JP2011162502A - Method for producing absolute ethanol - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing absolute ethanol from a raw material including ethanol and water as the main components under a low operating pressure. <P>SOLUTION: The method for producing absolute ethanol has a process which comprises supplying the raw material including ethanol and water as the main components into the middle part of a secondary distillation tower T2, supplying a hydrocarbon solvent into the upper part of the secondary distillation tower, drawing a vapor occurring in the secondary distillation tower and practically consisting of a hydrocarbon solvent and water and not including ethanol from a tower top, and drawing a liquid mixture occurring in the secondary distillation tower and practically consisting of a hydrocarbon solvent and ethanol and not including water from a tower bottom; and a process which comprises supplying the liquid mixture occurring in the secondary distillation tower to the central part of a third distillation tower T3, supplying the hydrocarbon solvent to the upper part of the third distillation tower, drawing a vapor occurring in the third distillation tower and practically consisting of ethanol and a hydrocarbon solvent not including water from the tower top, and drawing anhydrous ethanol practically not including a hydrocarbon solvent from the tower bottom. The hydrocarbon solvent is propane, propylene, normal butane, isobutane, or a solvent mixture thereof. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an absolute ethanol production method for producing absolute ethanol from a raw material mainly composed of ethanol and water, and more specifically, an ethanol aqueous solution produced by biomass fermentation ethanol or synthetic ethanol, after use in various applications The present invention relates to a method for producing absolute ethanol, in which raw materials such as a collected ethanol aqueous solution and a high-concentration ethanol aqueous solution mixed with moisture in the transport process are concentrated or dehydrated with less energy to produce absolute ethanol.

  In recent years, with increasing environmental awareness, in order to reduce carbon dioxide emissions, there is an active movement to actively use biomass instead of fossil fuel as an energy source. A typical example is a method of producing ethanol by saccharification and fermentation of biomass.

  Ethanol obtained by fermentation is a low-concentration ethanol aqueous solution, the ethanol concentration is about 6 to 10 wt%, the remainder is almost moisture, and contains a few impurities.

  When this bioethanol is added to gasoline, it is necessary to use absolute ethanol having an ethanol concentration of 99.6 wt% or more in order to prevent water problems.

  In addition, when ETBE (Ethyl Tertiary-Butyl Ether) is synthesized by reaction with isobutylene and added to gasoline, anhydrous ethanol with an ethanol concentration of 99.99 wt% or more is used to prevent poisoning of the synthesis reaction catalyst. Need to be ethanol.

  Patent Document 1 (Japanese Patent Application Laid-Open No. 3-27336) discloses a method in which a countercurrent extraction tower using a hydrocarbon solvent (propane, propylene, normal butane, isobutane or a mixed solvent thereof) and a tower top cooling reflux are combined. It is disclosed. A method is disclosed in which concentrated ethanol having an ethanol concentration of about 94 wt% is separated and recovered from a low-concentration ethanol aqueous solution, and anhydrous ethanol having an ethanol concentration of about 99.9 wt% or more is separated and recovered by a solvent extraction distillation column using a hydrocarbon solvent. ing.

  Patent Document 2 (Japanese Patent Laid-Open No. 3-157340) discloses an integrated process (solvent) comprising a solvent extraction distillation column using a hydrocarbon solvent (propane, propylene, normal butane, isobutane or a mixed solvent thereof) and a solvent recovery column. Extractive distillation method). A method for separating and recovering absolute ethanol from a concentrated ethanol aqueous solution by this integrated process is disclosed.

Japanese Patent Laid-Open No. 3-27336 JP-A-3-157340

  The method disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 3-27336) is a method of concentrating a low-concentration ethanol aqueous solution raw material with low energy to an ethanol concentration of about 94 wt%, and then dehydrating to an ethanol concentration of 99.9 wt% or more. It is a technology that can be concentrated and dehydrated with a high recovery rate of 99% or more. However, the operating pressure of the countercurrent extraction column (concentration) is as high as about 10 MPa (supercritical pressure), and the operating pressure of the solvent extractive distillation method (dehydration) is about to reduce the pressure difference from the countercurrent extraction column. 2 to 3 MPa. In either case, the operation pressure is high, so the operation is subject to the high-pressure gas safety law and requires skill. For this reason, reduction of the pressure at the time of concentration dehydration is desired.

  Further, in the method disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 3-27336), ethanol having a concentration that requires wastewater treatment may be dissolved in the wastewater discharged from the water separation tank of the solvent extraction distillation method. Countermeasures are required.

