A process and equipment for resource utilization of sodium-based vanadium extraction wastewater

Abstract

The present invention is a kind of sodium method vanadium extraction wastewater resource utilization process and equipment, adopts MVR thermal salt separation technology, the sodium sulfate and sodium chloride in the vanadium extraction wastewater after pretreatment are separated, obtain the sodium sulfate product that meets the commercial standard and the sodium chloride product that reuses the standard, the condensed water of recovery is used as factory industrial water, realizes zero discharge and resource utilization of vanadium extraction wastewater.Through the implementation of this process, it is possible to obtain a sodium sulfate product with a purity stable at more than 98.5%, and product quality meets the requirements of GB / T6009-2014 "Industrial Anhydrous Sodium Sulfate" Class II first-class product, and reaches commercial standard.Sodium chloride MVR evaporation crystallization system can obtain a sodium chloride product with a sodium chloride content of more than 85%, meets the requirements of vanadium plant reuse, realizes the recycling of sodium chloride, and reduces the procurement cost of sodium chloride.

Description

Technical Field

[0001] The invention relates to a process and equipment for resource utilization of wastewater from vanadium extraction using a sodium method. Background Art

[0002] Vanadium slag extraction technologies are divided into roasting and non-roasting methods. Roasting methods are divided into sodium and calcium methods. The sodium method is a widely used vanadium extraction technology that primarily involves adding sodium chloride or soda ash to vanadium-containing raw materials for roasting. The sodium method produces a large amount of wastewater high in salt, ammonia nitrogen, and heavy metals (primarily high-valent vanadium and chromium). Currently, mature and reliable processes are available for heavy metal removal and deammonification, but there is no effective solution for the subsequent large amount of high-salt wastewater. The Pangang Vanadium and Titanium Products Plant uses multi-effect evaporation to produce a mixed salt of sodium sulfate and sodium chloride, which can only be treated as solid waste, occupying a large amount of space and incurring disposal costs.

[0003] Patent CN114560587A also uses evaporative crystallization to separate sodium sulfate and sodium chloride, but adds a cooling crystallization step. The salt separation process alternates between evaporative crystallization and cooling crystallization, increasing system energy consumption during the heating and cooling processes, but without significantly improving product purity. Patent CN210559766U uses frozen crystallization instead of the cooling crystallization of the aforementioned patent and adds nanofiltration equipment, resulting in a higher-purity product. However, the process becomes longer and the system energy consumption is significantly increased.

[0004] Therefore, the present application provides an energy-saving and efficient wastewater salt resource utilization process, which reduces investment costs and operating costs while obtaining products that meet the requirements. Summary of the Invention

[0005] The present invention aims to address the shortcomings of existing sodium-based vanadium extraction wastewater treatment technologies by providing an energy-efficient, efficient, and simple process and equipment for resource utilization of sodium-based vanadium extraction wastewater. This process utilizes MVR thermal salt separation technology to separate sodium sulfate and sodium chloride from pretreated vanadium extraction wastewater, yielding a sodium sulfate product that meets commercial standards and a sodium chloride product that meets recycling standards. The recovered condensate is then used as industrial water for the plant, achieving zero discharge and resource utilization of vanadium extraction wastewater.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a process for resource utilization of wastewater from sodium-based vanadium extraction, the specific process of which is as follows:

[0008] 1) After the wastewater is treated by the vanadium extraction wastewater pretreatment system and the pH value is controlled at 6-9, it passes through the condensate preheater and steam preheater in sequence, the wastewater temperature is raised to the evaporation temperature, and then enters the falling film evaporator;

[0009] 2) After the wastewater is initially concentrated in the falling film evaporator, it enters the first-stage forced circulation evaporator for further concentration to a solution concentration of about 25-35%;

[0010] 3) The secondary steam flashed from the primary forced circulation evaporator enters the falling film evaporator as the evaporation heat source. The secondary steam flashed from the falling film evaporator enters the 1#MVR compressor, and after being pressurized and heated by the 1#MVR compressor, enters the primary forced circulation evaporator as the heat source of the primary forced circulation evaporator, realizing heat self-circulation;

