Hello Andrew, John >Quoting john owens <[EMAIL PROTECTED]>: > > > hi > > I just finished designing and building a batch processor based on the > > journey to forever 90 ltr processor I now want to design an ofm flow tube. > > Is there any other sites other than cambridge That would be usefull. > > John > >I've thought about this, but think that the OFM technology might not >be the best >for yields. I know that the Cambridge site mentions biodiesel production but >posts to this list make me think that the agitation may actually harm yield. I >base this on a post I made and the subsequent replies I got when >Mike Allen was >designing Deep Throat,
Aarghhh! Deep Thort! LOL! >http://www.journeytoforever.org/biodiesel_processor8.html >- I think it was during then, but anyway, someone was designing a reactor... > > The designer had mentioned that they where using a motor with a >gear box so >that the mixing blades rotate at a relatively slow speed hence not churning >everything up. That's Michael's view, yes. There are 10 big paddles on that mixer though, slow speed's all that's needed, 100 rpm. I like that way of doing it with a mixer rather than high speeds with a couple of small paddles. I decided to use a pump instead with the JtF 90-litre processor, and Michael tut-tutted, all that agitation in the pump chamber, but it works very well anyway. Maybe it's different, slow agitation of the whole volume inside a tank or fast agitation of just a small part of the volume outside the tank with very little agitation inside the tank. >I asked the question that wouldn't it be better to "flog the crap >out of it" so that there was rapid and complete contact between all of the >component chemicals. The reply was that due to the equilibrium (reaction >kinematics???) of the oil/methoxide -> biodiesel/glycerine reaction, it was >better to do things slowly and allow the glycerine to "drop out" of >the reation, >down to the bottom of the reation, hence a tall slender reator is >better that a >low squat one. It appears that the presence of the glycerine will hinder the >conversion from oil to BioD. We hadn't discussed it, but we both ended up with processors that drop out a lot of the glycerine during the process, both intentionally, but doing it in different ways. >We have the idea that the level of the mixing tank outlet to the >pump relative to the bottom of the tank is quite important. With our >processor the mixing outlet is set somewhat higher than the level >the glycerine by-product will settle at. That level will vary >according to the oil (and process) you use. Especially with the rose >at the inlet in the lid, there's not much agitation in the tank, >mainly just circulation. The necessary agitation takes place inside >the pump. The pump pulls the oil in from the tank outlet, but that's >not very violent. As a result, a lot of the glycerine by-product >settles out during the processing, which is a Good Thing. We think >almost half of it settles out before the processing's finished. This >does also remove some of the excess methanol, which is dissolved in >the by-product. > >Aleks Kac's Foolproof two-stage acid-base process has an optional >step of draining off some of the glycerine during the base stage. >("The process runs fine without this step," he says. "It's just a >twitch to get higher yield" if your processor has a bottom drain.) >He said this about it: > >"The process is running on the smallest sensible volume of alcohol. >While removing a small portion of it with the by-product would seem >to slow the reaction down, the rather large mass of removed >by-product will tip the scale toward ester production." > >We find that's the case -- the settled out glycerine by-product more >than offsets any methanol removed, with very satisfactory results. > >CAPTION: The sample on the left was taken from the top of the >processor a couple of minutes before switching the pump off at the >end of the process. Immediately after processing the whole batch is >pumped into the holding tank via the processor's bottom drain. What >comes out first is already-settled glycerine by-product. Pumped into >the holding tank at the lid, it all gets mixed up again before >settling. The sample on the right is of the same batch, taken from >the top of the holding tank immediately after transfer -- twice as >much glycerine by-product. -- Journey to Forever 90-litre processor http://journeytoforever.org/biodiesel_processor10.html The photograph is interesting. Best wishes Keith > How is this relevant to OFM? With the OFM technology, all of the >components >are in the tube, hence the glycerine does not get a chance to drop >out, in fact >it is mixed up in the agitating components thus will probably hinder the >reaction. I could see OFM being good for commercial situations where you could >break the reaction down into, say, 3 parts/stages, the first part is run with >the source oil but only a 1/3 of the required methoxide - and some >glycerine is produced, but not enough to hinder the reaction. The results of >this are run through a centrifuge/settling tank with the glycerine being >removed, then the oil with the next 1/3 of the methoxide added is run through >the next section, more glycerine is produced, but once again not enough to >hinder things, the results centrifuged and then the oil plus >remaining methoxide >run through the final stage, by now the original oil being fully converted and >the resulting small amount of glycerine centrifuged off. This is probably a >viable process for 100,000l/day plants but with centrifuges costing $10K each, >probably not for the backyarder. > > Please bear in mind that this view of things is based on reading >posts here, >a bit of other research and being a Civil Engineer, not an organic chemist or >Chemical Engineer. If I've misunderstood anything or got something >wrong, please >feel free to correct me. > > Regards, > Andrew _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
