Distillation device and distillation method

Abstract

To reduce required power of a compressor.SOLUTION: A distillation device includes: a batch type distillation column; a reboiler that heats a liquid, supplied to the distillation column, to evaporate the liquid to form vapor; a volumetric compressor that causes a fluid for heating the liquid to flow in so as to raise pressure and temperature of the fluid and supply the fluid to the reboiler; a condenser that condenses column top vapor of the distillation column to obtain a condensate; a distillate vent part for venting the condensate condensed by the condenser; and a column bottom liquid venting part that vents a residual liquid inside the distillation column. The compressor has an actual volume flow rate adjustment mechanism for changing the actual volume flow rate of the fluid the pressure and temperature of which is increased by the compressor in accordance with a change in the heating temperature required by the reboiler during operation of the distillation device.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a distillation apparatus and a distillation method. [Background technology]

[0002] Patent Document 1 describes a distillation apparatus including a distillation column, a reboiler, a compressor, and a condenser. It describes hydrous ethanol containing a trace amount of methanol as the liquid supplied to the distillation column.

[0003] The distillation apparatus of Patent Document 1 has an indirect heat pump that uses water as a working fluid (refrigerant). In an indirect heat pump, steam that is pressurized and heated by a compressor is supplied to a condenser (reboiler of the distillation apparatus). The temperature of the steam supplied to the condenser (reboiler of the distillation apparatus) is set to be higher than the temperature of the hydrous ethanol at the bottom of the distillation tower. Therefore, the steam discharged to the condenser (reboiler of the distillation apparatus) gives heat to the hydrous ethanol and condenses. The condensed water is sent to the evaporator (condenser of the distillation apparatus). In addition, by heating in the condenser (reboiler of the distillation apparatus), the vapor of the defective alcohol is discharged from the top of the distillation tower and sent to the evaporator (condenser of the distillation apparatus). The temperature of the water sent to the evaporator (condenser of the distillation apparatus) is set to be lower than the temperature of the vapor of the defective alcohol. Therefore, the vapor of the defective alcohol gives heat to the water and condenses, and most of it returns to the distillation tower through piping. A part of the condensed vapor at the top of the tower is extracted as defective alcohol liquid. Then, the aqueous ethanol from which the methanol has been removed is discharged from the bottom of the distillation column. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 168501 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the distillation apparatus in Patent Document 1 and the like includes a batch distillation apparatus and a continuous distillation apparatus. In a batch distillation apparatus, the liquid to be treated is filled in the distillation tower, and then distillation is performed. Therefore, in a batch distillation apparatus, the amount of liquid in the distillation tower decreases as the distillation progresses.

[0006] In a batch distillation apparatus, as the distillation proceeds, the liquid that is more difficult to evaporate, in other words, the liquid with a higher boiling point, becomes more retained in the distillation column. Therefore, as the distillation proceeds, it is necessary to increase the heating temperature in the reboiler.

[0007] However, the compressor used in the distillation apparatus of Patent Document 1 and the like is generally a centrifugal type, and the centrifugal type compressor is suitable for performing approximately constant pressure increase and temperature increase under the condition that the flow rate of the fluid is approximately constant. Specifically, the centrifugal type compressor has a specific impeller shape designed according to the components and flow rate of the fluid at the design point. Here, consider the case where a certain heat pump distillation system is applied to a system in which the heating temperature required for the reboiler changes widely. In that case, it is considered that the compression ratio of the compressor is set so that the heat pumping width of the heat pump covers the entire range of heating temperature change required for the reboiler. On the other hand, it is also considered that the discharge pressure and temperature of the compressor are increased by appropriately setting the compression ratio of the compressor while increasing the suction pressure of the compressor in accordance with the change in heating temperature required for the reboiler. In this case, it is possible to suppress the temperature pumping width, i.e., the compression ratio, to a smaller value compared to the above-mentioned case in which the heat pumping width of the heat pump is set to cover the entire range of heating temperature change required for the reboiler. However, in such an operation, the density of the fluid increases by increasing the pressure of the suction fluid of the compressor, so that the actual volumetric flow rate becomes smaller than the actual volumetric flow rate at the design point. As a result, there is a risk that the centrifugal compressor will deviate from the range of the actual suction volumetric flow rate at which it can normally operate. Here, the lower limit of the range of the actual suction volumetric flow rate at which a general centrifugal compressor can normally operate is, for example, 80%, assuming that the design point is 100%. As a requirement of the distillation apparatus, even if the flow rate of the fluid sucked by the compressor becomes 80% or less of the design point, it is necessary to perform circulation operation using a kickback line so that the actual suction volumetric flow rate processed by the compressor can be maintained at 80% of the design point. Therefore, the compressor will be operated with a large power by the amount of fluid circulating. Furthermore, as mentioned above, the shape of the impeller of the centrifugal compressor is designed according to the components and flow rate of the fluid at the design point, and when the components and flow rate of the fluid change, there is a risk that the specified boosting ability cannot be exhibited.In view of the above, it is difficult to apply a heat pump using a centrifugal compressor to a system in which the heating temperature required for the reboiler varies widely, or there is a risk that the energy saving effect expected from the heat pump distillation system cannot be achieved.

[0008] Heat pumps that form a heat pump cycle using a separately selected working fluid, such as the heat pump in Patent Document 1, are also called indirect heat pumps. Unlike indirect heat pumps, heat pumps that form a heat pump cycle using a process fluid as the working fluid are also called direct heat pumps. [Means for solving the problem]

[0009] The distillation apparatus of the first aspect includes a batch-type distillation column, a reboiler that heats a liquid supplied to the distillation column to evaporate it into vapor, a positive displacement compressor that introduces a fluid for heating the liquid, pressurizes and heats the fluid, and supplies the fluid to the reboiler, a condenser that condenses the overhead vapor of the distillation column to produce a condensate, a distillate extraction section that extracts the condensate, and a bottoms extraction section that extracts the residual liquid in the distillation column, wherein the fluid retains the condensation heat of the vapor, and after being pressurized and heated by the compressor, the fluid is condensed in the reboiler by imparting the condensation heat to the liquid, and the compressor has an actual volumetric flow rate adjustment mechanism that changes the actual volumetric flow rate of the fluid pressurized and heated by the compressor in accordance with changes in the heating temperature required for the reboiler during operation of the distillation apparatus.

