CN108046989B - Device and method for purifying bioethanol - Google Patents
Device and method for purifying bioethanol Download PDFInfo
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- CN108046989B CN108046989B CN201711483907.8A CN201711483907A CN108046989B CN 108046989 B CN108046989 B CN 108046989B CN 201711483907 A CN201711483907 A CN 201711483907A CN 108046989 B CN108046989 B CN 108046989B
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- 238000000034 method Methods 0.000 title abstract description 31
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 112
- 238000000926 separation method Methods 0.000 claims abstract description 46
- 238000010533 azeotropic distillation Methods 0.000 claims abstract description 42
- 238000011084 recovery Methods 0.000 claims abstract description 41
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 37
- 239000000463 material Substances 0.000 claims description 43
- 239000012071 phase Substances 0.000 claims description 37
- 239000000203 mixture Substances 0.000 claims description 24
- 230000006835 compression Effects 0.000 claims description 13
- 238000007906 compression Methods 0.000 claims description 13
- IDGUHHHQCWSQLU-UHFFFAOYSA-N ethanol;hydrate Chemical compound O.CCO IDGUHHHQCWSQLU-UHFFFAOYSA-N 0.000 claims description 13
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical group CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 12
- 238000000605 extraction Methods 0.000 claims description 9
- 239000007791 liquid phase Substances 0.000 claims description 7
- 238000010992 reflux Methods 0.000 claims description 6
- 239000012498 ultrapure water Substances 0.000 claims description 6
- RJUFJBKOKNCXHH-UHFFFAOYSA-N Methyl propionate Chemical compound CCC(=O)OC RJUFJBKOKNCXHH-UHFFFAOYSA-N 0.000 claims description 4
- 238000001704 evaporation Methods 0.000 claims description 4
- 230000008020 evaporation Effects 0.000 claims description 4
- 229940017219 methyl propionate Drugs 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 abstract description 14
- 238000004821 distillation Methods 0.000 abstract description 6
- 230000000694 effects Effects 0.000 abstract description 3
- 239000002918 waste heat Substances 0.000 abstract description 3
- 235000019441 ethanol Nutrition 0.000 description 33
- 239000000047 product Substances 0.000 description 11
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 9
- 239000002351 wastewater Substances 0.000 description 9
- 239000007789 gas Substances 0.000 description 6
- 230000008901 benefit Effects 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- 239000000446 fuel Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000002808 molecular sieve Substances 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 4
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000002028 Biomass Substances 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 208000005156 Dehydration Diseases 0.000 description 2
- 230000000295 complement effect Effects 0.000 description 2
- 230000018044 dehydration Effects 0.000 description 2
- 238000006297 dehydration reaction Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000000855 fermentation Methods 0.000 description 2
- 230000004151 fermentation Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
- C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
- C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
- C07C29/82—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation by azeotropic distillation
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L1/00—Liquid carbonaceous fuels
- C10L1/02—Liquid carbonaceous fuels essentially based on components consisting of carbon, hydrogen, and oxygen only
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention provides equipment and a method for purifying bioethanol, wherein the equipment comprises the following steps: a pre-separation tower, an azeotropic distillation tower, an entrainer recovery tower, a phase separator, a flash tank, a condenser, a reboiler and a mixer. The device for purifying the bioethanol mainly adopts a pre-separation tower, an azeotropic distillation tower, an entrainer recovery tower, a compressor, a phase separator and the like, and the bioethanol-water solution sequentially passes through three distillation towers to obtain the absolute ethanol with the mass fraction of 99.9% or more. The method for purifying the bioethanol effectively recovers the steam heat at the top of the rectifying tower, further utilizes the process waste heat, realizes the self-recovery of the heat in the system, realizes the sufficient heat exchange among process streams, reduces the using amount of public works, saves the operation cost, and has obvious economic effect.
Description
Technical Field
The invention belongs to the technical field of chemical industry, and particularly relates to equipment and a method for purifying bioethanol.