  The method disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 3-157340) is a technology that can dehydrate 99.9 wt% or more of high purity absolute ethanol from concentrated ethanol raw material with a high recovery rate of 99% or more with less energy. It is. In this method, the operating pressure is a relatively low pressure of 0.2 to 1 MPa, but a large amount of high-purity hydrocarbon solvent is required. Such a high-purity hydrocarbon solvent is expensive and difficult to obtain in large quantities, and therefore a hydrocarbon solvent that is inexpensive and easily available is desired.

  The objective of this invention is providing the manufacturing method of the absolute ethanol which can manufacture absolute ethanol from the raw material which has ethanol and water as a main component by low operating pressure.

  Another object of the present invention is to provide a method for producing absolute ethanol, which can produce absolute ethanol from a raw material mainly composed of ethanol and water, using an inexpensive and easily available hydrocarbon solvent.

  As a result of intensive studies to solve the above problems, the inventors of the present application used a distillation method that can be operated at a low pressure for concentrating the raw material of the ethanol aqueous solution, and a hydrocarbon solvent that is inexpensive and readily available. By using it, it was found that 99.9 wt% or more of high purity absolute ethanol can be dehydrated with a high recovery rate of 99% or more with less energy. Moreover, it discovered that a waste_water | drain process could be made unnecessary by returning the waste_water | drain extracted from the water phase of a water separation tank to the raw material of ethanol aqueous solution.

  Therefore, in the method for producing absolute ethanol according to one embodiment of the present invention, a raw material mainly composed of ethanol and water is supplied to the middle part of the second distillation column, and a hydrocarbon solvent is supplied to the upper part of the second distillation column. From the top of the second distillation column, a second distillation column vapor comprising a hydrocarbon solvent substantially free of ethanol and moisture is taken out, and water is substantially removed from the bottom of the second distillation column. The step of taking out the second distillation column mixed liquid composed of the hydrocarbon solvent and ethanol not contained, and the second distillation column mixed liquid taken out from the bottom of the second distillation column into the middle of the third distillation column A hydrocarbon solvent is supplied to the upper part of the third distillation column, and a third distillation column vapor comprising a hydrocarbon solvent substantially free of ethanol and moisture is supplied from the top of the third distillation column. Take out, from the bottom of the third distillation column, Removing anhydrous ethanol which does not contain a hydrocarbon solvent qualitatively, mixing the second distillation column vapor and the third distillation column vapor and compressing them with a second compressor, The second pressurized steam compressed by the machine is used as a heating source for the reboiler of the second distillation column, and then supplied to the separation tank, and the hydrocarbon solvent separated in the separation tank is supplied to the second distillation column. The hydrocarbon solvent is recycled to the top of the column and the top of the third distillation column, and the hydrocarbon solvent is propane, propylene, normal butane, isobutane, or a mixed solvent thereof.

  In the method for producing absolute ethanol described above, the hydrocarbon solvent is normal butane, isobutane, or a mixed solvent thereof, and the pressure of the second distillation column and the third distillation column is 0.3 to 1. The pressure may be in the range of 0 MPa.

  In the method for producing absolute ethanol described above, the hydrocarbon solvent is normal butane, and the pressure of the second distillation column and the third distillation column is a pressure within a range of 0.3 to 0.6 MPa. It may be.

  In the method for producing absolute ethanol described above, the hydrocarbon solvent is propane, propylene, or a mixed solvent thereof, and the pressure of the second distillation column and the third distillation column is 1.1 to 1.4 MPa. You may make it the pressure within the range.

  In the method for producing absolute ethanol described above, a raw material mainly composed of ethanol and water is supplied to the middle part of the first distillation column, and the first distillation column vapor composed of ethanol is taken out from the top of the first distillation column, First substantially steam-free water is taken out from the bottom of the first distillation column, the first distillation column steam is compressed by a first compressor, and the first pressurized steam compressed by the first compressor Is used as a heating source for the reboiler of the first distillation column, and then refluxed to the top of the first distillation column, and the remainder of the first pressurized steam is transferred to the middle of the second distillation column. You may make it further have the process of supplying.

  In the method for producing absolute ethanol described above, the aqueous phase obtained by separating the hydrocarbon solvent in the separation tank may be supplied to the middle part of the first distillation column.

