JP2018058025A - Apparatus and method for recovering low boiling point substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for recovering a low boiling point substance which can recover a low boiling point substance in a high concentration and which can achieve energy saving.MEANS: An apparatus 1 for recovering ammonia comprises: a distillation tower 2 for carrying out steam stripping into which steam for heating is blown; an evaporator 3 for exchanging heat between ammonia-containing vapor discharged from the top of the distillation tower 2 and water to evaporate the water; a compression device 4 for compressing the steam discharged from the evaporator 3 to raise its temperature and for discharging it as the steam for heating into the distillation tower 2; a concentration tower 5 for taking in the ammonia-containing vapor concentrated in the evaporator 3, for cooling the vapor and for removing moisture, to raise a concentration of the ammonia-containing vapor to a high concentration, for example 20 wt.% or higher; a first absorption tower 6 for making the ammonia-containing vapor from the concentration tower 5 absorb the moisture, to generate recovered aqueous ammonia of a predetermined concentration; and a second absorption tower 7 for preventing the uncondensed ammonia-containing vapor in the first absorption tower from being discharged to the outside.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a recovery apparatus and a recovery method for separating and recovering low-boiling substances from waste water containing low-boiling substances such as ammonia.

  A steam stripping method is known as a method for separating and removing ammonia-containing wastewater. In a general ammonia recovery apparatus using this steam stripping method, a distillation column for performing steam stripping is provided, the ammonia-containing vapor discharged from the top of the distillation column is fractionated by a condenser, and the condensed water is The refluxed liquid is returned to the top of the distillation tower, and the remaining concentrated ammonia-containing vapor is supplied to the absorption tower and absorbed in water and taken out as recovered ammonia water.

  By the way, the steam stripping method used in such an ammonia recovery apparatus is a method in which water vapor is directly blown into the bottom of a distillation column, and since a large amount of water vapor is used, running cost is high and reduction of processing cost is required. ing. On the other hand, in this method, ammonia-containing water vapor is generated in an amount almost equal to the amount of water vapor that was added. To make this into the reflux liquid and the recovered ammonia liquid to the top of the distillation tower, it was installed at the top of the tower. It needs to be cooled by a heat exchanger (condenser) and the energy is disposable.

  In order to solve such problems, there has been proposed a method in which steam discharged from the top of a distillation column is compressed by a steam compressor and heat recovery is performed by a reboiler to reduce the amount of water vapor (the following patent documents) 1). Also, make-up water is supplied to a condenser for partial condensation of the ammonia-containing steam discharged from the top of the distillation tower, the make-up water is evaporated by exchanging heat with the ammonia-containing steam, and then led to a steam compressor for compression / A configuration in which the temperature is raised and reused as water vapor has been proposed (see Patent Document 2 below).

JP 2002-28637 A JP 2004-114029 A

  In the conventional examples disclosed in Patent Documents 1 and 2, the heat of the ammonia-containing steam discharged from the top of the distillation column is effectively used to save energy and reduce the running cost.

However, in the configuration of the conventional example including at least a distillation column, a heat exchanger (reboiler or condenser: these reboiler or condenser corresponds to the evaporator of the present application), and a vapor compressor, for example, 20 wt% or more When trying to recover high-concentration ammonia, the following problems arise. That is, if only a heat exchanger (equivalent to the evaporator of the present application) is used to increase the concentration, the temperature difference between the inlet and the outlet of the ammonia-containing steam in the heat exchanger increases, and the steam compressor load is increased accordingly. Becomes too large, which is against the demand for energy saving by using a steam compressor. Note that the above problem is not limited to ammonia, but is common to recovery devices that contain a wide range of low-boiling substances.
Therefore, there has been a demand for a low boiling point substance recovery device that can recover ammonia at a high concentration and save energy.

  The present invention has been conceived in view of the above problems, and an object of the present invention is to provide a low-boiling point substance recovery device and a recovery method capable of recovering low-boiling substance at a high concentration and saving energy. It is.

