Honeycomb wet scrubber for acidic gas control: modeling and long-term test results

Abstract

A laboratory scale, 1.0 CMM (m3 min− 1) wet scrubber packed with water-absorbing honeycomb material (HWS) with a very large geometric surface area of 480 m2 m− 3 and a low pressure drop developed in our previous study was shown to achieve a very high removal efficiency for acidic gases but there were no long-term test data. In this study, the HWS scaled up to operate at a 100 CMM flow rate was tested for removing mixed acidic gases at a semiconductor fab for a very long period of 3.5 yr. Results showed that the removal efficiency for the mixed gases emitted from the fab always maintained as high as > 95% for HF, CH3COOH, HCl, HNO3, HNO2, and H2SO4 with the inlet concentrations ranging from supper-ppmv to sub-ppmv, during a 3.5-yr period. With water jet cleaning of the honeycomb modules once per year, the pressure drop of the HWS remained to be low at 0.5–0.8 cm H2O, indicating minimal scaling in the HWS. Additionally, the predicted height and removal efficiencies of the HWS were very close to the experimental data. The excellent long-term performance of the HWS warrants its potential applications in many areas in which liquid absorption is the preferred treatment method and the theoretical equations can facilitate the design of the HWS.

Continuous Improvements and Future Challenges of Air Pollution Control at an Advanced Semiconductor Fab

“…In addition, it was found that using structured packing materials can help to reduce the operation cost with less amount of dosing chemicals and shorter residence time (Le et al, 2021). Also, for the semiconductor exhaust flow treatment, the WSs need to be feasible for mixed acid or alkaline gases with a wide range of concentrations from ppm levels to ppb levels, which could not be handled effectively by existing conventional WSs (Chien et al, 2015a).…”

“…It is to be noted that the removal efficiency of the acid gases is not high enough and the increase in the residence time and packing height can lead to an increase in the pressure drop, power consumption and operation cost when the traditional packing materials such as rachig rings are used. Some WSs packed with structured packing materials such as honeycomb wet scrubber (HWS) or parallel-plate WS (PPWS) (Chien et al, 2015a(Chien et al, , 2015cLe et al, 2021) can be the better alternative control methods. The PPWS was proved to achieve a very high removal efficiency of > 99% for HF, HCl and CH3COOH with very low concentration (sub-ppm level) in a short residence time (0.5 s).…”

“…But it is costly to scale up the PPWS with the nano-TiO2 coated plates for industrial applications. The HWS, which uses water-absorbing polypropylene (PP) fabric with a higher specific surface area of 483 m 2 m -3 as packing material, can achieve very high efficiency (> 95%) for the mixed acid gases of HF, CH3COOH, HCl, HNO3, HNO2, and H2SO4 with the inlet concentrations ranging from supper-ppmv to sub-ppmv during a long operation period of 3.5-yr period (2017-2021) (Le et al, 2021). The pressure drop of HWS is also very small ranging from 0.5-0.8 cm H2O.…”

Computational Fluid Dynamics Simulation Approach for Scrubber Wash Water pH Modelling

“…The mass flow rate, defined within the simulation, is considered to be uniform and normal to the boundary. The mass influx [20] will be calculated by using:…”

“…Based on these assumptions, the standard k-ε; turbulence model was used. The model is a semi-empirical one [20,21]; the rate of dissipation (ε) and turbulence kinetic energy (k) are based on the below transport equations [20]:…”