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

Tom Miles tmiles at trmiles.com
Sat Jan 16 17:13:41 CST 2016


Thanks for these comments.  Researchers in Japan have found that a vegetable
oil scrubber using rice husk char as a media has very good tar removal for
gasifiers which illustrates some of the points that you make. 


-----Original Message-----
From: Gasification [mailto:gasification-bounces at lists.bioenergylists.org] On
Behalf Of James Joyce
Sent: Saturday, January 16, 2016 2:29 PM
To: gasification at lists.bioenergylists.org
Subject: Re: [Gasification] Characterization of waste water from biomass
gasification equipment: A case-study from Cambodia

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

- 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

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




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
Message-ID: <8D31E93D7DA4606-1F38-3863F9 at webmail-vm013.sysops.aol.com>
Content-Type: text/plain; charset="us-ascii"

 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.?
Leland T. "Tom" Taylor
Thermogenics Inc.?

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