The cement manufacturing process used to produce Portland Type 1 cement at Arawak is a dry-process, rotary kiln with a five-stage suspension preheater and a grate cooler.
2.1 QUARRY OPERATIONS
The raw materials used to produce cement is obtained from a limestone quarry adjacent to the plant and from a shale (clay) quarry in Greenland. The limestone is quarried by drilling and blasting, while the shale is quarried by an excavator and transported by truck to the plant.
2.2 RAW MATERIAL PREPARATION
The raw material is crushed by two separate crusher systems and mixed in specified proportions. A fully automatic sampling station analyses the limestone-shale mixture as it emerges from the crushing plant. This is done in order to maintain correct and consistent chemical balance of the pre-blend materials. The pre- blend mixture is stored in two 8500 MT piles in the prehomo building. The mixture is then reclaimed from the building and fed to a roller mill, where it is ground to the consistency of powder. This powder is called raw meal. It is then transported pneumatically and mechanically to a storage silo from where it is fed to the kiln for burning.
2.3 KILN PLANT OPERATIONS
The raw meal is fed to the kiln for “clinkering” via a five stage preheater. At around 1200o - 1300o chemical changes occur where raw meal is converted to clinker. This clinker can either be exported or ground with gypsum to produce cement. Cement is then produced by grinding clinker and gypsum in a two-chamber ball mill.
2.4 DISPATCH OF CEMENT
The cement is stored in two 5000 MT cement silos and is then dispatched for the export and local markets. Facilities are available to dispatch cement in bulk via bulk trucks or to pack it in standard (42.5 kg) bags by means of two rotary packing machines. The bags can then be loaded directly onto ships for export or onto trucks for local delivery.
The plant has a port loading facility for unloading vessels up to 6,000 tdw. A reversible belt conveyor runs from the plant to the platform, three hundred (300) meters out to sea, where a special combi-ship loader system has been installed. These facilities also accommodate for the importation of fuel, iron ore and gypsum and the exportation of clinker, bulk and bagged cement.
2.5 FUEL AND ENERGY PRODUCTION
A constant supply of energy required for the plant is guaranteed by a 12MW diesel power station. The kiln was originally fired by fuel oil No. 6 (Bunker C). When the Kiln was restarted in 1997, orimulsion, an emulsion of bitumen and water was introduced. The orimulsion is pumped from the dock through a pipeline into the storage tanks. It is then pumped to the kiln burner via a metering and volume control system.
2.6 ENVIRONMENTAL PROTECTION
As a result of tourism being a major foreign exchange earner for Barbados, the plant was designed to blend in with its surroundings while minimising emissions. Systems such as dust extraction guarantee that the operation has the smallest effect on the environment.
2.7 PRODUCTION PROCESS
The production process is monitored and controlled from the Central Control Room. The Control Panel Operator has control over the processes involving the raw mill, kiln feeding, kiln operation, and the cement milling circuits. Separate panel operators control the crusher, packing operations, ship loading and unloading, and the power station.
2.8 QUALITY CONTROL
Process and product quality are monitored by the Quality Control Department. The laboratory regularly analyses raw materials, intermediate and final products using physical and chemical testing.
2.9 LIME DIVISION
The Lime Division produces both quick and hydrated lime products. The Plant, built in 1992 was acquired by Arawak in 1997.
The lime manufacturing process is quite similar to that of clinker manufacturing where heat energy is used to induce<