Distillation method

Abstract

To reduce required power of a compressor.SOLUTION: A distillation method comprises: a supply step of supplying a liquid to a batch-type distillation column; a pressurizing and temperature-raising step of pressurizing and temperature-raising a fluid for heating the liquid by means of a compressor, and supplying the fluid to a reboiler; a heating step of, in the reboiler, performing heat exchange between the liquid supplied from the distillation column and the pressurized and temperature-raised fluid to heat the liquid and condense the fluid; a condensation step of sending column top vapor of the distillation column to a condenser by heating in the heating step, and condensing the vapor by the heat exchange to obtain a condensate; a distillate extraction step of extracting the condensate; and a bottom product extraction step of extracting a residual liquid in the distillation column. The method further comprises a pressure adjustment step of adjusting a pressure of the distillation column so that the liquid can be distilled by heating with a heat pump operating in a smaller temperature elevation range in the pressurizing and temperature-raising step.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a distillation method.

Background Art

[0002] Patent Document 1 describes a distillation apparatus including a distillation column, a reboiler, a compressor, and a condenser. As the liquid supplied to the distillation column, it describes water-containing ethanol containing trace amounts of methanol.

[0003] The distillation apparatus of Patent Document 1 has an indirect heat pump using water as a working fluid (refrigerant). In the indirect heat pump, water vapor pressurized and heated by a compressor (also referred to as a compressor) is supplied to a condenser (the reboiler of the distillation apparatus). The temperature of the water vapor supplied to the condenser (the reboiler of the distillation apparatus) is set to be higher than the temperature of the water-containing ethanol at the bottom of the distillation column. Therefore, the water vapor discharged to the condenser (the reboiler of the distillation apparatus) gives heat to the water-containing ethanol and condenses. The condensed water is sent to an evaporator (the condenser of the distillation apparatus). Also, due to the heating in the condenser (the reboiler of the distillation apparatus), the vapor of poor alcohol is discharged from the top of the distillation column and sent to the evaporator (the condenser of the distillation apparatus). The temperature of the water sent to the evaporator (the condenser of the distillation apparatus) is set to be lower than the temperature of the vapor of poor alcohol. Therefore, the vapor of poor alcohol gives heat to the water and condenses, and most of it returns to the distillation column through the piping. A part of the condensed top vapor is withdrawn as a poor alcohol liquid. And the water-containing ethanol from which methanol has been removed is discharged from the bottom of the distillation column. [[ID=]17]

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, distillation apparatuses such as those described in Patent Document 1 include batch-type distillation apparatuses and continuous-type distillation apparatuses. In a batch-type distillation apparatus, the liquid to be processed is filled into the distillation column before distillation is performed. Therefore, in a batch-type distillation apparatus, the amount of liquid in the distillation column decreases as distillation progresses.

[0006] In batch-type distillation apparatuses, as distillation progresses, a larger amount of liquid that is less likely to evaporate—in other words, liquid with a higher boiling point—remains in the distillation column. Therefore, as distillation progresses, it was necessary to increase the heating temperature in the reboiler.

[0007] However, the compressors used in distillation apparatuses such as those described in Patent Document 1 are generally centrifugal, and centrifugal compressors are suitable for situations where the fluid flow rate is approximately constant and a nearly constant pressure and temperature increase is required. Specifically, centrifugal compressors are designed with a specific impeller shape to match the fluid composition and flow rate at the design point. Now, let's consider the case where a heat pump distillation system is applied to a system where the heating temperature required for the reboiler changes over a wide range. In that case, it is conceivable to set the compression ratio of the compressor so that the heat pump's heat pumping range covers the entire range of heating temperature changes required for the reboiler. On the other hand, it is also conceivable to increase the compressor's discharge pressure and temperature by appropriately adjusting the compression ratio of the compressor while increasing the compressor's suction pressure in accordance with the change in heating temperature required for the reboiler. In this case, the temperature pumping range, i.e., the compression ratio, can be kept smaller compared to the case described above where the heat pump's heat pumping range covers the entire range of heating temperature changes required for the reboiler. However, in such operations, increasing the pressure of the compressor's suction fluid increases the fluid density, resulting in an actual volumetric flow rate that is less than the actual volumetric flow rate at the design point. Consequently, there is a risk that the centrifugal compressor will fall outside the normal operating range of suction volumetric flow rates. Here, the lower limit of the normal operating range of suction volumetric flow rates for a typical centrifugal compressor is, for example, 80% when the design point is set to 100%. The distillation apparatus requires that even when the flow rate of the fluid drawn into the compressor falls below 80% of the design point, the compressor's processed suction volumetric flow rate must remain at 80% of the design point through circulating operation using a kickback line. Therefore, the compressor will operate with increased power due to the amount of circulating fluid. Furthermore, as mentioned above, the shape of the impeller of a centrifugal compressor is designed to match the fluid composition and flow rate at the design point, and there is a risk that the predetermined pressure boosting capacity may not be achieved when the fluid composition or flow rate changes.Considering the above, applying a heat pump using a centrifugal compressor to a system where the required heating temperature of the reboiler changes over a wide range may be difficult, or it may not be possible to achieve the energy-saving effects expected from a heat pump distillation system. [Means for solving the problem]

