The thermodynamic interactions between sulphur anions and iron, chromium, nickel as well as molybdenum in modern digesting

The review is focused on the modern kraft digesting, their polysulphide chemistry and the construction materials of digesters. The most common structural materials of digesters; like austenitic and duplex stainless steels, were studied in alkaline oxidative kraft liquor. The study of structural materials based on thermodynamic. The different chemical behaviours between sulphur anions and the alloying elements of stainless steels; like iron, chromium, nickel and molybdenum, were predicted by potential - pH diagrams. The study is based on the free polysulphide concentrations in digesting liquors while only the concentration of polysulphides or their decomposition products can be harmful for structural material of cooking department. The review can be used when laboratory experiments are planned. Also the review shows the limits of thermodynamic. The thermodynamic data available based on the ideal diluted solutions where the concentration of ions was below 0.01 M. For this reason experimental research is also needed