Distillation apparatus

Abstract

Provided is a distillation apparatus suitable for a distillation process of bioethanol capable of improving the energy-saving effect and achieving CO2 emission reduction. 【Solution means】A first distillation system for distilling 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, and a second distillation system for distilling the liquid side-cut from the first distillation system. Both the first distillation system and the second distillation system have a heat pump that recovers the thermal energy of cooling water used for cooling the overhead vapor and heats the bottom liquid. The intermediate distillate in the first distillation system is a condensate mainly composed of ethanol, the overhead distillate is a liquid containing a low-boiling component, the intermediate distillate in the second distillation system is a liquid containing a high-boiling component, and the overhead distillate is a condensate mainly composed of ethanol.

Description

Technical Field

[0001] The present disclosure relates to a distillation apparatus using a heat pump, and more specifically, to a distillation apparatus that distills a feed 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 feed liquid, and recovers a distillate mainly composed of ethanol.

Background Art

[0002] In the domestic and international decarbonization trends, the momentum for introducing SAF in the aviation industry is increasing. SAF is an abbreviation for "Sustainable Aviation Fuel", which is a sustainable aviation fuel that is carbon-neutral and uses biomass or waste as raw materials. 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, it is expected to significantly reduce CO2 emissions.

[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 popularization 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 via 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, and a distillation process for concentrating it to a high concentration is required. Conventionally, boiler steam has been used in this distillation process. However, in the process of manufacturing SAF aiming at reducing CO2 emissions, a large amount of CO2 is emitted by the boiler, which has been an issue.

[0006] Thus, the need for energy conservation in distillation equipment is increasing more and more, and various proposals have been made. As one of such energy-saving technologies, a distillation apparatus has been proposed in which a heat pump is incorporated into the distillation apparatus to improve the thermal efficiency (see, for example, Patent Document 1). In the distillation apparatus of Patent Document 1, the heat possessed by the cooling water used to cool the top vapor of the distillation column in the top condenser 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 reheating the bottom liquid of the distillation column to achieve energy conservation.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, the distillation apparatus of Patent Document 1 is not optimized for the distillation of bioethanol, and a distillation process for producing SAF from bioethanol that can achieve energy conservation and CO2 emission reduction is required.

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

[0010] An object of the present disclosure is to provide a distillation apparatus suitable for a bioethanol distillation process that can improve the energy-saving effect and achieve CO2 emission reduction.

Means for Solving the Problems

[0011] To achieve the above object, the distillation apparatus of the present disclosure is configured as follows.

[0012] The distillation apparatus of the present disclosure includes a first distillation column, a second distillation column, a second condenser, a second heat pump, a third distillation column, a third condenser, a second reboiler, a second reflux line, a third reflux line, a first condenser, a first heat pump, a fourth distillation column, a fourth condenser, a first reboiler, a first reflux line, a fourth reflux line, and a pressure control mechanism. The first distillation column distills a feed liquid containing ethanol, water, low-boiling components having a boiling point lower than that of ethanol, and high-boiling components having a boiling point higher than that of ethanol. The second distillation column distills the liquid side-cut from the first distillation column. The second condenser cools and condenses the second overhead vapor taken out from the top of the second distillation column with the circulating cooling water for the second condenser, and separates it into a second condensate and a second vapor. The second heat pump recovers heat from the circulating cooling water for the second condenser, which is used for cooling the second overhead vapor in the second condenser and has its temperature raised, and raises the temperature level of the recovered heat by electricity to heat the warm water. The third distillation column distills 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 overhead vapor taken out from the top of the third distillation column with the circulating cooling water for the third condenser, and recovers the third condensate mainly composed of ethanol. The second reboiler reheats the bottom liquid of the second distillation column with the warm water heated by the second heat pump. The second reflux line refluxes a part of the second condensate in the second condenser to the second distillation column. The third reflux line refluxes a part of the third condensate in the third condenser to the third distillation column. The first condenser cools the first overhead vapor taken out from the top of the first distillation column with the circulating cooling water for the first condenser, and separates it into a first condensate mainly composed of ethanol and a first vapor containing a higher proportion of components with a lower boiling point 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 is used for cooling the first overhead vapor in the first condenser and has its temperature raised, and raises the temperature level of the recovered heat by electricity to heat the warm 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 and condenses the fourth overhead vapor taken out from the top of the fourth distillation column with the circulating cooling water for the fourth condenser, and discharges a small amount of the fourth condensate containing ethanol and low-boiling components. The first reboiler reheats the bottom liquid of the first distillation column with the warm water heated by the first heat pump. The first reflux line refluxes a part of the first condensate in the first condenser to the first distillation column. The fourth reflux line refluxes a part of the fourth condensate in the fourth condenser to the fourth distillation column. The pressure control mechanism controls the pressure in the system so that the temperatures of the bottom liquids of the first distillation column and the second distillation column are maintained at a predetermined temperature.

