High-strength ceramsite prepared from coal gangue as well as preparation method and application of high-strength ceramsite

Abstract

The invention relates to the technical field of fired ceramsite, and particularly discloses high-strength ceramsite prepared from coal gangue as well as a preparation method and application of the high-strength ceramsite. The invention discloses a preparation method for preparing ceramic particles from coal gangue. The preparation method comprises the following steps: drying; performing pyrolysis; decarburization: carrying out heating combustion-supporting on a material layer from top to bottom by hot air with the temperature of 450-600 DEG C from the pyrolysis section and the cooling section in the decarburization section, and completing decarburization of the ceramsite from top to bottom; hot air from the cooling section is subjected to heat compensation and temperature rise to heat ceramsite, the temperature of a ceramsite material layer is 1000-1140 DEG C, and the ceramsite material layer is subjected to heating combustion supporting from top to bottom; and cooling: cooling the roasted ceramsite to 80-100 DEG C. By means of the technical scheme, the treatment scale of the coal gangue ceramsite can be increased, the production cost is effectively reduced, and the ceramsite meets the requirements for decarburization, low water absorption and high strength.

Description

Technical Field

[0001] The present application relates to the technical field of fired ceramsite, and in particular to a high-strength ceramsite made from coal gangue, and a preparation method and application thereof. Background Art

[0002] Coal gangue is solid waste generated during coal mining and washing, mainly composed of minerals such as carbonaceous shale, mudstone, sandstone, etc. Its chemical composition is complex, usually containing high silicon, aluminum, iron and other 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 also may cause environmental pollution problems, such as spontaneous combustion, dust, water pollution, etc. Therefore, how to effectively utilize coal gangue and realize its resource utilization has always been an important topic in the field of environmental protection and comprehensive resource utilization.

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

[0004] However, since gangue ceramsite (especially low-rank coal) releases volatiles and burns to release heat when heated, this stage will cause the gangue ceramsite to easily cause the material layer to heat up rapidly under high-temperature ignition. When the material layer temperature reaches 1100-1200℃, a liquid phase is formed on the surface of the green ball, blocking the micropores on the surface of the green ball, preventing oxygen from oxidizing with the carbon inside the green ball, and the gangue is not completely decarbonized, resulting in a black core. At the same time, the liquid-phase ceramsite will adhere and compact, 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. The above factors make it difficult to obtain high-strength ceramsite. Summary of the invention

[0005] In order to solve the above technical problems, the present application provides a high-strength ceramsite made from coal gangue and a preparation method and application thereof.

[0006] In a first aspect, the present application provides a method for preparing high-strength ceramsite made from coal gangue, which specifically comprises the following steps in sequence: (1) Drying: The ceramsite green balls are fed into the drying section, and the hot air from the roasting section is cooled to 200-250°C and then pressurized and sent to the drying section to dry the green balls. The wind speed of the material layer is 1-2 Nm / s. The ceramsite green balls are made by mixing coal gangue raw materials, binder, sodium rosin acid, and water in a weight ratio of 100:5-25:2-4:2-4, and then roasting. (2) Pyrolysis: The hot air from the decarbonization section is temperature-adjusted to 300-400°C and introduced into the pyrolysis section to remove volatiles from the green balls and ignite them. The hot air generated by the volatiles from the green balls penetrates the material layer and enters the upper cover of the pyrolysis section. The combustible components generated react and release heat and are introduced into the decarbonization section. (3) Decarbonization: The 450-600℃ hot air from the pyrolysis section and the cooling section heats the material layer from top to bottom in the decarbonization section to assist combustion, thus completing the decarbonization of the ceramsite from top to bottom; (4) Calcination: The hot air from the cooling section heats the ceramsite through supplementary heat. The temperature of the ceramsite layer is 950~1140℃. The material layer is heated from top to bottom to assist combustion. After the decarbonized ceramsite is heated in this process section, the solid phase and liquid phase are solidified. (5) Cooling: The calcined ceramsite is cooled to 80-100°C and transported to the silo. The wind speed of the material layer in the cooling section is 1-2 Nm / s. The high-temperature air generated is introduced into the decarbonization section. The oxygen content of the hot air meets the oxygen content requirements of the entire hot air cycle.

