Nickel sulfate continuous crystallization system

Abstract

The utility model belongs to the technical field of industrial crystallization, and discloses a nickel sulfate continuous crystallization system. Comprising a stock solution storage tank, a pretreatment unit, a concentration unit and a crystallization unit, wherein the pretreatment unit comprises an iron remover, a filter and a preheating assembly which are sequentially communicated with a stock solution storage tank; the concentration unit comprises a forced circulation evaporator and a crystallization separator, and the crystallization unit comprises a cooling crystallizer, a cooling circulation pump, a hot crystal eliminator, a condenser, a condensed water tank, a vacuum pump, a thickener and a centrifugal machine. The nickel sulfate continuous crystallization system disclosed by the utility model is convenient to operate, high in continuous cooling crystallization efficiency and suitable for crystallization of nickel sulfate with different particle size requirements.

Description

Technical Field

[0001] The utility model belongs to the technical field of industrial crystallization and relates to a nickel sulfate continuous crystallization system. Background Art

[0002] As an important chemical raw material, nickel sulfate is widely used in civil, construction, aerospace equipment, defense industry and other fields, especially in the fields of batteries and electroplating. Industrial production mainly focuses on nickel sulfate hexahydrate. Nickel sulfate solution undergoes acid adjustment, evaporation, crystallization, centrifugal drying, screening and packaging to produce nickel sulfate products. In the entire production process, the crystallization process is very critical and directly affects the quality of nickel sulfate products.

[0003] The preparation of nickel sulfate is generally carried out by evaporating and concentrating a dilute solution to a certain specific gravity, and then obtaining the nickel sulfate product by intermittent crystallization. The intermittent crystallization process of nickel sulfate crystals has the following disadvantages: (1) single-pot crystallization is used, which requires many process parameters to be controlled and results in low product batch uniformity; (2) batch operation is completed, resulting in low production efficiency; (3) high investment cost and large land occupation; (4) high energy consumption during the evaporation and concentration process. Utility Model Content

[0004] In view of the problems existing in the prior art, the purpose of the utility model is to provide a nickel sulfate continuous crystallization system.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0006] A nickel sulfate continuous crystallization system comprises a stock solution storage tank, a pretreatment unit, a concentration unit, and a crystallization unit; wherein:

[0007] The pretreatment unit comprises an iron remover, a filter and a preheating assembly which are sequentially connected to the stock liquid storage tank;

[0008] The concentration unit comprises a forced circulation evaporator and a crystal separator, the preheating assembly is connected to the feed port of the crystal separator, the slurry circulation outlet of the crystal separator is connected to the slurry feed port of the forced circulation evaporator, and the slurry outlet of the forced circulation evaporator is connected to the slurry circulation reflux port of the crystal separator;

[0009] The crystallization unit includes a cooling crystallizer, a cooling circulation pump, a hot crystal eliminator, a condenser, a condensate tank, a vacuum pump, a thickener and a centrifuge. The slurry discharge port of the crystallization separator and the bottom circulation discharge port of the cooling crystallizer are connected with the feed port of the cooling crystallizer through the cooling circulation pump. The fine crystal discharge port of the cooling crystallizer is connected with the fine crystal reflux port of the cooling crystallizer through the hot crystal eliminator. The secondary steam outlet of the cooling crystallizer is connected with the condenser, the condensate tank and the vacuum pump in sequence; the crystal discharge port of the cooling crystallizer is connected with the thickener and the centrifuge in sequence.

[0010] Furthermore, the crystal separator is a FC crystal separator.

[0011] Furthermore, the cooling crystallizer is a DTB cooling crystallizer.

[0012] Furthermore, the preheating component includes a distilled water preheater, a non-condensable gas preheater and a steam preheater which are connected in sequence, the distilled water preheater is connected to the filter, and the steam preheater is connected to the crystallization separator.

[0013] Further preferably, it also includes a distilled water tank, and the condensed water outlet of the forced circulation evaporator, and / or the steam outlet of the forced circulation evaporator, and / or the non-condensable gas preheater, and / or the distilled water preheater are connected to the distilled water tank.

[0014] Further preferably, the steam outlet of the crystallizer separator is connected to the secondary separator, the steam compressor and the forced circulation evaporator in sequence.

