Method for preparing high-strength ceramsite through reverse flotation decarburization and desulfurization of coal gangue

Abstract

The invention discloses a method for preparing high-strength ceramsite through reverse flotation decarburization and desulfurization of coal gangue, which comprises the following steps: (1) crushing and finely grinding the coal gangue to obtain finely ground coal gangue; (2) mixing the finely ground coal gangue with water to obtain coal gangue ore pulp; (3) adding an inhibitor, a collecting agent and a foaming agent into the coal gangue ore pulp, carrying out reverse flotation decarburization and / or desulfurization on the coal gangue, and carrying out suction filtration and drying on precipitates in a flotation tank to obtain a decarburized and / or desulfurized coal gangue filter cake; (4) crushing and finely grinding the decarbonized and / or desulfurized coal gangue filter cake, pelletizing after fine grinding, pelletizing while adding water to obtain a ceramsite green body, and screening the green body to obtain a green body with qualified granularity for subsequent ceramsite firing; (5) paving backing materials and rim charges on a trolley, and carrying out material distribution, drying, preheating, roasting and cooling treatment on the green bodies with qualified particle sizes to obtain roasted pellets; and (6) screening the roasted pellets obtained in the step (5) to obtain roasted pellets with qualified granularity, namely the high-strength ceramsite.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive utilization of solid waste, and particularly relates to a method for preparing high-strength ceramsite by reverse flotation of coal gangue for decarbonization and desulfurization. Background Art

[0002] Coal gangue is a solid waste generated during coal mining and washing processes. As the largest coal-consuming and coal-producing country in the world, China produces 0.15 - 0.20 tons of coal gangue for every ton of coal produced. Coal gangue is currently the solid waste with the largest emissions and stockpiles in China. Among them, coal gangue with high carbon content and high sulfur content is extremely prone to spontaneous combustion under the condition of open stacking without treatment and long-term heat storage. There are 1500 - 1700 coal gangue mountains formed by the existing coal gangue stacks in China, more than 300 of which are in a state of long-term spontaneous combustion, not only occupying a large amount of land resources, but also containing heavy metals such as Hg, Pb, Cd, As and weathering decomposition of Cl + , NCO 3+ , K + and other toxic and harmful substances cause serious pollution to soil, surface water and groundwater; each square meter of the burning area of the perennial spontaneous combustion coal gangue mountain will emit 10.8 g of CO, about 2 g of H2S and NO X , about 6.5 g of SO2, and polycyclic aromatic hydrocarbon organic pollutants such as benzo[a]pyrene and benzo[b]fluoranthene, and particulate matter, causing air pollution.

[0003] When the carbon content of coal gangue is greater than 20% and the calorific value is between 4181 - 6272 kJ / kg, the coal gangue is blended with coal slime, medium coal, etc. for boiler power generation. The coal gangue with a calorific value greater than 6272 kJ / kg can be directly used as boiler fuel; while the coal gangue with a carbon content lower than 4% and a calorific value lower than 2090 kJ / kg is suitable for the building materials field. The main chemical components of coal gangue are SiO2 and Al2O3, which are similar to the chemical composition of clay. Therefore, coal gangue can replace clay to prepare ceramsite, enabling its resource utilization. High-strength lightweight ceramsite is an ideal material for preparing precast components such as partition boards and blocks due to its advantages of light weight and high strength. In recent years, the prefabricated building industry has developed vigorously, and high-strength ceramsite has a huge market. When preparing ceramsite, the carbon content and sulfur content of coal gangue should be lower than 4% and 1% respectively. This is because appropriate amounts of carbon and sulfur in coal gangue can act as pore-forming agents during the ceramsite roasting process; however, if the carbon and sulfur contents are too high, on the one hand, it is easy to cause the pores of the ceramsite to be too developed, thereby reducing its strength, and on the other hand, a large amount of CO2, CO, and SO2 are emitted during the ceramsite firing process, which will lead to an increase in flue gas treatment costs and is likely to cause corrosion to the equipment and affect its service life. But for high-carbon low-sulfur coal gangue (carbon content 4% - 20%, according to the above, coal gangue with a carbon content higher than 20% can be used for power generation, sulfur content lower than 1%), high-carbon high-sulfur coal gangue (carbon content higher than 4%, sulfur content higher than 1%), and low-carbon high-sulfur coal gangue (carbon content lower than 4%, sulfur content higher than 1%), they cannot be directly used for power generation in thermal power plants, nor can they be directly used for preparing building materials. How to resourcefully utilize these types of coal gangue has become an urgent problem to be solved.