[0007] The purpose of this application is to use a pellet static roasting equipment - a belt roasting machine, to provide a process scheme for decarbonizing coal gangue ceramsite to prepare high-strength ceramsite; to increase the processing scale of coal gangue ceramsite, maximize the energy utilization of coal gangue itself, reduce production costs, and enable the ceramsite to meet the decarbonization and high-strength effects required for soil improvement.

[0008] The present invention provides a method for preparing high-strength ceramsite by using coal gangue, which not only meets the process requirements of each stage of green ball roasting, but also effectively utilizes the hot air characteristics of each stage in the roasting process, thereby minimizing external energy consumption. In addition, the method also solves the common problems of agglomeration and incomplete decarbonization in the preparation process of coal gangue ceramsite. Through this scheme, not only can the coal gangue solid waste be effectively treated, but also the low-quality energy in the 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.

[0009] This application adopts static material layer roasting technology, which 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 follows: Figure 1As shown, the hot air process system is personalized and precisely designed according to the characteristics of the raw materials to achieve optimal heat distribution. This method is particularly suitable for the utilization of high-volatile coal gangue, which solves the problem of poor controllability and difficulty in maintaining a stable temperature during the combustion of high-volatile coal gangue. By utilizing its volatile matter to provide the heat required for decarbonization, the early removal of volatiles 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 plant, with the advantages of short process, less heat dissipation, high heat recovery utilization rate, small footprint, high thermal efficiency and low overall energy consumption. In particular, the present application further improves the strength of ceramsite by further accurately designing the process parameters of roasting and cooling, so that the internal and external quality of the ceramsite is uniform and stable.

[0010] The present invention is to prepare ceramsite green balls by roasting coal gangue raw materials, a binder, sodium rosin acid and water. The addition of the binder strengthens the internal structure of the ceramsite, so that it can maintain a stable shape during the roasting process, and improves the strength and durability of the ceramsite. Sodium rosin acid helps to improve the mixing uniformity of the raw materials, making the roasted ceramsite more uniform and dense, making the internal and external quality of the ceramsite uniform and stable, and further improving the strength of the ceramsite.

[0011] Preferably, the ceramsite green balls are prepared by roasting coal gangue raw materials; The performance parameters of the coal gangue raw material are: calorific value is 400-750 kcal / kg, volatile matter is 7-14%, fixed carbon content is 4-8%, green ball thickness is 300-500 mm, green ball particle size is 8-16 mm; The process parameters of roasting are: roasting cycle 140-180 minutes, drying time 30-50 minutes, ignition time 15-25 minutes, decarburization time 50-70 minutes, and cooling time 30-50 minutes.

[0012] Preferably, the ceramsite green ball is prepared by uniformly mixing coal gangue raw material, binder, sodium rosin acid and water in a weight ratio of 100:10-20:2-4:2-4, and then roasting; the roasting process parameters are: roasting cycle 140-180min, drying time 30-50min, ignition time 15-25min, decarbonization time 50-70min, cooling time 30-50min.

[0013] Furthermore, the binder is composed of one or more of clay, bentonite, water glass, starch, sludge, slaked lime, quicklime and cement.

[0014] The materials in this application are green balls (with a certain calorific value) made by processing coal gangue into balls, which are arranged on a static roasting machine. The green balls move with the trolley of the static roasting machine, and are processed by the hot air system in the roasting machine furnace to become finished balls with qualified indicators (cylinder pressure strength>8.5Mpa, water absorption rate<10%), and are unloaded at the tail of the roasting machine.

[0015] Through experimental analysis, it can be known that the present application selects the above-mentioned process to improve the preparation method of expanded clay raw balls, thereby further improving the strength of expanded clay.

[0016] Preferably, the drying includes a first drying stage and a second drying stage; the specific steps are: The ceramsite raw balls are first fed into the drying stage. The 100-150℃ flue gas from the drying stage 2 is pressurized by the drying stage 1 blower and fed into the drying stage 1 bellows to dry the raw balls. The flue gas penetrates the material layer and enters the upper cover. The waste gas from the drying stage 1 upper cover is discharged through the flue gas blower. The green balls heated in the first drying stage enter the second drying stage. The 950-1150℃ high-temperature hot air flue gas from the roasting stage is cooled to 200-250℃ and then pressurized by the drying fan to the second drying stage bellows to heat the green balls and discharge the moisture from them.

