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 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, 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 a vapor compressor. More specifically, it relates 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 global decarbonization trend, the momentum for introducing SAF in the aviation industry is increasing. SAF is an abbreviation for "Sustainable Aviation Fuel," which is a carbon-neutral and sustainable aviation fuel 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 by 2030 to SAF. 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 manufacturing process of 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 for cooling 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 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, and 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, but it is not appropriate to use equipment that consumes more energy than the heat of combustion of ethanol to produce the ethanol used as energy.

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

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 third distillation column, a third condenser, a second heat pump, a separator, a steam compressor, 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 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 third distillation column distills by bringing the second vapor in the second condenser into gas-liquid contact with a 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 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 used for cooling the third overhead vapor in the third condenser and has been heated up, and raises the temperature level of the recovered heat by electricity to heat 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 steam compressor compresses the steam evaporated in the separator to generate steam with an increased temperature. The second reboiler reheats the bottom liquid of the second distillation column with the steam whose temperature has been raised by the steam compressor. 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 has been used for cooling the first overhead vapor in the first condenser and has been heated up, and raises the temperature level of the recovered heat by electricity to heat hot water. The fourth distillation column distills by bringing the first vapor in the first condenser into gas-liquid contact with a 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 fourth condensate containing ethanol and components with a lower boiling point. The first reboiler reheats the bottom liquid of the first distillation column with the hot 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 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.

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 capable of improving the energy-saving effect and realizing CO2 emission reduction.

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 describing 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 third distillation column, a third condenser, a second heat pump, a separator, a steam compressor, 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 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 third distillation column distills the second vapor in the second condenser by bringing it into gas-liquid contact with a 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 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 used for cooling the third overhead vapor in the third condenser and has been heated up, and raises the temperature level of the recovered heat by electricity to heat 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 steam compressor compresses the steam evaporated in the separator to generate steam with an increased temperature. The second reboiler reheats the bottom liquid of the second distillation column with the steam whose temperature has been raised by the steam compressor. 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 has been used for cooling the first overhead vapor in the first condenser and has been heated up, and raises the temperature level of the recovered heat by electricity to heat hot water. The fourth distillation column distills the first vapor in the first condenser by bringing it into gas-liquid contact with a 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 fourth condensate containing ethanol and low-boiling components. The first reboiler reheats the bottom liquid of the first distillation column with the hot 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 within 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 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] 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 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] In the distillation apparatus according to the fourth aspect of the present disclosure, in the distillation apparatus of any one of the first aspect to the third aspect, 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, and the features of the present disclosure will be described in more detail.

[0021] In this embodiment, a raw material liquid (liquid to be treated: bioethanol) containing 5 wt% 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 is distilled to separate the low-boiling component and the high-boiling component from the raw material liquid, and a distillate mainly composed of ethanol is recovered. A distillation apparatus will be described by taking as an example a distillation apparatus 100 according to this embodiment, which is designed to improve energy efficiency by using a heat pump and a steam compressor.

[0022] As shown in FIG. 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 for performing a distillation process using the 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 for performing a distillation process 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 a low-boiling component. The intermediate distillate in the second distillation system 102 is a liquid containing a high-boiling component, 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 this embodiment, a packed column is used for the concentration section and a packed 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, distillation of ethanol is carried out by gas-liquid contact between the vapor containing the components of the feed liquid and the reflux liquid which is the condensate condensed in the first condenser 2. The bottom liquid (bottom product: containing a large amount of high-boiling components) from which ethanol and low-boiling components have been 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 containing ethanol and low-boiling components at a higher ratio than the feed 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 ratio of low-boiling 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 part of the first condensate to the first distillation column 1 as reflux liquid through the first reflux line 15.

[0029] The fourth distillation column 3 is connected to the first condenser 2, and distillation is carried out by gas-liquid contact with the fourth condensate (the condensate of the fourth condenser 4) for the first vapor separated in the first condenser 2. 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 overhead vapor taken out from the top of the fourth distillation column 3 with the circulating cooling water for the fourth condenser, and discharges the fourth condensate containing ethanol and low-boiling components. A second pump 13 for sending out the discharged fourth condensate as drain liquid is provided. 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 used for cooling the first overhead vapor in the first condenser 2 and has increased in temperature, 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 by a pump (not shown) between the first condenser 2 and the first heat pump HP1. 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 thus circularly utilizes the thermal energy.

