A. Szlęk

Methods of choosing the optimal parameters for solid fuel combustion in stoker-fired boilers

Stoker-fired boilers are used for the combustion of coal and solid wastes. The most important disadvantage is their low thermal efficiency. The authors present methods of choosing the optimal rate of travel of the grid and height of the fuel layer basing on both realscale and laboratory measurements. Basing on industrial-scale experiments the authors calculated the optimal thermal efficiency and main energy losses using the least squares adjustment method. The stepwise regression method was used to correlate the main energy losses as functions of grid operating parameters. These correlations were used in the optimization method to estimate the optimal rate of travel of the grid and height of the fuel layer. The minimum retention time of the coal can be also calculated.

Identification of the boundary surfaces in 3D finite element codes

Abstract For a given 3D FEM net defined by a domain connectivity array a boundary connectivity array is generated. The latter contains boundary nodes over which subsequent boundary elements are spanned. An algorithm can be used to check the consistency of the input connectivity array. It can also be useful in pre and postprocessors in hidden lines removal. A list of appropriate routines is included.

Ignition characteristics of vegetable fuel oils in fuel spray

AbstractThe present paper concerns the ignition of single droplets of mixtures of rapeseed oil and fuel oil that was used as the biofuel. A special apparatus was built to measure fuel ignitability. On the basis of the measurements the ignition delay time of a droplet was determined as a function of temperature, biofuel composition and droplet size.The experimental results show that the biofuel composition as well as the ambient temperature in the experimental cylinder has a fundamental impact on the ignition phenomenon. Moreover, the results show that the droplet size is also of significance. The influence of the main factors on the delay time of ignition was given by an equation describing the ignition delay time as a function of temperature and the fuel oil fraction.

Optimisation of a heating curve in a district heating network with respect to heat transport cost

AbstractThe aim of the present work was to optimise a heating curve (relationship between supply water temperature and outside temperature) in an exemplary district heating network and to evaluate possible savings of the heat transport cost. A numerical model of the heat network was built up in order to simulate and analyse behaviour of the network in respect to many parameters (e.g. temperatures, pressures, water flows). The results showed that the optimal heating curve differed from the one presently used. Selection of the optimal supply water temperatures should be carried out taking into account geometry, characteristic of a given network and prices of heat and electricity. The optimisation of the heating curve appears to be a practically costless process that can bring a significant decrease in the heat transport cost in the heat network.

Characterization of Biomass Fuels in Isothermal Plug Flow Reactor (IPFR)

Spalovani fosilnich paliv je jednim z nejdůležitějsich zdrojů energie. Nicmeně nizkouhlikova politika a environmentalni zavazky ovlivňuji vývoj spalovacich a spolu-spalovacich technologii. Využivani paliv z biomasy může být odpovědi na nove výzvy, i když je zapotřebi vice výzkumu o efektivnim využiti těchto paliv. V soucasne době spalovani paliv z biomasy, zejmena slamy, způsobuje řadu technických problemů, zejmena tvorbu strusky, zanaseni výměniků tepla uvnitř spalovaci komory a nedostatecne vyhořeni paliva. Tento přispěvek se zaměřuje na analýzu spalovanibiomasy. Lepsi znalost chovani procesů při spalovani biomasy může přispět k optimalizaci navrhu praskoveho kotle a vyhnout se tim technickým problemům. Výsledky výzkumu ukazuji, že teplota a koncentrace kysliku v reaktoru hraji významnou roli v procesu tvorby prchave hořlaviny a vyhořeni tuheho zbytku. Napřiklad během experimentů s vyhořelým tuhým zbytkem při teplotě 850 ° C při 14% koncentraci kysliku po 200 ms bylo dosaženo vice než 80% ubytku hmotnosti. Ve srovnani se 700 ° C při 14% koncentraci kysliku byla stejna uroveň ubytku hmotnosti dosažena po 500 ms. Experimenty provedene na izotermickem reaktoru (IPFR) v Institutu energetických procesů a technologii paliv (IEVB) na TU Clausthal byly soucasti projektu mezi IEVB a „Karlsruhe Institute of Technology (KIT)“ v Německu.