Background
Bioethanol is a renewable energy source produced by using biomass as a raw material, and the yield of ethanol produced by the method accounts for 93% of the total yield of ethanol in the world. Bioethanol is currently the most promising sustainable fuel, and has the advantage of being easily blended with existing fuel systems (e.g. 5% to 85% blend with gasoline) and can be used directly as automotive fuel without changing the engine performance. In addition, the bioethanol can be used as a gasoline octane number improver to improve the oxygen content of gasoline so as to reduce the emission of carbon dioxide and hydrocarbon pollutants in automobile exhaust.
The biomass raw material is generally subjected to pretreatment, fermentation and other processes to obtain a fermentation alcohol solution with the ethanol content of 5-12 wt%, and dehydration treatment is required to achieve the available purity standard. In general, when bioethanol is used as a fuel or additive, the purity of ethanol should be no less than 99.5 wt%, and in order to achieve this purity requirement, a large amount of energy is consumed to break up the ethanol-water binary azeotrope. Reducing the energy consumption of the separation process and improving the energy utilization rate of the separation process are research hotspots which are always concerned by scientific researchers.
Patent CN1644703 discloses a complete set of technology special for anhydrous ethanol production, which is composed of the procedures of raw material treatment, fermentation, rectification, molecular sieve adsorption dehydration and waste mash treatment. However, the water in the mixed solution is directly removed by adopting the molecular sieve, the water is not pretreated, the molecular sieve load is increased, the molecular sieve is required to be adsorbed and regenerated, and the problems of complex operation, long process and the like exist.
Patent WO2014023137A1 discloses a method for separating ethanol-water azeotrope by using a compression heat pump rectifying tower device and a compression heat pump rectifying tower process, which can obviously reduce the public engineering consumption in the separation process for gas-phase feeding, but does not obviously reduce the consumption for liquid-phase feeding.
Patent CN101157890A discloses an anhydrous ethanol production device and method, wherein a rough distillation tower and a rectification tower in a two-tower process are respectively split into two rough distillation towers and two rectification towers, and the anhydrous ethanol is produced by a mash tower, a rectification tower and a recovery tower. In the flow, although only one tower of the recovery tower uses fresh steam for heating, the crude wine processed by the recovery tower has too large amount, so that the fresh steam used by the recovery tower has too large amount; in addition, the heat of the absolute ethyl alcohol steam dehydrated by the adsorption tower is not utilized, so that the whole system is not optimized, and the energy consumption is very high.
Disclosure of Invention
One object of the present invention is to provide an apparatus for purifying bioethanol.
The apparatus for purifying bioethanol of the present invention comprises: a pre-separation tower, an azeotropic distillation tower, an entrainer recovery tower, a phase separator, a flash tank, a condenser, a reboiler and a mixer.
The device for purifying the bioethanol mainly adopts a pre-separation tower, an azeotropic distillation tower, an entrainer recovery tower, a compressor, a phase separator and the like, and the bioethanol-water solution sequentially passes through three distillation towers to obtain the absolute ethanol with the mass fraction of 99.9% or more. In the process, a heat pump technology is introduced into the pre-separation tower and the azeotropic distillation tower, and the heat of the steam at the tops of the pre-separation tower and the azeotropic distillation tower is fully utilized to provide heat for the reboilers of the three distillation towers, so that a thermal coupling network is formed. The method for purifying the bioethanol effectively recovers the steam heat at the top of the rectifying tower, further utilizes the process waste heat, realizes the self-recovery of the heat in the system, realizes the sufficient heat exchange among process streams, reduces the using amount of public works, saves the operation cost, and has obvious economic effect.
In addition, the apparatus for purifying bioethanol according to the above embodiment of the present invention may further have the following additional technical features:
furthermore, the device for purifying the bioethanol further comprises a plurality of compressors, a plurality of coolers, a plurality of heat exchangers and a plurality of pressure reducing valves.
Further, the plurality of compressors includes at least three, the plurality of coolers includes at least 2, the plurality of heat exchangers includes at least 5, and the plurality of pressure reducing valves includes at least 2.
Furthermore, the theoretical plate number of the pre-separation tower is 15-25, and the operating pressure is 5.05 multiplied by 104Pa～2.02×105Pa, the temperature at the top of the tower is 60-95 ℃, the temperature at the bottom of the tower is 82-120 ℃, and the feeding position of the mixture of ethanol and water is 10 th-20 th tower plates.
