Methods for High-Temperature Coal Powder Recovery and Utilization in Lignite Drying Production

Abstract

This invention belongs to the field of lignite drying technology and discloses a method for recovering and utilizing high-temperature coal powder in lignite drying production. High-temperature coal powder enters a closed-loop oxygen-barrier screw conveyor from the bottom of a cyclone dust collector. The screw blades inside the closed-loop oxygen-barrier screw conveyor rotate under the drive of an explosion-proof geared motor, moving the high-temperature coal powder towards the discharge port. The coal powder then enters a closed-loop humidifying mixer through a pipeline. Water sprayed from the spray pipes inside the humidifying mixer comes into contact with and mixes with the coal powder. Under the stirring of the mixer, the coal powder and water are fully mixed to form wet fine coal powder, which is then transported to the discharge port of the humidifying mixer. The wet fine coal powder falls from the discharge port onto a belt conveyor below the humidifying mixer and is transported to the finished product warehouse. This invention produces dust-free production, avoiding environmental pollution; the closed-loop oxygen-barrier screw conveyor improves production safety and realizes the recovery and utilization of high-temperature coal powder.

Description

Technical Field

[0001] This invention belongs to the field of lignite drying technology, specifically relating to a method for high-temperature coal powder recovery and utilization in lignite drying production. Background Technology

[0002] Existing methods for producing lignite pulverized coal mainly employ integrated drying, upgrading, and pulverizing processes, as well as superheated steam drying and molding processes. In both of these processes, cyclone dust collectors are the core equipment for achieving gas-solid separation. After the dust-laden, high-temperature flue gas enters the cyclone dust collector, most of the dried pulverized coal is separated and collected under centrifugal force, while the purified gas either enters subsequent dust removal equipment or is directly emitted.

[0003] In traditional separation and collection methods, cyclone dust collectors are usually equipped with star-shaped unloaders to unload the separated coal powder into pipelines, and then use Roots blowers for pneumatic conveying to storage tanks. The disadvantages of this method are quite prominent: (1) The collected coal powder is at a high temperature and has certain flammable and explosive properties. When it mixes with air during the conveying process, it is very easy to form an explosive environment, which poses a great safety hazard; (2) The dust is serious during the pneumatic conveying process, which not only causes material loss, but also poses a threat to the working environment and the health of operators; (3) The coal powder collected in this way is difficult to store stably directly and often requires additional cooling, explosion suppression or inerting treatment, which increases the complexity of the process and the operating cost. Summary of the Invention

[0004] The purpose of this invention is to provide a method for high-temperature coal powder recovery and utilization in lignite drying production, so as to solve the safety hazards and serious dust problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for recovering and utilizing high-temperature coal powder in lignite drying production, comprising the following steps: Step 1: High-temperature coal powder with sparks at 140-160℃ enters the closed oxygen barrier screw conveyor from the bottom of the cyclone dust collector. The screw blades inside the closed oxygen barrier screw conveyor rotate under the drive of the explosion-proof geared motor, which moves the high-temperature coal powder towards the discharge port. The closed oxygen barrier screw conveyor delivers the high-temperature coal powder in a timely manner, keeping the ash discharge port at the bottom of the cyclone dust collector unobstructed. Step 2: Pulverized coal enters a closed-loop humidifying mixer from an oxygen-barrier screw conveyor through a pipeline, where the temperature drops to 95-115℃; Step 3: The water sprayed from the spray pipe inside the humidifying mixer comes into contact with and mixes with the coal powder. Under the stirring of the mixer, the coal powder and water are fully mixed to form wet fine coal powder, which is then transported to the discharge port of the humidifying mixer. At this time, the temperature of the wet fine coal powder is 40-50℃. Step 4: The wet fine coal powder falls from the discharge port into the belt conveyor below the humidifying mixer and is transported to the finished product warehouse, where the temperature drops to 30-40℃.

[0006] Preferably, the enclosed oxygen-barrier screw conveyor includes a sealing pipe, a rotating shaft, screw blades, flange A, a sealed bearing, and an explosion-proof geared motor; both ends of the sealing pipe are provided with flange A; the rotating shaft passes through the sealing pipe and flange A, and screw blades are fixedly provided on the outer wall of the shaft inside the sealing pipe, with the outer edge of the screw blades contacting and connecting with the inner wall of the sealing pipe; one end of the rotating shaft is connected to the explosion-proof geared motor, and the other end is rotatably connected through the sealed bearing; a mechanical seal is used between the rotating shaft and flange A; one end of the sealing pipe is sealed and connected to the ash discharge port of the cyclone dust collector through a pipe and flange B, and the other end has a dust outlet for connecting with a humidifying mixer.

[0007] Preferably, the humidifying mixer is a twin-shaft humidifying mixer with a sealing cover on top; a spray pipe is connected to the side wall of the humidifying mixer, and multiple nozzles are distributed on the spray pipe located inside the humidifying mixer.

