Integrated supercritical water gasification and a combined cycle for microalgal utilization

Highlights: • Innovative integration of supercritical water gasification and power generation for microalgae. • Enhanced process integration is applied including exergy recovery and process integration. • Microalgae Spirulina sp. is selected due to high gasification efficiency. • High efficiency of energy conversion can be achieved. - Abstract: Integrated energy utilization processes for microalgae based on enhanced process integration are proposed in this study. They consist of supercritical water gasification and combined cycle for power generation. The enhanced process integration is developed based on exergy recovery and process integration technologies. Exergy recovery deals with effective heat circulation throughout a single process which is achieved by exergy elevation and efficient heat coupling. In addition, process integration utilizes the unrecoverable heat from a single process for other processes, thus minimizing the total exergy destruction of the whole integrated processes. Microalga Spirulina sp. is selected as the sample due to its higher gasification and carbon conversion efficiencies than any other microalgae. Process simulation is performed to evaluate the total energy efficiency, specifically the effect of steam flow rate (fluidization velocity), gasification pressure and turbine inlet temperature. Simulation reveals that the proposed integrated processes harvest the energy from microalgae with total energy efficiency exceeding 40%. A temperature–enthalpy diagram shows that the heat involved in the whole processes is recovered effectively