Coal slime dehydration method based on synergistic conditioning of biomass and nanoparticles

Abstract

The invention relates to the technical field of coal slime treatment, and discloses a coal slime dehydration method based on biomass and nanoparticle synergistic conditioning, which comprises the following steps: (1) carbonizing a biomass raw material to obtain pretreated biomass; the preparation method comprises the following steps: mixing nano SiO2 and nano TiO2 / Fe2O3 to obtain nano particles; (2) adding the pretreated biomass and nano-particles into an ethanol water solution, stirring and mixing, and then drying to obtain a conditioner; (3) adding a conditioner and water into the coal slurry, stirring and mixing, and performing ultrasonic treatment and ultraviolet irradiation at the same time to obtain pretreated coal slurry; (4) sequentially carrying out pre-concentration dehydration and high-pressure dehydration on the pretreated coal slurry to obtain a first mud cake; biomass framework construction and nanoparticle surface modification are combined and applied to coal slime conditioning, advantage complementation is achieved, water discharge is accelerated, and therefore the dehydration effect is cooperatively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal slime treatment, and in particular to a coal slime dehydration method based on synergistic conditioning of biomass and nanoparticles. Background Art

[0002] Coal slime is a byproduct of the coal washing process. It typically has fine particle size, strong water retention, high ash content, and high viscosity. Dehydration is particularly difficult when it contains a large amount of ultrafine particles (e.g., <0.045 mm) and clay minerals. Traditional methods for dehydrating coal slime rely primarily on chemical flocculants and mechanical filter presses.

[0003] Chemical flocculants include inorganic coagulants (such as polyaluminum chloride and ferric sulfate) and / or organic polymer flocculants (primarily various types of polyacrylamide (PAM), sometimes supplemented with surfactants). These agents, through actions such as charge neutralization and adsorption bridging, cause fine coal slime particles to aggregate into larger flocs, thereby accelerating sedimentation and improving filtration performance during subsequent mechanical dewatering. However, this approach has the following significant drawbacks: First, chemical residue and pollution. Large amounts of chemical agents used can remain in the filtrate (circulating water) and mud cake, polluting the circulating water system and increasing water treatment costs. Discharge can also cause environmental pollution. Second, product quality can be affected. The addition of inorganic agents (such as iron and aluminum salts) increases the ash content of the final coal slime product, reducing its calorific value as a fuel. Organic agent residues can also negatively impact certain subsequent uses of the coal slime (such as specific chemical applications). Third, the cost is high and applicability is limited. Chemical agents are expensive, and their effectiveness is often sensitive to coal slime properties (such as pH, ionic strength, and particle size composition), requiring targeted selection and optimization of dosage. Therefore, for some particularly difficult-to-treat coal slimes, relying solely on chemical flocculants may have limited effects or be too costly.

[0004] Mechanical filter pressing methods focus on improving dewatering efficiency through equipment or process improvements. For example, high-pressure diaphragm filter presses, belt filter presses, and decanter centrifuges are used to apply increased mechanical force or utilize centrifugal force to force dewatering. However, high-efficiency dewatering equipment typically requires large investments, high energy consumption, and complex maintenance. For ultrafine coal sludge with a high clay content, the resulting filter cake is extremely compressible and has very poor permeability. Simply increasing mechanical pressure often has limited effectiveness and can easily cause problems such as filter cloth clogging and wear. Another example is a multi-stage concentration process, where the coal sludge concentration is first increased in a concentrator or cyclone. Alternatively, coarse particles (such as coarser coal particles or, in some cases, even inert materials such as sand) can be incorporated into the fine coal sludge to serve as a "framework" to increase the porosity and permeability of the filter cake and improve filter press performance. However, the addition of inert coarse particles will seriously reduce the calorific value of the product, while the addition of coarse coal particles is limited by the coal source and process conditions, and may not be effective in improving the viscosity problem caused by clay. The complexity of the process may also increase the difficulty and cost of operation.

[0005] In recent years, there have been studies attempting to add crushed biomass (such as crop straw, sawdust, rice husks, etc.) as a physical conditioner to coal slime. For example, the coal slime dehydration method disclosed in the patent with publication number CN116444126A is to blend biomass with coal slime. The principle is to use the fibrous structure of biomass to form a porous, relatively rigid skeleton in the coal slime, reduce the compressibility of the filter cake, and provide a channel for the discharge of water. In addition, biomass itself is a combustible material and can increase the calorific value of the final dehydrated coal slime product. However, biomass itself also has a certain water absorption capacity, which may limit the dehydration effect to a certain extent, and the uniform mixing and effective combination of biomass and ultrafine coal slime particles will also be a challenge. Summary of the Invention

[0006] In order to solve the problems of low dehydration efficiency, high final moisture content, chemical pollution, high energy consumption, and low added value of the final product in the existing technology when treating high-viscosity, high-ash, and ultra-fine-grained coal slimes, the present invention provides a coal slime dehydration method based on the synergistic conditioning of biomass and nanoparticles. By combining biomass skeleton construction and nanoparticle surface modification for coal slime conditioning, the advantages are complementary, which can not only maintain the high porosity and low compressibility of the filter cake, but also anchor the nanoparticles on the coal slime surface, giving it a rough structure, weakening the bondage to moisture, and accelerating moisture discharge, thereby synergistically improving the dehydration effect.

