Multi-Stream Heat Exchanger for a Fuel Cell System

• US 20110053027A1
• Filed: 09/01/2010
• Published: 03/03/2011
• Est. Priority Date: 09/02/2009
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: Kalika, Vlad, Perry, Martin, Venkataraman, Swaminathan, Weingaertner, David
• Granted Patent: US 8,445,156 B2
• Time in Patent Office: Days
• US Class Current: 429/440
• CPC Class Codes: F28D 2021/0043 for fuel cells heat exchange in fuel cell H01M8/04007
• CPC Class Codes: F28D 21/0001 Recuperative heat exchangers
• CPC Class Codes: F28D 9/005 the plates having openings therein for both heat-exchange media
• CPC Class Codes: F28D 9/0093 Multi-circuit heat-exchangers, e.g. integrating different heat exchange sections in the same unit or heat-exchangers for more than two fluids
• CPC Class Codes: F28F 2280/02 Removable elements
• CPC Class Codes: H01M 8/04014 Heat exchange using gaseous fluids; Heat exchange by combustion of reactants
• CPC Class Codes: H01M 8/04022 Heating by combustion
• CPC Class Codes: H01M 8/04067 Heat exchange or temperature measuring elements, thermal insulation, e.g. heat pipes, heat pumps, fins
• 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 8/0618 Reforming processes, e.g. autothermal, partial oxidation or steam reforming
• CPC Class Codes: H01M 8/0637 Direct internal reforming at the anode of the fuel cell
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A multi-stream heat exchanger includes at least one air preheater section, at least one cathode recuperator section, and at least one anode recuperator section, wherein each section is a plate type heat exchanger having two major surfaces and a plurality of edge surfaces, a plurality of risers through at least some of the plates, and a plurality of flow paths located between plates. The cathode recuperator section is located adjacent to a first edge surface of the anode recuperator, and the air preheater section is located adjacent to a second edge surface of the anode recuperator section.

Claims

1. A multi-stream heat exchanger comprising:

a stack of intermediate plates located between two end plates;

at least one air preheater section located adjacent to one end plate of the stack, at least one cathode recuperator section located adjacent to the other end plate, and at least one anode recuperator section located between the air preheater and the cathode recuperator sections, wherein each section is comprised of at least two plates;

a plurality of risers through the end plates and the stack of intermediate plates; and

a plurality of flow paths located between plates.

2. The heat exchanger of claim 1, wherein the stack of intermediate plates is brazed with brazed borders.

3. The heat exchanger of claim 1, wherein each plate is rectangular or trapezoidal and has four holes near one end and four holes near the other end.

4. The heat exchanger of claim 1, wherein each end plate has two holes near one end and two holes near the other end.

5. The heat exchanger of claim 1, wherein the cathode recuperator sections and the anode recuperator sections alternate within the stack.

6. The heat exchanger of claim 1, wherein there are eight risers.

7. The heat exchanger of claim 1, further comprising:

four inlets, wherein a fuel cell fuel inlet line is connected to a first inlet;

a fuel cell air inlet line is connected to a second inlet;

a fuel cell anode exhaust line is connected to a third inlet; and

a fuel cell cathode exhaust line is connected to a fourth inlet.

8. The heat exchanger of claim 7, wherein:

a fuel cell fuel inlet stream and a fuel cell anode exhaust stream flow through the anode recuperator section and exchange heat;

the fuel cell anode exhaust stream and a fuel cell air inlet stream flow through the air preheater section and exchange heat; and

the fuel cell air inlet stream and a fuel cell cathode exhaust stream flow through the cathode recuperator section and exchange heat.

9. A method of operating a multi-stream heat exchanger, comprising:

flowing a fuel cell fuel inlet stream into a first inlet and through a stack of intermediate plates and two end plates;

flowing a fuel cell air inlet stream into a second inlet and through a stack of intermediate plates and two end plates;

flowing a fuel cell anode exhaust stream through a third inlet and through a stack of intermediate plates and two end plates; and

flowing a fuel cell cathode exhaust stream through a fourth inlet and through a stack of intermediate plates and two end plates;

wherein;

the fuel cell fuel inlet stream and the fuel cell anode exhaust stream flow through an anode recuperator section and exchange heat;

the fuel cell anode exhaust stream and the fuel cell air inlet stream flow through the air preheater section and exchange heat;

the fuel cell air inlet stream and the fuel cell cathode exhaust stream flow through the cathode recuperator section and exchange heat; and

the air preheater section is located adjacent to one end plate of the stack, the cathode recuperator section is located adjacent to the other end plate, and the anode recuperator is section located between the air preheater and the cathode recuperator sections.

