Re: BioC: Re: Pyrolysis vs. Gasification

[VHarris001@aol.com]

Hello Dr. Parker,

Based on the definitions you provided below, can I safely assume that the 
primary process occurring in a suction air-biomass (not coal) gasifier is 
"starved-air combustion?"  For instance, since it uses air, the process is 
not primarily pyrolysis.  Since external energy is not being added, the 
process is not primarily gasification.  And finally, since oxygen is not 
being added, it is not primarily autothermic gasification.

By my reckoning, that leaves starved-air combustion as the primary process 
occurring, producing CO and VOC's.  So, am I safe in assuming that the 
wood-gas vehicles that were running around Europe during WW2 were, for the 
most part, running on the products of starved-air combustion (CO and VOC's) 
and NOT the products of the water-gas reaction (CO + H2)?

Thanks,
Vernon Harris

In a message dated 12/29/2000 11:09:06 AM Eastern Standard Time, 
H.Parker@ttu.edu writes:

> Hello all,
>  
>  Some quick definitions in response to your note.  They might require some
>  additions and alterations as we think about them a bit more.
>  
>  PYROLYSIS - heating in the absence of air to a sufficient temperature to
>  decompose organic materials to char, liquids and gas.  500F will do many
>  organics, but 1200F is forsure decomposition.  Some compounds like dioxin
>  may be exceptions.
>  
>  GASIFICATION - reaction of organic carbon with steam, the water gas
>  reaction.  The reaction is highly endothermic.  Both steam and energy must
>  be supplied.  Gasification does not care about the source of organic
>  matter --- coal, wood,etc. Currently natural gas is gasified to produce
>  ammonia, methanol, diesel fuel etc.   This is usually done in large gas
>  fired furnaces called reformers.  (Current high natural gas prices are
>  causing domestic ammonia and methanol plants to close. Both ammonia and
>  methanol can be conveniently imported from remote locations where natural
>  gas is in excess.)
>  
>  AUTOTHERMIC GASIFICATION  - when the energy needed for gasification is
>  supplied by including oxygen as well as steam in the reaction mixture.  The
>  oxygen burns part of the carbon to CO2 to supply the  needed energy.  This
>  is a common practice with coal as per the SASOL plants in South Africa,
>  Eastman Chemical's plant in Kingsport TN, and Great Plains Gasification
>  Plant in ND.   This commonly done at high pressure with pure O2 for
>  convenience in further processing.
>  
>  STARVED AIR COMBUSTION  -  Supplying an insufficient amount of air to burn
>  all of the fuel it contacts.  The result is CO, VOC'c in the combustion
>  gases.   These gases are then usually immediately burned in a second stage
>  of combustion with an excess of air.  Starved air combustion is done to
>  limit temperatures in the fuel and to minimize formation of NOX.
>  
>  Harry
>  
>  Harry W. Parker, Ph.D., P.E.
>  Professor of Chemical Engineering
>    & Consulting Engineer
>  Texas Tech University

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