Patent ID: 8820078
Filing Date: 2014-09-02
Classification: F01K,F22B,Y02E

Abstract:
1. A method of starting a high pressure heat recovery steam generator in a combined cycle system including a gas turbine; a high pressure superheater, a reheater section, a high pressure evaporator, a high pressure economizer, said heat recovery system disposed to extract energy in the form of high pressure steam from said gas turbine exhaust gas entering said final high pressure superheater section at the entrance of said heat recovery steam generator, a high pressure final superheater header drain receiver system at the high pressure steam headers, said header drain system including a drain valve to said condenser and an outlet steam valve to the main steam line, a circuit water drain system to remove and control the flow rate of water out of the high pressure steam generator circuits at the at the economizer inlet end, a final reheater section immediately downstream of said final high pressure superheater, said high pressure economizer circuits receiving water from a feedwater control valve regulating the flow from a high pressure pump, high pressure steam exiting said final high temperature superheater directed to the high pressure section of the steam turbine, and said reheater disposed along the steam flow path receives cold steam from the steam exiting the high pressure turbine, reheated steam is returned to the steam turbine systems, the method to start comprising: flowing feed water into said high pressure economizer prior to start through the feedwater control valve into said economizer through said evaporator, and said high pressure superheater, causing the high pressure steam generator to be completely full of water prior to ignition of said gas turbine engine, at ignition said high pressure final superheater outlet header system drain valve is opened to discharge fluid out of final superheater headers and water-steam mixture is caused to flow out of the final superheater drain system as the water steam mixture heats and expands, water is also caused to flow out of said high pressure steam generator through said economizer by opening said high pressure circuit drain control valve, the flow from both drains controls the steam outlet pressure and temperature to produce dry steam, when dry steam is sensed said final superheater header receiver steam valve to the main steam line is opened and the receiver drain valve is closed, opening said steam outlet valve from the header receiver to said main steam line causes dry warming steam to flow into said main steam line and through said reheater by opening a high pressure steam turbine bypass valve, and an intermediate turbine bypass valve, diverting steam flow into the intermediate turbine bypass desuperheater and then into the condenser, controlling steam temperature and pressure with control obtained by adjusting the said high pressure steam receiver outlet steam valve and said circuit water drain control valve, at a preset temperature the circuit drain control valve is closed transferring temperature control function to the high pressure feedwater control valve to transition to normal mode of control as the steam generator warms, by diverting at a predetermined temperature a flow of steam to the high pressure turbine and intermediate turbine to warm the turbine systems as steam temperature and pressure are increased as the startup control system transitions the water evaporation dryout zone to its normal position in the high pressure evaporator.