Sintering method for extracting alumina clinker from coal gangue by using cement clinker calcining kiln

Abstract

The invention discloses a sintering method for extracting alumina clinker from coal gangue by using a cement clinker calcining kiln, the coal gangue is added into preheaters by adopting a multi-point adding mode, and 38.0-42.0% of the total amount of the coal gangue is added into a five-stage preheater; 28.0-32.0% of the total amount of the coal gangue is added into the fourth-stage preheater; 18.0-22.0% of the total amount of the coal gangue is added into the third-stage preheater; the residual coal gangue is added from the second-stage preheater, and other raw materials except the coal gangue are still normally added from the first-stage preheater. By the adoption of the technical scheme, the phenomena of nodulation and blockage of the cyclone preheater are avoided, and accidents such as deformation and collapse of the cyclone preheater are avoided. A new invention that coal gangue replaces fly ash and alumina clinker is calcined on a cement clinker kiln is completed. The method realizes extraction of alumina from coal gangue through a limestone sintering method, the alumina clinker is obtained through sintering in a cement calcining kiln, and the alumina clinker has good performances that the pulverization rate of the clinker can reach 92.8%, and the alumina dissolution rate of the clinker can reach 73.4%.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for sintering alumina clinker, in particular to a method for sintering alumina clinker from coal gangue using a cement clinker calcining kiln. BACKGROUND

[0002] With the rapid development of China's economy, the demand for aluminum metal is growing rapidly. The limestone sintering method developed by our company to extract alumina from fly ash requires the use of a limestone sintering kiln to obtain clinker. If we want to increase the production scale of alumina, we will inevitably have to build a new limestone sintering kiln, which will undoubtedly increase the cost of the enterprise. Therefore, after long-term research, we successfully developed a calcination process for extracting alumina clinker from fly ash using a limestone sintering method based on a cement clinker calcining kiln, and applied for a related patent with the application number 2025106574258. The raw materials used in this method include limestone, high-alumina fly ash, carbide slag, and mineralizing agent. This method has achieved a qualified alumina sintered clinker with a pulverization rate of 92.0% and a clinker alumina dissolution rate of 72.0%.

[0003] Currently, there are also methods for obtaining alumina using coal gangue in the industry. Therefore, we are also researching whether coal gangue can replace fly ash to achieve a sintering method for extracting alumina clinker in a cement clinker calcining kiln. However, after trying, we found that unlike the limestone sintering method for extracting alumina from fly ash and sintering clinker in a cement calcining kiln, due to the high carbon content in coal gangue, which is generally 8.0% to 15.0%, and can reach about 20.0%, the high carbon content in coal gangue will cause the coal gangue to burn prematurely in the cyclone preheater, causing the temperature of the cyclone preheater to rise, which can lead to the formation of nodules and blockage of the cyclone preheater. When the temperature is too high, the cyclone preheater can deform and collapse. Therefore, how to solve the above problems and successfully develop a sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln has become a technical problem that needs to be solved urgently. SUMMARY

[0004] The purpose of the present application is to provide a sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln. This method expands the way to obtain alumina clinker and is based on the existing cement clinker calcining kiln. Not only does it realize the resource utilization of the cement clinker calcining kiln, but it also reduces the production cost of alumina clinker.

[0005] The technical solution of this invention is a sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln. The coal gangue is added to the preheater at multiple points, wherein 38.0-42.0% of the total coal gangue is added to the fifth-stage preheater; 28.0-32.0% of the total coal gangue is added to the fourth-stage preheater; 18.0-22.0% of the total coal gangue is added to the third-stage preheater; the remaining coal gangue is added from the second-stage preheater, and other raw materials besides coal gangue are still added normally from the first-stage preheater.

[0006] In the aforementioned sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln, two waste heat boilers are connected in series at the flue gas outlet of the cement clinker calcining kiln.

[0007] In the aforementioned sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln, the cement clinker calcining kiln includes a grate cooler at the tail end, and the grate plate of the grate cooler is densely covered with air outlet holes.

[0008] In the aforementioned sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln, the coal gangue and other raw materials are all ground using the same set of raw material grinding equipment, but are ground and stored separately.

[0009] In the aforementioned sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln, the coal gangue ground by the raw material mill is stored separately in a raw material silo, which is equipped with multiple discharge ports, each corresponding to a multi-stage preheater.

[0010] In the aforementioned sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln, a set of screw feeding equipment is connected to each discharge port.

[0011] The beneficial effects of this invention are as follows: Compared with the prior art, this invention, by adopting the above-mentioned technical solution and adding coal gangue in batches, can reduce the residence time of coal gangue in the preheater and the combustion time, thereby reducing the harm caused by the rise in tail temperature due to coal gangue combustion. An additional waste heat boiler is added at the flue gas outlet to further reduce the tail gas temperature and recover tail gas heat. Through the cooling effect of the added waste heat boiler, the flue gas temperature is reduced to 300℃-350℃, meeting the requirements of the denitrification process. The denitrified flue gas enters the next stage waste heat boiler to continue recovering heat, thus meeting emission requirements. Furthermore, the cooling air outlet of the grate cooler, which was previously vented through grate gaps, is now vented through perforations on the grate, thereby improving the driving effect of the cooling air on the clinker, accelerating the clinker's movement speed, shortening the clinker's cooling time, and reducing the clinker's cooling intensity. Through these improvements, the occurrence of nodule formation and blockage in the cyclone preheater, as well as accidents such as deformation and collapse of the cyclone preheater, are avoided. A novel invention has been developed to replace fly ash with coal gangue in the calcination of alumina clinker in cement clinker kilns. This invention enables the extraction of alumina from coal gangue using a limestone sintering method, followed by sintering in a cement calcining kiln to obtain alumina clinker. The clinker exhibits excellent performance, achieving a pulverization rate of 92.8% and an alumina dissolution rate of 73.4%. Attached Figure Description

