How to calculate the spray water volume for a gas cooling spray tower
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Could some expert please advise on how to calculate the spray water volume for a gas cooling spray tower? Is it based on the gas-liquid ratio?
It can’t be determined simply based on the gas-liquid ratio; heat calculations are also necessary
The spray towers designed by our company are, based on heat balance calculations, required to use a very small amount of cooling water, as the amount of heat that needs to be removed from the gas is minimal. Yet in practice, the cooling water towers used in our operating units have to handle a much larger heat load; we don’t understand how this is possible
Enter the parameters: design parameters and those obtained from actual calculations
For a project currently under design, the volume of exhaust gas is 100,000 Nm3/h; its density is assumed to be 1.3 kg/m3. The temperature of the gas entering the tower is 45°C, and it is required to be cooled by 10°C, so the exit temperature should be 35°C. The temperature of the cooling water entering the tower is 32°C, while its exit temperature is 40°C. Based on these figures, only 41.4 m3/h of cooling water is needed. However, for previous projects we have used cooling towers with a capacity of 800 m3/h. We would appreciate your advice on this matter
Visually, the heat transfer temperature difference is too small. Pay attention to this: when the temperature of waste heat in the actual operating plant drops by 10°C, what are the temperatures of the cooling water entering and leaving the tower? If the temperature difference is small, a large amount of water flow is required.
In actual operation, the temperature difference monitored by the DCS is very small. If the spraying volume is reduced, there is a concern that the spraying area may not be sufficient. The spray tower designed currently has a diameter of DN4600. How can we determine whether this tower diameter is adequate for the required spraying volume? I would appreciate some advice
You can refer to the algorithm for heat exchangers; heat balance calculations are not applicable.
Use software for simulation by oneself, and have the tower internals manufacturer conduct verification. Given the small temperature difference, why not recycle the water at the bottom of the tower to the top of it?
The amount of water required, calculated on a calorific basis, is indeed very small; however, if the gas-liquid ratio is not met, it is impossible to spray such a large volume of gas evenly