[0007] The purpose of the present invention is achieved through the following technical solutions: The present invention provides a coal slime dehydration method based on the synergistic conditioning of biomass and nanoparticles, comprising the following steps: (1) carbonizing a biomass raw material to obtain pretreated biomass; mixing nano-SiO2 and nano-TiO2 / Fe2O3 to obtain nanoparticles; (2) adding the pretreated biomass and nanoparticles into an ethanol aqueous solution, stirring and mixing, and then drying to obtain a conditioning agent; (3) adding a conditioning agent and water to the coal slurry, stirring and mixing, and then performing ultrasonic treatment and ultraviolet irradiation to obtain a pretreated coal slurry; (4) The pretreated coal slurry is subjected to pre-concentration dehydration and high-pressure dehydration in sequence to obtain a first mud cake.

[0008] Biomass raw materials can be mixed with coal slime as a skeleton structure to reduce the compressibility of the mud cake, thereby enhancing the dehydration effect of the coal slime; nanoparticles can form micro-nano structures on the surface of coal slime particles, increase the roughness of coal slime, reduce the resistance to water flow, and improve the dehydration effect. The present invention is to pre-treat the biomass raw materials with low-temperature carbonization, retain the cellulose / lignin skeleton, and generate a microporous structure at the same time. Nanoparticles are blended with the pretreated biomass, and the agglomeration of nanoparticles is reduced by adsorption or hydrogen bonding. Nanoparticles fill the pores while enhancing mechanical strength to form a biomass-nanoparticle composite skeleton. This composite skeleton is combined with coal slime to maintain the high porosity and low compressibility of the filter cake, and to use biomass as a bridge to anchor the nanoparticles on the surface of the coal slime, directly giving a rough structure, weakening the bondage to water, and accelerating water discharge, thereby synergistically improving the dehydration effect.

[0009] At the same time, the nanoparticles include nano-SiO2 and nano-TiO2 / Fe2O3. Nano-SiO2 is rich in hydroxyl groups, which is conducive to forming a stable interface with oxygen-containing functional groups (such as carboxylic acid groups and phenolic hydroxyl groups) in the coal slime, inducing the nanoparticles to align on the surface of the coal slime, forming an ordered or disordered micro-nano composite structure, and improving the roughness. Nano-TiO2 / Fe2O3 has photocatalytic activity. Nano-TiO2 is mainly photocatalytic under ultraviolet light, and the added Fe2O3 can also expand its catalytic activity under visible light. Therefore, during the ultrasonic and ultraviolet treatment stages, not only can the clay agglomerate structure be destroyed by ultrasonic treatment and the dispersion of the conditioning agent in the coal slime be promoted, but the colloidal organic matter in the coal slime can also be catalytically decomposed by nano-TiO2 / Fe2O3 under ultraviolet light, which helps to destroy the clay agglomerate structure and reduce the binding of these sticky components to water, thereby improving the dehydration effect. Furthermore, after nano-TiO2 is surface-loaded with Fe2O3, the positively charged Fe2O3 surface neutralizes the negative charge of the coal slime particles, reducing electrostatic repulsion, promoting flocculation, forming larger flocs, and improving the sedimentation of ultrafine coal slime particles. During the subsequent high-pressure dehydration process, mechanical extrusion, pressure, or hydraulic shear forces may cause some of the biomass-adsorbed nanoparticles to detach, or dynamically release internal nanoparticles, migrating to the surface of the coal slime particles, thereby forming a new surface roughness structure, thereby improving the dehydration effect and obtaining a low-moisture mud cake.

[0010] Preferably, in step (1), the biomass raw material is one or more of straw, sawdust and rice husk, with a particle size of no more than 0.3 mm; and the carbonization is carried out under an inert atmosphere at 200-300° C. for 1-2 h.

[0011] Preferably, in step (1), the preparation method of nano-TiO2 / Fe2O3 comprises the following steps: adding ferric nitrate to a sodium hydroxide aqueous solution, then adding nano-TiO2 and Tween for mixing and grinding, filtering and drying, and calcining in air at 400-450°C for 1-2h to obtain nano-TiO2 / Fe2O3.

