A kind of high-strength 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 high-strength ceramsite made of coal gangue, its preparation method and application. The preparation method of the coal gangue ceramsite disclosed in this application is as follows: drying; pyrolysis; decarbonization: the hot air at 450-600°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; roasting: the hot air from the cooling section is heated by supplementary heating to heat the ceramsite, the temperature of the ceramsite material layer is 1000-1140°C, and the material layer is heated from top to bottom to assist combustion; cooling: the ceramsite after roasting is cooled to 80-100°C. Using the technical solution of this application can improve the processing scale of coal gangue ceramsite, effectively reduce production costs, and enable the ceramsite to meet the requirements of decarbonization, low water absorption and high strength.

Description

Technical Field

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

[0002] Coal gangue is a solid waste generated during coal mining and washing processes, mainly composed of minerals such as carbonaceous shale, mudstone, and sandstone. Its chemical composition is complex, usually containing relatively high amounts of silicon, aluminum, iron oxides, as well as small amounts of calcium, magnesium, potassium, sodium and other elements. The accumulation of coal gangue not only occupies a large amount of land, but may also cause environmental pollution problems such as spontaneous combustion, dust, and water pollution. Therefore, how to effectively utilize coal gangue and achieve its resource utilization has always been an important topic in the fields of environmental protection and comprehensive resource utilization.

[0003] Ceramsite is a lightweight and porous artificial aggregate, usually baked and expanded at high temperatures from raw materials such as clay, shale, and coal gangue. Ceramsite has excellent properties such as light weight, high strength, heat preservation, heat insulation, and sound absorption, and is widely used in fields such as construction, horticulture, and sewage treatment. High-strength ceramsite is particularly suitable for projects with high material performance requirements such as high-rise buildings, bridges, and roads due to its relatively high compressive strength and durability.

[0004] However, since coal gangue ceramsite (especially low-rank coal) releases volatile matter and burns to release heat when heated, this stage will cause the coal gangue ceramsite to easily cause a sharp temperature rise in the material layer under high-temperature ignition. When the material layer temperature reaches 1100 - 1200 °C, a liquid phase forms on the surface of the green balls, blocking the fine pores on the surface of the green balls and hindering the oxidation reaction of oxygen with carbon inside the green balls. The decarbonization of coal gangue is incomplete, resulting in black cores. 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; the roasting process has strict requirements on parameters such as temperature and time, and the process control is difficult. All these factors make it difficult to obtain high-strength ceramsite. Summary of the Invention

[0005] To solve the above technical problems, this application provides a high-strength ceramsite made from coal gangue, its preparation method and application.

[0006] In the first aspect, this application provides a preparation method for a high-strength ceramsite made from coal gangue, specifically including the following steps carried out in sequence:

[0007] (1) Drying: The green balls of ceramsite are fed into the drying section. The hot air from the roasting section is cooled and pressurized to 200 - 250 °C and sent to the drying section to dry the green balls. The air velocity of the material layer is 1 - 2 Nm / s; the green balls of ceramsite are obtained by uniformly mixing coal gangue raw materials, binder, sodium rosinate, and water in a weight ratio of 100:5 - 25:2 - 4:2 - 4, and then obtained through roasting.

[0008] (2) Pyrolysis: The hot air from the decarbonization section is temperature-adjusted to 300 - 400 °C and introduced into the pyrolysis section to remove the volatile matter from the green pellets and ignite them. The hot air generated by the volatile matter of the green pellets penetrates the material layer and enters the upper hood of the pyrolysis section; the reaction heat generated by the combustible components is introduced into the decarbonization section.

[0009] (3) Decarbonization: The hot air at 450 - 600 °C from the pyrolysis section and the cooling section heats and supports combustion of the material layer from top to bottom in the decarbonization section, and the decarbonization of the ceramsite is completed from top to bottom.

[0010] (4) Roasting: The hot air from the cooling section is heated by supplementary heating to roast the ceramsite. The temperature of the ceramsite material layer is 950 - 1140 °C, and it heats and supports combustion of the material layer from top to bottom, so that the ceramsite after decarbonization is heated up in this process section and then completes solid-phase and liquid-phase consolidation.

[0011] (5) Cooling: The roasted ceramsite is cooled to 80 - 100 °C and conveyed 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.

