Wyniki wyszukiwania - Biblioteka Nauki

1

Wpływ starzenia chemicznego na zmiany rezystywności toru prądowego samonośnej linii napowietrznej

100%

Nowak-Woźny D.

Przegląd Elektrotechniczny

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2001

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tom R. 77, nr 3

79-83

2

Zależność rezystywności od stopnia deformacji plastycznej toru prądowego napowietrznych linii samonośnych

100%

Nowak-Woźny D.

Przegląd Elektrotechniczny

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2001

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tom R. 77, nr 6

164-167

3

Mineral phase transformation of wood and cereal pellets – electrical test and factsagetm calculations

63%

Gonzalez Valdes L. , Nowak-Woźny D.

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2016

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tom nr 3

126--134

EN

The fusion behaviour of biomass ash-forming materials is an important factor in assessing the propensity to form undesirable slag and fouling deposits in the boiler. The characteristics of the fuel used affect the extent and severity of the problem, thus growing efforts are put on finding reliable methods for its characterization. Combustion and co-combustion of biomass have gained popularity in combating climate change and reducing carbon dioxide emissions into the atmosphere. Nevertheless, biomass encompasses a wide range of different types and its use increases operational risks due to the diversity of the chemical composition. This study is based on characterising the mineral phase transformations of two kinds of biomass (wood pellets and cereal pellets) using various laboratory-based methods on fuel ashes. Measurements of changes in the electrical properties of the ash during the sintering process (dielectric loss factor) were performed using a QuadTech Plus 7600 bridge in the frequency range 500Hz - 1MHz. Thermodynamic analyses were performed by means of FactSage™ modelling. The results were compared with those of standard tests, AFT and oxide index calculations, which were employed to predict slagging and fouling propensities. The observed changes in dielectric loss depend on the frequency and temperature of sintering. FactSageTM thermodynamic equilibrium calculations proved very useful in predicting the ash melting behaviour and the chemical changes occurring in the ash. The existence of a melt phase, occurring at even lower temperatures of those given by the AFT, is in accordance with the high slagging and fouling hazards predicted by empirical indices.

4

Modyfikacja właściwości nieliniowych ceramiki warystorowej.

51%

Mielcarek W. , Nowak-Woźny D. , Prociów K. , Marycha J.

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tom Vol. 44, nr 18

21-24

PL

Typowe warystory ZnO produkuje się prasując mieszaninę ZnO z matą ilością (poniżej 3wt%) innych tlenków metali. Podczas procesu spiekania ziarna ZnO są otaczane izolującą warstwą międzyziarnową a na granicy ziaren tworzy się bariera potencjału odpowiedzialna za własności warystorowe. Warstwa międzyziarnową, której głównym składnikiem jest Bi2O3 ma tendencję do aglomeracji. Poprawę dystrybucji fazy międzyziarnowej, a tym samym własności warystorowych ceramiki ZnO otrzymano modyfikują Bi2O3 tlenkami innych metali. Biorąc jako kryterium wartość współczynnika nieliniowości w zakresie prądów 10-6 A - 10-2 A uszeregowanie stosowanych modyfikatorów Bi2Oi, od najgorszego do najlepszego, wyglądałoby następująco: Sb2O3-MnO-PbO-SrO- Co2O3.

EN

Varistor ceramics based on ZnO its non-linear current-voltage characteristics possesses due to small amount of other metal oxide and micro structure developed during sintering. Bi2O3 segregating at the ZnO grain boundaries relates directly to the value of the non-linearity coefficient a. Modifying Bi2O3 with other metal oxides appeared effective for imposing the better varistors property into the ZnO ceramics.

5

Electrical Properties of the Sintered Biomass, Sewage Sludge and Coal Ash – Part 2

51%

Nowak-Woźny D. , Moroń W. , Hrycaj G. , Rybak W.

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2013

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tom R. 89, nr 9

254-256

EN

In this paper the results of both AC electrical measurements (dissipation factors) and pressure tests carried out during the sintering of some fuel ashes are presented. The activation energies of the particular sintering processes were calculated basing on the changes of dissipation factors and assumption that the relation is of Arrhenius type. The presented results give the reason for claiming that the AC electrical method of evaluation of the ash sintering process is promising but requires further study.

PL

W niniejszej pracy zaprezentowano wyniki badań elektrycznych zmiennoprądowych (pomiary współczynnika strat dielektrycznych) oraz testów ciśnieniowych prowadzonych w trakcie procesu spiekania popiołów uzyskanych z wybranych paliw. Na podstawie zmian współczynnika strat dielektrycznych oraz przy założeniu modelu Arrheniusa, obliczono wartości energii aktywacji procesów zachodzących w popiołach podczas ich spiekania. Na podstawie otrzymanych wyników oraz przeprowadzonej ich analizy, stwierdzono że metoda badań procesu spiekania popiołów, oparta na pomiarach zmiennoprądowych, jest obiecująca lecz wymaga dalszych badań.