  As described above, according to the present invention, the raw material mainly composed of ethanol and water is supplied to the middle part of the second distillation column, the hydrocarbon solvent is supplied to the upper part of the second distillation column, From the top of the column, a second distillation column vapor consisting of a hydrocarbon solvent substantially free of ethanol and water is taken out, and a hydrocarbon solvent substantially free of water and ethanol are extracted from the bottom of the second distillation column. A step of taking out the second distillation column mixed liquid comprising: a second distillation column mixed liquid taken out from the bottom of the second distillation column is fed into the middle of the third distillation column, and placed above the third distillation column. A hydrocarbon solvent is supplied, and a third distillation column vapor composed of a hydrocarbon solvent substantially free of ethanol and moisture is taken out from the top of the third distillation column, and from the bottom of the third distillation column, Removing anhydrous ethanol that does not contain any hydrocarbon solvent. The second distillation tower steam and the third distillation tower steam are mixed and compressed by the second compressor, and the second pressurized steam compressed by the second compressor is used as a heating source for the reboiler of the second distillation tower. The hydrocarbon solvent supplied to the separation tank is recycled to the top of the second distillation tower and the top of the third distillation tower, and the hydrocarbon solvents are propane and propylene. , Normal butane, isobutane, or a mixed solvent thereof, it is possible to produce absolute ethanol from raw materials mainly composed of ethanol and water at a low operating pressure.

It is a figure for demonstrating the manufacturing method of the absolute alcohol by 1st Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the absolute alcohol by 2nd Embodiment of this invention. It is a graph (the 1) which shows the precision of the process simulator used for devising the manufacturing method of the anhydrous alcohol by this invention. It is a graph (the 2) which shows the precision of the process simulator used in order to devise the manufacturing method of the anhydrous alcohol by this invention. It is a graph which shows the calculation result of the required energy in each fermentation ethanol concentration by the integrated process of this invention. 2 is a graph (part 1) showing a result of Example 1. 6 is a graph (part 2) showing a result of Example 1. 10 is a graph showing the results of Example 2.

(First embodiment)
A method for producing anhydrous alcohol according to a first embodiment of the present invention will be described with reference to FIG.

  The “low-concentration ethanol aqueous solution raw material” in this embodiment is a raw material mainly composed of ethanol and water having an ethanol concentration of about 80 wt% or less. For example, fermented ethanol (sugars obtained from biomass such as corn and sugarcane fermented with yeast, raw material with an ethanol concentration of about 4 to 10 wt%), synthetic ethanol (by reacting water and ethylene using a catalyst) For example, a raw material having an ethanol concentration of about 20 wt%), a waste ethanol solvent (a raw material in which water adhering to various inorganic substances is washed away by ethanol, and a raw material having an ethanol concentration of about 1 to 80 wt%).

  The “high-concentration ethanol aqueous solution raw material” in the present embodiment is a raw material mainly composed of ethanol and water having an ethanol concentration of about 80 to 99 wt%. For example, the ethanol aqueous solution raw material concentrated by the distillation method described later, the aqueous ethanol raw material mixed with water during transportation of hydrous ethanol or absolute ethanol, and unreacted in the synthesis process of ETBE (Ethyl Tertiary-Butyl Ether) Ethanol aqueous solution raw material.

  In this embodiment, “anhydrous ethanol” is one having an ethanol concentration of about 99.6 wt% or more.

  FIG. 1 is an example of a process for performing a method for producing anhydrous alcohol according to a first embodiment of the present invention.

  In the process of this embodiment, three first distillation columns T1, second distillation columns T2, third distillation columns T3, one water separation tank V1, four reboilers E1A, E1B, E2A, E3A, three heat exchangers E1C, E2B, E3B, two first compressors C1, and a second compressor C2 are used.

  The low-concentration ethanol aqueous solution is concentrated by the first distillation column T1, and the high-concentration ethanol aqueous solution is dehydrated by the second distillation column T2 and the third distillation column T3 to produce absolute ethanol.

  First, the low-concentration ethanol aqueous solution raw material is preheated by the heat exchanger E2B and the heat exchanger E1C, and is supplied to the middle of the first distillation column Tl by the line 3.

  The low-concentration ethanol aqueous solution raw material is distilled by the first distillation column T 1, and about 88 to 94 wt% of concentrated ethanol vapor is taken out from the top of the first distillation column T 1 and sent to the line 4.

  The concentrated ethanol vapor sent to the line 4 is compressed by the first compressor C 1 and sent to the line 7.

