JPH10118402A - Method for concentrating liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a device and to reduce the cost of equipment and running cost by introducing condensate into a preheater from a condensate tank for invariably controlling the height of condensate level of vapor in the outside of a heat transfer pipe and pulling out concentrate from the tower bottom of an evaporator in accordance with a signal showing the height of liquid level in the evaporator and sending the concentrate to a storage tank thereof. SOLUTION: Vapor generated in a concentrator 8 is compressed by a screw type compressor 10 through a line 9 and temperature rise is performed. Obtained compressed vapor is supplied to the outside of the heat transfer pipe of the concentrator 8 through lines 11, 25 and heats liquid in the heat transfer pipe to evaporate the liquid. Thereby, vapor itself in the outside of the heat transfer pipe is condensed and liquefied. Condensate is stored in a condensate tank 13 through a line 12 from the lower part of the concentrator 8. To prevent loss of noncondensed vapor caused by discharge to the outside of the system, the liquid level of the condensate tank 13 is controlled so as to be held higher than the position of the line 12 for taking out condensate from the concentrator 8 to the condensate tank 13. Condensate is sent from a line 15 to a preheater 5 and herein heat-exchanged for waste water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to the concentration of various liquids,
Regarding the improvement of the vapor compression type concentrating technology suitable for distillation, etc., more specifically, when concentrating the stock solution by evaporating the water in the stock solution, the generated steam from the stock solution is compressed and heated by a compressor. And a liquid concentrating method utilizing the undiluted solution as a heat source for evaporating the undiluted solution.

[0002]

2. Description of the Related Art For example, a conventional vapor-compression evaporator shown in the drawings of Japanese Patent Application Laid-Open No. 59-26184 discloses a closed evaporator having a stock solution chamber at the bottom. A number of heat transfer tubes are provided at the top of the heat transfer tube, and on the outer surface of each heat transfer tube,
The undiluted solution sent by the undiluted solution pump is evaporated by spraying with a sprayer, and the steam generated by the evaporation is compressed by a blower compressor to increase the temperature. By supplying into each heat transfer tube, the stock solution sprayed on the outer surface of each heat transfer tube is heated and evaporated, and a non-condensable gas such as air is blown from each heat transfer tube into a vacuum generating means such as a vacuum pump. The pressure in the evaporator is maintained at a pressure lower than the atmospheric pressure.

However, this type of vapor compression type evaporator has the following problems.

[0004] b. The compression efficiency of the blower compressor body is low, the amount of power required to compress the unit stock solution increases, the operating cost increases, and the equipment increases.

[0005] b. Since the undiluted solution is sprayed on the outer surface of each heat transfer tube via the sprayer, there is a reduction in the heat transfer coefficient of the heat exchanger caused by poor liquid dispersion.

C. Effective for reducing the heat transfer coefficient due to clogging and poor dispersion due to sludge at the nozzle of the liquid disperser, contamination of the outer surface of each heat transfer tube, increase in liquid specific gravity or viscosity, etc. due to increase in the concentration ratio of the stock solution or continuous operation. Can not deal with.

In addition, it is often difficult to remove scale attached to the outer surface of each tube because the liquid is dispersed and the liquid flow velocity to the outer surface of the heat transfer tube is slow.

D. As a result of the above b and c, the concentration process
It must be carried out in a state where the evaporation amount per unit sectional area is always low. Therefore, in order to increase the amount of evaporation per unit time, the heat transfer area must be increased, or a blower compressor having a high compression ratio must be used. However, there is a problem that the bulk increases.

E. In addition, depending on the type of the stock solution, foaming may occur during the concentration process, and the stock solution may be scattered on the generated steam side, making it impossible to continue the operation.

[0010]

SUMMARY OF THE INVENTION Accordingly, the present invention is to provide a vapor compression type enrichment technology which is small in size and inexpensive in equipment and operation costs by eliminating or alleviating the problems of the prior art as described above. Its main purpose is to:

[0011]

Means for Solving the Problems The present inventor has conducted intensive studies in view of the state of the art as described above, and as a result, by using a screw compressor to compress steam generated in a concentrator, A new liquid concentration technology has been completed.

That is, the present invention provides the following liquid concentrating method.