[0034] Specifically, the circulating cooling water for the first condenser at 67.3°C is supplied to the first condenser 2, used for cooling the first overhead vapor, and rises in temperature to 72.3°C. The circulating cooling water for the first condenser at 72.3°C has heat recovered 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] On one hand, in the first heat pump HP1, hot water whose temperature level has been raised to 107.4 °C by the heat recovered from the circulating cooling water for the first condenser and electricity is supplied to the first reboiler 5. The hot water whose temperature has dropped to 102.4 °C in the first reboiler 5 is returned to the first heat pump HP1. After the temperature level is raised to 107.4 °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. 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 by the hot water in the first reboiler 5, 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 packed column is used as the second distillation column 21. Note that, as the second distillation column 21, various configurations such as a tray column may be used in addition to the packed column.

[0038] In the second distillation column 21, ethanol distillation is performed 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 in the second condenser 22. The bottom liquid from which ethanol and some high-boiling components have been separated (removed) is discharged out of the system from the second distillation column 21 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 a second condensate containing high-boiling components and a second vapor. A third pump 32 is provided to send out the separated second condensate as drain liquid. The third pump 32 sends out the second condensate as drain liquid and also refluxes a part of the second condensate to the second distillation column 21 as reflux liquid through a second reflux line 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 through a pipeline, and performs distillation by bringing the second vapor separated by the second condenser 22 into gas-liquid contact with a 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 an integrated 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 a third condensate mainly composed of ethanol. A fourth pump 33 is provided to send out the recovered third condensate as a product. 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 a third reflux line 36.

[0042] In the second distillation system 102, a second heat pump HP2, a separator 26, a cooler 27, a steam compressor 28, and a second reboiler 25 are further provided.

[0043] The second heat pump HP2 recovers heat from the circulating cooling water for the third condenser, which is used for cooling the third tower top vapor in the third condenser and has its temperature raised, and raises the temperature level of the recovered heat by electricity to heat the warm water.

[0044] The cooling water for the second condenser is supplied to the second condenser 22 by the fifth pump 34, and a circulation path is provided such that the cooling water for the second condenser discharged from the second condenser 22 is supplied to the second condenser 22 again by the fifth pump 34. A part of the cooling water for the second condenser is branched off from the circulation path and supplied as warm water to the second heat pump HP2. The warm water whose temperature level has been raised by the second heat pump HP2 is supplied to the separator 26. A part of the cooling water for the second condenser heated by the second condenser 22 is supplied to the separator 26. The separator 26 mixes the warm water heated by the second heat pump HP2 and the cooling water for the second condenser heated by the second condenser 22 and causes flash evaporation.

[0045] The vapor compressor 28 is connected to the separator 26 through a pipeline so that the vapor flash-evaporated in the separator 26 is supplied. The vapor compressor 28 compresses the vapor supplied from the separator 26 to generate vapor with an increased temperature. As the vapor compressor 28, for example, a motor with an external fan cooling type is used.

[0046] The vapor whose temperature has been raised by the vapor 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 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 in the second reboiler 25 using the vapor, and the heated bottom liquid is supplied to the second distillation column 21. The vapor used for heating the bottom liquid in the second reboiler 25 becomes warm water and is returned to the separator 26 by the sixth pump 38.

[0047] Specifically, the circulating cooling water for the third capacitor at 72.2°C is supplied to the second heat pump HP2 for heat recovery, and the circulating cooling water for the third capacitor with its temperature reduced to 67.2°C is circulated and supplied to the third capacitor 24. The circulating cooling water for the third capacitor is cooled by using another cooling water in the cooler 27, which is a heat exchanger, during the process of being circulated and supplied to the third capacitor 24 and then supplied to the third capacitor 24. The hot water at 81.3°C (a part of the circulating cooling water for the second capacitor) is supplied to the second heat pump HP2 by the fifth pump 34. In the second heat pump HP2, the hot water with its temperature level raised to 86.3°C by the recovered heat and electric power is supplied to the separator 26. Note that a soft water supply line is connected to the steam (and hot water) circulation line composed of the separator 26, the steam compressor 28, the second reboiler 25, and the sixth pump 38, and it is possible to supply soft water as required.

