Distillation apparatus

Abstract

To provide a distillation apparatus that is improved in energy-saving efficiency, by effectively utilizing heat that cooling water for cooling an overhead vapor has and suppressing scale from being generated in a distillation column.SOLUTION: A distillation apparatus is provided with: a first distillation column 1; an evaporator that heats soft water to generate vapor to be blown into the first distillation column; a first capacitor 11 that cools first overhead vapor to separate the vapor into first condensed water and first vapor; a heat pump HP1 which recovers heat from heated cooling water for the first capacitor and increases a level of the temperature of the recovered heat by electric power to heat the soft water; a second distillation column 2 that brings the first vapor in gas-liquid contact with second condensed liquid to distillate the vapor; a second capacitor 22 that cools and condenses second overhead vapor taken out from the second distillation column to recover the second condensed liquid; and a heat pump HP2 that recovers heat from heated second circulating / cooling water for the second capacitor and increases a level of the temperature of the recovered heat by electric power to heat the soft water.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a distillation apparatus using a heat pump, and more particularly to a distillation apparatus used for distilling a raw material liquid containing water and a low-boiling point component having a boiling point lower than that of water, and separating the low-boiling point component from the raw material liquid. [Background technology]

[0002] In recent years, the need for energy saving in distillation apparatus has been increasing, and various proposals have been made.

[0003] As one such energy-saving technology, a distillation apparatus has been proposed in which a heat pump is incorporated in the distillation apparatus to improve thermal efficiency (see, for example, Patent Document 1). In the distillation apparatus of Patent Document 1, the heat pump is used to pump up the heat of the cooling water used to cool the overhead vapor in the overhead condenser that cools the overhead vapor of the distillation tower. The heat pumped up by the heat pump is used as a heat source for a reboiler that reheats the bottom liquid of the distillation tower, thereby saving energy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6612936 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the case of the distillation apparatus of Patent Document 1, the heat pumped up by the heat pump is used to heat the bottom liquid of the distillation tower. For example, when the bottom liquid of the distillation tower contains substances that cause scale generation, such as calcium or silica, scale will be generated on the heat transfer surface (surface in contact with the bottom liquid) of the reboiler (heater) for reheating the bottom liquid of the distillation tower. That is, there is a problem that scale is generated on the heat transfer surface (surface in contact with the bottom liquid) of the heat exchanger (reboiler heater), which reduces the heat transfer efficiency and impairs the energy saving effect. Even though the heat pump is used to pump up and utilize the heat of the overhead condenser, it leads to a situation where the intended energy saving effect cannot be obtained.

[0006] In recent years, there has been a strong demand for energy-saving effects in the distillation process in devices that distill low-concentration bioethanol, which is used as a raw material for fuels such as SAF (Sustainable Aviation Fuel (Alcohol to Jet)), to a concentration below the azeotropic point with water.

[0007] An object of the present disclosure is to provide a distillation apparatus that can effectively utilize the heat contained in the cooling water used to cool the overhead vapor by using a heat pump as a heat source for performing a distillation operation, and that can suppress the formation of scale on the equipment even when the liquid to be treated contains substances that cause scale formation, without requiring a reboiler for reheating the bottom liquid of the distillation tower as in the distillation apparatus of Patent Document 1, thereby enabling stable, continuous operation with improved energy saving efficiency. [Means for solving the problem]

[0008] In order to achieve the above object, the distillation apparatus of the present disclosure is configured as follows.

[0009] The distillation apparatus of the present disclosure includes a first distillation column, a first condenser, a first heat pump, an evaporator, a second distillation column, a second condenser, a second heat pump, a first reflux path, a second reflux path, and a pressure control mechanism. The first distillation column distills a raw material liquid containing water and a low-boiling point component having a boiling point lower than that of water. The first condenser cools a first overhead vapor taken out from the top of the first distillation column with circulating cooling water for the first condenser, and separates the first overhead vapor into a first condensate and a first vapor containing a higher proportion of low-boiling point components than the first condensate. The first heat pump recovers heat from the circulating cooling water for the first condenser, which has been used to cool the first overhead vapor in the first condenser and has been heated, and uses the recovered heat to increase the temperature level by electric power to heat soft water. The second distillation column distills the first vapor, which is the vapor after partial condensation in the first condenser, by bringing the first vapor into gas-liquid contact with the second condensate. The second condenser cools and condenses the second overhead vapor taken out from the top of the second distillation column by the second condenser circulating cooling water, and recovers a second condensate mainly composed of low boiling point components. The second heat pump recovers heat from the second condenser circulating cooling water, which has been used to cool the second overhead vapor in the second condenser and has been heated, and uses the recovered heat to raise the temperature level by electric power to heat the soft water. The evaporator directly flash evaporates the soft water heated by the first heat pump and the soft water heated by the second heat pump, generating steam to be blown into the bottom liquid of the first distillation column. The first reflux path refluxes the first condensate in the first condenser to the first distillation column as a reflux liquid for the first distillation column. The second reflux path refluxes a part of the second condensate in the second condenser to the second distillation column as a reflux liquid for the second distillation column. The pressure control mechanism controls the pressure within the system so that the temperature of the bottom liquid of the first distillation column is maintained at a predetermined temperature. Effect of the Invention

