System and method for generating electricity and heat from the combustion of tail gas containing biogenic methane using a gas turbine
View Patent ↗A system and method for generating electricity and heat from the combustion of tail gas containing biogenic methane using a gas turbine are provided. A gas turbine can generate electricity and heat from process tail gases (comprising biomethane, but also comprising fixed gases such as carbon dioxide, nitrogen, oxygen, hydrogen, carbon monoxide, as well as trace gases) as a secondary fuel while using natural gas as the primary fuel in the gas turbine. The tail gases from biogenic methane purification processes can have heating values as low as 42 BTU/SCF. The gas turbine will reduce net energy consumption, reduce greenhouse gas emissions, and reduce operating costs for biogenic methane purification processes. The gas turbine can also destroy tail gases that would otherwise cause excessive air emissions without the use of pollution control equipment (such as a thermal oxidizer or flare).
1. A system comprising:
a gas turbine; and
a generator operably connected to the gas turbine and configured to utilize mechanical energy produced by the gas turbine to generate electricity,
wherein the gas turbine comprises:
a primary combustion chamber configured to combust a methane-rich natural gas with a combustion air stream,
a primary cooling jacket configured to preheat the combustion air stream and to cool the primary combustion chamber with the combustion air stream prior to the combustion air stream entering the primary combustion chamber,
a secondary combustion chamber configured to combust a tail gas supplied from a biogenic methane purification process, wherein the tail gas comprises biogenic methane, with a hot exhaust air stream from the primary combustion chamber, and
a secondary cooling jacket configured to preheat the tail gas and cool the secondary combustion chamber with the tail gas prior to the tail gas entering the secondary combustion chamber.
2. The system of claim 1 , wherein the methane-rich natural gas is supplied from the biogenic methane purification process.
3. The system of claim 1 , further comprising a tail gas compressor upstream of the gas turbine and configured to increase a pressure of the tail gas to an operating pressure of the secondary combustion chamber prior to introducing the tail gas into the secondary cooling jacket.
4. The system of claim 1 , further comprising a turboexpander upstream of the gas turbine and configured to volumetrically expand the methane-rich natural gas and generate electricity prior to introducing the methane-rich natural gas into the primary combustion chamber.
5. The system of claim 1 , wherein the tail gas further comprises at least one of carbon dioxide, nitrogen, oxygen, water vapor, hydrogen, carbon monoxide, and non-methane organic compounds.
6. The system of claim 1 , wherein the tail gas has a heating value of at least 42 BTU/SCF.
7. The system of claim 1 , wherein the gas turbine further comprises an air compressor configured to increase a pressure of the combustion air stream prior to introducing the combustion air stream into the primary cooling jacket.
8. The system of claim 7 , wherein the gas turbine further comprises a clutch that connects the tail gas compressor to the air compressor.
9. The system of claim 7 , wherein the clutch is configured to disengage the tail gas compressor from the air compressor during startup of the primary combustion chamber.
10. The system of claim 8 , wherein the clutch is configured to engage the tail gas compressor when combustion of natural gas in the primary combustion chamber and flow of compressed air to the primary combustion chamber are both stabilized.
11. The system of claim 1 , further comprising an electrical switchgear configured to receive the electricity generated from the generator and supply the electricity to a local power grid.
12. The system of claim 1 , further comprising an electrical switchgear configured to receive the electricity generated from the generator and supply the electricity back to the biogenic methane purification process.
13. A method comprising:
introducing a methane-rich natural gas into a gas turbine;
combusting the methane-rich natural gas in the gas turbine to produce mechanical energy, wherein the methane-rich natural gas is combusted with a combustion air stream in a primary combustion chamber of the gas turbine;
introducing a tail gas from a biogenic methane purification process into the gas turbine, wherein the tail gas comprises biogenic methane;
combusting the tail gas in the gas turbine to produce mechanical energy, wherein the tail gas is combusted with a hot exhaust air stream from the primary combustion chamber in a secondary combustion chamber of the gas turbine;
introducing the combustion air stream into a primary cooling jacket and cooling the primary combustion chamber with the primary cooling jacket prior to introducing the combustion air stream to the primary combustion chamber;
introducing the tail gas into a secondary cooling jacket and cooling the secondary combustion chamber with the secondary cooling jacket prior to introducing the tail gas to the secondary combustion chamber; and
using the mechanical energy from the gas turbine to generate electricity.
14. The method of claim 13 , wherein the methane-rich natural gas is from the biogenic methane purification process.
15. The method of claim 13 , further comprising depressurizing the methane-rich natural gas to volumetrically expand the methane-rich natural gas prior to introducing the methane-rich natural gas into the primary combustion chamber.
16. The method of claim 13 , further comprising pressurizing the tail gas to an operating pressure of the secondary combustion chamber prior to introducing the tail gas to the secondary combustion chamber.
17. The method of claim 13 , wherein the tail gas further comprises at least one of carbon dioxide, nitrogen, oxygen, water vapor, hydrogen, carbon monoxide, and non-methane organic compounds.
18. The method of claim 13 , further comprising the supplying of the electricity generated from the gas turbine to a local power grid.
19. The method of claim 13 , further comprising the supplying of the electricity generated from the gas turbine back to the biogenic methane purification process.