[0012] The purpose of this application is to use a pellet static roasting equipment - a traveling grate roaster to provide a process plan for decarbonizing coal gangue ceramsite to prepare high-strength ceramsite; to improve 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 functions of decarbonization and high strength required for soil improvement.

[0013] The present invention provides a method for preparing high-strength ceramsite using coal gangue. This method not only meets the process requirements of each stage of green pellet roasting, but also can effectively utilize the hot air characteristics of each stage in the roasting process, thereby minimizing external energy consumption to the greatest extent. In addition, this method also solves the common problems of caking and incomplete decarbonization in the preparation process of coal gangue ceramsite. Through this solution, not only can coal gangue solid waste be effectively treated, but also the low-quality energy in coal gangue can be used to create economic benefits. At the same time, the finished ceramsite as a product can also bring certain economic benefits.

[0014] This application adopts the static bed roasting technology and can process coal gangue on a large scale. For different sections such as drying, pyrolysis, decarbonization, roasting, and cooling, the process flow chart of preparing high-strength ceramsite from coal gangue in this application is as Figure 1As shown, the hot air process system is precisely designed according to the raw material characteristics to achieve optimal heat distribution. This method is particularly suitable for the utilization of high-volatile coal gangue, solving the problems of poor controllability and difficulty in maintaining a stable temperature during the combustion of high-volatile coal gangue. By using its volatile matter to provide the heat required for decarbonization, the early removal of volatile matter is achieved, and this part of the heat is used to complete the decarbonization process. The static roasting equipment integrates multiple process links such as drying, ignition, decarbonization, and cooling. All processes are arranged in a closed workshop, with advantages such as short process flow, less heat dissipation, high heat recovery utilization rate, small floor area, high thermal efficiency, and low overall energy consumption. Particularly, in this application, by further precisely designing the process parameters of roasting and cooling, the strength of the ceramsite is further improved, making the internal and external quality of the ceramsite uniform and stable.

[0015] This application makes ceramsite green balls by roasting coal gangue raw materials, binders, sodium rosinate, and water. The addition of the binder enhances the internal structure of the ceramsite, enabling it to maintain a stable shape during the roasting process, and improving the strength and durability of the ceramsite. Sodium rosinate helps to improve the mixing uniformity of the raw materials, making the roasted ceramsite more uniform and dense, with uniform and stable internal and external quality of the ceramsite, and further improving the strength of the ceramsite.

[0016] Preferably, the ceramsite green balls are obtained by roasting coal gangue raw materials;

[0017] The performance parameters of the coal gangue raw materials are: 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;

[0018] The process parameters of 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.

[0019] Preferably, the ceramsite green balls are obtained by uniformly mixing coal gangue raw materials, binders, sodium rosinate, and water in a weight ratio of 100:10 - 20:2 - 4:2 - 4 and then roasting; the process parameters of 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.

[0020] Furthermore, the binder is composed of one or more of clay, bentonite, water glass, starch, sludge, slaked lime, quicklime, and cement.

[0021] The materials of this application are green balls (with a certain calorific value) made from coal gangue through raw material treatment and pelletizing, which are arranged on a static roasting machine. The green balls move with the trolley of the static roasting machine and become finished balls with qualified indicators (cylinder compressive strength > 8.5 Mpa, water absorption < 10%) after being processed by the hot air system in the roasting furnace hearth, and are discharged at the tail of the roasting machine.

[0022] Through experimental analysis, it can be known that this application selects the above process to improve the preparation method of ceramsite green balls, further improving the strength of ceramsite.

[0023] Preferably, the drying includes a first drying stage and a second drying stage; the specific steps are as follows:

[0024] 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, and the waste gas from the upper hood of the first drying stage is discharged through a flue gas fan;

[0025] The green balls heated in the first drying stage enter the second drying stage. The high-temperature hot air flue gas at 950 - 1150 °C from the roasting 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 heat up the green balls and discharge the moisture of the green balls.

