Design requirements for VOCs waste gas spray/absorption tower

The spray tower is the most common pretreatment equipment for VOCs waste gas treatment equipment. It can not only reduce water-soluble organic waste gas, but also remove particulate matter and reduce the temperature of waste gas. The use of organic solvents in the spray tower can form absorption. The device is widely used in the refining and petrochemical industry, so what are some common reference values in the spray tower? The editor of Ausiyi Environmental Protection Engineering will explain it together.

 

1. Choose absorbents with low volatility or non-volatile, high absorption capacity (larger absorption capacity and faster absorption rate), low toxicity, low biodegradability or non-biodegradability, low cost, and low equipment corrosiveness to improve Purification efficiency of the purification device for organic pollutants

2. The air velocity of the packed tower is controlled at 0.5-1.2 m/s, the sieve-plate tower is 1-3.5 m/s, the turbulent tower is 1.5-6 m/s, and the bubbling tower is 0.2-3.5 m/s. The spray tower is 0.5 to 2 m/s. Control the residence time of exhaust gas in the equipment not less than 0.5s.

3. Generally, acid waste gas is added with NaOH, and the solution concentration is kept at 2% to 6%, and the pH is controlled at 7 to 9; the alkaline waste gas is added with sulfuric acid, and the pH is controlled at 10 to 11.

4. The surface temperature of the main body of the spray/absorption purification device should not be higher than 60℃.

5. Regularly add appropriate amount of chemicals and absorbing liquid to control the concentration (pH) of the absorbing liquid, and pay attention to the anti-scaling and blockage of the system, temperature, pressure, sealing, leakage, etc.

6. If the liquid-gas ratio is too large, the absorbent will be wasted; if the ratio is too small, the absorption efficiency will be affected. The actual liquid-gas ratio is 1.1 to 1.5 times of the minimum liquid-gas ratio.

Attachment: Problems and solutions encountered in the operation of spray towers of VOCs treatment facilities

1: Why is the water in the water tank less pumped here and more there?

 Answer: Because the filter plate of the water tank is blocked, the flow of water is not smooth. Don't take out the filter plate, just use a broom to sweep the filter plate on the side with more water up and down a few times. If this happens frequently, it is recommended to add (A.B suspending agent) to the water tank. , After adding (A.B suspending agent) for 30 minutes, the sundries will naturally float on the water surface, and you can salvage them with a fine sand net. It will be used hereafter.

2: Why is the nozzle often blocked and how to clean it?

Answer: The reason for the blockage of the nozzle is: whether the filter plate of the water tank is intact. When cleaning the sundries in the water tank, do not take out the filter plate, just use a broom to sweep the filter plate up and down a few times. The cleaning method is: first, remove the window screws, remove the transparent plate, put on labor protection clothing and enter the spray tower, remove the nozzle to clean it, and then put the cleaned nozzle back on. People come out to flatten the filler in the spray tower, and then put the window rubber pads in place, and the transparent plate can be locked with screws.

3: What should I do if the mist removal layer and mist removal effect of the spray tower are not good?

Answer: Normally, the size of our spray tower is calculated according to the air volume, (the spray tower is bigger or not smaller). If the defogging layer cannot remove the fog, first fill the spray tower defogging layer with multi-sided balls. Under the condition of maintaining the original air volume, if the fog still cannot be removed, put it on the air outlet of the spray tower, that is, above the big and small heads. Make a mist eliminator and that's it.

4: Why does the filler in the spray tower run to the side and how to deal with it?

Answer: Because the air volume of the fan is too large, the size of the spray tower is inconsistent with the air volume of the fan, causing the filler to run to one side. Flatten the filler, lay a layer of mesh board with a diameter of less than 5 cm on top of the filler, and put it on top.

5: Why is the filler often blocked and how to deal with it?

Answer: The blockage of the filler is caused by the high concentration of exhaust particles. Triethanolamine or other cleaning solvents can be added to the water tank in the spray tower, and a little detergent can be added when adding chemicals, so as to keep adding them frequently, in a small amount and frequently. In the end, there will be a lot of dirt in the water tank and spray tower. It is necessary to add A.B suspending agent in the water tank to let the dirt naturally float on the water surface. The dirt should be salvaged with a fine sand net in time, and then cleaned up according to the situation.

6: Why does the water in the water tank flow into the tower when the fan is turned on, and why does the water fill the water tank when it stops?

Answer: 1. The air volume is too large and the inlet and outlet dimensions are inconsistent. It is necessary to add a frequency converter to the fan to control the air volume. 2. The size of the water flow hole between the water tank and the spray tower is too large, and the hole needs to be made smaller. 3. Open the overflow port of the water tank a little higher and the float a little lower.

7: The water pump is running normally, and the water volume of the nozzle is very small, why?

Answer: Check whether the water inlet at the bottom of the pump is dirty and blocked. If so, please clean it up in time. Check whether the water pump wheel is blocked by impurities. Check whether the nozzle is blocked, remove the window to check the water spray condition of the nozzle, and clean and repair it in time.