[0017] Preferably, the decarburization includes a first decarburization stage and a second decarburization stage; the specific steps are: The green balls enter the first stage of decarburization. The hot flue gas from 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 heat the green balls in the first stage of decarburization. The temperature of the material layer gradually increases. The temperature of the high-temperature hot air flue gas in the wind box of the first stage of decarburization is 450-600℃. The high-temperature hot air flue gas is led out by the decarburization fan and the waste heat is utilized. The green balls enter the second decarbonization stage, and the hot air from the upper part of the pyrolysis stage heats the green balls, and the temperature of the material layer gradually increases; the temperature of the high-temperature hot air flue gas in the wind box of the second decarbonization stage is 450-600℃; the high-temperature hot air flue gas is drawn out through the pyrolysis blower and the temperature is adjusted to 300-400℃ before entering the pyrolysis stage wind box.

[0018] Preferably, in the roasting stage, the temperature of the ceramsite layer is 1110-1140°C, the temperature of the flue gas in the wind box is 1100-1150°C, and the high-temperature hot air flue gas is cooled and then used in the drying stage.

[0019] Through experimental analysis, it can be known that the application chooses to control the roasting process parameters to the above conditions, which can further improve the strength performance of ceramsite.

[0020] Preferably, the cooling includes cooling stage one and cooling stage two; the specific steps are: The ceramsite material layer that has been roasted enters the first cooling stage. The low-temperature hot air of 260-340℃ from the furnace cover of the second cooling stage is fed into the first cooling stage wind box through the first cooling fan to cool the material layer and heat the flue gas at the same time. The wind box temperature is 260-340℃. The material layer enters the second cooling stage, and fresh air cools down the expanded clay and heats up the air through the second cooling fan. The flue gas temperature is 260-340℃. After cooling, the expanded clay with a temperature below 100℃ is transported to the silo.

[0021] Preferably, the cooling includes cooling stage one and cooling stage two; the specific steps are: The ceramsite material layer that has been roasted enters the first cooling stage. The low-temperature hot air of 300-330℃ from the furnace cover of the second cooling stage is fed into the first cooling stage wind box through the first cooling fan to cool the material layer and heat the flue gas at the same time. The wind box temperature is 300-330℃. The material layer enters the second cooling stage, and fresh air cools down the expanded clay and heats up the air through the second cooling fan. The flue gas temperature is 300-330℃. After cooling, the expanded clay with a temperature below 100℃ is transported to the silo.

[0022] Through experimental analysis, it can be known that the present application chooses to control the cooling process parameters to the above conditions, which can further improve the strength performance of ceramsite.

[0023] In a second aspect, the present application provides a high-strength expanded clay made from coal gangue, which is prepared using the above-mentioned preparation method.

[0024] Preferably, the high-strength ceramsite product has a fixed carbon content of <1.0%, a water absorption rate of ≤10%, and a cylinder pressure strength of ≥8.5MPa.

[0025] In a third aspect, the present application provides the application of the above-mentioned high-strength expanded clay made from coal gangue in sand and gravel aggregates, soil improvement or water treatment.

[0026] In summary, the technical solution of this application has the following effects: The process of the present application is realized by static roasting equipment, which integrates drying, pyrolysis, decarbonization, roasting and cooling into one equipment, which is arranged in a closed factory building. Due to its short process, less heat dissipation, high heat recovery utilization rate, small footprint, high thermal efficiency and low overall energy consumption, it is suitable for the heating treatment process of preparing ceramsite from coal gangue, especially the treatment of coal gangue with high volatility classification.

[0027] The process route provided in this application can provide appropriate amount of heat and temperature increase according to different product requirements through the heat supplement combustion system, which can make the expanded clay barrel pressure strength reach >8.5Mpa; the starting burner is turned off after the production line is started and does not participate in the system operation; the exhaust gas in the furnace reaches 500-550℃ and can be used as waste heat.

[0028] The present application further improves the strength of ceramsite by improving the preparation method of ceramsite raw balls. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a process flow chart for preparing high-strength ceramsite from coal gangue in this application.

[0030] Figure 2 This is a process flow chart for preparing high-strength expanded clay from coal gangue in Example 1 of the present application. DETAILED DESCRIPTION

[0031] The present application is further described in detail below in conjunction with examples, comparative examples and performance testing experiments. These examples should not be construed as limiting the scope of protection claimed in the present application. Example Example 1

[0032] Example 1 provides a method for preparing high-strength expanded clay from coal gangue.