[0010] According to the distillation apparatus of the present disclosure, the heat of the cooling water used to cool the overhead vapor can be pumped up by a heat pump and effectively utilized as a heat source for performing the distillation operation. Furthermore, unlike the distillation apparatus of Patent Document 1, a reboiler for reheating the bottom liquid of the distillation tower is not required. Therefore, even if the liquid to be treated contains a substance that causes scale generation, it is possible to provide a distillation apparatus that can suppress the generation of scale on the equipment and perform stable and continuous operation with improved energy saving efficiency. [Brief description of the drawings]

[0011] [Figure 1] A flow chart showing the configuration of a distillation apparatus according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Prior to describing the embodiments of the present disclosure, aspects of the distillation apparatus of the present disclosure will be described.

[0013] The distillation apparatus according to the first aspect of the present disclosure includes a first distillation column, a first condenser, a first heat pump, an evaporator, a second distillation column, a second condenser, a second heat pump, a first reflux path, a second reflux path, and a pressure control mechanism. The first distillation column distills a raw material liquid containing water and a low-boiling point component having a boiling point lower than that of water. The first condenser cools a first overhead vapor taken out from the top of the first distillation column with circulating cooling water for the first condenser, and separates the first overhead vapor into a first condensate and a first vapor containing a higher proportion of low-boiling point components than the first condensate. The first heat pump recovers heat from the circulating cooling water for the first condenser, which has been used to cool the first overhead vapor in the first condenser and has been heated, and uses the recovered heat to increase the temperature level by electric power to heat the soft water. The second distillation column distills the first vapor, which is the vapor after partial condensation in the first condenser, by bringing the first vapor into gas-liquid contact with the second condensate. The second condenser cools and condenses the second overhead vapor taken out from the top of the second distillation column by the second condenser circulating cooling water, and recovers a second condensate mainly composed of low boiling point components. The second heat pump recovers heat from the second condenser circulating cooling water, which has been used to cool the second overhead vapor in the second condenser and has been heated, and uses the recovered heat to raise the temperature level by electric power to heat the soft water. The evaporator directly flash evaporates the soft water heated by the first heat pump and the soft water heated by the second heat pump, generating steam to be blown into the bottom liquid of the first distillation column. The first reflux path refluxes the first condensate in the first condenser to the first distillation column as a reflux liquid for the first distillation column. The second reflux path refluxes a part of the second condensate in the second condenser to the second distillation column as a reflux liquid for the second distillation column. The pressure control mechanism controls the pressure within the system so that the temperature of the bottom liquid of the first distillation column is maintained at a predetermined temperature.

[0014] In the distillation apparatus of the present disclosure, soft water from which components that cause scale formation, such as calcium and silica, have been removed in advance is supplied to an evaporator, the soft water is heated by a heat pump, the soft water is flash evaporated in the evaporator, and the generated steam is directly blown into the bottom liquid of the first distillation column. Therefore, even if the bottom liquid contains components that cause scale formation, such as calcium and silica, there is no risk of scale formation on the heat transfer surface of the reboiler, which would otherwise cause a decrease in heat transfer efficiency, as occurs when a reboiler is used to heat the bottom liquid of the distillation column.

[0015] Therefore, the heat of the cooling water used to cool the overhead vapor can be pumped up by a heat pump and effectively utilized as a heat source for the distillation operation. Furthermore, a distillation apparatus can be provided that can stably and continuously perform a distillation operation with improved energy saving efficiency without causing problems such as the formation of scale on the heat transfer surface.

[0016] Furthermore, since the evaporator only comes into contact with soft water, there is no risk of scaling or corrosion, and there is a high degree of freedom in selecting the type and constituent materials of the evaporator, making it possible to reduce costs.

[0017] A distillation apparatus according to a second aspect of the present disclosure is the distillation apparatus of the first aspect, further comprising a third condenser for cooling and condensing the vapor taken out from the second condenser with cooling water for the third condenser to recover a third condensate mainly composed of low boiling point components, and a third reflux path for refluxing the third condensate in the third condenser to the second condenser. This allows the capacity of the first condenser and the second condenser to be selected according to the amount of heat recovery required for vapor supply, and allows the distillation apparatus to be provided with improved energy saving efficiency by increasing the degree of freedom in design, such as by performing total condensation in the third condenser.

