CN113968651A - Method for extracting salt from complex iron catalyst sodium method desulfurization waste liquid - Google Patents

Method for extracting salt from complex iron catalyst sodium method desulfurization waste liquid Download PDF

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CN113968651A
CN113968651A CN202111237966.3A CN202111237966A CN113968651A CN 113968651 A CN113968651 A CN 113968651A CN 202111237966 A CN202111237966 A CN 202111237966A CN 113968651 A CN113968651 A CN 113968651A
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sodium
waste liquid
crystallization
temperature
oxidation
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焦志浩
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Jiao Zhihao
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Jiao Zhihao
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C3/00—Cyanogen; Compounds thereof
    • C01C3/20—Thiocyanic acid; Salts thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
    • C01D5/16—Purification
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/048—Purification of waste water by evaporation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/38—Treatment of water, waste water, or sewage by centrifugal separation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/18—Nature of the water, waste water, sewage or sludge to be treated from the purification of gaseous effluents

Abstract

The invention belongs to the technical field of desulfurization waste liquid treatment, and particularly relates to a method for extracting salt from a complex iron catalyst sodium-method desulfurization waste liquid. According to the method provided by the invention, firstly, sodium thiosulfate in the sodium desulfurization waste liquid can be converted into sodium sulfate through oxidation reaction, then, under the condition that the pH value is not less than 7, the oxidation waste liquid and the adsorbent are mixed, adsorbed and purified, iron ions in the sodium desulfurization waste liquid are removed to obtain purified waste liquid, and then, sodium sulfate and sodium thiocyanate are extracted step by step, so that a high-purity sodium sulfate product and a high-purity sodium thiocyanate product can be prepared by the method provided by the invention. The results of the examples show that the purity of the sodium sulfate obtained by the method provided by the invention is more than 95%, and the purity of the sodium thiocyanate is more than 99%.

Description

Method for extracting salt from complex iron catalyst sodium method desulfurization waste liquid
Technical Field
The invention belongs to the technical field of desulfurization waste liquid treatment, and particularly relates to a method for extracting salt from a complex iron catalyst sodium-method desulfurization waste liquid.
Background
At present, most coking plants generate a large amount of desulfurization waste liquid by sodium desulfurization, the desulfurization waste liquid generally contains sodium carbonate, sodium bicarbonate, sodium thiocyanate, sodium thiosulfate and sodium sulfate, and when a complex iron catalyst is adopted during sodium desulfurization, the desulfurization waste liquid also contains iron ion impurities. In industrial production, sodium desulfurization waste liquid needs to be further treated to extract industrial salt products such as sodium sulfate, sodium thiocyanate and the like from the waste liquid so as to reduce the cost.
The existing method mainly comprises the steps of adding sulfuric acid or a strong oxidant to oxidize sodium thiosulfate in the sodium desulfurization waste liquid into sodium sulfate, and finally obtaining sodium thiocyanate and sodium sulfate. However, no report about treatment of iron ion impurities remained in the complex iron catalyst sodium desulfurization waste liquid is provided, so that the purity of sodium thiocyanate and sodium sulfate products extracted from the complex iron catalyst sodium desulfurization waste liquid is only 80-90%.
Disclosure of Invention
In view of the above, the invention provides a method for extracting salt from a complex iron catalyst sodium-method desulfurization waste liquid, and the method provided by the invention can be used for obtaining sodium sulfate and sodium thiocyanate products with higher purity.
The invention provides a method for extracting salt from a complex iron catalyst sodium method desulfurization waste liquid, which comprises the following steps:
mixing the complex iron catalyst sodium desulfurization waste liquid with oxidizing gas for oxidation reaction to obtain oxidation waste liquid;
under the condition that the pH value is more than or equal to 7, mixing the oxidized waste liquid with an adsorbent, adsorbing and purifying to obtain purified waste liquid;
sequentially carrying out first reduced pressure evaporation crystallization, first temperature reduction crystallization and second reduced pressure evaporation crystallization on the purified waste liquid to obtain sodium sulfate and crystallization mother liquor;
and carrying out second cooling crystallization on the crystallization mother liquor to obtain sodium thiocyanate.
Preferably, the pH value of the complex iron catalyst sodium method desulfurization waste liquid during the oxidation reaction is less than or equal to 7, and the temperature of the oxidation reaction is 60-90 ℃.
Preferably, the mass content of the sodium thiosulfate in the oxidation waste liquid is 0.1-2 g/L.
