Analysis of the Effect of the Biomass Torrefaction Process on Selected Parameters of Dust Explosivity

Abstract

This article presents the findings of a study investigating the explosion and combustion parameters of dust from the raw biomass of wheat straw and energy willow and from the products of biomass torrefaction generated at temperatures ranging from 220 to 300 °C. Agricultural waste and energy crops and their modifications, e.g., in the torrefaction process, did not find a place in explosive risk research, which the authors decided to present in their work. The study was designed to estimate explosion hazard during the processing of the materials into fuels and during the storage process. The measurements recorded a maximum explosion pressure Pmax in the case of dust from biomass ranging from 7.2 to 7.3 bar and for dust from torrefied materials amounting to 7.5–9.2 bar, and a maximum rate of pressure rise over time (dp/dt)max in raw biomass ranging from 201.4 to 261.3 bar/s and in torrefied materials amounting to 209.6–296.6 bar/s. The estimated explosion index Kstmax for raw biomass was 55–72 m*bar/s and for torrefied materials was in the range from 57 to 81 m*bar/s. In the results, the authors present values for specific types of fuel which differ significantly depending on the type of biomass. The research findings show that the torrefaction process used in fuel production is not associated with a significantly greater risk of explosion and the materials obtained may safely be used as an alternative to conventional solid fuels. Given the growing interest in the use of biomass and in the variety of biomass processing methods for energy-related purposes, it seems there is a need for research to develop appropriate guidelines and for effective practices to be introduced in the energy industry in order to ensure the safety of the processes used in the production of novel fuels especially in small installations converting these materials into more efficient energy material.