H. Haykiri-Acma

Combustion characteristics of different biomass materials

In this study, the combustion characteristics of some biomass samples, such as sunflower shell, colza seed, pine cone, cotton refuse and olive refuse, were investigated. Non-isothermal thermogravimetry, where the sample was heated in air and the temperature of which increased at a linear rate of 20 K/min to 1273 K, was used to investigate the combustion characteristics of the biomass samples. The burning profiles of the samples were derived by applying the derivative thermogravimetry technique. The differences in the DTG curves of the samples were determined and discussed in detail. It was observed that the investigated biomass materials showed different combustion characteristics.

Production of fuel briquettes from olive refuse and paper mill waste

Some processes have been widely applied to biomass in order to take advantage of its energy potential. In particular, these processes are based on pyrolysis or gasification. In this study, briquetting was applied to olive refuse and paper mill waste to form fuel briquettes. For this purpose, the particle sizes of both biomass samples were decreased to −250 μm and then they were briquetted in a steel die under pressure between 150 and 250 MPa at ambient temperature. Effects of the moisture content of the biomass samples and briquetting pressure on the shatter index, compressive strength, and water resistance of the briquettes obtained were investigated. This study showed that the mechanical strength of the briquettes produced only from the olive refuse was not high enough. On the other hand, strong briquettes were produced using paper mill waste. When olive refuse was blended with fibrous paper mill waste, briquettes with sufficiently high mechanical strength could be produced. Burning profiles of the samples were derived applying derivative thermogravimetry technique under dynamic dry air atmosphere up to 1273 K with a heating rate of 40 K·min−1 and then combustion characteristics of the briquettes were compared.

FUEL BRIQUETTES FROM BIOMASS-LIGNITE BLENDS

In this study, a western Turkish lignite (Kutahya-Seyitomer) was blended with some biomass samples such as molasses, pine cone, olive refuse, sawdust, paper mill waste, and cotton refuse, and these blends was used in the production of fuel briquettes. Blends were subjected to briquetting pressures between 50 and 250 MPa; the ratio of biomass to lignite was changed between 0 and 30 wt.%. The mechanical strength of obtained briquettes was investigated considering shatter index and compressive strength. Effects of the ratio of biomass to lignite and applied pressure on the strength of the briquettes were examined. This study indicated that the mechanical strength of the briquettes produced from Kutahya-Seyitomer lignite can be improved by adding some biomass samples. For example, the presence of paper mill waste increased the shatter index of the briquettes obtained. Similarly, sawdust and paper mill waste increased compressive strength of the briquettes. Water resistance of the briquettes can be augmented by adding olive refuse, cotton refuse, pine cone or paper mill waste.

Effect of mineral matter on the reactivity of lignite chars

In this study, the effect of mineral matter on the combustion reactivity of chars produced from 25 lignite samples originating from various parts of Turkey was investigated. Char samples were produced from both original and demineralized lignites. Non-isothermal thermogravimetry has been used to determine the combustion reactivity of the samples. The combustion activation energies were calculated by the Coats-Redfern and Zsako methods from their TG data. Burning profiles of the original and demineralized lignite chars were also compared and discussed. The relationship between the carbon contents of the parent lignites and the conversions of their chars at 1273 K was studied as well. It was observed that the mineral species showed an important effect on the combustion reactivity of the char samples.

Effect of lignite properties on reactivity of lignite

The purpose of this study is to relate the combustion reactivity of lignite to its physical and chemical properties. Non-isothermal thermogravimetry, where the sample whose temperature increased at a linear rate (40 K/min) was heated in air, has been used to investigate the combustion reactivities of 25 lignite samples originating from different areas of Turkey. Since combustion reactivity is affected by the chemical and physical properties of coal, the combustion reactivity of the lignites used in this study was related to their proximate and ultimate analysis results and physical properties such as pore structure and surface area. The calculated activation energy values for the combustion reactions of the lignites ranged between 64 and 139 kJ/mol. Definite correlations between the activation energy values and the above-mentioned properties were found.

