Removal of ozone from air by absorption in a rotating packed bed Chia-Chang Lin a,b, *, Cheng-Yu Chao a , Mei-Yun Liu a a Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan, Taiwan, ROC b Pollution Prevention Group, Green Technology Research Center, Chang Gung University, Taoyuan, Taiwan, ROC 1. Introduction To enhance the gas–liquid mass transfer, Ramshaw and Mallinson [1] invented a rotating packed bed (RPB), generating a centrifugal acceleration as high as several hundred g values by rotating a doughnut-shaped packing element. This novel technol- ogy was referred to as ‘‘Higee’’ (an acronym for high gravity). Under a high gravity field, the liquid within the RPB would be uniformly distributed and interact rigorously with the gas stream conse- quently. The RPB could permit large processing throughput with a smaller size in comparison with the conventional packed bed. Moreover, owing to thinner liquid film and/or tiny droplet induced by the centrifugal force, the RPB could enhance the gas–liquid mass transfer by 1–2 orders of magnitude. Therefore, the size of the RPB would be dramatically reduced and, thus, the capital and operating costs would be reduced simultaneously [2]. The RPB has been applied to a variety of applications such as distillation [3–4], absorption [5–20], stripping [21–24], deaeration [25–29], reactive precipitation [30], and ozone oxidation [31–34]. To remove the residual O 3 from some processes before discharging it to outside environment, Lin and Su [35] first adopted Fe 2+ solution as an absorbent for O 3 absorption in the RPB. Their results demonstrated that the O 3 removal efficiency of more than 95% was obtained at the appropriate operating conditions [35]. To increase applicability of the RPB in O 3 absorption, investigating the mass transfer performance of the RPB is necessary using other absorbents for O 3 absorption. According to the work proposed by Staehelin and Hoigne [36],H 2 O 2 can react with O 3 , obeying the following mechanism: O 3 þ OH  ! HO 2  þ O 2 (1) H 2 O 2 , HO 2  þ H þ (2) HO 2  þ O 3 ! O 2  þ OH  þ O 2 (3) Based on the above mechanism, H 2 O 2 can produce HO 2  at the basic condition owing to that the pK a of Eq. (2) is 11.6 [36]. HO 2  induced from H 2 O 2 can react with O 3 further, finally producing some free radicals. Therefore, the aim of this work is to examine the mass transfer performance of the RPB in the O 3 absorption process using H 2 O 2 solution as the absorbent, including the effect of operating variables such as pH of H 2 O 2 solution, O 3 concentration, H 2 O 2 concentration, RPB speed, gas flow rate, liquid flow rate, and RPB type. Results in this work would provide further insight into the feasibility of this O 3 absorption process in the RPB. 2. Experimental Fig. 1 schematically illustrates the experimental setup in this work for O 3 absorption using H 2 O 2 solution, in which the system was continuously operated under atmospheric pressure. The liquid influent containing H 2 O 2 solution was introduced from the influent Journal of Industrial and Engineering Chemistry 16 (2010) 140–146 ARTICLE INFO Article history: Received 22 November 2008 Accepted 5 August 2009 Keywords: Rotating packing bed Ozone Absorption Mass transfer High gravity ABSTRACT This work investigated the feasibility of ozone (O 3 ) absorption by H 2 O 2 solution in a rotating packed bed (RPB). The overall volumetric gas-phase mass transfer coefficients (K G a) were determined as functions of pH of H 2 O 2 solution, O 3 concentration, H 2 O 2 concentration, RPB speed, gas flow rate, liquid flow rate, and RPB type. The K G a values were highly dependent on the pH of H 2 O 2 solution. Also, the K G a values increased with O 3 concentration and H 2 O 2 concentration. As expected, the RPB speed positively affected the K G a values for all RPBs. Furthermore, the obtained results indicated that the K G a values increased as the inner radius of the bed was increased and the outer radius of the bed was decreased. Moreover, the K G a values increased with an increasing liquid flow rate and an increasing gas flow rate for all RPBs. The dependences of K G a on the gas flow rate and the liquid flow rate indicated that the resistance to mass transfer in the gas-phase for O 3 absorption was higher than that in the liquid phase in the RPB. ß 2010 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. * Corresponding author at: Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan, Taiwan, ROC. Tel.: +886 3 2118800x5760; fax: +886 3 2118800x5702. E-mail address: higee@mail.cgu.edu.tw (C.-C. Lin). Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry journal homepage: www.elsevier.com/locate/jiec 1226-086X/$ – see front matter ß 2010 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jiec.2010.01.005