Dry Washing Biodiesel

• ION Exchange Resins
• Keg Resin Tower
• Magnesol

ION Exchange Resins

ION exchange resins are high tech man made resins that are capable of trapping soap molecules on the surface of a resin bead. Different ION exchange resins work in different ways and use different techniques to clean the biodiesel. All of them generate a new waste stream, the spent beads.

Available Resins

A partial listing of the available resins:

• Amberlite bd10dry is made by Rohm and Hass Chemical Co.
• PD206 is made by Purolite, a subsidiary of 3M
• Lewatit GF 202 is made by Lanxess
• Dowex DR-G8 made by Dow Chemical

Pros and Cons

Each resin works in a slightly different way so there are some fine differences between them. They are enough alike from a Homebrewer’s perspective that we can lump them all together for this discussion. They all do work and remove the soaps from your biodiesel but they are not very economical using our standard processing techniques.

These resins are designed to work best on biodiesel with less than 500ppm of soap. That’s how much you usually have after the first or second wash. Commercial biodiesel producers using new oil can meet the 500 ppm level in unwashed biodiesel. Homebrewers using or standard single stage base method on WVO will have three to five times that much soap in our unwashed biodiesel. That means we would be using it three to five times faster than a commercial biodiesel producer. To make it economical, you would have to wash using some other ’wash’ technique first to bring your soap levels down. The manufactures typically recommend an acid eserification stage if you plan to use waste cooking oil.

Some of these can be partially regenerated using either methanol or an acid, but all of them eventually become used up or spent. Once spent, you will have to find a way to dispose of the waste.

With the exception of the Lewatit GF202 the resins remove the soap by replacing the metal ion in the soap with a hydrogen ion forming FFA that is passed through the resin and left in the biodiesel. That means that if you have high soap levels, you will have a high acid number. You can check the acid number by doing a titration on your finished biodiesel. There is no public data available relating soap content to finished acid numbers.

Two problems that home brewers run into when using resins are "compaction" and "fouling". Compaction is caused when the beads grow in size over their normal lifespan and do not move up the tube adjusting for the increase in size. Compaction can cause ruptured resin tubes, burst resin beads, and decreasing flow rates and eventually stopping the flow altogether. Compaction requires a resettling of the beads to resolve the problem. This can sometimes be accheived by backflowing biodiesel through the bed at a high rate to upset the beads. Fouling is a coating of the top layer of resin with contaminates, typically glycerin or undissolved soaps, that result in flow stoppages. It is usually prevented by a combination of increased settling times and filtering. Backflushing with biodiesel or methanol are the usual methods for resolving fouling.

Fouling can be prevented by giving the biodiesel enough time to clear up before passing over to the resin bed. In unwashed biodiesel that has had no water introduced, the cloudiness is caused by soap particles not dissolved in the biodiesel. Settling is the cheap way to remove the cloudiness. A major factor in getting settling to work is having a wide temperature variation. As the biodiesel chills at night more soaps become undissolved and fall out to the bottom. When it warms up in the daytime, the soaps dissolve back into the biodiesel and clear up. If you are settling in a location with little or no temperature variation you may never clear up. To get it to clear up you will either have to filter the undissolved soaps out with a 10-20 micron filter or you can heat the biodiesel until it clears, usually 10 degrees F or so.

Dowex^TM DR-G8
DOWEX^TM DR-G8 is a dried cation resin designed as a processing aid to reduce and remove trace salts, soaps, glycerin and other organics from a crude biodiesel stream. This dried media will also serve as a desiccant media to retain and remove trace water. It is designed to be used after settling out the glycerin and removing the methanol.
Product Information Web site

LEWATIT^® GF 202
The GF202 resin is a Sodium based macroporous design that will remove glycerin and soap from biodiesel. It operates as an adsorber with the glycerin sticking to the bead and the soaps attaching to the glycerin, so it can be regenerated by flushing with Methanol many times. Being sodium based it does not convert soap into FFA and introduce acid to the finished biodiesel like all the other resins. The manufacture recommends removing the methanol down to 0.1% before passing through the beads. Soap levels are recommended to be less than 500ppm. They are shipped wet and do not swell with use like the other resins, meaning no compaction issues. They can however foul if the biodiesel is below 40C or if it has not sufficiently settled. Recommended flow rates are 1-1/2 to 2 bed volumes per hour. It is shipped in 25 liter bags and 200 liter kegs. Pricing is about $12 per liter. The beads are shipped wet and must be flushed with 5 bed volumes of dry methanol before use.
Product Information Web Site

Amberlite^TM BD10dry^TM
Amberlite^TM BD10dry^TM made by Rohm and Haas is an ion exchange resin. It will remove both glycerin, and soap. It is designed to be used after glycerin separation and before the methanol is removed. It can be regenerated for use with glycerin removal, but not soap removal. When it becomes saturated with soap, it must be removed and disposed of properly.
Product Information Web Site

PUROLITE^® PD206
Purolite® PD206 is a dry ion exchange resin that functions as a combined desiccant and ion exchange media it is specially formulated to enable maximum removal of free glycerin as well as catalyst, soaps and salts from crude biodiesel. It is designed for use after settling the glycerin and before or after methanol recovery. Purolite expands roughly 200% during use. Manufactures recommeded maximum flow rate is 0.3 gallons per hour per pound of resin. Maximum recommended soap levels are 750-1000ppm if ASTM Acid numbers are to be met. Manufacture recommend a tower that is three times taller than is wide to prevent compaction and channeling. Purolite is an American company and is aggressively marketing their product in the US. Pricing is about $10 per pound.
Product Information Web Site

Cornelius Keg ION Exchange Resin Tower

Sunbreak Biofuels posted this dry wash design on the Infopop forum. We’ve added it here with their permission.

