A Method and System for Desulfurization of High-Sulfur Coal Gangue Based on Fenton-like Oxidation

Abstract

This invention belongs to the field of resource and environmental technology, specifically relating to a method and system for desulfurizing high-sulfur coal gangue based on a Fenton-like oxidation process. The method includes: sequentially subjecting lumpy high-sulfur coal gangue raw materials to mechanical crushing and wet ball milling to obtain fine powder; then using hydrogen peroxide solution as a cleaning agent, employing a multi-stage countercurrent washing method to oxidize and dissolve the sulfur in the coal gangue, transferring it to the liquid phase for removal. This invention uses pyrite in the coal gangue as a catalyst, oxidizing and removing most of the sulfur element from the coal gangue through a Fenton-like oxidation process. This desulfurization process is green and environmentally friendly, and the treated coal gangue powder can be used to produce high-value-added building materials, resulting in high economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of resource and environmental technology, and specifically relates to a method and system for desulfurization of high-sulfur coal gangue based on a Fenton-like oxidation method. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining and washing. It is a dark gray rock with a low carbon content and harder than coal, which is associated with coal seams during coal formation. Coal gangue is a major industrial solid waste, not only occupying large amounts of arable land but also containing 1% to 8% sulfides, most of which exist in the inorganic sulfur form of FeS2. FeS2 is chemically unstable and slowly oxidizes in air, releasing heat. Over time, this can lead to spontaneous combustion, causing serious environmental pollution and endangering the safety of surrounding residents and the ecological environment.

[0003] my country is one of the few countries that relies on coal as its primary energy source. The National Development and Reform Commission has proposed the overall goal of "promoting the green, efficient, high-quality, high-value, and large-scale utilization of bulk solid waste, improving the comprehensive utilization level of bulk solid waste, and achieving a comprehensive utilization rate of 60% by 2025." At the same time, it has given specific guidance on "orderly guiding the use of coal gangue and fly ash to produce new wall materials, decorative and finishing materials, and other green building materials."

[0004] Effective removal of FeS2 from coal gangue not only benefits the storage and transportation of coal gangue, preventing spontaneous combustion accidents, but also effectively reduces the sulfur content in coal gangue, thereby significantly improving its resource utilization value and effectively reducing the desulfurization load during resource utilization. In the prior art, invention patent CN111780099B discloses a circulating fluidized bed combustion desulfurization method using co-combustion of coal gangue and biomass. This invention utilizes a circulating fluidized bed boiler and achieves good desulfurization results by controlling the particle size of coal gangue and biomass, the ratio of coal gangue to biomass usage, and the relationship between the amount of coal gangue and biomass mixture and the amount of primary and secondary air in the circulating fluidized bed boiler. Summary of the Invention

[0005] This invention reveals that Fe in FeS2 is ferrous iron, a good Fenton reagent, and can be used for Fenton-like advanced oxidation reactions. Therefore, replacing air with H2O2 transforms the slow oxidation under natural conditions into a rapid Fenton-like oxidation, enabling efficient removal of inorganic sulfur from coal gangue.

[0006] In view of this, one of the objectives of the present invention is to provide a method for removing sulfur from high-sulfur coal gangue based on a Fenton-like oxidation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for removing sulfur from high-sulfur coal gangue based on a Fenton-like oxidation process includes the following steps:

[0009] (1) Crushing and grinding: The high-sulfur coal gangue raw material is successively crushed by mechanical crushing and wet ball milling and ground into fine powder;

[0010] (2) Wet desulfurization: using an aqueous solution of hydrogen peroxide as a cleaning agent, a multi-stage countercurrent cleaning method is adopted to remove sulfur from coal gangue by oxidizing and dissolving it into the liquid phase.

[0011] Furthermore, the high-sulfur coal gangue raw material is in block form.

[0012] Furthermore, in step (2), pyrite in the coal gangue serves as a catalyst for the oxidation reaction.

[0013] Furthermore, a Fenton-like reaction occurs during the countercurrent cleaning process, oxidizing and dissolving inorganic sulfur (FeS2) in the coal gangue into the cleaning solution to achieve wet desulfurization.

