High-sulfur coal gangue desulfurization method based on roasting-shock cooling synergistic enhanced reselection

Abstract

The invention discloses a high-sulfur coal gangue desulfurization method based on roasting-shock cooling synergistic enhanced reselection, which comprises the following steps: 1) carrying out liquid-phase ore grinding dissociation treatment on high-sulfur coal gangue, filtering and drying to obtain high-sulfur coal gangue powder; (2) the high-sulfur coal gangue powder is roasted and subjected to shock cooling treatment, and coal gangue ore pulp subjected to secondary dissociation is obtained; and (3) the coal gangue pulp obtained after secondary dissociation is subjected to gravity separation, suction filtration and drying, and concentrate and tailings are obtained. According to the method, the coal gangue and pyrite in the high-sulfur coal gangue are fully dissociated by adopting an ore grinding-roasting-shock cooling mode, and the number of intergrowth bodies is reduced, so that the gravity separation efficiency is improved, and the low-sulfur tailings are obtained and can be used for manufacturing building materials such as ceramsite, cement and baking-free bricks. The desulfurization method provided by the invention is free of chemical agent addition in the whole process, low in treatment cost and convenient to popularize, and has relatively good economic and social values.

Description

Technical Field

[0001] The invention belongs to the technical field of mineral processing, and in particular relates to a high-sulfur coal gangue desulfurization method based on roasting-quenching synergistic enhanced gravity separation. Background Art

[0002] Gangue is a mineral associated with coal, produced during the mining and washing processes. Its calorific value is generally less than 6.3 MJ / kg. It contains inorganic ash, such as Al2O3, SiO2, and Fe2O3, which together account for 60%-95% of the total gangue. Due to its difficulty in utilization, it has become an industrial solid waste. In recent years, extensive research has been conducted on the applications of gangue, primarily including its use in filling abandoned mines, using gangue powder to improve coal combustion efficiency, refining agricultural soils, extracting useful substances from gangue, and preparing building materials.

[0003] However, research on the use of gangue as an aggregate material has rarely examined high-sulfur gangue. Currently, China produces 700-800 million tons of high-sulfur gangue annually, with reserves reaching 6 billion barrels. High-sulfur gangue accounts for the largest proportion of total gangue production. The sulfur in high-sulfur gangue occurs primarily in organic and inorganic forms. Research has shown that in the vast majority of mining areas in my country with high-sulfur coal, inorganic sulfur predominates, primarily in the form of pyrite (FeS2), which is easily oxidized. Depending on the degree of oxidation, pyrite can produce atmospherically polluting SO2 gas or H2SO4, forming acid mine drainage, which can cause irreversible damage to the surrounding environment. Furthermore, the oxidation reaction of pyrite continuously releases heat. When this heat accumulates to a certain level, it can cause spontaneous combustion of nearby combustible materials, a common cause of spontaneous combustion in gangue piles in mining areas. If high-sulfur gangue is used directly in construction materials, the acidic substances produced by oxidation may corrode cement mortar and steel bars, and the high temperatures caused by spontaneous combustion may endanger the safety of the building. Therefore, in order to reduce the risks of high-sulfur gangue aggregate during utilization and improve its comprehensive utilization rate, research on the desulfurization of high-sulfur gangue is imperative.

