A method for resource treatment of sodium sulfate wastewater from tungsten smelting

Abstract

The present invention belongs to the field of metallurgy technology, and specifically relates to a method for resource treatment of tungsten smelting sodium sulfate wastewater. The present invention concentrates the tungsten smelting sodium sulfate wastewater after impurities are removed, mixes it with barium hydroxide to carry out a first double decomposition reaction, and while continuously separating the generated barium sulfate precipitate, adds sodium sulfate and barium hydroxide to the first double decomposition reaction liquid to continue the first double decomposition reaction until the mass percentage of sodium hydroxide in the first double decomposition reaction liquid is ≥30%; the barium sulfate precipitate is dried and then reduced and roasted, and the obtained barium sulfide and liquid alkali (first double decomposition reaction liquid) are subjected to a second double decomposition reaction, and the obtained barium hydroxide crystals are reused in the sodium sulfate wastewater treatment process, and the sodium sulfide solution is evaporated and crystallized to obtain a sodium sulfide product that meets the quality standard of Class 2 first-class products in "GB 10500-2009 Industrial Sodium Sulfide Standard". The method can fully utilize the sodium sulfate wastewater as a resource and reduce the treatment cost.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for resource treatment of sodium sulfate wastewater from tungsten smelting. Background Art

[0002] At present, tungsten smelting enterprises mainly use alkaline pressure cooking-ion exchange, alkaline pressure cooking-extraction, acid decomposition-extraction and other processes to prepare APT, and the final wastewater produced is mainly sodium chloride and sodium sulfate wastewater. With the increasing requirements for environmental protection, many industrial parks do not allow high-salt wastewater to enter the park directly, and many companies have to use evaporation and crystallization technology for treatment. However, the evaporation and crystallization process has high energy consumption, and the by-product sodium sulfate produced cannot obtain a high value. If the purity of the produced sodium sulfate is not high, it may be hazardous waste, and its disposal cost is high. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a method for resource treatment of sodium sulfate wastewater from tungsten smelting, which method can convert sodium sulfate wastewater into sodium sulfide products and barium hydroxide that meet the quality standard of Class 2 first-class products in "GB 10500-2009 Industrial Sodium Sulfide Standard", and the barium hydroxide can be reused in the sodium sulfate wastewater treatment process. The intermediate products produced in the process of this method can be completely reused, and no other wastes (wastewater, waste gas, and waste residue) will be generated, which can make complete resource utilization of sodium sulfate wastewater and reduce treatment costs.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a method for resource treatment of tungsten smelting sodium sulfate wastewater, comprising the following steps:

[0006] The tungsten smelting sodium sulfate wastewater after impurities removal is concentrated to obtain concentrated sodium sulfate wastewater;

[0007] The concentrated sodium sulfate wastewater and barium hydroxide are mixed to perform a first double decomposition reaction, and the generated barium sulfate precipitate is separated to obtain a first double decomposition reaction liquid;

[0008] The separated barium sulfate precipitation is carried out simultaneously with the first double decomposition reaction, and sodium sulfate and barium hydroxide are added to the first double decomposition reaction liquid to continue the first double decomposition reaction until the mass percentage of sodium hydroxide in the first double decomposition reaction liquid is ≥30%;

[0009] After drying the barium sulfate precipitate, reduction roasting is performed under a reducing atmosphere to obtain barium sulfide;

[0010] The barium sulfide and liquid alkali are mixed to carry out a second double decomposition reaction to obtain barium hydroxide crystals and a sodium sulfide solution, respectively; the liquid alkali is provided by the first double decomposition reaction liquid;

[0011] The sodium sulfide solution is evaporated and crystallized to obtain a sodium sulfide product and an evaporated crystallization mother liquor respectively; the evaporated crystallization mother liquor is returned to the subsequent second double decomposition reaction for treatment.

[0012] Preferably, the hardness of the sodium sulfate wastewater after impurities removal is ≤0.5mmo1 / L, the concentration of COD is ≤10mg / L, the concentration of SS is ≤1mg / L, the concentration of SiO2 is ≤1mg / L, the concentration of total P is ≤0.1mg / L, the concentration of total Pb is ≤0.1mg / L, the concentration of total As is ≤0.1mg / L, and the concentration of total Cd is ≤0.1mg / L.

[0013] Preferably, the concentration of sodium sulfate in the concentrated sodium sulfate wastewater is 350-380 g / L.

[0014] Preferably, the temperature of the first metathesis reaction is 40-60° C.; the time of the first metathesis reaction is 2-4 hours.

[0015] Preferably, the molar ratio of the supplemented sodium sulfate to barium hydroxide is 1:(1-2).

[0016] Preferably, the reducing atmosphere is hydrogen.

[0017] Preferably, the reduction roasting temperature is 800-950° C., and the holding time is 2-3 hours.

[0018] Preferably, the temperature of the second metathesis reaction is 100-120° C., the pressure is 1-2 MPa, and the heat and pressure holding time is 2-3 h.

[0019] Preferably, the molar ratio of the barium element in the barium sulfide to the hydroxide in the liquid alkali is 1:(2-4).

