Distillation apparatus

Abstract

This invention provides a distillation apparatus suitable for the bioethanol distillation process, which improves energy efficiency and reduces CO2 emissions. [Solution] The system has a first distillation system that performs distillation of a raw material liquid containing ethanol, water, a low-boiling-point component having a lower boiling point than ethanol, and a high-boiling-point component having a higher boiling point than ethanol, and a second distillation system that performs distillation of a liquid side-cut from the first distillation system. Both the first and second distillation systems have a heat pump that recovers the thermal energy of the cooling water used to cool the top vapor of the column and heats the bottom liquid. The intermediate distillate in the first distillation system is a condensate mainly composed of ethanol, and the top distillate is a liquid containing a low-boiling-point component. The intermediate distillate in the second distillation system is a liquid containing a high-boiling-point component, and the top distillate is a condensate mainly composed of ethanol.

Description

Technical Field

[0005]

[0001] The present disclosure relates to a distillation apparatus using a heat pump and a vapor compressor. More specifically, it relates to a distillation apparatus that distills a raw material liquid containing ethanol, water, a low-boiling component having a boiling point lower than that of ethanol, and a high-boiling component having a boiling point higher than that of ethanol, separates the low-boiling component and the high-boiling component from the raw material liquid, and recovers a distillate mainly composed of ethanol.

Background Art

[0002] In the context of the decarbonization trends at home and abroad, the momentum for introducing SAF in the aviation industry is increasing. SAF is an abbreviation for "Sustainable Aviation Fuel" and refers to a sustainable aviation fuel that is carbon-neutral and made from biomass or waste. ICAO (International Civil Aviation Organization) and IATA (International Air Transport Association) aim to halve carbon dioxide emissions by 2050 compared to 2005. By airlines around the world introducing SAF, a significant reduction in CO2 emissions is expected.

[0003] The current global production volume of SAF remains less than 0.03% of demand. To achieve the environmental goals in 2050, related industries need to cooperate across the board to promote the development of SAF manufacturing technology, production, and utilization, and it is necessary to shift 10% of the fuel used to SAF by 2030. The Ministry of Land, Infrastructure, Transport and Tourism is also promoting the introduction and spread of SAF and has set a goal of "replacing 10% of the fuel used by Japanese airlines with SAF" by 2030.

[0004] One of the manufacturing methods for producing SAF using bioethanol as a raw material is the method of saccharifying and fermenting to pass through alcohol (ATJ method: Alcohol to Jet). The ATJ method enables large-scale production and is expected as a promising technology for SAF production.

[0005] However, the alcohol concentration of bioethanol immediately after fermentation is low, requiring a distillation process to concentrate it to a high concentration. Traditionally, boiler steam has been used for this distillation process. However, in the production process of SAF, which aims to reduce CO2 emissions, the large amount of CO2 emitted by the boiler has been a problem.

[0006] Thus, the need for energy conservation in distillation apparatuses is increasing, and various proposals have been made. As one such energy-saving technology, a distillation apparatus has been proposed that incorporates a heat pump to improve thermal efficiency (see, for example, Patent Document 1). In the distillation apparatus of Patent Document 1, the heat contained in the cooling water used to cool the top vapor in the top condenser that cools the top vapor of the distillation column is pumped up using a heat pump. The heat pumped up by the heat pump is used as a heat source for a reboiler that reheats the bottom liquid of the distillation column, thereby saving energy. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 6612936 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the distillation apparatus described in Patent Document 1 is not optimized for the distillation of bioethanol, and there is a need for a distillation process that can produce SAF from bioethanol while achieving energy savings and CO2 emission reductions.

[0009] Specifically, ethanol produced from biomass contains trace amounts of by-products such as methanol, and multiple distillation operations are necessary to ensure that purified, high-concentration ethanol does not contain these by-products. Therefore, a large amount of energy is required to purify ethanol to high purity, but equipment that uses more energy than the heat of combustion of ethanol is not suitable for producing ethanol that will be used as energy.

[0010] This disclosure aims to provide a distillation apparatus suitable for a bioethanol distillation process that can improve energy efficiency and reduce CO2 emissions. [Means for solving the problem]

[0011] To achieve the above-mentioned objectives, the distillation apparatus of this disclosure is configured as follows:

