阅读说明：本技术 一种气化黑水细渣残碳回收-尾渣降钙镁的方法 (Method for recycling carbon residue from gasified black water fine slag and reducing calcium and magnesium in tailings ) 是由 刘广学 彭团儿 邵伟华 张艳娇 郭珍旭 王力 冯乃琦 刘长淼 于 2021-05-25 设计创作，主要内容包括：本发明提出了一种气化黑水细渣残碳回收-尾渣降钙镁的方法,主要工艺路线为浓缩重选—精细分级—两段磁选,包括以下步骤：将气化黑水浓缩得到浓缩渣浆,浓缩渣浆进入重选作业,得到重选轻矿物和重选重矿物；重选轻矿物浓缩后进入分级作业,得到粗粒级产品和细粒级产品,将粗粒级产品浓缩、脱水得到高热值碳粉；重选重矿物和细粒级产品合并送至磁选作业,磁选作业包括一段中磁选和二段强磁选,一段中磁选和二段强磁选获得的磁性物浓缩脱水后得到富钙镁低碳尾渣,二段强磁选获得的非磁性物浓缩脱水后得到低钙镁富孔尾渣。本发明用以解决气化细渣残碳难以回收、提碳后尾渣钙镁碱性矿物含量高无法综合利用的技术难题。(The invention provides a method for recycling carbon residue of gasified black water fine slag and reducing calcium and magnesium in tailings, which mainly comprises the following steps of concentration and reselection, fine classification and two-stage magnetic separation: concentrating the gasified black water to obtain concentrated slag slurry, and performing gravity separation operation on the concentrated slag slurry to obtain gravity separated light minerals and gravity separated heavy minerals; concentrating gravity light minerals, performing grading operation to obtain coarse fraction products and fine fraction products, and concentrating and dehydrating the coarse fraction products to obtain high-heat-value carbon powder; heavy minerals and fine fraction products are reselected and are merged and sent to magnetic separation operation, the magnetic separation operation comprises first-stage medium magnetic separation and second-stage strong magnetic separation, magnetic substances obtained by the first-stage medium magnetic separation and the second-stage strong magnetic separation are concentrated and dehydrated to obtain calcium-magnesium-rich low-carbon tailings, and non-magnetic substances obtained by the second-stage strong magnetic separation are concentrated and dehydrated to obtain low-calcium-magnesium-rich pore tailings. The invention is used for solving the technical problems that the carbon residue of the gasified fine slag is difficult to recover, and the tailings after carbon extraction has high content of calcium and magnesium alkaline minerals and cannot be comprehensively utilized.)

1. A method for recycling carbon residue from gasified black water fine slag and reducing calcium and magnesium in tailings is characterized by comprising the following steps: the method comprises the following steps:

(1) concentrating the gasified black water to obtain concentrated slag slurry, performing gravity separation operation on the concentrated slag slurry to obtain gravity separated light minerals and gravity separated heavy minerals, wherein the gravity separated light minerals are pre-enriched carbon slurry, and the gravity separated heavy minerals are silicon-rich low-carbon tailings;

(2) concentrating the gravity-separated light minerals in the step (1), then performing grading operation to obtain coarse-grained products and fine-grained products, and concentrating and dehydrating the coarse-grained products to obtain high-heat-value carbon powder of a product 1;

(3) combining the gravity concentration heavy minerals in the step (1) and the fine-grained products in the step (2) and sending the mixture to magnetic separation operation, wherein the magnetic separation operation comprises first-stage medium magnetic separation and second-stage strong magnetic separation, nonmagnetic substances obtained by the first-stage medium magnetic separation and the second-stage strong magnetic separation enter the second-stage strong magnetic separation, the magnetic substances obtained by the first-stage medium magnetic separation and the second-stage strong magnetic separation are concentrated and dehydrated to obtain the calcium-magnesium-rich low-carbon tailings of the product 2, and the nonmagnetic substances obtained by the second-stage strong magnetic separation are concentrated and dehydrated to obtain the low-calcium-magnesium-rich pore tailings of the product 3.