[0015] Furthermore, a pH meter is provided at the inlet pipe of the iron remover.

[0016] Furthermore, a steam electric regulating valve is arranged on the steam inlet pipe of the steam preheater.

[0017] Furthermore, a first thermometer is provided on the liquid outlet pipe of the steam preheater.

[0018] Furthermore, a feed electric valve is provided on the feed liquid inlet pipeline of the crystallization separator;

[0019] Furthermore, the crystallization separator is provided with a third thermometer for monitoring the temperature of the material at the slurry discharge port and / or the slurry circulation discharge port.

[0020] Furthermore, the crystal separator is provided with a first liquid level meter for monitoring the liquid level in the crystal separator.

[0021] Furthermore, the crystallization separator is provided with a first density meter for monitoring the density of the material at the slurry discharge port.

[0022] Furthermore, the crystallizer separator is provided with a second thermometer for monitoring the temperature at the secondary steam outlet.

[0023] Furthermore, the crystallizer separator is provided with a second pressure gauge for monitoring the pressure at the secondary steam outlet.

[0024] Furthermore, the cooling crystallizer is provided with a second liquid level gauge for monitoring the liquid level in the cooling crystallizer.

[0025] Furthermore, the cooling crystallizer is provided with a fourth thermometer for monitoring the temperature at the steam outlet.

[0026] Furthermore, the cooling crystallizer is provided with a third pressure gauge for monitoring the pressure at the steam outlet.

[0027] Furthermore, the cooling crystallizer is provided with a fifth thermometer for monitoring the temperature at the crystallization discharge port.

[0028] Furthermore, the cooling crystallizer is provided with a first ultrasonic particle size analyzer for monitoring the growth of crystal particle size at the crystallization discharge port.

[0029] Furthermore, a flow promoter is arranged in the cooling crystallizer.

[0030] Furthermore, a raw steam regulating valve is provided on the raw steam inlet pipeline of the hot crystal eliminator.

[0031] Furthermore, a second ultrasonic particle size analyzer is arranged on the connecting pipe between the hot crystal eliminator and the fine crystal reflux port of the cooling crystallizer.

[0032] Furthermore, the thickener is provided with a second density meter for monitoring the density of the material at the bottom crystallization outlet.

[0033] Furthermore, a crystal discharge electric valve is provided on the connecting pipeline between the thickener and the centrifuge.

[0034] Furthermore, it also includes a control unit, and the pretreatment unit, and / or the concentration unit, and / or the crystallization unit are electrically connected to the control unit.

[0035] Compared with the prior art, the beneficial effects of the utility model are:

[0036] (1) The nickel sulfate continuous crystallization system of the utility model is easy to operate, has high continuous cooling crystallization efficiency, and can be applied to the crystallization of nickel sulfate with different particle size requirements.

[0037] (2) Factors affecting the cooling crystallization process of nickel sulfate include pH, temperature, density, stirring rate, and particle size growth during the crystallization process. The utility model creatively sets a control unit and a detection device or electronic control device electrically connected to the control unit and located on each component, which can indirectly or directly characterize all influencing factors, and optimize the nickel sulfate crystallization process by adjusting the parameters of each detection device or electronic control device to obtain a better product.

[0038] (3) The utility model can realize continuous cooling crystallization of nickel sulfate through PLC logic control of the control unit of the ultrasonic particle size analyzer, instrument, pump and valve. In the growth process of nickel sulfate crystals, gradient cooling is achieved to avoid the problem of nucleation caused by sudden temperature drop. The particle size distribution can also be monitored and analyzed in real time to obtain nickel sulfate crystals with ideal particle size.