[0004] Chinese Patent CN116238075A discloses a method and system for desulfurizing high-sulfur coal gangue based on the Fenton-like oxidation method. Using hydrogen peroxide solution as a cleaning agent, the sulfur in the coal gangue powder is oxidized and dissolved and transferred to the liquid phase for removal by the multi-stage countercurrent cleaning method. Chinese Patent CN113896444B discloses a decarbonized coal gangue powder, its preparation method, and its application as a concrete admixture. The flotation method is used to remove the combustible carbon components in the coal gangue powder. None of the above patents can achieve simultaneous decarbonization and desulfurization and are not suitable for high-carbon high-sulfur coal gangue.

[0005] Chinese Patent CN113526883B discloses a fuel-free self-heating ultra-high bed decarbonization process for coal gangue. Utilizing the automatic heat storage principle of the ultra-high bed and combining with the fixed carbon contained in the coal gangue, effective decarbonization and activation of coal gangue with a fixed carbon content of 2% - 5% can be achieved without adding external fuel.

[0006] Chinese Patent CN117776671B discloses a controllable heat flow decarbonization and desulfurization process for coal gangue modification. In the present invention, through the crushing and sorting of materials and the layered feeding, decarbonization and desulfurization of coal gangue are carried out. It can be seen that thermal decarbonization can achieve simultaneous decarbonization and desulfurization of coal gangue. However, coal gangue with high carbon and sulfur contents will generate a large amount of CO2, CO, SO2 and other harmful gases at high temperatures, which undoubtedly increases the flue gas treatment cost and will corrode the equipment, affecting the equipment life. Moreover, the phase composition of coal gangue changes after high-temperature treatment, beneficial minerals are decomposed, and at the same time, high-melting-point minerals are generated, which is not conducive to the preparation of high-strength ceramsite. Therefore, thermal decarbonization and desulfurization are not applicable to high-carbon low-sulfur, high-carbon high-sulfur, and low-carbon high-sulfur coal gangue. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue, aiming to efficiently decarbonize and / or desulfurize high-carbon low-sulfur, high-carbon high-sulfur, and low-carbon high-sulfur coal gangue, realizing the large-scale consumption and high-value utilization of coal gangue. After the coal gangue is pretreated by decarbonization and / or desulfurization through the method of the present invention, most of the carbon and / or sulfur are removed. A small amount of carbon and sulfur in the coal gangue can act as pore-forming agents, and the beneficial mineral kaolinite is also retained, which can replace clay as the raw material for building materials such as ceramsite.

[0008] To achieve the above technical objectives, the technical solution of the present invention is as follows:

[0009] The present invention provides a method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue, comprising the following steps:

[0010] (1) Crushing and finely grinding the coal gangue to obtain finely ground coal gangue;

[0011] (2) Mixing the finely ground coal gangue obtained in step (1) with water to obtain a coal gangue slurry;

[0012] (3) Adding an inhibitor, a collector, and a foaming agent to the coal gangue slurry obtained in step (2) to carry out reverse flotation decarbonization and / or desulfurization of the coal gangue, filtering and drying the precipitate in the flotation cell to obtain a decarbonized and / or desulfurized coal gangue filter cake;

[0013] (4) Crushing and finely grinding the decarbonized and / or desulfurized coal gangue filter cake obtained in step (3), and carrying out pelletizing while adding water, to obtain ceramsite green pellets. Screening the green pellets to select the green pellets with qualified particle size for subsequent ceramsite firing;

[0014] (5) Laying a bottom material and side materials on a trolley, and carrying out feeding, drying, preheating, roasting, and cooling treatments on the green pellets with qualified particle size obtained in step (4) to obtain roasted pellets;

[0015] (6) Screening the calcined pellets obtained in step (5) to select calcined pellets with a qualified particle size, namely the high-strength ceramsite.