2. The method for recycling gasified black water fine slag carbon residue-tailings calcium and magnesium reduction according to claim 1, which is characterized in that: in the step (3), the magnetic separation in the first section adopts a semi-counterflow roller type magnetic separator with the magnetic field intensity of 218-557KA/m, and the magnetic separation in the second section adopts a plate magnetic separator with the magnetic field intensity of 636-796KA/m or a high-gradient magnetic separator with the magnetic field intensity of 637-1195 KA/m.

3. The method for recycling gasified black water fine slag carbon residue-tailings calcium and magnesium reduction according to claim 1, which is characterized in that: in the step (1), the reselection operation selects one-stage reselection or two-stage reselection according to the content of the residual carbon in the fine slag and the component difference of the original slag, wherein the two-stage reselection process comprises primary reselection and secondary reselection, and the light minerals subjected to the primary reselection enter the secondary reselection; in the step (2), the grading operation comprises one-stage grading or two-stage grading, the two-stage grading comprises primary grading and fine grading, coarse-grained materials of the primary grading enter the fine grading, fine-grained materials of the primary grading and the fine grading are combined into fine-grained products, and heavy minerals of the primary reselection and the secondary reselection are combined into reselected heavy minerals.

4. The method for recycling gasified black water fine slag carbon residue-tailings calcium and magnesium reduction according to claim 3, wherein the method comprises the following steps: in the step (1), the two-stage reselection equipment is one or more of a centrifugal force field disc type separator, a check spiral chute, a dense medium classifier and a heavy liquid concentrator.

5. The method for recycling gasified black water fine slag carbon residue-tailings calcium and magnesium reduction according to claim 4, wherein the method comprises the following steps: and (3) secondary re-concentration is spiral chute concentration to obtain concentrated light minerals, concentrated medium minerals and concentrated heavy minerals, wherein the concentrated light minerals are screened by high frequency, the concentrated medium minerals are concentrated by a table concentrator, and the fine-fraction materials subjected to table concentrator concentration and high frequency screening and the concentrated heavy minerals and the heavy minerals subjected to primary re-concentration are combined and enter the magnetic separation operation in the step (3).

6. The method for recycling gasified black water fine slag carbon residue-tailings calcium and magnesium reduction according to claim 1, which is characterized in that: in the step (1), the concentrated slag slurry is firstly subjected to slag separation homogenization and then enters into gravity separation operation, and the specific method of slag separation homogenization comprises the following steps: separating coarse slag or foreign matter impurities from the concentrated slag slurry through a vibrating slag separating screen, wherein the aperture of a screen mesh of the slag separating screen is 0.5-2.5mm, and simultaneously scattering and homogenizing gasified fine slag which is locally precipitated and agglomerated in the concentration process through slag separating.

7. The method for recycling gasified black water fine slag carbon residue-tailings calcium and magnesium reduction according to claim 1, which is characterized in that: in the step (1), adding a flocculating agent into the concentrated overflow water for purification to obtain precipitate slag slurry and purified water, wherein the adding amount of the flocculating agent is 30-50 g/t; and (4) returning the overflow water and the sediment slurry after concentration in the steps (2) and (3) to the concentration operation in the step (1).

8. The method for recycling gasified black water fine slag carbon residue-tailings calcium and magnesium reduction according to claim 3, wherein the method comprises the following steps: the primary grading particle size range is 0.074-0.2mm, and the fine grading particle size range is 0.1-0.35 mm.

9. The method for recycling carbon residue from gasified black water fine slag-tailings to reduce calcium and magnesium according to claim 7, which is characterized in that: the flocculating agent is carbide slag or lime.

Technical Field

The invention relates to the technical field of comprehensive utilization of solid wastes, in particular to a method for recycling carbon residue in gasified black water fine slag in coal chemical industry and reducing calcium and magnesium in tailings, and particularly relates to a method for recycling carbon residue in gasified black water fine slag in Texaco furnace and reducing the content of calcium and magnesium in tailings after carbon extraction.