[0026] Preferably, the decarbonization includes a first decarbonization stage and a second decarbonization stage; the specific steps are as follows:

[0027] The green balls enter the first decarbonization stage. The hot flue gas in the upper hood of the pyrolysis stage and the hot air from the cooling stage are mixed and reach the first decarbonization stage through the furnace hood to heat the green balls, and the temperature of the material layer gradually rises; the temperature of the high-temperature hot air flue gas in the air box of the first decarbonization stage is 450 - 600 °C; the high-temperature hot air flue gas is led out through a decarbonization fan for waste heat utilization;

[0028] The green balls enter the second decarbonization stage. The hot air from the upper part of the pyrolysis stage heats the green balls, and the temperature of the material layer gradually rises; the temperature of the high-temperature hot air flue gas in the air box of the second decarbonization stage is 450 - 600 °C; the high-temperature hot air flue gas is led out through a pyrolysis fan and then adjusted to 300 - 400 °C and then fed into the air box of the pyrolysis stage.

[0029] Preferably, in the roasting stage, the temperature of the ceramsite material layer is 1110 - 1140 °C, the temperature of the flue gas in the air box is 1100 - 1150 °C, and the high-temperature hot air flue gas is cooled and used for the drying stage.

[0030] Through experimental analysis, it can be known that this application selects to control the process parameters of roasting to the above conditions, which can further improve the strength performance of ceramsite.

[0031] Preferably, the cooling includes a first cooling stage and a second cooling stage; the specific steps are as follows:

[0032] The calcined ceramsite layer enters the first stage of cooling. Low-temperature hot air at 260 - 340 °C from the hood of the second stage of cooling is fed into the air box of the first stage of cooling through the first cooling fan to cool the layer and simultaneously heat up the flue gas. The temperature of the air box is 260 - 340 °C;

[0033] The layer enters the second stage of cooling. Fresh air cools the ceramsite through the second cooling fan and simultaneously heats up the air. The temperature of the flue gas is 260 - 340 °C; After cooling, the ceramsite with a temperature below 100 °C is transported to the silo.

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

[0035] The calcined ceramsite layer enters the first stage of cooling. Low-temperature hot air at 300 - 330 °C from the hood of the second stage of cooling is fed into the air box of the first stage of cooling through the first cooling fan to cool the layer and simultaneously heat up the flue gas. The temperature of the air box is 300 - 330 °C;

[0036] The layer enters the second stage of cooling. Fresh air cools the ceramsite through the second cooling fan and simultaneously heats up the air. The temperature of the flue gas is 300 - 330 °C; After cooling, the ceramsite with a temperature below 100 °C is transported to the silo.

[0037] Through experimental analysis, it can be known that by controlling the process parameters of cooling to the above conditions in this application, the strength performance of the ceramsite can be further improved.

[0038] In the second aspect, this application provides a high-strength ceramsite made from coal gangue, which is prepared by using the above preparation method.

[0039] Preferably, the fixed carbon content of the high-strength ceramsite product is < 1.0%, the water absorption rate ≤ 10%, and the cylinder compressive strength ≥ 8.5 MPa.

[0040] In the third aspect, this application provides the application of the above high-strength ceramsite made from coal gangue in sand and gravel aggregates, soil improvement, or water treatment.

[0041] In summary, the technical solution of this application has the following effects:

[0042] The process of this application is realized by static calcination equipment, integrating drying, pyrolysis, decarbonization, calcination, and cooling into 1 piece of equipment, which is arranged in a closed workshop. Due to the short process, less heat dissipation, high heat recovery utilization rate, less land occupation, high thermal efficiency, and low overall energy consumption, it is suitable for the heating treatment process of preparing ceramsite from coal gangue, especially for the treatment of coal gangue with high volatile content.

[0043] The process route provided by this application can supplement heat and increase temperature as appropriate according to different product requirements through a supplementary heat combustion system, enabling the barrel pressure strength of ceramsite to reach >8.5 Mpa; the start-up burner is turned off after the production line is started and does not participate in the system operation; the waste gas in the furnace reaches 500 - 550 °C and can be utilized as waste heat.

[0044] This application improves the preparation method of ceramsite green balls, further enhancing the strength of ceramsite. Brief Description of the Drawings

[0045] Figure 1 It is the process flow diagram for preparing high-strength ceramsite from coal gangue in this application.

[0046] Figure 2 It is the process flow diagram for preparing high-strength ceramsite from coal gangue in Example 1 of this application. Detailed Description of the Embodiments

[0047] 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 in this application. Examples Example 1

[0048] Example 1 provides a method for preparing high-strength ceramsite from coal gangue and its preparation method.

[0049] The process flow diagram for preparing high-strength ceramsite from coal gangue in this example is as Figure 2 shown; the preparation method is specifically as follows.