[0010] A second aspect is the distillation apparatus according to the first aspect, in which the distillation column does not have any trays or packings therein and does not have a reflux section for returning the condensate to the distillation column, thereby performing simple distillation. A third aspect of the present invention is the distillation apparatus according to the first aspect, wherein the distillation column is a rectification column having trays or packing therein, and has a reflux section for returning the condensate to the distillation column.

[0011] A fourth aspect of the present invention relates to the distillation apparatus according to any one of the first to third aspects, wherein the actual volumetric flow rate adjustment mechanism is a staged capacity control system. A fifth aspect of the present invention relates to the distillation apparatus according to any one of the first to third aspects, wherein the actual volumetric flow rate adjustment mechanism is a stepless capacity control system.

[0012] A sixth aspect of the distillation apparatus according to any one of the first to fifth aspects is a distillation apparatus in which the fluid is a working fluid, the working fluid receives heat of condensation as the vapor condenses in the condenser, the working fluid having received the heat of condensation is pressurized and heated in the compressor, and when condensed in the reboiler, the condensation heat is imparted to a process fluid to cause condensation, the condensed working fluid is reduced in pressure by a pressure reducing valve to reduce its temperature, the reduced-pressure working fluid is separated into gas and liquid in a drum, and the distillation apparatus has an indirect heat pump mechanism in which liquid of the working fluid separated into gas and liquid is supplied to the condenser.

[0013] A seventh aspect is the distillation apparatus according to any one of the first to fifth aspects, wherein the fluid is vapor, and the distillation apparatus further comprises a direct heat pump mechanism in which the fluid is pressurized and heated by the compressor, and then the liquid supplied to the distillation column is evaporated into vapor in the reboiler, and the vapor of the fluid is condensed in the reboiler.

[0014] In an eighth aspect, in the distillation apparatus according to the seventh aspect, the distillation column is a rectification column having trays or packing therein, and has a reflux section for returning the condensate to the distillation column, and has a pressure reducing valve for applying heat to the reboiler to reduce the pressure of the condensed fluid and reflux the fluid to the distillation column.

[0015] A distillation method according to a ninth aspect of the present invention includes a supply step of supplying a liquid to a batch-type distillation column; a pressurizing and heating step of sucking in a fluid for heating the liquid using a volumetric compressor, pressurizing and heating the fluid, and supplying the fluid to a reboiler; a heating step of performing heat exchange in the reboiler between the liquid supplied from the distillation column and the pressurized and heated fluid to heat the liquid and condense the fluid; a condensation step of sending the overhead vapor of the distillation column heated in the heating step to a condenser and condensing the vapor by heat exchange to obtain a condensate; a distillate withdrawal step of withdrawing the condensate; and a bottoms withdrawal step of withdrawing the residual liquid in the distillation column. The gist of the distillation method according to the ninth aspect of the present invention is that in the pressurizing and heating step, an actual volumetric flow rate of the fluid pressurized and heated by the compressor is changed by an actual volumetric flow rate control mechanism in accordance with a change in the heating temperature required for the reboiler so that the liquid can be distilled by heating using a heat pump that operates at a smaller heating range.

[0016] The distillation method of a tenth aspect is the distillation method of the ninth aspect, wherein the distillation column does not have any trays or packing therein and does not have a reflux step for returning the condensate to the distillation column.

[0017] The distillation method of an eleventh aspect is the distillation method of the ninth aspect, wherein the distillation column has trays or packing therein and includes a reflux step of returning the condensate to the distillation column.

[0018] A twelfth aspect of the distillation method is the distillation method according to any one of the ninth to eleventh aspects, wherein the actual volume flow rate adjustment mechanism is a staged capacity control system. A thirteenth aspect of the distillation method is the distillation method according to any one of the ninth to eleventh aspects, wherein the actual volume flow rate adjustment mechanism is a stepless capacity control system.

[0019] The distillation method of aspect 14 is the distillation method according to any one of aspects 9 to 13, wherein the fluid is a working fluid and the liquid is a process fluid, the working fluid receives condensation heat produced when the vapor is condensed in the condenser, the working fluid having received the condensation heat is pressurized and heated in the compressor, the working fluid is condensed in the reboiler by imparting the condensation heat to the process fluid and is condensed, the pressure is reduced by a pressure reducing valve to reduce the temperature, and the liquid separated into gas and liquid in a drum is supplied to the condenser.

[0020] The distillation method of aspect 15 is the distillation method according to any one of aspects 9 to 13, wherein the fluid is the vapor, and the distillation method further comprises a direct heat pump mechanism in which the liquid supplied to the distillation column is pressurized and heated by the compressor, and then evaporated into vapor in the reboiler, and the vapor of the fluid is condensed in the reboiler.

