Oil processing and pipeline operations are their own best customers. Literally awash in raw energy, they use energy freely in operations – typically accounting for 5-10 percent of all operating expenses. But what if you could reduce those costs by 10 to 15 percent?
The cost of energy is rising for oil processing and pipeline operators along with everyone else; and incremental expenses for energy consumed are increasingly difficult to recover downstream.
So there is more economic pressure to better manage energy consumption. There’s social pressure too – reflected in sustainability goals and programs being adopted across the industry.
But it’s possible to cut energy consumption while reducing wear and tear on systems and facilities. Here’s how others are doing it.
Seek out control valves – and eliminate them
Fluid is typically moved from point to point in pipeline and oil processing operations today with the traditional technologies of pumps and control valves.
While it’s a time-tested approach that gives engineers great comfort, control valves are one of the most inefficient technologies in such common use in process industries today.
“We apply far more energy than necessary to move fluid from one location to another because the control valve consumes a large amount of the energy to control the flow,” offers David Huffman, Marketing Support Manager at ABB, and a chemical and process engineer with experience in the oil and gas markets. “This approach was developed because motors, at the time, only operated at a single speed.”
The alternative is to employ variable frequency drives (VFDs) to manage the flow of fluids through pipelines, cooling towers and other systems.
“By varying the speed of the motor itself,” Huffman says, “we’re able to vary the head produced by the pump, which can be used to directly control the flow of the fluid without a control valve.” The potential energy savings: 40 percent.
“When you consider how many pump-valve combinations are installed across the world today, we are looking at a very large quantity of energy that could be saved,” Huffman notes.
But that’s not the only benefit. The extra energy that control valves use is dissipated throughout the system in the form of sudden changes in pressure and other stresses. To deal with that, process lines are historically over-built – increasing costs from the time of construction right through the repair- maintain-replace lifecycle.
The pump curve is quadratic, points out Markus Eklund, ABB’s Global Market Manager for the chemical, oil and gas industries. “If you reduce speed of the motor by half, you reduce energy consumed by a factor of eight,” Eklund says. “You capture that savings with VFDs; that’s what makes them so efficient.”
VFDs also allow gradual and controlled changes in flow, easing stress on system components. This reduces maintenance costs, Eklund says. It also allows new lines to be designed with lighter components – and potentially fewer components – that have a less costly lifecycle.
Eklund and Huffman both concede that today’s reluctance to use VFDs is based on field experience form early experiments with them. But they say the technology has improved and is well worth considering as energy costs continue to rise.
“The oil and gas industries are known to be conservative in adopting new equipment, and adoption of variable-speed drives has taken a long time due to early concerns about their reliability,” Eklund says. “But there are many benefits in using VFDs and their adoption is increasing steadily.”
Among the benefits cited by Eklund are that they are soft- filling, which reduces airholes in pipes; they reduce the hammer effect, which decreases mechanical stress and damage, and reduces the resonance frequencies.
Other industry segments – most notably drilling applications – have successfully adopted the use of VFDs “because the benefit there has been more pronounced for longer,” Eklund says. “But with pipelines and oil processors under more pressure to manage their energy use, the benefit to them should be coming clear as well.”
Look at supporting processes
Boilers, compressors, steam systems, refrigeration systems and other supporting processes all use large amounts of energy, and all need to be optimized, Kelly says. “When you look at these things in total, there is a lot of opportunity for improvement.”
For example, old compressor motors tend to be less efficient than new ones. When they fail, replacement of older models may now provide better return on investment than repair.
“On a boiler system, it might be changing a set point on a control scheme to reduce excess air so the boiler consumes less fuel and runs closer to its optimal operating point,” Kelly says.
Conduct a third-party audit
Among its service offerings, ABB provides energy efficiency assessments, which map where in a facility energy is used. “We create a list of opportunities where energy is being lost and how that can be improved,” Kelly says. “Some of these opportunities don’t even require capital investment.”
Total site savings typically reach 10 to 15 percent of energy costs, Kelly says. “This level of potential improvement is fairly consistent across the industry.”
There are only two reasons companies in the industry pursue such savings, according to Kelly: social pressure and economics. “Both are more important than ever,” he says, “and the trend is toward increased energy costs and more stringent regulatory constraints.”
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