Coal gangue treatment method

Abstract

The present application provides a coal gangue treatment method, which comprises the following steps: step S1, crushing the coal gangue and then performing flotation to collect organic components and inorganic components respectively; step S2, removing Fe2O3, CaO and MgO in the inorganic components by using an acidic solution, and then pyrolyzing the inorganic components at 500-600 DEG C to obtain ash; step S3, removing SiO2 in the ash by using an alkaline solution to obtain silicon-containing compounds and / or aluminum-containing compounds. The mass concentration of the acidic compound in the acidic solution is 0.5-3 wt%. After the treatment, the organic components and the inorganic components in the coal gangue are effectively utilized, the organic components can be mixed into coal for combustion and power generation, and the inorganic components can be used as high-purity silicon-aluminum raw materials, which are high-quality silicon-aluminum mineral resources.

Description

Technical Field

[0001] This invention relates to the field of coal gangue processing technology, and more specifically, to a method for processing coal gangue. Background Technology

[0002] The Junggar Coalfield is my country's largest high-quality coal-bearing kaolin deposit. The coal seams are interbedded with gangue primarily composed of kaolinite and boehmite, with kaolinite exhibiting a crystallinity as high as 82.2% and abundant reserves. It is estimated that the kaolinite reserves in the Heidaigou mining area alone amount to 74 million tons, demonstrating a significant resource advantage. The inorganic mineral composition of the gangue contains over 90% silicon and aluminum oxides, while TFe₂O₃ and TiO₂ impurities are around 1%, and CaO and MgO impurities are all below 1%. How to process this portion of the gangue for effective utilization is a current technical problem to be solved. Summary of the Invention

[0003] The main objective of this invention is to provide a method for processing coal gangue, so as to solve the problem that coal gangue cannot be effectively utilized in the prior art.

[0004] To achieve the above objectives, according to one aspect of the present invention, a method for processing coal gangue is provided. The coal gangue comprises organic and inorganic components. The organic components are: 0.6–3.2 wt% water, 9.5–23.3 wt% volatile matter, 6.1–18.4 wt% fixed carbon, and trace amounts of unavoidable organic impurities. The inorganic components are: 30.1–58.5 wt% SiO2, 27.2–70.5 wt% Al2O3, 0.15–1.27 wt% Fe2O3, 0.02–1.35 wt% CaO, 0.01–1.26 wt% MgO, and trace amounts of unavoidable inorganic impurities. The processing method includes the following steps: Step S1, crushing the coal gangue and then performing flotation to collect the organic and inorganic components separately; Step S2, first using an acidic solution to remove Fe2O3, CaO, MgO and trace unavoidable inorganic impurities from the inorganic components, and then pyrolyzing the inorganic components at 500-600℃ to obtain ash; wherein the mass concentration of acidic compounds in the acidic solution is 0.5-3wt%; Step S3, using an alkaline solution to remove P2O5 and trace unavoidable inorganic impurities from the ash to obtain silicon-containing compounds and / or aluminum-containing compounds.

[0005] Further, in step S1, the coal gangue is crushed into particles with a particle size of <5mm.

[0006] Further, the flotation process includes: first, mixing crushed coal gangue with water to obtain a slurry with a solid content of 60-120 g / L; then, adding a collector to the slurry and stirring for 1-2 minutes, followed by adding a frother for flotation.

[0007] Furthermore, the foaming agent is selected from one or more of 2-octanol, methyl isobutyl alcohol, pine oil, pine alcohol oil, or No. 4 flotation oil.

[0008] Furthermore, the amount of foaming agent used is 0.1 to 0.25 kg per ton of dry weight of organic components.

[0009] Further, the collector is selected from one or more of kerosene, n-dodecane, or diesel oil; preferably, oleic acid diethanolamide may also be added to the collector, and the amount of oleic acid diethanolamide added is 3 to 15% of the weight of the collector.

