Optimal process synthesis, design and operation for energy saving in natural gas processing

Natural gas nowadays becomes a hot topic in fuel industry. As one of the cleanest fossil fuels, recent discoveries on natural gas plays and newly developed technology on extracting unconventional natural gas have drawn worldwide attention. Amongst all the factors existing along liquid natural gas (LNG) value chain, natural gas liquefaction and LNG receiving terminal are the two that cost the most. In this dissertation, the main work is focused on the optimization for natural gas liquefaction process, and a novel design for a LNG receiving terminal that integrates LNG re-gasification and shale gas NGL recovery.;Natural gas liquefaction is an energy-intensive process. Energy efficiency maximization is the major objective in liquefaction process design and operation. In this dissertation, two chapters have been dedicated on the work of optimizing natural gas liquefaction process by reducing energy consumption. The first work employs trial-and- error method using Apen Plus, based on the thorough thermodynamic analysis of the liquefaction process. Using the thermodynamic analysis results, an optimization simulation is successfully undertaken, and the results before and after optimization are compared to validate previous analysis.;The second work presents a novel methodology for natural gas liquefaction optimization on energy consumption minimization. This methodology is based on mathematical programming and deterministic global optimization. LINDOGlobal solver is employed to solve the optimization problem. Comprehensive thermodynamic analysis is also conducted in related chapter in this dissertation, in order to give deep understanding of the LNG refrigeration system and optimization procedure.;Another major part in this dissertation is about a newly designed LNG receiving terminal. This design integrates LNG re-gasification with shale gas NGL recovery, so that the tremendous cold energy from LNG can be utilized through NGL fractionation process. Besides, traditional ways for LNG re-gasification that cause environment concerns, such as using sea water or natural gas itself, can also be reduced or even avoided.;In related chapter within this dissertation, a novel conceptual design by integrating NGL recovery from shale gas and LNG re-gasification at receiving terminals has been developed. An MILP model is developed for this design. This model helps select the optimal operating conditions for each fractionation columns, which causes lowest operation cost. Heat exchange network design and analysis are also conducted to fulfill this process design.;To take this design to another level, uncertainty of shale gas flowrate is considered in next step. The expected profit is maximized under the stochastic optimization approach, with the estimation of the probability distribution of shale gas flowrate. The fluctuation of shale gas flowrate is embedded with the MILP model. The final results and analysis are also presented in this work.