[0050] In this example, the calorific value of the coal gangue raw material is 515 kcal / kg, the volatile matter is 10.8%, the fixed carbon content is 6.1%, and the green ball size is 8 - 14 mm; after mixing the coal gangue raw material, quicklime binder, sodium rosinate, and water evenly according to a weight ratio of 100:15:3:3, they are roasted in a roasting machine to obtain ceramsite green balls; the process parameters for roasting are: roasting cycle 160 min, drying time 40 min, ignition time 20 min, decarbonization time 60 min, and cooling time 40 min.

[0051] (1) Drying: The drying includes drying stage 1 and drying stage 2; the specific steps are as follows:

[0052] The ceramsite green balls are fed into drying stage 1, and the bed thickness is 340 mm. The 124 °C flue gas from drying stage 2 is pressurized by a drying stage 1 fan and fed into the drying stage 1 air box to dry the green balls. After the flue gas penetrates the bed, it enters the upper hood; the 93 °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.

[0053] The green balls after being heated in the first drying stage enter the second drying stage. The high-temperature hot flue gas at 983°C from the bellow of the roasting stage is cooled to 243°C and then pressurized by the drying fan and sent to the bellow of the second drying stage to heat up the green balls and discharge the moisture in the green balls. The moisture content in the green balls is 0.7%. The flue gas at 141°C from the upper cover of the second drying stage is pressurized by the first drying fan and fed into the bellow of the first drying stage. The wind speed of the material layer is 1.5 Nm / s.

[0054] (2)Pyrolysis: The green balls after dehydration in the second drying stage are fed into the pyrolysis stage. The high-temperature flue gas at 472°C from the bellow of the second decarburization stage is adjusted to 381°C and introduced into the bellow of the pyrolysis stage 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 to release heat. The hot air penetrates the material layer and enters the upper cover of the pyrolysis stage, and the temperature of the upper cover is 461°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 reaches the upper parts of the first and second decarburization stages through the furnace cover; the wind speed of the material layer is 1.3 Nm / s.

[0055] (3)Decarburization: Decarburization includes the first decarburization stage and the second decarburization stage; the specific steps are as follows:

[0056] The green balls enter the first decarburization stage. In the first decarburization stage, the hot air at 461°C from the upper part of the pyrolysis stage heats the green balls, and the temperature of the material layer gradually rises. The temperature of the flue gas in the bellow of the first decarburization stage is 511°C. The high-temperature flue gas is led out by the decarburization fan and used for waste heat utilization.

[0057] The green balls enter the second decarburization stage. In the second decarburization stage, the hot air at 461°C from the upper part of the pyrolysis stage heats the green balls, and the temperature of the material layer gradually rises. The temperature of the flue gas in the bellow of the second decarburization stage is 472°C. The high-temperature flue gas is led out by the pyrolysis fan, adjusted to 381°C, and then fed into the bellow of the pyrolysis stage.

[0058] (4)Roasting: The hot air from the upper part of the first cooling stage is heated by supplementary heat to heat the ceramsite. The temperature of the ceramsite material layer is 1096°C, and the material layer is heated from top to bottom to assist combustion, so that the ceramsite after decarburization is heated up in this process stage to complete solid-phase and liquid-phase consolidation, further improving the strength of the ceramsite; at the same time, making the quality inside and outside the ceramsite uniform and stable. The temperature of the flue gas in the bellow of the roasting stage is 983°C, and this high-temperature hot flue gas is cooled to 243°C and then used for the drying stage to save energy.

[0059] (5)Cooling: It includes the first cooling stage and the second cooling stage; the specific steps are as follows:

[0060] The material layer enters the first cooling stage. The low-temperature hot air at 291°C from the furnace cover of the second cooling stage is fed into the bellow of the first cooling stage by the first cooling fan to cool the material layer at 973°C, and at the same time heat up the flue gas. The temperature of the bellow is 275°C.

[0061] The material layer enters the second cooling stage. Fresh air at 25°C cools the ceramsite through the second cooling fan while heating up the air, and the flue gas temperature is 291°C. The cooled ceramsite at 95°C is transported to the silo.