Background

The annual increase of solid waste of gasified slag of 14 hundred million-ton large coal bases and 4-ton coal chemical industry bases in China is about 7500 million tons, and due to the restriction of the problems of large yield, high carbon residue, high water content, difficult utilization, high cost and the like, the comprehensive utilization progress of the gasified slag is slow, the comprehensive utilization rate is low, and the problems of centralized clearing and transportation, disposal in a slag yard stacking mode, black powder after stacking, land occupation, environmental pollution and resource waste are prominent at present.

Coal gasification is a leading and core technology for converting solid coal into gas clean energy in the field of coal chemical industry, and is an important direction for coal resources and energy utilization. In the coal gasification technology system, the inorganic mineral components associated with the raw coal, the added catalyst and the carbon remained after incomplete gasification are discharged in the form of residue (coal gasification slag). The gasified slag is divided into coarse slag and fine slag according to different discharge modes. The coarse slag, namely slurried coal particles are subjected to processes of melting, water quenching, chilling, condensation and the like under the high-temperature and high-pressure condition of the gasification furnace, and the water-containing slag discharged from a slag discharge lock hopper at the bottom of the gasification furnace has large fluctuation of 10-30% of residual carbon along with coal types, gasification furnace types and gasification furnace operating conditions, the particle size is intensively distributed between 16 meshes and 4 meshes, and the generated amount accounts for about 60-80% of the discharge amount of the gasification slag. The fine slag is water-containing slag obtained by carrying out crude gas flow from the top of the gasification furnace, primarily washing and purifying, precipitating solid-phase impurities in the gasified black water, and performing filter pressing, wherein the residual carbon content is higher and generally can reach more than 30%, the particle sizes are all smaller than 16 meshes, about one third of the residual carbon content is smaller than 200 meshes, and the generated amount accounts for about 20-40% of the discharge amount of the gasified slag.

The gasification slag is mainly characterized in that: (1) the carbon residue content is high, the carbon powder has a certain heat value, the carbon powder particle structure is loose, the gaps are rich, the specific surface area is large, the adsorbability is strong, and the dehydration is difficult; (2) the inorganic phase consists mainly of silicoaluminous minerals: SiO 2₂、Al₂O₃And Fe₂O₃The sum of the three>70 percent, and secondly, the content of CaO and MgO is higher. The chemical composition characteristics and the special mineral phase composition of the resources rich in silicon, aluminum and carbon are the basis of recycling of the gasified slag, the content of residual carbon is high, the material digestion and doping amount and the product performance of the gasified slag are seriously influenced, and carbon ash separation is required based on the material digestion and utilization of the aluminum-silicon-based gasified slag. And secondly, the ash slag has high content of alkali metal minerals such as calcium, magnesium and the like, so that the ash slag is used for building materials and the like, and the strength, the stability and the apparent property of the material utilization product are easily reduced.

In the prior art, CN110976075A discloses a method for extracting carbon and reducing ash by coarse grain tailing discarding and fine grain flotation of gasified slag, which realizes carbon ash separation, but has the following problems: firstly, due to the pore-rich structural characteristics of the gasified slag, the specific surface area is large, the adsorbability to medicaments is strong, the dosage of the medicaments in the flotation method is large, and the cost is high; secondly, the use of the medicament increases the viscosity of the ore pulp, and increases the dehydration difficulty of the product; thirdly, the process water is introduced with beneficiation reagent, so that the water return rate is low, and the water treatment cost is increased.

CN111644264A discloses a gasification slag gravity-magnetic combined separation process, and CN111644263A discloses a combined separation process for realizing carbon-ash separation of gasification slag, the above processes use a water medium cyclone and a classification cyclone to realize carbon-ash separation, the advantage is that the gravity-magnetic combined process realizes effective separation of high-carbon, carbon-rich and high-ash products, but has the following problems: firstly, the ash slag has high hardness, sharp edges and corners and large feeding pressure of 0.14MPa and 0.2MPa respectively, so that conveying equipment and sorting equipment are greatly abraded and the energy consumption is high; secondly, the soft carbon powder is crushed for the second time to reduce the recovery rate of the carbon powder; thirdly, although a magnetic separation method is used for extracting carbon and reducing ash in the scheme, the method does not relate to the separation and comprehensive utilization of high-calcium and high-magnesium components in the tailings.

