Hello there guys,
can i just say what a fantastic forum you have here,
the resources have been very useful.

anyway i have a question about the time difference it would take with scaling up,

for example if it takes 2 hours to react a 35 litre vessel. with a 100 W mixer and 1.5 KW heater,

does that mean it will still take 2 hours to react a 350 litre vessel as long as i up the mixer wattage to 1000 W and the heater wattage to 15 KW

this is a question i have been pondering over for a while now and was wondering if it would be worth scaling up if it would take much longer.

any help would be much appreciated,
thanks and regards,
Mubs

Hi Mubs,

I used to make 60lt per batch, and now make 180lt/batch. Once the oil is at the reaction temperature, the reaction time is the same for 180lt as it was for 60.

I'm not sure what you use for a mixer, but I use the same drill I used with my smaller batches.

Justin

ok thanks for that,
the thing is, i havent yet made a single litre of biodiesel lol
i am thinking of making and selling it commercially starting with 900lt batches.

and before you laugh, my neighbour started making biodiesel in batches of 900lt to sell commercially, and he is now selling his business.

i have done all of the research for it and i do have queit a background in chemistry, the only thing that seems difficult is the titration and i can do complex chemical titrations accurate to 0.001 ml with my eyes shut!

so with that said i have read a guide that tells me to use a 100w mixer to maintain agitation at 500-600rpm and a 1.5kw heater (to maintain temperatures at 55 degrees c)

i understand that if the initial temperature is right then the reaction should work but what would be the approximate wattage of heater that i would need to use?

if the guide says 1.5kw to heat 35lt, does that mean that i would need a 39 kw heater to heat 900 lt?

and there is a little confusion over the level of agitation.
the guide tells me to maintain mixing at the rate of 500-600 rpm.

will i have to increase this rate of agitation with the size of the batch? or just buy a larger stirrer that would cover the size of the reaction vessel?

thanks very much in advance,
regards,
Mubs

thanks for that

to be honest i havent yet made a litre of biodiesel lol.
and im thinking of jumping straight to 900l batches.

before you laugh at me i must admit that i do have queit a background in chemistry and i have done plenty of research for many months now on the topic of biodiesel. the only part that looks difficult is the titration but i am used to carrying out complex titrations accurate to 0.001 ml. furthermore my neighbour also started at 900l and he is thinking of selling his equipment to me.

back on topic however i only know of guides that talk about making 35lt batches using 1.5kw heaters to maintain the temperature at 55 degrees C and take one hour to heat.
My question is that will i need to scale up the wattage of the heater to 38kw to heat the vessel in the same amount of time? (1.5/35*900)

in the same way the guide mentions the use of a 100w mixer to maintain an agitation rate of 500-600rpm. does that mean that i would need a 2571w (100/35*900) mixer to maintain the same rate of agitation OR does it mean that i would have to increase the actual rate of agitation eg 1000 rpm instead of 500-600.

i have based my figures on scaling up the wattage only, i dont know if i am right or not. im just trying to scale up the wattage, but it may be some other complex equation to scale up the amount of heat needed.

sorry for the long winded post,
thanks in advance,
Mubs

Hello Mubbs, welcome to the forum! As Long as everything is liquid, The temperature the reaction is performed at is not critical. The cooler the reaction, the longer the mixing that is required.
RPM is not a measure of mixing vigour.
The only "Guide" I know of that talks about 500- 600 RPM mixing is the Foolproof "Disaster" and that particular procedure is a joke, it never makes high quality biodiesel.

As you say your friend already has a 900 litre reactor I suggest you ask him what he does.

Gday Mubbs,If you are planning on doing 900 litre batches i would like to know how you plan to mix your methanol and KOH or caustic soda? regards westwinds.

thats a good question.
i suppose ill have to mix it inside a 205 litre steel container (these are readily available to me)

but about the foolproof method,
thats what i was going to initially use.
whats wrong with it?

it seems ok in theory.

i did ask my friend however he uses the single stage process :S

thanks again thus far for all of your kind help,
Mubs

Hello Mubs
Much of the biodiesel information on the Journey to Forever site is hopelessly out of date and inaccurate.
Read this thread for more info regarding the Foolproof Joke.

aah i see.
well to be honest it is pretty carelss to just put standard amounts of sulphuric acid and methoxide into the reactor.

a better method would be to use the acid base method but to include a titration also. because realistically all of the ffa can be converted into biodiesel. turning it inot soap would be just a waste.

well anyway back on topic,
what method do you recommend i use?

single stage or 2 stage base-base method,

or is there any other method?
thanks and regards,
Mubs

Mubs,
I guess that a high FFA content of the oil would be the main driver for going to an Acid Base process.
Low FFA would not need the added complexity and expense of using acid then neutralising it as well as making the oil basic for the transesterification to proceed.

If maximising biodiesel production from your oil is a priority, you can turn any soap, in your single stage base process by-product, back into FFA by acidification. You would then be able to do most processing as single stage base, then use an acid / base process to make biodiesel from the reformed FFA from the single stage base processes,

Regards,
Tony