Advanced Amine and Ammonia Systems for Greenhouse Gas Control at Fossil Fuel Power Plants

In an effort to lower future CO₂ emissions, a wide range of technologies are being developed to scrub CO₂ from the flue gases of fossil fuel-based electric power and industrial plants. This thesis models two leading post-combustion CO₂ capture technologies, a chilled ammonia-based CO₂ capture process and an advanced amine-based CO₂ capture process, and presents performance and cost estimates of these systems on pulverized coal and natural gas combined cycle power plants.

The process modeling software package Aspen Plus® was used to develop performance and cost estimates for the chilled ammonia-based CO₂ capture technology and general response surface equations were created for the model. Assumptions about plant financing and utilization, as well as uncertainties in cooling costs and chemical reaction rates that affect absorber cost were found to produce a wide range of cost estimates for ammonia-based CO₂ capture systems. With uncertainties included, costs for a supercritical power plant with ammonia-based CO2 capture ranged from $80/MWh to $160/MWh, with the 95% confidence interval ranging from $95/MWh to $143/MWh (with all costs in constant 2007 US dollars).

For the advanced amine-based CO₂ capture technology, an existing amine-based response surface model developed using Protreat® simulations was modified to match the performance and cost characteristics of a modern amine-based system. The response surface models of both technologies were incorporated into the Integrated Environmental Control Model for use in developing performance and cost estimates of pulverized coal and natural gas combined cycle power plants with these technologies. The baseline costs for a supercritical power plant with advanced amine-based CO₂ capture was $105/MWh and for the natural gas combined cycle power plant with advanced amine-based CO₂ capture was $85/MWh.

Both post-combustion CO₂ capture technologies are then compared in terms of performance and cost for different ranges of fuel type, fuel cost, plant size, and CO2 capture system train size. A probabilistic cost difference analysis is also used to compare these technologies. The aminebased CO₂ capture system is found to have a higher revenue requirement in all the case studies and only a 2% chance of having a lower revenue requirement than the advanced amine system in the probabilistic cost difference. Combined, these results suggest that the advanced amine system will have a cost advantage over the ammonia system in most cases, in the absence of significant new improvements in the ammonia system design. Finally, the importance of these estimates for policy makers is discussed.