Drying of Lignite in a Pressurized Steam Fluidized Bed—Theory and Experiments

Hoehne, Olaf; Lechner, Stefan; Schreiber, M. R.; Krautz, Hans Joachim

doi:10.1080/07373930903423491

Cited by 59 publications

(32 citation statements)

References 4 publications

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“…Further studies introduced the concept of the inversion point as a temperature, over which drying in superheated steam becomes more efficient than in air (Yoshida and Hyodo, 1970). As the research developed, a superheated steam fluidized bed dryer (SSFBD) was proposed and introduced into practice for lignite (Potter et al, 1984;Hoehne et al, 2009). Such a system, working in self-heat recuperation configuration, allows for reducing heat losses by recovering both sensible heat and latent heat of water vaporization (Fushimi et al, 2010).…”

Section: Experimental Methods 21 Sample Preparationmentioning

confidence: 99%

Comprehensive study on the kinetics and modelling of superheated steam drying of Belchatow lignite from Poland

Zakrzewski

Komatsu

Ściążko

et al. 2016

Mechanical Engineering Journal

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In the modern fuel mix, the leading positions are occupied by hard coal and crude oil, both accounting for around 35% of annual mined energy content (Andruleit et al., 2012). With a 2% share, lignite does not compete with the former two in the global perspective. However, easy accessibility and low production costs ensure its important role in the energy policies of particular countries worldwide. Utilization of this energy carrier is limited, though, due to the water content often exceeding 50% of raw mass. High moisture content negatively affects calorific value and precludes transportation and storage. So, lignite is less advantageous than hard coal in terms of utilization in the power generation industry. On the other hand, the usage of lignite is also considered for a wide range of applications, including coking or briquetting, and considerable volatile matter content makes it a prospective fuel for gasification purposes. Thus, the efforts made to upgrade its quality seem justified.The removal of water, contributing to increase in thermal efficiency of lignite-fired power plants, can be performed by a variety of methods, separated into evaporative thermal drying, non-evaporative thermal drying and other Marcin ZAKRZEWSKI* , **, Yosuke KOMATSU***, Anna SCIAZKO*, Taro AKIYAMA***, Akira HASHIMOTO***, Naoki SHIKAZONO***, Shozo KANEKO***, Shinji KIMIJIMA** , ***, Janusz S. SZMYD* and Yoshinori KOBAYASHI*** AbstractLow calorific value of lignite, mostly attributed to high moisture content, undermines usability of this low rank coal. Upgrading the quality of this energy carrier, which benefits coal-fired power plant's thermal efficiency, can be effectively realized by means of drying. The kinetics of superheated steam drying was studied for 30 mm spherical samples from Belchatow lignite mine in Poland. The experiment featured simultaneous and continuous measurements of weight and temperature. The drying kinetics, described by curves of moisture content, drying rate and temperature profile, were evaluated using the data acquired. The appearance of the sample throughout the process was video-recorded. Widespread cracking and shrinkage, which differ depending on the conditions, along with series of droplets typical for larger sample, were observed. The examined particles were suitable for predictions of thermodynamically derived drying rate and time, as proposed in the previous study for 5 and 10 mm particles from the same coal deposit. However, in comparison they exhibited more uniform density distribution. On the basis of experimental results and material properties, the numerical model of drying process was applied. Simulated drying behavior was consistent with empirical observations. Extensive investigation, revealing features of variously-sized samples as well as diameter dependence on drying process, is required for purposes of designing industrial drying system dedicated to specific type of coal.

