Maciej PAWLIK
Technologically advanced power units – New challenges
To keep the stability of a power network, when facing the growing share of renewable sources in electric energy generation, it is necessary to increase the flexibility of conventional power stations: coal-fired and combined cycle gas-turbine ones. The lack of significant power output from hydroelectric power plants or possibility to store big amounts of energy (except the already existing pumped storage power plants) will force the need to fulfil such function by the technologically advanced conventional power stations including, to a large degree, new generations of combined cycle power plants. In comparison with the previously built conventional power plants, the present units are characterized by bigger flexibility that concerns mostly the gas-fired systems. So the replacement of older, non-flexible and inefficient coal-fired plants with highly efficient and flexible coal-fired units, and especially the combined cycle ones, can become an effective solution of a network stability problem with considerable CO2, SO2 and NOx emission reduction at the same time. Characterized are the main features of these technologies with controllability in the first place and shown are directions of further activities aiming at the operational flexibility increase. In conditions of our country it is rather the increase of combined cycle power plants share in the Polish power system that is preferable because of their ability to change fast the rate and range of the load and their short start-up time.
Keywords: power units, flexible coal-fired and combined cycle units, controllability properties
Janusz BUCHTA
Coal-fired unit with full and partial separation of CO2
Among the considered methods of CO2 emission reduction by the coal-based power industry we can distinguish post-combustion, pre-combustion and oxy-combustion technologies. Especially the post-combustion installations can be the key solution for the Polish power industry as most of the existing domestic thermal power plants are equipped with pulverized coal-fired boilers. If, in turn, it comes to the prospective technologies of CO2 separation from flue gases, we can talk about methods like chemical absorption, physical adsorption, membrane separation and criogenic methods - all these methods are under intensive investigation and tested in pilot installations. The aim of the presently carried on research is integration of CCS installation elements, process optimization and CCS technology chain certification. Presented are results of simulation calculations of a 800 MW ultrasupercritical thermal unit system equipped with a CO2 capture installation using absorption method. Made is an assessment of the influence of the installation integrated with the thermal cycle on the power unit efficiency. Considered are cases of partial and full CO2 separation. Ascertained is that the CCS installation application results in reduction of a unit efficiency and in increase of energy demand by the auxiliaries and, in addition, brings about bigger investment, operational fixed and variable costs that increase the final cost of electric energy production. Efficiency of a unit equipped with a CCS absorption installation depends on the type of a sorbent used.
Keywords: coal-fired power units, CO2 separation, CCS technology chain
Andrzej OZIEMSKI, Jarosław JĘDRZEJCZYK
Analysis of operational reliability of power units installed in Bełchatów power station
Assessment is made of failure frequency and availability of lignite-fired power units installed in PGE Górnictwo i Energetyka Konwencjonalna S.A. Oddział Elektrownia Bełchatów. Investigations were performed on the basis of data filed in the computer base by the workers of Wydział Gospodarki Energetycznej and concerning operational incidents that happened between the commissioning of the first power unit and the end of the year 2012. Thanks to application of highly efficient equipment in the 858 MW power unit and especially the supercritical steam generator, a very high efficiency of the electric energy production process has been achieved what enabled fuel consumption minimization and, as a consequence, reduction of air pollution emission. The new power unit meets all legal requirements being in force in Poland and the appropriate criteria of European Union Directives.
Keywords: lignite-fired power units, failure frequency and availability of power units, electric energy generation efficiency of the 858 MW power unit
Mariusz PAWLAK, Jacek KARCZEWSKI
Electrohydraulic governor for the TK-120 turbine
Presented are activities connected with implementation and operation of electrohydraulic output governors constructed in Oddział Techniki Cieplnej “ITC” of the Institute of Power Engineering. The governors were applied on five of the 120 MW units in one of the Polish power stations. Presented is the structure of the governor and its functions. Described is operational experience of automatic control systems (ACS) of turbine-generator sets taking part in the process of power system controlling (primary, secondary and third control). Discussed are test results of ACS equipped with the governors – the tests were carried out on real objects (120 MW units) and their aim was the assessment of ACS work by making use of solutions implemented by “ITC”. Described is the possibility of adapting the governors to the now being under implementation in the Polish power industry LFC (Load Frequency Control) system. Application of modern computer control systems allows constructing electrohydraulic output governors equipped with many new, useful functions and leads to improvement of control quality, increases operational security and improves operating conditions. Thanks to the governors it is possible for instance to connect individual units with the Automatic Frequency and Power Control System and the system of primary control. The presented ACS structures, using advanced diagnostic technologies [5,8], can contribute to electric energy generation technology development and elongation of power units operational lifetime.
Keywords: condensing turbines, output governors, electrohydraulic governors
Eugeniusz RUSIŃSKI, Jerzy CZMOCHOWSKI, Artur GÓRSKI, Wiktor SŁOMSKI, Michał PADUCHOWICZ
Identification of stress state of a fluidized power unit primary air duct
Proper designing of air ducts structures and their mountings is extremely important from the point of view of ensuring proper strength of the power equipment. Presented are selected aspects of structural analysis of a primary air duct supplying the preheated primary air from fans to a rotary air preheater LUVO. Examined were also the duct displacements in order to verify the appropriateness of the applied support elements. On the basis of obtained calculation results it was ascertained that in places where the real object cracks arise, there occur high stresses reduced according to the Huber-Mises hypothesis, considerably exceeding the construction material yield limit. Low values of the duct longitudinal displacements show the possibility of the excessive bracing of supporting construction. Moreover, because of the lack of bracing around the whole air outlet rim, there appears a sudden stiffness drop of the duct plating in this place. These two factors can have crucial impact on the occurrence of the duct plating stress concentration. In order to eliminate the high stress values one should first of all ensure the possibility of adequate displacement compensation in the area of coil mountings and apply additional bracing construction. The relevance of the above changes should be confirmed by carrying out the structural stress analysis of the modified model with the use of finite element method.