[0021] The distillation method of a sixteenth aspect is the distillation method of the fifteenth aspect, further comprising a reflux step of returning the condensate to the distillation column and a pressure reduction step of reducing the pressure with a pressure reducing valve, and further comprising a direct heat pump mechanism including the pressure reduction step in the reflux step. Effect of the Invention

[0022] According to the distillation apparatus of the present invention, the actual volumetric flow rate of the fluid pressurized and heated by the compressor can be appropriately changed in accordance with the change in the heating temperature required for the reboiler during operation of the distillation apparatus. By appropriately changing the actual volumetric flow rate of the fluid pressurized and heated by the compressor, the temperature range pumped by the heat pump can be kept small, and the power required for the compressor can be reduced. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic diagram of a batch distillation apparatus having an indirect heat pump mechanism. [Diagram 2] FIG. 2 is a schematic diagram of a batch distillation apparatus having a direct heat pump mechanism. [Diagram 3]FIG. 3 is a schematic diagram showing temperature control by an actual volumetric flow rate adjustment mechanism of a staged capacity control system (eg, unloader type). [Figure 4] FIG. 4 is a schematic diagram showing temperature control by an actual volume flow rate adjustment mechanism of a stepless capacity control system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] First Embodiment A first embodiment of the distillation apparatus of the present invention will now be described. The distillation apparatus of the first embodiment is a batch distillation apparatus and has an indirect heat pump mechanism.

[0025] As shown in FIG. 1, the distillation apparatus 20 includes a batch-type distillation column 30 and a reboiler 40 that heats the liquid (hereinafter also referred to as process fluid) supplied to the distillation column 30 as a raw material. The distillation apparatus 20 also includes a volumetric compressor 50 that introduces a fluid (hereinafter also referred to as working fluid) for heating the process fluid, pressurizes and heats the working fluid, and supplies the working fluid to the reboiler 40. The distillation apparatus 20 also includes a condenser 60 that condenses the steam discharged from the top of the distillation column 30. The distillation apparatus 20 also includes a pressure reducing valve 22 that reduces the pressure of the working fluid condensed in the reboiler 40. The distillation apparatus 20 also includes a distillate extraction section 2a that extracts the process fluid, which is the condensate condensed in the condenser 60. Extracting the process fluid in the distillate extraction section 2a is also referred to as distillation.

[0026] The process fluid to be distilled is not particularly limited, and examples thereof include aromatic hydrocarbons, aliphatic hydrocarbons, alcohols, etc. The working fluid is not particularly limited, and examples thereof include water, alcohols, etc.

[0027] Each of the components constituting the distillation apparatus 20 will be described below. (Distillation tower 30) As shown in Fig. 1, distillation column 30 has sump 35 in which a predetermined amount of process fluid can be charged. Sump 35 may be a separate vessel from distillation column 30 and connected to distillation column 30 via piping, or may be directly connected. Sump 35 has a supply section 31 that supplies the process fluid, which is a raw material, into distillation column 30. Distillation column 30 is a batch-type distillation column in which distillation is performed after the raw material is supplied into distillation column 30.

[0028] The distillation tower 30 has a discharge section 32 at the top of the tower for discharging the process fluid evaporated in the distillation tower. A pipe 1 (hereinafter also referred to as a first pipe) communicating with a condenser 60 is connected to the discharge section 32. The distillation tower 30 may also be provided at the top of the tower with a reflux section 33 to which the process fluid condensed in the condenser 60 returns. A pipe 2 (hereinafter also referred to as a second pipe) through which the condensed liquid condensed in the condenser 60 flows is connected to the reflux section 33.

[0029] When the distillation apparatus 20 is an apparatus that performs simple distillation, the reflux section 33 may be omitted. When the distillation apparatus 20 is an apparatus that performs rectification, the reflux section 33 is included. When the distillation apparatus 20 is an apparatus that performs simple distillation (simple distillation apparatus), i.e., when the distillation method is a simple distillation operation, the distillation column 30 does not need to have trays or packing inside. When the distillation apparatus 20 is an apparatus that performs rectification (rectification apparatus), i.e., when the distillation method is a rectification operation, the distillation column 30 (rectification column) preferably has trays or packing inside. The packing is not particularly limited, and known packing used in distillation apparatuses can be used.

[0030] Alternatively, the distillation column 30 may have a condenser 60 at the top thereof without using the first pipe, and a discharge section 32 for discharging the condensed process fluid at a position below the condenser 60. A pipe 3 (hereinafter also referred to as a third pipe) that supplies a process fluid to a reboiler 40 is connected to the bottom of the distillation tower 30. A pipe 4 (hereinafter also referred to as a fourth pipe) through which the process fluid heated in the reboiler 40 returns to the distillation tower 30 is connected above the connection point of the third pipe. The sump 35 also has a bottoms discharge section 34 at the bottom from which the process fluid, which is a residual liquid, is discharged. The discharge of the process fluid at the bottoms discharge section 34 is also referred to as bottoms. The reboiler 40 may be provided in the sump 35 without the third and fourth pipes (i.e., the third and fourth pipes are omitted because the heat exchange section through which the heating side fluid flows is inserted or connected to the sump 35), and the bottoms discharge section 34 for discharging the process fluid may be provided below the reboiler 40.

[0031] (Reboiler 40) The reboiler 40 in the first embodiment corresponds to a condenser of a heat pump cycle. As shown in FIG. 1, the reboiler 40 is connected to the distillation column 30 via a third pipe and a fourth pipe. In addition, a pipe 5 (hereinafter also referred to as a fifth pipe) communicating with a compressor 50 is connected to the reboiler 40. An end of the fifth pipe opposite to the compressor 50 side 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 be installed at the bottom of the distillation column 30 without the third pipe and the fourth pipe.

[0032] The reboiler 40 is supplied with the process fluid in the distillation column 30 through a third pipe, or by gravity if the reboiler 40 is installed inside the distillation column 30. This process fluid is heated by the heat of the working fluid supplied from the compressor 50 through a fifth pipe. That is, the reboiler 40 heats the process fluid by performing heat exchange between the process fluid and the working fluid. The heated process fluid is returned to the distillation column 30 through a fourth pipe.

[0033] (Compressor 50) The compressor 50 is a positive displacement type. Positive displacement types include reciprocating and screw types. The reciprocating type is also called a reciprocating type, and compresses the process fluid by the reciprocating motion of a piston inside a cylinder. The screw type compresses the process fluid by rotating male and female screw rotors inside a casing.

