Process method for producing coal gangue ceramsite by microwave drying

Abstract

This application relates to the field of ceramsite, and specifically discloses a process method for producing coal gangue ceramsite by microwave drying, which includes the following steps: Coal gangue pretreatment: Granulate coal gangue powder and bicarbonate under the action of a wetting agent to form green coal gangue balls, and dry the green coal gangue balls with microwave; 90 - 100 parts of coal gangue powder, 1 - 4 parts of bicarbonate, 3 - 8 parts of wetting agent; The wetting agent includes raw materials in the following weight parts: 1 - 3 parts of polyvinyl alcohol, 1.5 - 4 parts of sodium carboxymethylcellulose, 0.5 - 1 part of surfactant; Coal gangue ceramsite preparation: After pyrolysis, decarbonization, sintering, and cooling of the dried green coal gangue balls, ceramsite is formed; Pyrolysis includes: Gradient oxygen-controlled pyrolysis of the dried green coal gangue balls, the pyrolysis temperature is 250 - 450 °C, and at the same time, air flow is intermittently introduced to impact the material layer. This method can significantly reduce the bursting rate of ceramsite, the surface of the ceramsite has no cracks, the strength is high, and the product quality is excellent.

Description

Technical Field

[0001] The present application relates to the field of coal gangue ceramsite, and more specifically, it relates to a process method for producing coal gangue ceramsite by microwave drying. Background Art

[0002] Coal gangue is an industrial solid waste generated during the production and processing of coal. The annual discharge volume is large and the annual discharge rate continues to increase. It is a solid waste with a very large stock in China. For a long time, coal gangue has mainly been stored in piles, which not only occupies a large amount of land resources, but also produces a large amount of sulfur dioxide, carbon dioxide and dust when coal gangue burns spontaneously, polluting the local environment.

[0003] Producing ceramsite is an important way to recycle coal gangue. At present, the mainstream processes for preparing ceramsite from coal gangue include the rotary kiln process and the roasting process. During the production of coal gangue ceramsite, since the green balls of coal gangue contain a certain amount of moisture, drying and dehydration are required. Generally, hot air drying is used. The hot air introduced is not easy to quickly penetrate into the interior of the green balls, and it is easy to form a high-temperature zone on the surface of the coal gangue green balls, resulting in the bursting of the coal gangue green balls due to excessive temperature difference between the inside and outside. The bursting substances cause a sudden drop in the porosity of the material layer, and the deterioration of the air permeability of the material layer further leads to heat accumulation. When it comes to the pyrolysis and decarburization processes, it is more difficult for the high-temperature gas to disperse, resulting in the appearance of a liquid phase on the surface of the green balls, causing the material layer to adhere and agglomerate, seriously affecting the production of coal gangue. The produced ceramsite not only has a high bursting rate, but also has a large number of cracks on the surface of the ceramsite, low strength, and poor product quality. Summary of the Invention

[0004] The present application provides a process method for producing coal gangue ceramsite by microwave drying, which can significantly reduce the bursting rate of ceramsite, and the obtained ceramsite has no cracks on the surface, high cylinder compressive strength, and excellent product quality.

[0005] The process method for producing coal gangue ceramsite by microwave drying provided by the present application adopts the following technical solutions:

[0006] A process method for producing coal gangue ceramsite by microwave drying, comprising the following steps:

[0007] Pretreatment of coal gangue: Granulating coal gangue powder and bicarbonate under the action of a wetting agent to form coal gangue green balls, and drying the coal gangue green balls by microwave; calculated by weight, 90 - 100 parts of coal gangue powder, 1 - 4 parts of bicarbonate, and 3 - 8 parts of wetting agent;

[0008] The wetting agent comprises the following raw materials in parts by weight: 1 - 3 parts of polyvinyl alcohol, 1.5 - 4 parts of sodium carboxymethylcellulose, and 0.5 - 1 part of surfactant;

