Homogenisation of raw material or meal To stabilise the chemical variations in a raw material, raw meal or a blended mixture of raw materials a storage facility with homogenising effect is used. The relation between the standart deviation of a chemical component entering and leaving the store is calculated as the homogenising factor (H). This factor rarely exceeds 10. Typically it is 2-6. Segretion can lower the efficiency of homogenisation.
To ensure a stable kiln product and operating condition the raw meal must be homogenous with little variation of the chemical properties of the feed for the cement kiln. The homogenising factor of a store is determined by the relation between the standart variation of material entering and leving the store. The lower standart deviation of the store output to input the higher the homogenising factor. Homogenisastion test (24 jam) 24 hourly samples of input and output material are collect ed, 48 samples total. The time dela y from sampling of input to output material shall correspond to the mean retention time of the material or until the quantity of material extracted from the silo corresponds to the content of the silo at the start of the test period. Each sample is prepared and analysis (X1, X2) 2 times, for either CaCO3, CaO, LSF or C3S. For set of data-input and output the following calculations are made. No 1 2 3 4 5 24
) (( ) ( ) The standart deviation of a material is calculate as follows:
q represents the number of analysis made on a sample (normally 2). When it is not possible to prepare and analyse the samples 2 times )as when using the hourly routine analysis from log sheet) one or more similiar samples cn be prepared and analysed repeatedly to estimate the analytical standart deviation Sanalysis. In case that homogenisation is calculated based on single analysis of sample set q=1. Calculate the store homogenisation factor (H) as bellow: H =Smaterial(input)/ Smaterial (output)
If the deviation Smaterial (output) of the kiln feed from a homogenisation silo is less than one of the folllowing values : 0,2 for %CaCO 3, 0,11 for % CaO, 1 for LSF or 3 for % C 3S, then the kiln feed is considered homogenous. A calculation of the homogenisation factor will become meaningless when Smaterial (Output) approaches 0 or becomes negative. FLSmidth homogenisation