Dioxin and Furan reduction/elimination trough filtration 1

[MedicineEng]

Dear All:
I would like to ear from you regarding this issue. In a industrial scale incinerator is it possible to reduce or eliminate dioxins or furans by filtering the combustion gases? As far as I understand ( and I am not an expert), dioxins and furans are formed due to too short residence time of the contaminants in the combustion chamber and once formed it will be virtually impossible to reduce them.
Thanks

 

[25362]

US Patent # 5021229 may have some answers.

 

[MedicineEng]

Thanks a lot. I went trough the patent description and I found reference to several methods but none referes filtration of flue gas.
I also made a search in the site to see if there were any patents regarding dioxins and filtration and I couldn't find any.
I am getting to the conclusion that dioxin reduction trough filtration doesn't exist.

 

[MMcLean]

I dont believe filtration would be possible. By holding combustion at the correct conditions in a direct thermal oxidiser for example, you will not form dioxins and furans.

Contact a company called Megtec for more info

Mark McLean

 

[mbeychok]

MedicineEng:

First of all, there is no doubt whatsoever that the fly ash from large-scale municipal waste incinerators contains dioxins and furans ... both those formed during combustion and those formed post-combustion.

Second of all, the regulatory agencies (U.S. national EPA as well as state environmnetal agencies) are completely aware of that fact and their regulations regarding emissions from such incinerators and their required control measures reflect that fact.

So, obviously, capture and removal of fly ash, or treatment of the fly ash, are ways of reducing the amount of dioxins and furans released by incinerators. You weren't very specific as to what you meant by "filters''. There are many types of equipment for capturing fly ash: electrostatic precipitators, cyclones, baghouses, etc. I don't know whether the type of filter you had in mind will be effective for reducing dioxins and furans from incinerators.

To learn more, use Google's advanced search function simultaneously on the phrase "incinerator fly ash" and the word "dioxin" ... and you'll get more hits than you can read.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[MedicineEng]

mbeychock:
Thanks a lot for your feedback. Let me just elaborate little bit more my case.
We have an industrial recovery boiler that burns the byproducts of our production process. After the combustion and boiler to produce steam, the flue gases are cooled down trough a quencher and then neutralized in a scrubber. The last step of the flue gas treatment is a set of demister filters that have the fuction to retain some water carried over from the scrubber and according with the supplier, also reduce some dioxin level. The main point is this one, our dioxin level even if complying with local regulations, is higher than the design value (all the other parameters are Ok ad dust and ash are very residual). Meanwhile, the demisters never worked properly since the every time that we put htere a set it would clog in a matter of hours, due to the fact that the porosity was extremely tight.
This has been like that for some time, and the supplier insists that the dioxin problem is caused by the fact that we don't have there those filters (despite the fact that he cannot find any suitable supplier to meet his design).
That's why I tried to dig a little bit on the subject to avoid this to drag until the end of times.

 

[siretb]

The dioxins from an incinerator are concentrated
1) in the fly ash, they are collected by the precipitator
2) in the flue gas downstream the ESP
the fraction of the dioxins carried by the flus can be further split in
2.1) the gazeous part ; they can be removed by filtration, if you add activated carbon upstream of a baghouse filter, and operate the filter at a low enough temperature (say less than 200°C) ; note that other processes than filtration will get rid of the dioxins (SCR, adsorption/adsorption, wet scrubbers involving catalytical destruction, ....)
2.2) the particulate part. dioxins are bound to the fine particles tht escape the precipitator. They will be removed by a filter.

To sum up, yes, filtration with additives will work, provided that T is not too high.