Coalwater

Coalwater, or coal-water slurry fuel (CWSF), is a suspension of finely ground coal in water, sometimes with additives to improve stability and combustion. It is designed to be pumped and burned much like a liquid fuel in specially prepared burners, while leveraging coal as the energy source.

Production typically involves milling coal to a fine particle size and mixing it with water to create a viscous slurry. Solid contents commonly range from about 40 to 70 percent by weight, depending on the desired viscosity and pumpability. Additives such as stabilizers or surfactants may be used to enhance suspension stability and flow characteristics. The rheology of the slurry affects handling, transport, and atomization in burners.

Applications have included industrial boilers, cement kilns, and retrofitted power plant burners in certain regions. Coalwater slurry can enable the use of coal in systems originally designed for liquid fuels, potentially reducing dust and handling hazards compared with dry coal and providing an alternative to oil or gas in some contexts. It has been explored as a way to utilize lower-grade coals that are less suitable for direct combustion.

Advantages and limitations are balanced. Advantages include improved flow properties for transport, reduced dust, and potential compatibility with existing oil or gas-fired equipment after conversion. Limitations include lower energy density per unit mass due to the water content, higher pumping energy requirements, and viscosity-related challenges. Combustion still releases carbon dioxide and other pollutants associated with coal, and water management as well as ash handling remain considerations. Corrosion and erosion from the slurry can affect plant components if not properly designed.

Historically, coalwater slurry research emerged in the mid-20th century and has persisted as a niche technology in some regions, notably in parts of Asia and Eastern Europe, where it is pursued in pilots or retrofit projects rather than as a widespread utility fuel.