[0011] 4) the concentrated solution obtained in step 2) enters a secondary forced circulation evaporator for further evaporation to precipitate a large amount of sodium sulfate solids, and the sodium sulfate solid concentration in the secondary forced circulation evaporator is controlled to be 10% to 20% before entering a sodium sulfate thickening tank, where the sodium sulfate solid concentration is increased to 35% to 50%;

[0012] 5) the solid material in the sodium sulfate thickening tank enters a sodium sulfate primary centrifuge for solid-liquid separation, the sodium sulfate mother liquor in the sodium sulfate thickening tank enters a sodium sulfate mother liquor tank, and the sodium sulfate mother liquor after centrifugation of the sodium sulfate primary centrifuge also enters the sodium sulfate mother liquor tank. The outlet of the sodium sulfate mother liquor tank is connected to a secondary forced circulation evaporator, and circular sampling is performed to detect the chloride ion content in the sodium sulfate mother liquor in the sodium sulfate mother liquor tank. If the chloride ion content in the sodium sulfate mother liquor is lower than 180,000 mg / L, the sodium sulfate mother liquor enters the secondary forced circulation evaporator again, until the chloride ion content in the sodium sulfate mother liquor is not lower than 180,000 mg / L and not higher than 200,000 mg / L, the sodium sulfate solid enters a salt washing tank to wash away sodium chloride, a portion of the sodium sulfate mother liquor enters a sodium chloride forced circulation evaporator, and evaporation and crystallization are continued to obtain sodium chloride solid containing a small amount of impurities, and the solid concentration in the sodium chloride forced circulation evaporator is controlled to be 10% to 20% to enter the sodium chloride thickening tank, and the concentration of the sodium chloride solid in the sodium chloride thickening tank is increased to 35% to 50%;

[0013] 6) The material in the salt washing tank enters the sodium sulfate secondary centrifuge for solid-liquid separation, and the centrifuged mother liquor returns to the salt washing tank. The chloride ion content in the salt washing mother liquor of the salt washing tank is detected by cyclic sampling to control the chloride ion content of the salt washing mother liquor to be no higher than 120,000 mg / L. At this time, the salt washing mother liquor returns to the secondary forced circulation evaporator, and the solid discharge of the sodium sulfate secondary centrifuge enters the sodium sulfate drying and packaging system for processing to obtain a sodium sulfate product with a purity of ≥98.5%; if the chloride ion content of the salt washing mother liquor is higher than 120,000 mg / L, the salt washing cycle is always carried out, and the washing brine is replaced. The salt washing mother liquor out of the salt washing tank enters the secondary forced circulation evaporator and continues to be supplied to ensure the quality of sodium sulfate;

[0014] 7) The secondary steam flashed from the secondary forced circulation evaporator in step 4) passes through the steam wash tank and then enters the 2#MVR compressor. After being pressurized and heated by the 2#MVR compressor, it enters the secondary forced circulation evaporator as an evaporation heat source to achieve heat self-circulation; the total salt content (TDS) of the circulating washing water in the steam wash tank in step 7) is controlled to not exceed 10,000 mg / L to ensure the water quality of the condensate from the secondary forced circulation evaporator;

[0015] 8) a portion of the sodium sulfate mother liquor in step 5) enters a sodium chloride forced circulation evaporator, continues evaporation and crystallization, and obtains sodium chloride solid containing a small amount of impurities. The solid concentration in the sodium chloride forced circulation evaporator is controlled to be 10% to 20% and enters the sodium chloride thickening tank. The concentration of sodium chloride solid in the sodium chloride thickening tank is increased to 35% to 50%;

[0016] 9) The material in the sodium chloride thickener enters the sodium chloride centrifuge for solid-liquid separation, the sodium chloride mother liquor returns to the sodium chloride forced circulation evaporator for further evaporation, and the sodium chloride solid enters the sodium chloride drying and packaging system to obtain a sodium chloride product with a sodium chloride content of ≥85%. The concentration of chloride ions can be controlled to meet the factory reuse standard;

[0017] 10) The secondary steam flashed by the sodium chloride forced circulation evaporator in step 8) enters the sodium chloride MVR compressor, and after being pressurized and heated by the sodium chloride MVR compressor, enters the sodium chloride forced circulation evaporator as an evaporation heat source to achieve heat self-circulation;

[0018] 11) The amount of the sodium chloride mother liquor in step 9) returned to the vanadium extraction wastewater pretreatment system is determined based on the degree of impurity enrichment.

