CN107583934B - Treatment process of waste salt mud in sodium chlorate production - Google Patents
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Abstract
The invention discloses a treatment process of waste salt mud in sodium chlorate production, which comprises the following steps: (1) grinding waste salt slurry, (2) oxidizing, (3) dissolving out chromium ions, (4) washing, and (5) reducing. THE ADVANTAGES OF THE PRESENT INVENTIONThe method is characterized in that chromium ions wrapped in the waste salt mud are released by grinding and crushing, and then the chromium ions are removed from the waste salt mud by carrying out oxidation, dissolution, washing, reduction and other treatments on the waste salt mud, so that the problems of high treatment difficulty and incomplete removal of the chromium ions in the waste salt mud are solved; carrying out leaching toxicity test on the chromium content in the dechromization filter residue obtained after treatment according to the national standard (HJ/T299-2007), and carrying out Cr leaching on the Cr content in the leaching solution6+The content is 0mg/l, the total chromium content is 2.4mg/l, the environment-friendly comprehensive utilization standard (HJ/T301-2007) is achieved, the reduction detoxification rate is 99.5%, the chromium content of the treated waste salt mud is lower than the national standard, and the national environment-friendly discharge standard is met.
Description
The technical field is as follows:
the invention relates to the field of industrial waste treatment, in particular to a treatment process of waste salt mud in sodium chlorate production.
Background art:
in the production process of sodium chlorate, sodium dichromate is added into a system for catalyzing main reaction, reducing the generation amount of oxygen, controlling the pH value in an electrolytic cell and removing perchlorate ions generated by electrolytic reaction; about 0.118kg of sodium dichromate is required to be added for each ton of sodium chlorate. Meanwhile, in the production process of sodium chlorate, in order to remove calcium ions, magnesium ions and sulfate ions in raw material salt, sodium hydroxide, sodium carbonate and calcium chloride are added into a production system to precipitate the calcium ions, the magnesium ions and the sulfate ions; in the process, chromium ions added in the production system enter a clarifier along with industrial wastewater in the form of sodium dichromate and calcium chromate to precipitate so as to form 'waste salt mud'. In a daler clarifier, white waste salt mud which takes calcium carbonate, sodium chloride and a small amount of calcium sulfate, calcium chromate and sodium chromate as main components is generated; in the sulphate clarifier, a yellow waste salty mud is produced, based on calcium sulphate, sodium chlorate, calcium chromate and small amounts of sodium chromate and calcium carbonate.
The chromium ions in the waste salt mud are mainly Cr3+And Cr6+，Cr6+High toxicity of Cr3+Is oxidized to Cr6+(ii) a Generally, the chromium ions in the waste salt slurry are washed out and treated mainly by washing. However, because the existing forms of the chromium ions in the waste salt mud are various, including various forms such as free form, adsorption form and coating form, the chromium ions can only be removed by simply washing the waste salt mud, but the chromium ions existing in the adsorption form and the coating form cannot be removed; if chromium ions existing in the adsorption and packaging forms are not treated, residual Cr in the waste salt mud3+Can be oxidized into Cr again along with environmental change6+The chromium ions in the waste salt mud are difficult to detoxify and cannot be thoroughly removed, the surrounding ecological environment is continuously polluted, and great harm is caused to the ecological environment and the health of people. Meanwhile, chromium is a silvery white and glossy metal, has excellent characteristics of hardness, brittleness, corrosion resistance and the like, is widely applied to the fields of metallurgy, chemical industry, cast iron, fire resistance, high-precision science and technology and the like, is a very important mineral resource, and if chromium ions in the waste salt mud can be recycled, the problem of environmental pollution of the waste salt mud is solved, the bottleneck restricting sodium chlorate production is broken, and the problem of how to treat the waste salt mud in the sodium chlorate production is urgently needed to be solved.
At present, a treatment method of chromium ions in waste salt mud is not mature, and most of the treatment methods are in a theoretical research stage. The patent with publication No. CN101209873A, chromium separation and recovery method of waste residue containing hexavalent chromium, adopts sodium carbonate or sodium bicarbonate as mineralizer to increase Cr content6+But Cr in the waste salt mud3+The chromium content in the waste salt mud exceeds the standard due to difficult dissolution. CN105016387A patent "a method for treating chromium salt mud" by adding oxidant, leaching agent, etc. to make Cr in chromium salt mud3+Conversion to Cr6+And dissolving out to increase Cr6+The dissolution rate of the waste salt mud is improved, and the chromium ion in the waste salt mud is improvedThe removal rate of the seeds; however, it has the following problems: 1. the waste salt mud has hard particles and is not easy to dissolve, the waste salt mud is not treated, and Cr coated in the waste salt mud3+Difficult leaching, incomplete treatment of chromium ions and standard exceeding of the total chromium content in the waste salt mud. 2. The waste salt mud is generated by adding medicines to remove calcium ions, magnesium ions and sulfate ions in raw salt and perchlorate ions generated in the electrolysis of sodium chlorate production in the production process of sodium chlorate, after the waste salt mud is treated, even if the dechromization liquid is crystallized to remove sulfate, a large amount of other medicines such as an oxidant, a leaching agent, a reducing agent and the like and a large amount of perchlorate ions are still remained in the dechromization liquid, the dechromization liquid after the crystallization treatment is directly returned to a chlorate production system, the perchlorate ions are enriched in the sodium chlorate production system, the system is seriously exploded, and extremely serious potential safety hazards exist; and the precipitator used in the crystallization treatment of the dechromization liquid contains metal ions, once the metal ions such as barium ions enter the sodium chlorate production system, the anode of the electrolytic cell can be disabled, and the excessive metal ions can aggravate the load of the sodium chlorate production system and influence the normal operation of the sodium chlorate production system. Therefore, the problem to be solved is to find a treatment method suitable for the waste salt mud of the sodium chlorate plant.
The invention content is as follows:
the first purpose of the invention is to provide a treatment process of waste salt mud in sodium chlorate production, which is thorough in chromium ion treatment and beneficial to environmental protection.
The first purpose of the invention is implemented by the following technical scheme: the treatment process of the waste salt mud in the production of sodium chlorate is characterized by comprising the following steps: (1) grinding waste salt slurry, (2) oxidizing, (3) dissolving out chromium ions, (4) washing, and (5) reducing; wherein,
(1) grinding waste salt slurry: grinding the waste salt slurry to 100-150 meshes to obtain a grinding material;
(2) and (3) oxidation: and (1) after the waste salt slurry is ground, mixing the ground material with water according to a mass ratio of 1: 0.5-2, adding an oxidant, carrying out oxidation reaction at the temperature of 20-30 ℃ and the pressure of 0.3-0.5MPa, wherein the mass ratio of the oxidant to the grinding material is 1:15-40, the oxidation reaction time is 0.5-2h, and obtaining an oxidation slurry after the oxidation reaction is finished;
(3) dissolution of chromium ions: after the oxidation of the step (2) is finished, adding a hexavalent chromium ion dissolving agent into the oxidized slurry, wherein the hexavalent chromium ion dissolving agent is any one or combination of sodium bicarbonate and ammonium bicarbonate; the mass ratio of the hexavalent chromium ion dissolving agent to the grinding material is 1: 1.5-2, uniformly stirring at 90-120 ℃ and 0.3-0.5MPa to dissolve hexavalent chromium ions, wherein the stirring time is 0.5-1h, and after the stirring is finished, performing solid-liquid separation to obtain filter residue and filtrate; (4) washing: and (3) after the chromium ions are dissolved out, mixing the filter residue with washing water according to a mass ratio of 1: 1-5, uniformly mixing, washing at the temperature of 20-60 ℃ for 1-2 times, and after washing, performing solid-liquid separation to obtain a washing filtrate and dechromization filter residues;
(5) reduction: and (4) after the washing is finished, mixing the filtrate obtained in the dissolution of the chromium ions in the step (3) with the washing filtrate obtained in the washing in the step (4) to obtain a mixed solution, adding a reducing agent, and mixing the mixed solution with the grinding material and the reducing agent according to a mass ratio of 1: 15-25, carrying out reduction reaction at the temperature of 20-80 ℃ for 0.1-1h after uniformly mixing, and carrying out solid-liquid separation after the reduction reaction is finished to obtain chromium hydroxide precipitate and wastewater to be discharged.