[0033] The process flow chart of preparing high-strength ceramsite from coal gangue in this embodiment is as follows Figure 2 The specific preparation method is as follows.

[0034] In this embodiment, the coal gangue raw material has a calorific value of 515 kcal / kg, a volatile matter of 10.8%, a fixed carbon content of 6.1%, and a green ball particle size of 8 to 14 mm; the coal gangue raw material, quicklime binder, sodium rosin acid, and water are uniformly mixed in a weight ratio of 100:15:3:3, and then roasted in a roaster to obtain ceramsite green balls; the roasting process parameters are: roasting cycle 160 min, drying time 40 min, ignition time 20 min, decarbonization time 60 min, and cooling time 40 min.

[0035] (1) Drying: Drying includes drying stage 1 and drying stage 2; the specific steps are as follows: The ceramsite raw balls are fed into the first drying stage, and the material layer thickness is 340mm. The 124℃ flue gas from the second drying stage is pressurized by the first drying blower and fed into the first drying blower to dry the raw balls. The flue gas penetrates the material layer and enters the upper cover; the 93℃ waste gas from the first drying upper cover is discharged through the flue gas blower; the wind speed of the material layer is 1.5Nm / s.

[0036] The green balls heated in the first drying stage enter the second drying stage. The 983℃ hot air flue gas from the roasting stage wind box is cooled to 243℃ and then pressurized by the drying fan to the second drying stage wind box to heat the green balls and discharge the moisture in the green balls. The moisture in the green balls is 0.7%; the 141℃ flue gas from the upper cover of the second drying stage is pressurized by the first drying fan and fed into the first drying stage wind box. The wind speed of the material layer is 1.5Nm / s.

[0037] (2) Pyrolysis: The green balls after dehydration in the second drying stage are fed into the pyrolysis stage. The 472°C high-temperature flue gas from the second decarbonization stage wind box is adjusted to 381°C and introduced into the pyrolysis stage wind box by the pyrolysis blower to heat and pyrolyze the green balls. Under the action of high temperature, the volatile matter in the green balls begins to release and the reaction releases heat. The hot air penetrates the material layer and enters the upper cover of the pyrolysis stage. 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 section and passes through the furnace cover to the upper part of the first and second decarbonization stages; the wind speed of the material layer is 1.3Nm / s.

[0038] (3) Decarburization: Decarburization includes decarburization stage 1 and decarburization stage 2. The specific steps are as follows: The green balls enter the first stage of decarbonization. In the first stage of decarbonization, the 461℃ hot air from the upper part of the pyrolysis section heats the green balls, and the temperature of the material layer gradually increases. The flue gas temperature in the first stage of decarbonization wind box is 511℃. The high-temperature flue gas is drawn out by the decarbonization fan and the waste heat is utilized.

[0039] The green balls enter the second decarbonization stage. In the second decarbonization stage, the 461℃ hot air from the upper part of the pyrolysis stage heats the green balls, and the temperature of the material layer gradually increases. The flue gas temperature in the wind box of the second decarbonization stage is 472℃. The high-temperature flue gas is drawn out through the pyrolysis blower and the temperature is adjusted to 381℃ before entering the wind box of the pyrolysis stage.

[0040] (4) Calcination: The hot air from the upper part of the cooling section heats the ceramsite through supplementary heat. The temperature of the ceramsite layer is 1096°C. The material layer is heated from top to bottom to assist combustion. After the decarbonized ceramsite is heated in this process section, the solid and liquid phases are consolidated, further improving the strength of the ceramsite. At the same time, the quality of the inside and outside of the ceramsite is uniform and stable. The flue gas temperature in the bellows of the calcination section is 983°C. The high-temperature hot air flue gas is cooled to 243°C and then used in the drying section to save energy.

[0041] (5) Cooling: including cooling stage 1 and cooling stage 2; the specific steps are as follows: The material layer enters the first cooling stage. The 291℃ low-temperature hot air from the second cooling stage furnace cover is fed into the first cooling stage wind box through the first cooling fan to cool the 973℃ material layer and heat up the flue gas at the same time. The wind box temperature is 275℃.

[0042] The material layer enters the second cooling stage. 25℃ fresh air cools the ceramsite and heats the air through the second cooling fan, and the flue gas temperature is 291℃. The cooled ceramsite is transported to the silo at 95℃.