[0012] The distillation apparatus of the present disclosure comprises a first distillation column, a second distillation column, a second condenser, a third distillation column, a third condenser, a second heat pump, a separator, a vapor compressor, a second reboiler, a second reflux channel, a third reflux channel, a first condenser, a first heat pump, a fourth distillation column, a fourth condenser, a first reboiler, a first reflux channel, a fourth reflux channel, and a pressure control mechanism. The first distillation column performs distillation of a raw material liquid containing ethanol, water, a low-boiling-point component with a lower boiling point than ethanol, and a high-boiling-point component with a higher boiling point than ethanol. The second distillation column performs distillation of the liquid that is side-cut from the first distillation column. The second condenser cools and condenses the second top vapor, taken from the top of the second distillation column, using the circulating cooling water for the second condenser, separating it into a second condensate and a second vapor. The third distillation column distills the second vapor in the second condenser by bringing it into vapor-liquid contact with the third condensate. The third condenser cools and condenses the third top vapor, taken from the top of the third distillation column, using the circulating cooling water for the third condenser, and recovers a third condensate mainly composed of ethanol. The second heat pump recovers heat from the circulating cooling water for the third condenser, which has been heated to a higher temperature for cooling the third top vapor in the third condenser, and uses the recovered heat to raise the temperature level using electricity to heat the hot water. The separator flash-evaporates the hot water heated by the second heat pump and the cooling water for the second condenser heated by the second condenser. The vapor compressor compresses the vapor evaporated in the separator to generate heated vapor. The second reboiler reheats the bottom liquid of the second distillation column with steam heated by the steam compressor. The second reflux channel refluxes a portion of the second condensate from the second condenser to the second distillation column. The third reflux channel refluxes a portion of the third condensate from the third condenser to the third distillation column. The first condenser cools the first top vapor extracted from the top of the first distillation column with circulating cooling water for the first condenser, separating it into a first condensate mainly composed of ethanol and a first vapor containing a higher proportion of lower-boiling-point components than the first condensate, and recovers the first condensate. The first heat pump recovers heat from the circulating cooling water for the first condenser, which has been heated by the cooling of the first top vapor in the first condenser, and uses electricity to raise the temperature level of the recovered heat and heat the hot water. The fourth distillation column distills the first vapor in the first condenser by bringing it into gas-liquid contact with the fourth condensate. The fourth condenser cools the fourth top vapor extracted from the top of the fourth distillation column with circulating cooling water for the fourth condenser to condense it, and discharges the fourth condensate containing ethanol and low-boiling-point components. The first reboiler reheats the bottom liquid of the first distillation column with hot water heated by the first heat pump. The first reflux channel refluxes a portion of the first condensate in the first condenser to the first distillation column. The fourth reflux channel refluxes a portion of the fourth condensate in the fourth condenser to the fourth distillation column. The pressure control mechanism controls the pressure within the system so that the temperature of the bottom liquid in the first and second distillation columns is maintained at a predetermined temperature. [Effects of the Invention]

[0013] The distillation apparatus of this disclosure provides a distillation apparatus suitable for a bioethanol distillation process that can improve energy efficiency and reduce CO2 emissions. [Brief explanation of the drawing]

[0014] [Figure 1] Flow sheet showing the configuration of a distillation apparatus according to one embodiment of the present disclosure [Figure 2] The table in Figure 1 shows the material balance at each point when distillation is performed on the raw material liquid using the distillation apparatus. [Modes for carrying out the invention]

[0015] (Modes of the distillation apparatus of this disclosure) In order to describe the embodiments of this disclosure, the configuration of the distillation apparatus of this disclosure will be described.

[0016] A distillation apparatus according to a first aspect of the present disclosure comprises a first distillation column, a second distillation column, a second condenser, a third distillation column, a third condenser, a second heat pump, a separator, a vapor compressor, a second reboiler, a second reflux channel, a third reflux channel, a first condenser, a first heat pump, a fourth distillation column, a fourth condenser, a first reboiler, a first reflux channel, a fourth reflux channel, and a pressure control mechanism. The first distillation column performs distillation of a raw material liquid containing ethanol, water, a low-boiling-point component with a lower boiling point than ethanol, and a high-boiling-point component with a higher boiling point than ethanol. The second distillation column performs distillation of the liquid that is side-cut from the first distillation column. The second condenser cools and condenses the second top vapor, taken from the top of the second distillation column, using the circulating cooling water for the second condenser, separating it into a second condensate and a second vapor. The third distillation column distills the second vapor in the second condenser by bringing it into vapor-liquid contact with the third condensate. The third condenser cools and condenses the third top vapor, taken from the top of the third distillation column, using the circulating cooling water for the third condenser, and recovers a third condensate mainly composed of ethanol. The second heat pump recovers heat from the circulating cooling water for the third condenser, which has been heated to a higher temperature for cooling the third top vapor in the third condenser, and uses the recovered heat to raise the temperature level using electricity to heat the hot water. The separator flash-evaporates the hot water heated by the second heat pump and the cooling water for the second condenser heated by the second condenser. The vapor compressor compresses the vapor evaporated in the separator to generate heated vapor. The second reboiler reheats the bottom liquid of the second distillation column with steam heated by the steam compressor. The second reflux channel refluxes a portion of the second condensate from the second condenser to the second distillation column. The third reflux channel refluxes a portion of the third condensate from the third condenser to the third distillation column. The first condenser cools the first top vapor extracted from the top of the first distillation column with circulating cooling water for the first condenser, separating it into a first condensate mainly composed of ethanol and a first vapor containing a higher proportion of lower-boiling-point components than the first condensate, and recovers the first condensate. The first heat pump recovers heat from the circulating cooling water for the first condenser, which has been heated by the cooling of the first top vapor in the first condenser, and uses electricity to raise the temperature level of the recovered heat and heat the hot water. The fourth distillation column distills the first vapor in the first condenser by bringing it into gas-liquid contact with the fourth condensate. The fourth condenser cools the fourth top vapor extracted from the top of the fourth distillation column with circulating cooling water for the fourth condenser to condense it, and discharges the fourth condensate containing ethanol and low-boiling-point components. The first reboiler reheats the bottom liquid of the first distillation column with hot water heated by the first heat pump. The first reflux channel refluxes a portion of the first condensate in the first condenser to the first distillation column. The fourth reflux channel refluxes a portion of the fourth condensate in the fourth condenser to the fourth distillation column. The pressure control mechanism controls the pressure within the system so that the temperatures of the bottoms liquids of the first distillation column and the second distillation column are maintained at a predetermined temperature.

