FOULING NIGHTMARE

[taraleta]

My name is Francisco Di Buono, I’m a mechanical engineer working for an alcohol factory. I’m writing to you from Argentina, so because my English is a little bit rusty please ask me if something is not clear.

In the past 4 year we have start up 3 ethanol plants (alcohol from corn fermentation). The 3 of them were bought to a Chinese company named JINTA. They have been working Great with any Stop for cleaning since the startup.
Beside this we have made 2 more distilleries to upgrade the alcohol quality with our own engineering and they are also working perfect (they were calculated with Chemcad).

But nothing is a bed of roses so here comes the main reason of this post. 6 month ago we started working in a development to add modular distilleries to our main plant. They should be able to process 5 m3/h of fermented mash containing 13% of alcohol and the energy source is direct vapor. But we are stuck in the Beer Stripping section. We have tried everything, 3 different types of columns (sieve, bubble cap and trays in that order) and all of them reported the same problem. Mash sticking in the upper trays.

First we started with sieve trays of 12mm they last 2 days (all the time since star up the delta pressure between the bottom and the top of the column was decreasing) and star loosing too much alcohol (1.5%) from the bottom. After that because our Boss have worked well with bubble caps in a distillery at Arcor (a candy factory) we tried that. Also fail at the same time. At that instance the separation or trays was of 350mm. so we decided to make a tray of 550 mm. same effect. A curios fact of the bubble cap trays is that at some point after half of the bubble caps were cover up it didn’t advance more.
So our last try was using the same technology that our beloved Chinese columns... "Valve Trays". 2 days and stuck again.

All of the columns were of 750mm diameter with 50 mm of weir height and 35 mm of downcomer clearance and flood of 70%

Another rare symptom is that de delta pressure of the column was greater than what chemcad says (this is probably because some property of the corn mash is not well specify). Besides that always the initial hours are off perfect working.

The rare thing here is that the Chinese columns work perfect. Clearly we are not seeing something but here in our country we have no experience voice to give us advice. So I will be extremely grateful is you could provide me some tip based on your experience.

[emptyglass]

This is basically a hobby forum, we are just a bunch of guys having a go at home.

But I think your wash/beer is too dirty and your running too hard. You seem to have too much solid mass entering the column.

As a stop gap, try reducing the charge volume, this will allow a lot of solids to drop out of the vapour before it enters the column and clogs your plates. Not all, but a lot.

Reduce charge volume to 50% of boiler capacity and allow a "boiler chest"

[Bushman]

I like EG, response. A book I have covers this in detail but it has been a while since I read it. It is a University book for commercial plants such as yours. The book is called Distillation Design and is written by Henry Kister. It has all the calculations for rigorous distilllation, packing capacity, etc.

[taraleta]

I´m Planing going to a Henry Kister exposition at london in september. It's a Great book. But almost all the bibliography that exist is about liquid/gas columns, Because the money for developments is at the petrochemical industry most of researchers work there. Havent found a particulary book for distilation of mash/beer,

Emptyglass. what do you mean exactly bu charge volume. Is that input feed?. If it is that Already have try that, the only difference is that it takes longer to get dirty.

[NZChris]

Put video cameras in the columns so that you can compare how the Chinese column behaves compared to yours.