JPH10118403A - 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 performing removal treatment of an organic substance and/or nitrogen compound for condensate discharged from a preheater just as it is or after it is heated again and pulling out condensate from the tower bottom of an evaporator in accordance with a signal showing height of liquid level in the evaporator and sending the condensate to a storage tank thereof. SOLUTION: The vapor phase part of a condensate tank 13 is connected to a vapor line 19 of the outside of a heat transfer pipe through a line 14. Noncondensable gas such as air in a concentrator 8, which affects efficiency and power consumption of a compressor 10, is discharged to the outside of an evaporator by opening/closing a solenoid valve 20 provided in the vapor line 19. If necessary, gas to be discharged is applied to adsorption treatment by activated carbon or bubbled in liquid of a concentrate tank 17 to remove a harmful component and thereafter the gas is discharged to the atmosphere. Concentrate in the concentrator 8 is discharged to a concentrate tank 22 through a line 21 of the lower part of the concentrator 8 and a control valve by a signal sent from a liquid level indicator in the concentrator 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to the concentration of various liquids,
Regarding the improvement of vapor compression concentration technology suitable for distillation, etc., more specifically, when concentrating a stock solution by evaporating water in the stock solution, compressing and elevating the temperature of generated steam from the stock solution with a compressor. The present invention relates to a liquid concentrating method utilizing the stock solution as a heat source for evaporating the stock 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 flow velocity of the liquid to the outer surface of the heat transfer tube is low.

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.

F. The vapor generated by the evaporation is used as a heat source for heating and evaporating the undiluted solution, then collected as a condensate, and reused or discharged. However, if the stock solution contains organic substances such as low-boiling components, nitrogen compounds, etc., some of these harmful components may be transferred to the condensate. Processing or tertiary processing is required. For such a treatment, it is necessary to use a distillation column having tens of stages (several hundred stages depending on the contained components) of the rectification rack, or to remove it with an adsorbent such as activated carbon. However, when the concentration of harmful components in the condensate is high, high rectification is performed or a large amount of adsorbent is used, which is extremely disadvantageous economically.

[0011]

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:

[0012]

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 concentration 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 the condensate from the condensate tank to the preheater for controlling the height of the condensate level of the vapor outside the heat transfer tube to a constant level, and (6) adding the condensate exiting the preheater as it is or again. (C) extracting the concentrated liquid from the bottom of the evaporator tower in response to the signal indicating the liquid level in the evaporator; A method for concentrating liquid, comprising a step of sending the liquid to a 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] FIG. 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.

14. In the step (6), the condensate is
In the presence of oxygen and / or ozone and / or hydrogen peroxide in excess of the theoretical amount of oxygen necessary to decompose organic substances and nitrogen compounds in the liquid while maintaining the temperature at 340 ° C. and the pressure for maintaining the liquid phase. Item 2. The liquid concentrating method according to Item 1, wherein the liquid concentration is performed by wet oxidation.

15. Item 15. The liquid concentrating method according to Item 14, wherein the wet oxidation treatment of the condensate is performed in the presence of a catalyst.

16. Item 16. The liquid concentrating method according to Item 15, wherein the catalytically active component is at least one of iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, and tungsten, and water-insoluble or hardly water-soluble compounds of these metals.

17. A catalytically active component is supported on a carrier, and the carrier comprises at least one of alumina, silica, zirconia, titania and a composite metal oxide containing these metals.
Item 17. The liquid concentrating method according to Item 16, which is a seed.

18. The amount of the catalytically active component carried on the carrier is
Item 18. The liquid concentrating method according to any one of Items 15, 16, and 17, which is 0.01 to 25% by weight.

19. Item 6. The liquid concentrating method according to the above item 1, wherein in the step (6), the condensate is stripped.

20. Item 2. The liquid concentrating method according to Item 1, wherein in the step (6), the condensate is treated with a bubble column.