[0018] In a third aspect of the present disclosure, the distillation apparatus of the second aspect is such that the pressure control mechanism includes a vacuum suction means for suctioning the vacuum through the second condenser and the third condenser so that the inside of the system is at a predetermined vacuum level. This makes it possible to control the temperature inside the system to a temperature at which the heat recovered by the heat pump can be efficiently utilized without requiring equipment with a complex structure, thereby making it possible to more effectively utilize the distillation apparatus of the present disclosure.

[0019] A distillation apparatus according to a fourth aspect of the present disclosure is the distillation apparatus according to any one of the first to third aspects, in which the pressure control mechanism controls the pressure in the system so that the temperature of the bottom liquid in the first distillation column is not more than 90° C. With this configuration, the heat pump can be operated under high COP conditions, thereby achieving higher energy saving efficiency.

[0020] A distillation apparatus according to a fifth aspect of the present disclosure is the distillation apparatus according to any one of the first to fourth aspects, in which the raw material liquid contains a lower proportion of low boiling point components than water. In the distillation apparatus of the present disclosure, steam generated in an evaporator is blown into the bottom liquid of the first distillation column. This makes it possible to perform efficient stripping and separate the low boiling point components when the raw material liquid contains a lower proportion of low boiling point components than water, and allows the distillation apparatus of the present disclosure to be used more effectively.

[0021] In this disclosure, "soft water" that is heated to generate steam in an evaporator refers to water from which components that cause scale formation, such as calcium and silicon, have been removed in advance using a water softening device that uses ion exchange resin (so-called soft water), or water from which components that cause scale formation, such as calcium and silicon, have been removed in advance by purifying the water using a reverse osmosis membrane filter (so-called RO water).

[0022] The following describes in more detail the features of the present disclosure by illustrating embodiments of the present disclosure.

[0023] In this embodiment, a distillation apparatus is used as an example to distill a raw material liquid (liquid to be treated) containing 5 wt% ethanol, a low boiling point component, and the remainder (95 wt%) being water, a high boiling point component, in order to separate and recover ethanol from the raw material liquid.

[0024] The distillation apparatus 100 according to this embodiment is a distillation apparatus that uses a heat pump to improve energy saving performance.

[0025] As shown in FIG. 1, the distillation apparatus 100 according to this embodiment includes a first distillation column 1, an evaporator 3, and a first condenser 11 that cools the overhead vapor (first overhead vapor) extracted from the top of the first distillation column 1.

[0026] The distillation apparatus 100 also includes a second distillation column 2 that distills the vapor (first vapor) after partial condensation in the first condenser 11, and a second condenser 22 that cools the overhead vapor (second overhead vapor) taken out from the top of the second distillation column 2. The distillation apparatus 100 also includes a first heat pump HP1 that recovers heat from the circulating cooling water for the first condenser, and a second heat pump HP2 that recovers heat from the circulating cooling water for the second condenser.

[0027] In this embodiment, the first condenser 11 for cooling the first overhead vapor and the second distillation column 2 for distilling the vapor (first vapor) after partial condensation in the first condenser 11 are integrally configured. That is, the second distillation column 2 is installed so as to be directly connected to the upper side of the first condenser 11, and the first condenser 11 and the second distillation column 2 are configured so that the first vapor, which is the vapor after partial condensation in the first condenser 11, is directly supplied to the bottom of the second distillation column 2. It is only necessary that the first vapor, which is the vapor after partial condensation in the first condenser 11, is supplied to the bottom of the second distillation column 2, and the first condenser 11 and the second distillation column 2 may be configured separately.

[0028] The distillation apparatus 100 is equipped with a pressure control mechanism 40 that controls the pressure within the system so that the temperature of the bottom liquid of the first distillation column 1 is maintained at a predetermined temperature.

[0029] The pressure control mechanism 40 includes a vacuum suction means 34 that performs vacuum suction via the second condenser 22 and a third condenser 23 (top condenser) described below so that the inside of the system reaches a predetermined vacuum level. A vacuum pump may be used as the vacuum suction means 34. The pressure control mechanism 40 also includes a pressure sensor that detects the pressure inside the system, and a control system that controls the vacuum suction of the vacuum suction means 34 based on pressure information from the pressure sensor.

[0030] In the distillation apparatus 100, as described below, the pressure in the system is controlled by the pressure control mechanism 40 to maintain the temperature of the bottom liquid of the first distillation column 1 at a predetermined temperature. Such a predetermined temperature is, for example, kept at 60°C or lower, and is kept at 58.8°C in this embodiment.