[0017] The distillation apparatus according to the second aspect of the present disclosure is the distillation apparatus of the first aspect, wherein the first distillation column, the first condenser, the fourth distillation column, and the fourth condenser constitute a first distillation system that performs a distillation process on the feed liquid with respect to the raw material liquid, and the second distillation column, the second condenser, the third distillation column, and the third condenser constitute a second distillation system that performs a distillation process on the liquid side-cut from the first distillation column. The intermediate distillate in the first distillation system is a first condensate mainly composed of ethanol, and the top distillate is a liquid containing low-boiling components. The intermediate distillate in the second distillation system is a liquid containing ethanol and high-boiling components, and the top distillate is a third condensate mainly composed of ethanol.

[0018] The distillation apparatus according to the third aspect of the present disclosure is the distillation apparatus of the second aspect, wherein in the second distillation column, distillation is performed on the liquid side-cut from the first distillation column, and the amount of the side-cut liquid is set in the range of 50% or more and 98% or less with respect to the amount of the raw material liquid supplied to the first distillation column.

[0019] The distillation apparatus according to the fourth aspect of the present disclosure is the distillation apparatus of any one of the first aspect to the third aspect, wherein the COP of the vapor compressor is set higher than the COP of the first heat pump.

[0020] (Embodiment) The embodiments of the present disclosure are shown below to explain more specifically the features of the present disclosure.

[0021] In this embodiment, we will describe a distillation apparatus as an example that distills a raw material liquid (liquid to be processed: bioethanol) containing 5 wt% ethanol, water, a low-boiling-point component with a lower boiling point than ethanol, and a high-boiling-point component with a higher boiling point than ethanol, to separate the low-boiling-point and high-boiling-point components from the raw material liquid and recover a distillate mainly composed of ethanol. The distillation apparatus 100 according to this embodiment is a distillation apparatus that improves energy efficiency by using a heat pump and a vapor compressor.

[0022] As shown in Figure 1, the distillation apparatus 100 according to this embodiment includes two distillation systems: a first distillation system 101 and a second distillation system 102.

[0023] The first distillation system 101 includes a first distillation column 1, a first condenser 2, a fourth distillation column 3, and a fourth condenser 4, and is a system that performs distillation on the raw material liquid as the feed liquid. The second distillation system 102 includes a second distillation column 21, a second condenser 22, a third distillation column 23, and a third condenser 24, and is a system that performs distillation on the liquid that is side-cut from the first distillation column 1 in the first distillation system 101.

[0024] In the first distillation system 101, the intermediate distillate is a liquid mainly composed of ethanol, and the top distillate is a liquid containing low-boiling-point components. In the second distillation system 102, the intermediate distillate is a liquid containing high-boiling-point components, and the top distillate is a liquid mainly composed of ethanol.

[0025] (First distillation system 101) The first distillation column 1 is a distillation column that performs distillation of bioethanol (ethanol aqueous solution (95 wt% water)) containing, for example, 5 wt% ethanol as the raw material liquid. In this embodiment, the first distillation column 1 uses a packed column for the concentration section and a packed column for the recovery section. The first distillation column 1 may be composed of either a packed column or a tray column, or both.

[0026] In the first distillation column 1, ethanol is distilled by vapor containing components of the raw material liquid and reflux liquid, which is the condensate condensed in the first condenser 2, coming into gas-liquid contact. The bottom liquid (bottom output: containing a large amount of high-boiling-point components), from which ethanol and low-boiling-point components have been separated (removed), is discharged from the first distillation column 1 by the first bottom output pump 11. Meanwhile, the first top vapor, which contains ethanol and low-boiling-point components in a higher proportion than the raw material liquid, is supplied to the first condenser 2.

[0027] Side cutting is performed in the first distillation column 1, and the side-cut liquid is sent to the second distillation column 21 of the second distillation system 102 by the side-cut pump 30.

