Random Packing installation method v Capacity loss ? 1

[mrtangent]

I've just re-read the KISTER Chapter on repacking distillation columns. He seems to suggest by floating random packings into columns you can increase capacity by 5%. and other authors/refs suggest by 50 %. Its on the operational book pg268 1989/90 edition.

With Plastic packing this is not possible (it floats), we'd normally load via a manway and just dump the packing in or shot it in.

Has anyone see this efficiency loss or even gains ?

From a practically point of view we've just loaded the most ergonomic way possible and assume the random packing would settle in the column to be "acceptable". Without using a shoot I dont see another way - is this normal ?


So whats peoples experience

 

[unclesyd]

When we used a lot of plastic packing it was just dumped from the top or an upper manway as you state. We could always depend on operations to "bump" packing and rearrange it. Our distribution trays or distributors were the strongest in the area.

The only packing we floated in was ceramic, both Raschig and Berl Saddles.

Personally I don’t see how you could measure a 5% increase/decrease in packing in a chemical/industrial setting. I know on our systems (more than 50) this type measurement would be impossible due to all the variables.

 

[pmureiko]

You can wet load the plastic packing. Only the top layer will float, the remainder will be held down by the weight of the packing on top. The top layer will sink after you drain the water out.

I'd use wet loading to get better packing distribution and eliminate breakage.

The 5% capacity increase is due to the elimination of packing breakage. Broken packing fills the void spaces between packing elements and reduces the open area for flow. As a consequence the the pressure drop and operating % of flood increase.

 

[mrtangent]

Pmureiko,

Thanks for the comment. But, I dont aggree that plastic packing will break PVDF/TEFZEL is very non breakable. (I've accidentally dropped in from the top of the plant and it bounces)

So if it does'nt break do you still stand by wet loading. We dont really want to wet load as it adds shutdown time and wastes a lot of water.

 

[Montemayor]

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

 

[mrtangent]

Art,

Thanks for the info.

When you mean "listing of users" do you find it usual for operators to share expereince of packed beds operation. Typically we have not done this with our company.

I have already contacted Koch whom supply the packing with the same question and I am waiting a responce.I just was curious in case anyone on the forum has seen this improvement.

We have already defined process modifications which will gain us capacity(new unit op and change to PFD) due to be installed in about a years time but we were curious if we could get a few % additional by packing better between then and now.

 

[Montemayor]

James:

In my experience, if you're dealing with Koch, you already have a reputable supplier on your side. In the past, while seeking experience with certain types of packing, it was always very normal for operators to share expertise in packed beds' operation. However, in the last 10 years or so, the industry has undergone a flux and several setbacks. We no longer have persons like Ralph Strigle, John Eckert, Max Leva, and other pioneers/experts who literally "wrote" the book on the tecnniques. US Stoneware/Norton Ind. has dissolved and St. Gobain, the French company who took the technology Norton had, doesn't seem to be distributing it as efficiently as it was before. But there are other suppliers out there. Certainly, Koch is one of the leaders. Jaeger Products, Inc is another and there is always Glitsch Products.

This industry has always demonstrated a willingness to share know-how and improvements in the past. In the past, persons like Jose Bravo with Jaeger Products, furnished identification, specifics and detailed results of specific packed tower applications in processing plants. All of these companies keep a database of the industrial applications of their products and keep close contact with the successful operations, sometimes obtaining permission to "showcase" the application. I'm sure if you inquire, you will get cooperation.

Today, there is definite improvement in the technology that I applied over the last 40 years. Items such as redistribution techiques, structured packing, injection trays, etc. are things that definitely improve the past efficiency of gas-liquid contact and mass transfer.

I hope you succeed in obtaining the assistance and information you seek.

Art Montemayor
Spring, TX