Systems to combat air pollution from combustion processes generally inject a chemical into the gas stream that is designed to neutralize a specific pollutant. For example, limestone slurry is sprayed into sulfur-dioxide-laden flue gas to neutralize the potential acid and form gypsum. There are other similar combinations, but one pollutant just won’t cooperate: carbon dioxide. There’s no way to turn carbon dioxide into something more useful or at least benign, so it must be captured and utilized somehow, or sequestered.

Capturing carbon dioxide requires a complex process in itself: amine absorption. This isn’t the only possibility, but it is by far the most widely commercialized and deployed process. It’s expensive and has its own energy requirements, so it is critical to have it working as effectively and efficiently as possible. Making this happen is the topic of my article in Process Instrumentation, Improving Carbon Dioxide Capture Efficiency of Amine Processes Using Advanced Measurement Technologies. How does it work?

The amine process runs continuously and involves chemical absorption, where a gas stream containing CO₂ is placed in contact with a liquid solvent containing amines. CO₂ is absorbed by the amine solution, allowing CO₂ lean gas to exit at the top. CO₂ rich amine is sent to a desorber to strip CO₂ and recycle the lean amine back into the process.

Simple enough, right? In concept, yes, but in practice, less straightforward.

As with any process, the primary objective is to optimize energy and performance, while maintaining safety. Accurate measurements for timely actions are critical in meeting these objectives. In an amine treating process, there are several critical measurements that need to be monitored and controlled to ensure efficient CO₂ capture, process safety and solvent longevity. These include flow, pressure, temperature and chemical composition.

So where do we start? The article looks at five areas:

• Mass balance, so the amine process can follow the primary process. This depends on accurate flow measurements, a great fit for Emerson’s Micro Motion™ ELITE Peak Performance Coriolis Flow and Density Meters as these can handle CO₂ in all of its phases.
• Heat exchangers are critical to efficiency, so proper instrumentation is essential for detecting heat exchanger fouling and ensuring optimal efficiency. Monitoring requires instruments such as Emerson’s Rosemount™ 848T Wireless Temperature Transmitters, Rosemount™ X-well Technology, Rosemount™ 3051SFC Wireless Compact Flow Meters, and Rosemount™ 3051S Wireless DP Transmitters.
• Steam management requires effective flow measurement. Emerson’s Rosemount™ 8800 Series Vortex Flow Meters use a shedder bar design with an integral temperature sensor to improve accuracy of steam measurements by compensating for pressure and temperature variations.
• Monitoring corrosion because CO₂ can create corrosive compounds. Emerson’s Rosemount™ Wireless ET310 Corrosion and Erosion Transmitters can be mounted permanently at strategic points on piping and vessels to continuously monitor corrosion activity.
• Amine solvent quality calls for measuring online density with a Micro Motion™ Compact Density Meter to manage amine make-up rate to achieve desired CO₂ capture efficiency.

There’s a lot there to think about, but all those suggestions are practical, won’t break the budget, and can be implemented incrementally. Emerson is well position to help:

As a global innovator, Emerson has a deep legacy of solving the most complex challenges facing process plants and related facilities. We combine advanced technologies, industry-leading expertise and an insatiable curiosity about the world around us to create sustainable solutions.

For more information, visit our Optimizing Carbon Capture pages at Emerson.com. You can also connect and interact with other engineers in the Oil & Gas and Chemical Groups at the Emerson Exchange 365 community.