The Basics Of Dry Wash Resins Arbor Biofuels Company puts it this way,
"The ability of a resin to remove impurities works on the principle of ion exchange
(or in laymen’s terms: atom replacement in a molecule). The reason this "exchange" benefits
or purifies is because usually the atom(s) used to replace the unwanted atom(s) (or contamination)
is Hydrogen or Hydroxide.
So you have water which is contaminated with some mineral and it's making the water taste funny;
lets say Sodium. The Sodium then is replaced by Hydrogen - the Hydrogen will immediately bond with
other molecules most likely producing water; and magically the Sodium is replaced with essentially more water...
A large surface area is imperative to this process because, in order for this to work effectively, the bead(s)
has to "hold" millions of hydrogen atoms ready to be donated for the cause. Therefore, the total surface area of
the bead has to be covered in "dangling" hydrogen’s (or that are loosely bonded - chemically).
Chemists figured out that the best way to increase the surface area of the bead were to make it "porous" so that each
bead not only had the external spherical surface area; it now had an immense internal surface area of its
thousands of micro-channels. These micro-channels were then also coated with the appropriate dangling atoms
ready to purify even more water per bead.
In our case, the beads are typically coated with hydrogen from sulfuric acid. This is accomplished by taking specially
formulated and manufactured plastic beads and soaking them in a bath of highly concentrated sulfuric acid. A portion of
the sulfuric acid's molecule (sulfonic group) actually starts bonding to the exposed surface area of the bead. These bonded
molecules provide the dangling Hydrogens (by the millions). After draining off the acid and drying the resin beads, the beads
are now activated and you have a fully charged ion exchange resin.
Micro-Channels
This brings us to the "micro-channels". Being that these micro pathways are relatively tiny as compared to the size of
liquid molecules; water can flow into them where as oils cannot. Therefore water can penetrate the pores of these micro-channel
resins and oils like vegetable oil and Biodiesel (long chain hydrocarbons) can't so this means that water which is a good
solvent of impurities, can transport these impurities to the total available activated surface area and take full advantage
or the beads ion exchange properties and come out clean on the other side -- biodiesel cannot.
That is until Macro-Channel (or Macroporous) resin was invented! These resin beads had larger pores;
in fact, the pores are so large that now even large hydrocarbon chain molecules can penetrate to the beads
inner surfaces thus making them ideal for not only water purification but oil purification (and in our case Biodiesel!).
Example Of Thermax Porous Surface Area Dry Wash Resin
We've teamed up with Arbor Biofuels Company,
specialists in dry washing Biodiesel with ion exchange resins, to bring you this exciting product to
help with your dry washing needs. Should you have any technical questions about using this great dry wash exchange resin,
they're poised and ready to offer a wealth of information!
Thermax can either be used until it's spent and discarded or regenerated by using a methanol wash.
Thermax vs. Other Dry Wash Resins
Thermax is similar to the Amberlite & Purolite dry wash resins which we sell.
The chemical properties are similar however mechanically it is very different due to its tremendous porosity (as stated above).
Top - Amberlite & Thermax, Bottom - Purolite
Most studies have shown that dry wash resins do an excellent job of dry washing Biodiesel.
Thermax, Purolite and Amberlite are all based on a hydrogen form dry resin and built around
the same chemical ion exchange resin protocol. In other words, because they are built similarly
and function similarly, it comes down to individual biodiesel production preferences.
In several ways Thermax T-45 BD Macro resin has exhibited preferential production properties:
significantly less compaction issues and pressure build-ups in dry wash towers (Ion Exchange Columns)
due to reduced bead swelling, significantly longer life expectancy due to its greater number of
molecular cross-linking, a reduction in the formation of gelatinous fouling layer which can form
on the top of resin beds and significantly impact resin bed performance.
Read More About Why Thermax Is Better
How Do You Use Resin To Purify (Dry Wash) Biodiesel?
The resin beads are placed inside of a holding vessel and unwashed Biodiesel is flowed through the resin beads.
Typically the vessel employed is tubular and is referred to as an Ion Exchange Resin Column.
The resin beads, when deposited in the column, form a "resin bed" at the base of the vessel.
How Much Biodiesel Can The Resin Purify? Arbor Biofuels Company (ABC)
indicates that 1 lb of Thermax can be expected to
treat approximately 125 gallons of home brewed Biodiesel made from used cooking oil.
They further indicated that to achieve these results, the resin should be
used according to manufacturer's recommendations.
Examples of Thermax Recommendations
1- Depth of resin bed needs to be a minimum of 36"
2- Dry wash vessel's resin bed should be designed on a 1 to 3 aspect ratio.
For every width in diameter, the resin bed depth/height should be
three times the diameter. For example, the 36" deep resin bed
would have a maximum column diameter of 12".
3- Dry wash vessel should be capable of handling 50% resin bed expansion since the resin swells as
it adsorbs the impurities out of the Biodiesel. For example, the 36" deep resin bed
mentioned previously would need a resin vessel with a minimum height of 54"
4- There should be no more than 2000 ppm (Parts Per Million) of total impurities
(glycerin, soap, unused catalyst and other trace impurities) in the Biodiesel to be dry washed but
1000 ppm is highly recommended.
How Fast Should I Flow The Biodiesel Through The Towers?
Every tower is different in it's construction so flow rates will vary depending on the particular dry wash tower being used, but
Arbor Biofuels Company recommends the following flow rates
when using our Dry Wash Towers: 6" Tower - 9 Gallons Per Hour (0.15 GPM) 10" Tower - 25 Gallons Per Hour (0.42 GPM) 12" Tower - 50 Gallons Per Hour (0.83 GPM)
What Kind Of Pump Should I Use? Arbor Biofuels Company recommends using
a diaphragm style pump that can deliver a consistent flow through the towers for extended periods of time.