[0043] The ceramsite product prepared in this embodiment 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 pressure strength of 8.92 MPa. The material layer is not compacted, and the production is smooth. Example 2

[0044] Example 2 provides a high-strength expanded clay made from coal gangue and a preparation method thereof.

[0045] The ceramsite raw balls entering the drying stage in this embodiment are the same as those in Example 1.

[0046] The method for preparing high-strength ceramsite from coal gangue in this embodiment is different from that in Embodiment 1 in that the roasting section in step (4) and the cooling section in step (5) are different; the details are as follows.

[0047] (4) Calcination: The hot air from the upper part of the cooling section heats the ceramsite through supplementary heat. The temperature of the ceramsite layer is 1123°C. The material layer is heated from top to bottom to assist combustion. After the decarbonized ceramsite is heated in this process section, the solid and liquid phases are consolidated, further improving the strength of the ceramsite. At the same time, the quality of the inside and outside of the ceramsite is uniform and stable. The flue gas temperature in the bellows of the calcining section is 1035°C. The high-temperature hot air flue gas is cooled to 243°C and then used in the drying section to save energy.

[0048] (5) Cooling: including cooling stage 1 and cooling stage 2; the specific steps are as follows: The material layer enters the first cooling stage. The 320℃ low-temperature hot air from the second cooling stage furnace cover is fed into the first cooling stage wind box through the first cooling fan to cool the 1008℃ material layer and heat up the flue gas at the same time. The wind box temperature is 311℃.

[0049] The material layer enters the second cooling stage. 25℃ fresh air cools the ceramsite and heats the air through the second cooling fan, and the flue gas temperature is 320℃. The cooled ceramsite is transported to the silo at 95℃.

[0050] The ceramsite product prepared in this embodiment 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 pressure strength of 11.78 MPa. The material layer is not compacted, and the production is smooth. Example 3

[0051] Example 3 provides a method for preparing high-strength expanded clay from coal gangue.

[0052] The ceramsite raw balls entering the drying stage in this embodiment are the same as those in Example 1.

[0053] The method for preparing high-strength ceramsite from coal gangue in this embodiment is different from that in Embodiment 1 in that the roasting section and the cooling section of step (3) are different; the details are as follows.

[0054] (4) Calcination: The hot air from the upper part of the cooling section heats the ceramsite through supplementary heat. The temperature of the ceramsite layer is 1140℃. The material layer is heated from top to bottom to assist combustion. After the decarbonized ceramsite is heated in this process section, the solid and liquid phases are consolidated, further improving the strength of the ceramsite. At the same time, the quality of the inside and outside of the ceramsite is uniform and stable. The flue gas temperature in the bellows of the calcination section is 1083℃. The high-temperature hot air flue gas is cooled to 243℃ and then used in the drying section to save energy.

[0055] (5) Cooling: including cooling stage 1 and cooling stage 2; the specific steps are as follows: The material layer enters the first cooling stage. The 345℃ low-temperature hot air from the second cooling stage furnace cover is fed into the first cooling stage wind box through the first cooling fan to cool the 1012℃ material layer and heat up the flue gas at the same time. The wind box temperature is 323℃.

[0056] The material layer enters the second cooling stage. 25℃ fresh air cools the ceramsite and heats the air through the second cooling fan, and the flue gas temperature is 345℃. The cooled ceramsite is transported to the silo at 95℃.

[0057] 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 pressure strength of 9.82 MPa. The material layer is not compacted, and the production is smooth. Embodiment 4-9

[0058] Examples 4-9 respectively provide a method for preparing high-strength expanded clay from coal gangue and a preparation method thereof.

[0059] The difference between the above embodiment and embodiment 2 is that the ceramsite raw balls entering the drying section are different.

[0060] In Example 4, ceramsite green balls are prepared by mixing coal gangue raw material, starch binder and water in a weight ratio of 100:15:3 and then roasting. The ceramsite product prepared in this example 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 pressure strength of 8.51 MPa.

[0061] In Example 5, ceramsite green balls are prepared by mixing coal gangue raw material, bentonite binder and water in a weight ratio of 100:15:3 and then 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 cylinder pressure strength of 8.73 MPa.

[0062] In Example 6, ceramsite green balls are prepared by mixing coal gangue raw material, quicklime binder, sodium rosinate and water in a weight ratio of 100:5:3:3 and then 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 cylinder pressure strength of 8.86 MPa.