[0028] The first condenser 2 is connected to the top of the first distillation column 1 via a pipeline. The first condenser 2 cools the first top vapor, which is taken from the top of the first distillation column 1, with circulating cooling water for the first condenser, separating it into a first condensate mainly composed of ethanol and a first vapor containing a higher proportion of lower boiling point components than the first condensate. A first pump 12 is provided to send out the separated first condensate for recovery as a product. The first pump 12 sends out the first condensate as a product and also refluxes a portion of the first condensate back into the first distillation column 1 as reflux liquid through the first reflux channel 15.

[0029] The fourth distillation column 3 is connected to the first condenser 2, and distillation is performed by bringing the first vapor separated in the first condenser 2 into gas-liquid contact with the fourth condensate (the condensate of the fourth condenser 4). The condensed liquid is returned to the first condenser 2, and the fourth top vapor is extracted from the top of the fourth distillation column 3. It is sufficient that the first vapor, which is the vapor after partial condensation in the first condenser 2, is supplied to the bottom of the fourth distillation column 3, and the first condenser 2 and the fourth distillation column 3 may be in a separate structure.

[0030] The fourth condenser 4 is connected to the top of the fourth distillation column 3 via a pipeline. The fourth condenser 4 cools and condenses the fourth top vapor taken from the top of the fourth distillation column 3 with circulating cooling water for the fourth condenser, and discharges the fourth condensate containing ethanol and low-boiling-point components. A second pump 13 is provided to send the discharged fourth condensate as wastewater. The second pump 13 sends the fourth condensate as wastewater and also refluxes a portion of the fourth condensate back into the fourth distillation column 3 as reflux liquid through the fourth reflux channel 16.

[0031] The first distillation system 101 is further equipped with a first heat pump HP1 and a first reboiler 5.

[0032] The first heat pump HP1 recovers heat from the circulating cooling water for the first condenser 2, which has been heated by being used to cool the first tower top vapor, and uses electricity to raise the temperature level of the recovered heat and heat the hot water.

[0033] The circulating cooling water for the first condenser is circulated between the first condenser 2 and the first heat pump HP1 by a pump (not shown). The first heat pump HP1, for example, recovers heat from the circulating cooling water used in the first condenser 2, and reuses the thermal energy by raising the temperature level of the recovered heat using electricity to heat the hot water.

[0034] Specifically, circulating cooling water for the first condenser at 67.3°C is supplied to the first condenser 2 and used to cool the first tower top vapor, raising its temperature to 72.3°C. The circulating cooling water for the first condenser at 72.3°C is then used to recover heat in the first heat pump HP1, and the circulating cooling water for the first condenser, whose temperature has dropped to 67.3°C, is circulated and supplied to the first condenser 2.

[0035] Meanwhile, in the first heat pump HP1, the hot water whose temperature level has been raised to 107.4°C by the heat and electricity recovered from the circulating cooling water for the first condenser is supplied to the first reboiler 5. The hot water whose temperature has decreased to 102.4°C in the first reboiler 5 is returned to the first heat pump HP1, where its temperature level is raised to 107.4°C before being supplied back to the first reboiler 5.

[0036] The first reboiler 5 is connected to the bottom of the first distillation column 1. A portion of the bottom liquid (bottom liquid) is supplied to the first reboiler 5 by the first bottom liquid pump 11. The bottom liquid is heated in the first reboiler 5 using hot water, and the heated bottom liquid is supplied to the first distillation column 1.

[0037] (Second distillation system 102) The second distillation column 21 is a distillation column that performs distillation of the liquid that has been side-cut from the first distillation column 1. The liquid that has been side-cut in this way contains ethanol at a lower proportion than the raw material liquid. In this embodiment, a packed column is used as the second distillation column 21. However, in addition to a packed column, various other configurations such as a tray column may be used as the second distillation column 21.

[0038] In the second distillation column 21, ethanol is distilled by vapor containing components of the side-cut liquid and reflux liquid, which is the condensate condensed in the second condenser 22, coming into gas-liquid contact. The bottom liquid, from which ethanol and some high-boiling-point components have been separated (removed), is discharged from the second distillation column 21 by the second boiler outlet pump 31. Meanwhile, the second top vapor, which contains ethanol and high-boiling-point components in a higher proportion than the side-cut liquid, is supplied to the second condenser 22.

[0039] The second condenser 22 is connected to the top of the second distillation column 21 via a pipeline. The second condenser 22 cools the second top vapor, which is taken from the top of the second distillation column 21, with circulating cooling water for the second condenser, separating it into a second condensate containing high-boiling-point components and the second vapor. A third pump 32 is provided to send the separated second condensate out as wastewater. The third pump 32 sends out the second condensate as wastewater and also recirculates a portion of the second condensate back into the second distillation column 21 as reflux liquid through the second reflux channel 35. A fifth pump 34 is provided to circulate the circulating cooling water for the second condenser.

[0040] The third distillation column 23 is connected to the second condenser 22 via a pipeline, and distillation is performed by bringing the second vapor separated in the second condenser 22 into gas-liquid contact with the third condensate (condensate of the third condenser 24). The condensed liquid is returned to the second condenser 22, and the third top vapor is extracted from the top of the third distillation column 23. It is sufficient that the second vapor, which is the vapor after partial condensation in the second condenser 22, is supplied to the bottom of the third distillation column 23, and the second condenser 22 and the third distillation column 23 may be integrated into a single structure.

