Calcium-based solid waste slurry desulfurization agent, preparation method, desulfurization method, and soil remediation agent

Abstract

A preparation method for a calcium-based solid waste slurry desulfurization agent comprises: performing sedimentation treatment on a calcium-based solid waste slurry to obtain a calcium-based solid waste slurry reaction solution; adding a phase change inhibitor to the calcium-based solid waste slurry reaction solution to obtain a mixed slurry; performing solid-liquid separation on the mixed slurry to obtain a solid phase substance; and mixing the solid phase substance with water and adding a conditioning agent to obtain a calcium-based solid waste slurry desulfurization agent.

Description

Calcium-based solid waste slurry desulfurizing agent, preparation method, desulfurization method and soil remediation agent

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application No. 202510006382.7, filed on January 3, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of solid waste utilization technology, and in particular to a calcium-based solid waste slurry desulfurizing agent, its preparation method, desulfurization method, and soil remediation agent. Background Technology

[0004] In the process of producing alumina from bauxite, impurities from the high-pressure leaching reaction of alumina need to be reacted with calcium-based materials to obtain a mixture of hydrated calcium aluminate, calcium carbonate, calcium aluminate, and their hydrates with alkaline solution. After the reaction, the alkaline solution is separated and returned to the alumina system for continued use, and the remaining mixture is calcium-based solid waste slurry. After solid-liquid separation, the calcium-based solid waste slurry is sent to a red mud storage facility as general solid waste. However, there is currently no literature documenting how to utilize the calcium-based solid waste slurry to achieve waste recycling. Summary of the Invention

[0005] This disclosure provides a calcium-based solid waste slurry desulfurizing agent, preparation method, desulfurization method, and soil remediation agent, solving the problem of how to utilize calcium-based solid waste slurry.

[0006] In a first aspect, this disclosure provides a method for preparing a calcium-based solid waste slurry desulfurization agent, comprising:

[0007] A calcium-based solid waste slurry reaction solution was obtained;

[0008] A phase change inhibitor was added to the calcium-based solid waste slurry reaction solution to obtain a mixed slurry;

[0009] The mixed slurry is subjected to solid-liquid separation to obtain a solid phase; and

[0010] The solid material is added to water and mixed with a conditioning agent to obtain a calcium-based solid waste slurry desulfurizing agent;

[0011] The pH value of the calcium-based solid waste slurry desulfurizer is 7-10. Attached Figure Description

[0012] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0013] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 shows a schematic flowchart of a method for preparing a calcium-based solid waste slurry desulfurizer according to some embodiments of the present disclosure;

[0015] Figure 2 shows a schematic diagram of a calcium-based solid waste slurry desulfurization method according to some embodiments of the present disclosure. Embodiments of the present invention

[0016] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0017] Various embodiments of this disclosure may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this disclosure; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range such as 1, 2, 3, 4, 5, and 6, regardless of the range; furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0018] In this document, terms such as “comprising” mean “including but not limited to”. Relational terms such as “first” and “second” are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. “And / or” describes the relationship between related objects, indicating that there can be three relationships, for example, A and / or B can mean: A alone, A and B simultaneously, or B alone; where A and B can be singular or plural. “At least one” means one or more, “more” means two or more; “at least one,” “at least one of the following,” or similar expressions refer to any combination of these items, including any combination of single or plural items; for example, “at least one of a, b, or c,” or “at least one of a, b, and c,” can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts representation" such as parts by weight or parts by mass indicates the proportional relationship between components. In the proportional relationships discussed in this article, the parameters that need to be described by proportion should be understood as the first term of the proportion in the order of description, and the proportion figures should be understood as the second term of the proportion. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportion figures in the proportion in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0019] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0020] Figure 1 shows a schematic flowchart of a method for preparing a calcium-based solid waste slurry desulfurizer according to some embodiments of the present disclosure.

[0021] As shown in Figure 1, this embodiment of the present disclosure provides a method for preparing a calcium-based solid waste slurry desulfurizer, comprising: S1, obtaining a calcium-based solid waste slurry reaction solution; S2, adding a phase change inhibitor to the calcium-based solid waste slurry reaction solution to obtain a mixed slurry; S3, performing solid-liquid separation on the mixed slurry to obtain a solid phase substance; and S4, adding water to the solid phase substance and mixing it with a conditioning agent to obtain a calcium-based solid waste slurry desulfurizer; wherein the pH value of the calcium-based solid waste slurry desulfurizer is 7~10.

[0022] In the above embodiments, the obtained calcium-based solid waste slurry reaction liquid mainly contains unstable hydrated calcium aluminate, calcium carbonate, calcium aluminate and their hydrates, and also contains calcium hydroxide, alumina and sodium oxide from the reaction raw materials or reaction products. A phase change inhibitor is added to the calcium-based solid waste slurry reaction liquid to obtain a mixed slurry. The phase change inhibitor inhibits the reaction between calcium hydroxide and alumina in the reaction liquid by adsorbing onto the reactive sites of calcium hydroxide and alumina, reducing the production of hydrated calcium aluminate and further reducing the formation of stable calcium aluminate and its hydrates, while promoting the conversion of calcium hydroxide to calcium carbonate and reducing alumina loss. The mixed slurry is subjected to solid-liquid separation, and most of the sodium oxide and alumina are discharged through the filtrate, leaving solid substances such as calcium carbonate, calcium aluminate and its hydrates, and hydrated calcium aluminate. The solid substances are mixed with a conditioning agent to obtain a calcium-based solid waste slurry desulfurizer. After conditioning, the pH value of the calcium-based solid waste slurry desulfurizer is 7-10, which can improve the desulfurization performance of calcium aluminate and its hydrates, break the gelling properties of active silicon, aluminum and magnesium, reduce the agglomeration of active silicon and alumina, and enhance the oxidation and filtration performance of desulfurization by-products.

[0023] This method uses calcium-based solid waste slurry as raw material to prepare desulfurizing agent, realizing the resource utilization of solid waste. It achieves zero emission of solid waste and reduces the operating cost of flue gas desulfurization and the production cost of alumina.

[0024] In some embodiments, a calcium-based solid waste slurry reaction solution is obtained, comprising:

[0025] S11. Settling the calcium-based solid waste slurry yields the calcium-based solid waste slurry underflow; and

[0026] S12. Dilute the underflow of calcium-based solid waste slurry to obtain calcium-based solid waste slurry reaction solution.

