james1030bruce:
I don't know what Kister means by stating that he can obtain 5% more capacity by floating in the packing. 5% more than WHAT or more than WHOM? I always "floated" my packed towers with ceramic or steel packing. So I don't think Kister could outdo me in efficiency. Everyone I've known that has installed random packing has used the floating method with the exception being plastic packing -as unclesyd so ably points out. The key object is to avoid channeling of the fluids when in operation, so floating in the packing has always been the norm.
I never heard of Kister nor his books when I studied Chem E; he probably wasn't born yet. He is a "Johnny-come-lately" who presumedly writes a good story. I've tutored and helped young engineers get their degrees and they have quoted Kister's opinions to me. Some of the things I've heard about Kister's writings go against common, empirical sense and are simply not true. But, that's to be expected of Chemical Engineers who have had to spend a lot of time writing the books instead of doing the work. For example, Kister is said to claim that engineered or stacked packing is more expensive than trays. Wrong! This is a common fault of academic persons who fail to understand or conform to the reality of actual, empirical plant life: you need to access plate internals to clean, maintain, inspect and repair; for that you need ladders, platforms, manways, davits, lighting, and structural steel. All of this, plus the safety procedures and personnel make plate internals in a tower multiple times more expensive than engineered packing. In fact, today's efficiencies show that engineered packing is more economic and dependable than the customary random packing for many applications now in use.
My point is that you should not rely on operating an actual process plant by simply following general recommendations in a Chemical Engineering text book. The real answers are out in the plant in the form and shape of your operating and maintenance personnel. I believe that their experience and know-how is not only much more credible, but comes directly from real stake-holders in your operations. These people have a lot more to lose if it doesn't work right than any text book author. Please don't interpret my comments as negative to Chemical Engineering authors; I have a lot of respect for the academic learnings and ideas that they expound from their positions. We owe a lot to the Perry's, Browns, Souders, Little's, Badgers, McCabes, Walkers, Lewis, and Radasch. However, I'm sure that were most of them alive today, they would all concur in telling you that your actual field experience is worth more than the theory that supports it - primarily because it is what sustains and makes your operations work.
If improving your random-packed towers' operation is what you're after, I would recommend you obtain a listing of users from your packing supplier and look up their results in using the different methods to load, handle and design their packed beds. You will find that their experience will be to your advantage - if they will share it with you. Installing re-distributors and shortening packed heights will easily increase absorber efficiency by more than 10% - this is my personal field experience.
Art Montemayor
Spring, TX
