Supersonic Ejectors for Hydrocarbon Emissions Capture
Supersonic ejectors can be applied to capture low-pressure leakage gas from the gas seal vents of a centrifugal compressor. This captured gas can be re-injected into the fuel gas line of the gas turbine driver or the captured gas can be used as a fuel for gas fired utility heaters. By capturing the gas that is normally emitted to the atmosphere the operator can reduce operating cost and enjoy a reduction in hydrocarbon foot print. Because the supersonic ejector does not have moving parts, the system operating and maintenance costs are lower than functionally comparable traditional systems. In this study, a prototype of a supersonic ejector system was developed and tested at a pipeline compressor station. The obtained test data were used for developing and tuning a mean-line aerodynamic analysis tool, which predicts the ejector’s operating map. A family of three ejectors was designed to cover a range of operating conditions associated with gas turbine driven pipeline compressors. These ejectors were built, installed on a specially designed panel, described as the ejector system, and tested on inert gas at the original equipment manufacturer’s (OEM’s) facility. A comparison of predicted and as-tested supersonic ejector performance maps is discussed and conclusions are made about the system operating range.