  In the first compressor C1, the concentrated ethanol vapor is compressed so as to be condensed at a temperature about 10 ° C. to 30 ° C. higher than the bottom temperature of the first distillation column T1. If the temperature difference from the bottom temperature of the first distillation column T1 is 10 ° C. or less, a large heat transfer area is required, which is not preferable. Further, if the temperature difference from the column bottom temperature of the first distillation column T1 is 30 ° C. or more, energy required for compression increases, which is not preferable.

  When the amount of heat is insufficient due to the compression of the first compressor C1, heating steam or the like may be supplied to the reboiler E1B.

  The first pressurized steam compressed by the first compressor C1 and sent to the line 7 is deprived of heat by the reboiler E1A to become the first liquid and sent to the line 8.

  A part of the first liquid sent to the line 8 is refluxed to the upper part of the first distillation column Tl by the line 9. The remainder of the 1st liquid sent to the line 8 is supplied to the middle part of the 2nd distillation column T2 by the pump (not shown) by the line 10 as a 1st concentrated ethanol aqueous solution raw material.

  Water substantially free of ethanol is extracted from the bottom of the first distillation column T1, cooled by the heat exchanger E1C, and discharged from the line 6 as waste water.

  The operating pressure of the first distillation column T1 may be near atmospheric pressure. The number of stages and the reflux amount of the first distillation column T1 are designed by ordinary chemical engineering techniques.

  Next, a liquid hydrocarbon solvent is supplied to the upper part of the second distillation column T2 from the line 21A.

  From the top of the second distillation column T2, the second distillation column vapor, which is composed of a hydrocarbon solvent and moisture and substantially does not contain ethanol, is taken out and sent to the line 11.

  From the bottom of the second distillation column T2, a bottom mixed liquid composed of anhydrous ethanol and a hydrocarbon solvent substantially free of moisture is taken out and sent to the line 12.

  The bottom mixed liquid sent to the line 12 is preheated by the heat exchanger E3B, and is supplied from the line 13 to the middle part of the third distillation column T3.

  Liquid hydrocarbon solvent is delivered to line 24 and fed from line 22 to the top of third distillation column T3.

  From the top of the third distillation column T 3, the third distillation column vapor of a hydrocarbon solvent substantially free of ethanol and moisture is taken out and sent to the line 16.

  From the bottom of the third distillation column T3, absolute ethanol substantially free of hydrocarbon solvent is taken out and sent to the line. The absolute ethanol sent to the line 14 is cooled by the heat exchanger E3B and sent to the line 15. Collect the product absolute ethanol from line 15.

  The absolute ethanol sent to the line 14 is heated by the reboiler E3A and supplied to the lower part of the third distillation column T3. Superheated steam or the like is used as a heat source for the reboiler E3A.

  The reboiler E3A is a heat source for distillation in the third distillation column T3.

  Next, the second distillation column steam taken out from the top of the second distillation column T2 and sent to the line 11, and the third distillation column vapor taken out from the top of the third distillation column T3 and sent to the line 16; Is supplied to the second compressor C2 through the line 17. This distillation column steam is compressed by the second compressor C2 and sent to the line 18 as second pressurized steam and used as a heat source for the reboiler E2A.

  In the 2nd compressor C2, these distillation column vapor | steam is compressed so that it may condense at about 10-30 degreeC temperature higher than the column bottom temperature of 2nd distillation column T2. If the temperature difference from the bottom temperature of the second distillation column T2 is 10 ° C. or less, a large heat transfer area is required, which is not preferable. Moreover, if the temperature difference with the column bottom temperature of 2nd distillation column T2 is 30 degreeC or more, since energy required for compression will increase, it is unpreferable.

  The second pressurized steam sent to the line 18 is deprived of heat by the reboiler E2A and condensed to become the second liquid, which is sent to the line 19. The second liquid sent to the line 19 is further cooled by the heat exchanger E2B to be completely liquid and supplied to the water separation tank V1.

  The column bottom temperature of the second distillation column T2 is controlled to be about 10 to 20 ° C. higher than the column top temperature by the amount of heat supplied to the reboiler E2A. Thereby, it is not necessary to excessively compress the pressure of the second pressurized steam compressed by the second compressor C2, and the power of the second compressor C2 can be reduced.

  In the water separation tank V1, due to the difference in specific gravity of the liquid, the water phase is phase-separated at the bottom and the hydrocarbon solvent phase is phase-separated at the top.

  The water phase-separated by the water separation tank V1 may be usually drained by extracting water from the lower part of the water separation tank V1.