1. In a liquid concentration method using a calandria type evaporator, (1) heat exchange is performed between a stock solution and a condensate of vapor from the outside of a heat transfer tube in an evaporator in a preheater,
A step of preheating the undiluted solution, (2) a step of introducing the preheated undiluted solution into the liquid between the liquid surface in the evaporator and the heat transfer tube, and (3)
The steam generated in the evaporator is compressed by a screw compressor.
(4) supplying the obtained compressed steam to the outside of the heat transfer tube to heat and evaporate the liquid in the heat transfer tube;
(5) a step of introducing condensate from a condensate tank to a preheater for controlling the condensate level of the vapor outside the heat transfer tube to a constant level; and (6) a signal indicating the level of the liquid level in the evaporator. 3. A method for concentrating a liquid, comprising the steps of: extracting a concentrated liquid from the bottom of an evaporator in accordance with the method (1) and sending the concentrated liquid to a concentrated liquid storage tank.

2. Item 2. The liquid concentrating method according to Item 1, wherein the preheater in the step (1) is a plate heat exchanger.

3. Item 2. The liquid concentrating method according to the above item 1, wherein a back pressure valve is provided in the stock solution introduction line in the step (2).

4. 2. The liquid concentrating method according to the above item 1, wherein in the step (2), the bottom liquid of the evaporator tower is withdrawn by a pump in order to adjust the liquid level in the evaporator and circulated to a line for introducing a stock solution.

5. Item 2. The liquid concentrating method according to the above item 1, wherein the motor rotation speed of the screw compressor in the step (3) is controlled by an inverter device.

6. Item 6. The liquid concentrating method according to the above item 5, wherein in the step (3), the number of revolutions of the motor of the screw compressor is controlled in accordance with the amount of vapor generated in the evaporator.

[7] 2. The liquid concentrating method according to the above item 1, wherein in the step (3), a plurality of screw compressors are provided according to the amount of vapor.

8. Item 2. The liquid concentrating method according to the above item 1, wherein the upper gas phase portion of the condensate tank in the step (5) is connected to a vapor line outside the heat transfer tube.

9. Item 2. The liquid concentrating method according to Item 1, wherein an electromagnetic valve for periodically discharging the non-condensable gas in the evaporator is provided in the vapor line outside the heat transfer tube.

10. Item 2. The liquid concentrating method according to Item 1, wherein the operating pressure in the evaporator is normal pressure or reduced pressure.

11. Item 11. The liquid concentrating method according to Item 10, wherein a vacuum pump is provided on the downstream side of the electromagnetic valve of the steam line outside the heat transfer tube, the vacuum pump interlocking with the opening and closing of the electromagnetic valve during the decompression operation.

12. Item 2. The auxiliary heat source is introduced into the bottom of the evaporator or the outlet line of the compressor in order to cope with a decrease in the amount of evaporation due to fouling of the preheater and / or the heat transfer tube in the evaporator during start-up or long-term operation. Liquid concentration method.

13. Item 13. The liquid concentrating method according to Item 12, wherein the auxiliary heat source is steam.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The compressor used in the present invention is a screw type compressor which has not been used in the conventional concentration technology, and has the following characteristics.

A. High pressure and high efficiency operation is possible from low speed rotation.

B. Has high responsiveness.

C. Small, compact and easy to install.

D. The motor rotation speed of the screw compressor can be controlled according to the amount of generated steam.

The screw type compressor used in the present invention comprises:
It usually has a structure in which a pair of male and female cylinders are built in a casing part made of aluminum alloy.

When a screw-type compressor having the above-mentioned structure and exerting its effects is used, the cost of equipment and operation is significantly lower than when a conventional compressor is used. Become.

The screw type compressor used in the present invention comprises:
As an example, high characteristics such as a maximum discharge pressure of 160 kPa, a maximum allowable discharge temperature of 160 ° C., a maximum intake air amount of 760 m ³ / hr (in air conversion), and a compression ratio of about 2.3 can be exhibited.

The compression ratio limit of a conventional roots blower as a compressor is about 1.8, and the total adiabatic efficiency is about 45 to 60%, whereas the screw type compressor has a total adiabatic efficiency of about 1.5 at a compression ratio of 1.5. High performance of about 65% and about 70% with a compression ratio of 2 to 2.3 can be achieved.