[0031] The distillation apparatus 100 is equipped with a first reflux line 31 for refluxing the condensate from the first condenser 11 to the first distillation column 1, and a second reflux line 32 for refluxing the condensate from the second condenser 22 to the second distillation column 2.

[0032] The configuration of the distillation apparatus 100 of this embodiment will be described in detail.

[0033] The first distillation column 1 is a distillation column that distills, for example, an aqueous ethanol solution (95 wt % water) containing 5 wt % ethanol as a raw material liquid. In this embodiment, a packed column is used as the first distillation column 1. Note that, as the first distillation column 1, a column having various configurations such as a plate column may be used in addition to a packed column.

[0034] The evaporator 3 is one that directly flash evaporates the soft water heated by the first heat pump HP1 and the soft water heated by the second heat pump HP2 to generate steam for directly heating the bottom liquid of the first distillation column 1. Specifically, an evaporator 3 made of stainless steel (SUS304) is used as the evaporator 3. A soft water pump 51 is provided that supplies soft water to the evaporator 3 via the first heat pump HP1 or the second heat pump HP2, and supplies the soft water that has not been supplied as steam and remains in the evaporator 3 to the first heat pump HP1 or the second heat pump HP2.

[0035] In this embodiment, the soft water supplied to the first heat pump HP1 and the second heat pump HP2 is RO water, which has been purified using a reverse osmosis membrane filter to remove components such as calcium and silicon that cause scale formation. Such soft water may be water from which components such as calcium and silicon that cause scale formation have been removed.

[0036] The distillation apparatus 100 includes a soft water preheater 41 and a bottoms pump 52. The soft water preheater 41 heats the soft water supplied to the first heat pump HP1 and the second heat pump HP2. The bottoms pump 52 supplies the bottoms liquid (bottoms) extracted from the bottom of the first distillation column 1 to the soft water preheater 41. In the soft water preheater 41, the soft water is heated by heat exchange with the bottoms, and energy is recovered. Note that the bottoms may be used to heat the raw material liquid (feed liquid) to further recover energy.

[0037] In the first distillation column 1, ethanol distillation is carried out by gas-liquid contact between the steam generated in the evaporator 3, the raw material liquid, and the reflux liquid which is the condensate condensed in the first condenser 11. The column bottom liquid (bottom liquid) from which ethanol has been separated (removed) is discharged from the first distillation column 1 to the outside of the system by the bottom liquid pump 52. Meanwhile, the column overhead vapor (first column overhead vapor) which contains a higher proportion of ethanol than the raw material liquid is supplied to the first condenser 11. Note that when the raw material liquid contains impurities with a lower boiling point than ethanol, it is possible to take out the impurities from the first distillation column 1 as a side cut.

[0038] The first condenser 11 cools the overhead vapor (first overhead vapor) taken out from the top of the first distillation column 1 by using circulating cooling water for the first condenser, and separates it into a first condensate and a first vapor containing a higher proportion of ethanol than the first condensate. Then, this first condensate is returned as a reflux liquid to the top of the first distillation column 1. That is, in the first condenser 11, mainly high boiling point components (water) are condensed, and the condensate (aqueous ethanol solution) containing 61 wt % ethanol is returned to the top of the first distillation column 1 as a reflux liquid.

[0039] The first heat pump HP1 is used for partial condensation of the first overhead vapor in the first condenser 11, recovering heat from the heated circulating cooling water for the first condenser (39.8°C in this embodiment), and using the recovered heat to raise the temperature level and heat the soft water using electricity.

[0040] The circulating cooling water for the first condenser is circulated between the first condenser 11 and the first heat pump HP1 by the heat source water pump 53. The first heat pump HP1, for example, recovers heat from the circulating cooling water for the first condenser used in the first condenser 11, and uses the thermal energy in a circulating manner by increasing the temperature level of the recovered heat using electric power to heat the soft water.

[0041] Specifically, the circulating cooling water for the first condenser at 34.8° C. is supplied to the first condenser 11 and used to cool the first tower overhead vapor, raising the temperature to 39.8° C. The circulating cooling water for the first condenser at 39.8° C. undergoes heat recovery in the first heat pump HP1, and the circulating cooling water for the first condenser whose temperature has been reduced to 34.8° C. is circulated and supplied to the first condenser 11.

[0042] Meanwhile, in the first heat pump HP1, the soft water whose temperature has been raised to 65.4°C by electric power is supplied to the evaporator 3, where a portion of it is flash evaporated and the steam is supplied to the first distillation column 1. The temperature of the remaining soft water (including soft water from condensed steam) is reduced to 60.4°C in the evaporator 3 and the soft water pump 51 returns it to the first heat pump HP1, where it is raised to 65.4°C and then supplied to the evaporator 3 again.

