A slime dewatering method based on biomass and nanoparticle synergistic conditioning

Abstract

This invention relates to the technical field of coal slime treatment, and discloses a method for coal slime dewatering based on the synergistic conditioning of biomass and nanoparticles, comprising the following steps: (1) carbonizing biomass raw materials to obtain pretreated biomass; mixing nano-SiO2 and nano-TiO2 / Fe2O3 to obtain nanoparticles; (2) adding the pretreated biomass and nanoparticles to an ethanol aqueous solution and stirring to mix, then drying to obtain a conditioning agent; (3) adding the conditioning agent and water to the coal slime slurry, stirring to mix, and then subjecting it to ultrasonic treatment while simultaneously subjecting it to ultraviolet irradiation to obtain a pretreated coal slime slurry; (4) subjecting the pretreated coal slime slurry to pre-concentration dewatering and high-pressure dewatering in sequence to obtain a first slime cake. This invention combines biomass framework construction and nanoparticle surface modification in coal slime conditioning to achieve complementary advantages, accelerate water removal, and thus synergistically improve the dewatering effect.

Description

Technical Field

[0001] This invention relates to the technical field of coal slime treatment, and in particular to a coal slime dewatering method based on the synergistic conditioning of biomass and nanoparticles. Background Technology

[0002] Coal slime is a byproduct of coal washing and beneficiation. It is typically characterized by fine particle size, high water retention, high ash content, and high viscosity. Its dewatering process is particularly challenging when it contains a large amount of ultrafine particles (e.g., <0.045mm) and clay minerals. Traditional methods for dewatering coal slime mainly rely on chemical flocculants and mechanical pressure filtration.

[0003] Chemical flocculants include inorganic coagulants (such as polyaluminum chloride, ferric sulfate, etc.) and / or organic polymeric flocculants (mainly various types of polyacrylamide, PAM), sometimes supplemented with surfactants. These agents promote the aggregation of fine coal slime particles into larger flocs through charge neutralization, adsorption bridging, etc., thereby accelerating sedimentation and improving the filtration performance of subsequent mechanical dewatering. However, this method has the following significant drawbacks: First, chemical residues and pollution: large amounts of chemical agents used will remain in the filtrate (circulating water) and sludge cake, not only polluting the circulating water system and increasing water treatment costs, but also causing environmental pollution if discharged. Second, affecting product quality: the addition of inorganic agents (such as iron salts and aluminum salts) will increase the ash content of the final coal slime product and reduce its calorific value as fuel; organic agent residues may also have adverse effects on certain subsequent uses of coal slime (such as specific chemical applications). Third, high cost and insufficient applicability: chemical agents are expensive, and their effects are often sensitive to the properties of coal slime (such as pH, ionic strength, particle size distribution), requiring targeted selection and optimization of dosage. Therefore, for some particularly difficult-to-treat coal slime, relying solely on chemical flocculants may have limited effectiveness or be too costly.

[0004] Mechanical filtration focuses on improving dewatering efficiency by modifying equipment or processes. For example, high-pressure diaphragm filter presses, belt filter presses, and horizontal screw centrifuges are used to force dewatering by applying higher mechanical forces or utilizing centrifugal force. However, high-efficiency dewatering equipment typically involves large investments, high energy consumption, and complex maintenance. For ultrafine coal slime with high clay content, the resulting filter cake has extremely high compressibility and extremely poor permeability. Simply increasing mechanical pressure often yields limited improvement and can easily cause problems such as filter cloth clogging and wear. Alternatively, a multi-stage thickening process can be used, first increasing the coal slime concentration using a thickener or hydrocyclone; or in some cases, inert materials such as coarse particles (e.g., coarser coal particles, or even sand) can be added to the fine coal slime as a "skeleton" to increase the porosity and permeability of the filter cake and improve filtration performance. However, adding inert coarse particles will severely reduce the calorific value of the product, while adding coarse coal particles is limited by coal source and process conditions, and may not be effective in improving the stickiness problem caused by clay. The complexity of the process may also increase the difficulty and cost of operation.