[0027] In the above embodiment, the calcium-based solid waste slurry is settled in a settling tank to obtain a calcium-based solid waste slurry underflow and a settling tank overflow with a higher solids content. The settling tank overflow is sent to an alumina slurry dilution tank to recover a portion of the sodium hydroxide; the calcium-based solid waste slurry underflow is sent to an alkali recovery reaction tank for dilution to prepare a calcium-based solid waste slurry reaction solution. The settling process not only increases the solids content of the prepared calcium-based solid waste slurry reaction solution but also reduces the alkali concentration in the prepared calcium-based solid waste slurry reaction solution.

[0028] In some embodiments, the solid-liquid ratio of the calcium-based solid waste slurry reaction liquid is (0.1~1):1. The reason for controlling the solid-liquid ratio in the calcium-based solid waste slurry reaction liquid to (0.1~1):1 is that a suitable solid-liquid ratio helps improve the sodium oxide removal effect and reduces the water content of the solid phase obtained after subsequent solid-liquid separation. When the solid-liquid ratio of the calcium-based solid waste slurry reaction liquid is greater than 1:1, it will affect the solid-liquid separation effect, resulting in a higher sodium oxide content in the solid phase after solid-liquid separation; when the solid-liquid ratio of the calcium-based solid waste slurry reaction liquid is less than 0.1:1, it will increase the solid-liquid separation time, resulting in a higher water content in the solid phase after solid-liquid separation. For example, the solid-liquid ratio can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, or 1:1.

[0029] In some embodiments, the calcium-based solid waste slurry underflow is diluted by: mixing the calcium-based solid waste slurry underflow with hot water, and controlling the mixing temperature at 70°C to 100°C and the mixing time at 0.5h to 5h, so that the calcium-based solid waste slurry underflow and hot water are fully mixed to obtain a uniform calcium-based solid waste slurry reaction solution.

[0030] In some embodiments, the temperature of the calcium-based solid waste slurry reaction liquid is maintained in the range of 70°C to 100°C, and a phase change inhibitor is added to the calcium-based solid waste slurry reaction liquid within this temperature range to obtain a mixed slurry.

[0031] In other embodiments, the calcium-based solid waste slurry underflow is diluted by: mixing the calcium-based solid waste slurry underflow with hot water, and controlling the mixing temperature to be 72°C to 98°C and the mixing time to be 0.5h to 5h, so that the calcium-based solid waste slurry underflow and hot water are fully mixed to obtain a uniform calcium-based solid waste slurry reaction solution.

[0032] In other embodiments, the temperature of the calcium-based solid waste slurry reaction liquid is maintained in the range of 72°C to 98°C, and a phase change inhibitor is added to the calcium-based solid waste slurry reaction liquid within this temperature range to obtain a mixed slurry.

[0033] In the above embodiments, the temperature of the calcium-based solid waste slurry reaction solution is controlled to be between 72°C and 98°C when the phase change inhibitor is added because temperature directly affects the reaction between calcium oxide and alumina in the calcium-based solid waste slurry reaction solution. When the temperature is higher than 98°C, the loss of alumina increases, generating more hydrated alumina; when the temperature is lower than 72°C, the reaction between calcium oxide and alumina in the calcium-based solid waste slurry reaction solution is almost impossible, resulting in poor reaction efficiency. For example, when the phase change inhibitor is added, the temperature of the calcium-based solid waste slurry reaction solution can be 72°C, 75°C, 78°C, 80°C, 82°C, 85°C, 88°C, 90°C, 92°C, 95°C, or 98°C.

[0034] In some embodiments, the mass of the phase change inhibitor is 0.02% to 0.15% of the total mass of sodium and aluminum in the calcium-based solid waste slurry reaction solution.

[0035] In the above embodiments, the reason for controlling the mass of the phase change inhibitor added to the calcium-based solid waste slurry reaction solution to be 0.02%~0.15% of the total mass of sodium and aluminum in the calcium-based solid waste slurry reaction solution is to ensure that all calcium hydroxide in the calcium-based solid waste slurry reaction solution is converted into calcium carbonate and to avoid the participation of alumina in the reaction, thereby reducing the loss of alumina. If the mass of the phase change inhibitor added to the calcium-based solid waste slurry reaction solution is less than 0.02% of the total mass of sodium and aluminum in the calcium-based solid waste slurry reaction solution, the phase transformation of calcium hydroxide cannot be promoted; if the mass of the phase change inhibitor added to the calcium-based solid waste slurry reaction solution is greater than 0.15% of the total mass of sodium and aluminum in the calcium-based solid waste slurry reaction solution, the promoting effect of the phase change inhibitor on the phase transformation process of calcium hydroxide is no longer significantly enhanced. At this time, all calcium hydroxide has been converted into calcium carbonate, resulting in a waste of the phase change inhibitor and an increase in cost. For example, the mass of the phase change inhibitor added to the calcium-based solid waste slurry reaction liquid is 0.02%, 0.04%, 0.05%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, and 0.15% of the total mass of sodium and aluminum in the calcium-based solid waste slurry reaction liquid.

[0036] The working principle of phase change inhibitors is as follows: phase change inhibitors can be adsorbed on the active sites on the surface of the unstable mesophase of calcium aluminate, inhibiting the diffusion reaction of active substances in the calcium-based solid waste slurry reaction liquid on these active sites, thereby accelerating the transformation of the unstable mesophase of calcium aluminate into calcium carbonate and aluminum oxide.

[0037] In some embodiments, the phase change inhibitor includes at least one of the following: glycoside, cellulose, calcium lignosulfonate, and sodium humate. In some embodiments, the glycoside can be calcium gluconate or potassium gluconate. In some embodiments, the phase change inhibitor includes at least one of the following: calcium gluconate, potassium gluconate, cellulose, calcium lignosulfonate, and sodium humate.

[0038] In the above embodiments, the phase change inhibitor can be any one of calcium gluconate, potassium gluconate, cellulose, calcium lignosulfonate, and sodium humate, or a mixture of any two of calcium gluconate, potassium gluconate, cellulose, calcium lignosulfonate, and sodium humate, or a mixture of any three or four of calcium gluconate, potassium gluconate, cellulose, calcium lignosulfonate, and sodium humate, or a mixture of five substances such as calcium gluconate, potassium gluconate, cellulose, calcium lignosulfonate, and sodium humate as a phase change inhibitor.

[0039] In some embodiments, the mixed slurry is subjected to solid-liquid separation to obtain a solid phase, including:

[0040] The mixed slurry is subjected to a first-time pressure filtration. Then, under pressure, the solids remaining after the first-time pressure filtration are washed with hot water and subjected to pressure filtration again to obtain solid phase material and first-time filtrate.