The Amberlite user guide calls for the following:

• 3:1 Column height-width ratio
• A flow rate of 0.36gph/lb dry resin
• Resin raised 2" from bottom with #80 (175 micron) screen

Projected flow rate of 10 gallons/hour.

The column needs to be able to handle pressure up to 25 psi, be easy to clean and be made of a biodiesel compatible material. For an added bonus the perfect column would be practical for the typical backyard brewer, be constructed from readily available materials and scalable for the small scale producer.

Cornelius kegs, used to dispense fountain drinks, are stainless, handle up to 125 psi, have a large hatch in the top, and have dry connect fittings with a pickup tube routed straight to the bottom They are readily available used for about $25 each..

There are two versions of the Cornelius keg, a 22" keg and a 27" keg. The short one has a height to width ratio of 2.44:1 and the tall one is 3.38:1. The 22" keg will hold about 5.8 gallons, while the 27" keg will hold about 5.3 gallons. Either would allow for 10 lbs of resin to be added to each column and still have sufficient room for 300% expansion.

10 lbs of resin gives a maximum flow rate of 3.6 gallons per hour. Three in parallel will meet the 10 gallon per hour target with a 10.8 gph maximum.

Basic three keg Design

Using one keg will give you a flow rate of about 3 gallons per hour. We’re going to do a three keg setup for about 10 gallons per hour. To do a single keg, you will just remove two kegs from this design. Start with biodiesel which has had the methanol already removed. Filter to 20 microns while pumping into top gravity feed tank. Taking biodiesel from bottom, through a 100 micron pickup screen and filter through a 5 micron paper filter. Then pass biodiesel through the Cornelius keg towers flowing from the top down to the bottom. Use a needle valve on the output of the kegs to regulate the flow rate. The biodiesel should be at 65F to 75F and if colder needs to be heated before passing it through the resin.

Here we see the setup using totes for upper and lower tanks. Biodiesel drains from the lower tank, through the blue 5 micron filter, then through an inline heater then through the Cornelius kegs and back to the top of the lower tote through a needle valve. This setup is located outside in a Northern State and needs heating to bring the biodiesel and resin up to the operating temperature. He is using an inline coffeemaker heater to supply the heat needed.

Filling the keg

(1)Add 2 lbs of glass marbles to the bottom of the keg.
(2)Starting with an 10" square of #80 mesh stainless, cut a 9" circle with scissors.
(3)Use a hole punch to put a 1/4" hole in the middle of the screen.
(4)Install a small rubber grommet in the newly created hole.
(5)Cut a piece of the cheapest flimsy garden hose you can find to the exact inside circumference of the keg.
(6)Curl screen and place inside keg and carefully place at bottom over settled marbles.
(7)Replace stainless pickup tube, oil to easily slide through screen grommet.
(8)Let garden hose act as a bumper around the perimeter of the screen.
(9)Add 1.5 gallons clean biodiesel to keg.
(10)Pour 2 lbs increments of Amberlite in top of keg, rotate as you pour to disperse the Amberlite around the outer perimeter of the screen. This will also help squash the garden hose to the outer edge under the weight of the Amberlite.
(11)After you add 10 lbs of Amberlite backflush the column at 2.5 gph with clean biodiesel. If there is the slightest bit of methanol or soap in the biodiesel used to flush it will precipitate out and clog up the resin bed. After two hours and all air being purged, the column is ready to use.

For each Cornelius Keg you will need:

• 1 ea Five gallon stainless steel Cornelius keg
• 2 ea quick connect fittings + hose barb nipples
• 4 lb glass marbles
• 10 ft ¼" clear hose
• 10" x 10" #80 mesh stainless screen
• 1 ea rubber grommet
• 21" of flimsy garden hose

• 1 each needle valve
• 1 each 5 micron paper filter and mounting head
• 1 ea 100 micron pickup screen

Economics and Final Notes

At the time of this writing each keg tower cost about $130 for the parts and resin and will clean about 320 to 640 gallons of biodiesel. That translates into 20 to 40 cents per gallon for the first load of resin and about 11 to 22 cents per gallon starting with your first resin change. 18 cents per gallon for the first load and 7 cents per gallon on the refills have been reported. Your mileage may vary.

Please note that this design is based on settling for a week or more before passing it through the resin. Incomplete settling will shorten the life of the resin. Experience has shown that settling for four weeks without using a prewash results in the resin lasting for 800-1100 gallons.

The resin depends on methanol being present to act as a solvent for the soap. If the soap is not completely dissolved in the biodiesel, it will tend to clog up the resin. Settling is the best way to reduce the soaps to the level that the methanol can properly dissolve. Longer settling times will reduce the mass of soap in the biodiesel. One test to determine if enough of the soaps have settled out is that the biodiesel will be clear, not cloudy or turbid.

If you use your top gravity tank as a settling tank, it would be better to use a standpipe and take biodiesel out of the middle of the tank rather than from the bottom. That way any soaps and glycerin that has settled in the tank will not be deposited in the resins, shortening the life of the resin.

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