with a hot water outlet pipeline of the kettle of the methanol purification tower 3, hot water outlet of the kettle of the methanol purification tower 3 (125-135 ℃) enters a flash tank and then is subjected to flash evaporation, the hot water is subjected to secondary utilization (used as a heat source of a reboiler of other rectification towers), and the temperature of the hot water after flash evaporation is about 95 ℃. The medium temperature value of the acetaldehyde crude separation tower 8 is regulated and controlled by a heat source inlet regulating valve of the reboiler c of the acetaldehyde crude separation tower, and because the heat source of the reboiler c of the acetaldehyde crude separation tower is liquid phase, when a heating medium inlet and a heating medium outlet of the reboiler are designed, the lower inlet and the upper outlet are adopted, and the direction of the inlet and the outlet of the reboiler using steam is opposite to the direction of the inlet and the outlet of the reboiler using steam, so that the heat transfer is facilitated. Therefore, through the arrangement, the feeding stability and the column pressure stability of the acetaldehyde crude separation column 8 can be ensured, the operation of the acetaldehyde crude separation column 8 and the acetaldehyde refining column 9 is well controlled, the unqualified yield of distilled acetaldehyde of the acetaldehyde refining column 9 is reduced, and the circulating quantity of acetaldehyde in a system is greatly reduced.
The distillation condenser of the methyl acetate purifying tower 2 adopts an automatic regulation mode, namely, a fixed pressure parameter is set in a control system, and the automatic regulation system automatically switches a circulating water control valve according to the gas quantity to automatically regulate the using amount of circulating water; the medium temperature value control of the acetaldehyde crude separation tower 8 is realized by setting fixed temperature parameters in a control system, and a regulating valve automatically regulates and controls the heat source flow of a reboiler c of the acetaldehyde crude separation tower according to the medium temperature of the acetaldehyde crude separation tower 8; the feeding amount of the acetaldehyde coarse separation tower can be stably controlled through the control, and the load change can be adapted.
At present, the distilled gas phase of the acetic acid purification tower 6 in the recovery device of the polyvinyl alcohol waste liquid is condensed by circulating water, the waste heat is not fully utilized, and the methyl acetate crude separation tower 1 is heated by using extra steam, so that energy is wasted. In this embodiment, the methyl acetate crude separation tower 1 is connected with a methyl acetate crude separation tower reboiler d, the methyl acetate crude separation tower reboiler d is used in parallel with an original reboiler i of the methyl acetate crude separation tower 1, steam is introduced into the reboiler i as a heat source, the heat source of the methyl acetate crude separation tower reboiler d is a distillation gas phase of the acetic acid purification tower 6, and the distillation gas phase of the acetic acid purification tower 6 is required to be used as a heat source for heat exchange and recycling, so that the distillation gas phase of the acetic acid purification tower 6 is separated from the steam by adopting a mode of parallel connection of the reboilers, so that the distillation gas phase of the acetic acid purification tower 6 and the steam are prevented from being mixed in one reboiler, and the load of a subsequent processing unit is increased when the distillation gas phase of the acetic acid purification tower 6 is mixed with the steam after heat exchange. Specifically, the heat source inlet of the methyl acetate crude separation tower reboiler d is connected with the distilled gas phase outlet of the acetic acid purification tower 6 through a pipeline, and the heat source outlet of the methyl acetate crude separation tower reboiler d is connected with the distilled condenser inlet of the acetic acid purification tower 6 through a pipeline. The method is characterized in that n-butyl acetate steam (with the temperature of 75-85 ℃) is distilled off from an acetic acid purification tower 6 to serve as a heat source of a reboiler d of a methyl acetate crude separation tower, heat exchange is carried out on cold materials (with the temperature of 40-55 ℃) in a tower kettle of the methyl acetate crude separation tower 1, a liquid phase (with the temperature of 50-60 ℃) of the n-butyl acetate after heat exchange is sent to the acetic acid purification tower 6 to be distilled off from a condenser for secondary cooling, the n-butyl acetate steam distilled off from the acetic acid purification tower 6 is completely used as the heat source of the reboiler d of the methyl acetate crude separation tower, steam is used for supplementing the part with insufficient heat through a reboiler i, the steam usage is automatically adjusted, namely, a medium temperature value of the methyl acetate crude separation tower is set in a control system, and the control system can automatically switch the steam usage of the reboiler i according to the medium temperature, so that the steam usage is effectively reduced and the circulating water usage is saved. According to 1 ten thousand tons of PVA produced in a year, the steam consumption can be reduced by 0.185 ten thousand tons/year, the circulating water consumption is saved by about 8.31 ten thousand tons/year, and the direct economic benefit is generated by about 26.92 ten thousand yuan/year.