  In order to achieve the above object, the invention described in claim 1 is a low boiling point substance recovery apparatus, wherein a raw solution containing a low boiling point substance is brought into contact with steam for heating, and the low boiling point substance is separated from the raw solution and gasified. A distillation column that discharges from the top of the tower as a low-boiling substance-containing vapor and stores treated water from which the low-boiling substance has been removed from the stock solution at the bottom of the tower, and a low-boiling substance that is discharged from the top of the distillation tower An evaporator that heat-exchanges the steam and water, thereby condensing the steam containing the low-boiling substance, condensing the steam containing the low-boiling substance, and evaporating the water and discharging it as steam; The steam discharged from the evaporator is compressed and heated, the compressed and heated steam is led to the distillation tower, and the steam is used as heating steam used in the distillation tower, and the steam is reduced by the evaporator. Contains later low-boiling substances It captures the vapors, and comprising the further the concentration column for concentrating vapor containing low-boiling material to remove moisture by cooling the steam.

According to the above configuration, the evaporator and the concentrating tower disposed at the latter stage of the evaporator are provided, and the ammonia-containing vapor discharged from the distillation tower is concentrated at a predetermined level by two-stage concentration by the evaporator and the concentrating tower. Vapor containing low-boiling substances having a concentration (for example, 20 wt% or more) can be generated. With such a configuration, it is possible to prevent the load on the compression device from becoming too large as compared to a configuration in which the concentration is concentrated to a predetermined high concentration (for example, 20 wt% or more) using only the evaporator. As a result, it is possible to obtain a recovery device that can save energy and can generate a low-boiling-substance-containing vapor having a high concentration (for example, 20 wt% or more).
Examples of the “low boiling point substance” include alcohols such as ammonia and methanol, ketones such as acetone, esters such as methyl acetate, and the like.
As “water”, pure water, soft water, ion-exchanged water and the like can be applied.

  The invention according to claim 2 is the low boiling point substance recovery apparatus according to claim 1, wherein the evaporator is provided in the middle of a discharge line for discharging treated water stored at the bottom of the distillation column to the outside. The pre-heater which heat-exchanges the water used in this by exchanging heat with the said treated water previously, It is characterized by the above-mentioned.

  According to the said structure, the energy saving at the time of the heat exchange in an evaporator is achieved by preheating the water used in an evaporator.

  The invention according to claim 3 is the low boiling point substance recovery apparatus according to claim 1, wherein the low boiling point substance recovery device is provided in the middle of a circulation line that guides the stored liquid stored at the bottom of the concentrating tower to the top of the tower. A heat exchanger that exchanges heat between the flowing stored liquid and cooling water to cool the stored liquid, a temperature sensor that detects the temperature of the stored liquid stored in the bottom of the concentrating tower, and a detection result of the temperature sensor And a control valve for adjusting the flow rate of the cooling water passing through the heat exchanger.

  According to the said structure, the opening degree of a control valve is controlled according to the detection result of a temperature sensor, and the flow volume of the cooling water which passes a heat exchanger is adjusted. Thereby, the ammonia-containing vapor having a predetermined high concentration (for example, 20 wt% or more) is obtained by cooling and spraying the stored liquid (condensate of the low-boiling substance-containing vapor) stored at the bottom of the concentration tower to a predetermined temperature. Can be generated.

  According to a fourth aspect of the present invention, there is provided the low boiling point substance recovery apparatus according to the first aspect, wherein the compression device is configured by connecting a plurality of vapor compressors in parallel.

  A fifth aspect of the present invention is the low boiling point substance recovery apparatus according to any one of the first to fourth aspects, wherein the low boiling point substance is ammonia.

  The invention according to claim 6 is a method for recovering a low-boiling substance, wherein steam for heating is blown into a distillation column, the steam for heating is brought into contact with a stock solution containing the low-boiling substance, and the low-boiling substance is separated from the stock solution. A first step of gasifying and discharging a low-boiling-point substance-containing vapor from the top of the distillation column and storing treated water from which the low-boiling point substance has been removed from the stock solution at the bottom of the distillation column; By exchanging heat between the steam containing the low-boiling substance discharged from the top and water, the steam containing the low-boiling substance is condensed by condensing the steam containing the low-boiling substance, and the water is evaporated. And the second step of discharging the steam as steam, the steam discharged from the evaporator is compressed and heated, the compressed and heated steam is guided to the distillation tower, and used as heating steam used in the distillation tower Third step and the evaporation In partial condensation uptake vapor containing low-boiling substances subsequent, characterized by comprising a fourth step of further concentrating the vapor containing low-boiling substances by cooling the steam to remove water, the.