[0010] Furthermore, the weight ratio of the foaming agent to the collector is 1:3 to 5.

[0011] Further, the acidic solution is selected from one or more of hydrochloric acid aqueous solution, sulfuric acid aqueous solution, acetic acid aqueous solution, oxalic acid aqueous solution or citric acid aqueous solution; preferably, the acidic solution is a hydrochloric acid aqueous solution with a mass concentration of 0.5 to 3 wt% HCl; more preferably, the weight ratio of inorganic component to hydrochloric acid aqueous solution is 1:3 to 6.

[0012] Further, the alkaline solution is selected from one or more of sodium hydroxide aqueous solution, calcium oxide aqueous solution, or sodium carbonate aqueous solution; preferably, the alkaline solution is a sodium hydroxide aqueous solution with a NaOH molar concentration of 0.1 to 0.5 mol / L; more preferably, the weight ratio of ash to sodium hydroxide aqueous solution is 1:3 to 7.

[0013] Furthermore, the oxygen introduction rate during pyrolysis is 30–80 mL / min, preferably 40–50 mL / min.

[0014] Coal gangue is composed of complex organic and inorganic components. Crushing effectively separates these components. The crushed gangue then undergoes flotation, a process that separates and collects the organic and inorganic components separately. Flotation not only allows for the separate collection of organic and inorganic components but also removes impurities from the organic components. The resulting organic component is primarily combustible carbon with a high fixed carbon content, relatively low ash content, and a high calorific value, making it suitable for mixing with coal for combustion and power generation. Further processing of the inorganic components involves using an acidic solution to remove Fe₂O₃, CaO, MgO, and trace amounts of unavoidable inorganic impurities (such as K₂O and Na₂O). The mass concentration of acidic compounds in the acidic solution is limited to 0.5–3 wt%. SiO2 does not participate in the reaction, and Al2O3 participates only in trace amounts. This effectively removes Fe2O3, CaO, MgO, and trace amounts of unavoidable inorganic impurities from the inorganic components while meeting the requirements for silicon-aluminum oxide recovery. The inorganic components are then pyrolyzed at 500–600℃ to obtain ash. During this low-temperature pyrolysis process, trace amounts of organic components are further removed from the inorganic components. Finally, alkali is used to remove P2O5 and trace amounts of unavoidable inorganic impurities (such as SO3 and V2O5) from the ash, yielding silicon-containing compounds and / or aluminum-containing compounds. After this treatment, both the organic and inorganic components in the coal gangue are effectively utilized. The organic components can be mixed into the coal for combustion and power generation; the inorganic components can be used as high-purity silicon-aluminum raw materials, representing a high-quality silicon-aluminum mineral resource with applications in papermaking, ceramics, rubber, chemicals, coatings, pharmaceuticals, and defense industries, with huge demand. Moreover, this invention uses low-cost physical separation and acid-base treatment to obtain silicon-aluminum compounds with high purity, thus saving production investment costs. Detailed Implementation

[0015] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0016] As described in the background section of this application, there is a problem with the prior art in that it cannot effectively utilize coal gangue. To solve this problem, this application provides a method for processing coal gangue, wherein the coal gangue comprises organic and inorganic components. The organic components consist of 0.6–3.2 wt% moisture, 9.5–23.3 wt% volatile matter, 6.1–18.4 wt% fixed carbon, and trace amounts of unavoidable organic impurities. The inorganic components consist of 30.1–58.5 wt% SiO2, 27.2–70.5 wt% Al2O3, 0.15–1.27 wt% Fe2O3, 0.02–1.35 wt% CaO, 0.01–1.26 wt% MgO, and trace amounts of unavoidable inorganic impurities.

