JPH10118405A - Method for concentrating liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide thermocompression concentration technology which requires only a small-sized device and saves on equipment cost and operating expenses. SOLUTION: A vapor condensate originating from the outside of a heat transfer pipe in a Calandria evaporation drum 8 and a raw liquid are subjected to a heat exchange process using a preheater 5, and the preheated raw liquid is introduced into a liquid from a liquid level to the heat transfer pipe in the evaporation drum 8. Further, a vapor generated in the evaporation drum 8 is compressed using a screw compressor 10 to heat up the vapor. The compressed vapor thus obtained is supplied to the outside of the heat transfer pipe to heat and evaporate the liquid inside the heat transfer pipe. Then, to control the liquid level of the vapor condensate outside the heat transfer pipe so that it is maintained at a constant height, the condensate from a condensate tank 13 is introduced into the preheater 5. The condensate coming out of the preheater 5 is used as it is or is again heated to remove an organic matter and/or a nitrogen compound. In addition, a concentrate is extracted from the Calandria tower bottom based on a signal indicating the height of the condensate level inside the evaporation drum 8 and then is sent to a concentrate storage tank. At the same time, piping including the preheater 5 and the heat transfer pipe inside the evaporation drum 8 are internally cleaned.

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, since the liquid is dispersed, it is often difficult to remove the scale attached to the outer surface of each tube, for example, the flow speed of the liquid 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.

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 migrate to the condensate. Next or tertiary processing is required. For such processing,
It is necessary to use a distillation column having several tens of stages (several hundred stages depending on the contained components) of the rectification shelf, or to remove by an adsorbent such as activated carbon. However, when the concentration of harmful components in the condensate is high, it is extremely disadvantageous in terms of economics because a high degree of rectification is performed or a large amount of adsorbent is used.

G. In addition, the stock solution to be concentrated may contain various metal components. In this case, scales are deposited at various parts of the apparatus during the concentration process, and the heat transfer coefficient is reduced and the processing capacity is reduced. May be. Tokiko Sho 58-120
In the scale processing method described in No. 41 Public Law, the formation of scale is dealt with by alternately switching the pipeline or the evaporator. However, with this method, equipment costs and operating costs are high.

[0012]

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:

[0013]

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 concentrating method using a concentrating device having a calandria type heat transfer tube, (1) a step of preheating a stock solution by exchanging heat in a preheater between a stock solution and a condensate of steam outside the heat transfer tube, (2) preheating Introducing the undiluted solution into the liquid between the surface of the calandria and the heat transfer tube, (3) compressing and elevating the temperature of the steam generated in the calandria with a screw compressor, and (4) obtaining the obtained compression. Supplying steam to the outside of the heat transfer tube to heat and evaporate the liquid in the heat transfer tube; (5) removing condensate from a condensate bath for controlling the height of the condensate level of the vapor outside the heat transfer tube to be constant; A liquid concentrating method comprising: a step of introducing the liquid into the preheater; and (6) a step of extracting the concentrated liquid from the bottom of the calandria in response to a signal indicating the liquid level in the calandria and sending the concentrated liquid to a concentrated liquid storage tank. Method.

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 calandria bottom liquid is withdrawn by a pump in order to adjust the level of the liquid level in the calandria, and is circulated to an undiluted liquid introduction line.

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 Item 5, wherein in the step (3), the number of rotations of the motor of the screw compressor is controlled in accordance with the amount of steam generated in the calandria.

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. 2. The liquid concentrating method according to the above item 1, wherein an electromagnetic valve for periodically discharging the non-condensable gas in the calandria 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 calandria 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. In order to cope with a decrease in evaporation due to contamination of the preheater and / or the calandria heat transfer tube during start-up or long-term operation, an auxiliary heat source is introduced into the calandria inner bottom or the compressor outlet line.
3. The liquid concentrating method according to 2. above.

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 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. Item 17. The liquid concentrating method according to Item 16, wherein the catalytically active component is supported on a carrier, and 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 carried on the carrier is
Item 18. The liquid concentrating method according to any one of Items 15, 16, and 17, wherein the amount 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 14-21, wherein the treated liquid is further subjected to biological treatment and / or adsorption treatment with activated carbon.
The method for concentrating a liquid according to any one of the above.

23. Item 1 above, wherein the washing in the step (8) is performed with water and / or an acid and / or an alkali.
3. The liquid concentrating method according to 2. above.

24. 2. The method according to the above item 1, wherein the washing is performed while the liquid concentration treatment is stopped.

25. 2. The liquid concentrating method according to the above item 1, wherein the cleaning is performed by switching the supply of the stock solution and the cleaning solution during the liquid concentration process.

[0040]

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 equipment cost and the operating cost are 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 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 the compressor in accordance with the amount of generated steam and to efficiently perform the evaporation in the evaporator. In the present invention, a motor composed of a high-speed rotating 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 generated steam is detected by an orifice type flow meter provided on the upstream side of the pressure machine, a float type flow meter, etc., 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.

If the stock solution contains a component (such as a surfactant) that may cause foaming under the concentration condition, a silicon-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.
It is 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 of 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, the above-mentioned problems such as a decrease in the flow rate due to the dispersion of the liquid and promotion of foaming are eliminated.