Furthermore, the number of theoretical plates of the entrainer recovery tower is 5-15, and the operating pressure is 3.03 multiplied by 104Pa～1.01×105Pa, the temperature at the top of the tower is 50-78 ℃, and the temperature at the bottom of the tower is 70-100 ℃.
Further, the pre-separation tower is a plate tower or a packed tower; the azeotropic distillation tower is a plate tower or a packed tower; the entrainer recovery tower is a plate tower or a packed tower.
Furthermore, the compression ratio of each compressor is 2-4.
Another object of the present invention is to propose a method for purifying bioethanol using the above apparatus.
The method for purifying the bioethanol by using the device comprises the following steps: s101: feeding an ethanol and water mixture from the lower middle part of a pre-separation tower, extracting steam consisting of an ethanol-water azeotrope from the tower top, wherein the tower kettle is high-purity water, the steam at the tower top is pressurized and heated by a first compressor, then enters a first heat exchanger at the tower kettle of the pre-separation tower, enters a flash tank after heat exchange, a gas-phase material flow after flash evaporation enters a second compressor, an outlet material flow of the second compressor enters a second heat exchanger, an outlet material flow of the second compressor provides heat for a fourth heat exchanger at the tower kettle of an entrainer recovery tower, and finally the gas-phase material flow and a liquid-phase material flow of the second compressor after heat exchange are mixed by a mixer, and then part of the gas-phase material flow and the liquid-phase material flow are returned to the tower top of the pre-separation; s102: feeding an ethanol-water azeotrope from the middle lower part of an azeotropic distillation tower, extracting a high-purity ethanol product from a tower kettle, preheating tower top steam by a second heat exchanger, then feeding the preheated tower top steam into a third compressor for pressurization and temperature rise to provide a heat source for a third heat exchanger of the tower kettle of the azeotropic distillation tower, decompressing and cooling a heat-exchanged material flow by a second pressure reducing valve and a second cooler in sequence, feeding the heat-exchanged material flow into a phase separator, returning an entrainer-rich phase and a supplementary entrainer to the top of the azeotropic distillation tower, and taking a water-rich phase as the feed of an entrainer recovery tower; s103: and the rich water phase enters the entrainer recovery tower from the tower top, part of steam at the tower top is used as tower top reflux after being condensed by a condenser, part of steam enters the tower top of the azeotropic distillation tower, the outlet material flow of the second compressor provides heat for a fourth heat exchanger at the tower bottom of the entrainer recovery tower, the material flow at the tower bottom of the pre-separation tower provides heat for a fifth heat exchanger, and high-purity water is extracted from the tower bottom.
Further, the entrainer is at least one of cyclohexane, benzene, ethyl acetate and methyl propionate.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
FIG. 1 is a process flow diagram of the method of purifying bioethanol of the present invention;
in the figure, 1-a pre-separation tower, 2-an azeotropic distillation tower, 3-an entrainer recovery tower, 4-a pre-separation tower top compressor, 5-a flash tank outlet gas phase compressor, 6-an azeotropic distillation tower top compressor, 7-a pre-separation tower kettle auxiliary reboiler, 8-a pre-separation tower kettle heat exchanger, 9-a flash tank, 10-an azeotropic distillation tower top preheater, 11-a mixer, 12, 15-a pressure reducing valve, 13, 16-a cooler, 14-an azeotropic distillation tower kettle heat exchanger, 17-a phase splitter, 18-an entrainer recovery tower top condenser, 19, 20-an entrainer recovery tower kettle heat exchanger, 101-an ethanol and water mixture, 102-a pre-separation tower top steam, 103-a flash tank gas phase discharge, 104-a flash tank liquid phase discharge, 105-compressor outlet material flow 1, 106-compressor outlet material flow 2, 107-pre-separation tower top reflux, 108-ethanol-water azeotrope, 109, 110-pre-separation tower bottom extraction, 111-azeotropic distillation tower top steam, 112-entrainer phase reflux, 113-rich water phase, 114-supplement entrainer, 115-azeotropic distillation tower kettle ethanol product, 116-entrainer recovery tower top extraction, and 117-entrainer recovery tower kettle extraction.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
As shown in figure 1, the device adopted by the invention mainly comprises a pre-separation tower (1), an azeotropic distillation tower (2), an entrainer recovery tower (3), compressors (4, 5, 6), a phase separator (17), a flash tank (9), coolers (13, 16), a condenser (18), a reboiler (7), heat exchangers (8, 10, 14, 19, 20), pressure reducing valves (12, 15), a mixer (11) and other auxiliary equipment.