[0034] 1, a pipe 6 (hereinafter, referred to as a sixth pipe) communicating with a condenser 60 is connected to the compressor 50. An end of the sixth pipe opposite to the compressor 50 side is connected to a circulation pump 23. In addition, a pipe 7 (hereinafter, also referred to as a seventh pipe) communicating with the drum 21 is connected to the circulation pump 23.

[0035] Furthermore, a pipe 8 (hereinafter also referred to as an eighth pipe) communicating with the drum 21 is connected between the compressor 50 and the condenser 60 in the sixth pipe. The compressor 50 has an actual volume flow rate adjusting mechanism that changes the actual volume flow rate of the working fluid pressurized and heated by the compressor 50 in accordance with changes in the heating temperature required for the reboiler 40 during operation of the distillation apparatus 20. The actual volume flow rate adjusting mechanism will be described later.

[0036] (Capacitor 60) The condenser 60 in the first embodiment corresponds to an evaporator in a heat pump cycle.

[0037] As shown in FIG. 1, the condenser 60 is connected to a first pipe. The condenser 60 is also connected to a sixth pipe. The condenser 60 is also connected to a pipe 9 (hereinafter also referred to as a ninth pipe) that communicates with the drum 24. The drum 24 is connected to a pipe 10 (hereinafter also referred to as a tenth pipe) that communicates with the pump 25. The pump 25 is connected to a second pipe that communicates with the distillation column 30. The condenser 60 may be installed at the top of the distillation column 30 without passing through the first pipe, the ninth pipe, the drum 24, the tenth pipe, the pump 25, and the second pipe. (That is, a heat exchanger 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.)

[0038] The process fluid evaporated in the distillation column 30 is supplied into the condenser 60. This process fluid condenses by imparting heat to the working fluid supplied through the sixth pipe, and becomes a condensed liquid. That is, in the condenser 60, the process fluid is condensed by performing heat exchange between the process fluid and the working fluid.

[0039] (Second piping, distillate extraction section 2a) As shown in Fig. 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, the drum 24, the tenth pipe, the pump 25, and the second pipe. Therefore, the second pipe functions as a pipe for refluxing the condensed liquid condensed in the condenser 60 to the distillation column 30. In addition, the second pipe has a distillate withdrawal section 2a that withdraws the condensed liquid condensed in the condenser 60. In the distillate withdrawal section 2a, the distilled process fluid is withdrawn.

[0040] When the distillation apparatus 20 is an apparatus that performs simple distillation, the second pipe for refluxing to the distillation column 30 may be omitted. When the distillation apparatus 20 is an apparatus that performs rectification, the second pipe for refluxing to the distillation column 30 is provided.

[0041] When the condenser 60 is installed at the top of the distillation column 30, the distillation column may be provided with a distillate withdrawal section 2a at a position below the condenser 60 at the top of the distillation column 30. (Trim Capacitor 70) As shown in FIG. 1, the trim condenser 70 is connected to a 14th pipe. Also, the trim condenser 70 is connected to a 15th pipe communicating with the drum 24. The trim condenser 70 is connected to a cooling water pipe 28. The trim condenser 70 is installed to absorb the imbalance in the heat load between the cooling section and the condensing section of the heat pump system to ensure stable operation. Depending on the distillation system, a trim reboiler, i.e., a reboiler heated by an external heat source, may be installed in parallel with the reboiler 40 instead of the trim condenser 70.

[0042] The distillation apparatus 20 is made up of the above-mentioned components. 1, the distillation apparatus 20 of the first embodiment is also provided with a plurality of control valves 26, a pump 27, etc. Furthermore, the arrows on each pipe indicate the flow direction of the process fluid or working fluid flowing through each pipe.

[0043] In the following, an indirect heat pump mechanism will be described. (Indirect heat pump mechanism) As shown in Fig. 1, the working fluid that flows into the compressor 50 through the sixth pipe is pressurized and heated in the compressor 50, and is 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 a temperature that is higher than the temperature of the process fluid in the reboiler 40 and promotes evaporation of the process fluid. The working fluid supplied to the reboiler 40 provides heat to the process fluid in the reboiler 40 and is condensed.

[0044] That is, the working fluid retains the heat of condensation of steam, and after being pressurized and heated by the compressor 50, when it is condensed in the reboiler 40, it imparts the heat of condensation to the process fluid and is condensed. The pressure of the condensed working fluid is reduced when it passes through the pressure reducing valve 22 in the fifth pipe, and the temperature drops. Depending on the conditions, part of the working fluid evaporates. Furthermore, in the drum 21, the evaporated part of the working fluid is separated from the remaining working fluid into gas and liquid, and the liquid part circulates through the condenser 60 via the seventh pipe, the circulation pump 23, and the sixth pipe. The evaporated part of the working fluid is returned from the drum 21 to the compressor 50 via the eighth pipe and the sixth pipe.

[0045] The process fluid evaporated in the distillation column 30 is supplied to the condenser 60. At this time, the temperature of the working fluid is set to a temperature lower than the temperature of the process fluid and capable of condensing the process fluid. The process fluid supplied to the condenser 60 imparts heat to the working fluid and is condensed to become a condensate. The working fluid receives heat from the process fluid in the condenser 60 and evaporates, flows through the sixth pipe into the compressor 50, and is pressurized and heated again for heating in the reboiler 40.

[0046] As described above, in an indirect heat pump mechanism, the process fluid is not directly pressurized and heated by a compressor, but rather the working fluid is heated and evaporated in a condenser, and then pressurized and heated by compressor 50, indirectly heating the process fluid and condensing the working fluid. The condensed working fluid is reduced in pressure by a pressure reducing valve, lowering its temperature. Depending on the conditions, part of the working fluid may evaporate. The reduced pressure working fluid is then separated into gas and liquid in a drum, after which the liquid portion is further cooled by the condenser, and the working fluid itself is evaporated, thereby distilling the process fluid.

