A municipal sewage treatment plant was built in 2006 and put into operation in January 2007. In 2010, the total expansion scale reached 60000 tons, and the actual treatment capacity was 55000-60000 tons. A2O process is adopted, and roots blower is originally adopted, with single unit air volume of 58m ³/ Min, boosting 70kpa, power 132kw, dual-use and two standby operation, high power consumption, noise greater than 120dB, and high failure rate. The original design effluent quality meets the national first-class B standard. Now it is required that the effluent quality meets the national first-class a standard. Therefore, it is necessary to upgrade the standard. Due to the higher requirements of effluent quality, the oxygen demand is correspondingly increased, and the fan flow is required to be 110m ³/ Min, while roots blower has been used for many years, the gear clearance increases, the impeller clearance and side clearance increase, the efficiency decreases greatly, and the air volume cannot meet the requirements. It needs to replace or start three to meet the requirements. Before the transformation, the power consumption cost accounts for 75% of the total sewage treatment cost, while the power consumption of the fan accounts for 70% of the total sewage treatment cost, that is, the operation cost of the blower accounts for half of the sewage treatment cost. Therefore, it is urgent to select an energy-saving blower.

Type selection of fan

According to the requirements of the national evaluation standard for the operation quality of urban sewage treatment plants, the energy consumption of sewage treatment plants is required to reduce energy consumption, reduce noise and avoid secondary pollution. Therefore, the sewage treatment plant first pays attention to the new high-speed centrifugal blower when selecting fans, and compares the type selection of imported magnetic suspension blower, imported air suspension blower and domestic magnetic suspension blower with the same air volume, pressure rise and shaft power, as follows.

2. Introduction of domestic magnetic suspension blower

The magnetic suspension blower adopts the high-speed permanent magnet synchronous motor main shaft supported by the magnetic suspension bearing with independent intellectual property rights and is directly connected with the high-efficiency three-dimensional flow impeller, which saves the mechanical transmission loss, realizes non-contact and friction free rotation, and eliminates the lubrication system. The fan adopts variable frequency speed regulation and intelligent control, with a wide range of regulation and control, which is suitable for the variable working conditions of water level and water quality, and can realize local and remote monitoring.

2.1 magnetic bearing

The magnetic bearing levitates the main shaft of the motor by means of electromagnetic force. The displacement sensor monitors the position of the main shaft and feeds back the displacement deviation signal to the bearing controller. After calculation, the bearing controller adjusts the magnetic force around the magnetic bearing by adjusting the current, so as to keep the main shaft rotating at the bearing center.

2.2 high speed permanent magnet synchronous motor

A permanent magnet is installed on the main shaft of the high-speed permanent magnet motor to ensure the magnetism of the main shaft. The coil wound by the silicon steel sheet of the stator of the motor generates oscillating magnetic force, and the rotating speed and the oscillating field are consistent during the operation to achieve synchronization. High speed permanent magnet synchronous motor has the advantages of high efficiency, high speed and easy control.

2.3 three dimensional flow impeller

The three-dimensional flow impeller is made of high-strength aluminum alloy material. After CAE finite element analysis, Z reduces the moment of inertia to a great extent while ensuring the strength. The impeller adopts backward bending design and CFD pneumatic design, with high efficiency and wide working range.

2.4 intelligent control system

The domestic magnetic levitation blower adopts vector free frequency conversion control to adjust the speed to control the fan flow and pressure rise to meet various working conditions. The intelligent control system can predict surge and realize local control. The equipment is equipped with GPRS system to realize remote monitoring and data transmission.

3. Equipment installation

The maglev blower adopts a skid mounted structure as a whole. The equipment integrates the fan body, control system, filter system, etc. into the box structure, which is easy to install. Directly place the blower on the standby fan platform in the sewage treatment plant and connect the exhaust pipe to complete the construction. The total construction cost plus material cost shall not exceed 10000 yuan, and the installation construction shall be completed within one day.

4. Energy saving comparison

As is known to all, for centrifugal fans, the air volume of the fan is directly proportional to the fan speed, the pressure rise is directly proportional to the square of the fan speed, and the power is directly proportional to the cubic of the fan speed. Increasing the fan speed is significantly higher than the power in terms of air volume and pressure. Therefore, high-speed centrifugal fans have obvious energy-saving advantages over ordinary fans; Since the magnetic levitation fan itself has no contact, no friction, no transmission loss and no excess power loss; The efficiency of permanent magnet synchronous motor is 5-7% higher than that of ordinary motor; In addition, the magnetic levitation fan itself can adjust the speed according to the working condition demand to adjust the air volume and pressure without venting and waste. To sum up, the energy-saving effect of Maglev blower is obvious, which is 45% less than the original fan. The following is the power consumption record of the wind turbine for one week before and after the transformation of the sewage treatment plant, which can be clearly obtained through comparison.

Before transformation: from June 15 to 21, the average daily power consumption is 5385kwh;

2） From July 15 to July 21, the actual power consumption curve of every 12 hours is as follows:

After transformation: from July 15 to 21, the average daily power consumption is 3218kwh;

According to the above measurement results, it can be concluded that:

Power saving rate: Ψ== 40.2%

Annual energy saving: w = (5385-3218) × 365=790955KWh

Industrial power consumption per kWh is calculated as 0.8 yuan

Energy saving: 790955 × 0.8 = 632764 yuan

Annual carbon emission reduction: Tec = 790955 × 320 ÷ 106 = 253.1 tons

Annual carbon dioxide emission reduction: tCO2 = 790955 × 0.75 ÷ 1000 = 593.2 tons

Through calculation, it can be seen that the energy-saving effect of domestic magnetic suspension blower is obvious, 253 tons of standard coal can be saved each year, and 593.2 tons of carbon dioxide emissions can be reduced. If the domestic magnetic levitation blower is popularized and applied in the sewage treatment plants throughout the country, it will greatly reduce the carbon dioxide emissions, improve the air quality, and return the blue sky and white clouds to everyone.

5. Operation effect

The equipment has been running steadily since July. The energy saving effect is obvious. The on-site noise is significantly reduced. The noise at 1m of the equipment is 83db. After two months of operation, it has been proved that the domestic maglev blower technology is very mature and can completely replace the imported maglev blower, reduce the procurement cost and operation cost for the sewage treatment plant and save the maintenance cost. The launch of domestic magnetic levitation blower will bring revolutionary changes to the sewage treatment industry and make greater contributions to the national energy conservation and emission reduction cause.

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