JP5599168B2 - Solidification equipment for solution and waste liquid - Google Patents

Description

The present invention is, from the solution and liquids produces a highly concentrated solution relates to a device for solid separating the crystals from the highly concentrated solutions, in particular enhance the energy efficiency, solidification apparatus of the solution, waste liquid so as to achieve energy saving about the.

  As a solidification apparatus for waste liquid containing ammonium chloride, an apparatus having a configuration in which a concentrating device is used for pre-concentration and the concentrated liquid is crystallized by a heated steam crystallizer is known. In the process using this heated steam crystallizer, a multi-effect evaporator is used as the pre-concentration, or a configuration in which live steam is injected from the outside is used. Furthermore, in order to improve energy efficiency, the example which uses a vapor | steam compression-type evaporative concentration apparatus is also known (for example, refer the following patent document 1). However, in the process using this heating vapor crystallizer, the energy efficiency of the entire system is poor because a large amount of vapor is required in the crystallization step regardless of which method is used for the pre-concentration.

  On the other hand, in the case of treating a solution / waste solution containing a substance having a large solubility difference due to a temperature difference such as ammonium chloride, a configuration using a cooling type crystallizer is known. Since crystallization is achieved by utilizing the difference in solubility, energy saving can be achieved as compared with the process using the above-described heated steam crystallizer. However, in the process using this cooling-type crystallizer, the current situation is that a multi-effect evaporator is used as the pre-concentration, or live steam is injected. Steam is used, which is still not enough from the viewpoint of energy saving.

JP-A-62-136204

  Therefore, there has been a demand for a solution / waste liquid solidification device and a solution / waste liquid solidification method that can achieve energy saving.

The present invention has been conceived in view of the above problems, and its purpose is to combine an energy-efficient vapor compression evaporation concentrator as a pre-stage concentrator and a cooling crystallizer as a post-stage crystallizer. Accordingly, it is an object of the present invention to provide a solution / waste liquid solidifying apparatus that uses substantially no steam and enables significant energy saving.

In order to achieve the above object, the solution / waste liquid solidifying device according to the present invention includes an evaporator that evaporates the supplied processing liquid, a compressor that adiabatically compresses generated steam, and a vacuum inside the evaporator. and a vacuum pump for maintaining the concentrated by evaporation of the supplied process liquid as a heat source for temperature and pressure to vaporize the processing solution returns the elevated steam evaporator in a vacuum state by the compressor A vapor compression type evaporation concentrator, and a cooling type crystallizer for cooling and evaporating the evaporative concentrate obtained by the vapor compression type evaporative concentration device to crystallize and precipitate the solute in the evaporative concentrate. It is characterized by having.

  As described above, the former stage of concentration is performed by the vapor compression type evaporation concentrator and the latter stage of crystallization is performed by the cooling type crystallizer, so that the steam is hardly used and the energy can be greatly saved. That is, in order to use the cooling crystallization, it is necessary to raise the concentrated liquid produced in the previous stage to a high temperature. In this case, energy consumption is large in the case of conventional steam heating. On the other hand, when vapor compression is used as in the present invention, energy efficiency is high and energy saving is achieved.

  The present invention may include a solid-liquid separation device that separates crystals precipitated by the cooling crystallizer from a liquid. The crystallized solid can be taken out, and the solid can be used for, for example, fertilizer.

The solution / waste liquid solidifying apparatus according to the present invention includes an evaporator that evaporates the supplied processing liquid, a compressor that adiabatically compresses generated steam, and a vacuum pump that maintains the inside of the evaporator in a vacuum state. A vapor compression type evaporation concentrating apparatus for evaporating and concentrating the processing liquid supplied in a vacuum state by returning the steam whose temperature and pressure have been increased by the compressor to the evaporator and evaporating the processing liquid A cooling crystallizer that cools the evaporated concentrate obtained by the vapor compression evaporator and lowers the solubility and causes the solute in the evaporated concentrate to crystallize and precipitate, and the cooling crystallizer. A solid-liquid separator for separating the precipitated crystals from the liquid, and a return line for returning the filtrate separated and removed by the solid-liquid separator to the vapor compression evaporation concentrator and mixing it with the processing liquid And characterized by having That. With such a configuration, the amount of discharged waste liquid can be reduced.

