AVESTAR Team Advances Dynamic Modeling and Control for Solid-Sorbent CO2 Capture
The U.S. Department of Energy’s Carbon Capture Simulation Initiative (CCSI) is focused on commercialization of CO2 capture technologies from discovery to development, demonstration, and ultimately the widespread deployment to hundreds of power plants. One element of the CCSI is focused on improving the operation and control of carbon capture systems since this can have a significant impact on the extent and the rate at which commercial-scale capture processes will be scaled-up, deployed, and used in the years to come. As part of this work, the AVESTAR team completed development of a one-dimensional, non-isothermal, pressure-driven dynamic model of a two-stage bubbling fluidized bed (BFB) adsorber reactor for solid-sorbent-based post-combustion CO2 capture. The BFB model for the flow of gas through a continuous phase of downward moving solids considers three regions: emulsion, bubble, and cloud-wake. Both the upper and lower reactor stages are of overflow-type configuration, i.e., the solids leave from the top of each stage. In addition, dynamic models have been developed for the downcomer that transfers solids between the stages and the exit hopper that removes solids from the bottom of the bed. The models of all auxiliary equipment such as valves and gas distributor have been integrated with the main model of the two-stage adsorber reactor. A paper titled “Dynamic Modeling and Control Studies of a Two-Stage Bubbling Fluidized Bed Adsorber-Reactor for Solid-Sorbent CO2 Capture,” which describes details of the dynamic BFB adsorber model was recently published in the peer-reviewed journal, Industrial & Engineering Chemistry Research. The paper presents results showing the transient responses of various process variables such as CO2 capture rate and flue gas outlet temperatures when facing typical disturbances such as changes in the temperature, flowrate, and composition of the incoming flue gas from a pulverized coal-fired power plant. As the flue gas flowrate is expected to be the dominant and most frequent disturbance for a CO2 capture process, a 20% step increase in the flue gas flowrate is introduced to evaluate the performance of the control strategies. Results show that the performance of a linear model predictive controller is superior to a traditional proportional-integral-derivative controller and a more complex feedback-augmented feedforward controller, in terms of maintaining the overall CO2 capture rate at a desired level in the face of typical disturbances.
Modekurti, S., D. Bhattacharyya, and S.E. Zitney, “Dynamic Modeling and Control Studies of a Two-Stage Bubbling Fluidized Bed Adsorber-Reactor for Solid-Sorbent CO2 Capture,” Industrial & Engineering Chemistry Research, DOI: 10.1021/ie400852k, June (2013).