[0005] In recent years, some studies have attempted to add pulverized biomass (such as crop straw, sawdust, rice husks, etc.) as a physical conditioner to coal slime. For example, patent CN116444126A discloses a coal slime dewatering method that blends biomass with coal slime. The principle is to utilize the fibrous structure of biomass to form a porous, relatively rigid skeleton in the coal slime, reducing the compressibility of the filter cake and providing channels for water removal. Furthermore, biomass itself is combustible, which can increase the calorific value of the final dewatered coal slime product. However, biomass also has a certain degree of water absorption, which may limit the dewatering effect to some extent, and achieving uniform mixing and effective bonding of biomass with ultrafine coal slime particles will also be a challenge. Summary of the Invention

[0006] To address the problems of low dewatering efficiency, high final moisture content, chemical pollution, high energy consumption, and low added value of the final product in existing technologies for processing high-viscosity, high-ash, and ultrafine coal slime, this invention provides a coal slime dewatering method based on the synergistic conditioning of biomass and nanoparticles. By combining biomass framework construction and nanoparticle surface modification in coal slime conditioning, complementary advantages are achieved. This method maintains the high porosity and low compressibility of the filter cake while anchoring nanoparticles to the coal slime surface, imparting a rough structure, reducing water binding, and accelerating water discharge, thereby synergistically improving the dewatering effect.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention provides a method for dewatering coal slime based on the synergistic conditioning of biomass and nanoparticles, comprising the following steps:

[0009] (1) Carbonize the biomass raw material to obtain pretreated biomass; mix nano-SiO2 and nano-TiO2 / Fe2O3 to obtain nanoparticles;

[0010] (2) The pretreated biomass and nanoparticles were added to an ethanol aqueous solution and stirred and mixed, and then dried to obtain a conditioning agent;

[0011] (3) Add conditioning agent and water to coal slurry, stir and mix, and then perform ultrasonic treatment and ultraviolet irradiation to obtain pretreated coal slurry.

[0012] (4) The pretreated coal slurry is subjected to pre-concentration and dewatering and high-pressure dewatering in sequence to obtain the first slurry cake.

[0013] Biomass feedstock can be mixed with coal slime as a skeletal structure to reduce the compressibility of the slime cake, thereby enhancing the dewatering effect of the coal slime. Nanoparticles can form micro-nano structures on the surface of coal slime particles, increasing the roughness of the slime, reducing resistance to water flow, and improving the dewatering effect. This invention pre-treats the biomass feedstock with low-temperature carbonization, retaining the cellulose / lignin skeleton while generating a microporous structure. Nanoparticles are then blended with the pre-treated biomass, and through adsorption or hydrogen bonding, nanoparticle aggregation is reduced. The nanoparticles fill the pores while enhancing mechanical strength, forming a biomass-nanoparticle composite skeleton. This composite skeleton, combined with the coal slime, maintains the high porosity and low compressibility of the filter cake, while also using biomass as a bridge to anchor the nanoparticles to the coal slime surface, directly imparting a rough structure, weakening water binding, and accelerating water drainage, thereby synergistically improving the dewatering effect.

[0014] Meanwhile, the nanoparticles include nano-SiO2 and nano-TiO2 / Fe2O3. Nano-SiO2 is rich in hydroxyl groups, which facilitates the formation of stable interfacial bonds with oxygen-containing functional groups (such as carboxylic acid groups and phenolic hydroxyl groups) in coal slime, inducing the nanoparticles to oriented and align on the coal slime surface, forming ordered or disordered micro-nano composite structures and improving roughness. Nano-TiO2 / Fe2O3 has photocatalytic activity. Nano-TiO2 mainly exhibits photocatalytic activity under ultraviolet light, while the added Fe2O3 can further extend its catalytic activity under visible light. Therefore, during the ultrasonic and ultraviolet treatment stages, not only can ultrasonic treatment destroy the clay agglomeration structure and promote the dispersion of the conditioner in the coal slime, but nano-TiO2 / Fe2O3 can also catalytically decompose colloidal organic matter in the coal slime under ultraviolet light, helping to destroy the clay agglomeration structure, reduce the binding of these sticky components to water, and thus improve the dehydration effect. Furthermore, after nano-TiO2 is loaded onto the Fe2O3 surface, the positively charged Fe2O3 surface can neutralize the negative charge of the coal slime particles, reducing electrostatic repulsion, promoting flocculation, forming larger flocs, and improving the settling properties of ultrafine coal slime particles. During the subsequent high-pressure dewatering process, mechanical extrusion, pressure, or hydraulic shear may cause some of the biomass-adsorbed nanoparticles to detach or dynamically release internal nanoparticles, which then migrate to the surface of the coal slime particles, forming a new rough surface structure. This improves the dewatering effect and yields a low-moisture cake.

