Compressor Q&A: Mitsubishi Heavy Industries Compressor International

Explain why compressor technology is so crucial to downstream operations.

Downstream applications such as petrochemical operations involve many complex processes where boosting the pressure of the gas helps promote catalytic reactions, thermal decomposition, refrigeration operations and generation of byproducts. For example, in an ethylene plant, the hydrocarbon feedstocks are cracked at temperatures between 1470°F and 1580°F (800°C and 860°C). The cracked gas is then quenched and cooled before it enters the compressor. The compressed crack gas goes through acid removal, drying and cryogenic separation processes (i.e. further fractionation) in order to separate into different byproducts such as ethylene and propylene, etc. Multiple compressors are used in the above process, i.e. for cracked gas compression, ethylene and propylene refrigeration.

Compressors are crucial in these processes as they strongly influence overall plant performance, efficiency (power consumption), and operational reliability, including safety and environmental impact.

How can compressor technology help to improve efficiency in gas processing and downstream operations?

In the example of an ethylene cracker plant (provided in my previous answer), compressors constitute the largest energy consumption. Typically, petrochemical plants spend millions of dollars each year in fuel for steam production or electricity to power these compressors. Compressor power consumption is directly proportional to its overall polytropic efficiency, and therefore every percent of efficiency improvement translates to reduction in overall power consumption and plant operating costs.

What steps do you take to improve equipment reliability and safety?

Centrifugal compressors handling high pressure and high density gas can sometimes encounter rotor instability, high bearing temperatures and vibrations while in operation. MHI has continuously improved the reliability of compressors by coming up with various ways to attenuate the rotor vibration by performing various rotor dynamic analyses during the design stage and mechanical run tests.

Typically, in a cracked gas compressor, fouling is a common phenomenon which not only has a crippling effect on compressor performance but also causes the unit to shut down due to increased vibration levels. Thus in order to ensure safe and reliable operations, we use anti-fouling techniques such as SermaLon coating to avoid corrosion and foulant deposition on the surfaces and water injection to avoid the polymerisation at high temperatures, by keeping the gas temperatures lower.

Incorporating features such as remote monitoring helps with predictive maintenance of the equipment, thereby allowing us to take early action prior to fault detection. The goal behind remote monitoring is to increase the availability by avoiding unscheduled maintenance and minimise the scheduled down time. In addition to this, solutions such as extended overhaul intervals, smaller maintenance windows, compact and light equipment, modularisation or package standardisation as a means of reducing cycle time and cost, all help to ensure safe and reliable operations.

How can compressor technology help to reduce emissions in downstream operations?

Petrochemical plants (along with others like steel, cement, etc.) emit carbon due to the complex thermal processes and high temperature heat requirements. As such, carbon capture, utilisation and sequestration (CCUS) is one of the most mature and cost-effective options to reduce emissions. CO₂ compressors are intrinsic to this process. In addition to improving the compressor efficiency to reduce the overall emissions, the plant owners are also considering options such as vent recovery systems and using large electric motors instead of traditional steam turbine drivers to reduce the carbon footprint.

What has been your company’s biggest recent achievement or innovation in compressor technology?

Increasing demand for products such as plastics, fertilizers, etc., in the world is driving plant sizes/capacities and, in turn, compressor sizes. This trend is common for not only the greenfield plants but also brownfield expansions. In order to meet the increased train capacity, and maximise process efficiency with minimum equipment and CAPEX, MHI has been continuously making improvements to the compressor design by incorporating impellers with large flow coefficient impellers and improved efficiency, etc. MHI also has vast experience with ‘Footprint replacement’ (FPR) applications where the existing compressors and/or steam turbines are replaced with new higher performance machines whilst keeping the same foundation/footprint. The FPR feature allows for a larger expansion capacity (e.g. ethylene plant 711 000 tpy -> 1.1 million tpy) at a lower cost compared to traditional revamp/re-rotoring of existing machines.

How has the COVID-19 pandemic impacted the downstream/gas processing compressor market?

As 2021 came into effect, the industry has seen a lot of pent-up demand due to the slowdown in 2020 as a result of the pandemic. The first six months of 2021, at least for MHI, have been extremely busy. Not only are the orders focused in ammonia and fertilizer and urea-type projects, but we are also meeting customer needs from traditional petrochemical, olefin and refinery facilities as well. Recently, MHI picked up a revitalisation project for the power generation sector. There is a lot of demand for projects that probably should have happened in 2020. Now, we would like to think that our customers are back on track expanding their businesses.

MHI’s recent achievement includes providing new compression equipment to the world’s largest ethylene (2.3 million tpy) and ammonia (3600 tpd) plants.

All questions answered by Pallavi Baddam, Manager of US Applications Engineering & Process Automation, Mitsubishi Heavy Industries Compressor International (MCO-I).

Pallavi Baddam is the Manager of US Applications Engineering & Process Automation at Mitsubishi Heavy Industries Compressor International (MCO-I) in Houston, Texas, US. Pallavi began her career as a control systems engineer for gas turbines with Rolls-Royce Energy Systems Inc. (now Siemens Energy). She later worked for Dresser-Rand Co. as a Proposal Development Engineer prior to joining Mitsubishi Heavy Industries where she leads the application engineering group and also heads the development of automated design tools. She has extensive experience (over 15 years) in turbomachinery used for the oil and gas industry and has worked on many challenging projects.

This was a preview of the 'Compressor Q&A', which featured in the August issue of Hydrocarbon Engineering. To read the full Q&A, which includes answers from a number of leading experts in compressor technology, sign in here or register for a free trial subscription.

Read the article online at: https://www.hydrocarbonengineering.com/special-reports/13082021/compressor-qa-mitsubishi-heavy-industries-compressor-international/