[0039] (4) The utility model is provided with an ultrasonic particle size analyzer to perform preliminary screening of the particle size that meets the requirements during the crystal growth stage. After the proportion reaches the requirements, the particle size is discharged to the thickener for thickening, thereby improving the qualified rate of crystals with the required particle size. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0041] Figure 1 This is a schematic diagram of the structure of the nickel sulfate continuous crystallization system of the utility model;

[0042] Figure 2 This is a schematic diagram of the structure of the crystallization separator of the utility model;

[0043] Figure 3 This is a schematic diagram of the structure of the forced circulation evaporator of the utility model;

[0044] Figure 4 This is a schematic diagram of the structure of the cooling crystallizer of the utility model;

[0045] In the figure:

[0046] 1—iron remover, 101—pH meter;

[0047] 2—precision filter;

[0048] 3—water inlet pump;

[0049] 4—Distilled water preheater;

[0050] 5—Non-condensable gas preheater;

[0051] 6—steam preheater, 601—steam electric regulating valve, 602—first thermometer;

[0052] 7—crystallization separator, 701—feeding electric valve, 702—first liquid level gauge, 703—second thermometer, 704—second pressure gauge, 705—first density meter, 708—third thermometer, 706—crystal slurry discharge port, 707—crystal slurry circulation discharge port, 709—crystal slurry circulation reflux port, 710—crystalization separator feed port, 711—crystalization separator steam outlet;

[0053] 8—Forced circulation pump;

[0054] 9—forced circulation evaporator, 901—secondary steam inlet, 902—crystal slurry inlet, 903—condensed water outlet, 904—steam outlet, 905—raw steam inlet, 906—non-condensable gas outlet, 907—crystal slurry outlet;

[0055] 10—Slurry discharge pump;

[0056] 11—cooling crystallizer, 1101—slurry feed electric valve, 1102—feed port, 1103—fine crystal discharge port, 1104—fourth thermometer, 1105—third pressure gauge, 1106—second liquid level gauge 1107—fifth thermometer, 1108—first ultrasonic particle size analyzer, 1109—bottom circulation discharge port, 1110—fine crystal reflux port, 1111—second ultrasonic particle size analyzer, 1112—flow pusher, 1113—crystallization discharge port, 1114—steam outlet of cooling crystallizer;

[0057] 12—Cooling circulation pump;

[0058] 13—thermal crystal elimination pump;

[0059] 14—hot crystal eliminator, 1401—raw steam regulating valve;

[0060] 15—condenser;

[0061] 16—condensate tank;

[0062] 17—Vacuum pump;

[0063] 18—Crystallization discharge pump;

[0064] 19—thickener, 1901—second density meter, 1902—crystallization discharge electric valve;

[0065] 20 - centrifuge;

[0066] 21—steam compressor;

[0067] 22—secondary separator, 2201—sixth thermometer, 2202—fourth pressure gauge.

[0068] 23—distilled water tank;

[0069] 24—Concentrated liquid storage tank. DETAILED DESCRIPTION

[0070] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

[0071] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present utility model.

[0072] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0073] Example 1

[0074] like Figure 1 As shown, this embodiment discloses a nickel sulfate continuous crystallization system, including a pretreatment unit, a concentration unit, and a crystallization unit.

[0075] As one of the preferred solutions of this embodiment, it also includes a control unit, and the pretreatment unit, the concentration unit, and the crystallization unit are electrically connected to the control unit.

[0076] In this embodiment, the purpose of the pretreatment unit is to purify and preheat the feed liquid. The pretreatment unit includes: an iron remover 1, a filter 2, a water inlet pump 3, a distilled water preheater 4, a non-condensable gas preheater 5, and a steam preheater 6.

[0077] As one of the preferred solutions of this embodiment, a pH meter 101 is provided at the inlet pipe of the iron remover 1 to monitor the pH value of the feed liquid.

[0078] As one of the preferred solutions of this embodiment, the iron remover 1 adopts permanent magnet or electromagnetic specifications, and can effectively remove ferromagnetic fine impurities in the slurry by using the strong magnetic field attraction.

[0079] As one of the preferred solutions of this embodiment, the filter 2 adopts a precision filter, the filtration accuracy of the precision filter is less than 0.1 μm, and it can effectively intercept non-magnetic impurities in the liquid.

[0080] In this embodiment, an iron remover 1 and a filter 2 are arranged at the inlet end of the feed liquid to intercept and remove magnetic and non-magnetic impurities in the feed liquid, and the nickel sulfate crystal product is refined and purified at the initial end. Then, the product is pumped into the preheating assembly through the water inlet pump 3.