[0012] Preferably, the ratio of the added amounts of ferric nitrate, sodium hydroxide aqueous solution, nano-TiO2 and Tween is 6-8g:50mL:9-12g:1-3mL; the mass concentration of the sodium hydroxide solution is 3-5%; the particle size of the nano-TiO2 is 10-50nm; and the mixing and grinding time is 20-40min.

[0013] Preferably, in step (1), the particle size of the nano-SiO2 is 10-50 nm; and the mass ratio of the nano-SiO2 to nano-TiO2 / Fe2O3 is 2-4:1.

[0014] Preferably, in step (2), the mass ratio of the pretreated biomass to the nanoparticles is 5-7:1; the ratio of the added amount of the nanoparticles to the ethanol aqueous solution is 1-5g:50mL; the stirring and mixing speed is 50-100rpm, and the time is 30-60min.

[0015] Preferably, in step (3), the coal slurry has a solid content of 30-40% (mass percentage), an ash content (dry basis) of 50-60%, and a particle size analysis shows that the fine particle size (-0.045 mm) content exceeds 60%.

[0016] High-viscosity, high-ash, and ultrafine coal slimes present the following challenges during dehydration: High viscosity leads to poor fluidity, easily clogging pipes or causing localized accumulation, reducing dehydration efficiency; high ash content strongly adsorbs water molecules, making water difficult to remove; and ultrafine particles easily form low-porosity mud cakes, where water is trapped by capillary forces, resulting in poor permeability and low dehydration efficiency. Consequently, these slimes exhibit high viscosity, difficulty in settling, and difficulty in dehydration.

[0017] Preferably, in step (3), the mass ratio of dry basis coal slime to conditioner in the coal slime slurry is 4-8:1; the amount of water added is such that the water content of the slurry is 60-70%; the stirring and mixing speed is 50-100 rpm, and the time is 10-30 min.

[0018] Preferably, in step (3), the frequency of the ultrasound is 10-20 kHz, and ultraviolet light with a power of 150-200 W is simultaneously applied for 20-45 min.

[0019] Preferably, in step (4), the moisture content of the slurry after pre-concentration and dehydration is 40-55%.

[0020] The slurry moisture content (60-70%) is reduced to a state that is easy for subsequent high-pressure dehydration (40-55%). The filtrate (overflow) discharged at this stage can be reused as circulating water.

[0021] Preferably, in step (4), the pressure of high-pressure dehydration is 1-2 MPa; and the moisture content of the first mud cake is 18-25%.

[0022] Preferably, the first mud cake is dried naturally or through ventilation to further reduce the moisture content to less than 10% to obtain a second mud cake, and the second mud cake is crushed and granulated to obtain coal slime fuel particles.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) By combining biomass skeleton construction and nanoparticle surface modification in coal slime conditioning, the advantages are complementary, which can not only maintain the high porosity and low compressibility of the filter cake, but also use biomass as a bridge to anchor the nanoparticles on the coal slime surface, directly giving it a rough structure, weakening the bondage to water, and accelerating water discharge, thereby synergistically improving the dehydration effect; (2) Ultrasonic treatment combined with ultraviolet catalytic treatment is used to ensure the full, uniform and effective combination of the conditioning agent and the coal slime particles. At the same time, nano-TiO2 / Fe2O3 is used to decompose the colloidal organic matter in the coal slime, which helps to destroy the clay agglomeration structure, reduce the binding of these viscous components to water, and further improve the dehydration efficiency; (3) Before high-pressure deep dehydration, a combination of ultrasonic ultraviolet treatment and pre-concentration dehydration is used to reduce viscosity, improve dehydration properties, and increase dehydration efficiency; (4) This method is particularly suitable for the dehydration of high-viscosity, high-ash, and ultrafine-grained coal slimes. It can significantly reduce the moisture content of the mud cake through the combined mechanism of conditioning agent conditioning, ultrasonic ultraviolet treatment, and high-pressure deep dehydration. (5) It mainly uses cheap and readily available biomass waste and a relatively small amount of nanoparticles, which greatly reduces or avoids the use of chemical flocculants, reduces the burden of circulating water treatment and environmental pollution. DETAILED DESCRIPTION

