Distillation Apparatus

Abstract

To provide a distillation apparatus for achieving energy saving by using a steam compressor and capable of acquiring a higher energy saving effect by suppressing energy to be consumed by the steam compressor.SOLUTION: A distillation tower 100 is divided into two distillation towers of a first distillation tower 1 and a second distillation tower 2, the first distillation tower is provided with a first reboiler 11, the second distillation tower is configured to include a second reboiler 12, and includes a heat recovery condenser 21 for cooling a second overhead vapor and evaporating circulating cooling water for the heat recovery condenser with heat own by the second overhead vapor, steam evaporated from the cooling water of the heat recovery condenser 21 is distributedly supplied to two kinds of steam compressors of a first steam compressor SC1 for the first reboiler and a second steam compressor SC2 for the second reboiler, and steam obtained by increasing a temperature level by being compressed by the respective steam compressors is supplied to the first reboiler for the first distillation tower and the second reboiler for the second distillation tower.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a distillation apparatus using a vapor compressor, and more particularly to a distillation apparatus used for distilling a raw material liquid containing a low boiling point component at a higher concentration than a high boiling point component to separate the low boiling point component and the high boiling point component. [Background technology]

[0002] The need for energy conservation in distillation apparatus has been increasing in recent years, and various proposals have been made to achieve this.

[0003] As one such energy saving technique, a distillation apparatus has been proposed in which a heat pump is incorporated into the distillation apparatus to improve thermal efficiency (see, for example, Patent Document 1).

[0004] The distillation apparatus of Patent Document 1 is a distillation apparatus including a distillation column, a distillation condenser, a distillation reboiler, and a reflux pipe for returning the output fluid flowing out from the distillation condenser to the distillation column.

[0005] This distillation apparatus is equipped with a heat pump for providing the heat received by the working medium (water) in the distillation condenser to the distillation reboiler. The heat pump is configured to include a circulation flow path that connects the distillation condenser and the distillation reboiler and through which the working medium circulates.

[0006] Furthermore, with this distillation apparatus, the thermal energy of the output fluid flowing out from the top of the distillation column is effectively recovered in the distillation reboiler by the heat pump, and by effectively utilizing the thermal energy of the output fluid, it is possible to reduce the thermal energy required to heat the output fluid in the distillation reboiler. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 06-009641 Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, as one method for achieving energy saving in a distillation apparatus, the above-mentioned method of using a heat pump is considered to be one of the most effective methods.

[0009] However, in the case of a distillation column using a general-purpose heat pump that uses water as the working medium, the temperature of the high-temperature side working medium (high-temperature side hot water) of the general-purpose heat pump is less than 100°C, so it cannot be used in the high-temperature range, and if steam is generated from the cooling water of the condenser used to cool the top vapor of the distillation column and is to be supplied to the reboiler as a heat source, it is necessary to use a high-compression type steam compressor to compress the steam and raise its temperature to the desired temperature. As a result, there is a problem that the performance coefficient (COP) of the steam compressor becomes small and the energy saving effect is also small.

[0010] The present invention is devised to solve the above-mentioned problems, and aims to provide a distillation apparatus that uses a vapor compressor in the distillation apparatus to achieve energy savings in the high temperature range of 100°C or higher, while also suppressing the energy consumed by the vapor compressor to achieve further energy savings. [Means for solving the problem]

[0011] In order to solve the above problems, the distillation apparatus of the present invention comprises: a second distillation column for distilling a liquid containing a high boiling point component and a low boiling point component having a higher concentration than the high boiling point component, and separating the liquid into a second overhead vapor mainly containing the low boiling point component and a second bottom liquid containing the high boiling point component at a higher ratio than the low boiling point component; a second reboiler for circulating a mixed liquid of the second bottom liquid and the raw material liquid containing the high boiling point component and the low boiling point component having a higher concentration than the high boiling point component, to heat and evaporate the mixed liquid and supply the evaporated liquid to the bottom of the second distillation column; a heat recovery condenser that cools and condenses the second overhead vapor, which is mainly composed of the low boiling point components and is taken out from the top of the second distillation column, with circulating cooling water for a heat recovery condenser, recovers the condensate mainly composed of the low boiling point components as a distillate, and evaporates the circulating cooling water for the heat recovery condenser by heat of the second overhead vapor; a second steam compressor configured to supply a portion of steam generated from the circulating cooling water for the heat recovery condenser in the heat recovery condenser, compress the steam to raise the temperature level, and supply the steam to the second reboiler as second reboiler steam; a first distillation column for distilling the second bottom liquid, the second bottom liquid supplied to a top of the first distillation column being distilled to separate the second bottom liquid into a first overhead vapor withdrawn from the top of the first distillation column and a first bottom liquid withdrawn from the bottom of the first distillation column, and the first overhead vapor being supplied to the bottom of the second distillation column; a first reboiler that circulates the first column bottom liquid, heats and evaporates the liquid, and supplies the liquid to the bottom of the first distillation column; a first steam compressor configured to supply the remainder of the steam generated from the circulating cooling water for the heat recovery condenser in the heat recovery condenser, excluding the portion supplied to the second steam compressor, and compress the steam to raise its temperature level and supply the steam to the first reboiler as first reboiler steam; Equipped with The COP value of the second steam compressor is configured to be 2.0 or more higher than the COP value of the first steam compressor. It is characterized by:

