B&W's supercritical and ultra-supercritical boiler designs offer the flexibility and reliability to meet the most demanding steam generation needs of our customers.
At supercritical pressures, steam turbine efficiency improves significantly compared to the typical subcritical cycle. Ultra-supercritical steam conditions provide even greater efficiency improvements. The combination of utilizing supercritical throttle pressures along with an increase in throttle temperatures results in cost reductions in fuel usage and handling, flue gas treatment and ash disposal. B&W's supercritical and ultra-supercritical boilers are designed to take full advantage of variable pressure turbine operation.
Specific advantages include:
During startup of a once-through boiler, the waterside components must have a minimum water flow maintained to ensure adequate cooling. B&W startup systems are well proven to provide reliable flow to the waterside components to produce short startup times and low thermal stresses.
The main components of B&W’s startup system are the vertical steam separators, water collecting tank and boiler recirculation pump. The steam separator acts like a drum in a natural circulation boiler. The fluid from this separator is recycled to the economizer inlet where it mixes with feedwater to maintain the minimum flow through the boiler furnace. Once minimum load is achieved, the startup system is put in warm standby for quick use when required. The steam from the separator passes through to the superheater and then on to the turbine.
The startup operation parallels that of a drum boiler. This system provides the maximum amount of heat recovery back to the boiler during startup allowing for rapid startups with the least amount of thermal stress on the components.