Effect of burning supplementary waste fuels on the pollutant emissions by cement plants: a statistical analysis of process data

Abstract

This paper shows how some statistical tools can be applied in the process analysis of real plant data, e.g. in the clinker production process by using alternative fuels (shredded tyres and waste oils) as alternative fuels in clinker kilns of two different cement plants. Statistical Student's t-tests, stepwise linear regression models and factor analysis were employed in the data analysis to evaluate the effect on the atmospheric stack emission of these alternative fuel feeding. Moreover a quite large improvement in the knowledge of the process have been obtained by statistical analysis of the data process that very often suffer of internal correlation among the process variables under investigation. Experimental results statistically analysed have shown encouraging results, if less than 20% of regular fuel is replaced with alternative one: in particular clinker characteristics were unmodified, and stack emissions (NO x , SO 2 and CO mainly) were, in the case of tyres, slightly incremented, but remaining almost always below the law imposed limits; in the case of waste oils, polluted gas emissions were even decreased. Some empirical equations relating the stack emissions with some process data have been also obtained to be used for process analysis purposes.