[0047] The actual volume flow rate adjustment mechanism will be described below. (Real volume flow rate adjustment mechanism) The actual volume flow rate regulating mechanism of the positive displacement compressor 50 can be a stepped capacity control system (for example, stepped capacity control by an unloader) or a stepless capacity control system.

[0048] The actual volumetric flow rate means a value obtained by dividing the actual intake gas mass flow rate of the compressor 50 by the gas density. Each of these will be explained in detail below.

[0049] (Step Capacity Control System) The reciprocating compressor 50 having the staged capacity control system is equipped with a suction valve unloader and a clearance pocket. In addition, the reciprocating compressor 50 having the staged capacity control system can adjust the flow rate by pressing and opening the suction valve plate of the cylinder, and causing the gas once sucked in to flow back to the suction side so as not to perform compression work. However, since this is an opening and closing operation, the adjustment is stepwise. Alternatively, the flow rate can be adjusted by changing the cylinder gap (clearance) volume by opening and closing a clearance pocket attached to the cylinder head or the like, thereby changing the volumetric efficiency. As a result, the inflow rate of the working fluid can be controlled over a wider range than in a centrifugal compressor. Therefore, in an indirect heat pump mechanism, by increasing the suction pressure of the working fluid of the compressor 50, it is possible to increase the discharge pressure of the compressor 50 even if the actual volumetric flow rate is reduced. Specifically, if the volumetric flow rate during initial operation is 100%, it is possible to perform stepwise capacity control such as 75%, 50%, 25%, etc., and increase the discharge pressure stepwise.

[0050] 3, in a batch distillation apparatus, as the distillation progresses, a process fluid that is less likely to evaporate, in other words, has a higher boiling point, remains in a large amount in the distillation column 30. Therefore, as the distillation progresses, it is necessary to increase the discharge pressure of the compressor 50 and set the heating temperature in the reboiler 40 to a temperature equal to or higher than the temperature required for distillation, as indicated by the solid line TP in FIG.

[0051] In Fig. 3, the horizontal axis represents the passage of time, and shows that the suction pressure P1 and discharge pressure P2 of the compressor 50 are increased to increase the heating temperature in the reboiler 40 to achieve a temperature rise width ΔT. At the end of the distillation, the compressor 50 is stopped.

[0052] 3, if the actual volumetric flow rate adjusting mechanism of the stepped capacity control system is provided, the actual volumetric flow rate of the working fluid pressurized and heated by the compressor 50 can be changed in stages while maintaining the required temperature rise width ΔT. That is, the suction pressure P1 of the working fluid sucked into the compressor 50 can be changed in stages, and the discharge pressure P2 of the working fluid discharged from the compressor 50 can be changed in stages.

[0053] As a result, the temperature T1 of the working fluid sucked into the compressor 50 and the temperature T2 of the working fluid discharged from the compressor can be changed in stages in accordance with the change in the heating temperature TP required for the reboiler 40. Specifically, the temperature T1 of the working fluid sucked into the compressor 50 and the temperature T2 of the working fluid discharged from the compressor 50 can be increased in stages. This makes it possible to pressurize and heat the working fluid while suitably controlling its temperature, making it possible to distill the liquid by heating with a heat pump that operates at a smaller temperature rise width ΔT than in a heat pump distillation system using a centrifugal compressor. Here, there is no particular restriction on the smaller temperature rise width ΔT. It is assumed that the evaporation temperature of the process fluid in the reboiler and the condensation temperature of the process fluid in the condenser are both TP. Then, in an indirect heat pump using a centrifugal compressor, the temperature difference required for heat exchange in which the working fluid receives heat from the process fluid in the condenser and evaporates when TP is minimum is, for example, 10°C. Similarly, when TP is at its maximum, the temperature difference required for heat exchange in the reboiler to condense the working fluid by giving heat to the process fluid is, for example, 10°C. Therefore, the temperature rise ΔT is the difference between the minimum and maximum values ​​of TP plus 20°C. If the difference between the minimum and maximum values ​​of TP is, for example, 50°C, the temperature rise ΔT is 70°C. On the other hand, with an indirect heat pump using a volumetric compressor with a staged capacity control system, it is sufficient to have the temperature difference required for heat exchange during the time covered by each stage of capacity control, such as the four stages shown in T1 and T2 in Figure 3. Therefore, if the difference between the minimum and maximum values ​​of TP during the time covered by each stage is, for example, 15°C, the temperature rise ΔT can be 35°C.

[0054] (Stepless Capacity Control System) Compressor 50 having a stepless capacity control system can steplessly control the amount of suction of the working fluid. Specific examples of stepless capacity control systems include a reciprocating compressor having a stepless capacity control system (product name: Hydrocom) manufactured by HOERBIGER AG, and a screw compressor having a stepless capacity control system using a slide valve.

[0055] 4, when there is an actual volumetric flow rate adjustment mechanism using a stepless capacity control system, it is possible to continuously change the actual volumetric flow rate of the working fluid pressurized and heated by the compressor 50 while the compression ratio of the compressor 50 is constant. In other words, by continuously changing the suction pressure P1 of the working fluid flowing into the compressor 50, it is possible to continuously change the discharge pressure P2 of the working fluid discharged from the compressor 50.

[0056] As a result, the temperature T1 of the working fluid flowing into the compressor 50 and the discharge temperature T2 of the working fluid discharged from the compressor 50 can be continuously changed in accordance with the change in the heating temperature TP required for the reboiler 40. Specifically, the temperature T1 of the working fluid flowing into the compressor 50 and the temperature T2 of the working fluid discharged from the compressor 50 can be continuously increased. As a result, it is possible to pressurize and heat the working fluid while suitably controlling the temperature of the working fluid, so that it is possible to distill the liquid by heating with a heat pump that operates with a smaller temperature rise width ΔT compared to a heat pump distillation system using a centrifugal compressor. Here, there is no particular limitation on the smaller temperature rise width ΔT. If the process fluid temperature behavior is the same as the example of the heat pump related to the above-mentioned stage capacity control, the temperature of the working fluid can be continuously controlled in accordance with the temperature of the process fluid, as shown by T1 and T2 in FIG. 4. Therefore, the temperature rise width ΔT only needs to have a temperature difference required for heat exchange, and can be, for example, 20°C.

