A water-retaining ceramsite made from coal gangue, its preparation method and application

Abstract

This application relates to the technical field of firing ceramsite, and specifically discloses a coal gangue-based water-retaining ceramsite, its preparation method and application. The preparation method of the coal gangue-based ceramsite disclosed in this application is as follows: Drying: The green balls of ceramsite are fed into the drying section, and the hot air from the decarbonization section is cooled and then sent to the drying section to dry the green balls; The green balls of ceramsite are prepared by uniformly mixing coal gangue raw materials and modified silica sol and then calcined. Pyrolysis: The hot air generated from the decarbonization section is heated to 350-400 °C and then introduced into the pyrolysis section to pyrolyze the green balls. Decarbonization: The hot air from the pyrolysis section and the cooling section heats and supports combustion of the material layer in the decarbonization section to complete the decarbonization of the ceramsite. Cooling: The decarbonized ceramsite is cooled by blowing air. Using the technical solution of this application, the processing scale of coal gangue ceramsite can be increased, the energy utilization of coal gangue itself can be maximized, the production cost can be effectively reduced, and the ceramsite can meet the requirements of decarbonization, water retention and strength.

Description

Technical Field

[0001] This application relates to the technical field of firing ceramsite, and particularly relates to a water-retaining ceramsite made from coal gangue, its preparation method and application. Background Art

[0002] The coal gangue produced by coal mines is a solid waste, which occupies a large amount of cultivated land and pollutes the environment. The comprehensive utilization technology of coal gangue has a broad market prospect and is a business in the energy conservation and environmental protection field strongly supported by the state. Its fired ceramsite products are mainly applied to the sand and gravel aggregate market, soil improvement and water treatment.

[0003] The current technical routes for preparing ceramsite from coal gangue at home and abroad are: using a traditional rotary kiln to prepare ceramsite by adding coal gangue and other materials. Its main problems are: high energy consumption; inability to utilize waste heat; small production capacity, making it difficult to utilize coal gangue in large quantities; difficult to achieve full utilization of coal gangue and can only be used as a supplementary fuel ingredient; large residual loss on ignition in ceramsite. The market application range is small.

[0004] At present, the production line of ceramsite does not take into account the characteristics of coal gangue. Since coal gangue ceramsite (especially low-rank coal) releases volatile matter and burns to release heat when heated, this stage will cause the temperature of the coal gangue ceramsite layer to rise sharply under high-temperature ignition. When the temperature of the material layer reaches 1100 - 1200 °C, a liquid phase is formed on the surface of the green balls, blocking the fine pores on the surface of the green balls and hindering the oxidation reaction between oxygen and carbon inside the green balls. The coal gangue is not completely decarbonized, resulting in a black core. At the same time, the ceramsite with a formed liquid phase adheres and agglomerates, affecting the normal operation of production and making it impossible to produce qualified ceramsite.

[0005] Therefore, a process that fully considers the spontaneous combustion property of coal gangue ceramsite needs to be proposed. Summary of the Invention

[0006] In order to solve the above technical problems, this application provides a water-retaining ceramsite made from coal gangue, its preparation method and application.

[0007] In the first aspect, this application provides a preparation method of a water-retaining ceramsite made from coal gangue, which specifically includes the following steps carried out in sequence:

[0008] (1)Drying: The green pellets of ceramsite are fed into the drying section. The hot air from the decarbonization section is cooled and pressurized to 200 - 250 °C and then sent to the drying section to dry the green pellets. The air velocity of the material layer is 1 - 2 Nm / s. The preparation method of the green pellets of ceramsite is as follows: The coal gangue raw material and the modified silica sol are mixed evenly according to the weight ratio of 100:3 - 17, and then obtained through roasting. The preparation method of the modified silica sol is as follows: Tetraethyl orthosilicate and titanate coupling agent are added to a 40 - 60 wt% ethanol aqueous solution, and the mixture is sealed and reacted in a water bath at a temperature of 40 - 60 °C for 2 - 4 h; then zirconium butoxide is added, and the mixture is sealed and reacted in a water bath at a temperature of 60 - 80 °C for 4 - 8 h to obtain the modified silica sol. Among them, the weight ratio of tetraethyl orthosilicate, titanate coupling agent, ethanol aqueous solution, and zirconium butoxide is 14 - 20:3 - 9:40 - 50:0.5 - 2.5;

[0009] (2)Pyrolysis: The hot air from the decarbonization section is adjusted to 350 - 400 °C and introduced into the pyrolysis section to remove the volatile matter from the green pellets and ignite them; the generated combustible components react and release heat and are introduced into the decarbonization section;

[0010] (3)Decarbonization: The hot air at 450 - 700 °C from the pyrolysis section and the cooling section heats the material layer from top to bottom in the decarbonization section to assist combustion, and the decarbonization of the ceramsite is completed from top to bottom; specifically, it includes the first decarbonization stage, the second decarbonization stage, and the third decarbonization stage;

[0011] In the first decarbonization stage, the hot air from the upper part of the pyrolysis section heats the green pellets, and the high-temperature hot air flue gas in the air box is led out through the decarbonization fan and then used for waste heat utilization;

[0012] In the second decarbonization stage, the hot air from the upper part of the pyrolysis section heats the green pellets, and the high-temperature hot air flue gas in the air box is led out through the pyrolysis fan, adjusted in temperature, and then introduced into the air box of the pyrolysis section;

[0013] In the third decarbonization stage, the hot air from the upper part of the cooling section is heated after heat supplementation and then heats the ceramsite. The temperature of the material layer rises to 600 - 750 °C, the temperature of the high-temperature hot air flue gas in the air box is 650 - 800 °C, and after being cooled and mixed, it is used for the drying section;

[0014] (4)Cooling: The ceramsite after decarbonization is cooled to 80 - 100 °C and then transported to the silo; the air velocity of the material layer in the cooling section is 1 - 2 Nm / s, and the generated high-temperature air is introduced into the decarbonization section, and the oxygen content of the hot air meets the requirements of the oxygen content in the entire hot air cycle.

[0015] The purpose of this application is to use the pellet static roasting equipment - the traveling grate stoker to provide a process plan for decarbonizing coal gangue ceramsite and improving its water retention performance and strength; to increase the processing scale of coal gangue ceramsite, maximize the utilization of the energy of coal gangue itself, reduce production costs, and enable the ceramsite to meet the requirements of decarbonization and water retention for soil improvement.

[0016] This application meets the technological requirements of each stage of green pellet roasting, can reasonably utilize the characteristics of hot air in each stage of the roasting process, and saves external energy to the greatest extent. It also solves the problems of caking and incomplete decarbonization during the preparation of coal gangue ceramsite. While treating coal gangue solid waste, on the one hand, the low-quality energy in coal gangue generates economic benefits, and on the other hand, the finished pellets can also produce a certain economic value as products.

