Improving the Efficiency of the Decomposition of the Aluminate Liquor by Preparing and Introducing an Active Seed into the Decomposition Process

Abstract

The objective of the study was to determine the optimal parameters for preparing and dosing an active seed (finely divided aluminum hydroxide) to stabilize the decomposition process of the aluminate liquor during decomposition in the Bayer process. Laboratory tests were carried out on an Intronics temperature-controlled rotating water bath (Australia). Granulometric analysis of the obtained aluminum hydroxide was performed using the VideoTest automatic image analysis system with an Axioskop-40 microscope (Carl Zeiss, Germany) equipped with the Image Analysis program. Laboratory studies were conducted to obtain finely divided aluminum hydroxide (active seed) by mixing the alkali aluminate liquor and the process water in various ratios. It was determined that the process water should be the first to be fed and then the cooled alkali aluminate liquor should be introduced. The following optimal conditions for obtaining an active seed were found: the solution should be held for 48–72 h at a temperature of 50°C at a ratio of the aluminate liquor to the process water of 60 to 40%. Laboratory studies were conducted on dosing the obtained active seed into the head decomposers of the decomposition process. It was shown that the use of the active seed in the continuous process of decomposition stabilizes the granulometric composition of the product aluminum hydroxide. It was observed that the presence of the active seed allows reducing the initial temperature of the decomposition process from 62 to 58°C without changing the granulometric composition of aluminum hydroxide. In addition, the positive effect of introducing the active seed on increasing the degree of decomposition of the aluminate liquor to 1.5% was confirmed. Thus, based on the results of the studies, it was established that the use of a new method for preparing and dosing an active seed into the head decomposers allows intensifying the decomposition process in the production of alumina.