Pneumatics move ahead in efficiency
Tom Shelley reports on energy saving and using new pneumatic devices to pump mud and burrow through the ground
Because of the convenience of pneumatic power and the appearance of new devices that use it to do things that are difficult to accomplish by other means, the compressor industry remains competitive, with a strong emphasis of improving energy efficiency.
Last year, Eureka reported on Atlas Copco's "Carbon Zero" compressors that recovered their waste energy in the form of hot water. This year, the same company has brought out retrofit heat recovery units for its GA11-90 rotary screw compressor range that recover between 72% to 94% of wasted heat energy from air compression in the form of what energy audit manager Anthony Cornes described to us as, "A fair amount of warm water or a lesser amount of hot water up to 90°C."
All compressor manufacturing companies are making efforts to improve the energy efficiency of their products. Atlas Copco has issued a paper entitled, "Theoretical and experimental study on energy efficiency of twin screw blowers compared to rotary lobe blowers" that attempts to "Prove" that rotary screw compressors are inherently more efficient than lobe and other "External compression" devices, so we took the opportunity of the just held Energy Event to put this view to Andy Jones, general manager of Mattei Compressors. He expressed the view that his company's latest vane compressors, "Were every bit as efficient as screw compressors", because they did not have a "Blowhole" in their compression process, and required only 5.4kW of electricity to produce 1m3 /minute of compressed air. He also added that he considered that they were inherently more reliable than screw compressors, because they did not have, thrust bearings to wear out and so were now being offered with an up to 10 years, unlimited hours, air end warranty.
Mattei also includes heat recovery systems in its range of products, and both companies argue the case for very large savings that can be obtained by making use of variable speed drives to match variable demand. The other solution to reducing compressed air consumption in an industrial system is to turn compressors off. This is best achieved using a central controller. Atlas Copco has announced that as an aid to such practice, its ES130V master controller is now qualified for the Enhanced Capital Allowance Scheme and has been included in the Energy Technology List.
As regards applications that would be very hard to accomplish without using compressed air, two have recently come to our attention that struck us as particularly ingenious.
One is a range of Australian sludge and mud pumps that use a venturi to suck material into a holding tank, whose contents are then blown out under pressure before they have time to settle and compact.
Made by Supavac in Queensland, they use a venturi to suck material into a holding tank, whose contents are then blown out under pressure before they have time to settle and compact. Timers regulate the suck and blow cycles which last 10 to 15s each. Pump sizes range from the 10,000 litre/hour SV60 to the 25 to 40m3 per hour for SV400. The pumps recently saw service in the Gulf of Mexico oil spill cleanup.
In the UK, Mike Brice, proprietor of Geo-Mole in Faversham, Kent, has developed the Geo-Mole - a penetrator that drives itself into and through the ground under the action of a reciprocating piston, driven by compressed air. At the end of each stroke, the hammer force is about 28tonf. Its latest application is to install pipes for ground source heat pumps. As the penetrator proceeds, it tows behind it a compressed air line and an exhaust line. When a suitable length, typically 100m has been laid, the two lines are joined, and become the heat extracting circuit for the pump. The penetrator is cheap enough to be left where it is. The rate of progress is about 1m/minute, which means that 100m of pipes can be inserted in 1h 40min, halving the normal cost of this operation
* Waste heat from air compression can be used to produce hot water by retrofitting heat exchangers to screw compressors
* The efficiencies of all compressors continue to improve, whether they are based on screws or vanes
* Mud and sludge can be very conveniently pumped by using compressed air to create suction, depositing material in a vessel which is then blow out
* A reciprocating piston burrowing machine halves the cost of installing pipes for ground source heat pumps
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