What is an air suspension fan? Can it save energy and reduce consumption in sewage treatment? As we all know, if the sewage treatment industry wants to save energy and protect the environment, it generally needs to choose from two levels, one is the choice of production process, the other is the choice of machinery and equipment.
The first one is nothing to say. Most of the sewage treatment plants put into use in China now use activated sludge aerobic process. On the second point, I want to talk about fans.
In the process of sewage treatment, the blower used to provide aeration in the biological pool accounts for 50%~70% of the unit power consumption, which is called the electric tiger in the sewage treatment system, accounting for more than 70% of the total cost of sewage treatment. Therefore, it is of great significance to select a blower with better performance for energy saving and consumption reduction and operation management of the sewage plant.
The previous generation of aeration fan - traditional roots fan and multi-stage centrifugal fan, both of which originated in the last century, have the common disadvantages of high power consumption, complex structure, need for lubrication, high failure rate, large volume, high noise and high maintenance cost.
With the development of the times and the progress of science and technology, the air suspension centrifugal fan and magnetic suspension centrifugal fan have become the representatives of new fans.
Today, Xiao Bian will take water friends to learn more about the air suspension fan. The article is divided into five parts, which can be read as needed.
·What is air suspension fan
·Composition and principle of air suspension fan
·Technical advantages of air suspension fan
·Application cases in sewage treatment plants
·Video explanation of air suspension fan
01
What is an air suspension fan?
The air suspension blower is a kind of blower in which the air will produce a dynamic pressure effect between the rotor and the foil bearing surface when the blower rotor rotates at a high speed, forming a high-pressure air film and supporting the rotor.
The main function of sewage treatment is to aerate the water to increase the oxygen content in the water, so as to remove iron, manganese or promote aerobic microorganisms to degrade organic matters, so as to remove the oxidizable precipitates.
In addition, aeration can make water and air fully contact to exchange gaseous substances to remove volatile substances in water, such as removing the odor of water or harmful gases such as carbon dioxide and hydrogen sulfide; It can also be used to aerate the bottom sediments through the air inlet and air blast at the bottom of the air duct and discharge them through the waste water pump.
02
Composition and principle of air suspension fan
The air suspension fan mainly includes impeller, air suspension bearing, frequency converter, high-speed permanent magnet motor and its structure control system.
The main shaft of the motor is coaxial with the fan impeller, and the high-speed rotor system is directly supported by the air suspension bearing. Its main core technologies are air suspension bearing technology, high-speed permanent magnet synchronous motor and its control technology. The air suspension bearing takes air as the working medium, elastic flat foil as the supporting surface, and elastic wave foil as the supporting component.
Initially, the impeller rotor contacts the bearing, but when the rotor enters the high-speed rotating state, due to the viscosity of the air and the role of the wedge, the dynamic pressure effect will occur between the planes. On the surface of the foil and the rotor, the flat foil and corrugated foil are elastically deformed, the flat foil is pushed away, and the rotor is suspended.
The uneven circumferential air pressure enables the foil bearing to bear the load. Or more simply, during the high-speed rotation of the rotor, a high-pressure gas film is formed between the rotor and the foil, thereby lifting the rotor.
03
Technical advantages of air suspension fan
1) Energy saving and high efficiency
With suspension bearing, no contact loss and mechanical loss, the high speed stepless speed regulation is realized, and the fan operation efficiency can reach about 95%.
2) Low noise, small size, convenient installation
All components are integrated and installed on the common base without special fixed foundation. The equipment is small in size, light in weight, easy to install and operate, low in noise and vibration during operation, and the noise level is less than 80dB.
3) High system integration
The blower itself has integrated the local control and frequency conversion system, so it is unnecessary to set up a separate frequency conversion cabinet and operation cabinet. Through the control panel of the fan itself, you can set various functions and query the parameters of fluid temperature, motor revolutions, air outlet pressure, air volume, power consumption, etc.
4) Simple to use, simple to maintain, low cost and long service life
The blower motor is directly connected with the impeller. There is no gear speed increasing device, no mechanical contact, no lubricating oil system, no wear and energy loss, low maintenance cost, and power transmission efficiency of more than 95%.
The impeller is made of high-strength aviation aluminum and Ti materials, with excellent wear resistance and deformation resistance, and its service life is more than 30 years. The frequency converter is used to regulate the air volume, which is more energy-saving than the throttle valve, and the air volume regulation range is wide, generally 50%~100%.
5) High cooling efficiency
The cooling system adopts the combination of air cooling and water cooling, which can effectively protect the motor and enable the fan to start and stop at any time.
6) Remote control
PLC+GPRS is adopted. It can not only be controlled by the central control room, but also can implement remote maintenance and commissioning in case of fan failure.
04
Application cases in sewage treatment plants
After the standard raising and expansion project of a sewage treatment plant, due to the adoption of A/A/O-MBR high sludge concentration process, the original roots blower could not meet the aeration requirements, so the roots blower was transformed into an air suspension blower.
The sewage plant has three roots blowers, two in service and one as standby, which have been used for nearly nine years. Their performance has gradually declined. Two blowers need to be started for aeration in the biological pond. During normal operation, the temperature of the blower motor is high, which can reach about 100 ℃. The high temperature for a long time has led to the deterioration of the lubricating grease of the motor bearing and the loss of lubrication, resulting in high failure rate of the fan motor and frequent repair, Unable to meet normal process requirements.
In addition, the operating noise of roots blower in blower room is too loud, about 110dB. In order to meet the needs of normal production, To ensure that the effluent quality meets the discharge standard, and to improve the working environment of the blower room, it is decided to use the air suspension blower to replace the old fan, which is configured as one for use and one for standby, and the air volume is adjusted every day according to the actual water volume and quality. Since the air suspension blower has its own acoustic enclosure and no friction during normal operation, the noise in the machine room is greatly reduced, about 70dB below.
After the project transformation, it is adjusted that only one air suspension blower needs to be started to meet the aeration requirements, instead of 2~3 Roots blowers that must be started previously; The noise in the blower room is greatly reduced; Under the condition of stable treatment capacity and water quality, the water quality of effluent basically remains unchanged, and the air suspension fan saves about 20% energy than Roots fan.
A total of 1.59 million yuan was invested in this project, Under the current treatment capacity and water quality, if the air suspension fan saves 0.061kwh/m3 of energy than Roots fan, 402773kwh of electricity can be saved every year, and the unit price of electricity is about 1.1 yuan/kw · h It can save about 400000 yuan/year for the sewage treatment plant, and it is estimated that the investment cost can be recovered within 4 years. If 42000 yuan is added to the annual overhaul of Roots blower, it is estimated that the investment cost can be recovered within three years.
05
epilogue
At present, the secondary biological treatment stage of sewage treatment mostly adopts blower bottom aeration process, so the selection of blower will directly affect investment and long-term benefits. As one of the common equipment for sewage treatment in the future, the air suspension blower has the advantages of high efficiency, high performance, low noise, low energy consumption, and less maintenance workload. It has a huge application prospect in the sewage treatment industry!
