Ignition of promising coal-water slurry containing petrochemicals: Analysis of key aspects

An experimental study of the macroscopic laws of the ignition of coal-water slurry containing petrochemicals (CWSPs) based on coal and flammable liquids processing waste is presented. Investigations have been performed to determine the prospects for burning such fuel mixtures prepared from raw materials in power plants at temperatures ranging from minimal (700-800 K) to high (not <1000 K). Oxidizer flow velocities varied between 0.5 and 5 m/s. The study specifies the main stages of the processes at different heating rates and heat flows through a fuel surface element (a droplet or a particle). Investigations have been conducted on a single droplet (radius from 0.25 mm to 1.5 mm) of a specified fuel composition (we have considered over 20 different compositions). With the use of cross-correlation and high-speed video cameras coupled with software applications Tema Automotive, Actual Flow, we have examined the interactions of oxidizer flow with a fuel droplet surface. The ignition delay time and durations up to complete combustion of CWSP droplets have been measured. The experimental results allowed us to elaborate the heat and mass transfer mathematical model including phase transitions and chemical reactions in the main stages of the processes under study, which are: the inert heating up of the sample, the evaporation of moisture from a superficial layer (water and flammable liquid), the thermal decomposition of coal in the superficial layer of a droplet, the mixing of volatiles with an oxidizer, the combustion initiation of the emerging gas mixture, the heating up of coke, and its heterogeneous ignition. From the mathematical model and experimental data, we have defined the necessary and sufficient conditions for the ignition of CWSP. (C) 2016 Elsevier B.V. All rights reserved.