Wuxi Zechuan Environment, a professional manufacturer of RTO incinerators, RTO, RCO, and VCU equipment, on October 14, 2024, excerpted from the VOCs reduction workstation VOCs treatment system. The energy consumption of the fan is a very important part, which involves the daily operation and operating costs of the VOCs treatment facilities. For a good VOCs treatment system, the selection of fans is very scientific and crucial. Of course, many enterprises currently also adopt variable frequency fans. Now let's take a look at the VOCs waste gas treatment system. How is the power of the fan generally designed and selected?
The power required by the fan in the VOCs waste gas treatment system usually needs to take into account the following key factors comprehensively
Air volume (Q) : Firstly, it is necessary to know the air volume designed for the VOCs system, that is, the volume of gas that needs to be processed per hour (m³/h or Nm³/h). When we were formulating the VOCs treatment plan in the early stage, the air volume value required for the VOCs waste gas system could be provided by the owner or calculated based on the scenarios where VOCs were collected.
Wind pressure (P) : Calculate the total pressure head (Pa or kPa) that the entire system needs to overcome based on the system design requirements, pipeline layout, and component resistance (such as pressure drop caused by filters, adsorption equipment, elbows, valves, etc.). Generally speaking, the overall pressure loss can be divided into pipeline pressure loss and equipment pressure loss (such as the pressure loss of filters and spray towers, which is usually 500-1000Pa each). It specifically depends on the design of these devices.
Fan performance curve: Refer to the performance curve graph or data sheet provided by the fan manufacturer to find the fan's working efficiency point under the corresponding air volume and air pressure. This can be achieved by asking the fan supplier of the VOCs system to provide a copy. Each brand of supplier will have a fan curve. The efficiency of a fan determines the extent to which input power is converted into output power when operating under a given air volume and air pressure.
Power calculation formula
The VOCs waste gas system basically adopts centrifugal fans. The required power can be estimated using the following simplified formula:
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P represents the power of the fan (kW)
Q is the air volume (m³/h) converted to the air volume under standard conditions and then converted to the inlet state of the fan.
ΔP is the total pressure head (Pa).
K is a constant and may range from 1.0 to 1.1 depending on the country and region.
η represents the total efficiency of the fan, typically ranging from 60% to 90%, with the specific value determined by the fan's performance.
5. Detailed hydraulic calculation: For complex systems, it is usually necessary to use professional HVAC design software to conduct detailed hydraulic calculations to accurately calculate the pressure losses of all components and ensure that the fan can provide sufficient energy to drive the gas through the entire system. In our VOCs waste gas treatment system, this step is basically not used, except in VOCs treatment projects with extremely high system pressure requirements, such as the VOCs waste gas treatment in the semiconductor industry. The difficulty of VOCs treatment in this industry is not high, but some sections have very strict requirements for collection pressure. Especially in the past few years, it was also a highly profitable industry (with a lot of hot money). As a result, several VOCs enterprises that often played in this industry have achieved considerable development in their niche markets and even gone public. Therefore, choosing the right track is very important. The technology doesn't necessarily have to be outstanding; what matters most is which industry to play in and with whom. How envious others are!
6. Safety margin and frequency conversion regulation: In actual engineering design, a certain safety margin also needs to be considered to deal with the increase in pressure drop caused by possible situations such as filter material blockage and pipeline blockage. Meanwhile, the use of a frequency converter to control the fan speed can achieve real-time adjustment of the air volume, thereby saving energy. This usually reserves a coefficient of 10 to 20%.
In conclusion, accurately calculating the power of a fan usually involves a series of complex engineering calculations and performance analyses rather than simple formula applications. In the actual design of VOCs treatment engineering solutions, VOCs treatment engineers will make reasonable selections and designs based on the actual situation and experience. Generally, points 1, 2, 3 and 6 mentioned above can be considered.