Computer Simulation and Theoretical Tray Efficiency

A rather detailed and complete article on sour water stripper tray efficiency was published in 2012. It compares three ways of looking at tray efficiency for stripping NFIj out of water (reference 1)  

In general, according to this reference, stripping efficiency for NHj is 40 percent. For H S it s quite variable. However, H S is so easily stripped out of water, compared to NH3, that this variability for H S stripping is not important. 

The problem with this sort of approach to tray efficiency is that it is largely irrelevant. The main problems we have with tray efficiency in sour water strippers are  

Of course, no one could take into account such factors. They are unknown. But what is known is the performance of existing sour water strippers in pretty much identical services. There are decades worth of operating data available for sour water strippers. I helped design a sour water stripper in 1965 (with dumped ceramic packing, which did not work) for American Oil. It s far safer to design a new sour water stripper based on a prototype than on a purely theoretical basis. 

However, Reference 1 does contain a useful analysis of a factor that I have often thought about. That is, the trade-off between steam consumption and the number of trays. From Fig. IV of the reference, note that increasing the number of stripping trays from 18 to 32 reduces reboiler steam consumption by 23 percent for the same NH concentration in the stripped water. 

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