By Arthur Tenner
Many refineries boast about their energy conservation or efficiency improvement programs they have had in place for decades. With recent increases in energy costs, however, most have further room for improvement. Opportunities are likely to be abundant, particularly in areas often neglected.
One refinery designed for energy efficiency in the 1970s uses high pressure steam to power turbines that exhaust to a medium pressure header for process heating. The cold eyes perspective of an energy specialist showed refinery management how changes in run plans and operating conditions had resulted in steam system imbalances. Some medium pressure steam was being produced from a high pressure header let down station. Further, the low pressure header was balanced by a partially open let down station from the medium pressure header. Most alarming, low pressure steam was venting to the atmosphere. Not only was the refinery essentially venting high pressure steam, it was also losing highly valued polished water. Once identified, the problem was easily solved within hours and at no cost.
This refiner also misstated the marginal economics among his three steam systems. Although projects and operating plans were based on precise four-digit costs for each utility system, use of accounting data masked true economics. With a let down station open between high and medium pressure headers, what is the difference in marginal value for a pound of steam from each header? The answer is zero, and favoring the use of medium pressure steam has no incremental value over high pressure steam as long as the valve remains open.
Poorly maintained steam traps represent another common area of opportunity When asked about his program, one refiner reported that he had successfully engaged a trap vendor in a survey three years ago. A brief inspection of current operations, however, revealed incentives worth more than $1M/year to reinstate an ongoing maintenance program.
Speaking of maintenance, how effective is your program to clean fouling heat exchangers? One refinery was knowingly wasting energy by extending cleaning intervals to control its more highly visible maintenance budget. Plant management grew comfortable with this imbalance when energy costs were based on crude oil at less than $20/bbl. Incentives are now at least 50% greater to define and implement an effective exchanger cleaning program.
Energy is likely the single largest operating cost for a refinery. These are just a few typical examples of how CEI can help to improve energy efficiency in a plant. Through the application of our Energy Management Program or Fast Scope, we can help achieve world-class performance by focusing attention on the vital few major opportunity areas based on experience.