Compressed Air System

Compressed air is widely used throughout industry. It is sometimes called the “fourth utility”, after electricity, gas and water. From mining, lumber and paper mills, petroleum, chemical, textile and glass production to small manufacturing plants and hotels, compressed air provides critical services and can often represent the majority of the facility energy costs. It powers pneumatic tools, conveyors, hoists, pumps and machines. In processes, it is used for aeration, filtration, dehydration, oxidation and fractionation.

Since many facilities cannot function without compressed air, reliability is paramount, but given that sound operating practices can reduce energy consumption by 20% to 30%, efficiency is high on the agenda. Compressed air is a utility. It is normally the most expensive utility in manufacturing environments and many times not managed for low cost. Since it is not normally hazardous, it is often overlooked as a source for savings.

The energy and operating costs of a compressed air system are far higher than the cost of the compressor itself. Over the lifetime of a compressed air system, approximately 80% of the total cost of ownership is electricity. This can represent hundreds of thousands of euros or dollars. Initial capital costs are just 9%. In a typical water-cooled system, water runs at about 8% and maintenance at 3%.

Often, system improvements can result in electricity savings of 20 to 50%. Evidently, there is far more benefit in good management of the system, than there is in focusing on the initial purchase price of compressors and equipment.

Other benefits of a well managed system include reduced maintenance, less downtime, increased production and improved product quality.

Audit

Energy Savers will conduct a comprehensive study of the facilities compressed air system. Focusing on compressor performance, balanced system, and air leaks throughout the distribution system.

Air leaks can be a very costly source of wasted energy in an industrial compressed air system. It’s not unusual to find 10% of compressor output wasted in a good system, 20% in an average one, and 30% or more leakage in a poorly maintained system. On the other hand, proactive leak detection and repair can reduce leaks to less than 10 percent of compressor output.

Energy savers highly skilled engineers are able to collect accurate data, identify air leaks and optimise the compressor to its optimal performance efficiency.

Pre-cooling

Efficiency is affected by about 1% for every 5.5°C or 10°F change in inlet air temperature. Warmer temperature decreases and colder temperature increases efficiency

VFD

Variable speed control is an efficient approach with rotary screw compressors and can be used with caution with centrifugal and axial compressors as well.

Variable frequency drives continuously and efficiently adjust the motor speed to match variable demand requirements. Variable speed control is typically the most energy efficient method of control to meet variable loads. It can provide accurate pressure control down to very low flow.

Heat Recovery

Compressors convert 80% to 90% of their incoming energy to heat. 50% to 90% of this can be recovered and used for thermal energy. A 37 kW or 50 hp compressor rejects about 30 kW or 100,000 Btu per hour. It is possible to regain a significant amount of this in the form of heat recovery, perhaps 24kW or 80,000 Btu per hour.

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