Numerical Simulations of Airflow and Droplet Dispersion in a Horizontal Ammonia Scrubber

Ammonia released in pig production industries can lead to eutrophication of surface waters, soil acidification, fertilization of vegetation and changes in ecosystems, etc. Air scrubbers with spray of aerosolized sulphur solution were used to remove the ammonia mixed in the airflow ventilated out from a piggery.

In this study, numerical method were used to investigate airflow pattern, droplet dispersion, ammonia absorption at droplet surface and overall removal efficiency in an air cleaner. Droplet trajectories and elapsed time in air were adopted to characterize the absorption efficiency, and they were simulated by Eularian-Lagrangian method of Computation Fluid Dynamics (CFD). Realizable k-ε turbulence model were used to simulate airflow turbulence.

Strong vortex rotating around the main stream direction were found along the scrubber. To weaken the vortex, the impact of adding a regulating plate or a flow straightener were tested. Impact of nozzle velocity and droplet residue size were analysed. It is found that additional input on the pump pressure to increase the injection velocity may not cause any more benefit in our cases, and the ammonia removal efficiency of the horizontal scrubber is robust on different humidity conditions.