Heui-Seok Yi

A NOVEL MILP MODEL FOR PLANTWIDE MULTIPERIOD OPTIMIZATION OF BYPRODUCT GAS SUPPLY SYSTEM IN THE IRON- AND STEEL-MAKING PROCESS

A novel MILP model for plantwide multiperiod optimization of byproduct gas supply system in the iron- and steel-making process is proposed. Compared with the previous optimization model, proposed approach simultaneously optimizes the byproduct gasholder levels and gas distribution among conflicting objectives. Both integer and continuous variables are used in determining the optimal fuel load change according to the fuel types. Objectives include the minimization of the unfavorable byproduct gas emission or shortage, oil consumption, the number of turn on/off of the burner, maintaining the normal holder levels, and maximizing fuel usage efficiency. Case study results show that the proposed model finds the optimal solution in terms of total cost reduction and the different optimization model structure makes the solution more applicable than the previous approach.

Plant-wide Optimal Byproduct Gas Distribution and Holder Level Control in the Iron and Steel Making Process

A new plant-wide multiperiod optimization approach is proposed for optimal byproduct gas distribution to prevent unfavorable byproduct gas emission and equipment trip and simultaneously to maximize the efficiency of energy resource usage in the iron and steel making process. Compared with the previous approach, the proposed approach finds the optimal trade off among conflicting objectives such as holder level control, minimization of oil consumption and number of burner switching, and the maximization of generating electricity. To consider the different fuel load change operation according to the fuel types, both integer and continuous variables are used. Case studies were performed to verify the usefulness of the proposed approach, and the results show good performance in terms of the reduced number of burner switching which leads to the reduction of total cost and producing operation-easy solutions.

Plant-wide multiperiod optimal energy resource distribution and byproduct gas holder level control in the iron and steel making process under varying energy demands

Abstract In this paper, a new plant-wide multiperiod optimization model is proposed to determine the optimal energy supply to meet the varying energy demands and unit price changes. MILP (Mixed Integer Linear Programming) model is proposed to find the optimal trade-off among conflicting objectives such as reducing the number of burner on/off and reducing holder level changes, minimizing fuel consumption cost. In the cases study, the proposed approach is used to determine the optimal energy supply for the industrial size problem, and it shows that the proposed model successfully finds the optimal energy resource under varying energy demands and unit price changes.

The Integration of Complete Replanning and Rule-Based Repairing for Optimal Operation of Utility Plants

The integration methodology of complete replanning and plan repairing is proposed to handle the prediction errors for energy demands during multiperiod operational planning. Complete replanning is implemented periodically and plan repairing is triggered during the execution interval. The plan repairing is constructed by a rule-based system because of real-time limitations. The efficiency index of a utility pump is introduced to determine startup/shutdown of equipment without integer programming in plan repairing. Case studies show that the proposed method is more profitable than the conventional replanning method. The total operating costs are reduced by 0.3-9.0% compared with the conventional replanning method.

Periodical replanning with hierarchical repairing for the optimal operation of a utility plant

The integration methodology of periodical replanning and hierarchical repairing is proposed to handle the prediction errors of energy demands in the multiperiod operational planning. The periodical replanning is implemented by the decomposition method. The hierarchical repairing is triggered during the execution interval when prediction errors in energy demands exist. The hierarchical repairing uses the heuristic knowledge. The efficiency indices for utility pumps are introduced to determine the optimal configuration of motors and turbines for running utility pumps without integer programming. Case studies show that the proposed method is more profitable than the periodical replanning. The operational cost is reduced by 0.9–4.0% compared with the cost by the periodical replanning. r 2002 Elsevier Science Ltd. All rights reserved.

The development of the real time plant-wide optimal byproduct gas management system

Abstract The optimal byproduct gas management (OBGM) system was developed for the optimal management of the byproduct gases in the iron and steel making. Because it is difficult for the operator to calculate the optimum operation point in terms of total operation cost under continuously varying operation situation, OBGM system is necessary. The system was developed based on EXCEL environment. It supplies optimal byproduct gas distribution result as well as analysis including expected electricity generation, holder level change, amount of oil consumption, energy distribution to each boiler, and efficiency of energy resource. To verify the performance of the system, case studies for various situation was performed with the developed system, and it finds the optimum solution within an allowable time to be used for on-line application.

Real-time repairing of multiperiod operational plan to reduce the effect of prediction errors on utility plant operation

Abstract Plan repamng methodology to handle the prediction errors for energy demands during multiperiod operational planning is proposed. The plan repairing is constructed by knowledge-based system because of real-time limitation. The efficiency index for a utility pump is introduced to determine optimal startup/shutdown of equipment without integer programming. Two case studies show that the proposed methodology is more profitable than the conventional method. The operational cost is reduced by 1.0 ~ 9.0 % under the timing errors and 0.6 ~ 2.0 % under the quantity errors compared with the conventional method. The plan repairing is indispensable for handling the uncertainty and the unpredicted change of demands and supplies.