Method for resource utilization of metallurgical solid waste containing potassium

Abstract

This invention provides a method for the resource utilization of potassium-containing metallurgical solid waste. The method comprises seven steps: ash transportation and storage, pulping, leaching, filtration, carbon removal, water treatment, water storage, and irrigation. This invention achieves a potassium removal rate of over 95% and a sodium removal rate of over 89% after treating the potassium-containing metallurgical solid waste. The leaching residue is recycled in the sintering process of the metallurgical industry, reducing the alkali content of the sintered ore, improving the efficiency of blast furnace ironmaking, and realizing the low-cost recovery and effective utilization of potassium resources from potassium-containing metallurgical solid waste.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical engineering technology and relates to a method for the resource utilization of potassium-containing metallurgical solid waste. Background Technology

[0002] Blast furnace ironmaking evolved from and improved upon the ancient vertical furnace ironmaking process. Blast furnace ironmaking boasts excellent technical and economic indicators, a simple process, high production capacity, high labor productivity, and low energy consumption. This method produces over 95% of the world's total iron production. During blast furnace production, iron ore, coke, and flux (limestone) are charged from the top. Preheated air is blown in through tuyeres located at the bottom of the furnace. At high temperatures, the carbon in the coke (and sometimes auxiliary fuels such as pulverized coal, heavy oil, or natural gas in some blast furnaces) burns with the oxygen in the blown air to produce carbon monoxide. This carbon monoxide rises within the furnace, removing oxygen from the iron ore and reducing it to iron. The molten iron is discharged from the taphole. Unreducible impurities in the iron ore combine with the flux, such as limestone, to form slag, which is discharged from the slag outlet. The generated gas is extracted from the top of the furnace, precipitated for dust removal, and then used as fuel for hot blast stoves, heating furnaces, coke ovens, and boilers.

[0003] The main alkali metals in the blast furnace ironmaking process are K and Na. Since Zn behaves similarly to K and Na in the blast furnace, Zn is also classified as an alkali metal in actual production. The alkali metal and zinc content referred to in production generally refers to the content of K2O, Na2O, and ZnO per ton of molten iron, expressed in kg / t.

[0004] With the development of oxygen-enriched pulverized coal injection technology, the roles of coke as a reducing agent, exothermic agent, and carburizer have been partially replaced by pulverized coal injection. However, as a structural support for the blast furnace, coke's role in maintaining good permeability during blast furnace smelting is irreplaceable. The effectiveness of coke as a structural support directly affects the smooth operation and economic and technical indicators of the blast furnace. Alkali metals have a pulverizing effect on coke, with higher concentrations leading to more severe pulverization. This weakens coke's structural support role, reduces material permeability, and severely impacts heat and mass transfer in high-temperature metallurgical processes, resulting in reduced blast furnace smelting capacity. Secondly, alkali metals easily cause the blast furnace softening zone to rise, hindering the development of indirect reduction and increasing the coke ratio. Furthermore, alkali metal oxides in the upper part of the blast furnace adhere to the furnace wall, promoting thickening of the furnace wall and damaging the tuyeres and refractory materials, thus shortening the blast furnace's service life.

[0005] Sintering is the raw material preparation stage in blast furnace ironmaking. It involves mixing various powdered iron-containing raw materials with appropriate amounts of fuel and flux, adding water, and then subjecting the mixture to a series of physicochemical changes on sintering equipment. This process binds the mineral powder particles together into lumps. The sintering temperature of sintered ore is 1200-1300℃. Potassium salts have a melting point below 800℃ and a boiling point of around 1400℃. Therefore, under the high-temperature and negative-pressure conditions at the sintering machine head, the boiling point of potassium salts decreases, and gasification intensifies. The potassium salts, in gaseous form, enter the dust removal system along with the ash from the sintering machine head and are enriched in the dust collected at the machine head after cooling.