[0063] In Example 7, the ceramsite green ball is prepared by mixing coal gangue raw material, quicklime binder, sodium rosinate and water in a weight ratio of 100:25:1:3 and then 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 cylinder pressure strength of 9.01 MPa.

[0064] In Example 8, the ceramsite green ball is prepared by mixing coal gangue raw material, quicklime binder, sodium rosinate and water in a weight ratio of 100:10:4:3 and then 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 cylinder pressure strength of 11.63 MPa.

[0065] In Example 9, ceramsite green balls are prepared by mixing coal gangue raw material, quicklime binder, sodium rosinate, and water in a weight ratio of 100:20:2:3 and then 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 cylinder pressure strength of 11.24 MPa.

[0066] The remaining process parameters in the above embodiment are the same as those in Embodiment 2. Comparative Example Comparative Example 1

[0067] This comparative example provides a method for preparing ceramsite from coal gangue.

[0068] The ceramsite raw balls entering the drying stage in this comparative example are the same as those in Example 2.

[0069] The method for preparing ceramsite from coal gangue in this comparative example is different from that in Example 2 in that the decarburization step (3) and the calcination step (4) are different, as shown below.

[0070] (3) Decarburization: Decarburization includes decarburization stage 1, decarburization stage 2 and decarburization stage 3. The specific steps are as follows: The green balls enter the first stage of decarbonization. In the first stage of decarbonization, the 461℃ hot air from the upper part of the pyrolysis section heats the green balls, and the temperature of the material layer gradually increases. The flue gas temperature in the first stage of decarbonization wind box is 511℃. The high-temperature flue gas is drawn out by the decarbonization fan and the waste heat is utilized.

[0071] The green balls enter the second decarbonization stage. In the second decarbonization stage, the 461℃ hot air from the upper part of the pyrolysis stage heats the green balls, and the temperature of the material layer gradually increases. The flue gas temperature in the wind box of the second decarbonization stage is 472℃. The high-temperature flue gas is drawn out through the pyrolysis blower and the temperature is adjusted to 381℃ before entering the wind box of the pyrolysis stage.

[0072] 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 heats the ceramsite after supplementary heat, and the temperature of the ceramsite layer further rises to 705℃. The flue gas temperature in the wind box of the third stage of decarbonization is 752℃.

[0073] (4) Calcination: The hot air from the upper part of the cooling section heats the ceramsite through supplementary heat. The temperature of the ceramsite layer is 925°C. The material layer is heated from top to bottom to assist combustion. After the decarbonized ceramsite is heated in this process section, the solid phase and liquid phase are consolidated, further improving the strength of the ceramsite. At the same time, the quality of the inside and outside of the ceramsite is uniform and stable. The flue gas temperature in the bellows of the calcination section is 913°C. The high-temperature hot air flue gas is cooled to 241°C and then used in the drying section to save energy.

[0074] The ceramsite product prepared in this comparative example has a fixed carbon content of 1.28%, a calorific value of 42.4 kcal / kg, a water absorption rate of 10.1%, and a cylinder pressure strength of 6.5 MPa; the material layer has no compaction 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

[0075] This comparative example provides a method for preparing ceramsite from coal gangue.

[0076] The ceramsite raw balls entering the drying stage in this comparative example are the same as those in Example 1.

[0077] The method for preparing ceramsite from coal gangue in this comparative example is different from that in Example 1 in that the roasting section in step (4) and the cooling section in step (5) are different; the details are as follows.

[0078] (4) Calcination: The hot air from the upper part of the cooling section heats the ceramsite through supplementary heat. The temperature of the ceramsite layer is 1182°C. The material layer is heated from top to bottom to assist combustion. After the decarbonized ceramsite is heated in this process section, the solid and liquid phases are consolidated, further improving the strength of the ceramsite. At the same time, the quality of the inside and outside of the ceramsite is uniform and stable. The flue gas temperature in the bellows of the calcining section is 1108°C. The high-temperature hot air flue gas is cooled to 248°C and then used in the drying section to save energy.

[0079] (5) Cooling: including cooling stage 1 and cooling stage 2; the specific steps are as follows: The material layer enters the first cooling stage. The 246℃ low-temperature hot air from the second cooling stage furnace cover is fed into the first cooling stage wind box through the first cooling fan to cool the 1120℃ material layer and heat up the flue gas at the same time. The wind box temperature is 215℃.