[0043] The second distillation column 2 is a distillation column that distills the first vapor, which is the vapor after partial condensation in the first condenser 11, by bringing the first vapor into gas-liquid contact with the second condensate condensed in the second condenser 22, and extracts an overhead vapor (second overhead vapor) having a higher ethanol concentration from the top of the column. In this embodiment, a packed column is used as the second distillation column 2. However, the second distillation column 2 may be a column having various configurations other than a packed column, such as a plate column.

[0044] In the second distillation column 2 , the vapor after partial condensation in the first condenser 11 , which has a high ethanol concentration, is distilled, and ethanol is selectively extracted into the second condenser 22 .

[0045] The second condenser 22 cools the second overhead vapor, which is the overhead vapor of the second distillation column 2, with second condenser circulating cooling water, and condenses the ethanol and water contained in the second overhead vapor as a second condensate.

[0046] The second heat pump HP2 is used to condense the second overhead vapor in the second condenser 22, recovering heat from the heated circulating cooling water for the second condenser (26.0°C in this embodiment), and using the recovered heat by electricity to raise the temperature level and heat the soft water.

[0047] The circulating cooling water for the second condenser is circulated between the second condenser 22 and the second heat pump HP2 by the heat source water pump 55. The second heat pump HP2, for example, recovers heat from the circulating cooling water for the second condenser used in the second condenser 22, and uses the thermal energy in a circulating manner by increasing the temperature level of the recovered heat using electric power to heat the soft water.

[0048] Specifically, the circulating cooling water for the second condenser at 21.0° C. is supplied to the second condenser 22 and used to cool the second tower overhead vapor, thereby raising the temperature to 26.0° C. The circulating cooling water for the second condenser at 26.0° C. undergoes heat recovery in the second heat pump HP2, and the circulating cooling water for the second condenser whose temperature has been lowered to 21.0° C. is circulated and supplied to the second condenser 22.

[0049] Meanwhile, in the second heat pump HP2, the soft water whose temperature has been raised to 65.4°C by electric power is supplied to the evaporator 3, where a portion of it is flash evaporated and the steam is supplied to the first distillation column 1. The temperature of the remaining soft water (including soft water from condensed steam) is reduced to 60.4°C in the evaporator 3 and the soft water pump 51 returns it to the second heat pump HP2, where it is raised to 65.4°C and then supplied to the evaporator 3 again.

[0050] That is, in the distillation apparatus 100, the first heat pump HP1 and the second heat pump HP2 each heat soft water, supply the heated soft water to the evaporator 3, and supply the steam flash evaporated in the evaporator 3 to the first distillation column 1. The soft water pump 51 circulates and supplies the soft water to each of the path to the first heat pump HP1 and the path to the second heat pump HP2. The flow rate may be adjusted using a valve or the like to set the amount of soft water supplied to each path. Also, a pump that circulates and supplies the soft water to the path to the first heat pump HP1 and a pump that circulates and supplies the soft water to the path to the second heat pump HP21 may be provided separately.

[0051] A second condensate pump 54 for extracting the second condensate is connected to the second condenser 22. A part of the second condensate is recovered by the second condensate pump 54 as a recovered solvent (distillate: condensate containing 94 wt % ethanol (aqueous ethanol solution)), and the remaining condensate is returned to the top of the second distillation column 2 as a reflux liquid.

[0052] The distillation apparatus 100 includes a first reflux line 31 for refluxing the first condensate in the first condenser 11 to the first distillation column 1 as a reflux liquid for the first distillation column 1.

[0053] The distillation apparatus 100 also includes a second reflux line 32 that refluxes the second condensate in the second condenser 22 to the second distillation column 2 as a reflux liquid for the second distillation column 2.

[0054] The distillation apparatus 100 includes a third condenser 23 (top condenser) that cools and condenses the vapor extracted from the second condenser 22 with third condenser cooling water, and condenses ethanol and water contained in the vapor as a third condensate. The third condensate in the third condenser 23 is returned to the second condenser 22 as a return liquid through a third return path 33. As the third condenser cooling water, for example, cooling water (chiller water) cooled by a refrigerator (chiller) may be used.

[0055] The second condenser 22 is set to recover a heat amount necessary to generate the necessary amount of steam in the steam canister 3. Therefore, depending on the set value of the heat amount to be recovered, the second condenser 22 does not completely condense the second tower overhead vapor, and some of the vapor remains. The remaining vapor is condensed in the third condenser 23, and the third condensate is returned to the second condenser 22 to become the second condensate, which is recovered as the recovered solvent. Note that, when impurities with a boiling point lower than that of ethanol are contained in the vapor, it is also possible to extract the third condensate outside the system without returning it entirely to the second condenser 22.

