[Gasification] Retort gasses

[Jonathan F. Pratt]

The figures given in the FAO source seem erroneous to me.  Other sources put 
the retort gas output at virtually no N2 and much lower CO2 levels.  FAO 
itself mentioned that the gas output is affected by the scrubbing process 
(water) in which other gasses may be "picked up" by the raw gas passing 
through.  So there are variables in the type of retort and filtration 
process.  FAO also said the energy content of the retort gasses is only 10% 
that of the charcoal produced?  That can't be right as 2/3 of the energy is 
contained in the volitile gasses given off.

As for the Riche specifically, I wasn't advocating using the Riche design 
exactly but a setup similar in which the gas passes through the hotest 
layers of char formed.  I would love to know more about your own retort with 
higher efficiency.

Besides the "Vertical Column - bottom heated" style retort itself one can 
imagine using one or more additional chambers filled with charcoal and 
heated glowing hot to better breakdown the tar and reduce the CO2 resident 
in the raw pyrolysis gasses.  Instead of one straight tube, perhapps a base 
that is designed a little different (for the glowing char zone) to yield 
better results in the output gas.

> ------------------------------
>
> Message: 4
> Date: Mon, 29 Jan 2007 00:47:30 -0500
> From: "Mark & Elena Gallmeier" <mgallmeir at comcast.net>
> Subject: Re: [Gasification] Why is nitrogen dilution bad?
> To: <gasification at listserv.repp.org>
> Message-ID: <022a01c74368$f7ba4cf0$6402a8c0 at c9y1p2>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
> Jonathon,
>
>>> The retort will produce a gas free of nitrogen and will mainly be a mix
>>> of
>>> methane, H2 and CO and a bunch of other hydrocarbons in small
>>> percentages.
>
> According to http://www.woodgas.com/gasification.htm:
>
> "Producer Gas" made with air:       (CO 22%; H2 18%; CH4 3%, CO2 6% and N2
> 51%).
> "Synthesis Gas" made with O2:    (CO 40%,  H2 40%, CH4 3% and CO2 17%)
>
> Meanwhile the UN FAO gives the following analysis for "Retort Gas":
>
> "Retort Gas"  (CO 23%, H2 2%, CH4 17%, CO2 38%, O2 2%, N2 18%)
>
> See
> http://www.fao.org/docrep/X5555E/x5555e07.htm#6.10%20using%20retort%20or%20converter%20gas
>
> The problem with retort gas is the hydrogen deficiency for the methanol
> synthesis reaction:  CO + 2H2 ---> CH3OH.
>
> Using straight retort gas I doubt one would improve on the 'natural'
> methanol yield of 2% from destructive distillation.  The hydrogen balance
> needs improving by some means, whether Steam Methane Reformation, water 
> gas
> shift or both.  A regular gasifier will yield a better balanced CO-H2 gas
> and be easier to build.
>
>>>The Riche style retort is essentially a long
>>> vertical tube heated from the bottom,
>
> This retort I built accomplishes everything a Riche gas producer does, but
> without the firebrick masonry flue of the stock Riche, and with far less
> fuel consumption:
>
> http://gasifiers.bioenergylists.org/?q=gallmeierretort
>
>>>the gasses generated in the retort
>>> pass through the glowing char formed at the bottom and to some extent
>>> breaktown the tars and other constituents in the raw pyrolysis gas.
>
> Even the higher temperatures obtainable in a retort won't do much tar
> cracking.
>
> Mark
>