ABSTRACT
Regenerative Heat Exchange ......................................................... 153 5.4.2 Reactor Modeling ......................................................................................... 153 5.4.3 Transient Operation Issues ........................................................................... 154
5.4.3.1 During Normal Operations ........................................................... 154 5.4.3.2 During Start-Up............................................................................. 155 5.4.3.3 Deactivation of the Catalyst .......................................................... 156
5.4.4 Temperature Uniformity of Gases Contacting the Catalyst and Thermal Stresses .................................................................................... 156
5.4.5 Catalytic Unit: Choice of Catalyst and Support Structure, Deactivation, and Guard Bed....................................................................... 157
5.4.5.1 Platinum......................................................................................... 157 5.4.5.2 Palladium ....................................................................................... 157 5.4.5.3 Metal Oxides.................................................................................. 157 5.4.5.4 Perovskites ..................................................................................... 158 5.4.5.5 Support Structures ......................................................................... 158 5.4.5.6 Guard Beds .................................................................................... 158
5.4.6 Environmental and Safety Issues.................................................................. 158 5.4.6.1 Operating Pressure ......................................................................... 159 5.4.6.2 Steam Plume and Stack Exit Velocity ........................................... 159 5.4.6.3 Operating Below Lower Explosive Limit (LEL) ........................... 159 5.4.6.4 Catalyst Disposal ........................................................................... 159 5.4.6.5 Burner Safety Systems ................................................................... 159 5.4.6.6 Residual Emissions from the Catalytic Oxidizer ........................... 159
5.4.7 Pilot-Scale Trials ........................................................................................... 161 5.5 Adsorption of VOC Emissions: A Concentration Step Prior to
Catalytic Oxidation................................................................................................... 161 5.5.1 Fixed-Bed Adsorber...................................................................................... 161 5.5.2 Rotary Adsorber and Other Moving-Bed Configurations ........................... 162 5.5.3 Adsorption Combined with Incineration in a Single Fixed Bed.................. 162 5.5.4 Adsorption-Catalytic Reverse Flow Processes for
Oxidation of VOCs....................................................................................... 163 5.6 Case Studies.............................................................................................................. 164 5.7 Future Outlook......................................................................................................... 164
5.7.1 Destruction of Chlorinated Volatile Organics.............................................. 164 5.7.2 Catalytic Filters ............................................................................................ 165 5.7.3 Oxidation of Benzene over Hydrophobic Cryptomelane-Type
Octahedral Molecular Sieves ........................................................................ 166 5.7.4 Oxidation of o-Xylene Over Pt and Pd Catalysts
Supported on Zeolites................................................................................... 166 5.7.5 Use of Perovskites as VOC Oxidation Catalysts.......................................... 166 5.7.6 High-Temperature and Short Contact Time VOC
Catalytic Incinerator..................................................................................... 167 5.7.7 Integrated Catalytic/Adsorption Processes for
Destruction of VOCs .................................................................................... 168 5.7.8 Oxidation of VOCs on Gold/Cerium Oxide Catalysts ................................. 168
Acknowledgment............................................................................................................... 169 References ......................................................................................................................... 169
Environmental concerns about the impact of volatile organic carbon (VOC) emissions are a strong driver for the development of new technologies to minimize such releases to the atmosphere. There are a number of textbooks (e.g., [1-5]) that could be used to obtain an overview and introduction to this theme. VOC emissions arise from a wide variety of stationary applications and these can be controlled with the aid of structured catalysts and reactors. Technologies for the treatment of a wide range of organic emissions are readily available from a number of suppliers.