[0017] The technological characteristics of the static roasting hot air system for coal gangue ceramsite provided by this application are as follows: Adopting the static roasting method of the material layer, it can handle coal gangue in large quantities; the hot air process system in each section (such as drying, pyrolysis, decarbonization, cooling, etc.) is precisely designed according to the characteristics of the raw materials, with the optimal heat distribution; realizing the utilization of high-volatile coal gangue: solving the problem that the combustion process of high-volatile coal gangue has poor controllability and it is difficult to form a controllable temperature. Utilizing its characteristic of providing the heat required for decarbonization, early volatile matter removal is achieved and the decarbonization process is completed using its heat. The static roaster integrates processes such as drying, ignition, decarbonization, and cooling into one device, which is arranged in a closed workshop. Due to the short process, less heat dissipation, good heat recovery utilization, less floor area, high thermal efficiency, and low overall energy consumption.

[0018] The green pellets of this application are arranged on the static roaster. The green pellets move with the trolley of the static roaster and become qualified finished pellets after being processed by the hot air system in the furnace of the roaster, and are discharged at the tail of the roaster.

[0019] Among them, in the process of preparing ceramsite green balls, an ethanol aqueous solution is used as the medium. Tetraethyl orthosilicate hydrolyzes to generate silanol groups, which form a silica sol with a three-dimensional network structure after polycondensation, providing a high specific surface area and active sites. The titanium atom of the titanate coupling agent bonds with the Si-OH bond of the silica sol to form a Si-O-Ti bond. At the same time, its organic long chain can improve the compatibility between the silica sol and the coal gangue raw material and enhance the dispersibility. The introduction of zirconium n-butoxide (Zr(OBu)4) forms a Si-O-Zr bond with the silica sol, enhancing the thermal stability of the gel network and inhibiting the structural collapse during high-temperature sintering. Moreover, the prepared modified silica sol serves as a support phase during the roasting of the coal gangue raw material, preventing pore closure, increasing the porosity of the ceramsite, and thus improving the water absorption of the ceramsite. On the other hand, the coal gangue and the modified silica sol exhibit a synergistic effect. The composition of the coal gangue mainly contains kaolinite (Al2Si2O5(OH)4), quartz (SiO2), etc., providing an aluminum source and a silicon source; the modified silica sol provides a certain adhesiveness, wraps the coal gangue particles, and combines through Si-O-Al bonds to improve the green ball strength. At the same time, the gel network decomposes (releasing H2O, CO2, etc.) during pyrolysis to form through pores; zirconium / titanium oxides inhibit sintering densification and maintain the pore structure. From the above mechanism, it can be analyzed that by introducing the modified silica sol, the chemical composition (Si-Al-Zr-Ti-O system) and microstructure (porous network) of the ceramsite are regulated, enabling the multi-level pores (micropores-mesopores-macropores) inside the ceramsite to adsorb water through capillary physical action, and the residual hydrophilic groups such as -Si-OH and -Ti-OH on the surface bind water molecules through hydrogen bonds. Therefore, the technical solution provided in this application realizes the preparation of ceramsite with both high water retention and appropriate strength from multiple aspects.

[0020] In the subsequent preparation process, the ceramsite green balls are dried to remove physically adsorbed water to prevent cracking caused by rapid temperature rise. During the pyrolysis process, the organic matter in the coal gangue and the organic components in the silica sol (such as the residual chains of the coupling agent) decompose to form initial pores. During the decarbonization process: carbonaceous combustion creates pores, and at the same time, the silica sol reacts with the coal gangue to form a ceramic phase, endowing the framework with strength. The cooling step can control the cooling rate to avoid stress cracks and retain the porous structure.

[0021] Preferably, in the method for preparing the ceramsite green balls, the performance parameters of the coal gangue raw material are as follows: calorific value is 400 - 750 kcal / kg, volatile matter is 7 - 14%, fixed carbon content is 4 - 8%, the thickness of the green balls is 300 - 500 mm, and the particle size of the green balls is 8 - 16 mm;

[0022] The process parameters for roasting are: roasting cycle is 140 - 180 min, drying time is 30 - 50 min, ignition time is 15 - 25 min, decarbonization time is 50 - 70 min, and cooling time is 30 - 50 min.

[0023] Preferably, the method for preparing the ceramsite green balls is as follows: mix the coal gangue raw material and the modified silica sol in a weight ratio of 100:7-13 evenly, and then obtain them through roasting; the method for preparing the modified silica sol is as follows: add tetraethyl orthosilicate and titanate coupling agent to the ethanol aqueous solution, and carry out a closed reaction at a water bath temperature of 45-55°C for 2.5-3.5 h; then add zirconium butoxide, and carry out a closed reaction at a water bath temperature of 65-75°C for 5-7 h to obtain it; wherein, the weight ratio of tetraethyl orthosilicate, titanate coupling agent, ethanol aqueous solution, and zirconium butoxide is 16-18:5-7:43-47:1-2.

[0024] Preferably, the titanate coupling agent is selected from one or more of bis(dioctylpyrophosphato)oxyacetate titanium, isopropyltris(dodecylbenzenesulfonyl)titanate, isopropyltris(isostearoyl)titanate, and isopropyltris(n-ethylamino-ethylamino)titanate. Preferably, the drying includes a first drying stage and a second drying stage; the specific steps are as follows:

[0025] The ceramsite green balls are first fed into the first drying stage, and the flue gas at 100-150°C from the second drying stage is pressurized by a first drying fan and fed into the air box of the first drying stage to dry the green balls. After the flue gas penetrates the material layer, it enters the upper hood, and the waste gas from the upper hood of the first drying stage is discharged through a flue gas fan;

[0026] The green balls heated in the first drying stage enter the second drying stage, and the high-temperature hot flue gas at 650-800°C from the decarbonization section is cooled to 200-250°C and then pressurized by a drying fan and sent to the air box of the second drying stage to heat up the green balls, and the moisture of the green balls is discharged until the moisture content ≤ 1.5%.

[0027] Preferably, in the pyrolysis step, the hot air generated by the volatilization of the green balls penetrates the material layer and enters the upper hood of the pyrolysis section, and the temperature of the upper hood is 450-600°C; the hot flue gas in the upper hood of the pyrolysis section is mixed with the hot air from the cooling section and then reaches the decarbonization section through the furnace hood.

[0028] Preferably, the decarbonization includes a first decarbonization stage, a second decarbonization stage, and a third decarbonization stage; the specific steps are as follows:

[0029] The green balls enter the first decarbonization stage, and the hot air from the upper part of the pyrolysis section heats the green balls, and the temperature of the material layer gradually increases; the temperature of the high-temperature hot flue gas in the air box of the first decarbonization stage is 450-600°C; the high-temperature hot flue gas is led out by a decarbonization fan and then the waste heat is utilized;

[0030] The green balls enter the second decarbonization stage, and the hot air from the upper part of the pyrolysis section heats the green balls, and the temperature of the material layer gradually increases; the temperature of the high-temperature hot flue gas in the air box of the second decarbonization stage is 450-600°C; the high-temperature hot flue gas is led out by a pyrolysis fan and then adjusted to 350-400°C and then introduced into the air box of the pyrolysis section;

[0031] The green balls enter the third decarbonization stage. The hot air from the upper part of the first cooling stage is reheated and used to heat the ceramsite after temperature increase. The temperature of the ceramsite layer further rises to reach 600 - 750 °C, and the temperature of the high-temperature hot air flue gas in the wind box of the third decarbonization stage is 650 - 800 °C; the high-temperature hot air flue gas is cooled and then used in the drying stage.