In addition, gasification fine slag, generally gasification furnace black water, is comprehensively utilized after pretreatment measures such as secondary pulping, depolymerization and dispersion are carried out after strong flocculation, concentration and vacuum belt type filter pressing dehydration are carried out on the gasification fine slag in the prior art. The disadvantages are as follows: firstly, the black water of the gasification furnace is directly added with a strong flocculating agent, the dosage of the flocculating agent is large, generally about 150g/t, the requirements on the quality and the type of the flocculating agent are increased, the production cost is increased, in addition, the flocculation concentration causes the agglomeration of residual carbon and amorphous flocculent glass body, and causes the poor separation and comprehensive utilization effect of carbon ash; secondly, flocculation and dehydration are firstly carried out, depolymerization and slurry preparation are carried out during use, the comprehensive treatment process of the gasified slag is long, and the soft carbon powder particles are crushed and argillized in the treatment process and cannot be recovered, so that the recovery rate of residual carbon is low, the system operation cost is high, and the comprehensive economy is poor.

Disclosure of Invention

The invention provides a method for recycling fine slag carbon residue of gasified black water and reducing calcium and magnesium in tailings, which is used for solving the technical problems that the fine slag carbon residue of gasified black water is difficult to recycle, and the tailings after carbon extraction have high calcium and magnesium alkaline mineral content and cannot be comprehensively utilized.

The technical scheme of the invention is realized as follows: a method for recycling carbon residue from gasified black water fine slag and reducing calcium and magnesium in tailings comprises the following steps:

(1) concentrating the gasified black water to obtain concentrated slag slurry, performing gravity separation operation on the concentrated slag slurry to obtain gravity separated light minerals and gravity separated heavy minerals, wherein the gravity separated light minerals are pre-enriched carbon slurry, and the gravity separated heavy minerals are silicon-rich low-carbon tailings;

(2) concentrating the gravity-separated light minerals in the step (1), then performing grading operation to obtain coarse-grained products and fine-grained products, and concentrating and dehydrating the coarse-grained products to obtain high-heat-value carbon powder of a product 1;

(3) combining the gravity concentration heavy minerals in the step (1) and the fine-grained products in the step (2) and sending the mixture to magnetic separation operation, wherein the magnetic separation operation comprises first-stage medium magnetic separation and second-stage strong magnetic separation, nonmagnetic substances obtained by the first-stage medium magnetic separation and the second-stage strong magnetic separation enter the second-stage strong magnetic separation, the magnetic substances obtained by the first-stage medium magnetic separation and the second-stage strong magnetic separation are concentrated and dehydrated to obtain the calcium-magnesium-rich low-carbon tailings of the product 2, and the nonmagnetic substances obtained by the second-stage strong magnetic separation are concentrated and dehydrated to obtain the low-calcium-magnesium-rich pore tailings of the product 3.

Further, in the step (3), the magnetic separation in the first section adopts a semi-counterflow roller magnetic separator with the magnetic field strength of 218-.

Further, in the step (1), the reselection operation selects one-stage reselection or two-stage reselection according to the content of the carbon residue in the fine slag and the component difference of the original slag, wherein the two-stage reselection process comprises primary reselection and secondary reselection, and the light minerals subjected to the primary reselection enter the secondary reselection; in the step (2), the grading operation comprises one-stage grading or two-stage grading, the two-stage grading comprises primary grading and fine grading, coarse-grained materials of the primary grading enter the fine grading, fine-grained materials of the primary grading and the fine grading are combined into fine-grained products, and heavy minerals of the primary reselection and the secondary reselection are combined into reselected heavy minerals.

Further, the secondary re-concentration is spiral chute concentration to obtain concentrated light minerals, concentrated middlings and concentrated heavy minerals, the concentrated light minerals are screened by high frequency, the concentrated middlings are concentrated by a table concentrator, fine fractions subjected to table concentrator concentration and high frequency screening, the concentrated heavy minerals and the heavy minerals subjected to primary re-concentration are combined and enter the magnetic separation operation in the step (3).