[0008] The distillation method of embodiment 1 comprises a supply step of supplying liquid to a batch-type distillation column, a pressurizing and heating step of supplying a fluid for heating the liquid under pressure and heating with a compressor to a reboiler, a heating step of performing heat exchange between the liquid supplied from the distillation column and the pressurized and heated fluid in the reboiler to heat the liquid and condense the fluid, a condensation step of sending the top vapor of the distillation column to a condenser due to the heating in the heating step, condensing the vapor by heat exchange to form a condensate, a distillate decontamination step of extracting the condensate, and a bottom decontamination step of extracting residual liquid in the distillation column, wherein the fluid retains the heat of condensation of the vapor, and after being pressurized and heated by the compressor, the heat of condensation is transferred to the liquid during condensation in the reboiler, thereby causing condensation, and the method includes a pressure adjustment step of adjusting the pressure of the distillation column so that the distillation of the liquid can be performed by heating with a heat pump that operates with a smaller heating range in the pressurizing and heating step.

[0009] The distillation method of embodiment 2 is the distillation method of embodiment 1, wherein the distillation method is a simple distillation operation in a distillation column that does not have shelves or packing material inside and does not have a reflux step to return the condensate to the distillation column.

[0010] The distillation method of embodiment 3 is a distillation operation in the distillation method of embodiment 1, wherein the distillation column has shelves or packing material inside and has a reflux step in which the condensate is returned to the distillation column.

[0011] The distillation method of embodiment 4 is a distillation method according to any one embodiment of embodiments 1 to 3, and comprises a depressurization step in which the fluid condensed in the heating step is depressurized by a pressure reducing valve, wherein the fluid is a working fluid and the liquid is a process fluid, the working fluid receives the heat of condensation from the vapor condensing in the condenser, the working fluid that has received the heat of condensation is pressurized and heated by the compressor, the heat of condensation is transferred to the process fluid when it condenses in the reboiler and condenses, the temperature is reduced by the depressurization step and the liquid of the working fluid, which has been separated into gas and liquid in a drum, is supplied to the condenser, and has an indirect heat pump mechanism.

[0012] The distillation method of embodiment 5 is a distillation method according to any one embodiment of embodiments 1 to 3, wherein the fluid is the vapor, and after being pressurized and heated by the compressor, the liquid supplied to the distillation column is evaporated into vapor by the reboiler, and the vapor of the fluid is condensed in the reboiler, and the reboiler has a direct heat pump mechanism.

[0013] The distillation method of embodiment 6 is the distillation method of embodiment 5, further comprising a reflux step of returning the condensed liquid obtained by condensing the vapor back to the distillation column and a depressurization step of reducing the pressure with a pressure reducing valve, and having a direct heat pump mechanism that includes the depressurization step in the reflux step. [Effects of the Invention]

[0014] According to the distillation method of the present invention, the amount of heat pumped by the heat pump during the pressurized heating process can be kept small, thereby reducing the power required for the compressor. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a schematic diagram of a batch-type distillation apparatus having an indirect heat pump mechanism. [Figure 2] Figure 2 is a schematic diagram of a batch-type distillation apparatus having a direct heat pump mechanism. [Figure 3] Figure 3 is a schematic diagram showing the temperature increase range in the pressurized heating process. [Modes for carrying out the invention]

[0016] <First Embodiment> The following describes a first embodiment of the distillation method of the present invention. The distillation method of the first embodiment uses a batch-type distillation apparatus and has an indirect heat pump mechanism.

