Euy Soo Lee

A web-based, interactive virtual laboratory system for unit operations and process systems engineering education: issues, design and implementation

The development of real educational content and customized virtual education systems satisfying the needs of a specific engineering education domain is getting more and more research attention in this era of ubiquitous Web and virtual technologies. By analyzing the characteristics of computer-based educational methods and adopting the rapidly changing Internet and object component technologies, we have developed a Web-based, interactive virtual laboratory system for unit operations and process systems engineering education, and validated its effectiveness by surveying student users of the implemented prototype system. In this paper, we also discuss many technical issues in building Web-based interactive virtual education systems and share the experience obtained. The proposed system is expected to overcome many obstacles in performing the unit operations laboratory in the current setting. More teachware and experiment suites are being added for more extensive, quantitative evaluation of educational efficiency of the proposed methodology and the system.

Web-based interactive virtual laboratory system for unit operations and process systems engineering education

Abstract The development of the real educational contents and customized virtual education satisfying the needs of specific engineering education domain is getting more and more research attention in this area of Web and virtual technologies. By analyzing the characteristics of computer-based educational methods and using the rapidly changing Internet and object technologies, we developed a Web-based, interactive virtual laboratory system of unit operations and process systems engineering education. The proposed system is expected to overcome many obstacles in performing the unit operations laboratory at the current setting. More teachwares and experiments suites are being added for the extensive, quantitative evaluation on educational efficiency of the proposed system, and the result will be reported at the conference.

Intermediate storage tank operation strategies in the production scheduling of multi-product batch processes

Abstract Multi-product batch processes use intermediate storage tanks to increase plant productivity and operational efficiency. In this paper, relations are developed for production scheduling models of the multi-product batch processes with storage time constraints of the intermediate storage tank. Numerical formulas are obtained to determine the makespan and the completion times of products on each unit. These results are extended to accommodate the general serial process networks with storage time and the product constraints of the intermediate storage tank. Next, the effects of the location and the number of the intermediate storage tank on the production scheduling are considered. From the above analysis, a MIPL model to find the maximum makespan is proposed. Applications of the developed model are presented with an example.

Scheduling of non-sequential multipurpose batch processes under finite intermediate storage policy

Abstract In this study, we present a mathematical model for optimal scheduling of non-sequential multipurpose batch processes under finite intermediate storage (FIS) policy. In non-sequential multipurpose batch processes, the production routes of products may be different from one another and may be in opposite direction. Consequently, in order to reduce idle time of units and to raise the efficiency of process, we have to make operation sequences of products in each unit different by considering the production route of each product. For the formulation of this problem, we represented the starting and finishing time of a task in each unit with two coordinates. One is based on products, and the other is based on operation sequences. Then, we matched the variables used in the two coordinates into one with binary variables and logical constraints. We formulated this problem as an MILP model. Compared with Jung, J. H., Lee, H., Yang, D. R. and Lee, I. (1994) [Completion times and optimal scheduling for serial multi-product processes with transfer and setup times in zero wait (ZW) policy. Computers & Chemical Engineering , 18(6), 537] and Kim, M. S., Jung, J. H. and Lee I. (1996) [Optimal scheduling of multiproduct batch processes for various intermediate storage policies. Industrial Engineering & Chemical Research , 27, 1840] who used an MINLP model for multiproduct scheduling problems, we su9ggest an MILP model, even though we handle sequence dependent setup times in multipurpose processes. Therefore, the proposed model can guarantee the optimality of the solutions. We applied this model to two examples to show the effectiveness of the model. The MILP solver we used to solve these problems is GAMS/ OSL and H/W is IBM RS/6000 (model 350).

Optimal operation of quality controlled product storage

Abstract The mixed integer linear programming model has been developed for the production scheduling of polybutene (PB) process of Daelim Industrial Co. (DIC) in Korea. The PB process is composed of one reactor, 13 storage tanks and two package types. It produces seven reactor products. Most of the tanks are practically dedicated to a specific product but in general, any tanks can be shared by multiple products. Also, two major products use multiple tanks. The reactor is operated on block mode. The products are liquid and they should be stored in tanks before packaging. The unique characteristics of this scheduling problem exists on the fact that the product in tank should be locked for 3–15 days in order to check the quality specifications after run-down from the reactor. The primary objective of scheduling is reducing the number of quality checking process because it causes great loss in production time and tank utilization. The model is composed of about 1500–2000 integer variables. The branching priorities are adjusted according to the importance of variables based on current manual scheduling practice and it greatly enhanced the convergence of mixed integer model. The scheduling system was successfully implemented in real plant and replaced the manual work of scheduler.

