A method for extracting kaolin from coal gangue

Abstract

This invention relates to the field of solid waste resource utilization technology, specifically to a method for extracting kaolin from coal gangue, comprising the following steps: analyzing and crushing the coal gangue raw material; screening the crushed coal gangue fragments; feeding fragments with an actual particle size less than 5mm into a fluidized bed furnace for roasting to obtain construction sand; subjecting fragments with an actual particle size greater than 5mm to wet autogenous grinding and separating them into coal gangue slurry and cobblestone-like material; removing iron from the obtained coal gangue slurry; desulfurizing the iron-removed coal gangue slurry, separating and collecting pyrite by gravity separation; filtering and drying the desulfurized coal gangue slurry, then feeding it into a fluidized bed furnace for roasting and decarbonization, yielding roasted kaolin after roasting. This invention achieves the recovery of multiple products, including kaolin, cobblestone-like material, construction sand, and pyrite, thereby improving resource utilization.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically to a resource utilization method for extracting kaolin from coal gangue. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining and washing. It is a dark gray rock with low carbon content and a hardness greater than coal, which is associated with coal seams during coal formation. As the world's largest coal producer, my country's raw coal production reached 4.78 billion tons in 2024. Based on an estimated output rate of 15%-20%, the amount of coal gangue produced is approximately 717-956 million tons, mainly concentrated in coal-rich provinces such as Shanxi, Inner Mongolia, Shaanxi, and Xinjiang.

[0003] The accumulation of large amounts of coal gangue not only occupies valuable land resources but also causes serious environmental problems. The sulfides in coal gangue are prone to oxidation under natural conditions, leading to spontaneous combustion and releasing harmful gases such as sulfur dioxide and nitrogen oxides, polluting the atmosphere. Heavy metals and harmful substances contained in the leachate from coal gangue seep into the ground, polluting soil and groundwater and damaging the ecological environment.

[0004] Currently, the main uses of coal gangue include power generation, building material production, and backfilling of mined-out and subsidence areas. In power generation, coal gangue is burned to generate electricity using technologies such as circulating fluidized bed boilers; however, due to the limited calorific value of coal gangue, power generation efficiency is low. In building material production, coal gangue is used to make bricks, cement, and concrete aggregates, but the quality of some products is unstable, and market acceptance is insufficient. Backfilling faces challenges such as high transportation costs and demanding technical requirements. Existing utilization methods are mostly single, low-value uses. They not only fail to fully exploit valuable components such as kaolin in coal gangue, but also, traditional processing methods cannot effectively control the release of harmful substances or still pose a risk of secondary pollution after treatment. These methods cannot completely solve the resource waste and environmental problems caused by the large-scale accumulation of coal gangue, resulting in limited economic benefits. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a resource recovery method for extracting kaolin from coal gangue, which enables the recovery of multiple products such as kaolin, cobblestones, construction sand, and pyrite, thereby improving resource utilization.

[0006] To achieve the above objectives, the technical solution of the present invention is: a method for the resource utilization of kaolin extracted from coal gangue, comprising the following steps: S1. The coal gangue raw material is sampled and crushed, and the preset particle size of the crushing is set. S2. The crushed coal gangue fragments are screened according to their actual particle size to separate fragments with a particle size of less than 5 mm and fragments with a particle size of more than 5 mm. S3. Particles with a size of less than 5mm are fed into a fluidized bed furnace and subjected to deep decarbonization through roasting. The roasted material is cooled to obtain construction sand. S4. The fragments with a particle size greater than 5 mm are subjected to wet autogenous grinding and separated to obtain coal gangue slurry and cobblestone-like material. S5. The obtained coal gangue slurry is subjected to iron removal treatment. The weakly magnetic iron compounds in the coal gangue slurry are removed by using a strong magnetic iron removal device. If humic acid iron compounds are present in the sample analysis, a mixture of hydrochloric acid and hydrogen peroxide is added to the coal gangue slurry after the strong magnetic iron removal treatment and stirred to achieve the leaching and removal of humic acid iron compounds in the coal gangue slurry. S6. The iron-removed coal gangue slurry is desulfurized, and the pyrite is separated and collected by gravity separation. S7. The desulfurized coal gangue slurry is filtered and dried, and then sent to a fluidized bed furnace for roasting and decarbonization. After roasting, roasted kaolin is obtained.

