Integrated heat recovery systems and methods for increasing the efficiency of an oxygen-fired furnace

A method for increasing the energy efficiency of an oxygen-enriched combustion furnace, said method comprising the steps of:

• a) providing oxidant gas and fuel gas, the oxidant gas having an oxygen content higher than air;
• b) allowing at least one of the oxidant and fuel gases to flow through at least one heat exchanger system thereby heating at least one of the oxidant and fuel gases;
• c) combusting the heated oxidant and fuel gases in the furnace thereby providing flue gas;
• d) allowing the flue gas to flow through the at least one heat exchanger system thereby cooling the flue gas as the oxidant and fuel gases are heated;
• e) allowing feedwater and the flue gas to flow through a waste heat boiler such that heat from the flue gas is transferred to the feedwater thereby producing superheated steam;
• and
• f) allowing the superheated steam to be expanded through a turbine thereby producing mechanical power.

A system for increasing the energy efficiency of an oxygen-enriched combustion furnace in which oxidant gas and fuel gas are combusted thereby producing a hot flue gas, said system comprising:

• a) an air separation unit adapted to provide a flow of oxidant gas, said oxidant gas having a higher oxygen content than air, said air separation unit having a power requirement x needed for providing the flow of oxidant gas;
• b) at least one heat exchanger system adapted to receive a flow of hot flue gas and at least one of said flow of oxidant gas and the flow of fuel gas, thereby heating at least one of said flow of oxidant gas and the flow fuel gas and cooling the hot flow of flue gas;
• c) a waste heat boiler adapted to absorb heat energy from the cooled flow of flue gas and produce superheated steam and further cooling the cooled flow of flue gas;
• d) a turbine adapted to allow expansion of the superheated steam therethrough thereby producing mechanical power therefrom;
• and
• e) a shaft adapted to transfer the mechanical power from said turbine to said air separation unit, wherein said air separation unit, said at least one heat exchanger, said waste heat boiler, said turbine, and said shaft are adapted such that the mechanical power provides at least about 39% of said power requirement x.

A method for recovering energy from a combustion furnace that combusts oxygen-rich gas and fuel to gas to produce a hot flue gas, said method comprising the steps of:

• a) separating a source of air with an air separation unit into oxygen-enriched gas and oxygen-deficient gas, the oxygen-rich gas having an oxygen content higher than the air;
• the oxygen-deficient gas having an oxygen content lower than the air;
• b) providing a fuel gas;
• c) providing first and second heat exchangers;
• d) allowing one of the fuel gas and flue gas to flow through the first heat exchanger thereby providing heated fuel gas and cooled flue gas;
• e) allowing the other of the oxygen-rich gas and cooled flue gas to flow through the second heat exchanger thereby heating the oxygen-rich gas and further cooling the cooled flue gas, the further cooled flue gas having a temperature lower than the cooled flue gas;
• f) combusting the heated oxygen-rich gas and the heated fuel gas in the combustion furnace thereby providing the hot flue gas;
• g) allowing the further cooled flue gas to flow through a waste heat boiler such that heat is absorbed from the further cooled flue gas to produce superheated steam;
• h) allowing the superheated steam to be expanded through a turbine thereby producing mechanical power;
• and
• j) transferring the mechanical power to the air separation unit thereby decreasing more than 50% of a power requirement of the air separation unit that is needed to separate the air.