The researchers from many countries are currently developing new eco-efficient fuel compositions. Such promising fuels include water-coal suspensions (WCF). But the ignition delay times of WCF particles are sometimes tens of seconds (up to 30–40). One of the possible methods to increase the reactivity of WCF is to add additives “accelerating” the ignition process, for example biomass, to its structure. This is already a complex composite bio-water-coal fuel (Bio-WCF). The physical theory and mathematical base of the processes of ignition and combustion of Bio-WCF drops have not been developed yet. The article presents the results of the theoretical and experimental studies of the ignition of substantially inhomogeneous drops of bio-water-coal fuel based on long-flame coal and woodworking waste. We have found that the addition of wood to the composition of water-coal composites leads to a significant reduction (up to 50%) of the entire induction period (ignition delay time — tign). According to the results of the experiments, the influence of the type of wood on the characteristics and conditions of ignition of the bio-WCF drops has been analyzed. It has been shown that pine-based bio-water-coal fuels ignite faster than larch and birch bio-WCF. We have developed a mathematical model that describes the combined course of the main processes of heat and mass transfer under conditions of the intensive phase (water evaporation) and thermochemical transformations (thermal decomposition of organic coal and wood). The corresponding non-trivial problem has been solved. Based on the results of the numerical simulation, we have established the theoretical values of tign. A comparative analysis of the theoretical and experimental values of tign has shown their good agreement. According to the results of the mathematical modeling, the temperature regimes of ignition of the bio-WCF particles have been established, which significantly differ from the ignition regimes of drops of water-coal fuel. It has been shown that the dynamics of the ignition of the bio-water-coal fuel particles is significantly affected by the type of wood fuel component. Based on the results of the mathematical modeling, the effect of the composition of volatiles on the characteristics and conditions of ignition has been analyzed. It has been shown that the content of hydrogen and methane in coal has a significant effect on the dynamics of ignition. As a result of the mathematical modeling, the limiting (in terms of ambient temperature) ignition modes of the fuel have been established.
ASJC Scopus subject areas
- Civil and Structural Engineering
- Building and Construction
- Mechanical Engineering
- Industrial and Manufacturing Engineering
- Electrical and Electronic Engineering