[0080] The material layer enters the second cooling stage. 25℃ fresh air cools the ceramsite and heats the air through the second cooling fan, and the flue gas temperature is 246℃. The cooled ceramsite is transported to the silo at 95℃.

[0081] The ceramsite product prepared in this comparative example has a fixed carbon content of 0.72%, a calorific value of 34.2 kcal / kg, a water absorption rate of 7.9%, and a cylinder pressure strength of 6.9 MPa. The material layer is not compacted 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

[0082] This comparative example provides a method for preparing ceramsite from coal gangue.

[0083] The ceramsite raw balls entering the drying stage in this comparative example are the same as those in Example 1.

[0084] The method for preparing ceramsite from coal gangue in this comparative example is different from that in Example 1 in that the roasting section in step (4) and the cooling section in step (5) are different; the details are as follows.

[0085] (4) Calcination: The hot air from the upper part of the cooling section heats the ceramsite through supplementary heat. The temperature of the ceramsite layer is 932°C. The material layer is heated from top to bottom to assist combustion. After the decarbonized ceramsite is heated in this process section, the solid and liquid phases are consolidated, further improving the strength of the ceramsite. At the same time, the quality of the inside and outside of the ceramsite is uniform and stable. The flue gas temperature in the bellows of the calcination section is 989°C. The high-temperature hot air flue gas is cooled to 248°C and then used in the drying section to save energy.

[0086] (5) Cooling: including cooling stage 1 and cooling stage 2; the specific steps are as follows: The material layer enters the first cooling stage. The 392℃ low-temperature hot air from the second cooling stage furnace cover is fed into the first cooling stage wind box through the first cooling fan to cool the 908℃ material layer and heat up the flue gas at the same time. The wind box temperature is 375℃.

[0087] The material layer enters the second cooling stage. 25℃ fresh air cools the ceramsite and heats the air through the second cooling fan, and the flue gas temperature is 392℃. The cooled ceramsite is transported to the silo at 95℃.

[0088] The ceramsite product prepared in this comparative example has a fixed carbon content of 1.04%, a calorific value of 40.5 kcal / kg, a water absorption rate of 10.2%, and a cylinder pressure strength of 5.9 MPa. The material layer is not compacted 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

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

[0090] The difference between this comparative example and Example 2 is that the ceramsite raw balls entering the drying section are different.

[0091] In Comparative Example 4, ceramsite green balls are prepared by roasting coal gangue raw materials. The ceramsite product prepared in this example 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 pressure strength of 8.51 MPa.

[0092] The remaining process parameters in this comparative example are the same as those in Example 2.

[0093] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing high-strength ceramsite made from coal gangue, characterized in that: Specifically, the following steps are performed in sequence: (1) Drying: The ceramsite green balls are fed into the drying section, and the hot air from the roasting section is cooled to 200-250°C and then pressurized and sent to the drying section to dry the green balls. The wind speed of the material layer is 1-2 Nm / s. The ceramsite green balls are made by mixing coal gangue raw materials, binder, sodium rosin acid, and water in a weight ratio of 100:5-25:2-4:2-4, and then roasting. (2) Pyrolysis: The hot air from the decarbonization section is temperature-adjusted to 300-400°C and introduced into the pyrolysis section to remove volatiles from the green balls and ignite them. The hot air generated by the volatiles from the green balls penetrates the material layer and enters the upper cover of the pyrolysis section. The combustible components generated react and release heat and are introduced into the decarbonization section. (3) Decarbonization: The 450-600℃ hot air from the pyrolysis section and the cooling section heats the material layer from top to bottom in the decarbonization section to assist combustion, thus completing the decarbonization of the ceramsite from top to bottom; (4) Calcination: The hot air from the cooling section heats the ceramsite through supplementary heat. The temperature of the ceramsite layer is 950~1140℃. The material layer is heated from top to bottom to assist combustion. After the decarbonized ceramsite is heated in this process section, the solid phase and liquid phase are solidified. (5) Cooling: The calcined ceramsite is cooled to 80-100°C and transported to the silo. The wind speed of the material layer in the cooling section is 1-2 Nm / s. The high-temperature air generated is introduced into the decarbonization section. The oxygen content of the hot air meets the oxygen content requirements of the entire hot air cycle.