Further, in the reduction of the step (5), the pH value of the wastewater to be discharged is adjusted to 6-9, the wastewater to be discharged after the pH value is adjusted is detected according to CJ3082-1999, and the wastewater is conveyed to an incoming water pipeline of a wastewater plant after the detection is qualified.
Further, in the oxidation (2), the mass ratio of the grinding material to water is 1: 1.5-2, the oxidant is any one or combination of more of a high manganese acid agent, sodium peroxide or sodium perchlorate, the mass ratio of the oxidant to the grinding material is 1:20-30, and the oxidation reaction time is 0.5-1 h.
Further, in the washing in the step (4), the mass ratio of the filter residue to the washing water is 1: 1-3, the temperature is 30-40 ℃, and the washing times are 2 times; the washing water used for washing is derived from hot water generated by an electrolytic heat exchanger of the sodium chlorate production system.
Further, in the reduction in the step (5), the reducing agent is any one or a combination of several of ferrous sulfate, sodium sulfide and sodium metabisulfite, and the mass ratio of the grinding material to the reducing agent is 1:20 to 25 ℃, the temperature is 30 to 50 ℃, and the reduction reaction time is 0.1 to 0.5 h.
The invention has the advantages that: 1. chromium ions wrapped in the waste salt mud are released by grinding and crushing, the oxidation and dissolution efficiency is improved by carrying out pressurization treatment in the oxidation and dissolution steps, and then the treatment such as washing, reduction and the like is carried out to remove the chromium ions from the waste salt mud, so that the problems of high treatment difficulty and incomplete removal of the chromium ions in the waste salt mud are solved; 2. carrying out leaching toxicity test on the chromium content in the dechromization filter residue obtained after treatment according to the national standard (HJ/T299-2007), and carrying out Cr leaching on the Cr content in the leaching solution6+The content is 0mg/l, the total chromium content of the dechromization filter residue is 2.4mg/l, the comprehensive utilization standard of environmental protection (HJ/T301-2007) is achieved, the reduction detoxification rate is 99.97%, the chromium content of the treated waste salt mud is lower than the national standard, and the waste salt mud conforms to the national environmental protection discharge standard; 3. the dechromization filter residue can be used for producing coatings, refractory materials and the like, and cannot cause secondary pollution; chromium ions are recovered in a form of chromium hydroxide and sold, so that the operation of production enterprises is diversified, and the income of the production enterprises is increased; 4. the method has simple process, scientific and reasonable system design, thorough detoxification, no secondary pollution, higher social and economic benefits and better industrial application prospect; 5. on one hand, the system effectively utilizes the waste heat in the sodium chlorate production system, and recycles the flushing water in the system to the oxidation and dissolution reaction tank, so that the energy consumption is low, the water consumption is low, and the treatment cost is reduced; on the other hand, the wastewater containing a large amount of metal ions is conveyed to a wastewater plant for treatment, so that the wastewater is prevented from being recycled to a sodium chlorate production system, the production load is increased, and the normal operation of the sodium chlorate production system is prevented from being influenced.
Description of the drawings:
fig. 1 is a schematic diagram of system connection in embodiment 1.
The system comprises a grinder 1, an oxidation digestion reaction tank 2, an oxidant storage tank 3, a digestion agent storage tank 4, a water supply pipeline 5, an oxidation digestion centrifugal machine 6, a water collection tank 7, a slag collection tank 8, an electrolysis heat exchanger 9, a washing centrifugal machine 10, a washing water pipeline 11, a dechromization filter residue storage tank 12, a reduction reaction tank 13, a reducing agent storage tank 14, a reduction centrifugal machine 15, a chromium hydroxide storage tank 16, a wastewater adjusting tank 17 and a wastewater plant incoming water pipeline 18.
The specific implementation mode is as follows:
example 1:
as shown in figure 1, the treatment system of the waste salt mud in the sodium chlorate production comprises a grinding machine 1, an oxidation and dissolution system and a washing system, the discharge port of the grinder 1 is communicated with the feed port of the oxidation digestion reaction tank 2 of the oxidation digestion system, the outlet of the water receiving tank 7 of the oxidation digestion system is communicated with the inlet of the reduction reaction tank 13 of the reduction system, the liquid outlet of the reduction centrifuge 15 of the reduction system is communicated with the water inlet of the wastewater regulation tank 17, the outlet of the wastewater regulation tank 17 is communicated with the water supply pipeline 18 of a wastewater plant, the slag outlet of the oxidation digestion centrifuge 6 of the oxidation digestion system is communicated with the feed port of the slag receiving tank 8 of the washing system, the outlet of the slag receiving tank 8 is communicated with the inlet of the washing centrifuge 10, and the water outlet of the washing centrifuge 10 is respectively communicated with the water inlet of the oxidation digestion reaction tank 2 and the inlet of the water receiving tank 7 through a three-way valve.
The oxidation digestion system comprises an oxidation digestion reaction tank 2, an oxidant storage tank 3, a digestion agent storage tank 4, a water supply pipeline 5, an oxidation digestion centrifuge 6 and a water receiving tank 7, wherein the oxidation digestion reaction tank 2 is a pressurization stirring tank, a water inlet of the oxidation digestion reaction tank 2 is communicated with the water supply pipeline 5, the oxidation digestion reaction tank 2 is respectively communicated with the oxidant storage tank 3 and the digestion agent storage tank 4 through pipelines, an oxidation control valve is arranged on a pipeline between the oxidation digestion reaction tank 2 and the oxidant storage tank 3, a digestion control valve is arranged on a pipeline between the oxidation digestion reaction tank 2 and the digestion agent storage tank 4, an outlet of the oxidation digestion reaction tank 2 is communicated with an inlet of the oxidation digestion centrifuge 6, and a liquid outlet of the oxidation digestion centrifuge 6 is communicated with an inlet of the water receiving tank 7.
The washing system comprises a slag collecting tank 8, a washing centrifuge 10 and a dechromization filter residue storage tank 12, wherein a water inlet of the slag collecting tank 8 is communicated with a hot water outlet of an electrolytic heat exchanger 9 of the sodium chlorate production system, an outlet of the slag collecting tank 8 is communicated with an inlet of the washing centrifuge 10, a washing water inlet of the washing centrifuge 10 is communicated with a washing water pipeline 11, and a slag outlet of the washing centrifuge 10 is communicated with an inlet of the dechromization filter residue storage tank 12.
