Integrated hydrogen production and power generation from microalgae

An integrated system for hydrogen production, storage, and power generation from microalgae using enhanced process integration technology is proposed. Enhanced process integration has two core technologies: exergy recovery and process integration. Exergy recovery is performed through exergy elevation and heat coupling to minimize exergy destruction. The unrecoverable energy/heat in a single process is recovered and used in other processes through process integration. The proposed integrated system includes supercritical water gasification, hydrogen separation, hydrogenation, and a combined cycle. The microalga Chlorella vulgaris is used for modeling and evaluation. Microalgae are converted to syngas, then separated to produce highly pure hydrogen. To store the produced hydrogen, the toluene-methylcyclohexane cycle as a liquid organic hydrogen carrier is adopted. The remaining gas is used as fuel for combustion in the combined cycle to generate electricity. The effects of the fluidization velocity and gasification pressure on energy efficiency are evaluated. From process modeling and calculation, high total energy efficiency (higher than 60%), including electricity generation efficiency of about 40%, can be realized.