[Gasification] Clean Air Regulation requirements imposed

[Tom Miles]

The Formation of Polyaromatic Hydrocarbons and Dioxins During Pyrolysis:
A Review of the Literature with Descriptions of Biomass Composition, Fast
Pyrolysis Technologies and Thermochemical Reactions
June 2008 Manuel Garcia-Perez Washington State University With Contributions
of References from Judy Metcalf
Washington State University Extension Energy Program Library
Copyright C 2008 Washington State University WSUEEP08-010 June 2008

http://www.pacificbiomass.org/documents/theformationofpolyaromatichydrocarbo
nsanddioxinsduringpyrolysis.pdf

Tom Miles

T R Miles Technical Consultants Inc.
tmiles at trmiles.com
www.trmiles.com






-----Original Message-----
From: Gasification [mailto:gasification-bounces at lists.bioenergylists.org] On
Behalf Of Doug
Sent: Saturday, June 28, 2014 1:11 PM
To: gasification at lists.bioenergylists.org
Subject: Re: [Gasification] Clean Air Regulation requirements imposed

On Sat, 28 Jun 2014 05:21:47 +0000
James Joyce <james at jamesjoyce.com.au> 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.



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