High temperature fuel cell system with integrated heat exchanger network

• US 9,413,017 B2
• Filed: 03/04/2014
• Issued: 08/09/2016
• Est. Priority Date: 05/09/2005
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: Bandhauer, Todd M., Reinke, Michael J., Valensa, Jeroen
• Primary Examiner(s): Walls, Cynthia K
• Application Number:
  US14/196,342
• Publication Number:
  US 20140186729A1
• Time in Patent Office: 889 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: F28D 9/0075 the plates having openings therein for circulation of the heat-exchange medium from one conduit to another
• CPC Class Codes: H01M 8/04014 Heat exchange using gaseous fluids; Heat exchange by combustion of reactants
• CPC Class Codes: H01M 8/04074 Heat exchange unit structures specially adapted for fuel cell
• CPC Class Codes: H01M 8/04097 with recycling of the reactants H01M8/04119, H01M8/04104 take precedence
• CPC Class Codes: H01M 8/04708 of fuel cell reactants
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A fuel cell system includes a plurality of fuel cells arranged into a stack. A combustor receives a cathode exhaust flow from the fuel cell cathodes and a flow of fuel. The fuel is oxidized in the combustor by the cathode exhaust to produce a mixed exhaust flow. A cathode air flow path extends between a fresh air source and the fuel cell cathodes. An air preheater is arranged along the cathode air flow path, cathode air passing through the air preheater being heated therein by a flow of uncombusted anode exhaust from the fuel cell anodes. A cathode recuperator is arranged along the cathode air flow path, cathode air passing through the cathode recuperator being heated therein by the mixed exhaust flow. Water passing through a vaporizer is converted to steam by heat from the mixed exhaust flow and directed from the vaporizer to the fuel cell anodes.

Claims

1. A method of operating a fuel cell system, comprising:

providing a fuel cell stack;

heating an air inlet stream using heat from a fuel cell stack cathode exhaust stream;

heating the air inlet stream using heat from an uncombusted fuel cell stack anode exhaust stream; and

heating an anode feed stream using heat from the uncombusted fuel cell stack anode exhaust stream.

2. The method of claim 1, further comprising:

heating the air inlet stream using heat from the uncombusted fuel cell stack anode exhaust stream upstream of heating the air inlet stream using heat from the fuel cell stack cathode exhaust stream with respect to the air inlet stream; and

heating the anode feed stream using heat from the uncombusted fuel cell stack anode exhaust stream upstream of heating the air inlet stream using heat from the uncombusted fuel cell stack anode exhaust stream with respect to the uncombusted fuel cell stack anode exhaust stream.

3. The method of claim 2, further comprising:

heating the air inlet stream using heat from the fuel cell stack cathode exhaust stream such that the cathode exhaust stream exits at a temperature of at least 200°

C.;

providing the fuel cell stack inside a hot box;

heating the air inlet stream using heat from the fuel cell stack cathode exhaust stream inside the hot box;

heating the anode feed stream using heat from the uncombusted fuel cell stack anode exhaust stream inside the hot box; and

heating the air inlet stream using heat from an uncombusted fuel cell stack anode exhaust stream outside the hot box.

4. A fuel cell system, comprising:

a fuel cell stack;

an anode recuperator heat exchanger which is adapted to heat an anode feed stream using heat from an uncombusted fuel cell stack anode exhaust stream;

a cathode recuperator heat exchanger which is adapted to heat an air inlet stream using heat from a fuel cell stack cathode exhaust stream; and

an air preheater heat exchanger which is adapted to heat the air inlet stream using heat from the uncombusted fuel cell stack anode exhaust stream;

wherein the cathode recuperator heat exchanger is adapted to provide the cathode exhaust stream exiting the cathode recuperator heat exchanger at a temperature of at least 200°

C.;

wherein the fuel cell stack, the anode recuperator heat exchanger and the cathode recuperator heat exchanger are located inside a hot box; and

wherein an air blower which provides the air inlet stream is located outside the hot box.

5. A fuel cell system, comprising:

a plurality of fuel cells arranged into a stack, each fuel cell having an anode and a cathode;

a combustor receiving a cathode exhaust flow from the fuel cell cathodes and a flow of fuel, the fuel being oxidized in the combustor by the cathode exhaust to produce a mixed exhaust flow comprising cathode exhaust and combusted fuel;

a cathode air flow path extending between a fresh air source and the fuel cell cathodes;

an air preheater arranged along the cathode air flow path, cathode air passing through the air preheater being heated therein by a flow of uncombusted anode exhaust from the fuel cell anodes;

a cathode recuperator arranged along the cathode air flow path, cathode air passing through the cathode recuperator being heated therein by the mixed exhaust flow; and

a vaporizer, water passing through the vaporizer being converted to steam by heat from the mixed exhaust flow, the steam being directed from the vaporizer to the fuel cell anodes; and

a condenser to remove water from the uncombusted anode exhaust after the uncombusted anode exhaust has passed through the air preheater.