[0062] The ceramsite product prepared in this example has a fixed carbon content of 0.78%, a calorific value of 35.6 kcal / kg, a water absorption rate of 8.51%, and a cylinder compressive strength of 8.92 MPa. The material layer has no caking and the production is smooth. Example 2

[0063] Example 2 provides a method for preparing high-strength ceramsite from coal gangue and its preparation method.

[0064] The green ceramsite balls entering the drying section in this example are the same as those in Example 1.

[0065] The difference between the preparation method of high-strength ceramsite from coal gangue in this example and that in Example 1 lies in: the steps of the roasting section in step (4) and the cooling section in step (5) are different; specifically as follows.

[0066] (4) Roasting: The hot air from the upper part of the first cooling stage is heated through supplementary heating to heat the ceramsite. The temperature of the ceramsite material layer is 1123°C, and the material layer is heated from top to bottom to assist combustion, so that the ceramsite after decarbonization is heated up in this process section to complete solid-phase and liquid-phase consolidation, further improving the strength of the ceramsite; at the same time, the quality inside and outside the ceramsite is made uniform and stable. The flue gas temperature in the roasting section air box is 1035°C, and this high-temperature hot air flue gas is cooled to 243°C and then used in the drying section to save energy.

[0067] (5) Cooling: It includes the first cooling stage and the second cooling stage; the specific steps are as follows:

[0068] The material layer enters the first cooling stage. Low-temperature hot air at 320°C from the furnace hood of the second cooling stage is fed into the air box of the first cooling stage through the first cooling fan to cool the material layer at 1008°C, while heating up the flue gas, and the air box temperature is 311°C.

[0069] The material layer enters the second cooling stage. Fresh air at 25°C cools the ceramsite through the second cooling fan while heating up the air, and the flue gas temperature is 320°C. The cooled ceramsite at 95°C is transported to the silo.

[0070] The ceramsite product prepared in this example has a fixed carbon content of 0.63%, a calorific value of 33.2 kcal / kg, a water absorption rate of 7.52%, and a cylinder compressive strength of 11.78 MPa. The material layer has no caking and the production is smooth. Example 3

[0071] Example 3 provides a method for preparing high-strength ceramsite from coal gangue and its preparation method.

[0072] The green ceramsite balls entering the drying section in this example are the same as those in Example 1.

[0073] The difference between the preparation method of high-strength ceramsite from coal gangue in this embodiment and that in Embodiment 1 lies in that: the steps in the roasting section and the cooling section are different; specifically as follows.

[0074] (4) Roasting: The hot air from the upper part of the first cooling section is heated by supplementary heating to heat the ceramsite. The temperature of the ceramsite material layer is 1140 °C, and the material layer is heated from top to bottom to assist combustion, so that the ceramsite after decarbonization is heated up in this process section to complete solid-phase and liquid-phase consolidation, further improving the strength of the ceramsite; at the same time, the quality inside and outside the ceramsite is made uniform and stable. The temperature of the flue gas in the roasting section air box is 1083 °C, and this high-temperature hot air flue gas is cooled to 243 °C and then used in the drying section to save energy.

[0075] (5) Cooling: It includes the first cooling section and the second cooling section; the specific steps are as follows.

[0076] The material layer enters the first cooling section. The 345 °C low-temperature hot air from the furnace hood of the second cooling section is fed into the air box of the first cooling section through the first cooling fan to cool the 1012 °C material layer, and at the same time heat up the flue gas. The air box temperature is 323 °C.

[0077] The material layer enters the second cooling section. 25 °C fresh air cools the ceramsite through the second cooling fan and heats up the air at the same time. The flue gas temperature is 345 °C. The cooled ceramsite with a temperature of 95 °C is transported to the silo.

[0078] The ceramsite product prepared in this embodiment has a fixed carbon content of 0.67%, a calorific value of 33.8 kcal / kg, a water absorption rate of 8.12%, and a cylinder compressive strength of 9.82 MPa. There is no hardening in the material layer, and the production is smooth.

[0079] Embodiments 4 - 9

[0080] Embodiments 4 - 9 respectively provide a method for preparing high-strength ceramsite from coal gangue and its preparation method.

[0081] The difference between the above embodiments and Embodiment 2 is that: the green ceramsite balls entering the drying section are different.