[0012] Figure 1 This is a schematic diagram illustrating the extraction of alumina clinker from coal gangue using a cement clinker calcining kiln.

[0013] Figure 2 A schematic diagram of the improved grate plate structure of the grate cooler;

[0014] Figure 3 This is a schematic diagram of the grate plate structure of the grate cooler before the improvement. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0016] Embodiments of the present invention: A sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln. This invention addresses the characteristics of coal gangue mentioned in the background art by employing multiple treatment methods to ensure the safe and stable operation of the cyclone preheater.

[0017] 1. Multi-point feeding method: Normally, sintering materials are added from the primary cyclone preheater. Since coal gangue contains carbon, it can burn prematurely within the preheater. Therefore, if all materials are still added from the primary preheater, it will exacerbate the temperature rise within the cyclone preheater, making it difficult to control the temperature of each stage of the preheater. Therefore, this invention changes the addition of coal gangue from being concentrated in the primary preheater to being added in batches and in different amounts in different preheaters: that is, all other materials are added normally from the primary preheater, while coal gangue is added in the following manner:

[0018] The fifth-stage preheater contains 40.0% of the total coal gangue; the fourth-stage preheater contains 30.0%; the third-stage preheater contains 20.0%; and the second-stage preheater contains 10.0%. Adding the coal gangue in batches reduces both the residence time of the gangue in the preheater and the combustion time, thus mitigating the harmful effects of increased tail-end temperature caused by gangue combustion.

[0019] Therefore, it is necessary to modify the grinding and storage of coal gangue powder. Coal gangue and other raw materials will still be ground using the same raw material grinding equipment, but they will be ground and stored separately to avoid mixing with other raw materials.

[0020] The coal gangue, after being ground by the raw material mill, is stored separately in a raw material silo. The raw material silo is equipped with multiple discharge ports, which correspond to the secondary, tertiary, quaternary and quinary preheaters, respectively. Each discharge port is connected to a screw feeder. By adjusting the speed of the screw feeder, the amount of coal gangue powder being conveyed can be precisely controlled.

[0021] 2. Adding a waste heat boiler for flue gas cooling: Normal cement calcining kilns are designed with a waste heat boiler to recover heat from the flue gas. However, in the process of sintering alumina clinker from coal gangue, the high carbon content in the coal gangue leads to a significant temperature rise during combustion. Therefore, this invention adds a waste heat boiler at the flue gas outlet to further reduce the flue gas temperature and recover heat. This waste heat boiler lowers the flue gas temperature to 300℃-350℃, meeting the requirements of the denitrification process. The denitrified flue gas then enters the next waste heat boiler to continue recovering heat, controlling the outlet temperature to be above 120℃ and above the dew point, before being discharged after passing through a bag filter.

[0022] 3. Modify the grate cooler: For the extraction of alumina from coal gangue using the limestone sintering method, the clinker cooling regime differs from that of cement clinker, resulting in a significant reduction in cooling intensity. Therefore, it is necessary to modify the grate cooler's grate plate. The cooling air outlet of the grate plate will be changed from air outlet through the grate plate gaps to air outlet through perforations on the grate plate. This will improve the air's driving effect on the clinker, accelerate the rapid movement of the clinker, shorten the cooling time of the clinker, and reduce the cooling intensity of the clinker.

Claims

1. A method for sintering alumina clinker extracted from coal gangue using a cement clinker calcining kiln, characterized in that: The coal gangue is added to the preheater at multiple points: 38.0-42.0% of the total coal gangue is added to the fifth-stage preheater; 28.0-32.0% to the fourth-stage preheater; and 18.0-22.0% to the third-stage preheater. The remaining coal gangue is added from the second-stage preheater. Other raw materials besides coal gangue are added normally from the first-stage preheater.

2. The sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln according to claim 1, characterized in that: The flue gas outlet of the cement clinker calcining kiln is equipped with two waste heat boilers connected in series.

3. The sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln according to claim 1, characterized in that: The cement clinker calcining kiln includes a grate cooler at the tail end, and the grate plate of the grate cooler is densely covered with air outlet holes.

4. The sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln according to claim 1, characterized in that: The coal gangue and other raw materials are all ground using the same raw material grinding equipment, but are ground and stored separately.

5. The sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln according to claim 1, characterized in that: The coal gangue after being ground by the raw material grinding unit is stored separately in a raw material silo, which has multiple discharge ports, each corresponding to a multi-stage preheater.

6. The sintering method for extracting alumina clinker from coal gangue using a cement clinker calcining kiln according to claim 5, characterized in that: Each discharge port is connected to a screw feeder.

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