sCO2 Compression
Abstract
Supercritical Carbon Dioxide (sCO2) power cycles are a transformational technology for the energy industry, providing higher thermal efficiency compared to traditional heat-source energy conversion including conventional fossil and alternative energy sources. The novel cycle significantly reduces capital costs due to smaller equipment footprints and design modularity. In addition, it allows for rapid cyclic load and source following to balance solar and wind energy power swings. Compressing CO2 is not novel, but mostly at lower vapor pressures, and at higher pressure and lower temperatures as a liquid. Compression near the dome (near critical pressure and temperature) is a new interest that has many advantages and challenges. The key advantage is the low head requirement when compressing near the CO2 dome (95oF [35oC] and 1,233 psi [8.5 MPa]). To pressurize from 1,233 psi (target inlet pressure of power cycles) to 3,916 psi (27.0 MPa), only a single high-speed compressor stage is required. This low head requirement means less power is required to compress and leads to an increase in thermal efficiency of these cycles. High-efficiency compression technology can reduce the power of Enhanced Oil Recovery (EOR) and Carbon Capture and Sequestration (CCS) applications. This type of compression also brings many challenges. A compressor for this application pushes many current technology limits, including but not limited to: pressure rise per stage, bearing technologies, sealing technologies, damping, rotordynamics, compact machinery packaging, and high-density, high-speed compression. In addition, when compressing near the CO2 dome, there are large swings in density for slight changes in temperature. This is a unique challenge not observed when CO2 is pumped as a liquid or compressed as a vapor. Due to these large changes in density, range extension is required to maintain high compression efficiency and controlled mass flow over a range of operating temperatures. Recent testing finished on a state-of-the-art sCO2 compressor operating near the dome that was designed, manufactured, and tested by Southwest Research Institute (SwRI) and General Electric Global Research (GE-GRC). This tutorial will highlight many of the unique aspects of the design, especially those challenges and decisions that were focused on high pressure ratio compression stages, high-density and high-speed flow, special rotordynamic considerations, and the overall challenges of compact high-pressure turbomachinery. It will then cover how the design and analysis translated to testing with a real gas that experiences rapid changes in fluid properties for minimal fluctuations in temperature. In addition, due to its need for compact, high-power, and high-speed machinery, the development of sCO2 machinery aids in the development of many advanced components and hardware that can also be used in other applications. This includes high-pressure and high-temperature end seals, zero- to low-emission seals, hermetically sealed systems with gas or magnetic bearings, high-pressure single stage compressors, range extension technologies like variable Inlet Guide Vanes (IGVs), and high-density and high-critical speed ratio operation.
Description
TutorialCollections
Citation
Cich, Stefan D.; Moore, J. Jeffrey; Kulhanek, Chris; Mortzheim, Jason P. (2021). sCO2 Compression. Turbomachinery Laboratory, Texas A&M Engineering Experiment Station; Texas A & M University. Libraries; Texas A & M University. Libraries. Available electronically from https : / /hdl .handle .net /1969 .1 /196732.