Further, in the step (1), the concentrated slag slurry is firstly subjected to slag separation homogenization and then enters into gravity separation operation, and the specific method of slag separation homogenization comprises the following steps: separating coarse slag or foreign matter impurities from the concentrated slag slurry through a vibrating slag separating screen, wherein the aperture of a screen mesh of the slag separating screen is 0.5-2.5mm, and simultaneously scattering and homogenizing gasified fine slag which is locally precipitated and agglomerated in the concentration process through slag separating.

Further, in the step (1), adding a flocculating agent into the concentrated overflow water for purification to obtain sediment slurry and purified water, wherein the adding amount of the flocculating agent is 30-50 g/t; and (4) returning the overflow water and the sediment slurry after concentration in the steps (2) and (3) to the concentration operation in the step (1).

Further, the flocculating agent is carbide slag or lime.

Further, the primary classification particle size range is 0.074-0.2mm, and the fine classification particle size range is 0.1-0.35 mm.

The invention has the beneficial effects that:

1. the method is suitable for recovering the carbon residue of the Texaco gasified fine slag or the gasified slag with high calcium and magnesium content, and has the following advantages: (1) the recovered carbon fine powder has high ignition loss and high recovery rate, and is easy to be used in a high-value way; (2) the carbon residue of the ash after carbon extraction is low, the calcium and magnesium content is low, and the material utilization requirement is met; (3) the process is green and pollution-free; (4) the process is simple, the adaptability is strong, the cost is low, and the large-scale popularization and application are convenient; (5) the solid waste resources are comprehensively utilized to the maximum extent; (6) avoiding unnecessary process consumption such as flocculation depolymerization, dehydration and water addition in the preparation process of the black water fine slag raw material.

2. The treatment process has short flow and high recovery rate, and is mainly embodied in that the treatment of a slag yard is carried out outside the transfer without flocculation, dehydration, filter pressing and water draining in the main flow process of preparing the product, so that the consumption and the use of a flocculating agent are effectively saved, the agglomeration of carbon powder and amorphous flocculent ash residues is prevented from influencing the separation effect, soft carbon powder particles are protected, and the problems that secondary crushing and argillization cannot be recovered in the long-flow processing process are solved; only a flocculating agent is added into the concentrated overflow water obtained by concentrating the gasified black water in the step (1), so that the using amount is reduced by 70-80%, the variety is cheap, the quality requirement on the flocculating agent is low, and the production cost is reduced;

3. the process comprehensively recovers high-heat-value carbon fine powder from gasified black water fine slag, the ignition loss is more than 80%, the recovery rate is more than 65%, the dry-based carbon residue of the gasified fine slag is more than 35%, the water content of a carbon raw material of the gasified slag is about 40-50%, and the carbon content is generally expressed by the weight ratio of carbon in dry substances after the gasified fine slag is dried. Because the gasified slag is treated at high temperature, the carbon content is generally expressed by the dry-based ignition loss of the gasified fine slag;

4. effective separation of calcium-magnesium-rich mineral components is realized through a two-stage magnetic separation process, and calcium-magnesium-rich low-carbon tailings and low-calcium-magnesium-rich pore tailings are obtained. The calcium-magnesium-rich low-carbon tailings have the ignition loss of less than 5 percent, the CaO + MgO content of more than 14 percent and the recovery rate of more than 55 percent; the loss on ignition of the low-calcium magnesium pore-rich tailings is about 40-45%, and the content of CaO and MgO is less than 7%;

5. the process is used for recycling carbon powder and grading and utilizing tailings, so that the comprehensive utilization of all solid waste resources of gasified slag is realized. The calcium-magnesium-rich low-carbon tailings can be used for an acid soil conditioner to decompose hardened soil and increase soil air permeability, or a high-strength thermal insulation material is prepared by utilizing the high-temperature phase reconstruction melt strength high characteristic and the pore enrichment characteristic of the low-carbon high-silicon aluminum-based component, so that the use requirements of building material products on the properties such as product strength and the like are met; the low-calcium magnesium porous tailings can be compounded with organic fertilizers and chemical fertilizers to be used as slow-release fertilizers or used for blending and burning to prepare light building materials or ceramsite proppant raw materials;

6. the gasification slag and carbon residue recovery adopts a combined process of two-section spiral chute reselection and middling table concentration, the spiral chute equipment has a simple structure, no moving parts, energy conservation and consumption reduction, small floor area and large treatment capacity, is suitable for industrial popularization and application, and is favorable for further improving the enrichment ratio and the recovery rate of carbon residue products by adopting the cooperation, and is superior to other process schemes.