Combustion reactivity of different rank coals

Abstract In this study, the combustion reactivity of different rank coals, such as peat, lignite, bituminous coal and anthracite samples, was investigated. Non-isothermal thermogravimetry has been used to determine the combustion reactivities of the samples. The differences observed in the burning profile of the samples were studied. The calculated activation energy values of the samples were investigated, regarding carbon content, volatile matter content and burning profile peak temperature. The relationship between ignition temperature and carbon content (dmf) of the coal samples was also studied. The weight loss percentages of the different rank coal samples were discussed, depending on temperature.

Is torrefaction of polysaccharides-rich biomass equivalent to carbonization of lignin-rich biomass?

Waste biomass species such as lignin-rich hazelnut shell (HS) and polysaccharides-rich sunflower seed shell (SSS) were subjected to torrefaction at 300°C and carbonization at 600°C under nitrogen. The structural variations in torrefied and carbonized biomasses were compared. Also, the burning characteristics under dry air and pure oxygen (oxy-combustion) conditions were investigated. It was concluded that the effects of carbonization on HS are almost comparable with the effects of torrefaction on SSS in terms of devolatilization and deoxygenation potentials and the increases in carbon content and the heating value. Consequently, it can be proposed that torrefaction does not provide efficient devolatilization from the lignin-rich biomass while it is relatively more efficient for polysaccharides-rich biomass. Heat-induced variations in biomass led to significant changes in the burning characteristics under both burning conditions. That is, low temperature reactivity of biomass reduced considerably and the burning shifted to higher temperatures with very high burning rates.

Kinetic modelling of RDF pyrolysis: Model-fitting and model-free approaches

In this study, refuse derived fuel (RDF) was selected as solid fuel and it was pyrolyzed in a thermal analyzer from room temperature to 900°C at heating rates of 5, 10, 20, and 50°C/min in N2 atmosphere. The obtained thermal data was used to calculate the kinetic parameters using Coats-Redfern, Friedman, Flylnn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods. As a result of Coats-Redfern model, decomposition process was assumed to be four independent reactions with different reaction orders. On the other hand, model free methods demonstrated that activation energy trend had similarities for the reaction progresses of 0.1, 0.2-0.7 and 0.8-0.9. The average activation energies were found between 73-161kJ/mol and it is possible to say that FWO and KAS models produced closer results to the average activation energies compared to Friedman model. Experimental studies showed that RDF may be a sustainable and promising feedstock for alternative processes in terms of waste management strategies.

Effect of demineralization on the reactivity of lignites

In this study, effect of demineralization on the combustion reactivity of 25 lignite samples, originating from different areas of Turkey, was investigated. Non-isothermal thermogravimetry, where the sample was heated in air where temperature increased at a linear rate of 40 K/min to 1273 K, has been used to investigate the combustion reactivities of the original and demineralized lignite samples. The activation energies calculated by two different methods and the burning profiles of the original and demineralized samples were compared and discussed. It was observed that the combustion reactivity of the samples was considerably influenced by the demineralization process applied.

THERMOGRAVIMETRIC INVESTIGATION ON THE THERMAL REACTIVITY OF BIOMASS DURING SLOW PYROLYSIS

Agricultural biomass samples such as sunflower shell, colza seed, cotton refuse, and olive refuse were submitted to nonisothermal thermogravimetric analysis to examine the effects of the sample properties on the thermal reactivity during slow pyrolysis with heating rate of 20 K/min from ambient to 1273 K. The activation energies were determined in the range of 37.4–46.6 kJ/mol. The proximate- and ultimate- analysis results and the major constituents in biomass such as hemicellulosics, cellulosics, and lignin were found to have significant influences on thermal behavior such as the maximum decomposition rates and their temperatures, and the char yields.