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Combustion characteristics were studied experimentally for single droplets of fuel slurries based on wet coal processing waste with municipal solid waste components (cardboard, plastic, rubber, and wood) and used turbine oil. We established the ignition delay time for three various groups of fuel compositions in motionless air at 600–1000 °C. The minimum values are 3 s, and the maximum ones are 25 s. The maximum temperatures in the droplet vicinity reach 1300 °C during fuel combustion for compositions with 10% of used oil. The combustion temperatures of fuel compositions without oil are 200–300 °C lower. The concentrations of anthropogenic emissions in flue gases do not exceed those from dry coal combustion. Adding used oils to composite fuels reduces the concentrations of dioxins and furans in flue gases when municipal solid waste in the fuel burns out due to high combustion temperatures. Based on the experimental research findings, we have elaborated a strategy of combined industrial and municipal waste recovery by burning it as part of composite fuels, as illustrated by three neighboring regions of the Russian Federation with different industrial structures and levels of social development. This strategy suggests switching three typical coal-fired thermal power plants (one in each of the regions) to composite liquid fuel. It will reduce the hazard of waste to the environment and decrease the consumption of high-quality coals for power generation. Implementing the developed strategy for 25 years will save 145 Mt of coal and recover 190–260 Mt of waste. The positive economic effect, considering the modernization of fuel handling systems at thermal power plants and the construction of a fuel preparation plant, will make up 5.7 to 6.9 billion dollars, or 65–78%, respectively, of the main costs of three thermal power plants operating on coal within the identical period.

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An experimental study has been conducted into the ignition and combustion processes of composite fuel droplets fed into a heated muffle furnace on a holder. Consistent patterns and characteristics of physical and chemical processes have been established for a group of fuel compositions: wet coal processing waste (a mixture of fine coals and water) 85% + municipal solid waste (wood, or plastic, or rubber) 10% + used oil 5%. Burning a coal-water slurry instead of dry coal dust is characterized by a positive environmental effect. Adding used oil to a coal-water slurry results in better energy performance characteristics of the composite fuel during combustion. Adding fine municipal solid waste (MSW) to the fuel composition makes it possible to effectively recover it by burning in boiler furnaces with energy performance characteristics of combustion and environmental characteristics of flue gases that are as good as those of composite fuel compositions without MSW. Sustainability of the composite fuel ignition process and complete burnout of liquid and solid combustible components have been determined. The values of the guaranteed ignition delay times for droplets with a size (diameter) of about 2 mm have been established for the composite fuel compositions under study in the ambient temperature range 600–1000 °C. The minimum values of ignition delay times are about 3 s, the maximum values are about 15 s under the near-threshold ignition conditions. The obtained findings enabled to elaborate the main elements of the strategy for combined recovery of industrial and municipal waste by burning it as part of composite fuels.