  According to the above configuration, a low-boiling substance recovery method that can recover a low-boiling substance at a high concentration and save energy is constructed.

  According to the present invention, low-boiling substances can be recovered at a high concentration, and energy saving can be achieved.

1 is an overall configuration diagram of an ammonia recovery device according to an embodiment. An enlarged view of the vicinity of the evaporator. The enlarged view near the concentrating tower.

  Hereinafter, the present invention will be described in detail based on embodiments. In the following embodiment, the low boiling point substance recovery device will be described by exemplifying an ammonia recovery device that uses ammonia-containing wastewater as a stock solution and separates and removes ammonia from the ammonia-containing wastewater. As a low boiling point substance, in addition to ammonia, it can also be applied to alcohols such as methanol, ketones such as acetone, and esters such as methyl acetate.

(Embodiment)
FIG. 1 is an overall configuration diagram of an ammonia recovery apparatus according to an embodiment. An ammonia recovery device (corresponding to the low boiling point material recovery device of the present invention) 1 includes a distillation column 2 for performing steam stripping by blowing steam for heating, an ammonia-containing vapor and water discharged from the top of the distillation column 2 3 that exchanges heat with water, evaporates the water, compresses the water vapor discharged from the evaporator 3, compresses and heats it to the distillation tower 2 as heating water vapor, and ammonia concentrated in the evaporator 3 Concentrated tower 5 that takes in the contained steam, cools the steam to remove moisture, and raises the concentration of ammonia-containing steam to a high concentration (for example, 20 wt% or more), and absorbs moisture in the ammonia-containing steam from the concentrated tower 5 A first absorption tower 6 that generates recovered ammonia water of a predetermined concentration, and a second absorption tower 7 that prevents uncondensed ammonia-containing vapor in the first absorption tower from being discharged to the outside. Here, the outline of the characteristics of the ammonia recovery device 1 according to the first embodiment will be described. The evaporator 3 and the concentrating tower 5 disposed at the rear stage of the evaporator 3 are provided and discharged from the distillation tower 2. The ammonia-containing vapor is configured so that ammonia water having a predetermined high concentration (for example, 20 wt% or more) can be recovered by two-stage concentration by the evaporator 3 and the concentration tower 5.

Hereinafter, a specific configuration of the ammonia recovery apparatus 1 including the above-described characteristic configuration will be described.
The distillation column 2 may be a multi-stage one, and is not limited to this, and a non-multi-stage one may be used. That is, for the distillation tower 2, a plate tower or a packed tower can be used. The stock solution (ammonia-containing wastewater) is supplied to the top of the distillation column 2 via the stock solution supply pipe L1. Note that the pH of the stock solution may be adjusted in advance.

  The steam for heating from the steam ejector 10 is supplied to the bottom of the distillation column 2 via the heating steam supply pipe L3. The bottom of the distillation column 2 is connected to the heat recovery tank 11 via a pipe L4 so that the stored liquid (low concentration ammonia water) at the bottom of the tower is supplied to the heat recovery tank 11 via a pipe L2. It has become. The steam ejector 10 is a steam compression means for sucking and compressing steam, and a steam supply pipe L5 through which steam supplied from a high-pressure steam source (not shown) such as a boiler circulates and the heat on the steam suction side 10a. A steam reuse pipe L6 extending from the recovery tank 11 is connected. With such a configuration, the stored liquid in the heat recovery tank 11 is flash-evaporated and sucked and compressed by the steam ejector 10 and mixed with the steam from the steam supply pipe L5 to be heated to the bottom of the distillation column 2 as steam. Be blown into. As described above, the stored liquid in the heat recovery tank 11 is flash-evaporated and reused as a part of the steam for heating, and heat is recovered.

