Re: GAS-L: feeding biomass into pressurised systems

[Arnt Karlsen <arnt@c2i.net>]

On Fri, 02 Aug 2002 20:26:00 +0100, 
AJH <andrew.heggie@dtn.ntl.com> wrote in message 
<h3llkus9jagmrg162j5pklvsu9o70ngp3m@4ax.com>:

> Some time back Tom Reed criticised an expensive US government
> sponsored gasification system in Hawaii, Tom Miles refuted the money
> was wasted as valuable lessons were learned( and by inference many
> researchers wages paid), though appeared to acknowledge few of the
> lessons won at such large expense had yet been applied.
> 
> 
> I was intrigued by the feed method and hoped Tom Miles would be able
> to explain more. 

..link?

> My quest is not at an industrial gasification scale
> but in the micro scale of cook stoves. 

..hah!  ;-)  But there _is_ wisdom in your statement;  400 years of
tinkering has effectively thaught "mankind" and investors gasification
is messy and expensive and "does not work".

..so doing it in cook stove scale, can be done out of your own pocket.
Doing it profitably at that scale, means it'll pay for itself on
scale-up.  

> Whilst there is a lot of
> current expertise in direct combustion of biomass for cooking most of
> the work is on natural draught with (in some cases) draught assisted
> by chimney effect. At least Tom Reed and myself, and presumably some
> others are tinkering with "blown" stoves achieving near complete
> combustion without chimneys. This to my mind has several advantages in
> cost, stability and ability to burn "poor" or "green/fresh" fuels.
> 
> I think that if I slightly pressurise the primary combustion I can use
> the power in the off gases to entrain and turbulently combine with
> secondary air.

..pressurization costs you some in the reduction of combustion
gases, typically you like to do this at 1050 - 1100C° and _low_ 
pressure, for a downdrafter.  Many ways to skin this cat, though.

> This is OK when batch loaded but leads to problems of cleanly burning
> the residual char at the end of a run. So there is a need for a cheap
> simple method of metering fuel into the combustion chamber. At the
> moment I have to rely on a low powered fan for combustion air, so I
> can accept a similar electrical method of fuel metering.
> 
> In the previous discussion a plug screw system was mentioned, I take
> it this is a variable pitch auger such as in a meat mincer, the
> biomass becomes temporarily formed into a plug where the auger flights
> become closer and hence form a seal. If I am correct does the friction
> make this a power hogging device? If not how does it function.

..this one is viable, extrudes fuel out into the gasifier, against a 
wedge in there, so extruded fuel breaks off in properly sized chunks.
This also buys you a sealed fuel feed.

-- 
..med vennlig hilsen = with Kind Regards from Arnt... ;-)
...with a number of polar bear hunters in his ancestry...
  Scenarios always come in sets of three: 
  best case, worst case, and just in case.


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