[0019] Preferably, the present invention adopts MVR evaporation technology, but the same effect can be achieved by adopting multi-effect evaporation, but correspondingly, the operating cost will be greatly increased.

[0020] The inlet and outlet steam temperature rise of the used 2#MVR compressor, 1#MVR compressor and sodium chloride MVR compressor is not less than 16°C. Preferably, the inlet and outlet steam temperature rise is 20°C.

[0021] In a second aspect, the present invention provides a sodium process vanadium extraction wastewater resource utilization device, which includes a pretreatment system for impurity removal, a condensate preheater, a steam preheater, a falling film evaporator, a primary forced circulation evaporator, a 1#MVR compressor, a secondary forced circulation evaporator, a 2#MVR compressor, a gas washing tank, a sodium sulfate thickening tank, a sodium sulfate primary centrifuge, a sodium sulfate mother liquor tank, a salt washing tank, a sodium sulfate secondary centrifuge, a sodium sulfate drying and packaging system, a sodium chloride forced circulation evaporator, a sodium chloride thickening tank, a sodium chloride MVR compressor, a sodium chloride mother liquor tank, a sodium chloride centrifuge, and a sodium chloride drying and packaging system.

[0022] The outlet of the pretreatment system is connected to the condensate preheater, steam preheater, and falling film evaporator in sequence. The wastewater outlet of the falling film evaporator is connected to the primary forced circulation evaporator. The secondary steam outlet of the primary forced circulation evaporator is connected to the steam inlet of the falling film evaporator. The steam outlet of the falling film evaporator is connected to the inlet of the 1#MVR compressor. The outlet of the 1#MVR compressor is connected to the primary forced circulation evaporator through the raw steam pipeline.

[0023] The wastewater outlet of the primary forced circulation evaporator is connected to the secondary forced circulation evaporator, the sodium sulfate liquid outlet of the secondary forced circulation evaporator is connected to the sodium sulfate thickening tank, and the solid outlet of the sodium sulfate thickening tank is sequentially connected to the sodium sulfate primary centrifuge, the salt washing tank, the sodium sulfate secondary centrifuge, and the sodium sulfate drying and packaging system; the mother liquor outlet of the sodium sulfate secondary centrifuge is connected to the liquid inlet of the salt washing tank, and the mother liquor outlet of the salt washing tank is connected to the liquid inlet of the secondary forced circulation evaporator;

[0024] The mother liquor outlets of the sodium sulfate primary centrifuge and the sodium sulfate thickening tank are both connected to the inlet of the sodium sulfate mother liquor tank, and the outlet of the sodium sulfate mother liquor tank is connected to the liquid inlet of the secondary forced circulation evaporator on the one hand, and to the liquid inlet of the sodium chloride forced circulation evaporator on the other hand; the steam outlet of the secondary forced circulation evaporator is sequentially connected to the scrubber tank and the 2#MVR compressor, and the outlet of the 2#MVR compressor is connected to the steam inlet of the secondary forced circulation evaporator;

[0025] The liquid outlet of the sodium chloride forced circulation evaporator is connected to a sodium chloride thickening tank, a sodium chloride centrifuge, and a sodium chloride drying and packaging system in sequence; the mother liquor outlets of the sodium chloride thickening tank and the sodium chloride centrifuge are both connected to a sodium chloride mother liquor tank, which is connected to the liquid inlet of the sodium chloride forced circulation evaporator on the one hand and to a pretreatment system on the other hand;

