Electric power is one of the most important energy industries, at present, there are steam, wind, water, geothermal, tidal power, solar power. These plants have in common the vaporization of water into steam, which drives a gas turbine that drives a generator to produce electricity. The difference is that the energy used to convert water into steam is different: natural gas, oil, coal, atomic heaps. The structure of each kind of power station is basically the same, we first take the combined cycle power station as an example to describe the selection of control valve briefly, and then explain the different parts of each power station briefly.
The power flow is actually the circulation flow of water and steam, in which the selection of control valve is simple and complex. Simple is the process medium is simple, only water and steam two, the complex is the water and steam temperature and pressure fluctuations in a large range, bringing a series of problems such as flash, cavitation, erosion, noise, corrosion. But the first thing to consider is the safety and reliability of the control valve.
Main Water Supply Valve, Auxiliary Boiler Water Supply Valve, Compound Water Supply Control Valve
Control Requirements: Control Boiler Water, maintain boiler liquid level and steam flow.Operating Requirements: Boiler Starting Valve pressure difference up to 100-300 kg, small flow, normal operation of smaller pressure difference, large flow, flow adjustable ratio of 75:1-100:1.Valve requirements: Valve Body material WCB / WC9, for the dual valve system to start the valve requirements of Cavitation, Class V closed class, for the composite water valve to use the characteristics of valve components to meet the needs of boiler start-up and normal operation. General Valve selection for the fault off, it should be noted that in general feed water, hydrazine is added to remove dissolved oxygen, which may cause adverse reactions to the satellite 6 alloy or other similar alloy. Therefore, it is better not to use the 316 + STELLITE surfacing method to treat the valve internals. Instead, the 416 stainless steel material can be directly selected.
Minimum Flow Circulating Valve For Boiler Feed Pump
Control Requirements: to make the boiler feed pump safe start and operation, to eliminate too small flow, temperature increase, water erosion caused by the pump damage. Old-fashioned power stations have on-off type minimum flow control valves, as well as the use of mechanical pump automatic circulation valves.Operating conditions: pressure drop of 160-350 kg, is the power station system to bear the largest pressure differential valve, the flow is generally 30% of the normal flow.Valve requirements: anti-cavitation, anti-blocking structure, class V seal class, pump start and stop operation of the valve continuous work, pump normal start after the secondary valve closed, the valve is usually open for failure.
High / Low Heater Trap Feedwater Heater Trap, Condensate Heater Trap
Control Requirements: control the location of condensate in the heater, timely discharge of condensate, that is, high water level discharge, normal water level drainage.Working Condition: the medium is saturated water, the pressure difference between the control valves between the heaters is generally 6-30 kg, the last trap directly connected to the condenser or deaerator.Valve requirements: Flash Resistance, V or VI seal class, valve is usually open for failure.
Deaerator Level Control Valve (DALC)
Control Requirements: to provide flow to maintain the normal water level deaerator, by adding steam to raise the water temperature to eliminate dissolved gases in water.Operating Conditions: the start-up phase flow smaller, larger pressure difference, the normal flow of large, small pressure difference, operating conditions similar to water valve.Valve requirements: effective cavitation resistance at low flow rates,
Temperature Reducing Valve
Control Requirements: high-pressure water injection into the steam so that the steam temperature to meet the control requirements.Working Condition: Medium is water, pressure difference is big, valve request: type is various: nozzle type, auxiliary atomization type, self-contained type and clamp type.
Temperature And Pressure Reducing Valve
Control Requirements: high-temperature high-pressure steam adjusted to a certain temperature and pressure of the steam; to provide a bypass channel to the turbine, the boiler can work independently of the turbine.Operating conditions: High temperature and high pressure steam temperature and pressure reduction.Valve requirements: Thermal Shock Resistance, noise reduction, rapid response.
Post time: Nov-25-2021