Processor Design
When we set out to design a biodiesel processor we first decided to look at some previous designs. There are many types of processors out there. We had the opportunity to check out Piedmont Biofuels processor as well as the Coop in Burlington N.C. at T.S. Designs. In the end we loosly modeled our processor after the one at Piedmont, with a few modifications. First we set out to find some stainless steel tanks. We got lucky and found a good deal at a salvage yard for four tanks a 120 gallon tank for the processor, another 120 gallon tank with a conical bottom for settling, and two 250 gallon tanks for washing.
From left to right: Paul Feather cleaning out the inside of the processor before it got welded shut...The inside of the processor before the lid was welded on notice the built in heat exchanger in the bottom...One of the large 250 gallon wash tanks
These tanks were perfect except a few modifications were needed. We hauled all four tanks to a local welding shop to have some nipples welded on, the wash tanks got stacked and the processor had a stainless steel lid welded on. The lid for the processor was an important addition because no methoxide fumes can escape during the process. It also allows us to be able to pull a vacuum on the tank for the purpose of distilling out the methanol after each batch.
Another important tank in the process is the methoxide tank which is used to mix the methanol with the catalyst (NaOH or KOH). We decided to use a 35 gallon HDPE conicalbottom tank similar to what both Piedmont Biofuels and Burlington's Coop uses. This is a cheap option which offers good functionality. We mix the methoxide by first putting the catalyst into a strainer we built into the tank and spraying methanol over it.
After we had the modified tanks we were ready to pick out some pumps. There are two main ways to mix biodiesel. You can either do it with a propeller on a drill of some sort to stir or you can use a pump to circulate the oil and catalyst during the reaction. Propeller mixing is a far superior way of mixing the down side is that it cannot easily be done in a closed tank. For reasons already discussed we had sealed up the processor tank eliminating propeller mixing as an option. Beacause of this we are using a pump to mix the biodiesel. After looking around extensively for a pump we settled on a American Stainless centrifugal pump. It has stainless steel construction and is explosion proof. Also all of the seals are viton so the biodiesel and catalyst won't degrade them. We have also installed a static mixing tube which helps in the mixing process. This pump willalso be used to transfer the biodiesel from the processor into the settling tank or to one of the wash tanks.
In order to increase our production at the facility we have a settling tank and an extra washing tank. The settling tank serves the purpose of seperating the biodiesel from the glycerine. After a batch has been made in the processor it can be transfered into this tank so that another batch can be made. This effectivly doubles our production potential from 90 gallons to 180 gallons in one day. Because of this increased production we felt a second wash tank would be appropriate to prevent bottle necks in the washing process.
