Gasification slag combined treatment process

Abstract

The present application relates to solid waste recycling technical field, disclose a kind of gasification slag combined treatment process.The present application is in carbon extraction dewatering step, using two-stage multi-stage carbon extraction process of spiral separation and magnetic separation, further reduce the ash content of clean coal product, improve the product value of clean coal, and by using new vacuum filter dewatering to clean coal, using disc vacuum filter dewatering to medium coal and tail residue, according to different product characteristics targeted selection different dewatering mode, reduce the moisture content of gasification slag product;Dehydrated tail residue is activated, reduction iron extraction and melting extraction step, iron element in dewatered tail residue is fully recovered, the rest active tail residue can be used as active material sales, effectively improve the comprehensive utilization rate of gasification slag, and the generated flue gas waste heat can be used to generate electricity, cooling waste heat is used for heating, can energy self-circulation self-supply, realize the resource utilization of waste heat and waste water, reduce thermal pollution and water consumption.

Description

Technical Field

[0001] This invention relates to the field of solid waste recycling technology, specifically a combined treatment process for gasification slag. Background Technology

[0002] Gasification slag is a solid byproduct produced during coal gasification, mainly composed of inorganic minerals and residual carbonaceous particles from the coal. During coal gasification, coal is converted into combustible gas, but not all coal is completely converted; the unconverted portion forms gasification slag. Gasification slag includes two types: coarse slag and fine slag. Coarse slag is the water-containing slag discharged from the bottom slag hopper of the gasifier after the slurry coal particles undergo melting, quenching, and condensation processes under high temperature and pressure in the gasifier. Its residual carbon content is generally 10%-30%, and the particle size is concentrated between 16 mesh and 4 mesh. It accounts for approximately 80% of the total gasification slag discharge. Fine slag is the water-containing slag obtained by being carried out by the gas flow from the top of the gasifier and undergoing preliminary washing, purification, and sedimentation. It has a higher residual carbon content, generally exceeding 30%, and the particle size is less than 16 mesh, with about one-third being less than 200 mesh. It accounts for approximately 20% of the total gasification slag discharge.

[0003] In recent years, the output of gasification slag has been increasing with the promotion of coal gasification technology and the development of the coal chemical industry. According to statistics, in 2023 alone, my country's annual emissions of coal gasification slag exceeded 33 million tons, making it an important type of industrial solid waste. However, due to the complex physical properties, high moisture content, and high processing efficiency and low cost of gasification slag, the resource utilization rate of gasification slag is still low. Most of the gasification slag is still landfilled or stockpiled as solid waste. This not only occupies a large amount of land resources but may also pollute the ecological environment. A small portion of gasification slag treatment technologies, due to high input and low output, are basically still at the most basic treatment stage, such as simple dehydration or simple carbon extraction. After carbon extraction, a large amount of tailings still needs to be returned to the slag yard, resulting in low overall product value.

[0004] Current gasification slag utilization technology mainly focuses on further recovering residual carbon from the gasification slag for sale as power coal blending. However, the extracted residual carbon suffers from limited ash reduction and excessive moisture content. Due to the special structure of gasification slag, the ash content cannot be further reduced beyond 15%. Coupled with the difficulty in removing moisture, this severely affects the calorific value of the clean coal, directly leading to low selling prices and poor economic benefits for enterprises. Furthermore, a large amount of tailings remains after carbon extraction from the gasification slag. This part belongs to the secondary solid waste after treatment of coal chemical gasification slag solid waste. Therefore, due to its low usable components, high technical difficulty in treatment, and disproportionate input and output, there is no good treatment method, and it still has to be returned to the slag yard for stockpiling. This results in a low comprehensive utilization rate of gasification slag, only around 40%, making the disposal and treatment of gasification slag solid waste ineffective. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a combined treatment process for gasification slag.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A combined treatment process for gasification slag includes the following steps:

[0008] S1. Carbon extraction and dehydration: After the gasification slag undergoes a multi-stage carbon extraction process, different products are obtained. The different products are separated into clean coal, middlings and tailings according to their carbon content. The clean coal, middlings and tailings are dehydrated to obtain dehydrated clean coal, dehydrated middlings and dehydrated tailings respectively.

[0009] S2. Activation and modification: The dewatered tailings are granulated into balls so that the granulated dewatered tailings meet the particle size requirements for the activation furnace. The spherical dewatered tailings that meet the particle size requirements for the activation furnace are fed into the activation furnace for calcination to obtain calcined tailings and calcined flue gas.

