Overview of negative pressure pneumatic conveying
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refers to a pneumatic conveying system
that uses a Roots fan (Roots vacuum pump) to generate negative pressure and pumps the powdery and granular materials that are evenly mixed with the air in the warehouse pump to the material sealing pump device through the pipeline. Conveying system whose pressure is lower than the local air pressure. Pressure suction type air conveying is the earlier practical, reliable and mature conveying method for the entire air conveying. According to the different working pressure, it can be divided into two forms: low vacuum (vacuity less than 1000mm water column) and high vacuum (vacuity less than 1000mm water column). Mainly used in ash treatment system of coal-fired power plant, also known as negative pressure pneumatic ash removal system,
Working principle of negative pressure pneumatic conveying
Negative pressure suction-type pneumatic conveying fluidized bin uses air to make the fly ash particles fully fluidized, so that the fly ash can enter the negative pressure ash suction positive pressure conveying pipeline smoothly. The interior of the negative pressure ash suction fluidization bin is composed of two porous thin steel plates, and a breathable layer is sandwiched between the upper and lower porous plates.
Negative pressure pneumatic conveying generally uses a Roots vacuum pump as the power source to draw a certain vacuum state from the pipeline and the tank silo, which promotes the air inlet to form a two-phase flow of material powder and gas under the action of atmospheric pressure. Enter the cyclone. The two-phase flow separates most of the material from the gas in the cyclone due to centrifugal force and gravity. A small amount of material and gas enter the dust collector, and the powder is separated from the gas by the action of the filter bag, and the gas is discharged into the atmosphere. The perforated plates inside the entire fluidization bin are arranged at a certain slope (4% -10%). Fly ash enters the combined pump from the separator, and enters the fluidization bin from the combined pump, and the feeding equipment is added to the breathable layer of the feeding opening of the upper casing. The air enters the lower casing from the fluidization bin, and passes through the breathable layer along the fluidization bin to fluidize the fly ash. Feeding into the conveying machinery or entering into the positive pressure conveying equipment, the positive pressure generated by the air compressor or the roots fan passes the feeding pipeline to send the material into the bulk material warehouse (warehouse). The clean air is discharged from the upper part of the separator through the exhaust duct, and is discharged into the atmosphere from the roots of the Roots blower (vacuum pump).
1. Reliable airtightness, the dust in the pipeline will not leak to the environment;
2. Equipment manufacturing and maintenance requirements are low, and the operability of workers is strong;
3. The pressure (vacuum degree) used is small and the safety is high;
4. Large amount of material to be transported, long distance to be transported, and the material transport line is not restricted by terrain
5. Conveying is continuous or intermittent, and there is no accumulation in the pipeline;
6. Multi-point feeding and multi-point discharging;
7. Use centrifugal fan and roots fan as gas power source, with long service life;
8. Strong adaptability to conveying materials, powder and granular materials can be conveyed smoothly.