[0004] Domestic coal desulfurization technology is mainly to control the emission of sulfur dioxide in coal. The main measures include desulfurization before combustion, desulfurization during combustion and desulfurization after combustion. In the current research on coal desulfurization technology, desulfurization before combustion is the most economical and feasible technology for coal desulfurization. At present, the desulfurization methods before combustion of coal include gravity separation, magnetic separation, flotation, electrochemical method and microbial leaching method. 1) Gravity separation is to separate the materials by using the difference in relative density and the different movement speed and direction in the medium. The density of pyrite is generally greater than 3.5 g / cm 3 , the density of coal is generally less than 2.2 g / cm 3The large density difference can separate the two; however, gravity separation only removes inorganic sulfur and is ineffective against organic sulfur. Furthermore, gravity separation is ineffective for desulfurization of fine-grained coal. As the coal particle size decreases, the particles cannot be effectively stratified by density, making pyrite difficult to remove through gravity separation. 2) Magnetic separation utilizes the magnetic differences between coal and coal-bearing pyrite and other ash minerals to separate coal-bearing pyrite and other minerals within a strong magnetic separation space, achieving both desulfurization and deashing. While the technical cost is low, desulfurization is incomplete. 3) Flotation utilizes flotation or flotation columns as separation equipment based on the different surface physical and chemical properties of coal and pyrite, achieving desulfurization through the addition of appropriate inhibitors. Flotation desulfurization is one of the most widely used methods for desulfurization of fine and ultrafine coal, but the process is complex and requires the addition of various reagents, which are costly and pose environmental risks. 4) Electrochemical desulfurization involves an electrochemical reaction at the anode, oxidizing the inorganic and organic sulfur in the coal into soluble sulfides, thereby removing sulfur. This method is generally categorized into alkaline and acidic electrochemical methods. Electrochemical desulfurization can be operated at room temperature, is highly efficient, and can remove organic sulfur. However, electrochemical desulfurization has not yet been applied in industrial trials in China and is still in the development stage. 5) Microbial desulfurization utilizes microorganisms to decompose the inorganic and organic sulfur in coal into soluble sulfides. Research on microbial desulfurization of high-sulfur coal is ongoing in China, but much of this research remains in the laboratory, with limited industrial trials. While these methods have achieved some experimental results, they still face challenges such as high cost, low desulfurization efficiency, and environmental pollution. Summary of the Invention

[0005] The present invention aims to solve, at least to some extent, one of the technical problems in the related art. To this end, the main purpose of the present invention is to provide a method for desulfurizing high-sulfur coal gangue based on roasting-quenching synergistic enhanced gravity separation, aiming to address the problems of existing high-sulfur coal desulfurization methods such as high cost, low desulfurization efficiency, and environmental pollution.

[0006] The purpose of the present invention is achieved through the following technical solutions: A method for desulfurizing high-sulfur coal gangue based on roasting-quenching synergistic enhanced gravity separation comprises the following steps: 1) The high-sulfur coal gangue is subjected to liquid phase grinding and dissociation treatment, and then filtered and dried to obtain high-sulfur coal gangue powder; 2) calcining and quenching the high-sulfur gangue powder obtained in step 1) to obtain a secondary dissociated gangue slurry; 3) The secondary dissociated gangue slurry in step 2) is subjected to gravity separation, filtration, and drying to obtain concentrate and tailings.

[0007] The present invention found that due to the different thermal expansion coefficients of carbon and pyrite in high-sulfur coal gangue, the two expand to different degrees at high temperatures through roasting, generating shear stress at the interface and thus microcracks. Then, they are quickly put into room temperature water to achieve sudden cooling. Since the shrinkage rates of the two are also different during cooling, the interfacial stress is further increased, resulting in the expansion of microcracks and ultimately the dissociation of carbon and sulfur.

[0008] The solvent in the liquid phase grinding dissociation treatment is water; In certain specific embodiments, the mass proportion of high-sulfur coal gangue with a particle size of 0.05-0.2 mm in step 1) is 60-80%, more preferably 70-75%.

[0009] In certain specific embodiments, during the liquid-phase grinding and dissociation treatment in step 1), the solid content of the grinding slurry is 30-80%, preferably 40-60%, and in the obtained dissociated slurry, the mass proportion of high-sulfur coal gangue powder with a particle size of -0.075 mm (0-0.075 mm) is 70-95%, more preferably 85-95%.

[0010] In certain specific embodiments, the calcination process conditions in step 2) are: calcination at a temperature of 300-800° C. for 1-3 hours.

[0011] In certain specific embodiments, the calcination process conditions in step 2) are: calcination at a temperature of 400-600° C. for 1-2 hours.

[0012] In some specific embodiments, the quenching method in step 2) is water cooling.

[0013] In certain specific embodiments, during the gravity separation process in step 3), the pulp concentration is 15-40%, preferably 15-25%.

[0014] In certain specific embodiments, during the gravity separation process in step 3), the gravity separation feed rate is 0.5-3 t / h, preferably 1-2 t / h.

[0015] In certain specific embodiments, during the gravity separation process in step 3), the opening of the heavy component discharge port is ≤ 40%, preferably 10-40%.

[0016] As the same inventive concept, the present invention also provides a concentrate and tailings product obtained by a high-sulfur coal gangue desulfurization method based on roasting-quenching synergistic enhanced gravity separation.

