Oil production from microwave-assisted pyrolysis of a low rank American brown coal

Obtaining energy from brown coal is an everlasting pursuit. This study detailed the oil production from microwave-assisted pyrolysis of a low rank American brown coal. The effects of feedstock load (20, 30, 40, 50, and 60 g), pyrolysis temperature (550, 600, 650, 700, and 750 °C) and heating time (10, 15, 20, 25, and 30 min) on the oil yields and compounds were also investigated. The results showed that the oil yields obtained were 13.17–22.97 wt% of the brown coal on ash free basis, and it increased initially and then decreased with increasing feedstock load, pyrolysis temperature, and heating time. Light oil and heavy oil accounted for 33.49–65.08 wt% and 34.92–61.94 wt% of the oil yields, and the compound weights were 1.21–5.41 wt% and 90.75–98.14 wt%, respectively. The highest oil yield was achieved at the feedstock load of 50 g, pyrolysis temperature of 700 °C and heating time of 20 min, and it was very close to the oil yield at high heating rates of 2000–10,000 °C/s for the electrical heating pyrolysis. The results obtained from this study not only detailed the oil yields and compounds obtained from microwave-assisted pyrolysis of a brown coal but also demonstrated the effects of feedstock load, pyrolysis temperature and heating time on the oil production. The results also indicated that microwave-assisted pyrolysis may be a more suitable technology for obtaining oil from brown coals than electrical heating pyrolysis.