[0009] Preparation of coal gangue ceramsite: Forming ceramsite by subjecting the dried coal gangue green balls to pyrolysis, decarburization, sintering, and cooling;

[0010] The pyrolysis includes: subjecting the dried green balls of coal gangue to gradient-controlled oxygen pyrolysis, and intermittently introducing an air flow to impact the material layer;

[0011] The gradient-controlled oxygen pyrolysis includes a first-stage pyrolysis and a second-stage pyrolysis. The oxygen concentration in the first-stage pyrolysis is 12-18%, the pyrolysis temperature is 250-350 °C, and the pyrolysis time is 10-20 min; the oxygen concentration in the second-stage pyrolysis is 7-11%, the pyrolysis temperature is 350-450 °C, and the pyrolysis time is 10-15 min.

[0012] Further, the particle size of the coal gangue powder is less than 2 mm, and the particle size of the bicarbonate is less than 100 μm.

[0013] Further, the pressure of the introduced air flow is 1-1.5 kPa.

[0014] By adopting the above technical solution, granulation is carried out with bicarbonate and coal gangue powder under the action of a wetting agent. The bicarbonate is thermally unstable and decomposes to produce carbonate, carbon dioxide and water vapor. At this time, not only can internal connected pores be formed to accelerate the uniform penetration of microwave heat through the green balls of coal gangue, but the generated carbon dioxide can also promote gas flow and relieve the heat accumulation on the surface of the green balls, avoiding the cracking of the green balls of coal gangue due to excessive temperature difference between the inside and outside. At the same time, the generated water vapor and the wetting agent have a good wetting effect on the surface of the green balls of coal gangue, relieving the surface hardening speed and effectively reducing the phenomenon of cracks on the surface of the green balls, significantly improving the product quality. The carbonate generated by the thermal decomposition of the bicarbonate can also react with other minerals in the coal gangue in the subsequent process, further improving the strength and stability of the ceramsite product.

[0015] Selecting polyvinyl alcohol, sodium carboxymethyl cellulose and a surfactant for compounding to obtain a wetting agent can not only reduce the surface tension between particles, enhance the bonding effect between particles, be conducive to the formation of dense spherical particles, improve the mechanical strength of the green balls of coal gangue, but also effectively inhibit the cracking of the green balls of coal gangue, reduce the appearance of cracks on the surface of the green balls, and improve the comprehensive quality of the ceramsite product.

[0016] Using microwave drying can selectively heat water molecules, giving priority to acting on water molecules, further reducing the moisture content of the green balls of coal gangue. Moreover, microwave has strong penetrability, which can excite the internal molecular vibration of the material to generate heat, improve the reactivity of the subsequent pyrolysis reaction, achieve bulk heating, avoid surface overheating, and have a small temperature gradient between the inside and outside, making the green balls of coal gangue heated more evenly, significantly reducing the risk of cracking of the ceramsite, and the wetting agent can also effectively reduce the phenomenon of cracks on the surface of the ceramsite, improving the comprehensive quality of the ceramsite product.

[0017] During the pyrolysis stage, an air stream is introduced to impact the material layer. This can break the crust on the surface of the green balls, improve the heat penetration rate, vibrate the green ball particles with the air stream to ensure uniform distribution of the green balls, and avoid the hardening of the material layer or heat accumulation. The intermittently introduced air stream is usually targeted at areas prone to heat accumulation. The introduction of the air stream can increase the ventilation of the material layer, relieve the local high temperature caused by heat accumulation, prevent the formation of liquid phase on the surface of the green balls, avoid adhesion or even melting, and further ensure that the porosity of the material layer is within a reasonable range, with the porosity > 0.3.

