Integration of a CaO-Based Thermal Storage System in an IGCC Plant With Carbon Capture

Using pre-combustion CO2-capture, IGCC plants show significant potential for efficient power generation with carbon capture. The gasification and gas processing steps however have multiple temperature and flow constraints which severely limit the flexibility of IGCC plants to meet the dynamic demands of the current grid. To address this issue, a CaO-based energy storage system has recently been proposed to substantially increase the load range of a base IGCC plant without cycling the gasifier island. In this work, further storage configurations have been assessed, addressing the inefficiencies identified in previous work. In particular, the following cases have been investigated: directly fired calciners with varying make-up flow rate to minimize the purge stream energy loss, directly fired calciners with improved heat integration to reduce the calciner syngas demand and an indirectly fired calciner to minimize the ASU penalty. Additionally, an alternative storage integration strategy after the Selexol unit has been compared both with respect to its performance and its impact on the base IGCC plant design and operation. To this end, process simulation was undertaken in Aspen Plus™. As demonstrated, the CaO based energy storage system can be effectively used to modulate the IGCC net power output by ±20–25%, while maintaining the capture capacity of 90% of the CO2-emissions. Improvement of the particle reactivity and the internal heat recuperation were found to impact the round-trip efficiency the most.