Influence of process parameters in superheated steam drying on fire and explosion parameters of woody biomass

Abstract

Studying of the drying kinetics and fire and explosion characteristics of biomass is a fundamental aspect in designing material drying systems based on superheated steam, and proper selection of explosion and fire protection systems. The paper presents studies on osier willow (Salix viminalis) drying kinetics under isothermal conditions (120 °C, 140 °C, 160 °C, 180 °C) and their use for process calculations of the proposed one-dimensional model of superheated steam pneumatic dryer. The model included empirical parameters in order to describe the volumetric heat transfer and specific surface of the wood particles of irregular shapes.In addition, a 20-L spherical explosion chamber, Hartmann tube apparatus, hot plate apparatus and Godbert-Greenwald furnace apparatus were used to investigate the explosion and fire characteristics of willow dusts. Based on the studies it was confirmed that the operating parameters of superheated steam drying system for woody biomass have a major impact on the explosion and fire characteristics of the formed dust. The results indicate that the lower the moisture content in the willow, the more likely the dust cloud to be ignited, the faster the explosion flame propagation, and the greater the explosion severity. Despite the fact that the superheated steam drying system for woody biomass is considered safe, the probability of occurrence of fire or explosion incidents related to the dust and air biomass mixture is high. The maximum temperature for superheated steam drying equipment covered with up to 5 mm thick layer of osier willow dust should not exceed 215 °C.