[0082] In Embodiment 4: The green ceramsite balls are obtained by uniformly mixing coal gangue raw materials, starch binder, and water in a weight ratio of 100:15:3, and then roasting. The ceramsite product prepared in this embodiment has a fixed carbon content of 0.81%, a calorific value of 36.6 kcal / kg, a water absorption rate of 8.74%, and a cylinder compressive strength of 8.51 MPa.

[0083] In Example 5: The ceramsite green balls are prepared by uniformly mixing coal gangue raw materials, bentonite binder, and water in a weight ratio of 100:15:3, and then obtained through roasting. The ceramsite product prepared in this example has a fixed carbon content of 0.80%, a calorific value of 36.6 kcal / kg, a water absorption rate of 8.02%, and a cylindrical compressive strength of 8.73 MPa.

[0084] In Example 6: The ceramsite green balls are prepared by uniformly mixing coal gangue raw materials, quicklime binder, sodium rosinate, and water in a weight ratio of 100:5:3:3, and then obtained through roasting. The ceramsite product prepared in this example has a fixed carbon content of 0.78%, a calorific value of 34.3 kcal / kg, a water absorption rate of 8.53%, and a cylindrical compressive strength of 8.86 MPa.

[0085] In Example 7: The ceramsite green balls are prepared by uniformly mixing coal gangue raw materials, quicklime binder, sodium rosinate, and water in a weight ratio of 100:25:1:3, and then obtained through roasting. The ceramsite product prepared in this example has a fixed carbon content of 0.76%, a calorific value of 34.7 kcal / kg, a water absorption rate of 7.95%, and a cylindrical compressive strength of 9.01 MPa.

[0086] In Example 8: The ceramsite green balls are prepared by uniformly mixing coal gangue raw materials, quicklime binder, sodium rosinate, and water in a weight ratio of 100:10:4:3, and then obtained through roasting. The ceramsite product prepared in this example has a fixed carbon content of 0.70%, a calorific value of 33.4 kcal / kg, a water absorption rate of 7.51%, and a cylindrical compressive strength of 11.63 MPa.

[0087] In Example 9: The ceramsite green balls are prepared by uniformly mixing coal gangue raw materials, quicklime binder, sodium rosinate, and water in a weight ratio of 100:20:2:3, and then obtained through roasting. The ceramsite product prepared in this example has a fixed carbon content of 0.64%, a calorific value of 32.8 kcal / kg, a water absorption rate of 7.68%, and a cylindrical compressive strength of 11.24 MPa.

[0088] In the above examples, the remaining process parameters are the same as those in Example 2. Comparative Example Comparative Example 1

[0089] This comparative example provides a method for preparing ceramsite from coal gangue and its preparation method.

[0090] In this comparative example, the ceramsite green balls entering the drying section are the same as those in Example 2.

[0091] The difference between the preparation method of ceramsite from coal gangue in this comparative example and that in Example 2 lies in steps (3) decarbonization and (4) roasting steps, which are specifically as follows.

[0092] (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:

[0093] The green pellets enter the first stage of decarbonization. In the first stage of decarbonization, the hot air at 461 °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 air box of the first stage of decarbonization is 511 °C. The high-temperature flue gas is led out by the decarbonization fan and then used for waste heat utilization.

[0094] The green pellets enter the second stage of decarbonization. In the second stage of decarbonization, the hot air at 461 °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 air box of the second stage of decarbonization is 472 °C. The high-temperature flue gas is led out by the pyrolysis fan and then adjusted to 381 °C and then introduced into the air box of the pyrolysis section.

[0095] 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 heat supplementation and then heats the ceramsite, and the temperature of the ceramsite material layer further increases to reach 705 °C. The flue gas temperature in the air box of the third stage of decarbonization is 752 °C.

[0096] (4)Roasting: The hot air from the upper part of the first stage of cooling is heated after heat supplementation and then heats the ceramsite. The temperature of the ceramsite material layer is 925 °C, and the material layer is heated from top to bottom to assist combustion, so that the ceramsite after decarbonization is heated in this process section to complete solid-phase and liquid-phase consolidation, further improving the strength of the ceramsite; at the same time, the quality inside and outside the ceramsite is made uniform and stable. The flue gas temperature in the air box of the roasting section is 913 °C, and the high-temperature hot air flue gas is cooled to 241 °C and then used in the drying section to save energy.