[0007] Preferably, in step S1, the preset particle size is 100~200mm.

[0008] Preferably, in step S3, the calcination temperature is 500~800°C and the calcination time is 20~60 min.

[0009] Preferably, in step S4, the water-to-material ratio in the wet auto-grinding process is 3-6:1, and the grinding time is 2-10 hours.

[0010] Preferably, in step S5, the magnetic field strength of the strong magnetic iron removal device is ≥1T; the hydrochloric acid concentration is 0.05~0.5mol / L, the hydrogen peroxide concentration is 0~0.1mol / L, and the stirring time is 2h.

[0011] Preferably, in step S7, the calcination temperature is 500~800°C and the calcination time is 20~120 min.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] 1. This invention optimizes the processing technology of coal gangue by using wet autogenous grinding to process crushed pieces with an actual particle size greater than 5mm. Pyrite, which has a high specific gravity and hardness, will not be ground into fine particles during autogenous grinding and will remain as a whole in the slurry. During sieving, large pieces of pyrite are removed, while smaller pieces are removed during gravity separation and magnetic separation. The coal gangue slurry has a relatively high carbon content, which can be used as a heat source during the roasting of kaolin. This achieves high-value utilization of all components of coal gangue, improves resource utilization, and effectively solves the land occupation and pollution problems caused by coal gangue accumulation.

[0014] 2. This invention effectively removes impurities such as iron and sulfur from coal gangue through a multi-step purification process, resulting in high-purity roasted kaolin with stable properties, resembling pebbles and used as building sand, thus improving the quality of multiple products.

[0015] 3. This invention integrates roasting decarburization and heat recovery technologies, realizing energy cascade utilization, reducing process energy consumption, and improving economic benefits. Attached Figure Description

[0016] Picture 1 This is a process flow diagram of the present invention. Detailed Implementation

[0017] 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.

[0018] Example 1

[0019] refer to Picture 1 A resource utilization method for extracting kaolin from coal gangue includes the following steps: S1. The coal gangue raw material is sampled and crushed, and the preset particle size is set to facilitate subsequent screening and grinding. S2. The crushed coal gangue fragments are screened according to their actual particle size to separate fragments with a particle size of less than 5 mm and fragments with a particle size of more than 5 mm. S3. Particles with a size of less than 5mm are fed into a fluidized bed furnace and subjected to deep decarbonization through roasting. The roasted material is cooled to obtain construction sand. S4. The fragments with a particle size greater than 5mm are subjected to wet autogenous grinding. By utilizing the hardness difference between kaolin and natural stone materials, the kaolin and carbon layer are separated, and coal gangue slurry and cobblestone-like materials are obtained. S5. The obtained coal gangue slurry is subjected to iron removal treatment. The weakly magnetic iron compounds in the coal gangue slurry are removed by using a strong magnetic iron removal device. If humic acid iron compounds are present in the sample analysis, a mixture of hydrochloric acid and hydrogen peroxide is added to the coal gangue slurry after the strong magnetic iron removal treatment and stirred to achieve the leaching and removal of humic acid iron compounds in the coal gangue slurry. S6. The iron-removed coal gangue slurry is desulfurized, and the pyrite is separated and collected by gravity separation. S7. The desulfurized coal gangue slurry is filtered and dried, and then sent to a fluidized bed furnace for roasting and decarbonization. After roasting, roasted kaolin is obtained.

[0020] In step S1, the preset particle size is 100~200mm.