7. The whole process does not use chemical agents, and is a full physical pollution-free process;

8. the wastewater in the whole process is completely recycled after secondary purification treatment, and zero discharge of the wastewater is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 is a process flow diagram of example 1;

FIG. 3 is a process flow diagram of example 2.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.

As shown in figure 1, the method for recycling carbon residue from gasified black water fine slag-tailings to reduce calcium and magnesium comprises the following steps:

(1) concentrating the gasified black water to obtain concentrated slag slurry, performing gravity separation operation on the concentrated slag slurry to obtain gravity separated light minerals and gravity separated heavy minerals, wherein the gravity separated light minerals are pre-enriched carbon slurry, and the gravity separated heavy minerals are silicon-rich low-carbon tailings;

and (3) gasifying and concentrating fine slag in black water: naturally precipitating and concentrating coal gasification black water with the solid content of fine slag of 1-2% by a rake thickener, concentrating underflow until the solid content is 10-25%, adding a flocculating agent into overflow water of the thickener to perform secondary precipitation and purification to obtain precipitated slag slurry and purified water, returning the purified water to the slurry mixing process of the coal water slurry for recycling, wherein the adding amount of the flocculating agent is 30-50g/t, and the flocculating agent is carbide slag or lime.

Carrying out slag separation and homogenization pretreatment on concentrated slag slurry: separating coarse slag or foreign matter impurities from the concentrated slag slurry obtained in the step (1) through a vibrating slag separating screen, wherein the screen mesh diameter of the slag separating screen is 0.5-2.5mm, so that equipment abrasion and pipeline blockage in the conveying process are avoided, and meanwhile, dispersing and homogenizing the local precipitated, caked and gasified slag in the concentration process through slag separating.

And (4) reselection operation: and (2) conveying the gasified fine slag ore pulp subjected to slag separation treatment obtained in the step (1) by a slag slurry pump into a gravity separation operation feeding stirring barrel, wherein the gravity separation operation equipment is one or more of a centrifugal force field disc type separator, a repeated selection spiral chute, a shaking table, a heavy medium classifier and a heavy liquid concentrator.

And (4) selecting a first-stage reselection process or a second-stage reselection process according to the content of the carbon residue in the fine slag and the component difference of the original slag in the reselection operation. The secondary reselection process comprises primary reselection and secondary reselection, wherein the light minerals subjected to the primary reselection enter the secondary reselection, the light minerals subjected to the secondary reselection are pre-enriched carbon slurry, and the heavy minerals subjected to the secondary reselection are silicon-rich low-carbon tailings.

(2) Concentrating the gravity-separated light minerals in the step (1), then performing grading operation to obtain coarse-grained products and fine-grained products, and concentrating and dehydrating the coarse-grained products to obtain high-heat-value carbon powder of a product 1;

grading and upgrading pre-enriched carbon slurry: concentrating the gravity concentration light mineral pulp obtained in the step (2) to a solid content of 10-25%, and conveying the concentrated pulp to a classification operation through a slurry pump for coarse and fine classification, wherein the classification equipment is one or more of a high-frequency vibrating screen, a rotary screen, a linear screen or a cyclone, and the fine classification granularity range is 0.074-0.35 mm.

According to different scale of materials to be treated, the grading operation comprises first-stage grading or second-stage grading according to working condition characteristics, the second-stage grading comprises first-stage grading and fine grading, coarse-grained materials subjected to the first-stage grading enter the fine grading, the range of the first-stage grading granularity is 0.074-0.2mm, and the range of the fine-grading granularity is 0.1-0.35 mm. And (3) carrying out classification operation to obtain a coarse fraction product, and concentrating and dehydrating the coarse fraction product to obtain a product 1: high loss on ignition refined carbon powder.

