Method for regenerating and recycling baking soda desulfurized fly ash resources

Abstract

The invention discloses a method for regenerating and recycling baking soda desulfurized fly ash resources. The method comprises the following steps: S1, performing pretreatment and impurity removal on baking soda desulfurized fly ash to obtain a sodium sulfate solution; s2, adding the ammonium bicarbonate solution into the sodium sulfate solution, and performing double decomposition reaction to obtain sodium bicarbonate and residual mother liquor; s3, heating the residual mother liquor to decompose ammonium bicarbonate into carbon dioxide and ammonia gas, and performing evaporative crystallization on the residual mother liquor to obtain ammonium sulfate and sodium sulfate. The baking soda desulfurized fly ash is used as a raw material, baking soda is prepared through pretreatment impurity removal and double decomposition reaction, resource utilization of the baking soda desulfurized fly ash is achieved, the process is pure, and no new solid waste is generated.

Description

Technical Field

[0001] The invention belongs to the technical field of desulfurization ash resource utilization and relates to a method for recycling and regenerating baking soda desulfurization ash resources. Background Art

[0002] Baking Soda Desulfurization Technology Ultrafine NaHCO provided by Baking Soda Grinder System 3 The powder undergoes desulfurization reaction in the process of expansion and decomposition in high-temperature flue gas. It has high desulfurization efficiency, no wastewater and smoke are generated, and the operation resistance is low. It is especially suitable for use in gas boilers, coke ovens and other occasions. At present, baking soda desulfurization technology has become an effective and commonly used means of flue gas desulfurization. Its main process is to use NaHCO 3 As a desulfurizing agent, baking soda is ground into ultrafine powder of 15-20 mm by a mill and sprayed into high-temperature flue gas above 130-140°C. It expands and decomposes in the flue and reactor to generate Na 2 CO 3 , H 2 O and CO 2 Under high temperature, the particle volume increases rapidly, and a porous structure is formed on the particle surface, which is fully in contact with the flue gas, undergoing physical and chemical reactions and reacting with SO 2 , HC1 and other acidic gases to achieve the effect of removing acidic gases. The main reaction is shown in reaction formulas (1) and (2), and the side reaction is shown in reaction formulas (3) and (4);

[0003] 2NaHCO 3 (s) = Na 2 CO 3 (s) + H 2 O(g) + CO 2 (g) (1)

[0004] SO 2 (g) +O 2 (g) + Na 2 CO 3 (s) =Na 2 SO 4 (s) + CO 2 (g) (2)

[0005] SO 3 (g) + Na 2 CO 3 (s) =Na 2 SO 4 (s) + CO 2 (g) (3)

[0006] 2HCl(g) + Na 2CO 3 (s) = 2NaCl(s) + CO 2 (g) (4)

[0007] The main component of the sodium-based desulfurization ash obtained by baking soda desulfurization technology is sodium sulfate, and sodium sulfite and sodium chloride are also present, as shown in Table 1.

[0008] Table 1 Composition of sodium-based desulfurization ash

[0009]

[0010] At present, sodium-based desulfurization ash belongs to general solid waste, and is generally landfilled or incinerated according to the method of solid waste. According to the composition table shown in Table 1, sodium sulfate accounts for more than 85%, which is a bulk chemical raw material. If the desulfurization ash is directly landfilled or incinerated, it is a waste of resources. In addition, there are secondary pollution problems in landfilling or incineration. Landfilling will have the potential hazard of easy migration of soluble salts. Once the soluble salts migrate to the soil and water bodies, the soil salinization will be aggravated; the sodium ions will replace the calcium ions on the surface of the soil colloid, causing the soil structure to be destroyed and the soil to be compacted; the air permeability and water permeability of this compacted soil will affect the growth of plant roots and the absorption of water and nutrients. Direct incineration of high-salt solid waste will have a strong erosion effect on the refractory lining of the incinerator, causing cracks or even falling off of the refractory, which brings great safety hazards and economic losses to the continuous and stable operation of the incinerator.

[0011] Chinese patent CN114751429B discloses a processing technology for preparing baking soda from desulfurization ash, which mainly introduces the process of obtaining sodium bicarbonate by reacting baking soda desulfurization ash with ammonium bicarbonate after dissolution and impurity removal. However, the patent makes the mother liquor after separating the baking soda into impurity salt. Such a process route not only reduces the utilization rate of ammonium bicarbonate and sodium sulfate, but also regenerates new solid waste.

