Did you notice how yield was effected? Also, did you notice the sawdust being saturated more quickly?
Yes, the sawdust absorbs more biodiesel and a lot more quickly. There is some yield lost to absorption initially but then there is none lost in subsequent batches. So yes, sawdust absorbs more than shavings, but again it absorbs soap and glycerol more quickly too.
I'm thinking of the following set-up:
1) - 200L stainless steel reactor
2) - 200L drum 3/4 filled with sawdust with steel mesh filter and tap on bottom
3) - 200L low black plastic rectangular domestic cold water tank
4) - 200L storage tank
Pump raw batch (about 160L) into sawdust drum and gravity filter into the long tank; when this is full pump into the storage tank.
Easy - negligible cost, negligible labour, crystal cear biodiesel. The drum of sawdust will last for months, and when its spent makes great fuel for the stainless steel reactor.
I have all these components ready to put in place; in fact my current set up is identical except I'm using a small drum for the sawdust, which entails a lot of decanting by hand - the large filtering tank will eliminate that.
Many believe that 'clear and bright' indicates completely clean fuel, and that further tests are unnecessary. It's possible that a lot of BD makers have been using fuel they honestly believed was completely clean, but would have failed one or more of the simple tests like the water shake test, 3:27 test, freeze-thaw test, or vapor test.
Based on reports that wood chip column 'cleaned' BD fails tests, it may be that an initial pass through a wood chip column could reduce the amount of mist washing required but not replace it.
On the other hand, many of us think that fuel which isnt clear and bright is unclean fuel.
A glass of water may appear clean and bright but that does not mean it's safe to drink.
How much soap will wood chips remove before it has to be replaced?
What's causing the soap to form in the first place?
I just thought I’d share this with you. Obviously there’s more than one way to skin a rabbit, but this is what works for us after 8 years of small-scale commercial production. Not to dwell on the upstream processes, but in a nutshell:
· We collect oil mostly from country pubs
· It is dried by heating to 120 deg.C with a glycerol burner
· Settled to remove fine food particles
· 2-stage base-base reaction with KOH; 750 litre batches
· Purify with hardwood shavings, a water wash and heated spray dry
· Antioxidant added during the drying stage.
This is the new information:
· After at least 24 hours cooling & settling, 2nd stage glyc drained off
· Syphon slowly (1 to 2 litres/minute) biodiesel through a contact tower charged with hardwood shavings. These have been prepared by sieving out the dust, then steeping in methanol in a cheese cloth tube before hanging up to dry.
· The contact tower is about 30 litres in volume, bottom-feed, with the shavings contained in another cheesecloth tube for ease of subsequent removal
· Outlet from the contact tower gravitates to IBC washing tank
· There we give it just one bubble wash to remove the methanol
· The soap is intercepted by the wood shavings and one charge is only good for one batch. Trying to get a second batch through means having to do 2 water washes. This is possibly not as good as EcoPure, but the material is free!
· Nevertheless, the resinous methanol has to be distilled for re-use and the sieving operation is a little tedious…..so the material is not really free.
· Now this bit is quite interesting: Washing in water can regenerate the spent wood shavings. The water is not in the least oily but is brown (glyc) and soapy. We have been doing this by tipping the shavings into an expanded metal waste paper basket, then immersing in a bucket of harvested rainwater, giving it a bit of a swirl. 2 changes of water are needed, but it’s still a lot less than a conventional water wash of the biodiesel.
· After washing, the shavings are left to air-dry
· Before we started regenerating, we would use the spent shavings to light the Turk burners, but we have other ways to do that.
For the future, we plan to de-meth the bio under vacuum before it goes to the tower. This should precipitate more of the soap and glyc dissolved in the XS meth. We will always polish with a water wash and final dry; just don’t believe that a fully dry wash system can produce pure fuel (but that’s another debate).
Finally, a question: can EcoPure be regenerated in the same way?
I always thought the wood chips could be washed, dried, and reused.
You mention bubble washing after the wood chips to remove the methanol. How much is left in the biodiesel and how do you know.
I like the way you think.