Preferably, the temperature of adsorption purification is 60-80 ℃, the heat preservation time of adsorption purification is 0.5-3 h, and the pH value of a mixed system of oxidation waste liquid and an adsorbent is 7-11 during adsorption purification.
Preferably, the mass of the adsorbent accounts for 3-8 per mill of the mass of the oxidation waste liquid.
Preferably, the vacuum degree of the first reduced pressure evaporative crystal and the vacuum degree of the second reduced pressure evaporative crystal are independent and are not less than-0.08 MPa, and the heat preservation temperature of the first reduced pressure evaporative crystal and the heat preservation temperature of the second reduced pressure evaporative crystal are independent and are 80-90 ℃.
Preferably, the termination temperature of the first temperature-reducing crystallization is 30-80 ℃.
Preferably, the termination temperature of the second temperature-reducing crystallization is 30-60 ℃.
Preferably, the cooling rate of the first cooling crystallization and the second cooling crystallization is 8-15 ℃/h independently.
Preferably, the complex iron catalyst sodium method desulfurization waste liquid contains sodium carbonate, sodium bicarbonate, sodium thiocyanate, sodium thiosulfate, sodium sulfate and iron ions, the mass content of the sodium carbonate is 5-10 g/L, the mass content of the sodium bicarbonate is 5-20 g/L, the mass content of the sodium thiocyanate is 160-280 g/L, the mass content of the sodium thiosulfate is 10-50 g/L, the mass content of the sodium sulfate is 30-80 g/L, and the mass content of the iron ions is 30-1000 PPM. .
The invention provides a method for extracting salt from a complex iron catalyst sodium method desulfurization waste liquid, which comprises the following steps: mixing the complex iron catalyst sodium desulfurization waste liquid with oxidizing gas for oxidation reaction to obtain oxidation waste liquid; under the condition that the pH value is more than or equal to 7, mixing the oxidized waste liquid with an adsorbent, adsorbing and purifying to obtain purified waste liquid; sequentially carrying out first reduced pressure evaporative crystallization, first temperature reduction crystallization and second reduced pressure evaporative crystallization on the purified waste liquid to obtain sodium sulfate and first crystallization mother liquor; and carrying out second cooling crystallization on the first crystallization mother liquor to obtain sodium thiocyanate. According to the method provided by the invention, firstly, sodium thiosulfate in the sodium desulfurization waste liquid can be converted into sodium sulfate through oxidation reaction, then under the condition that the pH value is not less than 7, iron ions in the oxidized waste liquid are converted into ferric hydroxide precipitate, the ferric hydroxide precipitate is adsorbed and purified through an adsorbent, the iron ions in the sodium desulfurization waste liquid are removed to obtain purified waste liquid, and then sodium sulfate and sodium thiocyanate are extracted in steps, so that a high-purity sodium sulfate product and a high-purity sodium thiocyanate product can be prepared through the method provided by the invention. The results of the examples show that the purity of the sodium sulfate obtained by the method provided by the invention is more than 95%, and the purity of the sodium thiocyanate is more than 99%.
Drawings
FIG. 1 is a process flow diagram of an embodiment of the present invention.
Detailed Description
The invention provides a method for extracting salt from a complex iron catalyst sodium method desulfurization waste liquid, which comprises the following steps:
mixing the complex iron catalyst sodium desulfurization waste liquid with oxidizing gas for oxidation reaction to obtain oxidation waste liquid;
mixing the complex iron catalyst sodium desulfurization waste liquid with oxidizing gas for oxidation reaction to obtain oxidation waste liquid;
under the condition that the pH value is more than or equal to 7, mixing the oxidized waste liquid with an adsorbent, adsorbing and purifying to obtain purified waste liquid;
sequentially carrying out first reduced pressure evaporative crystallization, first temperature reduction crystallization and second reduced pressure evaporative crystallization on the purified waste liquid to obtain sodium sulfate and first crystallization mother liquor;
and carrying out second cooling crystallization on the first crystallization mother liquor to obtain sodium thiocyanate.
In the invention, the waste liquid of the complex iron catalyst sodium method desulfurization is preferably obtained by adopting the complex iron catalyst sodium method desulfurization, and the invention has no special requirement on the source of the complex iron catalyst, and can adopt the complex iron catalyst which is well known by the technical personnel in the field. In particular embodiments of the invention, the complexed iron catalyst is preferably purchased from Hebei Hessian environmental protection technologies, Inc., Shanghai Jiaji, Inc., or Changchun Dong Shi, Inc.