Keywords: fluidized power unit, primary air ducts, construction strentgh
Mariusz SUSIK, Andrzej BŁASZCZYK, Adam PAPIERSKI
Optimization of suction intakes of vertical axis pumps
The need for optimization of suction intakes in axial-flow cooling water pumps with vertical axis is associated with the assurance of required impeller flow conditions. The conditions are closely related to acceptance criteria of the water flowing into the pump, specified in the standard ANSI/HI 9.8-1998. They concern non-uniformities of the flow velocity at the outlet of the suction intake and swirling of water before the impeller eye. Non-compliances may cause significant power fluctuations of a power unit. Presented are results of geometry comparison of suction intake being in operation with the suction intake after optimization. Big differences in geometry parameters between the basic intake and the optimized one suggest introduction of some superior function - e.g. costs of making new intakes. In order to finally select the intake construction, the assessment of costs of making new intakes in comparison with obtained effects of pump impellers working conditions improvement should be made.
Keywords: cooling water systems of power units, water pump suction intakes, optimization of suction intakes
Andrzej KANICKI, Józef WIŚNIEWSKI
Selection of parameters for a 1000 MW power unit generator breaker
Presented is a method of selecting generator breaker parameters for a 1000 MW power unit. Standardized calculations of short-circuit values are made in order to compare them with a breaker nominal parameters. Simulation calculations of the short-circuit current flow from generator and from the network as well as the simulation of its switching-off in the generator breaker are carried out. Research results show that at such moments there can be no fault current transition through zero for several periods so it makes interrupting of the fault current a difficult thing for the generator breaker. Simulation calculations of a short-circuit current flow from generator and simulations of switching-off the fault current by the generator breaker are performed as well as the simulations of recovery voltages between the terminals of the generator breaker. Observed is the lack of the fault current transition through zero in several first periods in one phase what makes its switching-off by the generator breaker a difficult thing to do. In that case we must pay special attention to the breaker ability to switch-off such a strongly asymmetric current.
Keywords: 1000 MW power units, generator breakers, selection of parameters for generator breakers
Tomasz KOTLICKI
Improvement of energy efficiency in auxiliaries system of a power station
Presented are calculations of energy savings resulting from application of various options of load adjustment with reference to main auxiliaries. Considered were devices with different flow profiles and most of the methods of load control applied currently in modern installations. Calculations were conducted on the basis of real load profiles and characteristics of auxiliary devices operating in power units working for the domestic power system. The calculated annual efficiency factors do not determine explicitly which of the variants is the most advantageous one. In case of a feed water pump the most advantageous control option is the application of an inverter, and the least effective – the standard hydrokinetic torque converter. Pretty good results we can obtain using the throttle control (practically costless), therefore probaly this particular option would be the most advantageous even when taking inverter costs into consideration. In case of cooling water the differences between individual variants are pretty distinct. The least energy consuming is the inverter option but the most energy consuming is the one with the use of throttle control. All options of pump control are distinctively less energy consuming than the option with throttle control so we can assume that the economic effects in a long time period will also be advantegeous after considering the investment costs connected with the application of an inverter or a torque converter. In case of a mill fan the most economic control is the one with the use of inverter. The rest of options do not differ much therefore the most advantageous solution can be the cheapest one from the investment point of view – with the use of guide vanes control.
Keywords: energy efficiency, power station auxiliaries, efficiency control and energy savings
Andrzej WAWSZCZAK
Variable speed drives with frequency converters in thermal power plant auxiliaries
Presented is, against a background of some other methods, a variable speed drive (VSD) method realized by changing frequency of the voltage supplying squirrel cage motors driving a thermal power plant auxiliaries. Main attention is here paid to medium voltage (MV) (6-10 kV) high power drives. Presented are current offers proposed by the leading producers in the world. Estimated are possibilities to apply such drives in big, modern unit-type power stations and their influence on a power station work. Monitoring the development of high power MV converter drives during the last twenty years, we can observe a big progress in this branch. It seems that futher grow of interest from the “big power industry” in such drives will push their development in the direction of reducing their costs and sizes. One should only have high hopes of widespread application of semiconductor power electronic devices produced on the base of silicon carbides (SiC) for the high power converter drives.
Keywords: thermal power stations, auxiliaries, variable speed control
Marcin SZUNIEWICZ
Integrated Early Fire Detection and Extinguishing System for Dolna Odra power station stoking system
Described is the Integrated Early Fire Detection and Extinguishing System for the coal/biomass stoking system realized at the PGE Dolna Odra Power Plant in Nowe Czarnowo. It is the first and innovatory system designed and executed in Poland of such scale which task is elimination of explosion and fire hazards often occurring in stoking installations. The system was installed and implemented in the year 2012 and now its application in some other power station areas, e.g. cable tunnels, is considered. It is a complex design for the whole stoking system, paying special attention to potential hazard sources and the type of fuel used. The system is able to detect various kinds of hazards (fires without flames, damaged elements of conveyor mechanical system as heat sources etc.). All individual systems are integrated what reduces the necessity to organize additional service trainings for the staff. The system enables instantaneous informing of the staff about arising hazards, accelerates the decision making process through clear and understandable announcements and program procedures allowing focusing the staff attention on an endangered area and also it is a tool supporting making decisions concerning fire fighting action. It is a redundant system, i.e. in sensitive spots of the system responsible for detection and making decisions its reliability has been increased by multiplexing of some elements (server redoubling, multiplexing of working stations, double-track transmission, “ring” type connections).
Keywords: coal-fired power stations, stoking system, automatic fire detection and extinguishing system