[0012] Chinese patent publication number CN118180104 A discloses a method for resource utilization of sodium-based desulfurization ash, and introduces a method for preparing sodium sulfate by dissolving, filtering, removing impurities, and evaporating and crystallizing baking soda desulfurization ash. The advantage of this method is that the impurities of sodium sulfate are removed based on the properties of baking soda desulfurization ash to obtain high-purity sodium sulfate. The disadvantage of this method is that the value of sodium sulfate is low, the method described in this invention patent may be costly, and the impurity removal method is complicated. Summary of the invention

[0013] In view of the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a method for regenerating and recycling baking soda desulfurization ash resources. Baking soda desulfurization ash is used as raw material, and sodium bicarbonate (baking soda) is prepared by pre-treatment impurity removal and double decomposition reaction. Not only the resource utilization of baking soda desulfurization ash is realized, but also the process is pure and no new solid waste is generated.

[0014] To achieve the above object, the present invention adopts the following technical solution:

[0015] The present invention provides a method for recycling and regenerating baking soda desulfurization ash resources, comprising the following steps:

[0016] S1, sodium sulfate solution is obtained by pre-treatment of baking soda desulfurization ash to remove impurities;

[0017] S2, adding the ammonium bicarbonate solution to the sodium sulfate solution to obtain sodium bicarbonate and a remaining mother liquor through a double decomposition reaction;

[0018] S3, heating the remaining mother liquor to decompose the ammonium bicarbonate into carbon dioxide and ammonia, and then evaporating and crystallizing the remaining mother liquor to obtain ammonium sulfate and sodium sulfate.

[0019] Preferably, in step S1, the pre-treatment impurity removal process is as follows:

[0020] S11, dissolve baking soda desulfurization ash with water:

[0021] S12, using an electro-flocculation method to remove impurities, and then obtaining a sodium sulfate solution after standing, settling and filtering.

[0022] Preferably, in step S11, when dissolving baking soda desulfurization ash with water, the water-to-ash ratio is controlled to be 3 to 4:1 and the dissolution temperature is controlled to be 35°C to 40°C.

[0023] Preferably, in said S12, during the impurity removal process by electrocoagulation, the electrode material of the electrocoagulation is aluminum or iron, and the current density of the current is 5 to 60 A / m 2 The power-on time is 30 to 60 minutes.

[0024] Preferably, in step S12, the concentration of sodium sulfate in the sodium sulfate solution is 240 g / L to 280 g / L.

[0025] Preferably, in step S2:

[0026] The mass ratio of sodium sulfate to ammonium bicarbonate is 1.1-1.5:1;

[0027] The reaction temperature of the double decomposition reaction is 35°C to 40°C;

[0028] In the double decomposition reaction, the sodium bicarbonate precipitated in solid form is washed with hot water and then dried, and the dried sodium bicarbonate accounts for 50% to 60% of the amount of ammonium bicarbonate added.

[0029] Preferably, in step S3:

[0030] The heating treatment temperature is 60°C to 65°C;

[0031] The evaporation temperature of the evaporation crystallization is 90°C to 100°C.

[0032] The present invention has the following beneficial effects:

[0033] 1. The present invention uses baking soda desulfurization ash as raw material, and prepares baking soda and ammonium sulfate through double decomposition reaction. The baking soda is returned to the desulfurization system as a desulfurizing agent, and the ammonium sulfate can be exported as an industrial product, thus realizing the innovation of resource recycling;

[0034] 2. The pretreatment impurity removal of the present invention adopts the principle of electric flocculation impurity removal, and the impurities in the baking soda desulfurization ash are removed through one-step impurity removal, and the whole impurity removal process is simple;

[0035] 3. After the baking soda is prepared by the double decomposition reaction, the mother liquor is further heated to decompose the ammonium bicarbonate, and the decomposed product can be reused in the double decomposition reaction;

[0036] 4. The method for recycling and reusing the baking soda desulfurization ash resources of the present invention can realize resource circulation, has a pure process, and does not generate "three wastes" in the whole process. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic flow diagram of the method for regenerating and recycling the sodium bicarbonate desulfurization ash resources of the present invention;

[0038] Figure 2 It is a schematic flow diagram of the metathesis reaction of the present invention. DETAILED DESCRIPTION

[0039] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with embodiments.

[0040] Combination Figure 1 , Figure 2 As shown, the present invention provides a method for recycling and reusing baking soda desulfurization ash resources, comprising the following steps:

[0041] S1, sodium sulfate solution is obtained by pre-treatment of baking soda desulfurization ash to remove impurities;

[0042] This step is the pre-treatment impurity removal process, as follows:

[0043] S11, dissolve baking soda desulfurization ash with water:

[0044] Dissolution of baking soda desulfurization ash: Dissolve baking soda desulfurization ash with water, control the water-ash ratio to 3-4:1, and the dissolution temperature to 35℃-40℃.