[0020] Preferably, the impurity removal comprises: adjusting the pH value of the sodium sulfate wastewater to 8-10, adding a coagulant for coagulation and precipitation, adjusting the pH value of the obtained supernatant to 6-7.5, and then performing activated carbon treatment.

[0021] The invention provides a method for resource treatment of tungsten smelting sodium sulfate wastewater, comprising the following steps: concentrating the tungsten smelting sodium sulfate wastewater after impurities are removed to obtain concentrated sodium sulfate wastewater; mixing the concentrated sodium sulfate wastewater and barium hydroxide to carry out a first double decomposition reaction, separating the generated barium sulfate precipitate, and obtaining a first double decomposition reaction liquid; the separated barium sulfate precipitate and the first double decomposition reaction are carried out simultaneously, and sodium sulfate and barium hydroxide are supplemented in the first double decomposition reaction liquid to continue the first double decomposition reaction until the mass percentage of sodium hydroxide in the first double decomposition reaction liquid is ≥30%; drying the barium sulfate precipitate, and then reducing roasting it in a reducing atmosphere to obtain barium sulfide; mixing the barium sulfide and liquid alkali to carry out a second double decomposition reaction to respectively obtain barium hydroxide crystals and a sodium sulfide solution; the liquid alkali is provided by the first double decomposition reaction liquid; evaporating and crystallizing the sodium sulfide solution to respectively obtain a sodium sulfide product and an evaporation and crystallization mother liquor; and the evaporation and crystallization mother liquor is returned to the subsequent second double decomposition reaction for treatment.

[0022] The method provided by the present invention prepares sodium sulfide products and barium hydroxide from tungsten smelting sodium sulfate wastewater that meet the quality standard of Class 2 first-class products in "GB 10500-2009 Industrial Sodium Sulfide Standard", the sodium sulfide products can be sold, and the barium hydroxide can be reused in the treatment process of tungsten smelting sodium sulfate wastewater, the intermediate products generated in the process of the method can be completely reused, and no other wastes (wastewater, waste gas, and waste residue) are generated, the sodium sulfate wastewater can be fully utilized as a resource, the treatment cost is reduced, and the market value of the conversion product is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of the method for resource treatment of tungsten smelting sodium sulfate wastewater. DETAILED DESCRIPTION

[0024] The present invention provides a method for resource treatment of tungsten smelting sodium sulfate wastewater, comprising the following steps:

[0025] The tungsten smelting sodium sulfate wastewater after impurities removal is concentrated to obtain concentrated sodium sulfate wastewater;

[0026] The concentrated sodium sulfate wastewater and barium hydroxide are mixed to perform a first double decomposition reaction, and the generated barium sulfate precipitate is separated to obtain a first double decomposition reaction liquid;

[0027] The separated barium sulfate precipitation is carried out simultaneously with the first double decomposition reaction, and sodium sulfate and barium hydroxide are added to the first double decomposition reaction liquid to continue the first double decomposition reaction until the mass percentage of sodium hydroxide in the first double decomposition reaction liquid is ≥30%;

[0028] After drying the barium sulfate precipitate, reduction roasting is performed under a reducing atmosphere to obtain barium sulfide;

[0029] The barium sulfide and liquid alkali are mixed to carry out a second double decomposition reaction to obtain barium hydroxide crystals and a sodium sulfide solution, respectively; the liquid alkali is provided by the first double decomposition reaction liquid;

[0030] The sodium sulfide solution is evaporated and crystallized to obtain a sodium sulfide product and an evaporated crystallization mother liquor respectively; the evaporated crystallization mother liquor is returned to the subsequent second double decomposition reaction for treatment.

[0031] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used in the preparation, and commercially available products known to those skilled in the art can be used.

[0032] The invention concentrates the tungsten smelting sodium sulfate waste water after impurities are removed to obtain concentrated sodium sulfate waste water.

[0033] In the present invention, the COD concentration in the tungsten smelting sodium sulfate wastewater is preferably 100-600 mg / L, SO4 2- The concentration of Na is preferably 100000~150000mg / L. + The concentration of is preferably 100000~150000mg / L, the concentration of SiO2 is preferably 10~30mg / L, the pH is preferably 6~7, and the Ca 2+ The concentration of Mg is preferably less than 50 mg / L. 2+ The concentration of is preferably <5 mg / L, the concentration of total P is preferably 0.1~0.5 mg / L, the concentration of total Pb is preferably 1~5 mg / L, the concentration of total As is preferably 2~10 mg / L, the concentration of total Cd is preferably 0.25 mg / L, and the concentration of SS is preferably 15 mg / L.

[0034] In the present invention, the hardness of the tungsten smelting sodium sulfate wastewater after impurities removal is preferably ≤0.5mmo1 / L, the COD concentration is preferably ≤10mg / L, the SS concentration is preferably ≤1mg / L, the SiO2 concentration is preferably ≤1mg / L, the total P concentration is preferably ≤0.1mg / L, the total Pb concentration is preferably ≤0.1mg / L, the total As concentration is preferably ≤0.1mg / L, and the total Cd concentration is preferably ≤0.1mg / L.

