How to quickly calculate the aeration rate of sewage treatment? How to select the rotary fan of Roots blower

For the selection of sewage treatment fan, the fan pressure is generally determined according to the depth of water in the pool and the pressure loss of the pipeline. This is the simplest, but many people can't calculate the fan air volume, especially because the calculation formula of aeration volume is complex. In the process of customer service, Xin Qianshun“ The "pollution engineers" summarized some empirical formulas to calculate the oxygen consumption quickly and easily, simplifying the complex work, but the empirical formulas are only limited to exchange and comparison, and it is prohibited to use empirical formulas to calculate the aeration rate in the design scheme!

For example: parameter: water volume: 46t/h, COD: 1200mg/L

No BOD data, calculated as BOD=0.5 * COD=600mg/L

1. Calculated according to gas water ratio:

Contact oxidation tank 15:1, then the air volume is: 15 × 46=690m ³/ h

At 10:1 in the activated sludge tank, the air volume is: 10 × 46=460m ³/ h

At 5:1 in the regulating tank, the air volume is 5 × 46=230m ³/ h

Total air volume: 690+460+230=1380m3/h=23m ³/ min

2. Calculated as 1.5 kg O2 required to remove 1 kg BOD

The removal amount of BOD per hour is 0.6kg/m ³ ×1100m3/d÷24=27.5kgBOD/h

Oxygen demand: 27.5 × 1.5=41.25kgO2

Weight of oxygen in air: 0.233kgO2/kg air

Then the air demand is 41.25kgO2 ÷ 0.233O2/kg air=177.04kg air

The density of air is 1.293kg/m3

Then the air volume is 177.04kg ÷ 1.293kg/m3=136.92m3

The oxygen utilization rate of microporous aerator is 20%,

Then the actual air demand is: 136.92m3 ÷ 0.2=684.6m3=11.41m3/min

3. Calculated by aeration intensity per unit pool area

The aeration intensity is generally 10-20m3/m2h, taking the middle value, and the aeration intensity is 15m ³/ m ² h

Total area of contact oxidation tank and activated sludge tank: 125.4m2

Then the air volume is 125.4 × 15=1881m3/h=31.35m ³/ min

Aeration intensity of regulating tank is 3m ³/ m ² h. Area: 120m ²

Then the air volume is 3 × 120=360m ³/ h=6m ³/ min

37.35m in total ³/ min

4. Calculated by the number of aeration heads

The tank capacity is calculated according to the residence time, and then 350 aeration heads are calculated, with a gas demand of 3m ³/ H

The total air required is 350 × 3=1050m ³/ h=17.5m ³/ min

In addition, the air demand of the regulating tank is 6m ³/ Min, total air demand: 23.5m ³/ min

5. Calculated by experience value

For reference only, large design institutes generally use gas and water. Our design experience value is about 1kg COD, which requires 1kg oxygen, and 1kg ammonia nitrogen, which requires 45.7kg oxygen.

According to the above experience, we can roughly determine the aeration amount, and then we can know the required fan air volume. Then we can determine the required fan pressure according to the depth of the pool. Next, it is much simpler. We can use the existing selection system to determine the size of Roots fan. You can search "Xinqianshun Fan", enter the Xinqianshun Company website, and click the navigation bar "Fan Selection" Click the button to enter the selection page, select the required pressure, input the required air volume, and click the "Selection" button to query the required detailed parameters such as the model, motor power, speed, price, and weight of Roots blower, so as to achieve mobile phone selection anytime, anywhere, and also can be used on the computer. The model selection price inquiry system is common to the parameters of Roots blower and rotary blower of most manufacturers on the market, and users can query and compare prices.

In this way, you can not only estimate the air volume pressure, but also find out the model and price of Roots blower. It is a great skill to read this article.