ppc riebeeck mine and cement factory - Aurecon AME ...

PPC Riebeeck West: Storm water Management Plan Page 25
Coal mills
Planetary
coolers
Figure 1-14: Two rotary kilns currently being used on site.
Kiln 1
Kiln 2
The clinker reaches the end of the kiln and drops into a “planetary cooler” which begins the
cooling process of the clinker. Air heated up from clinker cooling is recycled as combustion air
for the kiln so as to maximise the benefit of the heating process. From the planetary cooling
system the clinker is transported via incline dragchains to the clinker storage area in the crane
store.
Off gases such as sulphur dioxide, nitrogen oxides and particulate matter generated as a result
of the burning process in the kiln are cooled down in the conditioning tower in kiln 2 and with
fresh air for kiln 1 and released through a stack. Monitoring of emissions is undertaken through
online monitors (OPSIS on kiln 2 stack) and by calculating (doing) mass balances. Monitoring
results are used to ensure compliance to permit allocations.
Particulate emissions from the kilns are reduced through the use of electrostatic precipitators.
1.6.5 Cement milling and cement storage
Clinker, gypsum, other extenders (currently NDM limestone) and a grinding media / strength
enhancer are fed into one of 2 finishing mills (cement mills). The finishing mills are ball mills,
consisting of large steel tubes filled with steel balls rotating around their axes. On entering the
mill, the grinding media first crush the clinker particles and then, by attrition, grind them to a fine
powder. Prior to entering the mill, a small quantity of gypsum is added to the clinker. The
purpose of gypsum is to retard the setting of the cement.
PPC Riebeeck currently produces Ordinary Portland Cement (OPC) and Rapo (this may
change based on market demands). The difference in the products is that Rapo uses a