[0018] In the first stage of pyrolysis, it is mainly the oxidation reaction of pyrite in coal gangue, the dehydration reaction of clay minerals, and the low-temperature oxidation of carbonaceous substances. The heat released by the reaction is not significant. Sufficient oxygen concentration promotes the full progress of each reaction, and the coal gangue is pyrolyzed sufficiently. In the second stage of pyrolysis, it is mainly the deep oxidation and phase change of pyrite, the destruction of the clay mineral structure, and the high-temperature oxidation of carbonaceous substances. In this stage, the oxygen concentration is reduced to slow down the reaction rate, facilitate the removal of a large amount of heat released, avoid excessive temperature rise and local heat accumulation, and avoid the formation of liquid phase on the surface of the green balls, thus avoiding the hardening and adhesion of the material layer.

[0019] Gradient-controlled oxygen pyrolysis can be used to synergistically achieve pore grading regulation with bicarbonate. The carbon dioxide generated by the decomposition of bicarbonate forms micropores in the system. The gases generated by the carbon oxidation in the first and second stages of pyrolysis further expand the pores to form a through-pore network. After the pores of the green balls are fully formed, in the decarbonization stage, high temperature and sufficient oxygen content are used. Oxygen quickly diffuses to the core, and the fixed carbon burns continuously and controllably, accelerating decarbonization, completely removing the internal carbon, optimizing the pore structure, and being able to balance combustion and heat dissipation at the same time. With the above scheme, there is no hardening of the material layer, the carbon residue is extremely low, and the product quality is effectively improved.

[0020] After adopting this process, the porosity of the material layer can be maintained at 30 - 40%. The good air permeability enables the heat to be dissipated quickly and completely, effectively avoiding the accumulation of high-temperature gases, ensuring the thorough decarbonization process, enabling the production to proceed continuously and stably, and significantly improving the production efficiency and product quality of coal gangue ceramsite.

[0021] Preferably, the surfactant is at least one of sodium dodecylbenzenesulfonate and Tween-80.

[0022] Furthermore, the surfactant is preferably a mixture of sodium dodecylbenzenesulfonate and Tween-80 with a mass ratio of 1:(0.5 - 1).

[0023] By adopting the above technical scheme, the selection of the surfactant is optimized, promoting the adhesion and shaping between particles and improving the quality of coal gangue green balls.

[0024] Preferably, the bicarbonate includes one of magnesium bicarbonate, sodium bicarbonate, and potassium bicarbonate.

[0025] Furthermore, it is preferred that the bicarbonate is magnesium bicarbonate.

[0026] Preferably, the power density of the microwave is 1.5 - 2.5 W / g, and the green pellets of coal gangue are dried and preheated to 200 - 250 °C.

[0027] Furthermore, the moisture content of the green pellets of coal gangue after microwave drying is reduced to less than 2%.

[0028] By adopting the above technical solution, optimizing the conditions of the microwave, the heating speed is fast, the efficiency is high, almost no additional heat loss is generated during the process, the energy utilization rate is high, the temperature gradient is effectively eliminated, the moisture inside the green pellets of coal gangue is further removed, and the pyrolysis reaction activity of the subsequent green pellets of coal gangue is enhanced.

[0029] Furthermore, the decarbonization includes: under the conditions that the temperature of the pyrolyzed green pellets of coal gangue is 500 - 700 °C and the oxygen concentration is 11 - 15%, decarbonization is carried out for 40 - 60 min.

[0030] Preferably, the sintering conditions are: temperature 900 - 1200 °C, sintering for 10 - 15 min.

[0031] Preferably, the particle size of the green pellets of coal gangue is 8 - 25 mm.

[0032] In summary, the present application has the following beneficial effects:

[0033] 1. Granulation is carried out by using bicarbonate and coal gangue powder under the action of a wetting agent. The bicarbonate is thermally unstable and decomposes to produce carbonate, carbon dioxide and water vapor. At this time, not only can internal connected pores be formed to accelerate the uniform penetration of heat through the green pellet particles of coal gangue, but the generated carbon dioxide can also promote gas flow and relieve the heat accumulation on the surface of the green pellets, avoiding the bursting of the green pellets of coal gangue due to excessive internal and external temperature differences. At the same time, the generated water vapor and the wetting agent have a good wetting effect on the surface of the green pellets of coal gangue, relieve the surface hardening speed, effectively reduce the phenomenon of cracks on the surface of the green pellets, and significantly improve the product quality.

