[Gasification] Candle filter experiences

Doug doug.williams.nz at gmail.com
Tue Oct 31 05:09:57 CDT 2017

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 

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 

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,


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
> _______________________________________________
> Gasification mailing list
> to Send a Message to the list, use the email address
> Gasification at bioenergylists.org
> to UNSUBSCRIBE or Change your List Settings use the web page
> http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org
> for more Gasifiers,  News and Information see our web site:
> http://gasifiers.bioenergylists.org/

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/gasification_lists.bioenergylists.org/attachments/20171031/f5942608/attachment.html>

More information about the Gasification mailing list