Influence of the initial temperature of coal water slurries containing petrochemicals on their ignition characteristics

Highlights: • Gas-phase or heterogeneous ignition modes dominate at different initial temperature. • Decrease of initial temperature to 0 °C leads to 11–35% decrease of ignition delay. • The duration of combustion is virtually independent of the initial fuel temperature. • The minimum ignition temperature loosely depends on the initial fuel temperature. • Initial fuel temperature does not significantly boost the combustion temperature. In this research, we determined how the low temperatures of coal water slurry containing petrochemicals (CWSP) influence the ignition conditions. We have included research findings on fuel compositions that filter cakes of non-baking, low-caking and gas coals, and typical used turbine oil. The main research parameters are as follows: ignition delay time; minimum temperature sufficient for sustainable ignition; complete combustion time; maximum temperature of a droplet during the combustion process. In the experiments, we varied the following factors: types of solid and liquid components, temperature in the combustion chamber, initial size of fuel droplets. It was found that when CWSPs of five different compositions were cooled down from 20 °C to 0 °C, the ignition delay times decreased by 11–35%. The change in minimum ignition temperatures was insignificant. The difference between the maximum combustion temperatures of cooled down CWSPs as compared to ones of room-temperature fuels was 20–50 °C. The decrease in the initial fuel temperature also had very little effect on the mass of the unburnt residue and the combustion duration. Regardless of the cooling temperature, CWSP ignition delay times decreased by 70–77% when the temperature in the model furnace varied in the range of 400–900 °C. An increase in the initial temperature from 20 °C to 60 °C did not have a pronounced effect on the combustion temperature, ignition temperature, combustion temperature or ignition delay time.