[0032] In a specific implementation, during the actual production process, the temperature of the lower wind box of the first and second decarbonization stages is generally 400 - 650 °C.

[0033] Preferably, the green balls enter the third decarbonization stage. The hot air from the upper part of the first cooling stage is reheated and used to heat the ceramsite after temperature increase. The temperature of the ceramsite layer further rises to reach 650 - 720 °C, and the temperature of the high-temperature hot air flue gas in the wind box of the third decarbonization stage is 680 - 750 °C; the high-temperature hot air flue gas is cooled and then used in the drying stage.

[0034] Preferably, the cooling includes the first cooling stage and the second cooling stage; the specific steps are as follows:

[0035] The ceramsite layer that has completed decarbonization enters the first cooling stage. The low-temperature hot air at 150 - 250 °C in the furnace hood of the second cooling stage is fed into the wind box of the first cooling stage through the first cooling fan to cool the material layer and simultaneously heat the flue gas. The temperature of the wind box is 150 - 250 °C;

[0036] The material layer enters the second cooling stage. The fresh air at 25 °C cools the ceramsite through the second cooling fan and simultaneously heats the air. The temperature of the flue gas is 150 - 250 °C; after cooling, the ceramsite with a temperature lower than 100 °C is transported to the silo.

[0037] In the second aspect, the present application provides a water-retaining ceramsite made from coal gangue, which is prepared by using the above preparation method.

[0038] Preferably, the fixed carbon content of the water-retaining ceramsite product is < 1.5%, the water absorption rate > 15%, and the cylindrical compressive strength is 3 - 5 MPa.

[0039] In the third aspect, the present application provides the application of the above-mentioned water-retaining ceramsite made from coal gangue in sand and gravel aggregates, soil improvement, or water treatment.

[0040] To sum up, the technical solution of the present application has the following effects:

[0041] The process of the present application is realized by static roasting equipment, which can be a traveling grate, a circular roasting machine, or other trolley-type sintering machines.

[0042] The process of the present application is applicable to the heating treatment process of preparing ceramsite from coal gangue, especially the treatment of coal gangue with high volatile content; the calorific value of the coal gangue for preparing ceramsite is between 400 - 750 kcal / kg.

[0043] The static calcination process of this application integrates drying, pyrolysis, decarbonization, and cooling into one device, which is arranged in a closed workshop. Due to the short process, less heat dissipation, good heat recovery utilization, less floor area, high thermal efficiency, and low overall energy consumption.

[0044] This application can achieve stepped heat utilization, fully recover and utilize heat, and realize self-heating decarbonization for coal gangue with a calorific value > 400 Kcal.

[0045] On the one hand, this application solves the problems that during the process of preparing ceramsite from coal gangue, the heat of the material layer suddenly increases, causing the material layer to agglomerate and the surface of the ceramsite to melt, resulting in the production being unable to proceed or the quality of the ceramsite being poor; and the volatiles released by the ceramsite in the pyrolysis section avoid the sudden increase in heat of the material layer and utilize the heat energy generated in this process section through this process means. At the same time, the internal heat of the process provided by this application is optimized for utilization, and the flue gas penetrates through the high-temperature material layer in sequence, and the temperature increases in sequence. For coal gangue green balls with a calorific value > 400 kcal / kg, self-heating decarbonization can be achieved. This application utilizes the heat generated by ceramsite decarbonization as waste heat for utilization to generate economic value. Brief Description of the Drawings

[0046] Figure 1 It is the process flow diagram for preparing water-retaining ceramsite from coal gangue in this application.

[0047] Figure 2 It is the process flow diagram for preparing water-retaining ceramsite from coal gangue in Example 1 of this application. Detailed Description of the Embodiment

[0048] The following further describes this application in detail in combination with examples, comparative examples, and performance detection tests. These examples should not be construed as limiting the scope claimed by this application. Examples

[0049] As Figure 1 shown is the process flow diagram for preparing water-retaining ceramsite from coal gangue in this application, and the specific process method is as follows.

[0050] (1) Drying: The drying includes drying stage one and drying stage two; the specific steps are as follows:

[0051] The ceramsite green balls are fed into drying stage one, and the thickness of the material layer is 300 - 500 mm. The flue gas at 100 - 150 °C from drying stage two is pressurized by a drying stage one fan and fed into the drying stage one air box to dry the green balls. After the flue gas penetrates through the material layer, it enters the upper hood; the < 100 °C waste gas from the upper hood of drying stage one is discharged through a flue gas fan. The wind speed of the material layer is 1 - 2 Nm / s.

[0052] The green balls after being heated in the first drying stage enter the second drying stage. The high-temperature hot air flue gas at 650 - 800 °C from the third decarbonization stage air box is cooled to 200 - 250 °C and then pressurized by the drying fan and sent to the second drying stage air box to heat the green balls and discharge the moisture of the green balls; the flue gas at 100 - 150 °C on the upper cover of the second drying stage is pressurized by the first drying fan and fed into the first drying stage air box. The air velocity of the material layer is 1 - 2 Nm / s.

[0053] (2)Pyrolysis: The green balls after dehydration in the second drying stage are fed into the pyrolysis stage. The high-temperature flue gas from the second decarbonization stage air box is adjusted to 350 - 400 °C and introduced into the pyrolysis stage air box by the pyrolysis fan to heat and pyrolyze the green balls. Under the action of high temperature, the volatile components in the green balls begin to be released and react with heat release. The hot air penetrates the material layer and enters the upper cover of the pyrolysis stage, and the temperature of the upper cover is 450 - 600 °C. The hot flue gas in the upper cover of the pyrolysis stage is mixed with the hot air from the cooling stage and then passes through the furnace cover to reach the upper parts of the first and second decarbonization stages. The air velocity of the material layer is 1 - 2 Nm / s.

[0054] (3)Decarbonization: Decarbonization includes the first decarbonization stage, the second decarbonization stage and the third decarbonization stage; the specific steps are as follows:

[0055] The green balls enter the first decarbonization stage. In the first decarbonization stage, the hot air at 450 - 600 °C from the upper part of the pyrolysis stage heats the green balls, and the temperature of the material layer gradually rises. The high-temperature flue gas is led out by the decarbonization fan and then the waste heat is utilized.

