Dry scrubbing of potgas has become an integrated and important part of the aluminium production process. For efficient removal and recovery of gaseous fluorides from the modern prebake cells with high emissions, the properties of the alumina used in dry scrubbing are important.
The alumina must be suitable for the dry process, particularly with regards to specific surface area and particle size distribution. The alumina being introduced in the dry scrubber will be handled and exposed to various mechanisms that may alter its properties. Possible attrition and degradation of the alumina should be carefully considered when designing a dry scrubber. Inevitably, changes to the impurity content and chemical composition of the alumina being in contact with the raw gas is seen. Means or measures to reduce this effect are available.