Digestion pressure refers to the operating pressure maintained inside the digestion vessels during the Bayer Process alumina extraction from bauxite, and it is a critical parameter that directly influences the temperature, reaction kinetics, and overall efficiency of the dissolution of aluminium minerals. Pressure in digesters is primarily a function of temperature, since the process liquid — caustic soda solution — is maintained at conditions near or above the normal boiling point of water; elevated pressure is therefore required to keep the liquid phase in the reaction and to facilitate higher digestion temperatures. For gibbsite-rich bauxites, digestion is typically conducted at relatively low pressures (around 300–500 kPa) and temperatures of 140–150°C. Boehmite-bearing ores require moderate conditions (500–2,000 kPa, 200–240°C), while diaspore-dominant bauxites demand the highest pressures and temperatures — up to 3,000–4,000 kPa and 250–300°C. Accurate pressure control is critical for safety, equipment integrity, and consistent process performance. Pressure relief systems, robust vessel construction, and automated instrumentation are essential for managing digestion pressure in industrial alumina refineries, where deviations can lead to equipment failure or suboptimal alumina extraction.