Advantages of the Invention

[0013] According to the distillation apparatus of the present disclosure, it is possible to provide a distillation apparatus suitable for a bioethanol distillation process in which the energy saving effect is improved and CO2 emission reduction can be achieved.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0015] (Aspect of the distillation apparatus of the present disclosure) In explaining the embodiments of the present disclosure, the aspect of the distillation apparatus of the present disclosure will be described.

[0016] The distillation apparatus according to the first aspect of the present disclosure includes a first distillation column, a second distillation column, a second condenser, a second heat pump, a third distillation column, a third condenser, a second reboiler, a second reflux path, a third reflux path, a first condenser, a first heat pump, a fourth distillation column, a fourth condenser, a first reboiler, a first reflux path, a fourth reflux path, and a pressure control mechanism. The first distillation column distills a feed liquid containing ethanol, water, low-boiling components having a boiling point lower than that of ethanol, and high-boiling components having a boiling point higher than that of ethanol. The second distillation column distills the liquid side-cut from the first distillation column. The second condenser cools and condenses the second overhead vapor withdrawn from the top of the second distillation column with the circulating cooling water for the second condenser, and separates it into a second condensate and a second vapor. The second heat pump recovers heat from the circulating cooling water for the second condenser, which is used for cooling the second overhead vapor in the second condenser and has its temperature raised, and raises the temperature level of the recovered heat by electricity to heat the warm water. The third distillation column distills 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 overhead vapor withdrawn from the top of the third distillation column with the circulating cooling water for the third condenser, and recovers the third condensate mainly composed of ethanol. The second reboiler reheats the bottom liquid of the second distillation column with the warm water heated by the second heat pump. The second reflux line refluxes a part of the second condensate in the second condenser to the second distillation column. The third reflux line refluxes a part of the third condensate in the third condenser to the third distillation column. The first condenser cools the first overhead vapor withdrawn from the top of the first distillation column with the circulating cooling water for the first condenser, and separates it into a first condensate mainly composed of ethanol and a first vapor containing a higher proportion of components with a lower boiling point 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 is used for cooling the first overhead vapor in the first condenser and has its temperature raised, and raises the temperature level of the recovered heat by electricity to heat the warm 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 and condenses the fourth overhead vapor withdrawn from the top of the fourth distillation column with the circulating cooling water for the fourth condenser, and discharges a small amount of the fourth condensate containing ethanol and low-boiling components. The first reboiler reheats the bottom liquid of the first distillation column with the warm water heated by the first heat pump. The first reflux line refluxes a part of the first condensate in the first condenser to the first distillation column. The fourth reflux line refluxes a part of the fourth condensate in the fourth condenser to the fourth distillation column. The pressure control mechanism controls the pressure in the system so that the temperatures of the bottom liquids of the first distillation column and the second distillation column are maintained at a predetermined temperature.

[0017] In the distillation apparatus according to the second aspect of the present disclosure, in the distillation apparatus of the first aspect, 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 raw material liquid as a feed 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] In the distillation apparatus according to the third aspect of the present disclosure, in the distillation apparatus of the second aspect, 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 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] In the distillation apparatus according to the fourth aspect of the present disclosure, in the distillation apparatus of any one of the first to third aspects, the COP of the second heat pump is set higher than the COP of the first heat pump.

[0020] (Embodiment) The embodiments of the present disclosure are shown below, and the features of the present disclosure will be described in more detail.

[0021] In the present embodiment, a raw material liquid (liquid to be treated: bioethanol) containing 5 wt% ethanol, water, low-boiling components having a boiling point lower than that of ethanol, and high-boiling components having a boiling point higher than that of ethanol is distilled to separate low-boiling components and high-boiling components from the raw material liquid, and a distillation apparatus for recovering a distillate mainly composed of ethanol will be described as an example. The distillation apparatus 100 according to the present embodiment is a distillation apparatus that uses a heat pump to improve energy efficiency.

