A method for purifying and recycling flue gas desulfurization solid waste

Abstract

The present invention provides a method for purifying and recycling flue gas desulfurization solid waste, and belongs to the technical field of energy conservation and environmental protection. The present invention mixes flue gas desulfurization solid waste with water to obtain desulfurized solid waste slurry; in a closed environment, carbon dioxide is introduced into the desulfurized solid waste slurry, and impurity metals in the desulfurized solid waste slurry undergo precipitation reaction to obtain carbonate precipitation and supernatant; the supernatant is subjected to carbon dioxide desorption to obtain desorption clear liquid and carbon dioxide; the desorption clear liquid is placed in a membrane separation electrolytic cell for electrolysis to obtain NaOH and H 2 SO 4 Compared with the prior art, the process of the present invention is simple, green and economical, and can achieve Na removal from desulfurized solid waste while purifying desulfurized solid waste. + and SO 4 2‑ It is a resource-based resource with good environmental benefits.

Description

Technical Field

[0001] The invention relates to the technical field of energy conservation and environmental protection, and in particular to a method for purifying and recycling solid waste from flue gas desulfurization. Background Art

[0002] In recent years, my country's nonferrous industry has developed rapidly. With the rapid development of the nonferrous industry, the environmental protection situation has become increasingly severe. In the process of nonferrous metallurgy, a considerable concentration of SO2 will be produced. If it is not recycled or purified, it will cause serious pollution. At present, for high-concentration SO2 flue gas, the technical route of first acid production and then flue gas desulfurization is generally adopted; while for smelting flue gas with relatively low SO2 concentration, flue gas desulfurization is generally carried out directly. For SO2 flue gas with large emissions, wet desulfurization is the most widely used. However, wet flue gas desulfurization will produce additional wastewater, leading to new environmental pollution. Therefore, the use of dry desulfurization has received more and more attention. The commonly used dry desulfurization is to absorb SO2 with alkaline substances, but the treatment of Na2SO4 / Na2SO3 solid waste generated after SO2 absorption is an urgent problem to be solved.

[0003] Chinese patent CN201810960974.2 discloses "a new technology for the treatment and recovery of flue gas desulfurization solid waste". This process recovers sodium carbonate, sodium sulfate and sodium chloride from desulfurization solid waste by two-stage evaporation. This process solves the problem of utilization of desulfurization solid waste, but is limited by the types of desulfurization solid waste and cannot be used as a resource for complex desulfurization solid waste. At present, the treatment of complex desulfurization solid waste is still limited to extracting and concentrating crystallized Na2SO4, and Na2SO4 is not effectively used to produce high value-added products. Summary of the invention

[0004] The purpose of the present invention is to provide a method for purifying and recycling flue gas desulfurization solid waste, which can purify the desulfurization solid waste and realize the recovery of Na + and SO4 2- of resources.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for purifying and recycling flue gas desulfurization solid waste, comprising the following steps:

[0007] Mixing flue gas desulfurization solid waste with water to obtain desulfurization solid waste slurry; the content of sodium sulfate in the flue gas desulfurization solid waste is greater than 50wt%;

[0008] In a closed environment, carbon dioxide is introduced into the desulfurized solid waste slurry, and the impurity metals in the desulfurized solid waste slurry undergo precipitation reaction to obtain carbonate precipitate and supernatant liquid;

[0009] Desorbing carbon dioxide from the supernatant to obtain a desorbed supernatant and carbon dioxide;

[0010] The desorbed clear liquid is subjected to membrane separation electrolysis to obtain NaOH and H2SO4.

[0011] Preferably, the method further comprises calcining the carbonate precipitate to obtain a metal oxide.

[0012] Preferably, the calcination temperature is 600-900° C., the holding time is 1-3 hours, and the calcination atmosphere is oxygen-enriched air with an oxygen content of ≥40 vol%.

[0013] Preferably, the mass ratio of the flue gas desulfurization solid waste to water is 1:4-10.

