ABSTRACT
A copper smelter in Chile monitors the copper content of slag every three hours. To prepare such sample several increments of the molten material are collected within three hours to make a three-hour composite. The plant must comply with the following specifications believed to work best for an economic optimization: the Targeted Average TA is set at 10%; the Upper Specification US, above which too much money is lost is 14%, and the Lower Specification LS, below which too much money is spent for the process to perform high copper recovery is 7%. At times, the plant encounters difficulties taming the process variability within the specifications. Explanations for these difficulties have eluded management for some time. It was believed that the variability investigation of existing data was a good start: 217 consecutive three-hour copper assays shown in Figure 35.1 are collected to perform the chronostatistical study. The collected data is listed in Table 35.1. The following sequence is a step-by-step strategy to approach such difficulties. Percent copper in a smelter slag, sampled and estimated every three hours. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781351105934/7fcc19d8-d59f-45bd-9ddf-91c689ba414e/content/fig35_1_PB.tif"/> https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781351105934/7fcc19d8-d59f-45bd-9ddf-91c689ba414e/content/fig35_1_OC.tif"/>
