On the empty tower gas velocity of corrugated plate packing towers
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Dear experts, what I need to design now is a packed tower for cooling natural gas flue gas using spray water. The flue gas flow rate is 690 t/h, and the spray water flow rate is 860 t/h (these values are fixed based on design calculations); the density of the flue gas is approximately 1.255 g/L. I need to determine the tower diameter, but I’m encountering issues with the gas velocity in an empty tower. . . I calculated the flooding velocity using the Bain’s formula, and then took 0.75 of that value as the empty tower velocity; the resulting value was 7.19. After rounding the tower diameter, the velocity became 5.4. But here’s the problem: a velocity of 5.4 m/s corresponds to a gas kinetic energy factor of 18.95, while the reference value given in the literature is 2.4. This made me very worried. . I’m asking all the experts to help me figure out where the problem lies, or whether this is normal. I’m not from a chemical engineering background; I just need to work on this equipment and have had to consult a lot of information. My ability to distinguish between different things in this area isn’t very good. Please explain things to me clearly – I’d be extremely grateful! ! !
First, select the packing; determine the appropriate F factor based on the type of packing, calculate the tower diameter using this F factor, and then compute the liquid spray density.
I have already chosen the packing – BX type corrugated plate packing. The value of F referred to is around 2.4; however, using this value results in an extremely low gas velocity in the empty tower, which means my tower diameter has to be very large
This spray water is used to cool the natural gas flue gas tower; it is intended solely for cooling the flue gas, and no high mass transfer efficiency is required. Therefore, it is unnecessary and inappropriate to use BX packing. You can choose a baffle tower or a random-packed filler tower.
Our design is similar to that of a cooling tower; its actual function is to extract the residual heat from flue gas for use in heating purposes, that is, to reduce the temperature of the flue gas from 90 degrees to 20 degrees, and to recover the sensible and latent heat contained in the flue gas (natural gas flue gas contains a high amount of moisture). Therefore, efficiency is an important consideration. Moreover, our space is limited – the client has provided a site with a diameter of only 6 meters. . .
Flue gas usually contains dust, and BX is a wire mesh filler, which is not suitable for dusty gas. It’s better to use bulk packing or plate columns. Your tower should be considered a type of tower for direct contact heat exchange, with low requirements regarding mass transfer efficiency.
The type I chose is the corrugated plate type; I referred to the book \"Complete Guide to Chemical Equipment Design – Tower Equipment\" for this decision. Our tower also has a function to switch between winter and summer modes: it operates normally in winter, while in summer the packing is removed. The reason for choosing a packed tower is related to pressure drop and the corrosive nature of the flue gas. Is there relatively less dust in natural gas flue gas? Are there any good solutions for this?