[0022] As shown in FIG. 1, the distillation apparatus 100 according to the present 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 treatment using a raw material liquid as a 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 treatment on the liquid side-cut from the first distillation column 1 in the first distillation system 101.

[0024] The intermediate distillate in the first distillation system 101 is a liquid mainly composed of ethanol, and the top distillate is a liquid containing low-boiling components. The intermediate distillate in the second distillation system 102 is a liquid containing high-boiling 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 distills, for example, bioethanol (ethanol aqueous solution (95 wt% water)) containing ethanol at a ratio of 5 wt% as a raw material liquid. In the present embodiment, a packed column is used for the concentration section and a tray column is used for the recovery section as the first distillation column 1. Note that the first distillation column 1 may be configured by either a packed column or a tray column, or both.

[0026] In the first distillation column 1, ethanol is distilled by the gas-liquid contact between the vapor containing the components of the raw material liquid and the reflux liquid, which is the condensate condensed by the first condenser 2. The bottom liquid (bottom product: containing a large amount of high-boiling components) from which ethanol and low-boiling components are separated (removed) is discharged from the first distillation column 1 to the outside of the system by the first bottom product pump 11. On the other hand, the first top vapor, which contains ethanol and low-boiling components at a higher ratio than the raw material liquid, is supplied to the first condenser 2.

[0027] In the first distillation column 1, a side cut is made, 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 through a pipeline. The first condenser 2 cools the first top vapor taken out from the top of the first distillation column 1 with the circulating cooling water for the first condenser, and separates it into a first condensate mainly composed of ethanol and a first vapor containing a higher proportion of components with a lower boiling point 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 part of the first condensate to the first distillation column 1 as reflux liquid through the first reflux path 15.

[0029] The fourth distillation column 3 is connected to the first condenser 2, and distillation is performed by bringing the first vapor separated by 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 a fourth top vapor is taken out from the top of the fourth distillation column 3. Note that it is only necessary to be configured such 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 have a separated structure.

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

[0031] In the first distillation system 101, a first heat pump HP1 and a first reboiler 5 are further provided.

[0032] The first heat pump HP1 recovers heat from the circulating cooling water for the first condenser that has been heated by being used for cooling the first overhead vapor in the first condenser 2, and raises the temperature level of the recovered heat by electricity to heat the warm 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 for the first condenser used in the first condenser 2, raises the temperature level of the recovered heat by electricity to heat the warm water, and thereby circulates and utilizes the thermal energy.

[0034] Specifically, the circulating cooling water for the first condenser at 9.6°C is supplied to the first condenser 2, used for cooling the first overhead vapor, and heated to 14.6°C. The circulating cooling water for the first condenser at 14.6°C has heat recovered in the first heat pump HP1, and the circulating cooling water for the first condenser whose temperature has dropped to 9.6°C is circulated and supplied to the first condenser 2.

[0035] On the other hand, in the first heat pump HP1, the warm water whose temperature level has been raised to 57.4°C by the heat recovered from the circulating cooling water for the first condenser and electricity is supplied to the first reboiler 5. The warm water whose temperature has dropped to 52.4°C in the first reboiler 5 is returned to the first heat pump HP1, and after the temperature level is raised to 57.4°C in the first heat pump HP1, it is supplied to the first reboiler 5 again.

[0036] The first reboiler 5 is connected to the bottom of the first distillation column 1, and a part of the bottom liquid (bottoms) is supplied to the first reboiler 5 by the first bottoms pump 11. The bottom liquid is heated in the first reboiler 5 using warm 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 distills the liquid side-cut from the first distillation column 1. The liquid side-cut in this way is a liquid containing ethanol at a lower ratio than the raw material liquid. In the present embodiment, a plate column is used as the second distillation column 21. Note that, as the second distillation column 21, various configurations such as a packed column may be used in addition to the plate column.