[0015] 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; the carbonization is carried out in an inert atmosphere at 200-300°C for 1-2 hours.

[0016] Preferably, in step (1), the preparation method of the nano TiO2 / Fe2O3 includes the following steps: adding ferric nitrate to an aqueous sodium hydroxide solution, then adding nano TiO2 and Tween for mixing and grinding, filtering, drying, and calcining in air at 400-450℃ for 1-2 hours to obtain nano TiO2 / Fe2O3.

[0017] Preferably, the ratio of the added 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.

[0018] Preferably, in step (1), the particle size of the nano-SiO2 is 10-50 nm; the mass ratio of the nano-SiO2 to the nano-TiO2 / Fe2O3 is 2-4:1.

[0019] Preferably, in step (2), the mass ratio of the pretreated biomass to the nanoparticles is 5-7:1; the ratio of the amount of nanoparticles to the amount of ethanol aqueous solution added is 1-5g:50mL; the stirring speed is 50-100rpm and the time is 30-60min.

[0020] Preferably, in step (3), the solid content of the coal slurry is 30-40% (mass percentage), the ash content (dry basis) is 50-60%, and particle size analysis shows that the fine particle size (-0.045mm) content exceeds 60%.

[0021] High-viscosity, high-ash, and ultrafine coal slime presents the following problems during dewatering: high viscosity leads to poor fluidity, easily clogging pipes or forming localized accumulations, reducing dewatering efficiency; high ash content results in strong adsorption of water molecules, making water difficult to remove; ultrafine particles easily form low-porosity slime cakes, where water is locked in by capillary forces, resulting in poor permeability and low dewatering efficiency. Therefore, it exhibits characteristics of high viscosity, difficulty in settling, and difficulty in dewatering.

[0022] Preferably, in step (3), the mass ratio of dry coal slime to conditioner in the coal slurry is 4-8:1; the amount of water added is such that the water content of the slurry is 60-70%; the stirring speed is 50-100 rpm and the time is 10-30 min.

[0023] Preferably, in step (3), the frequency of the ultrasound is 10-20kHz, and ultraviolet light with a power of 150-200W is applied for 20-45 minutes.

[0024] Preferably, in step (4), the moisture content of the pre-concentrated and dehydrated slurry is 40-55%.

[0025] The moisture content of the slurry (60-70%) is reduced to a state that is easy to follow up with high-pressure dewatering (40-55%). The filtrate (overflow) discharged at this stage can be reused as circulating water.

[0026] Preferably, in step (4), the pressure of high-pressure dehydration is 1-2 MPa; the moisture content of the first cake is 18-25%.

[0027] Preferably, after the first mud cake is naturally air-dried or ventilated, its moisture content is further reduced to less than 10% to obtain a second mud cake. The second mud cake is then crushed and granulated to obtain coal slime fuel pellets.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) By combining biomass framework construction and nanoparticle surface modification in coal slime conditioning, complementary advantages can be achieved. This can maintain the high porosity and low compressibility of the filter cake, and use biomass as a bridge to anchor nanoparticles on the surface of coal slime, directly imparting a rough structure, weakening the binding of water, accelerating water discharge, and thus synergistically improving the dehydration effect.

[0030] (2) By combining ultrasonic treatment with ultraviolet photocatalytic treatment, the conditioner and coal slime particles are fully, uniformly and effectively combined. At the same time, nano-TiO2 / Fe2O3 is used to decompose colloidal organic matter in coal slime, which helps to destroy the clay agglomeration structure, reduce the binding of these sticky components to water, and further improve the dehydration efficiency.

[0031] (3) Before high-pressure deep dehydration, ultrasonic ultraviolet treatment and pre-concentration dehydration are combined to reduce viscosity and improve dehydration properties, thereby increasing dehydration efficiency.