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Section: Experimental Methods 21 Sample Preparationmentioning

confidence: 99%

Comprehensive study on the kinetics and modelling of superheated steam drying of Belchatow lignite from Poland

Zakrzewski

Komatsu

Ściążko

et al. 2016

Mechanical Engineering Journal

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“…Zastosowanie pary przegrzanej w technologii suszenia węgla brunatnego redukuje zagrożenie samozapłonem, zapewnia wyższy współczynnik przejmowania ciepła oraz ochronę przed utlenianiem [7]. Ze względu na powyższe cechy, zastosowanie praktyczne znalazły suszarki fluidyzacyjne na parę przegrzaną [3,5].…”

Section: Suszenie Parą Przegrzanąunclassified

Eksperymentalna charakterystyka suszenia węgla brunatnego za pomocą pary przegrzanej

Zakrzewski¹,

Ściążko²,

Komatsu³

et al. 2014

ZN PRz Mechanika

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Artykuł przedstawia wybrane zagadnienia związane z wykorzystaniem oraz osuszaniem węgla brunatnego dla potrzeb przemysłu energetycznego. Badania eksperymentalne przeprowadzono dla próbek węgla ze złoża Bełchatów suszonych w przegrzanej parze wodnej w zakresie temperatur 110 -170 [ o C] pod ciśnieniem atmosferycznym. Pomiary obejmowały zmiany wagi, rozkład profilu temperatur oraz zmiany struktury próbki. Kinetykę zjawiska opisano w formie krzywych suszenia oraz zależności szybkości suszenia i profilu temperatur od czasu, na podstawie których wyróżniono charakterystyczne fazy procesu. Charakterystyki suszenia wyznaczone w eksperymencie są niezbędne do zaprojektowania efektywnego przemysłowego systemu osuszania węgla umożliwiającego wykorzystanie ciepła utajonego zawartego w odparowanej z węgla wodzie.Słowa kluczowe: krzywe suszenia, złoże "Bełchatów", ciśnienie atmosferyczne, ciepło utajone, Okres Stałej/Malejącej Szybkości Suszenia WprowadzenieZe względu na niski koszt wydobycia, który korzystnie wpływa na cenę produkcji energii elektrycznej, węgiel brunatny jest ważnym surowcem energetycznym dla krajów dysponujących jego zasobami. Wśród państw europejskich odpowiadających za 53% globalnej produkcji tego paliwa, Polska ustępuje je-

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“…The key benefit, though, is the capability for latent heat recovery. One of the applications realizing such an idea is the superheated steam fluidized bed dryer [8,9]. In this concept, the drying system operating in a self-heat recuperation configuration enables the collection of steam from the moisture in the raw fuel, followed by the recirculation of its latent and sensible heat for the drying of another fuel portion [10,11].…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of single and multiple particles of Belchatow lignite dried in superheated steam

et al. 2018

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Low production costs have contributed to the important role of lignite in the energy mixes of numerous countries worldwide. High moisture content, though, diminishes the applicability of lignite in power generation. Superheated steam drying is a prospective method of raising the calorific value of this fuel. This study describes the numerical model of superheated steam drying of lignite from the Belchatow mine in Poland in two aspects: single and multi-particle. The experimental investigation preceded the numerical analysis and provided the necessary data for the preparation and verification of the model. Spheres of 2.5 to 30 mm in diameter were exposed to the drying medium at the temperature range of 110 to 170°C. The drying kinetics were described in the form of moisture content, drying rate and temperature profile curves against time. Basic coal properties, such as density or specific heat, as well as the mechanisms of heat and mass transfer in the particular stages of the process laid the foundations for the model construction. The model illustrated the drying behavior of a single particle in the entire range of steam temperature as well as the sample diameter. Furthermore, the numerical analyses of coal batches containing particles of various sizes were conducted to reflect the operating conditions of the dryer. They were followed by deliberation on the calorific value improvement achieved by drying, in terms of coal ingredients, power plant efficiency and dryer input composition. The initial period of drying was found crucial for upgrading the quality of coal. The accuracy of the model is capable of further improvement regarding the process parameters.Keywords Superheated steam drying . Low-rank coal .

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Drying of Lignite in a Pressurized Steam Fluidized Bed—Theory and Experiments

Cited by 59 publications

References 4 publications

Comprehensive study on the kinetics and modelling of superheated steam drying of Belchatow lignite from Poland

Comprehensive study on the kinetics and modelling of superheated steam drying of Belchatow lignite from Poland

Eksperymentalna charakterystyka suszenia węgla brunatnego za pomocą pary przegrzanej

Numerical analysis of single and multiple particles of Belchatow lignite dried in superheated steam

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