Jaeheum Jung

Simultaneous synthesis of a heat exchanger network with multiple utilities using utility substages

Abstract Heat exchanger network synthesis (HENS) has progressed by using mathematical programming-based simultaneous methodology. Although various considerations such as non-isothermal mixing and bypass streams are applied to consider real world alternatives in modeling phase, many challenges are faced because of its properties within non-convex mixed-integer nonlinear programming (MINLP). We propose a modified superstructure, which contains a utility substage for use in considering multiple utilities in a simultaneous MINLP model. To improve model size and convergence, fixed utility locations according to temperature and series connections between utilities are suggested. The numbers of constraints, discrete, and continuous variables show that overall model size decreases compared with previous research. Thus, it is possible to expand the feasible search area for reaching the nearest global solution. The models effectiveness and applications are exemplified by several literature problems, where it is used to deduce a network superior to that of any other reported methodology.

Optimal operation strategy of batch vacuum distillation for sulfuric acid recycling process

Abstract Vacuum distillation techniques are widely used in food, biological, pharmaceutical, and wastewater treatment industries. Because of its operation at low temperatures, vacuum distillation prevents the thermal decomposition of materials and alleviates corrosion processes; however, condenser size can be dramatically increased because of reductions in mean temperature differences under the vacuum operation. In batch vacuum distillation processes, vapor generation rate and mean temperature differences are changed with time. In view of these characteristics of batch operation, this paper suggests a novel methodology to minimize the condenser size in batch vacuum distillation processes. The target process is a sulfuric acid recycling system in semiconductor manufacturing plants. In this paper, an equation-oriented dynamic model is established and optimization problem is formulated. By solving the nonlinear programming problem, the condenser size is dramatically reduced when operation time is fixed. In contrast, operation time is greatly shortened when the installed condenser surface area is fixed.

Simultaneous Optimization Models for Heat Exchanger Network Synthesis with Multiple Utilities: A New Strategy by Using Utility Sub-stage

Abstract In simultaneous method area of heat exchanger network synthesis (HENS), a mixed integer nonlinear programming (MINLP) model with stagewise superstructure is developed to minimize the total annualized cost (TAC). However, most of the preceding researches do not allow to consider the multiple utilities. Unlike previous superstructure, the utility sub-stage is located between the stages and multiple utilities are arranged in series. The heuristic, the optimal utility position should not be located in splitting stream, increase the searching area by expanding the number of stage and reduce the model size which is related to convergence of model. To verify the model, two examples are proposed and they show the effectiveness by deducing a network superior to any reported methodology.