21. Item 19. The condensate is treated using at least one of air, hydrogen peroxide and ozone.
Or the liquid concentrating method according to 20.

22. Item 22. The liquid concentrating method according to any one of Items 14 to 21, wherein the treatment liquid is further subjected to biological treatment and / or adsorption treatment with activated carbon.

[0036]

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 exhibiting its function is used, the equipment and operation costs are significantly lower than when a conventional compressor is used. Becomes

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 the 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 1.5 at the compression ratio. 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 the control of the compressor to perform suction and discharge by a 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.

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.

If 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 evaporator used in the present invention, a calandria evaporator is used in order to prevent a decrease in heat transfer coefficient due to poor liquid dispersion 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.

Further, if necessary, the bottom liquid in the calandria is withdrawn by a pump and circulated to the undiluted liquid introduction position, whereby the liquid flow velocity in the heat transfer tube can be increased to increase 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 to the outside 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 concentrate is discharged from the bottom of the column through a control valve upon receiving a signal from a 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 (vapor from a gas-fired boiler) may be used to raise the temperature of the entire apparatus at startup, or to reduce the amount of evaporation due to contamination of the preheater or calandria heat transfer tube after long-term operation. Etc.) into the calandria inner bottom or compressor outlet line.

The condensate used for heating the undiluted solution in the preheater is used as it is or after being re-heated as required.
In order to remove harmful components such as organic substances (eg, alcohols, aldehydes, carboxylic acids, etc.) and nitrogen compounds (eg, ammonia, etc.) in the condensate, the condensate is subjected to a secondary treatment or even a tertiary treatment. You.

Examples of such a treatment method include wet oxidation treatment, catalytic wet oxidation treatment, stripping treatment, biological treatment, treatment with a bubble column, and adsorption treatment with activated carbon. These processes can be implemented in combination as needed.

When performing the wet oxidation treatment, the condensate is
While maintaining a temperature of about 340 ° C. and a pressure for maintaining a liquid phase, the reaction is performed in the presence of oxygen and / or ozone at a theoretical oxygen amount or more necessary for decomposing organic substances and nitrogen compounds in the liquid. Such a wet oxidation treatment is described in, for example, JP-A-53-20663.
And the wet oxidation treatment method of various wastewaters disclosed in Japanese Patent Application Laid-Open No. 55-152591 and Japanese Patent Application Laid-Open No. 55-152591.

As the oxygen source in the wet oxidation catalyst, air, oxygen-enriched air, oxygen, hydrogen peroxide and the like are used.

When the wet oxidation treatment is carried out in the presence of a catalyst, the catalytic activity of iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper and tungsten and water-insoluble or poorly water-soluble compounds of these metals It is preferred to use at least one. Further, the catalytically active component is preferably supported on a carrier. The carrier is preferably at least one of alumina, silica, zirconia, titania and a composite metal oxide containing these metals. The amount of the catalytically active component carried on the carrier is usually about 0.01 to 25% by weight,
More preferably, it is about 0.1 to 3% by weight.

When the condensate is subjected to a stripping treatment, for example, “industrial water”, No. 448,
pp6-12 (1996), "Water treatment technology", Vol.21, No.1, pp13
To 24 (1980) and the like. As the gas for the stripping process, air, hydrogen peroxide, ozone, or the like is used.

When the condensed liquid is subjected to bubble column treatment, for example, “water treatment technology”, Vol. 17, No. 8,
p735 (1976), "PPM", Vol. 17, No. 10, p3 (1986). As the processing gas, air, hydrogen peroxide, ozone, or the like is used.

When the condensate is subjected to biological treatment, for example, “industrial water”, No. 411, pp. 85-93 (1
992), `` Environmental Technology '', Vol.20, No.7, pp432-436 (1991)
And the like.

When the condensed liquid is subjected to the adsorption treatment with activated carbon, for example, “Pollution and countermeasures”, Vol.
25, No.3, pp10-13 (1989), "Water and wastewater", Vol.30,
No. 11, pp41-47 (1988).