A discharge pipe L7 for discharging treated water (for example, low-concentration ammonia water of 30 ppm or less) is connected to the bottom of the heat recovery tank 11. On the discharge pipe L7, a treated water discharge pump P1, And three heat exchangers H1, H2 and H3 are provided. The heat exchanger H1 is a water heater that heats water by exchanging heat between water and treated water. The water heated by the heat exchanger H1 is supplied to the bottom of the evaporator 3 through the water supply pipe L8. The heat exchanger H2 is a stock solution preheater that heats the stock solution by exchanging heat between the stock solution and treated water. The stock solution preheated by the heat exchanger H2 is supplied to the top of the distillation column 2 via the stock solution supply pipe L1. The heat exchanger H3 is a cooler that performs heat exchange between the cooling water and the treated water to cool the treated water. The treated water cooled by the heat exchanger H3 is discharged out of the system through the discharge pipe L7.
The heat exchangers H1, H2, and H3 are located on the downstream side of the treated water discharge pump P1 on the discharge pipe L7, and are installed in the following order. That is, on the exhaust pipe L7, the heat exchanger H1 is installed on the upstream side of the heat exchanger H2. By installing in this order, the amount of heat given from the treated water to the water becomes the largest, and thus energy saving is achieved in the evaporator 3 that heats the water. Moreover, since the reason for installing the heat exchanger H3 is to cool the treated water, the heat exchanger H3 is installed downstream of the heat exchangers H1 and H2.

  The evaporator 3 includes a horizontal tube evaporator 12 and includes a spreader 13 and an indirect heater 14. Note that the evaporator is not limited to the horizontal tube type, and for example, an evaporator such as a thin film flow (vertical tube) type may be used. As shown in FIG. 2, the indirect heater 14 includes a heat transfer tube group 15 including one or a plurality of horizontal heat transfer tubes, and a pair of left and right headers 16A and 16B. Further, the bottom of the evaporator 12 serves as a storage part 17 for storing water supplied via the pipe L8. The stored liquid (water) in the storage unit 17 is supplied to the spreader 13 provided in the upper part of the evaporator 12 through the pipe L9 by the circulation pump P2, and from the spreader 13 to the outer surface of the heat transfer tube group 15. After spraying in the direction of circulation, it is configured to circulate such that it flows down to the lower storage portion 17 in the evaporator 12.

The header 16B is connected to the top of the distillation tower 2 via a steam supply pipe L10, and the top steam (ammonia-containing steam) discharged from the top of the distillation tower 2 passes through the steam supply pipe L10. 16B, and further circulates in the heat transfer tube group 15. Here, the evaporator 3 has a pressure lower than the pressure of the top vapor, and therefore, the circulating liquid (water) sprayed by the sprayer 13 evaporates into a thin film on the surface of the heat transfer tube group 15, and the water vapor Will occur. This water vapor is supplied to the compressor 4. Here, the principle of vaporizing water in the evaporator 3 will be described in more detail. In the evaporator 3, the pressure outside the heat transfer tube where the water to be heated is present from the tower top steam (inside the heat transfer tube) serving as a heating source. Since it is low, water evaporates. The pressure difference is generated by the compressor 4 (specifically, the steam compressors 18 and 19). This is because the outside of the evaporator heat transfer tube connected to the suction side of the compression device 4 is low, and the pressure in the distillation column 2 connected to the discharge side of the compression device 4 and thus the top vapor is high. In addition, the steam supplied from the steam ejector 10 also increases the pressure in the distillation column 2 and contributes to the evaporation of water in the evaporator 3.
The condensed water (low-concentration ammonia water) condensed through circulation in the heat transfer tube group 15 is stored in the header 16A, and the top of the distillation column 2 is supplied as a reflux liquid via the tube L11 by driving the condensed water pump P3. Returned to The remaining surplus steam (concentrated ammonia-containing steam) is discharged to the top of the concentrating tower 5 via the pipe L12.

