Rotary kiln for preparing ceramic particles from fly ash

Abstract

The invention provides a rotary kiln for preparing ceramsite from fly ash, which mainly solves the problems of treatment of tail gas dioxin and pollution caused by pre-washing of the fly ash in the process of sintering the fly ash ceramsite in the rotary kiln, and is mainly characterized in that the existing rotary kiln is technically improved, and a secondary high-temperature dioxin decomposition and post-washing process in the rotary kiln is added, so that in the production process of the rotary kiln, the waste gas is reduced, and the production cost is reduced. The content of dioxin in the tail gas reaches the standard and is discharged, and meanwhile, a fly ash front washing process is changed into a rear washing process, so that only soluble chlorine salt exists in washing water, the treatment difficulty of the washing water in the later period is reduced, and the pollution to the environment is reduced.

Description

Technical Field

[0001] The invention relates to fly ash resource utilization production equipment, in particular to a fly ash ceramsite making rotary kiln. Background Art

[0002] Waste incineration power generation is a waste disposal method that reduces volume and makes it harmless. After waste incineration, slag and fly ash collected from chimneys will be produced. The slag can be used for brick making and other purposes after treatment. Fly ash is listed as hazardous waste by the state because it is rich in dioxins and other harmful substances. Currently, landfill and a small amount of cement kiln coordinated disposal processes are mainly used, but landfill is an emergency solution. In order to make more reasonable use of and harmlessly dispose of fly ash, the state has introduced policies to vigorously promote the disposal and reuse of fly ash. The resource utilization of waste incineration fly ash is mainly based on the control of dioxins, heavy metals, and soluble chlorine. In recent years, practice has proved that the use of sintered expanded clay to solidify heavy metals in fly ash is a feasible and stable technology. The current technical solution for making expanded clay from fly ash is mainly divided into three steps: first, pre-washing and dechlorination of fly ash; second, high-temperature sintering to solidify heavy metals and eliminate dioxins in fly ash; and third, secondary combustion of tail gas to decompose waste gas. Dioxins in the fly ash, but this process has found many problems in practical production. First, the pre-washing process of fly ash cannot completely separate the fly ash from the water in the washing, which causes some heavy metals and dioxins to enter the washing water, causing the pollution to expand and increasing the difficulty of the later disposal of the washing water. Second, it is difficult to use the secondary combustion chamber for secondary combustion of tail gas. The fly ash is mainly made into ceramsite by using a rotary kiln. The rotary kiln itself requires a certain amount of air to participate in the fuel combustion process, but under the action of induced draft, a large amount of useless air will enter the various connecting parts of the rotary kiln, causing the amount of exhaust gas that finally reaches the secondary combustion chamber to increase exponentially, causing the energy consumption of the secondary combustion chamber to rise sharply, and the high temperature of nearly 1,000 degrees makes it more difficult to remove the dust in the later stage of the exhaust gas. Therefore, the existing technical solution for making ceramsite from fly ash is not feasible. Tianjin is one of the earliest cities in China to propose the use of fly ash to make ceramsite, but the project eventually stagnated due to the immaturity of the existing technology. Summary of the invention

[0003] The present invention provides a fly ash ceramsite rotary kiln which can better solve the above-mentioned problems, and mainly solves the problems of dioxin disposal in tail gas and fly ash pre-washing pollution in the process of sintering fly ash ceramsite in the rotary kiln. The present invention mainly improves the existing rotary kiln technically, adds secondary high-temperature decomposition of dioxin in the kiln and post-washing process, so that the content of dioxin in tail gas meets the emission standards during the production process, and at the same time changes the fly ash pre-washing process to post-ceramsite washing, so that only soluble chlorine exists in the washing water, reduces the difficulty of later treatment of the washing water, and reduces pollution to the environment.

[0004] The technical solutions provided by the present invention are as follows: 1. A technical improvement solution for a rotary kiln; the rotary kiln provided by the present invention is mainly composed of a front sintering kiln and a rear drying kiln. The rear drying kiln can be regarded as a combination of the drying kiln part of the existing traditional rotary kiln and a secondary combustion chamber. It mainly involves laying a guide pipe in the rear drying kiln, and using the guide pipe to change the direction of the airflow in the kiln so as to achieve the effect of a secondary combustion chamber in the kiln. The guide pipe is U-shaped, and a secondary high-temperature plate is connected to the front end of the rear drying kiln, which is close to the high-temperature zone at the front end of the front sintering kiln. One side of the rear end of the U-shaped guide pipe is an exhaust port, which is located at the tail end of the rear drying kiln, and the other side is an air inlet, which can be installed at any position in the kiln according to requirements. Its working principle is that when the equipment is working, the high temperature zone at the front end of the front sintering kiln will be kept at a constant temperature between 1200℃ and 1350℃, and the secondary high temperature plate is close to the high temperature zone of the front sintering kiln, so it is also kept at a high temperature of about 1200℃. Under the action of the induced draft fan, the high temperature exhaust gas generated in the high temperature zone at the front end of the front sintering kiln enters the air inlet at the rear end of the rear drying kiln from the front end of the rear drying kiln. At this time, there are particles made of fly ash in the rear drying kiln. During the movement of the high temperature exhaust gas, the fly ash particles in the rear drying kiln are dried and preheated, and at the same time, its own temperature drops. After entering the air inlet of the U-shaped guide pipe, the exhaust gas begins to go back along the U-shaped guide pipe and flows to the rear drying kiln. At the front end of the kiln, the exhaust gas enters the secondary high-temperature plate. Because the secondary high-temperature plate is kept at a constant temperature of about 1200℃, the exhaust gas is heated by the secondary high temperature after entering the secondary high-temperature plate. At this time, the dioxins produced when the exhaust gas is preheated to dry the particles made of fly ash are effectively decomposed. The heated exhaust gas moves along the other end of the U-shaped guide pipe to the exhaust port. During the movement, it passes through the metal surface of the guide pipe and releases heat in the post-drying kiln. The temperature begins to drop gradually again. However, at this time, the exhaust gas is in an oxygen-deficient state in the pipeline and does not contact other substances in the rotary kiln. Therefore, it no longer produces dioxins. When it reaches the exhaust port, its temperature is controlled at about 500℃, and then it is discharged outward at the tail end of the post-drying kiln for emergency treatment. After cooling, dust removal, desulfurization and other post-treatments, the particles made of fly ash after drying and preheating are sintered at 1200℃ to 1350℃ in the high temperature zone at the front end of the pre-sintering kiln under the rotation of the rotary kiln to form ceramsite, which is discharged after heat recovery in the heat recovery zone at the rear end of the pre-sintering kiln. At this time, the ceramsite has completed the solidification of heavy metals, the elimination of organic and harmful substances, and the decomposition of dioxins in the fly ash, but it still contains some soluble chloride salts. The ceramsite discharged from the kiln enters the post-water washing tank. Because the ceramsite at this time has completed the complete elimination of its organic and harmful substances, the water in the post-water washing tank contains relatively few harmful substances except soluble chloride salts, which reduces the difficulty of subsequent disposal of the washing water.

