Performance evaluation of poly-urethane foam packed-bed chemical scrubber for the oxidative absorption of NH and HS gases.

The feasibility of open-pore polyurethane (PU) foam as packing material for wet chemical scrubber was tested for NH and HS removals. The foam is inexpensive, light-weight, highly porous (low pressure drop) and provides large surface area per unit volume, which are desirable properties for enhanced gas/liquid mass transfer. Conventional HCl/HOCl (for NH) and NaOH/NaOCl (for HS) scrubbing solutions were used to absorb and oxidize the gases. Assessment of the wet chemical scrubbers reveals that pH and ORP levels are important to maintain the gas removal efficiencies >95%. A higher re-circulation rate of scrubbing solutions also proved to enhance the performance of the NH and HS columns. Accumulation of salts was confirmed by the gradual increase in total dissolved solids and conductivity values of scrubbing solutions. The critical elimination capacities at >95% gas removals were found to be 5.24 g NH-N/m-h and 17.2 g HS-S/m-h at an empty bed gas residence time of 23.6 s. Negligible pressure drops (< 4 mm HO) after continuous operation demonstrate the suitability of PU as a practical packing material in wet chemical scrubbers for NH and HS removals from high-volume dilute emissions.