[0041] In the above embodiment, after adding a phase change inhibitor to the calcium-based solid waste slurry reaction solution and allowing it to fully react, a mixed slurry is obtained. The mixed slurry is then processed through a procedure involving two filtrations and one washing: First, the mixed slurry undergoes a single filtration to achieve solid-liquid separation, allowing most of the sodium oxide and alumina-containing solution to be discharged. Under pressure, fresh hot water is added to the solids remaining after the first filtration to soak them again, followed by a second filtration to remove any residual alkali and aluminum. Through this two-filtration and one-washing process, alkali and alumina are recovered from the mixed slurry, while the filtrate containing alkali and aluminum can be directly sent to an alumina red mud settling system for recycling.

[0042] In some embodiments, the conditioning agent includes at least one of the following: citric acid, citrate, gluconate, tannic acid, or aminocarboxylate;

[0043] In the above embodiments, citrate is one or more of calcium citrate, ferric citrate, magnesium citrate, and ammonium citrate; gluconate is a mixture of calcium gluconate and sodium gluconate; and aminocarboxylate is one or more of trisodium aminetriacetate, tetrasodium ethylenediaminetetraacetate, and magnesium disodium ethylenediaminetetraacetate.

[0044] In some implementations, the mass of the conditioning agent is 0.005% to 0.5% of the mass of the calcium-based solid waste slurry desulfurizer.

[0045] In the above embodiments, the reason for controlling the mass of the conditioning agent to be 0.005%~0.5% of the mass of the calcium-based solid waste slurry desulfurizer is that the conditioning agent can change the desulfurization efficiency of the calcium-based solid waste slurry desulfurizer slurry, enhance the agglomeration and precipitation performance of impurities, improve the desulfurization performance of calcium aluminate, and at the same time break up the aggregation of carbon and active silicon in the slurry, reduce slurry foaming, and promote the discharge of aluminum ions. When the mass of the conditioning agent is greater than 0.5% of the mass of the calcium-based solid waste slurry desulfurizer, it not only wastes the conditioning agent, but also causes more substances to enter the calcium-based solid waste slurry desulfurizer slurry, resulting in a decrease in desulfurization efficiency. When the mass of the conditioning agent is less than 0.005% of the mass of the calcium-based solid waste slurry desulfurizer, the conditioning effect of the conditioning agent on the calcium-based solid waste slurry desulfurizer slurry is not significant, and it does not change the desulfurization efficiency and slurry desulfurization performance.

[0046] Secondly, based on a general inventive concept, this disclosure provides a desulfurizing agent prepared using the preparation method of the calcium-based solid waste slurry desulfurizing agent described in the first aspect.

[0047] The desulfurizing agent is prepared using the preparation method of the calcium-based solid waste slurry desulfurizing agent described above. The steps of the preparation method of this calcium-based solid waste slurry desulfurizing agent can be referred to the above embodiments. Since the desulfurizing agent has all the technical features of some of the above embodiments, it has at least all the beneficial effects brought about by some of the above embodiments, and will not be repeated here.

[0048] Thirdly, this disclosure provides a desulfurization method, including:

[0049] The second aspect is the calcium-based solid waste slurry desulfurizer;

[0050] The calcium-based solid waste slurry desulfurizing agent is reacted with the flue gas to be desulfurized to obtain desulfurization slurry;

[0051] The pH range for the desulfurization reaction is 4.8 to 6.2.

[0052] In the above embodiments, the calcium-based solid waste slurry desulfurizer reacts with flue gas to achieve desulfurization, enabling the recycling and reuse of the calcium-based solid waste slurry. Simultaneously, the addition of a conditioning agent to the calcium-based solid waste slurry desulfurizer also achieves the following effects: the addition of the conditioning agent not only reduces the enrichment of aluminum ions in calcium aluminate and its hydrates in the desulfurization slurry, allowing aluminum ions to be discharged from the desulfurization system along with desulfurization byproducts; it also reduces the impact of sodium on desulfurization efficiency, decreases the sodium-calcium enrichment reaction in the desulfurization system, and reduces clogging and scaling in the desulfurization system; finally, the addition of the conditioning agent also improves the filtration performance of the desulfurization slurry, reduces the silicon-aluminum agglomeration properties of the desulfurization slurry, breaks down the gelling properties of active silicon, aluminum, and magnesium in the desulfurization slurry, and reduces the moisture content of desulfurization byproducts. For example, the pH of the desulfurization reaction can be 4.8, 4.9, 5.0, 5.1, 5.2, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1 or 6.2.

[0053] In some embodiments, a calcium-based solid waste slurry desulfurizing agent is reacted with the flue gas to be desulfurized to obtain a desulfurized slurry, comprising:

[0054] The calcium-based solid waste slurry desulfurizing agent is fed into the desulfurization reactor and undergoes a reverse desulfurization reaction with the flue gas to be desulfurized to obtain desulfurized slurry.

[0055] In the above embodiments, the reverse desulfurization reaction can ensure that the flue gas to be desulfurized is in full contact with the desulfurizing agent, thereby maximizing the desulfurization reaction.

[0056] In some implementations, the temperature of the flue gas to be desulfurized in the desulfurization reaction is 50℃~150℃.

[0057] In the above embodiments, the temperature of the flue gas to be desulfurized is controlled at 50℃~150℃ because temperature affects desulfurization efficiency and sulfur fixation. When the flue gas temperature exceeds 150℃, the reaction temperature is too high, the evaporation of the desulfurization slurry is large, the solid-liquid ratio is difficult to control, and the desulfurization efficiency decreases; when the flue gas temperature is below 50℃, the flue gas desulfurization efficiency is slow, and the amount of desulfurization slurry used is large. For example, the temperature of the flue gas to be desulfurized in the desulfurization reaction is 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, or 150℃.

[0058] In some embodiments, after reacting the calcium-based solid waste slurry desulfurizing agent with the flue gas to be desulfurized to obtain a desulfurized slurry, the process further includes:

[0059] The desulfurization slurry is subjected to solid-liquid separation to obtain desulfurization solution and desulfurization solid slag.

[0060] In the above embodiments, the desulfurization solution contains excess alkali, aluminum, silicon, and other substances. These excess alkali, aluminum, silicon, and other substances can participate in the preparation process of calcium-based solid waste slurry desulfurization agents, or they can be neutralized and used for later use. The main components of the desulfurization solid slag are calcium sulfate, calcium oxide, silicon oxide, aluminum oxide, etc. The pH value of the desulfurization solid slag is 6-9, which can be used as a soil modifier.