[0041] The third condenser 24 is connected to the top of the third distillation column 23 via a pipeline. The third condenser 24 cools and condenses the third top vapor taken from the top of the third distillation column 23 with circulating cooling water for the third condenser, and recovers a third condensate mainly composed of ethanol. A fourth pump 33 is provided to send the recovered third condensate as a product. The fourth pump 33 sends the third condensate as a product and also refluxes a portion of the third condensate back into the third distillation column 23 as reflux liquid through the third reflux channel 36.

[0042] The second distillation system 102 is further equipped with a second heat pump HP2, a separator 26, a cooler 27, a steam compressor 28, and a second reboiler 25.

[0043] The second heat pump HP2 recovers heat from the circulating cooling water for the third condenser 24, which is used to cool the third tower top vapor and has been heated. It also uses electricity to raise the temperature level of the recovered heat and heat the hot water.

[0044] Cooling water for the second condenser is supplied to the second condenser 22 by the fifth pump 34, and a circulation path is provided so that the cooling water for the second condenser discharged from the second condenser 22 is supplied back to the second condenser 22 by the fifth pump 34. A portion of the cooling water for the second condenser is branched off from the circulation path and supplied as hot water to the second heat pump HP2. The hot water, whose temperature level has been raised by the second heat pump HP2, is supplied to the separator 26. The separator 26 is supplied with a portion of the cooling water for the second condenser that has been heated by the second condenser 22. The separator 26 mixes the hot water heated by the second heat pump HP2 with the cooling water for the second condenser heated by the second condenser 22 and performs flash evaporation.

[0045] The steam compressor 28 is connected to the separator 26 via a pipeline so that it is supplied with steam that has been flash-evaporated by the separator 26. The steam compressor 28 compresses the steam supplied from the separator 26 to generate heated steam. As the steam compressor 28, for example, one with an externally cooled motor is used.

[0046] Steam heated by the steam compressor 28 is supplied to the second reboiler 25. The second reboiler 25 is connected to the bottom of the second distillation column 21, and a portion of the bottom liquid (bottle output) is supplied to the second reboiler 25 by the second boiler output pump 31. In the second reboiler 25, the bottom liquid is heated using steam, and the heated bottom liquid is supplied to the second distillation column 21. The steam used to heat the bottom liquid in the second reboiler 25 becomes hot water, which is returned to the separator 26 by the sixth pump 38.

[0047] Specifically, circulating cooling water for the third condenser at 72.2°C is supplied to the second heat pump HP2 for heat recovery, and the circulating cooling water for the third condenser, whose temperature has decreased to 67.2°C, is circulated and supplied to the third condenser 24. On its way to the third condenser 24, the circulating cooling water for the third condenser is cooled using another cooling water in the heat exchanger cooler 27 before being supplied to the third condenser 24. Hot water at 81.3°C (part of the circulating cooling water for the second condenser) is supplied to the second heat pump HP2 by the fifth pump 34. In the second heat pump HP2, the hot water, whose temperature level has been raised to 86.3°C by the recovered heat and electricity, is supplied to the separator 26. A soft water supply line is connected to the steam (and hot water) circulation line, which consists of the separator 26, steam compressor 28, second reboiler 25, and sixth pump 38, and soft water can be supplied as needed.

[0048] The steam that has been flash-evaporated in the separator 26 is supplied to the steam compressor 28 as vacuum steam at 80.8°C, where it is compressed and heated to 103.3°C and supplied to the second reboiler 25.

[0049] The circulating cooling water for the fourth condenser and the cooling water for the cooler 27 may be supplied from a cooling tower or the like.

[0050] The distillation apparatus 100 includes a pressure control mechanism that controls the pressure within the first distillation system 101 and the second distillation system 102 so that the temperature of the bottom liquid in the first distillation column 1 and the second distillation column 21 is maintained at a predetermined temperature.

[0051] The pressure control mechanism includes a vacuum pump 17 that performs vacuum suction in the system via a fourth condenser 4 to maintain a predetermined pressure within the system, and a vacuum pump 37 that performs vacuum suction in the system via a third condenser 24. The pressure control mechanism also includes a pressure sensor that detects the pressure within the system, and a control system that controls the vacuum suction of the vacuum pumps 17 and 37 based on the pressure information from the pressure sensor. In this embodiment, the predetermined pressure may be, for example, a range from a very low vacuum level close to atmospheric pressure to a pressure higher than atmospheric pressure.

[0052] In the distillation apparatus 100, the pressure control mechanism controls the pressure within the system to maintain the temperature of the bottom liquid in the first distillation column 1 and the second distillation column 21 at a predetermined temperature. Such a predetermined temperature is, for example, maintained at 50°C or higher. For example, it may be maintained at 100°C or higher, but it is preferable to set the temperature range according to design requirements such as the size of the apparatus and equipment specifications.

