Coal Water Slurry (CWS) is a homogeneous mixture of finely milled coal or other carbonaceous materials with water or an aqueous emulsion:
CWS = Coal (58% … 70%) + water emulsion (29% … 40%)
CWS has almost the same viscosity as mazut (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 (lignite), 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.
Coal Water Slurry Benefits
- CWS is used as a full or partial substitution of gas, oil, or coal in water heating and steam boilers.
- Heat produced from CWS is cheaper than from Oil, Diesel, Gas
- Ash after the CWS combustion is an ideal amendment to cement
- Gas or oil/diesel still could be used as a major or reserve fuel
- CWS could be produced from the most types of coal: brown, gas, gas-flame and anthracite.
- UNIQUE from EET: CWS produced from oil coke (petcoke) and pyro-carbon (carbon from tyres) is a perfect low-ash fuel for steam/heat boilers