[0026] The steam inlet and the steam outlet of the sodium chloride forced circulation evaporator are respectively connected to the outlet and the steam inlet of the sodium chloride MVR compressor, and the inlet of the sodium chloride MVR compressor is simultaneously connected to the raw steam pipeline.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a sodium-based vanadium extraction wastewater resource utilization process that can achieve zero discharge and resource utilization of vanadium extraction wastewater. Through the implementation of this process, a sodium sulfate product with a stable purity of more than 98.5% can be obtained. The product quality meets the requirements of Class II first-class products in GB / T6009-2014 "Industrial Anhydrous Sodium Sulfate" and reaches the market standard. The sodium chloride MVR evaporation crystallization system can obtain a sodium chloride product with a sodium chloride content of more than 85%, which meets the requirements of vanadium plant reuse, realizes the recycling of sodium chloride, and reduces the procurement cost of sodium chloride. The provision of a gas washing tank ensures that the conductivity of the condensed water obtained from each evaporator does not exceed 400μS / cm, reduces the phenomenon of liquid entrainment in the evaporated gas, meets the water quality requirements of the plant's reused water, and saves water resources. Only the MVR thermal salt separation method can be used to obtain a sodium sulfate product that meets the market standard and a sodium chloride product that meets the reuse standard. Compared with multi-effect evaporation, it reduces operating costs, and there is no cooling crystallization or freezing crystallization process, and the system energy consumption is also greatly reduced. Through the implementation of this process, zero discharge and resource utilization of vanadium extraction wastewater can be achieved, with excellent economic and social benefits. Currently, the process has been successfully implemented, and all indicators have met the design requirements, showing good prospects for application and promotion.

[0029] The invention provides a connection process of a sodium process vanadium extraction wastewater resource utilization device, and can obtain a sodium sulfate product meeting a market standard and a sodium chloride product meeting a recycling standard without adding a freezing crystallization or cooling crystallization process. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the connection of the sodium method vanadium extraction wastewater resource utilization equipment of the present invention.

[0031] Among them, the pretreatment system 1, condensate preheater 2, steam preheater 3, falling film evaporator 4, first-level forced circulation evaporator 5, 1#MVR compressor 6, second-level forced circulation evaporator 9, 2#MVR compressor 8, gas washing tank 7, sodium sulfate thickening tank 10, sodium sulfate first-level centrifuge 12, sodium sulfate mother liquor tank 11, salt washing tank 13, sodium sulfate second-level centrifuge 14, sodium sulfate drying and packaging system 15, sodium chloride forced circulation evaporator 17, sodium chloride thickening tank 18, sodium chloride MVR compressor 16, sodium chloride mother liquor tank 21, sodium chloride centrifuge 19, sodium chloride drying and packaging system 20. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the embodiments and drawings. The specific embodiments are only for further detailed description and explanation of the invention and are not intended to limit the scope of protection of the claims of the present invention.

[0033] The sodium process vanadium extraction wastewater resource utilization equipment of the present invention comprises a pretreatment system 1 for removing impurities, a condensed water preheater 2, a steam preheater 3, a falling film evaporator 4, a primary forced circulation evaporator 5, a 1# MVR compressor 6, a secondary forced circulation evaporator 9, a 2# MVR compressor 8, a gas washing tank 7, a sodium sulfate thickening tank 10, a sodium sulfate primary centrifuge 12, a sodium sulfate mother liquor tank 11, a salt washing tank 13, a sodium sulfate secondary centrifuge 14, a sodium sulfate drying and packaging system 15, a sodium chloride forced circulation evaporator 17, a sodium chloride thickening tank 18, a sodium chloride MVR compressor 16, a sodium chloride mother liquor tank 21, a sodium chloride centrifuge 19, and a sodium chloride drying and packaging system 20.

[0034] The outlet of the pretreatment system is connected to the condensate preheater, steam preheater, and falling film evaporator in sequence. The wastewater outlet of the falling film evaporator is connected to the primary forced circulation evaporator. The secondary steam outlet of the primary forced circulation evaporator is connected to the steam inlet of the falling film evaporator. The steam outlet of the falling film evaporator is connected to the inlet of the 1#MVR compressor. The outlet of the 1#MVR compressor is connected to the primary forced circulation evaporator through the raw steam pipeline.