[0053] A feed liquid preheater 18 is provided to exchange heat between the feed liquid supplied to the first distillation column 1 and the bottom liquid from the first distillation column 1 and the second distillation column 21. In the feed liquid preheater 18, the feed liquid is heated using the heat from the bottom liquid.

[0054] By applying the distillation apparatus 100 of this embodiment, energy can be saved by performing efficient distillation using the first distillation system 101 and the second distillation system 102 to recover heat, while reliably separating and recovering ethanol as a high-concentration aqueous ethanol solution by separating low-boiling-point components with a boiling point lower than ethanol and high-boiling-point components with a boiling point higher than ethanol from the raw material liquid.

[0055] The features of the distillation apparatus 100 of this embodiment will be described below.

[0056] The first distillation column 1, to which the feed liquid (raw material liquid) is sent, has its liquid removed from the recovery section (side cut) to prevent the accumulation of high-boiling-point components and to ensure that the purity of the high-concentration ethanol extracted from the first condenser 2 does not decrease. While it is common practice to perform a side cut to stabilize the composition of the distillate and bottom deposit during the distillation operation, discarding the removed liquid will result in a decrease in the yield of the distillate and bottom deposit. Therefore, in normal side cuts, it is common to target the stage with the highest concentration of by-products accumulating in the distillation column and to minimize the amount of waste. In the distillation apparatus 100 of this embodiment, the liquid removed from the first distillation column 1 by side cut in the first distillation system 101 is distilled in the second distillation system 102, so that even if a large amount of liquid is removed, the yield does not decrease or even improves.

[0057] The distillation apparatus 100, which uses bioethanol as the raw material, has four outlets for water and by-product liquids, and the main extracted substances are as follows: Bottom output from distillation column 1: Water, acetic acid (contains trace amounts of ethanol) Bottom output from distillation column 21: Water, acetic acid (contains trace amounts of ethanol) Distillate from the second condenser 22: water, acetic acid, isobutanol, (containing low-concentration ethanol and trace amounts of methanol) Distillate from the fourth condenser 4: methanol, acetaldehyde, (including high-concentration ethanol)

[0058] Furthermore, trace by-products with boiling points close to these are also produced. In other words, by-products other than ethanol are extracted through these four outlets, resulting in a higher yield of ethanol.

[0059] In the first distillation system 101 of the distillation apparatus 100, the intermediate distillate is a first condensate mainly composed of ethanol, and the top distillate is a liquid containing low-boiling-point components. In the second distillation system 102, the intermediate distillate is a liquid containing high-boiling-point components, and the top distillate is a third condensate mainly composed of ethanol.

[0060] In the first distillation system 101, the distillate is high-concentration ethanol and the bottom deposit is water, resulting in a large temperature difference between the top and bottom of the column due to the difference in their boiling points and pressure drop. On the other hand, in the second distillation system 102, the distillate is mainly low-concentration ethanol and by-products, and the bottom deposit is acetic acid and water, resulting in a small difference in boiling points and fewer stages, thus a smaller pressure drop and a smaller temperature difference.

[0061] To explain the characteristics of using a heat pump, the heat pump recovers heat from the cooling water of the condenser and supplies hot water to the reboiler as a heat source. The smaller the temperature difference between the cooling water and the hot water, the larger the COP (Coefficient of Performance). In other words, the COP of the vapor compressor 28 in the second distillation system 102 is larger than that of the first heat pump HP1 in the first distillation system 101. Since COP is the power consumption per unit of heat, a higher COP indicates greater energy efficiency. That is, in the distillation apparatus 100 of this embodiment, the first heat pump HP1 and the vapor compressor 28 are arranged to maximize energy efficiency.

[0062] Furthermore, in order to reduce the load on the first heat pump HP1, which has a lower COP than the vapor compressor 28, the amount of side-cut liquid from the first distillation column 1 is set to be as large as possible. By setting it in this way, the energy efficiency of the distillation apparatus 100 as a whole can be improved. For example, it is preferable to supply the second distillation column 21 with a side-cut amount of liquid that is 50% or more of the amount of raw material liquid supplied to the first distillation column 1. The amount of liquid that is side-cut may be set in the range of 50% to 98% of the amount of raw material liquid supplied to the first distillation column 1.

[0063] The fourth distillation column 3 uses the surplus heat from the first distillation column 1 as its heat source. The heat recovered from the cooling water of the first condenser 2 is used as the heat source for the first reboiler 5 by the first heat pump HP1. The power of the first heat pump HP1 is converted into heating energy and supplied to the first reboiler 5, resulting in overheating. This causes the first condenser 2 to undergo a partial contraction operation, and the surplus heat supplies vapor to the fourth distillation column 3.

[0064] In this embodiment, the distillation apparatus 100 employs a configuration using a reboiler, but other configurations may also be adopted. For example, a configuration may be adopted in which softened water is supplied to a heat pump, the softened water heated by the heat pump is directly flashed, and the flashed steam is blown into the bottom liquid of the distillation column.