[0017] As shown in Figure 1, the distillation apparatus 20 comprises a batch-type distillation column 30 and a reboiler 40 for heating the liquid raw material (hereinafter also referred to as process fluid) supplied to the distillation column 30. It also includes a compressor 50 that introduces a fluid for heating the process fluid (hereinafter also referred to as working fluid), pressurizes and heats the working fluid, and supplies it to the reboiler 40. Furthermore, it includes a condenser 60 for condensing the top vapor of the distillation column 30. It also includes a pressure reducing valve 22 for reducing the pressure of the working fluid condensed in the reboiler 40. In addition, it includes a distillate drain section 2a for extracting the process fluid, which is the condensate condensed in the condenser 60. Extracting the process fluid in the distillate drain section 2a is also called distillation. Furthermore, it includes a trim condenser 70 for adjusting the amount of condensation of the process fluid. The trim condenser 70 constitutes a pressure adjustment section.

[0018] The process fluid to be distilled is not particularly limited and can include, for example, aromatic hydrocarbons, aliphatic hydrocarbons, and alcohols. The working fluid is also not particularly limited and can include, for example, water and alcohols.

[0019] The following describes each component that makes up the distillation apparatus 20. (Distillation column 30) As shown in FIG. 1, the distillation column 30 has a sump 35 into which a predetermined amount of process fluid can be charged. The sump 35 may be connected to the distillation column 30 by piping as a separate container from the distillation column 30, or may be directly connected. The sump 35 has a supply section 31 for supplying the process fluid as a raw material into the distillation column 30. The distillation column 30 is a batch distillation column that performs distillation after supplying the raw material into the distillation column 30.

[0020] The distillation column 30 has a discharge section 32 at the top of the column for discharging the process fluid evaporated in the distillation column. A pipe 1 (hereinafter also referred to as the first pipe) communicating with the condenser 60 is connected to the discharge section 32. Further, at the top of the distillation column 30, a reflux section 33 for the process fluid condensed by the condenser 60 to return may be provided. A pipe 2 (hereinafter also referred to as the second pipe) through which the condensate condensed by the condenser 60 flows is connected to the reflux section 33.

[0021] When the distillation apparatus 20 is an apparatus for performing simple distillation, the reflux section 33 may be omitted. When it is an apparatus for performing rectification, it has a reflux section 33. Further, when the distillation apparatus 20 is an apparatus for performing simple distillation, that is, when the distillation method is a simple distillation operation, the distillation column 30 may not have trays or packing inside. When the distillation apparatus 20 is an apparatus for performing rectification, that is, when the distillation method is a rectification operation, it is preferable that the distillation column 30 has trays or packing inside. The packing is not particularly limited, and known packing used in distillation apparatuses can be adopted.

[0022] As shown in FIG. 1, the condenser may not be provided outside the distillation column, the distillation column 30 may have a condenser 60 at the top of the column, and may have a discharge section 32 for discharging the process fluid condensed at a position below the top of the column.

[0023] A pipe 3 (hereinafter also referred to as the third pipe) that supplies process fluid to the reboiler 40 is connected to the bottom of the distillation column 30. Above the connection point of the third pipe, a pipe 4 (hereinafter also referred to as the fourth pipe) that returns the process fluid heated in the reboiler 40 back to the distillation column 30 is connected. The distillation column 30, or the sump 35, also has a bottom outlet vent section 34 for removing process fluid. Removing process fluid from the bottom outlet vent section 34 is also called bottom outlet.

[0024] The third and fourth pipes are omitted (i.e., the third and fourth pipes are omitted because the heat exchange section through which the heated fluid flows is inserted into or connected to the sump 35), and the sump 35 may have a reboiler 40, with a boiler outlet vent 34 located below it for discharging the process fluid.

[0025] (Reboiler 40) In the first embodiment, the reboiler 40 corresponds to the condenser of the heat pump cycle. As shown in Figure 1, the reboiler 40 is connected to the distillation column 30 via the third and fourth pipes. In addition, a pipe 5 (hereinafter also referred to as the fifth pipe) that communicates with the compressor 50 is connected inside the reboiler 40. The end of the fifth pipe opposite to the compressor 50 communicates with the drum 21. The fifth pipe has a pressure reducing valve 22 between the reboiler 40 and the drum 21. The reboiler 40 may also be installed at the bottom of the distillation column 30 without going through the third and fourth pipes.

[0026] The reboiler 40 is supplied with process fluid from the distillation column 30, either through the third pipe or, if the reboiler 40 is installed inside the distillation column 30, by gravity. This process fluid is heated by the heat of the working fluid supplied from the compressor 50 through the fifth pipe. In other words, the reboiler 40 heats the process fluid by exchanging heat between the process fluid and the working fluid. The heated process fluid is returned to the distillation column 30 through the fourth pipe.