[0056] The green balls enter the second decarbonization stage. In the second decarbonization stage, the hot air at 450 - 600 °C from the upper part of the pyrolysis stage heats the green balls, and the temperature of the material layer gradually rises. The high-temperature flue gas is led out by the pyrolysis fan and then adjusted to 350 - 400 °C and then fed into the pyrolysis stage air box.

[0057] The green balls enter the third decarbonization stage. In the third decarbonization stage, the hot air from the upper part of the first cooling stage is heated after supplementary heating and then heats the ceramsite, and the temperature of the ceramsite material layer further rises to 600 - 750 °C. The temperature of the flue gas in the third decarbonization stage air box is 650 - 800 °C. The high-temperature flue gas is cooled and then used for drying. After being cooled to 200 - 250 °C, it is pressurized by the drying fan and sent to the second drying stage air box.

[0058] (4)Cooling: It includes the first cooling stage and the second cooling stage; the specific steps are as follows:

[0059] The material layer enters the first cooling stage. The low-temperature hot air at 150 - 250 °C in the furnace cover of the second cooling stage is fed into the first cooling stage air box by the first cooling fan to cool the material layer and at the same time heat the flue gas, and the temperature of the air box is 150 - 250 °C.

[0060] The material layer enters the second cooling stage. The fresh air at 25 °C cools the ceramsite through the second cooling fan and at the same time heats the air, and the temperature of the flue gas is 150 - 250 °C. The temperature of the cooled ceramsite is 80 - 100 °C and is transported to the silo. Example 1

[0061] Example 1 provides a method for preparing water-retaining ceramsite from coal gangue and its preparation method.

[0062] In this example, the process flow chart for preparing water-retaining ceramsite from coal gangue is as Figure 2 shown; the specific preparation method is as follows.

[0063] In this example, the calorific value of the coal gangue raw material is 630 kcal / kg, the volatile matter is 10.5%, the fixed carbon content is 5.5%, and the raw pellet size is 8 - 14 mm. The preparation method of the ceramsite raw pellets is: the coal gangue raw material and modified silica sol are mixed evenly according to a weight ratio of 100:11, and then obtained through roasting; the preparation method of the modified silica sol is: tetraethyl orthosilicate and titanate coupling agent isopropyl tris(isostearoyl) titanate are added to a 50 wt% ethanol aqueous solution, and the mixture is sealed and reacted at a water bath temperature of 50 °C for 3 h; then zirconium butoxide is added, and the mixture is sealed and reacted at a water bath temperature of 70 °C for 6 h to obtain the modified silica sol; among them, the weight ratio of tetraethyl orthosilicate, titanate coupling agent, ethanol aqueous solution, and zirconium butoxide is 17:6:45:1.5; the process parameters of roasting are: roasting cycle 160 min, drying time 40 min, ignition time 20 min, decarbonization time 60 min, and cooling time 40 min.

[0064] (1) Drying: Drying includes drying stage 1 and drying stage 2; the specific steps are as follows:

[0065] The ceramsite raw pellets are fed into drying stage 1, and the bed thickness is 350 mm. The 135 °C flue gas from drying stage 2 is pressurized by a drying fan 1 and fed into the air box of drying stage 1 to dry the raw pellets. After the flue gas penetrates the bed, it enters the upper hood; the 95 °C waste gas from the upper hood of drying stage 1 is discharged through a flue gas fan. The bed wind speed is 1.5 Nm / s.

[0066] The raw pellets heated in drying stage 1 enter drying stage 2. The 731 °C high-temperature hot flue gas from the decarbonization stage 3 air box is cooled to 228 °C and then pressurized by a drying fan and sent to the air box of drying stage 2 to raise the temperature of the raw pellets and discharge the moisture in the raw pellets. The moisture content in the raw pellets is 0.9%; the 135 °C flue gas from the upper hood of drying stage 2 is pressurized by a drying fan 1 and fed into the air box of drying stage 1. The bed wind speed is 1.5 Nm / s.

[0067] (2)Pyrolysis: The green balls after drying and secondary dehydration are fed into the pyrolysis section. The high-temperature flue gas at 493 °C from the decarbonization secondary air box is adjusted to 365 °C and introduced into the pyrolysis section air box by the pyrolysis fan to heat and pyrolyze the green balls. Under the action of high temperature, the volatile components in the green balls begin to be released and react with heat release. The hot air penetrates the material layer and enters the upper cover of the pyrolysis section, and the temperature of the upper cover is 483 °C. The hot flue gas in the upper cover of the pyrolysis section is mixed with the hot air from the cooling section and then reaches the upper parts of the decarbonization first stage and the decarbonization second stage through the furnace cover. The air velocity of the material layer is 1.2 Nm / s.

[0068] (3)Decarbonization: Decarbonization includes the decarbonization first stage, the decarbonization second stage and the decarbonization third stage; the specific steps are as follows:

[0069] The green balls enter the decarbonization first stage. In the decarbonization first stage, the hot air at 483 °C from the upper part of the pyrolysis section heats the green balls, and the temperature of the material layer gradually increases. The temperature of the flue gas in the decarbonization first stage air box is 515 °C. The high-temperature flue gas is led out by the decarbonization fan for waste heat utilization.

[0070] The green balls enter the decarbonization second stage. In the decarbonization second stage, the hot air at 483 °C from the upper part of the pyrolysis section heats the green balls, and the temperature of the material layer gradually increases. The temperature of the flue gas in the decarbonization second stage air box is 493 °C. The high-temperature flue gas is led out by the pyrolysis fan, adjusted to 365 °C and then introduced into the pyrolysis section air box.

[0071] The green balls enter the decarbonization third stage. In the decarbonization third stage, the hot air from the upper part of the cooling first stage is heated after supplementary heating and then heats the ceramsite, and the temperature of the ceramsite material layer further increases to 698 °C. The temperature of the flue gas in the decarbonization third stage air box is 731 °C. The high-temperature flue gas is cooled and then used for drying. After being cooled to 228 °C, it is pressurized by the drying fan and sent to the drying second stage air box.

[0072] (4)Cooling: It includes the cooling first stage and the cooling second stage; the specific steps are as follows:

[0073] The material layer enters the cooling first stage. The low-temperature hot air at 193 °C in the furnace cover of the cooling second stage is fed into the cooling first stage air box by the cooling first fan to cool the material layer and at the same time heat the flue gas, and the temperature of the air box is 183 °C.

[0074] The material layer enters the cooling second stage. The fresh air at 25 °C cools the ceramsite through the cooling second fan and heats the air at the same time, and the temperature of the flue gas is 193 °C. The cooled ceramsite at 95 °C is transported to the silo.

[0075] The fixed carbon content of the ceramsite product prepared in this example is 0.95%, the calorific value is 45 kcal / kg, the water absorption rate is 23.5%, and the cylinder pressure strength is 3.9 MPa. There is no caking in the material layer and the production is smooth. Example 2

[0076] Example 2 provides a water-retaining ceramsite made from coal gangue and its preparation method.