[0014] Preferably, the positive pressure of the carbon dioxide introduced into the closed environment is 0.1-1.0 MPa.

[0015] Preferably, the carbon dioxide desorption is carried out in a reduced pressure autoclave, and the vacuum degree in the reduced pressure autoclave is 20 to 50 kPa.

[0016] Preferably, the temperature in the reduced pressure autoclave is maintained at 40-80°C.

[0017] Preferably, the carbon dioxide desorption time is 0.5 to 1 hour.

[0018] Preferably, the carbon dioxide generated by the carbon dioxide desorption is used for precipitation reaction.

[0019] Preferably, the voltage of the membrane separation electrolysis is 50 to 80 V, and the current is 50 to 65 mA.

[0020] The present invention provides a method for purifying and recycling flue gas desulfurization solid waste, comprising the following steps: mixing flue gas desulfurization solid waste with water to obtain desulfurized solid waste slurry; the content of sodium sulfate in the flue gas desulfurization solid waste is greater than 50wt%; in a closed environment, introducing carbon dioxide into the desulfurized solid waste slurry, causing the impurity metals in the desulfurized solid waste slurry to undergo precipitation reaction to obtain carbonate precipitates and supernatant liquid; desorbing carbon dioxide from the supernatant liquid to obtain desorbed clear liquid and carbon dioxide; placing the desorbed clear liquid in a membrane separation electrolysis cell for electrolysis to obtain NaOH and H2SO4. The present invention achieves the precipitation of impurity metals by CO2 pressurization, and simultaneously desorbs CO2 by vacuum, and achieves NaOH by membrane separation electrolysis. + and SO4 2-Compared with the prior art, the process of the present invention is simple, green and economical, and can purify the desulfurized solid waste while realizing the recovery of Na in the desulfurized solid waste. + and SO4 2- It is a resource-based resource with good environmental benefits.

[0021] The present invention can comprehensively utilize all components in complex component desulfurization solid waste and can realize full automation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a schematic diagram of the purification and resource utilization process of flue gas desulfurization solid waste according to the present invention. DETAILED DESCRIPTION

[0023] The present invention provides a method for purifying and recycling flue gas desulfurization solid waste, comprising the following steps:

[0024] Mixing flue gas desulfurization solid waste with water to obtain desulfurization solid waste slurry; the content of sodium sulfate in the flue gas desulfurization solid waste is greater than 50wt%;

[0025] In a closed environment, carbon dioxide is introduced into the desulfurized solid waste slurry, and the impurity metals in the desulfurized solid waste slurry undergo precipitation reaction to obtain carbonate precipitate and supernatant liquid;

[0026] Desorbing carbon dioxide from the supernatant to obtain a desorbed supernatant and carbon dioxide;

[0027] The desorbed clear liquid is subjected to membrane separation electrolysis to obtain NaOH and H2SO4.

[0028] The present invention mixes flue gas desulfurization solid waste with water to obtain desulfurization solid waste slurry.

[0029] In the present invention, the main component of the flue gas desulfurization solid waste is sodium sulfate; the content of sodium sulfate in the flue gas desulfurization solid waste is preferably >50wt%, more preferably >70wt%, and further preferably >90wt%. In the present invention, the flue gas desulfurization solid waste inevitably contains impurity metals, such as metal dust impurities such as Fe, Cu, and Hg.

[0030] In the present invention, the mass ratio of the flue gas desulfurization solid waste to water is preferably 1:4 to 10, more preferably 1:5 to 9, and further preferably 1:6 to 8. In the present invention, the mixing is preferably carried out in a closed stirring tank at room temperature, and the stirring time is preferably 1 to 2 hours.

[0031] After obtaining the desulfurized solid waste slurry, the present invention introduces carbon dioxide into the desulfurized solid waste slurry in a closed environment, and the impurity metals in the desulfurized solid waste slurry undergo precipitation reaction to obtain carbonate precipitate and supernatant.