The reduction system comprises a reduction reaction tank 13, a reducing agent storage tank 14, a reduction centrifuge 15 and a chromium hydroxide storage tank 16, wherein the reduction reaction tank 13 is communicated with the reducing agent storage tank 14 through a pipeline, a reduction control valve is arranged on the pipeline between the reduction reaction tank 13 and the reducing agent storage tank 14, an outlet of the reduction reaction tank 13 is communicated with an inlet of the reduction centrifuge 15, and a slag outlet of the reduction centrifuge 15 is communicated with an inlet of the chromium hydroxide storage tank 16.
The working process is as follows:
(1) grinding waste salt slurry: conveying the waste salt slurry to a grinding machine 1 for grinding to obtain a grinding material; the purpose of grinding is to fully release chromium ions wrapped in the waste salt slurry so as to improve the efficiency of subsequent oxidation, dissolution and reduction.
(2) And (3) oxidation: (1) after the grinding of the waste salt slurry is finished, conveying the grinding material into an oxidation and dissolution reaction tank 2, adding water into the oxidation and dissolution reaction tank 2 through a water supply pipeline 5, uniformly mixing, adding an oxidant into the oxidation and dissolution reaction tank 2 through an oxidant storage tank 3, carrying out oxidation reaction at the temperature of 20 ℃ and the pressure of 0.5MPa for 2 hours, and obtaining oxidation slurry after the oxidation reaction is finished; the oxidation effect is to oxidize the trivalent chromium ions into hexavalent chromium ions through an oxidant, and the oxidation reaction is carried out under the pressurization condition, so that the oxidation reaction can be promoted, the oxidation reaction is carried out more thoroughly, and the oxidation reaction efficiency is higher.
(3) Dissolution of chromium ions: (2) after the oxidation is finished, adding a hexavalent chromium ion dissolving agent into the oxidized slurry through a dissolving agent storage tank 4, uniformly stirring at the temperature of 50 ℃ and the pressure of 0.5MPa to dissolve hexavalent chromium ions, wherein the stirring time is 0.5h, and after the stirring is finished, conveying the material to an oxidation dissolving centrifuge 6 for solid-liquid separation to obtain filter residue and filtrate; the purpose of the dissolution is to dissolve hexavalent chromium ions in the oxidized slurry, improve the dissolution under a pressurized condition, improve the dissolution rate of the hexavalent chromium ions, and further improve the recovery rate of the chromium ions and the dechromization rate of the waste salt mud.
(4) Washing: (3) after the dissolution of chromium ions is finished, conveying filter residues to a residue collection tank 8, adding washing water into the residue collection tank 8 through an electrolytic heat exchanger 9 of a sodium chlorate production system, uniformly mixing, washing at the temperature of 20 ℃, wherein the washing frequency is 2 times, and after the washing is finished, conveying the materials to a washing centrifuge 10 for solid-liquid separation to obtain washing filtrate and dechromization filter residues; the washing aims at fully removing hexavalent chromium ions from the filter residue after the dissolution treatment so as to carry out the next reduction treatment; washing water used for washing is derived from hot water generated by an electrolytic heat exchanger 9 of a sodium chlorate production system, and the washing water does not need to be heated during washing, so that the energy consumption and the water consumption of the system are reduced, and the treatment cost is lower; in the washing step (4), the dechromized filter residue obtained after the solid-liquid separation is detected according to the environmental protection comprehensive utilization standard (HJ/T301-2007), if the detection result of the environmental protection comprehensive utilization standard (HJ/T301-2007) is unqualified, washing water is introduced into the washing centrifuge 10 through a washing water pipeline 11, the dechromized filter residue is washed by the washing water until the detection result of the environmental protection comprehensive utilization standard of the dechromized filter residue is qualified, and then the dechromized filter residue is conveyed to a dechromized filter residue storage tank 12 for storage; the aim of detecting the dechromization filter residue is to ensure that the content of hexavalent chromium ions in the dechromization filter residue does not exceed the national standard requirement, so that the dechromization filter residue meets the requirement of recycling, can be used for producing coatings, refractory materials and the like, and cannot cause secondary pollution; the washing water after washing returns to the oxidation digestion reaction tank 2 for preparing oxidation slurry, so that the water consumption of the oxidation reaction is reduced, and the water resource is saved.
(5) Reduction: (4) after washing is finished, conveying the filtrate obtained in the dissolution of the chromium ions in the step (3) and the washing filtrate obtained in the washing in the step (4) to a water receiving tank 7 for mixing to obtain a mixed solution, conveying the mixed solution to a reduction reaction tank 13, adding a reducing agent into the reduction reaction tank 13 through a reducing agent storage tank 14, uniformly mixing, carrying out reduction reaction at the temperature of 20 ℃, wherein the reduction reaction time is 1h, after the reduction reaction is finished, carrying out solid-liquid separation through a reduction centrifuge 15 to obtain chromium hydroxide precipitate and wastewater to be discharged, conveying the chromium hydroxide to a chromium hydroxide storage tank for storage, and conveying the wastewater to be discharged to a wastewater adjusting tank 17; the reduction aims to reduce hexavalent chromium ions in the filtrate obtained in the step (3) of dissolving out the chromium ions and the washing filtrate obtained in the step (4) of washing into chromium hydroxide through a reducing agent, and the chromium hydroxide can be recovered and sold, so that the operation of production enterprises is diversified, and the income of the production enterprises is increased. (5) In the reduction, the pH value of the wastewater to be discharged is adjusted to 6, the wastewater to be discharged after the pH value is adjusted is detected according to CJ3082-1999, and the wastewater is conveyed to a wastewater plant water inlet pipeline 18 after the detection is qualified. The wastewater to be discharged is directly conveyed to the wastewater plant through the incoming water pipeline 18 of the wastewater plant for treatment, and is not returned to the sodium chlorate production system, so that the wastewater treatment process can be omitted, and the wastewater treatment cost can be saved; on the other hand, perchlorate ions and metal ions are prevented from returning to a sodium chlorate production system along with the perchlorate ions and the metal ions, system equipment is prevented from being damaged, and safety accidents are reduced.
Example 2:
the process for treating waste salt mud from sodium chlorate production carried out in example 1 comprises the following steps: (1) grinding waste salt slurry, (2) oxidizing, (3) dissolving out chromium ions, (4) washing, and (5) reducing; wherein,
(1) grinding waste salt slurry: grinding the waste salt slurry to 50 meshes to obtain a grinding material; the purpose of grinding is to fully release chromium ions wrapped in the waste salt slurry so as to improve the efficiency of subsequent oxidation, dissolution and reduction.
(2) And (3) oxidation: (1) after the waste salt slurry is ground, grinding materials and water are mixed according to the mass ratio of 1: 0.5, adding an oxidant, carrying out oxidation reaction at the temperature of 20 ℃ and the pressure of 0.5MPa, wherein the oxidant is a high manganese acid agent, the mass ratio of the oxidant to the grinding material is 1:15, the oxidation reaction time is 2 hours, and obtaining an oxidation slurry after the oxidation reaction is finished; the oxidation effect is to oxidize the trivalent chromium ions into hexavalent chromium ions through an oxidant, and the oxidation reaction is carried out under the pressurization condition, so that the oxidation reaction can be promoted, the oxidation reaction is carried out more thoroughly, and the oxidation reaction efficiency is higher.
