[Gasification] Characterization of waste water from biomass gasification equipment: A case-study from Cambodia

[James Joyce]

Hi Tom, I might make a few comments and caution people not to discard the char filtering option based on a couple of negative experiences. It may not so much be the case that char filtering does not work ... just that it does not work the way it has been tried.

- Not all biochars are the same and neither are all activated carbons. Most activated carbons are highly microporous, which is not very useful for liquid phase adsorption. If you did not use one known to be highly mesoporous (like a wood char rather than nut char) then it is worth revisiting.

- Dry chars tend to be hydrophobic. That makes them useless for liquid phase adsorption until they have had a chance to condition and be able to "wet" through into the pores. If the pores are full of air that needs to be displaced before you can adsorb anything else. In my experience mixing time, elevated temperature and perhaps acidity? can facilitate the wetting process. Packed bed filters don't allow for much in the way of mixing time.
 
- Particle size will play an important role, as it interacts with the surface tension of suspended matter. If a packed bed filter did not work then I would try mixing fine char with the water in a mixing tank (possibly at elevated temperature) before filtering that mixture through a packed bed char filter.

- Aged tarry water may well be a different beast to fresh tarry water.


One other idea: 
In coal processing interface change agents such as diesel and MIBC are commonly used to alter the surface interaction between fine coal and air bubbles for the purposes of floating out the diesel and fine coal. See https://en.wikipedia.org/wiki/Froth_flotation . A similar process might work for the hydrophobic fraction of the tarry water. The remaining soluble and hydrophilic fractions are probably more biodegradeable.

Froth flotation is also used in sugar refineries and is very effective at removing very finely dispersed colloidal matter from solutions of soluble matter.

In either process the key is to introduce fine solids that the colloidal matter and air bubbles can attach to.


Regards,

James

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Date: Sat, 16 Jan 2016 11:41:12 -0500
From: linvent at aol.com
To: gasification at lists.bioenergylists.org, spaco at baldwin-telecom.net
Cc: gasifiers at bioenergylists.org, biochar at yahoogroups.com
Subject: Re: [Gasification] Characterization of waste water from
	biomass gasification equipment: A case-study from Cambodia
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 I have tried commercial activated charcoal and it doesn't work. It is far superior to bio char in adsorptivity, and the tarry water passes through it without removal.?
Sincerely,
Leland T. "Tom" Taylor
Thermogenics Inc.?