A process for increasing the specific output of a combined cycle power plant and providing flexibility in the power plant rating, both without a commensurate increase in the plant heat rate, is disclosed The present invention demonstrates that the process of upgrading thermal efficiencies of combined cycles can often be accomplished through the strategic use of additional fuel and/or heat input In particular, gas turbines that exhaust into HRSGs, can be supplementally fired to obtain much higher steam turbine outputs and greater overall plant ratings, but without a penalty on efficiency This method by and large defines a high efficiency combined cycle power plant that is predominantly a Rankine (bottoming) cycle Exemplary embodiments of the present invention include a load driven by a topping cycle engine, powered by a topping cycle fluid which exhausts into a heat recovery device

High density combined cycle power plant process

A combined cycle electric power plant includes in interconnected relationship a steam turbine, two gas turbines, three electric generators, two heat recovery steam generators, a hybrid computer control system, a plant protection system and various items of auxiliary equipment. A computerized simulator is interfaced with the control system at the factory site to test the controls and the control system is then modularly disassembled in various structures and shipped to the field site for reassembly without need for extensive field testing. The control system includes a digital control computer, a digital monitor computer and modular analog controls for the turbines. Various levels of automated control can be employed including coordinated plant control which involves supervisory operation of the analog controls by the control computer. In analog control, complete plant operation is produced by operation of the analog controls without the control computer.

Gas turbine and steam turbine combined cycle electric power generating plant having a coordinated and hybridized control system and an improved factory based method for making and testing combined cycle and other power plants and control systems therefor

In a method of operating a combined cycle system including a gas turbine, a steam turbine and a multi-pressure heat recovery steam generator, an improvement includes supplying gas turbine cooling duty steam from a high pressure section of the steam turbine and from an intermediate pressure evaporator in the multi-pressure heat recovery steam generator, conducting the gas turbine cooling duty steam to the gas turbine for cooling hot gas turbine parts, and then returning the gas turbine cooling duty steam to an intermediate pressure section of the steam turbine. In a start-up procedure, steam is extracted from a first pass of a high pressure superheater in the multi-pressure heat recovery steam generator, mixed with steam discharged from the high pressure superheater and then supplied to the gas turbine cooling duty system. In this same start-up procedure, the gas turbine cooling duty steam is returned to the system condenser, bypassing the intermediate pressure section of the steam turbine. Related apparatus is also disclosed.

Combined cycle with steam cooled gas turbine

In a combined cycle system including a gas turbine (412), a steam turbine (420) and a heat recovery steam generator (436), wherein gas turbine exhaust is used in the heat recovery steam generator (436) for reheating steam for the steam turbine (420), an improvement wherein steam is extracted from the high pressure section (422) of the steam turbine 420), conducted to the gas turbine (412) for cooling hot gas turbine parts, and returned to the intermediate pressure section (424) of the steam turbine (420).

Steam cycle for combined cycle with steam cooled gas turbine

A combined cycle electric power plant includes gas and steam turbines and a steam generator for recovering the heat in the exhaust gases exited from the gas turbine and for using the recovered heat to produce and supply steam to the steam turbine. The steam generator includes a superheater tube through which a fluid, e.g. water, is directed to be additionally heated into superheated steam by the exhaust gas turbine gases. An afterburner further heats the exhaust gas turbine gases passed to the superheater tube. The temperature of the gas turbine exhaust gases is sensed for varying the fuel flow to the afterburner by a fuel valve, whereby the temperatures of the gas turbine exhaust gases and therefore of the superheated steam, are controlled. Further, override signals are generated to prevent the temperature of the superheated steam from falling below a predetermined minimum level and for preventing the temperature and pressure of the superheated steam from exceeding maximum levels.

Combined cycle electric power plant and a heat recovery steam generator having improved temperature control of the steam generated

A combined cycle power plant has a number of gas turbines each feeding exhaust gas to an associated heat recovery steam generator to generate steam which is supplied to a common header. Provision can also be made for supplementary firing of the heat recovery steam generator to produce additional steam flow. The combined cycle plant also has a steam turbine with a special control system to control steam pressure in the header and to supply the balance of the plant load. An overall combined plant control system assigns load to the individual gas turbine control systems, while the steam turbine control system controls steam pressure in the common header. The steam pressure level setpoint is ramped between selected operating pressure levels when adding or removing load, in accordance with the steam turbine valve positions, in order to achieve optimum operation of the steam turbine. A steam bypass valve control system is used to control pressure in the header during startup, and a supplementary firing control for the heat recovery steam generators may be included to achieve peak loads.

Lawrence R Mizen

Papers

Combined steam turbine and gas turbine power plant control system