In order to reduce the thermal expansion and the required clearance, the rotor of the screw type compressor is preferably made of an aluminum alloy having a small expansion coefficient.
A fluororesin (for example, commercially available from DuPont under the trade name “Teflon”)-based coating material is applied to the surface of the rotor. The compressor, depending on the amount of steam generated,
A plurality can be provided.

Conventionally, it has been difficult in terms of control of the compressor to perform suction and discharge by the compressor in accordance with the amount of generated steam, and to efficiently perform evaporation in the evaporator. In the present invention, a motor composed of a high-speed rotation type induction motor is used as a drive source of the compressor, and an inverter device is used as a rotation speed control mechanism of the motor. That is, the amount of steam generation is detected by an orifice type flow meter, a float type flow meter, etc. provided on the upstream side of the compressor, and this input signal is sent to the controller, and the output signal from this controller is input to the inverter. The amount of generated steam can be made constant, or the number of revolutions of the motor can be increased or decreased in accordance with the amount of generated steam. As a result, the entire apparatus is simplified, and control at the time of starting or the like becomes easy.

In the present invention, a plate-type heat exchanger can be used for preheating the stock solution in order to reduce the size and cost of the apparatus. By making the pressure in this preheater and the stock solution introduction line higher than the pressure in the evaporator,
A back pressure valve is provided on the preheater outlet (calandria evaporator inlet) side to prevent a decrease in the heat transfer coefficient due to the formation of bubbles in the preheater.

When the stock solution contains a component (such as a surfactant) that may cause foaming under the concentration condition, a silicone-based antifoaming agent may be added in advance.
The addition amount of the defoaming agent may be determined in consideration of the content of the foaming component and the like, and is not particularly limited.
About 500 mg / l.

In the calandria type evaporator used in the present invention, the calandria type evaporator is used in order to prevent the heat transfer coefficient from being reduced due to poor liquid dispersion, which is caused by the prior art.
It is preferable to introduce the liquid at a position about 15 to 50% from above the liquid depth from the inner liquid level to the upper part of the heat transfer tube (hereinafter sometimes simply referred to as "calandria"). Thus, the liquid
While being constantly held in the heat transfer tube, it is heated and evaporated by the compressed steam outside the heat transfer tube. In the conventional liquid supply method, foaming may be promoted, and as a result, concentration processing may not be performed. However, in the method of the present invention, problems such as a reduction in flow rate due to the dispersion of the liquid and promotion of foaming are as follows.
Will be resolved.

If necessary, the bottom liquid in the calandria is withdrawn by a pump and circulated to the undiluted liquid introduction position, thereby increasing the liquid flow velocity in the heat transfer tube and increasing the heat transfer coefficient.

The vapor outside the heat transfer tube heats the liquid inside the heat transfer tube, evaporates, and then condenses. In the present invention, a condensed liquid tank is provided in order to keep the condensed liquid level of the vapor outside the heat transfer tube constant, thereby preventing loss due to discharge of the compressed vapor to the outside of the system. The liquid in the condensed liquid tank is discharged from the liquid level control valve via the preheater to the outside of the system, and is reused or discharged. The connection between the upper gas phase portion of the condensate tank and the vapor line outside the heat transfer tube stably controls the liquid level in the condensate tank.

A non-condensable gas such as air in the calandria that affects the efficiency and power consumption of the compressor is discharged out of the calandria by opening and closing a solenoid valve provided in a steam line outside the heat transfer tube. Exhaust gas is released into the atmosphere after removal of a predetermined component by activated carbon adsorption or the like, if necessary, or after bubbling the liquid in the concentrated solution tank to absorb and remove the predetermined component, in accordance with the components in the gas. Released.
Alternatively, in a gas-fired boiler for generating steam as an auxiliary heat source to be described later, it is mixed with air and burned. The opening and closing of the solenoid valve is automatically performed by a method linked with the pressure in the calandria or by setting an arbitrary timer.

The concentrated liquid is discharged from the bottom of the column through a control valve upon receiving a signal from the liquid level gauge in the concentrator.