[0057] A distillation method using the distillation apparatus 20 will be described below. (Distillation method) The distillation method includes a supply step, a pressurization and heating step, a heating step on the distillation side (a condensation step in a heat pump cycle (also referred to as a heat pump cycle side condensation step)), a pressure reduction step, a condensation step on the distillation side (also referred to as an evaporation step in a heat pump cycle), a distillate removal step, and a bottoms removal step. In addition, a reflux step may be included after the condensation step, and when an indirect heat pump mechanism is included, a pressure reduction step may be included after the heating step (also referred to as a heat pump cycle side condensation step), and when a direct heat pump mechanism and a reflux step are included, the reflux step may include a pressure reduction step.

[0058] The supply step is a step of supplying a process fluid to the batch distillation column 30. The pressurizing and heating step is a step in which the working fluid is flowed into a positive displacement compressor 50 to pressurize and heat the working fluid, and then supplied to the reboiler 40 .

[0059] In the heating step on the distillation side (the condensation step on the heat pump cycle side), heat is exchanged in the reboiler 40 between the process fluid supplied from the distillation column 30 and the pressurized and heated working fluid. The process fluid is then heated and returned to the distillation column 30, and the working fluid is condensed.

[0060] The pressure reduction step is a step in which the working fluid condensed in the heating step on the distillation side (the condensation step in the heat pump cycle) is reduced in pressure by the pressure reduction valve 22. The temperature of the reduced-pressure working fluid decreases, and depending on the conditions, a part of the working fluid evaporates.

[0061] In the condensation step (the evaporation step in the heat pump cycle), the overhead vapor of the distillation column 30 is sent to the condenser 60 by heating in the heating step (the condensation step on the heat pump cycle side). The vapor is then condensed by heat exchange to produce a condensate. The heat exchange is carried out with the working fluid sent to the condenser 60.

[0062] The reflux step is a step in which the process fluid that has undergone the condensation step on the distillation side (the evaporation step in the heat pump cycle) is refluxed to the distillation column 30. The distillate withdrawal step is a step in which the condensate condensed in the condensation step on the distillation side (the evaporation step in the heat pump cycle) is withdrawn from the distillate withdrawal section 2a.

[0063] The bottoms discharge step is a step in which the residual liquid in the distillation column 30 is discharged from the bottoms discharge section 34. Distillation can be carried out by carrying out each of the above steps. The order of each step may be appropriately changed.

[0064] <Second embodiment> A second embodiment of the distillation apparatus 20 of the present invention will now be described. The distillation apparatus 20 of the second embodiment is a batch distillation apparatus having a direct heat pump mechanism. Detailed description of components that overlap with those of the distillation apparatus 20 of the first embodiment will be omitted.

[0065] As shown in Fig. 2, the distillation apparatus 20 includes 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. The distillation apparatus 20 also includes a positive displacement compressor 50 that receives the process fluid, pressurizes and heats the process fluid, and supplies the process fluid to the reboiler 40 (condenser 60). The compressor 50 has an actual volume flow rate adjustment mechanism, similar to the compressor 50 of the first embodiment.

[0066] The distillation apparatus 20 also includes a trim condenser 70 that condenses the vapor that has been discharged from the distillation column 30 and then pressurized and heated by the compressor 50. The distillation apparatus 20 also includes a distillate extraction section 2a that extracts the process fluid condensed in the reboiler 40 (condenser 60) and the trim condenser 70. The distillation apparatus 20 may also include a second pipe that is a pipe for returning the process fluid condensed in the reboiler 40 (condenser 60) and the trim condenser 70 to the distillation column 30. The second pipe has a pressure reducing valve 22 between the drum 24 and the distillation column 30.

[0067] As shown in Fig. 2, distillation column 30 has a discharge section 32 at the top of the column, which discharges the process fluid evaporated within distillation column 30. Discharge section 32 is connected to pipe 6(1) (hereinafter also referred to as sixth (1) pipe), which communicates with drum 29. In drum 29, liquid droplets that may be generated due to an accidental temperature drop or pressure rise are removed from the vapor.

[0068] 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 the drum 29 side is connected to a compressor 50. 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 a reboiler 40 (condenser 60). The reboiler 40 (condenser 60) is connected to the drum 24 via 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.

[0069] A pipe 14 (hereinafter also referred to as a 14th pipe) is connected between the compressor 50 and the reboiler 40 (condenser 60) in the fifth (1) pipe. The 14th pipe is connected to a trim condenser 70. A pipe 15 (hereinafter also referred to as a 15th pipe) communicating with the drum 24 is connected to the trim condenser 70. A pipe 28 for cooling water is connected to the trim condenser 70.

[0070] In the following, a direct heat pump mechanism is described. (Direct heat pump mechanism) As shown in Fig. 2, the process fluid evaporated in the distillation column 30 flows into the drum 29 through the sixth (1) pipe. It then flows into the compressor 50 through the sixth (1) pipe. After being pressurized and heated by the compressor 50, it is supplied to the reboiler 40 (condenser 60) through the fifth (1) pipe.