Feeding an ethanol and water mixture (101) from the lower middle part of a pre-separation tower (1), extracting steam (102) formed by ethanol-water azeotropy from the top of the tower, wherein the tower bottom is high-purity water (109), the steam (102) at the top of the tower enters a first heat exchanger (8) at the bottom of the pre-separation tower (1) after being pressurized and heated by a first compressor (4), enters a flash tank (9) after heat exchange, a gas phase material flow (103) after being flashed enters a second compressor (5), a material flow (1) and a material flow (105) at the outlet of the compressor enter a second heat exchanger (10), a material flow (2) and a material flow (106) at the outlet of the compressor provide heat for a fourth heat exchanger (19) at the bottom of an entrainer recovery tower (3), and after the gas phase material flow and a liquid phase material flow (104) of the second compressor (5) after heat exchange are mixed by a mixer (11), the gas phase material flow and the gas phase material, and part of the raw material is used as the feeding material of the azeotropic distillation tower (2).
Feeding an ethanol-water azeotrope (108) from the middle lower part of the azeotropic distillation (2), extracting a high-purity ethanol (115) product from a tower kettle, preheating tower top steam (111) by a second heat exchanger (10), then entering a third compressor (6) for pressurizing and heating to provide a heat source for a third heat exchanger (14) of the tower kettle of the azeotropic distillation tower (2), decompressing and cooling a heat-exchanged material flow by a second decompression valve (15) and a second cooler (16) in sequence, then entering a phase separator (17), returning an entrainer-rich phase (112) and a complementary entrainer (114) to the tower top of the azeotropic distillation tower (2), and feeding a water-rich phase (113) serving as an entrainer recovery tower (3).
The water-rich phase (113) enters the azeotropic agent recovery tower (3) from the top of the tower, part of the tower top steam is used as tower top reflux after being condensed by a condenser (18), part of the tower top steam enters the top of the azeotropic distillation tower (2), the outlet material flow (106) of the second compressor (5) provides heat for the fourth heat exchanger (19) of the tower bottom of the azeotropic agent recovery tower (3), the tower bottom material flow (109) of the pre-separation tower (1) provides heat for the fifth heat exchanger (20), and high-purity water (117) is extracted from the tower bottom.
In the operation process, the pre-separation tower (1), the azeotropic distillation tower (2) and the entrainer recovery tower (3) are plate towers or packed towers. The entrainer is one of cyclohexane, benzene, ethyl acetate and methyl propionate. In the present invention, streams 109 and 117 are wastewater with a purity of 99.9 wt% and above, and stream 115 is high purity ethanol with a purity of 99.9 wt% and above.
The invention can be illustrated by the following examples.
Example 1
The specific flow of the equipment and the process of the invention is shown in figure 1.
The pre-separation tower (1) is a plate tower, the number of theoretical plates is 15, and a mixture (101) of ethanol and water flows from the 10 th part of the pre-separation tower (1)Block theoretical plate feed, operating pressure 5.05X 104Pa, the temperature of the top of the tower is 60 ℃, the temperature of the bottom of the tower is 82 ℃, the steam (102) at the top of the tower enters a first compressor (4) for pressurizing and heating, the compression ratio is 2, the steam enters a first heat exchanger (8) at the bottom of a pre-separation tower (1), the steam enters a flash evaporation tank (9) after heat exchange, the gas-phase material flow (103) after flash evaporation enters a second compressor (5), the compression ratio is 2, water (109) with the mass fraction of 99.9% is extracted from the bottom of the pre-separation tower (1), and the ethanol-water azeotrope (108) at the top of the tower enters an azeotropic distillation.