[0014]

[0015] Furthermore, the mechanical crushing involves using a pulverizer to crush the coal gangue to a size of 10μm to 500μm; the wet ball milling involves using grinding balls to crush the mechanically crushed coal gangue to a size of 1μm to 10μm.

[0016] Preferably, the crusher is a jaw crusher.

[0017] Furthermore, the grinding ball is any one or more of steel balls and ceramic balls.

[0018] Preferably, the steel ball is a stainless steel ball; the ceramic ball is a zirconia ball.

[0019] Furthermore, in the wet ball milling process, the liquid medium is water; the ball-to-material ratio is 2:1 to 5:1; the liquid-to-solid ratio is 1:1 to 5:1; and the grinding time is 1 hour to 5 hours.

[0020] Preferably, the ball-to-material ratio is 4:1; the liquid-to-solid ratio is 3:1; and the grinding time is 3 hours.

[0021] Furthermore, the multi-stage countercurrent cleaning involves using a cleaning agent and coal gangue filter cake to flow in multiple countercurrent stages. Each stage of cleaning employs a stirrer to keep the liquid and solid phases in a turbulent state. After cleaning, the solution is filtered to obtain sulfur-containing filtrate and desulfurized coal gangue filter cake.

[0022] Furthermore, the number of cleaning stages in the multi-stage countercurrent cleaning is n = 1 to 10.

[0023] As a preferred option, the number of cleaning stages n = 3.

[0024] Furthermore, the hydrogen peroxide concentration in the cleaning agent is 0.1% to 5%.

[0025] Preferably, the hydrogen peroxide concentration is 2%.

[0026] Furthermore, in the multi-stage countercurrent cleaning, the liquid-to-solid ratio of each stage is 5:1 to 20:1; and the cleaning time of each stage is 15 min to 120 min.

[0027] Preferably, the liquid-to-solid ratio for each cleaning stage is 10:1 to 20:1; and the cleaning time for each stage is 15 min to 30 min.

[0028] As a better option, the liquid-to-solid ratio for each cleaning stage is 10:1; and the cleaning time for each stage is 30 minutes.

[0029] Furthermore, the effluent obtained after countercurrent washing is recycled after impurities are removed by flocculation and acid-base neutralization.

[0030] The second objective of this invention is to provide a system for desulfurizing high-sulfur coal gangue using the method described in the first objective.

[0031] To achieve the above objectives, the present invention adopts the following technical solution:

[0032] A system for desulfurizing high-sulfur coal gangue using the method described in Objective 1, the system comprising a crushing unit, a ball milling unit, a washing unit, and a tailwater treatment unit; the crushing unit, ball milling unit, washing unit, and tailwater treatment unit are connected in sequence; high-sulfur coal gangue raw material is crushed and ground sequentially through the crushing unit and the ball milling unit to obtain coal gangue powder; the coal gangue powder is cleaned in the washing unit using an aqueous solution of hydrogen peroxide as a cleaning agent, and sulfur is removed from the coal gangue through multi-stage countercurrent washing and oxidation; the tailwater obtained after countercurrent washing is treated by flocculation and acid-base neutralization in the tailwater treatment unit and then recycled.

[0033] The beneficial effects of this invention are as follows:

[0034] This invention starts with the chemical form of sulfur in coal gangue and removes over 90% of the inorganic sulfur from the coal gangue using a simple Fenton-like oxidation method. The desulfurized coal gangue powder after washing is characterized by small particle size and low sulfur content, and can be used to prepare high-value-added building materials, such as kaolin, new wall materials, and decorative materials. The wastewater after washing is recycled after removing impurities through flocculation and acid-base neutralization. The entire process is green, environmentally friendly, simple to operate, and low in cost. Attached Figure Description

[0035] Figure 1This is a schematic diagram of the wet desulfurization method for coal gangue according to the present invention; wherein, A: mechanical crushing; B: wet ball milling; C: countercurrent washing; D: coal gangue filter cake; E: washing liquid; F: hydrogen peroxide; n: washing stage. Detailed Implementation

[0036] The technical solution of the present invention will be described more clearly and completely below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0037] Example 1: Coal gangue from an abandoned coal mine (total sulfur content 4.5%, of which inorganic sulfur content is 3.5%)