[0048] The steam flash-evaporated in the separator 26 is supplied to the steam compressor 28 as vacuum steam at 80.8°C, compressed in the steam compressor 28 to increase the temperature, and becomes pressurized steam at 103.3°C and is supplied to the second reboiler 25.

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

[0050] The distillation apparatus 100 is provided with a pressure control mechanism for controlling the pressure within 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.

[0051] The pressure control mechanism includes a vacuum pump 17 that performs vacuum suction inside the system through a fourth capacitor 4, and a vacuum pump 37 that performs vacuum suction inside the system through a third capacitor 24, so that the inside of the system reaches a predetermined pressure. The pressure control mechanism also 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. Note that the predetermined pressure in the present embodiment may be, for example, a range from a fine vacuum level close to the atmospheric pressure level to a pressure higher than the atmospheric pressure level.

[0052] 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 may be maintained, for example, at 50°C or higher. For example, even when it is maintained at 100°C or higher, it is preferable to set the temperature range according to the design requirements such as the apparatus size and equipment specifications.

[0053] A feed liquid preheater 18 is provided for heat exchange between the feed liquid supplied to the first distillation column 1 and the bottoms liquid of 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 of the bottoms liquid.

[0054] 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, heat recovery is performed to save energy, and 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.

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

[0056] The first distillation column 1 to which the feed liquid (raw material liquid) is sent extracts the liquid in the recovery section of the first distillation column 1 so as to prevent the accumulation of high-boiling components and prevent the purity of the high-concentration ethanol extracted from the first condenser 2 from decreasing (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 deteriorate. Therefore, in normal side cut, it is common to aim for the stage where the concentration of by-products accumulating 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 does not decrease or improves even if a large amount of liquid is extracted.

[0057] 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 from the second condenser 22: water, acetic acid, isobutanol, (containing low-concentration ethanol and a small amount of methanol) Distillate from the fourth condenser 4: methanol, acetaldehyde, (containing high-concentration ethanol)

[0058] Also, trace by-products with boiling points close to these are entrained. That is, by-products other than ethanol are extracted from these four outlets, and the yield of ethanol can be increased.

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

[0060] In the first distillation system 101, since the distillate is high-concentration ethanol and the bottoms 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 is acetic acid and water, the boiling point difference is small, the number of stages is small, the pressure loss is small, and the temperature difference is small.

[0061] 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 vapor compressor 28 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 the COP, the higher the energy saving performance. That is, in the distillation apparatus 100 of the present embodiment, the first heat pump HP1 and the vapor compressor 28 are arranged so as to have higher energy saving performance.

[0062] Furthermore, in order to reduce the load of the first heat pump HP1 having a smaller COP compared to the vapor compressor 28 as much as possible, the side cut amount from the first distillation column 1 is set to be as large as possible. By setting in this way, the energy saving performance of the entire distillation apparatus 100 can be improved. For example, it is preferable to supply, as a side cut, a liquid amount of 50% or more with respect to the amount of the raw material liquid supplied to the first distillation column 1 to the second distillation column 21. The liquid amount to be side cut may be 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 1.

[0063] The fourth distillation column 3 uses the surplus heat of the first distillation column 1 as a heat source. The heat recovered from the cooling water of the first condenser 2 is used as a heat source for the first reboiler 5 by the first heat pump HP1. Since the 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 vapor is supplied to the fourth distillation column 3 by the surplus heat.

[0064] In the distillation apparatus 100 of the present embodiment, the configuration using the reboiler is adopted in this way, but other configurations may be adopted. For example, softened water may be supplied to the heat pump, and an evaporator may be provided that directly flashes the softened water heated by the heat pump and blows the flashed steam into the bottom liquid of the distillation column.

