D Dragoslava Stojiljkovic

A steady state model of agricultural waste pyrolysis: A mini review

Agricultural waste is one of the main renewable energy resources available, especially in an agricultural country such as Serbia. Pyrolysis has already been considered as an attractive alternative for disposal of agricultural waste, since the technique can convert this special biomass resource into granular charcoal, non-condensable gases and pyrolysis oils, which could furnish profitable energy and chemical products owing to their high calorific value. In this regard, the development of thermochemical processes requires a good understanding of pyrolysis mechanisms. Experimental and some literature data on the pyrolysis characteristics of corn cob and several other agricultural residues under inert atmosphere were structured and analysed in order to obtain conversion behaviour patterns of agricultural residues during pyrolysis within the temperature range from 300 °C to 1000 °C. Based on experimental and literature data analysis, empirical relationships were derived, including relations between the temperature of the process and yields of charcoal, tar and gas (CO2, CO, H2 and CH4). An analytical semi-empirical model was then used as a tool to analyse the general trends of biomass pyrolysis. Although this semi-empirical model needs further refinement before application to all types of biomass, its prediction capability was in good agreement with results obtained by the literature review. The compact representation could be used in other applications, to conveniently extrapolate and interpolate these results to other temperatures and biomass types.

Devolatilisation of some pulverised Eastern European lignites

AbstractThe devolatilisation behaviour of two pulverised lignites from Eastern Europe was investigated particularly with respect to the kinetics of pyrolysis. Two rapid heating methods, the heated wire mesh and a Pyroprobe have been used to determine the yield of the volatiles and particularly the nitrogen containing species, HCN and CH3CN. The kinetic parameters for devolatilisation have been obtained from thermogravimetric apparatus and by wire mesh experiments. The experimental data were compared with values predicted using the theoretical model coal pyrolysis, model FG-DVC and with other studies on lignites.

Biomass gasification technology: The state of the art overview

The reduction of imported forms of energy, and the conservation of the limited supply of fossil fuels, depends up on the utilization of all other available fuel energy sources. Biomass is a renewable energy source and represents a valid alternative to fossil fuels. The abundance of biomass ranks it as the third energy resource after oil and coal. Moreover, when compared to fossil fuels, biomass fuels possess negligible sulphur concentrations, produce less ash, and generate far less emissions in to the air. In other words, biomass can deliver significant greenhouse gas reductions in electricity, heat and transport fuel supply. The energy in biomass may be realized by different thermochemical technologies of which gasification is most promising alternative routes to convert biomass to power/heat generation and production of transportation fuels and chemical feedstock. This paper deals with the state of the art biomass gasification technologies, evaluating advantages and disadvantages, the potential use of the syngas and the application of the biomass gasification. Also, this paper provides short overview of the current status of the biomass gasification in Serbia.

Mathematical Modelling and Performance Analysis of a Small-Scale Combined Heat and Power System Based on Biomass Waste Downdraft Gasification

The paper presents a simple mathematical model for designing, optimizing and simulating small–medium CHP scale plant with use of biomass waste downdraft gasification. A downdraft gasifier has been used as the starting point in the study, due to its low tar content and effective way of using heat in the engine’s exhaust gases to dry and pyrolyze the different solid biomass waste. Hot water from the cooling circuit of the engine and from producer gas cooling is directly used for the district heating network, air or steam preheating. The mathematical model includes modelled components as a downdraft gasifier, an internal combustion engine using the characteristic equation approach method. The mathematical model enables the outputs of the plant to be evaluated and calculated for different types of biomass and operating conditions. The results demonstrate that it is a useful tool for assessing the performance of CHP plants using several types of biomass waste and enables comparisons to be made between operating conditions for real applications.

TGA-DSC-MS Analysis of Pyrolysis Process of Various Biomasses with Isoconversional (Model-Free) Kinetics

Slow pyrolysis characteristics of different biomasses (hazelnut shell (HS), sawdust (Beech), and sawdust chemically treated (SDCT)) were investigated by simultaneous thermal analysis (STA), coupled with mass spectrometry (MS). Thermal decomposition of these samples was divided into three stages corresponding to removal of water, devolatilization, and formation of bio-char. It was found that differences in thermal behavior of the samples are due to differences in their composition. Mass spectrometry results showed that H2, CH4, H2O, CO2 (C3H8), CO, and C2H6 were the main gaseous products released during pyrolysis. It was shown that HS could be a good fuel, since during its pyrolysis at high temperature, more gaseous products are released compared to other systems. Isoconversional (model-free) method was used in order to determine variation magnitudes of effective activation energy (Ea) values on conversion fraction (α) during pyrolysis. It was found that identified variations of Ea with α arise from the different chemical structures among cellulose, hemicelluloses and lignin in tested samples that may affect on their effective activation energies.

Thermogravimetric kinetic study of solid recovered fuels pyrolysis

In the Republic of Serbia there are significant quantities of coffee and tire wastes that can be utilized as Solid Recovered Fuel (SRF) and used as an additional fuel for co–combustion with coal and biomass in energy production and cement industry sectors. Differences between SRF and base fuel are cause of numerous problems in design of burners. The objective of this study was to determine the kinetic parameters for the thermochemical conversion of selected SRF using Simultaneous Thermal Analysis (STA). Samples of coffee and tire waste were used for the experimental tests. Thermal analysis was carried out in nitrogen atmosphere at three different heating rates 10, 15 and 20 K/min for each sample, while it was heated from room temperature up to 900°C. Two sample sizes x <0.25 mm and 0.25 < x <0.5 mm of each SRF were used in experiments, in order to obtain reliable Thermal Gravimetric Analysis (TGA) data for estimation of kinetic parameters for SRF pyrolysis. Experimental results were used for determination of pre-exponential factor and activation energy according to methods presented in the literature. Presented research provide valuable data of coffee and tire waste, that can be used for the burners design.

Research Overview, Gaps, and Recommendations

Abstract Modeling biomass supply and logistics has been included both directly and indirectly in European research and several initiatives have taken place through the last 15 years. Research has evolved from narrow assessments covering single or a few feedstock types and specific regions to harmonized approaches with consistent algorithms applied across Europe at different regional and temporal scales. The aim of this chapter is to provide an overview of research work in the area, identify gaps in research knowledge, and provide recommendations for future to research in the field of modeling biomass supply and logistics.

Investigations of combustion process in combined cooker-boiler fired on solid fuels

The aim of the investigation was to make some reconstructions on the existing stove used for cooking and baking and to obtain the combined cooker-boiler which will fulfill the demands of European standard EN 12815. Implementation of modern scientific achievements in the field of combustion on stoves and furnaces fired on solid fuels was used. During the investigations four various constructions were made with different fresh air inlet and secondary air supply with the intention to obtain more complete combustion with increased efficiency and reduced CO emission. Three different fuels were used: firewood, coal, and wood briquette. A numerous parameters were measured: fuel weight changes during the combustion process, temperature of inlet and outlet water, flue gas composition (O2, CO, SO2, CO2, NOx), flue gas temperature, ash quantity etc. The result of the investigations is the stove with the efficiency of more than 75% - boiler Class 1 (according EN 12815) and CO emission of about 1% v/v. The results obtained during the measurements were used as parameters for modeling of combustion process. .