Skip to content

Compressor Role in Plant Energy Efficiency

Compressors: What You Need to Know About Their Energy Usage

Compressors are essential to refinery operations and account for approximately 12% of the total electricity used. In this article, we will discuss the different types of compressors, how they use energy, and how to optimize their energy efficiency.

Types of Compressors

There are several types of compressors used in industrial settings, including reciprocating compressors, screw compressors, vane compressors, and centrifugal compressors. Each type is suitable for different flow rates and pressure levels and has its own energy efficiency.

Reciprocating compressors are the most commonly used type and are suitable for small flow rates. They may be single or double stage for higher pressure levels, with efficiency decreasing with increased pressure.

Screw compressors are used for higher flow rates, while vane and centrifugal compressors are suitable for the highest flow rates. Axial compressors are the most efficient type, but have a much narrower range of operation.

Energy Usage of Compressors

The energy usage of compressors is affected by several factors, including pressure ratio, inlet pressure and temperature, molecular weight, and cooling efficiency. Compressors have a minimum flow point known as the surge limit, which can be affected by factors like compressor type, pressure ratio, and inlet temperature. It is important to avoid operating compressors at or below the surge limit to prevent damage to the machine.

Optimizing Compressor Energy Efficiency

The energy efficiency of compressors can be improved by ensuring that they are correctly sized for the application and that they are regularly maintained and serviced. The use of energy-efficient motors and cooling systems can also help to reduce energy consumption. Finally, an anti-surge control loop should be installed to prevent operation at or below the surge limit.

Conclusion

Compressors are essential to refinery operations and consume a significant amount of energy. It is important to understand the types of compressors available, how they use energy, and how to optimize their energy efficiency. By taking measures to ensure that compressors are correctly sized and maintained, the energy efficiency of these machines can be improved and costs can be reduced.

Compressed Air Maintenance for Improved Efficiency and Lower Costs

Compressed air is one of the most widely used forms of energy in industry, but it can come with a very high cost if not properly maintained. Poor maintenance can lead to decreased efficiency, increased air leakage, higher operating temperatures, and inadequate moisture control. Proper maintenance can help to reduce these problems, save energy, and ultimately save money.

Blocked Pipeline Filters

Blocked pipeline filters can cause a significant pressure drop, which can lead to a decrease in system efficiency and higher energy costs. To prevent this, filters should be inspected and cleaned regularly and should be replaced when the pressure drop exceeds 2-3 psig. Installing filters in parallel can also help to reduce pressure drop. Additionally, using high-quality filters with a pressure drop of just 1 psi can lead to substantial energy savings.

Motor Cooling

Proper motor cooling is essential to ensure that motor temperatures and winding resistance remain low. This helps to extend the life of the motor, while also reducing energy consumption. Compressors and motors should be lubricated and cleaned regularly and the lubricant should be sampled and analyzed every 1000 hours.

Fan and Water Pump Inspections

Inspecting fans and water pumps can help to ensure that they are running at peak efficiency and can help to reduce energy costs. Additionally, regularly inspecting drain traps can help to prevent energy waste. Some users leave automatic condensate traps open at all times, which is a significant waste of energy. Instead, installing simple pressure-driven valves can help to reduce this waste.

Coolers and Belts

The coolers on the compressor should be inspected to ensure that the dryer gets the lowest possible inlet temperature. Belts should also be inspected for wear and adjusted every 400 hours of operation.

Water Cooling Systems

Water cooling systems should be checked for water quality, flow, and temperature. Filters and heat exchangers should be cleaned and replaced according to the manufacturer’s specifications.

Minimizing Leaks and Regulators

Leaks should be minimized as much as possible and regulators should be specified that close when they fail. Additionally, applications that require compressed air should be checked for excessive pressure, duration, or volume and should be regulated either by production line sectioning or by pressure regulators on the equipment itself. Poor quality regulators tend to drift and lose more air, resulting in higher system pressures, shorter equipment life, and higher maintenance costs.

Compressed air maintenance is essential for improved efficiency, lower energy costs, and longer equipment life. Regularly inspecting and cleaning filters, maintaining motors and coolers, and minimizing leaks can all help to reduce energy consumption and ultimately save money.

The Benefits of Proper Monitoring and Maintenance for Compressed Air Systems

Compressed air systems are an essential part of many businesses, and proper monitoring and maintenance can save a lot of energy and money. Monitoring a compressed air system includes using pressure gauges on each receiver or main branch line and differential gauges across dryers, filters, etc.; temperature gauges across the compressor and its cooling system to detect fouling and blockages; flow meters to measure the quantity of air used; and dew point temperature gauges to monitor the effectiveness of air dryers. Additionally, kWh meters and hours run meters should be installed on the compressor drive.

Reducing Leaks in Compressed Air Systems

Leaks can be a major source of wasted energy in compressed air systems. A typical plant that has not been well maintained could have a leak rate between 20 to 50% of total compressed air production capacity. Leak repair and maintenance can reduce this number to less than 10%, potentially resulting in a 20% reduction of annual energy consumption in compressed air systems.