6

Electrical Properties of the Sintered Biomass, Sewage Sludge and Coal Ash

51%

Nowak-Woźny D. , Moroń W. , Hrycaj G. , Rybak W.

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tom R. 89, nr 2a

75--77

PL

W pracy przedstawiono wyniki badań właściwości elektrycznych (rezystywności i współczynnika strat dielektrycznych) oraz testów ciśnieniowych, prowadzonych w trakcie procesu spiekania, popiołów z osadów ściekowych, węgla kamiennego i biomasy. Na podstawie zmian rezystywności i przy założeniu modelu Arrheniusa, obliczono wartości energii aktywacji procesów spiekania. Wyniki porównano z danymi literaturowymi a także ze zmianami wartości współczynnika strat dielektrycznych (dla popiołu z węgla kamiennego). Na podstawie uzyskanych wyników stwierdzono, że metoda elektryczna oceny stopnia spiekania popiołów z badanych paliw jest obiecująca lecz wymaga dalszych badań.

EN

In this paper there are presented the results of the electrical experiments (resistivity and dissipation factor) and pressure drop test conducted during sintering process of the biomass ash, sewage sludge ash and coal ash. The activation energies of sintering processes were calculated based on resistivity changes and assuming the Arrhenius type relation. The results were discussed with the literature data and with the changes of dissipation factor (for coal ash). On the basis of the presented study it was found that the electrical method of evaluation the sintering process is promising but requires further study.

7

Bi2O3 modification for use in varistors

51%

Mielcarek W. , Prociów E. , Nowak-Woźny D.

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2003

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tom Vol. 38, nr 13

311-316

EN

Varistor operating voltage is very close to working voltage of the protected device and are not allowed to change much with time. ZnO ceramics accesses varistor property during sintering, due to addition of small amount of Bi2O3 and other metal oxides by developing potential barriers at ZnO grain boundaries. The degradation occurs, among others because a decrease in barrier height is caused by migration of oxygen ions that exist in the intergranular layers. The initial varistor properties could be restored by annealing at about 400 grad C or by doping with PbO-B2O3 based glasses. An entirely new approaches how to prevent ZnO varistor from degradation consists in modifying Bi2O3 ionic conductivity by doping it with metal ions. Ionic conductivity of systems constituted with ZnO and metal ion doped Bi2O3 were measured. It was found out that doping Bi2O3 with metal ion is effective tool of hindering varistor degradation but varistor susceptibility for degradation is not strictly connected with the high ionic B12O3 conductivity.

8

Steatite ceramics mechanical durability behavior with regard to steatite polymorphism

51%

Mielcarek W. , Nowak-Woźny D. , Prociów K.

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2004

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tom Vol. 40, nr 15

224-228

EN

Crystallites developed in steatite ceramics during sintering are the protoenstatite. The size of crystallites depends on temperature. During cooling protoenstatite crystallites invert to clinoenstatite ones, what is the cause of steatite ceramics deterioration and the loss on steatite mechanical endurance. The loss of mechanical endurance is strictly correlated with the degree of proto to clinoenstatite inversion. It was find out that there is much greater tendency for large protoenstatite to invert to clinoenstatite than for small ones. The temperature 1350 °C was find optimal for formation small, well crystallized protoenstatite crystals. This is also the temperature for which the temperature of protoenstatite to clinoenstatite inversion is the lowest and it is 250 °C.

9

Sintering Tendency of Some Ash in Correlation with Electric Resistivity and Phase Equilibrium Calculations

51%

Nowak-Woźny D. , Moroń W. , Hrycaj G. , Rybak W.

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tom Vol. 30 nr 3

177-191

EN

In order to prevent operational problems arising from ash deposition, through comprehension of the phenomena taking place within the furnace, appropriate sampling and characterization of the deposits are necessary. One of the most common approaches for the assessment of operational problems related to ash deposition is based on determining the fusion behavior of ash by measurement of its sintering temperature. In this paper are presented the results of mechanical, thermal and electrical measurements of the ash samples prepared from brown and bituminous coal, some sewage sludge and biomass. The sintering tendency of the ashes was based on the chemical analysis, Ash Fusion Test data and Equilibrium Phase Diagrams. The sintering temperature is here determined by the change in the resistivity of ash while heated at a constant rate. On the basis of these experiments results, it was made the correlation between the ashes sintering temperature and electrical resistivity of the samples. It was observed the significant changes of the electrical resistivity during the heating process. To explain the electrical characteristics of the sample, some thermodynamic calculation was made and the equilibrium phase was determined. The characteristic resistivity changes were correlated with the equilibrium phases formed during heating process.