Filtration of Compounded Products

[Gundog48]

We've been having some issues with the filtration equipment I've inherited at the distillery I work at and I want to review our procedures. Currently, we use a 20x20cm plate and frame filter and typically filter everything through 10 micron filters after fining the tank with DE and allowing to settle for several weeks. We use this for our infused gins which have a heavy loading of steeped fruit.

We use 18 of 20x20cm sheets. Sometimes the filters will blind very quickly, sometimes it will sail through, but over time our products invariably drop a precipitate. I imagine these are DE ultrafines, as well as proteins that were small enough to get through the filter pad and have floculated together post filtration. After talking to other distillers, it seems that something like a 2uM final filtration would be adequate to permanently remove these. 

With other products in the pipeline, I'd like to seriously review our filtration procedures and equipment. We do very low volume, we generally filter about 1000L at a time which we would do at a rate of about 4lpm. Cartridge filters look like an attractive option, but I've no idea how to appropriately size them. Whether I'd replace our plate and frame filter altogether is another option, using a 2-3 stage filtration. My main concern is overloading the cartridges, and cleaning. Most of these seem to be priced at a point where they have to be reused to be commercially viable, but given that we have 3 different products that require filtration, this may not always be possible as the flavour/colour of one could contaminate the other.

Can anyone recommend any reading or procedures for determining the suitability of filtration systems? Are you guys having your products anylised, doing it yourself? How should I determine what size pleated cartridge is required? 

[MichaelAtTCW]

Hey Gundog48. We sell a lot of filtration systems. By far we sell more cartridge filtration systems to distilleries in particular unless they are running at huge volumes. For the users producing liqueurs or botanicals with a higher solids content they typically go with multi-stage cartridge setup to step down incrementally from coarse to fine, and some do start with lenticular or 40 x 40 plate and frame setups.

The rule of thumb is that a typical commercial depth cartridge filters 3-5 GPM per 10 inches. So an unloaded 30" cartridge filters at a rate of 9-15 GPM. Coarser filters might have a higher flow rate. Finer filters usually have a lower flow rate. Flow rate is one consideration, but also bear in mind that even if you don't need the flow rate of a 30" filter, you will get more onstream life since 30" gives you more surface area, and therefore more dirt-holding capacity.

In terms of initial sizing, desired flow rate is the most important step. There are lots of cartridges available for standard Code 7 housing, from ultra-coarse to ultra-fine, and in lots of different materials. At that point you could spend lots of time and money on testing which cartridges, but it's usually easier to just buy a small range of cartridges and try them out to find out what works best for you. Since Code 7 cartridges twist and lock into place, you can use 10", 20" and 30" cartridges in a 30" housing, so I typically recommend people get a 30" housing. The difference in price is nominal. Then you can buy a few 10" cartridges for testing, which is much cheaper.

So, if you're initial product is fairly solids-heavy, and you're trying to get to 2µm in final filtration, a 2 or 3-stage setup should get you there. Here's what we offer in terms of all-in-one packages that distilleries like a lot:

TCW DoublePlus

TCW TriplePlus (good for liqueurs and heavy botanical-products where the users were previously having to run multiple passes, and were able to filter in a single pass).

[Patio29Dadio]

Based on your description I would consider a 2-pass with 10-micron and then .45 micron.   We also use a 5-micron polishing filter in our bottle filler.