Re: GAS-L: Gasification = mass burn incineration?

[LINVENT@aol.com]

In a message dated 4/30/02 8:10:14 AM, Andries.Weststeijn@essent.nl writes:

<< Fernando,


Are you differentiating between toxic concentrations (in the product gas or

flue gas) and absolute quantities released?


Generally speaking, I could imagine that the toxic concentrations in the

product gas from oxygen gasification are higher than in the (diluted) flue

gas from burning. But also, that there could be an advantage in removing the

toxic components from the smaller quantity of higher concentrated product

gas.

I can see a parallel with sulfur removal after coal gasification: i.e.

removal of a higher concentration of sulfur from a smaller volume of coal

gas, than removing that same amount of sulfur from a higher volume of flue

gas from coal burning (diluted with lots of nitrogen from the combustion

air).


Your message quotes one specific project which intends to gasify selected

"cellulosic material with recyclables and plastics removed". Sounds pretty

clean to me! That for this project absolute emissions from this selected

cellulosic fuel would be "equal or greater than mass burn incineration"

doesn't appear to be logical. 


It looks to me that the key of your question is in the specific gasification

fuels chosen by USEPA for comparison with general mass waste incineration. 

Also, clearly, the technological level of gas and flue gas cleaning

considered (or predicted) by USEPA for each route is of importance.  


I could imagine the following sequence of comparisons:

1) compare landfill with mass solid waste incineration (combustion)

2) select certain higher potential waste fuels from incineration

3) optimize specific emissions controls going with the dedicated

gasification of these selected fuels

3) compare emissions of gasification of selected waste fuels with mass solid

waste incineration (not landfill).


best,

Andries >>

Dear Andries et. al,
    Unfortunately, even with a "clean fuel" such as plastics removed and the 
like, combustion to steam conversion efficiency is not very high. In areas 
where power generation is viable, this can work economically. Separation 
needs to be quite good to prevent metals contamination of the gas stream as 
even little watch batteries can add heavy metals to the gas stream. 
    Gasification can yield much higher conversion efficiency as IC engines or 
gas turbines have better efficiency than steam boilers. Waste heat from the 
engines can add more efficiency in a combined cycle configuration. 
    Thermogenics has re-demonstrated the ability to remove sulfur from the 
gas stream from sulfur containing fuels in gasification. Recent flame 
photometry and GC/MS conducted by Sandia National Laboratories has shown no 
detectable sulfur from tire gasification in the producer gas. Heating value 
was over 200 btu/scf. This system does not have any specific sulfur removing 
equipment in the gas cleaning train, only aerosol, tars, oils and water 
removal design which is standard equipment for the gasifier we offer. The 
suspected methodology of removal is an interesting study in physics. 
    Prior tests by Radian have shown minor organic sulfur compounds in the 
gas stream when operated at near combustion on automobile shredder fluff 
which contained 1.2% sulfur. Although we have not run coal, we expect the 
same outcome. 
    We are of the opinion that this will have a dramatic impact upon the 
ability of a gasification system to operate a catalyst or other system which 
is very sulfur sensitive. Chlorine has had similar results. Hence, removal of 
plastics has not been necessary and we are interested in projects where 
plastics are a major portion of the feed stream. 


Sincerely,
Leland T. Taylor
 President
 Thermogenics Inc. 
7100-2nd St. NW, Albuquerque, New Mexico 87107 
phone 505-761-5633 fax 505-341-0424
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