[0035] In the present invention, the hardness refers to the total concentration of calcium and magnesium ions in water.

[0036] In the present invention, the impurity removal preferably includes: adjusting the pH value of the tungsten smelting sodium sulfate wastewater to 8-10, adding a coagulant for coagulation and precipitation, adjusting the pH value of the obtained supernatant to 6-7.5, and then performing activated carbon treatment. In the present invention, the concentration of sodium sulfate in the tungsten smelting sodium sulfate wastewater is preferably ≤150g / L, and more preferably 100~150g / L; the reagent used to adjust the pH value of the tungsten smelting sodium sulfate wastewater is preferably sodium hydroxide; the coagulant is preferably magnesium sulfate; the ratio of the coagulant to the total molar amount of phosphorus, arsenic and silicon in the tungsten smelting sodium sulfate wastewater is preferably (1~2):1, and more preferably (1~1.5):1; the coagulation and precipitation time is preferably 2~4h, and more preferably 2.5~3.5h; the reagent used to adjust the pH value of the supernatant is preferably an acid solution, and more preferably a sulfuric acid solution; the concentration of the sulfuric acid solution is preferably ≥90%, and more preferably ≥98%; the activated carbon treatment is preferably: the supernatant with a pH value adjusted to 6~7.5 is passed into a reaction column filled with activated carbon for adsorption; the flow rate of the supernatant is preferably 2~4m 3 / h, more preferably 3~4m 3 / h; the dosage ratio of the supernatant and activated carbon is preferably 1m 3 / h: (200~500) kg, more preferably 1m 3 / h:(300~400)kg.

[0037] The present invention removes the hardness, heavy metal ions, COD and suspended solids (SS) of tungsten smelting sodium sulfate wastewater by coagulation and precipitation, and removes the remaining hardness, heavy metal ions, COD and suspended solids (SS) in the wastewater by activated carbon adsorption.

[0038] In the present invention, the equipment used for concentration is preferably a mechanical vapor recompression technology, and more preferably a multiple-effect evaporation concentration equipment; the concentration of sodium sulfate in the concentrated sodium sulfate wastewater is preferably 350-380 g / L, and more preferably 360-370 g / L.

[0039] The present invention concentrates the concentration of sodium sulfate in sodium sulfate wastewater to 380g / L through a multiple-effect evaporation concentration device, which is equivalent to concentrating the raw water by 2 to 3 times. Therefore, the energy consumption of concentration using the multiple-effect evaporation concentration device is not large.

[0040] After obtaining the concentrated sodium sulfate wastewater, the present invention mixes the concentrated sodium sulfate wastewater and barium hydroxide to perform a first double decomposition reaction, separates the generated barium sulfate precipitate, and obtains a first double decomposition reaction liquid.

[0041] In the present invention, the separated barium sulfate precipitation is carried out simultaneously with the first double decomposition reaction, and sodium sulfate and barium hydroxide are added to the first double decomposition reaction liquid to continue the first double decomposition reaction until the mass percentage of sodium hydroxide in the first double decomposition reaction liquid is ≥30%.

[0042] In the present invention, the temperature of the first metathesis reaction is preferably 40-60°C, more preferably 45-50°C; the time of the first metathesis reaction is preferably 2-4h, more preferably 2.5-3h; the first metathesis reaction is preferably carried out under stirring; the stirring rate is preferably 200-500rpm, more preferably 500rpm; the molar ratio of the supplemented sodium sulfate and barium hydroxide is preferably 1:(1-2), more preferably 1:(1-1.5); the method of separating the generated barium sulfate precipitate is preferably filter pressing or suction filtration, more preferably filter pressing; the filter press used for the filter pressing is preferably a 300m² filter press.

[0043] In the first double decomposition reaction process of the present invention, the generated barium sulfate precipitate is separated while sodium sulfate and barium hydroxide are added, which can promote the reaction and avoid a large number of large barium sulfate particles generated from wrapping the barium hydroxide and sodium sulfate, resulting in an insufficient and incomplete reaction. The concentration of sodium hydroxide in the obtained first double decomposition reaction liquid (liquid caustic soda) can be higher, and the added value of the product can be higher.

[0044] According to the present invention, the barium sulfate precipitate is preferably subjected to a first stirring and washing process, and then subjected to a first filter press. The barium sulfate filter cake obtained by the first filter press is subjected to a second stirring and washing process, and then subjected to a second filter press to obtain a barium sulfate product. The first stirring and washing time is preferably 30 minutes. The reagent used in the first stirring and washing is preferably a sulfuric acid solution. The mass concentration of the sulfuric acid solution is preferably 10-20%, and more preferably 15%. The filtrate obtained by the first filter press is returned to the first double decomposition reaction process to continue to undergo a first double decomposition reaction with barium hydroxide. The second stirring and washing time is preferably 30 minutes. The reagent used in the second stirring and washing is preferably tap water. The filtrate obtained by the second filter press is preferably prepared into a sulfuric acid solution with a mass concentration of 10-20% as the reagent used for the first stirring and washing. The ratio of the total amount of reagents used in the first stirring and washing and the second stirring and washing to the mass of barium sulfate in the barium sulfate product is preferably (8-25) L:1 kg, more preferably (10-20) L:1 kg, and further preferably (12-18) L:1 kg.

