The design of pressure safety systems in the alumina industry

Abstract

The alumina refinery presents the designer with multiple challenges. For a given process flowsheet, the mechanical equipment installed must be routinely inspected and maintained. Piping systems must also be inspected routinely for signs of erosion and/or corrosion. Rapid deposits of chemical species such as lime, silica, and alumina on equipment and piping need special consideration in the mechanical design of the facilities, such that fluid flows are not unduly interrupted. Above and beyond all else, the process plant must be a safe place of work for refinery personnel. Although much of the alumina plant flowsheet is executed at atmospheric pressure, the digestion facility and boiler plant are two principal areas of the refinery that operate at conditions of up to 400 degrees celcius and 100 Bar pressures. The digestion facility in particular may be comprised of many alternative process designs displaying either inherent mechanical simplicity or complexity. This paper outlines some of the pressure safety considerations to be incorporated into the mechanical design of the digestion facilities for some alternate process flow sheets. Armed with these considerations at the process flowsheet definition stage, optimisation of the process and/or equipment selection is possible preserving the delicate balance of process facility performance, plant operability and maintainability, and personnel safety. © 2016 by The Minerals. Metals & Materials Society.