Flexible Calcium Looping System for CO2 Capture From Coal-Fired Power Plants: A Comprehensive Modelling Study on Part-Load and Dynamic Performance and Economic Optimization of the Sorbent Storage System

In this work, an advanced Calcium looping (CaL) power plant with thermochemical energy storage system is assessed. The CaL system is equipped with two solids storage silos storing calcined solids from the calciner and carbonated solids from the carbonator. The presence of the solids storage allows to design and operate the CaL calciner line (calciner, ASU, CPU) on the average load of the existing power plant, while the carbonator can follow the load of the conventional power plant with air-blown boiler. The economic analysis carried out shows that the optimal size of the storage system from an economic and logistical point of view is on the daily cycle, which shows a cost of CO2 avoided (CCA) of 31 €/tCO2, about 16% less than the case without storage. In addition, the adoption of the storage system allows the CaL steam cycle to operate with a higher average daily electrical efficiency than without storage, limiting the operation at partial load. Moreover, by exploiting the secondary storage it is possible to have an increase of about 20 MWe respect to the nominal condition, and a reduction of about 56 MWe below the minimum load. As demonstrated by studying the dynamics of the system, the increase in power output can be produced in a relatively short time (40% within 40s and the remaining 60% within 300s) by boosting the hot CaO flow through the sorbent cooling line.