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How to cut compressed air energy consumption in the chemical industry

In the chemical industry, compressed air is largely used as a safe and versatile power source. Chemical processes rely on the availability of compressed air to power critical applications, which keep plants performing, sometimes 24/7. However, compressed air isn’t a free resource. Generating it can be quite intensive, representing between 5-30% of a site’s total energy bill.

Along with these significant expenses, poor practices and housekeeping can also contribute to unnecessary wastage. With the right energy-saving techniques, compressed air users in the chemical industry can save nearly 33% on these costs over a 15 year period.

In this article, Glaston Compressor Services discusses the key factors which chemical industry businesses need to consider when embarking on a compressed air energy reduction programme. This article will highlight important areas to cut energy within a typical compressed air system, such as where waste occurs and how businesses can minimise it.

Compressed air energy explained

The chemical sector is the UK’s biggest industrial energy consumer by a sizeable margin. A report from the Chemical Industry Association revealed that chemical plants use the equivalent of 3.4m t/y of oil, resulting in around £2bn on fuel and electricity. This also contributes to around 18m t of CO2 to the sectors overall emissions, with 36% of this being made up of electrical energy. Coupled with the rise of carbon and climate change hitting UK headlines, calling for governments to act now and limit environmental change, it’s no surprise that operators are keen to take steps and reduce their reliance on electrical energy.

The government’s Clean Growth Strategy for meeting the UK’s legally-binding carbon commitments is aiming to help businesses decarbonise. Part of this strategy includes the Industrial Decarbonisation and Energy Efficiency Roadmap Action Plan. Collaborating with the Chemical Growth Partnership, this plan seeks to reduce greenhouse gas emission and becoming more energy efficient, whilst remaining competitive during the UK’s low carbon transition.

While most businesses are already taking steps to reduce reliance on electrical energy, with so much emphasis on carbon reduction, compressed air is often overlooked. However, the potential for wastage is substantial and represents a considerable overhead, not to mention reducing carbon footprints.

In 2020, the British Compressed Air Society (BCAS) celebrates 90 years as the UK’s sole trade body for compressed air and vacuum users. BCAS is campaigning throughout the year to ensure users are aware of the simple steps they can take to reduce compressed air energy consumption. Below, Glaston Compressor Services has listed a few simple, low-cost steps that businesses can follow to reduce their energy consumption from compressed air:

Energy saving techniques for compressed air users

Step 1: Take a system approach

When discussing efficiency and the potential savings that could be realised, it is important to take a full, system approach – from generation to air treatment to distribution and finally, the point of use.

Step 2: Identify wastage

Identify some of the key areas where valuable compressed air can be wasted by processes or people downstream of the compressor. For example, if you install the most efficient compressor available but connect it to a system with a 30% leak rate, all the benefits are lost. You should aim to improve the overall system efficiency. Efficiency in the generation of compressed air is one aspect but targeting avoidable waste in the system is even more important.

Most actions require elements of maintenance or equipment/system upgrade, but the human element should not be overlooked. You can make substantial efficiency improvements by implementing new processes and encouraging staff to use compressed air more efficiently and safely.

Step 3: Detect and fix leaks

Reducing air leaks can have the biggest impact on overall system efficiency. Leak rates in industrial systems are typically between 20–40%, meaning the compressor has to work harder and therefore, consume more energy to compensate for pressure losses. Even a tiny leak of just 3 mm can cost more than £700 a year in wasted energy. An out-of-hours survey can identify leaks easily; simply walk the site and listen for leaks. You can then confirm the location using an ultrasonic leak detector, a leak detection spray, or even a soap solution brushed on to pipe fittings.

Once you have identified the leaks, you can implement an improvement programme. Tag the leaks and record on a site plan. Next, grade the priorities, fixing the largest leaks first and as soon as possible. Finally, make monitoring a collaborative process by encouraging your staff to report leaks as soon as they are discovered. When leaks are repaired, you should check the pressure drop from the compressor to each point of use, as you may be able to reduce the generation pressure and save further energy.

Step 4: Switch off

Compressors can consume up to 70% of their full load power even when off-load. As such, units should be switched off when there is no demand for air. Check the time switch settings regularly to ensure you are optimising running hours to help reduce maintenance costs. When appropriate, consider installing energy management systems to turn compressors off whilst not in use.

Step 5: Recover heat

As much as 95% of energy consumption from compressors are converted to heat and, unless captured, will be wasted to the atmosphere. Many manufacturers of compressed air systems offer heat recovery systems, which can often be retrofitted. This allows you to recycle excess heat, redirecting the hot oil to an oil-to-water heat exchanger. This is of particular benefit in the chemical sector, where there is a high demand for process heat. The heat can be transferred to water to raise steam and to heat water, saving considerably on energy costs.

Step 6: Reduce the pressure

Compressed air is often generated at around 8 bar (800 kPa), even if the point of use only requires 6.5 bar. Your service provider will be able to turn down the pressure at the point of use, should this help your process with saving energy. It is important to be mindful of pressure drops, which should be less than 10% of the compressors discharge pressure, as measured from the compressor outlet to the point of use. For example, a pressure of 7 bar should have pressure drops of less than 0.7 bar.

Step 7: Review compressed air usage

Compressed air is energy-intensive to run and cheaper options might exist for certain processes, such as drying and ventilation. However, for applications where there are risks of explosion or electrical interference, compressed air remains the best option.

Step 8: Train and involve staff

Simple awareness sessions around advising staff about the costs and safe use of compressed air are recommended. For example, not allowing benches or equipment to be cleaned down with compressed air will save a significant amount of air being vented into the atmosphere. Using a vacuum system in this instance will help reduce the risk of injury.

Step 9: Optimise compressed air use

Ask yourself whether compressed air could be delivered more effectively. If your air knives feature open-ended pipes, fitting a venturi-type nozzle can use 30% less compressed air. By making the operation much quieter, it will improve the working environment too.

Step 10: Zoning your air distribution networks

As not all parts of your air distribution network operate at the same hours or pressures, compressed air in your system should be separated into zones. At the same time, consider isolating redundant pipework. You should also be considering alternatives to traditional galvanised steel when replacing piping. Aluminium and plastic pipes do not corrode and have a much smoother internal finish, causing less of a drop in pressure and thus saving energy.

Step 11: Don’t overtreat air

Treating air to remove damaging particles such as dirt, water, and oil is necessary, but can use a lot of energy. Your process is likely to only need a proportion of compressed air to be treated to high purity levels. Excellent savings are achievable by treating all the generated air to the minimum acceptable level and improving the purity (quality) to the desired level at the usage point.

Step 12: Service and maintain

Investing in regular air compressor maintenance will help retain low leak rates and reliability of equipment. You should also consider a policy that specifies energy-efficient options are purchased when replacing all equipment – whether it is a basic drain valve through to the actual compressor unit itself.

Benefits of cutting compressed air consumption

There are many reasons for wanting to reduce energy consumption from your compressed air system. The financial gains are significant, alongside tangible environmental benefits which can help improve the bottom-line profitability of your business, as well as its green credentials and your customer reputation. By implementing even just one or two of the steps highlighted above, you can help minimise avoidable waste drastically and benefit from a safer, effective and more reliable source of power.

To find out how your business can cut down on compressed air energy consumption, speak with Glaston Compressor Services today on 01695 51010, email info@glaston.com or complete our contact form.

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