[0032] (4) This method is particularly suitable for the dewatering of high viscosity, high ash content, and ultrafine coal slime. It can significantly reduce the moisture content of the slime cake through a combination of conditioning agent conditioning, ultrasonic ultraviolet treatment and high pressure deep dewatering mechanism.

[0033] (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, thus reducing the burden of circulating water treatment and environmental pollution. Detailed Implementation

[0034] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0035] A method for dewatering coal slime based on the synergistic conditioning of biomass and nanoparticles includes the following steps:

[0036] (1) Carbonize the biomass raw material at 200-300℃ under an inert atmosphere for 1-2 hours to obtain pretreated biomass; mix nano-SiO2 and nano-TiO2 / Fe2O3 at a mass ratio of 2-4:1 to obtain nanoparticles;

[0037] (2) Add the pretreated biomass and nanoparticles to an ethanol aqueous solution at a mass ratio of 5-7:1. The ratio of nanoparticles to ethanol aqueous solution is 1-5g:50mL, and the volume ratio of ethanol to water in the ethanol aqueous solution is 1:1. Stir and mix at a speed of 50-100rpm for 30-60min, and then dry to obtain the conditioner.

[0038] (3) Add a conditioner to the coal slurry, with a mass ratio of dry coal slurry to conditioner of 4-8:1; then add water (which can be the filtrate from the subsequent concentration and dewatering steps) to make the slurry water content 60-70%; stir and mix at a speed of 50-100 rpm for 10-30 min, then perform ultrasonic treatment at a frequency of 10-20 kHz, and simultaneously irradiate with ultraviolet light at a power of 150-200 W for 20-45 min to obtain the pretreated coal slurry;

[0039] (4) The pretreated coal slurry is pre-concentrated and dewatered, and the moisture content of the dewatered slurry is 40-55%; then it is dewatered under high pressure at 1-2 MPa to obtain the first mud cake with a moisture content of 18-25%.

[0040] (5) After the first mud cake is naturally sun-dried or ventilated and dried, the moisture content is further reduced to less than 10% to obtain the second mud cake; after the second mud cake is crushed and granulated, coal slime fuel particles are obtained.

[0041] In a specific embodiment of the present invention, 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.

[0042] In a specific embodiment of the present invention, in step (1), the particle size of nano-SiO2 is 10-50 nm.

[0043] In a specific embodiment of the present invention, step (1) of the preparation method of nano-TiO2 / Fe2O3 includes 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 20nm and Tween 60 and mixing and grinding for 30min. The ratio of the amount of ferric nitrate, sodium hydroxide aqueous solution, nano-TiO2 and Tween 60 added is 8g:50mL:11g:1.5mL. After filtration and drying, the temperature is raised to 400℃ in air at a rate of 5℃ / min, calcined for 2h, and then cooled to obtain nano-TiO2 / Fe2O3.

[0044] Example 1

[0045] The material being processed is flotation tailings slime from a coal preparation plant. Its characteristics are: solid content of approximately 35% (mass percentage), ash content (dry basis) as high as 55%, particle size analysis showing that fine particles (-0.045mm) content exceeds 60%, and it has high viscosity, is difficult to settle and dewater.

[0046] The above-mentioned coal slime is dewatered, including the following steps:

[0047] (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 at a mass ratio of 3:1 to obtain nanoparticles.

[0048] (2) The pretreated biomass and nanoparticles were added to an ethanol aqueous solution (ethanol and water volume ratio of 1:1) at a mass ratio of 6:1. The ratio of nanoparticles to ethanol aqueous solution was 4g:50mL. The mixture was stirred at 80rpm for 45min and then dried to obtain the conditioner.

[0049] (3) For each batch, 10 kg of dry coal slime is processed. 1.4 kg of conditioner is added to the coal slime slurry (the mass ratio of dry coal slime to conditioner in the coal slime slurry is 7.14:1). Water (which can be the filtrate from the subsequent dewatering step) is then added to make the moisture content of the slurry 60%. The mixture is stirred and mixed at a speed of 60 rpm for 30 min. Then, ultrasonic treatment is performed at a frequency of 20 kHz. At the same time, ultraviolet light with a power of 150 W is applied for 30 min to obtain the pretreated coal slime slurry.

