(532a) Continuous Carbon Recovery from HTL Aqueous Phase

Hydrothermal liquefaction (HTL) has emerged as a promising technology for the conversion of wet wastes and biomass to biocrude. A drawback of HTL, however, is the production of significant amounts of waste in the form of solid char and water-soluble organics. Carbon contained in the resultant aqueous phase represents a reduction in process energy recovery and therefore efficiency. The resultant aqueous phase from HTL accounts for over 75% of the total mass of the products and represents a significant fraction (> 25%) of the carbon in the starting material.

To combat this issue of waste and increase process efficiency a continuous packed bed reactor was designed and constructed for aqueous carbon recovery. Hydroxyapatite was evaluated as a stable heterogeneous catalyst for increased energy recovery and organic purification of hydrothermal liquefaction aqueous phase. The aqueous phase from sewage sludge and food waste has been found to contain between 22 – 50 g/L of carbon. The use of ex-situ HAP reduced this to 12 g/L, corresponding to a reduction of more than 50%.

Continuous purification was completed at 300 °C and 100 bar for a period of over 12 hours continuously with minimal catalyst deactivation. The system will be used for various HTL feedstocks and the efficiency and percent carbon reduction compared. Subsequent analysis will be useful for determination of water purity and disposal options consistent with wastewater regulations.