[0012] In the distillation apparatus of the present invention, the second vapor compressor is preferably configured to have a COP value that is 3.0 or more higher than the COP value of the first vapor compressor.

[0013] It is also preferable that a steam compressor having a COP value of 6.0 or more and 15.0 or less is used as the second steam compressor.

[0014] In addition, it is preferable that the first distillation column is configured so that the column diameter is smaller than the column diameter of the second distillation column.

[0015] In addition, the temperature of the second reboiler steam, which is supplied to the second reboiler by increasing the temperature level in the second steam compressor, is higher than the temperature of the steam used to evaporate the circulating cooling water for the heat recovery condenser in the heat recovery condenser by a range of 15°C to 40°C. The temperature of the first reboiler steam, which is supplied to the first reboiler by increasing the temperature level in the first steam compressor, is configured to be higher by 30°C or more and 60°C or less than the temperature of the steam obtained by evaporating the circulating cooling water for the heat recovery condenser in the heat recovery condenser. is preferred.

[0016] The present invention can also be suitably applied to the case where the low boiling point component is an organic solvent and the high boiling point component is water.

[0017] The present invention can also be suitably used in the case where both the low boiling point component and the high boiling point component are organic solvents. Effect of the Invention

[0018] The distillation apparatus of the present invention has the configuration described above and is configured so that the COP (coefficient of performance) value of the second vapor compressor is 2.0 or more higher than the COP value of the first vapor compressor, thereby making it possible to realize a distillation apparatus with excellent energy saving properties and high energy efficiency.

[0019] To explain in more detail, for example, in a conventional, widely used vapor compression distillation system equipped with a single distillation column, if steam is generated from the cooling water (circulating cooling water for the heat recovery condenser) of the heat recovery condenser for cooling the vapor at the top of the column, the temperature level is increased by compressing it with a steam compressor, and the steam compressor is supplied to the reboiler as a heat source, the COP (performance efficiency = heating capacity (kW) / power consumption (kW)) value of the steam compressor will be about 4.

[0020] In contrast, in the present invention, the distillation tower is divided into two distillation towers, a first distillation tower and a second distillation tower, the first distillation tower is equipped with a first reboiler, and the second distillation tower is equipped with a second reboiler. Steam is generated from the cooling water of the heat recovery condenser (circulating cooling water for the heat recovery condenser) and the generated steam is distributed to two types of steam compressors, a first steam compressor for the first reboiler and a second steam compressor for the second reboiler. The steam, whose temperature level has been raised by compression in each steam compressor, is supplied as a heat source to the first reboiler for the first distillation tower and the second reboiler for the second distillation tower.

[0021] Here, for example, if the steam compressed by each steam compressor and raised in temperature level is supplied 50% each to the first reboiler and the second reboiler, the COP of the first steam compressor for the first reboiler remains at about 4. However, if the distillation column is divided into two distillation columns, the first distillation column and the second distillation column, and the first distillation column is equipped with a first reboiler and the second distillation column is equipped with a second reboiler, as in the distillation apparatus of the present invention, it is possible to configure the COP value of the second steam compressor to be higher than the COP value of the first steam compressor. In the present invention, the COP value of the second steam compressor is configured to be 2.0 or more higher than the COP value of the first steam compressor.

[0022] With this configuration, for example, if the COP of the first steam compressor is 4 and the COP of the second steam compressor is 6 (=4+2), the overall COP of the two steam compressors, the first steam compressor and the second steam compressor, is (4+6) / 2=5, which is approximately 1.25 times more efficient than the COP of 4 in the conventional technology described above.

[0023] For example, if steam compressed and heated by the first steam compressor and the second steam compressor is supplied 50% each to the first reboiler and the second reboiler, the COP of the first steam compressor for the first reboiler will remain at about 4, but the COP of the second steam compressor for the second reboiler for heating the supply liquid can actually be set to a high value of 6.0 or more and 15.0 or less.