When the operating pressure in the calandria is a pressure reducing system, a vacuum pump is provided on the downstream side of the solenoid valve provided in the steam line outside the heat transfer tube in conjunction with the opening and closing of the solenoid valve.

If necessary, an auxiliary heat source (such as steam from a gas-fired boiler) is used to raise the temperature of the entire system at start-up, or to reduce the amount of evaporation due to contamination of the preheater or calandria heat transfer tube after long-term operation. ) Is introduced into the calandria inner bottom or the compressor outlet line.

Hereinafter, the present invention will be described in more detail with reference to the drawings. In the following, the concentration of wastewater will be described, but as described above, it goes without saying that the present invention can be applied to the concentration of other liquids.

FIG. 1 is a flow sheet showing an example of the wastewater concentration process according to the present invention. The wastewater to be concentrated is heated from a wastewater tank 1 through a line 2 to a predetermined pressure in a wastewater pump 3 and then sent to a preheater 5 from a line 4 where it is condensed with a condensate from a line 15 described later. Heat exchanged. If the wastewater contains a foaming component, a defoamer can be added from the defoamer tank 27.

The liquid exiting the preheater 5 is supplied from the line 6 to the concentrator.
(Calandria-type evaporator) 8. By providing the back pressure valve 7 between the preheater 5 and the concentrator 8, the preheater 5
Since the internal pressure in the inside or in the line 6 can be higher than the pressure in the concentrator 8, the generation of bubbles in the preheater 5 can be prevented, and the decrease in the heat transfer coefficient can be prevented. Back pressure valve 7
Of the liquid from the liquid level in the concentrator 8 to the upper part of the heat transfer tube at a position of 15 to 50% (position downward from the liquid level)
At the concentrator.

The steam generated in the concentrator 8 is compressed by a screw compressor 10 via a line 9 and is heated.
As described above, it is preferable to use a screw-type compressor in which a pair of male and female rotors are built in an aluminum alloy casing. The obtained compressed steam is supplied to the outside of the heat transfer tube of the concentrator 8 via the lines 11 and 25, and heats and evaporates the liquid in the heat transfer tube. Thereby, the steam itself outside the heat transfer tube is condensed and liquefied. The condensate is stored in the condensate tank 13 via the line 12 from the lower part of the heat transfer tube 8.

Discharge of uncondensed vapor outside the system (line 14 →
In order to prevent loss due to line 19 → solenoid valve 20 → line 21), the liquid level in condensate tank 13 is higher than the position of condensate removal line 12 from concentrator 8 to condensate tank 13. Control. The condensate is sent from line 15 to preheater 5 where it exchanges heat with wastewater, passes through a liquid level control valve (not shown) on line 16 and is sent to condensate tank 17 for reuse. Or is released.

The vapor phase of the condensate tank 13 is connected via a line 14 to a steam line 19 outside the heat transfer tube.

A non-condensable gas such as air in the concentrator 8 which affects the efficiency and power consumption of the compressor 10 is discharged to the outside of the evaporator by opening and closing a solenoid valve 20 provided in a steam line 19 outside the heat transfer tube. Is discharged. The opening and closing of this solenoid valve 20
It may be performed by interlocking with the pressure in the concentrator 8,
Alternatively, it may be performed automatically by setting a timer. If necessary, the exhaust gas is subjected to an adsorption treatment using activated carbon or the like, or is bubbled in the liquid in the concentrated liquid tank 17.

The concentrated liquid in the concentrator 8 is supplied to the concentrated liquid tank through a lower line 21 of the concentrator 8 and a control valve (not shown) in accordance with a signal from a liquid level gauge (not shown) in the concentrator 8. It is discharged to 22.

If necessary, the liquid in the condenser 8 is drawn out from the liquid draw-out line 21 by a circulation pump (not shown) and circulated to the stock solution line 6 to increase the liquid flow rate in the heat transfer tube. When the operating pressure in the concentrator 8 is a pressure reducing system, a vacuum pump (not shown) is provided on the downstream side of the solenoid valve 20 in conjunction with opening and closing of the solenoid valve 20. . When operating in a reduced pressure system, it is necessary to provide a condensate pump (not shown) on line 16 and a concentrate pump (not shown) on line 21.

