Emissions abatement help

[shaunmiller]

Looking for a little info on scrubbing techniques to help with the BAT (best available techniques)section of a PPC application. What I would like to know is:

Possible methods of scrubbing a low volume, low conc (20-250ppm)VOC(isopropyl alcohol) stream, and their advantages/disadvantages. Already searched for possible ways to scrub VOC's but could find no design info, basically want to demonstrate that it is not economically feasible to scrub these emissions.

Ways of scrubbing acid vapours (HF, HCl, HNO3 mix)and alkaline vapours(ammonia, caustic) other than using wetted packed columns. Especially any info on dry scrubbing techniques. Again, want to justify the use of wetted packed columns to perform the scrubbing operation as opposed to other techniques.

Any information is much appreciated.

Cheers
Shaun.

 

[NeedAHoliday]

Shaun,
With respect to removal of low conc low volume VOC mix there are several methods available, commonly you can remove via adsorption (activated media adsorption) and can be very efficient if designed well however without knowing process conditions can not verify if this is an appropriate method, for example at 1000m3/hr at 35C and atmospheric isopropanol will have a general adsorption of 6.5 - 15 g/g act carbon (generic calc) as such at 20 PPM your bed will last about 4 days max, while at 20 PPm bed will last about 23 days. These are quick and basic calcs but show you the general lifetime of your bed using basic act. carbon and assuming no other constituents that will preferentially adsorb over you isopropanol.

The second method is through thermal oxidation. If using an RTO for your conc range at 5000Nm3/hr you would have a burner around 130kW with a thermal efficieny of 96% with an autothermal point of between 1.4-1.6 g/Nm3 (your operating at 0.054 - 0.670 g/Nm3, these calcs are very rough and specific to the heat exchange media I have used for calculations).

The second question is more involved so I won't try to answer in full. Essentially there are dry technologies available I personally have found them to be low on efficiency for some of the compounds you list above (the exception is HF this is well documented for dry scrubbing, ref Brick industry). Generally a semi-dry/wet method is used as water is required to promote the surface absorption and reaction. Please note that a 2 stage method will need to be adopted to efficiently remove the acid gasses and alkaline gasses.

Hope this helps somewhat.

 

[shaunmiller]

Thank you for the info NeedAHoliday, it has been very useful. Thanks for taking the time to reply to my post.

Regards,
Shaun.