[0016] Preferably, in step (1), the coal gangue is one or more of high-carbon and low-sulfur coal gangue, high-carbon and high-sulfur coal gangue, and low-carbon and high-sulfur coal gangue.

[0017] More preferably, the high-carbon, low-sulfur coal gangue has a carbon content of 4wt% to 20wt% and a sulfur content of less than 1wt%; the high-carbon, high-sulfur coal gangue has a carbon content of more than 4wt% and a sulfur content of more than 1wt%; the low-carbon, high-sulfur coal gangue has a carbon content of less than 4wt% and a sulfur content of more than 1wt%.

[0018] Preferably, in step (1), the crushing is carried out by one or more of a jaw crusher, a roll crusher, a cone crusher, an impact crusher, an impact crusher, and a hammer crusher;

[0019] Fine grinding includes wet ball milling with water, high pressure roller milling under natural water content, and dry ball milling after drying. After crushing and fine grinding, the particle size of the gangue is less than 0.5 mm. Appropriate fine grinding of the gangue can fully dissociate the mineral monomers, thereby promoting the removal of carbon and / or sulfur. If the ore particles are too coarse, it is not conducive to the dissociation of the mineral monomers. Even if the minerals have been dissociated, they may not float because they exceed the buoyancy capacity of the bubbles. If the particles are too fine, the reverse flotation speed is fast and the selectivity is poor, which is also not conducive to reverse flotation and will increase the energy consumption of fine grinding in the early stage.

[0020] Preferably, in step (2), the concentration of the gangue slurry is 70 to 200 g / L.

[0021] Preferably, in step (3), adding an inhibitor can effectively inhibit the floating of clay minerals, and the inhibitor is one of sodium silicate, sodium carbonate, sodium hexametaphosphate, and carboxymethyl cellulose, and the amount used is 500-1500 g / t. These inhibitors can be adsorbed on the surface of clay minerals by chemical adsorption or physical adsorption, and can enhance the electrostatic repulsion between the clay minerals and the surface of carbon particles, thereby inhibiting the clay minerals from covering the surface of coal particles.

[0022] Preferably, in step (3), diesel or kerosene is used as a carbon collector in an amount of 50-700 g / t; xanthate or butyl xanthate is used as a sulfur collector in an amount of 50-600 g / t. When the raw material is high-carbon and low-sulfur coal gangue, only decarbonization is required, and only carbon collectors are used; when the raw material is high-carbon and high-sulfur coal gangue, decarbonization and desulfurization are required at the same time, and carbon and sulfur collectors are used at the same time; when the raw material is low-carbon and high-sulfur coal gangue, only desulfurization is required, so only sulfur collectors are needed.

[0023] Preferably, in step (3), the foaming agent is No. 2 oil (also known as pine oil alcohol), and the dosage is 10 - 100 g / t. The actual dosages of the inhibitor, collector, and foaming agent are determined by the concentration of the coal gangue slurry and the carbon and sulfur contents in the coal gangue.

[0024] Preferably, in step (3), after decarbonization of high-carbon and low-sulfur coal gangue, after decarbonization and desulfurization of high-carbon and high-sulfur coal gangue, and after desulfurization of low-carbon and high-sulfur coal gangue, the carbon content of the coal gangue is lower than 4 wt%, and the sulfur content is lower than 1 wt%.

[0025] Preferably, in step (4), the decarbonized and / or desulfurized coal gangue filter cake is crushed and finely ground, and the specific operation is the same as that in step (1) to obtain decarbonized and / or desulfurized coal gangue powder with a particle size of less than 0.074 mm accounting for more than 50%.

[0026] Preferably, in step (4), pelletizing is carried out using a disk pelletizer or a drum pelletizer. The pelletizing time is 6 - 12 min, the green pellet moisture content is 9 - 15%, and the obtained green pellets have a drop strength of more than 4 times / 0.5 m, a compressive strength of more than 10 N / piece, and a green pellet bursting temperature higher than 200 °C.

[0027] Preferably, in step (4), green pellets with a particle size of 5 - 16 mm are screened out.

[0028] Preferably, in step (5), the ceramsite firing equipment can be any one of a traveling grate, a chain grate based on horizontal movement of a moving bed, a static sintering tunnel kiln, a roller hearth kiln, and a rotary kiln.