[0050] (4) The pretreated coal slurry is pre-concentrated and dewatered. The slurry is initially dewatered by gravity in the gravity dewatering zone. The water content of the dewatered slurry is 40-55%. The discharged filtrate is collected in the collection tank and pumped to the circulating water tank for slurry conditioning in step (3). The slurry is then pumped to the feed inlet of the filter press and pressed at 1.0 MPa for 15 minutes. Then the pressure is increased to 1.6 MPa and pressed for another 30 minutes. After pressing, the pressure is released to obtain the first mud cake with a water content of 18-25%. The pressed filtrate discharged in this stage is also collected in the circulating water tank.

[0051] (5) After the first mud cake is naturally dried for 4 days, the moisture content is further reduced to less than 10% to obtain the second mud cake; the second mud cake is crushed and granulated to obtain coal slime fuel particles.

[0052] Example 2

[0053] The dewatering treatment of coal slime from the same source as in Example 1 includes the following steps:

[0054] (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 at a mass ratio of 3:1 to obtain nanoparticles.

[0055] (2) The pretreated biomass and nanoparticles were added to an ethanol aqueous solution (ethanol and water volume ratio of 1:1) at a mass ratio of 6:1. The ratio of nanoparticles to ethanol aqueous solution was 4g:50mL. The mixture was stirred at 80rpm for 45min and then dried to obtain the conditioner.

[0056] (3) For each batch of 10 kg dry coal slime, add 1.6 kg of conditioner to the coal slime slurry (the mass ratio of dry coal slime to conditioner in the coal slime slurry is 6.25:1), and then add water (which can be the filtrate from the subsequent dewatering step) to make the moisture content of the slurry 60%; stir and mix at a speed of 60 rpm for 30 min, and then perform ultrasonic treatment at a frequency of 20 kHz, while simultaneously irradiating with ultraviolet light at a power of 150 W for 30 min to obtain the pretreated coal slime slurry.

[0057] (4) The pretreated coal slurry is pre-concentrated and dewatered. The slurry is initially dewatered by gravity in the gravity dewatering zone. The water content of the dewatered slurry is 40-55%. The discharged filtrate is collected in the collection tank and pumped to the circulating water tank for slurry conditioning in step (3). The slurry is then pumped to the feed inlet of the filter press and pressed at 1.0 MPa for 15 minutes. Then the pressure is increased to 1.6 MPa and pressed for another 30 minutes. After pressing, the pressure is released to obtain the first mud cake with a water content of 18-25%. The pressed filtrate discharged in this stage is also collected in the circulating water tank.

[0058] (5) After the first mud cake is naturally dried for 4 days, the moisture content is further reduced to less than 10% to obtain the second mud cake; the second mud cake is crushed and granulated to obtain coal slime fuel particles.

[0059] Example 3

[0060] The dewatering treatment of coal slime from the same source as in Example 1 includes the following steps:

[0061] (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 at a mass ratio of 3:1 to obtain nanoparticles.

[0062] (2) The pretreated biomass and nanoparticles were added to an ethanol aqueous solution (ethanol and water volume ratio of 1:1) at a mass ratio of 6:1. The ratio of nanoparticles to ethanol aqueous solution was 4g:50mL. The mixture was stirred at 80rpm for 45min and then dried to obtain the conditioner.

[0063] (3) For each batch, 10 kg of dry coal slime is processed. 1.8 kg of conditioner is added to the coal slime slurry (the mass ratio of dry coal slime to conditioner in the coal slime slurry is 5.56:1). Water (which can be the filtrate from the subsequent dewatering step) is then added to make the moisture content of the slurry 60%. The mixture is stirred and mixed at a speed of 60 rpm for 30 min. Then, ultrasonic treatment is performed at a frequency of 20 kHz. At the same time, ultraviolet light with a power of 150 W is applied for 30 min to obtain the pretreated coal slime slurry.

