Compressor systems and control strategies: Lontra’s revolutionary Blade Compressor® delivers optimum energy efficiency
5 December 2016
Air compressors are a fundamental component in factories and plants across multiple industries, turning electricity into potential energy in the form of compressed air. Despite their universal usage, there hasn’t been an innovation within the compressor market for more than 80 years. For a market worth £25bn globally, this is an astonishing fact and the lack of evolution has some serious drawbacks.
At present, compressors are responsible for 10% of Europe’s industrial electricity use. This is significant as it points to the fact that compressors can be among the highest energy consumers on a manufacturing site or within a process. Compressors tend to be overlooked when manufacturers are targeting energy savings, which may be because maintaining the flowrate and pressure of compressed air is so important in the operation of factories that status quo prevails.
Traditional compressors compromise on one or more areas which jeopardise efficiency and reliability. These compromises exist as a result of the following issues: pressure drops during air intake; internal leaks of air through poor seals; blowing of air, rather than internally compressing it; and loss of air in the process of blowing out. Consequential to the low efficiency of traditional blowers are increased energy costs and a negative environmental impact.
The challenges involved in reducing compressor power, and increasing efficiency, are areas which have been, and continue to be, explored in great depth and it’s only now that a breakthrough has been made. That breakthrough is Lontra’s clean sheet air compressor technology.
Compressor performance: traditional control challenges
Compressors are generally chosen to deliver the maximum pressure and flowrate that may never be required by the factory or within a process. In many cases this peak demand is never seen, both because a safety margin is built into the specification and because few demands are continuous. Therefore, there is now a trend to employ a variable speed drive to match compressor output to actual plant demand.
It is often assumed that positive displacement compressors (e.g. screw compressors) have a constant energy-per-unit-air volume ratio, so that running at half speed should deliver half the maximum flowrate while consuming half the maximum power. Unfortunately, this assumption is far from accurate. Therefore, the amount of energy saving from turndown is limited and system optimisation will be poor without really knowing the exact energy-per-unit-air volume ratio.
The primary causes of reduced compressor efficiency at reduced speed (in positive displacement compressors such as screws) are internal leakages and rising temperatures. The internal leakage rates are not affected by speed, so at half-speed the proportion of leaked air to flowrate roughly doubles. In addition, this leaked air is recompressed so the temperature rises further. In oil free compressors this issue is worse, whereas in oil flooded compressors the effect is somewhat mitigated by the sealing and cooling effect of the oil.
Compressor performance: Lontra breakthrough
The Lontra Blade Compressor® addresses this problem thanks to its inherent geometry. Where other rotary compressors rely upon sealing ‘lines’ between compressor elements, the Lontra compressor has broad sealing ‘lands’. This means that sealing is much improved, even as oil free, so it can run at low speed without significant loss in energy or overheating. When used with a variable speed drive, greater energy savings are available, system optimisation is much easier and real energy savings achieved even on turndown.
Compressor performance: further benefits
Lontra has used the Blade Compressor’s® low-speed advantage by optimising the design of air ends to run at relatively low speed, particularly in comparison to oil free rotary compressors. This improves air flow and reduces friction resulting in an inherently cooler running, more durable and reliable machine.
Blade Compressor® in practice
Lontra’s Blade Compressor® has successfully been used at Severn Trent Water, one of the first companies to trial Lontra’s new design. At the trial they saw energy savings of 21% which Severn Trent Water translated into a potential 3% reduction in annual energy costs for the entire business; a saving of more than £1.8 million in electricity costs per annum.
The Blade Compressor® can be adapted, and can be applied across multiple industries, from food and drink to pharmaceutical, automotive and pneumatic conveying sectors, to work with any kind of gas or airflow equipment. As energy demands escalate across all aspects of our global society, fast-adopted technology breakthroughs such as the new form of air compressor offered by Lontra have the potential to provide industries with a “triple win”, being oil free, energy efficient and reliable. Lontra is entering the market offering energy saving resolution to the distinctive weaknesses of traditional compressors.
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