[0029] The thickness of the bottom layer and side layer materials is 0 - 50 mm, and the height of the green pellet feeding is 50 - 500 mm. The green pellets are dried using waste heat, the drying temperature is 100 - 300 °C, the drying time is 5 - 20 min, and the drying regime is mainly affected by the green pellet bursting temperature. The drying temperature cannot exceed the green pellet bursting temperature. If the temperature of the green pellets is relatively high, the drying temperature can be appropriately increased and the drying time can be shortened; if the temperature of the green pellets is relatively low, the drying temperature needs to be reduced and the drying time needs to be extended. The preheating temperature is 400 - 700 °C, and the preheating time is 4 - 10 min. The role of the preheating stage is to release a part of the gas to avoid cracking of the billet due to drastic temperature changes after entering the high-temperature zone. However, when the loss on ignition of the coal gangue after decarbonization and desulfurization is less than 10%, the preheating section can be omitted. The roasting temperature is 1050 - 1250 °C, and the roasting time is 10 - 35 min. In the roasting stage, the billet can be quickly heated to the roasting temperature as long as it does not crack, because by quickly heating to the target temperature, a suitable liquid phase can be formed on the surface of the billet to wrap the gas, thereby causing the billet to expand and form a relatively high strength.

[0030] Preferably, in step (6), roasted pellets with a particle size of 5 - 16 mm are screened out.

[0031] Preferably, in step (6), its performance is detected in accordance with GB / T 17431.1-2010 and GB / T 17431.2-2010.

[0032] More preferably, in step (6), the density grades of the high-strength ceramsite are 600 grade, 700 grade, 800 grade, and 900 grade. When the bulk density > 500 kg / m 3 and ≤ 600 kg / m 3 , the water absorption rate ≤ 10%, and the cylinder compressive strength ≥ 2.0 MPa. At this time, it is 600-grade ordinary ceramsite, and the cylinder compressive strength ≥ 4.0 MPa. At this time, it is 600-grade high-strength ceramsite; when the bulk density > 600 kg / m 3 and ≤ 700 kg / m 3 , the water absorption rate ≤ 10%, and the cylinder compressive strength ≥ 3.0 MPa. At this time, it is 700-grade ordinary ceramsite, and the cylinder compressive strength ≥ 5.0 MPa. At this time, it is 700-grade high-strength ceramsite; when the bulk density > 700 kg / m 3 and ≤ 800 kg / m 3 , the water absorption rate ≤ 10%, and the cylinder compressive strength ≥ 4.0 MPa. At this time, it is 800-grade ordinary ceramsite, and the cylinder compressive strength ≥ 6.0 MPa. At this time, it is 800-grade high-strength ceramsite; when the bulk density > 800 kg / m 3 and ≤ 900 kg / m 3 , the water absorption rate ≤ 10%, and the cylinder compressive strength ≥ 5.0 MPa. At this time, it is 900-grade ordinary ceramsite, and the cylinder compressive strength ≥ 6.5 MPa. At this time, it is 900-grade high-strength ceramsite.

[0033] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0034] 1. The present invention adopts reverse flotation to efficiently decarbonize high-carbon and low-sulfur coal gangue (carbon content 4% - 20%, sulfur content less than 1%), can simultaneously and efficiently decarbonize and desulfurize high-carbon and high-sulfur coal gangue (carbon content higher than 4%, sulfur content higher than 1%), and can efficiently desulfurize low-carbon and high-sulfur coal gangue (carbon content less than 4%, sulfur content higher than 1%). Compared with thermal decarbonization and desulfurization, reverse flotation decarbonization and desulfurization do not produce a large amount of CO2, CO, SO2, and other harmful gases, and will not corrode the equipment and affect the equipment life.

[0035] 2. High-carbon low-sulfur / high-carbon high-sulfur / low-carbon high-sulfur coal gangue, due to its relatively high carbon and sulfur content, if directly used for preparing ceramsite, on the one hand, the excessive development of pores in the ceramsite will be caused by a large loss on ignition, resulting in too low strength of the ceramsite; on the other hand, during the firing process of the ceramsite, a large amount of CO2, CO, SO2 and other harmful gases will be released, increasing the cost of flue gas treatment. The present invention uses reverse flotation to decarbonize and desulfurize the coal gangue and then prepares ceramsite, which can not only successfully prepare high-strength ceramsite, but also greatly reduce the pressure of flue gas treatment during the firing process of the ceramsite.

