Haruo Sakamoto

Short-term site-wide maintenance scheduling

Abstract Preventive maintenance is essential for every chemical production site to prevent failure and accidents, however, it upsets material and utility flows inside the site and also causes production loss. In order to minimize the loss, maintenance of each plant unit has to be carefully scheduled together with considerations on site-wide material and utility balances. This will involve both production and utility systems, and indeed is a very complicated problem. A scheduling strategy is then employed to handle the problem efficiently. It divides the scheduling into two steps, long-term and short-term. Long-term maintenance scheduling determines the combination of plant shutdown in a period of 2–5 years. Base upon the long-term schedule, a short-term maintenance scheduling optimizes the exact timing of plant shutdown, overhaul, inspection and startup within a maintenance period of 4–10 weeks. Short-term maintenance scheduling involves pre-set utility and material demand profiles during a plant shutdown, overhaul and startup making it a very challenging task. In this paper, a multi-period mixed integer linear programming (MILP) model, a site-model, is proposed as an aid to optimize short-term site-wide maintenance schedule. A special formulation is also developed to deal with the pre-set utility and material demand profiles in the site-model.

Multi-site utility integration—an industrial case study

Abstract Mitsubishi Kasei and Mitsubishi Petrochemical merged to become Mitsubishi Chemical in 1994 making it the largest chemical company in Japan. This allows two original companies’ production sites, especially for those are physically built next to each other, to improve themselves by multi-site integration. Mitsubishi Yokkaichi production plant site is one of the typical examples, which consists of three individual plant sites in the old company structure. Each plant site contains a utility plant to generate steam and electricity for chemical production. After the company merge, connecting steam and electricity among plant sites have been carried out for better flexibility, efficiency as well as capability of the utility systems. Besides these, there are still many other improvement alternatives. A site-model, which includes all three utility plants and production units, was then developed to explore further opportunities. In this paper, applications at Mitsubishi Yokkaichi production site are presented to illustrate the features of the site-model.

Electricity Contract Optimization for a Large-Scale Chemical Production Site

Abstract This paper presents a study on selecting and optimizing electricity contracts for a large-scale chemical production site, which requires electricity importation. Two common types of electricity contracts are considered, Time Zone (TZ) contract and Loading Curve (LC) contract. A multi-period linear programming model, Site-Model, is adopted for the contract selection and optimization. This model includes all site-wide information, such as, product demands, material and utility balances. Therefore, an optimal contract for maximizing the total site profit can be determined.

Flexibility study on site-modeling

Abstract In this paper, we conduct the flexibility study in a utility plant for the largescale chemical production site. It is known that utility plant is usually designed based on its nominal operating condition with attractive economic return. However, because of the fluctuating supply / demand on raw material / product (uncertainty) for the site, it is difficult to design the high efficiency and flexible utility plant. Principally, a good plant design should not only show an optimal balance between capital and operating costs, it must also show an feasibility characteristics which allows economic performance to be applicable in a general operating environment. Hence, the ultimate goal is let plant professionals plan, monitor and manage the plant flexibility in which the future supplies and demands are under uncertainties. For that reason, we would like to introduce an uncertainty study to stabilize the “Utility Plant Flexibility”. In fact, by ignoring the historical data of variations, the plant professionals of course can build a very big plant to deal with all the uncertain situations; however this kind of movement is definitely impractical and inefficient. Thus, the first step we have to define “Flexibility does not imply oversize design of utility plant”. This paper will introduce a new concept to measure the utility plant flexibility based upon the uncertain parameters. Basically the concept is foundation on the Grossmanns idea on flexibility measurement. It is believed that with proper flexible operation in the utility plant, the overall energy usage will be rationalized that generates merit to the company.

Pricing utilities for large-scale chemical production site

Abstract Pricing utilities is one of the major important economic evaluations in the chemical production industry. Usually, company will evaluate its utility price several times per year for chasing the market condition. With the proper pricing strategy, the actual values of utilities can be reflected, which would allow the company to make correct business decision. This paper recommends a new procedure to develop a strategy for the chemical production site to ste up utilities prices to reflect not only its real economic values or production costs but also to provide a better signal for business decisions. Using “Marginal Values Analysis” (MVA) technique is one of the effective ways for the pricing policy and this technique will be adopted for pricing. It is believed that with the proper utilities pricing, overall energy usage will be rationalized that generates merit to the company.

Simultaneous site-wide energy, waste and production optimization - industrial case studies

Abstract In a petrochemical plant site, production, waste treatment and utility systems are three essential elements. They interact with each other via the flows of utility, waste and material, hence creating a lot of options and economic trade-offs among them. To obtain the optimal solutions for the trade-offs, site-wide bottlenecks must be located accurately. Then the three systems could be debottlenecked and optimized simultaneously. This paper proposes the Site-Model, a mathematical model, to debottleneck and optimize the petrochemical plant site site-widely. The model adopts a technique called the marginal value analysis (MVA) for achieving the task.

Marginal values analysis for chemical industry

Abstract The paper proposes a systematic method called “Marginal Values Analysis” (MVA) to calculate marginal values of streams and process sections in a chemical production site. In the MVA, the marginal values are defined into three types to represent the marginal profit, production cost and product value of a stream. With these precise definitions, the marginal values can be used for locating process bottlenecks, pricing utilities, intermediate materials and energy flows. They can also be applied on developing site-wide management strategies, assisting business decisions. A general linear programming model, site-model, that includes all the heat and mass balances and interactions of a chemical production site is adopted for generating the marginal values. By proper formulations in the site-model, all the three marginal values of a stream can be obtained simultaneously. A case study of investment decision-making on a utility system is presented to illustrate the capability of MVA on debottlenecking.