[0024] The technical solutions of the present invention are described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0025] A method for dehydrating coal slime based on synergistic conditioning of biomass and nanoparticles comprises the following steps: (1) Carbonizing the biomass raw material at 200-300° C. for 1-2 hours under an inert atmosphere to obtain pretreated biomass; mixing nano-SiO2 and nano-TiO2 / Fe2O3 in a mass ratio of 2-4:1 to obtain nanoparticles; (2) adding the pretreated biomass and nanoparticles to an ethanol-water solution at a mass ratio of 5-7:1, wherein the ratio of the nanoparticles to the ethanol-water solution is 1-5 g:50 mL, and the volume ratio of ethanol to water in the ethanol-water solution is 1:1; stirring and mixing at a speed of 50-100 rpm for 30-60 minutes, and then drying to obtain a conditioning agent; (3) adding a conditioning agent to the coal slurry, wherein the mass ratio of dry basis coal slurry to conditioning agent in the coal slurry is 4-8:1; then adding water (which may be the filtrate from the subsequent concentration and dehydration step) to make the water content of the slurry 60-70%; stirring and mixing at a speed of 50-100 rpm for 10-30 minutes, and then performing ultrasonic treatment at a frequency of 10-20 kHz, and simultaneously performing ultraviolet light irradiation with a power of 150-200 W for 20-45 minutes to obtain a pretreated coal slurry; (4) The pretreated coal slurry is pre-concentrated and dehydrated, and the moisture content of the dehydrated slurry is 40-55%; then high-pressure dehydration is performed under the condition of 1-2 MPa to obtain a first mud cake with a moisture content of 18-25%; (5) After the first mud cake is naturally air-dried or ventilated to dry, the moisture content is further reduced to less than 10% to obtain a second mud cake; the second mud cake is crushed and granulated to obtain coal slime fuel particles.

[0026] In a specific embodiment of the present invention, in step (1), the biomass raw material is one or more of straw, wood chips and rice husks, and the particle size is not greater than 0.3 mm.

[0027] In a specific embodiment of the present invention, in step (1), the particle size of nano-SiO2 is 10-50nm.

[0028] In a specific embodiment of the present invention, in step (1), the preparation method of nano-TiO2 / Fe2O3 comprises the following steps: adding ferric nitrate to a sodium hydroxide aqueous solution with a mass concentration of 3-5%, then adding nano-TiO2 with an average particle size of 20 nm and Tween 60 and mixing and grinding for 30 minutes, wherein the ratio of the added amounts of ferric nitrate, sodium hydroxide aqueous solution, nano-TiO2 and Tween 60 is 8g:50mL:11g:1.5mL; after filtering and drying, heating to 400°C in air at a rate of 5°C / min, calcining for 2h, and cooling to obtain nano-TiO2 / Fe2O3.

[0029] Example 1 The treatment object is flotation tailings from a coal preparation plant. Its characteristics are: solid content is about 35% (mass percentage), ash content (dry basis) is as high as 55%, particle size analysis shows that the fine particle size (-0.045mm) content exceeds 60%, and it has high viscosity and is difficult to settle and dehydrate.

[0030] The above-mentioned coal slime is dehydrated, comprising the following steps: (1) The biomass raw material (rice husk, particle size not greater than 0.3 mm) was carbonized at 200°C for 2 h under an inert atmosphere to obtain pretreated biomass; nano-SiO2 (average particle size of 20 nm) and nano-TiO2 / Fe2O3 were mixed in a mass ratio of 3:1 to obtain nanoparticles.

[0031] (2) The pretreated biomass and nanoparticles were added to an ethanol-water solution (the volume ratio of ethanol to water was 1:1) in a mass ratio of 6:1, and the ratio of the added amount of nanoparticles to the ethanol-water solution was 4 g:50 mL; the mixture was stirred at a speed of 80 rpm for 45 minutes, and then dried to obtain a conditioner.

[0032] (3) 10 kg of dry coal slime was processed in each batch, 1.4 kg of conditioning agent was added to the coal slime slurry (the mass ratio of dry coal slime to conditioning agent in the coal slime slurry was 7.14:1), and then water (which could be the filtrate from the subsequent dehydration step) was added to make the water content of the slurry 60%; the mixture was stirred and mixed at a speed of 60 rpm for 30 minutes, and then ultrasonic treatment was performed at a frequency of 20 kHz, and ultraviolet light with a power of 150 W was simultaneously applied for 30 minutes to obtain pretreated coal slime slurry.

[0033] (4) The pretreated coal slurry is pre-concentrated and dehydrated. The slurry relies on its own gravity to initially remove free water in the gravity dehydration zone. The moisture content of the dehydrated slurry is 40-55%. The discharged filtrate is collected through a collection tank and pumped to a circulating water pool for slurry adjustment in step (3); the slurry is then pumped to the feed port of the filter press, first pressed at 1.0 MPa for 15 minutes, then increased to 1.6 MPa, and continued to press for 30 minutes. After the pressing is completed, the pressure is released to obtain a first mud cake with a moisture content of 18-25%; the pressed filtrate discharged at this stage is also collected in a circulating water pool.

[0034] (5) After the first mud cake is naturally aired for 4 days, the moisture content is further reduced to less than 10% to obtain a second mud cake; the second mud cake is crushed and granulated to obtain coal mud fuel particles.

[0035] Example 2 The coal slime from the same source as in Example 1 is dehydrated, comprising the following steps: (1) The biomass raw material (rice husk, particle size not greater than 0.3 mm) was carbonized at 200°C for 2 h under an inert atmosphere to obtain pretreated biomass; nano-SiO2 (average particle size of 20 nm) and nano-TiO2 / Fe2O3 were mixed in a mass ratio of 3:1 to obtain nanoparticles.

