Pyrolysis of pellets prepared from groundnut shell and crude glycerol: in-situ utilization of pyro-gas and characterization of products

During biodiesel production process crude glycerol (a polyol) is obtained as a by-product. In this paper, an effort has been made for using it for pellet production from groundnut shell. Three types of pellets containing 20 wt%, 40 wt% and 60 wt% crude glycerol were prepared. Palletisation led to easy handling of biomass and also increases energy density. Furthermore, characterisation of prepared pellets was performed and subsequently, pyrolized. An increase of volatile matter from 72.45 wt% to 85.18 wt% in pellets was noted with addition of glycerol. Pyrolysis of glycerol containing pellets was carried out in batch (0.5kg) scale along with in-situ circulation of generated pyro-gas. Bio-oil yield increased from 30 wt% to 41 wt% in batch scale as glycerol content increased from 0 wt% to 60 wt%. Pyrolysis products were thoroughly characterised to understand the effects of crude glycerol addition. Calorific value of bio-char was increased from 20.89 MJ/kg to 23.67 MJ/kg as glycerol content increased. Calorific value of bio-oil was 32.66 MJ/kg. The pyro-gas produced was utilized to heat the pyrolysis reactor. Pyro-gas yield increased from 28 wt% to 32 wt% in batch scale as glycerol content increased. In-situ utilization of pyro-gas led to ~ 17% electricity saving.