A desulfurized gypsum-fly ash based mayenite-based chlorine scavenger and a preparation method thereof

Abstract

This invention provides a calcium aluminate-based dechlorination agent based on desulfurized gypsum and fly ash, and its preparation method. The agent uses industrial solid waste desulfurized gypsum and fly ash as main raw materials, and particularly relates to a calcium aluminate-based dechlorination agent prepared using desulfurized gypsum and fly ash as main raw materials, and its preparation method. Addressing the technical problems of existing calcium aluminate-based dechlorination agents, such as high cost due to reliance on natural minerals for raw materials, low utilization rate of the high-value industrial solid waste desulfurized gypsum and fly ash, and insufficient stability of dechlorination performance due to the influence of the preparation process, this invention prepares a highly crystalline calcium aluminate dechlorination agent by controlling the raw material ratio, the type of activator, and the calcination process. This achieves the dual goals of solid waste resource utilization and efficient treatment of chlorine-containing wastewater, while simultaneously reducing the preparation cost of the dechlorination agent and improving its dechlorination efficiency and performance stability.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment and solid waste resource utilization technology, specifically to a calcium aluminum stone-based dechlorination agent and its preparation method, and more particularly to a calcium aluminum stone-based dechlorination agent and its preparation method prepared using desulfurized gypsum and fly ash as main raw materials. Background Technology

[0002] High chloride ion content in industrial chlorinated wastewater (such as circulating water or process wastewater discharged from the power, chemical, and metallurgical industries) can easily cause equipment corrosion and water quality deterioration, seriously affecting production safety and environmental quality. Therefore, efficient treatment with dechlorination agents is necessary. Calcium aluminum silicate, due to its excellent adsorption and complexation capabilities for chloride ions, has become a research hotspot in the field of dechlorination materials in recent years.

[0003] The preparation of existing calcium aluminate-based dechlorination agents largely relies on natural bauxite, limestone, and other mineral raw materials. This not only results in high raw material extraction costs but also leads to significant resource consumption and a heavy environmental burden. my country's industrial production generates a massive annual output of desulfurization gypsum (a byproduct of flue gas desulfurization recovery after burning sulfur-containing fuels) and fly ash (solid waste from coal-fired power plants). Currently, these are mostly disposed of through stockpiling or primary landfilling, which not only occupies land resources but also easily causes environmental problems such as dust and groundwater pollution. Although some desulfurization gypsum is used in primary applications such as gypsum building materials, high-value resource utilization pathways remain scarce, and it has not been effectively combined with dechlorination functions.

[0004] While existing technologies have attempted to use single solid wastes for the preparation of dechlorination materials, they suffer from several drawbacks: first, the single raw material results in poor crystallinity of calcium aluminate, leading to low dechlorination efficiency; second, the lack of systematic control over key parameters such as alumina content, activator type, and calcination process results in insufficient material performance stability; and third, the synergistic effect of the two types of industrial solid wastes is not fully utilized, making it difficult to balance solid waste resource utilization rate with material cost-effectiveness. Therefore, developing a calcium aluminate-based dechlorination agent that uses two types of industrial solid wastes as raw materials, has a controllable process, high dechlorination efficiency, and low cost is crucial for solving the problems of solid waste accumulation and chlorine-containing wastewater treatment. Summary of the Invention

[0005] Objective of the Invention: To address the technical problems of existing calcium aluminum gypsum-based dechlorination agents, such as high cost due to reliance on natural minerals as raw materials, low utilization rate of high-value industrial solid waste desulfurization gypsum and fly ash, and insufficient stability of dechlorination performance due to the influence of preparation process, this invention provides a calcium aluminum gypsum-based dechlorination agent based on desulfurization gypsum and fly ash and its preparation method. Using industrial solid waste desulfurization gypsum and fly ash as the main raw materials, and by controlling the raw material ratio, activator type and calcination process, a highly crystalline calcium aluminum gypsum dechlorination agent is prepared, achieving the dual goals of solid waste resource utilization and efficient treatment of chlorine-containing wastewater, while reducing the preparation cost of the dechlorination agent and improving its dechlorination efficiency and performance stability.

[0006] Technical Solution: A calcium aluminum gypsum-fly ash-based dechlorination agent, the raw materials of which consist of main materials, activators and auxiliary materials; the main materials are industrial by-product desulfurization gypsum and coal-fired power plant by-product fly ash, with fly ash accounting for 5-35% of the main materials by mass and desulfurization gypsum accounting for 65-95%; the activator is selected from one or more of calcium hydroxide, potassium hydroxide, and sodium hydroxide, and the addition amount is 2-8% of the total mass of the raw materials; the auxiliary material is deionized water, which is only used for wet mixing, and the water to total mass ratio of the raw materials is 0.2-0.4:1.

