Dynamic modeling and scenario analysis of a circulating fluidized bed gasifier supported by variable renewable energy

Rapid implementation of variable renewable energies elevates the importance of grid excess electricity management. Power-to-X can be considered as a viable solution for this surplus power, and gasification process can act as a potential sink. This work develops a plant-wide dynamic model of a 2 MWth Circulating Fluidized Bed (CFB) biomass gasifier in APROS (a dynamic process simulation platform) and evaluates electrified operation where exogenous electric heat substitutes part of in-reactor oxidation at fixed biomass feed. A temperature-guarded PI loop adjusts the O2/steam composition of an agent nozzle to maintain the maximum riser temperature. Steady simulations at 0-470 kWe show progressive steam substitution for oxygen, reaching an all-steam (zero O2 fraction) condition at 470 kWe. Dense-bed temperature increases with electric input, the dilute-zone remains nearly unchanged, and the product gas shifts toward higher H2 and CO with lower CO2 by about 9%. Cold-gas efficiency rises from about 60% to about 80%, and the incremental electric-to-chemical efficiency ranges from roughly 77% to 86% on a dry-gas LHV basis. A 144-h sequence of step tests confirms repeatable transients and recovery to quasi-steady conditions up to 400 kWe. Near the all-steam limit, the loop becomes constraint-bound and at 472 kWe both dense-bed and dilute-zone temperatures develop a sustained upward drift. The results define a practical operating ceiling near 470 kWe and show that within this envelope, the electrified CFB gasifier can act as a controllable sink for surplus electricity while improving product-gas quality.