Classification of blowers

Roots blower

Roots blower is a positive displacement blower and a rotary blower. It uses two blade rotors or three blade rotors to make relative movement in the cylinder to transport gas. Due to the continuous rotation of the rotor, the extracted gas is sucked into the air between the rotor and the pump housing from the air inlet, and then discharged through the exhaust port. The gas has no internal compression process through the Roots blower.

Roots blower is commonly used in small and medium-sized sulfuric acid plants. When the required air volume is small, the centrifugal blower is often not applicable because the impeller diameter is small and it is difficult to reach the pressure head required for sulfuric acid production at the speed of 2950 revolutions per minute. Roots blower has the advantages of both reciprocating compressor and centrifugal blower. It has the characteristics that the air pressure of reciprocating compressor changes slightly when the rotating speed is fixed, and the air supply volume can remain unchanged, that is, the proportional relationship between rotating speed and air volume is maintained. It also has the advantages of centrifugal blower, such as high rotating speed, no air valve and crankshaft, light weight, convenient application, etc. The disadvantage is that when the outlet is blocked, it is easy to increase the pressure and even cause damage to the machine itself. After a long time of use, the air supply volume decreases due to the expansion of the gap between the two rotors and the gap between the rotor and the casing.

Blast furnace blower

At present, all blast furnace blowers adopt blade type fans, mainly including centrifugal type and axial flow type. The centrifugal blower has the advantages of simple structure, reliable operation, high design point efficiency, low noise, etc. The centrifugal blast furnace blower has relatively mature manufacturing and application experience in China, and blast furnaces below 400m3 are widely used in regions and countries with backward industries. However, with the increase of the blast furnace, the adjustment loss, overall dimensions and fan weight of the centrifugal blower have increased significantly, which brings great difficulties to manufacturing, transportation, installation and maintenance. At the same time, it is also limited by the strength of rotating parts - impeller material, spindle stiffness, motor startup and other factors, which also reduces the reliability and economy of the fan operation. The axial flow blower is widely used in large-scale and modern blast furnaces because of its compact structure, small volume, light weight, good load regulation, wide application range, small fan moment of inertia, and easy motor startup. In China, axial flow blowers are widely used in blast furnaces of more than 500m3, and certain experience has been accumulated in manufacturing and operation.

Magnetic suspension blower

The magnetic suspension blower is a kind of turbine that adopts magnetic suspension bearings. Its main structure is that the blower impeller is directly installed on the extension end of the motor shaft, while the rotor is vertically suspended on the active magnetic bearing controller. It does not need the speed increaser and coupling, and is directly driven by the high-speed motor. The core of single-stage high-speed centrifugal blower with speed regulated by frequency converter is magnetic bearing and permanent magnet motor technology. The main technical features of the magnetic suspension blower are:

(1) High efficiency impeller: The high efficiency impeller is designed with three-dimensional flow, and the five axis machining technology ensures the manufacturing accuracy of the impeller.

(2) Magnetic bearing: no mechanical wear, low energy, semi permanent life.

(3) Integration of structural design: the fan impeller is directly installed on the motor shaft end, integrated with the control system, and packaged in the box, with simple and concise structure.

(4) Convenient installation and maintenance: no lifting equipment and large space, no special foundation, convenient maintenance, and saving the infrastructure cost of the machine room.

(5) Modular design of the system: according to different user flows, multiple blowers are allowed to work in parallel, with wide adjustment range and strong flexibility.

Advantages of magnetic suspension blower:

(1) Energy saving and high efficiency: the magnetic suspension bearing is used, without contact loss and mechanical loss, to realize the stepless speed change regulation of high speed.

(2) High system integration: with imported filter, cooling system, fully automatic anti surge system, power failure and fault protection system, it brings safety, convenience and reliability of operation.

(3) High cooling efficiency: the cooling system adopts an external condenser, which can effectively protect the fan system and enable the fan to start and stop at any time.

Single pole high-speed centrifugal blower

The monopole high-speed centrifugal blower is a product developed in the 1990s with the application of the "three-dimensional flow theory" in the design of centrifugal compressors and blowers. Three dimensional flow design theory is adopted in the design of the monopole high-speed centrifugal blower, which makes the efficiency of the monopole centrifugal blower reach more than 82%, far superior to that of the multipole centrifugal blower. The axial inlet guide vane adjustment device is adopted in the structure. Under constant pressure, the flow is adjusted to 65%~105% of the rated current, and the flow adjustment range of a single set is 45%~100%, making the operation under low load conditions more efficient, This is an advantage that low speed multipole blower and roots blower do not have. Due to its small size, light weight, high efficiency, energy saving, wide range of performance adjustment and high automation level, the monopole high-speed centrifugal blower has become the mainstream product of the aeration blower in the sewage treatment industry.

Multistage centrifugal blower

Centrifugal blower, also known as turbine blower, can realize continuous air supply by increasing the pressure and flow rate of gas under the action of rotating impeller. 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 added 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 operation of multistage low-speed centrifugal blower refers to the centrifugal blower with two or more impellers connected in series on the same main shaft, at most eight stages of blades, and a rotor speed of 3000~3600r/min. Centrifugal blowers generally use inlet throttling to regulate the flow and pressure, so that the fan can operate at a lower power without venting regulation, and can maintain the same efficiency as the rated working condition, which is used for working conditions with unstable pressure and flow.

The air supply volume of multistage centrifugal blower is generally large, but the air pressure generated is not high, the outlet gauge pressure is generally ≤ 110kPa, and the flow is generally about 130m3/min. Compared with Roots blower, low-speed multi-stage centrifugal blower has gradually replaced Roots blower in foreign sewage treatment plants since 1980s due to its advantages of low noise, stable and reliable fan operation, and high efficiency. However, it still has the disadvantages of large volume, heavy mass, poor flow regulation performance, low efficiency, and large energy consumption.

Air suspension centrifugal blower

The air suspension centrifugal blower is a new concept centrifugal blower. It uses the turbine engines of aviation and spacecraft for reference, and applies advanced air suspension technology, Two high-end core technologies, "high-speed direct coupled motor" and "air suspension bearing", have been adopted to improve the speed gear coupling, cooling system and oil lubrication system of the traditional single-stage high-speed turbine blower, greatly improving the technical performance and operational reliability of the product.

The air suspension single-stage centrifugal blower is made of SVS titanium alloy, and the impeller has strong deformation resistance. The efficiency is up to 88% when the best efficiency angle is selected; BLDCM permanent magnet brushless super high speed motor is a new type of motor with the development of permanent magnet material technology, semiconductor technology and control technology, which is more efficient and energy-saving; Frequency conversion adjustment mode is adopted to make the adjustable range of suspension centrifugal blower wider; The use of air self cooling technology can ensure that the blower can still maintain reliable working performance in hot summer. Due to the use of high-speed direct coupled motor, air suspension bearing and three-dimensional simulation turbine wheel, the energy consumption caused by mechanical transmission and mechanical friction is greatly reduced, so the efficiency is extremely high; Air suspension bearing has longer service life than magnetic suspension bearing, and the replacement price is relatively low; The startup and shutdown do not depend on the power supply, and the operation is more stable and reliable than the magnetic suspension centrifugal blower; It can save 25%~35% energy compared with Roots blower, 15%~20% energy compared with traditional multi-stage centrifugal blower, and 10%~15% energy compared with traditional single-stage high-speed centrifugal blower. The air volume is 35~160 m3/min, and the maximum outlet air pressure reaches 100kPa.