In the invention, the complex iron catalyst sodium method desulfurization waste liquid preferably contains sodium carbonate, sodium bicarbonate, sodium thiocyanate, sodium thiosulfate, sodium sulfate and iron ions, the mass content of the sodium carbonate is preferably 5-10 g/L, the mass content of the sodium bicarbonate is preferably 5-20 g/L, the mass content of the sodium thiocyanate is preferably 160-280 g/L, the mass content of the sodium thiosulfate is preferably 10-50 g/L, the mass content of the sodium sulfate is preferably 30-80 g/L, and the mass content of the iron ions is preferably 30-1000 PPM.
The method mixes the complex iron catalyst sodium method desulfurization waste liquid and the oxidizing gas for oxidation reaction to obtain the oxidation waste liquid.
In the present invention, the oxidizing gas is preferably an oxygen-containing gas, more preferably oxygen or air, and in a specific embodiment of the present invention, the oxidizing gas is specifically air.
In the invention, the mixing and oxidation reaction is preferably carried out in an oxidation tower, and in the invention, the complex iron catalyst sodium method desulfurization waste liquid is preferably conveyed into the oxidation tower through a desulfurization waste liquid tank, and the oxidizing gas is introduced from the bottom of the oxidation tower when the liquid level of the complex iron catalyst sodium method desulfurization waste liquid in the oxidation tower is preferably 80-90%. And the oxidizing gas enters an oxidation tower to contact and mix with the complex iron catalyst sodium method desulfurization waste liquid from bottom to top to generate oxidation reaction.
In the present invention, the flow rate of the oxidizing gas is preferably 6 to 20Nm3A/min, more preferably 8 to 15Nm3/min。
In the invention, during the oxidation reaction, the pH value of the complex iron catalyst sodium method desulfurization waste liquid is preferably less than or equal to 7, and more preferably 6-7. In a specific embodiment of the present invention, before the complex iron catalyst sodium desulfurization waste liquid and the oxidizing gas are mixed, a pH regulator is preferably used to regulate the pH value of the complex iron catalyst sodium desulfurization waste liquid, and in the present invention, the pH regulator is preferably sulfuric acid, and the mass percentage of the sulfuric acid is preferably 93-95%. According to the invention, the pH value of the complex iron catalyst sodium method desulfurization waste liquid is preferably adjusted to be less than or equal to 7, so that sodium carbonate and sodium bicarbonate in the complex iron catalyst sodium method desulfurization waste liquid can be removed before the oxidation reaction.
In the invention, the temperature of the oxidation reaction is preferably 60-90 ℃, and more preferably 65-80 ℃.
In the invention, the heat preservation time of the oxidation reaction is preferably 4-8 h, and more preferably 4.5-7.5 h. In the invention, sampling and analyzing are carried out in the oxidation reaction process, when the mass content of the sodium thiosulfate in the oxidation waste liquid is preferably 0.1-2 g/L, the oxidizing gas is stopped from being introduced into the oxidation tower, and the oxidation reaction is finished.
The invention oxidizes the sodium thiosulfate in the complex iron catalyst nano-method desulfurization waste liquid through oxidation reaction to generate sodium sulfate and sulfur.
In the invention, the tail gas generated by the oxidation reaction enters the tail gas absorption tower through the exhaust port at the top of the oxidation tower to be absorbed.
In the present invention, it is preferable that the oxidation reaction liquid after the oxidation reaction is subjected to solid-liquid separation to obtain the oxidation waste liquid. In the present invention, the solid-liquid separation is preferably carried out in a plate and frame filter, and the present invention has no particular requirement on the specific embodiment of the solid-liquid separation. The present invention removes sulfur generated during the oxidation reaction by solid-liquid separation.
After the oxidized waste liquid is obtained, the oxidized waste liquid and the adsorbent are mixed, adsorbed and purified to obtain the purified waste liquid under the condition that the pH value is more than or equal to 7.
In the present invention, the adsorbent is preferably activated carbon. The invention has no special requirement on the source of the adsorbent, and can adopt a commercial product.
In the invention, the mass of the adsorbent is preferably 3-8 per mill, and more preferably 3.5-6 per mill of the mass of the oxidation waste liquid.
