1. How to long term shutdown the GAC columns
o From your description it appears as if you sweeten off the columns and then circulate condensate for one month. Is that correct?
o If this is what you are doing then I will think that you will have a problem with butyric acid being formed in the columns during the long term re-cycle. This is caused by very small quantities of sugar fermenting in the columns over the month. The smell is the butyric acid which is formed as part of the fermentation reaction. You will notice the same type of smell in your spent carbon tank.
o Normally you will take the spent carbon and burn the carbon in an oxygen poor environment which will remove any sugar or other organic material. Therefore the carbon which is in the regenerated carbon will smell okay.
o From my experience one of the problems with GAC technology is that it is difficult to shutdown. In a normal shutdown you will recirculate liquor through the columns at a slow rate 5 KL/hr. This stops/slows down deterioration of the sugar liquor (acid inversion) but this method is only suitable for a week or so.
o Unfortunately if you want to shutdown the plant for a month then the only way I know is to desweeten the columns and to regenerate the carbon in the columns. Unfortunately I don’t think you can just circulate hot water.
o I am sorry that I am not able to suggest a better solution.