[0017] The processing method includes the following steps: Step S1, crushing the coal gangue and then performing flotation to collect organic and inorganic components (here, the inorganic component refers to the coal gangue after flotation); Step S2, first using an acidic solution to remove Fe2O3, CaO, and MgO from the inorganic component, and then pyrolyzing the inorganic component at 500–600℃ to obtain ash (here, the ash is the coal gangue after low-temperature pyrolysis); Step S3, using an alkaline solution to remove SiO2 from the ash to obtain silicon-containing compounds and / or aluminum-containing compounds. The mass concentration of the acidic compounds in the acidic solution is 0.5–3 wt%.

[0018] Coal gangue is composed of complex organic and inorganic components. Crushing effectively separates these components. The crushed gangue then undergoes flotation, a process that separates and collects the organic and inorganic components separately. Flotation not only allows for the separate collection of organic and inorganic components but also removes impurities from the organic components. The resulting organic component is primarily combustible carbon with a high fixed carbon content, relatively low ash content, and a high calorific value, making it suitable for mixing with coal for combustion and power generation. Further processing of the inorganic components involves using an acidic solution to remove Fe₂O₃, CaO, MgO, and trace amounts of unavoidable inorganic impurities (such as K₂O and Na₂O). The mass concentration of acidic compounds in the acidic solution is limited to 0.5–3 wt%. SiO2 does not participate in the reaction, and Al2O3 participates only in trace amounts. This effectively removes Fe2O3, CaO, MgO, and trace amounts of unavoidable inorganic impurities from the inorganic components while meeting the requirements for silicon-aluminum oxide recovery. The inorganic components are then pyrolyzed at 500–600℃ to obtain ash. During this low-temperature pyrolysis process, trace amounts of organic components are further removed from the inorganic components. Finally, alkali is used to remove P2O5 and trace amounts of unavoidable inorganic impurities (such as SO3 and V2O5) from the ash, yielding silicon-containing compounds and / or aluminum-containing compounds. After this treatment, both the organic and inorganic components in the coal gangue are effectively utilized. The organic components can be mixed into the coal for combustion and power generation; the inorganic components can be used as high-purity silicon-aluminum raw materials, representing a high-quality silicon-aluminum mineral resource with applications in papermaking, ceramics, rubber, chemicals, coatings, pharmaceuticals, and defense industries, with huge demand. Moreover, this invention uses low-cost physical separation and acid-base treatment to obtain silicon-aluminum compounds with high purity, thus saving production investment costs.

[0019] To further improve the separation effect between organic and inorganic components, in a preferred embodiment, in step S1, the coal gangue is crushed into particles with a particle size of <5mm, preferably 0.2 to 5mm, for example, 0.2mm, 1mm, 2mm, 3mm, 4mm or 5mm.

[0020] In a preferred embodiment, flotation includes: first, mixing crushed coal gangue with water to obtain a slurry with a solid content of 60–120 g / L, for example, the solid content can be 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, or 120 g / L; then, adding a collector to the slurry and stirring for 1–2 minutes, followed by adding a frother for flotation. Based on this, this application can not only collect the organic and inorganic components separately, but also separate impurities from the organic components.

[0021] To further improve flotation efficiency, the preferred flotation frother is selected from one or more of 2-octanol, methyl isobutyl methanol, pine oil, pine alcohol oil, or No. 4 flotation oil; and the amount of frother used is 0.1 to 0.25 kg per ton of organic component dry weight, for example, 0.1 kg, 0.15 kg, 0.2 kg, or 0.25 kg.

[0022] To further improve flotation efficiency by ensuring better compatibility between the frother and collector, the collector is preferably selected from one or more of kerosene, n-dodecane, or diesel oil. Preferably, oleic acid diethanolamide may also be added to the collector, and the amount of oleic acid diethanolamide added is 3% to 15% of the weight of the collector, for example, 3%, 5%, 10%, or 15%. The weight ratio of the frother to the collector is 1:3 to 5, for example, 1:3, 1:3.5, 1:4, 1:4.5, or 1:5.