  However, in this embodiment, water extracted from the lower part of the water separation tank V1 is supplied to the line 2 via the line 23 on the assumption that ethanol may be dissolved in the aqueous phase and the waste water concentration standard may not be satisfied. Send out and reuse as low-concentration ethanol aqueous solution. Thereby, the vapor | steam taken out from the tower top of 2nd distillation tower T2 and 3rd distillation tower T3 is finally taken out as waste water which does not contain ethanol from the tower bottom of 1st distillation tower T1.

  The hydrocarbon solvent phase-separated by the water separation tank V1 is sent to the line 21, supplied to the upper part of the second distillation column T2 and the upper part of the third distillation column T3, and recycled.

  If ethanol is entrained in the hydrocarbon solvent to be recycled and the ethanol concentration increases with each cycle, the process becomes inoperable.

  The hydrocarbon solvent used in this embodiment is propane, propylene, normal butane, isobutane, or a mixed solvent thereof.

  However, since these pure solvents are expensive and difficult to obtain in large quantities, the inventors of the present application paid attention to a mixed solvent of normal butane and isobutane, which is an intermediate product of crude oil refining process, which is inexpensive and can be obtained in large quantities.

  As an example, this mixed solvent has a normal butane to isobutane ratio of about 7 to 3, and contains several percent or less of pentane, propane, etc. The inventors have found that this works.

  The pressures of the second distillation column T2 and the third distillation column T3 are below the critical pressure of the hydrocarbon solvent to be used, and the saturation temperature of the hydrocarbon solvent is a temperature at which water does not freeze at the top of each distillation column. It is desirable that the pressure be equal to or higher than the saturated vapor pressure at which the temperature is 0C.

  More preferable pressures of the second distillation column T2 and the third distillation column T3 are such that the energy used in the second compressor C2 and the reboiler E3A is small, the purity of the absolute ethanol recovered from the line 15 and the recovery rate are high, and the circulation of the line 21 It is a necessary and sufficient condition that the ethanol in the hydrocarbon solvent does not increase with circulation.

  The pressure in the second distillation column T2 and the third distillation column T3 satisfying such conditions is a pressure in the range of 0.3 to 0.6 MPa when the hydrocarbon solvent is normal butane, and 0 in the case of isobutane. The pressure is within the range of 3 to 1.0 MPa, and in the case of a mixed solvent of normal butane and isobutane, the pressure is within the range of 0.3 to 1.0 MPa depending on the mixing ratio, and propane, propylene, or In the case of these mixed solvents, the present inventors have found that the pressure is in the range of 1.1 to 1.4 MPa. Further, when normal butane or isobutane is used as the hydrocarbon solvent, the pressure is preferably 0.5 MPa or more.

(Second Embodiment)
A method for producing anhydrous alcohol according to a second embodiment of the present invention will be described with reference to FIG.

  Ethanol concentration of waste ethanol solvent, ethanol aqueous solution raw material mixed with water during transportation of hydrous ethanol or absolute ethanol, unreacted ethanol aqueous solution raw material in ETBE (Ethyl Tertiary-Butyl Ether) synthesis process, etc. However, when using a high-concentration ethanol aqueous solution raw material having a concentration of about 80 wt% or more, it is not necessary to use the first distillation column T1 for concentrating the low-concentration ethanol aqueous solution.

  The process shown in FIG. 2 is obtained by removing the first distillation column T1 and the related structure from the process shown in FIG. Since the second distillation column T2 and the third distillation column T3 in the process shown in FIG. 2 and their related configurations are the same as those in the process shown in FIG. 1, detailed description thereof is omitted.

  In the process of the present embodiment, two second distillation columns T2, a third distillation column T3, one water separation tank V1, two reboilers E2A and E3A, two heat exchangers E2B, E3B and one second compressor C2 are used.

  In the present embodiment, the high-concentration ethanol aqueous solution is dehydrated by the second distillation column T2 and the third distillation column T3 to generate absolute ethanol.

  The high-concentration ethanol aqueous solution raw material is preheated by the heat exchanger E2B and supplied to the middle of the second distillation column T2 through the line 10.

  The liquid hydrocarbon solvent is supplied to the upper part of the second distillation column T2 through the line 21A, and is supplied to the upper part of the third distillation column T3 through the line 22.

  The absolute ethanol of the product is taken out from the bottom of the third distillation column T3 and supplied through the line 14, the heat exchanger E3B, and the line 15. The water phase-separated by the water separation tank V1 is collected as drainage from the lower part of the water separation tank V1.

