Ethanol batch distillation

[Gardar]

We have been developing an small ethanol plant that will produce neutral spirit for beverage production. We have two units, one stripper that distillate the wash from 15% abv to approx 40% and one rectifier with approx 13 hetp, that distill from 40% to 96%abv. We are not fully satisfied with the quality and therefore would I like to ask if someone have information or opinion to the following questions:

1. If the clarity on the wash has some importance in this case but both the stripper and the rectifier are of jacketed type so there are never high temp points that can burn remaining dead yeast cells. This question only concern the stripper as the raw spirit that is put in the rectifier is more or less completely clear from yeast or other solids. We do the stripping under vacuum so the temp is normally under or about 90 degress celsius.

2. If the column packing type is suitable but we are using ss structured packing of gauze type but I have seen studies that show poor performance of structured packings in some applications.

3. If it has some purpose to adjust the Ph value to neutral or even base before rectification to avoid esterefication on ethyl acetate and in general some tips how the ethyl acetate problem can best be handled. The raw spirit before rectification is around ph 4,2 but after rectification and dilution it ends in around Ph7.8

Thanks,

Gardar

 

[katmar]

Gardar,

I don't know if it is actually possible to make a beverage quality alcohol with only two columns, but I suppose it depends on what raw material you are fermentating. My experience has been with fermented sugar cane molasses, and in this case it is definitely necessary to take the 96% material from the second column and re-dilute it in a hydroselection column. The bottoms from the hydroselection column is then rectified back to 96%.

Are you bleeding fusel oils from the rectifier? This is necessary in both rectifiers, and taking a small heads stream from the initial wash column (sometimes referred to as degassing) can help with methanol and aldehyde removal.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[Gardar]

Thanks Katmar for your comments,

With a regard to your reply I just wonder if you think that we are operating a continous system? We are operating a batch still.

 

[katmar]

Gardar, you are absolutely correct - I was thinking of a continuous plant. Do you have some copper elements in the plant? From what I have seen, batch plants are often made of copper and even in the continous plants an effort is made to ensure that there is contact with copper somewhere.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[Gardar]

Copper has a story for many hundred years for this application. It has many benefical caracteristics and one of it is outstanding thermal conductivity and also it is believed it has some benefit to the spirit via influence on the sulphite. We do not currently have it in our system but in the beginning we had a small tube of it in the vessel to hold a temp sensor in selected place. We noticed it in short time turned to black and as I have undestood it looses it sulphite effect after it has turned to black. All further information concerning this are of an interest to us.

 

[BoBee]

Gardar,
Try to wash the copper element using mild citric acid solution (5%). It will turn to its originall color.