[0034] 2. The gradient-controlled oxygen pyrolysis can cooperate with the bicarbonate to realize the hierarchical regulation of pores. The carbon dioxide generated by the decomposition of the bicarbonate forms micropores in the system, and the gases generated by the carbon oxidation in the first stage and the second stage of pyrolysis further expand the pores to form a through-pore network. After the pores of the green pellets are fully formed, in the decarbonization stage, high temperature and sufficient oxygen content are adopted, and oxygen quickly diffuses to the core, and the fixed carbon burns continuously and stably and controllably, accelerating decarbonization, thoroughly removing the internal carbon, and the pore structure is optimized. At the same time, the balance between combustion and heat dissipation can be achieved, the material layer is not caked during the whole process, the carbon residue is extremely low, and the product quality is effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the diagram of the ceramsite product of Embodiment 1 of this application. Detailed implementation manners

[0036] The following will describe the implementation manners of the present invention in detail in combination with embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For the specific conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0037] Embodiment 1

[0038] A process method for producing coal gangue ceramsite by microwave drying includes the following steps:

[0039] Pretreatment of coal gangue: Granulate coal gangue powder with a particle size less than 2 mm (SiO2 52%, Al2O3 28%, calorific value 550 kcal / kg, fixed carbon content 6%, volatile matter 11%) and magnesium bicarbonate with a particle size less than 100 μm under the action of a wetting agent to form coal gangue green balls. The coal gangue green balls are passed through a double-layer sieve (upper sieve hole 14 mm, lower sieve hole 8 mm) to remove large-particle-size coal gangue green balls and coal gangue powder, effectively ensuring the quality of the coal gangue green balls; Use microwave with a power density of 2 W / g to dry the coal gangue green balls and preheat them to 250 °C, and the moisture content of the coal gangue green balls drops to 1.5%; By weight, 100 parts of coal gangue powder, 3 parts of magnesium bicarbonate, and 7 parts of wetting agent;

[0040] The wetting agent includes the following raw materials by weight: 2 parts of polyvinyl alcohol, 3 parts of sodium carboxymethyl cellulose, and 0.8 part of surfactant. The surfactant is sodium dodecylbenzenesulfonate and Tween-80 with a mass ratio of 1:1;

[0041] Preparation of coal gangue ceramsite: Perform gradient-controlled oxygen pyrolysis on the dried coal gangue green balls, and intermittently introduce air flow to impact the material layer at the same time. The air flow pressure is 1.5 kPa; The gradient-controlled oxygen pyrolysis includes pyrolysis stage 1 and pyrolysis stage 2. The oxygen concentration in pyrolysis stage 1 is 15%, the pyrolysis temperature is 300 °C, and the pyrolysis time is 15 min; The oxygen concentration in pyrolysis stage 2 is 9%, the pyrolysis temperature is 450 °C, and the pyrolysis time is 12 min;

[0042] Subsequently, decarburization is carried out. The decarburization temperature is 600 °C, the oxygen concentration is 13%, and the decarburization time is 48 min; Then sinter at 1050 °C for 12 min, and use the countercurrent cooling method with fresh air for cooling. The temperature of the ceramsite finished product ≤ 100 °C to form the ceramsite product.