(Examination of process optimization)
The inventors of the present application have optimized the process of obtaining absolute ethanol by concentrating and dehydrating fermented ethanol.

  The process is the process shown in FIG. 1 comprising three distillation columns T1, T2, and T3, using a self-vapor compression distillation method for the concentration step and a butane solvent extraction distillation method for the dehydration step.

  The phase equilibrium estimation formula that can be used in each step was examined, and the operation conditions in each step were examined by using the estimation formula in a process simulator PRO / II manufactured by Invensys. Next, the integration process was optimized based on these results, and the required energy of the process was obtained.

  In the examination of the concentration process, NRTL (Non Random Two Liquids Model) was used as a phase equilibrium estimation formula. As a result of examining the multi-effect distillation method and the self-vapor compression distillation method, it was decided to use the self-vapor compression distillation method with low energy in the concentration process. The operating conditions were a distillation column T1 pressure of 0.1 MPa, a recovery unit of 15 stages, a concentration unit of 15 stages, and an outlet pressure of the first compressor C1 of 0.5 MPa. The ethanol concentration at the top of the column was 90 wt%, and the ethanol concentration at the bottom was 10 ppm.

In the examination of the dehydration process, the relative volatility α ₂₁ (= K ₂ / K ₁ , K _i = y _i ) of C ₂ H ₅ OH (2) and H ₂ O (3) to n-C ₄ H ₁₀ (1) / X _i , x _i , y _i are the molar fractions of the i component in the liquid phase and the gas phase), α ₃₁ (= K ₃ / K ₁ ) and the phase equilibrium of each binary system. did.

  A comparison between the UNIFAC calculation formula and literature values is shown in FIGS.

FIG. 3 shows values in the UNIFAC calculation formula for n-C ₄ H ₁₀ (1) -C ₂ H ₅ OH (2) -H ₂ O (3) and Reference 1) (Horizoe et al., Mitsubishi Heavy Industries, Ltd.). Report, Vol.3, No.6, 527-530 (1993)) and comparison.

FIG. 4 shows the UNIFAC calculation value for n-C ₄ H ₁₀ (1) -C ₂ H ₅ OH (2) and reference 2) (T. Holderbamn, A. Utzig and J. Gmehling, Fluid Phase. It is a figure which shows the comparison with the value of Equilibria, 63, 219-226 (1971).

  As shown in FIG. 3 and FIG. 4, the value of the calculation formula and the value of the literature are in good agreement, indicating that the process simulator used is appropriate.

  In order to optimize the integrated process, an integrated process was constructed in consideration of heat recovery conditions and vapor compression conditions.

  The operating conditions are as follows: the pressure of the extractive distillation column T2 is 0.6 MPa, the recovery unit 30 stages / concentration unit 20 stages, the solvent recovery tower T3 is pressure 0.6 MPa, the recovery unit 10 stages / concentration unit 20 stages, and the second compressor C2. The outlet pressure was 0.85 MPa.

  Further, in order to reduce the energy applied to the second compressor C2, the temperature difference between the tower top and the tower bottom was adjusted by the tower bottom composition ratio of the extractive distillation tower T2.

  FIG. 5 shows calculation results of required energy at each fermentation ethanol concentration in the integrated process. In either case, the conditions were such that the product ethanol concentration was 99.9 wt% and the ethanol recovery rate was 99.8%.

  According to the method combining the self-vapor compression distillation method and the extractive distillation method, the concentration / dehydration energy is large when the fermentation ethanol concentration is low, but the concentration / dehydration energy is 2.5 MJ / L when the fermentation ethanol concentration is 10 wt%. It turned out that it can be made below -EtOH. Moreover, it has been found that the concentration can be made lower than the concentration / dehydration energy by the multi-effect distillation method at a fermented ethanol concentration of 10 wt%.

  Thus, it was found that the concentration / dehydration energy can be reduced to 2.5 MJ / L-EtOH or less by optimizing a new concentration / dehydration process.

  Examples of the present invention and comparative examples will be described.

Example 1
Energy required for producing 1 liter of absolute ethanol from a concentrated ethanol raw material having a concentration of 90 wt% and a concentrated ethanol raw material having a concentration of 94 wt% using propane and normal butane as hydrocarbon solvents using the process shown in FIG. The MJ was estimated by a process simulator while changing the operating pressure of each tower.

  It has been confirmed that the estimation accuracy of this process simulator has sufficient accuracy as shown in FIGS.