[0035] The wastewater outlet of the primary forced circulation evaporator is connected to the secondary forced circulation evaporator, the sodium sulfate liquid outlet of the secondary forced circulation evaporator is connected to the sodium sulfate thickening tank, and the solid outlet of the sodium sulfate thickening tank is sequentially connected to the sodium sulfate primary centrifuge, the salt washing tank, the sodium sulfate secondary centrifuge, and the sodium sulfate drying and packaging system; the mother liquor outlet of the sodium sulfate secondary centrifuge is connected to the liquid inlet of the salt washing tank, and the mother liquor outlet of the salt washing tank is connected to the liquid inlet of the secondary forced circulation evaporator;

[0036] The mother liquor outlets of the sodium sulfate primary centrifuge and the sodium sulfate thickening tank are both connected to the inlet of the sodium sulfate mother liquor tank, and the outlet of the sodium sulfate mother liquor tank is connected to the liquid inlet of the secondary forced circulation evaporator on the one hand, and to the liquid inlet of the sodium chloride forced circulation evaporator on the other hand; the steam outlet of the secondary forced circulation evaporator is sequentially connected to the scrubber tank and the 2#MVR compressor, and the outlet of the 2#MVR compressor is connected to the steam inlet of the secondary forced circulation evaporator;

[0037] The liquid outlet of the sodium chloride forced circulation evaporator is connected to a sodium chloride thickening tank, a sodium chloride centrifuge, and a sodium chloride drying and packaging system in sequence; the mother liquor outlets of the sodium chloride thickening tank and the sodium chloride centrifuge are both connected to a sodium chloride mother liquor tank, which is connected to the liquid inlet of the sodium chloride forced circulation evaporator on the one hand and to a pretreatment system on the other hand;

[0038] The steam inlet and the steam outlet of the sodium chloride forced circulation evaporator are respectively connected to the outlet and the steam inlet of the sodium chloride MVR compressor, and the inlet of the sodium chloride MVR compressor is simultaneously connected to the raw steam pipeline.

[0039] The specific process of the sodium method vanadium extraction wastewater resource utilization process of the present invention is:

[0040] 1) After the wastewater is treated by the vanadium extraction wastewater pretreatment system and the pH value is controlled at 6-9, it passes through the condensate preheater and steam preheater in sequence, the wastewater temperature is raised to the evaporation temperature, and then enters the falling film evaporator;

[0041] 2) After the wastewater is initially concentrated in the falling film evaporator, it enters the first-stage forced circulation evaporator for further concentration to a solution concentration of about 25-35%;

[0042] 3) The secondary steam flashed from the primary forced circulation evaporator enters the falling film evaporator as the evaporation heat source. The secondary steam flashed from the falling film evaporator enters the 1#MVR compressor, and after being pressurized and heated by the 1#MVR compressor, enters the primary forced circulation evaporator as the heat source of the primary forced circulation evaporator, realizing heat self-circulation;

[0043] 4) the concentrated solution obtained in step 2) enters a secondary forced circulation evaporator for further evaporation to precipitate a large amount of sodium sulfate solids, and the sodium sulfate solid concentration in the secondary forced circulation evaporator is controlled to be 10% to 20% before entering a sodium sulfate thickening tank, where the sodium sulfate solid concentration is increased to 35% to 50%;

[0044] 5) the solid material in the sodium sulfate thickening tank enters a sodium sulfate one-stage centrifuge for solid-liquid separation, the sodium sulfate mother liquor in the sodium sulfate thickening tank enters a sodium sulfate mother liquor tank, and the sodium sulfate mother liquor after centrifugation of the sodium sulfate one-stage centrifuge also enters the sodium sulfate mother liquor tank. The outlet of the sodium sulfate mother liquor tank is connected to a secondary forced circulation evaporator, and circular sampling is performed to detect the chloride ion content in the sodium sulfate mother liquor in the sodium sulfate mother liquor tank. If the chloride ion content in the sodium sulfate mother liquor is lower than 180,000 mg / L, the sodium sulfate mother liquor enters the secondary forced circulation evaporator again, until the chloride ion content in the sodium sulfate mother liquor is not lower than 180,000 mg / L and not higher than 2,000,000 mg / L, the sodium sulfate solid enters a salt washing tank to wash away sodium chloride, a portion of the sodium sulfate mother liquor enters a sodium chloride forced circulation evaporator, and evaporation and crystallization are continued to obtain sodium chloride solid containing a small amount of impurities, and the solid concentration in the sodium chloride forced circulation evaporator is controlled to be 10% to 20% to enter the sodium chloride thickening tank, and the concentration of the sodium chloride solid in the sodium chloride thickening tank is increased to 35% to 50%;