I have visited several other commercial plants using dry wash processes. In every case the 'finished' fuel smelled of methanol. Way back before the days of dry washing , I did a careful inventory of the origin & destination of materials in small batches of bio. In the case of methanol, 13% was used consumptively, the rest divided between the heavy & light phases (roughly 60% to 40% when distilled). Perhaps most tellingly, the spent wood shavings did not smell much (OK a bit!), suggesting that they were not extracting methanol as effectively as they were extracting soap & glyc.
There seems to be some confusion between wood chips, shavings, and sawdust. I'm not sure what size the wood chips are, but I imagine they have a much reduced surface area compared to the same volume of either shavings or sawdust.
I would recommend sawdust to either chips or shavings any day, now that Ive seen how quick and effective they are. The biodiesel I'm getting out is as good as I had with resin and is much cheaper - in fact I get it for next to nothing. On that note I wouldnt even think of trying to recycle it, I mix the spent stuff with some new stuff and burn it in a sawdust burner to heat my tank, thereby saving me hundreds a year on my elctric bill. If anyone wants to make a sawdust stove it takes minutes, and it can be used for lots of things -
I amtotally convinced drywashing has a benefit. What benefit is not to clear to me right now. I just need to see the redults for myself and not spend 500 bones to see if it works or not. If I was standing next to a dry wash column and I could run tests on the finished product; and kow how many gallons I could purify for that money then I would do it in a minute. Until then it is wood chips and wash for me.
I am still making the wood chipper but remembered something I thought of months ago. Referencing the picture of the wood chipper I posted last week, imagine a resin column next to it. Filled with the Morton salt pellets for water systems.
It would go like this- Gravity feed BD to the wood chipper and pump stir it in the wood chipper, circulating the Bd through the massive amount of wood chips. Then pumped through the column filled with the salt pellets and into the wash barrel. A lot of us use salt to nuetralize the soap to clear up an emulsion. Why not use it to nuetralize the the remaining soap. The pellets should hold up pretty well to the flow of BD through the column.
The first step of the wood chips gets us a long way on the road to removing the soap-why not tell the fat lady not to sing and end it right here and now. Nuetralize the remaining soap in the salt column and wash everything out in the wash barrel.
I`m with Jehu on his comment, if you water wash at any stage, post there not here.
Without trials NONE of use would be making Bio anyway.
This is in the process of a trial, it is being built as you type another comment. So far as water washing in this section not being allowed, does that include the pre-washers?
Really? Seeing youve just more or less said that dry washing with wood chips is a waste of time tell us what focus on experimenting youve done that has contributed to perfecting the process? But since its obvious youve nothing positive to say how about leaving the people who really are experimenting to get on with it in peace.
have you any thoughts on the salt column after the wood chips?This message has been edited. Last edited by: Shaun,
As to the points you raise, my reply is which of these staements by yourself is true:
"As long as one has an adequate supply of water, and not in a hurry, and wash water disposal isn't a problem then the 'dry wash' advantages are probably marginal", or;
"What I'm stating is that 'dry washing'...has been clearly demonstrated as an effective addition to the process which can reduce mist washing amount and time."
Maybe you can go one better and tell us what wood dry washing youve tried that you have so much to say about it?This message has been edited. Last edited by: Shaun,
I think you might be right. I should be able to finish this weekend, I can't wait to give it a try.
how about a picture or two of your bio setup john?
I think you might be right. I should be able to finish this weekend, I can't wait to give it a try.[/QUOTE]We've been mist washing the BD with good success, and the samples sent for ASTM testing all passed, so we've been going with the old 'if it ain't broke don't try to fix it' philosophy. If the wood chip and salt columns can show a significant advantage then we would try adding it to the process.[/QUOTE]
I think I will get it set up and then draw two samples. One straight from the settle tower and the other after it has been pushed through the salt and chips. That way I can do controlled testing for both samples and prove to myself it is significant. I want to get to the point where I can get it into the wash tank and beat the crap out of the first wash and then mist for a little while and be done with it. I have my titration down to a T so I can use an open hose on the first wash. On the second wash I can get pretty rough with with a power point.