[0027] (Compressor 50) The type of compressor 50 is not particularly limited. For example, a centrifugal compressor 50 can be used.

[0028] As shown in Figure 1, the compressor 50 is connected to a pipe 6 (hereinafter referred to as the sixth pipe) that communicates with the condenser 60. The end of the sixth pipe opposite to the compressor 50 is connected to the circulation pump 23. The circulation pump 23 is connected to a pipe 7 (hereinafter also referred to as the seventh pipe) that communicates with the drum 21.

[0029] Furthermore, a pipe 8 (hereinafter also referred to as the eighth pipe) that communicates with the drum 21 is connected between the compressor 50 and the condenser 60 in the sixth pipe. (Capacitor 60) In the first embodiment, the condenser 60 corresponds to the evaporator of the heat pump cycle. As shown in Figure 1, the first pipe is connected to the condenser 60. The sixth pipe is also connected to the condenser 60. The condenser 60 is also connected to the pipe 9 (hereinafter also referred to as the ninth pipe) which communicates with the drum 24. The drum 24 is connected to the pipe 10 (hereinafter also referred to as the tenth pipe) which communicates with the pump 25. The pump 25 is connected to the second pipe which communicates with the distillation column 30. The condenser 60 may be installed at the top of the distillation column 30 without going through the first pipe, the ninth pipe, the drum 24, the tenth pipe, the pump 25, and the second pipe. (That is, a heat exchange section through which a cooling fluid flows may be inserted or connected to the top of the distillation column 30, and the first pipe, the ninth pipe, the drum 24, the tenth pipe, the pump 25, and the second pipe may be omitted.)

[0030] The condenser 60 is supplied with process fluid evaporated in the distillation column 30. This process fluid transfers heat to the working fluid supplied through the sixth pipe, causing it to condense and become a condensate. In other words, the condenser 60 condenses the process fluid by exchanging heat between the process fluid and the working fluid.

[0031] (Second piping, distillate drain section 2a) As shown in Figure 1, the second pipe is connected to the reflux section 33 of the distillation column 30. The process fluid condensed in the condenser 60 is returned to the distillation column 30 through the ninth pipe, drum 24, tenth pipe, pump 25, and second pipe. Therefore, the second pipe functions as a pipe that refluxes the condensate condensed in the condenser 60 to the distillation column 30. The second pipe also has a distillate drain section 2a for removing the condensate condensed in the condenser 60. The distilled process fluid is removed in the distillate drain section 2a.

[0032] If the distillation apparatus 20 is a simple distillation apparatus, the second piping that refluxes to the distillation column 30 may be omitted. If it is a rectification apparatus, it has a second piping that refluxes to the distillation column 30.

[0033] If the condenser 60 is installed at the top of the distillation column 30, the distillate drain section 2a may be provided in the distillation column at a position below the condenser 60 at the top of the distillation column 30. (Pressure regulating section) As shown in Figure 1, the trim condenser 70, which acts as a pressure regulating unit, is installed in parallel with the condenser 60, and adjusts the top pressure of the distillation column 30 by adjusting the amount of condensation of the top vapor of the distillation column 30. Note that the method of adjusting the top pressure does not have to be by the amount of condensation in the trim condenser 70.

[0034] The distillation apparatus 20 is composed of the above-mentioned components. As shown in Figure 1, the distillation apparatus 20 of the first embodiment is also equipped with several control valves 26 and a pump 27. The arrows indicated on each pipe indicate the direction of flow of the process fluid or working fluid circulating through each pipe.

[0035] The following section describes the indirect heat pump mechanism. (Indirect heat pump mechanism) As shown in Figure 1, the working fluid that flows into the compressor 50 through the sixth pipe is pressurized and heated in the compressor 50, and then supplied to the reboiler 40 through the fifth pipe. At this time, the temperature of the pressurized and heated working fluid is set to be higher than the temperature of the process fluid in the reboiler 40, to promote the evaporation of the process fluid. The working fluid supplied to the reboiler 40 heats the process fluid in the reboiler 40 and condenses it. When the condensed working fluid passes through the pressure reducing valve 22 in the fifth pipe, the pressure is reduced and the temperature decreases. Depending on the conditions, a portion of the working fluid evaporates. Furthermore, in the drum 21, the evaporated portion of the working fluid and the remaining working fluid are separated into gas and liquid, and the liquid portion flows through the condenser 60 through the seventh pipe, circulation pump 23, and sixth pipe. The evaporated portion of the working fluid is returned to the compressor 50 from the drum 21 through the eighth pipe and sixth pipe.