[0045] 6) The material in the salt washing tank enters the sodium sulfate secondary centrifuge for solid-liquid separation, and the centrifuged mother liquor returns to the salt washing tank. The chloride ion content in the salt washing mother liquor of the salt washing tank is detected by cyclic sampling to control the chloride ion content of the salt washing mother liquor to be no higher than 120,000 mg / L. At this time, the salt washing mother liquor returns to the secondary forced circulation evaporator, and the solid discharge of the sodium sulfate secondary centrifuge enters the sodium sulfate drying and packaging system for processing to obtain a sodium sulfate product with a purity of ≥98.5%; if the chloride ion content of the salt washing mother liquor is higher than 120,000 mg / L, the salt washing cycle is continued, and the washing water is replaced. The salt washing mother liquor out of the salt washing tank enters the secondary forced circulation evaporator and continues to be supplied to ensure the quality of sodium sulfate.

[0046] 7) The secondary steam flashed from the secondary forced circulation evaporator in step 4) passes through the steam wash tank and then enters the 2#MVR compressor. After being pressurized and heated by the 2#MVR compressor, it enters the secondary forced circulation evaporator as an evaporation heat source to achieve heat self-circulation; the total salt content (TDS) of the circulating washing water in the steam wash tank in step 7) is controlled to not exceed 10,000 mg / L to ensure the water quality of the condensate from the secondary forced circulation evaporator;

[0047] 8) a portion of the sodium sulfate mother liquor in step 5) enters a sodium chloride forced circulation evaporator, continues evaporation and crystallization, and obtains sodium chloride solid containing a small amount of impurities. The solid concentration in the sodium chloride forced circulation evaporator is controlled to be 10% to 20% and enters the sodium chloride thickening tank. The concentration of sodium chloride solid in the sodium chloride thickening tank is increased to 35% to 50%;

[0048] 9) The material in the sodium chloride thickener enters the sodium chloride centrifuge for solid-liquid separation, the sodium chloride mother liquor returns to the sodium chloride forced circulation evaporator for further evaporation, and the sodium chloride solid enters the sodium chloride drying and packaging system to obtain a sodium chloride product with a sodium chloride content of ≥85%. The concentration of chloride ions can be controlled to meet the factory reuse standard;

[0049] 10) The secondary steam flashed by the sodium chloride forced circulation evaporator in step 8) enters the sodium chloride MVR compressor, and after being pressurized and heated by the sodium chloride MVR compressor, enters the sodium chloride forced circulation evaporator as an evaporation heat source to achieve heat self-circulation;

[0050] 11) The amount of the sodium chloride mother liquor in step 9) returned to the vanadium extraction wastewater pretreatment system is determined based on the degree of impurity enrichment.

[0051] The amount of sodium sulfate mother liquor entering the sodium chloride forced circulation evaporator is determined according to the following content: assuming that the feed amount is F0, the sodium sulfate mother liquor discharge amount in the sodium sulfate mother liquor tank is D, the chloride ion feed concentration ω0 is controlled, and the chloride ion discharge concentration ω1 is controlled; then, according to the material balance, the sodium sulfate mother liquor discharge amount D in the sodium sulfate mother liquor tank is D=(F0*ω0) / ω1. In this embodiment, the sodium sulfate mother liquor chloride ion discharge concentration ω1 in the sodium sulfate mother liquor tank is not less than 180,000 mg / L.

[0052] In step 5) of the present invention, the chloride ion content in the sodium sulfate mother liquor tank is controlled to be no less than 180,000 mg / L and no more than 2,000,000 mg / L, and in step 6), the chloride ion content in the salt washing mother liquor is controlled to be no more than 120,000 mg / L, thereby ensuring the quality of sodium sulfate and sodium chloride products.

[0053] The present invention uses MVR evaporation technology, but the same effect can be achieved by using multiple-effect evaporation, but the corresponding operating costs will be greatly increased. The evaporation in this process can be replaced by multiple-effect evaporation instead of MVR evaporation, and the same effect can be achieved by controlling the above process parameters.