[0036] (2) The pretreated biomass and nanoparticles were added to an ethanol-water solution (the volume ratio of ethanol to water was 1:1) in a mass ratio of 6:1, and the ratio of the added amount of nanoparticles to the ethanol-water solution was 4 g:50 mL; the mixture was stirred at a speed of 80 rpm for 45 minutes, and then dried to obtain a conditioner.

[0037] (3) 10 kg of dry coal slime was processed in each batch, 1.6 kg of conditioning agent was added to the coal slime slurry (the mass ratio of dry coal slime to conditioning agent in the coal slime slurry was 6.25:1), and then water (which could be the filtrate from the subsequent dehydration step) was added to make the water content of the slurry 60%; the mixture was stirred and mixed at a speed of 60 rpm for 30 minutes, and then ultrasonic treatment was performed at a frequency of 20 kHz, and ultraviolet light with a power of 150 W was simultaneously applied for 30 minutes to obtain the pretreated coal slime slurry.

[0038] (4) The pretreated coal slurry is pre-concentrated and dehydrated. The slurry relies on its own gravity to initially remove free water in the gravity dehydration zone. The moisture content of the dehydrated slurry is 40-55%. The discharged filtrate is collected through a collection tank and pumped to a circulating water pool for slurry adjustment in step (3); the slurry is then pumped to the feed port of the filter press, first pressed at 1.0 MPa for 15 minutes, then increased to 1.6 MPa, and continued to press for 30 minutes. After the pressing is completed, the pressure is released to obtain a first mud cake with a moisture content of 18-25%; the pressed filtrate discharged at this stage is also collected in a circulating water pool.

[0039] (5) After the first mud cake is naturally aired for 4 days, the moisture content is further reduced to less than 10% to obtain a second mud cake; the second mud cake is crushed and granulated to obtain coal mud fuel particles.

[0040] Example 3 The coal slime from the same source as in Example 1 is dehydrated, comprising the following steps: (1) The biomass raw material (rice husk, particle size not greater than 0.3 mm) was carbonized at 200°C for 2 h under an inert atmosphere to obtain pretreated biomass; nano-SiO2 (average particle size of 20 nm) and nano-TiO2 / Fe2O3 were mixed in a mass ratio of 3:1 to obtain nanoparticles.

[0041] (2) The pretreated biomass and nanoparticles were added to an ethanol-water solution (the volume ratio of ethanol to water was 1:1) in a mass ratio of 6:1, and the ratio of the added amount of nanoparticles to the ethanol-water solution was 4 g:50 mL; the mixture was stirred at a speed of 80 rpm for 45 minutes, and then dried to obtain a conditioner.

[0042] (3) 10 kg of dry coal slime was processed in each batch, 1.8 kg of conditioning agent was added to the coal slime slurry (the mass ratio of dry coal slime to conditioning agent in the coal slime slurry was 5.56:1), and then water (which could be the filtrate from the subsequent dehydration step) was added to make the water content of the slurry 60%; the mixture was stirred and mixed at a speed of 60 rpm for 30 minutes, and then ultrasonic treatment was performed at a frequency of 20 kHz. At the same time, ultraviolet light with a power of 150 W was applied for 30 minutes to obtain pretreated coal slime.

[0043] (4) The pretreated coal slurry is pre-concentrated and dehydrated. The slurry relies on its own gravity to initially remove free water in the gravity dehydration zone. The moisture content of the dehydrated slurry is 40-55%. The discharged filtrate is collected through a collection tank and pumped to a circulating water pool for slurry adjustment in step (3); the slurry is then pumped to the feed port of the filter press, first pressed at 1.0 MPa for 15 minutes, then increased to 1.6 MPa, and continued to press for 30 minutes. After the pressing is completed, the pressure is released to obtain a first mud cake with a moisture content of 18-25%; the pressed filtrate discharged at this stage is also collected in a circulating water pool.

[0044] (5) After the first mud cake is naturally aired for 4 days, the moisture content is further reduced to less than 10% to obtain a second mud cake; the second mud cake is crushed and granulated to obtain coal mud fuel particles.

[0045] Example 4 The coal slime from the same source as in Example 1 is dehydrated, comprising the following steps: (1) The biomass raw material (rice husk, particle size not greater than 0.3 mm) was carbonized at 200°C for 2 h under an inert atmosphere to obtain pretreated biomass; nano-SiO2 (average particle size of 20 nm) and nano-TiO2 / Fe2O3 were mixed in a mass ratio of 2:1 to obtain nanoparticles.

