Wrong-way behavior of packed-bed reactors: influence of an undesired consecutive reaction

Abstract

A sudden decrease in feed temperature or a sudden increase in the feed velocity may lead to a wrong-way behavior in a packed-bed reactor in which two consecutive, exothermic reactions occur. When the reactor has a unique steady state, the wrong-way behavior is associated with a down-stream-moving temperature front that causes a transient temperature rise and a loss of yield of the desired product. Increasing the rate of the undesired reaction increases the transient temperature rise and the velocity of the temperature front. When the reactor has multiple steady states, the wrong-way behavior may lead to ignition via slowly upstream-moving temperature waves. This ignition leads to a permanent yield loss of the desired product and may require reactor shutdown followed by a new startup. The impact of the wrong-way behavior in the two-reaction system is more pronounced and more likely to be encountered in practice than in the single-reaction case.