Changhyun Jeong

Hybrid Compressor Model for Optimal Operation of CDA System

Abstract CDA(Compressed Dry Air) is an essential utility to be used in a variety of processes in LCD(Liquid Crystal Display) production industry. Since the demands for CDA fluctuate largely from moment to moment, it is common to supply compressed air with a number of small-capacity compressors rather than few large-capacity ones. In order to meet the varying demands, operation conditions of compressors change at every second and hence the efficiency of compressors is low. To find optimal operating strategy of such compressor network, first a hybrid modeling technique of ideal model and empirical model is developed to predict efficiency and power consumption of each compressor in the network. Then, optimization procedure is applied to search optimal operation strategy. The proposed method was applied to actual off-line data of LCD production industry and about 5% of annual power consumption was saved by optimization.

Optimal hydrogen network design for byproduct recycling for yeosu petrochemical complex

This study presents a method for petrochemical complex to make most efficient use of hydrogen. Hydrogen is an important utility in the production of clean fuels such as low-sulfur gasoline and diesel. The methodology is based upon mathematical optimization of a superstructure and maximizes the amount of hydrogen recovered across a site. The techniques account for constraints as well as the existing equipment and are suited for revamping real, industrial systems. The optimum network of new equipment such as compressors and purification units is also considered. The methods are illustrated with an industrial case study, where both operating cost savings and hydrogen recovery are achieved. The approach in this study can account for economic issues such as payback time and capital budgets while delivering process designs that make best use of resources.

A sustainable design and simulation of waste sulfuric acid concentration process for semiconductor industry

Abstract In this work, a sustainable design for waste sulfuric acid concentration process that meets a set of constraints and easily integrable to the existing semiconductor fabrication system was pursued. The constraints are related to the stringent environmental, economical and process safety conditions. A set of candidate design was analyzed and the evaporation under vacuum was found to be a sustainable design model. The design model (based on symmetric electrolyte NRTL model 1 for thermodynamics property predictions) developed using ASPEN, identified the optimum operating temperature, pressure for the desired product purity and product rate specifications. The results from our steady state simulations were compared with the data from existing literature, and they showed good agreement. Further, the process compactness and its sensitivity to the process variables demand a strict start-up procedure and control of the operating variables. To address this, a dynamic simulation was carried out by developing a dynamic model using ASPEN Dynamics. Initial settling and set-point change behaviour were studied to get a better understanding of the process dynamics.