Could you provide some guidance on the design and costs of a spray tower (with gas cooling as the primary cooling method)?
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This post was last edited by hyfxp on 2009-9-6 at 12:26. We are working on a project involving a flow rate of 36,000 m3/hr and a temperature of 220 degrees Celsius; there are also soluble and insoluble VOCs present. The process involves spray absorption and cooling, followed by carbon fiber adsorption to ensure that emissions meet the required standards. The issue is that initially the owner said the temperature of the exhaust gas was only 80–90 degrees Celsius; however, measurements taken during technical verification showed it to be 150–160 degrees Celsius. At the same time, the owner requested that the design target be set at 220 degrees Celsius, which means the spray cooling system would need to be modified. The main goal is to reduce the gas temperature to below 40 degrees Celsius. The water used in the spray tower can serve as a heat exchanger, and there is about 1,000 tons of reclaimed water available per day. I would like to ask for some guidance regarding the design and cost of such a spray tower
It is necessary to provide the composition of the exhaust gases in order to analyze their corrosiveness and water content; the material of the pipe nozzles as well as the amount of water used have already been determined.
1. It can be considered: waste heat can be utilized by using heat exchangers to heat water, which can then be used for employees’ bathing needs; there are successful examples of this approach. 2. Use multi-stage (three stages should be sufficient) spray washing with reclaimed water, which can reduce the temperature to 40 degrees; pay attention to corrosion at the dry-wet interface in the first stage. 3. High-flow nozzles can be considered; previously we used the spiral non-clogging nozzles from American Spray Systems Company, which offer excellent cleaning and distribution performance, and they are of solid cone design. Some humble opinions, hoping they will be helpful.
Temperature changes can affect the water balance! It needs to be considered comprehensively!
The preliminary consideration is that with secondary spraying – 36,000 cubic meters per hour of gas being cooled from 160 degrees to 40 degrees – it will cause the 40 cubic meters per hour of reclaimed water to be heated from 30 degrees to 53 degrees Celsius. The key issue here is related to the spraying process; one manufacturer offers a solution that involves using 300 tons per hour of water for spraying, with the spray fluid then being used to exchange heat with the reclaimed water in order to cool it down. Discussions are currently underway to determine whether such an amount of spray fluid can be cooled using air-cooling equipment
What is the water vapor content in the exhaust gas? This is directly related to the water used in the spray tower; if the vapor content is very low, less water will be needed for the spray tower. :）
They are currently discussing this issue with the spray tower company. By the way, once the air is cooled using the spray tower, should the water content in that air be calculated based on the saturated vapor pressure?
It’s basically a saturated gas :）
About 2 tons of water are carried away per hour. I didn’t know it before, but once I calculated it, I was shocked
I did the calculations; at least about 10 tons of water are needed, and at that point the outlet temperature of the exhaust gas should be around 55 degrees； Only by increasing the spraying volume to 80 tons can the temperature be reduced to 40 degrees :)
The overall material and heat balance calculations are relatively simple, but the specific gas-liquid heat transfer calculations are not so easy to handle. Could you provide some guidance on this? Thank you