[Digestion] Biogas fueling a diesel

[gp baron]

Still on the "How long is this piece of string"" question, I looked at Diesel to Natural Gas engine conversions (for buses & some smaller vehicles) & found that the major work done involved:
	* pulling out the diesel injection system (nozzles, pump, etc.) and
	* replacing it with spark ignition system (plugs, distributor, etc.), adding a governor & adjusting the compression ratio. 
Diesel-type engines apparently are preferred for Natural Gas service (& presumably biogas since both are methane fuels) for their high compression ratios or ratios that can be lowered to suit Natural Gas (or biogas.) 

Since governors, gas pressure & flow controllers can be purchased off the shelf and installing spark ignition systems is a doable project, what are the ideal compression ratios needed when fueling with biogas?  

Thanks in advance for any info or continued discussions on this topic.

Gerry Baron
Philippines



----- Original Message ----
From: "Zietsman, Rex" <Rex at Process.co.za>
To: digestion at listserv.repp.org
Cc: Shelby <shelby at biogaspower.co.za>
Sent: Friday, May 9, 2008 7:59:11 AM
Subject: Re: [Digestion] Digestion Digest, Vol 23, Issue 3

Mike,

Realistically, you can get down to about 70% to 80% replacement but with
a whole lot of challenges. With bleeding into the air intake, you can
safely replace 50% of the diesel with low risk of mechanical problems -
over fueling, etc. If you are running at a nice steady load, you can
increase the replacement but, to get to the really high replacement
values, you need to control both the gas and the diesel. This is less
straight forward than simply bleeding in the biogas. 

For your information, there are engines out there that have pilot diesel
injectors in addition to the main injectors. They start with diesel on
the main injectors, introduce gas cutting back on the diesel until only
the pilot injectors are running. This cuts back the diesel to as low as
1%, just enough to fire the gas mixture. So, when answering your
question, it is a bit of "how long is a piece of string?".

I cannot answer the explosivity question but would imagine that the risk
is no more at a slightly hotter temperature than at a lower temperature.
The gas density is less but the risk of leaks is just as good at ambient
temperatures. Just make sure that the engine room is well ventilated to
allow leaks to dissipate.

All the best
Rex


Thanks Rex, and to all who have responded!

I have taken a look at the website and it seems reasonably easy. Are
there no explosion concerns about bleeding it into the air intake area?
I am thinking if the engine room or air intake gets real hot as it can
here in Jamaica.

I am wondering how much percent diesel usage I could possibly replace by
this arrangement?

Mike
JAMAICA

_______________________________________________
Digestion mailing list
Digestion at listserv.repp.org
http://listserv.repp.org/mailman/listinfo/digestion_listserv.repp.org
Beginner's Guide to Biogas
http://www.adelaide.edu.au/biogas/
http://info.bioenergylists.org