In addition, if necessary, for the purpose of heating / heating at the time of start-up, or after the long-term operation, the evaporation amount due to contamination of the heat transfer tubes of the preheater 5 and the concentrator 8 is reduced.
As an auxiliary heat source, for example, steam from a gas-fired boiler 23 is introduced via line 24, from line 25, or from line 26 via line 25.

If contamination of the heat transfer tubes of the preheater 5 and the concentrator 8 and a decrease in the heat transfer coefficient associated with the contamination occur, the supply of the waste water is temporarily interrupted during the operation, and the industrial water is supplied. By doing so, dirt can be washed and removed.

The present invention is directed to, for example, concentrating and reducing the volume of various industrial wastewaters, washing wastewaters, photographic developing solutions, fixing solutions, washing wastewaters, etc., separating and separating useful components or impurities in stock solutions,
It can be used in a wide range of fields, such as the concentration of solutions (dashi, juice, milk, etc.) in the food industry. The present invention can be used in other fields, and is not limited to use in the fields exemplified here.

[0058]

According to the method of the present invention, the following remarkable effects are achieved.

(1) As compared with the prior art, the process of concentrating the undiluted solution is simpler and the equipment is downsized, so that the equipment cost and
Operating costs are reduced.

(2) Continuous and stable operation is possible.

(3) Foaming in the concentration treatment can be suppressed.

[0062]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

Example 1 The method of the present invention was carried out according to the flow shown in FIG. That is, plating plant wastewater (copper ion concentration 5100mg / l, specific gravity 1.
01) was used as a stock solution and concentrated under normal pressure under the conditions shown in Table 1.

[0064]

[Table 1]

The power used in this embodiment is 24.7 kw
h / m ³ and the amount of city gas used to generate steam as an auxiliary heat source in the gas-fired boiler is 2.3 Nm ³ / m ³
Met. As a result, operating costs in the method of the present invention are:
About the operating cost in the prior art described in JP-A-59-26184
The cost was reduced by a factor of four. Further, the concentration treatment according to the method of the present invention could be stably continued.

Table 2 shows the specific gravity, copper ion concentration and the like of the concentrated solution obtained after the lapse of a predetermined time.

[0067]

[Table 2]

From the results shown in Table 2, the components in the concentrated solution were:
It is apparent that the copper ions have been transferred to the concentrated liquid in a total amount of about 10 times in about 20 hours after the operation. According to the present invention, these results can control the concentration step of the stock solution by the specific gravity of the concentrated solution that can be easily measured, so that it is not necessary to perform the concentration analysis of the components contained in the liquid, which requires complicated operations. Reveals no. As a result, the cost of treating undiluted liquid such as wastewater is greatly reduced.

Example 2 In accordance with the same method as in Example 1, the plating plant wastewater was concentrated under reduced pressure. Table 3 shows the conditions.

[0070]

[Table 3]

The power consumption for compression was increased about 1.4 times as compared with Example 1, but a more stable concentration treatment was possible. In the present embodiment, the reason for the increase in power consumption is that the specific volume of steam is 1.673 m ³ at 760 mmHg.
Since it is 5.842 m ³ / kg at 200 mmHg, it is because the steam flow rate for compression increases under reduced pressure.

Comparative Example 1 The same copper plating plant wastewater (containing about 3% of a surfactant) as in Example 1 was subjected to a concentration treatment in the same manner as in Example 1. Temperature is about 60 ° C
At the time when it began to exceed the limit. as a result,
The wastewater was discharged from the condenser line through the line 9, the compressor 10, the line 11, the outside of the condenser heat transfer tube, the condensate tank 13, and the preheater 5, and the operation became completely impossible.

Example 3 A silicone-based antifoaming agent was added to the wastewater treated in Comparative Example 1 at a concentration of 200 ppm, and the same treatment as in Example 1 was carried out. Not
Almost the same good processing results as in Example 1 were obtained.

Example 4 In the same manner as in Example 2, photographic wastewater (a mixed waste solution of a developing solution and a fixing solution) was concentrated under reduced pressure. Table 4 shows the conditions.
Shown in

[0075]

[Table 4]

Table 5 below also shows the properties of the wastewater used for the concentration treatment and the properties of the condensate obtained. In addition,
The COD of wastewater and condensate is a value measured by the manganese method.