[0010] S3. Reduction and iron extraction: The calcined tailings are fed into a rotary kiln, where they are further calcined and reduced at high temperature. The output is reduced tailings and reduced flue gas. The reduced tailings are cooled by a slag cooler, then ground to reduce particle size, and finally magnetically separated to obtain active tailings and ferrous tailings.

[0011] S4. Melting and refining: Iron tailings are mixed with binders and reducing agents and then granulated into pellets. The granulated iron tailings are fed into the melting furnace as raw materials. The iron tailings are smelted in the melting furnace to produce iron ingots and smelting flue gas.

[0012] S5. Waste heat power generation: calcination flue gas and smelting flue gas are input into the generator set to generate electricity, and the electricity generated is supplied to the plant's electrical load.

[0013] S6. Wastewater treatment: Wastewater produced from the dewatering of clean coal, middlings, and tailings is recycled after passing through the wastewater treatment system.

[0014] Preferably, step S1 includes:

[0015] S1.1 Multi-stage carbon extraction: The gasification slag is first passed through a spiral separator for preliminary spiral separation. The primary clean coal obtained from the preliminary spiral separation is fed into a primary magnetic separator for primary magnetic separation. The primary tailings obtained from the primary magnetic separation are fed into a secondary magnetic separator for secondary magnetic separation to further obtain carbon extraction tailings.

[0016] S1.2. The clean coal is dewatered by vacuum pressure filtration to obtain dewatered clean coal, and the middlings and tailings are dewatered by disc vacuum filtration to obtain dewatered middlings and dewatered tailings, respectively.

[0017] Preferably, in step S1.1, the primary magnetic separator uses a single-roller down-concentration magnetic separator, and the secondary magnetic separator uses a multi-roller magnetic separator; the magnetic circuit structure of the single-roller down-concentration magnetic separator is that the magnetic rollers are arranged in parallel and clustered phases, and the magnetic circuit is rotated by the magnetic rollers, with the N and S phases changing instantaneously, and the working magnetic field strength is not less than 8500 Gauss; the discharge plate of the single-roller down-concentration magnetic separator can be adjusted within a range of no more than 90°, and the water level and concentration can be controlled according to the iron content of the material, thereby controlling the grade and yield of the concentrate; the working magnetic field strength of the multi-roller magnetic separator is not less than 12500 Gauss.

[0018] Preferably, in step S2, the particle size of the activated furnace feed is required to be 2-5 mm; the activated furnace has a flue gas purification self-circulation structure, and the activated furnace flue gas output from the top of the activated furnace is converted into calcination flue gas and dust ash after passing through the gravity dust removal of the flue gas purification self-circulation structure, and the dust ash is circulated to the bottom of the activated furnace.

[0019] Preferably, in step S3, the calcined tailings are further calcined at high temperature in a rotary kiln to reduce the iron oxides in the calcined tailings to iron(III) oxide; the magnetic separation recovery of the reduced tailings uses a multi-roller magnetic separator to obtain active tailings and ferrous tailings respectively.

[0020] Preferably, in step S4, the reducing agent is one or more combinations of coke, carbon powder, and iron powder; the binder is one or more combinations of phosphate binder, cold-fixed iron concentrate pellet binder, and chromite powder binder.

[0021] Preferably, in step S4, when the granulated iron tailings are fed into the melting furnace as raw material, residual anodes and limestone are also added to the granulated iron tailings; the granulated iron tailings, residual anodes and limestone are fed into the charging hopper of the melting furnace by a loader; in the charging hopper of the melting furnace, the granulated iron tailings, residual anodes and limestone are fed into the charging port at the top of the melting furnace by a weighing feeder under the hopper in a fixed ratio.

[0022] Preferably, in step S4, the smelting flue gas is drawn from the top of the melting furnace into a gravity dust collector for preliminary dust removal by a fan, then enters a bag filter for secondary dust removal, and is then desulfurized and purified by a desulfurization tower. Part of the flue gas returns to the melting furnace as a supplementary heat source for the melting furnace, while the other part is input into the generator set for power generation.