(3) Dissolution of chromium ions: (2) after the oxidation is finished, adding a hexavalent chromium ion dissolving agent into the oxidized slurry, wherein the hexavalent chromium ion dissolving agent is sodium bicarbonate, and the mass ratio of the hexavalent chromium ion dissolving agent to the grinding material is 1:1, uniformly stirring at the temperature of 50 ℃ and the pressure of 0.5MPa to dissolve out hexavalent chromium ions, wherein the stirring time is 0.5h, and after the stirring is finished, performing solid-liquid separation to obtain filter residue and filtrate; the purpose of the dissolution is to dissolve hexavalent chromium ions in the oxidized slurry, improve the dissolution under a pressurized condition, improve the dissolution rate of the hexavalent chromium ions, and further improve the recovery rate of the chromium ions and the dechromization rate of the waste salt mud.
(4) Washing: (3) after the chromium ions are dissolved out, mixing the filter residue with washing water according to a mass ratio of 1:1, uniformly mixing, washing at the temperature of 20 ℃ for 2 times, and after washing, performing solid-liquid separation to obtain a washing filtrate and dechromization filter residues; the washing aims at fully removing hexavalent chromium ions from the filter residue after the dissolution treatment so as to carry out the next reduction treatment; the washing water used for washing is derived from hot water generated by the electrolytic heat exchanger 9 of the sodium chlorate production system, and the washing water does not need to be heated during washing, so that the energy consumption of the system is reduced; in the washing step (4), the dechromization filter residue obtained after the solid-liquid separation is subjected to detection of an environment-friendly comprehensive utilization standard (HJ/T301-2007), if the detection result of the environment-friendly comprehensive utilization standard (HJ/T301-2007) is unqualified, the dechromization filter residue is washed by using washing water until the detection result of the environment-friendly comprehensive utilization standard of the dechromization filter residue is qualified, so that the aim of ensuring that the content of hexavalent chromium ions in the dechromization filter residue does not exceed the national standard requirement is achieved, the dechromization filter residue meets the recycling requirement, and the dechromization filter residue can be used for producing coatings, refractory materials and the like without causing secondary pollution; and (3) returning the flushing water after flushing to the oxidation step (2) for preparing the oxidation slurry, so that the water consumption of the oxidation reaction is reduced, and the water resource is saved.
(5) Reduction: (4) after washing is finished, mixing the filtrate obtained in the step (3) of dissolving out the chromium ions and the washing filtrate obtained in the step (4) of washing to obtain a mixed solution, adding a reducing agent, and mixing the reducing agent and the grinding material according to the mass ratio of 1:15, uniformly mixing a reducing agent which is ferrous sulfate, carrying out reduction reaction at the temperature of 20 ℃ for 1h, and carrying out solid-liquid separation after the reduction reaction is finished to obtain chromium hydroxide precipitate and wastewater to be discharged; the reduction aims to reduce hexavalent chromium ions in the filtrate obtained in the step (3) of dissolving out the chromium ions and the washing filtrate obtained in the step (4) of washing into chromium hydroxide through a reducing agent, and the chromium hydroxide can be recovered and sold, so that the operation of production enterprises is diversified, and the income of the production enterprises is increased. (5) During reduction, the pH value of the wastewater to be discharged is adjusted to 7, the wastewater to be discharged after the pH value is adjusted is detected according to CJ3082-1999, and the wastewater is conveyed to a wastewater plant incoming water pipeline 18 after the detection is qualified. The wastewater to be discharged is directly conveyed to the wastewater plant through the incoming water pipeline 18 of the wastewater plant for treatment, and is not returned to the sodium chlorate production system, so that the wastewater treatment process can be omitted, and the wastewater treatment cost can be saved; on the other hand, perchlorate ions and metal ions are prevented from returning to a sodium chlorate production system along with the perchlorate ions and the metal ions, system equipment is prevented from being damaged, and safety accidents are reduced.
The total chromium content in the waste salt slurry used in the embodiment is 9400mg/kg, the chromium content of the dechromized filter residue after treatment is subjected to leaching toxicity test according to the national standard (HJ/T299-2007), and Cr in the leaching solution6+The content is 0mg/L, the total chromium content of the leachate is 2.4mg/L, the comprehensive utilization standard of environmental protection (HJ/T301-2007) is achieved, the reduction detoxification rate is 99.97%, the chromium content of the treated waste salt mud is lower than the national standard, and the waste salt mud conforms to the national environmental protection discharge standard.
Example 3:
the process for treating waste salt mud from sodium chlorate production carried out in example 1 comprises the following steps: (1) grinding waste salt slurry, (2) oxidizing, (3) dissolving out chromium ions, (4) washing, and (5) reducing; wherein,
(1) grinding waste salt slurry: grinding the waste salt slurry to 100 meshes to obtain a grinding material; the purpose of grinding is to fully release chromium ions wrapped in the waste salt slurry so as to improve the efficiency of subsequent oxidation, dissolution and reduction.
(2) And (3) oxidation: (1) after the waste salt slurry is ground, grinding materials and water are mixed according to the mass ratio of 1:1, adding an oxidant, and carrying out an oxidation reaction at the temperature of 30 ℃ and the pressure of 0.4MPa, wherein the mass ratio of the oxidant to the abrasive is 1:25, the oxidation reaction time is 0.5h, and after the oxidation reaction is finished, the oxidant is sodium peroxide, so as to obtain an oxidation slurry; the oxidation effect is to oxidize the trivalent chromium ions into hexavalent chromium ions through an oxidant, and the oxidation reaction is carried out under the pressurization condition, so that the oxidation reaction can be promoted, the oxidation reaction is carried out more thoroughly, and the oxidation reaction efficiency is higher.
(3) Dissolution of chromium ions: (2) after the oxidation is finished, adding a hexavalent chromium ion dissolving agent into the oxidized slurry, wherein the hexavalent chromium ion dissolving agent is ammonium bicarbonate, and the mass ratio of the hexavalent chromium ion dissolving agent to the abrasive is 1: 1.5, uniformly stirring at the temperature of 90 ℃ and the pressure of 0.4MPa to dissolve out hexavalent chromium ions, wherein the stirring time is 0.5h, and after the stirring is finished, performing solid-liquid separation to obtain filter residue and filtrate; the purpose of the dissolution is to dissolve hexavalent chromium ions in the oxidized slurry, improve the dissolution under a pressurized condition, improve the dissolution rate of the hexavalent chromium ions, and further improve the recovery rate of the chromium ions and the dechromization rate of the waste salt mud.