[0036] The condenser 60 is supplied with process fluid evaporated in the distillation column 30. At this time, the temperature of the working fluid is set lower than the temperature of the process fluid, to a temperature at which the process fluid condenses. The process fluid supplied to the condenser 60 heats the working fluid and condenses into a condensate. The working fluid evaporates in the condenser 60 by receiving heat from the process fluid, flows through the sixth pipe to the compressor 50, and is pressurized and heated again for heating in the reboiler 40.

[0037] As described above, in the indirect heat pump mechanism, the process fluid is not directly pressurized and heated by the compressor 50. Instead, the working fluid is heated in a condenser to evaporate, and then pressurized and heated by the compressor 50 to indirectly heat the process fluid, causing it to condense. The condensed working fluid is then depressurized by a pressure reducing valve, and its temperature decreases. Depending on the conditions, a portion of the working fluid evaporates. After the pressure is reduced, the working fluid is separated into gas and liquid in a drum, and the liquid portion is further cooled by the condenser and evaporated, thus performing distillation of the process fluid.

[0038] The following describes a distillation method using the distillation apparatus 20. (Distillation method) The distillation method comprises a supply step, a pressurized heating step, a heating step on the distillation side (also called a condensation step in the heat pump cycle (also called a heat pump cycle side condensation step)), a condensation step on the distillation side (also called an evaporation step in the heat pump cycle), a distillate removal step, a bottom removal step, and a pressure adjustment step. Furthermore, a reflux step may be included after the condensation step (evaporation step in the heat pump cycle), and if an indirect heat pump mechanism is present, a depressurization step may be included after the heating step on the distillation side (also called a heat pump cycle side condensation step), and if a direct heat pump mechanism and reflux step are present, the reflux step may include a depressurization step.

[0039] The supply process is the process of supplying process fluid to a batch-type distillation column 30. The pressurized heating process involves introducing the working fluid into the compressor 50, pressurizing and heating the working fluid, and then supplying it to the reboiler 40.

[0040] The heating process on the distillation side (heat pump cycle side condensation process) involves heat exchange between the process fluid supplied from the distillation column 30 and the pressurized and heated working fluid in the reboiler 40. This process heats the process fluid and returns it to the distillation column 30, while simultaneously condensing the working fluid.

[0041] The depressurization process is a process in which the working fluid condensed in the heating process on the distillation side (condensation process in the heat pump cycle) is depressurized by the pressure reducing valve 22. The temperature of the depressurized working fluid decreases, and depending on the conditions, a portion of the working fluid evaporates.

[0042] The condensation process (evaporation process in the heat pump cycle) involves sending the top vapor from the distillation column 30 to the condenser 60 through heating in the heating process (heat pump cycle side condensation process). In the condenser 60, the vapor is condensed into a condensate through heat exchange. Heat exchange takes place with the working fluid sent to the condenser 60.

[0043] The pressure adjustment process is a process in which the pressure in the distillation column is adjusted using a trim condenser 70 so that the distillation of the process fluid can be carried out under conditions where the temperature rise range is such that sufficient energy saving effect can be obtained by applying a heat pump during the pressurization and heating process.

[0044] In the pressure adjustment step, the system may be configured to monitor the temperature of the vapor discharged from the distillation column 30 and the temperature of the process fluid condensed in the condenser 60, and then determine the cooling conditions. Examples of cooling conditions include the temperature and flow rate of the cooling water. Alternatively, the pressure adjustment step may be configured to cool the process fluid without performing the above monitoring.

[0045] The reflux process is the process of refluxing the process fluid, which has gone through the condensation process (evaporation process in the heat pump cycle) and the pressure adjustment process on the distillation side, back to the distillation column 30. The distillate draining process is the process of removing the process fluid condensed in the condensation process (evaporation process in the heat pump cycle) on the distillation side from the distillate draining section 2a.

[0046] The bottom draining process is the process of removing the residual liquid in the distillation column 30 from the bottom draining section 34. Distillation can be carried out by performing the above steps. The order of the steps may be changed as appropriate.

[0047] The following section explains the operation of the pressure regulation process. (Operation of the pressure regulation process) As shown in Figure 3, in a batch-type distillation apparatus, as distillation progresses, a larger amount of process fluid that is less likely to evaporate, in other words, has a higher boiling point, accumulates in the distillation column 30. Therefore, as distillation progresses, the discharge pressure P20 of the compressor 50 is increased relative to the suction pressure P1. The heating temperature in the reboiler 40 needs to be approximately the same as, or higher than, the temperature required for distillation shown by the solid line TP1 in Figure 3, for example, the temperature shown by T20.

