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A simulation-based optimization framework is introduced. First, a base case design is conducted using the commercial simulator. Then, design variables are decided. Next, minimum and maximum ranges of the design variable are determined. We will call this the design space. A comprehensive simulation of the design space is executed. Next, empirical modeling of this design space is performed. This is called the process mapping step. After verification of the model using a test data set, the optimization problem is solved using the developed data-driven model. The methodology is applied to the optimal design of a natural gas liquefaction process for an offshore liquefied natural gas (LNG) plant.

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In this paper, a conceptual process design for a novel natural gas liquefaction plant developed especially for offshore application is presented. Onshore liquefied natural gas (LNG) production usually utilizes mixed refrigerant (MR)-based cycles for high efficiency, in terms of operating cost. This paper proposes a cascade process that uses nitrous oxide and nitrogen refrigerants. The liquefaction process can be subdivided into a precooling section in the vapor phase, a condensation section, and a subcooling section in the liquid phase. The vapor compression refrigeration cycle of nitrous oxide is applied to the precooling and the condensation sections, whereas the gas compression refrigeration cycle of nitrogen is applied to the subcooling section of LNG. The proposed process shows enhanced efficiency, compared to the conventional turbine-based processes with the specific power comparable to the MR processes.

We describe herein a systematic regeneration of waste sulfuric acid produced in semiconductor manufacturing, using batch vacuum distillation (BVD). During the recycling process, dilute sulfuric acid feed was continuously concentrated and fed back to the original wafer washing step. It consisted of a batch tank to charge the feed solution, condenser to capture generated vapor, receiving tank to receive condensed distillate liquid, and vacuum pump to reduce the system pressure. The improper control of the vacuum operation led to incomplete condensation; consequently, the vacuum pump became dysfunctional. The goal of this study was to prevent such mishap. After the feed condition was defined, a basic design was conceived, and the main characteristics of the BVD were determined. The results of sensitivity analyses on the feed and operating conditions have been discussed. The strategies for designing the vacuum pump’s capacity should be changed depending on phase equilibria at the target pressure.