[0065] In the second distillation system 102, the motor of the steam compressor 28 is externally cooled, so some of the energy is released to the outside, reducing the amount of heat input for heating. Therefore, a second heat pump HP2 is installed to compensate for the insufficient heat. The second heat pump HP2 recovers heat from the circulating cooling water for the third condenser 24 and heats the hot water before supplying it to the separator 26. The steam that flash-evaporates in the separator 26 is compressed by the steam compressor 28 and heated, then supplied to the second reboiler 25. Heat is recovered in the second condenser 22 for the second top vapor of the second distillation column 21, but the heating from the second heat pump HP2 and the surplus heat from the steam compressor 28 (i.e., the surplus heat from the second reboiler 25) serve as heat sources, and the second vapor is supplied from the second condenser 22 to the third distillation column 23.

[0066] A heat pump can perform cooling and heating simultaneously, and by selecting a heat pump that can operate at the required temperature and changing the operating vacuum, distillation can be performed over a wide temperature range. For example, if the feed liquid (raw material liquid) contains enzymes and is added for recovery, distillation at a lower temperature is desirable. On the other hand, in order to reduce the column diameter and lower equipment costs, it is desirable to lower the vacuum and perform distillation at near atmospheric pressure. In the distillation apparatus 100 of this embodiment, the system temperature is set to a predetermined temperature of 50°C or higher, and a hybrid system using a second heat pump HP2 and a vapor compressor 28 is adopted in the second distillation system 102. By adopting a hybrid system in the second distillation system 102, which has a higher energy load than the first distillation system 101, the energy saving effect can be improved.

[0067] In addition, in the first distillation system 101, instead of using only the first heat pump HP1, a configuration using a vapor compressor, similar to the second distillation system 102, may be adopted.

[0068] (Examples) Next, an example of the operating results when distillation is performed using the distillation apparatus 100 according to this embodiment with bioethanol as the raw material is shown as an example.

[0069] In this embodiment, the system is designed so that the bottom liquid temperature of the first distillation column 1 and the second distillation column 21 is 50°C or higher.

[0070] The specifications of the raw material liquid supplied to the distillation apparatus 100 are as follows: Supply fluid volume: 5,000 kg / hr Feed liquid temperature 35℃ Supply ethanol concentration: 5 wt% Concentration of feed solution by-products Methanol 10 ppm Acetaldehyde 20 ppm Isobutanol 100 ppm Acetic acid 1000 ppm

[0071] The specifications of the product liquid extracted from the distillation apparatus 100 are as follows: Concentrated ethanol concentration: 92.6 wt% (below the azeotropic point with water). Ethanol recovery rate: 99%

[0072] The specifications of the distillation apparatus 100 are as follows: Heat pump specifications Heat pump #1 HP1: Heating capacity 205kW, Energy consumption 42.0kW, COP 4.89 Second heat pump HP2: Heating capacity 264kW, Energy consumption 32.3kW, COP 8.19 Steam compressor: Heating capacity 725kW, Power consumption 83.0kW, COP 10.75 Total power: 157.3kW

[0073] Here, the material balance at each point when distillation is performed on the raw material liquid in the distillation apparatus 100 according to this embodiment is shown in the table in Figure 2. Each point 1 to 21 in the table in Figure 2 is shown in the line of the flow sheet in Figure 1 (numbers enclosed in square marks).

[0074] The calorific value of the 92.6 wt% ethanol obtained by distillation using distillation apparatus 100 is approximately 2,000 kW, while the total energy required for distillation is 157.3 kW. Even when compared in terms of primary energy, it can be seen that the energy required for distillation is significantly lower than the calorific value of the ethanol obtained by distillation. Therefore, it can be seen that distillation apparatus 100 is an energy-efficient distillation apparatus. Ethanol volume equivalent to 100% supply solution: 250 kg / hr Product recovery rate: 99% Ethanol combustion heat: 8.256 kWh / kg (※250×0.99×8.256=2043.4kW)

[0075] Therefore, according to the distillation apparatus 100 of this embodiment, it is possible to provide a distillation apparatus suitable for a bioethanol distillation process that can improve energy saving effects and reduce CO2 emissions.

[0076] It should be noted that the various quantities related to the raw material liquid, bottom liquid, condensate, vapor, etc., as well as values ​​such as temperature, concentration, energy consumption (kW), and pressure, described in the above embodiments or shown in Figures 1 and 2, are merely illustrative. This disclosure does not exclude cases where these values ​​differ from those in the above embodiments.

[0077] Furthermore, the low-boiling-point components, which have a lower boiling point than ethanol, and the high-boiling-point components, which have a higher boiling point than ethanol, contained in the raw material liquid are merely illustrative examples in the embodiments described above, and other components may also be included.