The azeotropic distillation tower (2) is a plate tower, the number of theoretical plates is 15, the ethanol-water azeotrope (108) is fed from the 10 th theoretical plate of the azeotropic distillation tower (2), cyclohexane is selected as the entrainer, and the operating pressure is 5.05 multiplied by 104Pa, the temperature at the top of the tower is 50 ℃, the temperature at the bottom of the tower is 62 ℃, the steam (111) at the top of the tower is preheated by a second heat exchanger (10), then enters a third compressor (6) for pressurizing and heating, the compression ratio is 2, ethanol with the mass fraction of 99.9 percent is extracted from the bottom of the tower, an entrainer-rich phase (112) and a complementary entrainer (114) in a phase separator (17) at the top of the tower are returned to the top of the azeotropic distillation tower (2), and a water-rich phase (113) is used as the feed of an entrainer recovery tower (3).
The entrainer recovery tower (3) is a plate tower, the theoretical plate number is 5, the water-rich phase (113) enters from the top of the tower, and the operation pressure is 3.03 multiplied by 104Pa, the temperature at the top of the tower is 50 ℃, the temperature at the bottom of the tower is 70 ℃, part of the steam at the top of the tower is used as the reflux at the top of the tower after being condensed by a condenser (18), part of the steam enters the top of the azeotropic distillation tower (2), the outlet material flow (106) of the second compressor (5) provides heat for the fourth heat exchanger (19) at the bottom of the azeotropic agent recovery tower (3), the material flow (109) at the bottom of the pre-separation tower (1) provides heat for the fifth heat exchanger (20), and water (117) with the mass fraction of 99.9% is extracted at the bottom of the.
The ethanol and water mixture (101), recycle entrainer (112), waste water (110, 117), product ethanol (115) flow and composition of example 1 are shown in table 1.
TABLE 1 flow rates and compositions of streams 101, 112, 110, 117 and 115 in example 1
As can be seen from the results, the purity of the product ethanol was 99.90 wt%, and the purity of the wastewater was 99.90 wt%.
Example 2
The same procedure as described in example 1, except that the preseparator (1) was a packed column, the number of theoretical plates was 25, the mixture of ethanol and water (101) was fed from the 20 th theoretical plate of the preseparator (1), and the operating pressure was 2.02X 105Pa, the temperature at the top of the tower is 95 ℃, the temperature at the bottom of the tower is 120 ℃, the compression ratio of the compressors (4 and 5) is 4, and water (109) with the mass fraction of 99.95 percent is extracted from the bottom of the pre-separation tower (1). The azeotropic distillation tower (2) is a packed tower, the number of theoretical plates is 30, the ethanol-water azeotrope (108) is fed from the 25 th theoretical plate of the azeotropic distillation tower (2), benzene is selected as the entrainer, and the operating pressure is 1.52 multiplied by 105Pa, the temperature at the top of the tower is 82 ℃, the temperature at the bottom of the tower is 90 ℃, the compression ratio of the third compressor (6) is 4, and ethanol with the mass fraction of 99.94 percent is extracted from the bottom of the tower. The entrainer recovery tower (3) is a packed tower, the number of theoretical plates is 15, and the operating pressure is 1.01 multiplied by 105Pa, the temperature at the top of the tower is 78 ℃, the temperature at the bottom of the tower is 100 ℃, and water (117) with the mass fraction of 99.95 percent is extracted at the bottom of the tower.
The ethanol and water mixture (101), recycle entrainer (112), waste water (110, 117), product ethanol (115) flow and composition of example 2 are shown in table 2.
TABLE 2 flow rates and compositions of streams 101, 112, 110, 117 and 115 in example 2
As can be seen from the results, the purity of the product ethanol was 99.94 wt%, and the purity of the wastewater was 99.95 wt%.
