JP2003080003A - Device for crystallizing by low pressure steam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for crystallizing by low pressure steam, which is able to improve the production efficiency and the quality of a crystal by crystallizing with a large amount of heat of the steam. SOLUTION: A pressure control valve 19 is connected to a steam supplying pipe 15 and a jacket part 6 of a crystallization tank 1 is connected to the steam supplying pipe 15 through a temperature control valve 23. Further, an ejector- type combined pump 16 as a sucking means is connected to the lower part of the jacket part 6 through a communication pipe 25. To the communication pipe 25, a steam trap 27 and a bypath valve 28 are attached. The ejector-type combined pump 16 is constituted by communicating an ejector 26, a tank 31 and a circulation pump 32. The inside of the jacket part 6 is maintained at about atmospheric pressure or a pressure lower than the atmospheric pressure by the ejector-type combined pump 16, and the crystallization tank 1 is heated by steam of about 100 deg.C or of a temperature lower than 100 deg.C.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystallization apparatus for separating and producing crystals such as fertilizers, pharmaceuticals, and rare earths from foods such as salt and sucrose. The present invention relates to a crystallizer using low-pressure steam as a source. 2. Description of the Related Art For example, a conventional crystallization apparatus shown in FIG. 2 has been used. In FIG. 2, a crystallization tank 1 for performing crystallization, a hot water tank 2 for supplying hot water for heating to the crystallization tank 1, a hot water pump 3, an inline mixer 4 provided at an outlet side of the hot water pump 3, A steam supply pipe 5 for supplying steam to the mixer 4;
The hot water and the steam are mixed to form hot water of a predetermined temperature, supplied to the jacket portion 6 covering the outer periphery of the crystallization tank 1, and the crystallization target is heated in the tank 1 for crystallization. [0003] The hot water deprived of heat by the heating in the jacket 6 reaches the hot water tank 2 again through the pipe 7 and the valve 8, is sent to the in-line mixer 4 by the pump 3 and circulates. A circulating water supply pipe 9 is connected to the hot water tank 2, and a temperature sensor 10 is attached between the in-line mixer 4 and the jacket section 6 to control the degree of opening and closing of the valve 11 of the steam supply pipe 5 so that the jacket section is opened. The temperature of the hot water supplied to 6 is controlled to a predetermined temperature. [0004] In the above-mentioned conventional crystallization apparatus, since warm water is used as a heating source, it takes a long time to start up the apparatus at an early stage, and a crystallization process is required. If the crystallized material undergoes a temperature change due to some disturbance or the like, there is a problem that it takes a relatively long time to return to the original set temperature. The long time required in the crystallization process leads to a decrease in production efficiency, and the instability of the set temperature causes the crystal quality, for example, particle size, particle size distribution, purity, etc.
It leads to a decrease in [0005] Warm water retains only sensible heat as a calorie, and since the retained calorie is small, it takes time to start up the apparatus or return to the original temperature after a temperature change has occurred once. . On the other hand, since steam has latent heat as a calorific value, its retained calorific value is much larger than that of hot water. An object of the present invention is to provide a crystallizer capable of improving production efficiency and improving crystal quality by performing crystallization with a large amount of heat held by steam. Means taken to solve the above problem are as follows. A crystallization tank contains an object to be crystallized, and the object to be crystallized is heated from a heating unit. In the analysis,
A vapor supply pipe is connected to the heating unit, and a suction unit is connected to the heating unit, and the inside of the heating unit is maintained at a low pressure state of about atmospheric pressure or less than atmospheric pressure by the suction unit, thereby lowering the pressure of the crystallized substance. It is heated by steam. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS By connecting a steam supply pipe and a suction means to a heating section to heat an object to be crystallized in a crystallization tank with low-pressure steam, low-pressure steam, ie, hot water It can be heated with steam having a large amount of heat at the same temperature as
The crystallization production efficiency and the crystal quality can be improved. [0009] Steam, more precisely saturated steam, is uniquely determined by its pressure and temperature. Usually, the temperature of steam at atmospheric pressure is 100 ° C., the temperature exceeds 100 ° C. at a pressure higher than the atmospheric pressure, and the temperature is 100 ° C. or lower at a vacuum pressure lower than the atmospheric pressure. Therefore, the heating temperature of the steam can be set to 100 ° C. or less by setting the suction unit to a pressure state equal to or lower than the atmospheric pressure. In this embodiment, as shown in FIG. 1, a jacket 6 as a heating unit is provided on the outer periphery of the crystallization tank 1 and integrally therewith. Means 1
6 is connected. The crystallization tank 1 has a cylindrical tank shape and contains a crystallized substance containing a rare earth element (not shown) therein. At the upper part of the crystallization tank 1, a temperature sensor 17 for detecting the temperature in the tank 1 is attached, and a precipitant tank 18 for supplying a precipitant into the tank 1 is connected. In addition, a jacket portion 6 that covers the entire periphery of the lateral outer periphery of the crystallization tank 1 is provided integrally. A steam supply pipe 15 is connected above the jacket 6. The steam supply pipe 15 has a pressure control valve 19, a condensate supply pipe 20, a gas-liquid separation separator 21, and a pressure sensor 2.
2, and the temperature control valve 23 are sequentially arranged. A bypass valve 24 is attached in parallel with the pressure control valve 19. The pressure sensor 22 is electrically connected to the pressure control valve 19. Also,
The temperature sensor 17 mounted on the upper part of the crystallization tank 1 is electrically connected to the temperature control valve 23. An ejector 26 of the suction means 16 is connected to a lower portion of the jacket 6 through a communication pipe 25. Communication pipe 2
5, a steam trap 27 which discharges only the condensed water in which the steam is condensed to the outlet side and does not discharge the steam, and a bypass valve 28 thereof are attached in parallel. The lower end of the communication tube 25 is connected to the suction chamber 29 of the ejector 26. A condensate pipe 30 hanging from the gas-liquid separation separator 21 joins the lower end of the communication pipe 25. In this embodiment, the suction means 16 is an ejector 26.