[0024] If the COP of the second steam compressor is 15, the overall COP of the two steam compressors, the first and second steam compressors, is (4 + 15) / 2 = 9.5, which is 2.37 times more efficient than the COP of 4 in the conventional technology described above.

[0025] In the above example, the steam compressed and heated by two types of steam compressors, the first steam compressor and the second steam compressor, is supplied to the first reboiler at a ratio of 50% and to the second reboiler at a ratio of 50%. However, in the distillation apparatus of the present invention, the amount of steam (amount of heat) supplied to the second reboiler is usually twice or more the amount of steam (amount of heat) supplied to the first reboiler. Therefore, by configuring the COP value of the second steam compressor to be 2.0 or more higher than the COP value of the first steam compressor, it is possible to obtain a sufficiently significant energy saving effect.

[0026] Furthermore, in the present invention, by configuring the second steam compressor so that the COP value is 3.0 or more higher than the COP value of the first steam compressor, it is possible to obtain an even higher energy saving effect.

[0027] Furthermore, in the present invention, if the second steam compressor is configured to have a COP value of 6.0 or more and 15.0 or less, it becomes easier to make the COP value of the second steam compressor much higher than the COP value of the first steam compressor, so it becomes possible to increase the overall COP of the first and second steam compressors, making the present invention more effective.

[0028] The distillation apparatus of the present invention includes a first distillation column and a second distillation column, and the second distillation column is supplied with a vapor obtained by heating and evaporating a mixture of the raw material liquid and the bottom liquid of the second distillation column, and with the top vapor of the first distillation column (first top vapor), whereas the first distillation column is supplied with only the bottom liquid of the second distillation column (second bottom liquid) from its top, and only the vapor obtained by heating and evaporating the bottom liquid of the first distillation column (first bottom liquid) that has flowed down from the first distillation column in the first reboiler is supplied to the first distillation column, so that the flow rate of the vapor of the first distillation column is significantly smaller than the flow rate of the vapor of the second distillation column. As a result, it is possible to make the diameter of the first distillation column smaller than the diameter of the second distillation column.

[0029] Specifically, it becomes possible to reduce the diameter of the first distillation column to, for example, 1 / 3 to 2 / 3 of the diameter of the second distillation column, making it possible to reduce the size and cost of the entire apparatus.

[0030] Furthermore, if the temperature of the second reboiler steam, which is supplied to the second reboiler by raising the temperature level in the second steam compressor, is higher by 15°C or more and 40°C or less than the temperature of the steam used to evaporate the circulating cooling water for the heat recovery condenser in the heat recovery condenser, and the temperature of the first reboiler steam, which is supplied to the first reboiler by raising the temperature level in the first steam compressor, is higher by 30°C or more and 60°C or less than the temperature of the steam used to evaporate the circulating cooling water for the heat recovery condenser in the heat recovery condenser, it becomes possible to make the COP value of the second steam compressor sufficiently higher than the COP value of the first steam compressor, making the present invention more effective.

[0031] Furthermore, when the present invention is applied to a system in which the low boiling point component is an organic solvent and the high boiling point component is water, a distillation apparatus with excellent energy saving efficiency can be realized.

[0032] The present invention can also be applied to a system in which both the low-boiling point component and the high-boiling point component are organic solvents, and in that case too, a distillation apparatus with good energy saving efficiency can be realized. [Brief description of the drawings]

[0033] [Figure 1] 1 is a flow sheet showing the configuration of a distillation apparatus according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] The features of the present invention will be described in more detail below with reference to the embodiments of the present invention.

[0035] In this embodiment, a distillation apparatus is used as an example to distill a raw material liquid (liquid to be treated) that contains 70 wt% methanol, a low boiling point component, and the remainder (30 wt%) is water (a high boiling point component), to separate and recover methanol.

[0036] The distillation apparatus 100 according to this embodiment is a distillation apparatus that uses a vapor compressor to improve energy saving performance.

[0037] As shown in FIG. 1, the distillation apparatus 100 according to this embodiment is equipped with a second distillation column 2 that distills a liquid containing water (a high boiling point component) and methanol (a low boiling point component) and separates the liquid into an overhead vapor (second overhead vapor) (methanol 99.9 wt%) mainly composed of low boiling point components and a bottom liquid (second bottom liquid) (methanol 52 wt%) containing a higher proportion of high boiling point components than the low boiling point components, and is equipped with a second reboiler 12 that is configured to circulate a mixture of a raw material liquid containing water (30 wt%) and methanol (70 wt%) and the bottom liquid of the second distillation column 2 (second bottom liquid), heat and evaporate the mixture, and supply the mixture to the bottom of the second distillation column 2.

