Reformate cooling system and method for use in a fuel processing subsystem

A reformate cooling system for use in a fuel processing subsystem for reducing a level of carbon monoxide in a reformate flow for a proton exchange membrane fuel cell system, the fuel processing system including first and second preferential oxidizers to oxidize the carbon monoxide carried in the reformate flow, the second preferential oxidizer located downstream from the first preferential oxidizer with respect to the reformate flow and requiring a lower catalytic reaction temperature range for the reformate flow than the first preferential oxidizer;

• the reformate cooling system comprising:
• a first heat exchanger unit to transfer heat from the reformate flow to a coolant flow, the first heat exchanger unit including first and second core portions through which the reformate flow and the coolant flow pass in heat exchange relation to each other, the first heat exchanger unit located upstream from the first preferential oxidizer with respect to the reformate flow, the first core portion connected to the second core portion to supply both the coolant flow and the reformate flow to the second core portion;
• and
• a second heat exchanger unit to transfer heat from the reformate flow to the coolant flow, the second heat exchanger unit including third and fourth core portions through which the reformate flow and the coolant flow pass in heat exchange relation, the second heat exchanger unit located upstream from the second preferential oxidizer and downstream from the first preferential oxidizer with respect to the reformate flow, the third core portion connected to the fourth core portion to supply the reformate flow to the fourth core portion, one of the third and fourth core portions connected to the first core portion to supply the coolant flow to the first core portion, the other of the third and fourth core portions connected to the second core portion to receive the coolant flow from the second core portion.

A reformate cooling system for use in a fuel processing subsystem for reducing a level of carbon monoxide in a reformate flow for a proton exchange membrane fuel cell system, the fuel processing system including first and second preferential oxidizers to oxidize the carbon monoxide carried in the reformate flow, the second preferential oxidizer located downstream from the first preferential oxidizer with respect to the reformate flow and requiring a lower catalytic reaction temperature range for the reformate flow than the first preferential oxidizer;

• the reformate cooling system comprising:
• a coolant flow path;
• a reformate flow path;
• and
• first, second, third and fourth heat exchanger core portions, each of the core portions including part of the coolant flow path and part of the reformate flow path in heat exchange relation to transfer heat from the reformate flow to a coolant flow, the core portions arranged in numbered sequence along the reformate flow path with the first and second core portions located upstream of the first preferential oxidizer and the third and fourth core portions located downstream of the first preferential oxidizer and upstream of the second preferential oxidizer, the first and second core portions arranged in numbered sequence along the coolant flow path, one of the third and fourth core portions arranged upstream of the first core portion along the coolant flow path and the other of the third and fourth core portions arranged downstream of the second core portion along the coolant flow path.

A method of cooling a reformate flow to desired temperature ranges for first and second catalytic reactions in a fuel processing subsystem for a proton exchange membrane fuel cell system wherein the reformate undergoes the first catalytic reaction before the second catalytic reaction, the method comprising the steps of:

• a) between the first and second catalytic reactions, transferring heat from the reformate flow to an initial pass of a coolant flow;
• b) before the first catalytic reaction, transferring heat from the reformate flow to the coolant flow heated in step a);
• c) before the first catalytic reaction, transferring heat from the reformate flow cooled in step b) to the coolant heated in step b);
• d) between the first and second catalytic reaction, transferring heat from the reformate flow cooled in step c) to the coolant heated in step c).