  The compressor 4 includes two steam compressors 18 and 19, and these steam compressors 18 and 19 are configured by connecting the bottom of the distillation column 2 and the top of the evaporator 10 in parallel. That is, the inlet side 18a of the vapor compressor 18 is connected to the upper portion of the evaporator 12 via a pipe L15, and the outlet side 18b of the vapor compressor 18 is connected to the bottom of the distillation column 2 via a pipe L15. . The inlet side 19a of the vapor compressor 19 is connected to the upper portion of the evaporator 10 via a branch pipe L17 branched from the pipe L5, and the outlet side 19b of the vapor compressor 19 is connected to the bottom of the distillation column 2 via a pipe L18. It is connected.

  Here, as the steam compressors 18 and 19, Roots type steam compressors having a large maximum differential pressure are used. However, in the present invention, not only a roots-type steam compressor but also a turbo-type steam compressor, a screw-type steam compressor, a vane-type steam compressor, or other steam compressors may be used. Further, in the present embodiment, the compression device 4 is composed of two steam compressors 18 and 19, but may be composed of one steam compressor or three or more steam compressors.

  The concentration tower 5 is composed of a spray-type scrubber. The stored liquid (condensate) stored at the bottom of the concentrating tower 5 flows through a spray pipe (corresponding to the circulation line of the present invention) L20, is guided to the top of the tower, and is sprayed toward the top of the tower. It has become. In the middle of the spray pipe L20, a circulation pump P4 and a heat exchanger H4 are provided. The stored liquid flowing through the spray pipe L20 is heat-exchanged with cooling water in the heat exchanger H4 and cooled. As shown in FIG. 3, a control valve V <b> 1 is provided in the pipe L <b> 21 through which the cooling water flows, and the opening degree is controlled by a temperature sensor T that detects the temperature of the stored liquid stored in the bottom of the concentration tower 5. Yes. That is, the opening degree of the control valve V1 is controlled according to the detection result of the temperature sensor T, and the flow rate of the cooling water passing through the heat exchanger H4 is adjusted. Thereby, the ammonia-containing vapor | steam of predetermined | prescribed high concentration (for example, 20 wt% or more) can be produced | generated by cooling and spraying a stored liquid (condensate) to predetermined temperature.

  Further, as shown in FIG. 2, the spray pipe L <b> 20 branches in the middle, and the branched branch pipe L <b> 22 is connected to the top of the distillation column 2. A control valve V2 is provided in the middle of the branch pipe L22. Further, as shown in FIG. 2, the concentration tower 5 is provided with a liquid level sensor S1 for detecting the liquid level of the stored liquid. The liquid level sensor S includes a level switch S1a that detects an upper limit setting level and a level switch S1b that detects a lower limit setting level. The opening level of the control valve V2 is controlled by the liquid level sensor S1, the stored liquid is maintained at a predetermined liquid level, and the stored liquid that has overflowed the predetermined liquid level is returned to the top of the distillation column 2. It has become.

  The first absorption tower 6 is composed of a spray-type scrubber similar to the concentrating tower 5, and a circulation pipe P5 and a heat exchanger H5 are provided in a spray pipe L23 through which the liquid stored in the first absorption tower 6 circulates. Is provided. In the heat exchanger H5, heat is exchanged between the stored liquid flowing through the spray pipe L23 and the cooling water, and the stored liquid is cooled. The cooled storage liquid is sprayed onto the ammonia-containing vapor having a high concentration (for example, 20 wt% or more) taken from the concentrating tower 5 through the pipe L24, thereby condensing and collecting the ammonia-containing vapor, and collecting the recovered ammonia water. Generate. The spray pipe L23 is branched in the middle, and the recovered ammonia water is discharged out of the system through the branched branch pipe L25.