[0043] Embodiment 2

[0044] The difference from Example 1 lies in the pretreatment of coal gangue: Coal gangue powder with a particle size less than 2 mm (SiO2 49%, Al2O3 30%, calorific value 600 kcal / kg, fixed carbon content 6.5%, volatile matter 10.7%) is granulated with sodium bicarbonate with a particle size less than 100 μm under the action of a wetting agent to form green coal gangue balls. The green coal gangue balls are screened through a double-layer sieve (upper sieve hole 24 mm, lower sieve hole 15 mm) to remove large-particle-size green coal gangue balls and coal gangue powder, effectively ensuring the quality of the green coal gangue balls; The green coal gangue balls are dried with microwaves with a power density of 2.5 W / g and preheated to 200 °C, and the moisture content of the green coal gangue balls is reduced to 2.5%; By weight, 90 parts of coal gangue powder, 1 part of sodium bicarbonate, and 3 parts of wetting agent;

[0045] The wetting agent includes the following raw materials by weight: 1 part of polyvinyl alcohol, 4 parts of sodium carboxymethylcellulose, and 1 part of surfactant, and the surfactant is sodium dodecylbenzenesulfonate;

[0046] The rest is the same as Example 1.

[0047] Example 3

[0048] The difference from Example 1 lies in the pretreatment of coal gangue: Coal gangue powder with a particle size less than 2 mm (SiO2 52%, Al2O3 28%, calorific value 550 kcal / kg, fixed carbon content 6%, volatile matter 11%) is granulated with potassium bicarbonate with a particle size less than 100 μm under the action of a wetting agent to form green coal gangue balls. The green coal gangue balls are screened through a double-layer sieve (upper sieve hole 14 mm, lower sieve hole 8 mm) to remove large-particle-size green coal gangue balls and coal gangue powder, effectively ensuring the quality of the green coal gangue balls; The green coal gangue balls are dried with microwaves with a power density of 1.5 W / g and preheated to 220 °C, and the moisture content of the green coal gangue balls is reduced to 2%; By weight, 100 parts of coal gangue powder, 4 parts of potassium bicarbonate, and 8 parts of wetting agent;

[0049] The wetting agent includes the following raw materials by weight: 3 parts of polyvinyl alcohol, 1.5 parts of sodium carboxymethylcellulose, and 0.5 part of surfactant, and the surfactant is Tween-80;

[0050] The rest is the same as Example 1.

[0051] Example 4

[0052] The difference from Example 1 lies in the preparation step of coal gangue ceramsite. After the dried green coal gangue balls are subjected to gradient oxygen-controlled pyrolysis, air flow is intermittently introduced to impact the material layer, and the air flow pressure is 1 kPa; The gradient oxygen-controlled pyrolysis includes pyrolysis stage 1 and pyrolysis stage 2. The oxygen concentration in pyrolysis stage 1 is 18%, the pyrolysis temperature is 250 °C, and the pyrolysis time is 20 min; The oxygen concentration in pyrolysis stage 2 is 11%, the pyrolysis temperature is 350 °C, and the pyrolysis time is 15 min;

[0053] The rest are the same as in Example 1.

[0054] Example 5

[0055] The difference from Example 1 lies in that in the preparation step of coal gangue ceramsite, the dried green balls of coal gangue are subjected to gradient oxygen-controlled pyrolysis, and at the same time, air flow is intermittently introduced to impact the material layer, and the air flow pressure is 0.5 kPa; the gradient oxygen-controlled pyrolysis includes the first stage of pyrolysis and the second stage of pyrolysis. The oxygen concentration in the first stage of pyrolysis is 8%, the pyrolysis temperature is 300 °C, and the pyrolysis time is 25 min; the oxygen concentration in the second stage of pyrolysis is 11%, the pyrolysis temperature is 380 °C, and the pyrolysis time is 10 min;

[0056] The rest are the same as in Example 1.

