The Corrosion Resistance of Stainless Steels in Weak, Hot Sulphuric and Sulphurous Acid Environments Applicable to the Pre-Hydrolysis of Biomass

摘要

The reason for this work is the current interest in the extraction of hemicelluloses from forest biomass, by acid prehydrolysis, for conversion to sugar streams and on to chemicals and fuels. Industrial process designs are not yet set, but the use of hot, weak, sulphuric or sulphurous acid environments are possible. By hot we mean 150°- 210°C; e.g., 150°C for typical mild acid hydrolysis, or 210C for steam explosion. By weak we mean a pH of around 1. Other anticipated process conditions are batch operations in digester-like vessels (although other process designs and vessels are certainly possible, such as for steam explosion) short pre-hydrolysis time (meaning frequent cycling of temperatures and fresh acid) and the presence of process contaminants from use of industrial grade acid, or crosscontamination from other kraft mill process streams. Biomass is inherently inhomogeneous and the effect of contaminant build-up is often ignored in the scale-up from laboratory to industrial scale.