Investigation on the properties of the bio-briquette fuel prepared from hydrothermal pretreated cotton stalk and wood sawdust

Abstract

The effects of the briquetting temperature, briquetting pressure and hydrothermal pretreatment (HT) on the physicochemical properties of the resulted briquettes prepared from one herbaceous biomass, cotton stalk (CS) and one woody biomass, Chinese pine wood sawdust (WS) were mainly addressed in the paper. The apparent density, compressive strength and combustion characteristics of the resulted briquettes (CS/WS-Bs and CS/WS-HT-Bs) were investigated to evaluate their feasibility as the biomass briquette fuels. The results showed that the increase of briquetting temperature and pressure was beneficial to the densification of CS/WS-Bs. Compared with CS/WS-B, the hydrothermal pretreatment significantly improved the physical properties of the resulted biomass briquettes. As the hydrothermal pretreatment temperature increased, the heating values of the resulted CS/WS-HT-Bs increased, the content of fixed carbon increased and the yields of volatiles decreased. Furthermore, HT promoted the combustion characteristics. In addition, the Mad and heating values of all CS/WS-HT-Bs meet the Sweden Standard (SS18 7120). The most cost effective CS/WS-HT200/230-Bs were prepared from the cotton stalk and wood sawdust hydrothermal pretreated at 200 °C and 230 °C under the briquetting conditions of 75 °C and 80 MPa. However, the changes in the physical and chemical properties of the briquettes prepared from CS and WS followed different trends.