Kun Soo Chang

Synthesis of maximum energy recovery networks in batch processes

In the heat integration problem for batch processes, there are two differences in treatment from continuous operations. The first is the occurrence of cocurrent heat exchange, this case may happen when a process can not be transferred to another process. The second is that time must be considered as a variable. We divide the problem into two cases, namely co-current heat exchange and counter-current one, and then intend to find the rules to satisfy the requirement of each case. For the former, a matching rule and a MILP formulation had been proposed but any method did not obtain the optimal solution. The latter including the time as a variable often occurs in the practical industry. The limitation of time has been reduced by changing the schedule of processing or using the heat storages. However, the systematic rule considering the batch cycle time has not been presented for the rescheduling and heat storage is not usually practical although it is reasonable concept. Therefore this paper presents general method for optimal rescheduling to maximize heat recovery and reduce batch cycle time when heat exchanges occur as counter-current type. In the exchanges of co-current type, the heuristic, called the modified H/H which can be used to find the optimal match sequence of heat exchange between hot and cold tanks, is proposed. The proposed heuristics have the advantages of simple calculation and small computation time.

THE DESIGN AND SYNTHESIS OF BATCH/SEMICONTINUOUS PROCESSES

Until now, an evolutionary method or empirical rule has been used to improve the initial design of batch/semicontinuous processes. In this paper, the proposed approach is to make a superstructure which fully contains all possible structures. And then suing a MINLP(mixed integer nonlinear programming) model, we obtain the optimal process network. MINLP model contains methodology deciding the candidates of merging tasks and using parallel equipments. Thus, the economic savings of capital cost of batch/semicontinuous processes are possible by adding equipment in parallel for bottleneck stages or merging/splitting tasks. MINLP model is solved by using a generalized reduced gradient algorithm. The effectiveness of MINLP model in single product batch plant is demonstrated by solving example problems. Also, by inserting intermediate storage tank, we reduce the capital cost for batch/semicontinuous processes and determine the optimal size of intermediate storage tank.

The Design and Synthesis of Batch/Semicontinuous Processes

Abstract Until now, many papers discussed the formulation of sizing problem for the optimal design of batch/semicontinuous processes. In this study it shows that the solutions for the sizing problem of batch/semicontinuous processes are applicable to retrofitting problem. Then several synthesis procedures have been proposed because the economic structural design and efficient equipment utilization can reduce the overall idle time in the processing units. In this study, to improve the initial design of batch/semicontinuous processes, an mathmatical procedure is proposed. The proposed approach is to make a superstructure which fully contains all possible structures. And then using a MINLP(mixed integer nonlinear programming) model, we obtain the optimal process network. The MINLP model contains methodology deciding the candidates of merging tasks and using parallel equipments. Thus, the economic savings of capital cost of batch/semicontinuous processes are possible by adding equipment in parallel for bottleneck stages or merging/splitting tasks. The MINLP model is then solved by using a generalized reduced gradient algorithm. The effectiveness of the MINLP model in single product batch plant is demonstrated by solving example problem. Also, by inserting intermediate storage tanks, we reduce the capital cost for batch/semicontinuous processes and determine the optimal size of the intermediate storage tank.

Rule-Based Expert System for Diagnosis of Energy Distribution in Steel Plant

Abstract In this paper, a rule-based expert system for diagnosing energy distribution in a steel plant is developed to maintain an intelligent balance between the supply and the demand of gases being used as major energy sources in the plant. About 300 rules are incorporated into the expert system to imitate the action of the operators at the energy center. The expert system draws a conclusion by inference through the rules using the data obtained from the sensors or the gauges installed in several unit plants. It then displays the results of the inference on the CRT in the energy center to guide the operators. To infer conclusions, a commercial expert system shell Nexpert Object is used on a SUN 4 workstation.