[0036] 3. The present invention realizes the resource utilization of difficult-to-treat coal gangue such as high-carbon low-sulfur / high-carbon high-sulfur / low-carbon high-sulfur coal gangue. After efficiently decarbonizing and desulfurizing the coal gangue, high-strength ceramsite meeting the GBT17431.1-2010 standard can be prepared, broadening the source channels of raw materials for high-strength ceramsite. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the embodiments. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0038] Figure 1 It is the process flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0040] The following will further elaborate on the present application in detail with reference to the drawings and specific embodiments:

[0041] Example 1

[0042] Taking the coal gangue in Ningxia area as the raw material, its carbon content and sulfur content are 17.52% and 0.84% respectively. The coal gangue is crushed by a jaw crusher and further finely ground to -0.15 mm under natural moisture by a high-pressure roller mill. The finely ground coal gangue is mixed with water to obtain a coal gangue pulp with a pulp concentration of 130 g / L, and then added into a flotation machine. 1100 g / t of sodium silicate, 650 g / t of diesel oil and 35 g / t of No. 2 oil are added in sequence to decarbonize the coal gangue.

[0043] The decarbonized coal gangue slurry is subjected to suction filtration and drying. The filter cake is crushed using a jaw crusher and further ball milled using a dry ball mill to obtain decarbonized coal gangue powder with a particle size of -0.074 mm accounting for 60%. The carbon and sulfur contents of the decarbonized coal gangue powder are 3.41% and 0.56% respectively.

[0044] 4% water is pre-added to the decarbonized coal gangue powder and mixed evenly. Pellets are made using a disc pelletizer, with the green pellet moisture content being 13% and the pelletizing time being 8 min. A high-strength ceramsite is fired using a traveling grate machine, with the height of the bottom layer material being 20 mm and the height of the green pellet layer being 150 mm. The temperature of the first-stage suction drying is 150 °C and the drying time is 8 min; the temperature of the second-stage suction drying is 200 °C and the drying time is 8 min; then oxidation roasting is carried out, with the roasting temperature being 1175 °C and the roasting time being 20 min. After roasting, cold air is introduced for suction cooling, and the material is unloaded after cooling to 400 °C and naturally cooled to room temperature. The roasted pellets are screened to select roasted pellets with a particle size of 5 - 16 mm, which are the high-strength ceramsite.

[0045] The product performance is tested in accordance with GBT17431-2010. The bulk density of the ceramsite is 876 kg / m 3 , the water absorption rate in 1 h is 8.48%, and the apparent density is 1656 kg / m 3 , and the cylinder compressive strength is 7.79 MPa. The performance of the prepared ceramsite meets the performance requirements of high-strength ceramsite with a density grade of 900.

[0046] Example 2

[0047] Using coal gangue from the Shaanxi region as raw material, with its carbon content and sulfur content being 13.06% and 4.15% respectively. First, the coal gangue is dried, then crushed using a cone crusher, and further finely ground to -0.12 mm using a dry ball mill. The finely ground coal gangue is mixed with water to obtain a coal gangue slurry with a pulp concentration of 150 g / L and added to a flotation machine. Sodium carbonate 1000 g / t, butyl xanthate 450 g / L, kerosene 640 g / t, and No. 2 oil 25 g / t are added in sequence to carry out decarbonization and desulfurization of the coal gangue.

[0048] The decarbonized and desulfurized coal gangue slurry is subjected to suction filtration and drying. The filter cake is crushed using a pair-roll crusher and further ball milled using a dry ball mill to obtain decarbonized and desulfurized coal gangue powder with a particle size of -0.074 mm accounting for 70%. The carbon and sulfur contents of the decarbonized and desulfurized coal gangue powder are 3.15% and 0.79% respectively.