The second absorption tower 7 is composed of a spray-type scrubber similar to the first absorption tower 6, and water is supplied to the tower bottom of the second absorption tower 7 via a pipe L 30 and stored in the tower bottom. The water is sprayed from the top of the tower through the spray pipe L31 by driving the circulation pump P6. Between the first absorption tower 6 and the second absorption tower 7, a pipe L 32 that guides the uncondensed ammonia-containing vapor in the first absorption tower 6 to the top of the second absorption tower 7, and the second absorption tower 7 And a pipe L33 for returning the condensed water to the first absorption tower 6. Further, an exhaust pipe L34 for exhausting the vapor from which ammonium has been removed is provided at the top of the second absorption tower 7.
1 to 3, L40 is a cooling water supply pipe, L41 is a pipe branched from the cooling water supply pipe L40, L21 is a pipe branched from the cooling water supply pipe L40, and on the cooling water supply pipe L40, A heat exchanger H5 is provided, a heat exchanger H2 is provided on the tube L41, and a heat exchanger H4 is provided on the tube L21.

  Next, the processing operation of the ammonia recovery apparatus 1 configured as described above will be described. In the distillation column 2, steam for heating is blown and steam stripping is performed. That is, in the distillation tower 2, the raw solution is brought into contact with steam for heating, ammonia is separated from the raw solution, gasified, discharged from the top of the tower as vapor containing ammonia, and low-concentration aqueous ammonia from which ammonia has been removed from the raw solution (for example, 30 ppm or less) is stored in the tower bottom as treated water.

  The ammonia-containing steam discharged from the top of the distillation column 2 is led to the header 16B through the steam supply pipe L10, and further circulates in the heat transfer tube group 15, thereby being circulated by the sprayer 13. The liquid (water) evaporates in a thin film on the surface of the heat transfer tube group 15, and water vapor is generated. This water vapor is supplied to the vapor compressors 18 and 19. On the other hand, the condensed water (low-concentration ammonia water) condensed through circulation in the heat transfer tube group 15 is stored in the header 16A and returned to the top of the distillation column 2 as a reflux liquid via the tube L11, and the remaining surplus steam. The (concentrated ammonia-containing vapor) is supplied to the concentration tower 5 through the pipe L12.

  In the vapor compressors 18 and 19, the supplied water vapor is compressed and heated and heated to the bottom of the distillation column 2 as water vapor for heating. Thereby, the steam for heating supplied from the steam supply pipe L3 for heating can be reduced, and energy saving can be achieved.

  On the other hand, in the concentration tower 5, the opening degree of the control valve V1 is controlled according to the detection result of the temperature sensor T, and the flow rate of the cooling water passing through the heat exchanger H4 is adjusted. As a result, the storage liquid (condensate) cooled to a predetermined temperature is sprayed from the top of the concentrating tower 5 and the ammonia-containing vapor is partially condensed, so that the ammonia-containing vapor having a predetermined high concentration (for example, 20 wt% or more) is produced. Generated. The total amount of the condensed liquid is returned to the top of the distillation column 2 as a reflux liquid. Thus, the concentration tower 5 takes in the ammonia-containing vapor that has been partially condensed by the evaporator 3, removes moisture, and further concentrates the vapor containing ammonia, so that the evaporator 3 alone has a predetermined high concentration ( For example, the load of the steam compressors 18 and 19 can be prevented from becoming too large as compared with a configuration in which the concentration is increased to 20 wt% or more. As a result, energy saving can be achieved, and ammonia-containing vapor having a high concentration (for example, 20 wt% or more) can be generated.

  Next, in the first absorption tower 6, the ammonia-containing vapor introduced from the concentration tower 5 through the pipe L <b> 24 is condensed by the configuration in which the stored liquid at the bottom of the tower is sprayed from the top of the tower through the spray pipe L <b> 23. Ammonia recovered water containing high concentration of ammonia (recovered ammonia water) is generated. In the second absorption tower 7, uncondensed ammonia gas slightly remaining in the first absorption tower 6 is guided through the pipe L32, and water supplied from outside the system is sprayed from the top of the tower through the spray pipe L31. With this configuration, uncondensed ammonia gas is absorbed. The water that has absorbed ammonia is returned to the condensate in the first absorption tower 6. As a result, uncondensed ammonia gas is prevented from being discharged to the outside. The gas from which ammonia has been removed is exhausted from the exhaust pipe L34.