[0056] In the distillation apparatus 100, the gas within the system is discharged by the vacuum suction means 34 via the third condenser 33 and the second condenser 22, so that the distillation apparatus 100 is operated at an operating pressure (for example, 19 kPaA or more and atmospheric pressure or less) such that the temperature of the bottom liquid (bottom liquid) discharged from the bottom of the first distillation column 1 becomes 58.8°C. In addition, the temperature level is increased by the first heat pump HP1 and the second heat pump HP2 so that the temperature of the soft water supplied to the evaporator 3 becomes 65.4°C.

[0057] If the temperature level of the soft water obtained from the first heat pump HP1 and the second heat pump HP2 is about 65.4°C, and the return temperature of the soft water returning from the evaporator 3 to the first heat pump HP1 and the second heat pump HP2 is 60.4°C, the temperature of the steam generated in the evaporator 3 will be about 60.4°C, and the temperature of the bottom liquid will be 58.8°C. Therefore, the pressure (operating pressure) inside the equipment such as the first distillation column 1 and the second distillation column 2 is adjusted so that the temperature of the bottom liquid of the first distillation column 1 will be 58.8°C or less. As a result, in the distillation apparatus 100, the steam generated from the evaporator 3 can be stably blown into the bottom liquid of the first distillation column 1, and efficient and stable distillation operation can be performed.

[0058] A device may be provided to prevent flash evaporation of the soft water inside the first heat pump HP1 and the second heat pump HP2. For example, the evaporator 3 may be provided at a position higher than the heat pumps HP1 and HP2 to prevent flash evaporation due to the liquid depth (liquid pressure) of the soft water. For example, a valve (back pressure valve) may be provided between the heat pumps HP1 and HP2 and the evaporator 3 to prevent flash evaporation.

[0059] In the distillation apparatus 100, the raw material liquid supplied to the first distillation column 1 is an aqueous ethanol solution having an ethanol concentration of 5 wt%, and the ethanol concentration of the discharged liquid discharged from the bottom of the first distillation column 1 is set to 0.5 wt% or less.

[0060] In such a situation, by applying the distillation apparatus 100 of the present embodiment, it is possible to perform efficient distillation and heat recovery to save energy, while reliably separating and recovering ethanol, a low-boiling point component, from the raw material liquid.

[0061] Furthermore, in the distillation apparatus 100, the power of the first heat pump HP1 is added as a heat quantity to the evaporator 3 of the first distillation column 1, and the amount of cooling heat in the first condenser 11 is insufficient for the amount of heat added by the evaporator 3. This makes it possible to utilize the surplus heat in the second distillation column 2, and reduces the heat load on the second distillation column 2. As a result, it becomes possible to make the column diameter of the second distillation column 2 smaller than the column diameter of the first distillation column 1, and it is possible to reduce the equipment cost.

[0062] The capacities of the first condenser 11 and the second condenser 22 are set based on the amount of heat recovered to obtain the amount of steam required in the steam canister 3, and the capacity of the shortage for full condensation can be set by the capacity of the third condenser 23. In addition, the capacities of the first condenser 11 and the second condenser 22 can be determined so as to reduce the total power consumption of the first heat pump HP1 and the second heat pump HP2. Therefore, in the distillation apparatus 100, the degree of freedom in heat recovery design can be improved while taking into account the characteristics of the raw liquid (liquid to be treated), and distillation with improved energy saving efficiency for various types of raw liquid can be realized.

[0063] (Example) Next, an example of the operational result when a raw material liquid (liquid to be treated) containing ethanol and water is distilled using the distillation apparatus 100 according to the present embodiment will be described as an example.

[0064] When distilling the raw material liquid using the distillation apparatus 100, an aqueous ethanol solution having an ethanol concentration of 5 wt% and a temperature of 45°C was supplied as the raw material liquid to the first distillation column 1 at a rate of 21000 kg / hr. Here, the amount of ethanol in the raw material liquid supplied to the first distillation column 1 was 1050 kg per hour.

[0065] The soft water was preheated in the soft water preheater 41 and then flash evaporated in the evaporator 3. The generated steam was supplied to the first distillation column 1 by directly blowing it into the bottom liquid at a rate of 1,428 kg / hr.

[0066] As the bottom liquid (bottom water) of the first distillation column 1, water with a temperature of 55.8°C and an ethanol concentration of 0.5WT% or less (treated liquid from which most of the ethanol had been separated) was discharged to the outside of the system at a rate of 22857 kg / hr.

[0067] In the first distillation column 1, a vapor having a temperature of 47.3° C. and an ethanol concentration of 39 wt % is taken out as a column overhead vapor (first column overhead vapor) from the column top at a rate of 3088 kg / hr.