[0038] The distillation apparatus 100 according to this embodiment is also provided with a heat recovery condenser 21 for cooling the second overhead vapor, which is mainly composed of methanol and is taken out from the top of the second distillation column 2, with circulating cooling water for the heat recovery condenser, recovering a condensate mainly composed of methanol (methanol 99.9 wt%) as a distillate, and at the same time heating and evaporating its own cooling water (circulating cooling water for the heat recovery condenser) with the heat of the second overhead vapor. A falling film type heat exchanger is used as the heat recovery condenser 21.

[0039] The uncondensed second overhead vapor sent to the heat recovery condenser 21 and cooled is sent to the overhead condenser 61 and cooled, and methanol with a concentration of 99.9 wt% is recovered as a distillate. An adjustment valve 72 is provided in a line 71 that leads the vapor that has passed through the heat recovery condenser 21 to the overhead condenser 61, for maintaining the inside of the system at a predetermined pressurized state.

[0040] In addition, the distillation apparatus 100 according to this embodiment is equipped with a second steam compressor SC2 configured to supply a portion of the steam generated by heating and evaporating the circulating cooling water for the heat recovery condenser in the heat recovery condenser 21, compress the steam to increase the temperature level, and supply the steam to the second reboiler 12 as second reboiler steam.

[0041] Moreover, the distillation apparatus 100 according to this embodiment includes a first distillation column 1 that distills the bottom liquid (second bottom liquid) of the second distillation column 2, and a first reboiler 11 that is configured to circulate the bottom liquid (first bottom liquid) of the first distillation column 1 to heat and evaporate it, and to supply the generated steam to the bottom of the first distillation column 1.

[0042] The first distillation column 1 is configured so that the overhead vapor (first overhead vapor) is supplied to the bottom of the second distillation column 2 .

[0043] Furthermore, the distillation apparatus 100 of this embodiment is equipped with a first steam compressor SC1 that is configured to supply the remainder of the steam generated by heating and evaporating the circulating cooling water for the heat recovery condenser in the heat recovery condenser 21, excluding the portion sent to the second steam compressor SC2, compress the steam to increase its temperature level, and supply it to the first reboiler 11 as steam for the first reboiler. The distillation apparatus 100 according to this embodiment will be described in more detail below with reference to FIG.

[0044] The second distillation column 2 provided in the distillation apparatus 100 of the present invention is a distillation column for distilling an aqueous methanol solution as described above, and may have various configurations, such as a plate column or a packed column. In this embodiment, a structured packed column is used.

[0045] The second reboiler 12 heats and evaporates a mixture of the bottom liquid of the second distillation column 2, the bottom liquid of the second reboiler 12, and the raw material liquid (feed liquid), and in this embodiment, a falling film type indirect heat exchanger is used as the second reboiler 12. However, other types of heat exchangers can also be used.

[0046] This second reboiler 12 is an indirect heat exchanger that uses 130°C steam from the second steam compressor SC2 as a heating source, and the vapor generated by heating in the second reboiler 12 is supplied to the bottom of the second distillation column 2, as described above.

[0047] The bottom liquid of the second distillation column 2 is supplied to the top of the second reboiler 12 via the second circulating pump 42. The above-mentioned raw material liquid (feed liquid) is merged with the bottom liquid of the second distillation column 2 downstream of the second circulating pump 42 and supplied to the top of the second reboiler 12.

[0048] In the second distillation column 2, the vapor generated in the second reboiler 12 and the reflux liquid, which is a part of the condensate condensed in the heat recovery condenser 21, come into gas-liquid contact with each other, whereby methanol is distilled.

[0049] The overhead vapor of the second distillation column 2 contains a high concentration of methanol (99.9 wt%) and is condensed by being cooled in the heat recovery condenser 21. A portion of it is returned to the top of the second distillation column as reflux liquid, and the other portion (the remainder) is recovered as a distillate containing 99.9 wt% methanol.

[0050] The reflux to the second distillation column 2 is performed by returning a part of the condensate in the heat recovery condenser 21 to the top of the second distillation column 2 via a reflux pump 40.

[0051] The bottom liquid of the second distillation column 2 contains methanol at a ratio of 52 wt %. This bottom liquid of the second distillation column 2 is supplied to the top of the first distillation column 1 via a transfer pump 43.

