As we mentioned earlier about positive pressure pneumatic conveying, thenNegative pressure pneumatic conveyingHow is it transported,Negative pressure pneumatic conveyingIt refers to the pneumatic conveying system that uses a Roots blower (Roots vacuum pump) to thoroughly and uniformly mix the air and powder materials in the bin pump, and then pumps them through the pipeline to the material sealing pump. During the conveying process, the pressure value of the entire pipeline is lower than atmospheric pressure. The negative pressure pneumatic conveying system is one of the earliest practical applications in the entire pneumatic conveying system, and it is also a relatively reliable and mature conveying method. According to the pressure inside the pipeline, it can be divided into two forms: low vacuum and high vacuum. The vacuum degree of low vacuum is less than 1000mm water column, and the vacuum degree of high vacuum is greater than 1000mm water column. The negative pressure pneumatic conveying system is mainly used for ash treatment in coal-fired power plants, also known asNegative pressure pneumatic ash removal system。

As shown in the figure:

　　Working principle of negative pressure pneumatic conveying

　　The fluidized bed of negative pressure suction pneumatic conveying uses air to fully form a fluidized state of fly ash particles, so that fly ash can smoothly enter the negative pressure suction and positive pressure conveying pipeline. The interior of the negative pressure ash suction fluidized bed is composed of two porous thin steel plates, with a breathable layer sandwiched between the upper and lower porous plates.

　　Negative pressure pneumatic conveying generally uses a Roots vacuum pump as a power source to draw the pipeline and tank type warehouse into a certain vacuum state, promoting the formation of a two-phase flow of material powder particles and gas at the inlet under atmospheric pressure, and inputting it into the cyclone separator through the conveying pipeline. Two phase flow separates most of the material from the gas in the cyclone separator due to centrifugal force and gravity. A small amount of material and gas enter the dust collector, and through the action of filter bags, the powder and gas are separated, and the gas is discharged into the atmosphere. The porous plates inside the entire fluidized bed are arranged at a certain slope (4% -10%). Fly ash enters the combination pump through the separator, and then enters the fluidized bed through the combination pump. The feeding equipment is added to the breathable layer of the feeding port on the upper shell. Air enters the lower shell from the fluidized bed and passes through the breathable layer along the fluidized bed, making the fly ash fluidized. Entering the conveying machinery or entering the positive pressure conveying equipment, the positive pressure generated by the air compressor or Roots blower is fed into the bulk material warehouse (bin) through the feeding pipeline. The clean air is discharged from the upper part of the separator through the exhaust duct and discharged into the atmosphere through the exhaust port of the Roots blower (vacuum pump).

　　Technical Specifications

　　Features:

　　1. It has reliable airtightness, and the dust inside the pipeline will not leak into the environment;

　　2. The manufacturing and maintenance requirements of the equipment are low, and the operability of the workers is strong;

　　3. The pressure (vacuum degree) used is low and the safety is high;

　　4. The conveying volume is large, the conveying distance is long, and the conveying material route is not limited by terrain

　　5. The transportation is continuous or intermittent, and there is no accumulation in the pipeline;

　　6. Multiple feeding and unloading points are available;

　　7. Using centrifugal fans and Roots blowers as gas power sources, with a long service life;

　　8. Strong adaptability to conveying materials, both powder and granular materials can be smoothly conveyed.

       Negative pressure pneumatic conveying systemMainly used for centralized feeding, which means transportation from one point to another, such as raw material storage and transportation, workshop ash removal, etc,Negative pressure conveyingIt can effectively collect materials such as dust particles, which will not enter the atmosphere as dust. This not only protects the environment, but also increases production efficiency and reduces production costs. However, due to the vacuum state, the distance of the material is shorter than that of positive pressure conveying