Thermodynamic analysis of an integrated hydrogen and power production system by food waste supercritical water gasification

Supercritical water gasification (SCWG) technology has high hopes in the resource treatment of food waste. Current work focuses on the SCWG characterization of food waste at the mechanism level or the design of single-function SCWG systems such as hydrogen production, power generation, and heating. Therefore, this paper developed an integrated hydrogen and power production system by food waste supercritical water gasification to enrich the study of multi-energy fusion systems. Based on exergy flow analysis, significant exergy loss was found in the heat exchanger and cooler of the base case. Integrating the Organic Rankine Cycle (ORC) for waste heat recovery can produce an extra 2615.88 kW of electricity, increasing system energy efficiency by 8.66 % and exergy efficiency by 7.66 %. Sensitivity analysis showed that a lower ratio of preheated water to food waste slurry, higher feedstock concentration, lower oxidation temperature, and system pressure can improve the system efficiency. Because low ratio of preheated water to food waste slurry, high feedstock concentrations. and low oxidation temperature reduced the consumption of hydrogen-rich gas in the oxidation reactor. Higher pressure inhibited the steam reforming reaction, reducing H₂ production. The high energy input at elevated pressure combined with a decreased gas calorific value, resulted in lower system efficiency. Compared to other SCWG systems, this hydrogen-power polygeneration system is competitive due to the significant improvement of system performance by waste heat recovery. This work would be of great value for the optimal design of the food waste SCWG system.