[0061] In some implementations, when the desulfurization solution meets the set conditions, the desulfurization solution is neutralized to obtain secondary desulfurization solid slag.

[0062] The set conditions include: the total mass concentration of sodium and aluminum in the desulfurization solution is >25 g / L.

[0063] In the above embodiments, when the total mass concentration of sodium and aluminum in the desulfurization solution is less than or equal to 25 g / L, the desulfurization solution can be used to prepare calcium-based solid waste slurry desulfurizing agent, for example, in combination with a conditioning agent; while when the total mass concentration of sodium and aluminum in the desulfurization solution is greater than 25 g / L, a neutralization reaction is first required to remove sodium and aluminum from the filtrate and reduce the sodium and aluminum content in the filtrate.

[0064] In some embodiments, the desulfurization solution is neutralized, including: adding a neutralizing agent to the desulfurization solution and reacting; and performing solid-liquid separation on the desulfurization solution after the reaction to obtain secondary desulfurization solid residue and wash water filtrate.

[0065] The neutralizing agent includes at least one of lime, calcium silicate slag, and calcium silicate.

[0066] In the above embodiments, one or more of lime, calcium silicate slag and calcium silicate are used as neutralizing agents to react with the desulfurization solution. The calcium component in the neutralizing agent can react with sodium ions and aluminum ions in the desulfurization solution to generate calcium sulfate and aluminum hydroxide precipitates, thereby achieving the discharge of impurities.

[0067] In some implementations, the wash water filtrate can be incorporated into the desulfurizing agent preparation process and mixed with calcium-based solid waste slurry for recycling.

[0068] In some embodiments, the neutralization reaction is carried out at a temperature of 40°C to 100°C, the mass ratio of the desulfurization solution to the neutralizing agent is 10:(0.1~1.5), and the pH value of the reaction system is controlled at 7.2~10.5.

[0069] In the above embodiments, the reaction temperature is controlled at 40℃~100℃ because temperature affects the efficiency of the neutralization reaction. When the reaction temperature is below 40℃, the reaction rate is too slow, the reaction is incomplete, more neutralizing reagent needs to be added, and the cost is high; for example, the reaction temperature can be 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃.

[0070] Fourthly, this disclosure provides a soil remediation agent comprising desulfurization solids and / or secondary desulfurization solids, wherein the desulfurization solids and / or secondary desulfurization solids are prepared by the desulfurization method of the third aspect.

[0071] In the above embodiments, the desulfurization solid slag mainly contains calcium sulfate, calcium oxide, silicon dioxide, aluminum oxide, etc., and the pH value of the desulfurization solid slag is 6-9; the main components of the secondary desulfurization solid slag are calcium sulfate, calcium sulfite, aluminum sulfate, and silicon dioxide, and the pH value of the secondary desulfurization solid slag is 7.5-10. Both the desulfurization solid slag and the secondary desulfurization solid slag can be used as soil remediation agents.

[0072] In some embodiments, the soil remediation agent, by weight, may include 1-7 parts of desulfurization solid slag and / or secondary desulfurization solid slag, 10-25 parts of red mud, 1-3 parts of wood ash, and 1-6 parts of soil. In other embodiments, the soil remediation agent, by weight, may include 1-7 parts of desulfurization solid slag and / or secondary desulfurization solid slag, 10-25 parts of red mud, 1-3 parts of wood ash, and 2-6 parts of soil.

[0073] The reasons for controlling the mass fraction of the soil remediation agent in the above embodiments are as follows: Red mud is a clay mineral, mainly composed of silicates, iron oxide, aluminum hydroxide, and other substances; wood ash mainly contains carbonates and trace elements, which can adjust the soil pH and improve soil structure. Red mud and wood ash can be used in combination with desulfurization solids and / or secondary desulfurization solids as remediation agents for alkaline polluted sites.

[0074] The present disclosure is further illustrated below with reference to the embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0075] The experimental conditions for the desulfurization reaction in the following examples and comparative examples are as follows: the concentration of SO2 in the flue gas to be desulfurized is 1000 mg / m3 to 10000 mg / m3, and the pH value of the desulfurization slurry is lower than 4.8 as the control index for the desulfurization reaction time.

[0076] Example 1

[0077] This embodiment provides a desulfurizing agent, the preparation method of which includes the following steps:

[0078] S1. The calcium-based solid waste slurry is fed into a pre-settling tank for settling to obtain the underflow of the settling tank (i.e., the calcium-based solid waste slurry underflow); the underflow of the settling tank is sent to an alkali recovery reaction tank and diluted with hot water and stirred for 0.5 hours to obtain the calcium-based solid waste slurry reaction liquid; wherein, the temperature of the calcium-based solid waste slurry reaction liquid is 70℃ and the solid-liquid ratio is 0.4;

[0079] S2. Add a phase change inhibitor to the calcium-based solid waste slurry reaction solution to obtain a mixed slurry; wherein, the amount of phase change inhibitor is 0.05% of the total mass of sodium and aluminum in the reaction solution; by mass, the phase change inhibitor includes 3 parts calcium gluconate, 5 parts potassium gluconate and 2 parts cellulose.

[0080] S3. The mixed slurry is subjected to pressure filtration, washing, and further pressure filtration in a primary liquid-solid separation device to obtain primary filtrate and solid phase material;

[0081] S4. Mix the solid material with water, adjust the temperature to 65℃, and add a conditioning agent to obtain a calcium-based solid waste slurry desulfurizer with a pH value of 8.2; wherein the mass of the conditioning agent accounts for 0.01% of the total mass of the calcium-based solid waste slurry desulfurizer; by mass, the conditioning agent includes 1 part calcium citrate, 1 part sodium citrate, 3 parts disodium magnesium ethylenediaminetetraacetate, and 0.5 parts each of calcium gluconate and sodium gluconate.

[0082] The obtained calcium-based solid waste slurry desulfurizing agent is used in a desulfurization reaction, which includes the following steps:

[0083] The prepared calcium-based solid waste slurry desulfurizing agent is sent to the desulfurization reactor and undergoes a reverse desulfurization reaction with the flue gas to be desulfurized at 50°C to obtain desulfurization slurry.

[0084] When the pH value of the desulfurization slurry is lower than 4.8, the desulfurization slurry is sent to a secondary solid-liquid separation device for solid-liquid separation to obtain desulfurization solution and desulfurization solid slag.

[0085] The sodium and aluminum content in the desulfurization solution does not exceed 25 g / L, so the desulfurization solution can be used directly as a feed water for solid substances.

