A method and a system for carbon neutral power generation
AssigneeNuovo Pignone Tecnologie Srl
InventorsManeesh PANDEY, Manjush GANIGER
Life of this patent
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Abstract
A method and a system for carbon neutral power generation integrating generating power by means of a gas turbine using hydrogen as fuel. Hydrogen is produced by a modular natural gas steam reforming unit. Carbon capture and heat recovery from the turbine exhaust gases to heat the natural gas and the steam fed to the steam reforming step are also provided.
Claims19
A method for carbon neutral power generation, the method comprising the following steps:
- producing hydrogen by steam reforming of natural gas from a natural gas pipeline to obtain hydrogen and tail gases;
- combusting hydrogen from the hydrogen production step together with air in a gas turbine coupled with an electric generator, to produce electric energy and a hot hydrogen combustion exhaust gas;
- capturing a CO2 fraction from the tail gases from said hydrogen production step, to obtain CO2 free tail gases;
- exchanging heat of the hot exhaust gas from the hydrogen combustion step with the natural gas to be used in said hydrogen production step by steam reforming, to obtain hot natural gas and a residual hot exhaust gas;
- and,
- exchanging heat of the residual hot exhaust gas from the preceding step with water and/or steam to be used in said hydrogen production step by steam reforming, to obtain hot compressed steam and a residual exhaust gas.
A system for carbon neutral power generation comprising:
- a natural gas feed line, connected to a natural gas pipeline;
- a steam feed line;
- a hydrogen production unit by steam reforming of natural gas to obtain hydrogen and tail gases stream, the hydrogen production unit being connected upstream to the natural gas feed line and the steam feed line, the hydrogen production unit being connected downstream to a hydrogen stream line and a tail gases stream line;
- a gas turbine connected upstream to the hydrogen stream line, the gas turbine being configured to combust hydrogen together with air from an air feed line to obtain an exhaust gas, the gas turbine being coupled with an electric generator to produce electric energy;
- a first heat exchanger, with a first inlet connected to an exhaust gas outlet of said gas turbine through a gas turbine exhaust line and a second inlet connected to said natural gas feed line, the first heat exchanger being configured to heat the feed of natural gas upstream the hydrogen production unit by steam reforming of natural gas by exchanging heat with the exhaust gas from the gas turbine;
- a second heat exchanger, with a first inlet connected to an exhaust gas outlet of said first heat exchanger through a first heat exchanger exhaust line and a second inlet connected to a steam feed line, the second heat exchanger being configured to heat a stream of water or steam flowing inside said steam feed line upstream the hydrogen production unit by exchanging heat with the exhaust gas from the gas turbine downstream the first heat exchanger to obtain a stream of hot compressed steam;
- a first carbon capture unit connected upstream to the tail gases stream line.
The system of an 2, wherein, upstream the first heat exchanger, a gas turbine is arranged along a natural gas feed line, the gas turbine being configured to generate power by reducing the pressure of the natural gas down to 8-10 bar.
The system of an, comprising a thermodynamic system connected upstream to a flue gas outlet of the second heat exchanger and configured to exchange residual heat of the flue gas with a working fluid in a thermodynamic cycle, such as an organic Rankine cycle, a steam Rankine cycle or a CO2 cycle.
The system of 9, wherein the hydrogen production unit comprises the following sub-units:
- a steam reformer, configured to react hot natural gas from the natural gas feed line together with hot compressed steam from the steam feed line on a catalyst, by providing heat, to obtain a first gas mixture of hydrogen and carbon monoxide together with residual natural gas and steam;
- a water gas shift reactor, connected upstream to the steam reformer and configured to react carbon monoxide and steam of the first gas mixture from the steam reformer to obtain heat and a second gas mixture with a higher concentration of hydrogen together with carbon dioxide and residual natural gas, steam and carbon monoxide;
- a hydrogen pressure swing adsorbing unit, connected upstream to the water gas shift reactor and configured to separate hydrogen from the remaining components of the second gas mixture from the water gas shift reactor, by adsorbing the remaining components of the second gas mixture on an adsorbent material, and periodically desorbing the adsorbed components by dropping the pressure to produce tail gases;
- and comprising a heat exchanger configured to exchange heat of the second gas mixture from the water gas shifting reactor with water to obtain steam to be used in the first carbon capture unit and/or in the second carbon capture unit.
Dependencies are inferred from the claim text.