Progress and recent utilization trends in combustion of Chinese oil shale

The gradual decrease in conventional energy resources, and the growth of heavy industry, have placed great pressure on China's energy supplies. As a result of technological development, clean and diverse energy utilization facilities have become available in the energy market. Oil shale with combustible organic materials is widespread throughout the earth; many researchers have been motivated to investigate efficient means to use oil shale as an alternative energy as soon as possible.

In China, the conventional utilization of oil shale is concentrated mainly on oil shale retorting, and burning oil shale in pulverized furnaces, or bubbling fluidized beds. To improve the availability of oil shale, many specialists have advocated burning oil shale in a circulating fluidized bed (CFB), which has a satisfactory combustion efficiency, low NO_X and SO₂ emission, adaptability to low-grade coal, etc. In Huadian, China, a plant incorporating three units of 65 t h⁻¹ oil shale-fired CFB began successful commercial operation in 1996, proving that burning oil shale in a CFB produces both high combustion efficiency and environmental protection. For effective utilization of oil shale, its pyrolysis and combustion characteristics, emission performance of gaseous pollutants from an oil shale-fired CFB pilot setup, co-combustion characteristics of oil shale and high sulfur coal—as well as the operating performance of the Huadian CFB boiler—were further studied. The resulting experimental data and theoretical analysis prove that oil shale resources have significant potential use in the combustion field.

This paper introduces these fundamental characteristics and the industrial application of oil shale in combustion. Three projects are recommended for the future use of oil shale, based on the current status of energy and the characteristics of oil shale: (1) co-combustion of oil shale and high sulfur fuel for furnace desulfurization; (2) large-scale development of oil shale-fired CFBs; (3) a comprehensive oil shale utilization project to produce shale oil, burn oil-shale semicoke in a CFB boiler to generate electricity and supply heat, and produce building materials with oil shale ash.