  The present invention heat-exchanges the mixed liquid of the filtrate and the processing liquid returned by the return pipe and the condensed water obtained by the vapor compression evaporation concentrator, and heats the mixed liquid with the condensed water. A preheater may be provided. Since the temperature of the treatment liquid is raised by heat exchange with the condensed water, the efficiency of heat recovery is high, and the system as a whole achieves energy saving while suppressing the amount of steam used.

According to the present invention, by combining a cooling type crystallizer and an energy-efficient vapor compression type evaporation concentrator as a pre-stage concentrator, a solution / waste solution that can save energy substantially without using any steam. the solidification apparatus can be realized in.

The whole block diagram of the solidification apparatus of the solution and waste liquid which concerns on embodiment. The whole block diagram of the solidification apparatus of the solution and waste liquid which concerns on an Example.

Hereinafter, the present invention will be described in detail based on embodiments. Note that the present invention is not limited to the following embodiments.
FIG. 1 is an overall configuration diagram of a solution / waste liquid solidifying apparatus according to an embodiment. The solution / waste liquid solidifying device 1 is a device that, for example, concentrates a solution / waste liquid containing ammonium chloride to extract a solid content. This solidifying device 1 is a vapor compression type evaporation concentrating device 2 for concentrating the supplied solution / waste liquid to near saturation, and a concentrated solution produced by the vapor compression type evaporation concentrating device 2 is cooled to lower the solubility to evaporate and concentrate. It has a cooling crystallization apparatus 3 that crystallizes and precipitates a solute in the liquid, and a solid-liquid separation apparatus 4 that separates crystals precipitated by the cooling crystallization apparatus 3 from the liquid. Connected to the solid-liquid separator 4 is a return line 5 for returning the filtrate after the solids are separated and removed to the vapor compression evaporator 2 side. The filtrate returned via the return line 5 is mixed with the processing liquid (raw solution), and the mixed liquid is heat-exchanged with the condensed water from the vapor compression evaporation concentrator 2 via the preheater 6. Yes.

  The vapor compression evaporative concentration apparatus 2 includes an evaporator that evaporates the supplied processing liquid and a compressor that adiabatically compresses the generated steam, and returns the steam whose temperature and pressure have been increased by the compressor to the evaporator and performs processing. It is comprised so that it may become a heat source for evaporating a liquid. One compressor may be provided, and two compressors are provided in series when a necessary compression temperature difference cannot be obtained by one-stage compression. Furthermore, there are cases where three units are provided in series.

  As the cooling crystallization apparatus 3, there are known a cooling crystallization apparatus using a jacket or an internal coil, an external circulation cooling crystallization apparatus, and the like, and there is no particular limitation. The jacket-type crystallizer is a type that has a jacket around a container for crystallization, passes cold water (or a refrigerant) through the jacket, and cools it through the wall surface of the container. The internal coil crystallizer is a type in which a cooling coil is disposed in a container for crystallization, and cold water (or refrigerant) from a chiller is passed through the cooling coil to cool the solution in the container. The external circulation cooling type crystallizer is formed by a circulation path composed of piping, valves, etc., between the crystallization tank and a cooler arranged outside thereof, and a multi-tube type cooler is suitable as the cooler. used. A container equipped with a stirring blade and a baffle in which the internal solution can be satisfactorily stirred is preferable. Moreover, it is preferable that any type has a draft tube inside for the improvement of a mixing property. In addition, in the Example mentioned later, an internal coil type crystallizer is illustrated.

  Examples of the solid-liquid separation device 4 include a centrifuge and a rotary vacuum filter. In addition, in the Example mentioned later, a centrifuge is illustrated.

  The outline of the processing of the solidifying device 1 having the above-described configuration is as follows. In the present embodiment, a treatment liquid (stock solution) containing ammonium chloride having a concentration of about 13% by weight is supplied to the solidifying device 1 for about 5 t per day. Then, it is concentrated to near saturation by the vapor compression type evaporation concentrating device 2 to produce a concentrated liquid (concentration of about 37% by weight) at about 70 ° C. In this pre-stage concentration, by using the vapor compression type evaporation concentrator 2, the steam generated in the evaporator is adiabatically compressed by the compressor and lifted to a high temperature, so that energy efficiency is better than in the case of steam heating and energy saving is achieved. Figured.