[0054] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A process for resource utilization of wastewater from sodium-based vanadium extraction, characterized in that: The specific process of this technology is: 1) After the wastewater is treated by the vanadium extraction wastewater pretreatment system and the pH value is controlled at 6-9, it passes through the condensate preheater and steam preheater in sequence, the wastewater temperature is raised to the evaporation temperature, and then enters the falling film evaporator; 2) After the wastewater is initially concentrated in the falling film evaporator, it enters the first-stage forced circulation evaporator for further concentration to a solution concentration of 25-35%; 3) The secondary steam flashed from the primary forced circulation evaporator enters the falling film evaporator as the evaporation heat source. The secondary steam flashed from the falling film evaporator enters the 1#MVR compressor, and after being pressurized and heated by the 1#MVR compressor, enters the primary forced circulation evaporator as the heat source of the primary forced circulation evaporator, realizing heat self-circulation; 4) the concentrated liquid obtained in step 2) enters a secondary forced circulation evaporator for further evaporation to precipitate a large amount of sodium sulfate solids, and the sodium sulfate solid concentration in the secondary forced circulation evaporator is controlled to be 10% to 20% before entering a sodium sulfate thickening tank, where the sodium sulfate solid concentration increases to 35% to 50%; 5) solid material in sodium sulfate thick tank enters sodium sulfate one-level centrifuge, carry out solid-liquid separation, the sodium sulfate mother liquor in the sodium sulfate thick tank enters sodium sulfate mother liquor tank, the sodium sulfate mother liquor after the sodium sulfate one-level centrifuge is centrifugal also enters sodium sulfate mother liquor tank simultaneously, the outlet of sodium sulfate mother liquor tank connects secondary forced circulation evaporator, circulation sampling detects the chloride ion content in the sodium sulfate mother liquor in the sodium sulfate mother liquor tank, if chloride ion content is lower than 180000mg / L in the sodium sulfate mother liquor, then sodium sulfate mother liquor enters secondary forced circulation evaporator again, until chloride ion content is not less than 180000mg / L in the sodium sulfate mother liquor, and when being not higher than 2000000mg / L, sodium sulfate solid enters salt washing tank and washes away sodium chloride, and a part of sodium sulfate mother liquor enters sodium-chlor forced circulation evaporator; 6) The material in the salt washing tank enters the sodium sulfate secondary centrifuge for solid-liquid separation, and the centrifuged mother liquor returns to the salt washing tank. The chloride ion content in the salt washing mother liquor of the salt washing tank is detected by cyclic sampling to control the chloride ion content of the salt washing mother liquor to be no higher than 120,000 mg / L. The solid discharge of the sodium sulfate secondary centrifuge enters the sodium sulfate drying and packaging system for processing to obtain a sodium sulfate product with a purity of ≥98.5%; If the chloride ion content of the salt washing mother liquor is higher than 120,000 mg / L, the salt washing mother liquor from the salt washing tank will enter the secondary forced circulation evaporator and replace the salt washing water to ensure the quality of sodium sulfate; 7) The secondary steam flashed from the secondary forced circulation evaporator in step 4) passes through the scrubber tank and then enters the 2#MVR compressor. After being pressurized and heated by the 2#MVR compressor, it enters the secondary forced circulation evaporator as an evaporation heat source, achieving heat self-circulation; the total salt content (TDS) of the circulating washing water in the scrubber tank in step 7) is controlled to be no more than 10,000 mg / L; 8) a portion of the sodium sulfate mother liquor in step 5) enters a sodium chloride forced circulation evaporator, continues evaporation and crystallization, and obtains sodium chloride solid containing a small amount of impurities. The solid concentration in the sodium chloride forced circulation evaporator is controlled to 10% to 20% before entering a sodium chloride thickening tank, where the sodium chloride solid concentration is increased to 35% to 50%; 9) The material in the sodium chloride thickening tank enters the sodium chloride centrifuge for solid-liquid separation, the sodium chloride mother liquor returns to the sodium chloride forced circulation evaporator for further evaporation, and the sodium chloride solid enters the sodium chloride drying and packaging system to obtain a sodium chloride product with a sodium chloride content of ≥85%; 10) The secondary steam flashed by the sodium chloride forced circulation evaporator in step 8) enters the sodium chloride MVR compressor, and after being pressurized and heated by the sodium chloride MVR compressor, enters the sodium chloride forced circulation evaporator as an evaporation heat source to achieve heat self-circulation; 11) The amount of the sodium chloride mother liquor in step 9) returned to the vanadium extraction wastewater pretreatment system is determined based on the degree of impurity enrichment.

