Real-time Monitoring Spurs Energy Savings

One of the world's largest energy companies, Total, Paris, is committed to improving its refineries' energy efficiency, not only to comply with new environmental standards but also to minimize production costs and enhance competitiveness. As part of this effort, the Normandy refinery, Total's largest refinery complex in France and one of the largest in Europe, asked ProSim, Labège, France, to implement its Ariane utilities-management and power-plant-optimization software in the refinery's production system.

In the dynamic environment of a refinery, executing the actions necessary for optimum utilities-system management requires the help of online optimization software. The main objective of implementing Ariane was to provide guidance and practical daily suggestions for optimizing the production of steam, hot water and electricity within the refinery.

Implementation was divided into several essential steps. The first consisted of gathering information on the Normandy refinery and integrating it into the software to build a model. ProSim engineers, together with operators, gathered all the necessary information to map out the site's processes and to identify the degrees of freedom of the plant optimization. The second step involved software integration, i.e., inserting the Ariane model into a larger application that automates the inputs/outputs, and handles user parameters and options management. These steps were completed in late 2011.

DAILY REPORT

Figure 1. This gives summaries of calculations of utilities production and consumption as well as recommendations.

The third step is ongoing. It uses the refinery's current state (consumption as determined by online calculations that consolidate real-time raw data, as well as predictive data provided by the operators in the units) to plan the next day's production and anticipate potential problems.Overall, Ariane accounts for the recovery of raw measurements and their automated processing, the detection of equipment failures, and the calculation options (i.e., selection of the optimization degrees of freedom). Users supply data not measured (e.g., parameters such as purchase and resale prices) needed by the model. After the calculations, the application archives its results and provides editable reports for the operators. It's easy to compile the results into tables and graphs via an executable file using an Excel model.In the units, plant operators fill their production program into data files that are analyzed by the planning application to transform the operations' loads (expressed in process throughput) into steam demand in the different refinery headers. By compiling these results and starting from the current operating point, the planning application can predict plant production patterns for periods as long as 72 hours.The operators get real-time advice on how to adjust the production plant, manage the turbines' settings, and order the opening/closing of certain valves located in the processing units. The daily report can be edited on demand to import optimal plant operating instructions.The project has been a real success. The convergence rates are excellent. The Normandy refinery has achieved substantial benefits because of the online optimization software — a minimum estimated savings of €930,000 ($1.24 million) for 2011 alone. The total gains amount to more than 2.5% of the plant steam-purchase and electricity budget. This doesn't take into account aspects such as maximizing electricity production or gains regarding fuel management. In addition, the refinery is realizing some global energy-efficiency improvement thanks to real-time followup of the electricity and steam production system.Moreover, the real-time follow-up provides better knowledge of the refinery steam networks and associated economic issues. In practice, this tool:• improves the real-time management of the internal networks by integrating them into the refinery optimization process; and• helps identify new energy-optimization projects thanks to better network balancing. Since its implementation, the site operators are making more efficient and realistic decisions based on the system recommendations. The next step, which has just been completed, is to go further with simulation, linking ProSim's optimization software to Belsim's VALI data reconciliation tool. The developed software architecture already provides a common platform for utilities production sites; the platform combines the data reconciliation benefits with the online optimization of utilities production cost. This collaboration between Total, ProSim and Belsim is leading to a robust and efficient solution for refineries and petrochemical plants.

PHILIPPE BAUDET is a process engineer for ProSim, Labège, France. FABIEN JOLY is project manager at Total's Normandy Refinery, Harfleur, France. E-mail them at [email protected] and [email protected].