[0064] (4) The pretreated coal slurry is pre-concentrated and dewatered. The slurry is initially dewatered by gravity in the gravity dewatering zone. The water content of the dewatered slurry is 40-55%. The discharged filtrate is collected in the collection tank and pumped to the circulating water tank for slurry conditioning in step (3). The slurry is then pumped to the feed inlet of the filter press and pressed at 1.0 MPa for 15 minutes. Then the pressure is increased to 1.6 MPa and pressed for another 30 minutes. After pressing, the pressure is released to obtain the first mud cake with a water content of 18-25%. The pressed filtrate discharged in this stage is also collected in the circulating water tank.

[0065] (5) After the first mud cake is naturally dried for 4 days, the moisture content is further reduced to less than 10% to obtain the second mud cake; the second mud cake is crushed and granulated to obtain coal slime fuel particles.

[0066] Example 4

[0067] The dewatering treatment of coal slime from the same source as in Example 1 includes the following steps:

[0068] (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 at a mass ratio of 2:1 to obtain nanoparticles.

[0069] (2) The pretreated biomass and nanoparticles were added to an ethanol aqueous solution (ethanol and water volume ratio of 1:1) at a mass ratio of 7:1. The ratio of nanoparticles to ethanol aqueous solution was 3g:50mL. The mixture was stirred at 80rpm for 45min and then dried to obtain the conditioner.

[0070] (3) For each batch, 10 kg of dry coal slime is processed. 1.4 kg of conditioner is added to the coal slime slurry (the mass ratio of dry coal slime to conditioner in the coal slime slurry is 7.14:1). Water (which can be the filtrate from the subsequent dewatering step) is then added to make the moisture content of the slurry 60%. The mixture is stirred and mixed at a speed of 60 rpm for 30 min. Then, ultrasonic treatment is performed at a frequency of 20 kHz. At the same time, ultraviolet light with a power of 200 W is applied for 35 min to obtain the pretreated coal slime slurry.

[0071] (4) The pretreated coal slurry is pre-concentrated and dewatered. The slurry is initially dewatered by gravity in the gravity dewatering zone. The water content of the dewatered slurry is 40-55%. The discharged filtrate is collected in the collection tank and pumped to the circulating water tank for slurry conditioning in step (3). The slurry is then pumped to the feed inlet of the filter press and pressed at 1.0 MPa for 15 minutes. Then the pressure is increased to 1.6 MPa and pressed for another 30 minutes. After pressing, the pressure is released to obtain the first mud cake with a water content of 18-25%. The pressed filtrate discharged in this stage is also collected in the circulating water tank.

[0072] (5) After the first mud cake is naturally dried for 4 days, the moisture content is further reduced to less than 10% to obtain the second mud cake; the second mud cake is crushed and granulated to obtain coal slime fuel particles.

[0073] Comparative Example 1

[0074] The difference from Example 1 is that the pretreatment parameters of the biomass raw material are different. Specifically, the biomass raw material (rice husk, particle size not greater than 0.3 mm) is carbonized at 400°C for 3 hours under an inert atmosphere to obtain pretreated biomass.

[0075] Comparative Example 2

[0076] The difference from Example 1 is that the conditioning agent is added separately.

[0077] The dewatering treatment of coal slime from the same source as in Example 1 includes the following steps:

[0078] (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 at a mass ratio of 3:1 to obtain nanoparticles.

[0079] (2) For each batch, 10 kg of dry coal slime is processed. 1.2 kg of pretreated biomass and 0.2 kg of nanoparticles are added to the coal slime slurry, and then water (which can be the filtrate from the subsequent dewatering step) is added to make the moisture content of the slurry 60%. The mixture is stirred and mixed at 60 rpm for 30 min, and then ultrasonic treatment is performed at a frequency of 20 kHz. At the same time, ultraviolet light with a power of 150 W is applied for 30 min to obtain the pretreated coal slime slurry.

[0080] (3) The pretreated coal slurry is pre-concentrated and dewatered. The slurry is initially dewatered by gravity in the gravity dewatering zone. The water content of the dewatered slurry is 40-55%. The discharged filtrate is collected in the collection tank and pumped to the circulating water tank for slurry conditioning in step (3). The slurry is then pumped to the feed inlet of the filter press and pressed at 1.0 MPa for 15 minutes. Then the pressure is increased to 1.6 MPa and pressed for another 30 minutes. After pressing, the pressure is released to obtain the first mud cake with a water content of 18-25%. The pressed filtrate discharged in this stage is also collected in the circulating water tank.