[0007] The desulfurized gypsum has a purity of ≥85% and a moisture content of ≤10%; the fly ash has an alumina content of ≥15%.

[0008] A method for preparing a calcium aluminum stone-based dechlorination agent based on desulfurized gypsum and fly ash includes the following steps: (1) Dry the desulfurized gypsum in an oven at 105℃-110℃ for 4-6 hours, crush it and pass it through a 100-mesh sieve; pass the fly ash through an 80-mesh sieve to remove impurities and set it aside. (2) Weigh the pretreated desulfurized gypsum, fly ash and activator according to the proportion, and mix them by dry or wet method; when mixing by dry method, put the raw materials into the mixer and stir at 300-500 r / min for 15-20 min to obtain a uniform dry powder mixture; when mixing by wet method, add the preset amount of deionized water to the raw materials and stir at 400-600 r / min for 25-30 min to obtain a uniform slurry mixture. (3) Place the mixture obtained in step (2) in a muffle furnace and heat it to 200-850℃ at a heating rate of 5-10℃ / min. Keep it at the temperature for 2-4 hours, cool it naturally to room temperature, crush it and pass it through a 200-mesh sieve to obtain calcium aluminum stone-based dechlorinating agent.

[0009] Key process control: The total alumina content in the mixed raw materials is controlled to be 3-12% by adjusting the proportion of fly ash addition to ensure the full formation of calcium aluminum crystalline phase; the alumina dissolution rate is highest when calcium hydroxide and sodium hydroxide are compounded at a mass ratio of 1:1; low-crystallinity calcium aluminum crystalline phase is formed in the 200-550℃ range, and high-crystallinity calcium aluminum crystalline phase is formed in the 650-850℃ range.

[0010] Beneficial effects: Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The raw material cost is low and environmentally friendly. It uses desulfurized gypsum and fly ash as the main industrial solid wastes to replace traditional natural minerals. The solid waste utilization rate reaches 100%, and the cost is reduced by 30-50% compared with traditional dechlorination agents. It reduces solid waste storage pollution and meets the requirements of "dual carbon" and circular economy.

[0011] (2) Excellent dechlorination performance. The prepared calcium aluminum stone-based dechlorinating agent has an adsorption capacity of 80-120 mg / g for chloride ions. When treating industrial wastewater with an initial chlorine concentration of 500-1000 mg / L, the dechlorination rate is ≥90%. The material has good stability in the pH range of 4-10 and is applicable to a wide range of wastewater pH.

[0012] (3) The process is highly controllable. By adjusting the fly ash ratio, the type of activator and the calcination temperature, the crystallinity and dechlorination performance of calcium aluminum stone can be precisely controlled to meet the treatment needs of different chlorine-containing wastewater.

[0013] (4) The product can be reused. The calcium aluminum stone-based dechlorinating agent that adsorbs chloride ions after dechlorination can be further used as raw material to prepare building materials such as gypsum board, realizing the closed-loop utilization of "dechlorination-building material regeneration" without generating secondary solid waste. Attached Figure Description

[0014] Figure 1. Scanning electron microscope image of calcium aluminum stone-based dechlorination agent; Figure 2. XRD pattern of calcium carbonate-based dechlorination agent; Detailed Implementation

[0015] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0016] Example 1 (1) Raw material ratio: Accurately weigh 90 kg of industrial by-product desulfurization gypsum (purity 88%, moisture content 8%) and 10 kg of coal-fired power plant by-product fly ash (alumina content 18%), and separately weigh 3 kg of calcium hydroxide activator (accounting for 3% of the total raw material mass) for later use; (2) Preparation steps: Raw material pretreatment: Place the desulfurization gypsum in a 105℃ forced-air drying oven and dry for 5 hours, then crush and pass through a 100-mesh sieve; pass the fly ash through an 80-mesh sieve to remove impurities and set aside for later use; Mixing: Add the pretreated raw materials to the mixture. The mixture was stirred in a double spiral conical mixer at 400 r / min for 18 min to obtain a dry powder mixture; calcination: the temperature was raised to 650℃ at 8℃ / min, kept warm for 3 h, and then ground through a 200-mesh sieve after natural cooling to obtain calcium aluminum stone-based dechlorinating agent; (3) performance test: 2 g of dechlorinating agent was added to 100 mL of industrial circulating water sample with an initial chlorine concentration of 800 mg / L, and the sample was shaken and adsorbed at 25℃ and 150 r / min for 2 h. The dechlorination rate was 92% and the adsorption capacity was 95 mg / g.

