Optimal parameters and structural composition of bio-oil and biochar from intermediate pyrolysis of red algal biomass

Abstract

Intermediate pyrolysis of red algal biomass was performed in a fixed-bed tubular reactor. To study the parametric effect on product distribution, the experiments were carried out at different temperatures ranging from 400 to 600 °C and different heating rates of 15, 30 and 50 °C/min. The objective of this study is to understand the effect of pyrolysis temperature and heating rate on the yields and compositions of the pyrolysis products of red algal biomass. The bio-oil, biochar and biogas yields ranged between 33 and 45 wt%, 29 and 42 wt%, and 18 and 35 wt%, respectively, at different pyrolysis conditions. The highest bio-oil yield (45.02%) was obtained at 450 °C temperature at a heating rate of 50 °C/min. The bio-oil was characterized by proximate and ultimate analysis, FTIR, 1H-NMR and GC–MS analysis whereas the biochar was characterized by proximate, ultimate, FTIR, SEM and BET. Higher heating value and density of the bio-oil were 20.11 MJ/kg, $1289~\mathrm{kg}/\mathrm{m}^{3}$, respectively. The bio-oil with relatively high fuel potential can be obtained from the pyrolysis of the red algal biomass. The characterization of bio-oil showed a high percentage of aliphatic functional groups and presence of phenolic, ketone- and nitrogen-containing groups. The characterization results showed that the bio-oil obtained from red algal biomass can be potentially valuable as a source of value-added chemicals. The biochar obtained with a high heating value of 22.89 MJ/kg can be used as an adsorbent as well as a solid fuel.

Keywords

• Intermediate pyrolysis
• Red algal biomass
• Fixed-bed reactor
• Bio-oil
• Biochar