As part of an ongoing initiative to improve the plant and its environmental performance, RAWEC is implementing an effluent treatment plant to enhance treatment of the Flue Gas Desulfurizers (FGD) residue slurry.
The function of the FGD’s is to reduce the sulfur dioxide (SO2) emissions to the atmosphere. This is achieved through a chemical reaction where limestone slurry is brought in contact with the exhaust gases and as a result gypsum is produced. As part of the existing process, residue gypsum slurry is generated. Presently this slurry is being discharged to mud ponds, then mixed with dry gypsum and finally transferred to an open gypsum storage area where it is left to dry. This gypsum is then partially recycled in local cement plants and used in the cement production process.
RAWEC has now engaged a water treatment plant company to build an Effluent Treatment Plant (ETP). The new ETP will treat the residue gypsum slurry and separate the water from the gypsum. The produced gypsum will be sufficiently dry to directly dispose of to cement plants by trucks and the produced water will be of sufficiently good quality to re-use in the FGD process.
The benefits of the new ETP will be manifold. The main benefit is a reduction in gypsum handling requirement that will save costs and reduce dust. Furthermore, the need to utilize the gypsum settlement ponds will be eliminated which will reduce contamination of the roads by gypsum when transporting the slurry. Dried up slurry on the roads and traffic movement on it is currently the main contributor to dust emissions in the plant. Reduction in dust will address environmental concerns as well as resolving technical issues related to contamination. Last but not least, particularly important in a country that has very limited natural water reserves, the new ETP will reduce water consumption because the water that is removed from the gypsum slurry can be re-introduced into the FGD process.