[0048] In Figure 3, the horizontal axis represents the passage of time. By using the compressor 50 to maintain constant suction pressure P1 and discharge pressure P20, the heating temperature of the reboiler 40 is set to the target temperature T20, which is the temperature rise ΔT1 relative to the initial temperature T1.

[0049] As shown in Figure 3, the compressor 50 is designed to handle the maximum temperature in batch distillation. Therefore, there are times when the temperature rise is excessively large, such as immediately after the start of the distillation operation. When the temperature rise is excessive, such as the temperature rise ΔT1, excessive compression is performed, and the energy-saving effect of applying a heat pump is diminished.

[0050] In such cases, by performing a pressure adjustment process and lowering the pressure inside the distillation column 30, it becomes possible to suitably lower the boiling point of the process fluid inside the distillation column 30. Specifically, as shown by the dashed line TP2 in Figure 3, the temperature TP2 required for distillation can be lowered, and the temperature rise range can be reduced to ΔT2. This makes it possible to reduce the power of the compressor and obtain a significant energy saving effect.

[0051] There are no particular limitations on the smaller heating range ΔT2. Assume that the evaporation temperature of the process fluid in the reboiler 40 and the condensation temperature of the process fluid in the condenser 60 are both TP. Then, in an indirect heat pump using a centrifugal compressor, the temperature difference required for heat exchange for the working fluid to receive heat from the process fluid and evaporate in the condenser 60 when TP is at its minimum is, for example, 10°C. Similarly, the temperature difference required for heat exchange for the working fluid to transfer heat to the process fluid and condense in the reboiler when TP is at its maximum is, for example, 10°C. Therefore, the heating range ΔT1 is obtained by adding 20°C to the difference between the minimum and maximum values ​​of TP1, and if the difference between the minimum and maximum values ​​of TP1 is, for example, 50°C, then the heating range ΔT1 is 70°C. On the other hand, by performing a pressure adjustment process and lowering the pressure in the distillation column 30, it is sufficient to have the temperature difference required for heat exchange from the minimum and maximum values ​​of TP2, as shown in ΔT2 in Figure 3. If the difference between the minimum and maximum values ​​of TP2 is, for example, 35°C, then the heating range ΔT2 can be set to 55°C.

[0052] In other words, in the pressure adjustment process, the pressure in the distillation column is adjusted so that the process fluid can be distilled under conditions that result in a temperature increase range that allows for sufficient energy savings when a heat pump is applied in the pressurized heating process. This makes it possible to efficiently distill the process fluid using, for example, a centrifugal compressor 50.

[0053] <Second Embodiment> A second embodiment of the distillation apparatus 20 of the present invention will be described below. The distillation apparatus 20 of the second embodiment is a batch-type distillation apparatus and has a direct heat pump mechanism. Detailed explanations of components that overlap with the distillation apparatus 20 of the first embodiment are omitted.

[0054] As shown in Figure 2, the distillation apparatus 20 comprises a batch-type distillation column 30 and a reboiler 40 that heats the process fluid supplied to the distillation column 30. The reboiler 40 also functions as a condenser 60. It also includes a compressor 50 that introduces the process fluid, pressurizes and heats it, and supplies it to the reboiler 40 (condenser 60).

[0055] Furthermore, the distillation apparatus 20 includes a trim condenser 70 as a pressure regulating unit that condenses the steam that has been pressurized and heated by the compressor 50 after being discharged from the distillation column 30. It also includes a distillate draining unit 2a for extracting the process fluid condensed in the reboiler 40 (condenser 60) and the trim condenser 70. A second piping may also be included, which is piping that returns the process fluid condensed in the reboiler 40 (condenser 60) and the trim condenser 70 to the distillation column 30. The second piping has a pressure reducing valve 22 between the drum 24 and the distillation column 30.

[0056] As shown in Figure 2, the distillation column 30 has a discharge section 32 at the top of the column for discharging the process fluid evaporated within the distillation column 30. A pipe 6(1) (hereinafter also referred to as the 6(1) pipe) that communicates with the drum 29 is connected to the discharge section 32.