[0081] As one of the preferred schemes of this embodiment, during the operation of the preheating component, the heat source of the distilled water preheater 4 comes from the distilled water of the entire system, which raises the temperature of the feed liquid from 30~36°C to 45~48°C; the non-condensable gas preheater 5 is arranged after the distilled water preheater 4, and uses the non-condensable gas generated by the system to continue to raise the temperature of the feed liquid by 5~10°C to 55~65°C, and enters the steam preheater 6; the steam preheater 6 uses raw steam to heat the feed liquid to 90°C and enters the concentration unit.

[0082] As one of the preferred solutions of this embodiment, a steam electric regulating valve 601 is arranged on the steam inlet pipe of the steam preheater 6, and a first online thermometer 602 is arranged on the slurry outlet pipe of the steam preheater 6. The steam electric regulating valve 601 and the first thermometer 602 are electrically connected via a control unit to realize linkage, and the valve opening of the steam electric regulating valve 601 is accurately controlled by the set slurry temperature, thereby accurately controlling the steam consumption.

[0083] In this embodiment, the concentration unit includes a forced circulation evaporator 9 , a crystal separator 7 and a steam compressor 21 .

[0084] In this embodiment, the crystal separator 7 is a FC crystal separator.

[0085] As one of the preferred solutions of this embodiment, during the operation of the concentration unit, the nickel sulfate feed liquid heated to 90°C enters the FC crystal separator 7 for flash evaporation, the steam enters the secondary separator 22 through the crystal separator steam outlet 711 for purification, and then enters the steam compressor 21 for pressurization and temperature increase, and the feed liquid is pumped into the forced circulation evaporator 9 through the bottom slurry circulation outlet 707 by the forced circulation pump 8, heated to 90-98°C, and then refluxed to the FC crystal separator 7. Until the concentrated saturation concentration reaches the set value of the first density meter 705, it is transported to the crystal unit through the slurry discharge pump 10.

[0086] Specifically, the temperature rise of the steam compressor 21 must be higher than the boiling point rise of the nickel sulfate solution, so as to meet the requirement that the boiling point rises when the concentration of the nickel sulfate solution increases.

[0087] As one of the preferred schemes of this embodiment, a feed electric valve is provided on the feed liquid inlet pipeline of the crystal separator; the crystal separator is provided with a third thermometer for monitoring the material temperature at the slurry discharge port and / or the slurry circulation discharge port; the crystal separator is provided with a first liquid level gauge for monitoring the liquid level in the crystal separator; the crystal separator is provided with a first density gauge for monitoring the material density at the slurry discharge port; the crystal separator is provided with a second thermometer for monitoring the temperature at the secondary steam outlet; the crystal separator is provided with a second pressure gauge for monitoring the pressure at the secondary steam outlet; the cooling crystallizer is provided with a second liquid level gauge for monitoring the liquid level in the cooling crystallizer ; The cooling crystallizer is provided with a fourth thermometer for monitoring the temperature at the steam outlet; the cooling crystallizer is provided with a third pressure gauge for monitoring the pressure at the steam outlet; the cooling crystallizer is provided with a fifth thermometer for monitoring the temperature at the crystallization discharge port; the cooling crystallizer is provided with a first ultrasonic particle size analyzer for monitoring the crystal particle size growth at the crystallization discharge port, and the first ultrasonic particle size analyzer 1108 has an imaging function; a flow pusher is provided in the cooling crystallizer; a raw steam regulating valve is provided on the raw steam inlet pipe of the hot crystal eliminator; a second ultrasonic particle size analyzer is provided on the connecting pipe between the hot crystal eliminator and the fine crystal reflux port of the cooling crystallizer.

[0088] Specific:

[0089] A feed electric valve 701 is provided on the feed liquid inlet pipeline of the crystal separator 7 and is electrically connected to the first liquid level meter 702 through a control unit, and the opening of the feed electric valve is determined by the height of the liquid level in the crystal separator.

[0090] A second thermometer 703 and a first pressure gauge 704 are provided near the steam outlet 711 at the top of the crystallizer separator 7 to monitor the temperature and pressure of the steam in the upper part of the container.

[0091] The crystal separator 7 cylinder is provided with a first liquid level meter 702, a feed port 710, a slurry circulation reflux port 709, a third thermometer 708, a slurry circulation discharge port 707, a first density meter 705 and a slurry discharge port 706 in order from high to low.