[0045] S12, using an electro-flocculation method to remove impurities, and then obtaining a sodium sulfate solution after standing, settling and filtering.

[0046] Baking soda desulfurization ash impurity removal: The electric flocculation method is used for impurity removal, and the current density is 5-60A / m 2 (For example, 15~60A / m 2 ), the power-on time is 30 to 60 minutes; the electrode material of the electroflocculation is aluminum or iron. The impurities generated here are organic matter, fluoride, and silicate. After collection, hazardous waste identification is carried out and handed over to solid waste disposal units for disposal.

[0047] In the above sodium sulfate solution, the concentration of sodium sulfate is between 240g / L and 280g / L.

[0048] The above-mentioned electro-flocculation impurity removal principle is as follows: electro-flocculation is a wastewater treatment process that combines complex adsorption with oxidation-reduction, acid-base neutralization, and flotation separation; the electro-flocculation mechanism shows that the positively charged flocculant and pollutant particles are complexed and aggregated through electrostatic attraction and van der Waals forces to form settleable floccules for removal; organic molecules can be decomposed into small molecules through anodic oxidation and are easily adsorbed by flocculants, and dyes and dissolved metal ions can be separated from the water body through the electro-reduction deposition of the cathode. The electrodes used in electro-flocculation are generally aluminum or iron, and highly active polymorphic polyaluminum or polyiron flocculants are generated in situ to aggregate pollutant particles in the water body and settle or separate them by flotation.

[0049] S2, adding the ammonium bicarbonate solution to the sodium sulfate solution to obtain sodium bicarbonate and a remaining mother liquor through a double decomposition reaction;

[0050] This step is the process of preparing sodium bicarbonate, based on the following principles:

[0051] 2(NH 4 )HCO 3 +Na 2 SO 4 =2NaHCO 3 +(NH 4 ) 2 SO 4

[0052] The ammonium bicarbonate solution is slowly added to the sodium sulfate solution, and the mass ratio of sodium sulfate to ammonium bicarbonate in the sodium sulfate solution is controlled to be 1.1-1.5:1; the ammonium bicarbonate and sodium sulfate undergo double decomposition reaction to generate NaHCO 3(baking soda) and (NH 4 ) 2 SO 4 , wherein the reaction temperature of the double decomposition reaction is 35° C. to 40° C. In the above double decomposition reaction, since baking soda has a low solubility, it will precipitate in the form of solid, and the precipitated sodium bicarbonate is washed with hot water and then dried, and the dried sodium bicarbonate accounts for 50% to 60% of the amount of ammonium bicarbonate added.

[0053] The baking soda prepared in this step can be returned to the desulfurization system for use as a desulfurizing agent.

[0054] S3, heating the remaining mother liquor to decompose the ammonium bicarbonate into carbon dioxide and ammonia, and then obtaining ammonium sulfate and sodium sulfate through evaporation and crystallization.

[0055] This step is the further processing of the remaining mother liquor, specifically based on the following principles:

[0056] (NH 4 )HCO 3 =NH 3 +CO 2 +H 2 O(heat decomposition)

[0057] The remaining mother liquor contains NaHCO generated by the reaction. 3 NH 4 ) 2 SO 4 As well as ammonium bicarbonate and sodium sulfate as reactants, after the remaining mother liquor is heated to 60°C to 65°C, the ammonium bicarbonate is decomposed into carbon dioxide and ammonia, and these two substances return to the double decomposition reaction unit to participate in the preparation of baking soda.

[0058] The remaining sodium sulfate and ammonium sulfate in the remaining mother liquor are separated by evaporation and crystallization, the evaporation temperature is 80°C to 100°C, the ratio of the output of sodium sulfate to the amount of ammonium bicarbonate added is 0.6 to 1.1, and the ratio of the output of ammonium sulfate to the amount of ammonium bicarbonate added is 0.4 to 0.5.

[0059] The by-product ammonium sulfate in this step can be exported as fertilizer.

[0060] The following is a further introduction to the method for regenerating and recycling baking soda desulfurization ash resources of the present invention with reference to specific examples.

