Microalgae-based coproduction of ammonia and power employing chemical looping process

Abstract Hydrogen (H 2 ) production and storage technologies are the main challenges in the realization of H 2 utilization in which the goal is to achieve high conversion efficiencies and a high storage density. In this study, microalgae gasification and ammonia (NH 3 ) production are proposed to efficiently convert microalgae to NH 3 for efficient H 2 storage. The integrated system comprises drying, gasification, syngas chemical looping (SCL), NH 3 synthesis, and power generation. Microalgae are converted to syngas in the gasification module and then introduced into the SCL module to produce high-purity H 2 and a separated carbon dioxide (CO 2 ) stream. SCL is also employed to produce a nitrogen (N 2 )-rich stream, which can replace a conventional air separation unit (ASU) system. The three operating parameters that are evaluated in this study include the steam to biomass (S/B) ratio during gasification, reducer operating temperature during chemical looping, and recycle to feed streams ratio. An increase in the S/B ratio has a negative effect on the total energy efficiency because the efficiency decreases owing to the reduced production of H 2 in the oxidizer. To maximize the efficiency of NH 3 production, a higher recycle ratio is favorable. The proposed integrated system can obtain high total energy efficiency of up to 64.3%, comprising 63.8% NH 3 production efficiency and 0.05% power generation efficiency.