[0081] (4) After the first mud cake is naturally dried for 4 days, the moisture content is further reduced to less than 10% to obtain the second mud cake; the second mud cake is crushed and granulated to obtain coal slime fuel particles.

[0082] Comparative Example 3

[0083] The difference from Example 1 is that no nano-TiO2 / Fe2O3 was added, and no ultraviolet light treatment was performed.

[0084] The dewatering treatment of coal slime from the same source as in Example 1 includes the following steps:

[0085] (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.

[0086] (2) The pretreated biomass and nanoparticles were added to an ethanol aqueous solution (ethanol and water volume ratio of 1:1) at a mass ratio of 6:1. The ratio of nanoparticles to ethanol aqueous solution was 4g:50mL. The mixture was stirred at 80rpm for 45min and then dried to obtain the conditioner.

[0087] (3) Process 10 kg of dry coal slime per batch, add 1.4 kg of conditioner to the coal slime (the mass ratio of dry coal slime to conditioner in the coal slime is 7.14:1), and then add water (which can be the filtrate from the subsequent dewatering step) to make the moisture content of the slurry 60%; stir and mix at 60 rpm for 30 min, and then perform ultrasonic treatment at a frequency of 20 kHz for 30 min to obtain the pretreated coal slime.

[0088] (4) The pretreated coal slurry is pre-concentrated and dewatered. The slurry is initially dewatered by gravity in the gravity dewatering zone. The water content of the dewatered slurry is 40-55%. The discharged filtrate is collected in the collection tank and pumped to the circulating water tank for slurry conditioning in step (3). The slurry is then pumped to the feed inlet of the filter press and pressed at 1.0 MPa for 15 minutes. Then the pressure is increased to 1.6 MPa and pressed for another 30 minutes. After pressing, the pressure is released to obtain the first mud cake with a water content of 18-25%. The pressed filtrate discharged in this stage is also collected in the circulating water tank.

[0089] (5) After the first mud cake is naturally dried for 4 days, the moisture content is further reduced to less than 10% to obtain the second mud cake; the second mud cake is crushed and granulated to obtain coal slime fuel particles.

[0090] Comparative Example 4

[0091] The difference from Example 1 is that nano-TiO2 / Fe2O3 is replaced with nano-TiO2.

[0092] The dewatering treatment of coal slime from the same source as in Example 1 includes the following steps:

[0093] (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 at a mass ratio of 3:1 to obtain nanoparticles.

[0094] (2) The pretreated biomass and nanoparticles were added to an ethanol aqueous solution (ethanol and water volume ratio of 1:1) at a mass ratio of 6:1. The ratio of nanoparticles to ethanol aqueous solution was 4g:50mL. The mixture was stirred at 80rpm for 45min and then dried to obtain the conditioner.

[0095] (3) For each batch, 10 kg of dry coal slime is processed. 1.4 kg of conditioner is added to the coal slime slurry (the mass ratio of dry coal slime to conditioner in the coal slime slurry is 7.14:1). Water (which can be the filtrate from the subsequent dewatering step) is then added to make the moisture content of the slurry 60%. The mixture is stirred and mixed at a speed of 60 rpm for 30 min. Then, ultrasonic treatment is performed at a frequency of 20 kHz. At the same time, ultraviolet light with a power of 150 W is applied for 30 min to obtain the pretreated coal slime slurry.

[0096] (4) The pretreated coal slurry is pre-concentrated and dewatered. The slurry is initially dewatered by gravity in the gravity dewatering zone. The water content of the dewatered slurry is 40-55%. The discharged filtrate is collected in the collection tank and pumped to the circulating water tank for slurry conditioning in step (3). The slurry is then pumped to the feed inlet of the filter press and pressed at 1.0 MPa for 15 minutes. Then the pressure is increased to 1.6 MPa and pressed for another 30 minutes. After pressing, the pressure is released to obtain the first mud cake with a water content of 18-25%. The pressed filtrate discharged in this stage is also collected in the circulating water tank.

[0097] (5) After the first mud cake is naturally dried for 4 days, the moisture content is further reduced to less than 10% to obtain the second mud cake; the second mud cake is crushed and granulated to obtain coal slime fuel particles.