[0032] In the present invention, the positive pressure of the carbon dioxide introduced into the closed environment is preferably 0.1-1.0 MPa, more preferably 0.2-0.8 MPa, and further preferably 0.3-0.7 MPa. In the present invention, the closed environment is preferably provided by a closed stirring kettle. After the carbon dioxide pressure reaches the above value, the present invention preferably continues stirring for 0.5-1h to promote the precipitation reaction of the impurity metal. In the present invention, impurity metals such as Fe, Cu, and Hg in the desulfurization solid waste slurry will form corresponding carbonate precipitates.

[0033] The present invention preferably calcines the carbonate precipitate to obtain metal oxides for use as chemical raw materials. In the present invention, the calcination temperature is preferably 600-900°C, more preferably 700-800°C; the holding time is preferably 1-3 hours, and the calcination atmosphere is preferably oxygen-enriched air with an oxygen content of ≥40 vol%.

[0034] The present invention desorbs carbon dioxide from the supernatant to obtain a desorbed supernatant and carbon dioxide. In the present invention, the carbon dioxide desorption is preferably carried out in a reduced pressure kettle. In the present invention, the supernatant is preferably transported to the reduced pressure kettle by a pump. In the present invention, the vacuum degree in the reduced pressure kettle is preferably 20-50 kPa, more preferably 25-45 kPa, and further preferably 30-40 kPa; the temperature in the reduced pressure kettle is preferably maintained at 40-80 ° C, more preferably 50-70 ° C, and further preferably 55-65 ° C; the carbon dioxide desorption time is preferably 0.5-1 h. In the present invention, the carbon dioxide desorption time is preferably 0.5-1 h, and the carbon dioxide desorption is preferably carried out under stirring conditions. If not desorbed, the CO2 present in the liquid phase and the carbonate ions dissolved and generated will affect the purity of the electrolysis product H2SO4 in the subsequent electrolysis process, and will also cause an increase in power consumption. The carbon dioxide obtained by desorption is preferably stored in a carbon storage tank in the present invention and reused for the precipitation reaction.

[0035] After obtaining the desorption clear liquid, the present invention performs membrane separation electrolysis on the desorption clear liquid to obtain NaOH and H2SO4.

[0036] The present invention has no special requirements for the membrane separation electrolysis process, and the membrane separation electrolysis process known in the art can be used. In the present invention, the voltage of the membrane separation electrolysis is preferably 50 to 80 V, and the current is preferably 50 to 65 mA. The present invention has no special requirements for the type of ion exchange membrane, and any membrane separation electrolysis process known in the art that can achieve Na + and SO4 2- Any separation exchange membrane may be used.

[0037] After membrane separation and electrolysis, the present invention obtains NaOH in the cathode chamber and H2SO4 in the anode chamber. The present invention preferably concentrates the anode chamber and cathode chamber solutions to obtain the final NaOH and H2SO4.

[0038] Figure 1 The figure is a schematic diagram of the purification and resource utilization process of flue gas desulfurization solid waste of the present invention. Figure 1 As shown, the present invention mixes flue gas desulfurization solid waste with water to obtain desulfurized solid waste slurry; in a closed environment, carbon dioxide is introduced into the desulfurized solid waste slurry, and impurity metals in the desulfurized solid waste slurry undergo precipitation reaction to obtain carbonate precipitate and supernatant; the carbonate precipitate is roasted to obtain metal oxide; the supernatant is desorbed with carbon dioxide to obtain desorbed clear liquid and carbon dioxide; the carbon dioxide generated by desorption is used for precipitation reaction; the desorbed clear liquid is subjected to membrane separation electrolysis to obtain NaOH and H2SO4.