[0045] The present invention uses a dilute sulfuric acid solution + water stirring and washing method to wash the residual sodium hydroxide in the barium sulfate more cleanly, improve the purity of the barium sulfate, and reduce the amount of washing water.

[0046] After obtaining the barium sulfate precipitate, the present invention dries the barium sulfate precipitate and then performs reduction roasting in a reducing atmosphere to obtain barium sulfide.

[0047] In the present invention, the drying temperature is preferably 100-200° C., more preferably 100-150° C.; the drying time is preferably 1-3 h, more preferably 2-2.5 h; and the drying equipment is preferably a microwave dryer.

[0048] In the present invention, the reducing atmosphere is preferably hydrogen; the temperature of the reducing calcination is preferably 800-950° C., more preferably 800-900° C., and the holding time is preferably 2-3 h, more preferably 2-2.5 h.

[0049] During the reduction roasting process, the following reaction occurs: BaSO4+4H2=BaS+4H2O.

[0050] After obtaining the barium sulfide, the present invention mixes the barium sulfide and liquid alkali to carry out a second double decomposition reaction to obtain barium hydroxide crystals and sodium sulfide solution respectively.

[0051] In the present invention, the liquid caustic soda is provided by the first double decomposition reaction liquid; the molar ratio of the barium element in the barium sulfide to the hydroxide in the liquid caustic soda is preferably 1:(2-4), more preferably 1:(2.5-3.5); the temperature of the second double decomposition reaction is preferably 100-120°C, more preferably 100-110°C, the pressure is preferably 1-2MPa, more preferably 1-1.5MPa, and the insulation time is preferably 2-3h, more preferably 2-2.5h.

[0052] During the second metathesis reaction, the following reaction occurs: BaS+2NaOH=Ba(OH)2+Na2S.

[0053] After the second double decomposition reaction, the present invention preferably cools the reaction solution obtained by the second double decomposition reaction to 50-60° C., separates the solid from the liquid, and obtains barium hydroxide crystals and sodium sulfide solution.

[0054] In the present invention, the barium hydroxide crystals are preferably used as a source of supplementary barium hydroxide in the first metathesis reaction.

[0055] After obtaining the sodium sulfide solution, the present invention evaporates and crystallizes the sodium sulfide solution to obtain a sodium sulfide product and an evaporated crystallization mother liquor, respectively; the evaporated crystallization mother liquor is returned to the subsequent second double decomposition reaction for treatment.

[0056] In the present invention, the temperature of the evaporation crystallization is preferably 50-80° C., more preferably 60-70° C.; the time of the evaporation crystallization is preferably 1-3 h, more preferably 2-2.5 h.

[0057] In the present invention, the sodium sulfide product meets the quality standard of Class 2 first-class product in "GB 10500-2009 Industrial Sodium Sulfide Standard". In the present invention, the sodium sulfide product is preferably packaged and sold.

[0058] Figure 1 The flowchart of the method for resource treatment of sodium sulfate wastewater from tungsten smelting in the present invention is as follows. Figure 1 As shown, after the sodium sulfate wastewater from tungsten smelting is impurity-removed and concentrated, barium hydroxide is added to carry out double decomposition reaction, and during the reaction process, barium sulfate is continuously separated by filter pressing to obtain a barium sulfate filter cake, while barium hydroxide and sodium sulfate are continuously added to the double decomposition reaction liquid until the mass concentration of sodium hydroxide in the double decomposition reaction liquid reaches the liquid alkali standard, the barium sulfate filter cake is microwave-dried to obtain barium sulfate, hydrogen is introduced for roasting to obtain barium sulfide, the barium sulfide and liquid alkali are reacted under high temperature and high pressure, the temperature is reduced for crystallization, the generated barium hydroxide is returned to the double decomposition reaction, and the generated sodium sulfide is concentrated and crystallized to obtain a sodium sulfide product.

[0059] The method provided by the present invention converts tungsten smelting sodium sulfate wastewater into sodium sulfide products and barium hydroxide that meet the quality standard of Class 2 first-class products in "GB 10500-2009 Industrial Sodium Sulfide Standard". The sodium sulfide product can be sold externally, and the barium hydroxide can be reused in the sodium sulfate wastewater treatment process. The intermediate products generated in the process of the method can be fully reused, and other wastes (wastewater, waste gas, and waste residue) will not be generated. The sodium sulfate wastewater can be fully utilized as a resource, the treatment cost can be reduced, and the market value of the conversion product can be increased.