The magnitude of a leak varies with the size of the hole in the pipes or equipment. For example, a compressor operating 2,500 hours per year at 6 bar (87 psi) with a leak diameter of ½ mm is estimated to lose 250 kWh/year. In addition to increased energy consumption, leaks can make pneumatic systems/equipment less efficient and adversely affect production, shorten the life of equipment, and lead to additional maintenance requirements and increased unscheduled downtime.

Detecting and Repairing Compressed Air Leaks

Leak detection and repair is key to reducing energy consumption and maximizing efficiency in compressed air systems. A simple way to detect large leaks is to apply soapy water to suspect areas. The best way to detect leaks is to use an ultrasonic acoustic detector, which can recognize the high frequency hissing sounds associated with air leaks. After identification, leaks should be tracked, repaired, and verified. Leak detection and correction programs should be ongoing efforts.

Conclusion

Compressed air systems are essential for many businesses, and proper monitoring and maintenance is key to maximizing efficiency and reducing energy consumption. Proper monitoring includes using pressure gauges, temperature gauges, flow meters, and dew point temperature gauges. Leaks can be a major source of wasted energy, and leak detection and repair should be ongoing efforts. By following these practices, businesses can save energy, money, and maximize efficiency in their compressed air systems.

How to Reduce Compressor Energy Use

Reducing the energy used by compressors is an important step in improving the efficiency of manufacturing processes. There are a number of strategies that can be employed to reduce the energy used by compressors, including reducing the inlet air temperature, maximizing allowable pressure dew point at air intake and the use of control systems.

Reducing Inlet Air Temperature

Reducing the inlet air temperature can reduce energy used by the compressor. This can be done by taking suction from outside the building, which can have paybacks of up to 5 years depending on the location of the compressor air inlet. As a rule of thumb, each 3°C will save 1% compressor energy use.

Maximizing Allowable Pressure Dew Point at Air Intake

Choosing the dryer that has the maximum allowable pressure dew point and best efficiency can help reduce compressor energy use. Desiccant dryers consume 7 to 14% of the total energy of the compressor, whereas refrigerated dryers consume 1 to 2% as much energy as the compressor. Consider using a dryer with a floating dew point.

Controls

The objective of any control strategy is to shut off unneeded compressors or delay bringing on additional compressors until needed. All compressors that are on should be running at full load, except for one, which should handle trim duty. Positioning of the control loop is also important; reducing and controlling the system pressure downstream of the primary receiver results in reduced energy consumption of up to 10%. Start/stop, load/unload, throttling, multi-step, variable speed, and network controls are all options for compressor controls.

Conclusion

Reducing the energy used by compressors is an important step in improving the efficiency of manufacturing processes. Strategies such as reducing the inlet air temperature, maximizing allowable pressure dew point at air intake and the use of control systems can help reduce compressor energy use.

Compressed Air System Optimization for Maximum Efficiency

Compressed air systems are an integral part of many industrial processes, and optimizing them for maximum efficiency is essential for any business that wants to reduce its energy costs. By properly sizing regulators and pipes, heat recovery for water preheating, implementing adjustable speed drives (ASDs), and installing high efficiency motors, businesses can significantly reduce their annual energy consumption and save money in the process.

Properly Sized Regulators

Properly sizing regulators is critical for optimal performance and savings in compressed air systems. By choosing regulators that close when failing, businesses can avoid wasting air that would otherwise be released as excess air. Additionally, using regulators that are sized correctly for the current compressor system can help reduce pressure losses, leaks, and generating costs.

Sizing Pipe Diameter Correctly

The pipe diameter of a compressor system also needs to be sized correctly for optimal performance. Increasing the pipe diameter by just a few millimeters can reduce annual energy consumption by 3%. Businesses should take the time to assess their current compressor system and consider resizing the pipes for the best performance.

Heat Recovery for Water Preheating

Up to 80-93% of the electrical energy used by an industrial air compressor is converted into heat. By installing a heat recovery unit, businesses can recover 50-90% of this thermal energy for a variety of uses, such as space heating, industrial process heating, water heating, makeup air heating, boiler makeup water preheating, industrial drying, industrial cleaning processes, heat pumps, laundries or preheating aspirated air for oil burners. In some cases, the payback period for implementing this measure can be less than one year.

Adjustable Speed Drives (ASDs)

Installing adjustable speed drives in rotary compressor systems can save up to 15% of annual energy consumption. The profitability of installing an ASD depends largely on the load variation of the particular compressor, so businesses should assess their current compressor system to determine whether this measure would be beneficial.

High Efficiency Motors

Replacing existing motors with high efficiency motors can reduce annual energy consumption by 2%. This measure typically has a payback period of less than three years, and the largest savings are usually found in small compressors operating less than 10 kW.

By taking the time to properly assess their compressed air systems and implementing the measures outlined above, businesses can reduce their annual energy consumption and save money in the process.

Leave a Reply

Your email address will not be published. Required fields are marked *