Integrated Refrigeration for Gas Turbine Driven LNG Plants

By Xun Jin, Partha Ghosal, George Hu, and Rajeev Nanda

Technip Energies

A LNG liquefaction plant is constrained by the discrete power available from its gas turbine drivers, which in addition suffers a substantial decrease with increasing ambient temperature. Gas Turbine Inlet Air Chilling (IAC) promotes the power output and improves the fuel efficiency of gas turbine drivers, which also helps to stabilize the LNG plant’s seasonal production variation. Current industry experience often involves an auxiliary refrigeration system dedicated for IAC, on top of the refrigeration system already in place for liquefaction.

Integrated refrigeration aims to consolidate the refrigeration required for gas turbine IAC into the available liquefaction refrigeration system. Specifically, IAC refrigeration suited for cooling ambient air (e.g. 40~100F) is supplied from the pre-cooling cycle within a liquefaction process. This concept is applicable for all liquefaction processes, including single Mixed Refrigerant (MR), pre-cooled single MR, or cascade. However, based on cycle configuration and refrigerant used, each specific integration scheme will have to be tailored and optimized case by case.

This paper presents a project application developed based on US patent 6,324,867. In this case study, a slip stream of propane refrigerant from the Propane Pre-cooled Mixed Refrigerant (C3MR) process chills an intermediate cooling medium (e.g. glycol water), which in turn circulates to gas turbines for air chilling. When compared with a segregated mechanical refrigeration system, such an integrated design is found to offer:

• Significant savings in Capital Expenditure and potential savings in Operational Expenditure;
• Reduced number of equipment and plot space;
• Moderate increase in propane circulation and compressor size;
• Minimal impact on the rest of the plant