Handle With Care
Material handling accounts for a significant portion of the total cost of producing cement. Inefficient material handling will lead to loss of time and energy while nothing is added to the value of the product. Through effective plant and equipment, many material handling operations can be mechanised, shortening process duration. The choice of material handling methods and equipment is an integral part of the plant layout design.
In many factories, the initial layout is not well though out. Again, as an enterprise expands or changes some of its produce or processes, extra machines, equipment or offices are added wherever space can be found. In other cases, temporary arrangements are made to cope with an emergency situation, such as the sudden increase in demand for a product. But these arrangements remain on a permanent basis, even if the situation that provoked them subsequently changes.
Today, for economies of operations, plant capacities are increasing, throwing up more challenges in terms of material handling. As elaborated by Jai Gupta in this issue, better options have been explored for higher capacity equipment in the same portion of land, which is the need of the hour. Gupta further talks on a few innovative approaches for material handling.
Emissions during handling
In the raw mill, the raw material feeders, stackers, blenders and reclaimers can be a source of fugitive dust emissions. Transfer points on belt conveyor systems and bucket elevators that transport raw materials from storage to the raw mill department can also generate fugitive dust. Dry raw mills and the auxiliary equipment are all designed to run under negative pressure to suppress particulate emissions.
During colder weather, vents from dryers, raw mills and air separators may exhibit a steam plume that may be mistaken for particulate emissions. Fabric filters in the vent circuits for dryers, raw mills, and air separators must be insulated to prevent internal moisture condensation.
Dust in the clinker has a tendency to become airborne during handling. The free fall of clinker onto storage piles usually creates fugitive particulate emissions. Fugitive dust emissions from open storage piles are mitigated by rain and snow which causes a crust to form on the piles. Clinker in open piles is usually reclaimed with mobile equipment, such as front-end loaders. Clinker in storage halls is frequently handled with overhead bucket cranes.
In bagging and loading operations, particulate emissions are generated from silo openings, cement handling equipment, and the various bulk and package loading operations. The dust generated during the loading of trucks and railcars is controlled by venting the transport vessel to a fabric filter. With emission norms becoming stricter, material handling will require more attention than ever before.