Cement, Energy and Environment

In general, higher silica Mix 2 uses an iron oxide and Further data needed ratios are difficult to burn in the assumes that all the raw Chemistry cement kiln, this is due to the materials could be homogenized As well as basic data difficulty of milling and and the average compositions concerning the lime, silica, combining quartz when present used at all times. Whether this alumina and iron oxide in the in the feed. The silica was is possible depends on the raw materials, the presence of present largely as sandy configuration of the deposit, any other minor constituents needs inclusions in the oolitic part of restrictions on excavations and to be established at an early the sequence. The practicality the costs of recovery and stage. There are also other of grinding this sand in the same blending. possible constituents of the mill as the limestone would need Mixes 3 and 4 suggest that materials which need to be to be considered when adequate mixes with the same assessed, including alkalis and designing the plant for clinker clinker composition could be potentially dangerous elements, making. Excessively c;:o=ar:..:s:.::e_______________ ~ in particular arsenic, sand in the raw feed antimony, barium, leads to clusters of belite beryllium, cadmium, crystals as in Figure 1 chromium copper, lead with resulting poor manganese, quality and high energy molybdenum, mercury, costs. nickel, selenium, silver, Raw mix design The example mixes in Table-2 are not final designs, but are indications of the possibilities with the information available. The use of three raw materials to make cement clinker is acceptable, but would give limited control over the LSF, SR and AF. With three raw materials only two parameters could be controlled and the stability of the cement kiln might be comprised. With the raw materials available the AF Ratio cannot be reduced below about 2.5, the example in Table-1 is Mix 1 with AF 2.63. The use of a fourth material would be essential to optimize the feed burnability in the cement kiln with minimal energy expenditure and maximum output. The material should be iron oxide-rich so that the alumina-to-iron ratio could be maintained constant. This would prolong kiln campaigns and maximum output from the kiln. made from the averages of the either the bioclastic limestone or the oolite (as estimated from the limited data available) and therefore that the whole of the deposit should theoretically be usable. From the borehole logs and the variability of the chemical analyses, the quality of the argillites would need further analysis. This would require modelling of the deposit to determine the possibilities for extracting consistent material at the same time as extracting the underlying limestones. titanium, thallium, vanadium and zinc. Reserves available Even at this early stage the quantity of material available is of primary concern. The moisture contents of the deposit needs to be established as well as the relative position of the different materials in the ground and the possible implications for working the deposits and blending to produce the desired raw feed . Types of cement possible In the absence of an iron oxide component the raw materials would support the production of a clinker of light colour and high silica ratio. The cement could be of high strength but would not provide best economy in terms of fuel consumption in the kiln and electricity for grinding the clinker to cement. With an iron oxide component the range of clinker possible would extend to low LSF clinkers with good combination. 17