Particularly, a centrifugal force field high-speed disc type separator is adopted in the first stage reselection, a spiral chute is adopted in the second stage reselection, middlings in the spiral chute are carefully selected by a table concentrator, and light minerals in the spiral chute are combined by a high-frequency fine screening process, so that the ignition loss of refined carbon powder is higher than 80%, the recovery rate is higher than 65%, and the process is superior to other process schemes.

(3) And (3) combining the gravity minerals obtained in the step (1) and the fine-grained products obtained in the step (2), adjusting the mixture to a proper concentration to be used as a low-carbon tailing intermediate product, and sending the intermediate product to magnetic separation operation, wherein the magnetic separation operation comprises first-stage medium magnetic separation and second-stage strong magnetic separation, the nonmagnetic substances obtained in the first-stage medium magnetic separation enter the second-stage strong magnetic separation, the magnetic substances obtained in the first-stage medium magnetic separation and the second-stage strong magnetic separation are concentrated and dehydrated to obtain the product 2 rich in calcium and magnesium low-carbon tailings, and the nonmagnetic substances obtained in the second-stage strong magnetic separation are concentrated and dehydrated to obtain the product 3 low-calcium and magnesium rich in pore tailings.

Magnetic separation of calcium and magnesium components: conveying the low-carbon tailing intermediate product to magnetic separation operation through a slurry pump, wherein a semi-countercurrent drum-type magnetic separator with the magnetic field intensity of 218-557KA/m is adopted in the first-stage magnetic separation, a plate magnetic separator with the magnetic field intensity of 636-796KA/m or a high-gradient magnetic separator with the magnetic field intensity of 637-1195KA/m is adopted in the second-stage strong magnetic separation, magnetic separation substances obtained by the two magnetic separation operations are combined, and the combined magnetic separation substances are concentrated and dehydrated to serve as a product 2: and concentrating and dehydrating the nonmagnetic substances obtained by the two-stage strong magnetic separation to obtain the low-calcium-magnesium-rich low-carbon tailings of the product 3.

Based on the research result of the high calcium and magnesium components and iron-containing minerals closely associated process mineralogy of tailings after carbon extraction, the method for realizing the separation and comprehensive utilization of calcium and magnesium-rich components by using a magnetic separation method is provided. Wherein, the product 1 adopts a vacuum belt filter press, and the products 2 and 3 adopt equipment such as a vacuum disc filter or a dewatering screen for dewatering.

And (3) intensively conveying the whole process wastewater to the thickener in the step (1), and performing secondary precipitation and purification on overflow water of the thickener to obtain purified water of a product 5, and returning the purified water to the coal water slurry mixing process for recycling.

The comprehensive utilization scheme of the recovered product is as follows:

the product 1 is high-calorific-value carbon fine powder, the ignition loss is more than 80%, and the carbon fine powder is comprehensively utilized by the following three modes: according to the utilization mode 1, the coal water slurry is prepared by uniformly mixing the concentrated and dehydrated coal water slurry with gasified raw material coal, and is recycled, so that the resource utilization rate is improved; in the utilization mode 2, high-heat-value carbon fine powder is concentrated and dehydrated, then is dried by using the waste heat of a coal chemical device through a rotary kiln, the water content of a discharged product is controlled to be less than 20%, and the product is uniformly mixed with fuel coal and is used for mixed combustion of a thermoelectric boiler; in the utilization mode 3, the recovered carbon powder is dried and then is used for preparing adsorbing materials such as activated carbon and the like;

product 2: after being compounded with organic fertilizer, the calcium-magnesium-rich low-carbon tailings are used as an acid soil conditioner to decompose hardened soil and increase soil permeability, or are used for brick making and cement admixture based on low-carbon high-silicon aluminum-based components;

product 3: the low-calcium magnesium porous tailings can be compounded with organic fertilizers and chemical fertilizers to be used as slow-release fertilizers or used for blending and burning to prepare light building materials or ceramsite proppant raw materials.

