The Production of aluminium is one of such industrial processes that have the potential to release great quantities of dangerous toxic material into the atmosphere. To protect the environment, the Alucam Company has put in place two collection and treatment stations. The main indicator of performance of this system is the collection and treatment efficiency. All other parameters kept constant, this efficiency is proportional to the fume flow rate at the chimney. But the key parameters to control in case of variation are poorly mastered. The collection efficiency of the treatment stations can deteriorate at any moment without any successful intervention to bring back the situation to normal. This article presents the first part of a research work which intends to solve this problem of variations in the flow rate by increasing the fume flow rate and controlling the system within specified limits. We use a Continuous Improvement Methodology which involves the use of Six Sigma tools at the completion of the analysis phase of which we get the fundamental causes of the low performance.

The collection efficiency is the major indicator for the evaluation of the pollution rate and the environmental performance of the aluminium electrolysis process. This efficiency is proportional to the flow rate of the released gases at the chimney. Since December 2009, the normal flow rate has being decreasing and fluctuating in the Alucam smelting factory. At the Analysis step of the DMAIC methodology, the fundamental causes of the variations and the decrease in the gas normal fume flow rate were identified in a previous study. We intend here to stabilize the flow rate, to Improve the efficiency and to put into place a reliable mechanism of Control in order to maintain target variables within Six Sigma limits. Therefore, we propose an appropriate model of the pipeline network which permits us to identify the causes of the process low capability by excluding the interpretation controversy of the relation between the stopping of pots and the decrease in the fume collection and treatment installation. Then, we choose to achieve the modulation of the suction fan to adapt to changes in system load, and the replacement of the fan impeller to reach the continuous regulation of the flow rate. Benefits cannot be over emphasized because the company may improve on its collection and treatment efficiency, hence an effective reduction of dangerous gaseous fluoride emissions.