[0038] In the second distillation column 21, ethanol is distilled by the gas-liquid contact between the vapor containing the components of the side-cut liquid and the reflux liquid which is the condensate condensed by the second condenser 22. The bottom liquid from which ethanol and some high-boiling components are separated (removed) is discharged from the second distillation column 21 to the outside of the system by the second bottoms pump 31. On the other hand, the second overhead vapor containing ethanol and high-boiling components at a higher ratio 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 through a pipeline. The second condenser 22 cools the second overhead vapor taken out from the top of the second distillation column 21 with the circulating cooling water for the second condenser, and separates it into the second condensate containing high-boiling components and the second vapor. A third pump 32 is provided to send out the separated second condensate as drain. The third pump 32 sends out the second condensate as drain and also refluxes a part of the second condensate to the second distillation column 21 as reflux liquid through the second reflux path 35.

[0040] The third distillation column 23 is connected to the second condenser 22, and performs distillation by bringing the second vapor separated by the second condenser 22 into gas-liquid contact with the third condensate (the condensate of the third condenser 24). The condensed liquid is returned to the second condenser 22, and a third overhead vapor is taken out from the top of the third distillation column 23. Note that it is only necessary to be configured such 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 have a separated structure.

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

[0042] In the second distillation system 102, a second heat pump HP2 and a second reboiler 25 are further provided.

[0043] The second heat pump HP2 recovers heat from the circulating cooling water for the second condenser that has been used for cooling the second overhead vapor in the second condenser 22 and has increased in temperature, and raises the temperature level of the recovered heat by electricity to heat the warm water.

[0044] The circulating cooling water for the second condenser is circulated by a pump (not shown) between the second condenser 22 and the second heat pump HP2. The second heat pump HP2, for example, recovers heat from the circulating cooling water for the second condenser used in the second condenser 22, raises the temperature level of the recovered heat by electricity to heat the warm water, and thereby circulates and utilizes the thermal energy.

[0045] Specifically, the circulating cooling water for the second condenser at 21.8°C is supplied to the second condenser 22, used for cooling the second overhead vapor, and the temperature rises to 26.8°C. The circulating cooling water for the second condenser at 26.8°C undergoes heat recovery in the second heat pump HP2, and the circulating cooling water for the second condenser with the temperature reduced to 21.8°C is circulated and supplied to the second condenser 22.

[0046] On the other hand, in the second heat pump HP2, the hot water whose temperature level has been raised to 57.1 °C by the heat and power recovered from the circulating cooling water for the second condenser is supplied to the second reboiler 25. The hot water whose temperature has dropped to 52.1 °C in the second reboiler 25 is returned to the second heat pump HP2, and after the temperature level is raised to 57.1 °C in the second heat pump HP2, it is supplied to the second reboiler 25 again.

[0047] The second reboiler 25 is connected to the bottom of the second distillation column 21. A part of the bottom liquid (bottom product) is supplied to the second reboiler 25 by the second bottoms pump 31. The bottom liquid is heated by the hot water in the second reboiler 25, and the heated bottom liquid is supplied to the second distillation column 21.

[0048] The distillation apparatus 100 is provided with a chiller unit 19 for circulating and supplying the circulating cooling water for the fourth condenser and the circulating cooling water for the third condenser, respectively. The chiller unit 19 supplies, for example, cooling water at 12 °C as cooling water at 5 °C.

[0049] The distillation apparatus 100 includes a pressure control mechanism that controls the pressure inside the first distillation system 101 and the second distillation system 102 so that the temperatures of the bottom liquids of the first distillation column 1 and the second distillation column 21 are maintained at a predetermined temperature.

[0050] The pressure control mechanism includes a vacuum pump 17 that performs vacuum suction inside the system through the fourth condenser 4 and a vacuum pump 37 that performs vacuum suction inside the system through the third condenser 24 so that the inside of the system reaches a predetermined degree of vacuum. Further, the pressure control mechanism includes a pressure sensor that detects the pressure inside 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.

[0051] In the distillation apparatus 100, the pressure inside the system is controlled by the pressure control mechanism so that the temperatures of the bottom liquids of the first distillation column 1 and the second distillation column 21 are maintained at a predetermined temperature. Such a predetermined temperature is maintained, for example, at 50 °C or lower, and in this embodiment, it is maintained at about 49 °C.

[0052] By applying the distillation apparatus 100 of the present embodiment, efficient distillation is performed using the first distillation system 101 and the second distillation system 102, and heat recovery is performed to save energy. At the same time, low-boiling components with boiling points lower than ethanol and high-boiling components with boiling points higher than ethanol are separated from the raw material liquid, and ethanol can be reliably separated and recovered as a high-concentration aqueous ethanol solution.