[0052] The bottom liquid (first bottom liquid) that flows down the first distillation column 1 is sent to the top of the first reboiler 11 via the first circulation pump 44, where it is reheated. The vapor generated is returned to the bottom of the first distillation column 1 and used for distillation.

[0053] As the first distillation column 1, for example, a plate column, a packed column, or other column of various configurations can be used. In this embodiment, a structured packed column is used.

[0054] The first reboiler 11 is configured to reheat and evaporate the mixture of the first column bottom liquid and the column bottom liquid of the first reboiler 11, and the vapor generated by reheating in the first reboiler 11 is returned to the bottom of the first distillation column 1.

[0055] Furthermore, the second steam compressor SC2 provided in the distillation apparatus 100 in this embodiment is configured to compress the steam generated from the circulating cooling water for the heat recovery condenser (109°C in this embodiment) that is heated by being used to cool the second column top vapor in the heat recovery condenser 21, thereby raising the temperature level and supplying it to the second reboiler 12 as steam (130°C in this embodiment).

[0056] That is, in the distillation apparatus 100 according to the present invention, the second steam compressor SC2 is used to compress the steam generated from the circulating cooling water for the heat recovery condenser, raise the temperature level, and supply it to the second reboiler 12, thereby enabling the thermal energy to be circulated and reused.

[0057] Specifically, steam evaporated from the circulating cooling water for the heat recovery condenser at a temperature of 109°C, which is used to cool the second tower overhead vapor in the heat recovery condenser 21, is sent via a supply line 45 to the second steam compressor SC2, compressed, and supplied to the second reboiler 12 as steam at 130°C, thereby being used as a heat source for the second reboiler 12.

[0058] Furthermore, by making the temperature difference between the steam generated from the circulating cooling water for the heat recovery condenser and the steam whose temperature level has been raised by compression in the second steam compressor SC2 (i.e., steam whose thermal energy level has been raised using electricity and which is supplied to the second reboiler 12) smaller than in the case of conventionally used steam compressors, it becomes possible to perform heat recovery with a high COP.

[0059] Moreover, the steam heated in the second steam compressor SC2 and supplied to the second reboiler 12 becomes steam drain in the second reboiler 12, and this steam drain is flash-cooled in the evaporator 22, and then circulated and supplied to the heat recovery condenser 21 again as cooling water for the heat recovery condenser 21 (circulating cooling water for the heat recovery condenser). The evaporator 22 is also configured to function as a separator for separating the steam and the steam drain.

[0060] In addition, in the distillation apparatus 100 according to the present invention, the cooling water for the overhead condenser used in the overhead condenser 61 is guided to the cooling tower 51, cooled therein, and then circulated to the overhead condenser 61.

[0061] Furthermore, in the distillation apparatus 100 of this embodiment, a portion of the steam generated from the circulating cooling water for the heat recovery condenser at a temperature of 109°C, which is used to cool the second tower overhead vapor in the heat recovery condenser 21 (steam excluding the steam supplied to the second steam compressor SC2) is sent via the supply line 45 to the first steam compressor SC1 and compressed, thereby raising the temperature level.

[0062] In addition, in the first steam compressor SC1, Steam evaporated from the cooling water for the heat recovery condenser at a temperature of 109°C is compressed in the first steam compressor SC1 and supplied to the first reboiler 11 as steam at a temperature level of 156°C, and is configured to be used as a heat source for the first reboiler 11.

[0063] On the other hand, the steam drain condensed by using the steam (steam at 156°C) whose temperature level has been raised in the first steam compressor SC1 in the first reboiler 11 is flash-cooled in the evaporator 22 and is then supplied to the heat recovery condenser 21 again as cooling water for the heat recovery condenser 21 (circulating cooling water for the heat recovery condenser).

[0064] In the distillation apparatus 100 according to the present embodiment, seven small general-purpose steam compressors are used as the second steam compressor SC2, and one spare steam compressor is also provided. In this embodiment, the seven steam compressors are configured to have a total power of 407 kW.

[0065] Furthermore, three small general-purpose steam compressors are used as the first steam compressor SC1, and one spare steam compressor is also provided. The total power of the three steam compressors is configured to be 375 kW.

[0066] The second steam compressor SC2 and the first steam compressor SC1 are both configured to have their capacities adjusted by controlling the number of units including a standby unit and by inverter control.

[0067] In addition, since the second steam compressor SC2 and the first steam compressor SC1 are each equipped with one spare steam compressor, operational stability is ensured against unexpected breakdowns and maintenance can be performed during operation.

