[Digestion] Biogas fueling a diesel

[gp baron]

Mike,

Thanks for the link. It looks like a whole book read that should prove interesting for my rusty engineer's brain.

A few years ago, I thrust a 3/4" water hose delivering biogas into the air filter of a 25 kVA genset with a naturally aspirated 4 cylinder Nissan Diesel engine. Biogas delivery pressure would have been the combined digester output pressure & engine suction. Flow (or quantity), is what the engine sucked plus some air. The latter didn't matter since it was supposed to be free.

At 30-40% genset load, diesel consumption was 5-6 liters/hr. With biogas added, diesel consumption dropped to 3-4 liter/hr. At experiment time, electricity cost P8/kwhr and diesel cost P30/liter. The approximately 8kw produced was worth P64 while fuel used cost P60. The "savings" was too small at that time to choose running the genset continuously.

Now that diesel is more expensive & if biogas can decrease diesel consumption by greater than 50% (with "simple?" improvements in the way biogas is added), I need to conduct the experiment again. Any ideas & comments to make the experiment better would be appreciated & I shall keep you posted on my findings.

Gerry Baron
Philippines   


----- Original Message ----
From: Michael Barnett <dreadlox at cwjamaica.com>
To: gp baron <gpbaron4091 at yahoo.com>; "Zietsman, Rex" <Rex at Process.co.za>; digestion at listserv.repp.org
Cc: Shelby <shelby at biogaspower.co.za>
Sent: Saturday, May 10, 2008 1:01:27 AM
Subject: Re: [Digestion] Biogas fueling a diesel

Here is a resource online... in case you haven't seen it before.
http://www.gate-international.org/documents/publications/webdocs/pdfs/g36ene.pdf

Mike
JAMAICA


----- Original Message ----- 
From: "gp baron" <gpbaron4091 at yahoo.com>
To: "Zietsman, Rex" <Rex at Process.co.za>; <digestion at listserv.repp.org>
Cc: "Shelby" <shelby at biogaspower.co.za>
Sent: Friday, May 09, 2008 5:55 AM
Subject: Re: [Digestion] Biogas fueling a diesel


> 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
>
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