Example 1

The loss on ignition of raw ore of gasified black water fine slag of certain chemical enterprises in inner Mongolia is 48.48%, the total content of CaO and MgO is 7.08%, and other chemical components mainly comprise silicon dioxide, aluminum oxide and ferric oxide. By adopting the process flow shown in FIG. 2, the high-frequency screening operation is carried out to obtain products with a coarse fraction of +0.2mm and products with a fine fraction of-0.2 mm, the medium magnetic separation adopts a semi-counterflow roller type magnetic separator with the magnetic field intensity of 477KA/m, and the high magnetic separation adopts a plate magnetic separator with the magnetic field intensity of 716 KA/m. This example yielded a total of three products, product 1: the yield is 40.98%, the ignition loss is 81.31%, the total content of calcium oxide and magnesium oxide is 2.07%, and the carbon recovery rate is 67.36%, and the product can be subjected to dehydration and drying treatment to realize circulation gasification, thermoelectric co-combustion or secondary sale; product 3: the yield is 38.32%, the loss on ignition is 43.09%, and the content of CaO and MgO is 6.24%, and the product is used as slow release fertilizer or used for blending and burning to prepare light building materials or ceramsite proppant raw materials after being compounded with organic fertilizer and chemical fertilizer; product 2: the calcium-magnesium-rich low-carbon tailings with the yield of 20.70 percent, the loss on ignition of 5.55 percent and the CaO + MgO content of 14.88 percent can be used for an acid soil conditioner, decomposing hardened soil and increasing the soil permeability, or can be used for brick making and cement admixture based on low-carbon high-silicon aluminum-based components.

Chemical multi-item analysis result of fine slag crude ore

Composition (I)	Loss on ignition	Fe2O3	CaO	MgO	SiO2
						Content/%	48.48	8.30	6.35	0.73	43.00
Composition (I)	Al2O3	SO3	K2O	Na2O
						Content/%	9.50	1.70	0.96	1.16

Scheme and index for recovering carbon residue from gasified fine slag-separating product with high calcium and magnesium components in tailings

Example 2

The loss on ignition of raw ore of gasified black water fine slag of certain chemical enterprises in Ningxia is 36.40%, the total content of CaO and MgO is 6.35%, other chemical components are mainly silicon dioxide, aluminum oxide and iron oxide, the process flow shown in figure 3 is adopted, a coarse fraction product of +0.074mm and a fine fraction product of-0.074 mm are obtained through one-time grading high-frequency screening operation, a coarse fraction product of +0.2mm and a fine fraction product of-0.2 mm are obtained through fine grading high-frequency screening operation, a semi-counter-flow drum type magnetic separator with the magnetic field intensity of 557KA/m is adopted for medium magnetic separation, and a high-gradient high-magnetic separator with the magnetic field intensity of 1195KA/m is adopted for high magnetic separation. This example yielded a total of three products, product 1: the yield is 30.07%, the loss on ignition is 82.11%, the recovery rate is 67.02%, wherein the total content of calcium oxide and magnesium oxide is 1.57%, and the product can realize circulation gasification, thermoelectric co-combustion or secondary sale through dehydration and drying treatment; product 3: the yield is 43.45%, the loss on ignition is 26.05%, the content of CaO and MgO is 4.39%, the low-calcium magnesium product can be used for preparing the raw material of the lightweight building material or the ceramic proppant by utilizing the characteristics of the low-calcium magnesium and high-aluminum silicon components of the product, and the residual carbon is used as a heat source for supplementing the sintering material; product 2: the calcium-magnesium-rich low-carbon tailings with the yield of 26.46 percent, the loss on ignition of 1.57 percent and the CaO + MgO content of 15.01 percent can be used for an acid soil conditioner, decomposing hardened soil and increasing the soil permeability, or can be used for brick making and cement admixture based on low-carbon high-silicon aluminum-based components.

Chemical multi-item analysis result of fine slag crude ore

Composition (I)	Loss on ignition	Fe2O3	CaO	MgO	SiO2
						Content/%	36.40	7.28	5.48	0.87	30.38
Composition (I)	Al2O3	SO3	K2O	Na2O
						Content/%	13.94	1.42	1.29	1.05

Scheme and index for recovering carbon residue from gasified fine slag-separating product with high calcium and magnesium components in tailings

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.