[0061] Example 1

[0062] The baking soda desulfurization ash of this embodiment takes the coking desulfurization ash of a steel enterprise as an example, and its composition is shown in Table 1;

[0063] Table 1

[0064] Element Sodium sulfate Sodium chloride Sodium carbonate Sodium sulfite Silicate Sodium fluoride Moisture content(%) 83 7 6 0.1 0.5 0.4 3

[0065] The method for recycling and reusing the sodium bicarbonate desulfurization ash resources of the present embodiment is as follows:

[0066] (1) Weigh 200 g of baking soda desulfurization ash and place it in a beaker, add water to dissolve it, and dissolve it in a ratio of water: baking soda desulfurization ash = 3:1. The dissolution temperature is controlled at 35-40°C. After dissolution, filter and collect the filtrate;

[0067] (2) After the filtrate is collected, it enters the electrocoagulation unit. The electrode material of the electrocoagulation is aluminum, and the current density is controlled at 15A / m 2 , after 60 minutes of power on, filter and collect the filtrate, the filtrate at this time is a sodium sulfate solution, wherein the concentration of sodium sulfate is 270g / L;

[0068] (3) Double decomposition reaction: Control the temperature of the sodium sulfate solution at 35° C., add 147 g of ammonium bicarbonate according to the mass ratio of sodium sulfate to ammonium bicarbonate of 1.1:1, and react to obtain 91 g of sodium bicarbonate and the remaining mother liquor;

[0069] (4) The remaining mother liquor after the reaction is heated to 60-65° C. to recover ammonia and carbon dioxide; the remaining mother liquor is then further heated to 90° C. to first precipitate 85 g of sodium sulfate and finally obtain 71 g of ammonium sulfate.

[0070] Example 2

[0071] The baking soda desulfurization ash of this embodiment takes the coking desulfurization ash of a steel enterprise as an example, and its composition is shown in Table 2;

[0072] Table 2

[0073] Element Sodium sulfate Sodium chloride Sodium carbonate Sodium sulfite Silicate Sodium fluoride Moisture content(%) 85 6 2 1 0.7 0.5 4.8

[0074] The method for recycling and reusing the sodium bicarbonate desulfurization ash resources of the present embodiment is as follows:

[0075] (1) Weigh 200 g of baking soda desulfurization ash and place it in a beaker, add water to dissolve it, and dissolve it in a ratio of water: baking soda desulfurization ash = 3.5:1. The dissolution temperature is controlled at 35-40°C. After dissolution, filter and collect the filtrate;

[0076] (2) After the filtrate is collected, it enters the electrocoagulation unit. The electrode material of the electrocoagulation is aluminum, and the current density is controlled at 45A / m 2 , after 60 minutes of power on, filter and collect the filtrate, the filtrate at this time is a sodium sulfate solution, wherein the concentration of sodium sulfate is 241g / L;

[0077] (3) Double decomposition reaction: the temperature of the sodium sulfate solution was controlled at 40° C., 141 g of ammonium bicarbonate was added according to a mass ratio of sodium sulfate to ammonium bicarbonate of 1.2:1, and 86 g of sodium bicarbonate and the remaining mother liquor were obtained by reaction;

[0078] (4) The remaining mother liquor after the reaction is heated to 60-65° C. to recover ammonia and carbon dioxide; the remaining mother liquor is then further heated to 90° C. to precipitate 95 g of sodium sulfate first, and then obtain 68 g of ammonium sulfate.

[0079] Example 3

[0080] The baking soda desulfurization ash of this embodiment takes the coking desulfurization ash of a steel enterprise as an example, and its composition is shown in Table 3;

[0081] Table 3

[0082] Element Sodium sulfate Sodium chloride Sodium carbonate Sodium sulfite Silicate Sodium fluoride Moisture content(%) 85 6 2 1 0.7 0.5 4.8

[0083] The method for recycling and reusing the sodium bicarbonate desulfurization ash resources of the present embodiment is as follows:

[0084] (1) Weigh 200 g of baking soda desulfurization ash and place it in a beaker, add water to dissolve it, and dissolve it in a ratio of water: baking soda desulfurization ash = 3:1. The dissolution temperature is controlled at 35-40°C. After dissolution, filter and collect the filtrate;

[0085] (2) After the filtrate is collected, it enters the electrocoagulation unit. The electrode material of the electrocoagulation is aluminum, and the current density is controlled at 45A / m 2 , after 60 minutes of power on, filter and collect the filtrate, the filtrate at this time is a sodium sulfate solution, wherein the concentration of sodium sulfate is 281g / L;

[0086] (3) Double decomposition reaction: Control the temperature of the sodium sulfate solution at 42°C to 45°C, add 141 g of ammonium bicarbonate according to the mass ratio of sodium sulfate to ammonium bicarbonate of 1.2:1, and react to obtain 89 g of sodium bicarbonate and the remaining mother liquor;

[0087] (4) The remaining mother liquor after the reaction is heated to 60-65° C. to recover ammonia and carbon dioxide; the remaining mother liquor is then further heated to 80° C. to precipitate 92 g of sodium sulfate first, and then obtain 70 g of ammonium sulfate.