[0023] To further remove metallic impurities from the inorganic components, the acidic solution is preferably selected from one or more of hydrochloric acid aqueous solution, sulfuric acid aqueous solution, acetic acid aqueous solution, oxalic acid aqueous solution, or citric acid aqueous solution. More preferably, the acidic solution is a hydrochloric acid aqueous solution with a HCl concentration of 0.5–3 wt%, and the weight ratio of the inorganic components to the hydrochloric acid aqueous solution is 1:3–6, for example, 1:3, 1:4, 1:5, or 1:6. Based on this, SiO2 does not participate in the reaction, and Al2O3 participates in the reaction only in trace amounts. This effectively removes Fe2O3, CaO, MgO, and trace amounts of unavoidable inorganic impurities from the inorganic components while meeting the requirements for silicon-aluminum oxide recovery.

[0024] To further remove non-metallic impurities from the ash, the alkaline solution is preferably selected from one or more of sodium hydroxide aqueous solution, calcium oxide aqueous solution, or sodium carbonate aqueous solution. More preferably, the alkaline solution is a sodium hydroxide aqueous solution with a NaOH molar concentration of 0.1–0.5 mol / L, and the weight ratio of ash to sodium hydroxide aqueous solution is 1:3–7, for example, 1:3, 1:4, 1:5, 1:6, or 1:7.

[0025] In a preferred embodiment, the oxygen introduction rate during pyrolysis is 30–80 mL / min. This results in higher pyrolysis efficiency and further removal of trace amounts of organic components from the inorganic components. More preferably, the oxygen introduction rate during pyrolysis is 40–50 mL / min, for example, 40 mL / min, 45 mL / min, or 50 mL / min.

[0026] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0027] Example 1

[0028] The composition of coal gangue is shown in Table 1.

[0029] Table 1

[0030] Content / wt% 31.65 31.40 0.56 0.44 0.05 0.26 0.24 0.06 0.35 MnO <![CDATA[Li2O]]> <![CDATA[Ga2O3]]> CuO <![CDATA[Cr2O3]]> NiO <![CDATA[V2O5]]> <![CDATA[TiO2]]> Loss on ignition Content / wt% 0.00 0.05 0.01 0.00 0.00 0.00 0.01 0.99 34.08

[0031] Note: Loss on ignition includes fixed carbon, volatile matter, and moisture. These three indicators are listed separately in the industrial analysis of coal. However, when it comes to elemental content, loss on ignition is usually written.

[0032] a. Crush the coal gangue into particles with a diameter of <0.2mm.

[0033] b. First, the crushed coal gangue is mixed with water to obtain a slurry with a solid content of 100 g / L. Then, a collector is added to the slurry and stirred for 2 minutes, followed by the addition of a frother for flotation to collect the organic and inorganic components separately. The amount of frother used is 0.15 kg per ton of organic component dry weight. The weight ratio of frother to collector is 1:3.5. The frother is No. 4 flotation oil (Shandong Jiawei Chemical Co., Ltd.), and the collector is a mixture of kerosene (Shandong Jiawei Chemical Co., Ltd.) and oleic acid diethanolamide (ODEA). The amount of ODEA added is 7% of the collector weight.

[0034] 10 wt% of coal (organic components) can be recovered from coal gangue through flotation. The composition of the coal gangue after flotation (inorganic components and a small amount of organic components that inevitably adhere to the inorganic components) is shown in Table 2.

[0035] Table 2

[0036] Content / wt% 37.24 36.94 0.66 0.52 0.06 0.31 0.28 0.07 0.41 element MnO <![CDATA[Li2O]]> <![CDATA[Ga2O3]]> CuO <![CDATA[Cr2O3]]> NiO <![CDATA[V2O5]]> <![CDATA[TiO2]]> Loss on ignition Content / wt% 0.00 0.06 0.01 0.00 0.00 0.00 0.01 1.16 22.08

[0037] c. The coal gangue after flotation is soaked in a 1 wt% hydrochloric acid aqueous solution to remove Fe2O3, CaO, MgO and trace amounts of unavoidable inorganic impurities from the inorganic components. The mass ratio of inorganic components to hydrochloric acid aqueous solution is 1:3. The composition of the coal gangue after acid treatment is shown in Table 3.

