On Sat, 28 Jun 2014 05:21:47 +0000 James Joyce <[email protected]> wrote:
Hi James, While not right up-to the mark with the latest regulations regarding emission testing, Dioxin has been a long time interest of mine in regard to how it may affect gasification emissions of certain fuel types. > Leland we are working from a source separated feedstock ... but of course no > separation method is every perfect. As far as air toxics I think I will start > with the argument that if we get below the detection limit for a given > species when using good quality industrial analysers (not research lab > instruments) then our job is done. I agree with your stance on this, but you first have to prove you are operating under the limits. Then you will probably be forced to use a Certified Laboratory if you can find one before you lower the measuring equipment standard. The last report I had on emission testing from Australia, was that you had to send them to a New Zealand laboratory, but that might have improved in the last couple of years. > On a related note we normally use CO as an operational performance indicator > for all hydrocarbon derived compounds... in our systems it is by far the most > prevalent residual gas species and in my experience is that is the last > compound (apart from soot) to be oxidised completely in a biomass flue gas > ... is that the experience shared by others ? While CO as a gas is probably the last gas to oxidise, hydrocarbons can also survive, along with sub-micron carbon blacks which need much higher temperatures to oxidise than the gas. We use hot ceramic filter candles for the carbons with good results, but if any hydrocarbons are present, they just pass straight through most filtration processes if operating at elevated temperatures. > One aspect we may have to face is questions about dioxins. We do all the > right things to avoid formation in terms of feedstock selection and operating > temperatures/residence times ... however we have not done actual > measurements. I am told that Dioxin measurements are around $3000/analysis in > Australia ... is that the case elsewhere ? That makes performance data > collection prohibitively expensive. What are others doing for Dioxin analysis > ? Having faced the waste of money on unnecessary testing just to get a yes or no answer, you might consider a return to basics. We found that doing a field screen test first to establish the risks for Dioxin to form because you must have benzine present. As benzine is a lower distillation temperature gas, it's presence is always indicated by the formation of tar in the cold gas before oxidation. Normally in a oxidation situation, benzine is not a problem unless chlorine is present in your waste derived fuel, but if present will give you a Dioxin ash particle when oxidized. If there is no tar or pyrolysis oils present in your unoxidised gas samples, then you are in a very good place to then have a certified test done knowing the results will most likely be clear of Dioxin. Just don't waste your testing $$ if tar is present. > Artem, bag filtering at 600 deg C is interesting ... it keeps you well above > the Dioxin formation temperature range ... I could not see much detail on > your site. Can you provide any more information on this ? Are you referring > to Cerafume bags like those described here: > http://www.albkleinco.com/cerafume-high-temperature-gas-filters/ Without knowledge of your process which may negate this comment, Dioxin once formed at lower temperatures can be heated, but needs high temperature packed carbon bed reducing atmospheres (12-1500C) to separate the benzine from the chlorine before filtration. If you are collecting oxidised Dioxin ash particulates in any type of filter, then your real problem of how to dispose of them safely might be difficult to resolve. Hope this might be of some help. Doug Williams, Fluidyne Gasification. _______________________________________________ Gasification mailing list to Send a Message to the list, use the email address [email protected] 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/
