Electricity is one of the most important energy sector, there are steam, wind, hydro, geothermal, tidal power, solar power, this paper focuses on the selection of fuel oil, kerosene, gas and nuclear power plants in some typical control valve. Common in those plants is to water vapor into steam, using steam to drive a turbine driven generators to produce electricity, the difference is the energy of water into steam each are not identical, are: natural gas, fuel oil, coal, nuclear. The structure of various power plant similar to our first, combined cycle power plant as an example to briefly control valve selection, and then briefly explains the different parts of the station.
Power flow is actually a simple view of water, steam cycle process, in this process control valves used in both simple and complex. Simple is the process medium is simple, only water and steam two, complex temperature and pressure fluctuation range of water and steam, bringing a series of issues such as: flash, cavitation, erosion, noise, corrosion. But the first thing to consider is the safety and reliability of the control valve.
In accordance with our system to start flow control valve selection description.
1, the main water supply valve, auxiliary boiler feed water valve, water valve complex
Control requirements: control of boiler water, the maintenance of boilers and steam flow level.
Working requirement: the boiler starts up to 100-300 kg of pressure valves, low flow, low pressure drop during normal operation, traffic flow, adjustable flow ratio 75:1-100:1.
Valve requirements: body material to WCB/WC9, double valve system for the start valve requirements in cavitation, V level off level for the compound to the water valve, need to use properties of trim meet boiler startup and normal operation needs. General valve options for fault shutdown, (note that the general water to remove dissolved oxygen will be added hydrazine processed, it will produce adverse reactions, the SATELLITE 6 alloy or other similar alloy method, so it is best not to use 316+STELLITE surfacing processing valve parts, can be directly using 416 stainless steel).
2, boiler feed pump minimum flow recirculation valve
Control requirements: the safety of boiler feed pump start and run, to eliminate traffic is too small, temperature increase, water strong cavitation damage to the pump. (power switches are used to the old type, the minimum flow control valves, as well as use of mechanical pumps automatically cycle valve).
Conditions: the pressure drop up to 160-350 kg, is the largest power system to withstand pressure valves, flow is generally 30% of normal flow.
Valve requirements: resistance to cavitation, attempts to prevent the structure, the sealing of V grade valve continuous work, pump start and stop running, the pump normally starts off valve after the second valve, the valve is normally open fault.
3, high / low heater trap water heater hydrophobic, condensed water heater hydrophobic
Control requirements: to control the location of condensed water heater, timely condensate discharge, high water discharge, the normal water level of steam.
Conditions: the medium is saturated water, heater control valve between the pressure is generally 6-30 kg, and finally a trap directly connected to the condenser or deaerator.
Valve requirements: Flash erosion resistance, sealing rating of V or VI level, the valve is normally open fault.
4, the deaerator water level control valve (DALC)
Control requirements: to provide flow to maintain the normal water level of deaerator, by adding steam to increase temperature to eliminate the gas dissolved in water.
Condition: the flow of small start-up phase, a larger pressure difference, the normal flow rate, pressure difference, similar to the valve condition.
Valve requirements: low flow cavitation effect at the time,
5, reducing temperature valve (desuperheater)
Control requirements: the high-pressure water jet of steam into the steam temperature control requirements.
Conditions: the medium is water, a larger pressure difference, valve requirements: type diversity: nozzle type, assisted atomization type, self-contained type and the clip.
6, temperature and pressure reduction valve (high, low pressure bypass valve)
Control requirements: the steam of high temperature and high pressure steam to adjust to a certain temperature and pressure; to provide a bypass channel turbine, boiler and steam turbine capable of independent work.
Condition: the high temperature high pressure steam temperature and pressure reduction.
Valve requirements: thermal shock, noise reduction, quick response
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