JPH0237201B2 - NOSHUKUSHOSEKIHOHOOYOBINOSHUKUSHOSEKISOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a concentration crystallization method and apparatus for precipitating crystals from food-based, drug-based, and other various crystalline solutions.

[Conventional technology]

Generally, in order to perform a concentration crystallization operation of a crystalline solution, the liquid to be treated must be brought into a supersaturated state with respect to precipitated components. In order to achieve this supersaturated state, evaporation, cooling, or a combination of evaporation and cooling are carried out, and there are also methods of increasing the concentration of crystallized substances through chemical reactions or the addition of other salts, but these methods require special methods. Therefore, if we look at the commonly used methods related to evaporation and cooling, as shown in the concentration-temperature graph in Figure 1, there is a saturated solubility line A, and the liquid to be concentrated has a temperature of B. In order to crystallize when supplied to the crystallizer in the state of T ₀ and concentration ξ ₀ , the state of the liquid to be treated must be brought to the saturated solubility line A by some method, whether by evaporation or cooling. It is necessary to force it.

[Problem that the invention seeks to solve]

However, when various conventional crystallization methods are employed, each has the following drawbacks.

(a) In the case of cooling only...The process is from B to C in Figure 1, and a special low-temperature source for cooling (for example, cold ice made with a refrigerator) is required, and in addition, the amount of liquid to be treated is Since it is the same as the undiluted solution, a large amount of low-temperature heat source (for example, cold water) is required, which increases equipment and operating costs.

(b) In the case of evaporation alone...This is the process from B to D in Figure 1.

When using a process that involves evaporation, the evaporated vapor of the liquid to be treated that is generated in the crystallizer is generally compressed mechanically, and this is used as a heating source for evaporation of the liquid to be treated. Vapor compression is widely used due to its good efficiency.

However, in this case, if the process is performed at a relatively low temperature T ₀ (for example, below 50°C) as in the process shown in Figure 1, the vapor specific volume will increase significantly and the efficiency of the compressor will decrease. This results in a huge amount of data and reduces efficiency.

(c) Case caused only by evaporation at high temperatures...Figure 1B
→This is the process of E.

If evaporation is carried out at a high temperature to eliminate the drawback of (b), a large amount of steam will be required, and the solubility at point E will be large, so recovery of the solubility will become a problem. Furthermore, if the liquid to be treated is a corrosive solution, there is a risk that the compressor will be corroded by the generated steam and entrained droplets, so the material must be extremely expensive, making it impractical.

(d) When performing post-evaporation cooling at high temperatures...1st
This is the process shown in Figure B→F.

In order to solve the problem of recovering the solubility in (c), there is a method of performing evaporation at high temperature, stopping the evaporation before reaching the saturated solubility line, and performing cooling crystallization, but this method requires a large amount of cold heat source for cooling. It also requires a crystallizer in addition to the evaporator.
Equipment costs and operating costs are high. Further, depending on the temperature, the precipitated crystals may be colored or decomposed.

The present invention aims to eliminate the various drawbacks of these conventional methods. It does not require a large amount of steam for concentration, does not require a large amount of cold heat source for cooling, and uses water at room temperature. To provide a concentration crystallization method and a concentration crystallization device that can be used, have lower solubility than when carried out at high temperatures, so there is no problem of recovering the solubility, and can reduce coloring, decomposition, etc. of products because the operating temperature is low. The purpose is to

[Means for solving problems]

The concentration crystallization method of the present invention includes a heating concentration step in which a liquid to be treated is heated and concentrated by the latent heat of condensation of a working fluid of a heat pump, and a liquid to be treated is liquefied by vapor generated from the liquid to be treated in the heating concentration step. The liquid to be treated is concentrated by combining an evaporation step in which the working fluid is heated and evaporated, and then the concentrated liquid obtained in the heating concentration step is cooled by the latent heat of vaporization of the working fluid of the heat pump to crystallize the dissolved components. The method is characterized in that the dissolved components in the concentrated liquid are crystallized by combining a cooling crystallization step in which the evaporated working fluid is cooled and condensed using cooling water. This is a concentration crystallization method.