[0078] This disclosure is not limited to the embodiments described above in any other respect, and can be applied and modified within the scope of the disclosure. [Industrial applicability]

[0079] The distillation apparatus of this disclosure relates to a distillation apparatus using a heat pump and a vapor compressor, and is particularly useful for distillation apparatuses that distill a raw material liquid containing ethanol, water, a low-boiling-point component having a lower boiling point than ethanol, and a high-boiling-point component having a higher boiling point than ethanol, to separate the low-boiling-point component and the high-boiling-point component from the raw material liquid and recover a distillate mainly composed of ethanol. [Explanation of Symbols]

[0080] 1. First distillation column 2. First Capacitor 3. Fourth distillation column 4. Fourth Capacitor 5. First Reboiler 11. First canister liquid discharge pump 12. Pump No. 1 13. Pump No. 2 15. First Recirculation Channel 16. Fourth Recirculation Channel 17 Vacuum pump 18. Feed liquid preheater 19 Chiller Unit 21. Second Distillation Column 22 Second Capacitor 23 Third Distillation Column 24 Third Capacitor 25. Second Reboiler 26 Separators 27. Cooler 28. Steam compressor 30 Side-Cut Pump 31. Second canister liquid discharge pump 32 Third pump 33. Pump No. 4 34. Pump No. 5 35 Second Recirculation Channel 36 Third Recirculation Channel 37 Vacuum pump 38. Pump No. 6 100 distillation apparatus 101 First Distillation System 102 Second Distillation System HP1 First Heat Pump HP2 Second Heat Pump

Claims

1. A first distillation column for distilling a raw material liquid containing ethanol, water, a low-boiling-point component with a lower boiling point than ethanol, and a high-boiling-point component with a higher boiling point than ethanol, A second distillation column for distilling the liquid side-cut from the first distillation column, The second condenser cools and condenses the second top vapor extracted from the top of the second distillation column using circulating cooling water for the second condenser, separating it into a second condensate and a second vapor. A third distillation column for distilling the second vapor in the second condenser by bringing it into gas-liquid contact with the third condensate, The third condenser cools and condenses the third top vapor extracted from the top of the third distillation column using circulating cooling water for the third condenser, and recovers the third condensate which mainly consists of ethanol. A second heat pump recovers heat from the circulating cooling water for the third condenser, which is heated to a higher temperature in the third condenser and used to cool the third tower top vapor, and uses electricity to raise the temperature level of the recovered heat to heat the hot water. A separator that flash-evaporates the hot water heated by the second heat pump and the cooling water for the second condenser heated by the second condenser, A steam compressor that compresses the steam evaporated by the separator to generate heated steam, A second reboiler reheats the bottom liquid of the second distillation column with steam heated by the aforementioned steam compressor, A second reflux channel for refluxing a portion of the second condensate in the second condenser to the second distillation column, A third reflux channel that refluxes a portion of the third condensate in the third condenser to the third distillation column, The first top vapor extracted from the top of the first distillation column is cooled with circulating cooling water for the first condenser to separate it into a first condensate mainly composed of ethanol and a first vapor containing a higher proportion of the low-boiling point component than the first condensate, and the first condensate is recovered by the first condenser. The first condenser recovers heat from the circulating cooling water for the first condenser, which is heated to a higher temperature by being used to cool the first tower top vapor, and the recovered heat is used by an electric current to raise the temperature level of the hot water, and the first heat pump heats the hot water. A fourth distillation column for distilling the first vapor in the first condenser by bringing it into gas-liquid contact with the fourth condensate, The fourth condenser cools and condenses the fourth top vapor extracted from the top of the fourth distillation column with circulating cooling water for the fourth condenser, and discharges the fourth condensate containing ethanol and the low-boiling point component. A first reboiler reheats the bottom liquid of the first distillation column with the hot water heated by the first heat pump, A first reflux channel for refluxing a portion of the first condensate in the first condenser to the first distillation column, A fourth reflux channel that refluxes a portion of the fourth condensate in the fourth condenser to the fourth distillation column, A pressure control mechanism controls the pressure within the system so that the temperature of the bottom liquid in the first and second distillation columns is maintained at a predetermined temperature. A distillation apparatus equipped with the following features.

2. The first distillation column, the first condenser, the fourth distillation column, and the fourth condenser constitute a first distillation system that performs distillation treatment on the raw material liquid as the feed liquid. The second distillation column, the second condenser, the third distillation column, and the third condenser constitute a second distillation system that performs distillation on the liquid side-cut from the first distillation column. The intermediate distillate in the first distillation system is the first condensate, which mainly consists of ethanol, and the top distillate is a liquid containing the low-boiling point component. The distillation apparatus according to claim 1, wherein the intermediate distillate in the second distillation system is a liquid containing the high-boiling point component, and the top distillate is the third condensate mainly composed of ethanol.

3. The distillation apparatus according to claim 2, wherein in the second distillation column, distillation is performed on the liquid side-cut from the first distillation column, and the amount of the liquid side-cut is set to be in the range of 50% to 98% of the amount of the raw material liquid supplied to the first distillation column.

4. The distillation apparatus according to any one of claims 1 to 3, wherein the COP of the vapor compressor is higher than the COP of the first heat pump.

Images