[0039] The purification and resource utilization method of flue gas desulfurization solid waste provided by the present invention is described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0040] Example 1

[0041] (1) pouring desulfurized solid waste (calculated by mass percentage, mainly containing 95% Na2SO4, 2% Fe2(SO4)3, and 1% CuSO4) and water in a mass ratio of 1:8 into a closed stirring kettle and mixing and stirring at room temperature for 2 hours to generate desulfurized solid waste slurry;

[0042] (2) introducing CO2 gas from a carbon storage tank into the desulfurized solid waste slurry in a closed stirred tank until the closed stirred tank reaches a positive pressure of 0.1 MPa and continues stirring for 0.5 h, so that the impurity metals in the desulfurized solid waste slurry are precipitated to the bottom of the tank to obtain carbonate precipitate and supernatant liquid;

[0043] (3) The supernatant liquid is pumped into a vacuum kettle and stirred for 1 hour. During the stirring process, the vacuum degree in the vacuum kettle is adjusted to 20 kPa and the temperature of the vacuum kettle is adjusted to 80° C. to desorb the CO2 in the clear liquid, and the desorbed CO2 is stored in a carbon storage tank for reuse in the closed stirring kettle;

[0044] (4) The desorbed clear liquid is pumped to a membrane separation electrolytic cell. The electrolysis and membrane separation conditions are: working voltage 50 V, electrolysis current 54 mA, homogeneous cation exchange membrane and homogeneous anion exchange membrane. Na is separated by electrolysis and membrane separation. + and SO4 2- and obtain the final products NaOH and H2SO4 through a concentration process;

[0045] (5) The carbonate precipitate at the bottom of the closed stirring kettle is calcined to generate metal oxides. The calcination temperature is 600° C., the calcination time is 3 h, and the calcination atmosphere is oxygen-enriched air with an oxygen content of 40 vol%. The metal oxides can be used as chemical raw materials.

[0046] Through the present invention, the utilization rate of sodium sulfate in the desulfurized solid waste reaches 100%, the mass concentration of the product H2SO4 reaches 42%, and the mass concentration of the product NaOH reaches 92%.

[0047] Example 2

[0048] (1) pouring desulfurized solid waste (calculated by mass percentage, mainly containing 92% Na2SO4, 1.5% CuSO4, and 0.5% Hg2SO4) and water in a mass ratio of 1:4 into a closed stirring kettle and mixing and stirring at room temperature for 1 hour to generate desulfurized solid waste slurry;

[0049] (2) introducing CO2 gas from a carbon storage tank into the desulfurized solid waste slurry in a closed stirred tank until the closed stirred tank reaches a positive pressure of 1.0 MPa and continues stirring for 0.5 h, so that the impurity metals in the desulfurized solid waste slurry are precipitated to the bottom of the tank to obtain carbonate precipitate and supernatant liquid;

[0050] (3) The supernatant liquid is pumped into a vacuum kettle and stirred for 1 hour, and the vacuum degree in the vacuum kettle is adjusted to 35 kPa and the temperature of the vacuum kettle is adjusted to 40° C. to desorb the CO2 in the clear liquid, and the desorbed CO2 is stored in a carbon storage tank for reuse in the closed stirring kettle;

[0051] (4) The desorbed clear liquid is pumped to a membrane separation electrolytic cell. The electrolysis and membrane separation conditions are: working voltage 65 V, electrolysis current 60 mA, heterogeneous cation exchange membrane and heterogeneous anion exchange membrane. Na is separated by electrolysis and membrane separation. + and SO4 2- and obtain the final products NaOH and H2SO4 through a concentration process;

[0052] (5) The impure metal precipitates at the bottom of the closed stirring kettle are calcined to generate metal oxides. The calcination temperature is 900°C, the calcination time is 2 hours, and the calcination atmosphere is oxygen-enriched air with an oxygen content of 50 vol%. The metal oxides can be used as chemical raw materials.

[0053] Through the present invention, the utilization rate of sodium sulfate in the desulfurized solid waste reaches 100%, the mass concentration of the product H2SO4 reaches 57%, and the mass concentration of the product NaOH reaches 96%.

