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

[Tom Miles]

Thanks, Doug. 

Corrected link Link http://www.fluidynenz.250x.com/

A typical solution seems to be to clean as much as you can from the black
water and then burn off what you can't separate with activated carbon.
Gasifier char has been shown to be a pretty good filter.  

Once suggestion has been to heat the liquid to 100C to vaporize the
benzenes, etc. and then use the steam to gasify the char. Another has been
to use vapor compression techniques. We quickly get into tech heavy
solutions that go beyond the cash flow of a small scale gasifier project.
One scrubber supplier told me that they won't touch developing scrubbers for
small gasifiers unless you have a minimum of $150,00 to spend on
development. They find most developers of small scale gasifiers don't have
enough money for development of appropriate gas cleaning systems, not to
mention black water cleanup. You have to appreciate the development work
that Tom Taylor has done.

Tom  

-----Original Message-----
From: Gasification [mailto:gasification-bounces at lists.bioenergylists.org] On
Behalf Of Doug Williams
Sent: Wednesday, January 06, 2016 5:30 PM
To: Pete & Sheri <spaco at baldwin-telecom.net>
Cc: 'Discussion of biomass pyrolysis and gasification'
<gasification at lists.bioenergylists.org>; biochar at yahoogroups.com;
gasifiers at bioenergylists.org; 'Doug Williams' <doug.williams.nz at gmail.com>
Subject: SPAM: Re: [Gasification] Characterization of waste water from
biomass gasification equipment: A case-study from Cambodia

Hi Pete,
You ask:

> So---- what if one allowed the scrubber water to sit still for a 
>couple of days?  Would most of the "condensible hydrocarbons" and the 
>tar rise to the top?  (I assume that most that "bad stuff" isn't water 
>soluble.)

Heavier tars float but a lot goes into solution and that's the stuff usually
containing benzine and other nasties that are difficult to filter. 

>Then, could that top layer be sucked off, making for a concentrate that 
>might be easier to deal with?  And, would the remaining "water" be 
>useful in the >scrubber again?

Basically this is how the systems are managed, but the condensate is
carcinogenic and hard not to be exposed to it over a period of time.
Depending on what the condensible is, and there are huge variations, it can
be just very light pyrolysis oil without black tars, or the whole spectrum
of what is commonly referred to as stack gases. These are a very unstable
mix of distillates, and over 200 chemical combinations have been identified.
They don't all survive to condense, but the outcome is the same of creating
toxic black liquor. Sawdust will mop up pyrolysis oils, and the more
activated chars after gasification, can be used to filter "some black
liquor", but having said that, you do need lab analysis to be sure of the
outcomes.
> 
> My reason for asking the original question is this:
>   I have been testing a JXQ-10 for several years now.  I can get it to 
>make enough gas to run an Onan 6.5KW genset for up to about 4 hours per 
>batch, at > about 3KW net, max..  The thing that always ends the run is 
>when the reactor is full of wood chips to the top.

To give you a correct answer, I would need a step by step procedure of
starting it up and operating it over the four hours. It sounds like an open
core principle burning the pyrolysis gases in a very shallow layer which
continually moved upwards towards the incoming air. When it fills to the top
you must have a cylinder of charcoal left that acts like a plug so it just
slowly shuts down as the amount of exothermic heat drops away.

> As I watch maximum  power, and I see it begin to drop, I can add a 
>thin layer of wood chips and, IMMEDIATELY to power comes back up.  It 
>appears to me that it's the new wood chips that are the "new" energy 
>source, not the (rapid change in) dissociation of CO2 to CO and O2 or 
>the sudden "new" dissociation of H2O to H2 and O2.

The previous set of answers apply, but you are right in that new chips have
the pyrolysis gases to sustain the oxidation band as gas will burn first
turning the wood to char, but as the interface to the flame front keeps
moving up away from the char, it lacks air to maintain oxidation
> of the char. 

I'm pretty sure that is your situation, but give me the fuel operating info
and we can then see if I read your description correctly.

I just remembered (must be getting old) I did a report on condensates for
the Fluidyne Archive with photos. www.fluidynenz/250x.com

Doug Williams,
Fluidyne.

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