[0086] Desulfurization solidified slag is used in the preparation of soil remediation agents and can be used as a component of soil ecological remediation agents for alkaline polluted sites. By weight, the soil ecological remediation agent includes: 2 parts desulfurization solidified slag, 12 parts red mud, 1.3 parts wood ash, and 2.6 parts soil.

[0087] Chemical analysis of the desulfurization solid slag (unless otherwise specified, all components of the desulfurization solid slag are calculated on a dry basis) revealed that the desulfurization solid slag contained 35.1% sulfur, 0.02% sodium oxide, 0.49% aluminum oxide, and 7.8% moisture.

[0088] Example 2

[0089] This embodiment provides a desulfurizing agent, the preparation method of which includes the following steps:

[0090] S1. Calcium-based solid waste slurry is fed into a pre-settling tank for settling to obtain the underflow of the settling tank (i.e., calcium-based solid waste slurry underflow); the underflow of the settling tank is sent to an alkali recovery reaction tank and diluted with hot water and stirred for 3 hours to obtain calcium-based solid waste slurry reaction liquid; wherein, the temperature of the calcium-based solid waste slurry reaction liquid is 90℃ and the solid-liquid ratio is 0.3.

[0091] S2. Add a phase change inhibitor to the calcium-based solid waste slurry reaction solution to obtain a mixed slurry; wherein, the amount of phase change inhibitor is 0.11% of the total mass of sodium and aluminum in the reaction solution; by mass, the phase change inhibitor includes 1 part calcium gluconate, 5 parts potassium gluconate, 3 parts cellulose, 0.5 parts calcium lignosulfonate, and 0.1 parts sodium humate.

[0092] S3. The mixed slurry is subjected to pressure filtration, washing, and further pressure filtration in a primary liquid-solid separation device to obtain primary filtrate and solid phase material;

[0093] S4. Mix the solid material with water, control the temperature at 80℃, and add a conditioning agent to obtain a calcium-based solid waste slurry desulfurizer with a pH value of 7; wherein the mass of the conditioning agent is 0.5% of the total mass of the calcium-based solid waste slurry desulfurizer; by mass, the conditioning agent includes 3 parts of ammonium citrate, 0.8 parts of trisodium aminetriacetate, 3 parts of magnesium disodium ethylenediaminetetraacetate, and 0.5 parts each of calcium gluconate and sodium gluconate.

[0094] The obtained calcium-based solid waste slurry desulfurizing agent is used in a desulfurization reaction, which includes the following steps:

[0095] The prepared calcium-based solid waste slurry desulfurizing agent is sent to the desulfurization reactor and undergoes a reverse desulfurization reaction with the flue gas to be desulfurized at 60°C to obtain desulfurization slurry.

[0096] When the pH value of the desulfurization slurry is lower than 4.8, the desulfurization slurry is sent to a secondary solid-liquid separation device for solid-liquid separation to obtain desulfurization solution and desulfurization solid slag.

[0097] The sodium and aluminum content in the desulfurization solution does not exceed 25 g / L, so the desulfurization solution can be used directly as a feed water for solid substances.

[0098] Desulfurization solidified slag is used in the preparation of soil remediation agents and can be used as a component of soil ecological remediation agents for alkaline polluted sites. By weight, the soil ecological remediation agent includes: 1 part desulfurization solidified slag, 25 parts red mud, 3 parts wood ash, and 4 parts soil.

[0099] Chemical analysis of the desulfurization solid slag revealed that it contained 36.2% sulfur, 0.015% sodium oxide, 0.4% aluminum oxide, and 7.0% moisture.

[0100] Example 3

[0101] This embodiment provides a desulfurizing agent, the preparation method of which includes the following steps:

[0102] S1. Calcium-based solid waste slurry is fed into a pre-settling tank for settling to obtain the underflow of the settling tank (i.e., calcium-based solid waste slurry underflow); the underflow of the settling tank is sent to an alkali recovery reaction tank and diluted with hot water and stirred for 5 hours to obtain calcium-based solid waste slurry reaction liquid; wherein, the temperature of the calcium-based solid waste slurry reaction liquid is 95℃ and the solid-liquid ratio is 1.

[0103] S2. Add a phase change inhibitor to the calcium-based solid waste slurry reaction solution to obtain a mixed slurry; wherein, the amount of phase change inhibitor is 0.15% of the total mass of sodium and aluminum in the reaction solution; by mass, the phase change inhibitor includes 0.1 parts calcium gluconate, 0.5 parts potassium gluconate, 2 parts cellulose, 1 part calcium lignosulfonate, and 0.5 parts sodium humate.

[0104] S3. The mixed slurry is subjected to pressure filtration, washing, and further pressure filtration in a primary liquid-solid separation device to obtain primary filtrate and solid phase material;

[0105] S4. Mix the solid material with water, control the temperature at 90℃, and then add a conditioning agent to obtain a calcium-based solid waste slurry desulfurizing agent with a pH value of 10. The mass of the conditioning agent is 0.005% of the total mass of the calcium-based solid waste slurry desulfurizing agent. By mass, the conditioning agent includes 2 parts sodium citrate, 1 part ferric citrate, 1 part tetrasodium ethylenediaminetetraacetate, and 0.5 parts each of calcium gluconate and sodium gluconate.

[0106] The obtained calcium-based solid waste slurry desulfurizing agent is used in a desulfurization reaction, which includes the following steps:

[0107] The prepared calcium-based solid waste slurry desulfurizing agent is sent to the desulfurization reactor and undergoes a reverse desulfurization reaction with the flue gas to be desulfurized at 150°C to obtain desulfurization slurry.

[0108] When the pH value of the desulfurization circulating slurry is lower than 4.8, the desulfurization slurry is sent to a secondary solid-liquid separation unit for solid-liquid separation to obtain desulfurization solution and desulfurization solid slag.

[0109] The sodium and aluminum content in the desulfurization solution does not exceed 25 g / L, so the desulfurization solution can be used directly as a feed water for solid substances.

[0110] Desulfurization solidified slag is used in the preparation of soil remediation agents and can be used as a component of soil ecological remediation agents for alkaline polluted sites. By weight, the soil ecological remediation agent includes: 7 parts desulfurization solidified slag, 20 parts red mud, 1.5 parts wood ash, and 6 parts soil.

[0111] Chemical analysis of the desulfurization solid slag revealed that it contained 36.7% sulfur, 0.02% sodium oxide, 0.5% aluminum oxide, and 8% moisture.