Example 3
The same procedure as described in example 1, except that the number of theoretical plates of the preliminary separation column (1) was 18, and a mixture (101) of ethanol and water was taken from the preliminary separation column(1) Feeding the 14 th theoretical plate at an operating pressure of 1.01X 105Pa, the temperature at the top of the tower is 78 ℃, the temperature at the bottom of the tower is 100 ℃, the compression ratio of the compressors (4 and 5) is 3, and water (109) with the mass fraction of 99.91 percent is extracted from the tower bottom of the pre-separation tower (1). The azeotropic distillation tower (2) is a packed tower, the number of theoretical plates is 20, the ethanol-water azeotrope (108) is fed from the 15 th theoretical plate of the azeotropic distillation tower (2), the azeotropic agent is ethyl acetate, and the operating pressure is 8.08 multiplied by 104Pa, the temperature at the top of the tower is 62 ℃, the temperature at the bottom of the tower is 71 ℃, the compression ratio of the third compressor (6) is 3, and ethanol with the mass fraction of 99.95 percent is extracted from the bottom of the tower. The number of theoretical plates of the entrainer recovery tower (3) is 8, and the operating pressure is 5.05 multiplied by 104Pa, the temperature at the top of the tower is 59 ℃, the temperature at the bottom of the tower is 80 ℃, and water (117) with the mass fraction of 99.91 percent is extracted at the bottom of the tower.
The ethanol and water mixture (101), recycle entrainer (112), waste water (110, 117), product ethanol (115) flow and composition of example 3 are shown in table 3.
Table 3 flow rates and compositions of streams 101, 112, 110, 117 and 115 in example 3
As can be seen from the results, the purity of the product ethanol was 99.95 wt%, and the purity of the wastewater was 99.91 wt%.
Example 4
The same procedure as described in example 1, except that the preseparator (1) was a packed column, the number of theoretical plates was 22, the mixture of ethanol and water (101) was fed from the 18 th theoretical plate of the preseparator (1), and the operating pressure was 1.52X 105Pa, the temperature at the top of the tower is 84 ℃, the temperature at the bottom of the tower is 108 ℃, the compression ratio of the compressors (4 and 5) is 3.5, and water (109) with the mass fraction of 99.93 percent is extracted from the tower bottom of the pre-separation tower (1). The number of theoretical plates of the azeotropic distillation tower (2) is 25, the ethanol-water azeotrope (108) is fed from the 20 th theoretical plate of the azeotropic distillation tower (2), the entrainer is methyl propionate, and the operating pressure is 1.21 multiplied by 105Pa, the temperature at the top of the tower is 70 ℃, the temperature at the bottom of the tower is 82 ℃, the compression ratio of a third compressor (6) is 3.5, and ethanol with the mass fraction of 99.98 percent is extracted from the tower kettle. The entrainer recovery tower (3) is a packed tower, the number of theoretical plates is 12, and the operating pressure is 8.08 multiplied by 104Pa, the temperature at the top of the tower is 68 ℃, the temperature at the bottom of the tower is 90 ℃, and water (117) with the mass fraction of 99.93 percent is extracted at the bottom of the tower.
The ethanol and water mixture (101), recycle entrainer (112), waste water (110, 117), product ethanol (115) flow and composition of example 4 are shown in table 4.
Table 4 flow rates and compositions of streams 101, 112, 110, 117 and 115 in example 4
From the results, it can be seen that the purity of the product ethanol was 99.98 wt%, and the purity of the wastewater was 99.93 wt%.