[0006] In China, the utilization of sintering machine head ash mostly takes advantage of the fact that both Kcl and Nacl are easily soluble in water. Potassium-containing solutions are obtained through leaching, and then potassium fertilizer is prepared through evaporation. However, due to the high cost of this process, it is mostly still in the research stage and has limited industrial application. Summary of the Invention

[0007] In response to the problem that the self-recycling of potassium-containing metallurgical solid waste by iron and steel metallurgical enterprises in my country leads to an increase in the alkali content of sintered ore and a waste of potassium resources, and that domestic research on extracting agricultural potassium chloride fertilizer using leaching and evaporation methods is costly and difficult to industrialize, this invention is proposed in light of the imbalance in the production and application ratio of nitrogen, phosphorus and potassium fertilizers and the potassium deficiency in the soil in my country. The purpose of this invention is to provide a method for the resource utilization of potassium-containing metallurgical solid waste.

[0008] Therefore, the present invention adopts the following technical solution:

[0009] A method for the resource utilization of potassium-containing metallurgical solid waste includes the following steps:

[0010] Step 1, Ash Transportation and Storage: Dust removal ash is transported by tank truck, and then the dust removal ash in the tank is transported to the high-level ash receiving silo by a pneumatic negative pressure conveying device. The bottom of the ash receiving silo is equipped with a flat gate and a double-pipe screw weigher. The volume of the ash receiving silo can hold 165 tons to 330 tons of potassium-containing solid waste.

[0011] Step 2, Pulping: Open the flat gate at the bottom of the ash receiving silo, and feed the dust collector ash into the mixing tank at a rate of 30-50 t / h using a double-pipe screw conveyor with a width D × length L = 250 × 2000 mm. Simultaneously, open the new water supply valve and measure the amount of water added for pulverizing using an electromagnetic flow meter, with a flow rate of 90-150 m / s. 3 / h, ensuring the liquid-to-solid ratio of water to ash is 3-5;

[0012] Step 3: Leaching: The mortar is pumped to a mechanically stirred thickener for thorough leaching. 15-20 g / t of potassium carboxymethyl cellulose flocculant is added to accelerate the settling of solid particles and simultaneously remove some of the calcium. 2+ Mg 2+ Ions, ensuring that the concentration of suspended solids in the leachate is less than or equal to 100 mg / L;

[0013] Step 4, Filtration: The leaching residue is dewatered using filtration equipment. The dewatered water is reused for pulping, and the filter cake is returned to the sintering plant for recycling.

[0014] Step 5, Decarbonization: The leachate is transported to four 50m... 3 In the decarbonization tank, air is introduced into the bottom of the decarbonization tank by a blower, and carbon is discharged from the overflow weir of the decarbonization tank. It is filtered and dehydrated together with the leaching residue and then returned to sintering for reuse.

[0015] Step Six: The decarbonized leachate is transported to a 400m... 3 Add 5-7 g / m³ to the sedimentation tank. 3 Polyaluminum ferric chloride (PAFC) removes heavy metal ions such as iron, manganese, lead, and zinc from water; add 4-6 g / m³. 3 Polyferric sulfate (PFCS) is used for decolorization, deoiling, sterilization, and reduction of COD and BOD in water; add 2400-3600 g / m³. 3 Sulfuric acid is used to adjust the pH value to 7-8. The solids in the sedimentation tank are filtered and dehydrated together with the leaching residue and then returned to the sintering unit for recycling.

[0016] Step 7, Water Storage and Irrigation: Water with reduced heavy metal ions, BOD and COD but containing potassium chloride fertilizer is pumped to a reservoir for storage and used for irrigation of farmland and orchards.

[0017] Furthermore, the number of leaching stages in step three is 1-3.

[0018] Furthermore, the flocculant in step three is potassium carboxymethyl cellulose, which can not only flocculate fine solids and accelerate solid sedimentation, but also remove calcium from the water. 2+ Mg 2+ ion.