[0071] The temperature of the process fluid supplied to the reboiler 40 (condenser 60) is set to a temperature higher than the temperature of the process fluid in the reboiler 40 (condenser 60) and promotes evaporation of the process fluid. The process fluid discharged to the reboiler 40 (condenser 60) imparts heat to the process fluid in the reboiler 40 (condenser 60) and condenses. That is, in the reboiler 40 (condenser 60), the process fluid in the distillation column is heated by heat exchange between the process fluids. The condensed process fluid is supplied to the drum 24. In addition, a part of the process fluid that is pressurized and heated by the compressor 50 and not supplied to the reboiler 40 (condenser 60) 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 imparts heat to the cooling water and condenses. Furthermore, the process fluid is supplied to the drum 24 through the 15th pipe. The process fluid supplied to drum 24 is extracted through tenth pipe, pump 25, and distillate extraction section 2a. When distillation apparatus 20 of the second embodiment is a rectification apparatus having reflux section 33, the process fluid supplied to drum 24 is refluxed to distillation column 30 through the second pipe. When refluxing the process fluid, the second pipe has pressure reducing valve 22, and the pressure of the refluxed process fluid is reduced by pressure reducing valve 22, lowering the temperature. Depending on the conditions, part of the process fluid evaporates.

[0072] As described above, in the direct heat pump mechanism, a part of the process fluid is used as a working fluid. The part of the process fluid is pressurized and heated by the compressor 50, and the process fluid in the distillation column 30 is heated, thereby distilling the process fluid.

[0073] In the direct heat pump mechanism, part of the process fluid is used as the working fluid, and the properties of the working fluid itself change as the distillation proceeds. Therefore, it was difficult to change the flow rate of the fluid pressurized and heated by the compressor 50 in accordance with the change in the heating temperature required for the reboiler 40 (condenser 60) using a centrifugal compressor.

[0074] In the distillation apparatus 20 of the second embodiment, the compressor 50 also has an actual volume flow rate adjustment mechanism. Therefore, the actual volume flow rate of the process fluid flowing into the compressor 50 can be changed according to the change in the heating temperature TP required for the reboiler 40 (condenser 60) during the operation of the distillation apparatus 20. In the distillation apparatus 20 of the second embodiment, the functions of the reboiler 40 and the 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 gives heat to 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 temperature rise width ΔT is the temperature difference required for heat exchange, for example, 10°C at two locations, which had to be considered as 20°C in the indirect type, is 10°C, and the temperature change of the process fluid is added to it.

[0075] Therefore, in a direct heat pump mechanism using a volumetric compressor with a step-by-step capacity control system, if the difference between the minimum and maximum values ​​of TP during the time covered by each capacity control step is, for example, 15°C, the temperature rise range ΔT can be set to 25°C. Also, in a direct heat pump using a volumetric compressor with a stepless capacity control system, the temperature rise range can be set to, for example, 10°C.

[0076] In the distillation apparatus 20 of the second embodiment, distillation can be performed by the same distillation method as in the distillation apparatus 20 of the first embodiment. When the distillation apparatus 20 of the second embodiment does not have a reflux step, it does not have a pressure reduction step either.

[0077] <Actions and Effects of the Present Embodiment> The functions and effects of the first and second embodiments will be described. (1) The distillation column 30 is a batch-type distillation column 30, and the compressor 50 has an actual volumetric flow rate adjustment mechanism that changes the actual volumetric flow rate of the working fluid pressurized and heated by the compressor 50 in accordance with changes in the heating temperature TP required for the reboiler 40 during operation of the distillation apparatus 20.

[0078] Therefore, it is possible to change the suction pressure P1 of the working fluid flowing into the compressor 50 and the discharge pressure P2 of the working fluid discharged from the compressor 50. This makes it possible to change the discharge temperature T2 of the working fluid discharged from the compressor 50 in accordance with changes in the heating temperature TP required for the reboiler 40. Since it is possible to pressurize and heat the working fluid while appropriately controlling the temperature T2, it is possible to distill the liquid by heating with a heat pump that operates with a smaller temperature rise width ΔT compared to a heat pump distillation system using a centrifugal compressor.

[0079] Since the temperature range pumped by the heat pump can be kept small, the power required for the compressor 50 can be reduced, thereby achieving energy savings. (2) The actual volume flow rate adjustment mechanism is a stepped capacity control system, which makes it possible to pressurize and heat the working fluid while appropriately controlling the temperature of the working fluid in stages.

[0080] (3) The actual volumetric flow rate adjustment mechanism is a stepless capacity control system, which makes it possible to pressurize and heat the working fluid while continuously and appropriately controlling its temperature. (4) The distillation apparatus 20 has an indirect heat pump mechanism. Therefore, the actual volumetric flow rate of the working fluid pressurized and heated by the compressor 50 in the indirect heat pump mechanism can be suitably changed.

[0081] (5) The distillation apparatus 20 has a direct heat pump mechanism. Therefore, the actual volumetric flow rate of the working fluid pressurized and heated by the compressor 50 in the direct heat pump mechanism can be suitably changed.

[0082] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0083] The distillation apparatus may have either an indirect heat pump mechanism or a direct heat pump mechanism. In this embodiment, the distillation apparatus 20 includes the drum 21, the pressure reducing valve 22, the circulation pump 23, the drum 24, the pump 25, the control valve 26, the pump 27, the trim condenser 70, etc., but at least some of these may be omitted. Also, additional components may be provided in addition to the locations shown in Figures 1 and 2.

[0084] In the distillation apparatus 20 of the present embodiment, the trim condenser 70 is connected to the cooling water pipe 28, but this is not limited to the above. The trim condenser 70 may condense the process fluid by cooling means other than cooling water. Examples of cooling means other than cooling water include air blowing and a refrigerant. In the distillation apparatus 20 of the first embodiment, the trim condenser 70 may have a cooling means using cooling water, air blowing, or a refrigerant.

[0085] In the indirect heat pump mechanism of the first embodiment, the fifth pipe connecting the compressor 50 and the drum 21 does not need to go through the reboiler 40 (corresponding to a cooler of the heat pump device). A kickback pipe connecting the compressor 50 and the drum 21 may be connected.