[0057] Example 6

[0058] The difference from Example 1 lies in that in the preparation step of coal gangue ceramsite, the dried green balls of coal gangue are subjected to gradient oxygen-controlled pyrolysis, and at the same time, air flow is intermittently introduced to impact the material layer, and the air flow pressure is 1.3 kPa; the gradient oxygen-controlled pyrolysis includes the first stage of pyrolysis and the second stage of pyrolysis. The oxygen concentration in the first stage of pyrolysis is 12%, the pyrolysis temperature is 350 °C, and the pyrolysis time is 10 min; the oxygen concentration in the second stage of pyrolysis is 7%, the pyrolysis temperature is 400 °C, and the pyrolysis time is 10 min;

[0059] The rest are the same as in Example 1.

[0060] Example 7

[0061] The difference from Example 1 lies in that in the preparation step of coal gangue ceramsite, the pyrolyzed green balls of coal gangue are decarbonized for 60 min at a temperature of 700 °C and an oxygen concentration of 11%; then sintered at 1200 °C for 10 min, and cooled by the countercurrent cooling method with fresh air, and the temperature of the ceramsite finished product is ≤100 °C to form the ceramsite product

[0062] The rest are the same as in Example 1.

[0063] Comparative Example 1

[0064] The difference from Example 1 lies in that in the coal gangue pretreatment step, 100 parts of coal gangue powder and 1 part of wetting agent are directly granulated to obtain green balls of coal gangue; the rest are the same as in Example 1.

[0065] Comparative Example 2

[0066] The difference from Example 1 lies in that in the coal gangue pretreatment step, the wetting agent is polyvinyl alcohol, and the rest are the same as in Example 1.

[0067] Comparative Example 3

[0068] The difference from Example 1 lies in that in the coal gangue pretreatment step, bentonite is selected to replace magnesium bicarbonate in equal amount, and brine with a concentration of 5 wt% is selected to replace the wetting agent, and the rest is the same as in Example 1.

[0069] Comparative Example 4

[0070] The difference from Example 1 lies in that in the preparation step of coal gangue ceramsite, hot air is used to preheat the dried green balls of coal gangue to 250°C, pyrolyze for 30 min at 400°C under an oxygen concentration of 10%, then decarburize, the decarburization temperature is 600°C, the oxygen concentration during the decarburization process is 10%, and the decarburization time is 25 min. Finally, sinter at 1050°C for 12 min, and cool by using the countercurrent cooling method with fresh air, and the temperature of the ceramsite finished product ≤ 100°C to form a ceramsite product; the rest of the steps are the same as in Example 1.

[0071] The ceramsite products prepared in Examples 1-7 and Comparative Examples 1-4 were subjected to a cylinder compressive strength test according to GB / T 17431 "Lightweight Aggregates and Their Test Methods". 1000 ceramsite products prepared in Examples 1-7 and Comparative Examples 1-4 were sampled for screening, and the product bursting rate = the number of burst ceramsites / 1000 was calculated. At the same time, the ceramsites with cracks among the complete ceramsites were selected, and the ceramsite crack rate = the number of cracked ceramsites / the number of complete ceramsites was calculated, and the results were all recorded in Table 1.

[0072] Table 1

[0073] Cylinder compressive strength / MPa Bursting rate / % Crack rate / % Example 1 10.1 0.1 0.3 Example 2 8.7 0.3 0.5 Example 3 8.9 0.3 0.4 Example 4 9.1 0.2 0.4 Example 5 8 0.5 0.7 Example 6 9.5 0.2 0.5 Example 7 8.2 0.4 0.6 Comparative example 1 5.9 17 13 Comparative example 2 6.5 15 16 Comparative example 3 6.7 18 20 Comparative example 4 7.8 20 15

[0074] Combined with Examples 1-7 and Table 1 and Figure 1 It can be seen that by adopting the process method of the present application, the bursting rate of ceramsite can be significantly reduced. Combining with Figure 1 It can be seen that the obtained ceramsite product has no cracks on the surface, high cylinder compressive strength, and excellent product quality.

