Patent ID: 7950226

Claim:
A method of operating a power generation system, comprising: operating an engine to produce an exhaust comprising NO X ; channeling the exhaust through a fuel reformer; channeling the exhaust through a first lean NO X trap that adsorbs and stores a first portion of NO X from the exhaust and is configured downstream from the fuel reformer; channeling the exhaust through a second lean NO X trap that adsorbs and stores a second portion of NO X from the exhaust, the second lean NO X trap being configured downstream from the first lean NO X trap and having a different composition from that of the first lean NO X trap; generating a first control signal to denitrate the lean NO X traps; in response to the first control signal, supplying a rich fuel-exhaust mixture to the fuel reformer whereby the fuel reformer produces a reformate-containing rich exhaust-reductant mixture that denitrates the lean NO X traps; generating a second control signal to desulfate the lean NO X traps; and in response to the second control signal, heating the lean NO X traps and then supplying a rich fuel-exhaust mixture to the fuel reformer, whereby the fuel reformer produces reformate-containing rich exhaust-reductant mixture that desulfates the lean NO X traps; wherein the desulfation is carried out in such a manner that during the desulfation the second lean NO X trap reaches a peak volume average temperature at least about 25° C. higher than the first lean NO X trap and the difference in composition causes the first lean NO X trap to reach an effective desulfation rate at a lower temperature than that at which the second lean NO X trap reaches an effective desulfation rate.