2. The method for preparing high-strength ceramsite made from coal gangue according to claim 1, characterized in that: The ceramsite green balls are prepared by roasting coal gangue raw materials; the performance parameters of the coal gangue raw materials are: calorific value of 400-750kcal / kg, volatile matter of 7-14%, fixed carbon content of 4-8%, green ball thickness of 300-500mm, and green ball particle size of 8-16mm; the roasting process parameters are: roasting cycle of 140-180min, drying time of 30-50min, ignition time of 15-25min, decarbonization time of 50-70min, and cooling time of 30-50min.

3. The method for preparing high-strength ceramsite made from coal gangue according to claim 2, characterized in that: The ceramsite green ball is prepared by uniformly mixing coal gangue raw material, binder, sodium rosin acid and water in a weight ratio of 100:10-20:2-4:2-4, and then roasting. The binder is composed of one or more of clay, bentonite, water glass, starch, sludge, slaked lime, quicklime and cement; the roasting process parameters are: roasting cycle 140-180 minutes, drying time 30-50 minutes, ignition time 15-25 minutes, decarbonization time 50-70 minutes, cooling time 30-50 minutes.

4. The method for preparing high-strength ceramsite made from coal gangue according to claim 1, characterized in that: The drying process includes a first drying stage and a second drying stage; the specific steps are: The ceramsite raw balls are first fed into the drying stage. The 100-150℃ flue gas from the drying stage 2 is pressurized by the drying stage 1 blower and fed into the drying stage 1 bellows to dry the raw balls. The flue gas penetrates the material layer and enters the upper cover. The waste gas from the drying stage 1 upper cover is discharged through the flue gas blower. The green balls heated in the first drying stage enter the second drying stage. The 950-1150℃ high-temperature hot air flue gas from the roasting stage is cooled to 200-250℃ and then pressurized by the drying fan to the second drying stage bellows to heat the green balls and discharge the moisture from them.

5. The method for preparing high-strength ceramsite made from coal gangue according to claim 1, characterized in that: The decarburization includes a first decarburization stage and a second decarburization stage; the specific steps are: The green balls enter the first stage of decarburization. The hot flue gas from 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 heat the green balls in the first stage of decarburization. The temperature of the material layer gradually increases. The temperature of the high-temperature hot air flue gas in the wind box of the first stage of decarburization is 450-600℃. The high-temperature hot air flue gas is led out by the decarburization fan and the waste heat is utilized. The green balls enter the second decarbonization stage, and the hot air from the upper part of the pyrolysis stage heats the green balls, and the temperature of the material layer gradually increases; the temperature of the high-temperature hot air flue gas in the wind box of the second decarbonization stage is 450-600℃; the high-temperature hot air flue gas is drawn out through the pyrolysis blower and the temperature is adjusted to 300-400℃ before entering the pyrolysis stage wind box.

6. The method for preparing high-strength ceramsite made from coal gangue according to claim 1, characterized in that: In the roasting stage, the temperature of the ceramsite layer is 1110-1140°C, the temperature of the flue gas in the wind box is 1100-1150°C, and the high-temperature hot air flue gas is cooled and then used in the drying stage.

7. The method for preparing high-strength ceramsite made from coal gangue according to claim 1, characterized in that: The cooling includes cooling stage one and cooling stage two; the specific steps are: The ceramsite material layer that has been roasted enters the first cooling stage. The low-temperature hot air of 260-340℃ from the furnace cover of the second cooling stage is fed into the first cooling stage wind box through the first cooling fan to cool the material layer and heat the flue gas at the same time. The wind box temperature is 260-340℃. The material layer enters the second cooling stage, and fresh air cools down the expanded clay and heats up the air through the second cooling fan. The flue gas temperature is 260-340℃. After cooling, the expanded clay with a temperature below 100℃ is transported to the silo.

8. A high-strength ceramsite made from coal gangue, characterized in that: The preparation method is described in any one of claims 1 to 7.

9. The high-strength ceramsite made from coal gangue according to claim 8, characterized in that: The high-strength expanded clay product has a fixed carbon content of <1.0%, a water absorption rate of ≤10%, and a cylinder pressure strength of ≥8.5MPa.

10. Use of the high-strength ceramsite made from coal gangue according to any one of claims 8 to 9 in sandstone aggregate, soil improvement or water treatment.

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