[0112] Example 4

[0113] This embodiment provides a desulfurizing agent, the preparation method of which includes the following steps:

[0114] S1. The calcium-based solid waste slurry is fed into a pre-settling tank for settling to obtain the underflow of the settling tank (i.e., the calcium-based solid waste slurry underflow); the underflow of the settling tank is sent to an alkali recovery reaction tank and diluted with hot water and stirred for 3.5 hours to obtain the calcium-based solid waste slurry reaction liquid; wherein, the temperature of the calcium-based solid waste slurry reaction liquid is 100℃ and the solid-liquid ratio is 0.6;

[0115] S2. Add a phase change inhibitor to the calcium-based solid waste slurry reaction solution to obtain a mixed slurry; wherein, the amount of phase change inhibitor accounts for 0.08% of the total mass of sodium and aluminum in the reaction solution; by mass, the phase change inhibitor includes 1 part calcium gluconate, 0.8 parts cellulose, and 2 parts calcium lignosulfonate.

[0116] S3. The mixed slurry is subjected to pressure filtration, washing, and further pressure filtration in a primary liquid-solid separation device to obtain primary filtrate and solid phase material;

[0117] S4. Mix the solid material with water, control the temperature at 75℃, and add a conditioning agent to obtain a calcium-based solid waste slurry desulfurizing agent with a pH value of 8.1; wherein the mass of the conditioning agent is 0.01% of the total mass of the calcium-based solid waste slurry desulfurizing agent; by mass, the conditioning agent includes 2 parts of sodium citrate, 0.5 parts of trisodium aminetriacetate, 0.5 parts of tetrasodium ethylenediaminetetraacetate, 1.2 parts each of calcium gluconate and sodium gluconate, and 0.6 parts of tannic acid.

[0118] The obtained calcium-based solid waste slurry desulfurizing agent is used in a desulfurization reaction, which includes the following steps:

[0119] The prepared calcium-based solid waste slurry desulfurizing agent is sent to the desulfurization reactor and reacted with the flue gas to be desulfurized at 100°C in a reverse desulfurization reaction to obtain desulfurization slurry.

[0120] When the pH value of the desulfurization slurry is lower than 4.8, the desulfurization slurry is sent to a secondary solid-liquid separation device for solid-liquid separation to obtain desulfurization solution and desulfurization solid slag.

[0121] The sodium and aluminum content in the desulfurization solution exceeds 25 g / L. The desulfurization solution is neutralized with lime, and the mass ratio of desulfurization solution to neutralizing agent lime is controlled at 10:0.1. The reaction temperature is 40℃ and the reaction time is 5 h. The desulfurization solution after the reaction is sent to a three-stage solid-liquid separation device to obtain washing water filtrate and secondary desulfurization solid residue.

[0122] The wash water filtrate is sent to a pre-sedimentation tank and then enters the sedimentation or dilution process of calcium-based solid waste slurry to achieve the recycling of process water and alkaline components. The secondary desulfurization solid slag and the desulfurization solid slag mixture participate in the preparation of soil remediation agents and can also serve as components of soil ecological remediation agents for alkaline polluted sites. By weight, the soil ecological remediation agent comprises: 7 parts desulfurization solid slag and secondary desulfurization solid slag mixture, 17 parts red mud, 2 parts wood ash, and 2.5 parts soil.

[0123] Chemical analysis of the desulfurization solid slag revealed that it contained 35.5% sulfur, 0.018% sodium oxide, 0.45% aluminum oxide, and 7.5% moisture.

[0124] Example 5

[0125] This embodiment provides a desulfurizing agent, the preparation method of which includes the following steps:

[0126] S1. The calcium-based solid waste slurry is fed into a pre-settling tank for settling to obtain the underflow of the settling tank (i.e., the calcium-based solid waste slurry underflow); the underflow of the settling tank is sent to an alkali recovery reaction tank and diluted with hot water and stirred for 2 hours to obtain the calcium-based solid waste slurry reaction liquid; wherein, the temperature of the calcium-based solid waste slurry reaction liquid is 88℃ and the solid-liquid ratio is 0.75.

[0127] S2. Add a phase change inhibitor to the calcium-based solid waste slurry reaction solution to obtain a mixed slurry; wherein, the amount of phase change inhibitor is 0.06% of the total mass of sodium and aluminum in the reaction solution; by mass, the phase change inhibitor includes 1.5 parts calcium gluconate, 1.2 parts cellulose, 1.8 parts calcium lignosulfonate, and 0.1 parts sodium humate.

[0128] S3. The mixed slurry is subjected to pressure filtration, washing, and further pressure filtration in a primary liquid-solid separation device to obtain primary filtrate and solid phase material;

[0129] S4. Mix the solid material with water, control the temperature at 68℃, and add a conditioning agent to obtain a calcium-based solid waste slurry desulfurizer with a pH value of 7.6; wherein the mass of the conditioning agent is 0.09% of the total mass of the calcium-based solid waste slurry desulfurizer; by mass, the conditioning agent includes 1 part sodium citrate, 1.2 parts each of calcium gluconate and sodium gluconate, 0.5 parts of trisodium aminetriacetate, and 0.9 parts of disodium magnesium ethylenediaminetetraacetate.

[0130] The obtained calcium-based solid waste slurry desulfurizing agent is used in a desulfurization reaction, which includes the following steps:

[0131] The prepared calcium-based solid waste slurry desulfurizing agent is sent to the desulfurization reactor and undergoes a reverse desulfurization reaction with the flue gas to be desulfurized at 70°C to obtain desulfurization slurry.

[0132] When the pH value of the desulfurization slurry is lower than 4.8, the desulfurization slurry is sent to a secondary solid-liquid separation device for solid-liquid separation to obtain desulfurization solution and desulfurization solid slag.

[0133] The sodium and aluminum content in the desulfurization solution exceeds 25 g / L. The desulfurization solution is neutralized with a mixture of 0.5 parts lime, 1 part calcium silicate slag, and 0.5 parts calcium silicate by mass. The mass ratio of the desulfurization solution to the above neutralizing reagent mixture is controlled at 10:1.5, the reaction temperature is 100℃, and the reaction time is 1 hour. The desulfurization solution after the reaction is sent to a three-stage solid-liquid separation device to obtain wash water filtrate and secondary desulfurization solid slag.

[0134] The wash water filtrate is sent to a pre-sedimentation tank and then enters the sedimentation or dilution process of the calcium-based solid waste slurry to achieve the recycling of process water and alkaline components. The secondary desulfurization solid slag and the desulfurization solid slag mixture participate in the preparation of soil remediation agents and can also serve as components of soil ecological remediation agents for alkaline polluted sites. By weight, the soil ecological remediation agent comprises: 5 parts of desulfurization solid slag and the secondary desulfurization solid slag mixture, 13 parts of red mud, 3 parts of wood ash, and 1 part of soil.

