Method for preparing multifunctional ceramsite through energy and mass coupling of pure coal gangue

Abstract

The invention belongs to the technical field of comprehensive utilization of coal gangue, and particularly relates to a method for preparing multifunctional ceramsite through energy and mass coupling of pure coal gangue. The multifunctional ceramsite is obtained while the energy of the pure coal gangue ceramsite is recovered. According to the method, the ceramsite can be prepared from the pure coal gangue with the calorific value of 500-1500kcal / kg, heat generated in coal gangue combustion can be effectively recycled for producing steam, ceramsite products with different functions can be obtained through temperature process regulation and control, a multi-section pure coal gangue calcination technology and a heat exchange technology are combined, and the production cost is reduced. And the rapid decarbonization of the pure coal gangue ceramsite and the multifunctionality of the prepared product are realized, the performance and the production efficiency of the ceramsite product are greatly improved, and the overall energy consumption of equipment is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive utilization of coal gangue, and particularly relates to a method for preparing multifunctional ceramsite by energy-quality coupling of pure coal gangue. Background Art

[0002] With the gradual increase of coal mining difficulty and the continuous improvement of washing efficiency in China, the production of coal gangue is also increasing continuously. According to statistics, the cumulative stockpile of coal gangue in China has exceeded 6 billion tons at present, forming more than 2,600 large gangue mountains, occupying about 13,000 hectares of land. 2 The stockpiled coal gangue forms acidic water and dissociates toxic and harmful elements through weathering and rain leaching, which seeps into the ground, causing soil and water pollution. Self-igniting coal gangue generates a large amount of harmful gases such as SO2 and NO x etc., causing serious air pollution. The stockpiling of coal gangue restricts the construction of "waste-free cities" and the pace of "green development" of enterprises. Its large-scale and resource utilization are crucial for the high-quality development of the industry. The large-scale utilization of coal gangue can be divided into two categories: energy utilization and building material utilization according to its carbon content. From the perspective of energy utilization, coal gangue is a low-calorific value fuel. Generally, coal gangue with a calorific value of 1792-3000 kcal / kg can be directly used as the fuel of a circulating fluidized bed boiler, and coal gangue with a calorific value of 1500-1792 kcal / kg can be co-fired with coal slime, washed medium coal or tail coal and used as the fuel for power generation. Coal gangue with a calorific value lower than 500 kcal / kg is mainly used for ecological backfilling or the preparation of building materials. However, there are problems in the utilization of coal gangue with a calorific value of 500-1500 kcal / kg. If it is used for building material utilization, etc., decarbonization treatment is required, with high energy consumption and complex processes; if it is used for ecological backfilling, there is a risk of coal gangue spontaneous combustion and relatively high ecological environment risks. Therefore, the utilization of coal gangue with a calorific value of 500-1500 kcal / kg is a difficult point in the industry. Coal gangue with a calorific value of 500-1500 kcal / kg can be used to prepare ceramsite by mixing with fly ash, sludge, red mud, etc., but the blending ratio is limited. If the proportion of coal gangue is too high, there is often a problem of "incomplete burning" in industry, which restricts the industrialization process of preparing ceramsite with a high blending ratio of coal gangue. Therefore, using pure coal gangue to prepare multifunctional ceramsite is a need in the industry and also a difficult point.

