The study of co-combustion characteristics of coal and microalgae by single particle combustion and TGA methods

The co-combustion characteristics of coal and microalgae with different blending ratios and under different atmospheres are studied by single particle combustion and thermogravimetric analysis methods. The combustion processes of coal, microalgae and their blends in the single particle combustion experiment have two stages, while the combustion process of coal in the thermogravimetric analysis experiment only has one stage. With the increasing blending ratio of microalgae, flames of volatiles and char of fuels become dimmer and smaller, and the average flame temperature decreases from about 1400 degrees C to about 1200 degrees C. The ignition delay time decreases from 200 ms to 140 ms, and the experimental ignition delay time of blended fuels is lower than the theoretical ignition delay time, which demonstrates that the synthetic effect between coal and microalgae exists. To analyze the influence of oxy-fuel atmosphere on the combustion characteristics, the air is replaced by the O-2/CO2 atmosphere. The replacement decreases the luminosity, size and average temperature of flames. The average flame temperature of volatiles decreases from 1449.4 degrees C to 1151.2 degrees C, and that of char decreases from 1240.0 degrees C to 1213.4 degrees C. The replacement increases the ignition delay time of fuel from 80 ms to 100 ms. Increasing mole fraction of O-2 in O-2/CO2 atmosphere can offset these influences. With the increasing mole fraction of O-2, flames of volatiles and char of fuels become brighter and larger, the average flame temperature increases from about 1100 degrees C to about 1300 degrees C, while the ignition delay time decreases from 100 ms to 77 ms. (C) 2019 Energy Institute. Published by Elsevier Ltd. All rights reserved.