The condensed liquid after the secondary or tertiary treatment is reused or discharged.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a flow sheet showing an example of the wastewater concentration treatment 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 a defoamer tank (not shown).

The liquid leaving 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 through a line 9 and 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.

Emission of uncondensed vapor out of 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 the line 15 to the preheater 5 where it exchanges heat with the waste liquid, passes through a liquid level control valve (not shown) on the line 16 and is sent to the condensate tank 17 for reuse. Or is released.

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

The non-condensable gas such as air in the concentrator 8 which affects the efficiency and power consumption of the compressor 10 is moved out 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 gas to be discharged is subjected to an adsorption treatment using activated carbon or the like, or harmful components are removed by bubbling the liquid in the concentrated liquid tank 17 and then released to the atmosphere.

The concentrated liquid in the concentrator 8 is passed 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, and the concentrated liquid is stored in the concentrated liquid tank. It is discharged to 22.

Further, if necessary, the liquid in the concentrator 8 is extracted from the liquid extracting line 21 by a circulation pump (not shown) and circulated to the raw liquid line 6 to increase the liquid flow rate in the heat transfer tube. If the operating pressure in the concentrator 8 capable of increasing the heat transfer coefficient 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.

Further, 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.

In the case where contamination of the heat transfer tubes of the preheater 5 and the concentrator 8 and the resulting decrease in the heat transfer coefficient occur, the supply of wastewater is temporarily interrupted during operation, and the supply of industrial water is stopped. By doing so, dirt can be washed and removed.

The condensate discharged from the preheater is heated as it is or after reheating, and then passes through the line 16 to the condensate treatment device 24.
To remove harmful components. The treatment of the condensed liquid is performed by the above-mentioned method (wet oxidation treatment, stripping treatment, treatment with a bubble column, biological treatment, adsorption treatment with activated carbon, and the like).

Depending on the type and concentration of harmful components contained in the condensed liquid, the liquid discharged from the condensed liquid tank 13 is
After being heated as it is without being sent to the above, it may be subjected to the above treatment. In this case, since the undiluted solution is not preheated by the preheater 5, it is necessary to supply heat of an amount corresponding to the amount of heat by the steam from the boiler 23.

The present invention is directed to, for example, concentration and volume reduction of various industrial wastewaters, washing wastewaters, photographic developing solutions, fixing solutions and washing wastewaters, separation of useful components or impurities in a stock solution by distillation,
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.

[0080]

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

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

(2) Continuous and stable operation is possible.

(3) Organic substances and / or nitrogen compounds in the condensate can be easily removed, and the treated water can be reused or discharged.

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

[0085]

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, copper plating plant wastewater (copper ion concentration 5100mg / l, specific gravity
1.01) as a stock solution under normal pressure under the conditions shown in Table 1.
The concentration treatment was performed.

[0087]

[Table 1]

The electric 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.

[0089]

[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, a copper plating plant wastewater was concentrated under reduced pressure. Table 3 shows the conditions.

[0092]

[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 waste water (mixed waste liquid of a developing solution and a fixing solution) was concentrated under reduced pressure. Table 4 shows the conditions.
Shown in

[0097]

[Table 4]

Table 5 below 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.

[0099]

[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.

[0102]

[Table 6]

[0103]

[Table 7]

As is clear 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 the secondary treatment.

Example 6 A concentration treatment was performed in the same manner as in Example 1 except that alkaline wastewater from a food processing plant was used as wastewater. The conditions are shown in Table 8, and the properties of the wastewater and the obtained condensate are shown in Table 9.

