Manufacturing Сlinker Essay

Step1 Limestone benching, drilling and blasting In limestone benching, the quality of the input is assessed and compared with benchmarks before the additives are mixed. The benched limestone is then drilled and blasted into small pieces. Blasting takes place in two stages - primary and secondary - wherein if the limestone pieces are not small enough in the stage, they are further broken down in the second stage. After blasting, the limestone is extracted and transported for crushing.
Step 2 Crushing Here the limestone is crushed to make particles suitable for blending and storage. After this, all raw materials including additives are ground. The fineness depends on the grinding mill used. Generally, crushing is done in two stages, in a primary crusher and a secondary crusher. The primary crusher is either a mobile and self-propelled unit operating near the quarry face, or a semi-mobile unit moved at infrequent intervals, or a static unit. The secondary crusher is static unit and is used if required. Some new plants use mobile crushers, which are stationed at the mine's recovery site itself, considering the distance between the mine and the plant. At this stage, wobblers are used to eliminate already small limestone particles, which do not require crushing. This improves the crusher's throughput and reduces power consumption.
Step 3 Pre-homogeneous stage In this stage, crushed limestone is packed and transported to the reclaimer, where additives like silica, alumina, and iron ore are added to make the mixture uniform, so as to reduce chemical variations in limestone.
Step 4 Raw mill grinding Here, the raw meal (comprising limestone, clay and additives) is finely ground (so that it reacts fully) before being burnt in the kiln. There are two types of mills while vertical roller mills are used for huge capacities, ball roller mills are used for smaller plants. Choice of the mill is also influenced by the type of raw material, power consumed and project outlay. Modern mills use separators/classifiers, which separate the fine product and return the coarser particles to the grinder.
Step 5 Blending and storage The raw meal feed for a day is blended in silos, with two or more silos being used in series or in parallel. The feed is continuously blended in the first silo, while in the second one, it is homogenised further (i.e. mixed with other constituents). The feed could also be simultaneously blended and stored in one large silo, wherein blending is done through a series of orifices in the base, with limited fluidisation.
Step 6 Pre-heating stage and kiln After being blended, the raw meal is heated in a rotary kiln, or in recent times, it is also heated in a pre-heater and/ or a precalcinator to ensure better product quality. Vertical cyclone chambers are another option, where the raw material passes through the kiln and hot gases are used to pre-it as it swirls through the cyclones. The shape and size of the kiln is also central to cement-making.