High-efficiency parallel-plate wet scrubber (PPWS) for soluble gas removal

• A parallel-plate wet scrubber was designed to control soluble gas pollutants.
• Typical tower packings were replaced by a multi-parallel-plate module (MPPM).
• The MPPM enhances the absorption of acid gases effectively at low concentration.
• Experimental efficiencies are in good agreement with theoretical predictions.

A parallel-plate wet scrubber (PPWS) was designed and tested to control low-concentration soluble acid gases using a multi-parallel-plate module (MPPM) to replace typical tower packings. The parallel plates in the MPPM were made of polypropylene coated with nano-TiO2 particles to enhance hydrophilicity for scrubbing liquid to form uniform liquid film. The gap between the plates was maintained at 3 mm, providing channels through which soluble gas pollutants in the upward gas stream were absorbed by the downward scrubbing liquid film on the surfaces. The removal efficiency was tested using HCl, HNO3, and CH3COOH of 0.02–2 ppmv at different retention times and liquid-to-gas ratios. Results show that when the retention time was 0.1, 0.3 and 0.5 s, the removal efficiency of the present scrubber for HCl, HNO3, and CH3COOH in low concentration was greater than 91%, 95%, and 98%, respectively. The MPPM significantly enhances the removal efficiency of the present scrubber, especially in low inlet concentration range (0.02–1 ppmv), which was greater than 99% for HCl and HNO3 and 98% for CH3COOH at the liquid-to-gas ratio of 18.5 L/m3, the retention time of 0.5 s, and the pressure drop of 0.2 cm H2O. The experimental removal efficiencies of the MPPM are in good agreement with theoretical predictions. It is expected that the present PPWS can be scaled up as an efficient control device with low pressure drop for low-concentration soluble acid and basic gases.