[0088] Example 4

[0089] The baking soda desulfurization ash of this embodiment takes the coking desulfurization ash of a steel enterprise as an example, and its composition is shown in Table 4;

[0090] Table 4

[0091] Element Sodium sulfate Sodium chloride Sodium carbonate Sodium sulfite Silicate Sodium fluoride Moisture content(%) 85 6 2 1 0.7 0.5 4.8

[0092] The method for recycling and reusing the sodium bicarbonate desulfurization ash resources of the present embodiment is as follows:

[0093] (1) Weigh 200 g of baking soda desulfurization ash and place it in a beaker, add water to dissolve it, and dissolve it in a ratio of water: baking soda desulfurization ash = 3:1. The dissolution temperature is controlled at 35-40°C. After dissolution, filter and collect the filtrate;

[0094] (2) After the filtrate is collected, it enters the electrocoagulation unit. The electrode material of the electrocoagulation is aluminum, and the current density is controlled at 45A / m 2 , after 60 minutes of power on, filter and collect the filtrate, the filtrate at this time is a sodium sulfate solution, wherein the concentration of sodium sulfate is 281g / L;

[0095] (3) Double decomposition reaction: Control the temperature of the sodium sulfate solution at 45° C., add 120 g of ammonium bicarbonate according to the mass ratio of ammonium bicarbonate to sodium sulfate in the sodium sulfate solution of 1.4:1, and react to obtain 83 g of sodium bicarbonate and the remaining mother liquor;

[0096] (4) The remaining mother liquor after the reaction is heated to 60-65° C. to recover ammonia and carbon dioxide; the remaining mother liquor is then further heated to 100° C. to first precipitate 98 g of sodium sulfate and then obtain 65 g of ammonium sulfate.

[0097] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for recycling and reusing sodium bicarbonate desulfurization ash resources, characterized in that: The following steps are involved: S1, sodium sulfate solution is obtained by pre-treatment of baking soda desulfurization ash to remove impurities; S2, adding the ammonium bicarbonate solution to the sodium sulfate solution to obtain sodium bicarbonate and a remaining mother liquor through a double decomposition reaction; S3, heating the remaining mother liquor to decompose the ammonium bicarbonate into carbon dioxide and ammonia, and then evaporating and crystallizing the remaining mother liquor to obtain ammonium sulfate and sodium sulfate.

2. The method for recycling and utilizing sodium bicarbonate desulfurization ash resources according to claim 1, characterized in that: In step S1, the pre-treatment impurity removal process is as follows: S11, dissolve baking soda desulfurization ash with water: S12, using an electro-flocculation method to remove impurities, and then obtaining a sodium sulfate solution after standing, settling and filtering.

3. The method for recycling and utilizing sodium bicarbonate desulfurization ash resources according to claim 2, characterized in that: In the step S11, when the baking soda desulfurization ash is dissolved with water, the water-ash ratio is controlled to be 3-4:1 and the dissolution temperature is controlled to be 35°C-40°C.

4. The method for recycling and utilizing sodium bicarbonate desulfurization ash resources according to claim 2, characterized in that: In the above S12, during the impurity removal process using the electrocoagulation method, the electrode material for the electrocoagulation is aluminum or iron, and the current density is 5 to 60 A / m 2 The power-on time is 30 to 60 minutes.

5. The method for recycling and utilizing sodium bicarbonate desulfurization ash resources according to claim 2, characterized in that: In the step S12, the concentration of sodium sulfate in the sodium sulfate solution is 240 g / L to 280 g / L.

6. The method for recycling and utilizing sodium bicarbonate desulfurization ash resources according to claim 1, characterized in that: In step S2: The mass ratio of sodium sulfate to ammonium bicarbonate is 1.1 to 1.5:1; The reaction temperature of the double decomposition reaction is 35°C to 40°C; In the double decomposition reaction, the sodium bicarbonate precipitated in solid form is washed with hot water and then dried, and the dried sodium bicarbonate accounts for 55% to 65% of the amount of ammonium bicarbonate added.

7. The method for recycling and utilizing sodium bicarbonate desulfurization ash resources according to claim 1, characterized in that: In step S3: The heating treatment temperature is 60°C to 65°C; The evaporation temperature of the evaporation crystallization is 90°C to 100°C.

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