In the prior art, the tail gas of the catalytic decomposition tower 4 (the non-condensed gas phase of the catalytic decomposition tower distillation condenser g) and the tail gas of the methyl acetate (comprising the tail gas of the methyl acetate purification tower distillation tank (related connecting pipelines are not shown in fig. 1 and 2), namely the non-condensed gas phase of the methyl acetate crude separation tower distillation condenser, and not shown in fig. 1 and 2), share the methyl acetate tail gas condenser h, and because the condensation area of the methyl acetate tail gas condenser h is limited, the concentration of other tail gases in the device is not reduced due to the fact that the concentration of acetaldehyde distilled by the catalytic decomposition tower 4 exceeds the standard, the emptying amount is large, the content of acetaldehyde in the system is high due to the fact that the tail gas emission does not reach standards, and the quality of methanol and methyl acetate is affected.
In order to solve the above problems, in this embodiment, a catalytic decomposition tower tail gas condenser e is newly added to a catalytic decomposition tower 4 distillation condenser, the distilled gas phase of the catalytic decomposition tower 4 enters a catalytic decomposition tower distillation condenser g to be condensed, the condensed liquid is sent to a methyl acetate purification tower 2 to be further separated, the non-condensed gas phase (tail gas) enters the catalytic decomposition tower tail gas condenser e to be further condensed, and thus, the arrangement is that the distilled tail gas of the catalytic decomposition tower 4 can be separated from the methyl acetate tail gas, the non-condensed gas phase of the methyl acetate crude distillation condenser is connected with a gas phase inlet of a methyl acetate tail gas condenser h through a pipeline, so that the recycling and treatment of the non-condensed gas phase of the methyl acetate crude distillation condenser h are realized, and the condensed liquid of the methyl acetate tail gas condenser h enters a methyl acetate purification distillation tank f to be recycled. Furthermore, the uncondensed gas phase of the tail gas condenser e of the catalytic decomposition tower and the uncondensed gas phase of the distillation condenser (not shown in fig. 1 and 2) of the acetic acid crude separation tower can be connected with the gas phase inlet of the tail gas condenser h of the methyl acetate, and the uncondensed gas phase can be further recycled. The tail gas condenser e of the catalytic decomposition tower is cooled by chilled water, the lower liquid of the condenser directly enters a feeding tank (not shown in fig. 1 and 2) of the acetaldehyde refining tower 9, the uncondensed gas phase of the tail gas condenser of the catalytic decomposition tower is sent to the methyl acetate tail gas condenser h for secondary condensation, and the treatment capacity of the methyl acetate tail gas condenser h is greatly reduced, so that the device expansion requirement is met. The temperature monitoring point is additionally arranged on the liquid phase outlet pipeline of the tail gas condenser e of the newly added catalytic decomposition tower, and the opening of the freezing water valve can be timely adjusted according to the temperature point, so that the purpose of saving energy is achieved under the condition of adapting to load change, and the tail gas condenser e of the catalytic decomposition tower has the advantages of small volume, less investment and flexible arrangement.
In addition, the utility model can also solve the requirements of polyvinyl alcohol production enterprises on technical improvement, production expansion, quality improvement and efficiency improvement to a certain extent. With the increase of the front-end productivity of the alcoholysis production unit, the partial equipment treatment capacity of the original alcoholysis waste liquid recovery device is limited, the device operates under the condition of long-term high load, the quality and purity of intermediate products (methanol and methyl acetate) cannot meet the technological requirements, especially the treatment capacity of the methyl acetate crude separation tower 1 is severely limited, a new alcoholysis waste liquid treatment device is newly built, the investment cost is high, the existing land use area is limited, the partial equipment cannot be newly increased for ensuring the safety, the production load of a rectifying tower is too small, the energy consumption is high, and the operation cost is high. Through the arrangement, the waste liquid recovery device of the embodiment can also achieve the effect that the quality of distilled methanol of the methanol purification tower 3 is obviously improved, wherein the purity of the methanol is improved by 0.3%, and the activity is reduced by 13%. Under the condition that the front-end productivity is increased, only part of equipment is modified, the production requirement is met, the processing capacity of the methyl acetate rough separation tower 1 can be improved by 36% -40%, the investment cost and the running cost are saved, the device adopts an automatic regulating system, the low-load and high-load production requirement can be met, and the production operation elasticity of the alcoholysis waste liquid recovery device is obviously improved.
According to the embodiment of the utility model, the first distillation condenser and the second distillation condenser are arranged between the methyl acetate purification tower and the acetaldehyde crude separation tower, the distilled gas phase of the methyl acetate purification tower firstly enters the first distillation condenser, the gas phase and the liquid phase condensed by the first distillation condenser both enter the second distillation condenser, the distilled gas phase of the second distillation condenser enters the acetaldehyde crude separation tower, the feeding amount of the acetaldehyde crude separation tower is controlled by adjusting the opening of the circulating water inlet regulating valves of the first distillation condenser and the second distillation condenser, the regulating valve of the first distillation condenser is used for controlling the gas phase amount entering the second distillation condenser, the regulating valve of the second distillation condenser is used for automatically controlling the gas phase amount entering the acetaldehyde crude separation tower, so that the feeding stability of the acetaldehyde crude separation tower is ensured, and meanwhile, the reboiler of the acetaldehyde crude separation tower is arranged on the acetaldehyde crude separation tower so as to ensure the stable tower pressure of the acetaldehyde crude separation tower, the feeding stability of the acetaldehyde crude separation tower and the stable tower pressure are ensured, and the stable feeding component of the acetaldehyde refined tower is ensured, and the purity is ensured.
