HRSG Intermediate and High Pressure Steam System in combined cycle power plant production

The high-pressure (HP) steam generation system is located after the high-pressure economizer. It is used to generate steam of a specific quality, in terms of pressure and temperature, from the thermal energy contained in the gas turbine exhaust flow. The system supplies steam to the high-pressure steam drum and the main HP steam system. During operation it maintains the high-pressure superheated steam temperature within the allowed limits for the steam turbine and main steam system, and is also used during part load operation at high ambient temperatures and steam turbine start-up. It also supplies high-pressure spray-water to the HP attemperation system as well as discharges and attemperates HP steam directly to the cold reheat piping system and the high-pressure steam bypass reducing station, if it is not accepted by the steam turbine. The intermediated pressure (IP) steam generation system is located between the IP economizer and the intermediate superheater steam system. This system also generates steam, of intermediate pressure from the the gas turbine exhaust. The system delivers feedwater to the IP steam drum during start-up, shutdown and operation and feeds superheated IP steam to the cold reheat system. This superheated steam is combined with the cold reheat steam and fed via the reheat system into the intermediate section of the steam turbine.

The feedwater flowmeters are of high importance for process control and safety and need to cope with the high temperatures and pressures as well as meet the accuracy and redundancy requirements. Typically, venturi tubes or flow nozzles are used, installed in meter runs with redundant DP-transmitters according to ISO 5167 or ASME MFC-3M. The engineered KROHNE primary DP flow elements and meter runs are hot water factory calibrated at high Reynolds numbers. The state of the art OPTIBAR DP 7060 C pressure transmitters are 100% 3D-calibrated over the entire temperature and static pressure range and available with measurement capsules suitable for up to 700 bar line pressure. KROHNE supplies the complete flow solution with DP-flow element, DP-transmitter, pressure and temperature transmitter, process valves, engineering, calibration and documentation. A further option here is the OPTISONIC 3400/ 4400 series of ultrasonic flowmeters, which are suitable for the specific requirements of temperature, pressure, materials, redundancy, accuracy etc. KROHNE OPTISONIC meters are drift and maintenance free, have no pressure drop and an extremely wide turndown ratio which enables very good low-end accuracy. Also for Steam, Reheat, injection/ attemperation water, condensate and other typical flow applications KROHNE OPTIBAR DP and OPTISONIC Ultrasonic flowmeters are available.