[0068] In the distillation apparatus 100 according to the present embodiment, steam whose temperature level has been increased by compression in the second steam compressor SC2 and the first steam compressor SC1 is used as the heat source for the second reboiler 12 and the first reboiler 11 (i.e., steam heated to 130°C is used in the second reboiler 12, and steam heated to 156°C is used in the first reboiler 11). In order to operate the second reboiler 12 and the first reboiler 11 with steam at the above temperatures, the boiling points of the bottom liquids in the second distillation column 2 and the first distillation column 1 are adjusted by performing a predetermined pressurization operation in the system.

[0069] Moreover, in the distillation apparatus 100 according to this embodiment, the COP (coefficient of performance) value of the second vapor compressor SC2 is configured to be 2.0 or more higher than the COP value of the first vapor compressor SC1. Specifically, in this embodiment, the COP (coefficient of performance) value of the second vapor compressor SC2 is 11.3, the COP value of the first vapor compressor SC1 is 4.8, and the COP value of the second vapor compressor SC2 is configured to be 6.5 higher than the COP value of the first vapor compressor SC1.

[0070] Since the distillation apparatus 100 according to this embodiment is configured as described above, it is possible to realize a distillation apparatus that is excellent in energy saving and has high energy efficiency.

[0071] More specifically, in the distillation apparatus 100 according to the present embodiment, the distillation column is divided into two distillation columns, a first distillation column 1 and a second distillation column 2, and the first distillation column 1 is equipped with a first reboiler 11, and the second distillation column 2 is equipped with a second reboiler 12. The heat of the steam evaporated from the cooling water of the heat recovery condenser 21, which cools and condenses the top vapor of the second distillation column 2, is distributed to two types of steam compressors, a first steam compressor SC1 for the first reboiler 11 and a second steam compressor SC2 for the second reboiler 12. The steam (heat) heated by compressing it with this is supplied to each of the first reboiler 11 for the first distillation column and the second reboiler 12 for the second distillation column. Therefore, for example, it is possible to set the COP of the first steam compressor SC1 to a value between 3.0 and 6.0, while setting the COP of the second steam compressor SC2 to a high value between 6.0 and 15.0. This makes it possible to reduce the total power consumption of the first steam compressor SC1 and the second steam compressor SC2, thereby achieving a distillation apparatus with excellent energy saving and high energy efficiency.

[0072] With the above-described configuration, it is possible to fully satisfy the basic requirement of the present invention, that is, the requirement that the COP of the second steam compressor SC2 be 2.0 or more higher than the COP of the first steam compressor SC1.

[0073] That is, in the distillation apparatus 100 according to the present embodiment, the temperature level of the first reboiler steam (156°C) is increased by the first steam compressor SC1 and supplied to the first reboiler 11, and the temperature of the first reboiler steam (156°C) is used to cool the second overhead vapor in the heat recovery condenser 21, and is configured to be 47°C higher than the temperature of the steam (109°C) generated from the circulating cooling water for the heat recovery condenser. On the other hand, the temperature level of the second reboiler steam (130°C) is increased by the second steam compressor SC2 and supplied to the second reboiler 12, and the temperature of the second reboiler steam (130°C) is used to cool the second overhead vapor in the heat recovery condenser 21, and is configured to be 47°C higher than the temperature of the steam (109°C) generated from the circulating cooling water for the heat recovery condenser. In the case of the first steam compressor SC1, the second steam compressor SC2 is used to cool the second overhead vapor and is configured to have a temperature 21°C higher than the temperature (109°C) of the steam evaporated from the circulating cooling water for the heat recovery condenser. Since the temperature rise range (21°C) of the second steam compressor SC2 is smaller than the temperature rise range (47°C) of the first steam compressor SC1, it is possible to make the COP value of the second steam compressor SC2 (6.0 or more and 15.0 or less) higher than the COP value of the first steam compressor SC1 (3.0 or more and 6.0 or less), thereby making it possible to improve the overall energy saving efficiency.

[0074] In this embodiment, the energy input to the second distillation column 2 is the sum of 407 kW of the power of the second vapor compressor SC2 and 375 kW of the energy of the first overhead vapor supplied from the top of the first distillation column 1 to the bottom of the second distillation column 2 (= the power of the first vapor compressor SC1), totaling 782 kW (407 kW + 375 kW = 782 kW).

[0075] On the other hand, the energy input to the first steam compressor SC1 is 375 kW as the power for the first steam compressor SC1.

[0076] Therefore, if the COP of the second steam compressor SC2, which is driven by a large power of 407 kW, is set to 11.3, and the COP of the first steam compressor SC1, which is driven by a smaller power of 375 kW than the second steam compressor SC2, is set to 4.8, it is possible to increase the COP of the first steam compressor SC1 and the second steam compressor SC2 as a whole, and it becomes possible to obtain a sufficiently high energy saving effect.