[0038] Table 3

[0039] Content / wt% 38.60 35.82 0.23 0.05 0.02 0.18 0.08 0.07 0.43 element MnO <![CDATA[Li2O]]> <![CDATA[Ga2O3]]> CuO <![CDATA[Cr2O3]]> NiO <![CDATA[V2O5]]> <![CDATA[TiO2]]> Loss on ignition Content / wt% 0.00 0.06 0.01 0.00 0.00 0.00 0.01 0.57 22.89

[0040] d. The acid-treated coal gangue was subjected to low-temperature oxygen-enriched pyrolysis at 550℃ to obtain ash. The oxygen introduction rate was 45 mL / min. The composition of the coal gangue (ash) after low-temperature oxygen-enriched pyrolysis is shown in Table 4.

[0041] Table 4

[0042] Content / wt% 50.79 47.13 0.30 0.07 0.03 0.24 0.11 0.10 0.56 element MnO <![CDATA[Li2O]]> <![CDATA[Ga2O3]]> CuO <![CDATA[Cr2O3]]> NiO <![CDATA[V2O5]]> <![CDATA[TiO2]]> Loss on ignition Content / wt% 0.00 0.08 0.02 0.00 0.00 0.00 0.02 0.75 0.15

[0043] e. The coal gangue (ash) after low-temperature oxygen-enriched pyrolysis was treated with 0.2 mol / L sodium hydroxide aqueous solution to remove P2O5 and trace amounts of unavoidable inorganic impurities. The mass ratio of ash to sodium hydroxide solution was 1:3.5. The composition of the coal gangue after alkali treatment is shown in Table 5.

[0044] Table 5

[0045]

[0046]

[0047] The total content of silicon-aluminum compounds (silicon dioxide and aluminum oxide) in the product obtained after the above treatment reached 99 wt%.

[0048] Example 2

[0049] The only difference from Example 1 is that the coal gangue is crushed into particles with a particle size of <4.5mm.

[0050] The total content of silicon-aluminum compounds (silicon dioxide and aluminum oxide) in the product obtained after the above treatment reached 98.73 wt%.

[0051] Example 3

[0052] The only difference from Example 1 is:

[0053] In step S1, the coal gangue is crushed into particles with a particle size > 5 mm.

[0054] The total content of silicon-aluminum compounds (silicon dioxide and aluminum oxide) in the product obtained after the above treatment reached 96.58 wt%.

[0055] Example 4

[0056] The only difference from Example 1 is that the weight ratio of foaming agent to collector is 1:5.

[0057] The total content of silicon-aluminum compounds (silicon dioxide and aluminum oxide) in the product obtained after the above treatment reached 98.87 wt%.

[0058] Example 5

[0059] The only difference from Example 1 is that the weight ratio of foaming agent to collector is 1:2.

[0060] The total content of silicon-aluminum compounds (silicon dioxide and aluminum oxide) in the product obtained after the above treatment reached 97.33 wt%.

[0061] Example 6

[0062] The only difference from Example 1 is that the acidic solution is an aqueous solution of hydrochloric acid with a mass concentration of 3 wt% HCl.

[0063] The total content of silicon-aluminum compounds (silicon dioxide and aluminum oxide) in the product obtained after the above treatment reached 98.53 wt%.

[0064] Example 7

[0065] The only difference from Example 1 is that the acidic solution is an aqueous solution of hydrochloric acid with a mass concentration of 36 wt% (commercially available hydrochloric acid).

[0066] The total content of silicon-aluminum compounds (silicon dioxide and aluminum oxide) in the product obtained after the above treatment reached 97.96 wt%.

[0067] Example 8

[0068] The only difference from Example 1 is that the weight ratio of the inorganic component to the hydrochloric acid aqueous solution in step c is 1:6.

