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1

Higher order approximations to coal pyrolysis distribution

Paea S., McGuinness M.

Journal of Sustainable Mining

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2018

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Vol. 17, iss. 2

76--86

EN

Coal pyrolysis is a complex process involving a large number of chemical reactions. Pyrolysis is a key step in all coal conversion processes. The Distributed Activation Energy Model (DAEM) is a state-of-the art approach to the problem of predicting the amount of volatile released versus activation energy or time. The distribution of mass released is usually assumed to be Gaussian. We present an inverse iterative approach together with a smoothing function to estimate the underlying distribution directly from volatilisation data.

2

Method of choosing optimal composition of biomass mixtures

Katelbach-Woźniak A., Niestrój M., Szlęk A.

Archivum Combustionis

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2014

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Vol. 34 nr 1

27—34

EN

Biomass has high content of volatile matter, hence devolatilization process is rapid. Necessity of supplying high fluxes of combustion air is usually one of the factor which leads to high values of air excess ratio and, as a consequence to decrease of energy efficiency. However it is possible to use mixture of different sorts of biomasses and thus obtain fuel which might equalize devolatilization rate. In this paper procedure for choosing optimal mixture of given sorts of biomasses based on their composition is presented. First, pyrolysis process of hemicellulose, cellulose and lignin was conducted using thermobalance. Based on the results and assuming that there are no interactions between pure components, optimal composition of the mixture were calculated. In the next step, according to obtained optimal composition, proportions of oak, pine, rape straw and wheat straw were calculated. Finally, pyrolysis of selected biomass mixtures was carried out. It was found that due to the presence of cellulose, which decomposes in very narrow temperature range, all of mixtures are characterized by the devolatilization with local maximum occurring at the temperature around 350°C.

3

Proces pirolizy węgla w technologii podziemnego zgazowania węgla (PZW)

Urych B., Kabiesz J., Iwaszenko S.

Przegląd Górniczy

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2013

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T. 69, nr 12

42--50

PL

Podziemne zgazowanie węgla (PZW) jest kontrolowanym procesem konwersji surowca, jakim jest węgiel zalegający w pokładzie, na gaz syntezowy. Jednym z zagadnień efektywności energetycznej zgazowania jest optymalizacja zachodzących w jego trakcie procesów chemicznych, do których należy piroliza węgla. W artykule omówiono proces odgazowania calizny węgla i jego produkty. Scharakteryzowano również wpływ typu węgla i parametrów prowadzenia procesu zgazowania węgla na ilość i skład chemiczny gazu pirolitycznego. Rozpoznanie istoty procesu odgazowania w technologii PZW pozwoli w przyszłości na jego matematyczny opis, istotny z punktu widzenia zastosowań praktycznych w inżynierii chemicznej i procesowej.

EN

Underground Coal Gasification (UCG) is a controlled process which converts coal from the seam into syngas. Gasification efficiency depends on the optimization of chemical processes, including coal pyrolysis. This paper discusses the process of coal seam devolatilization and its products. It also presents the impact of coal type and process parameters on the amount and chemical composition of the pyrolysis gas. Identification of the coal devolatilization process in UCG technology will allow to produce a mathematical description in the future. This description may be a useful tool designed for practical applications in chemical and processing engineering.

4

Investigation of biomass mixture devolatilization process

Bibrzycki J., Katelbach-Woźniak A., Niestrój M., Szlęk A.

Archivum Combustionis

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2013

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Vol. 33 nr 3

155--167

EN

In this paper, pyrolysis of selected biomass types and their mixtures was investigated using thermogravimetric analyzer (TGA). The purpose of the work was to study interactions between components of biomass mixtures and influence of ash composition on pyrolysis up to 600°C, using two heating rates 1 K/min and 10 K/min. Five different biomass samples were taken into consideration: oak, pine, wheat straw, rape straw and energy crop (willow). It was found, that during slow pyrolysis (1 K/min) the volatiles yield increased and interactions were more noticeable. Results showed that increasing content of some components, like wheat straw, willow, in some biomass mixtures may favor occurrence of interactions. It was also found, that increasing heating rate accelerates devolatilization process and shifts extreme of DTG to higher temperature. Authors attempted to present volatiles yield, in a given temperature range, as a linear function of elemental composition of biomass.

5

Modeling of heat and mass transfer during thermal decomposition of a single solid fuel particle

Wardach-Święcicka I., Kardaś D.

Archives of Thermodynamics

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2013

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Vol. 34, no. 2

53--71

EN

The aim of this work was to investigate the heat and mass transfer during thermal decomposition of a single solid fuel particle. The problem regards the pyrolysis process which occurs in the absence of oxygen in the first stage of fuel oxidation. Moreover, the mass transfer during heating of the solid fuels is the basic phenomenon in the pyrolysis-derived alternative fuels (gas, liquid and solid phase) and in the gasification process which is focused on the generation of syngas (gas phase) and char (solid phase). Numerical simulations concern pyrolysis process of a single solid particle which occurs as a consequence of the particle temperature increase. The research was aimed at an analysis of the influence of particle physical properties on the devolatilization process. In the mathematical modeling the fuel grain is treated as an ideal sphere which consists of porous material (solid and gaseous phase), so as to simplify the final form of the partial differential equations. Assumption that the physical properties change only in the radial direction, reduces the partial derivatives of the angular coordinates. This leads to obtaining the equations which are only the functions of the radial coordinate. The model consists of the mass, momentum and energy equations for porous spherical solid particle heated by the stream of hot gas. The mass source term was determined in the wide range of the temperature according to the experimental data. The devolatilization rate was defined by the Arrhenius formula. The results of numerical simulation show that the heating and devolatilization time strongly depend on the physical properties of fuel. Moreover, proposed model allows to determine the pyrolysis process direction, which is limited by the equilibrium state.