[0046] (2) The pretreated biomass and nanoparticles were added to an ethanol-water solution (the volume ratio of ethanol to water was 1:1) in a mass ratio of 7:1, and the ratio of the added amount of nanoparticles to the ethanol-water solution was 3 g:50 mL; the mixture was stirred at a speed of 80 rpm for 45 minutes, and then dried to obtain a conditioner.

[0047] (3) 10 kg of dry coal slime was processed in each batch, 1.4 kg of conditioning agent was added to the coal slime slurry (the mass ratio of dry coal slime to conditioning agent in the coal slime slurry was 7.14:1), and then water (which could be the filtrate from the subsequent dehydration step) was added to make the water content of the slurry 60%; the mixture was stirred and mixed at a speed of 60 rpm for 30 minutes, and then ultrasonic treatment was performed at a frequency of 20 kHz. At the same time, ultraviolet light with a power of 200 W was applied for 35 minutes to obtain the pretreated coal slime slurry.

[0048] (4) The pretreated coal slurry is pre-concentrated and dehydrated. The slurry relies on its own gravity to initially remove free water in the gravity dehydration zone. The moisture content of the dehydrated slurry is 40-55%. The discharged filtrate is collected through a collection tank and pumped to a circulating water pool for slurry adjustment in step (3); the slurry is then pumped to the feed port of the filter press, first pressed at 1.0 MPa for 15 minutes, then increased to 1.6 MPa, and continued to press for 30 minutes. After the pressing is completed, the pressure is released to obtain a first mud cake with a moisture content of 18-25%; the pressed filtrate discharged at this stage is also collected in a circulating water pool.

[0049] (5) After the first mud cake is naturally aired for 4 days, the moisture content is further reduced to less than 10% to obtain a second mud cake; the second mud cake is crushed and granulated to obtain coal mud fuel particles.

[0050] Comparative Example 1 The difference from Example 1 is that the pretreatment parameters of the biomass raw material are different. Specifically, the biomass raw material (rice husk, with a particle size of not more than 0.3 mm) is carbonized at 400° C. for 3 h under an inert atmosphere to obtain pretreated biomass.

[0051] Comparative Example 2 The difference from Example 1 is that the conditioning agent is added separately.

[0052] The coal slime from the same source as in Example 1 is dehydrated, comprising the following steps: (1) The biomass raw material (rice husk, particle size not greater than 0.3 mm) was carbonized at 200°C for 2 h under an inert atmosphere to obtain pretreated biomass; nano-SiO2 (average particle size of 20 nm) and nano-TiO2 / Fe2O3 were mixed in a mass ratio of 3:1 to obtain nanoparticles.

[0053] (2) 10 kg of dry coal slime was processed in each batch, 1.2 kg of pretreated biomass and 0.2 kg of nanoparticles were added to the coal slime slurry, and water (which could be the filtrate from the subsequent dehydration step) was added to make the slurry have a moisture content of 60%; the mixture was stirred and mixed at a speed of 60 rpm for 30 minutes, and then ultrasonic treatment was performed at a frequency of 20 kHz, and ultraviolet light with a power of 150 W was applied for 30 minutes to obtain pretreated coal slime slurry.

[0054] (3) The pretreated coal slurry is pre-concentrated and dehydrated. The slurry relies on its own gravity to initially remove free water in the gravity dehydration zone. The moisture content of the dehydrated slurry is 40-55%. The discharged filtrate is collected through a collection tank and pumped to a circulating water pool for slurry adjustment in step (3); the slurry is then pumped to the feed port of the filter press, first pressed at 1.0 MPa for 15 minutes, then increased to 1.6 MPa, and continued to press for 30 minutes. After the pressing is completed, the pressure is released to obtain a first mud cake with a moisture content of 18-25%; the pressed filtrate discharged at this stage is also collected in a circulating water pool.

[0055] (4) After the first mud cake is naturally aired for 4 days, the moisture content is further reduced to less than 10% to obtain a second mud cake; the second mud cake is crushed and granulated to obtain coal mud fuel particles.

[0056] Comparative Example 3 The difference from Example 1 is that no nano-TiO2 / Fe2O3 is added and no ultraviolet light treatment is performed.

[0057] The coal slime from the same source as in Example 1 is dehydrated, comprising the following steps: (1) The biomass raw material (rice husk, particle size not greater than 0.3 mm) was carbonized at 200°C for 2 h under an inert atmosphere to obtain pretreated biomass; nano-SiO2 (average particle size of 20 nm) was used as nanoparticles.

[0058] (2) The pretreated biomass and nanoparticles were added to an ethanol-water solution (the volume ratio of ethanol to water was 1:1) in a mass ratio of 6:1, and the ratio of the added amount of nanoparticles to the ethanol-water solution was 4 g:50 mL; the mixture was stirred at a speed of 80 rpm for 45 minutes, and then dried to obtain a conditioner.