[0092] Among them: the third thermometer 708 is electrically connected to the forced circulation pump 8 through the control unit to realize linkage, and the frequency of the forced circulation pump 8 is adjusted by the temperature of the liquid in the cylinder, thereby adjusting the slurry reflux amount. The first density meter 705 is electrically connected to the slurry discharge pump 10 through the control unit to realize linkage, and the slurry discharge pump 10 is turned on when the liquid concentration in the cylinder reaches the set requirement, and the slurry in the cylinder is discharged to the crystallization unit.

[0093] In this embodiment, the crystallization unit includes: a cooling crystallizer 11, a cooling circulation pump 12, a hot crystal elimination pump 13, a hot crystal eliminator 14, a condenser 15, a condensate tank 16, a vacuum pump 17, a crystallization discharge pump 18, a thickener 19, and a centrifuge 20.

[0094] In this embodiment, the cooling crystallizer 11 adopts a DTB cooling crystallizer.

[0095] As one of the preferred schemes of this embodiment, the cooling crystallizer 11 is provided with a second liquid level gauge 1106 for monitoring the liquid level in the cooling crystallizer 11; the cooling crystallizer 11 is provided with a fourth thermometer 1104 for monitoring the temperature at the steam outlet 1114 of the cooling crystallizer; the cooling crystallizer 11 is provided with a third pressure gauge 1105 for monitoring the pressure at the steam outlet 1114 of the cooling crystallizer; the cooling crystallizer 11 is provided with a fifth thermometer 1107 for monitoring the temperature at the crystallization discharge port 1113; the cooling crystallizer 11 is provided with a first ultrasonic particle size analyzer 1108 for monitoring the growth of crystal particle size at the crystallization discharge port 1113; a flow pusher 1113 is arranged in the cooling crystallizer 11.

[0096] As one of the preferred solutions of this embodiment, a raw steam regulating valve 1401 is provided on the raw steam inlet pipe of the hot crystal eliminator 14; a second ultrasonic particle size analyzer 1111 is provided on the connecting pipe between the hot crystal eliminator 14 and the fine crystal reflux port 1110 of the cooling crystallizer 11.

[0097] As one of the preferred solutions of this embodiment, the thickener 19 is provided with a second densitometer 1901 for monitoring the density of the material at the bottom crystallization outlet; and a crystallization discharge electric valve 1902 is provided on the connecting pipeline between the thickener 19 and the centrifuge 20 .

[0098] Specific:

[0099] During the operation of the crystallization unit, the saturated nickel sulfate solution enters the cooling crystallizer 11, and the cooling rate is controlled by temperature, vacuum degree, and cooling cycle volume, and the temperature is slowly cooled to 40-45°C, and the supersaturation of the nickel sulfate solution is slowly reduced, thereby controlling the number and growth rate of crystals. The first ultrasonic particle size analyzer 1108 can monitor the growth of crystal particle size. If the set requirements are met, the crystal discharge pump 18 can be started to pump the crystals into the thickener 19 for solid-liquid separation. The second density meter 1901 is installed at the bottom of the thickener 19. The solid content meets the set requirements. The crystals with higher solid content enter the centrifuge 20 for centrifugal dehydration to form salt.

[0100] The cooling crystallizer 11 is a key device for continuous cooling crystallization of nickel sulfate. The temperature drop caused by the boiling of the feed liquid under negative pressure and the dual effect of the cooling circulation pump 12 form the supersaturation power of nickel sulfate. The frequency conversion control of the vacuum pump 17 and the cooling circulation pump 12 can make the supersaturation of the solution in the cooling crystallizer 11 always within the range of the crystallization metastable zone. At the same time, the evaporation temperature in the system is low, and the solubility of nickel sulfate is small, so the boiling point rises low, and nickel sulfate can be continuously crystallized in the cooling crystallizer 11. The cooling crystallizer 11 is provided with a fourth thermometer 1104, a fifth thermometer 1107 and a third pressure gauge 1105, which are controlled by the vacuum pump 17 and the cooling circulation pump 12 to control the control unit PLC logic control, so as to realize the gradient cooling of the cooling crystallizer 11 to control the supersaturation rate of the solution and control the growth rate of the crystal.