[0003] To meet the needs of the industry in China for the resource utilization of coal gangue, most studies have focused on using coal gangue as an auxiliary material or admixture to prepare ceramsite, with the admixture content being approximately 30% - 50%. For example, Patent CN117447184A mixes red mud and coal gangue, and through ball milling, mixing, kneading, pelletizing, activation, ball milling, sieving, ball rolling, drying and firing, finally obtains red mud coal gangue ceramsite. However, the addition of red mud reduces the treatment amount of coal gangue. Patent CN113651595A uses coal gangue and auxiliary materials to prepare ceramsite, and uses a static sintering tunnel kiln for static sintering to produce coal gangue ceramsite. Static sintering utilizes waste heat recycling to achieve the drying of ceramsite. The hot air in the soaking section of the ceramsite is sent as secondary air to the high-temperature section for reuse in the roasting section. The waste heat in the first cooling section is used as combustion-supporting air. Due to the addition of auxiliary materials in the process, the production cost increases, and the treatment amount of coal gangue is reduced. Moreover, since the ceramsite is in a static state, when the hot air passes through the ceramsite from top to bottom, it is easy to have the situation that the upper and lower layers of ceramsite are unevenly heated, ultimately resulting in inconsistent product performance. At the same time, there are also a small number of studies on preparing ceramsite from pure coal gangue. Although Patent CN113105258A involves a method for preparing undoped single coal gangue ceramsite based on a moving bed, the moving bed is a horizontally moving traveling grate, and the traveling grate is divided into a drying section, a preheating section, a roasting section, a first cooling section and a second cooling section in sequence from the feed inlet to the discharge outlet. However, the obtained ceramsite has extremely low strength, does not meet the requirements of high-strength ceramsite, and does not achieve the effective recovery of heat during the calcination of coal gangue ceramsite. Patent CN118834059A connects a belt firing device and an energy-saving rotary short kiln in series to form a two-stage calcination process. However, the belt firing device and the rotary kiln system need to provide additional energy to support the dynamic movement of the ceramsite, and the total time of the entire calcination stage of the ceramsite is long, greatly reducing the production efficiency of the ceramsite. The existing technologies cannot simultaneously meet the requirements that the ceramsite prepared from pure coal gangue reaches a high-strength level, the internal structure of the ceramsite has no black core, the production efficiency of the ceramsite is high with low energy consumption, and the combustion heat is recovered. Currently, there are few reports on the method for preparing high-strength multifunctional ceramsite by energy-quality coupling of pure coal gangue. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to overcome the deficiencies of the above-mentioned existing technologies and provide a method for preparing multifunctional ceramsite by energy-quality coupling of pure coal gangue. This method can obtain multifunctional ceramsite while recovering the energy of pure coal gangue ceramsite. It can not only realize the preparation of ceramsite from pure coal gangue with a calorific value of 500 - 1500 kcal / kg, but also effectively recover the heat generated during the combustion of coal gangue for steam production, and can obtain ceramsite products with different functions through temperature history regulation. By combining the multi-stage calcination technology of pure coal gangue with the heat exchange technology, the rapid decarbonization of pure coal gangue ceramsite and the multifunctionality of the prepared products are realized, greatly improving the product performance and production efficiency of the ceramsite, and reducing the overall energy consumption of the equipment.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preparing multifunctional ceramsite by energy quality coupling of pure coal gangue, comprising: placing pure coal gangue ceramsite in a vertical moving bed and successively performing preheating, combustion and firing treatments to obtain the product; the vertical moving bed adopts a vertical rotating structure, and inclined partitions arranged in a crosswise manner and closely arranged from top to bottom are provided between the central rotating shaft and the inner wall of the vertical moving bed, so that the pure coal gangue ceramsite moves from top to bottom between the inclined partitions; a calcination system, a combustion-supporting system and a heat exchange system are arranged inside the vertical moving bed; the calcination system is successively divided into a preheating stage, a combustion stage and a firing stage from the feed inlet to the discharge outlet; the combustion-supporting system is used to provide preheating air, primary air, combustion-supporting air and natural gas; the preheating air provides sufficient heat to the preheating stage, the primary air provides sufficient oxygen and heat to the combustion stage, and the combustion-supporting air and natural gas provide sufficient heat to the firing stage; the heat exchange system is used to recover the waste heat generated in the combustion stage and the firing stage, and realize the co-production of steam for industrial use.

[0007] Further, the preparation process of the pure coal gangue ceramsite specifically includes: crushing and screening coal gangue with a calorific value range of 500 - 1500 kcal / kg to obtain powdered coal gangue, and then mixing the powdered coal gangue with water for granulation treatment to obtain the product.

[0008] Furthermore, the mass ratio of the powdered coal gangue to water is 8 - 8.5:1.5 - 2.

[0009] Furthermore, the particle size of the powdered coal gangue is controlled below 74 μm.

[0010] Furthermore, the diameter of the pure coal gangue ceramsite is controlled at 10 mm - 15 mm.

[0011] Further, the temperature of the preheating stage is 100°C, the atmosphere has no requirement, and the time is 20 min; the temperature of the combustion stage is 900 - 1000°C, the atmosphere is controlled to be 18% - 21% O2, and the time is 25 - 30 min; the temperature of the firing stage is 1100 - 1200°C, the atmosphere has no requirement, and the time is 20 - 30 min.

[0012] Further, during the process of the pure coal gangue ceramsite moving from top to bottom between the inclined partitions, the residence time of the pure coal gangue ceramsite on the inclined partitions is controlled by the rotation speed of the central rotating shaft, and the accumulation of the pure coal gangue ceramsite inside the vertical moving bed is reduced, so that the pure coal gangue ceramsite is fully burned and releases heat.