(4) Washing: (3) after the chromium ions are dissolved out, mixing the filter residue with washing water according to a mass ratio of 1: 5, uniformly mixing, washing at 55 ℃ for 2 times, and after washing, performing solid-liquid separation to obtain washing filtrate and dechromization filter residue; the washing aims at fully removing hexavalent chromium ions from the filter residue after the dissolution treatment so as to carry out the next reduction treatment; the washing water used for washing is derived from hot water generated by the electrolytic heat exchanger 9 of the sodium chlorate production system, and the washing water does not need to be heated during washing, so that the energy consumption of the system is reduced; in the washing step (4), the dechromized filter residue obtained after the solid-liquid separation is subjected to detection of an environment-friendly comprehensive utilization standard, if the detection result of the environment-friendly comprehensive utilization standard (HJ/T301-2007) is unqualified, the dechromized filter residue is washed by using washing water until the detection result of the dechromized filter residue subjected to the environment-friendly comprehensive utilization standard (HJ/T301-2007) is qualified, so that the aim of ensuring that the content of hexavalent chromium ions in the dechromized filter residue does not exceed the national standard requirement is fulfilled, the dechromized filter residue meets the recycling requirement, and the dechromized filter residue can be used for producing coatings, refractory materials and the like without causing secondary pollution; and (3) returning the flushing water after flushing to the oxidation step (2) for preparing the oxidation slurry, so that the water consumption of the oxidation reaction is reduced, and the water resource is saved.
(5) Reduction: (4) after washing is finished, mixing the filtrate obtained in the step (3) of dissolving out the chromium ions and the washing filtrate obtained in the step (4) of washing to obtain a mixed solution, adding a reducing agent, and mixing the reducing agent and the grinding material according to the mass ratio of 1:20, the reducing agent is sodium sulfide, after uniform mixing, reduction reaction is carried out at the temperature of 60 ℃, the reduction reaction time is 0.5h, and after the reduction reaction is finished, solid-liquid separation is carried out to obtain chromium hydroxide precipitate and wastewater to be discharged. The reduction aims to reduce hexavalent chromium ions in the filtrate obtained in the step (3) of dissolving out the chromium ions and the washing filtrate obtained in the step (4) of washing into chromium hydroxide through a reducing agent, and the chromium hydroxide can be recovered and sold, so that the operation of production enterprises is diversified, and the income of the production enterprises is increased. (5) In the reduction, the pH value of the wastewater to be discharged is adjusted to 8, the wastewater to be discharged after the pH value is adjusted is detected according to CJ3082-1999, and the wastewater is conveyed to a water inlet pipeline 18 of a wastewater plant after the detection is qualified. The wastewater to be discharged is directly conveyed to the wastewater plant through the incoming water pipeline 18 of the wastewater plant for treatment, and is not returned to the sodium chlorate production system, so that the wastewater treatment process can be omitted, and the wastewater treatment cost can be saved; on the other hand, perchlorate ions and metal ions are prevented from returning to a sodium chlorate production system along with the perchlorate ions and the metal ions, system equipment is prevented from being damaged, and safety accidents are reduced.
The total chromium content in the waste salt slurry used in the embodiment is 9400mg/kg, the chromium content of the dechromized filter residue after treatment is subjected to leaching toxicity test according to the national standard (HJ/T299-2007), and Cr in the leaching solution6+The content is 0mg/L, the total chromium content of the leachate is 1.9mg/L, the comprehensive utilization standard of environmental protection (HJ/T301-2007) is achieved, the reduction detoxification rate is 99.98%, the chromium content of the treated waste salt mud is lower than the national standard, and the waste salt mud conforms to the national environmental protection discharge standard.
Example 4:
the process for treating waste salt mud from sodium chlorate production carried out in example 1 comprises the following steps: (1) grinding waste salt slurry, (2) oxidizing, (3) dissolving out chromium ions, (4) washing, and (5) reducing; wherein,
(1) grinding waste salt slurry: grinding the waste salt slurry to 150 meshes to obtain a grinding material; the purpose of grinding is to fully release chromium ions wrapped in the waste salt slurry so as to improve the efficiency of subsequent oxidation, dissolution and reduction.
(2) And (3) oxidation: (1) after the waste salt slurry is ground, grinding materials and water are mixed according to the mass ratio of 1: 1.5, adding an oxidant, carrying out oxidation reaction at the temperature of 25 ℃ and the pressure of 0.35MPa, wherein the oxidant is sodium perchlorate, the mass ratio of the oxidant to the grinding material is 1:30, the oxidation reaction time is 1h, and obtaining an oxidation slurry after the oxidation reaction is finished; the oxidation effect is to oxidize the trivalent chromium ions into hexavalent chromium ions through an oxidant, and the oxidation reaction is carried out under the pressurization condition, so that the oxidation reaction can be promoted, the oxidation reaction is carried out more thoroughly, and the oxidation reaction efficiency is higher.
(3) Dissolution of chromium ions: (2) after the oxidation is finished, adding a hexavalent chromium ion dissolving agent into the oxidation slurry, wherein the hexavalent chromium ion dissolving agent is a combination of sodium bicarbonate and ammonium bicarbonate, the adding mass ratio of the sodium bicarbonate to the ammonium bicarbonate is 1:1, and the mass ratio of the hexavalent chromium ion dissolving agent to the grinding material is 1: 1.8, uniformly stirring at the temperature of 120 ℃ and the pressure of 0.35MPa to dissolve out hexavalent chromium ions, wherein the stirring time is 1h, and after the stirring is finished, performing solid-liquid separation to obtain filter residue and filtrate. The purpose of the dissolution is to dissolve hexavalent chromium ions in the oxidized slurry, improve the dissolution under a pressurized condition, improve the dissolution rate of the hexavalent chromium ions, and further improve the recovery rate of the chromium ions and the dechromization rate of the waste salt mud.
(4) Washing: (3) after the chromium ions are dissolved out, mixing the filter residue with washing water according to a mass ratio of 1:3, uniformly mixing, washing at 40 ℃ for 2 times, and after washing, performing solid-liquid separation to obtain washing filtrate and dechromization filter residue; the washing aims at fully removing hexavalent chromium ions from the filter residue after the dissolution treatment so as to carry out the next reduction treatment; the washing water used for washing is derived from hot water generated by the electrolytic heat exchanger 9 of the sodium chlorate production system, and the washing water does not need to be heated during washing, so that the energy consumption of the system is reduced; in the washing step (4), the dechromized filter residue obtained after the solid-liquid separation is subjected to detection of an environment-friendly comprehensive utilization standard, if the detection result of the environment-friendly comprehensive utilization standard (HJ/T301-2007) is unqualified, the dechromized filter residue is washed by using washing water until the detection result of the dechromized filter residue subjected to the environment-friendly comprehensive utilization standard (HJ/T301-2007) is qualified, so that the aim of ensuring that the content of hexavalent chromium ions in the dechromized filter residue does not exceed the national standard requirement is fulfilled, the dechromized filter residue meets the recycling requirement, and the dechromized filter residue can be used for producing coatings, refractory materials and the like without causing secondary pollution; and (3) returning the flushing water after flushing to the oxidation step (2) for preparing the oxidation slurry, so that the water consumption of the oxidation reaction is reduced, and the water resource is saved.