[0065] In the second distillation system 102, since the motor of the steam compressor 28 is of the external fan cooling type, part of the energy is released to the outside, and the amount of heat input for heating decreases. Therefore, a second heat pump HP2 is arranged to supplement the insufficient amount of heat. The second heat pump HP2 recovers heat from the circulating cooling water for the third condenser 24 of the third condenser 24 and heats and supplies warm water to the separator 26. The steam flash-evaporated in the separator 26 is supplied to the second reboiler 25 as steam compressed and heated by the steam compressor 28. Heat is recovered by the second condenser 22 from the second overhead vapor of the second distillation column 21, but the heating of the second heat pump HP2 and the surplus heat of the steam compressor 28 (that is, the surplus heat of 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] The heat pump can perform heating that is paired with cooling at the same time, but by selecting a heat pump that can be operated at the required temperature and changing the operating vacuum, distillation in a wide temperature range becomes possible. 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, in order to reduce the column diameter and lower the equipment cost, it is desirable to lower the degree of vacuum and perform distillation near atmospheric pressure. In the distillation apparatus 100 of the present embodiment, the temperature inside the system is set to a predetermined temperature of 50°C or higher, and in the second distillation system 102, a hybrid method using the second heat pump HP2 and the steam compressor 28 is adopted. By adopting the hybrid method 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 the configuration using only the first heat pump HP1, a configuration using a steam compressor as in the second distillation system 102 may be adopted.

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

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

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

[0071] 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: 99%

[0072] The equipment specifications in the distillation apparatus 100 are as follows. Heat pump specifications First heat pump HP1: Heating amount 205 kW, Power consumption 42.0 kW, COP 4.89 Second heat pump HP2: Heating amount 264 kW, Power consumption 32.3 kW, COP 8.19 Steam compressor: Heating amount 725 kW, Power consumption 83.0 kW, COP 10.75 Total power consumption: 157.3 kW

[0073] Here, in the distillation apparatus 100 according to the present embodiment, the material balance at each point when distilling the feed liquid is shown in the table of FIG. 2. Each of the points 1 to 21 in the table of FIG. 2 is shown in the line of the flow sheet of FIG. 1 (the numbers enclosed by square marks).

[0074] 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 of 157.3 kW of electric power. 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: 99% Ethanol combustion heat: 8.256 kWh / kg (※250×0.99×8.256 = 2043.4 kW)

[0075] 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.

[0076] Note that the various amounts regarding the feed liquid, bottom liquid, condensate, vapor, etc., and the values such as temperature, concentration, energy consumption (kW), and pressure, which were described in the above-described embodiment or shown in FIGS. 1 and 2, are merely examples. The present disclosure does not exclude the case where those values are different from the values of the above-described embodiment.

[0077] Also, the low-boiling components having a boiling point lower than that of ethanol and the high-boiling components having a boiling point higher than that of ethanol contained in the feed liquid are also exemplified in the above-described embodiment, and may contain components different from those.

[0078] 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

[0079] The distillation apparatus of the present disclosure relates to a distillation apparatus using a heat pump and a steam compressor. Specifically, it is useful for applying 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.

Explanation of Reference Numerals

[0080] 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 18 Feed liquid preheater 19 Chiller unit 21 Second distillation column 22 Second condenser 23 Third distillation column 24 Third condenser 25 Second reboiler 26 Separator 27 Cooler 28 Steam compressor 30 Side cut pump 31 Second bottoms pump 32 Third pump 33 Fourth pump 34 Fifth pump 35 Second reflux path 36 Third reflux path 37 Vacuum pump 38th Pump 100 Distillation Unit 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 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 heat pump that recovers heat from the third condenser circulating cooling water that has been used to cool the third column overhead vapor in the third condenser and has been heated; a separator that generates steam by flash evaporation; a steam compressor that compresses the steam evaporated in the separator to generate heated steam; A second reboiler that reheats the bottom liquid of the second distillation column with the steam heated by the vapor compressor; 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 separator, and the separator mixes the hot water heated by the second heat pump with the second condenser circulating cooling water heated by the second condenser to generate the steam by flash evaporation. 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. 4. The distillation apparatus according to claim 1, wherein the COP of the vapor compressor is higher than the COP of the first heat pump.

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