Selection Method of Roots Blower for Negative Pressure Pneumatic Conveying

The following types of fans are basically used in the selection of air source fans: centrifugal fans, vortex air pumps and roots blowers. When using fans, we need to consider two important parameters, namely, air volume parameters and pressure parameters.

1. Air volume

Wind speed, pipe diameter and delivery capacity can be determined

2. Wind pressure

Determine the distance of material conveying, the number of bends, the height that can be lifted, and the conveying capacity.

The usual pressure comparison is as follows:

Wind pressure of Roots blower>vortex air pump>centrifugal blower

The negative pressure of Roots blower can reach - 60Kpa, the negative pressure of vortex air pump is generally - 30Kpa, and the wind pressure of centrifugal fan is generally below - 3Kpa.

We know that there is a term of pressure loss in pneumatic conveying. I believe that professionals who have done pneumatic conveying for many years may not know what pressure loss represents. What is pressure loss? What is the important meaning of pressure loss.

Pressure loss refers to: pressure loss, also known as pressure drop and pressure loss, is a technical and economic indicator indicating the amount of energy consumed by the device, expressed by the total pressure difference of the fluid at the inlet and outlet of the device, which essentially reflects the mechanical energy consumed by the fluid through the dust removal device (or other devices), and is proportional to the power consumed by the fan.

This explanation may not be clear to everyone, that is, the difference between high pressure and low pressure in the system is pressure loss. For example, if the positive pressure outlet pressure is 30Kpa and the pressure measured at the end of the pipe is 10Kpa, then the pressure loss is 20Kpa.

Negative pressure is to measure the pressure difference between the air inlet of the material pipe and the air inlet of the fan, which is the pressure loss. For example, if the air pressure at the air inlet of the material conveying pipe of the system is - 1Kpa, and the negative pressure at the air inlet of the fan is - 15Kpa, then the pressure loss of the whole system is 15Kpa.

The pressure loss is related to the roughness of the pipe inner wall, pipe diameter, conveying distance and lifting height. Generally, the rougher, longer and higher the pipeline is, the greater the pressure loss is. The larger the pipe diameter, the smaller the pressure loss. The pressure loss in the negative pressure system should also consider the impact of filter equipment.

Generally, the pressure loss of negative pressure pneumatic conveying includes three parts: 1. pressure loss caused by air flow; 2. Pressure loss caused by materials; 3. Pressure difference generated by cloth bag;

According to our previous experience, in order to make the system operate stably during design, it is better that the pressure loss of the whole system should be equal to 50% - 70% of the wind pressure of the fan. If the wind pressure is too large, it is easy to block materials, and if it is too small, the power consumption will increase.