Preblending (stacking and reclaiming) Question 1
While our plant was designed in 1998, the necessity of preblending stacker and reclaimer system was not incorporated based on the ground that run of mine limestone quality is very consistent(CaO standard deviation 0.60 per cent) and silica, iron or alumina oxide are very less in the range of 0.6,0.1,and 0.3 per cent respectively. Our raw meal is four-component limestone, silica rock (75 per cent purity as SiO2),iron ore (55 per cent purity as Fe2O3) and bauxite (48 per cent purity as Al2O3). Now since the beginning of this year from the mines receipt limestone CaO is reduced from 54 to 51.5 per cent and at the same time silica, alumina and iron oxide increased to the level of 3.5 to 4.00, 0.8 to 1.1,and 0.25 to 0.35 per cent respectively. The standard deviation for LSF on three random eight-hourly samples we are getting in the range 40 to 90. I would appreciate to have feedback from you which is the level of variation in run of mine limestone making it necessary for installation of preblending stacker and reclaimer system for a one million tonne dry process cement plant.
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Re: Preblending (stacking and reclaiming)
I do not believe a stacker/reclaimer should be necessary in your situation. With a good software system proportioning the materials into the mill you should be able to achieve less than two per cent standard deviation in kiln feed and clinker LSF. You have another big problem with your mix because it is heterogeneous and therefore of very low reactivity. Do you have problems with high fuel consumption or excursions of high free lime in the clinker. I would recommend strict control of the mineral composition of the clinker and possibly the introduction of Duplex grinding.