[0086] In the direct heat pump mechanism of the second embodiment, a kickback pipe that communicates between the compressor 50 and the drum 29 may be connected between the fifth (1) pipe that communicates between the compressor 50 and the drum 24 and the sixth (1) pipe that communicates between the distillation column 30 and the drum 29. [Explanation of symbols]

[0087] 2...second piping, 2a...distillate withdrawal section, 20...distillation apparatus, 30...distillation column, 40...reboiler, 50...compressor, 60...condenser.

Claims

1. a batch distillation column; a reboiler that heats the liquid process fluid supplied to the distillation column to evaporate it into vapor; a positive displacement compressor that receives a fluid for heating the liquid, pressurizes and heats the fluid, and supplies the fluid to the reboiler; a condenser for condensing the overhead vapor of the distillation column into a condensate; A distillation apparatus comprising: a distillate withdrawal section for withdrawing the condensed liquid; and a bottoms withdrawal section for withdrawing the residual liquid in the distillation column, The fluid retains the condensation heat of the overhead vapor, and after being pressurized and heated by the compressor, imparts the condensation heat to the liquid when condensing in the reboiler, thereby condensing the liquid, the compressor has an actual volume flow rate adjusting mechanism that changes the actual volume flow rate of the fluid pressurized and heated by the compressor in accordance with a change in the heating temperature required for the reboiler during operation of the distillation apparatus, a direct heat pump mechanism in which the fluid is the overhead vapor and the working fluid receives condensation heat from the condenser, and the working fluid condensed in the reboiler is reduced in pressure by a pressure reducing valve to lower its temperature and is supplied to the condenser; or

2. 2. The distillation apparatus according to claim 1, wherein the distillation column performs simple distillation without having any trays or packings inside and without having a reflux section for returning the condensate to the distillation column.

3. 2. The distillation apparatus according to claim 1, wherein the distillation column is a rectification column having trays or packing therein, and has a reflux section for returning the condensate to the distillation column.

4. 2. The distillation apparatus of claim 1, wherein the actual volumetric flow rate regulation mechanism is a staged capacity control system.

5. 2. The distillation apparatus according to claim 1, wherein the actual volume flow rate adjustment mechanism is a stepless volume control system.

6. A distillation apparatus as described in claim 1, wherein the working fluid that has received the heat of condensation is pressurized and heated by the compressor and condensed in the reboiler, the condensed working fluid is reduced in pressure by a pressure reducing valve to lower its temperature, the reduced pressure working fluid is separated into gas and liquid in a drum, and the liquid portion of the separated working fluid is supplied to the condenser, and the distillation apparatus has an indirect heat pump mechanism.

7. After the fluid is pressurized and heated by the compressor, the liquid supplied to the distillation column is evaporated in the reboiler; 2. The distillation apparatus according to claim 1, further comprising a direct heat pump mechanism in which the fluid pressurized and heated by the compressor in the reboiler is condensed.

8. 8. The distillation apparatus according to claim 7, wherein the distillation column is a rectification column having trays or packing therein, and has a reflux section for returning the condensate condensed in the reboiler to the distillation column, and further has a pressure reducing valve for reducing the pressure of the condensate condensed in the reboiler and refluxing it to the distillation column.

9. a feeding step of feeding a liquid to a batch distillation column; a pressurizing and heating step of sucking a fluid for heating the liquid using a positive displacement compressor, pressurizing and heating the fluid, and supplying the fluid to a reboiler; a heating step in which heat is exchanged in the reboiler between the liquid supplied to the distillation column and the pressurized and heated fluid, thereby heating the liquid to obtain overhead vapor and condensing the fluid; a condensation step in which the overhead vapor heated in the heating step is sent to a condenser and condensed by heat exchange to form a condensate; a distillate withdrawing step of withdrawing the condensate; A distillation method comprising a bottoms withdrawing step of withdrawing a residual liquid from the distillation column, In the pressurizing and heating step, an actual volumetric flow rate of the fluid pressurized and heated by the compressor is changed by an actual volumetric flow rate adjusting mechanism in accordance with a change in the heating temperature required for the reboiler so that the liquid can be distilled by heating using a heat pump operating at a smaller temperature rise range; a direct heat pump mechanism in which the fluid is the overhead vapor and the working fluid receives condensation heat from the condenser, and the working fluid condensed in the reboiler is reduced in pressure by a pressure reducing valve to lower its temperature and is supplied to the condenser; or

10. The distillation method according to claim 9, wherein the distillation method is a simple distillation operation in the distillation column which does not have any trays or packing inside and does not have a reflux step for returning the condensate to the distillation column.

11. The distillation method according to claim 9, wherein the distillation method is a rectification operation in a distillation column having trays or packing therein and having a reflux step of returning the condensate to the distillation column.

12. 10. The distillation method of claim 9, wherein the actual volumetric flow rate regulation mechanism is a staged capacity control system.

13. 10. The distillation method according to claim 9, wherein the actual volume flow rate adjustment mechanism is a stepless capacity control system.

14. A distillation method as described in Claim 9, having an indirect heat pump mechanism in which the working fluid that has received the heat of condensation is pressurized and heated in the compressor, condensed in the reboiler, reduced in pressure by a pressure reducing valve to lower its temperature, and the liquid portion obtained by gas-liquid separation in a drum is supplied to the condenser.

15. 10. The distillation method according to claim 9, further comprising the direct heat pump mechanism in which the fluid is pressurized and heated by the compressor, and then the liquid supplied to the distillation column is evaporated in the reboiler, and the fluid pressurized and heated by the compressor is condensed in the reboiler.

16. A distillation method as described in claim 15, comprising a pressure reduction step in which the condensate of the fluid obtained in the reboiler is reduced in pressure using a pressure reducing valve, and a reflux step in which the condensate after the pressure reduction step is returned to the distillation column.

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