A collaborative treatment method for steel by-product high-salt wastewater and blast furnace bag ash

Abstract

The invention discloses a collaborative treatment method for high-salt wastewater and blast furnace bag ash produced as a by-product of steel production, comprising the following steps: washing the blast furnace bag ash with high-salt wastewater, adding a reagent, and filtering to obtain a primary leaching slag and a primary leachate; washing the primary leaching slag with industrial water, adding a reagent, and filtering to obtain a secondary leaching slag and a secondary leachate; treating the secondary leaching slag with a rotary hearth furnace process to obtain metallized pellets and zinc oxide powder; mixing the primary leachate and the secondary leachate and using them as high-salt wastewater to wash the blast furnace bag ash again; when the chlorine content of the primary leachate is ≥15wt.%, purifying and removing impurities, and performing step-by-step evaporation and crystallization to prepare KCl and NaCl products. The present invention can fully recover the valuable components in the high-salt wastewater and blast furnace bag ash, realize the collaborative resource utilization of the high-salt wastewater and blast furnace bag ash, turn waste into treasure, and help achieve zero discharge of wastewater and solid waste in the steel process.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel process water and solid waste treatment, and particularly relates to a method for the coordinated treatment of steel by-product high-salt wastewater and blast furnace bag dust. Background Art

[0002] The steel industry is a high-water-consuming and high-emissions industry, producing approximately 8% of China's total wastewater, making it a major water and wastewater user. With the increasingly severe water resource situation, water conservation and emission reduction have become essential for the sustainable development of the steel industry. Conventional water treatment and reuse processes are no longer able to meet the water quality requirements and emission reduction targets of steel companies. Desalination processes are needed to further treat the wastewater after conventional treatment. This process concentrates salt and other substances in some wastewater, producing high-salinity wastewater. Direct discharge of high-salinity wastewater has a significant impact on local water quality, causing salinization, aquatic life mortality, and damage to the aquatic ecosystem. The commonly used treatment method is to evaporate and crystallize this high-salinity wastewater into a solid form. However, this process consumes a large amount of heat, is costly, and produces low-quality wastewater. Therefore, the economical, effective, and harmless treatment of high-salinity wastewater has become a critical step in the advanced wastewater treatment and zero wastewater discharge goals of steel companies.

[0003] During the blast furnace ironmaking process, raw gas discharged from the furnace top carries a large amount of raw fuel dust and particulates generated by intense reactions in the high-temperature zone. After passing through a gravity dust collector to remove coarser particles, it is further purified by bag filters before entering the gas pipeline network. The resulting dust is known as blast furnace bag dust. Blast furnace bag dust is fine-grained and contains significant amounts of harmful elements such as K, Na, Zn, and Cl. If recycled back into the ironmaking process, it can have significant negative impacts on production, including pipeline corrosion, coke degradation, furnace shaft buildup, and refractory erosion. Many domestic steel companies simply dump blast furnace bag dust. This disposal method has numerous drawbacks, including the large land occupation, even occupying arable land; fine dust particles drifting into the atmosphere, polluting the atmosphere; harmful elements seeping into the ground with rainwater, polluting rivers; and the waste of valuable elements such as Fe and C. Therefore, comprehensive treatment and resource recovery of blast furnace bag dust are urgently needed. Summary of the Invention

[0004] Technical problems to be solved: In response to the above technical problems, the present invention provides a method for the coordinated treatment of high-salt wastewater produced as a by-product of steel and blast furnace bag ash, which can fully recover the valuable components in high-salt wastewater and blast furnace bag ash, realize the coordinated resource utilization of high-salt wastewater and blast furnace bag ash, turn waste into treasure, and help achieve zero emission of wastewater and solid waste in the steel process.

[0005] Technical solution: A method for the coordinated treatment of high-salt wastewater produced as a by-product of steel production and blast furnace bag dust, comprising the following steps:

[0006] Step 1. Washing blast furnace bag ash with high-salt wastewater, adding a selective collector, and filtering to obtain primary leaching residue and primary leachate;

[0007] Step 2. Washing the primary leaching residue with industrial water, adding a selective collector, and filtering to obtain secondary leaching residue and secondary leachate;

[0008] Step 3. Using a rotary hearth furnace process to treat the secondary leaching residue to obtain metallized pellets and zinc oxide powder;

[0009] Step 4. The primary leachate and the secondary leachate are mixed and used as high-salt wastewater to wash blast furnace bag ash again;

[0010] Step 5. When the chlorine content of the primary leachate is ≥15 wt.%, the KCl and NaCl products are prepared by purification, impurity removal, step-by-step evaporation and crystallization.

[0011] Preferably, the reagents in step 1 are potassium carbonate and potassium hydroxide.

