Masaaki Muraki

A process-variability-based online scheduling system in multiproduct batch process

Online scheduling in batch processes is a difficult problem because of the complexities, dynamic behavior and process variability involved. In this paper, a process-variability-based online scheduling system (PVSS), which modifies a schedule based on the current process state and possible future processing time variations at short intervals and at the completion of each task, is proposed. The objective of schedule modification by PVSS is to maintain the performance of the schedule and to control the waiting time of each task within the range specified in a recipe under processing time variations. The effectiveness of PVSS is demonstrated by simulation experiments on a multiproduct batch process model. The results indicate that online scheduling systems should modify schedules based on the possible process variability in the future to improve their performance under processing time variations.

Evolutionary synthesis of a multicomponent multiproduct separation process

Abstract The introduction of stream division into the separation process that separates a raw material into multicomponent products is effective in reducing the separation cost. However, it is difficult to synthesize this separation process optimally because of information feedback between the separation sequence and introduction of stream division, and the high complexity of the relation between products when the number of products is more than two. The strategy in which two stages—search of the optimal separation sequence and search of the optimal division ratios—are repeated until the objective function is not improved further is adopted in this paper. Manipulation of a diagram which shows graphically the relation between the raw material and the streams outflowing from the separation process, and the functions of separation, division and blending, is effective in searching the optimal division ratios. A useful method for the generation of a suitable diagram (modified material allocation diagram) is developed by considering the species combination of the subproducts decomposed from the product and the outflowing streams. A four-component five-product separation process synthesis problem demonstrates the effectiveness of this method.

Synthesis of a multicomponent multiproduct separation process with nonsharp separators

Abstract It is necessary for the synthesis of the process separating a raw material into multicomponent products to consider the degrees of separation sharpness and the stream division ratios as design variables in addition to the separation sequence. It is difficult to synthesize this separation process optimally because there is information feedback between the separation sequence, stream division and separation sharpness. A useful method of two stages is developed for this synthesis problem. The first stage is to search for the separation sequence, the second stage is to search for these degrees and ratios, and these two stages are repeated until the optimal separation process is synthesized. It is found that the configuration constructed by manipulating the modified material allocation diagram is suitable for the initial one, that the ratios can be determined by solving the material balance equations when the degrees are known, and that material balance equations become linear by adopting the relative flow rates allocated from the outflowing streams to the products as the variables. These equations can be solved separately for individual products, so that the calculation load can be greatly reduced. There are often more or less variables than equations. This contradiction can be resolved by decomposing the subproducts further with the minimum increase in the separation mass load and/or adjusting the order of the products in solving the linear equations to supply additional relations between the variables. The proposed method is illustrated through the solution of a five-component five-product distillation separation process synthesis problem.

Technological information infrastructure for product lifecycle engineering

Abstract For sustainable development, it is requisite not only to assess multi-dimensional items such as environmental impacts, process safety, product safety, and so on, required from human society, environment, and markets, but also to feedback assessment results to product and process design/development. Through the investigation about requirements for manufactures at each stage in product lifecycle, it becomes clear that PDCA (plan—do—check—action) cycle is necessary to take actions properly from viewpoints of ecosystems, business systems, and society. We clarify required functions of supporting system of PDCA cycle, and then propose material supply chain models of hierarchy structure composed of unit process models. Based on proposed system and models, evaluations of PET bottle recycle system and greenhouse sheet recycle system are implemented as trials. Furthermore, we show the directions of future scope.

Life cycle oriented process synthesis at conceptual planning phase

Abstract Todays process industry is facing severe business conditions, such as mega-competition, and increased market uncertainty. In the circumstances, a life cycle oriented approach, which evaluates and makes decisions based on expected profit through plant life cycle, is critical as a new management principle in the process industry. In the plant life cycle consisting of planning, designing, construction, operation, and disposal, the planning and designing phases are the most important because about 85% of the life cycle cost is determined by the decisions made in these phases. For this reason, a process synthesis approach, which generates profitable process systems at the conceptual planning phase based on decisions considering plant life cycle, is essential to manage profitability under todays business conditions. In this paper, the life cycle oriented process synthesis approach which establishes a process plan at the conceptual planning phase so as to maximize the expected profit through the plant life cycle in consideration of capacity, life, availability, reliability, and mainatainability of each process unit, and future process scenarios, such as expansions, modifications, and shutdown is proposed. In addition, a heuristic process synthesis procedure for this approach is proposed. The effectiveness of the life cycle oriented process synthesis approach and the proposed process synthesis procedure are demonstrated. In addition, areas of further research and development related to the life cycle oriented process synthesis are addressed.