[0057] A pipe 6a(1) (hereinafter also referred to as the 6a(1) pipe) is connected to the drum 29. The end of the 6a(1) pipe opposite to the drum 29 is connected to the compressor 50. The drum 29 removes droplets that may be generated from the steam due to accidental temperature drops or pressure increases. A pipe 5(1) (hereinafter also referred to as the 5(1) pipe) is connected to the compressor 50. The 5(1) pipe is connected to the reboiler 40 (condenser 60). The reboiler 40 (condenser 60) is connected to the drum 24 through a pipe 5(9) (hereinafter also referred to as the 5(9) pipe). The 5(9) pipe has a control valve 26 between the reboiler 40 (condenser 60) and the drum 24.

[0058] In the piping of section 5(1), pipe 14 (hereinafter also referred to as pipe 14) is connected between the compressor 50 and the reboiler 40 (condenser 60). Pipe 14 is connected to the trim condenser 70. In addition, pipe 15 (hereinafter also referred to as pipe 15) which communicates with the drum 24 is connected to the trim condenser 70. Cooling water pipe 28 is connected to the trim condenser 70.

[0059] The direct heat pump mechanism will be described below. (Direct heat pump mechanism) As shown in Figure 2, the process fluid evaporated in the distillation column 30 flows into the drum 29 through the 6(1) pipe. It then flows into the compressor 50 through the 6a(1) pipe. After being pressurized and heated in the compressor 50, it is supplied to the reboiler 40 (condenser 60) through the 5(1) pipe.

[0060] The temperature of the process fluid supplied to the reboiler 40 (condenser 60) is set higher than the temperature of the process fluid inside the reboiler 40 (condenser 60) to promote evaporation of the process fluid. The process fluid supplied to the reboiler 40 (condenser 60) transfers heat to the process fluid inside the reboiler 40 (condenser 60), causing it to condense. In other words, the reboiler 40 (condenser 60) heats the process fluid in the distillation column by exchanging heat between the process fluids. The condensed process fluid is supplied to the drum 24. In addition, some of the process fluid, which has been pressurized and heated by the compressor 50, is supplied to the trim condenser 70 through the 14th pipe. Since cooling water is supplied to the trim condenser 70, the process fluid supplied to the trim condenser 70 through the 14th pipe transfers heat to the cooling water, causing it to condense. Furthermore, it is supplied to the drum 24 through the 15th pipe. The process fluid supplied to the drum 24 is withdrawn through the 10th pipe, the pump 25, and the distillate draining section 2a. Furthermore, if the distillation apparatus 20 of the second embodiment is a rectification apparatus having a reflux section 33, the process fluid supplied to the drum 24 is refluxed to the distillation column 30 through the second pipe. When refluxing the process fluid, the second pipe has a pressure reducing valve 22, which reduces the pressure of the refluxed process fluid and lowers its temperature. Depending on the conditions, a portion of the process fluid may evaporate.

[0061] As described above, in a direct heat pump mechanism, a portion of the process fluid is used as the working fluid. A portion of the process fluid is pressurized and heated by the compressor 50, and the process fluid in the distillation column 30 is heated to perform distillation of the process fluid.

[0062] The distillation method of the second embodiment differs from the distillation method of the first embodiment in that, in the heating step, a portion of the process fluid is pressurized and heated by a compressor 50, and then heated in a reboiler 40.

[0063] In the distillation apparatus 20 of the second embodiment, by employing a distillation method that includes a pressure adjustment step, it becomes possible to efficiently distill the process fluid using the compressor 50. In the distillation apparatus 20 of the second embodiment, the functions of the reboiler 40 and condenser 60 are combined from the perspective of the process fluid. As in the first embodiment, the condenser 60 receives heat from the process fluid, evaporates the working fluid, pressurizes and heats the working fluid, and the reboiler 40 heats the process fluid to condense the working fluid. Of these operations, two heat exchange operations between the process fluid and the working fluid are combined into one. Therefore, the heating range ΔT2 is the temperature difference required for heat exchange, for example, in the first embodiment, it was necessary to consider 20°C in two places of 10°C, but in this case it is 10°C, and the temperature change of the process fluid (heating range ΔT2) is added to this.

[0064] <Operation and Effects of This Embodiment> The operation and effects of the first and second embodiments will be described below. (1) The system has a pressure adjustment step to adjust the pressure of the distillation column 30 so that the temperature rise in the pressurized heating step can be reduced.

[0065] By having a pressure adjustment step to adjust the pressure in the distillation column 30, the pressure inside the distillation column 30 can be reduced. Reducing the pressure inside the distillation column 30 makes it possible to suitably lower the boiling point of the process fluid inside the distillation column 30. As a result, it becomes possible to evaporate the process fluid at a lower temperature. Consequently, heating can be performed by a heat pump operating with a smaller heating range using the compressor 50. Since the amount of heat pumped by the heat pump in the pressurized heating step can be kept small, the power required for the compressor can be reduced.