  Next, the concentrated liquid is supplied to the cooling crystallizer 3 while maintaining a high temperature of about 70 ° C. The cooling crystallizer 3 cools the concentrate produced by the vapor compression evaporator 2 to about 20 ° C. to lower the solubility, and causes the solute in the concentrate to crystallize and precipitate.

  Next, in the solid-liquid separator 4, it is separated from the liquid and an ammonium chloride crystal solid (water content 5 to 10%) is taken out. This ammonium chloride crystalline solid is used, for example, as a fertilizer. The filtrate from which the solid matter has been separated and removed is returned to the vapor compression evaporator 2 side via the return line 5. Thereby, the discharge amount of waste liquid is reduced. Further, the filtrate returned through the return line 5 is mixed with the processing liquid (raw solution), and the mixed liquid is heat-exchanged with the condensed water from the vapor compression evaporation concentrator 2 via the preheater 6. It has become. Therefore, the temperature of the processing liquid supplied to the vapor compression evaporation concentrator 2 can be increased, and a system with good heat recovery can be constructed.

  Thus, the solidification apparatus 1 in the present embodiment uses almost no steam by combining the vapor compression type evaporation concentrating apparatus 2 and the cooling crystallizer 3 that are energy efficient as pre-concentration. Significant energy savings can be realized. In addition, the filtrate returned through the return line 5 and the processing liquid (raw solution) are mixed, and the mixed liquid is heat-exchanged with the condensed water from the vapor compression evaporation concentrator 2 via the preheater 6. Thus, further energy saving can be realized.

It is preferable that the treatment liquid contains a substance having a characteristic that the solubility increases with an increase in temperature and has a large solubility difference with respect to the temperature difference. Here, “solubility” means the mass kg (= wt%) of the anhydrous compound dissolved in 100 kg of the saturated solution. Moreover, “the solubility difference with respect to the temperature difference is large” means, for example, that the solubility difference is 10 or more with respect to the temperature difference between 70 ° C. and 20 ° C. (that is, the temperature difference of 50 ° C.). Examples of the substance having a large solubility difference include sodium sulfate (Na ₂ SO ₄ ), copper sulfate (Cu ₂ SO ₄ ), nickel sulfate (NiSO ₄ ) and the like in addition to ammonium chloride. Na ₂ SO ₄ has a peak solubility around 34 ° C., but is cooled to about 20 ° C. in the crystallizer of the present invention, so that it can be efficiently crystallized.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the following examples.

  In the following examples, an apparatus for concentrating a solution / waste liquid containing ammonium chloride and taking out a solid content will be described as the solution / waste liquid solidifying apparatus 1. Further, as an example of the vapor compression evaporation concentrator 2, a vacuum vapor compression evaporation concentrator 2A will be described. The vacuum vapor compression type evaporation concentrating device 2A in the solution / waste liquid solidifying device 1 includes a horizontal tube type evaporator 10. The horizontal tube type evaporator 10 includes an evaporator 11, and this evaporator 11 is formed in a cylindrical shape so that a processing liquid can be stored therein. A pipe 12 for supplying a processing liquid such as a waste liquid is connected to the evaporator 11, and a raw liquid pump 13 for supplying the processing liquid is disposed in the pipe 12. On the top of the evaporator 11, a heater 14 including a pair of left and right headers 14 a and 14 b and a plurality of horizontal heat transfer tubes 14 c connecting the headers 14 a and 14 b is provided. The header 14a is disposed on the side where the steam enters, and the header 14b is disposed on the side where the steam is discharged. A pipe 15 for discharging condensed water of heating steam is connected to the header 14b, and a condensed water pump 16 for discharging condensed water is disposed in the pipe 15. The pipe 15 is provided with a preheater 6 that preheats the processing liquid passing through the pipe 12 by the heat of condensed water. The preheater 6 is a heat exchanger.

  The processing solution (stock solution) is supplied to the stock solution tank 20, mixed with the filtrate returned via the return line 6, and supplied to the horizontal tube type evaporator 10 by the stock solution pump 13.

  The horizontal tube type evaporator 10 in the present embodiment includes a circulation channel for processing liquid. A circulation pump 22 and a spreader 23 are arranged in the circulation channel. The circulation pump 22 is connected to the bottom of the evaporator 11. The circulation pump 22 is formed so that the treatment liquid 25 stored in the evaporator 11 can be transferred to the spreader 23 through the pipe 24. The circulation pump 22 is formed so that a part of the processing liquid 25 can be transferred to the concentrated liquid tank 30 through the pipe 26. The spreader 23 is formed so as to spread the treatment liquid 25 from above the horizontal heat transfer tube 14c toward the horizontal heat transfer tube 14c.