[0077]

[Table 5]

In this embodiment, the condensate has a water quality that can be discharged without performing secondary treatment. Further, the concentration treatment could be stably continued for a long time.

Example 5 A concentration treatment was performed in the same manner as in Example 1 except that wastewater from an electric equipment manufacturing plant was used as wastewater. The conditions are shown in Table 6, and the properties of the wastewater and the obtained condensate are shown in Table 7.

[0080]

[Table 6]

[0081]

[Table 7]

As is evident from the results shown in Table 7, the condensed water generated at a rate of about 90% of the wastewater can be discharged or reused without performing secondary treatment.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of a wastewater concentration process according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Waste water tank 3 ... Waste water pump 5 ... Preheater 7 ... Back pressure valve 8 ... Concentrator 10 ... Compressor 13 ... Condensate tank 17 ... Condensate tank 20 ... Electromagnetic valve 22 ... Concentrate tank 23 ... Boiler 27 ... Defoaming Liquid tank

Continued on the front page (72) Inventor Kenichi Yamazaki 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka Inside Osaka Gas Co., Ltd. (72) Inventor Tatsuo Kume 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka No. Osaka Gas Co., Ltd.

Claims (13)

[Claims] 1. A liquid condensing method using a calandria type evaporator, wherein (1) a step of preheating the undiluted solution by exchanging heat in a preheater between the undiluted solution and a condensate of vapor from outside the heat transfer tube in the evaporator. (2) a step of introducing the preheated stock solution into the liquid between the liquid level in the evaporator and the heat transfer tube; and (3) a step of compressing and raising the temperature of the vapor generated in the evaporator by the screw compressor. (4) supplying the obtained compressed steam to the outside of the heat transfer tube to heat and evaporate the liquid in the heat transfer tube; and (5) controlling the height of the condensed liquid surface of the steam outside the heat transfer tube to be constant. Introducing the condensed liquid from the condensate tank into the preheater, and (6) extracting the concentrated liquid from the bottom of the evaporator tower in response to the signal indicating the liquid level in the evaporator and sending it to the concentrated liquid storage tank A liquid concentrating method, comprising: 2. The liquid concentrating method according to claim 1, wherein the preheater in the step (1) is a plate heat exchanger. 3. The liquid concentrating method according to claim 1, wherein a back pressure valve is provided in the stock solution introduction line in the step (2). 4. In step (2), the bottom liquid of the evaporator tower is withdrawn by a pump to adjust the level of the liquid in the evaporator.
2. The liquid concentrating method according to claim 1, wherein the liquid is circulated to an undiluted solution introduction line. 5. The liquid concentrating method according to claim 1, wherein the number of revolutions of the motor of the screw compressor in the step (3) is controlled by an inverter device. 6. The liquid concentrating method according to claim 5, wherein, in step (3), the number of revolutions of the motor of the screw compressor is controlled in accordance with the amount of steam generated in the evaporator. 7. The liquid concentrating method according to claim 1, wherein in the step (3), a plurality of screw compressors are provided according to the amount of vapor. 8. The liquid concentrating method according to claim 1, wherein the upper gas phase portion of the condensate tank in the step (5) is connected to a vapor line outside the heat transfer tube. 9. The liquid concentrating method according to claim 1, wherein an electromagnetic valve for periodically discharging the non-condensable gas in the evaporator is provided in the vapor line outside the heat transfer tube. 10. The liquid concentrating method according to claim 1, wherein the operating pressure in the evaporator is normal pressure or reduced pressure. 11. The liquid concentrating method according to claim 10, wherein a vacuum pump is provided on the downstream side of the solenoid valve of the steam line outside the heat transfer tube, the vacuum pump interlocking with the opening and closing of the solenoid valve during the decompression operation. 12. An auxiliary heat source is introduced into the bottom of the evaporator or the outlet line of the compressor in order to cope with a decrease in the amount of evaporation due to fouling of the preheater and / or the heat transfer tube in the evaporator during startup or long-term operation. Item 6. The liquid concentrating method according to Item 1. 13. The method according to claim 12, wherein the auxiliary heat source is steam.