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.

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 the 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) is used to raise the temperature of the entire apparatus at startup, or according to a decrease in the amount of evaporation due to contamination of a preheater or a 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 reheating as necessary.
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, they are subjected to a secondary treatment or further to a tertiary treatment. .

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 required for decomposing organic substances and nitrogen oxides in the liquid. Such a wet oxidation treatment is described in, for example,
-20663, Japanese Patent Application Laid-Open No. 55-152591, etc. can be carried out according to the wet oxidation treatment of various wastewaters.

Examples of the oxygen source in the wet oxidation treatment include air, oxygen-enriched air, oxygen, and hydrogen peroxide.

When the wet oxidation treatment is carried out in the presence of a catalyst, iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper and tungsten as the catalytically active components and water-insoluble or poorly water-soluble compounds of these metals are used. It is preferred to use at least one of the following. 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 0.01 to 25% by weight, more preferably 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 treatment, air,
Hydrogen peroxide, ozone and the like are 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, pp432-4 (1991)
And the like.

When the condensate is subjected to an 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 treatment or the tertiary treatment is reused or discharged.

Many stock solutions contain metal components (Fe, Si, Mg, C
a, Ni, Cu, Al, etc.) and P.
In such a case, a scale is gradually generated and deposited in each part of the above-mentioned concentrating device, so that the heat transfer coefficient is reduced and the processing capacity of the liquid is reduced. In such a case, the concentrating device is washed at a necessary time, and the processing capacity is recovered by dissolving and removing the scale.

The cleaning of the concentrator may be performed by supplying a cleaning liquid instead of the raw water while the concentration process is stopped.
Alternatively, the supply of the raw water and the cleaning liquid may be appropriately switched during the concentration treatment. The cleaning liquid may be selected according to the type of the stock solution, the composition of the scale deposited, and the like, and water or hot water to hot water, an acid, an alkali, or the like is used.
You may wash repeatedly. For example, acid washing, alkali washing and water washing can be performed in an appropriate order. Although not particularly limited, examples of the acid include an aqueous solution of nitric acid (usually about 1 to 20%, preferably about 5 to 10%).
About 1 to 20%, preferably about 5 to 10%).

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 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 a defoamer tank (not shown).

The liquid exiting the preheater 5 is supplied from a line 6 to a 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 made 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 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 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 gas phase of the condensate tank 13 is connected to a steam line 19 outside the heat transfer tube via a line 14.

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

If necessary, the liquid in the concentrator 8 is extracted from the liquid extraction line 21 by a circulation pump (not shown) and circulated to the undiluted 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.

The condensate that has exited the preheater is heated as it is or again, and then passes through the line 16 to the condensate treatment device 24.
To remove harmful components. The treatment of the condensate is carried out by the above-mentioned method (wet oxidation treatment, catalytic wet oxidation treatment,
Biological treatment, stripping treatment, treatment with a bubble column, adsorption treatment with activated carbon, etc.).

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 the waste water is temporarily interrupted during the operation and the supply of the industrial water is performed. By doing so, dirt can be washed and removed.

In particular, when scale is deposited on various parts in the apparatus due to the metal components contained in the raw water, the cleaning liquid (acid, alkali, The scale is dissolved and removed by feeding hot water or the like, or by appropriately switching the supply of the raw water and the cleaning liquid during the concentration treatment.

When the preheater 5 is to be cleaned, the cleaning liquid is taken out from a withdrawal valve (not shown) provided on the line 6 and circulated to the cleaning liquid tank. When the concentrator 8 is to be washed, it is taken out from a withdrawal valve (not shown) provided on the line 21 and circulated to the washing liquid tank.

The present invention is intended to concentrate and reduce the volume of various industrial wastewaters, washing wastewaters, photographic developers, fixing solutions, washing wastewaters, etc., to separate and separate 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.

[0087]

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, so that the equipment cost and
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) Precipitation scales in equipment piping derived from components contained in raw water can be easily removed.

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

[0093]

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) was used as a stock solution and concentrated under normal pressure under the conditions shown in Table 1.

[0095]

[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:
The operating cost according to the prior art described in Japanese Patent Application Laid-Open No. 59-26184 was reduced to about 1/4, and significant cost reduction was achieved. Further, the concentration treatment according to the method of the present invention could be stably continued.

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

[0098]

[Table 2]

From the results shown in Table 2, the components in the concentrated solution were:
About 20 hours after the operation, the concentration was about 10-fold, and it is clear that all the copper ions have migrated to the concentrate side. According to the present invention, these results can control the concentration step of the stock solution by the specific gravity of the concentrate that can be easily measured.
It is clear that it is not necessary to analyze the concentration of the components contained in the liquid, which requires complicated operations. 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.

[0101]

[Table 3]

The power consumption for the operation of the steam compressor 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 the power consumption unit is that the specific volume of steam is 1.673 m ³ / kg at 760 mmHg, whereas it is 5.8 at 200 mmHg.
Since it is 42 m ³ / kg, the flow rate of steam for compression increases under reduced pressure.

