H. Łukowicz

Diverse configurations of the boiler feed pump drive for the ultra-supercritical 900-MW steam plant

Coal-based electric power generation remains the basic source of obtaining energy. With increasing pressure to reduce CO2 emissions, improving power unit efficiency has become an issue of utmost significance. Surely, one of the possibilities to improve the efficiency of new power units is raising the steam parameters. With improved power plant efficiency, there is a lower demand for power of almost all auxiliary equipment except the boiler feed pump. The reason for this is that the power needed to drive the feed pump is an almost linear function of the steam pressure. This means that, even though the steam mass flow (and, consequently, the feed water mass flow) is reduced and the efficiency of feed pumps is improved, their power increases. For this reason, it is very important to find the optimum drive of the boiler feed pump. The main aim of the conducted analysis was to compare various drive options of the boiler feed pump for a conceptual ultra-supercritical 900-MW steam power unit. The following drive configurations of the boiler feed pump were presented and compared:· A frequency-controlled electric motor· A condensing turbine fed with steam extraction from the immediate-pressure turbine· An extraction-backpressure turbine fed with steam from a cold reheat steam line with bleeds shifted from the low-pressure turbine· A backpressure turbine fed with steam from a hot reheat steam line operating in parallel with the intermediate-pressure turbine· An extraction-backpressure turbine fed with steam from a cold reheat steam line with bleeds shifted from the intermediate-pressure turbine (the master cycle idea).The analysis of the operation of the 900-MW unit with various configurations of the feed pump drive was carried out for three load levels: for the nominal mass flow of live steam and for the partial mass flow of 75% and 50%.

Analysis of Thermal and Stress States in Transient Operation of a Turbine Co-operating with Twinboiler

ABSTRACT The operating conditions of coal-fired power units are changing because of the current shift in the approach to technologies based on fossil fuels. Due to decarbonization issues, their function is now more often to balance shortages of electricity generated from renewable sources. A substantial rise can be observed nowadays in the significance of the capability of all the installation modules to operate under variable loads. One of the solutions improving the coal-fired power unit flexibility is the twin-boiler concept based on using a system with twin-boilers co-operating with one steam turbine. Such a solution makes it possible to obtain characteristics similar to gas-steam systems and achieve low values of the minimum load on the basic fuel. The solution operating characteristics cannot be determined fully unless issues related to the thermal and stress states of individual elements are discussed first. The subject of the numerical analyses presented in this paper are thermal and stress states arising in the elements of a turbine co-operating with 2 boilers during steady- and unsteady-state operation. Results of numerical simulation of the turbine steady operation, the start-up process and power change are presented. An analysis is conducted of the impact of the rate of changes in power on the level of stresses in the turbine elements and in consequence on the fatigue of the turbine rotors.

Thermo-Economic Analysis of the Ultra-Supercritical 900 MW Power Unit With the Various Configurations of the Auxiliary Steam Turbine

Coal-based electric power generation remains the basic source of obtaining energy. With increasing pressure to reduce CO2 emissions, improving power unit efficiency has become an issue of utmost significance. The development of technologies related to coal-fired power units does not focus solely on the steam parameters ahead of the turbine. Increasing the live steam parameters usually constitutes the greatest contribution to the rise in the efficiency of a power unit, but the sum of efficiency gains related to the application of other solutions can also be significant and can, in some cases, exceed the effects related to raising the temperature and steam pressure values. A paper presents thermodynamic and economic analysis of various configurations of the ultra-supercritical coal-fired 900 MW power unit with the auxiliary steam turbine. Main subject of research was a power unit considered within the Strategic Research Programme – Advanced Technologies for Energy Generation with the parameters of live and reheat steam: 30 MPa/650°C/670°C. The base configuration of the power unit has single steam reheat and electric drive boiler feed pump. Analysis of ultra-supercritical 900 MW power unit involves configuration with a single and double reheat. The following configurations of the auxiliary steam turbine will be presented and compared:• extraction-backpressure steam turbine fed with steam from cold reheat line with bleed and steam outlet directed to the feed water heaters;• extraction-backpressure steam turbine fed with steam from cold reheat line with bleed and steam outlet directed to the feed water heaters; the auxiliary turbine drives the boiler feed pump;• backpressure turbine fed with steam from a hot reheat steam line operating in parallel with the intermediate-pressure turbine; the auxiliary turbine drives the boiler feed pump.The analysis of the operation of the 900 MW unit was carried out for three load levels: for the nominal mass flow of live steam, and for the partial mass flow of 75% and 50%. For all presented solutions thermodynamic and economic analysis was performed, which has taken into account the charge for CO2 emissions.© 2012 ASME