[0021] In step S3, the roasting temperature is 500~800°C and the roasting time is 20~60 min.

[0022] In step S4, the water-to-material ratio in wet autogenous grinding is 3~6:1, and the grinding time is 2~10h.

[0023] In step S5, the magnetic field strength of the strong magnetic iron removal equipment is ≥1T; the concentration of hydrochloric acid is 0.05~0.5mol / L, the concentration of hydrogen peroxide is 0~0.1mol / L, and the stirring time is 2h.

[0024] In step S7, the roasting temperature is 500~800°C and the roasting time is 20~120 min.

[0025] This invention obtains four products—pebbles, construction sand, roasted kaolin, and pyrite—through the grading and precise separation of coal gangue raw materials. The various equipment used are connected in sequence through material conveying devices (such as conveyor belts and pipelines). At the same time, the fluidized bed roasting equipment is connected to the heat recovery system through heat exchange pipelines to recover the heat released during the roasting process for power generation or heating, thus realizing the conduction and recovery of heat. Pebble-like material: It is obtained by separating coal gangue fragments larger than 5mm through wet auto-grinding. It retains the physical properties of natural stone materials and can be used as building aggregate, etc. Construction sand: made from coal gangue fragments smaller than 5mm through deep decarbonization treatment, with reasonable particle size distribution, meeting the technical requirements for construction sand; Calcined kaolin: It is obtained through multiple purification steps such as crushing, screening, wet autogenous grinding, iron removal, desulfurization, calcination and decarburization. It has high purity and stable performance. Pyrite: It is obtained from coal gangue slurry through gravity separation and can be further utilized as a chemical raw material, etc. Heat recovery system: Utilizes the heat released during the decarburization process in a fluidized bed furnace to generate electricity, provide heating, or produce steam through matching heat exchange equipment.

[0026] Example 2

[0027] Based on Example 1, 20 kg of coal gangue sample was taken from a coal mine in Datong, and its composition was analyzed. The composition is shown in Table 1. Table 1. Compositional Analysis Results of Coal Gangue Samples from a Coal Mine in Datong <![CDATA[SiO2]]> 54.962 <![CDATA[Al2O3]]> 31.488 <![CDATA[SO3]]> 5.148 CaO 3.902 <![CDATA[Fe2O3]]> 2.029 <![CDATA[TiO2]]> 1.573 <![CDATA[K2O]]> 0.4 MgO 0.171 <![CDATA[P2O5]]> 0.106 <![CDATA[Sm2O3]]> 0.064 <![CDATA[ZrO2]]> 0.058 <![CDATA[Cr2O3]]> 0.032 MnO 0.023 SrO 0.023 <![CDATA[Ga2O3]]> 0.012 ZnO 0.01

[0028] First, the coal gangue raw material was sampled and analyzed. The XRD analysis results showed that its composition was approximately 30% kaolin. Then, it was crushed by a jaw crusher with a preset particle size of 100 mm to facilitate subsequent screening and grinding. The fragments with an actual particle size of less than 5mm are screened out and fed into a fluidized bed furnace for deep decarburization through roasting. The roasting temperature is 500°C and the roasting time is 60 minutes. After the roasted material is cooled, it becomes construction sand. The fragments with a particle size greater than 5 mm were subjected to wet autogenous grinding. The water-to-material ratio in the wet autogenous grinding was 3:1, and the grinding time was 2 hours, resulting in coal gangue slurry and cobblestone-like material. The obtained coal gangue slurry was subjected to iron removal treatment. The weak magnetic iron compounds in the coal gangue slurry were removed by a strong magnetic iron removal device with a magnetic field strength of 1T. The coal gangue slurry after iron removal is desulfurized, and the pyrite is separated and collected by gravity separation. The desulfurized coal gangue slurry was filtered and dried, and then sent to a fluidized bed furnace for roasting and decarbonization. The roasting temperature was 500°C and the roasting time was 120 minutes. After roasting, roasted kaolin was obtained.

