Re: GAS-L: Small Scale Gasifiers Defined

["Paul S. Anderson" <psanders@ilstu.edu>]

Jim and all   (with copy to Stoves list because Jim's message
did not go there.)

Your statement that terminology IS important for the list serve is
appreciated and agreed.

I have gone to the 3 websites (below) and I recommend them to anyone who
has not seen them before.

As a novice, I can candidly state that I am so impressed with the large
and commercial gasification processes and installations.  The work
by all of you in those fields is to be commended.

I agree with Jim that the same terminology needs to be appropriate for
both the large and the small installations.  

I have come to understand that the process of "gasification" is
correctly viewed as ending when the gases have been created. 

Therefore, gasification occurs with a piece of burning wood in an open
fire.  But the "average person" does not see it or does
not care much about it.  That gasification is just part of
"burning" the wood or part of "combustion" of the
wood.

For use on the Gasification and Stoves list serves, we really use the
word "gasify" in relation to the creation of the gases THAT ARE
IDENTIFIABLY REMOVED FROM THE LOCATION OF CREATION.

PERIOD.

In other words, what happens to the gases after being removed some
distance from the point of creation is NOT part of the issue of
gasification.  The gases can be:
a.  "scrubbed" or cleaned for "impurities"
b.  cooled
c.  compressed
d.  stored
e.  mixed with air  (dangerous but with the intention to be
ignited soon (but separately) after creation)
f.   literally "go up in smoke"
g.  [other]

Now, most of us are concerned with one or more of these
"post-gasification" activities.   But let us agree
that THEY are NOT "gasification".  You might earn your
living because of your work with the "post-gasification"
activities, and such topics ARE discussed on the "Gasification"
list serve.  Furthermore, these are really the INITIAL
"post-gasification" activities.

Following those INITIAL "post-gasification" activities, the
produced gases eventually are consumed in flames to give heat (exceptions
granted for fertilizer production and some other "non-burning"
"non-heat-generating" uses of some gases.)

What do we call that consumption in flames?  Tom Reed wrote recently
that he did not like the term "flaring" because it is
associated with waste gases at refineries, etc.  And I can accept
his comment.  But Tom did not give us another term.  

I had also suggested "flaming".  Any comments?  Or
any other terms??   [ a later thought added here:  perhaps
another term is "oxidation of gases", but I doubt that the lay
person (or the illiterate people in Mozambique with whom I do my stoves
work) would get much understanding from that expression. ]

But please do NOT call it "combustion" or
"burning".   Patrick is completely correct when he
wrote:   The first [term], "Combustion",
is very straight forward and covers projects utilizing standard fluidized
bed combustors which generate heat for process or power applications.

Well, I am not sure what a "fluidized bed" is.  I
just think of a fire as being combustion.  Solid biomass becomes
heat, H2O, CO2, some ash, and some generally undesirable
by-products.  That is combustion.  

So I suggest that "flaming of gases" or "gas-flaming"
or something like that is a suitable name for what happens to most gases
produced by gasifiers.  Production of the gases in a large or small
gasifier is not the issue, as Jim correctly notes.

Add in terms like "close-coupled" or "closely-staged"
or "closely-flamed" (I like that term) or "promptly
flamed" or something like that and you are understanding (and you
are able to explain to other people) what is going on in the
"small" devices.

Note that I did not say simply "small gasifiers" or
"simple gasifers" or "micro-gasifiers" because I want
the issue of "flaming of gases" to be seen as separate from the
creation of the gases.

But if I say "small gasifying heater" or "gasifying stove
- small scale model", I can define it once by saying that such a
heater or stove is a "small gasifer with close flaming".

For those who have read my earlier messages on the Stoves list serve, I
have consistently used the term "combustion chamber" when I
discuss the 4 components of "stoves"
1.  Fuel
2.  Combustion chamber (including how the important air is added to
the process)
3.  Structure of the stove (legs, type of oven, etc)
4.  Cooking practices.

Thanks for bearing with me as we went through this terminology
exercise.  At least for me I am now able to meaningfully describe
without conflicting terms what constitutes and what goes on inside the
"combustion chamber'' of the stoves I am designing.  

I leave it to others on the Gasification list to decide how they will
describe their "POST-gasification"
activities.    As Jim wrote:  "I think
use of the term
"combustion" to describe the ultimate fate of the syngas under
certain conditions is
appropriate."      Perhaps his words
"under certain conditions" are the key.  Be sure to
clarify the "certain conditions."  Such as, if ONLY gas is
present and it is clearly not "closely coupled" with the
gasification stage, then the gas can be combusted (as in an internal
combustion engine).  But when the people think of SOLID fuel turning
into useful heat (or electricity, etc), and those people see that as
combustion (and do not care about the process of gasification), then do
not be surprised when they do not understand the phrase "combustion
= gasification + combustion"  (translated to be
"lay-person's combustion = gasification +
technical-jargon-combustion-under-certain-conditions"

You can try to explain that to the lay-person, but do not be surprised
when you have to say that
"technical-jargon-combustion-under-certain-conditions" means
the "flaming of the gases."   (which is what it could
have been called from the start, as in   
"combustion = gasification + flaming of the gases".)