[0023] Compared with the prior art, the present invention provides a combined treatment process for gasification slag, which has the following beneficial effects:

[0024] 1. This combined gasification slag treatment process, through preliminary spiral separation followed by two magnetic separations, addresses the challenges of fine particle size distribution and complete dissociation of various components in the gasification slag. It also considers the high iron content and extremely high ash content of iron in the slag, along with other high-ash components such as inorganic matter embedded with iron. The process further separates the primary clean coal after the preliminary spiral separation using two magnetic separations, reducing the ash content in the resulting tailings by approximately 3%. This overcomes the current limit on ash content in gasification slag clean coal, effectively reducing the ash content of tailings obtained from multi-stage carbonization treatment of gasification slag. This reduces ash interference in subsequent processes and the energy waste caused by additional ash processing. Furthermore, iron is extracted through rotary reduction and iron extraction, not only recovering wasted resources but also increasing the product value of the remaining tailings and the carbonization tailings.

[0025] 2. This gasification slag co-processing technology, through vacuum pressure filtration and dewatering, produces dewatered clean coal with low ash content, low moisture content, and low volatile matter. When blended with high-volatile clean coal on the market, it can be sold as high-quality pulverized coal, greatly enhancing the market value of the clean coal. Furthermore, the moisture removed from the clean coal, middlings, and tailings can be fully utilized as process water in multi-stage carbon extraction, while the remainder is sent to a wastewater treatment plant. The treated wastewater can be used for waste heat power generation, reduction iron extraction, and smelting refining steps.

[0026] 3. In this combined gasification slag treatment process, during the activation and modification process, the crystalline phase of the spherical dewatered tailings is activated inside the activation furnace to generate a mineral phase. After the spherical dewatered tailings are coupled with high-temperature activation inside the activation furnace, the residual carbon is burned off and harmful components are removed. During the reduction and iron extraction process, the iron oxide is reduced to magnetite inside the rotary kiln and the reduced tailings are output, which facilitates subsequent magnetic separation of iron. In addition, the high-temperature treatment in the rotary kiln can effectively decompose and burn off residual organic matter and certain salts that are harmful to the activity, completely eliminating the risks of poor volume stability and efflorescence that may be brought about when gasification slag is used as a building material.

[0027] 4. This combined gasification slag treatment process employs a two-stage multi-stage carbon extraction process using spiral separation and magnetic separation in the carbon extraction and dehydration steps. This further reduces the ash content in the output dehydrated clean coal, dehydrated middlings, and dehydrated tailings, enhancing the product value of the clean coal. The clean coal is dehydrated using vacuum pressure filtration, while the middlings and tailings are dehydrated using disc vacuum filtration. Different dehydration methods are selected based on the moisture content, ensuring dehydration efficiency while saving energy. The dehydrated tailings undergo activation modification, reduction iron extraction, and smelting refining steps, fully recovering the iron elements. The remaining activated tailings can be sold as active materials, effectively improving the comprehensive utilization rate of gasification slag. The comprehensive utilization rate of gasification slag in the industry is generally around 40%, but with this combined gasification slag treatment process, the comprehensive utilization rate can reach 100%. Attached Figure Description

[0028] Figure 1 This is a process flow diagram of a combined gasification slag treatment process according to the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] As described in the background section, there are shortcomings in the existing technology. In order to solve the above-mentioned technical problems, this application proposes a combined gasification slag treatment process.

[0031] A combined treatment process for gasification slag includes the following steps:

[0032] S1. Carbon extraction and dehydration: After the gasification slag undergoes a multi-stage carbon extraction process, different products are obtained. The different products are separated into clean coal, middlings and tailings according to their carbon content. The clean coal, middlings and tailings are dehydrated to obtain dehydrated clean coal, dehydrated middlings and dehydrated tailings respectively.

[0033] Step S1 includes:

[0034] S1.1 Multi-stage carbon extraction: The gasification slag is first passed through a spiral separator for preliminary spiral separation. The primary clean coal obtained from the preliminary spiral separation is fed into a primary magnetic separator for primary magnetic separation. The primary tailings obtained from the primary magnetic separation are fed into a secondary magnetic separator for secondary magnetic separation to further obtain carbon extraction tailings.

[0035] The gasification slag first undergoes preliminary spiral separation using a spiral separator. The spiral separator can separate the slag based on the different densities of the clean coal and the tailings. The spiral separator can flexibly adjust the product quality by adjusting the position of the discharge pipe. After separation by the spiral separator, the gasification slag can achieve simple and efficient separation. The ash content of the primary clean coal obtained after preliminary spiral separation is about 15-20%.