The foregoing description of the preferred embodiments of the utility model is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the utility model.
Claims (10)
1. The utility model provides a recovery unit of polyvinyl alcohol waste liquid, includes methyl acetate purification tower (2) and acetaldehyde roughing tower (8), the distillation gaseous phase of methyl acetate purification tower (2) is sent to acetaldehyde roughing tower (8), its characterized in that, methyl acetate purification tower (2) with have first distillation condenser (a) and second distillation condenser (b) between acetaldehyde roughing tower (8), first distillation condenser (a) with second distillation condenser (b) are established ties or are parallelly connected, still be connected with acetaldehyde roughing tower reboiler (c) on the acetaldehyde roughing tower (8).
2. The recovery device of the polyvinyl alcohol waste liquid according to claim 1, wherein the recovery device of the polyvinyl alcohol waste liquid further comprises a methyl acetate crude separation column (1), a methanol purification column (3), a catalytic decomposition column (4), an acetic acid crude separation column (5) and an acetic acid purification column (6);
after the alcoholysis waste liquid enters the methyl acetate coarse separation tower (1), the distillate phase is sent to the methyl acetate purification tower (2) and the kettle liquid is sent to the methanol purification tower (3), and the kettle liquid of the methyl acetate purification tower (2) is sent to the methanol purification tower (3); and one part of the liquid phase of the distillation condenser of the methyl acetate purifying tower (2) is sent to the catalytic decomposition tower (4), the other part of the liquid phase of the distillation condenser of the methyl acetate purifying tower is sent to the upper part of the methyl acetate purifying tower (2) for reflux, the vapor phase of the distillation condenser of the methyl acetate purifying tower (2) is sent to the acetaldehyde crude separation tower (8), the kettle liquid of the catalytic decomposition tower (4) is sent to the acetic acid crude separation tower (5), and the kettle liquid of the acetic acid crude separation tower (5) is sent to the acetic acid purifying tower (6).
3. The recovery apparatus for waste polyvinyl alcohol liquid according to claim 2, wherein the heat source inlet of the reboiler (c) of the crude acetaldehyde separating column is connected with the hot water outlet of the methanol purifying column (3).
4. The polyvinyl alcohol waste liquid recycling apparatus according to claim 3, wherein a methyl acetate crude separation column reboiler (d) is connected to the methyl acetate crude separation column (1), a heat source inlet of the methyl acetate crude separation column reboiler (d) is connected to a distillation gas phase outlet of the acetic acid purification column (6), and a heat source outlet of the methyl acetate crude separation column reboiler (d) is connected to a distillation condenser inlet of the acetic acid purification column (6).
5. The recycling device of the polyvinyl alcohol waste liquid according to claim 3 or 4, characterized in that the recycling device of the polyvinyl alcohol waste liquid further comprises an acetaldehyde refining tower (9), wherein the kettle liquid of the acetaldehyde rough separation tower (8) is sent to a methyl acetate refining tower distillation tank (f), the distillate of the acetaldehyde rough separation tower (8) is sent to the acetaldehyde refining tower (9) for feeding, the distilled gas phase of the acetaldehyde refining tower (9) is condensed by a condenser and then sent to a tank area, and the kettle liquid of the acetaldehyde refining tower (9) is sent to the methyl acetate refining tower distillation tank (f); and one part of the distilled gas phase of the acetic acid crude separation tower (5) is sent to the methyl acetate purifying tower (2), and the other part is sent to an acetic acid crude separation tower distilled condenser.
6. The polyvinyl alcohol waste liquid recycling apparatus according to claim 5, wherein the catalytic decomposition tower (4) is connected with a catalytic decomposition tower tail gas condenser (e).
7. The device for recycling waste polyvinyl alcohol liquid according to claim 6, wherein the lower liquid outlet of the tail gas condenser (e) of the catalytic decomposition tower is connected with the feeding tank of the acetaldehyde refining tower (9).
8. The device for recycling polyvinyl alcohol waste liquid according to claim 6, wherein the catalytic decomposition tower (4) is connected with a catalytic decomposition tower distillation condenser (g), condensate of the catalytic decomposition tower distillation condenser (g) is sent to the methyl acetate purifying tower (2), and uncondensed gas of the catalytic decomposition tower distillation condenser (g) is sent to a catalytic decomposition tower tail gas condenser (e) for condensation.
9. The device for recycling polyvinyl alcohol waste liquid according to claim 6, wherein the non-condensed gas phase of the methyl acetate crude separation tower (1) distillation condenser is connected with the gas phase inlet of the methyl acetate tail gas condenser (h) through a pipeline, and the condensed liquid of the methyl acetate tail gas condenser (h) enters the methyl acetate purification tower distillation tank (f).
10. The apparatus according to claim 9, wherein the catalytic converter tail gas condenser (e) is a noncondensable gas phase and the acetic acid crude separation column (5) is a distillation condenser noncondensable gas phase and a gas phase inlet of the methyl acetate tail gas condenser (h).
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