Selection of aeration blowers for small and medium-sized sewage treatment plants in towns

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In the process design of small and medium-sized sewage treatment plants in towns, the aeration system typically uses forced aeration. In China’s urban sewage treatment systems, the energy consumption of aeration fans accounts for over 60% of the total energy consumption of such systems. Therefore, it is particularly important to choose the right aeration blower. Basic types and comparative analysis of blowers 1. Single-stage high-speed centrifugal blower: A rotary vane machine that converts the mechanical energy of an electric motor into gas pressure energy, offering a flow rate adjustment range of 45–100% by adjusting the angle of the inlet guide vanes or using variable frequency speed control. When the outlet pressure remains relatively constant, a single-stage high-speed fan operating at its designed operating point has a blower efficiency that is about 3%-5% higher than that of a multi-stage fan, and about 15%-20% higher than that of a Roots fan. Single-stage fans, due to the use of high-speed motors and the absence of multiple stages of transmission, offer significant advantages in terms of size and weight when a large volume of air is required. However, they generate considerable noise due to their high-speed operation. Single-stage high-speed centrifugal fans belong to the higher category among various types of fans, and their structure is complex. High level of technical complexity. Its maintenance and replacement costs are also high, which is not conducive to cost reduction. 2. Multi-stage low-speed centrifugal blowers: Their working principle is basically the same as that of single-stage high-speed centrifugal blowers; the difference lies in the fact that in multi-stage low-speed blowers, the gas passes through multiple impellers arranged in series, undergoing several stages of sequential compression to achieve the desired volume and pressure of air flow. Multi-stage centrifugal blowers can meet high outlet pressure requirements due to their use of multi-stage impellers to convey the medium. However, when the exhaust flow rate is high, in order to meet the required exhaust pressure and flow rate, the size and weight of such fans no longer offer any significant advantages over single-stage high-speed centrifugal fans. Therefore, when the flow rate at the fan outlet is greater than 300 m3/min, single-stage high-speed centrifugal blowers are preferred. 3. Roots blower: The Roots blower is connected to the motor via a belt; it compresses the gas inside the unit from the intake chamber and pushes it toward the exhaust port for discharge, thereby achieving the purpose of blowing air. According to the performance curve of the rotary vane blower’s outlet pressure and flow rate, when the outlet pressure changes significantly. The flow rate of the Roots blower experiences only minor fluctuations; due to its strong adaptability to varying head pressures, it is more suitable for making fine adjustments to the blower’s airflow in systems with variable liquid levels. Under constant pressure conditions, its efficiency is more than 10% lower than that of a centrifugal blower. It offers significant advantages in terms of volume and weight when operating at low airflow rates. Rotary vane blowers have a simple structure, require little routine maintenance, and have low costs for repair and replacement. Therefore, it is widely used in small municipal sewage treatment plants. It can be seen that for small sewage treatment plants with a daily processing capacity of less than 30,000 tons, choosing a Roots blower is a more appropriate option. For sewage treatment plants with a daily processing capacity of 30,000 to 100,000 tons, more attention must be paid to the performance of their fans, their efficiency, and the methods used for controlling them. The Shanghai Ruizhe Roots blower features stable performance and excellent quality; it is a good Roots blower.