Being able to adjust the flow rate is also crucial.
Example Pumps include Milton Roy Series, Liquid Metronics Incorporated (LMI), and Pulsafeeder Click Here to learn more about diaphragm pumps
If you have trouble finding a pump, contact Arbor Biofuels Company
as they can often help you find a used one.
What Temperature Is Best To Run The Biodiesel Through The Thermax?
Thermax is rated to handle Biodiesel as cold as 70° F and as hot as 150° F.
However, Arbor Biofuels has discovered that the best temperature to run
Biodiesel through the resin is between 100° F to 110° F.
How Much Resin Should I Buy? (Example Sizing Requirements)
If you're producing 30 gallons a week, estimate roughly 50 weeks of production,
that's 1500 gallons per year. To get enough resin to last a year, we'd recommend
purchasing at least 20 lbs. While 20 lbs is a little more than may be needed,
ABC recommends over shooting estimates to take into account times when you run
"less than desirable" Biodiesel containing over 1000 PPM total impurities through the resin bed.
Again, every tower is different in it's construction so resin amounts used will vary depending on the particular dry wash tower being used,
however, listed below are the amounts of resin shipped with our Dry Wash Towers
6" Tower - 20 lbs Resin - Treats up to 2,000 gallons 10" Tower - 70 lbs Resin - Treats up to 7,000 gallons 12" Tower - 120 lbs Resin - Treats up to 12,000 gallons
How Do I Test For Contaminants?
ABC has put together a handy soap testing kit for determining the amount of
soaps and unused catalyst. If proper settling techniques are used, very little free
glycerin or only the soluble glycerin will ever remain in your Biodiesel.
Do I Have To Remove The Un-reacted Methanol From The Biodiesel
Before It Is Dry Washed with Thermax T-45 BD Macro? (De-methylating)
ABC has found that the un-reacted methanol can cause contaminants to stay suspended in the Biodiesel.
These initial levels of contamination may prematurely exhaust a resin bed's capacity.
To help keep the system running properly, ABC recommends 3 different options for removing
residual methanol still left in Biodiesel prior to it being dry washed (purified).
1- Utilize the 5% Water Pre-Wash Method.
This method is the easiest of the three and is extremely effective in helping remove gross glycerin,
excess methanol, soaps, catalyst and other impurities.
2- Utilize the GL 1 Day Process.
This method is based on the simple chemistry principle that Biodiesel is immiscible with all these impurities and will fall
out if the un-reacted methanol is removed. Graham's process removes the methanol and then allows the impurities to settle
out naturally over 24 hours. At this point the clear, clean Biodiesel can be sent through the resin for complete purification.
Although this method when done properly (removing methanol content to < 0.15% and allowed to settle extensively) can produce
ASTM fuel – it has been shown to be problematic for many home brewers, particularly if using a Potassium catalyst.
3- If methanol removal is not performed a Centrifuge or settling the crude Biodiesel for as long as practical
prior to running it through the resin bed can be performed. The Thermax resin has an immense capacity for removing soap
relative to its capacity for absorbing glycerin – centrifuges and long settling times will help remove as much glycerin
as possible and ensure its most economical use.
How Do I Maintain The Resin? (Resin Clean-out)
The most common way to maintain your resin is by flushing it with methanol.
To do this, ABC recommends the resin column be filled with methanol until it completely covers the
resin bed. After the column is filled with methanol let the resin bed soak overnight (12 hours).
Then slowly pump methanol through the system until you've pumped approximately 5 vessel volumes through the column.
This "flooding with methanol" technique allows the glycerin and entrapped soaps that have been absorbed by the resin bed
to be flushed out by re-dissolving them into methanol and moving them away from the resin beads.
Initially when flushing the impurities out of the resin bed, the outlet methanol will be dark brown or at
least very cloudy with these impurities until the column is totally flushed. Once the beads are totally flushed,
the methanol will be clear. At that point stop the flushing and allow all the remaining methanol in the column
to drain out. It may be best to let the unit drain overnight to ensure as much methanol as possible to be removed.
How Do I Remove The Excess Methanol?
At this point the resin beads are still holding methanol and should be "dried" before reusing the resin.
Arbor Biofuels Company recommends drying the resin beads
by using one of these three options:
1-Flush With Biodiesel
The methanol in the resin bed can be flushed out by pumping Biodiesel through the column, however,
the Biodiesel used to flush the column will need to be de-methylated before being used.
2-Remove Beads And Air Dry
The beads can be removed from the vessel and air dried. To do this,
carefully remove the beads and place on a flat surface and allow to dry. Sunlight and a fan will greatly
speed up this process. When the resin beads are dry they can be re-installed in the dry
wash vessel and Biodiesel processing can begin again. CAUTION! If this method is used,
be sure to air dry the resin beads in a well ventilated area to avoid excessive methanol fume buildup.
3-Air Purge The Beads
A dry air or gas purge system can be used to force dry the methanol out of the resin beads.
Learn More About Regenerating With Methanol
Thermax has published a document that outlines how methanol regeneration works
and discusses the steps that should be followed to perform a methanol regeneration.
Click Here to download the document.
What Do I Do With The Methanol Afterwards?
Methanol used to clean out the resin can be re-used in your next Biodiesel reaction without any problems.
Arbor Biofuels Company recommends using 32% by volume instead of 20% methanol if this is the only methanol being
used in a Biodiesel reaction.
Because Thermax recommends specific size requirements for the towers that the T-45 BD Macro will be put into, we also
sell a great ion exchange tower kit and two pre-built ion exchange towers. As different sized towers have different
loading requirements, we're making our Thermax available in 20, 70, 100, and 120 lb increments.
