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Apr-2011

Energy performance monitoring

An integrated energy management system supports improvements to a refinery’s performance in energy consumption and emissions control

Robert Chares, Hervé Closon and Hugues Stefanski, Belsim
Jean-Claude Noisier, SIR

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Article Summary

For heavy energy consumers such as refineries, total energy expenses represent a considerable amount. On the other hand, complex processes require a certain minimal amount of energy to guarantee the desired production output. The question that naturally arises is how to use the given energy in the most efficient way or, in other words, how to increase energy efficiency.

There are several approaches to tackling the vast challenge of optimally using energy. One of these is the implementation of an energy management system (EMS) for closely monitoring and increasing energy performance. An EMS can be interpreted in different ways. Belsim’s conception of an EMS is to prepare all process-related energy information so that it is reliable, centralised and easily readable, and can be readily used as support for intelligent business decisions.

This information includes:
• Energy performance indicators (EPIs) of equipment, single units or the whole site
• Energy balances to determine accurately the energy consumption of equipment and units
• Monitoring of emissions (CO2, SO2, NOx).

It is measured on a short-term basis (hourly or daily) and is accessible via customised reporting tools. The results that are reported through an EMS are key to providing an insight into process performance, which is the basis for changes in operating mode to improve economic performance.

However, the quality of 
business decisions depends directly on the quality of the data on which the decisions are based. Therefore, an EMS should have an additional component that increases the quality of measurement data. In particular, EPIs are typically calculated based on other measurements. If those measurements are already false, their errors will propagate and amplify. Consider, for example, an efficiency defined as the ratio between two quantities, A and B. If A and B are both erroneous, it is possible that the efficiency would be calculated as higher than 100%, which is clearly impossible.

Advanced data validation and reconciliation (DVR) is a technology that uses measurement data and process information to correct measurements as little as necessary so that all process constraints (such as material and energy balances or thermodynamic equilibria) are satisfied, while taking into account the uncertainty of measurement.

Belsim’s EMSs always include a DVR component. There are two major reasons for this inclusion:
• The reported information is reliable and dedicated actions can be taken to improve energy performance
• The impact of the corrective actions can be seen directly, since energy-related data is cleared of any noise.

In that sense, an EMS can be viewed as a tool that gives continuous decision support to tackle various energy-related challenges arising in complex systems, such as refineries, leading to corrective actions that have to be taken to amend them. These challenges could be, for example, energy imbalances (fuel, electricity) around some process units or the 
inexplicably high energy consumption of some piece of equipment. They are observations on the process level based on measurement data.

The results supplied by an EMS:help to truly understand the process by providing 
transparent and reliable energy-related information that reflects the actual condition of the refinery; are presented in a transparent and easily readable manner; can be exported and used for further analysis; are quickly accessible and updated frequently to enable the right decision to be made at the right time.

Based on the results provided by an EMS, dedicated actions can be initiated at the management level — for example, sensors, equipment and control settings can be questioned and causes of poor efficiency can be detected — leading to a reproduction of better performances. The impact of these actions can be verified with the help of an EMS. In order to ensure a continuous improvement, there should be a frequent interaction between the EMS, situated at the process level, and the actions taken at the management level. This concept is illustrated in Figure 1.

Implementation of an EMS
This conception of energy performance monitoring has been successfully implemented at Société Ivoirienne de Raffinage (SIR) in Abidjan, Ivory Coast. SIR refines crude oil to produce various products for inland markets and for export. At the moment, about 3.8 million tonnes of crude oil are processed in the refinery each year. Within the framework of a complete revamp of the refinery’s information system (Projet d’Intégration de l’Information — PII), Belsim implemented an EMS that meets the following requirements:
• Implementation and configuration of a completely integrated solution that automatically calculates energy balances and EPIs with a high precision
• Accurate monitoring of air emissions for environmental reporting
• Energy performance monitoring of equipment, several units and the whole site
• Gives everybody in the refinery access to the results.

The overall objective of the implementation of the EMS was to improve the refinery’s performance and to make it more competitive within the West African area. This objective was to be achieved by calculating reliable and accurate EPIs and mass and energy balances, leading to an improved monitoring of fuel consumption, steam usage, electricity consumption and flare, and to a decrease in overall energy consumption.

The solution that was implemented at SIR is entirely integrated in PII via a third-party integration platform (m:pro) that is the connection point for the EMS and all of the other modules. It links different types of data and information coming from various systems in diverse forms and arriving at different frequencies. It includes reporting facilities that provide the requested information to the right person at the right time.


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