[0036] By feeding primary clean coal into a primary magnetic separator for primary magnetic separation, and then feeding the primary tailings obtained from the primary magnetic separation into a secondary magnetic separator for secondary magnetic separation, the ash content in the resulting carbon-enriched tailings can be reduced to 12-15%.

[0037] The primary magnetic separator uses a single-roller downward magnetic separator, while the secondary magnetic separator uses a multi-roller magnetic separator.

[0038] The magnetic circuit structure of the single-roller down-selection magnetic separator is that the same level is arranged and clustered together. The magnetic circuit is rotated by the magnetic roller, and the N and N levels change instantaneously. The working magnetic field strength is not less than 8500 Gauss.

[0039] The discharge plate of the single-roller down-selection magnetic separator can be adjusted within a range of no more than 90°, and the water level and concentration can be controlled according to the iron content of the material, thereby controlling the grade and yield of the concentrate.

[0040] The working magnetic field strength of the multi-roll magnetic separator is not less than 12,500 Gauss. The high magnetic field strength of the multi-roll magnetic separator can maximize the removal of iron from the carbon extraction tailings.

[0041] By first performing preliminary spiral separation followed by two magnetic separations, the ash content of the clean coal from gasification slag can be reduced by about 3%, overcoming the limit of ash content in clean coal from gasification slag in existing technologies. Starting from the perspective of the fine particle size of each component in coal gasification slag and the difficulty of complete dissociation, and combined with the high iron content in coal gasification tailings and the extremely high ash content of iron itself, as well as other high-ash components such as inorganic matter embedded with iron, elemental iron and its inorganic compounds are extracted through rotary reduction and iron extraction. This not only recovers wasted resources but also enhances the product value of the remaining tailings.

[0042] S1.2. The clean coal is dewatered by vacuum pressure filtration to obtain dewatered clean coal, and the middlings and tailings are dewatered by disc vacuum filtration to obtain dewatered middlings and dewatered tailings, respectively.

[0043] Gasification slag is characterized by high porosity and high fissure water content, with a moisture content of over 50%. Based on the carbon content, it is separated into clean coal, middlings, and tailings. Among them, the clean coal is dewatered by vacuum pressure filtration to obtain dewatered clean coal, which can reduce the moisture content of carbon-raising clean coal to 10%. The dewatered clean coal obtained by vacuum pressure filtration has the characteristics of low ash content, low moisture content, and low volatile matter. When blended with high volatile matter clean coal on the market, it can be sold as high-quality pulverized coal, which greatly enhances the market value of clean coal.

[0044] The middlings and tailings are dewatered by disc vacuum filtration to obtain dewatered middlings and dewatered tailings, respectively. The moisture content of the dewatered middlings and dewatered tailings can be reduced to below 30%.

[0045] Furthermore, the water removed from the above-mentioned clean coal, middlings, and tailings can be fully utilized as process water in step S1.1, while the remainder is sent to a wastewater treatment plant. The treated wastewater can be used for waste heat power generation, reduction iron extraction, and smelting and refining steps.

[0046] S2. Activation and modification: The dewatered tailings are granulated into balls so that the granulated dewatered tailings meet the particle size requirements for the activation furnace. The spherical dewatered tailings that meet the particle size requirements for the activation furnace are fed into the activation furnace for calcination to obtain calcined tailings and calcined flue gas.

[0047] The particle size requirement for the activated furnace feed is 2-5 mm;

[0048] The activation furnace has a flue gas purification self-circulation structure. The activation furnace flue gas output from the top of the activation furnace is subjected to gravity dust removal by the flue gas purification self-circulation structure to generate calcination flue gas and dust collection ash. The dust collection ash is circulated to the bottom of the activation furnace to continue the calcination process and obtain iron-containing active materials (calcination tailings).