[0019] Furthermore, the mechanical agitator thickener used in step three can be a peripheral drive thickener, a center drive thickener, or a deep cone thickener.

[0020] Furthermore, the filtration equipment in step four can be a box filter, a plate and frame filter press, or a pressure filter.

[0021] Furthermore, in step six, the chemical agents used to remove heavy metal ions such as iron, chromium, copper, lead, cadmium, and zinc from the water are polyaluminum chloride (PAC) and polyaluminum ferric chloride (PAFC); the chemical agents used for decolorization, deoiling, sterilization, removal of heavy metal ions, COD, and BOD are polyferric sulfate (PFCS). The pH adjuster is hydrochloric acid and sulfuric acid, both at a concentration of 1%-5%.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention uses tank trucks to transport dust and employs pneumatic negative pressure conveying to clean and environmentally friendly dust removal methods.

[0024] 2. In this invention, the dust removal ash is measured by a double-pipe screw weigher during pulping, and the amount of water added during pulping is measured by an electromagnetic flowmeter. This ensures that the liquid-solid ratio of water to ash is 3-5:1, which is beneficial to improving the leaching rate of potassium chloride.

[0025] 3. The mortar of this invention is fully leached in a mechanically stirred thickener, and a flocculant is added to accelerate the sedimentation of solid particles, which can ensure that the suspended solids in the leachate are ≤100mg / L;

[0026] 4. The leaching residue of this invention is dewatered using a filtration device, and the solid content of the filtrate is less than 100 ppm. The dewatered water is reused for pulping, reducing water consumption.

[0027] 5. The present invention removes carbon from the leachate, and after filtration and dehydration together with the leachate residue, it is returned to sintering for reuse, thereby maximizing the resource utilization of solid waste;

[0028] 6. This invention uses polyaluminum chloride (PAC) or polyaluminum ferric chloride (PAFC) to remove heavy metals such as iron, chromium, copper, lead, cadmium, and zinc from water; the technical measures of decolorization, deoiling, sterilization, and COD and BOD removal using polyferric sulfate (PFCS) are simple and efficient to implement.

[0029] 7. This invention achieves low-cost recovery and effective utilization of potassium resources in potassium-containing metallurgical solid waste. The cost of disposing of potassium-containing metallurgical solid waste is less than 50 yuan / ton. After treatment of potassium-containing metallurgical solid waste using the method of this invention, the potassium removal rate can reach more than 95%, and the sodium removal rate can reach more than 89%. The leaching slag can be reused in the sintering process of the metallurgical industry, and the alkali content of the sintered ore is reduced, which is conducive to increasing the production and smooth operation of blast furnace ironmaking. Attached Figure Description

[0030] Figure 1 This is a schematic diagram illustrating the process principle of the present invention. Detailed Implementation

[0031] The technical solution of the present invention will be described below with reference to the accompanying drawings and implementation methods.

[0032] This embodiment takes a steel company as an example. The steel company is located in the northwest border of China, which has a continental arid climate. The evaporation rate is 18 times the rainfall, and water resources are very precious. The local crops are mainly wheat, corn and potatoes. The crops need irrigation to grow, and there is an urgent need for potassium fertilizer.

[0033] The steel company produces 6.3 million tons of sintered ore annually, with an annual ash discharge from the sintering machine headstock of approximately 68,000 tons. The main chemical components of the headstock ash are shown in Table 1, with phase analysis revealing Fe2O3, KCl, and NaCl as the primary components, currently recycled within the sintering process. The company has two concentrators: the first concentrator produces 3.2 million tons of concentrate annually, and the second produces 1.8 million tons. The main chemical components of the concentrate powder are shown in Table 2. The company has seven blast furnaces, with potassium load information shown in Table 3. The alkali metals in the iron concentrate are primarily K2O, with trace amounts of Na2O and ZnO. The average alkali load (Na2O + K2O) in the domestic blast furnace ironmaking industry is approximately 2.5 kg / t, while the alkali load (K2O) of this steel company is 4.02-4.66 kg / t.