Comparative Example 1 Wastewater from a copper plating plant having substantially the same composition as in Example 1 (however,
The surfactant (containing about 3% of surfactant) was concentrated in the same manner as in Example 1. When the temperature in the calandria evaporator began to exceed about 60 ° C., an abnormal foaming phenomenon occurred. As a result, wastewater was discharged from the condensate line through the line 9, the compressor 10, the line 11, the outer side of the heat transfer tube in the evaporator, 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 rate such that the concentration became 200 ppm, and the treatment was carried out in the same manner as in Example 1. Not
Almost the same good results of the concentration treatment as in Example 1 were obtained.

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

[0106]

[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.

[0108]

[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 carried out 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.

[0111]

[Table 6]

[0112]

[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 concentrate are shown in Table 9.

[0115]

[Table 8]

[0116]

[Table 9]

Next, in order to remove organic components and nitrogen-containing compounds 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 , the temperature = 150 ° C., the pressure = 9.9 kg / cm ² , the amount of incoming air = The condensate was treated under the conditions of 1.1 times the theoretical oxygen amount and a reaction time of 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, NOx is emitted from the exhaust gas generated during the wet oxidation process.
_x , SO _x , NH ₃ , organic matter, etc. were not detected.

Example 7 The procedure of Example 6 was repeated except that the active component of the catalyst was changed.
Catalytic wet oxidation of the condensate was performed. 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 = 20mg / less than l, TN = 25
mg / l (d) 10% Co-TiO ₂ : COD = less than 22 mg / l, TN = 25 mg / l Example 8 A mixture of the same copper plating wastewater, alkali immersion liquid and electrolytic degreasing liquid as treated in Example 1. Was concentrated under the same conditions as in Example 1.

In this case, with respect to the amount of treated wastewater, the amount of condensed liquid, the amount of concentrated liquid, and the like, almost the same results as in Example 1 were obtained. The overall heat transfer coefficient in the calandria evaporator tube is
The treatment capacity decreased by about 15% compared to the initial operation.
Therefore, while maintaining the same concentration treatment conditions as at the beginning, the operation was performed by supplying industrial water instead of wastewater for about 2 hours, and then the supply of wastewater was restarted to continue the concentration treatment. As a result, the heat transfer coefficient and the processing capacity were restored to the same level as in the initial operation.

After the operation for 4 weeks, the total heat transfer coefficient in the preheater and the calandria type evaporator tube was reduced by about 50% as compared with the initial operation due to scale deposition. Therefore, when the amount of steam supplied as an auxiliary heat source to the inner bottom of Calandria was increased by 50%, the same processing capacity as in the initial operation could be secured.

After the operation for 8 weeks, the overall heat transfer coefficient in the preheater and the evaporator tube was reduced to 50% or less as compared with the initial operation, so the compressor 10 was stopped and the temperature in the evaporator was reduced to about 80%. ° C
Then, a 10% nitric acid solution was supplied for about 2 hours, and then a 10% aqueous sodium hydroxide solution was supplied for about 2 hours to wash the inside of the preheater and the evaporator tube. As a result, the overall heat transfer coefficient recovered to the initial value.

REFERENCE EXAMPLE 1 Under the same conditions as in Example 6, the operation of the concentrator was continued for 8 weeks without washing with a preheater and a calandria type evaporator tube or washing with an aqueous nitric acid solution and an aqueous sodium hydroxide solution. The deposited scale was collected and subjected to component analysis and a solubility test of each component. Table 10 shows the results. The scale solubility test was performed using a 10% nitric acid aqueous solution.
By adding 10 g of scale to each of 100 ml and 100 ml of 10% aqueous sodium hydroxide solution, and keeping at room temperature for 2 hours,
went.

[0125]

[Table 10]

From the results shown in Table 10, the scale component was
Since it is almost completely dissolved even at room temperature, it is clear that scale can be removed by washing the apparatus even at room temperature. It is also clear that the washing liquid can be selected according to the components of the scale.

[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 ... Concentration tower 10 ... Compression tower 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 Kenichi Yamazaki Kenichi Hiranocho, Chuo-ku, Osaka-shi, Osaka Osaka Gas Co., Ltd. (72) Inventor Tatsuo Kume 4-1-2 Hirano-cho, Chuo-ku, Osaka City, Osaka Prefecture Osaka Gas Co., Ltd.

Claims (25)

[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 condensed liquid that has exited the preheater to a treatment for removing organic substances and / or nitrogen compounds as it is or after reheating, and (7) corresponding to a signal indicating the liquid level in the evaporator. A step of extracting the concentrated liquid from the bottom of the calandria column and sending it to a concentrated liquid storage tank; and (8) a step of washing a pipe including a preheater and a heat transfer pipe in an evaporator. 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 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 of the condensate is carried out 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. 23. The method according to claim 1, wherein the washing in the step (8) is performed with water and / or an acid and / or an alkali. 24. The method according to claim 1, wherein the washing is performed while the liquid concentration process is stopped. 25. The liquid concentrating method according to claim 1, wherein the cleaning is performed by switching the supply of the stock solution and the cleaning solution during the liquid concentrating process.