[0049] Compositional analysis revealed that the dewatering tailings contained high levels of iron, silicon, and aluminum. Considering the high porosity of the dewatering tailings during gasification, the tailings were pressed into 2-5mm spheres using a roller press granulator (the particle size requirement for the activation furnace is also 2-5mm, with a moisture content below 15% and a calorific value of 1000 kcal). These spherical dewatering tailings, meeting the activation furnace particle size requirements, were then fed into the activation furnace for calcination. Inside the activation furnace (where the internal temperature is approximately 900℃), the remaining small amount of residue in the spherical dewatering tailings was burned. Carbon is used to preheat spherical dewatering tailings, making full use of its calorific value. This process breaks the chemical bonds of the less active crystalline phases (such as mullite and quartz) in the spherical dewatering tailings, transforming them into amorphous (glassy) or more active mineral phases (such as calcium silicate and calcium aluminate). This process yields calcined tailings from the bottom of the activation furnace (calcined tailings are amorphous substances transformed from crystalline phases, possessing high "potential activity" and containing iron as active materials). These active materials can be used as water-retaining and fertilizer-retaining materials, water storage materials, environmental protection materials, concrete additives, and in other fields.

[0050] During the activation and modification process, the crystalline phase of the spherical dewatering tailings is activated inside the activation furnace to produce a mineral phase. This type of activation furnace has the characteristics of strong feed adaptability, low feed calorific value requirement, and built-in tail gas purification system. After the spherical dewatering tailings are activated and coupled at high temperature inside the activation furnace, the residual carbon is burned off and the harmful components are removed, making it an active material with resource utilization value, thus ensuring the resource utilization of the spherical dewatering tailings.

[0051] S3. Reduction and iron extraction: The calcined tailings are fed into a rotary kiln, where they are further calcined and reduced at high temperature. The output is reduced tailings and reduced flue gas. The reduced tailings are cooled by a slag cooler, then ground to reduce particle size, and finally magnetically separated to obtain active tailings and ferrous tailings.

[0052] The calcined tailings are further calcined at high temperature in a rotary kiln to reduce the iron oxides in the calcined tailings to iron(III) oxide; the magnetic separation recovery of the reduced tailings uses a multi-roller magnetic separator to obtain active tailings and ferrous tailings respectively.

[0053] Compositional analysis revealed that iron in the dewatered tailings was primarily in the weakly magnetic form of ferric oxide (Fe2O3), resulting in extremely low recovery rates with direct magnetic separation. The calcined tailings from the activation furnace were further calcined at high temperatures in a rotary kiln, reducing the iron oxides to magnetite (Fe3O4) before being output as reduced tailings. The strong magnetism of the magnetite in the reduced tailings facilitates subsequent magnetic separation of iron. Furthermore, the high-temperature treatment in the rotary kiln effectively decomposes and burns away harmful residual organic matter and certain salts, completely eliminating the potential problems associated with using gasification tailings as building materials. Potential risks include poor volume stability and efflorescence. After the reduction tailings are cooled by a slag cooler and further dissociated and reduced in particle size by a grinding mill, they are then recovered by magnetic separation (using a multi-roller magnetic separator) to obtain active tailings and ferrous tailings. The ferrous tailings, due to their enriched iron content, can be sold directly as a product or further refined into bread iron in the melting and refining process. The magnetically separated active tailings can be used as an active material and applied in fields such as water-retaining and fertilizer-retaining materials, water storage materials, environmental protection materials, and concrete additives.

[0054] S4. Melting and refining: Iron tailings are mixed with binders and reducing agents and then granulated into pellets. The granulated iron tailings are fed into the melting furnace as raw materials. The iron tailings are smelted in the melting furnace to produce iron ingots and smelting flue gas.

[0055] The reducing agent is one or more combinations of coke, carbon powder and iron powder, with carbon in coke and carbon powder serving as the reducing raw material, and iron in iron powder serving as the reducing raw material.

[0056] The binder is one or more of phosphate binders, cold-setting iron concentrate pellet binders, and chromite powder binders. The phosphate binder is one or more of orthophosphates such as magnesium phosphate and aluminum phosphate, and polycondensed phosphates such as sodium hexametaphosphate and sodium tripolyphosphate. The phosphate binder maintains its structural stability at high temperatures. The cold-setting iron concentrate pellet binder is one or more of bentonite, magnesium chloride, sodium carboxymethyl cellulose, and polyacrylamide. This binder reduces ash content and smelting pollution. The chromite powder binder is one or more of polyacrylamide and humate. This binder does not affect the smelting quality of the iron ore powder.

[0057] When the granulated iron tailings are fed into the melting furnace as raw material, residual anodes and limestone are also added to the granulated iron tailings. By using residual anodes to replace coke as fuel and reducing agent for iron extraction, solid waste from other industries can be effectively utilized, and resource waste can be effectively reduced.