In the invention, the temperature of the adsorption purification is preferably 60-80 ℃, and more preferably 65-75 ℃. The heat preservation time of the adsorption purification is preferably 2-6 h, and more preferably 2.5-5 h. In the invention, during the adsorption purification, the pH value of the mixed system of the oxidation waste liquid and the adsorbent is not less than 7, preferably 7-11, and more preferably 8.5-10. According to the invention, the pH value of the adsorption purification is preferably controlled to be more than or equal to 7 by a pH value regulator, the pH value regulator is preferably a sodium hydroxide aqueous solution, and the mass percent of the sodium hydroxide aqueous solution is preferably 30-50%. In the embodiment of the present invention, the adsorption purification is preferably performed under stirring, and the present invention has no special requirement for the specific implementation process of the stirring.
In the invention, when the pH value of the oxidation waste liquid is more than or equal to 7, iron ions in the oxidation waste liquid are precipitated into ferric hydroxide, and the ferric hydroxide is absorbed and removed from the oxidation waste liquid through an adsorbent.
In the invention, the adsorbent can remove the sodium hydroxide and decolor the oxidation waste liquid at the same time.
In the present invention, the adsorption purification is preferably performed in a decolorizing tank, and in the present invention, the adsorption purification is performed to obtain an adsorption purification reaction solution, and in the present invention, the adsorption purification reaction solution is preferably subjected to solid-liquid separation to obtain the purified waste liquid.
In the present invention, the solid-liquid separation is preferably carried out in a plate and frame filter, and the present invention has no particular requirement on the specific embodiment of the solid-liquid separation. The invention removes the waste adsorbent after adsorption purification generated during the adsorption purification through solid-liquid separation, and when the adsorbent is specifically activated carbon, the waste activated carbon is obtained, and the waste activated carbon is preferably used by blending coal.
After the purified waste liquid is obtained, the purified waste liquid is sequentially subjected to first reduced pressure evaporation crystallization, first temperature reduction crystallization and second reduced pressure evaporation crystallization to obtain sodium sulfate and crystallization mother liquor.
The invention carries out first reduced pressure evaporation crystallization on the purified waste liquid to obtain a first concentrated solution. In the present invention, the degree of vacuum of the first reduced-pressure evaporative crystallization is preferably not more than-0.08 MPa, more preferably-0.08 MPa to-0.095 MPa. In the invention, the heat preservation temperature of the first reduced pressure evaporation crystallization is preferably 80-90 ℃. In the invention, when the purified waste liquid reaches the gas-liquid phase equilibrium at the heat preservation temperature, the first reduced pressure evaporation crystallization is finished to obtain a first concentrated solution. When the purified waste liquid reaches gas-liquid equilibrium, no solvent is evaporated in the purified waste liquid. In the first reduced-pressure evaporation crystallization, as the solvent in the first reduced-pressure evaporation crystallization system is evaporated, sodium sulfate crystals in the first reduced-pressure evaporation crystallization system are precipitated.
In the invention, the first concentrated solution is preferably discharged into a first crystallization kettle for first cooling crystallization to obtain the sodium sulfate and a first crystallization mother liquor. In the present invention, the initial temperature of the first temperature-decreasing crystallization is preferably 0 to 60 ℃, preferably 10 to 50 ℃ higher than the termination temperature, and in a specific embodiment of the present invention, the initial temperature of the first temperature-decreasing crystallization is preferably the holding temperature of the first reduced-pressure evaporative crystallization. In the invention, the termination temperature of the first temperature-reducing crystallization is preferably 30-80 ℃, and more preferably 40-70 ℃. In the invention, the cooling rate of the first cooling crystallization is preferably 8-15 ℃/h, and more preferably 8.5-13 ℃/h. In a specific embodiment of the present invention, the first temperature-reducing crystallization is preferably performed by cooling water.
In the invention, the first cooling crystallization liquid is obtained after the first cooling crystallization, and the first cooling crystallization liquid is preferably subjected to solid-liquid separation to obtain the sodium sulfate and the first cooling crystallization mother liquor. In the invention, the solid-liquid separation is preferably centrifugation, and the invention has no special requirement on the specific implementation process of the centrifugation. In the invention, the sodium sulfate is packaged and sold, and the first cooling crystallization mother liquor enters a mother liquor tank for standby.
After the first cooling crystallization mother liquor is obtained, the first cooling crystallization mother liquor is subjected to second reduced pressure evaporation crystallization to obtain sodium sulfate and crystallization mother liquor.
