Fuel cell system including anode exhaust diversion and method of operating the same

Patent metadata

Field	Value
Publication number	US-11973247-B2
Application number	US-202218053605-A
Country	US
Kind code	B2
Filing date	Nov 8, 2022
Priority date	Nov 12, 2021
Publication date	Apr 30, 2024
Grant date	Apr 30, 2024

Abstract

A method of operating a fuel cell system includes providing fuel and air to a stack of fuel cells located in a hotbox, operating the stack to generate an anode exhaust and a cathode exhaust, in a startup mode, providing a first amount of the anode exhaust and the cathode exhaust to an anode tail gas oxidizer (ATO) located in the hotbox to oxidize the anode exhaust and to generate heat which is provided to the stack, and in a steady-state mode, stopping providing the anode exhaust to the ATO or providing to the ATO a second amount of the anode exhaust which is smaller than the first amount, and providing the anode exhaust and the cathode exhaust outside the hotbox.

First claim

The invention claimed is:

1. A fuel cell system, comprising:
a stack of fuel cells configured to output an anode exhaust and a cathode exhaust;
an anode tail gas oxidizer (ATO) configured to oxidize the anode exhaust from the stack of fuel cells;
a cathode exhaust conduit configured to output the cathode exhaust and the anode exhaust from the fuel cell system;
a bypass conduit configured to divert the anode exhaust from the stack of fuel cells to the cathode exhaust conduit;
a bypass valve configured to control a flow of the anode exhaust through the bypass conduit;
an ATO conduit configured to provide the anode exhaust from the stack of fuel cells to the ATO;
an anode recuperator configured to heat fuel provided to the stack of fuel cells using the anode exhaust from the stack of fuel cells;
an anode exhaust conduit configured to provide the anode exhaust output from the stack of fuel cells to the anode recuperator;
and an anode exhaust cooler configured to heat air provided to the stack of fuel cells using the anode exhaust from the anode recuperator,
wherein the bypass conduit is configured to divert the anode exhaust from the stack of fuel cells that passed through the anode recuperator or that passed through both the anode recuperator and the anode exhaust cooler.

2. The fuel cell system of claim 1 , further comprising:
a hotbox housing the stack, the ATO, the anode recuperator, and the anode exhaust cooler; and
an exhaust oxidizer configured to oxidize the anode exhaust received from the cathode exhaust conduit, wherein the exhaust oxidizer is disposed outside of the hotbox.

3. The fuel cell system of claim 1 , further comprising:
an ATO injector comprising an annular space having an inner radial sidewall and an outer sidewall which extends into the ATO, and which contains one or more openings which fluidly connect an interior space of the ATO injector to an interior space of the ATO;
at least one column conduit which fluidly connects the ATO conduit to the interior space of the ATO injector, and which extends through a central column of the fuel cell system to the ATO injector;
a mixer configured to mix the anode exhaust with fresh fuel;
a first recycling conduit fluidly connecting an outlet of the anode recuperator to an inlet of the anode exhaust cooler;
a second recycling conduit fluidly connecting to an outlet of the anode exhaust cooler to the mixer; and
an anode recycle blower operatively connected to the second recycling conduit.

4. The fuel cell system of claim 3 , wherein:
the bypass conduit is fluidly connected to the second recycling conduit upstream of the anode recycle blower with respect to a flow direction of the anode exhaust through the second recycling conduit; and
the ATO conduit is fluidly connected to the bypass conduit.

5. The fuel cell system of claim 4 , wherein the bypass conduit is fluidly connected to the second recycling conduit downstream of the anode recycle blower with respect to a flow direction of the anode exhaust through the second recycling conduit, and further comprising a splitter configured to divert a portion of anode exhaust flowing through the first recycling conduit, wherein the ATO conduit fluidly connects the splitter to the ATO injector.

6. The fuel cell system of claim 3 , wherein:
the bypass conduit is fluidly connected to the first recycling conduit; and
the ATO conduit fluidly connects the bypass conduit to the ATO injector.

7. The fuel cell system of claim 1 , further comprising:
a system air blower configured to provide air to the stack via the anode exhaust cooler;
an ATO valve located outside the hotbox and configured to control a flow of the anode exhaust through the ATO conduit; and
a system controller configured to control the bypass valve, the ATO valve, and the system air blower;
wherein the system controller is configured to:
open the ATO valve and close the bypass valve during a startup mode of the fuel cell system; and
close the ATO valve and open the bypass valve during a steady-state mode of the fuel cell system after the stack of fuel cells reaches a steady-state operating temperature; and

wherein the system controller is configured to gradually reduce an operating speed of the system air blower during the steady-state mode to maintain the stack of fuel cells at the steady-state operating temperature.

8. The fuel cell system of claim 2 , further comprising a system exhaust conduit that fluidly connects an outlet of the exhaust oxidizer to a combined heat and power (CHP) system, and wherein the CHP system comprises:
a heat exchanger configured to generate hot water or steam using heat extracted from exhaust provided by the system exhaust conduit;
a boiler;
a turbine; and
a generator.

9. The fuel cell system of claim 1 , wherein the stack comprises a solid oxide fuel cell stack.

10. The fuel cell system of claim 1 , wherein:
in a startup mode, the fuel cell system is configured to provide a first amount of the anode exhaust and the cathode exhaust to the ATO located in a hotbox to oxidize the anode exhaust and to generate heat which is provided to the stack; and
in a steady-state mode, the fuel cell system is configured to stop providing the anode exhaust to the ATO or to provide to the ATO a second amount of the anode exhaust which is smaller than the first amount, and to provide the anode exhaust and the cathode exhaust outside the hotbox.

11. The fuel cell system of claim 1 , wherein:
in a low current draw steady-state mode in which insufficient current is drawn from the stack to sustain a predetermined steady-state stack operating temperature, the fuel cell system is configured to provide a first amount of the anode exhaust and the cathode exhaust to the ATO located in a hotbox to oxidize the anode exhaust and to generate heat which is provided to the stack; and
in a regular steady-state mode in which sufficient current is drawn from the stack to sustain the predetermined steady-state stack operating temperature, the fuel cell system is configured to stop providing the anode exhaust to the ATO or to provide to the ATO a second amount of the anode exhaust which is smaller than the first amount, and to provide the anode exhaust and the cathode exhaust outside the hotbox.

Assignees

• Bloom Energy Corp

Inventors

• Weingaertner David
• Petrucha Michael

Classifications

• H01M8/04014 Primary

  Heat exchange using gaseous fluids; Heat exchange by combustion of reactants · CPC title

• H01M8/04225

  during start-up · CPC title

• H01M8/04268

  Heating of fuel cells during the start-up of the fuel cells · CPC title

• H01M8/04302

  applied during start-up · CPC title

• H01M8/1231

  with both reactants being gaseous or vaporised · CPC title