[0054] Example 3

[0055] (1) pouring desulfurized solid waste (calculated by mass percentage, mainly containing 93% Na2SO4, 1.5% Fe2(SO4)3, 1% CuSO4, and 0.5% Hg2SO4) and water in a mass ratio of 1:10 into a closed stirring kettle and mixing and stirring at room temperature for 1 hour to generate desulfurized solid waste slurry;

[0056] (2) introducing CO2 gas from a carbon storage tank into the desulfurized solid waste slurry in a closed stirred tank until the closed stirred tank reaches a positive pressure of 0.5 MPa and continues stirring for 1 hour to allow the impurity metals in the desulfurized solid waste slurry to precipitate to the bottom of the tank to obtain carbonate precipitate and supernatant liquid;

[0057] (3) The supernatant liquid is pumped into a vacuum kettle and stirred for 0.5 h, and the vacuum degree in the vacuum kettle is adjusted to 50 kPa and the temperature of the vacuum kettle is adjusted to 60° C. to desorb the CO2 in the clear liquid, and the desorbed CO2 is stored in a carbon storage tank for reuse in the closed stirring kettle;

[0058] (4) The desorbed clear liquid is pumped to a membrane separation electrolytic cell. The electrolysis and membrane separation conditions are: working voltage 80 V, electrolysis current 63 mA, heterogeneous special cation exchange membrane and heterogeneous special anion exchange membrane. + and SO4 2- and obtain the final products NaOH and H2SO4 through a concentration process;

[0059] (5) The impure metal precipitates at the bottom of the closed stirring kettle are calcined to generate metal oxides. The calcination temperature is 700°C, the calcination time is 1 hour, and the calcination atmosphere is oxygen-enriched air with an oxygen content of 60 vol%. The metal oxides can be used as chemical raw materials.

[0060] Through the present invention, the utilization rate of sodium sulfate in the desulfurized solid waste reaches 100%, the mass concentration of the product H2SO4 reaches 51%, and the mass concentration of the product NaOH reaches 93%.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for purifying and recycling flue gas desulfurization solid waste, characterized in that: The following steps are involved: Mixing flue gas desulfurization solid waste with water to obtain desulfurization solid waste slurry; the content of sodium sulfate in the flue gas desulfurization solid waste is greater than 50wt%; In a closed environment, carbon dioxide is introduced into the desulfurized solid waste slurry, and the impurity metals in the desulfurized solid waste slurry undergo precipitation reaction to obtain carbonate precipitate and supernatant liquid; calcining the carbonate precipitate to obtain a metal oxide; Desorbing carbon dioxide from the supernatant to obtain a desorbed supernatant and carbon dioxide; The desorbed clear liquid is subjected to membrane separation electrolysis to obtain NaOH and H2SO4; The carbon dioxide generated by the carbon dioxide desorption is used for precipitation reaction.

2. The purification and resource recovery method according to claim 1, characterized in that: The calcination temperature is 600-900° C., the heat preservation time is 1-3 hours, and the calcination atmosphere is oxygen-enriched air with an oxygen content of ≥40 vol%.

3. The purification and resource recovery method according to claim 1, characterized in that: The mass ratio of the flue gas desulfurization solid waste to water is 1:4-10.

4. The purification and resource recovery method according to claim 1, characterized in that: The positive pressure of the carbon dioxide introduced into the closed environment is 0.1-1.0 MPa.

5. The purification and resource recovery method according to claim 1, characterized in that: The carbon dioxide desorption is carried out in a reduced pressure autoclave, and the vacuum degree in the reduced pressure autoclave is 20-50 kPa.

6. The purification and resource recovery method according to claim 5, characterized in that: The temperature in the reduced pressure autoclave is maintained at 40-80°C.

7. The purification and resource recovery method according to claim 1, 5 or 6, characterized in that: The carbon dioxide desorption time is 0.5~1h.

8. The purification and resource recovery method according to claim 1, characterized in that: The voltage of the membrane separation electrolysis is 50-80V, and the current is 50-65mA.

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