[0049] Pre-add 4% water to the decarbonized and desulfurized coal gangue powder and mix evenly. Use a cylindrical pelletizer to make pellets, with the green pellet moisture content being 13% and the pelletizing time being 6 min. Use a roller hearth kiln to fire high-strength ceramsite, with the height of the green pellet layer being 50 mm. The temperature of the first-stage suction drying is 120 °C and the drying time is 8 min; the temperature of the second-stage suction drying is 180 °C and the drying time is 10 min; then carry out oxidation roasting, with the roasting temperature being 1125 °C and the roasting time being 25 min. After roasting, unload the material and cool it naturally to room temperature. Screen the roasted pellets to select the roasted pellets with a particle size of 5 - 16 mm, which are the high-strength ceramsite.

[0050] Inspect the product performance according to GBT17431 - 2010. The bulk density of this ceramsite is 886 kg / m 3 , the water absorption rate in 1 h is 8.80%, and the apparent density is 1680 kg / m 3 , and the cylinder compressive strength is 7.54 MPa. The performance of the prepared ceramsite meets the performance requirements of high-strength ceramsite with a density grade of 900.

[0051] Example 3

[0052] Use the coal gangue in the Shanxi region as the raw material, with its carbon content and sulfur content being 1.81% and 6.08% respectively. Use a jaw crusher and a pair-roll crusher to crush the coal gangue, and further finely grind the coal gangue to -0.12 mm under natural moisture using a high-pressure roller mill. Mix the finely ground coal gangue with water to obtain a coal gangue slurry with a pulp concentration of 150 g / L, and add it to a flotation machine. Add carboxymethyl cellulose 1100 g / t, xanthate 550 g / L, and No. 2 oil 30 g / t in sequence to desulfurize the coal gangue.

[0053] Filter and dry the desulfurized coal gangue slurry by suction, use a cone crusher to crush the filter cake, and carry out high-pressure roller milling to obtain desulfurized coal gangue powder with a particle size of -0.074 mm accounting for 60%. The carbon and sulfur contents of the desulfurized coal gangue powder are 2.15% and 0.91% respectively.

[0054] Pre-add 4% water to the desulfurized coal gangue powder and mix evenly. Use a disc pelletizer to make pellets, with the green pellet moisture content being 12% and the pelletizing time being 10 min. Use a static sintering tunnel kiln to fire high-strength ceramsite, with the height of the green pellet layer being 200 mm. The temperature of the first-stage suction drying is 150 °C and the drying time is 5 min; the temperature of the second-stage suction drying is 200 °C and the drying time is 8 min; then preheat at 500 °C for 5 min; then carry out oxidation roasting, with the roasting temperature being 1150 °C and the roasting time being 25 min. After roasting, unload the material and cool it naturally to room temperature. Screen the roasted pellets to select the roasted pellets with a particle size of 5 - 16 mm, which are the high-strength ceramsite.

[0055] The product performance is inspected according to GBT17431-2010. The bulk density of the ceramsite is 839 kg / m 3 , the 1-hour water absorption rate is 8.24%, and the apparent density is 1616 kg / m 3 , and the cylinder compressive strength is 7.49 MPa. The performance of the prepared ceramsite meets the performance requirements of high-strength ceramsite with a density grade of 900.

[0056] Comparative Example 1

[0057] Taking coal gangue in Ningxia region as raw material, its carbon content and sulfur content are 17.52% and 0.84% respectively. The coal gangue is crushed by a jaw crusher and further finely ground by a high-pressure roller mill under natural moisture until the proportion of particles with a size of -0.074 mm accounts for 60%.

[0058] Add 4% water to the coal gangue powder in advance and mix evenly. Pellets are made by a disk pelletizer with a green pellet moisture of 13% and a pelletizing time of 8 min. High-strength ceramsite is fired by a traveling grate machine, with the height of the bottom layer of the bedding being 20 mm and the height of the green pellet layer being 150 mm. The first-stage suction drying temperature is 150 °C and the drying time is 8 min; the second-stage suction drying temperature is 200 °C and the drying time is 8 min; then oxidation roasting is carried out at a roasting temperature of 1175 °C and a roasting time of 20 min. After roasting, cold air is introduced for suction cooling, and the material is unloaded after cooling to 400 °C and naturally cooled to room temperature.

