A review on slurry-based fuels for engines and furnaces: Preparation, stability, emission characteristics and applications

Our society is mainly propelled by energy, which powers our daily activities, transportation, and industries. However, the continued reliance on fossil fuels to provide energy has led to several environmental problems, including air pollution, climate change, and the depletion of essential resources. Presently, the research focus is on getting energy from alternative resources to reduce the amount of greenhouse gasses that cause global warming. Slurry fuels can be used as alternative fuels in engines and furnaces. In this comprehensive review, we initiated the discussion by examining various slurry types, such as coal, charcoal, wood, etc., with a detailed focus on their respective advantages and disadvantages. Subsequently, we provided a summary of the preparation methods and feedstock, emphasizing the significance of each preparation process. The characterization of slurries, encompassing chemical composition and fuel properties as well as the influence of particle size, were systematically addressed. Additionally, we delved into the flow characteristics and the impact of surfactants on fuel stability. Furthermore, the review tackled ignition behavior and emission characteristics, essential properties for assessing the practicality of fuels. The challenges in using slurry fuels encompass a range of issues, from combustion efficiency, ignition characteristics, and engine wear to the intricate blending of combustible components with different thermophysical properties. These challenges are further complicated by non-linear relationships in ignition temperature. In the end, we highlighted the insight into opportunities and challenges associated with slurry fuels for future researchers.