[0053] The features of the distillation apparatus 100 of the present embodiment will be described below.

[0054] The first distillation column 1 to which the feed liquid (raw material liquid) is sent prevents the accumulation of high-boiling components, and extracts the liquid in the recovery section of the first distillation column 1 so that the purity of the high-concentration ethanol extracted from the first condenser 2 does not decrease (implementation of side cut). Although it is common to perform side cut to stabilize the composition of the distillate and bottoms in the distillation operation, when the extracted liquid is discarded, the yields of the distillate and bottoms will deteriorate. Therefore, in normal side cut, it is common to aim at the stage where the concentration of by-products accumulated in the distillation column is the highest and reduce the amount of waste. In the distillation apparatus 100 of the present embodiment, since the liquid extracted by side cut from the first distillation column 1 in the first distillation system 101 is configured to be distilled in the second distillation system 102, the yield will not decrease or will increase even if a large amount of liquid is extracted.

[0055] Four outlets for water and by-product liquid are provided in the distillation apparatus 100 using bioethanol as the raw material liquid, and the main extracted substances are as follows. Bottoms of the first distillation column 1: water, acetic acid (containing a small amount of ethanol) Bottoms of the second distillation column 21: water, acetic acid (containing a small amount of ethanol) Distillate of the second condenser 22: water, acetic acid, isobutanol, (containing low-concentration ethanol and a small amount of methanol) Distillate of the fourth condenser 4: methanol, acetaldehyde, (containing high-concentration ethanol)

[0056] In addition, trace by-products with boiling points close to these are also entrained. That is, by-products other than ethanol are withdrawn from these four outlets, and the ethanol yield can be increased.

[0057] The intermediate distillate in the first distillation system 101 of the distillation apparatus 100 is a first condensate mainly composed of ethanol, and the overhead distillate is a liquid containing low-boiling components. The intermediate distillate in the second distillation system 102 is a liquid containing high-boiling components, and the overhead distillate is a third condensate mainly composed of ethanol.

[0058] In the first distillation system 101, since the distillate is high-concentration ethanol and the bottoms liquid is water, the temperature difference between the top and bottom of the column increases due to the respective boiling point differences and pressure losses. On the other hand, in the second distillation system 102, since the distillate is mainly low-concentration ethanol and by-products and the bottoms liquid is acetic acid and water, the boiling point difference is small, the number of stages is small, so the pressure loss is small and the temperature difference is small.

[0059] Here, the characteristics when using a heat pump will be described. The heat pump recovers heat from the cooling water of the condenser and supplies warm water as a heat source to the reboiler. However, the smaller the temperature difference between the cooling water and the warm water, the larger the COP. That is, the COP of the second heat pump HP2 of the second distillation system 102 is larger than the COP of the first heat pump HP1 of the first distillation system 101. Since the COP is the power per heating amount, the larger it is, the higher the energy-saving performance. That is, in the distillation apparatus 100 of the present embodiment, the first heat pump HP1 and the second heat pump HP2 are arranged so as to have higher energy-saving performance.

[0060] Furthermore, in order to minimize the load on the first heat pump HP1, which has a lower coefficient of performance (COP) compared to the second heat pump HP2, the side cut amount 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 entire distillation apparatus 100 can be improved. For example, in the second distillation column 21, it is preferable to supply a side cut amount of 50% or more of the liquid amount with respect to the amount of the feed liquid supplied to the first distillation column 1. The side cut liquid amount may be set in the range of 50% or more and 98% or less with respect to the amount of the feed liquid supplied to the first distillation column 1.

[0061] The fourth distillation column 3 uses the surplus heat of the first distillation column 1 as a heating source. The heat recovered from the cooling water of the first condenser 2 is used as the heating source for the first reboiler 5 by the first heat pump HP1. Since the electric power of the first heat pump HP1 is converted into heating energy and supplied to the first reboiler 5, excessive heating occurs and the first condenser 2 undergoes a partial condensation operation, and the vapor is supplied to the fourth distillation column 3 by the surplus heat.

[0062] Note that in the distillation apparatus 100 of this embodiment, a configuration using a reboiler is adopted in this way, but other configurations may be adopted. For example, it may be configured to include an evaporator that supplies soft water to the heat pump, directly flashes the soft water heated by the heat pump, and blows the flashed vapor into the bottom liquid of the distillation column.

