Optimising petrochemical operations

Substantial increases in profit can be achieved in refinery/aromatics operations using methodology and modelling tools that incorporate multiple degrees of freedom regarding operating conditions, feedstock qualities, recycles and co-product dispositions across a refinery/petrochemical interface

John Philpot and Alan J McCartney, KBC Process Technology

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Article Summary

Optimising operations within a petrochemical complex or a refinery can lead to substantial increases in profitability. If the right methodology, tools and expertise are employed, there are always ways to improve profit. All operating companies are constantly attempting to do this, with varying degrees of success. 

Even greater opportunities for profit improvement exist at the interface between refining and adjacent petrochemicals facilities. In this context, “petrochemicals” means liquid feed olefin complexes and aromatics plants, where there are many degrees of freedom regarding operating conditions, feedstock qualities, recycles and co-product dispositions across this interface. The optimisation of these is a major source of increased profit for both parties.

If the refining and petrochemicals facilities were designed separately and are operated by different companies (even within the same group), there is usually room for improvement through the exchange or sharing of fuels, utilities, services and infrastructure, as well as stream transfers. Constraints upon such optimisation can include cultural issues and different perceptions of stream values and costs. This is why so few adjacent complexes are properly integrated, and why third-party facilitation is often required to enable progress. Even when the refining and petrochemicals facilities are operated by a single entity, the feedstock interface usually offers the greatest potential for profit improvement.

The techniques and processes for achieving the optimisation of the feedstock interface are to be discussed by way of a case study involving a recent Profit Improvement Program (PIP) at a Southeast Asian refinery. This is an integrated aromatics complex with a large front-end condensate fractionator, so it can be considered a simple refinery integrated with substantial aromatics facilities. Improvement opportunities were identified throughout the complex, with the feedstock interface yielding the largest profit gains. To date, 18 opportunities have been implemented, from which benefits exceed $6 million per year. The operator launched the second phase of the proprietary PIP methodology in August 2007 as a continuous effort in improving the company’s profitability.

The complex started up in June 2000. Main products are para-xylene and benzene, with jet kero, diesel, heavy aromatics, hydrogen LPG and other co-products. The process configuration is shown in Figure 1. 

Since commissioning, the company has sought to improve operational effectiveness and profitability through a series of initiatives. These included the launching of the proprietary Operational Excellence (OpX) programme, capability building, key performance indicator (KPI) development, equipment reliability improvement and successive stages of the proprietary Operational Performance Improvement (OPI) programme. This culminated in the launch of a PIP with KBC in late 2005. 

Profit improvement
From the beginning, it was essential to perform the following for a successful programme:
— Nominate a joint client/KBC team with a good skills mix
— Use Petro-SIM for refinery/aromatics simulation
— Use ProSteam and SuperTarget for energy optimisation
— Provide high-level management support and monitor progress.

The objective of the programme was to increase long-term profitability by identifying ways to improve yields and reduce energy at minimal capital expenditure, while transferring tools and skills to client personnel. The programme was developed in two phases over the span of one year, following the previously noted PIP methodology.

Rigorous modelling of existing operations and constraints within the proprietary Petro-SIM plant-wide flowsheeting software (Figure 2) was a key starting point. Client engineers assisted with model development during their training period at the KBC offices. The accuracy of the software and other models employed is at least as great as the accuracy of the plant measurements. Modelling with real plant data allows a full and reliable representation of the existing plant operations to be developed, and then permits potential changes to be accurately reflected in the model before final validation by test runs. When used to investigate potential opportunities, the model:
— Helps understanding of process impacts
— Gives confidence that predicted results will happen on the plant
— Estimates the potential economic benefits of changes.

The model was used throughout the project to evaluate improvement options identified by the team from their knowledge of similar situations elsewhere and of the client’s plant. Figure 3 shows the general style and detail included in the model.

Energy models
In addition to the use of Petro-SIM to evaluate possible process improvements, energy modelling software was used to determine energy consumption reduction opportunities. The process began by benchmarking the complex against the KBC definition of Best Technology (BT). A BT complex incorporates all justifiable energy conservation measures in areas such as:
—    Furnace efficiency
—    Optimised heat integration (pinch) and process features
—    Efficient steam and power systems
—    Efficient power generation
—    Yield efficiency.

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