  The horizontal tube type evaporator 10 includes a pipe 31 as a discharge pipe for discharging the vapor of the processing liquid to the outside. The pipe 31 is connected to the upper part of the evaporator 11. The horizontal tube type evaporator 10 includes a heat pump 32 as a vapor compressor. The heat pump 32 is connected to the pipe 31. The heat pump 32 is connected to the header 14a of the heater 14 at the outlet side, and is formed so that the vapor at the top of the evaporator 11 can be transferred to the header 14a. The heat pump 32 is formed to suck the vapor inside the evaporator 11 and raise the temperature of the compression. A vacuum pump 33 is connected to the header 14 b of the heater 14. The inside of the evaporator 11 is kept in vacuum by the vacuum pump 33. In addition, the pipe | tube 35 which supplies the raw steam is connected to the pipe | tube 34 which connects the exit side of the heat pump 32, and the header 14a, and the case of an auxiliary | assistant heat source at the time of starting and maintaining operating temperature is required Can be supplied with external heat.

  The cooling crystallizer 3 includes a crystal can 40. An internal coil 60 is disposed in the crystal can 40. The internal coil 60 is connected to a chiller 61 so that cold water from the chiller 61 passes through the internal coil 60. A circulation channel 41 for the solution in the crystal can 40 is connected to the crystal can 40. A crystal can circulation pump 42 is disposed in the circulation channel 41. The concentrated liquid stored in the concentrated liquid tank 30 is supplied to the circulation channel 41 by the crystallizer supply pump 43. The concentrated liquid is supplied to the bottom of the crystal can 40 by the crystal can circulation pump 42 and is discharged from the upper side of the side wall of the crystal can 40 to circulate.

  The crystal can 40 is connected to a tube 44 for discharging the slurry containing the crystallized solute. The tube 44 is connected to the centrifuge 4A (corresponding to the solid-liquid separator 4). A slurry pump 45 to be supplied is arranged. Further, a pipe 47 that guides the vapor in the crystal can 40 to the condenser 46 is connected to the upper portion of the crystal can 40. Cold water is supplied to the condenser 46, and condensed water is discharged from the bottom of the liquid storage of the condenser 46 by a crystallizer condensate water pump 48. Further, a vacuum pump 49 is connected to the condenser 46, and the condenser 46 and the crystal can 40 are maintained in a reduced pressure state.

  The slurry is supplied from the crystal can 40 by the slurry pump 45 to the centrifuge 4A. The crystalline solid separated from the liquid by the centrifuge 4A is discharged from the tube 50. The centrifuge 4A is connected to a return line 5 for returning the filtrate after the solids have been separated and removed to the vacuum vapor compression evaporation concentrator 2A side. A filtrate tank 51 and a filtrate pump 52 are arranged in the return line 5. The filtrate stored in the filtrate tank 51 is returned to the stock solution tank 20 by the filtrate pump 52 via the return line 5. Note that the blow liquid is discharged by the filtrate pump 52.

  Next, the processing operation of the solidifying device 1 having the above-described configuration will be described. A treatment solution (stock solution) containing ammonium chloride having a concentration of about 13% by weight of about 5 t per day is supplied to the stock solution tank 20. On the other hand, the filtrate is returned to the stock solution tank 20 via the return line 5. The processing liquid after being agitated and mixed in the stock solution tank 20 is supplied through the pipe 12 into the evaporator 11 held in a vacuum. In addition, a process liquid is heat-exchanged with condensed water in the preheater 6 in the middle of passing the pipe | tube 12, and temperature rises.

