Design and optimization of a packed bed scrubber for purification of waste gas containing ammonium

In this work, a two-stage packed bed scrubber was designed and optimized for purification of industrial waste gas containing ammonia at a concentration of 1400 mg m-3. Basic material balance equations, equilibrium data, and the generalized pressure drop correlation were used for the calculation. For the analysis of different configurations, Katmar software was utilized, which uses the generalized pressure drop correlation in order to calculate the scrubber diameter based on the allowable pressure drop and proximity to flooding conditions. It was found that optimal results are achieved in a two-stage device, using 70 vol.% sulfuric acid for chemisorption of ammonia. Pall rings, 50 mm in size and made of polypropylene, were selected as a column packing. Performances of scrubbers of three column diameters (i.e., Dc=2; 2.1 and 2.2 m) were analyzed. From the aspect of the liquid phase flow, the column diameter of 2 m provides satisfactory results. According to the packing specifications, the pressure drop through the packing layer would be about 900 Pa. It was found that the pressure gradient, and therefore the total pressure drop in the column decreases with increasing the column diameter. However, as the diameter of the column increases, the minimum flow rate of the liquid phase required to wet the packed bed increases, so the required liquid flow rate increases. Taking into account all of the analyzed process parameters, as well as the required purification degree of the waste gas, the optimal configuration of the device was proposed.