Further, the concentration crystallizer of the present invention is provided with a concentration crystallizer, a first heat exchanger, a second heat exchanger, an evaporator, and a compressor, and the flow of the liquid to be treated is controlled with respect to the concentration crystallizer can. , a heated side of the first heat exchanger;
A liquid passage to be treated is connected in parallel to the heating side of the second heat exchanger, and a working fluid is passed from the compressor to the compressor via the heating side of the first heat exchanger and the heated side of the evaporator. a heat pump path for circulating the heat pump to form a heat pump cycle, and a working fluid bypass path for guiding the working fluid in the low pressure side path of the heat pump path to the heated side of the second heat exchanger and returning it to the low pressure side for circulation. , an evaporation path for guiding the vapor evaporated in the concentration crystallizer to the heating side of the evaporator; Circulate while heating to evaporate and concentrate.
After reaching a predetermined concentration, the route of the liquid to be treated to the heated side of the first heat exchanger is cut off, and the route is switched to the route passing through the second heat exchanger, and the liquid to be treated is removed in the second heat exchanger. This is a concentrating crystallizer characterized by having a switching control mechanism that switches to cool.

[Effect]

The present invention includes a heating concentration step in which the liquid to be treated is heated and concentrated by the latent heat of condensation of the working fluid of the heat pump, and a concentrated liquid obtained in the heating concentration step is cooled by the latent heat of evaporation of the working fluid of the heat pump. When used in combination with a cooling crystallization process to crystallize dissolved components, a heat pump cycle is used to
Using an indirect pressure evaporation method similar to the self-vapor compression method, evaporation is performed by heating at the temperature T ₀ in Fig. 1, and when a certain concentration ξ ₁ is reached, cooling is performed to perform cooling crystallization, and the point G is reached. Crystallization is performed through a process that reaches .

〔Example〕

An embodiment of the present invention will be explained with reference to FIG. 2.
The concentration crystallizer includes a concentration crystallizer 1, a first heat exchanger 2, a second heat exchanger 3, an evaporator 4, and a compressor 5, and by connecting these devices with a pipe,
Switching control that detects the concentration of the liquid to be treated, the heat pump path, the working fluid bypass path, the steam path, and the liquid to be treated, and controls the switching of the liquid to be treated, the heat pump path, and the working fluid bypass path. A mechanism is provided.

The to-be-treated liquid path is connected to the heated side of the first heat exchanger 2 with respect to the flow of the to-be-treated liquid to the concentration crystallizer can 1;
The heating side of the second heat exchanger 3 is connected in parallel. or to the heating side of the second heat exchanger 3 and then returned to the concentration crystallizer 1 again. 8 is a supply port for the raw solution of the liquid to be treated, 9 is a flow control valve, and the level controller 10 of the liquid to be treated in the concentration crystallizer 1 is controlled so that the liquid level is maintained at a predetermined height. Ru. 11 is a stirrer, and 12 is an outlet for taking out the crystallized crystals together with the concentrated liquid. 13,1
4, 15, and 16 are conduits.

The vapor path consists of the gas-liquid separator 17, the heating side of the evaporator 4, the condensed water outlet 18, the vacuum pump 34, and the pipes 22', 35, 36 connecting them, etc. Evaporator 4 with evaporated steam
This is for heating. The vacuum pump 34 is for evaporating the inside of the concentration crystallizer 1 under a predetermined low pressure.
Pressure control is performed to keep the internal pressure constant.

The heat pump path includes the heated side of the evaporator 4, the compressor 5, the cooler 19, the heating side of the first heat exchanger 2, the expansion valve 20, and the pipe line 2 connecting these devices.
2, 23, 24, 25, etc., and performs a heat pump cycle by repeatedly circulating a working fluid such as fluorocarbon through a gas phase and a liquid phase.
Reference numeral 26 is a pump for pumping up the working fluid accumulated at the bottom of the heated side of the evaporator 4 and circulating the working fluid through pipes 27 and 28 for effective evaporation.

30 is a three-way valve that switches the flow of the working fluid to a working fluid bypass path, and this working fluid bypass path consists of the three-way valve 30, a pipe line 31, the heated side of the second heat exchanger 3, and a pipe line 32. , the working fluid on the low pressure side during the heat pump cycle is transferred to the second heat exchanger 3.
It leads to the heated side.

