Design of a catalyst system with periodic flow reversal for lean burn natural gas engines

by 1980- Ramamurthy, Balaji

The objective of this research is to accomplish methane conversion from lean burn natural gas engines. As methane conversion requires high temperatures, the concept of PFR (Periodic Flow Reversal) is used. The PFR is a heat trap that performs active heat recovery in addition to the heat retention capability of monolith solids. Cyclically alternating the direction of exhaust flow produces a thermal wave along the center of the catalyst thereby elevating the temperature above the engine exhaust temperature. The PFR loop is developed connecting catalyst canisters with a Four-Way Single Diversion Valve (FWSDV) using a set of pipes and pipe connectors. Two oxidation catalysts are used to develop exothermic reactions, which would increase the temperature further. The FWSDV is the main control device, which performs the switching of exhaust gases through the monolith reactor. It is designed and fabricated in the University of Tennessee. Gas dynamics and thermodynamics calculations determine the optimal dimensions and allowable leakage of the exhaust gases through the FWSDV. Special techniques have been implemented in the design to provide minimal leakage and several schemes are employed to minimize the valve size and to make the system compact and low cost. Actuator for FWSDV has been sized, which rotates the rotor assembly of the valve, thereby switching the direction of the exhaust gas flow. The Switching time, Gas Hourly Space Velocity (GHSV) and exhaust temperature are major factors in achieving methane conversion. Recommendations for supplemental fuel injections are given for further research as this would result in significant reduction of methane. v