[0066] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0067] In this embodiment, the distillation apparatus 20 included a drum 21, a pressure reducing valve 22, a circulation pump 23, a drum 24, a pump 25, a control valve 26, a pump 27, etc., but at least some of these may be omitted. In addition, additional components may be provided in locations other than those shown in Figures 1 and 2.

[0068] The trim condenser 70 is not limited to being connected to the 15th piping which communicates with the drum 24. The trim condenser 70 may be connected to the 5th (9) piping, installed inside the drum 24, or connected to the drum 24. Furthermore, the cooling means for the trim condenser 70 may be other than cooling water. Examples of cooling means other than cooling water include airflow or refrigerant.

[0069] In the distillation apparatus 20 of the second embodiment, a cooling water pipe 28 was connected to the trim condenser 70, but the invention is not limited to this embodiment. The trim condenser 70 may condense the process fluid by a cooling means other than cooling water. Examples of cooling means other than cooling water include blown air. In the distillation apparatus 20 of the first embodiment, the condenser 60 may have a cooling means using cooling water, blown air, or an external low-temperature heat source such as a refrigerant.

[0070] In the indirect heat pump mechanism of the first embodiment, the fifth pipe connecting the compressor 50 and the drum 21 does not necessarily have to pass through the reboiler 40 (corresponding to the cooler of the heat pump device). A kickback pipe connecting the compressor 50 and the drum 21 may also be connected.

[0071] In the direct heat pump mechanism of the second embodiment, a kickback pipe connecting the compressor 50 and the drum 29 may be connected between the fifth (1) pipe connecting the compressor 50 and the drum 24 and the sixth (1) pipe connecting the distillation column 30 and the drum 29. [Explanation of Symbols]

[0072] 2...Second piping, 2a...Distillate drain section, 20...Distillation apparatus, 30...Distillation column, 40...Reboiler, 50...Compressor, 60...Condenser.

Claims

1. A feeding process that supplies liquid to a batch-type distillation column, A pressurized heating step involves pressurizing and heating the fluid for heating the aforementioned liquid using a compressor and supplying it to a reboiler. In the reboiler, a heating step is performed in which heat exchange is carried out between the liquid supplied from the distillation column and the pressurized and heated fluid, thereby heating the liquid and condensing the fluid. The heating process involves sending the top vapor of the distillation column to a condenser, where the vapor is condensed by heat exchange to form a condensate. A distillate extraction step for removing the condensate, A distillation method comprising a bottom draining step for removing residual liquid from the distillation column, The fluid retains the heat of condensation of the steam, and after being pressurized and heated by the compressor, the heat of condensation is transferred to the liquid during condensation in the reboiler, causing condensation. A distillation method characterized by having a pressure adjustment step that adjusts the pressure of the distillation column so that the distillation of the liquid can be performed by heating with a heat pump that operates with a smaller heating range in the pressurized heating step.

2. The distillation method according to claim 1, wherein the distillation method is a simple distillation operation in a distillation column that does not have shelves or packing material inside and does not have a reflux step to return the condensate to the distillation column.

3. The distillation method according to claim 1, wherein the distillation method is a rectification operation in a distillation column having shelves or packing material inside and a reflux step in which the condensate is returned to the distillation column.

4. The process includes a depressurization step in which the fluid condensed in the heating step is depressurized using a pressure reducing valve. The distillation method according to claim 1, comprising an indirect heat pump mechanism in which the fluid is a working fluid and the liquid is a process fluid, the working fluid receives heat of condensation from the vapor condensing in the condenser, the working fluid that has received the heat of condensation is pressurized and heated in the compressor, the heat of condensation is transferred to the process fluid during condensation in the reboiler and condenses, the pressure is reduced in the depressurization step and the temperature drops, and the liquid of the working fluid, which has been separated into gas and liquid in the drum, is supplied to the condenser.

5. The distillation method according to claim 1, wherein the fluid is the vapor, and after being pressurized and heated by the compressor, the liquid supplied to the distillation column is evaporated into vapor by the reboiler, and the vapor of the fluid is condensed in the reboiler, comprising a direct heat pump mechanism.

6. The process includes a reflux step of returning the condensed vapor back to the distillation column and a depressurization step of reducing the pressure using a pressure reducing valve. The distillation method according to claim 5, comprising a direct heat pump mechanism that includes the vacuum step in the reflux step.

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