  As shown in FIG. 6 and FIG. 7, the following results were obtained for both the concentrated ethanol raw material with a concentration of 90 wt% and the concentrated ethanol raw material with a concentration of 94 wt%.

When the hydrocarbon solvent is normal butane _(n-C 4 H _10), the pressure has converged only range of 0.3 and 0.6. That is, it was found that when the pressure was 0.7 MPa or more, ethanol in the circulating solvent increased and the operation was impossible. On the other hand, when the pressure is 0.2 MPa or less, the temperature at the top of the tower is about 5 ° C. or less, and moisture may freeze, making operation difficult.

From these results, when the hydrocarbon solvent is normal butane (n-C ₄ H ₁₀ ), absolute ethanol is produced with a low required energy of 1.7 MJ or less in a pressure range of 0.3 to 0.6 MPa. I knew it was possible.

Further, as shown in FIGS. 6 and 7, when the hydrocarbon solvent is propane (C ₃ H ₈₎ has been all converged, pressure is required energy in 1.2MPa and 1.3 to 1.4 It was found that the required energy increases rapidly at lower or higher pressures.

That is, when the hydrocarbon solvent is propane (C ₃ H ₈ ), it has been found that absolute ethanol can be produced with a required energy as low as 1.7 MJ or less in a pressure range of 1.1 to 1.4 MPa.

  In each case, the absolute ethanol concentration was 99.9 wt% or more, and the ethanol recovery rate was 99.8% or more.

(Example 2)
Using the process shown in FIG. 2, propane, propylene, normal butane, isobutane, a mixed solvent, and a crude oil intermediate product equivalent solvent are used as hydrocarbon solvents, and 1 liter of absolute ethanol is produced from a concentrated ethanol raw material having a concentration of 90 wt%. The energy MJ required for this was estimated with a process simulator while changing the operating pressure of each tower.

  As shown in FIG. 8, when the hydrocarbon solvent is normal butane, only the pressure range of 0.3 to 0.6 MPa converged. That is, it was found that when the pressure was 0.7 MPa or more, ethanol in the circulating solvent increased and the operation was impossible. On the other hand, when the pressure is 0.2 MPa or less, the temperature at the top of the tower is about 5 ° C. or less, and moisture may freeze, making operation difficult.

  When the hydrocarbon solvent was isobutane, it converged regardless of the pressure, but when the pressure exceeded 1.0 MPa, the ethanol recovery rate was 99.8% or less, which was not preferable.

  When the hydrocarbon solvent is a mixed solvent of normal butane and isobutane, depending on the mixing ratio, the pressure converged in the range of 0.3 to 0.7 MPa in the case of the mixing ratio of the examples.

  From these results, it was found that when the hydrocarbon solvent is normal butane, absolute ethanol can be produced with a required energy as low as 1.7 MJ or less in a pressure range of 0.3 to 0.6 MPa.

  In addition, when the hydrocarbon solvent is isobutane, a mixed solvent, or a crude oil intermediate product equivalent solvent, it can be seen that absolute ethanol can be produced with a required energy as low as 2.2 MJ or less in a pressure range of 0.3 to 1.0 MPa. It was.

  In addition, as shown in FIG. 8, when the hydrocarbon solvent is propane or propylene, all converged, but the required energy is as low as 1.3 to 1.4 at a pressure of 1.2 MPa. It was found that the required energy increases rapidly at low or high pressure.

  That is, when the hydrocarbon solvent is propane or propylene, it was found that absolute ethanol can be produced with a required energy as low as 1.7 MJ or less within a pressure range of 1.1 to 1.4 MPa.

  In each case, the absolute ethanol concentration was 99.9 wt% or more, and the ethanol recovery rate was 99.8% or more.

(Example 3)
As Example 3, the process shown in FIG. 1 was used, a crude oil intermediate product phase-like solvent (n-butane: i-butane = 66.5: 28.5) was used as the hydrocarbon solvent, and a low-concentration ethanol raw material having a concentration of 10 wt%. From the concentrated ethanol raw material having a concentration of 90 wt%, the energy MJ necessary for producing 1 liter of absolute ethanol was determined by process simulation. The concentration step is vapor recompression distillation at normal pressure, and the dehydration step is extraction distillation at a pressure of 0.6 MPa.

  In Example 3, as the operating conditions of the dehydration step, the optimum conditions of Examples 1 and 2 (low pressure and low energy conditions) were used. The energy of the dehydration process is lower than the values in FIGS. 6 and 7 because the preheating of the concentration process is effectively used.