[0059] (3) 10 kg of dry coal slime was processed in each batch, 1.4 kg of conditioning agent was added to the coal slime slurry (the mass ratio of dry coal slime to conditioning agent in the coal slime slurry was 7.14:1), and then water (which could be the filtrate from the subsequent dehydration step) was added to make the water content of the slurry 60%; the mixture was stirred and mixed at a speed of 60 rpm for 30 minutes, and then ultrasonic treatment was performed at a frequency of 20 kHz for 30 minutes to obtain pretreated coal slime slurry.

[0060] (4) The pretreated coal slurry is pre-concentrated and dehydrated. The slurry relies on its own gravity to initially remove free water in the gravity dehydration zone. The moisture content of the dehydrated slurry is 40-55%. The discharged filtrate is collected through a collection tank and pumped to a circulating water pool for slurry adjustment in step (3); the slurry is then pumped to the feed port of the filter press, first pressed at 1.0 MPa for 15 minutes, then increased to 1.6 MPa, and continued to press for 30 minutes. After the pressing is completed, the pressure is released to obtain a first mud cake with a moisture content of 18-25%; the pressed filtrate discharged at this stage is also collected in a circulating water pool.

[0061] (5) After the first mud cake is naturally aired for 4 days, the moisture content is further reduced to less than 10% to obtain a second mud cake; the second mud cake is crushed and granulated to obtain coal mud fuel particles.

[0062] Comparative Example 4 The difference from Example 1 is that nano-TiO2 / Fe2O3 is replaced by nano-TiO2.

[0063] The coal slime from the same source as in Example 1 is dehydrated, comprising the following steps: (1) The biomass raw material (rice husk, particle size not greater than 0.3 mm) was carbonized at 200°C for 2 h under an inert atmosphere to obtain pretreated biomass; nano-SiO2 (average particle size of 20 nm) and nano-TiO2 (average particle size of 20 nm) were mixed in a mass ratio of 3:1 to obtain nanoparticles.

[0064] (2) The pretreated biomass and nanoparticles were added to an ethanol-water solution (the volume ratio of ethanol to water was 1:1) in a mass ratio of 6:1, and the ratio of the added amount of nanoparticles to the ethanol-water solution was 4 g:50 mL; the mixture was stirred at a speed of 80 rpm for 45 minutes, and then dried to obtain a conditioner.

[0065] (3) 10 kg of dry coal slime was processed in each batch, 1.4 kg of conditioning agent was added to the coal slime slurry (the mass ratio of dry coal slime to conditioning agent in the coal slime slurry was 7.14:1), and then water (which could be the filtrate from the subsequent dehydration step) was added to make the water content of the slurry 60%; the mixture was stirred and mixed at a speed of 60 rpm for 30 minutes, and then ultrasonic treatment was performed at a frequency of 20 kHz, and ultraviolet light with a power of 150 W was simultaneously applied for 30 minutes to obtain pretreated coal slime slurry.

[0066] (4) The pretreated coal slurry is pre-concentrated and dehydrated. The slurry relies on its own gravity to initially remove free water in the gravity dehydration zone. The moisture content of the dehydrated slurry is 40-55%. The discharged filtrate is collected through a collection tank and pumped to a circulating water pool for slurry adjustment in step (3); the slurry is then pumped to the feed port of the filter press, first pressed at 1.0 MPa for 15 minutes, then increased to 1.6 MPa, and continued to press for 30 minutes. After the pressing is completed, the pressure is released to obtain a first mud cake with a moisture content of 18-25%; the pressed filtrate discharged at this stage is also collected in a circulating water pool.

[0067] (5) After the first mud cake is naturally aired for 4 days, the moisture content is further reduced to less than 10% to obtain a second mud cake; the second mud cake is crushed and granulated to obtain coal mud fuel particles.

[0068] Table 1 Moisture content of slurry after pre-concentration and dehydration Moisture content of the first mud cake The moisture content of the second mud cake Example 1 50.6％ 23.9％ 8.8％ Example 2 48.3％ 20.5％ 6.7％ Example 3 47.7％ 19.4％ 6.9％ Example 4 51.2％ 22.7％ 8.1％ Comparative Example 1 48.8％ 27.0％ 10.3％ Comparative Example 2 51.5％ 26.2％ 9.7％ Comparative Example 3 56.4％ 32.6％ 12.5％ Comparative Example 4 51.7％ 25.3％ 9.1％ As shown in Table 1, the present invention significantly improves the dehydration effect in the high-pressure dehydration stage by adding a conditioning agent to the coal slime, thereby obtaining a first mud cake with a lower moisture content. Furthermore, after natural airing or ventilation drying, a second mud cake with an even lower moisture content can be obtained. The crushed pellet product can be directly used for boiler combustion or other resource utilization methods.