The method for purifying the bioethanol has the following advantages:
1. a pre-separation tower is added to purify the mixture of ethanol and water to the azeotropic point, and part of water is separated in advance, so that the subsequent operation load is reduced;
2. the comprehensive utilization of energy is considered, a heat pump technology is introduced into the pre-separation tower and the azeotropic distillation tower, the steam heat at the top of the distillation tower is effectively recovered, the waste heat in the process is further considered, the self-recovery of the heat in the system is realized, the sufficient heat exchange between process material flows is realized, the consumption of public works is reduced, the operation cost is saved, and the economic effect is obvious;
3. along with the reduction of the amount of the used public works, the emission of greenhouse gases is correspondingly reduced, and the environment benefit is good.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (5)
1. A bioethanol extraction process based on an apparatus for purifying bioethanol, said apparatus comprising: the system comprises a pre-separation tower, an azeotropic distillation tower, an entrainer recovery tower, a phase separator, a flash tank, a condenser, a reboiler and a mixer;
the extraction method comprises the following steps:
s101: feeding an ethanol and water mixture from the lower middle part of a pre-separation tower, extracting steam consisting of an ethanol-water azeotrope from the tower top, wherein the tower kettle is high-purity water, the steam at the tower top is pressurized and heated by a first compressor, then enters a first heat exchanger at the tower kettle of the pre-separation tower, enters a flash tank after heat exchange, a gas-phase material flow after flash evaporation enters a second compressor, an outlet material flow of the second compressor enters a second heat exchanger, an outlet material flow of the second compressor provides heat for a fourth heat exchanger at the tower kettle of an entrainer recovery tower, and finally the gas-phase material flow and a liquid-phase material flow of the second compressor after heat exchange are mixed by a mixer, and then part of the gas-phase material flow and the liquid-phase material flow are returned to the tower top of the pre-separation;
s102: feeding an ethanol-water azeotrope from the middle lower part of an azeotropic distillation tower, extracting a high-purity ethanol product from a tower kettle, preheating tower top steam by a second heat exchanger, then feeding the preheated tower top steam into a third compressor for pressurization and temperature rise to provide a heat source for a third heat exchanger of the tower kettle of the azeotropic distillation tower, decompressing and cooling a heat-exchanged material flow by a second pressure reducing valve and a second cooler in sequence, feeding the heat-exchanged material flow into a phase separator, returning an entrainer-rich phase and a supplementary entrainer to the top of the azeotropic distillation tower, and taking a water-rich phase as the feed of an entrainer recovery tower;
s103: the rich water phase enters an entrainer recovery tower from the top of the tower, part of steam at the top of the tower is used as tower top reflux after being condensed by a condenser, and part of steam enters the top of an azeotropic distillation tower, the outlet material flow of a second compressor provides heat for a fourth heat exchanger at the bottom of the entrainer recovery tower, the material flow at the bottom of a pre-separation tower provides heat for a fifth heat exchanger, and high-purity water is extracted from the bottom of the tower;
the entrainer is ethyl acetate or methyl propionate;
the number of theoretical plates of the pre-separation tower is 15-25, and the operating pressure is 5.05 multiplied by 104Pa～2.02×105Pa, the temperature at the top of the tower is 60-95 ℃, the temperature at the bottom of the tower is 82-120 ℃, and the feeding position of the mixture of ethanol and water is 10 th-20 th tower plates;
the number of theoretical plates of the entrainer recovery tower is 5-15, and the operating pressure is 3.03 multiplied by 104Pa～1.01×105Pa, the temperature at the top of the tower is 50-78 ℃, and the temperature at the bottom of the tower is 70-100 ℃.
2. The extraction process of claim 1, wherein the plant further comprises a plurality of compressors, a plurality of coolers, a plurality of heat exchangers, and a plurality of pressure reducing valves.
3. The extraction process of claim 2 wherein said plurality of compressors comprises at least three, said plurality of coolers comprises at least 2, said plurality of heat exchangers comprises at least 5, and said plurality of pressure reducing valves comprises at least 2.
4. The extraction process according to any one of claims 1 to 3, characterized in that the pre-separation column is a tray column or a packed column; the azeotropic distillation tower is a plate tower or a packed tower; the entrainer recovery tower is a plate tower or a packed tower.
5. The extraction method according to any one of claims 2 to 3, wherein the compression ratio of each compressor is 2 to 4.
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| CN102719282A (en) * | 2012-07-03 | 2012-10-10 | 华东理工大学 | Ethanol-water separation method based on automotive fuel and with methyl tertiary butyl ether (MTBE) serving as entrainer |
| CN104926608A (en) * | 2014-03-17 | 2015-09-23 | 中国石油化工股份有限公司 | Method for separating ethylene glycol and 1,2-butanediol |
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| CN102719282A (en) * | 2012-07-03 | 2012-10-10 | 华东理工大学 | Ethanol-water separation method based on automotive fuel and with methyl tertiary butyl ether (MTBE) serving as entrainer |
| CN104926608A (en) * | 2014-03-17 | 2015-09-23 | 中国石油化工股份有限公司 | Method for separating ethylene glycol and 1,2-butanediol |
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| 热泵自夹带共沸精馏分离乙醇 甲苯水三元共沸混合物;吕新宇等;《常州大学学报》;20171130;第29卷(第6期);第26-31段 * |
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