[0008] Preferably, the water in the spray pipe is a calcium hydroxide solution with a concentration of 18-25%; the mass ratio of calcium hydroxide solution to coal powder is 1:(3-5).

[0009] Preferably, the number of cyclone dust collectors is 1 to 2, or 3 or more, depending on the specific number of the induced draft fan used in the production line. When there are 2 cyclone dust collectors, they are connected in parallel. The ash discharge port at the bottom of each cyclone dust collector is connected to a closed oxygen-barrier screw conveyor. The dust-laden flue gas from the drum dryer enters the two cyclone dust collectors through pipes, and the gas from the two outlets is then connected to the conveying pipes.

[0010] Beneficial effects: The production process of this invention is dust-free, avoiding environmental pollution; the closed oxygen-barrier screw conveyor prevents oxygen from entering the cyclone dust collector, making the risk of combustion and explosion zero and improving production safety; this invention mixes the collected coal powder with alkaline water in a certain proportion to obtain wet fine coal powder, realizing the recycling of coal dust particles. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the present invention; Figure 2 This is an enlarged schematic diagram of the closed-loop oxygen-barrier screw conveyor of the present invention; Figure 3 This is a schematic diagram of the dried fine coal powder discharged from the humidifying mixer. Detailed Implementation

[0012] The embodiments of the present invention will be described in detail below with reference to the examples, but the scope of protection of the present invention is not limited to the following embodiments. Where specific techniques, connections, or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques, connections, or conditions described in the literature in the art or in accordance with the product manual. Materials, instruments, or equipment used without specified manufacturers are all conventional products that can be obtained by purchase. Example 1

[0013] like Figure 1 As shown, the method for high-temperature coal powder recovery and utilization in lignite drying production provided by the present invention comprises the following steps: Step 1: High-temperature coal powder with sparks at 150℃ enters the closed oxygen barrier screw conveyor 2 from the bottom of the cyclone dust collector 1. The screw blades inside the closed oxygen barrier screw conveyor 2 rotate under the drive of the explosion-proof geared motor, which drives the high-temperature coal powder to move towards the discharge port. The closed oxygen barrier screw conveyor 2 delivers the high-temperature coal powder in a timely manner, keeping the ash discharge port at the bottom of the cyclone dust collector unobstructed. Step 2: Pulverized coal enters the closed oxygen-barrier screw conveyor 2 through the pipeline into the closed humidifying mixer 3, where the temperature drops to 98℃; Step 3: The water sprayed from the spray pipe inside the humidifying mixer 3 comes into contact with and mixes with the coal powder. Under the stirring of the mixer, the coal powder and water are fully mixed to form wet fine coal powder, which is then transported to the discharge port 31 of the humidifying mixer 3. At this time, the temperature of the wet fine coal powder is 45℃. Alkaline water is a calcium hydroxide solution, which can be used as an absorbent to absorb sulfur dioxide. The following are the chemical reaction steps: SO2 is absorbed by the droplets: SO2 + H2O → H2SO3 Reaction with slaked lime: Ca(OH)₂ + H₂SO₃ → CaSO₃ + 2H₂O Crystallization: CaSO3 (liquid) → CaSO3 (solid) Partial oxidation: CaSO3(liquid) + 1 / 2O2(liquid) → CaSO4(liquid) Step 4: The wet fine coal powder falls from the discharge port 31 into the belt conveyor 4 below the humidifying mixer 3 and is transported to the finished product warehouse. At this point, the temperature drops to 36℃. This method generates no dust during the recovery of high-temperature coal powder, avoiding environmental pollution, and eliminates the risk of combustion and explosion, thus improving production safety. The finished product after drying the wet fine coal powder is shown below. Figure 3 As shown.

[0014] Specifically, such as Figure 2As shown, the enclosed oxygen-barrier screw conveyor 2 includes a sealing pipe 21, a rotating shaft 22, a screw blade 23, a flange A24, a sealed bearing 25, and an explosion-proof geared motor 26. Both ends of the sealing pipe 21 are provided with flanges A24. The rotating shaft 22 passes through the sealing pipe 21 and flange A24, and the screw blade 23 is fixedly mounted on its outer wall inside the sealing pipe 21. The outer edge of the screw blade 23 contacts and connects to the inner wall of the sealing pipe 21. One end of the rotating shaft 22 is connected to the explosion-proof geared motor 26, and the other end is rotatably connected via the sealed bearing 25. A mechanical seal connects the rotating shaft 22 and flange A24. One end of the sealing pipe 21 is sealed to the ash discharge port 11 of the cyclone dust collector 1 via a pipe and flange B5, and the other end has a dust outlet 27 for communication with the humidifying mixer 3. Because the spiral blades 23 in the closed oxygen barrier screw conveyor 2 are in contact with the inner wall of the thickened sealing pipe 21 (without gaps between them), the closed oxygen barrier screw conveyor 2 forms a unidirectional coal powder conveying channel, avoiding the risk of oxygen entering the cyclone dust collector and causing an explosion.

