The dilute-phase conveying usually adopts high air velocity and low solid-gas ratio, the conveying distance can reach at hundreds of meters. Conveying gas usually uses the air or nitrogen,its motivation  is often supplied by the roots blower.The material is of the suspended state in the pipeline. The transportation mode is divided into compression type(positive pressure) and suction type (negative pressure). The compression type conveyor has the following main characteristics are: Long transporting distance, stable operating. The suction type conveyor's main characteristics are It can be delivered from below (or the bulk place), multipoint to high, one point of delivery. The compression and suction delivery can be combined in order to meet the special delivery requirements. Apply to multipoint transmission mode for single point material. The material conveying speed is higher than the suspension speed. Suitable for conveying powder materials. Generally we use the negative pressure conveying.