Session: 14-02: Carbon Capture & Cleaner Fossil Fuel Technologies II

Paper Number: 169962

169962 - The Low-Pressure Oxy-Fueled Carbon Capture Power System: A Techno-Economic Overview 

Abstract: 

Traditionally, the viability of a power system can be reduced to the value of the electricity (and usable heat) it produces as compared to the system’s capital cost and operating costs, this last being highly dominated by the cost of fuel. These elements historically prioritize system efficiency, wherein the value of the electricity produced is maximized for the cost of the fuel consumed, which naturally pushes for higher turbine inlet temperatures (to maximize efficiency) and pressure ratios (to minimize size and material costs). 

A novel gas turbine configuration that subverts the traditional techno-economic framework for power systems has been developed. This system ingests a stoichiometric flow of oxygen and discharges a near-pure exhaust stream of carbon dioxide that is suitable for utilization, capture, and/or sequestration without the need for a costly and power-intensive downstream air separation unit (ASU). Design of the cycle has specifically targeted a low-capital cost system; for example, a moderate turbine inlet temperature and a synchronous shaft speed eliminates the need for both a gearbox and costly alloys in the engine hot section. The system operates at a peak pressure of 1 atmosphere, with sub-atmospheric pressure at the turbine exit; this unusual design choice provides a number of benefits by eliminating the fuel booster, the pressure-related challenges associated with supercritical CO2 systems, and the need to pressurize the incoming oxygen flow.  

In total, these features enable the straightforward integration of the system as a power block within a number of frameworks that are sources of abundant oxygen such as electrolyzers and ethanol plants; in the latter cases, there is also a significant need for both heat and CO2, further enhancing the economic value of the APOCC system. Cycle combustion at low pressure facilitates integration with “free” fuels such as waste biomass and oil recovery off-gas, thereby reducing the operating costs even further. 

This system specifically exploits the emerging and future carbon economy, in which there is real financial value associated with the capture of CO2. For this system, the revenue streams are not only the value of the electricity and heat generated, but also the CO2 exhaust stream which generates value via Carbon Intensity (CI) credits and Carbon Capture credits such as 45Q. In some cases, the actual value of the CO2 itself has been shown to exceed the value of the electricity and heat; in these cases, the system can be net profitable even if the electricity and heat are given away for free. Counterintuitively, these scenarios would argue for a minimum-efficiency design that maximizes the throughput of fuel and the corresponding carbon-based revenue. 

This presentation will provide a technical overview of the APOCC cycle, highlighting the features that differentiate it from a conventional gas turbine powerplant; economic case studies will also be presented, demonstrating the financial appeal of this new paradigm. 

Presenting Author: Shaun Sullivan Brayton Energy

Presenting Author Biography: Shaun Sullivan is the President and a Principal Engineer at Brayton Energy, an Engineering R&D Firm located 45 miles north of Boston. Shaun has worked in the field of cutting-edge energy- systems development for nearly 25 years, specializing in systems, heat transfer, and thermal modeling and analysis. At Brayton he has led projects in hybrid-electric fuel cell systems, concentrating solar power, supercritical carbon dioxide cycles, energy storage, low-emissions and alternatively-fueled combustors, advanced heat exchangers, and combined heat and power solutions. Prior to joining Brayton in 2008 he worked at Ingersoll Rand Energy Systems (now FlexEnergy), a leading manufacturer of small-scale (70 kWe and 250 kWe) turbines for backup, alternatively-fueled, and distributed power generation. Shaun holds an M.S. in Mechanical Engineering from the Massachusetts Institute of Technology (MIT) and a B.S. in Mechanical Engineering from Rensselaer Polytechnic Institute.