Optimized Ejector-Diffuser Design Procedure for Natural Gas Vapor Recovery

A procedure for designing optimized ejector-diffuser systems for recovering natural gas vapor from oil storage tanks is presented. The system utilizes high pressure gas from the separator to entrain the ambient pressure gas from the tanks and then pumps the mixture to the sales line. The analysis predicts the minimum separator pressure and the optimum nozzle Mach number and ejector area ratio required to accomplish this task. The results of a parametric study suggest that this system is feasible and that the higher the required ejector compression ratio the more critical is the use of an optimized design.