[0063] Also in the second distillation system 102, the same principle as that of the above-described first distillation system 101 applies, the electric power of the second heat pump HP2 becomes surplus heat, and the vapor is supplied to the third distillation column 24 by this surplus heat.

[0064] A heat pump can perform heating that is paired with cooling simultaneously. Selecting a heat pump that can be operated at the required temperature and changing the operating vacuum enable distillation over a wide temperature range. For example, when the feed liquid (raw material liquid) contains an enzyme and is added for the purpose of recovery, distillation at a lower temperature is desirable. On the other hand, to reduce the column diameter and lower the equipment cost, distillation near atmospheric pressure by lowering the degree of vacuum is desirable.

[0065] (Example) Next, as an example of the operation results when distillation is performed using the distillation apparatus 100 according to the present embodiment with bioethanol as the raw material liquid, an example is shown as an example.

[0066] In this example, in order to return the bottoms liquid of the first distillation column 1 and the second distillation column 21 to the reaction step in the front stage of the distillation apparatus 100, the system is designed so that the bottom liquid temperature of the first distillation column 1 and the second distillation column 21 becomes 50°C or lower.

[0067] The specifications of the raw material liquid supplied to the distillation apparatus 100 are as follows. Feed liquid amount 5,000 kg / hr Feed liquid temperature 35°C Feed ethanol concentration 5 wt% Concentration of by-products in the feed liquid Methanol 10 ppm Acetaldehyde 20 ppm Isobutanol 100 ppm Acetic acid 1000 ppm

[0068] The specifications of the product liquid taken out as a product from the distillation apparatus 100 are as follows. Concentrated ethanol concentration 92.6 wt% (below the azeotropic point with water). Ethanol recovery rate 98.15%

[0069] The equipment specifications in the distillation apparatus 100 are as follows. Heat pump specifications First heat pump HP1 Heating capacity 363.9 kW Power consumption 92.6 kW COP 3.93 Second heat pump HP2: Heating capacity 549.5 kW, Power consumption 99.9 kW, COP 5.5 Total: Heating capacity 913.4 kW, Power consumption 192.5 kW Chiller unit 19: Cooling capacity 157.3 kW, Power consumption 28.5 kW, COP 5.52 Pumps: Total power consumption 44.0 kW

[0070] Here, in the distillation apparatus 100 according to the present embodiment, the material balance at each point when distilling the raw material liquid is shown in the table of FIG. 2. Each point 1 to 15 in the table of FIG. 2 is shown in the line of the flow sheet of FIG. 1 (the numbers surrounded by square marks).

[0071] The calorific value of 92.6 wt% ethanol obtained by distillation using the distillation apparatus 100 is about 2,000 kW, while the energy required for distillation is a total power consumption of 265 kW. Even when comparing this in terms of primary energy conversion, it can be seen that the energy required for distillation is much lower than the calorific value of the ethanol obtained by distillation. Therefore, it can be seen that the distillation apparatus 100 is a distillation apparatus with excellent energy saving performance. Supply liquid 100% equivalent ethanol amount: 250 kg / hr Product recovery rate: 98.15% Ethanol combustion heat: 8.256 kWh / kg (※250×0.9815×8.256 = 2,025.8 kW)

[0072] Therefore, according to the distillation apparatus 100 of the present embodiment, it is possible to provide a distillation apparatus suitable for a bioethanol distillation process in which the energy saving effect is improved and CO2 emission reduction can be achieved.

[0073] Note that the various amounts, such as the raw material liquid, bottom liquid, condensate, vapor, etc., and the values of temperature, concentration, energy consumption (kW), pressure, etc., described in the above embodiments or shown in FIGS. 1 and 2 are merely examples. The present disclosure does not exclude the case where these values are different from the values of the above embodiments.

[0074] In addition, the low-boiling components with boiling points lower than ethanol and the high-boiling components with boiling points higher than ethanol contained in the raw material liquid are also exemplified in the above-described embodiments, and may include components different from those.

[0075] The present disclosure is not limited to the above-described embodiments in other respects either, and applications and modifications can be made within the scope of the disclosure.

Industrial Applicability

[0076] The distillation apparatus of the present disclosure relates to a distillation apparatus using a heat pump. Specifically, it is useful for applying to a distillation apparatus that distills a raw material liquid containing ethanol, water, low-boiling components with boiling points lower than ethanol, and high-boiling components with boiling points higher than ethanol, separates the low-boiling components and the high-boiling components from the raw material liquid, and recovers a distillate mainly composed of ethanol.

