With the improvement of national environmental protection standards and the enhancement of awareness of comprehensive utilization of fly ash, the conversion of hydraulic ash discharge to dry ash discharge in power plants has become a current development trend. In recent years, most dry ash transportation has used bin pumps. However, based on the current operating situation, the use of bin pumps has caused inconvenience to the storage and transportation of coal ash due to high air pressure, high power consumption, and high maintenance costs, which not only pollute the environment but also waste resources. The pneumatic conveyor developed and produced by our factory has the characteristics of low air pressure, simple operation, and low maintenance. It is widely used in industries such as power, cement, and chemical, and is an ideal equipment for conveying various powdered materials.

2、 Problems with single bin pumps and negative pressure conveying of fly ash

1. High power consumption and severe wear and tear

Due to the use of high-pressure gas supply ranging from 0.4Mpa to 0.6Mpa for the warehouse pump, the elbow pipes are severely worn. Wear through welding repair and frequent replacement, especially for the discharge valve, feed valve, and exhaust valve, which are severely worn and often stuck. In addition, the repair cost of the pneumatic three major components is high. Workers have to repair and climb the pump body, which is hot, harsh, and labor-intensive.

2. Complex operation

Due to the automatic control of material level and time in the warehouse pump, the console wiring is complex and slightly problematic, involving multiple professionals from the electrical, thermal, and ash removal maintenance departments to the ash yard, delaying maintenance time and causing many troubles for management, making it difficult to ensure normal production.

3. Extremely poor environment

Due to the above reasons, in order to ensure operation, there are many emergency repairs and equipment leaks everywhere, which endangers the environment of the factory and the living environment of the surrounding people, and has a great impact on civilized production.

4. Impact on the comprehensive utilization of fly ash

In order to carry out comprehensive utilization of fly ash, the enterprise has invested heavily in building a fly ash production line. However, due to frequent damage to the conveying system, the normal production of the air separation equipment system cannot be guaranteed, and there are ash pipelines that cannot be delivered, which affects the supply of ash to users and damages the image and interests of the enterprise.

5. Affects the normal operation of the sedimentation tank

Due to the design of ash separation and damage to the bin pump, water had to be used to flush into the sedimentation tank, resulting in insufficient flushing water and tight water supply. Moreover, due to the small fineness of the ash, it is easy to cause blockage of the network pipe, valve and ash pump pipeline, resulting in serious losses to the entire flushing system.

6. Although negative pressure conveying has less wear and tear, the phenomenon of insufficient ash delivery occurs as the air volume gradually decreases after several years of use of the fan.

3、 The superiority of using pneumatic conveyors

1. The equipment investment is small, and one pneumatic conveyor can replace two bin pumps, reducing equipment investment.

2. The gas pressure of the material sealing pump is 0.04Mpa-0.1Mpa, which reduces the gas supply pressure, saves gas consumption, and reduces motor power.

3. Reduced maintenance costs. After the system is installed, debugged, and put into operation, there is basically no need for operation and almost no maintenance. Maintenance workers only need to conduct regular inspections.

4. Low pressure conveying, good equipment sealing, reliable operation, no pipe blockage, and improved environmental appearance.

4、 Structure and working principle of pneumatic conveyor

The pneumatic conveyor is composed of a diffusion chamber, a pump body, a movable air duct, an actuator, and other parts. Low pressure air enters the diffusion chamber through the inlet duct and pump body. When the high-speed airflow passes through the pump body, it vaporizes the material around the nozzle. The airflow exiting the nozzle and entering the diffusion chamber forms a local negative pressure between the nozzle and the diffusion chamber, sucking the vaporized material into the conveying pipe and lifting it to the discharge point by the high-speed airflow.

7、 Installation, operation and maintenance of pneumatic conveyor

Pneumatic conveyors are generally installed at the bottom of the material warehouse and should be securely fixed, with fixed inlet and outlet ducts. At the same time, ensure that the air duct is on the horizontal line and all connections are sealed to prevent air leakage.

When a newly put into operation pneumatic conveyor or when changing the conveyed materials, sufficient lubricating oil should be added to the outer chamber of the movable air duct first, and then the distance between the nozzle and the spray head should be adjusted through the actuator to change the distance between the movable air duct. Through debugging, an ideal position should be selected and the scale should be marked at the same time to start normal operation. When stopping the machine, the nozzle and spray head should be closed and all the materials in the pipeline should be delivered before stopping the air flow.

The pneumatic conveyor can only work normally when the material level has a certain height. If the material level is below a certain value, the conveying capacity will decrease.

If the pipeline is blocked due to sudden gas stop or other reasons, the nozzle and spray head should be closed and air should be blown until the pipeline is unobstructed.

8、 Conclusion

The use of high-efficiency and low consumption pneumatic conveyors to eliminate single chamber pumps in the thermoelectric industry is an inevitable result of technological development. It can be expected that in the near future, this technology will replace silo pumps and lead the way in the thermal power industry, raising the comprehensive utilization level of fly ash to a new height and creating more economic and social benefits for enterprises.