A chemical production site consists of multiple production and utility plants that are interconnected with utility and material flow network. To achieve a smooth operation, keeping utility balance (mainly electricity, fuel, steam and water) inside the production site is very important. Usually, in order to keep the balance, the production site requires importing different kinds of utilities, such as electricity, fuels and sometimes steam for sustaining the production. To protect both the supplier and the customer, long-term supply contracts for these utilities are often required, such that the customer can acquire the amount of utility they desire and the supplier can also plan the schedule easily. Under conventional contracts, both parties should respect the spirit of the contracts in...[ Read more ]

A chemical production site consists of multiple production and utility plants that are interconnected with utility and material flow network. To achieve a smooth operation, keeping utility balance (mainly electricity, fuel, steam and water) inside the production site is very important. Usually, in order to keep the balance, the production site requires importing different kinds of utilities, such as electricity, fuels and sometimes steam for sustaining the production. To protect both the supplier and the customer, long-term supply contracts for these utilities are often required, such that the customer can acquire the amount of utility they desire and the supplier can also plan the schedule easily. Under conventional contracts, both parties should respect the spirit of the contracts in term of prices and peak consumption rates for any day type. A penalty will be charged, if any side violates the contract.

The idea of having an integrated mathematical model to assist in contract optimization is gradually being accepted by the industry. To elaborate applications of the contract optimization, a general mathematical model, Site Model, is adopted in this thesis. The model contains the main material and energy balances of production and utility plants and their interconnections inside the production site.

When considering the impact of demand uncertainty on the contract optimization, the probabilistic programming model will be used for selecting an electricity importation contract. Confidence Level is introduced for selection and optimization of the contract.

In this thesis, we explore the utility contract issue from the user's point of view to investigate the impact of utility contract on the chemical production site. The electricity contract is the main core in this research topic.

Lastly, the problem of quantitatively characterizing the flexibility of a chemical plant design has also been discussed. An algorithm to measure the plant flexibility has been proposed which provides a meaningful interpretation in that it corresponds to the turbine has what extend of probability to fulfill the demand variations. Several case studies have been presented to define and demonstrate the use of flexible indices in design options, with particular emphasis on the uncertain market conditions. The results of case studies show that the index can be a useful indication for assessing the flexibility of a design and for establishing proper trade-offs between flexibility and cost.