[0058] The granulated iron tailings, residual anodes, and limestone are fed into the charging hopper of the smelting furnace by a loader. In the charging hopper of the smelting furnace, the granulated iron tailings, residual anodes, and limestone are fed into the charging port at the top of the smelting furnace by a weighing feeder under the hopper in a fixed ratio. The molten iron is discharged through the discharge port at the bottom of the smelting furnace and cooled to form bread iron, which is then cooled and piled up on site. The smelted slag can be sold as cement clinker after water quenching.

[0059] Among them, residual anodes are solid waste generated in the alloy industry. In metal refining processes such as aluminum electrolysis and copper electrolysis, the anode material is gradually consumed during long-term electrolytic reactions, eventually forming residual anodes. Residual anodes have low moisture content, low ash content, low volatile matter, carbon content of over 97%, and high calorific value, with a heat value reaching 8000 kcal. One ton of residual anode is equivalent to the calorific value of 1.5 tons of metallurgical coke, and can be used as a reducing agent to participate in iron extraction.

[0060] The smelting flue gas is drawn from the top of the melting furnace by a fan into a gravity dust collector for preliminary dust removal, then enters a bag filter for secondary dust removal, and is then desulfurized and purified by a desulfurization tower. Part of the flue gas returns to the melting furnace as a supplementary heat source for the melting furnace, while the other part is fed into the generator set to generate electricity.

[0061] S5. Waste heat power generation: calcination flue gas and smelting flue gas are input into the generator set to generate electricity. The electricity generated is supplied to the plant's electrical load. The waste heat from power generation and rotary kiln cooling can be used for plant heating, bathing and other loads.

[0062] It can supply electricity and heating loads through waste heat, and can ensure that the waste heat of the activation furnace flue gas and the smelting furnace flue gas is not discharged. By generating electricity and supplying heating through waste heat of flue gas, energy is fully utilized, energy conservation and emission reduction are achieved, and it can bear the general electricity load of the entire project, while reducing the company's operating costs.

[0063] S6. Wastewater treatment: Wastewater produced from the dewatering of clean coal, middlings, and tailings is recycled after passing through the wastewater treatment system.

[0064] Due to the high moisture content of the coal gasification slag, the entire process is a water-producing process. Besides supplying the carbon extraction and dehydration steps, a large amount of excess water is produced. A wastewater treatment system is installed to treat this excess water using ultrafiltration and KRO wastewater treatment processes. After treatment, the effluent quality typically meets the Class A discharge requirements of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002). This system can be used in situations with high water quality requirements, truly achieving differentiated treatment and recycling of water resources, with no wastewater discharge.

[0065] This combined gasification slag treatment process employs a two-stage, multi-stage carbon extraction process using spiral separation and magnetic separation in the carbon extraction and dewatering steps. This further reduces the ash content of the output clean coal, enhancing its product value. The clean coal is dewatered using vacuum pressure filtration, while the middlings and tailings are dewatered using disc vacuum filtration. Different dewatering methods are selected based on the moisture content, ensuring efficiency while conserving energy. The dewatered tailings undergo activation, reduction for iron extraction, and smelting refining steps, fully recovering the iron elements. The remaining activated tailings can be sold as active materials, effectively improving the comprehensive utilization rate of gasification slag. While the overall utilization rate of gasification slag in the industry is generally around 40%, this combined gasification slag treatment process achieves a 100% utilization rate.

