Reclamation of ultra-fine coal with scenedesmus microalgae and comprehensive combustion property of the Coalgae® composite

Combustion of South African discard ultra-fine coal (i.e. coal dust), charcoal, microalgae biomass, and composites of the three under air were studied. The study involves to find out the effect of Scenedesmus microalgae biomass on the comprehensive combustion characteristics of the ultra-fines. Coal dust is considered as waste material, but it could be modified and combusted for energy. The composites were designed with Design Expert, and unlike blending with the dry microalgae biomass, fresh slurry was blended with the ultra-fine coal and charcoal. Non-isothermal combustion was carried out at heating rate of 15 C/min from 40 – 900 ºC and at flow rate of 20 ml/min, O2/CO2 air. Combustion properties of composites were deduced from TG-DTGA and analysed using multiple regression. On combustion, the interaction of coal-charcoal-microalgae was antagonistic (b = - 1069.49), while coal-microalgae (b = 39.17), and coal-charcoal (b = 80.37), was synergistic (p = 0.0061). The coal-microalgae (Coalgae®) indicated first order reaction mechanism unlike, coal, and the charcoal. Comprehensive combustion characteristics index of Coalgae®, (S-value = 4.52E8) was superior relative to ultra-fine (S-value = 3.16E8), which indicated high quality fuel. This approach to combusting ultra-fine coal with microalgae biomass is partly renewable, and it would advance the production of heat and electricity. Key words: coal-dust, combustion, s-value, Coalgae®, renewable.

Combustion kinetics of lignite preheated under oxygen-enriched conditions

This study bases on the testing of the solid-state kinetic models to determine the combustion kinetics of thermally pretreated Turkish lignite (Adiyaman–Golbasi) in O2-enriched environment. The lignite sample was first preheated in a horizontal tube furnace at temperatures of 200°C, 400°C and 600°C that correspond to torrefaction, partly devolatilization and partly ashing temperatures. Oxidative environments that have the O2 concentrations of 21, 30, 40 and 50 vol.%. were created during this treatment by changing the ratio of O2/N2 in the binary gas mixtures. The solid residues remaining after oxidation were then subjected to non-isothermal combustion conditions in a thermal analyzer up to 900°C under dry air atmosphere. The conversion degrees calculated from the thermogravimetric analysis were used to establish the kinetic parameters based on the Coats–Redfern method. It was concluded that the first-order reaction model fits well for both the combustion of volatiles and the burning of the char. It was also seen that the concentration of O2 in the pre-oxidation stage plays an important role as treatment temperature also increases. Moreover, it was also concluded that the activation energies for the char burning regions of the samples treated at 200°C and 400°C differ seriously.

Non-Isothermal Combustion Properties of Plant Biomaterial Using TG-DSC Technique

Nowadays, plant biomaterials have been used in several types of industries for related purposes for example energy and electricity production, as our world is facing energy shortage problems. In this paper, the combustion behavior of a typical plant biomaterial, corn cob, was investigated using TG-DSC technique. Combustion experiments were conducted from room temperature to 900 °C at three heating rates of 10, 20 and 30°C/min in air atmosphere. It is observed that the process can be divided into three stages: dehydration (25°C-150°C), pyrolysis (150°C-380°C) and combustion (above 380°C). Besides, ignition and burnout temperature were investigated based on DSC profiles. Finally, two model-free methods (FWO and KAS) were adopted to perform the kinetic analysis for combustion reaction process. It is found that activation energies values against conversion rate present a rising trend (from about 172.40 KJ/mol to 326.95 KJ/mol) in the pyrolysis stage, while an opposite tendency was observed in the combustion stage (from about 365.55 KJ/mol to 202.86 KJ/mol), indicating that corn cob combustion is a complex process and relatively complex reaction schemes should be adopted to describe its combustion. It is anticipated that our current work could be helpful in providing reference to the design of energy conversion facilitates.