[0013] Further, heat exchange openings with a diameter of 5 - 8 mm are arranged on the inclined partitions in the vertical moving bed, providing conditions for the full combustion and heat exchange of the pure coal gangue ceramsite.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] (1) The raw material of the ceramsite in the present invention is 100% coal gangue, which expands the value of medium and low calorific value coal gangue that cannot be combusted or has a risk of landfill, and realizes the large-scale and resource utilization of coal gangue.

[0016] (2) The vertical moving bed for preparing pure coal gangue ceramsite in the present invention is optimized into a three-stage structure, namely a preheating stage, a combustion stage and a firing stage. The preheating stage mainly dries the internal moisture of the coal gangue wet ceramsite; the combustion stage mainly burns the carbon in the coal gangue completely; the firing stage mainly calcines the ceramsite after complete combustion, causing phase changes and microstructural changes inside the ceramsite, so that the strength of the ceramsite far exceeds the requirement of 900 level for high-strength ceramsite in lightweight aggregates. The continuous three-stage structure of the ceramsite is more conducive to the continuous increase of the ceramsite temperature. The heat brought by the ceramsite from the previous stage will more easily reach the temperature requirement of the next stage, enabling efficient heat utilization in the preparation process of the ceramsite and making the equipment more energy-saving. At the same time, the ceramsite in the vertical moving bed can be completely burned out, without the problem of black cores, and the heat exchange system is used to recover the waste heat generated in the combustion stage and the firing stage, realizing the co-production of steam for industrial use.

[0017] (3) The vertical moving bed used in the present invention adopts a vertical rotation structure and is internally provided with inclined partitions to achieve uniform heat and oxygen transmission during the ceramsite combustion process. Specifically, the vertical rotation structure controls the downward movement time and rate of the ceramsite during its downward movement on the inclined partition, and sets different rotation speeds for the combustion duration of coal gangue with different calorific values, so that the ceramsite stays for different durations in the preheating, combustion and firing stages to obtain different target products; the internally arranged inclined partitions are closely arranged from top to bottom. On the one hand, the inclined partitions enable the ceramsite to roll down from top to bottom by using gravitational potential energy without external energy supply. On the other hand, the closely arranged partitions keep the ceramsite in a non-accumulated state during its downward movement, and the oxygen and the ceramsite are in a relatively dynamic movement process, and the oxygen concentration difference inside and outside the ceramsite remains at a stable value, so that there is no external factor hindering the diffusion of oxygen and heat from the outside to the inside of the ceramsite.

[0018] (4) The main structure of the present invention is equipped with a combustion-supporting system and a heat exchange system, enabling the equipment to have a better combustion environment and play a role in energy recovery. The preheated air in the combustion-supporting system maintains a stable temperature of 100 °C for the preheating system. The temperature at this stage can also be provided by the heat transfer from the temperature in the combustion stage. The primary air can not only maintain a stable temperature of 900 - 1000 °C for the combustion stage but also provide sufficient oxygen required for combustion. The combustion-supporting air in the combustion stage provides a temperature of 1100 - 1200 °C, and natural gas provides sufficient energy to reach a higher temperature. The heat exchange system exists between the high-temperature combustion stage and the firing stage. This system recovers excessive heat to reduce energy loss. Moreover, coal gangue with a certain calorific value in the combustion stage releases all the heat inside the ceramsite. The heat exchange system can recover the released heat and use it to generate co-produced steam for industrial use.

[0019] (5) The ceramsite prepared by the present invention can have various mechanical properties such as compressive strength, water absorption rate, and apparent density according to the three-stage combination conditions, and can be used in fields such as construction, environmental protection, and ocean engineering, or specifically for industrial scenarios such as extreme environments or high-value-added industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the process flow chart of the preparation of multifunctional ceramsite by energy and quality coupling of pure coal gangue according to the present invention;

[0021] Figure 2 is the front view of the process device for the preparation of multifunctional ceramsite by energy and quality coupling of pure coal gangue according to the present invention;

[0022] Figure 3 is the top view of the process device for the preparation of multifunctional ceramsite by energy and quality coupling of pure coal gangue according to the present invention;