(5) Reduction: (4) after washing is finished, mixing the filtrate obtained in the step (3) of dissolving out the chromium ions and the washing filtrate obtained in the step (4) of washing to obtain a mixed solution, adding a reducing agent, and mixing the reducing agent and the grinding material according to the mass ratio of 1: 23, uniformly mixing a reducing agent which is sodium metabisulfite, carrying out reduction reaction at the temperature of 50 ℃ for 0.3h, and carrying out solid-liquid separation after the reduction reaction is finished to obtain chromium hydroxide precipitate and wastewater to be discharged; the reduction aims to reduce hexavalent chromium ions in the filtrate obtained in the step (3) of dissolving out the chromium ions and the washing filtrate obtained in the step (4) of washing into chromium hydroxide through a reducing agent, and the chromium hydroxide can be recovered and sold, so that the operation of production enterprises is diversified, and the income of the production enterprises is increased. (5) In the reduction, the pH value of the wastewater to be discharged is adjusted to 8.5, the wastewater to be discharged after the pH value is adjusted is detected according to CJ3082-1999, and the wastewater is conveyed to an incoming water pipeline 18 of a wastewater plant after the detection is qualified. The wastewater to be discharged is directly conveyed to the wastewater plant through the incoming water pipeline 18 of the wastewater plant for treatment, and is not returned to the sodium chlorate production system, so that the wastewater treatment process can be omitted, and the wastewater treatment cost can be saved; on the other hand, perchlorate ions and metal ions are prevented from returning to a sodium chlorate production system along with the perchlorate ions and the metal ions, system equipment is prevented from being damaged, and safety accidents are reduced.
The total chromium content in the waste salt slurry used in the embodiment is 9400mg/kg, the chromium content of the dechromized filter residue after treatment is subjected to leaching toxicity test according to the national standard (HJ/T299-2007), and Cr in the leaching solution6+The content is 0mg/L, the total chromium content of the leachate is 2.3mg/L, the comprehensive utilization standard of environmental protection (HJ/T301-2007) is achieved, the reduction detoxification rate is 99.98%, the chromium content of the treated waste salt mud is lower than the national standard, and the waste salt mud conforms to the national environmental protection discharge standard.
Example 5:
the process for treating waste salt mud from sodium chlorate production carried out in example 1 comprises the following steps: (1) grinding waste salt slurry, (2) oxidizing, (3) dissolving out chromium ions, (4) washing, and (5) reducing; wherein,
(1) grinding waste salt slurry: grinding the waste salt slurry to 200 meshes to obtain a grinding material; the purpose of grinding is to fully release chromium ions wrapped in the waste salt slurry so as to improve the efficiency of subsequent oxidation, dissolution and reduction.
(2) And (3) oxidation: (1) after the waste salt slurry is ground, grinding materials and water are mixed according to the mass ratio of 1:2, adding an oxidant, and carrying out an oxidation reaction at the temperature of 30 ℃ and the pressure of 0.3MPa, wherein the oxidant is sodium perchlorate, the mass ratio of the oxidant to the grinding material is 1:20, the oxidation reaction time is 1.5h, and after the oxidation reaction is finished, obtaining an oxidation slurry; the oxidation effect is to oxidize the trivalent chromium ions into hexavalent chromium ions through an oxidant, and the oxidation reaction is carried out under the pressurization condition, so that the oxidation reaction can be promoted, the oxidation reaction is carried out more thoroughly, and the oxidation reaction efficiency is higher.
(3) Dissolution of chromium ions: (2) after the oxidation is finished, adding a hexavalent chromium ion dissolving agent into the oxidation slurry, wherein the hexavalent chromium ion dissolving agent is a combination of sodium bicarbonate and ammonium bicarbonate, the adding mass ratio of the sodium bicarbonate to the ammonium bicarbonate is 1:1, and the mass ratio of the hexavalent chromium ion dissolving agent to the grinding material is 1:2, uniformly stirring at the temperature of 150 ℃ and the pressure of 0.3MPa to dissolve out hexavalent chromium ions, wherein the stirring time is 1.5h, and after the stirring is finished, performing solid-liquid separation to obtain filter residue and filtrate; the purpose of the dissolution is to dissolve hexavalent chromium ions in the oxidized slurry, improve the dissolution under a pressurized condition, improve the dissolution rate of the hexavalent chromium ions, and further improve the recovery rate of the chromium ions and the dechromization rate of the waste salt mud.
(4) Washing: (3) after the chromium ions are dissolved out, mixing the filter residue with washing water according to a mass ratio of 1: 5, uniformly mixing, washing at the temperature of 60 ℃ for 1 time, and after washing, performing solid-liquid separation to obtain a washing filtrate and dechromization filter residues; the washing aims at fully removing hexavalent chromium ions from the filter residue after the dissolution treatment so as to carry out the next reduction treatment; the washing water used for washing is derived from hot water generated by the electrolytic heat exchanger 9 of the sodium chlorate production system, and the washing water does not need to be heated during washing, so that the energy consumption of the system is reduced; in the washing step (4), the dechromized filter residue obtained after the solid-liquid separation is subjected to detection of an environment-friendly comprehensive utilization standard, if the detection result of the environment-friendly comprehensive utilization standard (HJ/T301-2007) is unqualified, the dechromized filter residue is washed by using washing water until the detection result of the dechromized filter residue subjected to the environment-friendly comprehensive utilization standard (HJ/T301-2007) is qualified, so that the aim of ensuring that the content of hexavalent chromium ions in the dechromized filter residue does not exceed the national standard requirement is fulfilled, the dechromized filter residue meets the recycling requirement, and the dechromized filter residue can be used for producing coatings, refractory materials and the like without causing secondary pollution; and (3) returning the flushing water after flushing to the oxidation step (2) for preparing the oxidation slurry, so that the water consumption of the oxidation reaction is reduced, and the water resource is saved.
(5) Reduction: (4) after washing is finished, mixing the filtrate obtained in the step (3) of dissolving out the chromium ions and the washing filtrate obtained in the step (4) of washing to obtain a mixed solution, adding a reducing agent, and mixing the reducing agent and the grinding material according to the mass ratio of 1:25, the reducing agent is a combination of ferrous sulfate, sodium sulfide and sodium metabisulfite, the adding mass ratio of the ferrous sulfate, the sodium sulfide and the sodium metabisulfite is 1:1:1, the mixture is uniformly mixed and then subjected to reduction reaction at the temperature of 80 ℃, the reduction reaction time is 0.1h, and after the reduction reaction is finished, solid-liquid separation is carried out to obtain chromium hydroxide precipitate and wastewater to be discharged; the reduction aims to reduce hexavalent chromium ions in the filtrate obtained in the step (3) of dissolving out the chromium ions and the washing filtrate obtained in the step (4) of washing into chromium hydroxide through a reducing agent, and the chromium hydroxide can be recovered and sold, so that the operation of production enterprises is diversified, and the income of the production enterprises is increased. (5) In the reduction, the pH value of the wastewater to be discharged is adjusted to 9, the wastewater to be discharged after the pH value is adjusted is detected according to CJ3082-1999, and the wastewater is conveyed to a wastewater plant water inlet pipeline 18 after the detection is qualified. The wastewater to be discharged is directly conveyed to the wastewater plant through the incoming water pipeline 18 of the wastewater plant for treatment, and is not returned to the sodium chlorate production system, so that the wastewater treatment process can be omitted, and the wastewater treatment cost can be saved; on the other hand, perchlorate ions and metal ions are prevented from returning to a sodium chlorate production system along with the perchlorate ions and the metal ions, system equipment is prevented from being damaged, and safety accidents are reduced.