[0005] The beneficial effects of the present invention are as follows: the existing process of sintering ceramsite in a rotary kiln, equipping the tail gas with a secondary combustion chamber, which is a high energy consumption process, and pre-washing of fly ash, which causes secondary pollution to the environment, is changed; the secondary decomposition of dioxins is completed simultaneously in the rotary kiln, which eliminates the possibility of dioxin spillover, and no secondary pollution to the environment is generated, making the resource utilization of fly ash more scientific and safe. The project requires little investment and has quick results, and can achieve the national goal of zero landfill of fly ash in a short period of time. The produced ceramsite can also be used as a lightweight aggregate to replace crushed stone in various construction industries, which is beneficial to the country and the people. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 A side view of the present invention Figure 1 Middle; 1. Pre-sintering kiln 2. Post-drying kiln 3. Guide pipe 4. Secondary high-temperature plate 5. Air inlet 6. Exhaust port 7. External discharge port 8. Fly ash particle inlet 9. Fuel pipe 10. Power equipment 11. Ceramic pellet outlet 12. Rear water washing tank 13. Heat recovery area at the rear end of the pre-sintering kiln 14. High temperature area at the front end of the pre-sintering kiln DETAILED DESCRIPTION

[0007] Figure 1 In the process, the power equipment (10) is started. Since the front sintering kiln (1) and the rear drying kiln (2) are connected as a whole, they start to rotate synchronously. The fuel pipe (9) starts to spray fuel for combustion. At the same time, the external induced draft fan is started. The high-temperature exhaust gas generated after combustion in the high-temperature zone (14) at the front end of the front sintering kiln moves toward the air inlet (5). When the temperature of the high-temperature zone (14) at the front end of the front sintering kiln reaches 1200° C. to 1350° C., the fly ash particle inlet (8) starts to feed. The exhaust gas is preheated and dried in the process of being sucked into the air inlet (5). Then, it starts to return along the pipeline to the secondary high-temperature plate (4) for high-temperature thermal decomposition. The fly ash particles are dried and preheated in the post-drying kiln (2) and then enter the high-temperature zone (14) at the front end of the pre-sintering kiln to be sintered into ceramsite. After that, the fly ash is recovered by the heat recovery zone (13) at the rear end of the pre-sintering kiln for heat recovery. Finally, the fly ash is discharged through the post-drying kiln (2) through the metal surface of the pipe to the inside of the post-drying kiln (2) for water washing and dechlorination treatment, thereby forming a virtuous production cycle.

Claims

1. A fly ash ceramsite rotary kiln, comprising a front sintering kiln (1), a rear drying kiln (2) and a rear washing tank (12), characterized in that; The fly ash ceramsite rotary kiln is composed of a front sintering kiln (1) combined with a rear drying kiln (2) and a rear washing tank (12).

2. A fly ash ceramsite rotary kiln according to claim 1, characterized in that: The post-drying kiln (2) has a U-shaped flow guide pipe (3).

3. A fly ash ceramsite rotary kiln according to claim 2, characterized in that: The front end of the flow guide pipe (3) is connected to a secondary high-temperature disk (4).

4. The fly ash ceramsite rotary kiln according to claim 2, characterized in that: The guide tube (3) has an air inlet (5) and an air outlet (6) at the rear end.

5. A fly ash ceramsite rotary kiln according to claim 4, characterized in that: The air inlet (5) is located at any position in the kiln, and the air outlet (6) is located at the rear end of the post-drying kiln (2).

6. A fly ash ceramsite rotary kiln according to claim 1 or 3, characterized in that: The secondary high temperature plate (4) is located adjacent to the high temperature zone (14) at the front end of the pre-sintering kiln.

7. The fly ash ceramsite rotary kiln according to claim 1, characterized in that: The ceramsite produced from the heat recovery zone (13) at the rear end of the pre-sintering kiln is washed with water in the post-washing tank (12).

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