[0075] It can be seen from Example 1 and Comparative Examples 1-4 in combination with Table 1 that in Comparative Example 1, bicarbonate is lacking and the wetting agent is too little. In Comparative Example 2, only polyvinyl alcohol is used as the wetting agent, and the cylinder compressive strength of the ceramsite product decreases significantly, the number of products with cracks on the surface increases significantly, and the bursting rate during the production process increases significantly. In Comparative Example 3, bentonite is selected to replace magnesium bicarbonate equivalently, and brine with a concentration of 5wt% is selected to replace the wetting agent. Even though bentonite can improve the mechanical properties of the ceramsite to a certain extent, the overall cylinder compressive strength is still poor, the number of products with cracks on the surface increases significantly, and the bursting rate during the production process increases significantly, resulting in a serious decline in product quality. In Comparative Example 4, the traditional steps of pyrolysis, decarbonization, and sintering are used to prepare ceramsite. Heat accumulation and high-temperature zones appear during the production process, and a liquid phase appears on the surface of the green balls, causing the material layer to adhere and the porosity to decrease, seriously affecting the quality of the produced ceramsite products. Thus, it can be seen that the process method steps of the present application complement each other, cooperate with each other, and jointly solve the problems in the ceramsite production process and improve the comprehensive quality of the ceramsite.

[0076] This specific embodiment is only an explanation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A process for producing coal gangue ceramsite by microwave drying, characterized in that, It includes the following steps: Coal gangue pretreatment: Granulate coal gangue powder and bicarbonate under the action of a wetting agent to form green coal gangue balls, and use microwave to dry the green coal gangue balls; By weight, 90 - 100 parts of coal gangue powder, 1 - 4 parts of bicarbonate, and 3 - 8 parts of wetting agent; The wetting agent includes raw materials in the following weight parts: 1 - 3 parts of polyvinyl alcohol, 1.5 - 4 parts of sodium carboxymethyl cellulose, and 0.5 - 1 part of surfactant; Preparation of coal gangue ceramsite: After drying, the green coal gangue balls are pyrolyzed, decarbonized, sintered, and cooled to form ceramsite; The pyrolysis includes: Gradient oxygen-controlled pyrolysis of the dried green coal gangue balls, and at the same time, intermittently introducing air flow to impact the material layer; The gradient oxygen-controlled pyrolysis includes a first pyrolysis stage and a second pyrolysis stage. The oxygen concentration in the first pyrolysis stage is 12 - 18%, the pyrolysis temperature is 250 - 350 °C, and the pyrolysis time is 10 - 20 min; the oxygen concentration in the second pyrolysis stage is 7 - 11%, the pyrolysis temperature is 350 - 450 °C, and the pyrolysis time is 10 - 15 min.

2. The process method for producing coal gangue ceramsite by microwave drying according to claim 1, characterized in that: The surfactant is at least one of sodium dodecylbenzenesulfonate and Tween-80.

3. The process method for producing coal gangue ceramsite by microwave drying according to claim 2, characterized in that: The bicarbonate includes one of magnesium bicarbonate, sodium bicarbonate, and potassium bicarbonate.

4. The process method for producing coal gangue ceramsite by microwave drying according to claim 1, characterized in that: The power density of the microwave is 1.5 - 2.5 W / g, and the green coal gangue balls are dried and preheated to 200 - 250 °C.

5. The process method for producing coal gangue ceramsite by microwave drying according to claim 1, characterized in that: The decarbonization includes: Under the condition that the temperature is 500 - 700 °C and the oxygen concentration is 11 - 15%, the pyrolyzed green coal gangue balls are decarbonized for 40 - 60 min.

6. The process method for producing coal gangue ceramsite by microwave drying according to claim 1, characterized in that: The sintering conditions are: Temperature 900 - 1200 °C, sintering for 10 - 15 min.

7. The process method for producing coal gangue ceramsite by microwave drying according to any one of claims 1-6, characterized in that: The particle size of the green coal gangue balls is 8 - 25 mm.

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