[0060] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0061] Example 1

[0062] (1) Sodium hydroxide was added to the tungsten smelting sodium sulfate wastewater (the water quality is shown in Table 1) to adjust the pH value to 8, and magnesium sulfate was added in a ratio of 2:1 to the total molar amount of phosphorus, arsenic and silicon in the tungsten smelting sodium sulfate wastewater for coagulation and precipitation. The obtained supernatant was adjusted to pH 6 by adding sulfuric acid, and then 4 m 3 / h flow rate into the reaction column filled with activated carbon for adsorption and impurity removal. The ratio of the mass of activated carbon to the volume of the supernatant is 500kg:1m 3 / h, and obtain sodium sulfate wastewater after impurity removal, with hardness ≤0.5mmo1 / L, COD ≤10mg / L, SS ≤1mg / L, SiO2 ≤1mg / L, total P ≤0.1mg / L, total Pb ≤0.1mg / L, total As ≤0.1mg / L, total Cd ≤0.1mg / L;

[0063] (2) using a multi-effect evaporation concentration device to concentrate the sodium sulfate concentration of the tungsten smelting sodium sulfate wastewater after impurity removal to 380 g / L, thereby obtaining concentrated sodium sulfate wastewater;

[0064] (3) adding solid barium hydroxide into the concentrated sodium sulfate wastewater, and performing a first double decomposition reaction at 40° C. and 500 rpm for 2 h, wherein the chemical reaction equation is: Na2SO4+Ba(OH)2=2NaOH+BaSO4↓, and the barium sulfate produced is separated by suction filtration during the reaction process, and sodium sulfate and barium hydroxide are continuously added to the obtained first double decomposition reaction liquid, wherein the sodium sulfate is obtained by evaporating and crystallizing the sodium sulfate wastewater after impurities are removed, and the molar ratio of the added barium hydroxide to the sodium sulfate is 2:1. When the concentration of sodium hydroxide in the first double decomposition reaction liquid is measured to be ≥30%, the addition of sodium sulfate and barium hydroxide is stopped;

[0065] The barium sulfate separated by suction filtration is subjected to a first stirring and washing for 30 minutes with a 15wt% dilute sulfuric acid solution, and then subjected to a first filter press. The obtained barium sulfate filter cake is subjected to a second stirring and washing for 30 minutes with tap water, and then subjected to a second filter press to obtain a barium sulfate product; the filtrate obtained by the first filter press is returned to the first double decomposition reaction process to continue to undergo the first double decomposition reaction with barium hydroxide; the filtrate obtained by the second filter press is prepared into a 15wt% dilute sulfuric acid solution and returned to the first stirring and washing stage for use; the total amount of the 15wt% dilute sulfuric acid solution used in the first stirring and washing and the tap water used in the second stirring and washing to the mass ratio of the barium sulfate in the barium sulfate product is 10L:1kg; the filter press used is a 300m² filter press;

[0066] (4) placing the barium sulfate product in a microwave dryer, setting the heating temperature of the microwave dryer to 100° C., and drying for 1.5 hours to obtain dry barium sulfate;

[0067] (5) Put the dried barium sulfate into a fluidized bed calciner and introduce hydrogen for reduction calcination at a temperature of 800°C for 2 hours to obtain barium sulfide and water vapor. The reaction equation is: BaSO4+4H2=BaS+4H2O;

[0068] (6) putting the obtained barium sulfide into a high-pressure reactor to carry out a second double decomposition reaction with liquid alkali (the first double decomposition reaction liquid), the reaction temperature is 100° C., the reaction pressure is 1 MPa, the reaction time is 2 h, the molar ratio of the barium element in the barium sulfide to the hydroxide in the liquid alkali is 1:3, and the reaction equation is: BaS+2NaOH=Ba(OH)2+Na2S. After the reaction, the mixed solution is cooled to 60° C. to obtain barium hydroxide crystals and sodium sulfide solution. The sodium sulfide solution is evaporated and crystallized at 50° C. for 3 h to obtain a sodium sulfide product and an evaporated crystallization mother liquor, respectively; the evaporated crystallization mother liquor is returned to the subsequent second double decomposition reaction for treatment;

[0069] The obtained barium hydroxide crystals are returned to the first double decomposition reaction, and the obtained sodium sulfide product is packaged and sold.

[0070] The sodium sulfide product prepared in this embodiment has a purity of 63.05%, an iron mass percentage of 0.019%, and a water-insoluble matter mass percentage of 0.13%, which meets the quality standard of Class 2 first-class products in GB10500-2009.

[0071] Table 1 Water quality of sodium sulfate wastewater from tungsten smelting

[0072]

[0073] Example 2

[0074] (1) Sodium hydroxide was added to the tungsten smelting sodium sulfate wastewater (the water quality is shown in Table 2) to adjust the pH value to 9, and magnesium sulfate was added according to the total molar ratio of magnesium sulfate to phosphorus, arsenic and silicon in the tungsten smelting sodium sulfate wastewater of 1.5:1 for coagulation and precipitation. The obtained supernatant was adjusted to pH 7 by adding sulfuric acid, and then 3m 3 / h flow rate into the reaction column filled with activated carbon for adsorption and impurity removal. The ratio of the mass of activated carbon to the volume of the supernatant is 400kg:1m 3 / h, and obtain sodium sulfate wastewater after impurity removal, with hardness ≤0.5mmo1 / L, COD ≤10mg / L, SS ≤1mg / L, SiO2 ≤1mg / L, total P ≤0.1mg / L, total Pb ≤0.1mg / L, total As ≤0.1mg / L, total Cd ≤0.1mg / L;

