2 replies to this topic

[Minhaj]

Em working on a design project for the production of phthalic anhydride from catalytic oxidation of Ortho Xylene, in the process there is a switch condensor in which phthalic anhydride and other by products are sublimemed and off gas containing CO2,SO2,H2O and N2 is coming out of condensor. As off gas contains pollutant gases like SO2 and CO2 i have to scrubb the off gas stream . now guide me which kind of scrubber i should design ? and How ?
process parameters will be provided upon requirments.....

Thanx

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[milenkom]

I'm not sure about CO2 but for SO2 you could use scrubber by washing the gas stream with lime, CaO. Downstream of scrubber bag filter may be employed to remove particulates from the gas stream. There are few designs for a scrubber, wet/dry scrubbing techniques.

[kkala]

I suppose you are aware of
http://www.che.cemr....ic/phthal-a.PDF,
which gives general info on the process but not about the proper equipment to clean flue gases. It is apparent however that available ΔP of required scrubber is low (compressor's output is about 2 Barg, flue gas entrance to scrubber will probably have a pressure slightly higher than atmospheric, like e.g. boiler flue gases).

You have to concentrate on SO2 removal, since CO2 may contribute to greenhouse effect but its emission is permitted (even by paying some tax in EU, but quantities emitted are small in your case). A source of methods can be found in e.g. A. Kohl & F Riesenfeld's "Gas Purification", Chapter on "Sulfur dioxide removal". But at least in the available book (2nd edition, 1974), no method is commercially proven.

You may chose two methods of SO2 removal and select the most economical (if this project is an exercise), e.g. by using NH3 aqueous solution counter-currently in a packed tower or by considering the CuO process, where the absorber is CuO *("spread" into Al2O3 pellets) regenerated through H2 or CH4. Having briefly searched for the best method concerning phthalic anhydrite production to no avail, I cannot be specific. However it is known that SO2 removal from power station flue gases is not considered an easy task and local legislation permits lower SO2 removal efficiency for lower capacity of such plants. Peculiarities of phthalic anhydrite production may end up with few proven SO2 removal methods for the specific case. It is worth while searching for these methods (in books, web, or Best Available Techniques - BATs) before considering desulphurization methods in general.

* it can be in fluidized bed

Edited by Art Montemayor, 30 July 2010 - 06:32 PM.