[Gasification] Naphthalene Condensate Photos, GAST methodology
linvent at aol.com
Sat Apr 22 23:51:56 CDT 2017
One of the major reasons Caterpillar won't get heavily involved in producer gas engines is the naphthalene issue. One group that had an operating power plant for a municipality would operate their engines for a few hundred hours and the valves would begin knocking and the V-12 engine would have to have a valve job. ir
It is fairly easy to fix if one knows the properties of the gas. We do it as a matter of course as it doesn't make any sense to offer a system that has to have the engine rebuilt periodically. One engine manufacturer will not guarantee their engine unless it meets their strict standards.
As to the GAST report, I read some of it and some of the procedures can easily be improved such as measuring the air inlet flow using a typical mass:flow meter out of a car that is extremely accurate and can provide continuous monitoring. In the program we use for our systems, it automatically calculates the inlet air flow rate and with settable or automatic monitoring inputs such as temp, humidity, can provide continuous and accumulated air mass input.
There are also methods of measuring gas composition, to much better detail than is now being used. Fixed gases such as the usual by either GC or specific gas analyzers do not show the condensable gases such as ethanol, methanol, acetone, acetic acid, napthalene of course, and other compounds that may affect engine operation for the better or worse. The same system could be used for engine exhaust measuring of say formaldehyde, carcinogens, and everything except PAH and particulate.
None of the gasifiers monitored are as efficient as we would like to see in our designs. High carbon yield in the char/ash residue is an admission of the inefficiencies present.
As another note, virtually all emission testing is flawed because if the inlet air has a few ppm of NOx or CO, the output is going to be biased upward this amount and none of the EPA testing protocols take ambient air quality into account.
Leland T. "Tom" Taylor
From: Doug <doug.williams.nz at gmail.com>
To: 'Discussion of biomass pyrolysis and gasification' <gasification at lists.bioenergylists.org>
Sent: Sat, Apr 22, 2017 5:39 pm
Subject: [Gasification] Naphthalene Condensate Photos
Naphthalene in Producer Gas
Hi Gasification Colleagues,
Reading through the Italian Paper on gasifier monitoring in South Tyrol, the reference to Naphthalene caught my eye, because as a light pyrolysis oil, after dry filtration and condensation, I have only seen this in gas in the Northern hemisphere. Looking like yellow oil floating on aqueous condensate, exposed to air when tipped onto a concrete surface, it just completely vaporizes leaving only a carbon trace of stain. It makes a good mess inside pipes and diaphragm regulators and if being combusted in a flare or oxidation chamber, will add to the emissions from the stack. The bottom line is that we don't want this in our producer gas for either engine or combustion applications, but once condensed, it's very hard to clean out of the gas.
My questions to any one who might have some similar experience, is why Naphthalene may not show up in small gasifiers under say 100m3/hr, yet becomes a issue as the gas output increases from a larger system. I have observed this formation in N.Ireland and California and definitely related to just higher output. Could it be related to the amount or volume of the unstable pyrolysis gas in the fuel hopper? Can this create a chemistry that can survive an incandescent char bed, but reform as Naphthalene in the gas reduction phase?
I can assure you that it isn't about tar or bad design, as our bed analysis and pressure drop continuous monitoring has not shown bridging or channeling to be the culprit. Black tars are never present, nor is CH4 as Methane (<2%), so bed temperatures are not an issue, nor moisture content of the fuels (wood chips or blocks). Char under the grate is dry and clean, as is the <10 micron dust from the cyclones.
The photos show two samples from a larger system, one a first stage cooling containing ash and carbon with a purple colour from the ash. The second bag from the cooling condenser is yellow from the Naphthalene which did increase with more gas output . The square container is completely clear and comes from the Fluidyne Pacific Class gasifier (90m3/hr) and it has always made clear condensate in both hemispheres except when incorrectly fueled. It has not been possible to test larger gasifiers of our own design here in New Zealand, hence the questions.
Any discussion would be appreciated.
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