Improving sustainability: Tackle fugitive emissions from reciprocating compressors
Special Focus—Valves, Pumps, Turbomachinery and Compression
V. TATARINOV, Burckhardt Compression, Winterthur, Switzerland
Reciprocating gas compressors are used in many applications, and their operators demand excellent reliability. Unscheduled downtime can incur significant financial costs for the business. Therefore, most operators employ a proactive maintenance regime to ensure their compressors deliver reliable service between major overhauls.
At the same time, sustainability is an increasingly pressing issue, and all major assets have a role to play in reducing their carbon footprint and the resources they consume. In a world that uses various gases in industrial applications, compressors play a vital role and must operate in a reliable and sustainable manner.
To that end, fugitive emissions from gas compressors represent a significant issue for operators, both in terms of sustainability and operational efficiency. While leaks will not result in immediate problems or incur unplanned downtime, they should be addressed at the earliest opportunity.
Current practice. Industrial gas compressors are used around the world in many upstream, midstream and downstream applications to improve the efficiency of many processes. Gas leakage is inevitable to some degree—the aim of modern operators is to keep leakage to a minimum and optimize the sustainability of the process.
In many cases, any leaked gas is collected and sent to a flare stack, where it is burned with no attempt to capture the inherent energy. This is not just wasteful: it has an associated impact on carbon emissions that could be reduced through improved working practices. In fact, many countries are banning the flaring practice as part of their drive for improved sustainability. Some refineries are even monitored by infrared cameras to detect flaring events, which would result in considerable fines for contravention of environmental legislation.
Identifying sealing issues. Although gas leakage will not cause an immediate halt to a process, it will only worsen over time and can cause other issues, such as a rise in operating temperatures. This can lead to reduced efficiency and reliability issues, so tackling the problem at the earliest opportunity is essential. The key to determing the most effective solution is to look at the complete sealing system in a holistic manner.
During the compression process, most leakage occurs at the piston rod packing, and this should be the primary concern for the operator. Tackling this issue and implementing a proactive maintenance program will not only ensure compliance with local environmental legislation, but will also deliver a more reliable compressor that costs less to run.
The integrity of these seals is determined by several factors, including the ring design, material and the surface finish of the piston rod. For reciprocating compressors, increased wear rates and, therefore, seal leakage can be identified using a measurement of gas leakage flow, or by identifying a change in the leaking gas temperature.
Establishing scale. During inspections (FIG. 1), technicians can use gas leakage detectors or ‘sniffers’ to identify any leaks from areas such as cylinder covers, valve covers and other static seals on the compressor. Establishing the scale of the issue for an installation is not a simple task: precise figures can only be achieved by direct leakage measurements.
A more accurate representation of fugitive emissions can be achieved by collecting gas through leakage lines, enabling precise figures to be obtained on the extent of the issue. Flowmeters in the pipework that direct the gas to the flare stack can provide accurate data for gas leakage.
The extent of a leakage problem depends on the sealing system, which consists of many elements. The design of these systems is dictated by the gas itself, so seals for a larger molecule gas—such as methane—are easier to design compared to a system for hydrogen (H2), the smallest and lightest molecule on earth. The author’s company has considerable experience and success in working with industrial gases and creating durable sealing systems for these compressors.
Non-lubricated compressors offer some considerable challenges in terms of sealing, but the author’s company has a range of solutions that can be implemented, depending on the application.
In one example, a customer measured a leakage rate of 7 Nm3/hr from a single-stage, non-lubricated compressor. After assessing the current design, the best solution was to upgrade the three-ring piston seals to a four-ring design that added a support ring but made no changes to the materials used. The result was a significant drop in leakage to 1.2 Nm3/hr on average, even after 7,600 hr of operation.
Modeling the solutions. It is very difficult to obtain accurate data on gas leakage and to precisely predict the improvements that can be achieved by replacement parts based on modeling alone. This is due in part to the large number of factors impacting packing leakage. However, it is possible to demonstrate reduced leakage and improved reliability using real-world examples.
In one situation, a dry-running compressor working with 90% H2 and 10% methane exhibited a very high leakage rate, with the packing failing to achieve the minimum of 4,000 hr required by the maintenance schedule. The author’s company suggested a proprietary solutiona that included a set of multi-piece rings, which has been developed by the manufacturer’s in-house team of experts. This enabled the packing to significantly reduce gas leakage and achieve a minimum lifetime of 8,000 hr.
At the heart of any successful solution are years of experience and expertise that can be channeled into the development of new components and improved designs. This is now being enhanced by analysis tools that can optimize the performance of any compressor thanks to an assessment program that can be tailored to each application.
Industry challenges. Global targets for greenhouse gas (GHG) emissions and reducing the carbon footprint of industry in general have led to increased legislation, both local and international. The Global Gas Flaring Reduction Partnership comprises international oil companies (IOCs), national and regional governments, and international institutions. An initiative to achieve zero routine flaring by 2030 was launched by the World Bank and the United Nations in 2015 and has been endorsed by various major energy companies and national governments.