[0066] Furthermore, it can input calcination flue gas and smelting flue gas into the generator set to generate electricity, which supplies the electrical load. The waste heat from power generation and the waste heat from rotary kiln cooling can be used for heating and bathing in the plant area, thus enabling energy self-circulation and self-replenishment. It thoroughly practices the "zero waste" concept, realizes the resource utilization of waste heat and wastewater, reduces thermal pollution and water consumption, and has a good demonstration effect and social benefits.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A combined treatment process for gasification slag, characterized in that, Includes the following steps: S1. Carbon extraction and dehydration: After the gasification slag undergoes a multi-stage carbon extraction process, different products are obtained. The different products are separated into clean coal, middlings and tailings according to their carbon content. The clean coal, middlings and tailings are dehydrated to obtain dehydrated clean coal, dehydrated middlings and dehydrated tailings respectively. S2. Activation and modification: The dewatered tailings are granulated into balls so that the granulated dewatered tailings meet the particle size requirements for the activation furnace. The spherical dewatered tailings that meet the particle size requirements for the activation furnace are fed into the activation furnace for calcination to obtain calcined tailings and calcined flue gas. S3. Reduction and iron extraction: The calcined tailings are fed into a rotary kiln, where they are further calcined and reduced at high temperature. The output is reduced tailings and reduced flue gas. The reduced tailings are cooled by a slag cooler, then ground to reduce particle size, and finally magnetically separated to obtain active tailings and ferrous tailings. S4. Melting and refining: Iron tailings are mixed with binders and reducing agents and then granulated into pellets. The granulated iron tailings are fed into the melting furnace as raw materials. The iron tailings are smelted in the melting furnace to produce iron ingots and smelting flue gas. S5. Waste heat power generation: calcination flue gas and smelting flue gas are input into the generator set to generate electricity, and the electricity generated is supplied to the plant's electrical load. S6. Wastewater treatment: Wastewater produced from the dewatering of clean coal, middlings, and tailings is recycled after passing through the wastewater treatment system. Step S1 includes: S1.1 Multi-stage carbon extraction: The gasification slag is first passed through a spiral separator for preliminary spiral separation. The primary clean coal obtained from the preliminary spiral separation is fed into a primary magnetic separator for primary magnetic separation. The primary tailings obtained from the primary magnetic separation are fed into a secondary magnetic separator for secondary magnetic separation to further obtain carbon extraction tailings. S1.

2. The clean coal is dewatered by vacuum pressure filtration to obtain dewatered clean coal, and the middlings and tailings are dewatered by disc vacuum filtration to obtain dewatered middlings and dewatered tailings, respectively.

2. The gasification slag co-treatment process according to claim 1, characterized in that: In step S1.1, the primary magnetic separator uses a single-roller downward magnetic separator, and the secondary magnetic separator uses a multi-roller magnetic separator. The magnetic circuit structure of the single-roller down-selection magnetic separator is that the same level is arranged and clustered together. The magnetic circuit is rotated by the magnetic roller, and the N and N levels change instantaneously. The working magnetic field strength is not less than 8500 Gauss. The discharge plate of the single-roller down-selection magnetic separator can be adjusted within a range of no more than 90°, and the water level and concentration can be controlled according to the iron content of the material, thereby controlling the grade and yield of the concentrate. The working magnetic field strength of the multi-roller magnetic separator is not less than 12,500 Gauss.

3. The gasification slag co-treatment process according to claim 1, characterized in that: In step S2, the particle size requirement for the activated furnace feed is 2-5 mm. The activation furnace has a flue gas purification self-circulation structure. The activation furnace flue gas output from the top of the activation furnace is subjected to gravity dust removal by the flue gas purification self-circulation structure to generate calcination flue gas and dust collection ash. The dust collection ash is circulated to the bottom of the activation furnace.

4. The gasification slag co-treatment process according to claim 2, characterized in that: In step S3, the calcined tailings are further calcined at high temperature in a rotary kiln to reduce the iron oxides in the calcined tailings to iron(III) oxide. The magnetic separation and recovery of the reduction tailings uses a multi-roller magnetic separator to obtain active tailings and ferrous tailings respectively.

5. The gasification slag co-treatment process according to claim 1, characterized in that: In step S4, the reducing agent is one or more combinations of coke, carbon powder and iron powder; The binder is one or more combinations of phosphate binder, cold-cured iron concentrate pellet binder, and chromite powder binder.

6. The gasification slag co-treatment process according to claim 1, characterized in that: In step S4, when the granulated iron tailings are fed into the melting furnace as raw material, residual anode and limestone are also added to the granulated iron tailings. The ferrous tailings, residual anodes, and limestone, which are granulated into pellets, are fed into the charging hopper of the melting furnace by a loader. Iron-containing tailings, residual anodes, and limestone, granulated into balls in the charging hopper of the smelting furnace, are fed into the charging port at the top of the smelting furnace through a weighing feeder under the hopper in a fixed ratio.

7. The gasification slag co-treatment process according to claim 1, characterized in that: In step S4, the smelting flue gas is drawn from the top of the melting furnace into a gravity dust collector for preliminary dust removal by a fan, then enters a bag filter for secondary dust removal, and is then desulfurized and purified by a desulfurization tower. Part of the flue gas returns to the melting furnace as a supplementary heat source for the melting furnace, while the other part is input into the generator set to generate electricity.

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