A generic framework for an on-line scheduling and control system in batch process management

On-line scheduling and control systems, which dynamically adjust production schedules according to changes in scheduling conditions, are a vital issue in modern batch processes because of their dynamic behavior and the unpredictable market situation. In this paper, we propose a generic on-line scheduling and control framework to handle a wide variety of uncertainties by utilizing proven external scheduling algorithms. The framework provides fundamental mechanisms to define schedule modification timing and a modification space according to the changes of scheduling conditions, and dynamically modifies a schedule to minimize the effect of the changes by using adequate scheduling algorithms for each situation. The basic structure and mechanisms of the framework are described. Performance of the framework against typical fluctuations in ordinary batch process operations is demonstrated via simulation experiments with a multiproduct batch plant.

Short‐term maintenance scheduling for utility systems

Purpose – The purpose of this study is to optimize short‐term maintenance scheduling of utility systems satisfying network constraints.Design/methodology/approach – A mathematical programming model with network constraints is presented.Findings – There are some cases in which the maintenance of a certain unit affects the operations of non‐maintenance units. The schedule should be evaluated by labor cost, material cost and opportunity costs. However, most utility systems contain dual‐directional flows, making the interdependency of the units an unstable element. In such systems, the dependency between one unit and the other should be adjusted depending on the conditions.Practical implications – Power, steam and water are distributed by utility systems. Unit maintenance affects the operation of non‐maintenance units within the networks. Effective short‐term maintenance scheduling of utility systems must work within these network constraints. Unlike conventional scheduling methods, the excessive concentratio...

Multi-period resource allocation for estimating project costs in competitive bidding

In competitive bidding for project contracts, contractors estimate the cost of completing a project and then determine the bid price. Accordingly, the bid price is markedly affected by the inaccuracies in the estimated cost. To establish a profit-making strategy in competitive bidding, it is crucial for contractors to estimate project costs accurately. Although allocating a large amount of resources to cost estimates allows contractors to prepare more accurate estimates, there is usually a limit to available resources in practice. To the best of our knowledge, however, none of the existing studies have addressed the resource allocation problem for estimating project costs in competitive bidding. To maximize a contractor’s expected profit, this paper develops a multi-period resource allocation method for estimating project costs in a sequential competitive bidding situation. Our resource allocation model is posed as a mixed integer linear programming problem by making piecewise linear approximations of the expected profit functions. Numerical experiments examine the characteristics of the optimal resource allocation and demonstrate the effectiveness of our resource allocation method.

Production planning in remanufacturing/manufacturing production system

Remanufacturing end-of-use product is considered as one effective way to provide ecologically sustainable production industry. Realizing promising business opportunities of remanufacturing in addition to its contribution in saving the environment, this is the time for manufacturers to consider performing remanufacturing production activities accompanying their existing manufacturing. Including remanufacturing, production system is significantly different from conventional manufacturing production system. Instead of single forward flow of material in conventional supply chain, system now contains two material flows, named conventional manufacturing flow sourcing from new materials, and recovery flow sourcing from end-of-use products returned back to the production system. Therefore, to use current conventional production planning models in remanufacturing/manufacturing production system (RMPS) is questionable, and the optimal structure of the production system is still need to be further explored. This research focuses on this two flows characteristic and the return process that occurred in RMPS. We recognize that return process of end-of-use products forms sort of cyclical, or looping process in the system, that product release (sales to fulfill demands) and return affect each other, and have significant influence for system performance. For optimal production planning, a cyclic optimization approach is introduced here. The basic idea is to simultaneously consider the whole cyclical process in the system that caused by the return of end-of-use products, and allowing product release and return process to be treated as variables to be determined in generating optimal production plan. Besides remanufacturing and manufacturing production activities, disposing or sending excessive returned end-of-use parts (products) to material recycler are also carefully considered in production planning mechanism, along with all respective inventories. Based on the approach, a linear programming model for generating production plan in capacitated RMPS producing multi products with common parts is constructed, and applied in a numerical example. The result shows a superior optimality performance compared to conventional approach, as a merit that the whole cyclical process are now being included in optimal solution generation model.

A Heuristic Bidding Price Decision Algorithm Based on Cost Estimation Accuracy Under Limited Engineering Man-Hours in EPC Projects

In this paper, we develop a heuristic bidding price decision algorithm in consideration of cost estimation accuracy under limited engineering Man-Hours (MH) in Engineering, Procurement, Construction (EPC) projects. It allocates engineering MH for cost estimation, which determines the cost estimation accuracy, to each order under the limited volume of MH, and then determines the bidding price for maximizing the expected profit based on cost estimation accuracy under the deficit order probability constraint. Numerical examples show that the bidding price decision in consideration of cost estimation accuracy and deficit order probability is essential for the contractor in making a stable profit in EPC projects, and that the developed algorithm is effective for making such bidding price decision.