Best Available Technology
The Ohorongo plant incoprporates all the benefits of most modern technology, both in terms of output and environmental sensitivity. Use of highly efficient raw material and coal grinding mills allow for savings in the consumption of electrical power in excess of 30% compared to traditional mills. Through air staging and meal splitting the Precalciner reduces NOx emissions by more than half. By using state-of-the-art bag house filter technology, dust emissions are reduced to less that 20mg/ m³. In addition, the Ohorongo plant is fully equipped to replace up to 100% of coal with alternative fuels such as wood chips in its kiln.
Raw Material Production and Grinding
The most important raw materials for the production of cement are limestone, clay and marl. These raw ingredients are mined at Ohorongo’s quarry in specified ratios and then transported to the crusher where they are ground to the consistency of rough gravel.
Storage and Homogenisation
The crushed limestone, shale and marl are conveyed to the mixing bed where the gravel is mixed to a homogeneous material. The chemical composition of the material is carefully monitored to ensure that it contains the correct proportions of limestone, shale and marl. If the proportions differ from those specified by the quality department, the combination of materials is adjusted accordingly.
Drying and Primary Grinding
The essential additives quartz, sand and iron ore are added to the homogenised materia and this mixture is then ground to a powder with the consistency of fine flour. Simultaneously, the mixture is dried by means of heat generated from the firing process. After ascertaining once again that the chemical composition is correct in terms of the quality directives, the raw meal is then transferred into the raw mix silos.
In the 109m high preheater tower, the raw-meal is pre-heated by utilising the excess heat from the rotary kiln. By utilising the excess heat from the kiln, the actual burning process of transforming raw meal into clinker is shortened significantly, saving time and energy.
After the raw meal has been processed in the preheater it enters the rotary kiln where the material is burned to clinker at temperatures of 1,450 °C. After firing, the clinker is cooled and thereafter stored in clinker silos.
The clinker is dosed with an appropriated quantity of gypsum and, in specific cases, high grade limestone, if required, and finally milled to cement.
Loading, Packaging and Dispatch
Most of the cement produced at Ohorongo is dispatched and delivered in cement bags. However, bulk cement is available in loose form and is transported via road, rail and sea.
Highly-qualified personnel continuously monitor every step of the entire production process, from the quarry to dispatch, to ensure the highest quality standards and to provide absolute customer satisfaction. Wherever and whenever required, any part of the process is adjusted immediately.