Design, Modeling, and Implementation of an Electrically-Driven Seal Gas Booster

This paper outlines the simulation, evaluation, and implementation of an electrically-driven seal gas booster in a tandem dry seal application. The electric boost compressor makes it feasible to supply seal gas to a process compressor’s seals during indefinite pressurized hold. Extended pressurized hold times reduce gas compressor station hydrocarbon emissions by reducing the number of unplanned compressor depressurization events. Traditional pneumatic seal gas boosters require regular depressurized maintenance intervals. The paper addresses the overall decrease in utility demand of the electric seal gas booster when compared to a pneumatic seal gas booster. The total cost difference between the two systems was determined for both initial investment and operational cost. A steady-state simulation of a single impeller centrifugal boost compressor, within a package dry seal gas system utilizing differential pressure control to regulate seal gas flow, was conducted to evaluate overall system performance, design requirements, and constraints. The simulation validated a system design. The design was installed in an operational gas transmission compressor’s seal system for performance monitoring. The field testing data was compared to simulation output parameters to validate the simulation and confirm key performance characteristics. Additional process conditions and multi-body process compressor configurations were evaluated through simulation. The use of differential pressure control, when compared to a flow control for seal gas regulation, has some key differentiating characteristics with regards to implementation of the electric seal gas booster in a package dry seal system [1, 2]. Seal gas source location, supplied internally or externally, is an important consideration for the system’s performance. Continuous operational with the electric seal gas booster requires additional control strategies to manage the process compressor case pressure.