Cement Energy and Environment

00 .050 ·1.00 ,., 1 50 __j sao 60( 70C 10CO Figure 7: Comparison of thermal characteristics of fan deposition sample with those of kiln feed and fan outlet dust samples. Finally, based on the chemical and lower instances of fan deposition problem as was mineralogical analysis of the collected samples, observed in internal group audit, on the otherwise the increased sulphur levels in the system exit comparable process conditions and raw material gases are assumed to have significant role in the composition. fan deposition problem. Similarly, since alkali is maintained in the preheater systems to check the sulphur levels, its influence on the fan deposition in terms of increased values of alkali in the deposition sample could not be ruled out altogether. These observations support the theory of mechanism of chemical parameters and their influence on dust deposition as discussed earlier. Here, it should also be noted that the preheater kiln feed sample and fan outlet sample were taken in steady state conditions as opposed to the fan deposition sample, which was collected after the build-up has reached its maximum. Hence, presence of anhydrite in the fan deposit and absence of the same in other two samples supports the possibility of anhydrite formation in the top preheater cyclones followed by deposition or formation of anhydrite on the fan blades by reaction between S02 available in the gases with the calcite already deposited on the fan moving parts over the period of time in favourable conditions. In addition to this, thermal parameters like high impact velocities and fan inlet temperatures are also suspected to be responsible for increased deposition frequency because some plants having fan inlet temperatures in the range of 200-210°C are observed to be having considerably Summary: A detailed chemico-mineralogical characterization of hard preheater 10 fan deposition sample vis-a-vis top stage cyclone samples & kiln feed sample revealed that the fan blade material deposition problem is related to • combination of segregative deposition of fine clay and iron additive particles escaping from dust cycle set up in the top preheater cyclones and formation of anhydrite possibly due to increased sulphur levels in the preheater system as a result of petcoke firing . Based on the various analyses carried out of the samples following conclusions can be drawn. • Since the particle impact velocity and gas temperatures are quite high, these parameters are likely to aid further hardening of the deposited particles due to plastic deformation on the fan blades. • Additionally, ch loride levels in the fan deposition sample are also observed to increasing substantially indicating possibility of formation of lower melting 14 !