Carbon Filtration of Vodka Experience

[AK2]

Hello everyone,

I know carbon filtration has been discussed (two posts recently) but I wanted to post my experience with it so others can hopefully learn from my failures and not repeat the same mistakes.....or at least make different ones than I did.  Here goes a long post:

After much searching, researching, and numerous cold calls I received some answers on the carbon filter set up that I had.  Cabot was very helpful, but they only sell carbon by the pallet load, so I had to go with another supplier.  

 

Here is what I learned from Cabot:

 

1. They recommended their product called  NORIT GAC1240Plus
2.  They stated for best results feed from the top down in my vessel (I thought bottom up would be better)
3. They actually recommended running two vessels, a lead and lag (no explanation as to why).
4. They did not recommend cleaning the carbon once it was spent (they suggested disposal and buying new)
5. I stated I wanted to filter 100 gallons at a time, how long would the carbon last.  They responded that 90 days in the "lead" vessel (they assumed I had two vessels).  I believe they assumed I was doing 100 gallons per day, which is NOT the case.  So I do not really have a good idea how long my carbon will last doing 100 gallons every few weeks or months.  
6. Recommended filtering product at 100 proof
7. Recommended flow rate in the vessel I have .5 to 1.5 gpm

 

I purchased three bags from US Water Systems of 600-USW-CARB-SORB US Water Granular Activated Carbon  (1 CU/FT per bag).  I spoke to one of their techs named Ian and asked what he recommended, this was the product (I am only assuming it is similar to the Cabot product, but for all I know it is completely different).  

 

I put all three bags in the filter housing, and flushed with R.O. water top down.  After about 50 gallons of R.O. water it appeared that I had removed all the carbon dust.  I then started Vodka through the filter.  My pump acted strange, like it was dead heading.  Then I had a leak in the bottom portion of the cylinder (where the bottom cone clamps on).  What I discovered was that I was dead heading the pump (and forcing Vodka out the seal).  I did not clean this carbon enough.  The fines that remained formed a plug at the bottom screen.

 

I then decided to flush again (as any product coming out was black, and it overwhelmed my secondary filter).  I drained as much alcohol out as I could (I am going to add it into my next fermenter just before distillation so it will not be a total loss).  

 

I back flushed (bottom up) with 250 gallons of R.O. water.  I then forward flushed with 250 gallons of R.O. water.  I then back washed with 50 gallons of R.O. water that came out clean.  I had to remove the top screen when I back flushed because I again dead headed my pump with a "plug" of carbon dust.

 

After the second flush I restarted Vodka.  Here are the top points:

 

1. Even after the second flush the first 2 gallons had a slight tinge to them
2. I put on a 10 micron filter, this cleared everything up
3. There is much more water trapped in the system than I thought (I drained it best I could, but I am assuming the water hangs up in the carbon bed).  I filtered at 100 proof, I had very low proof for a very long time.  

Here is what I would recommend:

1. Backflush the carbon with R.O. water with the top screen out
2. When backflushing with no top screen keep rates VERY slow, if you go to fast you will lift the bed and you will lose carbon
3. Once done with the first back flushing, flush from top down.
4. Backflush a second time
5. Be prepared to capture the water/vodka combo for a long time (1 gpm does take a while to purge water out)

I did not have the courage to try this, but MAYBE you could push air through the bed from the top and get all the water out.  I was afraid of compacting the bed, making more dust, or creating a channel through the bed, so I opted to just add vodka at around 1 gpm.  

 

Again, sorry for the long post on a topic that has already been covered, but I wanted to share what worked and did not work for me.  Hopefully  I can save someone reading this some frustration!  My best advice is:  if you think your carbon is clean, flush it one more time!

 

Adam  

 

 

[Silk City Distillers]

Cabot is a gold standard in the industry.

Cabot sells carbon by the bag, not the skid, but it is very expensive (more expensive).  1240plus is around $7.00 a pound, plus freight.  While that's expensive, it's not even considered their expensive stuff (Ultra pure Norit ROX at $23.00 a pound - sells for $1,000 for a 40 pound bag).

The two vessel approach is to avoid breakthrough, that is, product making its way through the filter untreated.  The point of a primary and a secondary is that you can replace/refill the primary when it's exhausted, without risking unfiltered product from making its way through the filter, as the second would catch it.  It works because at slow flow rates, the first vessel will become exhausted long before the second vessel would.

Cabot would never recommend cleaning carbon, they sell carbon.  That said, nobody here would recommend cleaning carbon either.  It's not worth the time or energy.

The reason for the down flow is explained in the docs they would have sent you on the pilot column design (I'm guessing maybe they didn't)?

 

[Silk City Distillers]

For the backwash - read the comment about freeboard (empty space) and check that last curve.

[AK2]

Thanks for the info Silk!  Woulda been handy to have this document before I started!  Since I did not purchase from Cadot I am assuming that is why I did not get sent this document.  Again, thanks for the info!

 

Adam

[bluefish_dist]

Wow, I was buying for about $2/lb if I remember correctly from carbon Activated Corporation.  They sold it in 55 lb bags.  

[MG Thermal Consulting]

Just curious, what temperature is your vodka before running it through the A.C.?

[AK2]

MG:  We ran it through at ambient temp, which for me was right around 62F.  

[MG Thermal Consulting]

I would check with the vendor- to activate the carbon for carbon absorbers for odor and cloudiness removal, I believe you need to go colder on you product, in the 30's F.

Depends on your purpose for the GAC.

[FijiSpirits]

We filter at around 82f ambient and haven’t had plugging or cloudiness issues yet. 

 

My process is to hand wash the carbon in a container before putting it in the column.  Takes about ten complete rinses to get pretty clean and remove most of the floaters.  Then we leave it soaking in water for 24 hours to hydrate.  Once it is soaked it never leaves water. We fill the column then run water thru it to settle and rinse and final stuff out.   Product is filtered thru a cheezy 10 micron filter cloth as a final precaution.   We get no carbon in final product. 

 

I think the prewashing is a pretty big deal. A lot of stuff comes out during that process, even in “prewashed” carbon.