In the invention, the first temperature-reducing crystallization mother liquor is preferably decolorized before the second reduced-pressure evaporation crystallization. In the present invention, the decolorization is preferably: and mixing the first crystallization mother liquor with activated carbon for decolorization. In the invention, the mass of the activated carbon is preferably 3 to 8 per mill of the mass of the first crystallization mother liquor, and more preferably 3.5 to 6 per mill. In the invention, the decolorizing temperature is preferably 60-80 ℃, and more preferably 65-70 ℃. In the invention, the pH value of the decolorization is preferably 7-11, and more preferably 8.5-10. In the invention, the heat preservation time of the decolorization is preferably 2-6 h, and more preferably 2.5-5 h. In the present invention, after the decolorization, the solid-liquid separation is preferably performed on the decolorized first temperature-reduced crystallization mother liquor in the present invention. In the present invention, the solid-liquid separation is preferably carried out in a plate and frame filter, and the present invention has no particular requirement on the specific embodiment of the solid-liquid separation. The invention removes the waste activated carbon decolorized by the first cooling crystallization mother liquor through solid-liquid separation, and the waste activated carbon is preferably used by coal blending.
In the present invention, the degree of vacuum of the second reduced-pressure evaporative crystallization is preferably not more than-0.08 MPa, more preferably-0.08 MPa to-0.095 MPa. In the invention, the heat preservation temperature of the second reduced pressure evaporation crystallization is preferably 80-90 ℃. In the invention, when the first temperature-reducing crystallization mother liquor reaches gas-liquid phase equilibrium at the heat preservation temperature, the second reduced-pressure evaporation crystallization is finished. When the first temperature-reducing crystallization mother liquor reaches gas-liquid equilibrium, no solvent is evaporated in the first temperature-reducing crystallization mother liquor. In the second reduced-pressure evaporation crystallization, as the solvent in the second reduced-pressure evaporation crystallization system is evaporated, the sodium sulfate in the second reduced-pressure evaporation crystallization system is further crystallized and precipitated.
In the present invention, the second pressure-increasing evaporative crystallization is carried out to obtain a second reduced-pressure evaporative crystallization liquid, and in the present invention, it is preferable that the second reduced-pressure evaporative crystallization liquid is subjected to solid-liquid separation to obtain sodium sulfate and a crystallization mother liquor. In the invention, the solid-liquid separation is preferably plate-frame filtration or centrifugal filtration, and the invention has no special requirement on the specific implementation process of the plate-frame filtration or centrifugal filtration. In the present invention, the sodium sulfate is sold in bags.
After crystallization mother liquor is obtained, the crystallization mother liquor is subjected to second temperature reduction crystallization to obtain sodium thiocyanate.
In the present invention, the initial temperature of the second temperature-decreasing crystallization is preferably 20 to 60 ℃, preferably 30 to 50 ℃ higher than the termination temperature, and in a specific embodiment of the present invention, the initial temperature of the second temperature-decreasing crystallization is preferably the holding temperature of the second reduced-pressure evaporative crystallization. In the invention, the termination temperature of the second temperature-reducing crystallization is preferably 30-60 ℃, and more preferably 35-50 ℃. In the invention, the cooling rate of the second cooling crystallization is preferably 8-15 ℃/h, and more preferably 8.5-13 ℃/h. In a specific embodiment of the present invention, the second temperature-reducing crystallization is preferably performed by cooling water.
In the invention, a second cooling crystallization liquid is obtained after the second cooling crystallization, and the invention preferably performs solid-liquid separation on the second cooling crystallization liquid to obtain the sodium thiocyanate. In the invention, the solid-liquid separation is preferably centrifugation, and the invention has no special requirement on the specific implementation process of the centrifugation. And the crystallization mother liquor obtained after the solid-liquid separation enters a mother liquor tank for circulation.
In the invention, the sodium thiocyanate is preferably dried and then packaged for sale, and the invention preferably blows heated air into a dryer to continuously dry the sodium thiocyanate, wherein the inlet air temperature of the heated air is preferably equal to or more than 120 ℃, more preferably 120-150 ℃, and the outlet air temperature of the heated air is preferably 50-90 ℃. And during continuous drying, the discharging speed of the sodium thiocyanate is 1-2 t/h.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
According to the process flow shown in figure 1, delivering the complex iron catalyst sodium desulfurization waste liquid (the mass content of sodium carbonate is 5g/L, the mass content of sodium bicarbonate is 5g/L, the mass content of sodium thiocyanate is 160g/L, the mass content of sodium thiosulfate is 10g/L, the mass content of sodium sulfate is 30g/L, and iron ions are 500ppm) to an oxidation tower through a desulfurization waste liquid tank, controlling the liquid level in the oxidation tower to be 80%, adding concentrated sulfuric acid (96%) into the sodium desulfurization waste liquid to adjust the pH value to be 6-7, introducing air into the oxidation tower from the bottom of the oxidation tower to perform oxidation reaction, wherein the flow rate of the air is 6Nm3And/min, the temperature of the oxidation reaction is 60 ℃, the heat preservation time of the oxidation reaction is 4 hours, sampling analysis is carried out, when the mass content of the sodium thiosulfate in the oxidation reaction liquid in the oxidation tower is 0.5g/L, air is stopped to be introduced, the oxidation reaction liquid is conveyed to a plate and frame type filter through a chemical pump, and the oxidation reaction liquid is filtered and desulfurized to obtain oxidation waste liquid.