[0059] The product performance is inspected according to GBT17431-2010. The bulk density of the ceramsite is 673 kg / m 3 , the 1-hour water absorption rate is 15.05%, and the apparent density is 1382 kg / m 3 , and the cylinder compressive strength is 1.51 MPa. The performance of the prepared ceramsite does not meet the performance requirements of ordinary ceramsite and high-strength ceramsite with a density grade of 700.

[0060] Comparative Example 2

[0061] Taking coal gangue in Shaanxi region as raw material, its carbon content and sulfur content are 13.06% and 4.15% respectively. First, the coal gangue is dried, then crushed by a cone crusher, and further finely ground by a dry ball mill to obtain coal gangue powder with the proportion of particles with a size of -0.074 mm accounting for 70%.

[0062] Pre-add 4% water to the coal gangue powder and mix evenly. Use a cylindrical pelletizing machine to pelletize, with the green pellet moisture content of 13% and the pelletizing time of 8 min. Use a roller hearth kiln to fire high-strength ceramsite, with the green pellet layer height of 50 mm. The first-stage suction drying temperature is 120 °C and the drying time is 8 min; the second-stage suction drying temperature is 180 °C and the drying time is 10 min; then carry out oxidation roasting, with the roasting temperature of 1125 °C and the roasting time of 25 min. After roasting, unload the material and naturally cool it to room temperature.

[0063] Inspect the product performance according to GBT17431-2010. The bulk density of this ceramsite is 679 kg / m 3 , the 1-hour water absorption rate is 13.50%, and the apparent density is 1388 kg / m 3 , and the cylinder compressive strength is 1.21 MPa. The performance of the prepared ceramsite does not meet the performance requirements of ordinary ceramsite and high-strength ceramsite with a density grade of 700.

[0064] Comparative Example 3

[0065] Use the coal gangue in Shanxi area as the raw material, with its carbon content and sulfur content being 1.81% and 6.08% respectively. Use a jaw crusher to crush the coal gangue, and further finely grind the coal gangue under natural moisture with a high-pressure roller mill to obtain coal gangue powder with a proportion of -0.074 of 60%.

[0066] Pre-add 4% water to the coal gangue powder and mix evenly. Use a disk pelletizing machine to pelletize, with the green pellet moisture content of 12% and the pelletizing time of 8 min. Use a static sintering tunnel kiln to fire high-strength ceramsite, with the green pellet layer height of 200 mm. The first-stage suction drying temperature is 150 °C and the drying time is 5 min; the second-stage suction drying temperature is 200 °C and the drying time is 8 min; then preheat at 500 °C for 5 min; then carry out oxidation roasting, with the roasting temperature of 1150 °C and the roasting time of 25 min. After roasting, unload the material and naturally cool it to room temperature.

[0067] Inspect the product performance according to GBT17431-2010. The bulk density of this ceramsite is 750 kg / m 3 , the 1-hour water absorption rate is 10.43%, and the apparent density is 1501 kg / m 3 , and the cylinder compressive strength is 2.18 MPa. The performance of the prepared ceramsite does not meet the performance requirements of ordinary ceramsite and high-strength ceramsite with a density grade of 800.

[0068] It can be seen from Examples 1, 2, 3 and Comparative Examples 1, 2, 3 that using high-carbon low-sulfur / high-carbon high-sulfur / low-carbon high-sulfur coal gangue as raw materials, performing reverse flotation decarbonization treatment on high-carbon low-sulfur coal gangue, performing reverse flotation decarbonization and desulfurization treatment on high-carbon high-sulfur coal gangue, performing reverse flotation desulfurization treatment on low-carbon high-sulfur coal gangue, and then preparing ceramsite, high-strength ceramsite with excellent performance can be prepared. If high-carbon low-sulfur / high-carbon high-sulfur / low-carbon high-sulfur coal gangue is directly used to prepare ceramsite without reverse flotation pretreatment, due to excessive gas generation during the ceramsite firing process, the performance of the ceramsite will be unsatisfactory and high-strength ceramsite cannot be prepared.

[0069] The above content is only a specific implementation case of this application, rather than all application cases of this application. All solutions based on the technical idea of this application and those modified on the technical idea of this application are within the protection scope of the claims of this application.

