The use of Roots blower technology in sewage treatment accounts for a large proportion! What are the main fan technologies?

In the whole sewage treatment project, the energy consumed by fans accounts for a large proportion of the energy consumed by the whole system, so the selection of fans is particularly important. At present, the blowers of WWTP mainly include Roots blower, multi-stage centrifugal blower, single-stage high-speed centrifugal blower, etc.

Roots blower is a positive displacement blower, which is a kind of rotary blower. It uses two blade rotors or three blade rotors to make relative movement in the cylinder to transport gas.

Roots blower has simple structure, stable and reliable operation, high mechanical power, and easy maintenance; When the pressure changes in a certain range and the speed is constant, the flow rate is a constant; It has strong adaptability during operation and can be automatically adjusted when the flow is required to be stable and the resistance varies greatly. However, the noise is large, and there is a disadvantage that the lubricating oil leaks into the cylinder.

At a certain speed, when the pressure change of Roots blower is large, the change of air volume is very small and basically unchanged; The power increases with the increase of pressure.

Centrifugal blower is also called turbine blower. Under the action of rotating impeller, the gas can obtain the increase of pressure and residence, and can supply air continuously in four lines.

Its working principle is that when the motor rotates to drive the fan impeller to rotate, the gas is thrown out and changes the flow direction under the action of centrifugal force, the kinetic energy is converted into static pressure energy, and the gas is discharged from the exhaust port. At the same time, a certain negative pressure is formed between the impellers, so that the external gas can be fed under the action of atmospheric pressure to achieve the purpose of continuous blowing.

Centrifugal blowers are divided into multi-stage centrifugal blowers and single-stage centrifugal blowers according to the number of impellers. The normal multi-stage low-speed centrifugal blower refers to a centrifugal blower with two or more rotors connected in series on the same main shaft, at most eight stages of blades, and a rotor speed of 3000~3600r/min.

Compared with Roots blower, low-speed multistage centrifugal blower has the advantages of low noise, stable and reliable fan operation, and high efficiency, but it still has the disadvantages of large volume, heavy weight, poor flow regulation performance, low efficiency, and high energy consumption.

Single unit high-speed centrifugal blower has been developed since 1990s with the application of three-dimensional flow theory in the design of centrifugal compressor and blower. The single-stage centrifugal blower adopts a gear speed increase box for speed increase, and the gear speed increase box is lubricated and cooled with engine oil.

The single-stage high-speed centrifugal blower is designed based on the three-dimensional flow theory, which makes it more consistent with the fluid flow law. Its impeller efficiency is greatly improved compared with the multi-stage low-speed centrifugal blower using the two-dimensional impeller. It is a single-stage structure, with short flow and small loss. Its efficiency is 10%~15% higher than that of the multi-stage low-speed centrifugal blower, up to 82%.

The axial inlet guide vane regulating device is used in the structure. When the pressure is constant, the flow is adjusted to 65%~105% of the rated flow, so that it can also achieve high operating efficiency under low load conditions; Adopt automatic monitoring system, with high degree of automation; The assembled overall structure is adopted. Compared with the multi-stage centrifugal blower with the same flow and pressure, it saves energy, reduces the weight by 70% and occupies about 50% less land; At the same time, the diameter of the three-dimensional flow impeller is 30%~40% smaller than that of the ordinary two-dimensional flow impeller, so its rotor moment of inertia is small, and the start-up and shutdown time of the unit is short, without the need for high-level oil tank and accumulator.

Because single-stage high-speed centrifugal blower has the advantages of light weight, small size, energy saving, wide range of performance adjustment, high efficiency and high automation level, it has been widely used abroad and is the mainstream product in the sewage treatment industry at present.