  Next, when the circulation pump 22 is driven, the processing liquid 25 stored in the evaporator 11 is supplied to the spreader 23 through the pipe 24 and is spread from the spreader 23 toward the horizontal heat transfer pipe 14c. The processing liquid spread by the spreader 23 evaporates in a thin film on the surface of the horizontal heat transfer tube 14c. Vapor evaporated on the surface of the horizontal heat transfer tube 14c is sucked by the heat pump 32 through the tube 31, is adiabatically compressed by the heat pump 32, and is sent to the header 14a after the temperature and pressure rise. The steam that has entered the header 14a is guided to the inner side of the horizontal heat transfer tube 14c, and the circulating liquid sprayed to the outer side of the horizontal heat transfer tube 14c is evaporated and condensed at the same time as condensed water and flows into the header 14b. The condensed water is guided to the preheater 6 by the condensed water pump 16, cooled by the preheater 6, and discharged. By repeating such a process, the circulating liquid is concentrated to near saturation (70 ° C., concentration of about 37% by weight) and transferred from the outlet of the circulating pump 22 to the concentrated liquid tank 30 as a concentrated liquid.

The concentrate in the concentrate tank 30 is supplied to the circulation channel 41 by the crystallizer supply pump 43,
It is guided to the bottom of the crystal can 40 by the crystal can circulation pump 42. The circulating liquid (concentrated liquid) in the crystal can 40 is supplied to the bottom of the crystal can 40 by the crystal can circulating pump 42, discharged from the upper side of the side wall of the crystal can 40 and circulated. And the circulating liquid (concentrated liquid) in the crystal can 40 is cooled to 20 degreeC by the cold water (7-11 degreeC) which passes the internal coil 60, a solubility falls, and the solute in a concentrated liquid crystallizes and precipitates.

  The vapor in the crystal can 40 is led to the condenser 46 and condensed, and the condensed water is discharged out of the system by the condensed water pump 48.

  The slurry containing the crystallized solute in the crystal can 40 is supplied to the centrifuge 4A by the slurry pump 45. Then, the crystal solid separated from the liquid by the centrifuge 4A is discharged out of the system. On the other hand, the filtrate after the solid matter is separated and removed by the centrifuge 4 </ b> A is returned to the stock solution tank 20 via the return line 5.

  By performing the above treatment continuously, it is possible to produce a high-concentration solution from the waste liquid containing ammonium chloride, and to separate the crystals from the high-concentration solution to take out the crystalline solid. In addition, substantially no steam is used, and significant energy savings are possible.

  The present invention can be applied to an apparatus and a method for producing a high-concentration solution from a solution / waste liquid and solid-separating crystals from the high-concentration solution.

1: Solidification device for solution / waste liquid 2: Vapor compression evaporation concentrator 2A: Vacuum vapor compression evaporation concentrator 3: Cooling crystallizer
4: Solid-liquid separator 5: Return line
6: Preheater

Claims (4)

An evaporator that evaporates the supplied processing liquid, a compressor that adiabatically compresses the generated steam, and a vacuum pump that maintains the inside of the evaporator in a vacuum state, and vapor that has increased in temperature and pressure by the compressor is evaporated. A vapor compression type evaporation concentrating apparatus for evaporating and concentrating the processing liquid supplied so as to be returned to the can as a heat source for evaporating the processing liquid in a vacuum state ;
A cooling type crystallizer for cooling and evaporating the evaporative concentrate obtained by the vapor compression type evaporative concentration apparatus to crystallize and precipitate the solute in the evaporative concentrate;
An apparatus for solidifying solution / waste liquid.   The solution / waste liquid solidifying device according to claim 1, further comprising a solid-liquid separation device for separating crystals precipitated by the cooling type crystallizer from the liquid. An evaporator that evaporates the supplied processing liquid, a compressor that adiabatically compresses the generated steam, and a vacuum pump that maintains the inside of the evaporator in a vacuum state, and vapor that has increased in temperature and pressure by the compressor is evaporated. A vapor compression type evaporation concentrating apparatus for evaporating and concentrating the processing liquid supplied so as to be returned to the can as a heat source for evaporating the processing liquid in a vacuum state;
A cooling type crystallizer for cooling and evaporating the evaporative concentrate obtained by the vapor compression type evaporative concentration apparatus to crystallize and precipitate the solute in the evaporative concentrate;
A solid-liquid separator that separates crystals precipitated by the cooling crystallizer from the liquid;
A return line for returning the filtrate after being separated and removed by the solid-liquid separator to the vapor compression evaporation concentrator and mixing it with the processing liquid ;
An apparatus for solidifying solution / waste liquid.   A preheater for exchanging heat between the mixed liquid of the filtrate and the processing liquid returned by the return pipe and the condensed water obtained by the vapor compression evaporation concentrator and heating the mixed liquid with the condensed water; The solution / waste liquid solidifying apparatus according to claim 3.

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