[0012] Furthermore, the potassium carbonate accounts for 0-4% of the mass of the blast furnace bag ash, and the potassium hydroxide accounts for 0-2% of the mass of the blast furnace bag ash.

[0013] Preferably, the reagents in step 2 are potassium carbonate, potassium sulfide and potassium polyacrylate.

[0014] Furthermore, the potassium carbonate accounts for 0-0.3% of the mass of the primary leaching residue, the potassium sulfide accounts for 0-0.2% of the mass of the primary leaching residue, and the potassium polyacrylate accounts for 0-0.05% of the mass of the primary leaching residue.

[0015] Preferably, the wastewater generated in step 5 is used as a supplement to the industrial water in step 2 to wash the primary leaching residue.

[0016] Beneficial effects: Through the present invention, the coordinated resource utilization of high-salt wastewater and blast furnace bag ash can be achieved, and the elements K, Na, Cl, Fe, Zn, C and other elements in high-salt wastewater and blast furnace bag ash can be fully recovered, turning waste into treasure. At the same time, the two major problems of the treatment of high-salt wastewater and blast furnace bag ash, which are by-products of steel, are solved, and the zero emission of wastewater and solid waste in the steel process is promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0019] Example 1

[0020] like Figure 1 As shown, a method for co-processing high-salt wastewater produced as a by-product of steel production and blast furnace bag dust comprises the following steps:

[0021] Step 1. Washing blast furnace bag ash with high-salt wastewater, adding 4% of potassium carbonate and 2% of potassium hydroxide by weight of the blast furnace bag ash, respectively, and filtering to obtain a primary leaching residue and a primary leachate;

[0022] Step 2. Wash the primary leaching residue with industrial water, add 0.3% of potassium carbonate, 0.2% of potassium sulfide, and 0.05% of potassium polyacrylate by weight of the primary leaching residue, respectively, and obtain secondary leaching residue and secondary leachate after filtering;

[0023] Step 3. Using a rotary hearth furnace process to treat the secondary leaching residue to obtain metallized pellets and zinc oxide powder;

[0024] Step 4. The primary leachate and the secondary leachate are mixed and used as high-salt wastewater to wash blast furnace bag ash again;

[0025] Step 5. When the chlorine content of the primary leachate is ≥15wt.%, the product KCl and NaCl are prepared by purification, impurity removal, step-by-step evaporation and crystallization. The wastewater generated in this step is used as a supplement to the industrial water in step 2 for washing the primary leachate residue.

[0026] The present invention can fully recover valuable components in high-salt wastewater and blast furnace bag dust, realize the coordinated resource utilization of high-salt wastewater and blast furnace bag dust, turn waste into treasure, and help achieve zero discharge of wastewater and solid waste in the steel process.

Claims

1. A method for the coordinated treatment of high-salt wastewater produced as a by-product of steel and blast furnace bag dust, characterized in that: The steps are as follows: Step 1. Washing blast furnace bag ash with high-salt wastewater, adding selective collectors: potassium carbonate and potassium hydroxide, and filtering to obtain primary leaching residue and primary leaching liquid; Step 2. Washing the primary leaching residue with industrial water, adding selective collectors: potassium carbonate, potassium sulfide and potassium polyacrylate, and filtering to obtain secondary leaching residue and secondary leachate; Step 3. Using a rotary hearth furnace process to treat the secondary leaching residue to obtain metallized pellets and zinc oxide powder; Step 4. The primary leachate and the secondary leachate are mixed and used as high-salt wastewater to wash blast furnace bag ash again; Step 5. When the chlorine content of the primary leachate is ≥15 wt.%, the KCl and NaCl products are prepared by purification, impurity removal, step-by-step evaporation and crystallization.

2. The method for collaboratively treating steel by-product high-salt wastewater and blast furnace bag dust according to claim 1, characterized in that: In the step 1, potassium carbonate accounts for 0-4% of the mass of the blast furnace bag ash, and potassium hydroxide accounts for 0-2% of the mass of the blast furnace bag ash.

3. The method for collaboratively treating steel by-product high-salt wastewater and blast furnace bag dust according to claim 1, characterized in that: In the step 2, potassium carbonate accounts for 0-0.3% of the mass of the primary leaching residue, potassium sulfide accounts for 0-0.2% of the mass of the primary leaching residue, and potassium polyacrylate accounts for 0-0.05% of the mass of the primary leaching residue.

4. The method for collaboratively treating steel by-product high-salt wastewater and blast furnace bag dust according to claim 1, characterized in that: The wastewater generated in step 5 is used as a supplement to the industrial water in step 2 and is used to wash the primary leaching residue.

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