The New B100WH Biodiesel Reactor System with Purolite PD 206 Dry Wash in-line
While water washing is still by far the most popular method of final cleaning biodiesel for the homebased producer there exists yet another, more scientific, way using ion exchange resin beads. While there are a few companies offering biodiesel purification resin we will be focussing on Purolite PD-206 as this is the one we use.
We find that it is a natural progression in homebased biodiesel production to always be on the lookout for better methods that enable us to make an ever higher quality product, and this is what we have done by upgrading to using resin purification. The technology has been in use for big commercial biodiesel plants for a couple of years but is just now starting to find it's way into the homebased producing market.
While the initial cost of setting up for ion exchange resin purification is daunting for some we have found it to be well worth the expense in time saved, and the overall cost of only a cent or two per litre to the final product a reasonable one. Dry washing using resin has eliminated all water use in our homebased production of biodiesel, making of it an environmentally responsible choice. The decrease in power usage has also significantly dropped, as has the time needed to final process following the settling phase.
Those are just some of the more obvious benefits to using resin for dry washing. Another, less obvious, benefit is the quality of the final product. This type of resin is scientifically designed for use with methyl esters (biodiesel) and removes residual glycerine, impurities and leaves an end product worthy of the highest standards in the industry.
With the elimination of the need for water comes the elimination for the need for drying residual water from the biodiesel. This frees up floor space, making the reisn beds use up less of a physical footprint than the typical water wash methods.
In the above photo we can see our resin tanks and how they are hooked up in-line with our system. From the far right we have the settling tank; in that we have not changed anything from the old water washing method we used to use. Once the reaction is done we immediately transfer the biodiesel components to the settling tank equipped with a StandPipe so that glycerine will drop below the SP's outlet and we can drain off the biodiesel first and get the glycerine later from the floor drain.
Then is where we depart from the water wash method; the next tank is a standby tank; this is where the biodiesel, which is free of glyerine, will settle for a couple days (unless urgently needed) further reducing the impact of residual impurities on the resin beads thereby prolonging their life. In this standby tank we circulate the biodiesl using the standpipe's outlet to draw from and then a filter bag inside the tank helps to begin the purification process. We have kept the industrial 120degree full cone spray head from water washing for this purpose.
It is our hope to enventually include a methanol recovery unit at this juncture, again extending resin life, but for now we just run it straight from the standby tank after it has circulated for at least 2 hours through the filter bag and into the first resin tank, named "Lead Tank" in the photo. Before it enters the lead (leed) tank the flow is controlled by a ball valve who's handle has been removed once the correct flow volume has been achieved. The use of a second tank ("Lag Tank" in the photo) for many is redundant, but we feel that it serves a paramount purpose in polishing the biodiesel before it enters the final filter stage, a 2 micron CAT 1R-0749 filter can . The Advanced Efficiency CAT filter IS redundant, but we already had it (here mounted on a Perma Cool 1 1/14 threaded head) and it is there as a safeguard against any particulates that may get through the resin beds, say like a small hair or something. Our aim is crystal clear biodiesel that passes scrutiny from the highest standards.
While there are several designs used for resin exchange resin tanks/beds ours has been simplified to water purification tanks. These are what is called reverse flow tanks, and work essentially the same way a cnister type filter does, with the fuel entering ione side and then passing down into the tank to then filter through the resin media and come back up a center tube to the center of the cap where it leaves the tank.
The tanks come with a center tube in place complete with a basket type strainer cut to fit. These will have to be removed and discarded as they are too porous for the resin and eventually the resin will find itself migrating up that center tube and wanting to transfer to the other tank. This is not a good idea. We have modified ours so that this will not happen.
The tank's original equipment. |
70 mesh screen on a T. |
Tip mounted on the new 1/2" tube |
The inside of the cap. |
The cap is fitted on the tube. |
The tube's top must be beveled. |
The replacement tube is a 1/2" black iron pipe that scews into the T fitting which has it's ends capped with 70 mesh stainless steel screen. This is lowered into the tank and then measured off so that the fit will duplicate the original.
The 70 mesh screen is held in place using common hose clamps. Not very pretty, but effective. The top of the 1/2" pipe must be beveled so that it is not too tight a fit into the cap risking spliting it. It has to be just snug enough to allow it to fit very snugly but still be removable by hand. Be sure to taper the lip of the pipe so it does not cut into the cap.
The tanks used here are water purifying tanks. They can be acquired through any company that deals with water purifying. The recommended resin depth is 24", although with keeping in mind that resin will double in size the tanks we have would not accomodate this, so we have opted for 19" of media per tank, which still gives 38" total, above the minimum recommended by Purolite. Our tanks are 44" at the lip, 42" at the shoulder, so we have pretty much maximised bed allowance.
While filling the tanks for the first time it is very important to cover the pipe's opening so that no media get in it. Initial loading should be with finished biodiesel (if available) enough to cover the resin, but not fill the tank.