[0029] Example 3

[0030] Based on the sample from Example 2, the coal gangue raw material was first analyzed. XRD analysis results showed that its composition content was approximately 30% kaolin. Then, it was crushed by a jaw crusher with a preset particle size of 120 mm to facilitate subsequent screening and grinding. The fragments with an actual particle size of less than 5mm are screened out and fed into a fluidized bed furnace for deep decarburization through roasting. The roasting temperature is 600°C and the roasting time is 40 minutes. After the roasted material is cooled, it becomes construction sand. The fragments with a particle size greater than 5 mm were subjected to wet autogenous grinding. The water-to-material ratio in the wet autogenous grinding was 4:1, and the grinding time was 5 hours, resulting in coal gangue slurry and cobblestone-like material. The obtained coal gangue slurry was subjected to iron removal treatment. The weakly magnetic iron compounds in the coal gangue slurry were removed by a strong magnetic iron removal device with a magnetic field strength of 1.4T. The coal gangue slurry after iron removal is desulfurized, and the pyrite is separated and collected by gravity separation. The desulfurized coal gangue slurry was filtered and dried, and then sent to a fluidized bed furnace for roasting and decarbonization. The roasting temperature was 600°C and the roasting time was 80 minutes. After roasting, roasted kaolin was obtained, and the kaolin content in the final roasted kaolin was higher than 85%.

[0031] Example 4

[0032] Based on Example 1, 20 kg of coal gangue sample from a coal mine in Yangquan was taken and its composition was analyzed. The composition is shown in Table 2. Table 2. Compositional Analysis Results of Coal Gangue Samples from a Coal Mine in Yangquan <![CDATA[SiO2]]> 55.317 <![CDATA[Al2O3]]> 27.427 CaO 7.313 <![CDATA[SO3]]> 3.075 <![CDATA[Fe2O3]]> 2.946 <![CDATA[K2O]]> 1.663 <![CDATA[TiO2]]> 0.888 MgO 0.82 <![CDATA[Na2O]]> 0.314 <![CDATA[P2O5]]> 0.117 SrO 0.037 <![CDATA[ZrO2]]> 0.033 CuO 0.021 MnO 0.019 ZnO 0.011

[0033] First, a sample analysis of the coal gangue raw material was conducted, which revealed the presence of humic iron. The material was then crushed using a jaw crusher with a preset particle size of 180 mm to facilitate subsequent screening and grinding. The fragments with an actual particle size of less than 5mm are screened out and fed into a fluidized bed furnace for deep decarburization through roasting. The roasting temperature is 800°C and the roasting time is 20 minutes. After the roasted material is cooled, it becomes construction sand. The fragments with a particle size greater than 5 mm were subjected to wet autogenous grinding. The water-to-material ratio in the wet autogenous grinding was 6:1, and the grinding time was 10 hours, resulting in coal gangue slurry and cobblestone-like material. The obtained coal gangue slurry was subjected to iron removal treatment. A strong magnetic iron removal device was used to remove the weakly magnetic iron compounds in the coal gangue slurry. The magnetic field strength of the strong magnetic iron removal device was 1.4T. After the strong magnetic iron removal treatment, a hydrochloric acid mixture with a concentration of 0.05mol / L was added to the coal gangue slurry and stirred for 2 hours to achieve the leaching and removal of humic acid iron compounds in the coal gangue slurry. The coal gangue slurry after iron removal is desulfurized, and the pyrite is separated and collected by gravity separation. The desulfurized coal gangue slurry was filtered and dried, and then sent to a fluidized bed furnace for roasting and decarburization. The roasting temperature was 800°C and the roasting time was 20 minutes. After roasting, roasted kaolin was obtained.

