I'm looking at how to best use my newly aquired hardware to set up my process. I'm at least going to start with mist water washing and here's what I'm thinking of for my process.

Make 50 gallon batches in the 80 gallon HW heater based reactor. Reactor vent line discharges into 50 gallon HW heater based methanol recovery still for capture. Run at 160*F continuously recirculating with the pump for 2 hours (longer? shorter?).

Once the reaction is complete, pump the reactor contents into 70 gallon cone tank for settling.

Once settling is complete pump glycerol from cone tank into 50 gallon HW heater based methanol recovery still.

Water mist wash bio in 70 gallon cone tank & allow to settle.

Once settling is complete pump soapy water from cone tank into 50 gallon HW heater based methanol recovery still. Assuming glycerol is fully water soluble this will help thin the glycerol and keep it from gelling in the tank.

Pump bio back into reactor and heat/circulate to dry fuel and drive off unreacted methanol (not sure if there will be any after water washing?). All vapors from reactor will continue to be vented into methanol recovery still for capture. Continue to heat and circulate at 160*F until methanol recovery is complete (is that the right temp? Higher? Lower? For how long?).

Heat and circulate wash water/glycerol mixture in methanol recovery still to boil off methanol and recover methanol from vapor discharged through a condensor that is being chilled by cold water. Possibly with a vacuum pump installed between the still and the condensor to speed up the process.

Pump finished fuel from reactor into storage.

Pump methanol-free soapy water/glycerol mixture from still into drums for disposal.

SO, is there anything I'm missing?
Any steps that should be changed?
Any better ideas on how to run the process (excluding dry washing - we may do that but aren't going to be ready for it right out of the gate)?

Any and all opinions welcome.

 

Water washing is inefficient. It creates a potential for emulsion formation and generates toxic waste water.

Why not:

1 Allow BD and Glycerol to seperate

2 Recover methanol from BD

3 Wash BD with Magnesol

4 Recover ethanol from Glycerol

 

Come on Phydeau, that just isn't like you. You usually read what people write and respond accordingly...

I said...
So in the long term we probably WILL go to a Magnesol dry wash. But we're not going to be set up for that initially. It requires gear and supplies, and additional investment we aren't going to have at startup. Like a supply of Magnesol, and a diaphragm pump, and cannisters with replaceable sock filters...

"Potential for emulsion formation"? Tell me more. I know that vigorous mixing of any two non-miscable liquids can form an emulsion, but this is the first I've heard of this problem related to mist washing - which doesn't involve any agitation of the mixed liquids. But just so I know, what about mist washing can lead to forming an emulsion (so I can avoid it of course)?

Also, what is toxic about the waste water if I cook the methanol out of it? Any left over lye will combine with the fats in the glycerol and convert to soap, right? So what's toxic?

 

As to the subject in the title of this thread:

The three hydroxyl groups make glycerol very hydrophylic so it dissolves well in water.

 

Good info, thanks!

Now are you willing to elaborate on the other questions you raised?

Namely;

Causes of emulsification - and consequently how to prevent it?

and

What in the waste wash water (say that 3x fast!) will be toxic after the methanol is removed?

BTW, IIRC, one of the last times I saw one of your posts (before now) you were "battening down the hatches" for a hurricane. Then we didn't hear from you for a while. What happened man? Some of us were a bit concerned...

 

Second question question first

Shortly after the hurricane I was diagnosed with prostate cancer (an aggressive form)
and ended up having surgery. It took me a while to get back in form. I am currently doing well, not sure of my final status yet but hopeful.

First question

Emulsions occur when unreacted NaOH or KOH and FFAs (free fatty acids) and water get together resulting in soap formation. There are several factors that control whether or not soap forms ie incomplete transesterification, excess amounts of base, insufficient methanol, etc sometimes it is the condition of your feed stock. Anyway some of the factors you may not be aware are present until you have a mess on your hands.
When you add the agitation of water washing you end up with 50 gal of very tick mayonaise instead of BD. Emulsions can somtimes be broken and reprocessed but to often they end up being discarded after wuch head scratching and wondering "What the he** happened".

The waste water will contain unreacted base (there is always some) and other contaminants, it really should not be poured down your drain.

Magnesol eliminates both of those problems and produces a better end result.

 

Good to have you back, was wondering why hadn't seen you here in awhile...

 

Thanks, glad to be back

 

Ditto on seeing you back. Hope the prognosis continues to go your way and your status continues to improve.