[0068] In the first condenser 11, the overhead vapor of the first distillation column 1 (first overhead vapor) is partially condensed and separated into a first condensate and a first vapor. This first vapor has a temperature of 42.8°C and an ethanol concentration of 61 wt%, and is extracted at a rate of 2191 kg / hr. In the first condenser 11, circulating cooling water for the first condenser is supplied at 34.8°C and extracted at 39.8°C, and 624 kWh of heat is recovered.

[0069] In the second distillation column 2, a vapor having a temperature of 29.0° C. and an ethanol concentration of 93.8 wt % is taken out as a column overhead vapor (second column overhead vapor) from the column top at a rate of 3325 kg / hr.

[0070] In the second condenser 22, the overhead vapor of the second distillation column 2 (second overhead vapor) is cooled and condensed as a second condensate. This second condensate has a temperature of 19.5°C and an ethanol concentration of 94 wt% or more, and is produced at a rate of 3154 kg / hr. In the second condenser 22, circulating cooling water for the second condenser is supplied at 21.0°C and taken out at 26.0°C, and 837 kWh of heat is recovered.

[0071] Of the 3154 kg / hr of the second condensate, 2495 kg / hr (ethanol concentration: 94 wt%) is refluxed to the second distillation column 2, and a recovery solvent with an ethanol concentration of 94 wt% is recovered at a rate of 1000 kg / hr.

[0072] In the third condenser 23, the vapor from the second condenser 22 is cooled and condensed as a third condensate. This third condensate has an ethanol concentration of 94 wt% or more, is generated at a rate of 171 kg / hr, and is returned to the second condenser 22. In addition, chiller water at 20.0°C is supplied to the third condenser 23, and is heated to 25.0°C before being taken out.

[0073] Here, the amount of ethanol recovered as the recovered solvent is approximately 940 kg (1000 kg / hr x 0.94 = 940 kg).

[0074] When considering a conventional steam-type distillation apparatus that uses steam as the heating source (i.e., a boiler-based heating-type distillation apparatus), the amount of heat generated by the steam is 2063 kWh, so the primary energy is 2063 kWh.

[0075] On the other hand, in the case of the distillation apparatus 100 using the heat pump HP in this embodiment, the power consumption of the first heat pump HP1 is 119 kWh, the power consumption of the second heat pump HP2 is 251 kWh, and the power consumption of the refrigerator for circulating and supplying chiller water to the third condenser 23 is 10 kWh, resulting in a total power consumption of 380 kWh (total COP: 5.43).

[0076] The energy coefficients of a conventional distillation apparatus and the distillation apparatus 100 using the heat pump of this embodiment are calculated from the CO2 emission intensity and compared. 1) Industrial steam consumption rate: 0.06 [CO2-ton / GJ] 2) Electricity intensity (Tokyo Electric Power Company FY2021 results): 0.000451 [CO2-ton / kWh] 3) From 1) and 2) above, electricity / steam = 0.000451 / (0.06 x 3.6 x 10^-3) = 2.09 In other words, the CO2 emitted by 1kWh of steam heating is equivalent to 2.09kWh of electricity. Therefore, the energy reduction rate of the distillation apparatus 100 of this embodiment compared to the conventional distillation apparatus is 38.5%. (380 kWh - heat pump system of this embodiment x 2.09) / (2063 kWh - conventional steam system) = 38.5%

[0077] Therefore, by using the distillation apparatus 100 according to this embodiment, the energy reduction rate is 38.5% compared to the above-mentioned conventional steam-type distillation apparatus, making it possible to obtain a significant energy-saving effect.

[0078] In the distillation apparatus 100 according to the present embodiment, steam generated in the evaporator 3 is blown into the bottom liquid of the first distillation column 1. As described above, when the raw material liquid contains a lower proportion of low boiling point components than high boiling point components (5 wt% of ethanol as the low boiling point component and 95 wt% of water as the high boiling point component), efficient stripping can be performed to separate the low boiling point components.

[0079] The amounts of the raw material liquid, bottom liquid, first and second condensates, first and second vapors, and the like, as well as the values ​​of temperature, ethanol concentration, energy consumption (kWh), pressure, and the like, described in the above embodiment or shown in Fig. 1 are merely examples. The present disclosure does not exclude cases where these values ​​are different from those in the above embodiment.

[0080] In the above embodiment, the case where ethanol is recovered by distilling a raw material liquid in which the low boiling point component is ethanol and the high boiling point component is water is described as an example, but in the present disclosure, the type of the low boiling point component is not limited to the above embodiment. The low boiling point component may be acetone, ammonia, methanol, propanol, butanol, isopropyl alcohol, ethyl acetate, methyl acetate, ethyl formate, methyl propionate, ethyl propionate, methyl ethyl ketone, acetaldehyde, acetonitrile, allyl alcohol, chloroform, cyclohexane, carbon tetrachloride, dichloroethane, dichloromethane, carbon disulfide, diethyl ether, tetrahydrofuran, trichloroethylene, benzene, heptane, hexane, etc.