[0077] In addition, in Table 1, (1) A conventional steam distillation apparatus that uses steam as thermal energy without using a steam compressor. (2) A distillation apparatus in which the distillation column is not divided into two columns as in the present invention but is a single column type, and heat is recovered from the top vapor of the distillation column using a vapor compressor (in this case, the COP of the vapor compressor is about 4.8); (3) The distillation apparatus 100 according to the above embodiment, The energy consumption of each is shown.

[0078] However, the conditions are as follows: Raw material liquid supply amount: 10,000 kg / hr (methanol concentration 70 wt%) Recovered liquid: 7007kg / hr (methanol 99.9wt%) Annual operating hours: 8000 hours Electricity 15 yen / kW Steam: 3000 yen / 1000kg

[0079] [Table 1]

[0080] As shown in Table 1, a conventional steam distillation apparatus requires 5,800 kW of energy (steam heat).

[0081] In addition, in a single-column distillation apparatus, 1208.3 kW of power is required to drive the vapor compressor.

[0082] In contrast, the distillation apparatus 100 according to the present embodiment (a two-column distillation apparatus in which each distillation column is provided with a vapor compressor) consumes 782 kW of energy. Therefore, it is clear that the distillation apparatus of the present invention can achieve significant energy savings.

[0083] In addition, in the distillation apparatus 100 according to this embodiment, the temperature of the second reboiler steam supplied to the second reboiler 12 by raising the temperature level in the second steam compressor SC2 is higher than the temperature of the steam evaporated from the circulating cooling water for the heat recovery condenser in the heat recovery condenser 21, which is used to cool the second overhead vapor, by a range of 15°C to 40°C, and the temperature of the first reboiler steam supplied to the first reboiler 11 is higher than the temperature of the steam evaporated from the circulating cooling water for the heat recovery condenser in the heat recovery condenser 21, which is used to cool the second overhead vapor, by a range of 30°C to 60°C. This makes it possible to make the COP of the second steam compressor SC2 sufficiently higher than the COP of the first steam compressor SC1, and makes it possible to more reliably realize a distillation apparatus with a large energy-saving effect.

[0084] Furthermore, in the distillation apparatus 100 according to this embodiment, the column diameter of the first distillation column 1 is configured to be smaller than the column diameter of the second distillation column 2, and specifically, the column diameter of the first distillation column 1 is configured to be approximately 1 / 2 of the column diameter of the second distillation column 2.

[0085] That is, in the distillation apparatus 100 according to this embodiment, the amount of vapor passing through the second distillation column 2 (top vapor amount) is 21,489 kg / hr, while the amount of vapor passing through the first distillation column 1 (top vapor amount) is only 4,315 kg / h, which is small. Therefore, while ensuring proper gas-liquid contact, it is possible to make the column diameter of the first distillation column 1 approximately half the column diameter of the second distillation column 2, thereby enabling reduction in equipment costs.

[0086] The relationship between the column diameter of the first distillation column 1 and the column diameter of the second distillation column 2 is not limited to that in the above embodiment, and the column diameter of the first distillation column 1 can usually be made smaller in the range of 1 / 3 to 2 / 3 of the column diameter of the second distillation column 2. However, it is also possible to make the value exceed the above range.

[0087] In addition, in the above embodiment, the first distillation column 1 and the second distillation column 2 are configured as separate, independent columns. However, it is also possible to configure the first distillation column and the second distillation column as a single column, that is, to configure one column so that a part of the single column functions as the first distillation column and another part functions as the second distillation column.

[0088] In that case, for example, the upper portion of one tower can be configured as the first distillation tower and the lower portion can be configured as the second distillation tower, or the upper portion of one tower can be configured as the second distillation tower and the lower portion can be configured as the first distillation tower.

[0089] According to the present invention, it is possible to make the diameter of the first distillation column smaller than that of the second distillation column. Taking this into consideration, it is possible to further reduce equipment costs by appropriately designing a single column to include two columns, the first distillation column and the second distillation column.

[0090] It should be noted that the various amounts, temperatures, component concentrations, energy consumption (kW), pressures, and other values ​​relating to the raw material liquid, the circulating cooling water for the heat recovery condenser, the bottom liquids of the first and second distillation towers, and the overhead vapor of the second distillation tower described in the above embodiment or shown in FIG. 1 are merely examples, and the present invention does not exclude cases where these values ​​are different from those in the above embodiment.

