Coal Water Slurry / Carbon Slurry Fuel (CWS)
CWS is a mixture of finely milled coal or other carbonaceous materials with water or an aqueous emulsion:
CWS has almost the same viscosity as masut (heavy fuel oil) what makes it suitable both for pumping on short and long distances and for spraying into a boiler via specially designed nozzles.
Gas, oil/diesel, coal still could be used as a redundant fuel for boilers.
Coal Water Slurry Production
CWS production consists of three main parts:
- Coal crushing if the original coal size exceeds 12 mm
- Wet milling and homogenization in Wet Milling Machine
- Intermediate Storage of CWS (use and/or sale of CWS)
Raw materials for Coal Water Slurry:
- Coal of most types: brown (lignithe), gas-flame, anthracite
- Carbonaceous Raw Materials: pyrocarbon (carbon after pyrolysis of tires, rubber), petroleum coke, etc.
- Desired raw material ash content – up to 15 … 16%
Coal Water Slurry Combustion
CWS is sprayed into a boiler through EET’s pneumo-nozzle which is specially designed to spray slurry fuel.
There are three major methods for CWS combustion:
- Independent combustion in a swirl pre-chamber, which is installed in a front of boiler
- Co-firing together with existing fuel – coal, diesel/oil (HFO), gas
- Independent combustion with spraying CWS by oxygen (O2)
Combustion in swirl pre-chamber allows to burn CWS autonomously, diesel/gas required only for initial preheating.
Co-firing gives a flexibility for boiler owners to choose between fuels. Typical CWS/fuel ration is 80%/20%.
CWS can be burned in most of steam and hot water boilers. Existing boilers in most cases are upgradable by installing prechamber or simply CWS-nozzle.
Existing oil/gas boilers require installation of ash collection system or installation of pre-chamber.
CWS combustion method depends on boiler type, locally available raw materials, and other factors.
CWS Combustion in Pre-chamber
CWS co-firing in a coal boiler