[0106]

[Table 8]

[0107]

[Table 9]

Next, in order to remove organic substances and nitrogen oxides in the condensate, the condensate was subjected to catalytic wet oxidation treatment. That is, according to the method disclosed in Japanese Patent Application Laid-Open No. 55-152591, in a reaction tower filled with 2% Ru-TiO ₂ catalyst, the temperature = 150 ° C., the pressure = 9.9 kg / cm ² , = The theoretical amount of oxygen
The condensate was treated under conditions equivalent to 1.1 times the reaction time = 60 minutes.

The obtained processing solution had a COD of less than 20 mg / l and a TN of less than 5 mg / l, and could be reused as it was. In addition, NO _x , SO _x , NH ₃ , organic substances, and the like were not detected from exhaust gas generated by the wet oxidation treatment.

Example 7 A catalytic wet oxidation of a condensate was carried out in the same manner as in Example 6, except that the active component of the catalyst was changed. The properties of the obtained treated water were as follows.

(A) 2% Pd-TiO ₂ : COD = less than 20 mg / l, TN = less than 5 mg / l (b) 10% Ni-TiO ₂ : COD = less than 20 mg / l, TN = 15 mg / l (c ) 10% Mn--0.5% Se-TiO ₂ : COD = less than 20 mg / l, TN = 25
mg / l (d) 10% Co-TiO ₂ : COD = 22 mg / l, TN = 25 mg / l

[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 24 ... Condensate Processing equipment

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01J 23/755 C02F 1/04 Z C02F 1/04 1/20 A 1/20 1/28 D 1/28 1/72 ZABZ 1 / 72 ZAB 1/74 101 1/74 101 3/00 Z 3/00 9/00 502H 9/00 502 504A 504 504E B01J 23/74 321M (72) Inventor Hiroshi Fujiya Hirano-cho, Chuo-ku, Osaka 4-1-2, Osaka Gas Co., Ltd. (72) Inventor Harushi Okabe 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka-shi Osaka Gas Co., Ltd.

Claims (22)

[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 condensate into the preheater from the condensate tank of
(6) a step of subjecting the condensate discharged from the preheater as it is or after reheating to a step of subjecting the condensate to removal of organic substances and / or nitrogen compounds, and (7) a signal indicating the liquid level in the evaporator. Correspondingly, there is provided a step of extracting the concentrated liquid from the bottom of the evaporator tower and sending the concentrated liquid to a concentrated liquid storage tank. 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 contamination of the preheater and / or the heat transfer tube in the evaporator during start-up 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. 14. In the step (6), the condensate is added in an amount of 30 to 340.
C. and a pressure to maintain the liquid phase, and wet in the presence of oxygen and / or ozone and / or hydrogen peroxide in excess of the theoretical amount of oxygen necessary to decompose organic substances and nitrogen compounds in the liquid. The liquid concentrating method according to claim 1, wherein the liquid is concentrated. 15. The method according to claim 14, wherein the wet oxidation treatment of the condensate is performed in the presence of a catalyst. 16. The catalyst according to claim 16, wherein the catalytically active component is iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium,
The liquid concentrating method according to claim 15, which is at least one of platinum, copper, tungsten, and a water-insoluble or poorly water-soluble compound of these metals. 17. A catalyst, wherein the catalytically active component is supported on a carrier,
The liquid concentrating method according to claim 16, wherein the carrier is at least one of alumina, silica, zirconia, titania, and a composite metal oxide containing these metals. 18. The amount of the catalytically active component supported on the carrier is 0.01 to 0.01.
The liquid concentrating method according to any one of claims 15, 16 and 17, wherein the amount is from 25 to 25% by weight. 19. The liquid concentrating method according to claim 1, wherein in the step (6), the condensed liquid is stripped. 20. The liquid concentrating method according to claim 1, wherein in the step (6), the condensate is treated in a bubble column. 21. The liquid concentrating method according to claim 19, wherein the condensate is treated using at least one of air, hydrogen peroxide and ozone. 22. The liquid concentrating method according to claim 14, wherein the treatment liquid is further subjected to biological treatment and / or adsorption treatment with activated carbon.