[0077] In this embodiment, the green pellets of ceramsite entering the drying section are the same as those in Embodiment 1.

[0078] The preparation method of water-retaining ceramsite from coal gangue in this embodiment is specifically as follows.

[0079] (1) Drying: Drying includes the first drying stage and the second drying stage; the specific steps are as follows:

[0080] The green pellets of ceramsite are fed into the first drying stage, and the thickness of the material layer is 350 mm. The flue gas at 107 °C from the second drying stage is pressurized by the first drying fan and fed into the air box of the first drying stage to dry the green pellets. After the flue gas penetrates the material layer, it enters the upper hood; the waste gas at 89 °C from the upper hood of the first drying stage is discharged through the flue gas fan.

[0081] The green pellets heated in the first drying stage enter the second drying stage. The high-temperature hot flue gas at 678 °C from the air box of the third decarbonization stage is cooled to 208 °C and then pressurized by the drying fan and sent to the air box of the second drying stage to raise the temperature of the green pellets and discharge the moisture in the green pellets. The moisture content in the green pellets is 1.4%; the flue gas at 107 °C from the upper hood of the second drying stage is pressurized by the first drying fan and fed into the air box of the first drying stage.

[0082] (2) Pyrolysis: The green pellets dehydrated in the second drying stage are fed into the pyrolysis section. The high-temperature flue gas at 481 °C from the air box of the second decarbonization stage is adjusted to 358 °C and introduced into the air box of the pyrolysis section by the pyrolysis fan to heat and pyrolyze the green pellets. Under the action of high temperature, the volatile matter in the green pellets begins to be released and reacts with heat release. The hot air penetrates the material layer and enters the upper hood of the pyrolysis section, and the temperature of the upper hood is 475 °C. The hot flue gas in the upper hood of the pyrolysis section is mixed with the hot air from the cooling section and then passes through the furnace hood to reach the upper parts of the first decarbonization stage and the second decarbonization stage.

[0083] (3) Decarbonization: Decarbonization includes the first decarbonization stage, the second decarbonization stage and the third decarbonization stage; the specific steps are as follows:

[0084] The green pellets enter the first decarbonization stage. In the first decarbonization stage, the hot air at 475 °C from the upper part of the pyrolysis section heats the green pellets, and the temperature of the material layer gradually rises. The temperature of the flue gas in the air box of the first decarbonization stage is 508 °C. The high-temperature flue gas is led out by the decarbonization fan and then used for waste heat utilization.

[0085] The green pellets enter the second decarbonization stage. In the second decarbonization stage, the hot air at 475 °C from the upper part of the pyrolysis section heats the green pellets, and the temperature of the material layer gradually rises. The temperature of the flue gas in the air box of the second decarbonization stage is 481 °C. The high-temperature flue gas is led out by the pyrolysis fan and then adjusted to 358 °C and then introduced into the air box of the pyrolysis section.

[0086] The green pellets enter the third decarbonization stage. In the third decarbonization stage, the hot air from the upper part of the first cooling stage is heated after supplementary heating and then heats the ceramsite, and the temperature of the ceramsite material layer further rises to 627 °C. The temperature of the flue gas in the air box of the third decarbonization stage is 678 °C. The high-temperature flue gas is cooled and then used for drying. After being cooled to 208 °C, it is pressurized by the drying fan and sent to the air box of the second drying stage.

[0087] (4)Cooling: including the first cooling stage and the second cooling stage; the specific steps are as follows:

[0088] The material layer enters the first cooling stage. The 171°C low-temperature hot air from inside the furnace hood of the second cooling stage is fed into the first cooling stage air box through the first cooling fan to cool the material layer, while heating the flue gas. The temperature of the air box is 159°C.

[0089] The material layer enters the second cooling stage. 25°C fresh air cools the ceramsite through the second cooling fan while heating the air. The temperature of the flue gas is 171°C. The cooled ceramsite at a temperature of 95°C is transported to the storage bin.

[0090] The ceramsite product prepared in this embodiment has a fixed carbon content of 1.08%, a calorific value of 51 kcal / kg, a water absorption rate of 24.2%, and a cylindrical compressive strength of 4.6 MPa. The material layer has no caking and the production is smooth. Example 3

[0091] Example 3 provides a method for preparing water-retaining ceramsite from coal gangue and its preparation method.

[0092] The green ceramsite balls entering the drying section in this embodiment are the same as those in Example 1.

[0093] The preparation method of the water-retaining ceramsite prepared from coal gangue in this embodiment is specifically as follows.

[0094] (1)Drying: The drying includes the first drying stage and the second drying stage; the specific steps are as follows:

[0095] The green ceramsite balls are fed into the first drying stage, and the thickness of the material layer is 350 mm. The 148°C flue gas from the second drying stage is pressurized by the first drying fan and fed into the first drying stage air box to dry the green balls. After the flue gas penetrates the material layer, it enters the upper hood; the 98°C waste gas from the upper hood of the first drying stage is discharged through the flue gas fan.

[0096] The green balls heated in the first drying stage enter the second drying stage. The 749°C high-temperature hot air flue gas from the decarbonization third stage air box is cooled to 249°C and then pressurized by the drying fan and sent to the second drying stage air box to heat the green balls and discharge the moisture in the green balls. The moisture content in the green balls is 0.7%; the 148°C flue gas from the upper hood of the second drying stage is pressurized by the first drying fan and fed into the first drying stage air box.

[0097] (2)Pyrolysis: The green balls dehydrated in the second drying stage are fed into the pyrolysis section. The 573°C high-temperature flue gas from the decarbonization second stage air box is adjusted to 397°C and introduced into the pyrolysis section air box by the pyrolysis fan to heat and pyrolyze the green balls. Under the action of high temperature, the volatile components in the green balls begin to be released and react exothermically. The hot air penetrates the material layer and enters the upper hood of the pyrolysis section, and the temperature of the upper hood is 579°C. The hot flue gas in the upper hood of the pyrolysis section is mixed with the hot air from the cooling section and then passes through the furnace hood to reach the upper parts of the first decarbonization stage and the second decarbonization stage.

[0098] (3)Decarbonization: Decarbonization includes the first stage of decarbonization, the second stage of decarbonization, and the third stage of decarbonization; the specific steps are as follows:

[0099] The green pellets enter the first stage of decarbonization. In the first stage of decarbonization, the hot air at 579 °C from the upper part of the pyrolysis section heats the green pellets, and the temperature of the material layer gradually increases. The flue gas temperature in the wind box of the first stage of decarbonization is 585 °C. The high-temperature flue gas is led out by the decarbonization fan and then used for waste heat utilization.

[0100] The green pellets enter the second stage of decarbonization. In the second stage of decarbonization, the hot air at 589 °C from the upper part of the pyrolysis section heats the green pellets, and the temperature of the material layer gradually increases. The flue gas temperature in the wind box of the second stage of decarbonization is 573 °C. The high-temperature flue gas is led out by the pyrolysis fan and then adjusted to 365 °C and then introduced into the pyrolysis section wind box.