Conveying the oxidized waste liquid to a decolorizing tank, adjusting the pH value of the oxidized waste liquid to 8.5 by adopting a sodium hydroxide solution (40%), adding activated carbon (7 per mill of the mass of the oxidized waste liquid), stirring, mixing, adsorbing and purifying for 5 hours at the temperature of 60 ℃ to obtain an adsorption and purification reaction liquid, and pumping the adsorption and purification reaction liquid into a plate and frame filter to obtain the purified waste liquid.
Carrying out first reduced pressure evaporation crystallization on the purified waste liquid under the condition that the vacuum degree is-0.08 MPa, when the heat preservation temperature of the reduced pressure evaporation crystallization is 80 ℃, continuously volatilizing without solvent to obtain a first concentrated solution, conveying the first concentrated solution to a first crystallization kettle for cooling crystallization, and cooling to 60 ℃ at the speed of 8 ℃/h. After centrifugation, the sodium sulfate product is obtained with the purity of 95.5 percent.
And (3) carrying out second reduced-pressure evaporation crystallization on the centrifuged first cooled crystallization mother liquor under the condition that the vacuum degree is-0.08 MPa, when the heat preservation temperature of the reduced-pressure evaporation crystallization is 80 ℃, continuously volatilizing without solvent to obtain a second concentrated solution, conveying the second concentrated solution to a plate-frame filter, and filtering to obtain a sodium sulfate product with the purity of 95.5 percent and a crystallization mother liquor.
And (4) conveying the crystallization mother liquor to a second crystallization kettle for cooling crystallization, and cooling to 50 ℃ at the speed of 12 ℃/h. Centrifuging to obtain sodium thiocyanate, putting the sodium thiocyanate into a dryer for continuous drying, blowing heated air into the dryer to dry the sodium thiocyanate, wherein the inlet air temperature of the heated air is 120 ℃, the outlet air temperature of the heated air is preferably 90 ℃, and the discharging speed of the sodium thiocyanate is 2t/h, so that a sodium thiocyanate product is obtained, and the purity is 99.5%. And centrifuging to obtain a crystallization mother liquor, and feeding the crystallization mother liquor into a mother liquor tank for circulation.
Example 2
According to the process flow shown in fig. 1, the complex iron catalyst sodium method desulfurization waste liquid (the mass content of sodium carbonate is 10g/L, the mass content of sodium bicarbonate is 20g/L, the mass content of sodium thiocyanate is 280g/L, the mass content of sodium thiosulfate is 50g/L, the mass content of sodium sulfate is 80g/L, and iron ions are 800ppm) is conveyed into an oxidation tower through a desulfurization waste liquid tank, the liquid level in the oxidation tower is 85%, concentrated sulfuric acid (93%) is added into the sodium method desulfurization waste liquid to adjust the pH value to be 6-7, air is introduced into the oxidation tower from the bottom of the oxidation tower to perform oxidation reaction, and the flow of the air is airAt a speed of 15Nm3And/min, the temperature of the oxidation reaction is 85 ℃, the heat preservation time of the oxidation reaction is 8 hours, sampling analysis is carried out, when the mass content of the sodium thiosulfate in the oxidation reaction liquid in the oxidation tower is 1.5g/L, air is stopped to be introduced, the oxidation reaction liquid is conveyed to a plate and frame type filter through a chemical pump, and the oxidation reaction liquid is filtered and desulfurized to obtain oxidation waste liquid.
Conveying the oxidized waste liquid to a decolorizing tank, adjusting the pH value of the oxidized waste liquid to 11 by adopting a sodium hydroxide solution (30%), adding activated carbon (7 per mill of the mass of the oxidized waste liquid), stirring, mixing, adsorbing and purifying at 80 ℃ for 6 hours to obtain an adsorption and purification reaction liquid, and pumping the adsorption and purification reaction liquid into a plate and frame filter to obtain the purified waste liquid.