The total chromium content in the waste salt slurry used in the embodiment is 9400mg/kg, the chromium content of the dechromized filter residue after treatment is subjected to leaching toxicity test according to the national standard (HJ/T299-2007), and Cr in the leaching solution6+The content is 0mg/L, the total chromium content of the leachate is 2.2mg/L, the comprehensive utilization standard of environmental protection (HJ/T301-2007) is achieved, the reduction detoxification rate is 99.98%, the chromium content of the treated waste salt mud is lower than the national standard, and the waste salt mud conforms to the national environmental protection discharge standard.
Example 6:
the process for treating waste salt mud from sodium chlorate production carried out in example 1 comprises the following steps: (1) grinding waste salt slurry, (2) oxidizing, (3) dissolving out chromium ions, (4) washing, and (5) reducing; wherein,
(1) grinding waste salt slurry: grinding the waste salt slurry to 150 meshes to obtain a grinding material; the purpose of grinding is to fully release chromium ions wrapped in the waste salt slurry so as to improve the efficiency of subsequent oxidation, dissolution and reduction.
(2) And (3) oxidation: (1) after the waste salt slurry is ground, grinding materials and water are mixed according to the mass ratio of 1:2, adding an oxidant, and carrying out an oxidation reaction at the temperature of 30 ℃ and the pressure of 0.3MPa, wherein the oxidant is sodium perchlorate, the mass ratio of the oxidant to the grinding material is 1:40, the oxidation reaction time is 1.5h, and after the oxidation reaction is finished, obtaining an oxidation slurry; the oxidation effect is to oxidize the trivalent chromium ions into hexavalent chromium ions through an oxidant, and the oxidation reaction is carried out under the pressurization condition, so that the oxidation reaction can be promoted, the oxidation reaction is carried out more thoroughly, and the oxidation reaction efficiency is higher.
(3) Dissolution of chromium ions: (2) after the oxidation is finished, adding a hexavalent chromium ion dissolving agent into the oxidation slurry, wherein the hexavalent chromium ion dissolving agent is a combination of sodium bicarbonate and ammonium bicarbonate, the adding mass ratio of the sodium bicarbonate to the ammonium bicarbonate is 1:1, and the mass ratio of the hexavalent chromium ion dissolving agent to the grinding material is 1:2, uniformly stirring at the temperature of 150 ℃ and the pressure of 0.3MPa to dissolve out hexavalent chromium ions, wherein the stirring time is 1.5h, and after the stirring is finished, performing solid-liquid separation to obtain filter residue and filtrate; the purpose of the dissolution is to dissolve hexavalent chromium ions in the oxidized slurry, improve the dissolution under a pressurized condition, improve the dissolution rate of the hexavalent chromium ions, and further improve the recovery rate of the chromium ions and the dechromization rate of the waste salt mud.
(4) Washing: (3) after the chromium ions are dissolved out, mixing the filter residue with washing water according to a mass ratio of 1:3, uniformly mixing, washing at the temperature of 30 ℃ for 1 time, and after washing, performing solid-liquid separation to obtain a washing filtrate and dechromization filter residues; the washing aims at fully removing hexavalent chromium ions from the filter residue after the dissolution treatment so as to carry out the next reduction treatment; the washing water used for washing is derived from hot water generated by the electrolytic heat exchanger 9 of the sodium chlorate production system, and the washing water does not need to be heated during washing, so that the energy consumption of the system is reduced; in the washing step (4), the dechromized filter residue obtained after the solid-liquid separation is subjected to detection of an environment-friendly comprehensive utilization standard, if the detection result of the environment-friendly comprehensive utilization standard (HJ/T301-2007) is unqualified, the dechromized filter residue is washed by using washing water until the detection result of the dechromized filter residue subjected to the environment-friendly comprehensive utilization standard (HJ/T301-2007) is qualified, so that the aim of ensuring that the content of hexavalent chromium ions in the dechromized filter residue does not exceed the national standard requirement is fulfilled, the dechromized filter residue meets the recycling requirement, and the dechromized filter residue can be used for producing coatings, refractory materials and the like without causing secondary pollution; and (3) returning the flushing water after flushing to the oxidation step (2) for preparing the oxidation slurry, so that the water consumption of the oxidation reaction is reduced, and the water resource is saved.
(5) Reduction: (4) after washing is finished, mixing the filtrate obtained in the step (3) of dissolving out the chromium ions and the washing filtrate obtained in the step (4) of washing to obtain a mixed solution, adding a reducing agent, and mixing the reducing agent and the grinding material according to the mass ratio of 1:15, the reducing agent is a combination of ferrous sulfate, sodium sulfide and sodium metabisulfite, the adding mass ratio of the ferrous sulfate, the sodium sulfide and the sodium metabisulfite is 1:1:1, the mixture is uniformly mixed and then subjected to reduction reaction at the temperature of 30 ℃, the reduction reaction time is 0.1h, and after the reduction reaction is finished, solid-liquid separation is carried out to obtain chromium hydroxide precipitate and wastewater to be discharged; the reduction aims to reduce hexavalent chromium ions in the filtrate obtained in the step (3) of dissolving out the chromium ions and the washing filtrate obtained in the step (4) of washing into chromium hydroxide through a reducing agent, and the chromium hydroxide can be recovered and sold, so that the operation of production enterprises is diversified, and the income of the production enterprises is increased. (5) In the reduction, the pH value of the wastewater to be discharged is adjusted to 9, the wastewater to be discharged after the pH value is adjusted is detected according to CJ3082-1999, and the wastewater is conveyed to a wastewater plant water inlet pipeline 18 after the detection is qualified. The wastewater to be discharged is directly conveyed to the wastewater plant through the incoming water pipeline 18 of the wastewater plant for treatment, and is not returned to the sodium chlorate production system, so that the wastewater treatment process can be omitted, and the wastewater treatment cost can be saved; on the other hand, perchlorate ions and metal ions are prevented from returning to a sodium chlorate production system along with the perchlorate ions and the metal ions, system equipment is prevented from being damaged, and safety accidents are reduced.
The total chromium content in the waste salt slurry used in the embodiment is 9400mg/kg, the chromium content of the dechromized filter residue after treatment is subjected to leaching toxicity test according to the national standard (HJ/T299-2007), and Cr in the leaching solution6+The content is 0mg/L, the total chromium content of the leachate is 2.3mg/L, the comprehensive utilization standard of environmental protection (HJ/T301-2007) is achieved, the reduction detoxification rate is 99.98%, the chromium content of the treated waste salt mud is lower than the national standard, and the waste salt mud conforms to the national environmental protection discharge standard.
Example 7:
taking the example 3 as a test group, the operation contents of the control group are the same as those of the example 3 except that the grinding (1) is not carried out, and the leaching toxicity test is carried out on the dechromized filter residues obtained by the test group and the control group according to the national standard (HJ/T299-2007), wherein the reduction detoxification rate is the ratio of the total chromium content in the leaching solution of the dechromized filter residue obtained after the treatment to the total chromium content in the waste salt mud before the treatment, and the results are shown in the table 1.