2. The process for resource utilization of wastewater from sodium vanadium extraction according to claim 1, characterized in that: The quality of the sodium sulfate product can meet the requirements of GB / T6009-2014 "Industrial Anhydrous Sodium Sulfate" Class II first-class product and reach the market standard.

3. The process for resource utilization of wastewater from sodium vanadium extraction according to claim 1, characterized in that: The inlet and outlet steam temperature rise of the 2#MVR compressor, 1#MVR compressor and sodium chloride MVR compressor used shall not be lower than 16°C.

4. The process for resource utilization of wastewater from sodium vanadium extraction according to claim 3, characterized in that: The inlet and outlet steam temperature rise of the 2#MVR compressor, 1#MVR compressor and sodium chloride MVR compressor used is 20℃.

5. The process for resource utilization of wastewater from sodium vanadium extraction according to claim 1, characterized in that: The process uses sodium-based vanadium extraction wastewater resource utilization equipment, which includes a pretreatment system for impurity removal, a condensate preheater, a steam preheater, a falling film evaporator, a first-level forced circulation evaporator, a 1# MVR compressor, a second-level forced circulation evaporator, a 2# MVR compressor, a gas washing tank, a sodium sulfate thickening tank, a sodium sulfate first-level centrifuge, a sodium sulfate mother liquor tank, a salt washing tank, a sodium sulfate second-level centrifuge, a sodium sulfate drying and packaging system, a sodium chloride forced circulation evaporator, a sodium chloride thickening tank, a sodium chloride MVR compressor, a sodium chloride mother liquor tank, a sodium chloride centrifuge, and a sodium chloride drying and packaging system. The outlet of the pretreatment system is connected to the condensate preheater, steam preheater, and falling film evaporator in sequence. The wastewater outlet of the falling film evaporator is connected to the primary forced circulation evaporator. The secondary steam outlet of the primary forced circulation evaporator is connected to the steam inlet of the falling film evaporator. The steam outlet of the falling film evaporator is connected to the inlet of the 1#MVR compressor. The outlet of the 1#MVR compressor is connected to the primary forced circulation evaporator through the raw steam pipeline. The wastewater outlet of the primary forced circulation evaporator is connected to the secondary forced circulation evaporator, the sodium sulfate liquid outlet of the secondary forced circulation evaporator is connected to the sodium sulfate thickening tank, and the solid outlet of the sodium sulfate thickening tank is sequentially connected to the sodium sulfate primary centrifuge, the salt washing tank, the sodium sulfate secondary centrifuge, and the sodium sulfate drying and packaging system; the mother liquor outlet of the sodium sulfate secondary centrifuge is connected to the liquid inlet of the salt washing tank, and the mother liquor outlet of the salt washing tank is connected to the liquid inlet of the secondary forced circulation evaporator; The mother liquor outlets of the sodium sulfate primary centrifuge and the sodium sulfate thickening tank are both connected to the inlet of the sodium sulfate mother liquor tank, and the outlet of the sodium sulfate mother liquor tank is connected to the liquid inlet of the secondary forced circulation evaporator on the one hand, and to the liquid inlet of the sodium chloride forced circulation evaporator on the other hand; the steam outlet of the secondary forced circulation evaporator is sequentially connected to the scrubber tank and the 2#MVR compressor, and the outlet of the 2#MVR compressor is connected to the steam inlet of the secondary forced circulation evaporator; The liquid outlet of the sodium chloride forced circulation evaporator is connected to a sodium chloride thickening tank, a sodium chloride centrifuge, and a sodium chloride drying and packaging system in sequence; the mother liquor outlets of the sodium chloride thickening tank and the sodium chloride centrifuge are both connected to a sodium chloride mother liquor tank, which is connected to the liquid inlet of the sodium chloride forced circulation evaporator on the one hand and to a pretreatment system on the other hand; The steam inlet and the steam outlet of the sodium chloride forced circulation evaporator are respectively connected to the outlet and the steam inlet of the sodium chloride MVR compressor, and the inlet of the sodium chloride MVR compressor is simultaneously connected to the raw steam pipeline.

Images