Study of Granulated Gypsum Hardness Coming from the Granulation Process in Rotating Disk

摘要

The granulation process is a unit operation with broad application in the fertilizer industry. The granular fertilizer has a better physical appearance, facility of agricultural application and elimination of fugitive dust in the production and bagging units. Phosphogypsum is a residue from the production of phosphate fertilizers. It known that for every 1 t of phosphate fertilizer produced, about 4 t of phosphogypsum are obtained, causing problems in storage and risks to the environment. Such problems may be minimized by granulating the waste phosphogypsum and using it in agriculture. This work aims at the construction of a laboratory-scale rotating disk granulator with a pre-established combination of reagents to promote granulation of the waste from phosphate fertilizer production. For construction of the equipment a theoretical study was performed in order to establish the principal variables influencing the granulation technique and the dimensions required for building the granulator. The equipment attained the expected results and the disc speed (22 to 250 rpm) and disc inclination (0 to 90 degrees) can be manipulated. In this paper three binders used were: Manioc starch, carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA), each at three different concentrations. The tests were conducted using a rotating disk granulator and hardness tests on a universal mechanical testing machine. The figures of merit used in this study were percentage particle size, hardness and sphericity of the granules obtained. With the analysis of the data, it can be concluded that the granulation process was adequate, considering the settings employed.