[0038] See as follows Figure 1 The schematic diagram of the wet desulfurization method for coal gangue of the present invention illustrates the desulfurization of coal gangue (total sulfur content of 4.5%, of which inorganic sulfur content is 3.5%) from an abandoned coal mine. The method specifically includes the following steps: First, the coal gangue is mechanically crushed (A) using a pulverizer so that it can all pass through a 200-mesh sieve; then, it is prepared into a slurry with a liquid-to-solid ratio of 3:1, loaded into a ball mill jar, and continuously ball-milled (B) for 3 hours using stainless steel balls at a ball-to-material ratio of 5:1 to reduce the particle size to below 8μm; second, the grinding balls are separated by mechanical vibration screening, and the slurry (D) is transferred to a countercurrent cleaning unit (C). The cleaning process parameters are: cleaning stage n = 3, hydrogen peroxide (F) concentration in the cleaning solution (E) is 1%, liquid-to-solid ratio is 10:1, and single-stage cleaning time is 30 min; finally, after three stages of cleaning, desulfurized coal gangue powder is obtained. The total sulfur content of desulfurized coal gangue powder is 1.7%, of which the inorganic sulfur content is 0.2%, and the inorganic sulfur desulfurization rate reaches 94%. It can be used to fire high-value-added building materials such as wall decoration materials.

[0039] Example 2: Coal gangue from an abandoned coal mine (total sulfur content 6.1%, of which inorganic sulfur content is 4.9%)

[0040] See as follows Figure 1The schematic diagram of the wet desulfurization method for coal gangue of the present invention illustrates the desulfurization of coal gangue (total sulfur content of 6.1%, of which inorganic sulfur content is 4.9%) from an abandoned coal mine. The method specifically includes the following steps: First, the coal gangue is mechanically crushed (A) using a pulverizer so that it can all pass through a 200-mesh sieve; then, it is mixed into a slurry with a liquid-to-solid ratio of 1:1, loaded into a ball mill jar, and continuously ball-milled (B) for 5 hours using stainless steel balls at a ball-to-material ratio of 5:1 until the particle size is reduced to below 10 μm; second, the grinding balls are separated by mechanical vibration screening, and the slurry (D) is transferred to a countercurrent cleaning unit (C). The cleaning process parameters are: cleaning stage n = 10, hydrogen peroxide (F) concentration in the cleaning solution (E) is 0.5%, liquid-to-solid ratio is 20:1, and single-stage cleaning time is 15 min; finally, after ten stages of cleaning, desulfurized coal gangue powder is obtained. The total sulfur content of desulfurized coal gangue powder is 1.5%, of which the inorganic sulfur content is 0.3%, and the inorganic sulfur desulfurization rate reaches 94%. It can be used to produce high value-added industrial products such as ultrafine high-concrete.

[0041] Example 3: A coal gangue stockpile (total sulfur content 7.1%, of which inorganic sulfur content is 5.8%)

[0042] See as follows Figure 1 The schematic diagram of the wet desulfurization method for coal gangue of the present invention illustrates the desulfurization of coal gangue from a coal gangue stockpile with a total sulfur content of 7.1% and an inorganic sulfur content of 5.8%. The method includes the following steps: First, the coal gangue is mechanically crushed (A) using a pulverizer so that it can all pass through a 200-mesh sieve. Then, it is prepared into a slurry with a liquid-to-solid ratio of 3:1, loaded into a ball mill jar, and milled continuously for 5 hours using zirconia balls at a ball-to-material ratio of 4:1 (B) to reduce the particle size to below 2 μm. Second, the grinding balls are separated by mechanical vibration screening, and the slurry (D) is transferred to a countercurrent cleaning unit (C). The cleaning process parameters are: cleaning stage n = 5, hydrogen peroxide (F) concentration in the cleaning solution (E) is 2%, liquid-to-solid ratio is 10:1, and single-stage cleaning time is 30 min. Finally, after three stages of cleaning, desulfurized coal gangue powder is obtained. The total sulfur content of desulfurized coal gangue powder is 1.8%, of which the inorganic sulfur content is 0.5%, and the inorganic sulfur desulfurization rate reaches 91%. It can be used to produce high value-added industrial products such as ultrafine high-concrete.