[0069] However, in Comparative Example 1, since the biomass raw material used has been carbonized to a large extent, although the nanoparticles filling the pores can enhance the mechanical strength, it is still easy to cause the skeleton structure to collapse, especially during the high-pressure dehydration stage, and the low compressibility of the filter cake cannot be maintained, so the dehydration effect will be greatly affected. In Comparative Example 2, the pretreated biomass and nanoparticles are added separately. Since the mechanical properties of the pretreated biomass will be affected, the nanoparticles can enhance the mechanical strength while filling the pores, and the biomass skeleton structure when added separately will also be affected during high-pressure dehydration, and the moisture content of the resulting mud cake is relatively high. Comparative Example 3 does not add nano-TiO2 / Fe2O3, relying only on the synergistic conditioning of nano-SiO2 and biomass, which cannot be well applied to high-viscosity, high-ash coal slime, thereby reducing the dehydration efficiency. In Comparative Example 4, since only nano-TiO2 is added, it can catalyze the decomposition of colloidal organic matter in the coal slime during the ultrasonic ultraviolet treatment stage, which helps to destroy the clay agglomerate structure. However, since it is not compounded with Fe2O3, the treatment effect on ultrafine coal slime particles will be poor, which will also affect the moisture content.

[0070] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for dehydrating coal slime based on synergistic conditioning of biomass and nanoparticles, characterized in that: The steps include: (1) Carbonizing the biomass raw material to obtain pretreated biomass; mixing nano-SiO2 and nano-TiO2 / Fe2O3 to obtain nanoparticles; (2) adding the pretreated biomass and nanoparticles into an ethanol aqueous solution, stirring and mixing, and then drying to obtain a conditioning agent; (3) adding a conditioning agent and water to the coal slurry, stirring and mixing, and then performing ultrasonic treatment and ultraviolet irradiation to obtain a pretreated coal slurry; (4) The pretreated coal slurry is subjected to pre-concentration dehydration and high-pressure dehydration in sequence to obtain the first mud cake.

2. The method for dehydrating coal slime based on synergistic conditioning of biomass and nanoparticles according to claim 1, characterized in that: In step (1), the biomass raw material is one or more of straw, sawdust and rice husk, and the particle size is not greater than 0.3 mm; the carbonization is carried out under an inert atmosphere at 200-300° C. for 1-2 hours.

3. The method for dehydrating coal slime based on synergistic conditioning of biomass and nanoparticles according to claim 1, characterized in that: In step (1), the particle size of the nano-SiO2 is 10-50 nm; the mass ratio of the nano-SiO2 to nano-TiO2 / Fe2O3 is 2-4:

1.

4. The method for dehydrating coal slime based on synergistic conditioning of biomass and nanoparticles according to any one of claims 1 to 3, characterized in that: In step (1), the preparation method of nano-TiO2 / Fe2O3 comprises the following steps: adding ferric nitrate to a sodium hydroxide aqueous solution, then adding nano-TiO2 and Tween for mixing and grinding, filtering and drying, and calcining in air at 400-450°C for 1-2h to obtain nano-TiO2 / Fe2O3.

5. The method for dehydrating coal slime based on synergistic conditioning of biomass and nanoparticles according to claim 4, characterized in that: The ratio of the added amounts of ferric nitrate, sodium hydroxide aqueous solution, nano-TiO2 and Tween is 6-8g:50mL:9-12g:1-3mL; the mass concentration of the sodium hydroxide solution is 3-5%; and the particle size of the nano-TiO2 is 10-50nm.

6. The method for dehydrating coal slime based on synergistic conditioning of biomass and nanoparticles according to claim 1, characterized in that: In step (2), the mass ratio of the pretreated biomass to the nanoparticles is 5-7:1; and the added amount ratio of the nanoparticles to the ethanol aqueous solution is 1-5 g:50 mL.

7. The method for dehydrating coal slime based on synergistic conditioning of biomass and nanoparticles according to claim 1 or 6, characterized in that: In step (3), the mass ratio of dry basis coal slime to conditioning agent in the coal slime slurry is 4-8:1; and the amount of water added is such that the moisture content of the slurry is 60-70%.

8. The method for dehydrating coal slime based on synergistic conditioning of biomass and nanoparticles according to claim 1 or 6, characterized in that: In step (3), the frequency of the ultrasound is 10-20 kHz, and ultraviolet light with a power of 150-200 W is simultaneously applied for 20-45 minutes.

9. The method for dehydrating coal slime based on synergistic conditioning of biomass and nanoparticles according to claim 1, characterized in that: In step (4), the moisture content of the slurry after pre-concentration and dehydration is 40-55%.

10. The method for dehydrating coal slime based on synergistic conditioning of biomass and nanoparticles according to claim 1 or 9, characterized in that: In step (4), the pressure of high-pressure dehydration is 1-2 MPa; the moisture content of the first mud cake is 18-25%.