[0101] The green pellets enter the third stage of decarbonization. In the third stage of decarbonization, the hot air from the upper part of the first stage of cooling is heated after supplementary heating and then heats the ceramsite, and the temperature of the ceramsite material layer further increases to reach 736 °C. The flue gas temperature in the wind box of the third stage of decarbonization is 749 °C. The high-temperature flue gas is cooled and then used for drying. After being cooled to 249 °C, it is pressurized by the drying fan and sent to the drying second stage wind box.

[0102] (4)Cooling: It includes the first stage of cooling and the second stage of cooling; the specific steps are as follows:

[0103] The material layer enters the first stage of cooling. The low-temperature hot air at 238 °C in the furnace hood of the second stage of cooling is fed into the wind box of the first stage of cooling through the first cooling fan to cool the material layer and at the same time heat the flue gas. The wind box temperature is 217 °C.

[0104] The material layer enters the second stage of cooling. The fresh air at 25 °C cools the ceramsite through the second cooling fan and at the same time heats the air. The flue gas temperature is 238 °C. The cooled ceramsite at a temperature of 98 °C is transported to the silo.

[0105] The ceramsite product prepared in this embodiment has a fixed carbon content of 0.78%, a calorific value of 41 kcal / kg, a water absorption rate of 26.6%, and a cylinder compressive strength of 4.8 MPa. The material layer has no caking and the production is smooth.

[0106] Example 4 - 11

[0107] Example 4 - 11 respectively provides a method for preparing high-strength ceramsite from coal gangue and its preparation method.

[0108] The difference between the above example and Example 3 is that the green ceramsite pellets entering the drying section are different.

[0109] In Example 4: The preparation method of ceramsite green balls is as follows: The coal gangue raw material and modified silica sol are mixed evenly according to a weight ratio of 100:3, and then obtained through roasting. The fixed carbon content of the ceramsite product prepared in this example is 0.98%, the calorific value is 48 kcal / kg, the water absorption rate is 18.4%, and the cylinder compressive strength is 3.5 MPa. The material layer has no caking, and the production is smooth.

[0110] In Example 5: The preparation method of ceramsite green balls is as follows: The coal gangue raw material and modified silica sol are mixed evenly according to a weight ratio of 100:17, and then obtained through roasting. The fixed carbon content of the ceramsite product prepared in this example is 1.03%, the calorific value is 47 kcal / kg, the water absorption rate is 19.3%, and the cylinder compressive strength is 3.4 MPa. The material layer has no caking, and the production is smooth.

[0111] In Example 6: The preparation method of ceramsite green balls is as follows: The coal gangue raw material and modified silica sol are mixed evenly according to a weight ratio of 100:7, and then obtained through roasting. The fixed carbon content of the ceramsite product prepared in this example is 1.05%, the calorific value is 49 kcal / kg, the water absorption rate is 25.3%, and the cylinder compressive strength is 4.5 MPa. The material layer has no caking, and the production is smooth.

[0112] In Example 7: The preparation method of ceramsite green balls is as follows: The coal gangue raw material and modified silica sol are mixed evenly according to a weight ratio of 100:13, and then obtained through roasting. The fixed carbon content of the ceramsite product prepared in this example is 1.11%, the calorific value is 50 kcal / kg, the water absorption rate is 26.1%, and the cylinder compressive strength is 4.7 MPa. The material layer has no caking, and the production is smooth.

[0113] In Example 8: In the preparation method of modified silica sol, the weight ratio of tetraethyl orthosilicate, titanate coupling agent, ethanol aqueous solution, and zirconium n-butoxide is 14:9:40:2.5. The fixed carbon content of the ceramsite product prepared in this example is 0.97%, the calorific value is 49 kcal / kg, the water absorption rate is 17.5%, and the cylinder compressive strength is 3.4 MPa. The material layer has no caking, and the production is smooth.

[0114] In Example 9: In the preparation method of modified silica sol, the weight ratio of tetraethyl orthosilicate, titanate coupling agent, ethanol aqueous solution, and zirconium n-butoxide is 20:3:50:0.5. The fixed carbon content of the ceramsite product prepared in this example is 1.18%, the calorific value is 51 kcal / kg, the water absorption rate is 16.4%, and the cylinder compressive strength is 3.2 MPa. The material layer has no caking, and the production is smooth.

[0115] In Example 10: In the preparation method of the modified silica sol, the weight ratio of tetraethyl orthosilicate, titanate coupling agent, ethanol aqueous solution, and zirconium butoxide is 16:7:43:2. The fixed carbon content of the ceramsite product prepared in this example is 1.08%, the calorific value is 47 kcal / kg, the water absorption rate is 25.5%, and the cylinder compressive strength is 4.7 MPa. There is no caking in the material layer, and the production is smooth.

[0116] In Example 11: In the preparation method of the modified silica sol, the weight ratio of tetraethyl orthosilicate, titanate coupling agent, ethanol aqueous solution, and zirconium butoxide is 18:5:47:1. The fixed carbon content of the ceramsite product prepared in this example is 1.08%, the calorific value is 52 kcal / kg, the water absorption rate is 24.9%, and the cylinder compressive strength is 4.5 MPa. There is no caking in the material layer, and the production is smooth.

[0117] In the above examples, the remaining process parameters are the same as those in Example 3.

[0118] Comparative Example Comparative Example 1

[0119] This comparative example provides a method for preparing water-retaining ceramsite from coal gangue and its preparation method.

[0120] In this comparative example, the green ceramsite balls entering the drying section are the same as those in Example 1.

[0121] The difference between the preparation method of the water-retaining ceramsite from coal gangue in this comparative example and that in Example 1 lies in the pyrolysis and decarbonization steps, which are specifically as follows.

[0122] (2) Pyrolysis: The green balls after dehydration in the second stage of drying are fed into the pyrolysis section. The 571 °C high-temperature flue gas from the decarbonization second-stage air box is adjusted to 450 °C and introduced into the pyrolysis section air box by the pyrolysis fan to heat and pyrolyze the green balls. Under the action of high temperature, the volatile components in the green balls begin to be released and react exothermically. The hot air penetrates the material layer and enters the upper cover of the pyrolysis section, and the temperature of the upper cover is 563 °C. The hot flue gas in the upper cover of the pyrolysis section is mixed with the hot air from the cooling section and then passes through the furnace cover to reach the upper parts of the first and second stages of decarbonization.

[0123] (3) Decarbonization: Decarbonization includes the first stage of decarbonization, the second stage of decarbonization, and the third stage of decarbonization; the specific steps are as follows:

[0124] The green balls enter the first stage of decarbonization. In the first stage of decarbonization, the 563 °C hot air from the upper part of the pyrolysis section heats the green balls, and the temperature of the material layer gradually rises. The flue gas temperature in the air box of the first stage of decarbonization is 582 °C. The high-temperature flue gas is led out by the decarbonization fan and used for waste heat utilization.