[0034] Table 1. Main chemical components of sintering head ash from a steel company's ironmaking plant.

[0035]

[0036] Table 2. Main chemical composition of iron concentrate from a steel company's ore dressing plant

[0037]

[0038] Table 3. Main Potassium Load of a Blast Furnace in a Steel Company

[0039]

[0040] As shown in Table 1-3, the average K2O content of the dust collected from the sintering machine head is as high as 10.68%, and the average Na2O content is 0.396%. The alkali metals brought in by the sintering self-recycling of 68,000 tons of dust collected from the sintering machine head are equivalent to the amount of alkali metals brought in by 68,000 × (10.68 + 0.396) ÷ (0.36 + 0.02) = 1.98 million tons of iron concentrate.

[0041] Therefore, the method of the present invention for the resource utilization of potassium-containing metallurgical solid waste includes the following steps:

[0042] Step 1, Ash Transportation and Storage: Dust removal ash is transported by tank truck, and then the dust removal ash in the tank is transported to the high-level ash receiving silo by a pneumatic negative pressure conveying device. The bottom of the ash receiving silo is equipped with a flat gate and a double-pipe screw conveyor. The volume of the ash receiving silo is sufficient to hold 165-330 tons of potassium-containing solid waste.

[0043] Step 2, Pulping: Open the flat gate at the bottom of the ash receiving silo, and feed the dust ash into the mixing tank in a measured amount using a double-pipe screw weigher. At the same time, open the new water supply valve and use an electromagnetic flow meter to measure the amount of water added for slurry making, ensuring that the liquid-solid ratio of water to ash is 3-5:1.

[0044] Step 3, Leaching: The slurry is pumped to a mechanical agitator for thorough leaching, and flocculants are added to accelerate the settling of solid particles, ensuring that the concentration of suspended solids in the leachate is less than or equal to 100 mg / L;

[0045] Specifically, the leaching process in step three consists of 1-3 stages; the flocculant in step three is potassium carboxymethyl cellulose, which can not only flocculate fine solids and accelerate solid sedimentation, but also remove calcium from the water. 2+ Mg 2+ Ion; Mechanical stirring thickeners can be selected from peripheral drive thickeners, center drive thickeners, or deep cone thickeners;

[0046] Step 4, Filtration: The leaching residue is dewatered using filtration equipment. The dewatered water is reused for pulping, and the filter cake is returned to the sintering plant for recycling.

[0047] Specifically, in step four, the filtration equipment can be a box filter, a plate and frame filter press, or a pressure filter.

[0048] Step 5, Decarbonization: The leachate is transported to the decarbonization tank, and air is introduced into the bottom of the decarbonization tank. The carbon is discharged from the overflow weir of the decarbonization tank and is filtered and dehydrated together with the leachate residue before being returned to sintering for reuse.

[0049] Step 6, Water Treatment: The leaching solution after carbon removal is transported to a sedimentation tank to remove heavy metal ions such as iron, chromium, copper, lead, cadmium, and zinc, as well as BOD and COD. The solids in the sedimentation tank are filtered and dehydrated together with the leaching residue and then returned to the sintering for recycling.

[0050] Specifically, in step six, the chemical agents used to remove heavy metal ions such as iron, chromium, copper, lead, cadmium, and zinc from the water are polyaluminum chloride (PAC) and polyaluminum ferric chloride (PAFC); the chemical agents used for decolorization, deoiling, sterilization, removal of heavy metal ions, COD, and BOD are polyferric sulfate (PFCS); and the pH adjuster is hydrochloric acid and sulfuric acid, both at a concentration of 1%-5%.

[0051] Step 7, Water Storage and Irrigation: Water with reduced heavy metal ions, BOD, and COD but containing potassium chloride fertilizer will be pumped to a reservoir for storage and used for irrigation of farmland and orchards.

