[Gasification] Combustion vs. gasification

Toby Seiler seilertechco at yahoo.com
Tue Nov 30 08:01:27 CST 2010

Efficiency, like beauty, is in the eye of the beholder.  If your goal is electricity generation you can make ready comparison, but if you want a gas that is in the correct proportions to synthesize liquid fuel or make heat for a high value process, you have very different starting goals.  Efficiency as I see it, is how well you meet your goals that you went in expecting, versus what you get out.
For example, Indianapolis Indiana burns municipal waste making electricity and heat.  The heat is used for downtown heating needs.  They supply about 40% of the electrical need as well.  Is it efficient?  If your goal is only electric generation, probably not, heat only, probably not, but combined and taking in the fact that it is otherwise landfill waste, YES.  
So what are the goals Robert?  What high value use do you have for heat, both low and high grade?  Can you cook a food product, dry lumber, or ???? with the heat?  I can hardly see approaching your project as a stand alone generator system that sends huge amounts of heat into the atmosphere, rather than a combined heat and power system that has plans for making high value product from even low grade heat.  
One small note to "syngas" comment from Kevin.  I look at synthesis gas as having a high portion of the energy content derived from breaking water bonds.  The heat requirements to do it thermally are significant and very much different than "producer" gas, which for simplification is dry (8-14% moisture content) fuel and degrades considerably with higher moisture fuels in most gasification systems.   
A combustion system has reactions all occuring at once while gasification is concerned with stopping reactions from lack of oxygen and then cooling the gas for later, downstream use... usually combustion by adding more air.  The energy content of producer gas and synthesis gas is very different and so is the reject heat.  Gas coming from a producer or IC engine is perhaps 400-600f while gas coming from synthesis is 1600-1800f or so.  
I'm studying the combinations of producer gas making and synthesis gas making that may some day prove my theories on combined processes.  
Best wishes,
Toby Seiler
Seiler Technical Company  

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