Combined Cycle

Reheat Attemperator Background Reheat Attemperators are used as a final control element of steam temperature into the IP section (sometimes LP section depending on plant design) of the Steam Turbine. The steam extracted from the HP section of the turbine is passed back through the boiler and reheater prior to entering the next stage of the turbine.  These attemperators spray water into the reheat line to control the steam temperature. Like superheat attemperators, reheat attemperators are subject to the changes made in controlling flue gas temperature in combustion. However, the reheat steam pressures exiting the HP are much less than superheat steam pressures entering them – meaning the pressure drop across reheat temperature control valves is much greater. This dynamic can create cavitating process conditions creating rapid and excessive trim wear in these valves.  Using REXA Linear and Rotary actuators in reheat temperature control applications increases cycling power plants’ efficiency allowing for minimal valve throttling capabilities, tight shutoff and maximum trim life. Learn more in the full Application Spotlight below!  Literature Download the Attemperator Spray Control Application Spotlight! Download

Background on Inlet Guide Vanes Inlet Guide Vanes (IGVs) deliver air to the inlet of a gas turbine’s axial compressor. While maintaining proper fuel-to-air ratio through various load ranges, they minimize the potential for unwanted emissions. In present-day Combined Cycle power plants, IGVs ultimately control the exhaust gas temperature – a critical input to the Heat Recovery Steam Generator (HRSG). Stable control of the exhaust gas temperature enhances the combined unit’s level of efficiency.  Many current day turbines use low NOx combustors that require a lean air-fuel mixture. As hot gas temperatures decrease, the formation of NOx also decreases. With a higher air mix, it’s critical to control the exact amount of air in the combustors – especially during low loads.  The REXA Solution REXA’s Electraulic™ Actuators provide responsive, repeatable control for IGV applications on all major manufacturers’ combustion turbines. Designed for continuous modulating service, the patented self-contained and closed-loop hydraulic circuit within our actuators provides stiff and stable control in the harshest environments. This system does not need any filters or oil-based maintenance.  A membrane keypad on the enclosure cover ensures simple set-up and calibration. Actuator performance is unmatched within the industry with adjustable dead-band to 0.05% of stroke, resolution of <0.1% and frequency response of 1.5 to 5.0 Hz. Literature Download our full Application Spotlight on Inlet Guide Vanes to learn more! Download