Carbon dioxide power cycle

Claim 1

An improved direct fired power system generating and employing a combustion gas which includes carbon dioxide as a working fluid comprising: means defining a combustion chamber for burning a mixture which includes oxygen, a carbonaceous fuel and recycled carbon dioxide working fluid at a supercritical first pressure, thereby providing a combustion gas which includes carbon dioxide and water at substantially said first pressure, and a supercritical temperature, means defining a first turbine for receiving combustion gas from said combustion chamber and allowing said gas to expand therethrough to generate power and reduce the pressure of said combustion gas to a second pressure while maintaining a supercritical state, means for receiving said combustion gas from said first turbine and heating said gas at said second pressure to a higher temperature means defining a second turbine for receiving combustion gas from said means for heating and allowing said gas to expand therethrough to generate power and further reduce the pressure on said combustion gas to a third pressure while maintaining a supercritical state, means defining a heat exchanger having first and second ducts in heat exchange relationship, said first duct receiving combustion gas from said second turbine and conducting said gas therethrough, said second duct conducting recycled carbon dioxide working fluid at substantilly said first pressure and a temperature below that of said combustion gas in said first duct therethrough and having an output connected to said combustion chamber for providing at least a portion of said recycled carbon dioxide thereto, for enabling said combustion gas to transfer heat to said recycled carbon dioxide to condense at least a portion of the water in said combustion gas, but maintain the carbon dioxide thereof in a supercritical state, means for separating the condensed water from the remainder of said combustion gas first cooling means connected to the output of said first duct of said heat exchanger for receiving combustion gas therefrom and cooling said combustion gas to a supercritical first temperature, first compression means for receiving said combustion gas from said first cooling means and compressing said combustion gas to a fourth pressure below said first pressure, second cooling means for receiving said combustion gas from said first compression means and cooling said combustion gas to a second temperature at essentially the liquid/gas interface of said combuston gas and, second compression means for receiving said combustion gas from said second cooling means and compressing said gas to substantially said first pressure to thereby provide said recycled carbon dioxide working fluid, said second compression means being connected to the input of said second duct of said heat exchanger for providing said recycled carbon dioxide thereto.

Claim 15

A method for enhancing the efficiency of a power cycle which generates and employs a combustion gas including carbon dioxide as a working fluid comprising: introducing a mixture which includes oxygen, carbonaceous fuel and recycled carbon dioxide gas at a supercritical first pressure into a combustion chamber and burning said mixture to provide a combustion gas which includes carbon dioxide and water at substantially said first pressure and a supercritical temperature, allowing said combustion gas to expand through a first turbine to generate power and reduce the pressure of said combustion gas to a second pressure while maintaining a supercritical state, heating said combustion gas at substantially said second pressure to a higher temperature, allowing said reheated combustion gas to expand through a second turbine to generate power and further reduce the pressure of said combustion gas to a third pressure while maintaining a supercritical state, passing said combustion gas in heat exchange relationship with recycled carbon dioxide working fluid at said first pressure and a temperature lower than said combustion gas whereby heat is transferred from said combustion gas to said recycled carbon dioxide to condense at least a portion of the water in said combustion gas but maintain the carbon dioxide therein in a supercritical state, cooling said combustion gas to a first temperature, compressing said combustion gas to a fourth pressure below said first pressure, cooling said combustion gas to a second temperature at essentially the liquid/gas interface of said combustion gas, compressing said combustion gas to substantially said first pressure to provide said recycled carbon dioxide working fluid and separating condensed water from said combustion gas following either the heat exchange or cooling to a first temperature steps.

Claim 16

A method for enhancing the efficiency of a power cycle which generates and employs a combustion gas including carbon dioxide as a working fluid comprising: introducing a mixture which includes oxygen, carbonaceous fuel and recycled carbon dioxide gas at a supercritical first pressure into a combustion chamber and burning said mixture to provide a combustion gas which includes carbon dioxide and water at substantially said first pressure and a supercritical temperature, allowing said combustion gas to expand through a first turbine to generate power and reduce the pressure of said combustion gas to a second pressure while maintaining a supercritical state, heating said combustion gas at substantially said second pressure to a higher temperature, allowing said reheated combustion gas to expand through a second turbine to generate power and further reduce the pressure of said combustion gas to a third pressure while maintaining a supercritical state, passing said combustion gas in heat exchange relationship with recycled carbon dioxide working fluid at said first pressure and a temperature lower than said combustion gas whereby heat is transferred from said combustion gas to said recycled carbon dioxide to condense at least a portion of the water in said combustion gas but maintain the carbon dioxide therein in a supercritical state, cooling said combustion gas to a first temperature, compressing said combustion gas to a fourth pressure below said first pressure, cooling said combustion gas to a second temperature at essentially the liquid/gas interface of said combustion gas, compressing said combustion gas to substantially said first pressure to provide said recycled carbon dioxide working fluid and separating condensed water from said combustion gas following either the heat exchange or cooling to a first temperature steps.