Carrying out first reduced pressure evaporation crystallization on the purified waste liquid under the condition that the vacuum degree is-0.09 MPa, when the heat preservation temperature of the reduced pressure evaporation crystallization is 80 ℃, continuously volatilizing without solvent to obtain a first concentrated solution, conveying the first concentrated solution to a first crystallization kettle for cooling crystallization, and cooling to 60 ℃ at the speed of 8 ℃/h. After centrifugation, the sodium sulfate product is obtained, and the purity is 96%.
And (3) carrying out second reduced-pressure evaporation crystallization on the centrifuged first cooled crystallization mother liquor under the condition that the vacuum degree is-0.08 MPa, when the heat preservation temperature of the reduced-pressure evaporation crystallization is 80 ℃, continuously volatilizing without solvent to obtain a second concentrated solution, conveying the second concentrated solution to a plate-and-frame filter, and filtering to obtain a sodium sulfate product with the purity of 96% and a crystallization mother liquor.
And (4) conveying the crystallization mother liquor to a second crystallization kettle for cooling crystallization, and cooling to 50 ℃ at the speed of 12 ℃/h. Centrifuging to obtain sodium thiocyanate, putting the sodium thiocyanate into a dryer for continuous drying, blowing heated air into the dryer to dry the sodium thiocyanate, wherein the inlet air temperature of the heated air is 120 ℃, the outlet air temperature of the heated air is preferably 90 ℃, and the discharging speed of the sodium thiocyanate is 1t/h, so that a sodium thiocyanate product is obtained, and the purity is 99%. And centrifuging to obtain a second crystallization mother liquor, and feeding the second crystallization mother liquor into a mother liquor tank for circulation.
Example 3
According to the process flow of fig. 1, the complex iron catalyst sodium method desulfurization waste liquid (the mass content of sodium carbonate is 15g/L,the mass content of sodium bicarbonate is 15g/L, the mass content of sodium thiocyanate is 230g/L, the mass content of sodium thiosulfate is 35g/L, the mass content of sodium sulfate is 50g/L, and the iron ion content is 1000ppm), the sodium thiosulfate is conveyed into an oxidation tower through a desulfurization waste liquid tank, the liquid level in the oxidation tower is 85%, concentrated sulfuric acid (96%) is added into the sodium desulfurization waste liquid to adjust the pH value to be 6-7, air is introduced into the oxidation tower from the bottom of the oxidation tower to perform oxidation reaction, the flow rate of the air is 15Nm3And/min, the temperature of the oxidation reaction is 70 ℃, the heat preservation time of the oxidation reaction is 4 hours, sampling analysis is carried out, when the mass content of the sodium thiosulfate in the oxidation reaction liquid in the oxidation tower is 2g/L, air is stopped to be introduced, the oxidation reaction liquid is conveyed to a plate-and-frame type filter through a chemical pump, and the oxidation waste liquid is obtained after filtration and desulfurization.
Conveying the oxidized waste liquid to a decolorizing tank, adjusting the pH value of the oxidized waste liquid to 9 by adopting a sodium hydroxide solution (35%), adding activated carbon (7 per mill of the mass of the oxidized waste liquid), stirring, mixing, adsorbing and purifying for 4 hours at the temperature of 60 ℃ to obtain an adsorption and purification reaction liquid, and pumping the adsorption and purification reaction liquid into a plate-and-frame filter to obtain the purified waste liquid.
Carrying out first reduced pressure evaporation crystallization on the purified waste liquid under the condition that the vacuum degree is-0.08 MPa, when the heat preservation temperature of the reduced pressure evaporation crystallization is 80 ℃, continuously volatilizing without solvent to obtain a first concentrated solution, conveying the first concentrated solution to a first crystallization kettle for cooling crystallization, and cooling to 60 ℃ at the speed of 8 ℃/h. After centrifugation, the sodium sulfate product is obtained with the purity of 95.5 percent.
And (3) carrying out second reduced-pressure evaporation crystallization on the centrifuged first cooled crystallization mother liquor under the condition that the vacuum degree is-0.08 MPa, when the heat preservation temperature of the reduced-pressure evaporation crystallization is 80 ℃, continuously volatilizing without solvent to obtain a second concentrated solution, conveying the second concentrated solution to a plate-frame filter, and filtering to obtain a sodium sulfate product with the purity of 95.5 percent and a crystallization mother liquor.