[0034] Example 5

[0035] Based on Example 1, 20 kg of coal gangue sample from a coal mine was taken and its composition was analyzed, which showed that it contained iron humate; it was then crushed by a jaw crusher with a preset particle size of 200 mm. The fragments with an actual particle size of less than 5mm are screened out and fed into a fluidized bed furnace for deep decarburization through roasting. The roasting temperature is 700°C and the roasting time is 30 minutes. After the roasted material is cooled, it becomes construction sand. The fragments with a particle size greater than 5 mm were subjected to wet autogenous grinding. The water-to-material ratio in the wet autogenous grinding was 5:1, and the grinding time was 8 hours, resulting in coal gangue slurry and cobblestone-like material. The obtained coal gangue slurry was subjected to iron removal treatment. Weakly magnetic iron compounds in the coal gangue slurry were removed using a strong magnetic iron removal device with a magnetic field strength of 1.4T. After the strong magnetic iron removal treatment, a mixture of hydrochloric acid and hydrogen peroxide was added to the coal gangue slurry and stirred. The concentration of hydrochloric acid was 0.5mol / L and the concentration of hydrogen peroxide was 0.1mol / L. The stirring time was 2h, thereby achieving the leaching and removal of humic iron compounds in the coal gangue slurry. The coal gangue slurry after iron removal is desulfurized, and the pyrite is separated and collected by gravity separation. The desulfurized coal gangue slurry was filtered and dried, and then sent to a fluidized bed furnace for roasting and decarburization. The roasting temperature was 800°C and the roasting time was 20 minutes. After roasting, roasted kaolin was obtained.

[0036] 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 method for resource recovery of kaolin from coal gangue, characterized in that, Includes the following steps: S1. The coal gangue raw material is sampled and crushed, and the preset particle size of the crushing is set. S2. The crushed coal gangue fragments are screened according to their actual particle size to separate fragments with a particle size of less than 5 mm and fragments with a particle size of more than 5 mm. S3. Particles with a particle size of less than 5mm are fed into a fluidized bed furnace and subjected to deep decarbonization through roasting. The roasted material is cooled to obtain construction sand. S4. Wet autogenous grinding is performed on the fragments with a particle size greater than 5 mm, and coal gangue slurry and cobblestone-like particles are separated. S5. The obtained coal gangue slurry is subjected to iron removal treatment, and weak magnetic iron compounds in the coal gangue slurry are removed by using strong magnetic iron removal equipment. If humic acid iron compounds are present in the sample analysis, after strong magnetic iron removal treatment, a mixture of hydrochloric acid and hydrogen peroxide is added to the coal gangue slurry and stirred to achieve the leaching and removal of humic acid iron compounds in the coal gangue slurry. S6. The iron-removed coal gangue slurry is desulfurized, and the pyrite is separated and collected by gravity separation. S7. The desulfurized coal gangue slurry is filtered and dried, and then sent to a fluidized bed furnace for roasting and decarbonization. After roasting, roasted kaolin is obtained.

2. The method of claim 1, wherein the coal gangue is crushed to a size of 100 mm or less. In step S1, the preset particle size is 100~200mm.

3. The method of claim 2, wherein the coal gangue is crushed to a size of 100 mm or less. In step S3, the calcination temperature is 500~800°C and the calcination time is 20~60 min.

4. The method of claim 3, wherein the coal gangue is crushed to a size of 100 mm or less. In step S4, the water-to-material ratio in the wet auto-grinding process is 3~6:1, and the grinding time is 2~10h.

5. The method of claim 4, wherein the coal gangue is crushed to a size of 100 mm or less. In step S5, the magnetic field strength of the strong magnetic iron removal equipment is ≥1T; the hydrochloric acid concentration is 0.05~0.5mol / L, the hydrogen peroxide concentration is 0~0.1mol / L, and the stirring time is 2h.

6. The method of claim 5, wherein the coal gangue is crushed to a size of 100 mm or less. In step S7, the calcination temperature is 500~800°C and the calcination time is 20~120 min.

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