Effectively, this means that any new installations must avoid non-emergency flaring, while existing plants must eliminate it by 2030. In terms of compressors, implementing actions to minimize fugitive emissions will optimize performance, as well as enhance reliability and sustainability. However, there are many different designs of compressors depending on the application and the scale of the gas process, and they can be supplied by numerous original equipment manufacturers (OEMs).
Typically, when looking for technical support, the first port of call is the OEM, and responses can vary depending on the age of the compressor and the ability of the manufacturer to deliver local support.
Data is king. As with any key equipment, process data is essential to establishing important operating characteristics. The amount of information available from gas compressors fluctuates wildly, depending on the operator.
However, in situations where a minimal amount of data is available, additional sensors and data recording equipment can be temporarily installed as part of the performance analysis to establish the current operating conditions (FIG. 2). Going forward, the new data will enable the investigation and support continued, efficient operations.
Process data is essential to identify any issues with existing operations. Analysis can highlight problems that have gone unnoticed and have been exacerbated by the passage of time. The same data can also be used to make comparisons between the periods before and after any engineering modifications have been implemented to establish the degree of improvement.
Managing change. Establishing baseline data for a compressor is the first step in identifying any issues. This enables the objectives of the revamp project to be determined and how they will be best achieved. This is especially important for industrial compressors, which have been designed to offer decades of service. However, over this time, applications can change, process parameters can be adjusted and surrounding infrastructure replaced.
Furthermore, after years of service, compressor efficiency will be reduced without major corrective actions. This will directly impact energy efficiency and operating costs—without careful analysis of the operating data, these insights can be lost.
A thorough survey should highlight any bad actors, the potential for energy savings and the possibility of reducing gas emissions, as well as generating a process review to identify any changes in sealing and lubrication. It should consider the goals of the operator and set out a comprehensive proposal to address any issues.
Tailored solutions. Every application is different, and no single solution can be applied to all equipment. By assessing every compressor individually and creating a unique set of improvements, it is possible to deliver the optimum performance from that machine.
The author’s company’s structured assessment programb offers a structured assessment for any reciprocating compressor, using advanced measurement techniques and data analysis to identify potential issues, enhancing efficiency, reliability and sustainability. OEM expertise and decades of experience have been combined to deliver a comprehensive assessment process that reveals bad actors, gas leakages, excessive vibration and energy usage.
Taking the time to examine existing data, completing a thorough inspection and collecting additional process data allows the full picture of an installation to be established. The structured assessment programb identifies issues and presents a structured solution tailored to the application. Solutions can range from sealing material upgrades to adjustments in alignment and geometry, and major compressor upgrades, including the primary drive and new cylinders (FIG. 3).
The immediate achievements can be seen in decreased gas leakage, which has a direct impact on sustainability and operational efficiency. In the longer term, evidence of improved reliability and energy efficiency will become clear, enabling a reduced carbon footprint and lower operating costs.
Future considerations. As national governments increase their attention on sustainability, there could come a time when operators will be required to provide evidence of the measures they are implementing to reduce emissions. As discussed, data is essential, and the ability to highlight improvements and demonstrate improved efficiency and optimized performance will be very important.
The advent of the industrial metaverse, the use of cutting-edge communication technologies and engineering processes offer a great opportunity to optimize equipment performance. Moving from a preventative maintenance model to a predictive one will also support greater sustainability and longevity.
For equipment that may have been manufactured 20 yr–30 yr ago, many benefits can be gained from modern materials and the addition of data gathering devices. Greater levels of information enable the fast identification and resolution of any issues, leading to improved reliability and overall performance.
Takeaways. The increased focus on corporate sustainability requires businesses to look at every aspect of their operations and determine the improvements that can be achieved. Reducing emissions and waste, lowering energy usage and optimizing machine performance all support the goal of minimizing the overall carbon footprint.
To address any current issues and work towards new legislation, taking time to properly plan and implement a series of actions will be far more cost-effective than rushing the process to meet a looming deadline. With a combined approach to improve reliability and performance, it is possible to reduce operating costs while supporting sustainability goals.
The introduction of new materials or improved component designs can take time, but by planning the implementation properly and looking at the project as a whole, significant savings can be achieved and work can be completed during planned outages. Selecting a maintenance partner that has OEM expertise and experience in all other brands of compressors is the first step. Taking advantage of cutting-edge technology and advanced analysis techniques can deliver detailed proposals for an optimized compressor that makes the best possible contribution to improved sustainability. GP&LNG
NOTES
a Materials made from Persisto® 850
b Burckhardt Compression’s BC ACTIVATE
ABOUT THE AUTHOR
Vitaly Tatarinov graduated from the Faculty of Energetics and Environmental Sciences at Moscow Automobile State Technical University. From 2008–2011, he worked in laboratory research on polymer and composite materials for various industrial applications. Since 2011, he has worked in the gas compression industry in engineering positions, where he is responsible for the design, calculation and implementation of compressor upgrade and revamp solutions. Tatarinov joined the Burckhardt Compression Group in 2018, focusing on compressor assessments, the development and practical application of upgrade solutions for capacity optimization, reliability, energy efficiency and emissions management of reciprocating compressors.
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