[0023] Wherein: 1. Feed inlet, 2. Preheated air, 3. Primary air, 4. Primary air, 5. Natural gas, 6. Combustion-supporting air, 7. Heat exchange plate, 8. Discharge outlet, 9. Hopper truck, 10. Preheating stage, 11. Combustion stage, 12. Firing stage, 13. Central rotating shaft, 14. Discharge outlet partition, 15. Heat exchange opening. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0025] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0026] Unless otherwise specified, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0027] Example 1

[0028] This example provides a method for preparing multifunctional ceramsite by energy-quality coupling of pure coal gangue, specifically including:

[0029] Implementation device: The method for preparing multifunctional ceramsite by energy-quality coupling of pure coal gangue is implemented using a vertical moving bed. As Figure 2 shown, the vertical moving bed adopts a vertical rotating structure. Between the central rotating shaft 13 inside the vertical moving bed and the inner wall of the vertical moving bed, inclined partitions are arranged crosswise and tightly arranged from top to bottom, so that the pure coal gangue ceramsite rolls from top to bottom between the inclined partitions; heat exchange openings 15 with a diameter of 5-8 mm are arranged on the inclined partitions to provide conditions for the full combustion and heat exchange of the pure coal gangue ceramsite; and the residence time of the pure coal gangue ceramsite on the inclined partitions is controlled by the rotation rate of the central rotating shaft 13, and the accumulation of the pure coal gangue ceramsite inside the vertical moving bed is reduced, so that the pure coal gangue ceramsite is fully burned and the waste heat is released.

[0030] A calcination system, a combustion support system, and a heat exchange system are arranged inside the vertical moving bed; the calcination system is divided into a preheating stage 10, a combustion stage 11, and a firing stage 12 in sequence from the feed inlet 1 to the discharge outlet 8; the combustion support system is used to provide preheating air 2, primary air 3, 4, natural gas 5, and combustion support air 6; the preheating air 2 provides sufficient heat to the preheating stage 10; the primary air 3, 4 provides sufficient oxygen and heat to the combustion stage 11, playing a role in heating up and controlling the temperature; the combustion support air and natural gas provide sufficient heat to the firing stage 12, playing a role in heating up and controlling the temperature; the heat exchange system uses a heat exchange plate 7 to recover the waste heat generated in the combustion stage 11 and the firing stage 12, and realizes the co-production of steam for industrial use.

[0031] Implementation steps: As Figure 1 shown, the coal gangue with a calorific value range of 500-1000 kcal / kg is crushed and screened to obtain powdered coal gangue with a particle size below 74 μm, and then the powdered coal gangue is mixed with water in a mass ratio of 8.5:1.5, and pure coal gangue ceramsite is prepared after granulation treatment by a pelletizing machine.

[0032] Pour pure coal gangue ceramsite into the feed inlet 1 and reach the preheating stage 10. At a temperature of 100 °C, dry the pure coal gangue ceramsite for 20 min through the preheating air 2 to dry the internal moisture; then the dried pure coal gangue ceramsite enters the combustion stage 11. The primary air 3 and 4 provide 21% O₂ to the combustion stage 11 and adjust the combustion temperature to 900 °C. Control the rotation speed of the central rotating shaft 13 or increase the number of inclined partitions in the combustion stage 11 to control the combustion stage duration to 30 min to completely burn out the carbon-based substances in the pure coal gangue ceramsite; then the decarbonized pure coal gangue ceramsite enters the firing stage 12. Keep the firing temperature at 1200 °C through the natural gas 5 and the combustion-supporting air 6, and control the duration to 20 min. Finally, the pure coal gangue ceramsite cooled by the heat exchange plate 7 falls from the discharge outlet 8 and is sent to the hopper car 9 through the discharge outlet partition 14 to obtain the target ceramsite product. The bulk density of the ceramsite is 1075 kg / m 3 and the true density is 4302 kg / m 3 ; the 1-hour water absorption rate is 1.03%, the compressive strength is 40.14 MPa, and the density grade reaches the 1100 level.

[0033] Example 2

[0034] The method for preparing multifunctional ceramsite by energy-quality coupling of pure coal gangue in this example is basically the same as that in Example 1, except that: the temperature in the combustion stage is 1000 °C and the time is 25 min.

[0035] The bulk density of the obtained ceramsite is 1106 kg / m 3 and the true density is 4360 kg / m 3 ; the 1-hour water absorption rate is 0.65%, the compressive strength is 40.51 MPa, and the density grade reaches the 1200 level.

[0036] Example 3

[0037] The method for preparing multifunctional ceramsite by energy-quality coupling of pure coal gangue in this example is basically the same as that in Example 1, except that: the temperature in the firing stage is 1100 °C and the time is 30 min.