[0081] Furthermore, the predetermined temperature of the bottom liquid of the first distillation column 1, which is maintained by controlling the pressure within the system using the pressure control mechanism 40, may be set according to the characteristics of the raw material liquid, and may be appropriately set, for example, to a temperature of 90°C or lower.

[0082] The present disclosure is not limited to the above-described embodiments in any other respects either, and applications and modifications can be made within the scope of the disclosure.

[0083] For example, in the case of a distillation apparatus operated under conditions in which the top vapor of the distillation column is heated to a high temperature, heat can be recovered from the cooling water of a condenser used to cool the top vapor of the distillation column and used as a heating source. In this case, pure water can be used as the cooling water for the condenser, and this cooling water is evaporated by heat exchange with the top vapor of the distillation column in the condenser. The generated steam is compressed in a steam compressor, and the resulting pressurized steam is blown into the distillation column.

[0084] Any of the various embodiments described above can be appropriately combined to achieve the effects of each embodiment. [Industrial Applicability]

[0085] The distillation apparatus of the present disclosure can effectively utilize the heat of the cooling water used to cool the overhead vapor by pumping it up with a heat pump as a heat source for performing the distillation operation, and can stably and continuously perform highly energy-efficient operation. Therefore, the distillation apparatus of the present disclosure is useful for application to a distillation apparatus used for distilling a raw material liquid containing a lower ratio of low boiling point components than water, which is a high boiling point component, to separate the low boiling point components. [Explanation of symbols]

[0086] 1. First distillation tower 2. Second distillation tower 3 Evaporation tank 11 First capacitor 22 Second Capacitor 23 Third Capacitor 31 A first reflux line for refluxing the condensate of the first condenser to the first distillation column 32 A second reflux line for refluxing the condensate of the second condenser to the second distillation column 33 Third return passage for returning the condensate from the third condenser to the second condenser 34 Vacuum suction means (vacuum pump) 40 Pressure Control Mechanism 41 Soft water preheater 51 Soft water pump 52 Bottoms Pump 53 Heat source water pump 54 No. 2 Condensate Pump 55 Heat source water pump 100 Distillation Apparatus HP1 1st heat pump HP2 Secondary Heat Pump

Claims

1. a first distillation column for distilling a raw material liquid containing water and a low-boiling point component having a boiling point lower than that of water; 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 and a first vapor containing a higher proportion of the low boiling point component than the first condensate; a first heat pump that recovers heat from the first condenser circulating cooling water, the temperature of which has been increased by being used to cool the first column overhead vapor in the first condenser, and uses the recovered heat to raise the temperature level by electric power to heat soft water; a second distillation column for distilling the first vapor, which is the vapor after partial condensation in the first condenser, by vapor-liquid contact with a second condensate; a second condenser for cooling and condensing a second overhead vapor taken out from the top of the second distillation column by circulating cooling water for a second condenser, and recovering the second condensate mainly composed of the low boiling point component; a second heat pump that recovers heat from the second condenser circulating cooling water, the temperature of which has been increased by being used to cool the second column overhead vapor in the second condenser, and uses the recovered heat to raise the temperature level by electric power to heat soft water; an evaporator that directly flash evaporates the soft water heated by the first heat pump and the soft water heated by the second heat pump to generate steam to be supplied to the bottom liquid of the first distillation column; a first reflux line for refluxing the first condensate in the first condenser to the first distillation column as a reflux liquid for the first distillation column; a second reflux line for refluxing a portion of the second condensate in the second condenser to the second distillation column as a reflux liquid for the second distillation column; a pressure control mechanism for controlling the pressure in the system so that the temperature of the bottom liquid of the first distillation column is maintained at a predetermined temperature; A distillation apparatus comprising:

2. a third condenser for cooling and condensing the vapor taken out from the second condenser with a third condenser cooling water, and recovering a third condensate mainly composed of the low boiling point component; The distillation apparatus according to claim 1 , further comprising: a third reflux path for refluxing the third condensate in the third condenser to the second condenser.

3. 3. The distillation apparatus according to claim 2, wherein the pressure control mechanism comprises a vacuum suction means for performing vacuum suction via the second condenser and the third condenser so that a predetermined degree of vacuum is achieved within the system.

4. 2. The distillation apparatus according to claim 1, wherein the pressure control mechanism controls the pressure in the system so that the temperature of the bottom liquid of the first distillation column is 90° C. or lower.

5. 5. The distillation apparatus according to claim 1, wherein the raw material liquid contains a low boiling point component in a proportion smaller than that of water.

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