Fuel processors in portable fuel cell systems require high efficiency stable operation and rapid start up time External heating stabilizes operation of the conventional steam reforming system and allows higher hydrogen concentration in the reformate stream In this study we utilized a modified fuel processor that introduced a slip stream of air into the process line right before the water gas shift reactor The air stream rapidly heated the water gas shift reactor to the desired temperature eliminating initial CO concentration surges in the downstream CO concentration quickly stabilized at the minimum concentration without surges by rapid preheating of the water gas shift reactor The modified system reached a steady state within 10 min (C) 2010 Professor T Nejat Veziroglu Published by Elsevier Ltd All rights reserved