Zero-emission solutions
for odour control

    Cooling and recirculation: often your best option

    What happens with air in for instance a dryer? Basically, moisture is carried over from the product to the air. If one succeeds in removing the transferred water vapour from the exhaust air, recirculation of the exhaust air might be possible. If so, here is your most elegant, cost effective and environmental friendly solution to an odour situation. By recirculating 100%, even zero emission is feasible. As a minimum, an appropriate heat exchanger is required, like the MilieuPartners OCC-system.

    OCC: a combination of cooling and odour control

    Recirculation of exhaust air requires cooling to below to dew point temperature; condensing water will occur. The heat exchanger for the OCC system is made of plastic and features small smooth tubes permitting the condensing water to flow freely unlike e.g. in finned tube exchangers. The typical surface area (m2 per m3 of unit volume) is in the same order of magnitude as standard packing materials applied in scrubbers. Odorous components too will be removed from an air stream by condensing water vapour present in the exhaust air stream and subsequent absorption of these odorous components in the condense.

    In other words: by cooling an exhaust air stream below the dew point, recirculation is made possible and the air after the (OCC-)cooler contains significantly less odorous components.

Designing a recirculation system requires modelling. Computer models of relevant process equipment are necessary to calculate and design the appropriate cooling capacity and feasible recirculation cycles.

MilieuPartners have experience with designing zero emission recirculation systems for a number of applications, e.g. fish- and compound feed, various composting systems and starch dryers.

Odour control

 A system combining condensation, absorption and recirculation can also be considered, e.g. by extending the control system with an alkoxy scrubber, to improve the overall efficiency.The advantage of absorbing the bulk of the contaminant in the condense induced by the cooling effect is a saving on chemicals.

Odour control: recircultion and cooling 

Related topics: Plastic heat exchanger
References
Odour and its atmospheric dispersion


Applied for cooling process air at various composting plants the OCC appears to be capable to remove approximately 50% of the ammonia. If an efficiency of 80% is required, e.g. to meet the requirements for a biofilter, there is no need for a separate acid scrubber. The scrubbing effect can be integrated in the OCC, the so-called OCC-plus concept. The condensed water vapour is circulated and slightly acidified.