[0043] Example 4: A coal gangue stockpile (total sulfur content 3.6%, of which inorganic sulfur content is 2.8%)

[0044] See as follows Figure 1The schematic diagram of the wet desulfurization method for coal gangue of the present invention is shown. The total sulfur content of the coal gangue from a certain coal gangue stockpile is 3.6%, of which inorganic sulfur is 3.6%. First, the coal gangue is mechanically crushed (A) using a pulverizer so that it can all pass through a 200-mesh screen. Then, it is prepared into a slurry with a liquid-to-solid ratio of 5:1 and loaded into a ball mill jar. Zirconia balls are used as grinding balls, and the ball-to-material ratio is 4:1. The ball milling is carried out continuously (B) for 1 hour to reduce the particle size to below 1 μm. Next, the grinding balls are separated by mechanical vibration screening. The slurry (D) is transferred to the countercurrent cleaning unit (C). The cleaning process parameters are as follows: cleaning stage n = 1, hydrogen peroxide (F) concentration in the cleaning liquid (E) is 5%, liquid-to-solid ratio is 20:1, and cleaning time is 15 min. Finally, desulfurized coal gangue powder is obtained. The total sulfur content of desulfurized coal gangue powder is 1.1%, of which the inorganic sulfur content is 0.3%, and the inorganic sulfur desulfurization rate reaches 89%. It can be used to fire high-value-added building materials such as wall decoration materials.

Claims

1. A method for removing sulfur from high-sulfur coal gangue based on Fenton-like oxidation process, characterized in that, Includes the following steps: (1) Crushing and grinding: The high-sulfur coal gangue raw material is successively crushed by mechanical crushing and wet ball milling and ground into fine powder; (2) Wet desulfurization: using an aqueous solution of hydrogen peroxide as a cleaning agent, a multi-stage countercurrent cleaning method is used to remove sulfur from coal gangue by oxidative dissolution and transfer to the liquid phase; pyrite in the coal gangue is used as a catalyst for the oxidation reaction.

2. The method according to claim 1, characterized in that, The mechanical crushing refers to crushing coal gangue to 10μm~500μm using a pulverizer; the wet ball milling refers to crushing the mechanically crushed coal gangue to 1μm~10μm using grinding balls.

3. The method according to claim 1, characterized in that, In the wet ball milling process, the liquid medium is water; the ball-to-material ratio is 2:1 to 5:1; the liquid-to-solid ratio is 1:1 to 5:1; and the grinding time is 1 to 5 hours.

4. The method according to claim 1, characterized in that, The multi-stage countercurrent cleaning process involves using a cleaning agent and coal gangue filter cake to flow in multiple countercurrent stages. Each stage of cleaning employs a stirrer to keep the liquid and solid phases in a turbulent state. After cleaning, the solution is filtered to obtain sulfur-containing filtrate and desulfurized coal gangue filter cake.

5. The method according to claim 1, characterized in that, The number of cleaning stages in the multi-stage countercurrent cleaning is n = 1~10.

6. The method according to claim 1, characterized in that, The hydrogen peroxide concentration in the cleaning agent is 0.1% to 5%.

7. The method according to claim 1, characterized in that, In the multi-stage countercurrent cleaning, the liquid-to-solid ratio of each stage is 5:1 to 20:1; and the cleaning time of each stage is 15 min to 120 min.

8. The method according to claim 1, characterized in that, The effluent obtained after countercurrent washing is recycled after impurities are removed by flocculation and acid-base neutralization.

9. A system for desulfurizing high-sulfur coal gangue using the method described in any one of claims 1-8, characterized in that, The system includes a crushing unit, a ball milling unit, a washing unit, and a tailwater treatment unit; the crushing unit, ball milling unit, washing unit, and tailwater treatment unit are connected in sequence; high-sulfur coal gangue raw material is crushed and ground in the crushing unit and the ball milling unit to obtain coal gangue powder; the coal gangue powder is washed and oxidized in the washing unit using an aqueous solution of hydrogen peroxide as a washing agent to remove sulfur from the coal gangue; the tailwater obtained after countercurrent washing is treated by flocculation and acid-base neutralization in the tailwater treatment unit and then recycled.

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