10. The method of claim 9, further comprising flowing each stream into a riser formed through the end plates and stack of intermediate plates.

11. The method of claim 9, further comprising flowing each stream through a flow path between two plates.

12. A multi-stream heat exchanger comprising:

at least one air preheater section, at least one cathode recuperator section, and at least one anode recuperator section, wherein each section is a plate type heat exchanger having two major surfaces and a plurality of edge surfaces;

a plurality of risers through at least some of the plates; and

a plurality of flow paths located between plates;

wherein the cathode recuperator section is located adjacent to a first edge surface of the anode recuperator, and the air preheater section is located adjacent to a second edge surface of the anode recuperator.

13. The heat exchanger of claim 12, wherein the plates in each section are brazed with brazed borders.

14. The heat exchanger of claim 12, wherein each plate is rectangular or trapezoidal.

15. The heat exchanger of claim 12, wherein the first edge surface is adjacent to the second end surface.

16. The heat exchanger of claim 12, further comprising a wall to separate at least some flow paths in the air preheater section from at least some flow paths in the anode recuperator section.

17. The heat exchanger of claim 12, further comprising four inlets, wherein a fuel cell fuel inlet line is connected to a first inlet;

a fuel cell air inlet line is connected to a second inlet;

a fuel cell anode exhaust line is connected to a third inlet; and

a fuel cell cathode exhaust line is connected to a fourth inlet.

18. The heat exchanger of claim 12, wherein:

a fuel cell fuel inlet stream and a fuel cell anode exhaust stream flow through the anode recuperator section and exchange heat;

the fuel cell anode exhaust stream and a fuel cell air inlet stream flow through the air preheater section and exchange heat; and

the fuel cell air inlet stream and a fuel cell cathode exhaust stream flow through the cathode recuperator section and exchange heat.

19. A method of operating a multi-stream heat exchanger, comprising:

flowing a fuel inlet stream into a first inlet and through an anode recuperator section;

flowing an air inlet stream into a second inlet and through an air preheater section and a cathode recuperator section;

flowing an anode exhaust stream through a third inlet and through the anode recuperator section and the air preheater section; and

flowing a cathode exhaust stream through a fourth inlet and through the cathode recuperator section;

wherein the cathode recuperator section is located adjacent to a first edge surface of the anode recuperator, and the air preheater section is located adjacent to a second edge surface of the anode recuperator.

20. The method of claim 19, further comprising flowing each stream through a riser.

21. The method of claim 19, further comprising flowing each stream through a flow path between two plates.

22. The method of claim 19, wherein:

the fuel cell fuel inlet stream and the fuel cell anode exhaust stream flow through the anode recuperator section and exchange heat;

the fuel cell anode exhaust stream and the fuel cell air inlet stream flow through the air preheater section and exchange heat; and

the fuel cell air inlet stream and the fuel cell cathode exhaust stream flow through the cathode recuperator section and exchange heat.

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

providing a fuel inlet stream and an air inlet stream into a fuel cell stack;

providing a cathode exhaust stream from the fuel cell stack into an anode tail gas oxidizer;

providing an anode exhaust stream from the fuel cell stack into an anode recuperator to heat the fuel inlet stream;

splitting the anode exhaust stream after it exits the anode recuperator into a first anode exhaust stream and a second anode exhaust stream;

providing the first anode exhaust stream into the anode tail gas oxidizer;

providing the second anode exhaust stream into an air preheater to preheat the air inlet stream followed by recycling the second anode exhaust stream into the fuel inlet stream;

providing an anode tail gas oxidizer exhaust stream into a cathode recuperator to heat the air inlet stream followed by providing the anode tail gas oxidizer exhaust stream to a steam generator to generate steam; and

providing the steam into the fuel inlet stream.