[0015] The humidifying mixer 3 used in this invention is a twin-shaft humidifying mixer, which is commercially available. The top of the humidifying mixer 3 is equipped with a sealing cover 32; a spray pipe 33 is connected to the side wall of the humidifying mixer 3, and multiple nozzles 34 are distributed on the spray pipe 33 located inside the humidifying mixer 3. The water in the spray pipe 33 is a calcium hydroxide solution with a concentration of 18-25%; the mass ratio of the calcium hydroxide solution to the coal powder is 1:4.

[0016] In Example 1, there are two cyclone dust collectors 1 connected in parallel. The ash discharge port 11 at the bottom of each cyclone dust collector 1 is connected to a closed oxygen barrier screw conveyor 2. The dust-laden flue gas from the drum dryer enters the two cyclone dust collectors 1 through pipes, and the gas from the two air outlets 12 is then connected to the conveying pipes 13.

[0017] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering and utilizing high-temperature coal powder in lignite drying production, characterized in that, The steps are as follows: Step 1: High-temperature coal powder with sparks at 140-160℃ enters the closed oxygen barrier screw conveyor (2) from the bottom of the cyclone dust collector (1). The screw blades inside the closed oxygen barrier screw conveyor (2) rotate under the drive of the explosion-proof geared motor, which drives the high-temperature coal powder to move towards the discharge port. The closed oxygen barrier screw conveyor (2) delivers the high-temperature coal powder in time, keeping the ash discharge port at the bottom of the cyclone dust collector unobstructed. Step 2: Pulverized coal enters the closed oxygen-barrier screw conveyor (2) through the pipeline into the closed humidifying mixer (3), where the temperature drops to 95-115℃; Step 3: The water sprayed from the spray pipe inside the humidifying mixer (3) comes into contact with and mixes with the coal powder. Under the stirring of the mixer, the coal powder and water are fully mixed to form wet fine coal powder, which is then transported to the discharge port (31) of the humidifying mixer (3). At this time, the temperature of the wet fine coal powder is 40-50℃. Step 4: The wet fine coal powder falls from the discharge port (31) into the belt conveyor (4) below the humidifying mixer (3) and is transported to the finished product warehouse, where the temperature drops to 30-40℃.

2. The method for high-temperature coal powder recovery and utilization in lignite drying production according to claim 1, characterized in that, The closed oxygen barrier screw conveyor (2) includes a sealing pipe (21), a rotating shaft (22), a screw blade (23), a flange A (24), a sealed bearing (25), and an explosion-proof geared motor (26). Both ends of the sealing pipe (21) are provided with flanges A (24). The rotating shaft (22) passes through the sealing pipe (21) and the flange A (24). The screw blade (23) is fixed on the outer wall inside the sealing pipe (21). The outer edge of the screw blade (23) is in contact with the inner wall of the sealing pipe (21). One end of the rotating shaft (22) is connected to the explosion-proof geared motor (26), and the other end is rotatably connected through the sealed bearing (25). The rotating shaft (22) and the flange A (24) are connected by a mechanical seal. One end of the sealing pipe (21) is sealed to the ash discharge port (11) of the cyclone dust collector (1) through a pipe and flange B (5), and the other end is opened to have a dust outlet (27) for communication with the humidifying mixer (3).

3. The method for high-temperature coal powder recovery and utilization in lignite drying production according to claim 1 or 2, characterized in that, The humidifying mixer (3) is a twin-shaft humidifying mixer with a sealing cover plate (32) on top; a spray pipe (33) is connected from the side wall of the humidifying mixer (3), and multiple nozzles (34) are distributed on the spray pipe (33) inside the humidifying mixer (3).

4. The method for high-temperature coal powder recovery and utilization in lignite drying production according to claim 3, characterized in that, The water in the spray pipe (33) is a calcium hydroxide solution with a concentration of 18-25%; the mass ratio of calcium hydroxide solution to coal powder is 1:(3-5).

5. The method for high-temperature coal powder recovery and utilization in lignite drying production according to claim 1, 2, or 4, characterized in that, The number of cyclone dust collectors (1) is 1 to 2; when there are 2 cyclone dust collectors (1), the two cyclone dust collectors (1) are set in parallel; the ash discharge port (11) at the bottom of each cyclone dust collector (1) is connected to a closed oxygen barrier screw conveyor (2); the dust-laden flue gas from the drum dryer enters the two cyclone dust collectors (1) through the pipes respectively, and the gas from the two air outlets (12) is then connected to the conveying pipes (13) respectively.

Images