Combustion Characteristics of Ultrafine Coal Particles-Light Diesel Oil Mixtures in a Cylindrical Horizontal Furnace

Abstract

This work presents an experimental study that aims at investigating the effect of loading-ratio of coal in a coal-diesel fuel mixture on the combustion characteristics and exhaust emissions. Sub-bituminous coal from El-Maghara coal mine is utilized. It is washed, dried, and grounded to particle sizing of ≤ 30 μm. The experiments are conducted inside a horizontal, segmented water-cooled cylindrical furnace fitted with a coaxial burner having a central air assisted atomizer for oil-coal mixture admittance. All experiments are executed at constant input heat of 350 kW and air to fuel ratio of 15:1 while varying the percentage (mass basis: 5% and 10%) of coal in the fuel mixture. The measurements within the flame zone include mean gas temperatures, dry volumetric analyses of species (CO2, NOx, and O2) concentrations, and the accumulative heat transfer to the cooling jacket along the combustor. All measurements are compared regarding the pure oil flame. The results indicate that increasing the coal- loading ratio up to 5wt% leads to a progressive increase in the accumulated heat transferred and the combustor overall efficiency from 40% to 58% within a percentage increase around 45%. In addition a slight reduction in mean gas temperature within the flame zone when compared with the pure oil flame. The reduced flame temperature due to increasing the coal-loading ratio, caused a decline in the volumetric concentrations of NOx from 100 ppm to 20 ppm as expected.

The Combustion of a Diesel Oil-Based/Coal/Water Slurry in a Horizontal Cylindrical Furnace: An Experimental Investigation

“…A comparative analysis of the different mixtures was produced in terms of ignition delay times, minimum ignition temperatures, the heat of combustion, anthropogenic emissions concentration, and the relative efficiency of fuels. The combustion characteristics of sub-bituminous, ultrafine coal particles-light diesel oil mixtures were investigated inside a horizontal, water-cooled cylindrical furnace, with a coaxially fitted burner provided with an airassisted nozzle essential for the different-blended mixtures atomization [11]. To decrease the environmental impact of the burning of oils and coal-oil slurries, the coal-water slurry is considered a promising fuel to mitigate hazardous emissions such as nitrogen oxides and sulfur oxides.…”

“…The switching from conventional burning of Egyptian coal (EC) to oilbased, coal, and water slurries has not been investigated. The main objective of the present work is to extend our work in [11]and investigate the combustion characteristics of an oil-based, coal, and water slurry containing light diesel oil (grade 2), distilled water, and Egyptian coal (EC) without using chemical additives. Under constant input heat conditions and variable air/fuel ratios, experiments were conducted on two different combustion modes (Diesel oil flame, COWS flame) and three-different flames of various blends (Oil/Coal/Water).…”