Development Of Advanced Centrifugal Compressors And Pumps For Carbon Capture And Sequestration Applications

Lecturepg. 107-120In order to reduce the amount of carbon dioxide (CO2) greenhouse gases released into the atmosphere, significant work has been made in sequestration of CO2 from power plants and other major producers of greenhouse gas emissions. The compression of the captured CO2 stream requires significant power, which impacts plant availability, capital expenditures, and operational cost. Preliminary analysis has estimated that the CO2 compression process alone reduces the plant efficiency by 8-12 percent for a typical power plant. The goal of the present research is to reduce this penalty through development of novel compression and pumping processes. The research supports the U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL) objectives of reducing the energy requirements for carbon capture and sequestration in electrical power production. However, the technology presented here is applicable to other gases including hydrocarbons as well as smaller scale carbon capture projects including CO2 separation from natural gas. The primary objective of this study is to boost the pressure of CO2 from near atmospheric to pipeline pressures with the minimal amount of energy required. Previous thermodynamic analysis identified optimum processes for pressure rise in both liquid and gaseous states. Isothermal compression is well known to reduce the power requirements by minimizing the temperature of the gas entering downstream stages. Intercooling is typically accomplished using external gas coolers and integrally geared compressors. Integrally geared compressors do not offer the same robustness and reliability as in-line centrifugal compressors. The current research develops an internally cooled compressor diaphragm to remove heat internal to the compressor. Results documenting the design process will be presented including 3-dimensional (3D) conjugate heat transfer computational fluid dynamics (CFD) studies. Experimental demonstration of the design was performed using a centrifugal compressor closed loop test facility at the authors’ company. A range of operating conditions was tested to evaluate the effect on heat transfer. At elevated pressures, CO2 assumes a liquid state at moderate temperatures. This liquefaction can be achieved through commercially available refrigeration schemes. However, liquid CO2 turbopumps of the size and pressure needed for a typical power plant were not readily available. This paper describes the test stand design and construction as well as the qualification testing of a 150 bar cryogenic turbopump. A range of suction pressures were tested and net positive suction head (NPSH) studies were performed