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1

Analiza termodynamiczna ultra-nadkrytycznego bloku węglowego z turbiną pomocniczą

Stępczyńska-Drygas K., Dykas S.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2014

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z. 86 [290], nr 1

79--86

PL

Konieczność zmniejszenia emisji gazów cieplarnianych oraz poprawy ekonomiki wytwarzania energii elektrycznej spowodowały znaczny postęp w dziedzinie bloków węglowych. Nowe perspektywy otwiera generacja bloków na zaawansowane parametry ultra-nadkrytyczne pary o temperaturze 700°C/720°C. Znaczne zwiększenie temperatury pary, zwłaszcza wtórnie przegranej, pogłębia problem różnicy temperatur w podgrzewaczach regeneracyjnych zarówno wysoko jak i niskoprężnych, co skutkuje wzrostem strumieni generowanej entropii oraz problemami materiałowymi. Rozwiązaniem może być wprowadzenie do obiegu dodatkowej upustowo-przeciwprężnej turbiny pomocniczej. Obieg turbiny pomocniczej jest prostym obiegiem bez przegrzewu wtórnego. Skutkuje to tym, że ma on niższą sprawność w porównaniu do obiegu głównego. Zmniejsza się zysk z zastosowania przegrzewu międzystopniowego, gdyż znaczny strumień pary, który jest kierowany do turbiny pomocniczej nie zostaje przegrzany ponownie. Zysk wynikający z minimalizacji generacji entropii w podgrzewaczach regeneracyjnych powinien zatem zrekompensować straty wynikające ze znacznego zmniejszenia strumienia przegrzewanej pary. W artykule przedstawiono analizę termodynamiczną obiegu prostego oraz koncepcyjnego bloku węglowego na zaawansowane ultra-nadkrytyczne parametry pary o mocy 900 MW z upustowo-przeciwprężną turbiną pomocniczą.

EN

The necessity of the reduction of greenhouse gases emissions and improving the economics of electricity generation resulted in significant progress in the development of the coal-fired power plants. New perspectives gives the generation of power plants for advanced ultra-supercritical (A-USC) steam parameters of temperature of 700°C/720°C. A significant increase of the steam temperature, especially reheated, increases the problem of the temperature differences in the high and low-pressure feed water heaters. This results in the increase of generated entropy and material problems. The solution can be introducing into the steam cycle an auxiliary extraction-backpressure turbine (AT). The AT cycle is a simple cycle without steam reheating. As the result it has lower efficiency in comparison with the main cycle. The use of the AT leads to the reduction of profit resulting from the reheating of steam, because the mass flow of steam transmitted to the boiler reheater is reduced. The benefit resulting from the decrease of the entropy generation in the feed water heaters should then exceed the loss related with the reduction of the steam mass flow, which is reheated in the boiler. In the paper the thermodynamic analysis of the simple cycle and the conceptual 900 MW power plant with the auxiliary extraction-backpressure turbine is presented.

2

Analysis of fouling thermal resistance of feed-water heaters in steam power plants

Butrymowicz D., Głuch J., Hajduk T, Trela M., Gardzilewicz A.

Polish Maritime Research

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2009

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S 1

3-8

EN

In this paper a problem is discussed of thermal degradation of shell-and-tube recuperative feed-water heaters due to heat transfer surface fouling. Application (to an example steam cycle of power plant) of DIAGAR software system intended for the analysing of impact of degradation of a particular heat exchanger on whole recuperative system performance, is presented. On the basis of the systematically performed simulative calculations it was concluded that the degradation of feed-water heaters of the lowest extraction pressure results in an additional load imposed on the heaters of higher extraction pressures, moreover it was estimated that the degradation of the heaters due to presence of sediments of the thermal resistance reaching 5*10-4 m2*K/W, has resulted in the drop of turbine set efficiency by about 0.3%. Such drop depends on a given configuration of degree of degradation of particular feed-water heaters applied in a considered turbine set.

3

Analysis of application of feed-water injector heaters to steam power plants

Trela M., Kwidziński R., Głuch J., Butrymowicz D.

Polish Maritime Research

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2009

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S 1

64-70

EN

Steam-water injectors are devices in which exchange of mass, momentum and energy between two fluids being in direct contact, occurs. They can operate as pumps, mixers or direct contact heat exchangers. In the last aspect their use as feed-water heaters in Rankine thermal cycle of steam power plants both in land and sea applications (to merchant and naval ships) is very interesting. This paper presents selected results of heat-and-flow investigations of a supercritical steam-water injector, obtained in Institute of Fluid Flow Machinery, Polish Academy of Sciences (IMP PAN). On their basis value of average heat transfer coefficient for mixing chamber was determined; the obtained values were even a few dozens greater than those for classical shell-and-tube heaters. In the theoretical part of this work is presented an original injector model based on balances of mass, momentum and energy, written for control volumes containing separately particular elements of injector. On the basis of the model flow parameters in characteristic cross-sections of injector were determined. The calulations were performed for two different injectors tested in IMP PAN (Gdańsk) and SIET (Piacenza, Italy), and their good compliance with experimental data was achieved.

4

Feasibility study on application of steam injectors as feedwater heaters in supercritical Rankine cycle

Trela M., Kwidziński R., Głuch J., Butrymowicz D.

Archives of Thermodynamics

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2009

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Vol. 30, no. 4

133-147

EN

In the paper, a mathematical model of steam-water injector is presented. The model was used in heat balance calculations of Rankine cycle to examine the influence of novel injector feedwater heater system on efficiency of supercritical 600 MW coal-burned turbine unit. Also, the geometry of the injector system suitable for the considered Rankine cycle was determined. Analysis of cycle efficiency showed that application of steam-water injectors is most beneficial in the low pressure part of the Rankine cycle. Efficiency rise could be gained due to the absence of thermal degradation during the injector operation and due to its pumping work. Heat transfer coefficients for the injectors reach high values in the range of 190-806 kW/m[^2]K. Therefore, the heat transfer area in the system of injectors appeared to be smaller by a factor of 60 compared to equivalent shell-and-tube feedwater heaters. Size estimations of the new feedwater injectors shows that the overall dimensions and weight of the proposed injector system, consisting of several injectors connected in parallel, is significantly smaller compared to common shell-and-tube heaters. Exact proportions, however, will depend on detailed design of the entire system geometry.