Hi everybody I'm new. I was wondering what people thought about using pure starch to dry wash biodiesel. It is used to dehydrate ethanol since starch absorbs the hot water and not the ethanol. I'm thinking of trying it on bioidiesel since dewatering takes far too long for my liking. Any thoughts or experience?
You're going to have to filter or settle it out. You'll need to find out the particle size of your starch, and then filter to at least that size. You might also look into dry washing.
Dewatering is my only headache at the moment. I process cottonseed oil using a 2 stage reaction in a 1200l polyethylene conical tank, I demethylate in batches in a PEX lined water heater using an industrial vacuum cleaner attached to a coiled copper pipe with a condenser around it. 3 rounds of water washing including a salt water 2nd wash with compressed air bubbling. The last stage is a 'dry' wash through wood chips. My biodiesel passes every test apart from water content. The processes I've outlined might be many but they don't cost me much. I don't have time to sit and wait for the bio to settle out and separate naturally I have customers waiting. I'm just looking for a cheap way to remove the last traces of water, fast. The final bio goes through a 6 and then 4 micron filter. Not sure of the particle size for starch.
I note you do compressed air bubbling. Do you dry the air? If not, then it maybe saturated with water because of the temp drop it undergoes when expanding again upon release. You might consider heating the air, and or using something like an aquarium/pond air pump for your air supply instead of the compressor. Took a quick look at the climate description for Lusaka - humid subtropical. Your relative humidity(rh) of the air maybe too high to remove the water effectively w/o somehow changing the rh - hence my suggestions.
Had to come back to this one.
If you have a 2 tank/tower/barrel wood chip set up you could always add the starch to the first barrel by mixing it in with the sawdust. Or even before the bio goes into the barrels. This will let the sawdust act like a big depth filtration system.
It's much the same principle as how eco2pure works (I believe). The zeolites are interspered in the sawdust to remove methanol/water as well as the bio moves through it.
Although I'd definitely do a test run of this before moving to process scale. And I have no idea of your local regulations. Adding starch is going to increase your iodine value significantly I believe.