[0101] The fine crystal solution at the top of the cooling crystallizer 11 enters the hot crystal eliminator 14 through the fine crystal discharge port 1103, and after being heated by raw steam to eliminate fine crystals, it returns to the cooling crystallizer 11 through the fine crystal reflux port 1110. The fine crystal reflux pipeline is installed with a hot crystal elimination pump 13 and a second ultrasonic particle size analyzer 1111. The second ultrasonic particle size analyzer 1111 and the raw steam regulating valve 1401 of the hot crystal eliminator 14 are electrically connected through a control unit to achieve linkage, so as to dissolve the fine crystals with the lowest steam consumption.

[0102] The first ultrasonic particle size analyzer 1108, the flow promoter 1112, and the crystallization discharge pump 18 at the lower part of the cooling crystallizer 11 are electrically connected through the control unit to realize logical linkage. The driving rate of the flow promoter 1112 is conducive to the growth of the particle size. When the particle size meets the requirements, the crystallization discharge pump 18 is turned on to pump the crystals into the thickener 19, and the crystallization solution is separated into solid and liquid in the thickener 19. The second density meter 1901 at the bottom of the thickener 19 is electrically connected to the crystallization discharge electric valve 1902 through the control unit to realize linkage. When the second density meter 1901 reaches the set value, the crystallization electric valve 1902 is turned on, and the thickened crystallization solution enters the centrifuge 20 for dehydration and drying.

[0103] The fourth thermometer 1104, the fifth thermometer 1107, the third pressure gauge 1105, the vacuum pump 17 and the cooling circulation pump 12 provided in the cooling crystallizer 11 gradually reduce the vacuum degree of the cooling crystallizer 11 and the boiling point of the feed liquid through the frequency conversion regulation of the vacuum pump 17 and the cooling circulation pump 12. The continuous cooling crystallization of sulfuric acid is realized through the PLC logic control of the instrument and the pump, with high control accuracy and small equipment investment.

[0104] In this embodiment, the thermometer, level gauge and pressure gauge used all have recording, adjustment, display and remote transmission functions. The vacuum pump, circulation pump and discharge pump all have frequency conversion control function. The electric valves are all electric proportional control valves to accurately control the flow. All instruments such as level gauges, thermometers, valves and pumps are integrated into the control unit of the intelligent control system, and the control unit can be set with a remote control function to achieve remote control.

[0105] This embodiment can be applied to the crystallization of nickel sulfate with different particle sizes, and can also be used for the crystallization of other inorganic salt solutions.

[0106] As one of the preferred solutions of this embodiment, the nickel sulfate continuous crystallization system of this embodiment is used to prepare nickel sulfate crystal salt, comprising the following steps:

[0107] The salt content of the initial nickel sulfate solution in the stock solution storage tank 24 is 22%, the temperature is 32-36° C., and the pH value is 3-4.

[0108] The initial nickel sulfate liquid first passes through an iron remover 1 to remove magnetic fine matter, and then passes through a filter 2 to retain non-magnetic impurities. The nickel sulfate raw material liquid after impurities removal is pumped into a distilled water preheater 4, a non-condensable gas preheater 5 and a steam preheater 6 in sequence through a water inlet pump 3. The liquid is heated to 90°C and enters a crystallizer 7 through a crystallizer feed port 710.

[0109] The nickel sulfate liquid flashes in the crystallizer separator 7, and the steam enters the secondary separator 22 from the steam outlet 711 of the crystallizer separator 7. After purification, foam removal and impurity removal, it enters the steam compressor 21, is pressurized and heated to about 108°C, and the secondary steam enters the forced circulation evaporator 9 through the secondary steam inlet 901. After heat exchange with the material in the forced circulation evaporator 9, it becomes distilled water and enters the distilled water tank 23 through the condensed water outlet 903.

[0110] During the system startup, live steam is required, so the forced circulation evaporator 9 is provided with a live steam inlet 905 and a steam outlet 904. After the system is running, there is almost no need to replenish live steam, and the live steam inlet and outlet can be closed. The non-condensable gas of the forced circulation evaporator 9 enters the non-condensable gas preheater 5 through the non-condensable gas outlet 906.