22nd International Symposium on Combustion Processes

This special section of Energy & Fuels contains selected papers from the 22nd edition of the International Symposium on Combustion Processes (ISoCP 2015), held on September 22− 25, 2015, in Polish Jurassic Highland, Poland. The International Symposium on Combustion Processes has more than a 50 year tradition as the most important scientific event in Poland in the field of combustion science. It is organized every 2 years under the auspices of the Section of Thermodynamics and Combustion of the Polish Academy of Sciences and Polish Section of the Combustion Institute. The first symposium was organized in 1968. Originally, they were intended to provide a meeting place for scientists from the east and the west. Over the years, many distinguished scholars attended and presented papers and some of them came regularly for years. The Institute of Thermal Technology of the Silesian University of Technology in Gliwice had the honor of being the organizer of the 22nd edition of the symposium. The conference was held in Orle Gniazdo Hotel (The Eagle’s Nest) situated in the heart of the picturesque Polish Jurassic Highland (Jura Region). The Jura Region is a unique area in terms of both its history and its geography and lies in the south-central part of Poland, caught between Cracow in the south and Czestochowa in the north. Its main attractions include beautifully shaped karst landforms in Jurassic limestone, abundant caves, and medieval castles. The conference brought together 101 participants from 14 countries and 4 continents. The program of ISoCP 2015 included 70 oral presentations and over 30 posters covering a very broad range of topics, including gaseous, liquid, and solid fuels combustion chemistry and physics, combustion in engines, combustion-generated pollutants, high-temperature combustion, fires and explosions, detonations, combustion diagnostics, carbon capture and sequestration (CCS) technologies, gasification, and alternative fuels. Seven plenary lectures were delivered: (1) Mario Ditaranto (Sintef, Norway), Gas turbine combustion in carbon capture technologies; (2) Bogdan Dlugogorski (Murdoch University, Australia), Formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) and related molecules in combustion processes; (3) Jouni Hamalainen (VTT, Finland), Role of fossil fuels power plants in energy systems; (4) Janusz Kozinski (York University, Canada), Oxidation and flames in supercritical water; (5) Simona Merola (Instituto Motori, Italy), Optical diagnostics of combustion anomalies in SI engine; (6) Andrzej Sobiesiak (University of Windsor, Canada), Advanced fuels and combustion strategies for reduced combustion emissions from automotive engines; and (7) Roman Weber (Technical University of Clausthal, Germany), Contemporary problems of pulverized fuel combustion. The keynote speakers, the members of the scientific committee, and all session chairs are thanked for their generous contributions. The Organizing Committee expresses its gratitude to the Energy & Fuels editorial board, who agreed to devote a special section of the journal to publish the selected papers presented at ISoCP 2015. Andrzej Szlek, Conference Chair Institute of Thermal Technology, Silesian Technical University, Konarskiego 22, 44-100 Gliwice, Poland

Influence of biomass blending on pyrolysis process using TGA-FTIR technique

Devolatilization is the most important step in the biomass combustion. It is beneficial to use a fuel, which releases volatiles in a wider range of temperature that make easier proper air distribution. The main objective of this paper is influence investigation of biomass mixing on devolatilization process. Thermobalance coupled with FTIR spectrometer has been used for investigation of devolatilization process and analysis of released gases composition. For the experiments inert atmosphere, sample mass of 50 mg and heating rate of 10 K/min have been used. As investigated fuels, the most popular types of biomass such as pine, willow and wheat straw have been used. Results show that by mixing different types of biomasses one can influence maximal rate of pyrolysis (DTGmax), corresponding temperature and composition of released volatiles. Results prove existence of interactions between different sorts of biomass.

Boiler Modelling of Simple Combustion Processes

The aim of the work is to investigate coal combustion in fixed bed reactor. The experimental results were worked out in the form of approximation functions describing gas composition at the exit of fixed bed reactor. Furthermore, developed functions were applied for defining the boundary conditions at the interface between the fixed bed and gas phase using FLUENT. The simulations of a domestic boiler have been done and the relative effects of different factors in CFD code were evaluated by sensitivity analysis. The validity of the model was verified by measurements which were done in a 25 kW domestic boiler. Model predictions were compared with the experimental gas temperature and species concentration measurements.

SIMULATION OF COAL COMBUSTION PROCESS IN SMALL BOILER

The aim of the work is to develop a method of simple characterization of solid fuels combustion in fixed bed, which would be useful for CFD modelling. In this work, the measurements were performed in a test rig, where a combustion front propagates against the airflow. Concentrations of flue gas species were registered at the exit of a fixed bed reactor and the temperature of burning coal was measured in selected points of the reactor as functions of time.

Combustion characteristics of isothermal expansion

AbstractIn this paper, chemical calculations of methane combustion during isothermal expansion are presented. Such a process could be applied in an isothermal turbine, which would greatly increase the overall thermal efficiency of a gas turbine cycle. It has been found that by diluting combustion air with steam water, a mild combustion, without rapid pressure changes, can be achieved. It was also found that the emission of nitric oxides from such a process is extremely low.