Explanation of Signs

[0077] 1 First distillation column 2 First condenser 3 Fourth distillation column 4 Fourth condenser 5 First reboiler 11 First bottoms pump 12 First pump 13 Second pump 15 First reflux path 16 Fourth reflux path 17 Vacuum pump 19 Chiller unit 21 Second distillation column 22 Second condenser 23 Third distillation column 24 Third condenser 25 Second reboiler 30 Side cut pump 31 Second bottoms pump 32 Third pump 33 Fourth pump 35 Second reflux path 36 Third reflux path 37 Vacuum pump 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 having a boiling point lower than that of ethanol, and a high-boiling point component other than water that has a boiling point higher than that of ethanol; A second distillation column for distilling a liquid taken as a side cut from the first distillation column; a second condenser that cools and condenses a second overhead vapor taken out from the top of the second distillation column using circulating cooling water for a second condenser and separates the second overhead vapor into a second condensate and a second vapor; a second heat pump that recovers heat from the second condenser circulating cooling water that has been used to cool the second column overhead vapor in the second condenser and has been heated; a third distillation column for distilling the second vapor in the second condenser; a third condenser for cooling and condensing a third overhead vapor taken out from the top of the third distillation column by circulating cooling water for a third condenser, and recovering a third condensate mainly composed of ethanol; A second reboiler for reheating the bottom liquid of the second distillation column; a second reflux line for refluxing a portion of the second condensate in the second condenser to the second distillation column; a third reflux line for refluxing a portion of the third condensate in the third condenser to the third distillation column; a first condenser for cooling a first overhead vapor taken out from a top of the first distillation column with circulating cooling water for a first condenser to separate the first overhead vapor into a first condensate mainly composed of ethanol and a first vapor containing the low boiling point component at a higher ratio than the first condensate, and recovering the first condensate; a first heat pump that recovers heat from the first condenser circulating cooling water that has been used to cool the first column overhead vapor in the first condenser and has been heated; a fourth distillation column for distilling the first vapor in the first condenser; a fourth condenser that cools and condenses a fourth overhead vapor taken out from the top of the fourth distillation column using circulating cooling water for a fourth condenser, and discharges a fourth condensate containing ethanol and the low boiling point component; A first reboiler for reheating the bottom liquid of the first distillation column; a first reflux line for refluxing a portion of the first condensate in the first condenser to the first distillation column; a fourth reflux line for refluxing a portion of the fourth condensate in the fourth condenser to the fourth distillation column; a pressure control mechanism for controlling the pressure in the system so that the temperatures of the bottom liquids of the first distillation column and the second distillation column are maintained at predetermined temperatures; Equipped with The second heat pump uses recovered heat to raise the temperature level of the hot water circulating through a circulation flow path between the second heat pump and the second reboiler, thereby heating the hot water; and the second reboiler reheats the bottom liquid of the second distillation column using the hot water heated by the second heat pump. The first heat pump uses recovered heat to raise the temperature level of the hot water circulating through a circulation flow path between the first heat pump and the first reboiler, thereby heating the hot water; and the first reboiler reheats the bottom liquid of the first distillation column using the hot water heated by the first heat pump. The third distillation column distills the second vapor by bringing the second vapor into gas-liquid contact with the third condensate, The fourth distillation column is a distillation apparatus for distilling the first vapor by bringing the first vapor into vapor-liquid contact with the fourth condensate during distillation.

2. The first distillation column, the first condenser, the fourth distillation column, and the fourth condenser constitute a first distillation system for performing a distillation treatment on the raw material liquid as a supply liquid, The second distillation column, the second condenser, the third distillation column, and the third condenser constitute a second distillation system for performing a distillation treatment on a liquid side cut from the first distillation column, The middle distillate in the first distillation system is the first condensate containing ethanol as a main component, and the overhead distillate is a liquid containing the low boiling point component, 2. The distillation apparatus according to claim 1, wherein the middle distillate in the second distillation system is a liquid containing the high boiling point component, and the overhead distillate is the third condensate mainly composed of ethanol.

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

4. The distillation apparatus according to claim 1 , wherein the COP of the second heat pump is higher than the COP of the first heat pump.

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