[0098] Table 1

[0099] Moisture content of the slurry after pre-concentration and dewatering Moisture content of the first mud cake 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％

[0100] As shown in Table 1, by adding a conditioning agent to the coal slime, the present invention can significantly improve the dehydration effect of the high-pressure dehydration stage, and obtain a first mud cake with a low moisture content. After natural sun drying or ventilation drying, a second mud cake with an even lower moisture content can be obtained. The crushed granular product can be directly used for boiler combustion or other resource utilization.

[0101] However, in Comparative Example 1, the biomass raw material underwent significant carbonization. Although the nanoparticles filling the pores enhanced mechanical strength, they also easily led to the collapse of the skeletal structure, especially during the high-pressure dewatering stage. This resulted in the inability to maintain the low compressibility of the filter cake, significantly impacting the dewatering effect. In Comparative Example 2, pretreated biomass and nanoparticles were added separately. Since the mechanical properties of the pretreated biomass were affected, and the nanoparticles, while filling the pores, enhanced mechanical strength, the biomass skeletal structure was also affected during high-pressure dewatering, resulting in a higher moisture content in the resulting filter cake. Comparative Example 3, lacking the addition of nano-TiO2 / Fe2O3 and relying solely on the synergistic conditioning of nano-SiO2 and biomass, was not well-suited for high-viscosity, high-ash coal slime, thus reducing dewatering efficiency. Comparative Example 4, due to the addition of only nano-TiO2, can catalyze the decomposition of colloidal organic matter in coal slime during the ultrasonic ultraviolet treatment stage, which helps to break the clay agglomeration structure. However, since it is not combined with Fe2O3, the treatment effect on ultrafine coal slime particles will be poor, which will also affect the moisture content.

[0102] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for dewatering coal slurry based on synergistic conditioning of biomass and nanoparticles, characterized by, Includes the following steps: (1) Carbonize the biomass raw material to obtain pretreated biomass; mix nano-SiO2, nano-TiO2 and Fe2O3 to obtain nanoparticles; (2) The pretreated biomass and nanoparticles were added to an ethanol aqueous solution and stirred and mixed, and then dried to obtain a conditioning agent; (3) Add conditioning agent and water to coal slurry, stir and mix, and then perform ultrasonic treatment and ultraviolet irradiation to obtain pretreated coal slurry. (4) The pretreated coal slurry is subjected to pre-concentration and dewatering and high-pressure dewatering in sequence to obtain the first slurry cake.

2. The method for dewatering 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, with a particle size of no more than 0.3 mm; the carbonization is carried out in an inert atmosphere at 200-300℃ for 1-2 hours.

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

1.

4. The method according to any one of claims 1-3, wherein the biomass and nanoparticles are synergistically conditioned. In step (1), the preparation method of nano TiO2 and Fe2O3 includes the following steps: adding ferric nitrate to sodium hydroxide aqueous solution, then adding nano TiO2 and Tween for mixing and grinding, filtering and drying, and calcining in air at 400-450℃ for 1-2 hours to obtain nano TiO2 and Fe2O3.

5. The method for dewatering coal slime based on synergistic conditioning of biomass and nanoparticles according to claim 4, characterized in that, The ratio of the amounts of ferric nitrate, sodium hydroxide aqueous solution, nano-TiO2, and Tween added 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 dewatering coal slime based on synergistic conditioning of biomass and nanoparticles as claimed in claim 1, wherein, In step (2), the mass ratio of the pretreated biomass to the nanoparticles is 5-7:1; the ratio of the amount of nanoparticles to the amount of ethanol aqueous solution added is 1-5 g:50 mL.

7. The method according to claim 1 or 6, wherein the method is characterized by, In step (3), the mass ratio of dry coal slime to conditioner in the coal slurry is 4-8:1; the amount of water added is such that the water content of the slurry is 60-70%.

8. The method for dewatering 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 at the same time, ultraviolet light with a power of 150-200W is applied for 20-45 minutes.

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

10. The method according to claim 1 or 9, wherein the biomass and nanoparticles are synergistically conditioned. In step (4), the pressure of high-pressure dehydration is 1-2 MPa; the moisture content of the first cake is 18-25%.