[0075] (2) using a multi-effect evaporation concentration device to concentrate the sodium sulfate concentration of the tungsten smelting sodium sulfate wastewater after impurity removal to 370 g / L, thereby obtaining concentrated sodium sulfate wastewater;

[0076] (3) adding solid barium hydroxide into the concentrated sodium sulfate wastewater, and carrying out a first double decomposition reaction at 50° C. and stirring at 500 rpm for 2 hours, wherein the chemical reaction equation is: Na2SO4+Ba(OH)2=2NaOH+BaSO4↓, and the barium sulfate produced is separated by suction filtration during the reaction process, and sodium sulfate and barium hydroxide are continuously added to the obtained first double decomposition reaction liquid, wherein the sodium sulfate is obtained by evaporating and crystallizing the sodium sulfate wastewater after impurities are removed, and the molar ratio of the added barium hydroxide to the sodium sulfate is 1.5:1, and when the concentration of sodium hydroxide in the first double decomposition reaction liquid is measured to be ≥30%, the addition of sodium sulfate and barium hydroxide is stopped;

[0077] The barium sulfate separated by suction filtration is subjected to a first stirring and washing for 30 minutes with a 15wt% dilute sulfuric acid solution, and then subjected to a first filter press. The obtained barium sulfate filter cake is subjected to a second stirring and washing for 30 minutes with tap water, and then subjected to a second filter press to obtain a barium sulfate product; the filtrate obtained by the first filter press is returned to the first double decomposition reaction process to continue to undergo the first double decomposition reaction with barium hydroxide; the filtrate obtained by the second filter press is prepared into a 15wt% dilute sulfuric acid solution and returned to the first stirring and washing stage for use; the ratio of the total amount of the 15wt% dilute sulfuric acid solution used in the first stirring and washing and the tap water used in the second stirring and washing to the mass of the barium sulfate in the barium sulfate product is 15L:1kg; the filter press used is a 300m² filter press;

[0078] (4) placing the barium sulfate product in a microwave dryer, setting the heating temperature of the microwave dryer to 150° C., and drying for 2 hours to obtain dry barium sulfate;

[0079] (5) Put the dried barium sulfate into a fluidized bed calciner and introduce hydrogen for reduction calcination at a temperature of 900° C. for 2.5 h to obtain barium sulfide and water vapor. The reaction equation is: BaSO4+4H2=BaS+4H2O;

[0080] (6) The obtained barium sulfide is put into a high-pressure reactor to carry out a second double decomposition reaction with liquid alkali (the first double decomposition reaction liquid), the reaction temperature is 110° C., the reaction pressure is 1.5 MPa, the reaction time is 2.5 h, the molar ratio of the barium element in the barium sulfide to the hydroxide in the liquid alkali is 1:2, and the reaction equation is: BaS+2NaOH=Ba(OH)2+Na2S. After the reaction, the mixed solution is cooled to 60° C. to obtain barium hydroxide crystals and sodium sulfide solution. The sodium sulfide solution is evaporated and crystallized at 60° C. for 2.5 h to obtain a sodium sulfide product and an evaporated crystallization mother liquor, respectively; the evaporated crystallization mother liquor is returned to the subsequent second double decomposition reaction for treatment;

[0081] The obtained barium hydroxide crystals are returned to the first double decomposition reaction, and the obtained sodium sulfide product is packaged and sold.

[0082] The sodium sulfide product prepared in this embodiment has a purity of 62.31%, an iron mass percentage of 0.022%, and a water-insoluble matter mass percentage of 0.15%, which meets the quality standard of Class 2 first-class products in GB10500-2009.

[0083] Table 2 Water quality of sodium sulfate wastewater from tungsten smelting

[0084]

[0085] Example 3

[0086] (1) Sodium hydroxide was added to the tungsten smelting sodium sulfate wastewater (the water quality is shown in Table 3) to adjust the pH value to 10, and magnesium sulfate was added in a ratio of 1:1 to the total molar amount of phosphorus, arsenic and silicon in the tungsten smelting sodium sulfate wastewater for coagulation and precipitation. The obtained supernatant was adjusted to pH 7.5 by adding sulfuric acid, and then 2 m 3 / h flow rate into the reaction column filled with activated carbon for adsorption and impurity removal. The ratio of the mass of activated carbon to the volume of the supernatant is 200kg:1m 3 , and obtain sodium sulfate wastewater after impurity removal, with hardness ≤0.5mmo1 / L, COD ≤10mg / L, SS ≤1mg / L, SiO2 ≤1mg / L, total P ≤0.1mg / L, total Pb ≤0.1mg / L, total As ≤0.1mg / L, total Cd ≤0.1mg / L;

[0087] (2) using a multi-effect evaporation concentration device to concentrate the sodium sulfate concentration of the tungsten smelting sodium sulfate wastewater after impurity removal to 350 g / L, thereby obtaining concentrated sodium sulfate wastewater;

