Investigation of Mannich reaction during co-liquefaction of microalgae and sweet potato waste: Combustion performance of bio-oil and bio-char.

Microalgae (MA) was co-liquefied with sweet potato waste (SPW) to improve bio-oil and bio-char qualities via Mannich reaction. The influence of Mannich reaction on combustion performances of bio-oil and bio-char were investigated. Results suggested that the addition of SPW decrease the ignition temperature of bio-oil from 186.6 °C to 165.0 °C. In addition, the denitrification effect of Mannich reaction can decrease the HCN and NO emission of bio-oil, contributing to reducing pollutant emission. As for bio-char, Mannich reaction improved the combustible material content in bio-char, which decreased the risk of slagging problem. The comprehensive combustion indexes of bio-oil (1.23 × 10 × min×°C) and bio-char (4.79 × 10 × min×°C) from co-liquefaction were higher than those from liquefaction of MA (0.91 × 10 × min×°C for bio-oil and 1.24 × 10 × min×°C for bio-char), indicating that the combustion performance was promoted by adding SPW. Overall, Mannich reaction can be applied to improve the combustion performance of bio-oil and bio-char.