Study on molten salt on torrefaction and subsequent pyrolysis of elm branches

Abstract

Torrefaction was a promising pretreatment for enhancing biomass properties, and molten salt torrefaction could achieve superior torrefaction benefits at equivalent temperatures. To explore the difference between molten salt torrefaction (MT) and conventional torrefaction (CT) and the effect of which on the subsequent pyrolysis of biomass, torrefaction experiments at 260 ℃ and pyrolysis experiments were conducted in a horizontal furnace, a thermogravimetric mass spectrometry (TG-MS) and a pyrolysis gas-chromatography mass-spectrometry (Py-GC-MS), respectively. The results showed that the O/C of washed MT sample (MTw) decreased by 13.89 % and the volatile content decreased by 14.56 % compared with washed CT sample (CTw). Concurrently, the MTw sample demonstrated the highest calorific value and largest specific surface area among the samples. The maximum weight loss rate of MT sample during subsequent pyrolysis increased. In comparison with CT, MT could decrease the pyrolysis activation energy. Furthermore, MTw sample produced more H2 and CH4, while simultaneously less CO2 and CO during pyrolysis compared with CTw. The bio-oil derived from the MTw sample exhibited the lowest relative content of acidic compounds and the highest relative content of aromatic compounds, signifying its enhanced quality.