[0017] Compared with the prior art, the present invention has at least the following advantages: The high-sulfur gangue desulfurization method provided by the present invention utilizes a grinding-roasting-quenching process to fully dissociate the gangue and pyrite in the high-sulfur gangue, reducing the number of intergrowths and thereby improving gravity separation efficiency. Low-sulfur tailings can be produced, which can be used to make building materials such as ceramsite, cement, and unfired bricks. Furthermore, the desulfurization method of the present invention requires no chemical agents throughout the entire process, resulting in low processing costs, ease of promotion, and excellent economic and social value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present invention, the following briefly introduces the drawings required for the specific embodiments or the description of the prior art.

[0019] Figure 1 This is a process flow chart of the high-sulfur coal gangue desulfurization method based on roasting-quenching synergistic enhanced gravity separation provided by the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples are merely illustrative and non-restrictive, and should not be used to limit the scope of protection of the present invention.

[0021] When expressing a certain amount, concentration or other value or parameter in the form of a range, preferred range, or preferred upper and lower numerical limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper range limits or preferred numerical values ​​with any lower range limit or preferred numerical value, without considering whether the range is specifically disclosed. Unless otherwise indicated, the numerical range values ​​listed herein include the endpoints of the range and all integers and fractions within the range.

[0022] Unless otherwise indicated, all percentages, parts, ratios, etc. herein are by weight.

[0023] The materials, methods, and examples herein are illustrative and, unless otherwise indicated, are not to be construed as limiting.

[0024] In the following examples, high-sulfur coal gangue from Zunyi, Guizhou with an ash content of 77.21% and a sulfur content of 6.04% was used as raw material.

[0025] Example 1 This embodiment provides a method for desulfurizing high-sulfur coal gangue based on roasting-quenching synergistic enhanced gravity separation, which includes the following steps: Step (1): Grinding and dissociation The crushed high-sulfur gangue particles with a particle size of less than 2 mm (the mass proportion of high-sulfur gangue with a particle size of 0.05-0.2 mm is 70%) are added to the grinding machine, and water is added to control the slurry concentration to 45%. The grinding time is 8 minutes. After grinding and dissociation, the slurry fineness obtained is -0.075 mm, accounting for 90%. The dissociated slurry is then filtered and dried to obtain high-sulfur gangue powder; Step (2): Calcination-Quick Cooling The high-sulfur coal gangue powder obtained in step (1) is placed in a muffle furnace, and roasted to 500° C. and kept at this temperature for 2 hours under a nitrogen atmosphere. The roasted high-sulfur coal gangue powder is then quickly placed in room temperature water for cooling to obtain a secondary dissociated coal gangue slurry; Step (3): Reselect The secondary dissociated gangue slurry obtained in step (2) was subjected to gravity separation. The gravity separation feed rate was 1.5 t / h, the slurry concentration was 25%, and the opening of the heavy component discharge port was 20%. The heavy component was filtered and dried to obtain a concentrate product. The intermediate component and the light component were combined to obtain a tailings product. The experimental results were as follows: Example 2 Compared with Example 1, the only difference is that the grinding and dissociation time is: Group (1): 3 minutes; Group (2): 5 minutes; Group (3): 10 minutes. The experimental results are: The experimental results show that the grinding and dissociation time has an important influence on the yield and sulfur grade of the concentrate. If the grinding time is too short, the gangue cannot be fully dissociated and the sulfur cannot be fully released. During the gravity separation process, there are more large particles with high density, resulting in high yield and low sulfur content. If the grinding time is too long, the pyrite and gangue will be excessively dissociated and cannot be separated by density difference, resulting in a lower sulfur grade in the concentrate.

[0026] Example 3 Compared with Example 1, the only difference is that the calcination temperatures are: Group (1): 400°C; Group (2): 600°C. The experimental results are: The experimental results show that roasting temperature that is too high or too low has a great influence on the sulfur content of concentrate and tailings. If the roasting temperature is too low, it may be difficult to produce a significant thermal stress difference between gangue and pyrite, and the gangue and pyrite cannot be fully dissociated after sudden cooling, resulting in low gravity separation efficiency; if the roasting temperature is too high, the sulfur component may be melted and wrapped on the mineral surface, which cannot effectively dissociate the gangue and pyrite.

[0027] Example 4 Compared with Example 1, the only difference is that the calcination constant temperature time is: Group (1): 1h; Group (2): 3h. The experimental results are: The experimental results show that if the roasting constant temperature time is too short, the dissociation of gangue and pyrite may be insufficient, resulting in low gravity separation efficiency; if the roasting constant temperature time is too long, part of the pyrite may be decomposed into other substances, resulting in low gravity separation efficiency and increased energy consumption.

