Heat recovery steam generator and method for fast starting combined cycles
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
F01K-013/02
F01K-007/34
F01K-019/00
F01K-007/22
F22B-001/00
출원번호
US-0987540
(2013-08-06)
등록번호
US-8820078
(2014-09-02)
발명자
/ 주소
Duffy, Thomas Edward
출원인 / 주소
Duffy, Thomas Edward
인용정보
피인용 횟수 :
6인용 특허 :
1
초록▼
A once-through high pressure steam generator and reheater configured to eliminate the majority of components limiting cyclical life of fast start conventional HRSGs. Two remaining problematic components in conventional designs the final superheater and reheater tubes overheat while their headers rem
A once-through high pressure steam generator and reheater configured to eliminate the majority of components limiting cyclical life of fast start conventional HRSGs. Two remaining problematic components in conventional designs the final superheater and reheater tubes overheat while their headers remain colder in fast starts. In this inventive HRSG the critical components are arranged and started by a method that limits these damaging temperature differentials. At ignition when exhaust gas surges into a wet superheater steam flow starts minutes before conventional systems. This early steam flow cools the tubes while heating the headers, thereby reducing life damaging stresses. Steam temperature is controlled through the start and warms the rest of the plant earlier without attemperators with their problematic thermal stress history. Faster starts than conventional result without damaging fatigue life depletion with this low cost innovation.
대표청구항▼
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
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. 2. A method as in claim 1, to further control said high pressure steam generator and said final reheater outlet temperature in off-design over temperature conditions and severe transients, the method comprising: adjusting the position of the dryout zone in the high pressure steam generator circuit for adding or subtracting heat transfer area in superheater, said feedwater control valve increases flow to locate the dry out zone into the superheater reducing area and preventing over temperature outlet steam flow while using the high pressure circuit drain control valve to prevent overshoots with a rate of control to rapidly reduce area, said high pressure circuit drain controlvalve is rapidly opened to increase area to increase temperature preventing damaging wet steam excursions in rapid gas turbine download transients. 3. A method as in claim 1, of nitrogen blanketing said high pressure heat recovery steam generator and said reheater during cyclic operational short period shut downs of the combine cycle, the method comprising; retaining heat in said steam generator high pressure steam generator by isolating it at shutdown by closing outlet steam lines, drain lines and feedwater inlet control valve to and stack damper if installed, said reheaters are vented to the condenser for several minutes to evaporate any condensation while they are hot by opening the turbine bypass valves, the bypass valves are then closed to isolate the reheater, said nitrogen tank is connected to the main steam line by the nitrogen supply valve and nitrogen is caused to flow into the steam spaces and pressure is kept above atmospheric and said main steam lines are maintained above atmospheric pressure by the flow of nitrogen to replace steam as it condenses to near atmospheric pressure, said high pressure turbine bypass valve is opened to connect said reheaters to said main steam line and thereby connect said reheaters to the nitrogen supply, a nitrogen valve is opened in the hot reheater line to connect it to the a nitrogen unit to circulate nitrogen through the reheaters, said high pressure steam outlet valve to said main steam line on the header receiver drain system to connect the high pressure steam generator water side of the steam generator through said main steam line to said nitrogen tank to replace steam as it cools, nitrogen filling all the space above the water and all the water wetted surfaces. 4. A method as in claim 1, of dewatering the heat recovery steam generator, comprising; flowing air into to said main steam line from said air supply system valve, closing the high pressure turbine by-pass valve and opening the main steam line valve to said final superheater receiver header thus flowing pressurized air into the circuits, opening the circuit drain valve and said feedwater tank inlet valve to force water out of the circuits into the feedwater tank slowly, when most of the water is removed air pressure is increased to blow remaining water from said circuits to the feedwater tank to dry the tubes, close said main steam line valve to final high pressure receiver superheater headers and open the high pressure turbine bypass valve and the intermediate steam turbine bypass valve to the reheater thereby directing air through the reheaters and through the bypass bypass dusuperheater into said condenser, increase air flow to blow residual condensate from the said reheaters with high velocity air. 5. A method as in claim 1, of long term layup of said high pressure steam generator and said reheater, such method comprising; said high pressure steam generator and said reheater are laid up for long periods dry filled with nitrogen, after dewatering said high pressure steam generator and said reheaters, said nitrogen tank is connected to the main steam line and said high pressure turbine bypass valve is opened, said high pressure steam header steam receiver outlet to said main steam line valve is opened to connect and flow nitrogen to fill said high pressure steam generator circuits and said reheater circuits, said high pressure circuit drain control valve is opened to circulate the nitrogen to said nitrogen unit by opening a inlet valve to said nitrogen unit from the said circuit drain valve discharge line, a reheater to nitrogen unit isolation valve is also opened and dry nitrogen is circulated through said high pressure turbine bypass valve through said reheaters and returned back to said nitrogen unit, said nitrogen unit circulates nitrogen from said high pressure steam generator and reheater back to the nitrogen tank drying and venting air, reducing oxygen levels to prevent corrosion, said nitrogen supply unit is turned off and periodically started to then maintains the pressure in the system above ambient to account for valve seepage and periodically checks the system automatically for the duration of the layup.
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이 특허에 인용된 특허 (1)
Tomlinson Leroy O. (Schenectady NY) Smith Raub W. (Saratoga NY), Reheat steam cycle for a steam and gas turbine combined cycle system.
Alexander, Michael Joseph; Davis, Jr., Lewis Berkley; Snider, David August, Systems and methods to improve shut-down purge flow in a gas turbine system.
Alexander, Michael Joseph; Davis, Jr., Lewis Berkley; Snider, David August, Systems and methods to improve shut-down purge flow in a gas turbine system.
Snider, David August; Davis, Jr., Lewis Berkley; Alexander, Michael Joseph, Systems and methods to improve shut-down purge flow in a gas turbine system.
Snider, David August; Davis, Lewis Berkley; Rosson, Randy Scott; Alexander, Michael Joseph, Systems and methods to improve shut-down purge flow in a gas turbine system.
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