[0088] (3) adding solid barium hydroxide into the concentrated sodium sulfate wastewater, and performing a first double decomposition reaction at 60° C. and 500 rpm for 2 h. The chemical reaction equation is: Na2SO4+Ba(OH)2=2NaOH+BaSO4↓. During the reaction, the barium sulfate produced is separated by suction filtration. Sodium sulfate and barium hydroxide are continuously added to the obtained first double decomposition reaction liquid. Sodium sulfate is obtained by evaporating and crystallizing the sodium sulfate wastewater after impurities are removed. The molar ratio of the added barium hydroxide to sodium sulfate is 1:1. When the concentration of sodium hydroxide in the first double decomposition reaction liquid is measured to be ≥30%, the addition of sodium sulfate and barium hydroxide is stopped;

[0089] The barium sulfate separated by suction filtration is subjected to a first stirring and washing for 30 minutes with a 15wt% dilute sulfuric acid solution, and then subjected to a first filter press. The obtained barium sulfate filter cake is subjected to a second stirring and washing for 30 minutes with tap water, and then subjected to a second filter press to obtain a barium sulfate product; the filtrate obtained by the first filter press is returned to the first double decomposition reaction process to continue to undergo the first double decomposition reaction with barium hydroxide; the filtrate obtained by the second filter press is prepared into a 15wt% dilute sulfuric acid solution and returned to the first stirring and washing stage for use; the ratio of the total amount of the 15wt% dilute sulfuric acid solution used in the first stirring and washing and the tap water used in the second stirring and washing to the mass of the barium sulfate in the barium sulfate product is 20L:1kg; the filter press used is a 300m² filter press;

[0090] (4) placing the barium sulfate product in a microwave dryer, setting the heating temperature of the microwave dryer to 200° C., and drying for 2.5 hours to obtain dry barium sulfate;

[0091] (5) Put the dried barium sulfate into a fluidized bed calciner and introduce hydrogen for reduction calcination at a temperature of 950° C. for 3 h to obtain barium sulfide and water vapor. The reaction equation is: BaSO4+4H2=BaS+4H2O;

[0092] (6) putting the obtained barium sulfide into a high-pressure reactor to carry out a second double decomposition reaction with liquid alkali (the first double decomposition reaction liquid), the reaction temperature is 120° C., the reaction pressure is 2 MPa, the reaction time is 3 h, the molar ratio of the barium element in the barium sulfide to the hydroxide in the liquid alkali is 1:4, and the reaction equation is: BaS+2NaOH=Ba(OH)2+Na2S. After the reaction, the mixed solution is cooled to 50° C. to obtain barium hydroxide crystals and sodium sulfide solution. The sodium sulfide solution is evaporated and crystallized at 70° C. for 2 h to obtain a sodium sulfide product and an evaporated crystallization mother liquor, respectively; the evaporated crystallization mother liquor is returned to the subsequent second double decomposition reaction for treatment;

[0093] The obtained barium hydroxide crystals are returned to the first double decomposition reaction, and the obtained sodium sulfide product is packaged and sold.

[0094] The sodium sulfide product prepared in this embodiment has a purity of 61.05%, an iron mass percentage of 0.027%, and a water-insoluble matter mass percentage of 0.18%, which meets the quality standard of Class 2 first-class products in GB10500-2009.

[0095] Table 3 Water quality of sodium sulfate wastewater from tungsten smelting

[0096]

[0097] Comparative Example 1

[0098] The difference from Example 1 is that the ratio of the added magnesium sulfate to the total molar amount of phosphorus, arsenic and silicon in the tungsten smelting sodium sulfate wastewater is 0.7:1, which is less than 1:1, and the rest of the contents are consistent with the example.

[0099] The sodium sulfide product prepared in Comparative Example 1 has a purity of 55.13%, an iron mass percentage of 0.058%, and a water-insoluble mass percentage of 0.28%, which does not meet the quality standard of Class 2 first-class products in GB10500-2009.

[0100] Comparative Example 2

[0101] The difference from Example 1 is that the ratio of the mass of activated carbon to the volume of the supernatant is 180 kg: 1 m 3 / h, less than 200kg:1m 3 , the rest of the content is consistent with the embodiment.

[0102] The sodium sulfide product prepared in Comparative Example 2 has a purity of 58.87%, an iron mass percentage of 0.035%, and a water-insoluble matter mass percentage of 0.24%, which does not meet the quality standard of Class 2 first-class products in GB10500-2009.

[0103] Comparative Example 3

[0104] The difference from Example 1 is that the barium sulfate produced is separated by continuous filtration during the first double decomposition reaction, and the condition of continuously adding sodium sulfate and barium hydroxide to the obtained first double decomposition reaction liquid is changed to that after the first double decomposition reaction is completed, the mixed slurry obtained by the reaction of sodium sulfate wastewater and barium hydroxide is pumped into a filter press for filter press separation to directly obtain a barium sulfate filter cake and the first double decomposition reaction liquid (alkali solution), and the rest of the content is consistent with the embodiment. The mass concentration of sodium hydroxide in the first double decomposition reaction liquid obtained in Comparative Example 3 is 11%, which does not meet the reaction conditions of barium sulfide and liquid alkali, and barium hydroxide and sodium sulfide cannot be obtained.

