[Gasification] Low Calorific Gas for Stirling Engines

[Mark Loftin]

Tom,
I believe it is a 4-cylinder engine. They said they are completing 
testing of this model on landfill gas and I assume that primarily 
involves optimizing the design of the burner/HX cowling around the coils 
for that particular type of fuel.  I think that direct firing with 
natural gas would possible, but at a very high excess air to keep the 
flue temperature down.  The HX coils are made of either monel or inconel 
and can take a pretty high temp.  As you say, it seems a good fit for 
low btu gases like producer gas or landfill gas (50% CO2?).

That price is without any burner or HX coil cowling, but does include 
the HX coils as they are integral with the engine. The term "cowling" 
here is referring to the firebox, ducting and combustion air intake 
assembly that brings the hot flue into and out of the HX coils. But 
generating 1,100 SCFM of 1,850 °F flue gas from producer gas would 
require a pretty large downdraft unit (or several smaller units).  I 
also wouldn't recommend using it just for electricity generation due to 
the high $/kWe for the integrated system (gasifier/burner/generator). 

But, if you attach the gasifier/burner economics to the downstream 
process heat load (for example, natural gas usage offset) and attach the 
generator economics to the power generation, then you might have an 
integrated heat/power system that is both efficient and price 
competitive (at least in this size range).

M. Loftin

Tom Miles wrote:

>Thanks Mark. 
>
>The STM website and brochure don't give any "engine" specs. 
>
>Is the 55 kW unit one 4 piston module or several? The burner/heat exchanger
>for low btu gas would be larger than for landfill gas but the temperature
>would not be a problem.
>
>Is there an indication of what $1200/kW ($66,000 for a 55 kWe unit) would
>include? If it is just the engine then when you add the burner/heat
>exchanger, gasifier and solid fuel system you're going to be at $3,000 kWe
>or more. 
>
>Tom
>
>
>    
>
>-----Original Message-----
>From: gasification-bounces at listserv.repp.org
>[mailto:gasification-bounces at listserv.repp.org] On Behalf Of Mark Loftin
>Sent: Wednesday, September 06, 2006 7:23 AM
>To: gasification at listserv.repp.org
>Subject: Re: [Gasification] Low Calorific Gas for Stirling Engines
>
>List,
>FYI, I believe that a list discussion some time ago referenced STM Power's
>Stirling synchronous generators.
>
>http://www.stmpower.com/Technology/Technology.asp
>
>They sent us some technical data on the 55kWe unit, which requires around
>1,100 SCFM of 1,825°F flue gas. The working medium is hydrogen. 
>The units are primarily designed to be fired on natural gas (or landfill
>gas) and a burner/heat exchanger housing will have to be designed for each
>type of fuel you would use. I do not believe they have developed a
>synthesis/producer gas system yet.  It seems to me that this would be very
>efficient for combined heat/power applications using downdraft gasifiers (up
>to 80% overall).  Couple this unit to a heat recovery steam generator, kiln
>or other process that can utilize the exhaust heat and you would have
>something that a IC engine may not be able to duplicate in this size
>footprint.  Plus, maintenance would seem to be minimal, especially if you
>had a good producer gas stream (i.e., low char/tar/ash carryover). Last we
>checked, these units were going for around $1200/kWe and would be available
>for retail by year's end.
>
>Oh, by the way, these units come equipped with synchronous generators, so
>you'd have to have an existing 3-phase electrical grid to connect them to.
>They consume power until the coils heat up, then they start exporting
>current.
>
>M. Loftin
>
>
>
>
>
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