[0069] The total content of silicon-aluminum compounds (silicon dioxide and aluminum oxide) in the product obtained after the above treatment reached 98.68 wt%.

[0070] Example 9

[0071] The only difference from Example 1 is that the alkaline solution is an aqueous solution of sodium hydroxide with a NaOH molar concentration of 1 mol / L.

[0072] The total content of silicon-aluminum compounds (silicon dioxide and aluminum oxide) in the product obtained after the above treatment reached 97.74 wt%.

[0073] Example 10

[0074] The only difference from Example 1 is that the weight ratio of coal gangue (ash) after low-temperature oxygen-enriched pyrolysis to sodium hydroxide aqueous solution in step d is 1:10.

[0075] The total content of silicon-aluminum compounds (silicon dioxide and aluminum oxide) in the product obtained after the above treatment reached 95.83 wt%.

[0076] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for processing coal gangue, wherein the coal gangue comprises organic components and inorganic components, the organic components being: 0.6-3.2 wt% moisture, 9.5-23.3 wt% volatile matter, 6.1-18.4 wt% fixed carbon, and trace amounts of unavoidable organic impurities; the inorganic components being: 30.1-58.5 wt% SiO2, 27.2-70.5 wt% Al2O3, 0.15-1.27 wt% Fe2O3, 0.02-1.35 wt% CaO, 0.01-1.26 wt% MgO, and trace amounts of unavoidable inorganic impurities; characterized in that, The processing method includes the following steps: Step S1: The coal gangue is crushed and then subjected to flotation to collect the organic components and the inorganic components separately; Step S2: First, an acidic solution is used to remove Fe2O3, CaO, MgO, and trace amounts of unavoidable inorganic impurities from the inorganic component. Then, the inorganic component is pyrolyzed at 500-600℃ to obtain ash. The acidic solution is an aqueous hydrochloric acid solution with a mass concentration of 0.5-3wt% HCl, and the weight ratio of the inorganic component to the aqueous hydrochloric acid solution is 1:3-6. Step S3: Use an alkaline solution to remove P2O5 and trace amounts of unavoidable inorganic impurities from the ash to obtain silicon-containing compounds and aluminum-containing compounds; the alkaline solution is an aqueous sodium hydroxide solution with a NaOH molar concentration of 0.1~0.5 mol / L; the weight ratio of the ash to the aqueous sodium hydroxide solution is 1:3~7.

2. The coal gangue treatment method according to claim 1, characterized in that, In step S1, the coal gangue is crushed into particles with a particle size of <5mm.

3. The coal gangue treatment method according to claim 1 or 2, characterized in that, The flotation process includes: first, mixing the crushed coal gangue with water to obtain a slurry with a solid content of 60-120 g / L; then, adding a collector to the slurry and stirring for 1-2 minutes, followed by adding a frother for flotation.

4. The coal gangue treatment method according to claim 3, characterized in that, The foaming agent is selected from one or more of 2-octanol, methyl isobutyl methanol, pine oil, pine alcohol oil, or No. 4 flotation oil.

5. The coal gangue treatment method according to claim 4, characterized in that, The amount of foaming agent used is 0.1~0.25 kg per ton of the organic component by dry weight.

6. The coal gangue treatment method according to claim 5, characterized in that, The collector is selected from one or more of kerosene, n-dodecane, or diesel oil; The collector may optionally contain oleic acid diethanolamide, and the amount of oleic acid diethanolamide added is 3 to 15% of the weight of the collector.

7. The coal gangue treatment method according to claim 6, characterized in that, The weight ratio of the foaming agent to the collector is 1:3~5.

8. The coal gangue treatment method according to claim 1, characterized in that, The oxygen introduction rate during the pyrolysis process is 30~80 mL / min.

9. The coal gangue treatment method according to claim 8, characterized in that, The oxygen introduction rate during the pyrolysis process is 40~50 mL / min.

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