[0038] The bulk density of the obtained ceramsite is 885 kg / m 3 and the true density is 1467 kg / m 3 ; the 1-hour water absorption rate is 9.84%, the compressive strength is 10.21 MPa, and the density grade reaches the 900 level.

[0039] Example 4

[0040] In this embodiment, the method for preparing multifunctional ceramsite by energy-mass coupling of pure coal gangue is basically the same as that in Embodiment 1, except that: the temperature in the combustion stage is 1000 °C and the time is 25 min; the temperature in the firing stage is 1100 °C and the time is 30 min.

[0041] The bulk density of the obtained ceramsite is 923 kg / m 3 、and the true density is 1634 kg / m 3 、the water absorption rate in 1 h is 8.14%, the compressive strength is 14.32 MPa, and the density grade reaches the 1000 level.

[0042] The above are only embodiments for better explaining the present invention, and are not intended to limit it. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall fall within the scope covered by the present invention.

Claims

1. A method for preparing multifunctional ceramsite by energy-mass coupling of pure coal gangue, characterized in that: include: Pure coal gangue expanded clay is placed in a vertical moving bed and sequentially undergoes preheating, combustion and sintering stages to obtain the product; the vertical moving bed adopts a vertical rotating structure, and inclined partitions closely arranged from top to bottom are cross-arranged between the central rotating shaft and the inner wall of the vertical moving bed, so that the pure coal gangue expanded clay moves from top to bottom between the inclined partitions; a calcination system, a combustion-supporting system and a heat exchange system are arranged on the inner side of the vertical moving bed; the calcination system is sequentially divided into a preheating stage, a combustion stage and a sintering stage from an inlet to an outlet; the combustion-supporting system is used to provide preheating air, primary air, combustion-supporting air and natural gas; the preheating air provides sufficient heat to the preheating stage, the primary air provides sufficient oxygen and heat to the combustion stage, and the combustion-supporting air and natural gas provide sufficient heat to the sintering stage; the heat exchange system is used to recover the waste heat generated in the combustion stage and the sintering stage to achieve co-production of steam for industry.

2. The method for preparing multifunctional ceramsite by energy-mass coupling of pure coal gangue according to claim 1, characterized in that: The preparation process of the pure coal gangue ceramsite specifically includes: crushing and screening coal gangue with a calorific value ranging from 500 to 1500 kcal / kg to obtain powdered coal gangue, and then mixing the powdered coal gangue with water to perform granulation treatment to obtain the pure coal gangue ceramsite.

3. The method for preparing multifunctional ceramsite by energy-mass coupling of pure coal gangue according to claim 2, characterized in that: The mass ratio of the powdered coal gangue to water is 8-8.5:1.5-2.

4. The method for preparing multifunctional ceramsite by energy-mass coupling of pure coal gangue according to claim 2, characterized in that: The particle size of the powdered coal gangue is controlled to be below 74 μm.

5. The method for preparing multifunctional ceramsite by energy-mass coupling of pure coal gangue according to claim 2, characterized in that: The diameter of the pure coal gangue ceramsite is controlled to be 10 mm to 15 mm.

6. The method for preparing multifunctional ceramsite by energy-mass coupling of pure coal gangue according to claim 1, characterized in that: The temperature of the preheating stage is 100°C, the atmosphere is not required, and the time is 20 minutes; the temperature of the combustion stage is 900-1000°C, the atmosphere is controlled to 18%-21% O2, and the time is 25-30 minutes; the temperature of the sintering stage is 1100-1200°C, the atmosphere is not required, and the time is 20-30 minutes.

7. The method for preparing multifunctional ceramsite by energy-mass coupling of pure coal gangue according to claim 1, characterized in that: During the process of the pure coal gangue ceramsite moving from top to bottom between the inclined partitions, the residence time of the pure coal gangue ceramsite on the inclined partitions is controlled by the rotation rate of the central shaft, and the accumulation of the pure coal gangue ceramsite inside the vertical moving bed is reduced, so that the pure coal gangue ceramsite is fully burned and heat is released.

8. The method for preparing multifunctional ceramsite by energy-mass coupling of pure coal gangue according to claim 1, characterized in that: Heat exchange openings with a diameter of 5 to 8 mm are arranged on the inclined partitions in the vertical moving bed to provide conditions for the full combustion and heat exchange of the gangue ceramsite.

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