[0028] Example 5 Compared with Example 1, the only difference is that the recombinant separation degree during reselection is: Group (1): 0%; Group (2): 10%; Group (3): 30%; Group (4): 40%. The experimental results are: It can be seen from the experimental results that when using spiral chute gravity separation, the gravity separation efficiency is unsatisfactory if the opening is too large or too small. When the opening is too small, part of the pyrite will enter the intermediate component, the concentrate yield is small, the concentrate sulfur content is also low, and the tailings sulfur content is high; when the opening is too large, part of the gangue will enter the heavy component, resulting in a larger concentrate yield and a lower sulfur content, resulting in a lower tailings yield and relatively higher sulfur content.

[0029] Comparative Example 1 Compared with Example 1, the only difference is that the high-sulfur coal gangue after grinding and dissociation is not roasted and quenched, but directly re-selected. The experimental results are: Compared with Example 1, it can be seen that gravity separation after roasting and quenching can effectively improve the gravity separation efficiency, greatly increase the sulfur content of sulfur concentrate, and effectively reduce the sulfur content of tailings.

[0030] Comparative Example 2 Compared with Example 1, the only difference is that the high-sulfur coal gangue after roasting is allowed to cool naturally to room temperature before gravity separation. The experimental results are: The experimental results show that natural cooling after roasting cannot effectively dissociate the gangue and pyrite, resulting in low gravity separation efficiency, too low sulfur content in the concentrate, and high sulfur content in the tailings.

[0031] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for desulfurizing high-sulfur coal gangue based on roasting-quenching synergistic enhanced gravity separation, characterized in that: The steps include: 1) The high-sulfur coal gangue is subjected to liquid phase grinding and dissociation treatment, and then filtered and dried to obtain high-sulfur coal gangue powder; 2) calcining and quenching the high-sulfur gangue powder obtained in step 1) to obtain a secondary dissociated gangue slurry; 3) The secondary dissociated gangue slurry in step 2) is subjected to gravity separation, filtration, and drying to obtain concentrate and tailings.

2. The high-sulfur coal gangue desulfurization method based on roasting-quenching synergistic enhanced gravity separation according to claim 1 is characterized in that: The mass proportion of high-sulfur coal gangue with a particle size of 0.05-0.2 mm in step 1) is 60-80%.

3. The method for desulfurizing high-sulfur coal gangue based on roasting-quenching synergistic enhanced gravity separation according to claim 2, characterized in that: During the liquid-phase grinding and dissociation treatment in step 1), the solid content of the grinding slurry is 30-80%, and the mass proportion of high-sulfur coal gangue powder with a particle size of -0.075 mm in the obtained dissociated slurry is 70-95%.

4. The method for desulfurizing high-sulfur coal gangue based on roasting-quenching synergistic enhanced gravity separation according to claim 1, characterized in that: The calcination process conditions in step 2) are: calcination at a temperature of 300-800°C for 1-3 hours.

5. The method for desulfurizing high-sulfur coal gangue based on roasting-quenching synergistic enhanced gravity separation according to claim 4, characterized in that: The calcination process conditions in step 2) are: calcination at a temperature of 400-600°C for 1-2 hours.

6. The method for desulfurizing high-sulfur coal gangue based on roasting-quenching synergistic enhanced gravity separation according to claim 5, characterized in that: The quenching method in step 2) is water cooling.

7. The method for desulfurizing high-sulfur coal gangue based on roasting-quenching synergistic enhanced gravity separation according to claim 1, characterized in that: During the gravity separation process described in step 3), the pulp concentration is 15-40%.

8. The method for desulfurizing high-sulfur coal gangue based on roasting-quenching synergistic enhanced gravity separation according to claim 7, characterized in that: During the gravity separation process described in step 3), the gravity separation feed rate is 0.5~3t / h.

9. The method for desulfurizing high-sulfur coal gangue based on roasting-quenching synergistic enhanced gravity separation according to claim 8, characterized in that: During the gravity separation process described in step 3), the opening of the heavy component discharge port is ≤ 40%.

10. A concentrate and tailings product obtained by the high-sulfur gangue desulfurization method based on roasting-quenching synergistic enhanced gravity separation according to any one of claims 1 to 9.

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