Transient natural gas liquefaction process comparison-dynamic heat exchanger under transient changes in flow

• Two transient natural gas liquefaction processes were developed.
• Robust Model-predictive control (MPC) was designed for heat exchangers.
• Transient responses for both designs were compared.
• Natural gas consumption and liquefied natural gas production’s graphs were given.

This paper discusses transient Aspen HYSYS modeling and optimization of two natural gas liquefaction processes and identifies the rate-limiting components during load variations. The optimized model for both processes provides details for comparison. Flowrate variations included in this investigation drive transient responses of all units, especially compressors and heat exchangers. Heat exchangers commonly represent the most sensitive components to transients. This sensitivity decreases when using patent-pending dynamic heat exchanger designs and control methods. Model-predictive controls (MPC) effectively manage such heat exchangers and compare favorably with results using traditional controls. Transient efficiency graphs for both designs illustrate improvements during model predictive control. These new controls and designs optimize natural gas (NG) consumption and liquefied natural gas (LNG) production.