TABLE 1 results of leaching toxicity test of dechromized filter residues obtained from test group and control group according to national standard (HJ/T299-2007)
As can be seen from Table 1, the waste salty mud after grinding treatment is subjected to oxidation, dissolution, washing, reduction and other treatments, the chromium-removed filter residue is subjected to leaching toxicity test, and Cr in the leaching solution is6+The content is 0mg/L, the total chromium content of the leachate is 1.9mg/L, the comprehensive utilization standard of environmental protection (HJ/T301-2007) is achieved, the reduction detoxification rate is 99.98%, the chromium content of the treated waste salt mud is far lower than the national standard, and the waste salt mud conforms to the national environmental protection discharge standard; the chromium ions wrapped in the waste salt mud can be released by grinding and crushing, and then are removed from the waste salt mud by carrying out treatments such as solution oxidation, dissolution, washing, reduction and the like on the waste salt mud, so that the problems of high treatment difficulty and incomplete removal of the chromium ions in the waste salt mud are solved.
Taking example 3 as a test group, the operation contents of the control group are the same as example 3 except that (2) oxidation and (3) chromium ion dissolution are not pressurized, and the leaching toxicity test is carried out on the dechromized filter residue obtained by the test group and the control group according to the national standard (HJ/T299-2007), wherein the reduction detoxification rate is the ratio of the total chromium content in the leaching solution of the dechromized filter residue obtained after treatment to the total chromium content in the waste salt mud before treatment, and the results are shown in Table 2.
TABLE 2 results of leaching toxicity test of dechromized filter residues obtained from test group and control group according to national standard (HJ/T299-2007)
As can be seen from Table 2, after the (2) oxidation and (3) chromium ion elution and pressurization treatment, the dechromized residue was subjected to the leaching toxicity test, and Cr in the leaching solution was measured6+The content is 0mg/L, the total chromium content is 1.9mg/L, the environment-friendly comprehensive utilization standard (HJ/T301-2007) is achieved, the reduction detoxification rate is 99.98%, the chromium content of the treated waste salt mud is far lower than the national standard, and the national environment-friendly discharge standard is met; namely, the efficiency of oxidation and dissolution is improved by carrying out pressurization treatment in the steps of oxidation and dissolution, so that chromium ions are removed from the waste salt mud, and the problems of high treatment difficulty and incomplete removal of the chromium ions in the waste salt mud are solved.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (5)
1. The treatment process of the waste salt mud in the production of sodium chlorate is characterized by comprising the following steps: (1) grinding waste salt slurry, (2) oxidizing, (3) dissolving out chromium ions, (4) washing, and (5) reducing; wherein,
(1) grinding waste salt slurry: grinding the waste salt slurry to 100-150 meshes to obtain a grinding material;
(2) and (3) oxidation: and (1) after the waste salt slurry is ground, mixing the ground material with water according to a mass ratio of 1: 0.5-2, adding an oxidant, carrying out oxidation reaction at the temperature of 20-30 ℃ and the pressure of 0.3-0.5MPa, wherein the mass ratio of the oxidant to the grinding material is 1:15-40, the oxidation reaction time is 0.5-2h, and obtaining an oxidation slurry after the oxidation reaction is finished;
(3) dissolution of chromium ions: after the oxidation of the step (2) is finished, adding a hexavalent chromium ion dissolving agent into the oxidized slurry, wherein the hexavalent chromium ion dissolving agent is any one or combination of sodium bicarbonate and ammonium bicarbonate; the mass ratio of the hexavalent chromium ion dissolving agent to the grinding material is 1: 1.5-2, uniformly stirring at 90-120 ℃ and 0.3-0.5MPa to dissolve hexavalent chromium ions, wherein the stirring time is 0.5-1h, and after the stirring is finished, performing solid-liquid separation to obtain filter residue and filtrate; (4) washing: and (3) after the chromium ions are dissolved out, mixing the filter residue with washing water according to a mass ratio of 1: 1-5, uniformly mixing, washing at the temperature of 20-60 ℃ for 1-2 times, and after washing, performing solid-liquid separation to obtain a washing filtrate and dechromization filter residues;
(5) reduction: and (4) after the washing is finished, mixing the filtrate obtained in the dissolution of the chromium ions in the step (3) with the washing filtrate obtained in the washing in the step (4) to obtain a mixed solution, adding a reducing agent, and mixing the mixed solution with the grinding material and the reducing agent according to a mass ratio of 1: 15-25, carrying out reduction reaction at the temperature of 20-80 ℃ for 0.1-1h after uniformly mixing, and carrying out solid-liquid separation after the reduction reaction is finished to obtain chromium hydroxide precipitate and wastewater to be discharged.
2. The process for treating waste salt mud in sodium chlorate production as claimed in claim 1, wherein in the step (5), the pH value of the wastewater to be discharged is adjusted to 6-9, the wastewater to be discharged after the pH value is adjusted is detected according to CJ3082-1999, and the wastewater is conveyed to an incoming water pipeline of a wastewater plant after the detection is qualified.
3. The process for treating waste salt mud in sodium chlorate production according to claim 1, wherein in the step (2) of oxidizing, the mass ratio of the grinding material to the water is 1: 1.5-2, the oxidant is any one or combination of more of a high manganese acid agent, sodium peroxide or sodium perchlorate, the mass ratio of the oxidant to the grinding material is 1:20-30, and the oxidation reaction time is 0.5-1 h.
4. The process for treating waste salt mud in sodium chlorate production according to claim 1, wherein in the step (4), the mass ratio of the filter residue to the washing water is 1: 1-3, the temperature is 30-40 ℃, and the washing times are 2 times; the washing water used for washing is derived from hot water generated by an electrolytic heat exchanger of the sodium chlorate production system.
5. The process for treating waste salt mud in sodium chlorate production according to claim 1, wherein in the reduction (5), the reducing agent is any one or a combination of ferrous sulfate, sodium sulfide and sodium metabisulfite, and the mass ratio of the grinding material to the reducing agent is 1:20 to 25 ℃, the temperature is 30 to 50 ℃, and the reduction reaction time is 0.1 to 0.5 h.
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Effective date of registration: 20221205 Address after: 750336 south of Ulanbuhe street, Alxa Economic Development Zone, Alxa League, Inner Mongolia Autonomous Region (WuSitai town) Patentee after: INNER MONGOLIA LANTAI SODIUM INDUSTRY Co.,Ltd. Patentee after: China Salt Inner Mongolia Chemical Co.,Ltd. Address before: 750336 Helan District, Alashan Economic Development Zone, Alashan League, Inner Mongolia Autonomous Region Patentee before: China Salt Inner Mongolia Chemical Co.,Ltd. |
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Address after: 750336 south of Ulanbuhe street, Alxa Economic Development Zone, Alxa League, Inner Mongolia Autonomous Region (WuSitai town) Patentee after: China Salt Inner Mongolia Chemical sodium Industry Co.,Ltd. Patentee after: China Salt Inner Mongolia Chemical Co.,Ltd. Address before: 750336 south of Ulanbuhe street, Alxa Economic Development Zone, Alxa League, Inner Mongolia Autonomous Region (WuSitai town) Patentee before: INNER MONGOLIA LANTAI SODIUM INDUSTRY Co.,Ltd. Patentee before: China Salt Inner Mongolia Chemical Co.,Ltd. |
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