EFFECT OF STEAM EXPLOSION TREATMENT ON BIOMASS SIZE REDUCTION

Size reduction is essential for converting biomass into bio-fuel. It is usually performed using milling machines which consume large amount of energy. Steam explosion treatment which consists of auto-hydrolysis and rapid decompression steps, is a promising pre-treatment process to open up biomass fibers and to recover useful compounds from it. Numerous studies have investigated the effect of steam explosion on biomass composition and on bioethanol production. However, few studies have been conducted to investigate its effect on the reduction of biomass size. In this study, the effects of steam explosion conditions such as temperature and retention time, and type of biomass (hardwood and softwood) on biomass size reduction were investigated in detail using batch-type steam explosion equipment. Sakura (Prunus spp, hardwood) chips and Japanese cedar (Cryptomeria japonica, softwood) chips of 5-10 mm were used in this study. The treatment intensity is determined by a severity factor, which is established as correlation between process temperature and residence time. A rapid increase in the yield of solid biomass of size below 1 mm (fine particles) was observed when the severity factor was above 4.2. The fraction of fine particles crossed 80%, when the severity factor was 5.2. We concluded that temperature/pressure significantly influences biomass size reduction and that residence time and biomass type also influence biomass size reduction, particularly at lower severity (< 5.2). However, these factors were found to have no significant impact at high severities (> 5.2).