And an ejector-type combination pump in which the tank 31 and the circulation pump 32 are combined. Circulating fluid in the tank 31,
Normally, a predetermined amount of normal-temperature water is stored, and the water is circulated from the ejector 26 to the tank 31 by the circulation pump 32 to generate a suction force in the suction chamber 29 by the suction action of the ejector 26, and the crystallization tank 1 Is maintained at a predetermined pressure state, that is, an atmospheric pressure or a negative pressure lower than the atmospheric pressure. A circulating fluid supply pipe 33 is connected to the tank 31 via a valve 34. Since the suction force generated by the ejector 26 becomes a saturation pressure corresponding to the temperature of the fluid flowing down in the ejector 26, the fluid is replenished from the circulating fluid replenishing pipe 33 and the fluid temperature is appropriately adjusted, so that the ejector 26 The suction force can be arbitrarily controlled. For example, when a low-temperature steam of 80 ° C. is supplied into the jacket portion 6 to heat the material to be crystallized, the suction force of the ejector 26 is reduced to the saturation pressure of the steam at a temperature slightly lower than 80 ° C. A predetermined temperature state can be maintained by adjusting the temperature of the circulating fluid so that a suction force of a corresponding pressure is obtained. By lowering the temperature of the circulating fluid to lower the suction pressure of the ejector 26, the temperature of the heated steam can be further reduced. The circulation path 14 of the suction means 16 is branched and a surplus fluid discharge pipe 35 and a valve 36 are attached. Valve 36
By opening the valve, the excess fluid in the tank 31 can be discharged out of the system. The circulation path 14 is further branched, and a circulation fluid take-out pipe 37 is connected. The circulating fluid outlet pipe 37 communicates with the condensate supply pipe 20 via a valve 38,
A part of the circulating fluid, that is, condensate is injected from the condensate supply pipe 20 into the steam supply pipe 15 to lower the temperature of the steam in the steam supply pipe 15 to the saturation temperature. The mixed fluid of steam and condensate in the steam supply pipe 15 is separated into steam and condensate by a gas-liquid separation separator 21.
Condensate is drawn from the condensate pipe 30 to the ejector 26, while
The separated saturated steam is supplied from the temperature control valve 23 to the jacket 6. When crystallization is performed by heating the material to be crystallized in the crystallization tank 1, first, the bypass valve 28 is opened, and the ejector type combination pump 16 is driven to activate the jacket by the suction force of the ejector 26. The inside of the section 6 is set to a predetermined low pressure state. Further, by supplying heating steam of a predetermined pressure and temperature from the pressure control valve 19 and the temperature control valve 23 into the jacket portion 6, the temperature of the jacket portion 6 and the crystallization tank 1 is lowered to room temperature at the initial startup. Even if the heating is performed, by heating with a large amount of heat held by the steam, the temperature can be raised to a predetermined temperature in a short time and the startup time can be shortened. When the temperature of the jacket 6 reaches a predetermined temperature, crystallization is performed in the crystallization tank 1. The vapor whose heat has been removed by heating the crystallized substance is condensed and condensed, and is condensed. The vapor is sucked into the ejector 26 from the communication pipe 25 and the steam trap 27 or the bypass valve 28 and reaches the tank 31. In addition, the bypass valve 28 may be in a fully closed state during crystallization, or
It can also be in a slightly open state. When crystallization is carried out by supplying a precipitant from the precipitant tank 18 into the crystallization tank 1, the precipitant is supplied into the tank 1 because the temperature of the precipitant is generally as low as room temperature. Then, the temperature in the tank 1 immediately drops by about 1 degree to several degrees C from the set temperature. As described above, even if the set temperature changes due to disturbance, the temperature sensor 17 detects the change in temperature and adjusts the opening of the temperature control valve 23 to control the amount of steam supplied. Can be returned to the set temperature with a very slight time delay. When crystallization of a rare earth element is carried out as in this embodiment, steam heating is used in place of the conventional hot water heating, thereby eliminating the instability of the set temperature and sharpening the crystal particle size distribution. The variation in the particle size distribution of the particles is small, and the amount of crystals falling within a predetermined particle size range increases, so that more crystals that can be used as a product can be produced, and the production efficiency can be significantly improved. . According to the crystallization apparatus using low-pressure steam of the present invention,
By connecting a heating steam supply pipe and suction means to the heating section of the crystallization tank and heating the crystallization target in the crystallization tank with low-pressure steam, it can be heated with a large amount of retained heat of steam. ,
The crystallization production efficiency and the crystal quality can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing an embodiment of a low-temperature steam crystallization apparatus of the present invention. FIG. 2 is a configuration diagram showing a conventional crystallization apparatus. [Description of Signs] 1 Crystallization tank 6 Jacket section 15 Steam supply pipe 16 Suction means 17 Temperature sensor 19 Pressure control valve 21 Gas-liquid separation separator 23 Temperature control valve 26 Ejector 31 Tank 32 Circulation pump

Claims (1)

Claims 1. A crystallization tank containing an object to be crystallized and heating the object to be crystallized from a heating section, wherein a steam supply pipe is connected to the heating section. At the same time, the suction means is connected to the heating unit, and the inside of the heating unit is maintained at a low pressure of about atmospheric pressure or less than the atmospheric pressure by the suction means, thereby heating the crystallized substance with low-pressure steam. Crystallization equipment using low pressure steam.