(5f) Viability of Combined Cycle Drivers for LNG Plants

The LNG industry is seeing a surge in construction of high capacity trains to capitalize on the increasing demand for natural gas. This presents interesting challenges on LNG drivers configuration in the light of stricter environmental regulations on emissions and increasing focus on plant efficiency. Combined Cycle driven LNG plants are well suited to meet this challenge. Owners can increase both the production efficiency as well as thermal efficiency of their plants. In addition, Combined Cycle driven plants are more eco-friendly than conventional gas turbine driven LNG plants. This paper discusses the viability of Combined Cycle drivers for LNG plant based on ConocoPhillips Optimized CascadeSM process. Plant-wide dynamic simulation model is used as a tool to conceptually develop and test the application of Combined Cycle drivers.

The Optimized Cascade LNG process is characterized by three refrigeration systems that share the refrigeration load. In conventional plants, the refrigeration compressors are driven by three gas turbines to provide operational flexibility and reliability. The operational viability of Combined Cycle drivers was studied by recovering the waste heat from two gas turbines to power a steam turbine for the third compressor. The paper compares the conventional and combined cycle driven LNG plant at different operating conditions. In addition, the paper discusses the impact on cost, efficiency and reliability of Combined Cycle driven LNG plants.