Kinetic mechanism of dimethyl ether production process using syngas from integrated gasification combined cycle power plant

In a 1-step synthesis gas-to-dimethyl ether process, synthesis gas is converted into dimethyl ether (DME) in a single reactor. Three reactions are involved in this process: methanol synthesis, methanol dehydration and water gas shift, which form an interesting reaction network. The interplay among these three reactions results in excellent syngas conversion or reactor productivity. The higher syngas conversion or reactor productivity in the syngas-to-DME reaction system, compared to that in the syngas-to-methanol reaction system, is referred to as chemical synergy. This synergy exhibits a strong dependence on the composition of the reactor feed. To demonstrate the extent of this dependence, simulations with adjusted activity for each reaction were performed to reveal the relative rate of each reaction. The results show that the water gas shift reaction is the most rapid, being practically controlled by the equilibrium. Both methanol synthesis and methanol dehydration reactions are kinetically controlled. The role of the dehydration reaction is to remove the equilibrium barrier for the methanol synthesis reaction. However, the role of the water gas shift reaction is more complex; it helps the kinetics of methanol dehydration by keeping the water concentration low, which in turn enhances methanol synthesis. It also readjusts the H2 : CO in the reactor as the reactions proceed. In the CO-rich regime, the water gas shift reaction supplements the limiting reactant and H2, by reacting water with CO. This enhances both the kinetics and thermodynamic driving force of the methanol synthesis reaction. In the H2-rich regime, water gas shift consumes the limiting reactant, CO, which harms both the kinetics and thermodynamics of methanol synthesis. An understanding of these complex roles of the methanol dehydration and water gas shift reactions and of their dependence on the syngas composition explains why the synergy is high in the CO-rich regime, but decreases with the increasing H2 or CO2 content in the reactor feed. The analysis shows that the optimal H2 : CO for the LPDME reactor is around 1-to-1, in good agreement with the results from the simulation. While the 1-to-1 feed provides a good foundation for some process configurations, it does not match the composition of syngas, which typically has a H2 : CO of 3 : 1 or greater.

OPTIMAL DESIGN OF MULTISITE BATCH-STORAGE NETWORK UNDER SCENARIO-BASED DEMAND UNCERTAINTY

An effective methodology is reported for the optimal design of multisite batch production/transportation and storage networks under uncertain demand forecasting. We assume that any given storage unit can store one material type that can be purchased from suppliers, internally produced, internally consumed, transported to or from other plant sites, and/or sold to customers. We further assume that a storage unit is connected to all processing and transportation stages that consume/produce or move the material to which that storage unit is dedicated. Each processing stage transforms a set of feedstock materials or intermediates into a set of products with constant conversion factors. A batch transportation process can transfer one material or multiple materials at once between plant sites. The objective for optimization is to minimize the probability averaged total cost, which consists of the raw material procurement cost, the cost of setting up processes, inventory holding costs of the storage units, and the capital costs of processes and storage units. A novel production and inventory analysis formulation, the PSW (periodic square wave) model, provides useful expressions for the upper/lower bounds and average level of the storage inventory. The expressions for the Kuhn-Tucker conditions of the optimization problem can be reduced to two sub-problems. The first yields analytical solutions for determining lot sizes, and the second is a separable concave minimization network flow sub-problem whose solution yields the average material flow rates through the networks for the given demand forecast scenario. The result of this study will contribute to the optimal design and operation of large-scale supply chain systems.

Simulation of Surfactant Based Enhanced Oil Recovery

Surfactant flooding is an important process for enhanced oil recovery. A substantial amount of remaining oil resides in reservoirs especially in carbonate oil reservoirs that have low primary and water-flood oil recovery. Most of the surfactant flooding studies to date has been performed in water-wet sandstone reservoirs. As a result, the effects of heterogeneity and wettability of carbonates on surfactant flooding efficiency are fairly unknown. The purpose of this simulation study was to determine the effects of wettability and wettability alteration on Dodecylbenzene Sulfonate surfactant flooding in carbonate reservoirs. This study used the multi-phase, multi-component, surfactant flooding simulator called UTCHEM. The base case results showed that additional 27.8% of oil recovered after water-flooding process. Sensitivity analyses of key parameters such as chemical slug size and concentrations, salinity, reservoir heterogeneity and surfactant adsorption were performed to optimize a surfactant design for a mixed-wet dolomite reservoir. The study was then extended to simulating wettability alteration during the field scale surfactant flood. The results of modeling the wettability alteration showed that significant differences in injectivity and oil recovery are caused by the changes in the mobility of the injected fluid. As the use of surfactant flooding spreads into the reservoir especially oil-wet and mixed-wet reservoirs, the importance of surfactant-based wettability alteration will become important.

Effect of magnesium chloride on the isobaric vapor–liquid equilibria of formic acid–water system

Abstract Formic acid and water form a maximum-boiling azeotrope in their mixtures. To break the azeotropic boiling in this system, inorganic salts are frequently added, because the addition of electrolytes alters significantly the equilibrium nature of the original system. In this paper we report the vapor–liquid equilibrium data for the formic acid–water–magnesium chloride system over a wide range of salt concentrations at 760 mmHg. On the pseudo-binary assumption the equilibrium data were correlated with Halas model for liquid phase, by considering the chemical equilibrium in vapor phase. The model showed an excellent agreement with experimental data over a broad range of salt concentrations.

Characterization of crude feed and products from operating conditions by using continuous probability functions and inferential models

The purpose of this paper is to provide information for the characterization of the products and feed of a crude fractionator, hard to get from a hardware system, by using probability function and inferential model of realtime operating conditions. TBP is a major characteristic of CDU products and feed. It has become possible to consider that the TBP of component can be predicted by using an inferential modeling technique such as partial least square (PLS) or artificial neural network. On the other hand, knowing that the characteristic of each product of a crude distillation unit follows a continuous probability distribution function, variables of the probability distribution function can be calculated from operating conditions in the same way. In general, the proposed model can provide a tool for doing more efficient operations to maximize profit.