[0105] Comparative Example 4

[0106] The difference from Example 1 is that tap water is used for both the first stirring and the second stirring washing, and the rest of the contents are the same as those of the Example. The amount of water used for stirring and washing in Comparative Example 4 is 40 L / kg of barium sulfate.

[0107] It can be seen from Comparative Examples 1-2 and Examples 1-3 that if the amount of magnesium sulfate or activated carbon used in the impurity removal step is insufficient, the quality of the sodium sulfide product produced will be affected.

[0108] It can be seen from Comparative Example 3 and Examples 1 to 3 that the sodium hydroxide concentration in the first double decomposition reaction liquid obtained directly from the reaction of sodium sulfate wastewater and barium hydroxide is difficult to reach ≥30%, which does not meet the requirements of the reaction of barium sulfide with liquid alkali, and other processes such as concentration and concentration are required to improve its purity.

[0109] From Comparative Example 4 and Examples 1 to 3, it can be seen that the amount of water required for directly using tap water to stir and wash barium sulfate is much greater than that required for stirring and washing with dilute sulfuric acid and then continuing to stir and wash with tap water for a second time. It can be seen that using dilute sulfuric acid for one stirring and washing can save a lot of washing water.

[0110] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for resource treatment of tungsten smelting sodium sulfate wastewater, characterized in that: The following steps are involved: The tungsten smelting sodium sulfate wastewater after impurities removal is concentrated to obtain concentrated sodium sulfate wastewater; The concentrated sodium sulfate wastewater and barium hydroxide are mixed to perform a first double decomposition reaction, and the generated barium sulfate precipitate is separated to obtain a first double decomposition reaction liquid; The separated barium sulfate precipitate is carried out simultaneously with the first double decomposition reaction, and sodium sulfate and barium hydroxide are added to the first double decomposition reaction liquid to continue the first double decomposition reaction until the mass percentage of sodium hydroxide in the first double decomposition reaction liquid is ≥30%; the molar ratio of the added sodium sulfate and barium hydroxide is 1:(1-2); the temperature of the first double decomposition reaction is 40-60° C.; the time of the first double decomposition reaction is 2-4 hours; After the barium sulfate precipitate is stirred and washed for the first time, a first filter press is performed; after the barium sulfate filter cake obtained by the first filter press is stirred and washed for the second time, a second filter press is performed to obtain a barium sulfate product; the first stirring and washing time is 30 minutes; the reagent used for the first stirring and washing is a sulfuric acid solution; the mass concentration of the sulfuric acid solution is 10-20%; the filtrate obtained by the first filter press is returned to the first double decomposition reaction process to continue to undergo the first double decomposition reaction with barium hydroxide; the second stirring and washing time is 30 minutes; the reagent used for the second stirring and washing is tap water; the filtrate obtained by the second filter press is made into a sulfuric acid solution with a mass concentration of 10-20% as the reagent for the first stirring and washing; the ratio of the total amount of reagents used for the first stirring and washing and the mass of barium sulfate in the barium sulfate product is (8-25) L:1 kg; After the barium sulfate precipitate is dried, reduction roasting is performed under a reducing atmosphere to obtain barium sulfide; the reducing atmosphere is hydrogen; the temperature of the reduction roasting is 800-950° C., and the holding time is 2-3 hours; The barium sulfide and liquid alkali are mixed for a second double decomposition reaction to obtain barium hydroxide crystals and sodium sulfide solution, respectively; the liquid alkali is provided by the first double decomposition reaction liquid; the temperature of the second double decomposition reaction is 100-120° C., the pressure is 1-2 MPa, and the heat and pressure holding time is 2-3 hours; The sodium sulfide solution is evaporated and crystallized to obtain a sodium sulfide product and an evaporated crystallization mother liquor respectively; the evaporated crystallization mother liquor is returned to the subsequent second double decomposition reaction for treatment.

2. The method according to claim 1, characterized in that In the tungsten smelting sodium sulfate wastewater after impurities removal, the hardness is ≤0.5mmol / L, the COD concentration is ≤10mg / L, the SS concentration is ≤1mg / L, the SiO2 concentration is ≤1mg / L, the total P concentration is ≤0.1mg / L, the total Pb concentration is ≤0.1mg / L, the total As concentration is ≤0.1mg / L, and the total Cd concentration is ≤0.1mg / L.

3. The method according to claim 1, characterized in that The concentration of sodium sulfate in the concentrated sodium sulfate wastewater is 350-380 g / L.

4. The method according to claim 1, characterized in that: The molar ratio of the barium element in the barium sulfide to the hydroxide in the liquid alkali is 1:(2-4).

5. The method according to claim 1, characterized in that The impurity removal comprises: adjusting the pH value of the sodium sulfate wastewater to 8-10, adding a coagulant for coagulation and precipitation, adjusting the pH value of the obtained supernatant to 6-7.5, and then performing activated carbon treatment.

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