Model validation of a chemical air scrubber at a pig housing facility

Since 2004, newly built pig housing facilities in Flanders are legally required to be ammonia emission-low. This can be achieved by applying air scrubbers that remove ammonia from the outgoing ventilation air through absorption in water, followed by chemical and/or biological conversions. Apart from the ammonia removal requirements, there is a growing international concern for the livestock related greenhouse gases methane and nitrous oxide. To fully exploit the potential of air scrubbers, further process optimization in terms of design and control is required. To this end, in this study, modelling and simulation are combined with a full-scale monitoring campaign.
A mechanistic model for a chemical air scrubber was set up, including mass and heat balances, which are coupled (Van der Heyden et al., 2016). The model was validated for ammonia, nitrous oxide and methane removal, air temperature and relative humidity distribution using experimental data obtained at a chemical air scrubber installed at a conventional fattening pig housing facility.
The measured ingoing ammonia concentration varied between 18.1 and 23.6 ppm and was reduced in the air scrubber to an average outgoing ammonia concentration of 8.2 ± 1.2 ppm. The simulated outgoing ammonia concentration amounted 7.4 ± 0.6 ppm and followed the experimental ammonia concentration within one standard deviation of the measurements. Nitrous oxide and methane were not be removed. A good agreement between the measured data and the simulation results was also found for the air temperature and relative humidity.
Overall, the model was well able to predict the removal efficiency and water loss. It thus provides a useful tool for further process optimization in terms of design and control.