  In each case, the absolute ethanol concentration was 99.9 wt% or more, and the ethanol recovery rate was 99.8% or more.

  As a comparative example, the dehydration step was the same as in Example 3, and the energy MJ required to produce absolute ethanol was determined for the case where the concentration step was changed.

  In Comparative Example 1, the concentration step is distillation at normal pressure. Comparative Example 2 is a multi-effect (raw material distribution type) distillation in which the concentration step is performed at a pressure of 0.05 to 0.51 MPa. In Comparative Example 3, the concentration process is supercritical extraction at a pressure of 6 MPa.

  Other conditions in Comparative Examples 1 to 3 were the same as those in Example 3.

  As shown in Table 1, in Example 3, the energy required for the concentration step is 1.3 MJ / L, 6 MJ / L in Comparative Example 1, 2 MJ / L in Comparative Example 2, 1.4 MJ / L in Comparative Example 3 It was found that the required energy was the lowest compared to.

  As shown in Table 1, in Example 3, the pressure in the concentration step is normal pressure, compared with normal pressure in Comparative Example 1, 0.05 to 0.51 MPa in Comparative Example 2, and 6 MPa in Comparative Example 3, It was found that the pressure was relatively low.

  Therefore, it was found that Example 3 had a lower pressure and the least required energy as compared with Comparative Example 1, Comparative Example 2, and Comparative Example 3.

T1 ... 1st distillation column T2 ... 2nd distillation column T3 ... 3rd distillation column V1 ... Water separation tank E1A, E1B, E2A, E3A ... Reboiler E1C, E2B, E3B ... Heat exchanger C1 ... 1st compressor C2 ... 1st compressor 2 compressors

Claims (5)

A raw material mainly composed of ethanol and water is supplied to the middle part of the second distillation column, a hydrocarbon solvent is supplied to the upper part of the second distillation column, and substantially ethanol is introduced from the top of the second distillation column. A second distillation column composed of a hydrocarbon solvent not containing water and water, and a second distillation column consisting of a hydrocarbon solvent substantially free of water and ethanol from the bottom of the second distillation column Removing the mixed liquid;
The second distillation column mixed liquid taken out from the bottom of the second distillation column is supplied to the middle of the third distillation column, a hydrocarbon solvent is supplied to the upper portion of the third distillation column, and the third distillation A third distillation column vapor composed of a hydrocarbon solvent substantially free of ethanol and moisture is taken out from the top of the column, and substantially no hydrocarbon solvent is included from the bottom of the third distillation column. Removing absolute ethanol,
The second distillation tower steam and the third distillation tower steam are mixed and compressed by a second compressor, and the second pressurized steam compressed by the second compressor is supplied to the reboiler of the second distillation tower. After being used as a heating source, it is supplied to the separation tank, and the hydrocarbon solvent separated in the separation tank is recycled to the top of the second distillation tower and the top of the third distillation tower,
The method for producing anhydrous ethanol, wherein the hydrocarbon solvent is propane, propylene, normal butane, isobutane, or a mixed solvent thereof. The method for producing absolute ethanol according to claim 1,
The hydrocarbon solvent is normal butane, isobutane, or a mixed solvent thereof,
The method for producing absolute ethanol, wherein the pressure of the second distillation column and the third distillation column is a pressure within a range of 0.3 to 1.0 MPa. The method for producing absolute ethanol according to claim 1,
The hydrocarbon solvent is propane, propylene, or a mixed solvent thereof,
The method for producing absolute ethanol, wherein the pressure in the second distillation column and the third distillation column is a pressure within a range of 1.1 to 1.4 MPa. In the manufacturing method of the absolute ethanol of any one of Claims 1 thru | or 3,
A raw material mainly composed of ethanol and water is supplied to the middle part of the first distillation column, the first distillation column vapor made of ethanol is taken out from the top of the first distillation column, and from the bottom of the first distillation column. Water substantially free of ethanol is taken out, the first distillation column steam is compressed by a first compressor, and a part of the first pressurized steam compressed by the first compressor is converted into the first distillation. The method further comprises a step of refluxing to the top of the first distillation column and supplying the remainder of the first pressurized steam to the middle of the second distillation column after being used as a heating source for the reboiler of the column. A method for producing absolute ethanol. The method for producing absolute ethanol according to claim 4,
A method for producing absolute ethanol, wherein an aqueous phase obtained by separating a hydrocarbon solvent in the separation tank is supplied to the middle part of the first distillation column.

Images