The Cocurrent Downflow Contactor Reactor: A Promising Technology for Pollution Abatement

1. The Cocurrent Downflow Contactor Reactor: A Promising Technology for Pollution Abatement Muhammad Sarfraz Akram*, AsimRehman, ArshadChughtai Institute of Chemical Engineering and Technology, University of the Punjab, Lahore, Pakistan. Bubble Dispersion in CDCR Introduction The Cocurrent Downflow Contactor Reactor (CDCR) is a bubble column where gas (dispersed phase) and liquid (continuous phase) are introduced simultaneously at the top of a fully flooded column. The CDCR provides a high degree of mass transfer with chemical reaction making the process controlled by the reaction rate. This situation is common in the gas-liquid reactions in the presence of solid catalyst e.g. hydrogenations, oxidations, effluent treatment and many other applications. Recent studies are reported on application of the CDCR in effluent treatment e.g. removal of phenols, toluene, halogenated phenols, glycols, polychlorinated benzenes etc. These are obnoxious pollutants which should be treated before being discharged into the environment. In this work we studied catalytic hydrodechlorination of a halogenated pheonol (2,4 dichlorophenol ) in the CDCR. The CDCR Design and Operation The CDCR is designed and manufactured in this work is shown in Figure 1. It consists of a glass reactor, liquid feed tank and gas supply. The reactor is a vertical column with an orifice at the top from where both the liquid and gas phases enter in the reactor along with powdered catalyst. Vigorously agitated gas‐liquid dispersion with high interfacial area in a small operating volume is produced. It also prevents the formation of a permanent gas space at the top of the column and maintains a fully flooded situation. Results and Discussions Initial experiments are performed using a feed of 500 ppm 2,4 Dichlorophenol in order to investigate hydrodechlorination reaction: The effect of catalyst loading and pressure on conversion of 2,4DCP into less toxic compounds are studied. The initial results show that about 70% of initially loaded 2,4DCP is consumed in about 3 hr. Future Prospective Figure 1: The Cocurrent Downflow Contactor Reactor System Developed in This Work • The ongoing study is focusing on following aspects: • Catalyst preparation and characterization • Effect of catalyst loading • Effect of temperature • Effect of pressure Features • The simple design and operation of the CDCR offer following advantages over other conventional reactor systems, such as: • Low Power Consumption • Small Containment Volume • Higher gas hold-ups (50 - 60%) • Gas utilization (100% ) • Approach to equilibrium (95 %) • High of Interfacial Area (1000 - 6000 m2/m3) • Reliability • Safety • Tolerances to Particulates • Catalyst Structure • Low Cost Bibliography A.P Boyes, A. Chughtai, X,X. Lu, S.Raymahasay, S.Sarmento, M.W Tilston, J.M Winterbottom., The cocurrent downflow contactor (CDC) reactor- Chemically enhanced mass transfer & reaction studies for slurry & fixed bed catalytic hydrogenation, Chemical Engineering Science, 47, 13/14, 1992, 3729-3736. Adrian P.Boyes, Sugat Raymahasay, Mike W. Tilston, Xia X. Lu, Sandra Sarmento, Arshad Chughtai and John M. Winterbottom, The cocurrent downflow contactor- A novel reactor for gas-liquid solid catalysed reactions, Chem. Eng. Technol. 17 (1994) 307-312. A.P Boyes, J.M Winterbottom, operating and hydrodynamic characteristics of a cocurrent downflow bubble column reactor, Chemical Engineering Science, 49, 24B, 1994, 5719-5733. Muhammad Sarfraz Akram, MSc. Thesis, Catalytic Hydrodechlorination of 2,4 Dichlorophenol using Cocurrent Downflow Contactor Reactor, 2006-2007.