(Other matters)
(1) Although the above embodiment has been described as a configuration in which “water” is supplied to the evaporator 3 and the second absorption tower 7, this “water” specifically includes pure water, soft water, and ion-exchanged water. Etc. can be applied.

  (2) For reference, in the case of a configuration in which the distillation column vapor is directly compressed and used as a heat source for the distillation column (for example, Patent Document 1), the distillation column vapor is directly compressed. There is a possibility of corrosion due to contained substances and corrosion or leakage at the seal part. On the other hand, in the case of a configuration in which water is evaporated with an evaporator as in the present invention and used directly in the distillation column, the steam (steam) used directly in the distillation column does not contain contained substances, so Corrosion and leakage due to substances can be prevented.

  The present invention can be applied to a recovery apparatus and a recovery method for separating and recovering low-boiling substances from waste water containing low-boiling substances such as ammonia.

1: Ammonia recovery unit 2: Distillation column 3: Evaporator 4: Compression unit 5: Concentration column 6: First absorption column 7: Second absorption column 18, 19: Steam compressor

Claims (6)

A process in which a raw solution containing a low-boiling substance is brought into contact with heating steam, the low-boiling substance is separated from the raw solution, gasified, discharged from the top of the tower as a vapor containing a low-boiling substance, and the low-boiling substance is removed from the raw solution A distillation tower for storing water at the bottom of the tower;
Heat exchange between the steam containing the low boiling point substance discharged from the top of the distillation column and water, thereby condensing the steam containing the low boiling point substance and condensing the steam containing the low boiling point substance; and An evaporator that evaporates the water and discharges it as water vapor;
A compression device that compresses and raises the steam discharged from the evaporator, guides the steam that has been compressed and heated to the distillation tower, and uses it as steam for heating used in the distillation tower;
A condensing tower that takes in the vapor containing the low-boiling substance after partial condensation in the evaporator, cools the vapor to remove moisture, and further concentrates the vapor containing the low-boiling substance;
An apparatus for recovering low-boiling substances characterized by comprising:   A preheater is provided in the middle of a discharge line for discharging treated water stored at the bottom of the distillation column to the outside, and heats the water used in the evaporator by exchanging heat with the treated water in advance. The apparatus for recovering low-boiling substances according to claim 1. A heat exchanger that is provided in the middle of a circulation line that guides the stored liquid stored in the tower bottom of the concentrating tower to the tower top, heat-exchanges the stored liquid flowing through the circulation line with cooling water, and cools the stored liquid;
A temperature sensor for detecting the temperature of the stored liquid stored in the bottom of the concentration tower;
A control valve for adjusting a flow rate of cooling water passing through the heat exchanger according to a detection result of the temperature sensor;
The low boiling point substance recovery device according to claim 1, comprising:   The low-boiling-point substance recovery apparatus according to claim 1, wherein the compression apparatus is configured by connecting a plurality of vapor compressors in parallel.   The low boiling point substance recovery apparatus according to any one of claims 1 to 4, wherein the low boiling point substance is ammonia. Steam for heating is blown into the distillation tower, the steam for heating is brought into contact with the raw solution containing low-boiling substances, the low-boiling substances are separated from the raw solution, gasified, and discharged from the top of the distillation tower as vapor containing low-boiling substances. And a first step of storing the treated water from which the low-boiling substances have been removed from the stock solution at the bottom of the distillation tower,
Heat exchange between the steam containing the low boiling point substance discharged from the top of the distillation column and water, thereby condensing the steam containing the low boiling point substance and condensing the steam containing the low boiling point substance; and A second step of evaporating the water and discharging it as water vapor;
A third step of compressing and heating the steam discharged from the evaporator, introducing the compressed and heated steam to the distillation tower, and utilizing the steam as heating steam used in the distillation tower;
A fourth step of taking in the vapor containing the low-boiling point substance after partial condensation in the evaporator, cooling the vapor to remove moisture, and further concentrating the vapor containing the low-boiling point substance;
A method for recovering a low-boiling substance, comprising:

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