Hi James,
We have had quite a lot of experiences using candle filters for our
project at CalForests in California. They work well, but will clog in an
eye blink if start-up gas is not vented first. Life relates to
mechanical shock and flanged end seals, which we found shrinks so the
candle can leak and wobble. Any backfires into the filter will also
cause breakage which you don't see without opening the filter from both
sides. Inspection or access hatches can assist with servicing, but there
is no standard when these types of filters are used for gasification
applications. As our project was one of staged development, I cannot
tell you how many hours were recorded in total, but we expected an
annual replacement based on seasonal heating requirements. According to
the manufacturers of the candles, our project was the first of it's kind
in the USA applied to gasification, so you may not get to much practical
information.
They are really tops at removing the solids if your gas is tar free,
because any condensation will block the candle. We used condensers down
stream and at times some very light pyrolysis oils showed up which
destroys any diaphragm in gas regulators. If it doesn't do that, then it
blocks the control ports in the regulator/mixers, but it all depends on
the overall quality of the gas. Good luck with filtering pyrolysis gas,
you could loose your shirt as I have not heard of any success to date.
You can expect to collect a lot of very fine dust which is rather
difficult to flow from under the candles. Augers just drag out a core
and the dust stacks up over the trough, so you need some thought to
extraction.
This is just off the top of my head, and it's been about 4 years since
we changed the projects direction from engine generation to hot water
boiler heating. I was on site late July and we discussed building a new
candle filter for the boiler, so we are sold on them at least for our
type of project. I haven't put up the latest photos from the project as
yet on the Fluidyne Archive of the biochar maker, but you can see a few
photos of the candle filter trials. http://www.fluidynenz.250x.com/
Hope this helps a bit.
Doug Williams,
Fluidyne.
On 31/10/17 12:48, James Joyce wrote:
We are just about to order candles for a flue gas filtration application at 350
deg C. We have also been asked to design a 400 deg C candle filter system for
pyrolysis gas, for installation ahead of a condenser.
This is one example (not necessarily the supplier we will use)
http://www.herding.de/files/hGlobal/Downloads/Technical_product_descriptions/ALPHA/UK/Herding_ALPHA_Biomass_Filterunit_uk.pdf
I have read some of the case studies for larger gasifiers. I am interested to
know what experiences, if any, have been had with candle filters at the smaller
scale (say 2-20 tonnes per day of biomass gasified). Reliability is my main
interest, number of hours between replacement ... and performance as far as
downstream equipment such as condensers and engines are concerned.
Regards,
James
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