[0091] In the above embodiment, an example has been described in which methanol is recovered by distilling a raw material liquid containing methanol as a low boiling point component and water as a high boiling point component. However, in the present invention, the types of the low boiling point component and the high boiling point component are not limited to those in the above embodiment.

[0092] For example, the low boiling point component may be benzene, heptane, 1,4-dioxane, nitromethane, toluene, pyridine, acetic acid, and the like.

[0093] The high boiling point component may be NMP (N-methyl-2-pyrrolidone), butyl acetate, N-octane, 2-ethoxyethanol, 1-pentanol, acetylacetone, dibutyl ether, xylene, 1-hexanol, or the like.

[0094] The present invention is not limited to the above-described embodiment in any other respects, and applications and modifications can be made within the scope of the invention. [Explanation of symbols]

[0095] 1. First distillation tower 2. Second distillation tower 11 No. 1 reboiler 12 Second reboiler 21 Heat recovery capacitor 22 Evaporator 40 Circulation Pump 42 Second Circulation Pump 43 Transfer pump 44 First Circulation Pump 45 Supply Line 51 Cooling Tower 61 Top Condenser 71 Line 72 Adjustment valve 100 Distillation Apparatus SC1 No. 1 steam compressor SC2 Second steam compressor

Claims

1. a second distillation column for distilling a liquid containing a high boiling point component and a low boiling point component having a higher concentration than the high boiling point component, and separating the liquid into a second overhead vapor mainly containing the low boiling point component and a second bottom liquid containing the high boiling point component at a higher ratio than the low boiling point component; a second reboiler that circulates a mixed liquid of the second bottom liquid and the raw material liquid containing the high boiling point component and the low boiling point component having a higher concentration than the high boiling point component, to heat and evaporate the mixed liquid and supply the evaporated liquid to the bottom of the second distillation column; a heat recovery condenser for cooling and condensing the second overhead vapor, which is mainly composed of the low boiling point components and is taken out from the top of the second distillation column, with circulating cooling water for a heat recovery condenser, recovering the condensate mainly composed of the low boiling point components as a distillate, and evaporating the circulating cooling water for the heat recovery condenser by heat of the second overhead vapor; a second steam compressor configured to supply a portion of steam generated from the circulating cooling water for the heat recovery condenser in the heat recovery condenser, compress the steam to raise the temperature level, and supply the steam to the second reboiler as second reboiler steam; a first distillation column for distilling the second bottom liquid, the first distillation column being configured to distill the second bottom liquid supplied to a top thereof and separate it into a first overhead vapor withdrawn from the top thereof and a first bottom liquid withdrawn from the bottom thereof, and to supply the first overhead vapor to the bottom of the second distillation column; a first reboiler that circulates the first column bottom liquid to heat and evaporate it and supply it to the bottom of the first distillation column; a first steam compressor configured to supply the remainder of the steam generated from the circulating cooling water for the heat recovery condenser in the heat recovery condenser, excluding the portion supplied to the second steam compressor, and compress the steam to raise its temperature level and supply the steam to the first reboiler as first reboiler steam; Equipped with A steam compressor having a COP value of 3.0 or more and 6.0 or less is used as the first steam compressor, a steam compressor having a COP value of 6.0 or more and 15.0 or less is used as the second steam compressor, and the COP value of the second steam compressor is configured to be 2.0 or more higher than the COP value of the first steam compressor. A distillation apparatus characterized by:

2. The COP value of the second steam compressor is configured to be 3.0 or more higher than the COP value of the first steam compressor. The distillation apparatus according to claim 1 .

3. 3. The distillation apparatus according to claim 1, wherein the first distillation column has a smaller diameter than the second distillation column.

4. The temperature of the second reboiler steam, which is supplied to the second reboiler by increasing the temperature level in the second steam compressor, is higher than the temperature of the steam used to evaporate the circulating cooling water for the heat recovery condenser in the heat recovery condenser by a range of 15° C. to 40° C. The temperature of the first reboiler steam, which is supplied to the first reboiler by increasing the temperature level in the first steam compressor, is configured to be higher by 30° C. or more and 60° C. or less than the temperature of the steam obtained by evaporating the circulating cooling water for the heat recovery condenser in the heat recovery condenser. The distillation apparatus according to any one of claims 1 to 3,

5. The distillation apparatus according to any one of claims 1 to 4, characterized in that the low boiling point component is an organic solvent and the high boiling point component is water.

6. 5. The distillation apparatus according to claim 1, wherein the low boiling point component and the high boiling point component are both organic solvents.

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