[0097] The fixed carbon content of the ceramsite product prepared in this comparative example is 1.28%, the calorific value is 42.4 kcal / kg, the water absorption rate is 10.1%, and the cylinder pressure strength is 6.5 MPa; there is no caking in the material layer, and the production is smooth. However, the strength performance of the ceramsite product is poor and cannot meet the requirements of this application. Comparative Example 2

[0098] This comparative example provides a method for preparing ceramsite from coal gangue and its preparation method.

[0099] The green pellets of ceramsite entering the drying section in this comparative example are the same as those in Example 1.

[0100] The difference between the preparation method of ceramsite from coal gangue in this comparative example and Example 1 is that: the steps of the roasting section in step (4) and the cooling section in step (5) are different; the specific details are as follows.

[0101] (4)Roasting: The hot air from the upper part of the first cooling stage is heated through supplementary heating to heat the ceramsite. The temperature of the ceramsite material layer is 1182 °C, and the material layer is heated from top to bottom to assist combustion, so that the ceramsite after decarbonization is heated up in this process section to complete solid-phase and liquid-phase consolidation, further improving the strength of the ceramsite; at the same time, making the quality inside and outside the ceramsite uniform and stable. The flue gas temperature in the air box of the roasting section is 1108 °C, and this high-temperature hot air flue gas is cooled to 248 °C and then used in the drying section to save energy.

[0102] (5)Cooling: It includes the first cooling stage and the second cooling stage; the specific steps are as follows:

[0103] The material layer enters the first cooling stage. The low-temperature hot air at 246 °C from the furnace hood of the second cooling stage is fed into the air box of the first cooling stage through the first cooling fan to cool the material layer at 1120 °C, and at the same time heat up the flue gas. The air box temperature is 215 °C.

[0104] The material layer enters the second cooling stage. The fresh air at 25 °C cools the ceramsite through the second cooling fan and heats up the air at the same time. The flue gas temperature is 246 °C. The cooled ceramsite temperature is 95 °C and is transported to the silo.

[0105] The fixed carbon content of the ceramsite product prepared in this comparative example is 0.72%, the calorific value is 34.2 kcal / kg, the water absorption rate is 7.9%, and the cylindrical compressive strength is 6.9 MPa. There is no caking in the material layer and the production is smooth. However, the strength performance of the ceramsite product is poor and cannot meet the requirements of this application. Comparative Example 3

[0106] This comparative example provides a method for preparing ceramsite from coal gangue and its preparation method.

[0107] The green ceramsite balls entering the drying section in this comparative example are the same as those in Example 1.

[0108] The difference between the preparation method of ceramsite from coal gangue in this comparative example and that in Example 1 is that the steps in the (4) roasting section and the (5) cooling section are different; specifically as follows.

[0109] (4)Roasting: The hot air from the upper part of the first cooling stage is heated through supplementary heating to heat the ceramsite. The temperature of the ceramsite material layer is 932 °C, and the material layer is heated from top to bottom to assist combustion, so that the ceramsite after decarbonization is heated up in this process section to complete solid-phase and liquid-phase consolidation, further improving the strength of the ceramsite; at the same time, making the quality inside and outside the ceramsite uniform and stable. The flue gas temperature in the air box of the roasting section is 989 °C, and this high-temperature hot air flue gas is cooled to 248 °C and then used in the drying section to save energy.

[0110] (5)Cooling: It includes the first cooling stage and the second cooling stage; the specific steps are as follows:

[0111] The material layer enters the first stage of cooling. The low-temperature hot air at 392°C inside the hood of the second stage of cooling is fed into the air box of the first stage of cooling through the first cooling fan, cooling the material layer at 908°C and simultaneously heating the flue gas. The temperature of the air box is 375°C.

[0112] The material layer enters the second stage of cooling. 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 392°C. The cooled ceramsite at 95°C is transported to the silo.

[0113] The fixed carbon content of the ceramsite product prepared in this comparative example is 1.04%, the calorific value is 40.5 kcal / kg, the water absorption rate is 10.2%, and the cylinder compressive strength is 5.9 MPa. The material layer has no caking and the production is smooth. However, the strength performance of the ceramsite product is poor and cannot meet the requirements of this application. Comparative Example 4

[0114] This comparative example provides a method for preparing ceramsite from coal gangue and its preparation method.

[0115] The difference between this comparative example and Example 2 is that the green ceramsite balls entering the drying section are different.

