Ignition behaviour and flame stability of different ranks coals in oxy fuel atmosphere

• We present research studies on ignition and flame stability in the oxy-fuel atmosphere.
• We use five coals – three black coals and two brown coals.
• We use three atmospheres i.e. air, dry RFG and wet RFG.
• A type of gas with which O2 was mixed had a fundamental impact onto the characteristics of ignition.
• The specific thermal capacity and density of main gases making up a mixture with oxygen are of fundamental importance.

The aim of the research has been to investigate the impact of a type of atmosphere onto the ignition of fuel and the stability of dust–gas flames. Three black coals and two brown coals were applied in the research. It covered performing their physicochemical analyses and determining the induction time of ignition of single particles and dust–air cloud as well as parameters of dust flames and their stability. The research program referred to various aspects of the ignition of fuel, including: effects of its temperature, size of grains, type of atmosphere (air, O2/CO2), O2 share (5–30%) in the O2/CO2 atmosphere. The conducted research highlighted that the ignition of fuel is connected with a degree of its carbonisation, temperature and the type of atmosphere at which it takes place. The ignition of black coals is more difficult (hindered) than the one of brown coals. For its enhancement it is required to apply (among others): higher oxygen concentrations, higher dust concentrations, fined dust milling or higher ambient temperatures. A type of gas (N2, CO2) with which oxygen was mixed had a fundamental impact onto the characteristics of ignition. For all the examined coals, the induction times of ignition of dust cloud measured in the air atmosphere were shorter than the ones measured in the oxy atmosphere. The presented research demonstrated that – for the stability of flames and the parameters of fuel – the specific thermal capacity and density of main gases making up a mixture with oxygen are of fundamental importance.