Of course we could also comment on why "pyrolysis" has not been
part of the discussion.
"combustion = pyrolysis + gasification + flaming of the
gases"

Enough.   

Smile   :-)     Biomass does
burn!!    And in useful ways, too !!

Paul



At 09:13 AM 6/27/02 -0500, Jim Wimberly wrote:

To all subscribers of the gasification list:
 
It seems to me that clarifying terminology is one of the most important functions this group can serve.  As Tom Reed put it this morning, "we are in morass of terminology", although I consider the "we" to be not just the bioenergy folks but society at large.
 
Despite the recent postings on this thread, I think that the term "gasification" needs further clarification, regardless of whether we're talking small-scale or large-scale.  Specifically, I am concerned that close-coupled or two-stage systems not be confused (and lumped together terminology-wise) with systems that produce a syngas that can be conveyed/stored for subsequent use (either for "burning" in a separate "combustion" system, used as fuel in an engine, or as a feedstock for other processes [e.g., fermentation into ethanol, acetic acid, etc]).
 
The need for terminology clarification regarding gasification is increasing almost daily.  Numerous vendors are now using the term -- some apparently based on technical merit, others apparently for marketing purposes.  My concern is that regulators, politicians, and other policy makers are being confused (and sometimes intentionally misled) by this term. 
 
In my opinion, one reason the term "gasification" is increasingly being used is because it is more attractive and gets more attention (and potential support) than the term "combustion" (which is often associated with "incineration", which is unfortunate as the latter has evolved to having substantial negative connotation in our society). 
 
The confusion that results from misuse of this terminology may be advantageous to some people under certain conditions, but works against all of us in the long run.
 
So let's keep this discussion going... I'd like to see a consensus on use of the term gasification among bioenergy folks that can also be used in our communications with the various external audiences and interested parties.
 
Personally, I like the definitions provided by Pat Travis; the followup points from Paul Anderson have merit, but I think use of the term "combustion" to describe the ultimate fate of the syngas under certain conditions is appropriate.
 
Here are a few links that shed some additional light on the term in question (none of which provide truly succinct definitions of the term):
http://www.gasification.org/story/explaine/explaine.html
http://www.eren.doe.gov/biopower/projects/ia_tech_gas.htm
http://www.woodgas.com/Gasification.htm (with all due respect to Dr. Reed, the term "wood gas" is fine for certain situations, but not applicable to the gasified product from non-woody biomass feedstocks)
 
Jim Wimberly
Foundation for Organic Resources Management
 

----- Original Message -----

From: Pat Travis

To: tombreed@attbi.com ; gasification@crest.org ; Stoves@crest.org ; graeme@powerlink.co.nz

Sent: Wednesday, June 26, 2002 12:24 PM

Subject: Re: GAS-L: Small Scale Gasifiers Defined

Dear Tom and GAS-L subscribers,

 

When defining or putting a "label" onto a process such as gasification there are two distinct audiences that must be considered from a commercial standpoint. The first is the regulatory and technical community and the second is the general public.

 

EPI uses 3 terms for our energy systems. The first, "Combustion", is very straight forward and covers projects utilizing standard fluidized bed combustors which generate heat for process or power applications.

 

The second, "Gasification",  is used when we produce a low Btu gas (LBG) in an oxygen deficient atmosphere and burn the LBG in a second piece of equipment utilizing a specially designed LBG burner, such as a gas boiler, or by injecting it directly into an existing coal fired boiler as a reburn gas. In either case, the LBG is transferred to a separate piece of equipment for combustion. This is done without cooling the LBG, therefore radiant losses from transporting the LBG between the gasifier and the end use device is the only energy loss. This type of two part process is easy for the public to understand and the one I typically find associated with gasification. The same definition applies to processes where the LBG or MBG is cooled prior to use, such as in an engine or turbine.

 

The third, "Staged Combustion", is used to describe what some people may consider a close coupled gasifier. In this process we combine a fluidized bed gasifier bottom with the upper section from a combustor. We generate LBG in the lower portion of the vessel and when it reaches a specific elevation above the gasifier section, combustion air (including dirty process exhaust gases with a high VOC content) is injected and the LBG is ignited. This provides energy for process applications and/or for power production. Most lay people do not consider this close coupled system a gasifier. Therefore while we could call it "Staged Gasification" or a "Close Coupled Gasifier", we have elected to call it staged combustion.

 

I leave it to those better qualified than myself to set the legal definitions.

 

Patrick Travis     Energy Products of Idaho (EPI)

Paul S. Anderson, Ph.D.,  Fulbright Prof. to Mozambique 8/99 - 7/00

Rotary University Teacher Grantee to Mozambique >10 mo of 2001-2003

Dept of Geography - Geology (Box 4400), Illinois State University

Normal, IL  61790-4400   Voice:  309-438-7360;  FAX:  309-438-5310

E-mail: psanders@ilstu.edu - Internet items:
www.ilstu.edu/~psanders