[0111] The liquid in the crystal separator 7 is connected to the forced circulation pump 8 pipeline via the slurry circulation outlet 707 and pumped into the slurry inlet 902 of the forced circulation evaporator 9. The heated liquid refluxes into the slurry circulation reflux port 709 of the crystal separator 7 via the slurry circulation outlet 907.

[0112] The nickel sulfate slurry is circulated and concentrated between the crystal separator 7 and the forced circulation evaporator 9 until the concentration reaches 40-45%.

[0113] During the concentration process, if the first liquid level meter 702 detects a high liquid level, the feed valve electric valve 701 is closed, and the forced circulation pump 8 is turned on. The opening frequency of the forced circulation pump 8 is linked to the second thermometer 708. When the temperature is high, the circulation pump 8 has a low frequency, and when the temperature is low, the circulation pump 8 has a high frequency. As the slurry continues to evaporate, the slurry concentration increases, the liquid level in the cylinder decreases, and the feed electric valve 701 is opened to replenish the liquid. The first density meter at the bottom of the cylinder monitors the liquid density of 1.5~1.8g / cm 3 When the concentration reaches 45-50%, the slurry discharge pump 10 is turned on and the slurry is pumped into the crystal separator 7. When the first liquid level gauge 702 detects that the liquid level reaches the lowest point, the forced circulation pump 8 is turned off to protect the pump until the stock liquid is replenished to the set requirement, and the forced circulation pump 8 is turned on again.

[0114] A nickel sulfate solution with a temperature of 90-98°C and a concentration of 45-50% enters the cooling crystallizer 11, and the vacuum pump 17 slowly draws to reduce the negative pressure. The cooling circulation pump 12 extracts the liquid from the bottom circulation outlet 1109 of the cooling crystallizer 11, cools it, and enters the fine crystal reflux pipeline to return to the cylinder from the feed port 1102 of the cooling crystallizer 11. After the cooling reflux liquid is mixed with the feed liquid, the temperature of the feed liquid is reduced, reducing the temperature impact of the feed liquid on the system.

[0115] The liquid is continuously cooled in the cooling crystallizer 11, and crystals are continuously nucleated and grown. The fine crystals in the supernatant enter the hot crystal eliminator 14 through the fine crystal discharge port 1103 to be heated and dissolved, and then return to the cylinder from the fine crystal reflux port 1110.

[0116] During the process, the fine crystal reflux pipeline is provided with a second ultrasonic particle size analyzer 1111 which is electrically connected to the steam regulating valve 1401 of the hot crystal eliminator 14 to accurately control the steam consumption and ensure the complete dissolution of the fine crystals. When the second liquid level meter 1106 detects a high liquid level, it is closed; otherwise, when it reaches a low liquid level, the slurry feed electric valve 1101 is opened.

[0117] The first ultrasonic particle size analyzer 1108 is linked with the flow pusher 1112, the fifth thermometer 1107 and the crystallization discharge pump 18 through a control unit. The pushing rate of the flow pusher 1112 is conducive to the growth of the crystal nucleus. When 80% of the crystal nucleus particle size distribution is greater than 500μm, the crystallization discharge pump 18 is turned on to pump the crystals into the thickener 19.

[0118] The solution containing high-concentration nickel sulfate crystals is subjected to solid-liquid separation in the thickener 19. A second density meter 1901 is arranged at the bottom of the thickener 19. After reaching the set requirements, the solution enters the centrifuge through the crystallization discharge electric valve 1902 for centrifugal dehydration to obtain nickel sulfate crystal salt with a water content of less than 5%.

[0119] Part of the supernatant of the thickener 19 and the supernatant of the centrifuge 20 is returned to the raw water tank, and part is discharged to the system.

[0120] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the present invention.