[0135] Chemical analysis of the desulfurization solid slag revealed that the calcium-based solid waste slag contained 37.1% sulfur, 0.01% sodium oxide, 0.39% aluminum oxide, and 7.3% moisture.

[0136] Comparative Example 1

[0137] This comparative example provides a desulfurizing agent, which is prepared in the same way as in Example 5. The only difference is that no phase change inhibitor is added in this comparative example. Instead, a conditioning agent is directly added to the calcium-based solid waste slurry reaction liquid to obtain the calcium-based solid waste slurry desulfurizing agent.

[0138] The prepared calcium-based solid waste slurry desulfurizing agent was used for desulfurization reaction. The reaction steps were the same as those in Example 5. The final results showed that the sulfur content of the desulfurized solid slag in this comparative example was 22.4%, the sodium oxide content was 1.7%, the alumina content was 2.5%, and the water content was 20.6%.

[0139] Comparative Example 2

[0140] This comparative example provides a desulfurizing agent, the preparation method of which is the same as that in Example 5. The only difference is that no conditioning agent is added in this comparative example. The solid phase material after filtering the mixed slurry is directly mixed with water to obtain a calcium-based solid waste slurry desulfurizing agent.

[0141] The prepared calcium-based solid waste slurry desulfurizing agent was used for desulfurization reaction. The reaction steps were the same as those in Example 5. The final results showed that the sulfur content of the desulfurized solid slurry in this comparative example was 26.8%, the sodium oxide content was 0.05%, the alumina content was 1.2%, and the water content was 25.9%.

[0142] Comparative Example 3

[0143] This comparative example provides a desulfurizing agent, the preparation method of which is the same as that in Example 5. The only difference is that no phase change inhibitor and conditioning agent are added in this comparative example. The solid phase material is obtained by directly separating the solid and liquid of the calcium-based solid waste slurry reaction liquid. Then the solid phase material is mixed with water as a calcium-based solid waste slurry desulfurizing agent.

[0144] The prepared calcium-based solid waste slurry desulfurizing agent was used for desulfurization reaction. The reaction steps were the same as those in Example 5. The final results showed that the sulfur content of the desulfurized solid slurry in this comparative example was 20.8%, the sodium oxide content was 2.2%, the alumina content was 2.8%, and the water content was 37.1%.

[0145] Comparative Example 4

[0146] This comparative example provides a desulfurizing agent, which is prepared in the same way as in Example 5. The only difference is that the mixed slurry obtained by adding a phase change inhibitor in this comparative example does not undergo solid-liquid separation, and a conditioning agent is directly added to obtain a calcium-based solid waste slurry desulfurizing agent.

[0147] The prepared calcium-based solid waste slurry desulfurizing agent was used for desulfurization reaction. The reaction steps were the same as those in Example 5. The final results showed that the sulfur content of the desulfurized solid slurry in this comparative example was 27.3%, the sodium oxide content was 0.19%, the alumina content was 0.78%, and the water content was 9.2%.

[0148] Comparative Example 5

[0149] This comparative example provides a desulfurizing agent, the preparation method of which includes the following steps:

[0150] Calcium-based solid waste slurry was fed into a pre-settling tank for settling, yielding the underflow (i.e., calcium-based solid waste slurry underflow). The calcium-based solid waste slurry underflow was directly subjected to liquid-solid separation. The solid residue obtained after liquid-solid separation was mixed with water to prepare a calcium-based solid waste slurry desulfurizing agent, with the liquid-to-solid ratio the same as in Example 5. The above-mentioned fresh calcium-based solid waste slurry desulfurizing agent was then reacted with sulfur-containing flue gas. Analysis showed that the sulfur content of the desulfurized solid residue in this comparative example was 15.7%, the sodium oxide content was 2.5%, the alumina content was 4.7%, and the water content was 55%.

[0151] In summary, Examples 1-5 all used the desulfurizing agent preparation method provided in this disclosure to prepare the desulfurizing agent and conducted desulfurization experiments. The results showed that the sulfur content of the obtained desulfurized solid slag was greater than 35%, and the contents of sodium oxide and aluminum oxide were less than 1%. In contrast, Comparative Examples 1-5 replaced some of the technical means in Example 5 of this disclosure to prepare the desulfurizing agent. Compared with Example 5, the sulfur content was reduced, and the contents of sodium oxide and aluminum oxide in the desulfurized solid slag were higher. The reasons are analyzed as follows:

[0152] In Comparative Example 1, no phase change inhibitor was added during the preparation of the desulfurizer, thus the composition of the calcium-based solid waste slurry reaction liquid remained unchanged. Although a conditioning agent was added during the preparation of the desulfurizer, a large amount of alumina and sodium oxide entered the desulfurization system. Simultaneously, the solid phase contained substances such as calcium aluminate and hydrated alumina, limiting the conditioning effect. Consequently, the prepared desulfurizer affected the flue gas desulfurization efficiency and reduced the amount of sulfur fixed.

[0153] The desulfurizing agent provided in Comparative Example 2 was prepared without the addition of a conditioning agent. During the desulfurization process, as the desulfurization reaction proceeds, impurities begin to accumulate, the filtration performance of the desulfurizing agent slurry deteriorates, the desulfurization efficiency is affected, the contact area between the desulfurizing agent slurry and the flue gas decreases, leading to a decline in desulfurization performance and an increase in the moisture content of the desulfurization solid slag.

[0154] The desulfurizing agent provided in Comparative Example 3 is prepared by: diluting the sedimentation underflow of calcium-based solid waste slurry with hot water and stirring for 2 hours to obtain a calcium-based solid waste slurry reaction liquid; separating the solid and liquid phases of the obtained calcium-based solid waste slurry reaction liquid to obtain a solid phase substance; and mixing the solid phase substance with water as a desulfurizing agent. Since this preparation process does not introduce phase change inhibitors and conditioning agents, although the desulfurizing agent reduces the sodium oxide content in the solid phase substance to some extent after liquid-solid separation, it does not change the compositional properties of the solid phase substance. The solid phase substance still contains a relatively large amount of calcium aluminate, calcium aluminate hydrate, calcium aluminate hydrate, calcium hydroxide, sodium carbonate, and sodium hydroxide. When this desulfurizing agent is used in the desulfurization reaction, as the desulfurization reaction continues, soluble salts in the desulfurization slurry will continuously accumulate, increasing the viscosity of the desulfurization slurry, reducing the desulfurization efficiency, and resulting in poor desulfurization performance.

