Features of ignition and combustion of low-grade coal mixed with pyrolysis liquid

Abstract

THE RELEVANCE of the study lies in the need to use pyrolysis liquid from wood processing for combustion in boilers of medium and low power as part of mixtures with coal. The unpredictability of the ignition and combustion properties of such mixtures, as well as the lack of calculation methods, predetermined a predominantly experimental approach to the study of these processes. At the same time, for the widespread implementation of such technological solutions in practice, it is necessary to have relatively simple methods for assessing the ignition and combustion characteristics of these components. THE PURPOSE. Synthesize samples of pyrolysis liquid from two different sorts of wood and perform their characterization. Develop an experimental method for studying ignition and combustion characteristics of pyrolysis liquid mixed with low-reactivity coal. Perform research on ignition delay times and the composition of released gas-phase products. Determine the main mechanisms of action of the components in the mixture of low-grade coal with pyrolysis liquid they’re during ignition and combustion. METHODS. The study was carried out using an experimental technique based on a high-temperature muffle furnace equipped with a high-speed video camera and a once-through gas analyzer. RESULTS. The article presents the dependences of the ignition delay times and the concentration curves of gas-phase products released during combustion of mixtures of low-grade coal and two types of pyrolysis liquid in the temperature range of the heating medium 600-800 °C and additive concentrations from 0 to 20 wt.%. Linear approximation dependences of ignition delay times on additive concentrations were obtained, and the mechanism of action of the additive during combustion was formulated. CONCLUSION. It was found that an increase in the concentration of the additive in the mixture leads to a stable decrease in the ignition delay times, while the amount of gas-phase products formed varied additively with respect to the composition of the mixture. The shape of the concentration curves for the release of CO and NOx indicates the independent action of the components of the mixture. The mechanism of action of additives was proposed. It was based on significant contribution of their evaporation process followed by combustion in the gas phase, which, in turn, initiats the ignition of coal.