Reference numeral 33 denotes a switching control mechanism which detects the concentration of the liquid to be treated in the concentration crystallizer can 1 and, if the concentration is below a predetermined set value, operates the three-way valves 7 and 30 and controls the liquid to be discharged from the pump 6. The working fluid is supplied to the heated side of the first heat exchanger 2, and the working fluid discharged from the pump 26 is supplied to the heated side of the evaporator 4, so that the working fluid heats and evaporates the liquid to be treated, and the concentration is set. If the value is exceeded, the three-way valves 7 and 30 are switched, the liquid to be treated discharged from the pump 6 is switched to the heating side of the second heat exchanger 3, and the working fluid discharged from the pump 26 is switched to the heating side of the second heat exchanger 3. The liquid to be treated is guided to the heated side of the exchanger 3 so that the liquid to be treated is cooled and crystallized by the working fluid.

In the figure, 37 is a pressure controller, and 38 is a pressure control valve.

To explain the effect in the example in Figure 2, Figure 1B
The undiluted solution of the liquid to be treated in the state as shown in FIG. is filled with the liquid to be treated, and when the liquid level in the concentration crystallizer 1 reaches a predetermined height, the pump 6 is turned on.
The liquid to be treated is circulated. The internal pressure of this concentration crystallizer 1 is maintained at a predetermined low pressure by a vacuum pump 34.

On the other hand, the compressor 5 is operated with the three-way valve 30 being operated toward the heated side of the evaporator 4 to activate the heat pump cycle. That is, in the evaporator 4, the working fluid that has been heated and evaporated by the steam from the condensing crystallizer 1 is adiabatically compressed by the compressor 5 and raised in temperature. After adjusting the temperature, the liquid is guided to the heating side of the first heat exchanger 2, and heat is applied to the liquid to be treated to evaporate it.The working fluid itself is condensed, and the pressure is reduced by the expansion valve 20, and the liquid is 25, the water collects at the bottom of the evaporator 4, passes through a pipe 27, is guided to the top of the evaporator 4 by a pump 26, enters the heated side of the evaporator 4, and is drained from the concentration crystallizer 1 again. It is heated by steam and evaporates, forming a heat pump cycle.

When Freon 12 is used as the working fluid, the saturation temperature is 30 to 50 on the heating side of the first heat exchanger 2.
℃, and the temperature on the heated side of the evaporator 4 is about 0 to 10℃.

On the other hand, in the treated liquid path, the treated liquid discharged from the pump 6 is heated by the working fluid of the heat pump cycle on the heated side of the first heat exchanger 2, enters the concentration crystallizer 1, and is heated to a predetermined low pressure. It is evaporated and concentrated. The liquid to be treated thus concentrated is sucked into the pump 6 from the pipe line 13 again.
The mixture is circulated, heating in the first heat exchanger 2 is repeated, and evaporation continues, gradually concentrating and increasing the concentration. In this case, it is preferable to detect the pressure in the concentration crystallizer 1 and use the pressure controller 37 to maintain the pressure in the concentration crystallizer 1 at the saturated pressure at that temperature. That is, it passes along the route B→H in FIG. The evaporation temperature at this time is about 30°C.

The generated vapor of the liquid to be treated is led to the heating side of the evaporator 4 through the gas-liquid separator 17, heats the working fluid and evaporates it, and condenses itself to the evaporator 4.
The condensed water is discharged from the condensed water outlet 18.

When the concentration of the liquid to be treated increases and reaches a predetermined set value, the switching control mechanism 33 of the concentration crystallizer 1 detects this and outputs a switching signal to the three-way valves 7 and 30, causing the liquid to be discharged from the pump 6 to change. is directed toward the heating side of the second heat exchanger 3, and the working fluid discharged from the pump 26 is directed to the heating side of the second heat exchanger 3, and the working fluid discharged from the pump 26 is
1 to the heated side of the second heat exchanger 3, and passes through a working fluid bypass path.

The working fluid bypass path provides a low temperature working fluid on the low pressure side of the heat pump cycle. Therefore, the liquid to be treated guided by the pump 6 to the heating side of the second heat exchanger 3 is cooled by the working fluid, returns to the concentration crystallizer 1, is sucked into the pump 6 again, circulates, and is cooled. is repeated, and H→G in Figure 1
Following this path, the saturated solubility line A is reached and crystals precipitate. Crystals are grown by the stirring action of the stirrer 11 and are extracted from the outlet 12.

For the working fluid side cycle, the three-way valve 30
The working fluid led to the pipe line 31 cools the liquid to be treated in the second heat exchanger 3, but is heated and evaporated, returns to the evaporator 4 via the pipe line 32, and is transferred to the compressor 5. It is sucked into the cooler 19 and compressed.
(the first heat exchanger 2 does not operate), it is condensed, the pressure is reduced by the expansion valve 20, and the condensate becomes a low-pressure condensate that accumulates at the bottom of the evaporator 4 and flows through the pipe 27.
The water is sucked into the pump 26 and supplied to the pipe 31 again via the three-way valve 30 for circulation.