Claims

1. A nickel sulfate continuous crystallization system, characterized in that: It includes a raw liquid storage tank, a pretreatment unit, a concentration unit, and a crystallization unit; among which: The pretreatment unit comprises an iron remover, a filter and a preheating assembly which are sequentially connected to the stock liquid storage tank; The concentration unit comprises a forced circulation evaporator and a crystal separator, the preheating assembly is connected to the feed port of the crystal separator, the slurry circulation outlet of the crystal separator is connected to the slurry feed port of the forced circulation evaporator, and the slurry outlet of the forced circulation evaporator is connected to the slurry circulation reflux port of the crystal separator; The crystallization unit includes a cooling crystallizer, a cooling circulation pump, a hot crystal eliminator, a condenser, a condensate tank, a vacuum pump, a thickener and a centrifuge. The slurry discharge port of the crystallization separator and the bottom circulation discharge port of the cooling crystallizer are both connected to the feed port of the cooling crystallizer through the cooling circulation pump. The fine crystal discharge port of the cooling crystallizer is connected to the fine crystal reflux port of the cooling crystallizer through the hot crystal eliminator. The secondary steam outlet of the cooling crystallizer is connected to the condenser, the condensate tank and the vacuum pump in sequence; the crystal discharge port of the cooling crystallizer is connected to the thickener and the centrifuge in sequence.

2. The nickel sulfate continuous crystallization system according to claim 1, characterized in that: The preheating component comprises a distilled water preheater, a non-condensable gas preheater and a steam preheater which are connected in sequence, the distilled water preheater is connected to a filter, and the steam preheater is connected to a crystallization separator.

3. The nickel sulfate continuous crystallization system according to claim 2, characterized in that: It also includes a distilled water tank, and one or more of the condensed water outlet of the forced circulation evaporator, the steam outlet of the forced circulation evaporator, the non-condensable gas preheater and the distilled water preheater are connected to the distilled water tank.

4. The nickel sulfate continuous crystallization system according to claim 1 or 3, characterized in that: The steam outlet of the crystallization separator is connected with the secondary separator, the steam compressor and the forced circulation evaporator in sequence.

5. The nickel sulfate continuous crystallization system according to claim 1, characterized in that: A pH meter is arranged on the inlet pipe of the iron remover.

6. The nickel sulfate continuous crystallization system according to claim 2, characterized in that: A steam electric regulating valve is arranged on the steam inlet pipe of the steam preheater; A first thermometer is arranged on the liquid outlet pipeline of the steam preheater.

7. The nickel sulfate continuous crystallization system according to claim 1, characterized in that: A feed electric valve is arranged on the feed liquid inlet pipeline of the crystal separator; The crystallization separator is provided with a third thermometer for monitoring the temperature of the material at the slurry discharge port and / or the slurry circulation discharge port; The crystal separator is provided with a first liquid level gauge for monitoring the liquid level in the crystal separator; The crystal separator is provided with a first density meter for monitoring the material density at the slurry discharge port; The crystallizer separator is provided with a second thermometer for monitoring the temperature at the secondary steam outlet; The crystallizer separator is provided with a second pressure gauge for monitoring the pressure at the secondary steam outlet.

8. The nickel sulfate continuous crystallization system according to claim 1, characterized in that: The cooling crystallizer is provided with a second liquid level gauge for monitoring the liquid level in the cooling crystallizer; The cooling crystallizer is provided with a fourth thermometer for monitoring the temperature at the steam outlet; The cooling crystallizer is provided with a third pressure gauge for monitoring the pressure at the steam outlet; The cooling crystallizer is provided with a fifth thermometer for monitoring the temperature at the crystallization outlet; The cooling crystallizer is provided with a first ultrasonic particle size analyzer for monitoring the growth of crystal particle size at the crystallization discharge port; A flow pusher is arranged in the cooling crystallizer; A raw steam regulating valve is arranged on the raw steam inlet pipeline of the hot crystal eliminator; A second ultrasonic particle size analyzer is arranged on the connecting pipe between the hot crystal eliminator and the fine crystal reflux port of the cooling crystallizer.

9. The nickel sulfate continuous crystallization system according to claim 1, characterized in that: The thickener is provided with a second density meter for monitoring the density of the material at the bottom crystallization outlet; A crystal discharge electric valve is arranged on the connecting pipeline between the thickener and the centrifuge.

10. The nickel sulfate continuous crystallization system according to any one of claims 1 to 3 and 5 to 9, characterized in that: The system further comprises a control unit, and the pretreatment unit, and / or the concentration unit, and / or the crystallization unit are electrically connected to the control unit.

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