[0017] Example 2 (1) Raw material ratio: Accurately weigh 75 kg of industrial by-product desulfurization gypsum (purity 85%, moisture content 9%), 25 kg of coal-fired power plant by-product fly ash (alumina content 22%), and weigh 5 kg of calcium hydroxide and sodium hydroxide compound activator (mass ratio 1:1) (accounting for 5% of the total raw material mass), and 40 kg of deionized water for later use; (2) Preparation steps: Raw material pretreatment is the same as in Example 1; Mixing: Add deionized water, stir at 500 r / min for 28 min to obtain slurry mixture; Calcination: Heat to 750℃ at 10℃ / min, keep warm for 2.5 h, cool and grind through a 200 mesh sieve to obtain calcium aluminum stone-based dechlorinating agent; (3) Performance test: 2 g of dechlorinating agent treated 100 mL of chemical wastewater with an initial chlorine concentration of 1000 mg / L, the dechlorination rate was 95%, and the adsorption capacity was 110 mg / g.

[0018] Example 3 (1) Raw material ratio: Accurately weigh 85 kg of industrial by-product desulfurization gypsum (purity 90%, moisture content 7%) and 15 kg of coal-fired power plant by-product fly ash (alumina content 15%), and weigh 4 kg of potassium hydroxide activator (accounting for 4% of the total raw material mass) for later use; (2) Preparation steps: Raw material pretreatment is the same as in Example 1; Mixing: Stir at 350 r / min for 20 min to obtain a dry powder mixture; Calcination: Heat to 550℃ at 5℃ / min, keep warm for 4 h, cool and grind through a 200 mesh sieve to obtain calcium aluminum stone-based dechlorinating agent; (3) Performance test: 2 g of dechlorinating agent treated 100 mL of power industry circulating water with an initial chlorine concentration of 600 mg / L, and the dechlorination rate was 91%, and the adsorption capacity was 88 mg / g.

Claims

1. A method for preparing a calcium aluminum ore-based dechlorination agent based on desulfurized gypsum-fly ash, characterized in that, Includes the following steps: (1) Raw material pretreatment: Dry the desulfurized gypsum in an oven at 105-110℃ for 4-6 hours, crush it and pass it through a 100-mesh sieve; remove impurities from the fly ash by passing it through an 80-mesh sieve and set it aside. (2) Mixing: Weigh the pretreated desulfurized gypsum, fly ash and activator according to the proportion, and mix them by dry or wet method to obtain a uniform mixture; (3) Calcination: The mixture is heated to 200℃-850℃ at 5-10℃ / min, kept at the temperature for 2-4h, cooled and crushed through a 200-mesh sieve to obtain calcium aluminum stone-based dechlorination agent; the main materials are desulfurized gypsum and fly ash, with fly ash accounting for 5-35% of the main materials by mass and desulfurized gypsum accounting for 65-95%; the amount of activator added is 2-8% of the total mass of raw materials, and is selected from one or more of calcium hydroxide, potassium hydroxide and sodium hydroxide.

2. The preparation method according to claim 1, characterized in that, The desulfurized gypsum has a purity of ≥85% and a moisture content of ≤10%; the fly ash has an alumina content of ≥15%.

3. The preparation method according to claim 1, characterized in that, For dry mixing, the speed is 300-500 r / min, and the stirring time is 15-20 min. For wet mixing, deionized water is added, with a water-to-raw material mass ratio of 0.2-0.4:1, the speed is 400-600 r / min, and the stirring time is 25-30 min.

4. The preparation method according to claim 1, characterized in that, The activator is a mixture of calcium hydroxide and sodium hydroxide in a mass ratio of 1:

1.

5. The preparation method according to claim 1, characterized in that, A highly crystalline calcium aluminum stone-based dechlorinating agent was prepared by calcining at a temperature of 650-850℃.

6. A calcium-aluminum-based dechlorination agent based on desulfurization gypsum-fly ash, characterized in that, It is prepared by the preparation method described in any one of claims 1-5.

7. The calcium aluminum stone-based dechlorination agent according to claim 6, characterized in that, The chloride ion adsorption capacity is 80-120 mg / g, and the dechlorination rate is ≥90% when treating industrial wastewater with an initial chlorine concentration of 500-1000 mg / L.

8. The application of the calcium aluminum stone-based dechlorinating agent according to claim 6 in the treatment of industrial chlorine-containing wastewater.

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