[0116] In Comparative Example 4: The green ceramsite balls are obtained by roasting from coal gangue raw materials. The fixed carbon content of the ceramsite product prepared in this example is 0.81%, the calorific value is 36.6 kcal / kg, the water absorption rate is 8.74%, and the cylinder compressive strength is 8.51 MPa.

[0117] The remaining process parameters in this comparative example are the same as those in Example 2.

[0118] Although the present invention has been described in detail above with general descriptions and specific embodiments, on the basis of 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 high-strength ceramsite made from coal gangue, characterized in that, It is realized by a static roasting device, which integrates drying, pyrolysis, decarbonization, roasting, and cooling into one device and is arranged in a closed workshop; 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 roasting 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 green pellets of ceramsite are obtained by uniformly mixing coal gangue raw materials, quicklime binder, sodium rosinate, and water in a weight ratio of 100:10 - 20:2 - 4:2 - 4 and then roasting. (2) Pyrolysis: The hot air from the decarbonization section is adjusted to 300 - 400 °C and introduced into the pyrolysis section to remove volatile components from the green pellets and ignite them. The hot air generated by the volatile components of the green pellets penetrates the material layer and enters the upper hood of the pyrolysis section; the reaction heat generated by the combustible components is introduced into the decarbonization section. (3) Decarbonization: The hot air at 450 - 600 °C from the pyrolysis section and the cooling section heats and supports combustion of the material layer from top to bottom in the decarbonization section, and decarbonization of the ceramsite is completed from top to bottom; the decarbonization includes the first stage of decarbonization and the second stage of decarbonization; the specific steps are as follows: The green pellets enter the first stage of decarbonization. The hot flue gas in the upper hood of the pyrolysis section and the hot air from the cooling section are mixed and then reach the first stage of decarbonization through the furnace hood to heat 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 stage of decarbonization is 450 - 600 °C; the high-temperature hot air flue gas is led out by a decarbonization fan and then used for waste heat utilization. The green pellets enter the second stage of decarbonization. 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 stage of decarbonization is 450 - 600 °C; the high-temperature hot air flue gas is led out by a pyrolysis fan and then adjusted to 300 - 400 °C and then introduced into the air box of the pyrolysis section. (4) Roasting: The hot air from the cooling section is heated by supplementary heat to heat the ceramsite. The temperature of the ceramsite material layer is 1110 - 1140 °C, and it heats and supports combustion of the material layer from top to bottom, so that the ceramsite after decarbonization is heated in this process section and then completes solid-phase and liquid-phase consolidation; the temperature of the flue gas in the air box is 1100 - 1150 °C, and the high-temperature hot air flue gas is cooled and then used for the drying section. (5) Cooling: Cooling includes the first stage of cooling and the second stage of cooling; the specific steps are as follows: The ceramsite material layer after roasting enters the first stage of cooling. The low-temperature hot air at 260 - 340 °C in the furnace hood of the second stage of cooling is fed into the air box of the first stage of cooling by a cooling fan to cool the material layer, and at the same time heat the flue gas. The temperature of the air box is 260 - 340 °C. The material layer enters the second stage of cooling. Fresh air cools the ceramsite through a cooling fan and heats the air at the same time. The temperature of the flue gas is 260 - 340 °C; after cooling, the ceramsite after roasting is cooled to 80 - 100 °C and 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 whole hot air cycle.

2. The preparation method of high-strength ceramsite made from coal gangue according to claim 1, wherein The ceramsite green balls are obtained by roasting coal gangue raw materials; the performance parameters of the coal gangue raw materials 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; the process parameters of the 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 high-strength ceramsite made from coal gangue according to claim 2, wherein, The process parameters of the 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.

4. The preparation method of high-strength ceramsite made from coal gangue according to claim 1, characterized in that, The drying includes a first drying stage and a second drying stage; the specific steps are as follows: 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. The green balls heated in the first drying stage enter the second drying stage, and the high-temperature hot flue gas at 950 - 1150 °C from the roasting 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 heat up the green balls and discharge the moisture of the green balls.

5. A high-strength ceramsite made from coal gangue, characterized in that, Prepared by using the preparation method according to any one of claims 1 - 4.

6. Application of the high-strength ceramsite made from coal gangue according to claim 5 in sand and gravel aggregates, soil improvement or water treatment.

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