Solar pyrolysis of heavy metal contaminated biomass for gas fuel production

The study presented an innovative way to dispose and upgrade heavy metal (HM) contaminated biomass by solar pyrolysis. Pyrolysis of raw and HM (Cu and Ni) impregnated willow wood was performed in a solar reactor under different temperatures (600, 800, 1000, 1200, 1400 and 1600 °C) and heating rates (10 and 50 °C/s). The combined effects of HM and heating parameters (temperature and heating rates) on solar pyrolysis products were investigated. The results indicated that a threshold temperature of 1000 °C was required in impregnated willow pyrolysis to make sure copper and nickel catalytic effects on promoting the cracking and reforming reactions of tar. It led to the gas yields from copper or nickel impregnated willow pyrolysis at 1200 °C increased by 14.76% and 34.47%, respectively, compared with that from raw willow. In particular, the H2 and CO production from nickel impregnated willow were higher than those from raw willow (10.30 and 12.16 mol/kg of wood versus 6.59 and 8.20 mol/kg of wood) in case of fast pyrolysis (50 °C/s). Under heating rate of 10 °C/s, H2 and CO yields from only nickel impregnated willow increased compared with that from raw willow. Solar pyrolysis of HM contaminated biomass is a promising way to produce valuable syngas.