In addition, in order to carry out the present invention, in addition to the specific example shown in FIG. 2, it is also possible, for example, to share the first heat exchanger 2 and the second heat exchanger 3 in FIG. In some cases, the first heat exchanger 2 functions as a heater in which the working fluid is condensed in the process of concentrating the liquid to be treated, and on the other hand, in the process of cooling and crystallizing the concentrated machine-treated liquid, the first heat exchanger 2 functions as a heater in which the working fluid evaporates. It will function as a cooler using the latent heat of vaporization.
In this way, a concentrating crystallizer having fewer heat exchangers than the embodiment shown in FIG. 2 can be constructed.

〔Effect of the invention〕

The present invention skillfully combines a heat pump cycle, indirect pressurized evaporation, and cooling crystallization, and uses indirect heat transfer through indirect heating and indirect cooling. use,
Efficient evaporation and concentration of solutes does not require a large amount of steam for concentration, and does not require a large amount of cold heat source for cooling, using high or low temperature working fluid in the same heat pump cycle for heating and cooling. Therefore, there is no need for installation costs for a cold heat source, and operating costs can be greatly reduced.Furthermore, the evaporation concentration tank and concentration crystallization tank can be used together, and water at room temperature can be used. It is possible to provide an economical concentration and crystallization device that can utilize low solubility and concentrate at low temperature, eliminating the problem of recovering highly soluble components, and that the operating temperature is low, preventing coloring and decomposition of the product. It is possible to do so and has extremely great practical effects.

[Brief explanation of drawings]

FIG. 1 is a concentration-temperature graph illustrating the conventional method and the method of the present invention, and FIG. 2 is a flow diagram of an embodiment of the present invention. 1... Concentration crystallizer, 2... First heat exchanger, 3...
...second heat exchanger, 4...evaporator, 5...compressor,
6... Pump, 7... Three-way valve, 8... Supply port, 9
...Flow control valve, 10...Liquid level controller, 11...
Stirrer, 12... Outlet, 13, 14, 15, 1
6... Pipeline, 17... Gas-liquid separator, 18... Condensed water outlet, 19... Cooler, 20... Expansion valve, 2
2, 23, 24, 25...Pipeline, 26...Pump, 27,28...Pipeline, 30...Three-way valve, 3
1, 32...Pipeline, 33...Switching control mechanism, 34
...Vacuum pump, 35, 36...Pipe line, 37...
Pressure controller, 38...pressure control valve.

Claims (1)

[Scope of Claims] 1. A heating concentration step in which the liquid to be treated is heated and concentrated by the latent heat of condensation of the working fluid of the heat pump, and an operation in which the liquid to be treated is liquefied by steam generated in the heating concentration step. The liquid to be treated is concentrated by combining an evaporation step in which the fluid is heated and evaporated, and then the concentrated liquid obtained in the heating concentration step is cooled by the latent heat of vaporization of the working fluid of the heat pump to crystallize the dissolved components. and a cooling step in which the working fluid that evaporates in the cooling crystallization step is cooled and condensed using cooling water to crystallize the dissolved components in the concentrated liquid. Concentration crystallization method. 2 Concentration crystallizer, first heat exchanger, second heat exchanger,
An evaporator and a compressor are provided, and the heating side of the first heat exchanger and the heating side of the second heat exchanger are connected in parallel to the concentration crystallizer with respect to the flow of the liquid to be treated. a heat pump path for circulating working fluid from the compressor to the compressor via the heating side of the first heat exchanger and the heated side of the evaporator to form a heat pump cycle; a working fluid bypass path for guiding the working fluid in the low-pressure side path of the path to the heated side of the second heat exchanger and returning it to the low-pressure side for circulation; and a steam path leading to the heating side, and the liquid to be treated is circulated while being heated in the first heat exchanger to evaporate and concentrate the liquid to reach a predetermined concentration without using the path via the second heat exchanger. After that, the route of the liquid to be treated to the heated side of the first heat exchanger is cut off, the route is switched to the route passing through the second heat exchanger, and the liquid to be treated is cooled in the second heat exchanger. A concentration crystallizer characterized by having a switching control mechanism for switching.