Process for controlling carbon monoxide concentration out of a preferential oxidation reactor during turndown using staged multi-port air injection

A process of operating a preferential oxidation reactor in response to a significant change in the flow rate of a H2-rich gas flowing through the reactor, wherein the reactor is an isothermal reactor for the selective reaction of O2 with CO in said gas to form CO2, said reactor including an inlet and an exit for the H2-rich gas and a plurality of air injectors positioned along the length of the flow path of the H2-rich gas, and said plurality of injectors including at least a first injector being positioned relative closer to the inlet for the H2-rich gas, a second reactor positioned a greater distance from the inlet for the H2-rich gas than the first injector, and a third injector position a greater distance from the inlet for the H2-rich gas than from the second injector, comprising:

• during normal operating conditions of the fuel cell stack wherein the flow rate of the H2-rich gas is at a level X, injecting a relative amount of air into the reactor through at least the first injector relatively closer to inlet for the H2-rich gas;
• during a turndown condition of the fuel cell stack wherein the flow rate of the H2-rich gas is substantial less than level X, reducing the amount of air injected through the first injector relatively closer to the inlet for the H2-rich gas, and injecting a majority of the air through an injector being more distant from the inlet for the H2-rich gas than the first injector to provide unfavorable conditions for a reverse water gas shift reaction and control the CO concentration exiting the reactor during the turndown condition.

A process of operating a preferential oxidation reactor in response to a significant change in the electrical low demand of an associated fuel cell stack, wherein the reactor is an isothermal reactor for the selective reaction of O2 with CO, in a H2-rich gas flowing through the reactor, to form CO2, said reactor including an inlet and an exit for the H2-rich gas and a plurality of air injectors positioned along the length of the flow path of the H2-rich gas, and said plurality of injectors including a first injector being positioned relative closer to the inlet for the H2-rich gas, comprising:

• during normal operating conditions of the fuel cell stack wherein electrical load demand of the fuel cell stack is at a level X, injecting a relative amount of air into the reactor through at least the first injector relatively closer to inlet for the H2-rich gas;
• during a turndown condition of the fuel cell stack wherein the electrical load demand of the fuel cell stack is substantial less than level X, reducing the amount of air injected through the first injector relatively closer to the inlet for the H2-rich gas, and injecting a majority of the air through a second injector being positioned at a location more distant from the inlet for the H2-rich gas than the first injector to provide unfavorable conditions for a reverse water gas shift reaction and control the CO concentration exiting the reactor during the turndown condition.