[0125] The green balls enter the second stage of decarbonization. In the second stage of decarbonization, the 563 °C hot air from the upper part of the pyrolysis section heats the green balls, and the temperature of the material layer gradually rises. The flue gas temperature in the air box of the second stage of decarbonization is 571 °C. The high-temperature flue gas is led out by the pyrolysis fan and adjusted to 450 °C and then introduced into the pyrolysis section air box.

[0126] The green balls enter the third decarbonization stage. In the third decarbonization stage, the hot air from the upper part of the first cooling stage is heated after supplementary heating and then heats the ceramsite. The temperature of the ceramsite bed further increases to reach 741 °C. The flue gas temperature in the air box of the third decarbonization stage is 796 °C. The high-temperature flue gas is cooled by mixing and then used for drying. After being cooled by mixing to 228 °C, it is pressurized by a drying fan and sent to the air box of the second drying stage.

[0127] The fixed carbon content of the ceramsite product prepared in this comparative example is 0.34%, the calorific value is 39 kcal / kg, the water absorption rate is 7.3%, and the cylinder pressure strength is 7.1 MPa. There is no caking in the bed layer and the production is smooth; however, the water absorption performance of the ceramsite product is poor and cannot meet the requirements of this application. Comparative Example 2

[0128] This comparative example provides a method for preparing water-retaining ceramsite from coal gangue and its preparation method.

[0129] The green balls of ceramsite entering the drying stage in this comparative example are the same as those in Example 1.

[0130] The difference between the preparation method of water-retaining ceramsite from coal gangue in this comparative example and that in Example 1 lies in the different decarbonization steps, which are specifically as follows.

[0131] Decarbonization: Decarbonization includes the first decarbonization stage and the second decarbonization stage; the specific steps are as follows:

[0132] The green balls enter the first decarbonization stage. In the first decarbonization stage, the hot air at 483 °C from the upper part of the pyrolysis stage heats the green balls, and the temperature of the bed layer gradually increases. The flue gas temperature in the air box of the first decarbonization stage is 502 °C. The high-temperature flue gas is led out by a pyrolysis fan and then adjusted to 365 °C and introduced into the air box of the pyrolysis stage.

[0133] The green balls enter the second decarbonization stage. In the second decarbonization stage, the hot air at 483 °C from the upper part of the pyrolysis stage heats the green balls, and the temperature of the bed layer gradually increases. The flue gas temperature in the air box of the second decarbonization stage is 498 °C. The high-temperature flue gas is cooled by mixing and then used for drying. After being cooled by mixing to 228 °C, it is pressurized by a drying fan and sent to the air box of the second drying stage.

[0134] The fixed carbon content of the ceramsite product prepared in this comparative example is 2.38%, the calorific value is 61 kcal / kg, the water absorption rate is 21.1%, and the cylinder pressure strength is 1.3 MPa. There is caking in the bed layer and incomplete decarbonization; moreover, the cylinder pressure strength performance of the ceramsite product is poor and cannot meet the requirements of this application. Comparative Example 3

[0135] This comparative example provides a method for preparing water-retaining ceramsite from coal gangue and its preparation method.

[0136] The green balls of ceramsite entering the drying stage in this comparative example are the same as those in Example 1.

[0137] In this comparative example, the difference in the preparation method of water-retaining ceramsite from coal gangue compared with Example 1 lies in the decarbonization step, which is specifically as follows.

[0138] Decarbonization: Decarbonization includes the first decarbonization stage, the second decarbonization stage, and the third decarbonization stage; the specific steps are as follows:

[0139] The green balls enter the first decarbonization stage. In the first decarbonization stage, the 483°C hot air from the upper part of the pyrolysis section heats the green balls, and the temperature of the material layer gradually rises. The flue gas temperature in the air box of the first decarbonization stage is 515°C. The high-temperature flue gas is led out by the decarbonization fan and then used for waste heat utilization.

[0140] The green balls enter the second decarbonization stage. In the second decarbonization stage, the 483°C hot air from the upper part of the pyrolysis section heats the green balls, and the temperature of the material layer gradually rises. The flue gas temperature in the air box of the second decarbonization stage is 493°C. The high-temperature flue gas is led out by the pyrolysis fan and then adjusted to 365°C and then introduced into the air box of the pyrolysis section.

[0141] The green balls enter the third decarbonization stage. In the third decarbonization stage, the hot air from the upper part of the first cooling stage is heated after supplementary heating and then heats the ceramsite, and the temperature of the ceramsite material layer further rises to reach 1008°C. The flue gas temperature in the air box of the third decarbonization stage is 976°C. The high-temperature flue gas is cooled and then used for drying. After being cooled to 228°C, it is pressurized by the drying fan and sent to the air box of the second drying stage.

[0142] The ceramsite product prepared in this comparative example has a fixed carbon content of 0.61%, a calorific value of 36 kcal / kg, a water absorption rate of 6.9%, and a cylindrical compressive strength of 8.1 MPa. There is no caking in the material layer and the production is smooth; however, the water absorption performance of the ceramsite product is poor and cannot meet the requirements of this application.

[0143] Comparative Example 4

[0144] This comparative example provides a method for preparing ceramsite from coal gangue and its preparation method.

[0145] The difference between this comparative example and Example 3 is that the green ceramsite balls entering the drying section are different.

[0146] In Comparative Example 4: The green ceramsite balls are obtained by roasting coal gangue raw materials. The ceramsite product prepared in this example has a fixed carbon content of 1.83%, a calorific value of 40.8 kcal / kg, a water absorption rate of 8.01%, and a cylindrical compressive strength of 6.31 MPa.

[0147] All other process parameters in this comparative example are the same as those in Example 3. Comparative Example 5

[0148] This comparative example provides a method for preparing ceramsite from coal gangue and its preparation method.

[0149] The difference between this comparative example and Example 3 is that the green ceramsite balls entering the drying section are different.

[0150] In Comparative Example 5: The preparation method of ceramsite green balls is as follows: The coal gangue raw material and modified silica sol are mixed evenly according to a weight ratio of 100:1, and then obtained by roasting; The preparation method of the modified silica sol is: Add tetraethyl orthosilicate and the titanate coupling agent isopropyl tris(isostearoyl) titanate to a 50 wt% ethanol aqueous solution, and carry out a closed reaction at a water bath temperature of 70 °C for 3 h; Then add zirconium butoxide, and carry out a closed reaction at a water bath temperature of 50 °C for 6 h to obtain; Among them, the weight ratio of tetraethyl orthosilicate, titanate coupling agent, ethanol aqueous solution, and zirconium butoxide is 17:1:45:5. The fixed carbon content of the ceramsite product prepared in this example is 1.78%, the calorific value is 42.3 kcal / kg, the water absorption rate is 8.32%, and the cylinder pressure strength is 5.21 MPa.