And (4) conveying the crystallization mother liquor to a second crystallization kettle for cooling crystallization, and cooling to 50 ℃ at the speed of 12 ℃/h. Centrifuging to obtain sodium thiocyanate, putting the sodium thiocyanate into a dryer for continuous drying, blowing heated air into the dryer to dry the sodium thiocyanate, wherein the inlet air temperature of the heated air is 120 ℃, the outlet air temperature of the heated air is preferably 90 ℃, and the discharging speed of the sodium thiocyanate is 2t/h, so that a sodium thiocyanate product is obtained, and the purity is 98.7%. And centrifuging to obtain a second crystallization mother liquor, and feeding the second crystallization mother liquor into a mother liquor tank for circulation.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A method for extracting salt from a complex iron catalyst sodium method desulfurization waste liquid is characterized by comprising the following steps:
mixing the complex iron catalyst sodium desulfurization waste liquid with oxidizing gas for oxidation reaction to obtain oxidation waste liquid;
under the condition that the pH value is more than or equal to 7, mixing the oxidized waste liquid with an adsorbent, adsorbing and purifying to obtain purified waste liquid;
sequentially carrying out first reduced pressure evaporation crystallization, first temperature reduction crystallization and second reduced pressure evaporation crystallization on the purified waste liquid to obtain sodium sulfate and crystallization mother liquor;
and carrying out second cooling crystallization on the crystallization mother liquor to obtain sodium thiocyanate.
2. The method according to claim 1, wherein the pH value of the complex iron catalyst sodium desulfurization waste liquid during the oxidation reaction is less than or equal to 7, and the temperature of the oxidation reaction is 60-90 ℃.
3. The method according to claim 1 or 2, wherein the mass content of sodium thiosulfate in the oxidation waste liquid is 0.1-2 g/L.
4. The method according to claim 1, wherein the temperature of the adsorption purification is 60-80 ℃, the heat preservation time of the adsorption purification is 0.5-3 h, and the pH value of a mixed system of the oxidation waste liquid and the adsorbent during the adsorption purification is 7-11.
5. The method according to claim 1 or 4, wherein the mass of the adsorbent accounts for 3-8% of the mass of the oxidation waste liquid.
6. The method according to claim 1, wherein the vacuum degree of the first reduced pressure evaporative crystal and the vacuum degree of the second reduced pressure evaporative crystal are independently not less than-0.08 MPa, and the temperature of the first reduced pressure evaporative crystal and the temperature of the second reduced pressure evaporative crystal are independently 80-90 ℃.
7. The method according to claim 1, wherein the termination temperature of the first temperature-decreasing crystallization is 30 to 80 ℃.
8. The method according to claim 1, wherein the second reduced temperature crystallization termination temperature is 30 to 60 ℃.
9. The method of claim 7 or 8, wherein the cooling rate of the first and second temperature-reducing crystals is independently 8-15 ℃/h.
10. The method according to claim 1, wherein the complex iron catalyst sodium desulfurization waste liquid contains sodium carbonate, sodium bicarbonate, sodium thiocyanate, sodium thiosulfate, sodium sulfate and iron ions, the mass content of the sodium carbonate is 5-10 g/L, the mass content of the sodium bicarbonate is 5-20 g/L, the mass content of the sodium thiocyanate is 160-280 g/L, the mass content of the sodium thiosulfate is 10-50 g/L, the mass content of the sodium sulfate is 30-80 g/L, and the mass content of the iron ions is 30-1000 PPM.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103663496A (en) * 2013-09-24 2014-03-26 北京艾思合众环保科技有限公司 Method for improving purity of sodium thiocyanate in coking and desulfurizing waste liquid
CN109824061A (en) * 2019-03-22 2019-05-31 扬州康龙环保工程有限公司 The method of sodium sulfocyanate and sodium sulphate is extracted in oven gas alkali desulphurization waste liquid
CN109824019A (en) * 2019-03-22 2019-05-31 扬州康龙环保工程有限公司 The method of sodium sulfocyanate, sodium thiosulfate and sodium sulphate is extracted in oven gas alkali desulphurization waste liquid

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103663496A (en) * 2013-09-24 2014-03-26 北京艾思合众环保科技有限公司 Method for improving purity of sodium thiocyanate in coking and desulfurizing waste liquid
CN109824061A (en) * 2019-03-22 2019-05-31 扬州康龙环保工程有限公司 The method of sodium sulfocyanate and sodium sulphate is extracted in oven gas alkali desulphurization waste liquid
CN109824019A (en) * 2019-03-22 2019-05-31 扬州康龙环保工程有限公司 The method of sodium sulfocyanate, sodium thiosulfate and sodium sulphate is extracted in oven gas alkali desulphurization waste liquid

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