[0155] The desulfurizer provided in Comparative Example 4 had a phase change inhibitor added during its preparation. Because the mixed slurry was not separated into solid and liquid components after the addition of the phase change inhibitor, the alumina and sodium oxide in the slurry directly entered the desulfurization system. Compared to the examples, although the addition of the conditioning agent reduced the impact of impurities such as aluminum and sodium on the desulfurization process, it still reduced the amount of solidified sulfur. Furthermore, compared to Comparative Example 2 without the addition of a conditioning agent, it also shows that the addition of the conditioning agent helps improve the desulfurization performance of the slurry containing aluminum and sodium impurities and helps reduce the moisture content of the desulfurized solid slag.

[0156] The desulfurizing agent provided in Comparative Example 5 is prepared by: directly separating the calcium-based solid waste slurry sedimentation underflow into a solid phase to obtain a solid substance; and mixing the solid substance with water to obtain the desulfurizing agent. Because the solid substance obtained from the liquid-solid separation contains a large amount of components such as calcium aluminate, calcium aluminate hydrate, calcium aluminate hydrate, calcium hydroxide, sodium carbonate, and sodium hydroxide, soluble salts continuously accumulate in the desulfurization slurry, increasing the viscosity of the desulfurization slurry and reducing the desulfurization efficiency. Simultaneously, it leads to difficulties in filtering the desulfurization byproduct calcium sulfate (gypsum), resulting in poor desulfurization performance and a smaller amount of sulfur dioxide captured in the flue gas to be desulfurized.

[0157] In summary, this disclosure provides a method for preparing a calcium-based solid waste slurry desulfurizing agent, comprising: settling the calcium-based solid waste slurry to obtain a calcium-based solid waste slurry underflow and a settling tank overflow; sending the settling overflow to an alumina slurry dilution tank, adding hot water and a phase change inhibitor to the calcium-based solid waste slurry settling underflow to obtain a mixed slurry; separating the mixed slurry into solid and liquid phases to obtain a filter cake (i.e., solid phase material) and a filtrate; sending the filtrate to an alumina red mud settling separation and washing system, mixing the filter cake with water and adding a conditioning agent to obtain a calcium-based solid waste slurry desulfurizing agent; reacting the calcium-based solid waste slurry desulfurizing agent with flue gas to obtain a desulfurized slurry; after solid-liquid separation of the desulfurized slurry, obtaining a desulfurization solution and a desulfurized solid slag; after neutralization reaction treatment of the desulfurization solution, undergoing solid-liquid separation to obtain a wash water filtrate and a secondary desulfurized solid slag; and preparing a soil ecological restoration agent from the desulfurized solid slag and the secondary desulfurized solid slag. This disclosure utilizes calcium-based solid waste slurry emitted during alumina production to prepare a desulfurizing agent. This not only recovers alkali resources and reduces alumina loss, but also allows the desulfurizing agent to be used for flue gas desulfurization, achieving the goal of resource utilization of solid waste. It has the value and significance of pollution reduction, carbon reduction, and synergistic efficiency enhancement.

[0158] The above are merely specific embodiments of this disclosure, enabling those skilled in the art to understand or implement this disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined in this disclosure may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this disclosure.

Claims

1. A method for preparing a calcium-based solid waste slurry desulfurization agent, comprising: A calcium-based solid waste slurry reaction solution was obtained; A phase change inhibitor was added to the calcium-based solid waste slurry reaction solution to obtain a mixed slurry; The mixed slurry is subjected to solid-liquid separation to obtain a solid phase; and The solid substance is mixed with water and a conditioning agent to obtain a calcium-based solid waste slurry desulfurizing agent; The pH value of the calcium-based solid waste slurry desulfurizer is 7-10.

2. The preparation method according to claim 1, wherein, The obtained calcium-based solid waste slurry reaction solution includes: The calcium-based solid waste slurry is settled to obtain the calcium-based solid waste slurry underflow; The calcium-based solid waste slurry underflow is diluted to obtain a calcium-based solid waste slurry reaction solution, wherein the solid-liquid ratio of the calcium-based solid waste slurry reaction solution is (0.1~1):

1.

3. The preparation method according to claim 1, wherein, The mass of the phase change inhibitor added to the calcium-based solid waste slurry reaction solution is 0.02% to 0.15% of the total mass of sodium and aluminum in the calcium-based solid waste slurry reaction solution; And / or, The phase change inhibitor includes at least one of the following: glycoside, cellulose, calcium lignosulfonate, and sodium humate.

4. The preparation method according to claim 1, wherein, The conditioning agent includes at least one of the following: citric acid, citrate, gluconate, tannic acid, and aminocarboxylate; And / or, The mass of the conditioning agent is 0.005% to 0.5% of the total mass of the calcium-based solid waste slurry desulfurizer.

5. A calcium-based solid waste slurry desulfurizer, prepared by the method described in any one of claims 1 to 4.

6. A desulfurization method for the calcium-based solid waste slurry desulfurizer as described in claim 5, comprising: The calcium-based solid waste slurry desulfurizing agent is reacted with the flue gas to be desulfurized to obtain a desulfurized slurry. The pH of the desulfurization reaction is 4.8~6.

2.

7. The desulfurization method according to claim 6, further comprising, after reacting the calcium-based solid waste slurry desulfurizing agent with the flue gas to be desulfurized to obtain a desulfurized slurry: The desulfurization slurry is subjected to solid-liquid separation to obtain a desulfurization solution and a desulfurization solid residue.

8. The desulfurization method according to claim 7, wherein, When the desulfurization solution meets the set conditions, the desulfurization solution is subjected to a neutralization reaction to obtain secondary desulfurization solid slag; The set conditions include: the total mass concentration of sodium and aluminum in the desulfurization solution is >25 g / L.

9. A soil remediation agent comprising desulfurization solidification slag and / or secondary desulfurization solidification slag, wherein, The desulfurized solid slag is obtained by the desulfurization method according to claim 7, and the secondary desulfurized solid slag is obtained by the desulfurization method according to claim 8.

10. The soil remediation agent according to claim 9, wherein, By weight, it includes 1-7 parts of the desulfurization solid slag and / or the secondary desulfurization solid slag, 10-25 parts of red mud, 1-3 parts of wood ash, and 2-6 parts of soil.

11. The soil remediation agent according to claim 9, wherein, By weight, it includes 1-7 parts of the desulfurization solid slag and / or the secondary desulfurization solid slag, 10-25 parts of red mud, 1-3 parts of wood ash, and 1-6 parts of soil.

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