Jul-2010

Corporate energy optimisation

An energy management system can deliver major cost savings in a refinery from a relatively low outlay

Fred Hampton, Jason Mooney, Darryl Seillier and Jose Bird, Valero Energy
Nicholas Spates, Modular Process Control

Article Summary

Typically, 50% of a refinery’s operating expense comprises energy costs and thus presents a significant opportunity to capture savings. With the downturn in the economy, narrowing margins on crude distillates and increasing cost of capital, identifying, capturing and sustaining opportunities for low-cost energy reduction has become increasingly imperative. Historically, energy has been viewed as a relatively inexpensive resource and, consequently, was used without a great deal of consideration. In 2007, Valero management initiated an Energy Stewardship Program (ESP) and committed to the reduction of energy costs by $100 million/y. Of primary importance was the need to reduce energy use in the refineries without affecting throughput and quality. To date, the ESP has been deployed in 14 Valero refineries, with total savings of $150 million/yr captured.

Energy stewardship strategy
Valero Energy Corporation engaged Modular Process Control (MPC), an energy management consulting firm that assists manufacturing companies in reducing energy use with little or no capital, through the development and implementation of an energy management system. MPC’s primary role was to assist in three distinct project phases: evaluation, implementation and retention of energy improvement ideas.

Evaluation phase
Site assessment
The evaluation phase involves a high degree of participation among the refinery staff, corporate energy team and MPC. This phase begins with an onsite energy gap review to identify low-/no-cost opportunities. A system audit is also completed to assess workflow, significant energy users and energy performance measurements. Daily historical energy performance data are gathered to identify trends and establish correlations between energy consumption and key process input drivers. All key factors influencing energy consumption should be fully understood.

Analysis activities
Further investigations are performed by the refinery staff and MPC during the evaluation phase. As the data are only as good as the accuracy of instruments, a metering analysis is executed to improve measurement points for daily energy management. An energy ratio analysis is conducted to highlight energy consumption (as Btu/bbl) against key process inputs. Once energy ratios are developed, 
a historical analysis is completed 
to identify average energy 
performance compared with demonstrated benchmark levels of performance.

System analysis is performed to determine information gaps in energy tracking and reporting. An awareness survey is also completed to highlight the level of focus on energy by refinery personnel.

Implementation phase
Energy team formation
During the implementation phase, an energy team is formed and charged with facilitating and promoting the implementation of opportunities identified in the site’s energy gap review, as well as other ideas generated during the process. The energy team typically comprises the site energy coordinator and energy field coordinator, as well as representatives from technical, operations and maintenance. Each energy improvement opportunity identified is summarised as an energy action item (EAI) in an assignment log. The energy team assures that each EAI is quantified, prioritised and assigned to a responsible party. Accountability is needed to ensure the timely implementation of the improvement opportunities. The energy team conducts weekly meetings in which the responsible person(s) discusses the progress of the assigned EAI.

Energy system
development/ installation
To ensure ongoing management and control of energy resources in the refinery, an energy management system (EMS) is needed. Detailed indicators influencing relationships among energy consumption, production levels, product mixes, weather factors and other associated energy drivers are reviewed for significance. Energy ratios, defined as process unit energy consumption per volume of unit throughput, are developed for each key process area in the refinery. The energy ratio format is the basis for daily review of each process area. As a result, poor energy operating performance and negative trends impacting energy consumption are easily identified. The energy team is trained to 
utilise the EMS to identify variances that directly affect energy performance.

Another tool used for performance tracking is the key volume indicator (KVI) model. KVI models are developed to track current performance for all major utilities against historical energy performance. The KVI model is based on historical performance and predicts the refinery’s theoretical energy consumption, assuming the energy savings initiative had not been implemented. Thus, the KVI model provides a refinery energy consumption baseline used for quantification of the economic impact derived from implementation of the energy programme.

Retention phase
Retention team
The purpose of the retention phase is to ensure long-term sustainability of the energy savings realised throughout the energy initiative. MPC provides a retention manager to work closely with the site energy coordinator and refinery staff during project completion. Daily energy ratios are reviewed and recommendations made to improve energy performance. Frequent communication between the energy coordinator and the retention manager take place, with emphasis placed on opportunity implementation. Plant visits and system project installation audits are also conducted on a scheduled basis to support the sustainability of the programme. Continuous feedback is given to the refinery regarding areas where savings are not being sustained and energy improvement opportunities exist.

Houston refinery project overview
The Valero Houston Refinery, a 
150 000 b/d facility, was selected as the pilot site for the rollout of the ESP. A kick-off meeting was held to introduce the ESP concept and share with the refinery expectations both from Valero’s headquarters and MPC.