[0151] The rest of the process parameters in this comparative example are the same as those in Example 3.

[0152] Although the present invention has been described in detail with general descriptions and specific embodiments above, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A preparation method of water-retaining ceramsite made from coal gangue, characterized in that, Specifically, it includes the following steps in sequence: (1) Drying: The green pellets of ceramsite are fed into the drying section. The hot air from the decarbonization section is cooled and pressurized to 200 - 250 °C and then sent to the drying section to dry the green pellets. The air velocity of the material layer is 1 - 2 Nm / s; The preparation method of the green pellets of ceramsite is as follows: The coal gangue raw material and the modified silica sol are mixed evenly according to the weight ratio of 100:7 - 13, and then obtained through roasting. The preparation method of the modified silica sol is as follows: Tetraethyl orthosilicate and titanate coupling agent are added to 40 - 60 wt% ethanol aqueous solution, and sealed and reacted for 2 - 4 h in a water bath environment with a temperature of 40 - 60 °C; then zirconium butoxide is added, and sealed and reacted for 4 - 8 h in a water bath environment with a temperature of 60 - 80 °C, thus obtaining it. Among them, the weight ratio of tetraethyl orthosilicate, titanate coupling agent, ethanol aqueous solution, and zirconium butoxide is 16 - 18:5 - 7:43 - 47:1 - 2; (2) Pyrolysis: The hot air from the decarbonization section is adjusted to 350 - 400 °C and introduced into the pyrolysis section to remove volatile components from the green pellets and ignite them; The generated reaction heat of the combustible components is introduced into the decarbonization section; (3) Decarbonization: The hot air at 450 - 700 °C from the pyrolysis section and the cooling section heats the material layer from top to bottom in the decarbonization section to assist combustion, and the decarbonization of the ceramsite is completed from top to bottom; Specifically, it includes the first decarbonization section, the second decarbonization section, and the third decarbonization section; The green pellets enter the first decarbonization section, and the hot air from the upper part of the pyrolysis section heats the green pellets, and the temperature of the material layer gradually increases; The temperature of the high-temperature hot air flue gas in the air box of the first decarbonization section is 450 - 600 °C; The high-temperature hot air flue gas is led out by the decarbonization fan and then used for waste heat utilization; The green pellets enter the second decarbonization section, and the hot air from the upper part of the pyrolysis section heats the green pellets, and the temperature of the material layer gradually increases; The temperature of the high-temperature hot air flue gas in the air box of the second decarbonization section is 450 - 600 °C; The high-temperature hot air flue gas is led out by the pyrolysis fan and then adjusted to 350 - 400 °C and then introduced into the air box of the pyrolysis section; In the third decarbonization section, the hot air from the upper part of the cooling section is heated after heat compensation and then heats the ceramsite, and the temperature of the material layer rises to 600 - 750 °C. The temperature of the high-temperature hot air flue gas in the air box is 650 - 800 °C, and after cooling, it is used for the drying section; (4) Cooling: The ceramsite after decarbonization is cooled to 80 - 100 °C and then transported to the silo; The air velocity of the material layer in the cooling section is 1 - 2 Nm / s, and the generated high-temperature air is introduced into the decarbonization section, and the oxygen content of the hot air meets the requirements of the oxygen content in the entire hot air cycle.

2. The preparation method of the water-retaining ceramsite made from coal gangue according to claim 1, characterized in that, In the preparation method of the green pellets of ceramsite, the performance parameters of the coal gangue raw material are as follows: calorific value is 400 - 750 kcal / kg, volatile matter is 7 - 14%, fixed carbon content is 4 - 8%, the thickness of the green pellets is 300 - 500 mm, and the particle size of the green pellets is 8 - 16 mm; The technological parameters of roasting are as follows: roasting cycle is 140 - 180 min, drying time is 30 - 50 min, ignition time is 15 - 25 min, decarbonization time is 50 - 70 min, and cooling time is 30 - 50 min.

3. The preparation method of the water-retaining ceramsite made from coal gangue according to claim 1, characterized in that, The drying includes the first drying section and the second drying section; The specific steps are as follows: The ceramsite green balls are first fed into the first drying stage. The flue gas at 100 - 150 °C from the second drying stage is pressurized by a drying fan and fed into the air box of the first drying stage to dry the green balls. After the flue gas penetrates the material layer, it enters the upper hood. The waste gas from the upper hood of the first drying stage is discharged through a flue gas fan. The green balls heated in the first drying stage enter the second drying stage. The high-temperature hot flue gas at 650 - 800 °C from the decarbonization stage is cooled to 200 - 250 °C and then pressurized by a drying fan and sent to the air box of the second drying stage to raise the temperature of the green balls, and the moisture of the discharged green balls is reduced to a moisture content of ≤1.5%.

4. The preparation method of the water-retaining ceramsite made from coal gangue according to claim 1, characterized in that, In the pyrolysis step, the hot air generated by the volatilization of the green balls penetrates the material layer and enters the upper hood of the pyrolysis stage, and the temperature of the upper hood is 450 - 600 °C; the hot flue gas in the upper hood of the pyrolysis stage is mixed with the hot air from the cooling stage and then reaches the decarbonization stage through the furnace hood.

5. The preparation method of water-retaining ceramsite made from coal gangue according to claim 1, characterized in that, The green balls enter the third decarbonization stage. The hot air from the upper part of the first cooling stage is heated after supplementary heating to heat the ceramsite, and the temperature of the ceramsite material layer further rises to 650 - 720 °C. The temperature of the high-temperature hot flue gas in the air box of the third decarbonization stage is 680 - 750 °C; the high-temperature hot flue gas is cooled and then used in the drying stage.

6. The preparation method of water-retaining ceramsite made from coal gangue according to claim 1, characterized in that The cooling includes the first cooling stage and the second cooling stage; the specific steps are as follows: The ceramsite material layer that has completed decarbonization enters the first cooling stage. The low-temperature hot air at 150 - 250 °C in the furnace hood of the second cooling stage is fed into the air box of the first cooling stage by a cooling fan to cool the material layer and at the same time raise the temperature of the flue gas. The temperature of the air box is 150 - 250 °C. The material layer enters the second cooling stage. Fresh air at 25 °C cools the ceramsite through a second cooling fan and at the same time raises the temperature of the air. The temperature of the flue gas is 150 - 250 °C; after cooling, the ceramsite with a temperature lower than 100 °C is transported to the silo.

7. A water-retaining ceramsite made from coal gangue, characterized in that, Prepared by using the preparation method according to any one of claims 1 - 6.

8. The water-retaining ceramsite made from coal gangue according to claim 7, characterized in that, The fixed carbon content of the water-retaining ceramsite product is <1.5%, the water absorption rate is >15%, and the cylindrical compressive strength is 3 - 5 MPa.

9. Application of the coal gangue-based water-retaining ceramsite according to any one of claims 7 - 8 in sand and gravel aggregates, soil improvement or water treatment.

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