Claims

1. A method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue, characterized in that: The following steps are involved: (1) crushing and fine-grinding the coal gangue to obtain finely ground coal gangue; (2) mixing the finely ground coal gangue obtained in step (1) with water to obtain coal gangue slurry; (3) adding an inhibitor, a collector and a frother to the gangue slurry obtained in step (2), performing reverse flotation decarbonization and / or desulfurization on the gangue, and filtering and drying the precipitate in the flotation tank to obtain a decarbonized and / or desulfurized gangue filter cake; (4) crushing and finely grinding the decarbonized and / or desulfurized coal gangue filter cake obtained in step (3), pelletizing the finely ground coal gangue, adding water while pelletizing, to obtain ceramsite green bodies, screening the green bodies, selecting green bodies with a qualified particle size, and using them for subsequent ceramsite firing; (5) laying the bottom material and the side material on the trolley, and performing the following processes on the green pellets with the qualified particle size obtained in step (4), such as laying, drying, preheating, roasting and cooling, to obtain roasted pellets; (6) Screening the calcined pellets obtained in step (5) to select calcined pellets with a qualified particle size, namely the high-strength ceramsite.

2. The method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue according to claim 1, characterized in that: In step (1), the coal gangue is one or more of high-carbon and low-sulfur coal gangue, high-carbon and high-sulfur coal gangue, and low-carbon and high-sulfur coal gangue.

3. The method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue according to claim 2, characterized in that: The carbon content of high-carbon and low-sulfur coal gangue is 4wt% to 20wt%, and the sulfur content is less than 1wt%; the carbon content of high-carbon and high-sulfur coal gangue is higher than 4wt%, and the sulfur content is higher than 1wt%; the carbon content of low-carbon and high-sulfur coal gangue is lower than 4wt%, and the sulfur content is higher than 1wt%.

4. The method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue according to claim 1, characterized in that: In step (1), the crushing is carried out by one or more of a jaw crusher, a roll crusher, a cone crusher, an impact crusher, an impact crusher, and a hammer crusher; The fine grinding process includes wet ball milling with water, high pressure roller milling under natural moisture, and dry ball milling after drying. After crushing and fine grinding, the particle size of the coal gangue is less than 0.5mm.

5. The method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue according to claim 1, characterized in that: In step (2), the concentration of the gangue slurry is 70 to 200 g / L.

6. The method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue according to claim 1, characterized in that: In step (3), the inhibitor is one of sodium silicate, sodium carbonate, sodium hexametaphosphate, and carboxymethyl cellulose, and the amount used is 500 to 1500 g / t; Diesel or kerosene is used as a carbon collector, with a dosage of 50 to 700 g / t; Xanthate or butyl xanthate is used as a sulfur collector, with a dosage of 50-600 g / t; The foaming agent is No. 2 oil, and the dosage is 10-100g / t; After decarbonization of high-carbon and low-sulfur coal gangue, decarbonization and desulfurization of high-carbon and high-sulfur coal gangue, and desulfurization of low-carbon and high-sulfur coal gangue, the carbon content of the coal gangue is less than 4wt%, and the sulfur content is less than 1wt%.

7. The method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue according to claim 1, characterized in that: In step (4), the decarbonized and / or desulfurized coal gangue filter cake is crushed and finely ground, and the specific operation is the same as step (1), to obtain decarbonized and / or desulfurized coal gangue powder with a particle size of -0.074 mm accounting for more than 50%.

8. The method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue according to claim 1, characterized in that: In step (4), a disc ball making machine or a cylinder ball making machine is used for ball making, the ball making time is 6 to 12 minutes, the moisture content of the green body is 9 to 15%, the drop strength of the green body is greater than 4 times / 0.5m, the compressive strength is greater than 10N / piece, and the burst temperature of the green body is higher than 200°C.

9. The method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue according to claim 1, characterized in that: In step (5), the ceramsite firing equipment can be any one of a belt roaster, a chain grate machine based on horizontal movement of a moving bed, a static sintering tunnel kiln, a roller kiln, and a rotary kiln.

10. The method for preparing high-strength ceramsite by reverse flotation decarbonization and desulfurization of coal gangue according to claim 1, characterized in that: In step (6), the performance of the high-strength ceramsite is tested according to GB / T 17431.1-2010 and GB / T 17431.2-2010, and the density grades of the high-strength ceramsite are 600, 700, 800 and 900.

Images