[0052] The optimized process according to the present invention yields the following results:

[0053] 1. The removal rate of potassium chloride from potassium-containing metallurgical solid waste reaches over 95%, and the removal rate of sodium chloride reaches 89%, as shown in the table below.

[0054]

[0055] 2. The average alkali load (Na2O+K2O) in the blast furnace ironmaking process industry decreased from 4.45 kg / t to 2.67 kg / t, which is close to the domestic industry average. Blast furnace ironmaking production increased by 1.5-1.8%, and blast furnace production failures decreased by 5%.

Claims

1. A method for the resource utilization of potassium-containing metallurgical solid waste, characterized in that, Includes the following steps: Step 1, Ash Transportation and Storage: Dust removal ash is transported by tank truck, and then a pneumatic negative pressure conveying device is used to transport the dust removal ash in the tank to a high-level ash receiving silo. The bottom of the ash receiving silo is equipped with a flat gate and a double-pipe screw weigher. The volume of the ash receiving silo can hold 165-330 tons of potassium-containing solid waste. Step 2, Pulping: Open the flat gate at the bottom of the ash receiving silo, and feed the dust collector ash into the mixing tank at a rate of 30-50 t / h using a double-pipe screw weigher. Simultaneously, open the new water supply valve and use an electromagnetic flow meter to measure the amount of water added for pulping, with a flow rate of 90-150 m / s. 3 / h, ensuring the liquid-to-solid ratio of water to ash is 3-5:1; Step 3: Leaching: The mortar is pumped to a mechanically stirred thickener for thorough leaching. 15-20 g / t of potassium carboxymethyl cellulose flocculant is added to accelerate the settling of solid particles and simultaneously remove some of the calcium. 2+ Mg 2+ Ions, ensuring that the concentration of suspended solids in the leachate is less than or equal to 100 mg / L; Step 4, Filtration: The leaching residue is dewatered using filtration equipment. The dewatered water is reused for pulping, and the filter cake is returned to the sintering plant for recycling. Step 5, Decarbonization: The leachate is transported to four 50m... 3 In the decarbonization tank, air is introduced into the bottom of the decarbonization tank by a blower, and carbon is discharged from the overflow weir of the decarbonization tank. It is filtered and dehydrated together with the leaching residue and then returned to sintering for reuse. Step Six: The decarbonized leachate is transported to a 400m... 3 Add 5-7 g / m³ to the sedimentation tank. 3 Polyaluminum ferric chloride (PAFC) removes heavy metal ions such as iron, manganese, lead, and zinc from water; add 4-6 g / m³. 3 Polyferric sulfate (PFCS) is used for decolorization, deoiling, sterilization, and reduction of COD and BOD in water; add 2400-3600 g / m³. 3 Sulfuric acid is used to adjust the pH value to 7-8. The solids in the sedimentation tank are filtered and dehydrated together with the leaching residue and then returned to the sintering unit for recycling. Step 7, Water Storage and Irrigation: Water with reduced heavy metal ions, BOD and COD but containing potassium chloride is pumped to a reservoir for storage and used for irrigation of farmland and orchards.

2. The method for resource utilization of potassium-containing metallurgical solid waste according to claim 1, characterized in that, The number of leaching stages in step three is 1-3.

3. The method for resource utilization of potassium-containing metallurgical solid waste according to claim 1, characterized in that, The flocculant used in step three is potassium carboxymethyl cellulose.

4. The method for resource utilization of potassium-containing metallurgical solid waste according to claim 1, characterized in that, The mechanical agitator thickener used in step three can be a peripheral drive thickener, a center drive thickener, or a deep cone thickener.

5. A method for resource utilization of potassium-containing metallurgical solid waste according to claim 1, characterized in that, In step four, the filtration equipment can be a box filter, a plate and frame filter press, or a pressure filter.

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