Method and apparatus for capturing carbon dioxide during combustion of carbon containing fuel
A boiler system having a series of boilers. Each boiler includes a shell having an upstream end, a downstream end, and a hollow interior. The boilers also have an oxidizer inlet entering the hollow interior adjacent the upstream end of the shell and a fuel nozzle positioned adjacent the upstream end of the shell for introducing fuel into the hollow interior of the shell. Each boiler includes a flue duct connected to the shell adjacent the downstream end for transporting flue gas from the hollow interior. Oxygen is delivered to the oxidizer inlet of the first boiler in the series. Flue gas from the immediately preceding boiler in the series is delivered through the oxidizer inlet of each boiler subsequent to the first boiler in the series.
1. A method of reducing carbon-based byproducts when burning carbon-containing fuel, said method comprising:
introducing an oxidizer to an upstream boiler;
introducing carbon-containing fuel to the upstream boiler;
burning the oxidizer and carbon-containing fuel in the upstream boiler;
transporting flue gas emitted from the upstream boiler to a downstream boiler;
introducing the flue gas to the downstream boiler for use as an oxidizer;
introducing carbon-containing fuel to the downstream boiler; and
burning the flue gas and carbon-containing fuel in the downstream boiler;
wherein each of the steps of introducing oxidizer comprises providing a circumferentially and axially even distribution of oxidizer in the respective boiler; and
wherein each of the steps of introducing oxidizer comprises ensuring the oxidizer has a ratio of circular momentum to axial momentum of less than 0.2.
2. The method of claim 1 , wherein:
the upstream boiler is a first boiler;
the downstream boiler is a second boiler; and
the method further comprises:
transporting flue gas emitted from the second boiler to a third boiler;
introducing the flue gas from the second boiler to the third boiler for use as an oxidizer;
introducing carbon-containing fuel to the third boiler; and
burning the flue gas and carbon-containing fuel in the third boiler.
3. The method of claim 2 , further comprising:
transporting flue gas emitted from the third boiler to a fourth boiler;
introducing the flue gas from the third boiler to the fourth boiler for use as an oxidizer;
introducing carbon-containing fuel to the fourth boiler; and
burning the flue gas and carbon-containing fuel in the fourth boiler.
4. The method of claim 1 , further comprising:
providing a heat exchanger in each of said boilers; and
passing a fluid through the heat exchanger when burning the oxidizer and carbon-containing fuel thereby to heat said fluid.
5. The method of claim 4 , further comprising:
providing the heat exchanger with a superheater unit; and
providing the heat exchanger with a reheater unit.
6. The method of claim 5 , further comprising:
delivering fluid from the superheater unit to one or more turbines;
expanding fluid delivered from the superheater with the one or more turbines; and
delivering fluid from the one or more turbines to the reheater unit.
7. The method of claim 5 , further comprising:
delivering fluid from the reheater unit to one or more turbines;
expanding fluid delivered from the reheater unit with the one or more turbines; and
delivering fluid from the one or more turbines to the heat exchanger.
8. The method of claim 1 , further comprising:
separating oxygen from air; and
delivering the oxygen separated from air to the upstream boiler for use as the oxidizer.
9. The method of claim 1 , further comprising filtering flue gas emitted by the downstream boiler to separate fly ash from the flue gas.
10. The method of claim 1 , further comprising cooling flue gas emitted by the final downstream boiler.
11. The method of claim 1 , further comprising scrubbing flue gas emitted by the downstream boiler to remove sulphur oxides from the flue gas.
12. The method of claim 1 , wherein each of the steps of burning the oxidizer and carbon-containing fuel comprises pressurizing the respective boiler.