A heat recovery unit for generating a heated fluid by a hot exhaust gas includes a housing having an inlet for introducing hot exhaust gas and an outlet for discharging treated exhaust gas, and arranged in the housing at least one heat exchanger for heat exchange between the hot exhaust gas and a fluid, and an auxiliary combustor for combusting fuel with hot exhaust gas. The auxiliary combustor is provided with a fuel supply, which auxiliary combustor is arranged downstream of the at least one heat exchanger in the housing. An exhaust gas bypass for a part of the hot exhaust gas is provided, having an inlet for exhaust gas, and being positioned upstream of the at least one heat exchanger, and having an outlet in direct fluid communication with the auxiliary combustor.

A method for modifying a solar thermal power plant operating on conventional oil based technology into a hybrid solar thermal power plant includes: providing an oil-based solar thermal power plant, which includes a solar collection system with at least one radiation absorber tube containing a heat transfer oil to be heated by the solar collection system; providing a molten salts solar thermal power plant, which includes a solar collection system to heat a molten salts mixture; and coupling the respective plants such that the hybrid solar thermal power plant is configured to heat medium temperature steam generated by the oil based solar power plant by the molten salts mixture thereby producing high temperature steam and subsequently supplying it to a steam turbine to generate electricity.

A method for modifying a solar thermal power plant operating on conventional oil based technology into a hybrid solar thermal power plant includes: providing an oil-based solar thermal power plant, which includes a solar collection system with at least one radiation absorber tube containing a heat transfer oil to be heated by the solar collection system; providing a molten salts solar thermal power plant, which includes a solar collection system to heat a molten salts mixture; and coupling the respective plants such that the hybrid solar thermal power plant is configured to heat medium temperature steam generated by the oil based solar power plant by the molten salts mixture thereby producing high temperature steam and subsequently supplying it to a steam turbine to generate electricity.

A system for reheating a power generation system including a boiler having a waterwall and a steam drum with an input fluidly coupled to the waterwall and an auxiliary heat source to provide heated fluid. The system also includes a first flow control valve connected to the auxiliary heat source and the boiler to control a flow of heated fluid from the auxiliary heat source to the waterwall; a first isolation valve disposed at a waterwall, to isolate circulation of heated fluid from the steam drum to the waterwall; and a sensor to monitor at least one operating characteristic in the boiler. The system also includes a controller to control at least one of the flow control valve, the isolation valve, and the auxiliary heat source to control the amount of heated fluid supplied to the waterwall when the boiler is not generating steam.

A system for reheating a power generation system including a boiler having a waterwall and a steam drum with an input fluidly coupled to the waterwall and an auxiliary heat source to provide heated fluid. The system also includes a first flow control valve connected to the auxiliary heat source and the boiler to control a flow of heated fluid from the auxiliary heat source to the waterwall; a first isolation valve disposed at a waterwall, to isolate circulation of heated fluid from the steam drum to the waterwall; and a sensor to monitor at least one operating characteristic in the boiler. The system also includes a controller to control at least one of the flow control valve, the isolation valve, and the auxiliary heat source to control the amount of heated fluid supplied to the waterwall when the boiler is not generating steam.

A system for providing supercritical steam including a first boiler that generates steam via combusting a first fuel, and a second boiler fluidly connected to the first boiler via a conduit which heats the generated steam to supercritical steam temperatures via combusting a second fuel. A first temperature of the conduit may be below a critical corrosion temperature and a second temperature of the conduit is greater than or equal to the critical corrosion temperature. A combined carbon emission rate of the first boiler and the second boiler may be less than a combined carbon emission rate of generating and heating the steam to supercritical steam temperatures using boilers that only combust the first fuel. The first boiler may be fluidly connected to a heat exchanger that heats the generated steam to a supercritical steam temperature via a flue gas produced by a gas turbine.

A system for providing supercritical steam including a first boiler that generates steam via combusting a first fuel, and a second boiler fluidly connected to the first boiler via a conduit which heats the generated steam to supercritical steam temperatures via combusting a second fuel. A first temperature of the conduit may be below a critical corrosion temperature and a second temperature of the conduit is greater than or equal to the critical corrosion temperature. A combined carbon emission rate of the first boiler and the second boiler may be less than a combined carbon emission rate of generating and heating the steam to supercritical steam temperatures using boilers that only combust the first fuel. The first boiler may be fluidly connected to a heat exchanger that heats the generated steam to a supercritical steam temperature via a flue gas produced by a gas turbine.

A system for reheating a power generation system including a boiler having a waterwall and a steam drum with an input fluidly coupled to the waterwall and an auxiliary heat source to provide heated fluid. The system also includes a first flow control valve connected to the auxiliary heat source and the boiler to control a flow of heated fluid from the auxiliary heat source to the waterwall; a first isolation valve disposed at a waterwall, to isolate circulation of heated fluid from the steam drum to the waterwall; and a sensor to monitor at least one operating characteristic in the boiler. The system also includes a controller to control at least one of the flow control valve, the isolation valve, and the auxiliary heat source to control the amount of heated fluid supplied to the waterwall when the boiler is not generating steam.

The solution comprises a method of and a system for maintaining steam temperature and therefore electricity production efficiency with decreased loads of a steam turbine power plant comprising a fluidized bed boiler (12) and a fluidized bed superheater (2) adapted to superheat steam supplied to a steam turbine (3). According to the solution, the steam temperature may be maintained by providing, outside a furnace (10), additional heating to the fluidized bed material in its outer circulation, thereby increasing the amount of thermal energy available in the fluidized bed material to be transferred in the fluidized bed superheater (2) to the steam supplied to the steam turbine (3). Such additional heating may be performed by selectably supplying combustible gas with nozzles (111) into and/or burned with a burner in or in the vicinity of the fluidized bed material outside the furnace (10). As an additional aspect of the disclosed solution, the combustible gas may be produced with a gasifier (4).

The solution comprises a method of and a system for maintaining steam temperature and therefore electricity production efficiency with decreased loads of a steam turbine power plant comprising a fluidized bed boiler (12) and a fluidized bed superheater (2) adapted to superheat steam supplied to a steam turbine (3). According to the solution, the steam temperature may be maintained by providing, outside a furnace (10), additional heating to the fluidized bed material in its outer circulation, thereby increasing the amount of thermal energy available in the fluidized bed material to be transferred in the fluidized bed superheater (2) to the steam supplied to the steam turbine (3). Such additional heating may be performed by selectably supplying combustible gas with nozzles (111) into and/or burned with a burner in or in the vicinity of the fluidized bed material outside the furnace (10). As an additional aspect of the disclosed solution, the combustible gas may be produced with a gasifier (4).