Sustainability
The Critical Role of Gas Chromatography in CCUS Success
Process gas chromatography is one of the most consistent tools supporting the safe, compliant & optimal operation of processes using CCUS
By Jeff Elliott
Carbon capture initiatives are typically presented with a focus on new and emerging technologies, large-scale capital projects and ambitious decarbonization goals. Behind each successful carbon capture, utilization and storage (CCUS) project, however, there is a much less visible but equally important foundation upon which those projects depend: precise chemical composition measurement of gas streams.
For the power generation, cement, steel, refining, chemical and hydrogen production sectors, CCUS represents a primary method to reduce emissions associated with processes that have been traditionally difficult or impossible to decarbonize. Each of these sectors generates a large volume and continuous flow of carbon dioxide (CO2) gases, creating ideal conditions for capturing these gases before they enter the atmosphere. As regulatory standards continue to be implemented at a rapid pace and companies increase their commitment to addressing climate change, CCUS is rapidly evolving from a forward-looking concept to a necessity for operations.
The drivers behind this trend include both economic and strategic factors. Increasingly, governments have developed regulations on emissions, pricing mechanisms for carbon and incentives to drive development. In the United States, the federal 45Q tax credit is a major source of funding for each ton of CO2 captured and stored. Other global markets also provide similar subsidy structures or trade platforms.
At the same time, many large-scale industrial processors are aligned with net-zero targets through 2030 to 2050 and require solutions that will enable them to continue to produce and meet their environmental goals.
While the strategic and regulatory case for CCUS is increasingly well-established, its successful implementation ultimately depends on precise process monitoring and control.
However, the performance, reliability and cost-effectiveness of such technology is largely dependent upon an accurate description of the gas streams involved. As such, process gas chromatography continues to be one of the primary tools used in industrial processes for ensuring that CCUS systems are operating reliably, meeting all applicable regulatory requirements and achieving the best possible performance.
A process GC is an analytical tool used to continuously measure the chemical makeup of a gas stream flowing through industrial equipment.
Process Gas Chromatography
A process gas chromatography (GC) is an analytical tool used to continuously measure the chemical makeup of a gas stream flowing through industrial equipment. One of the most significant advantages of using gas chromatography is the ability to analyze a complex gas mixture and split it into individual components during a single measurement. Understanding the chemical composition of a gas is important for several reasons: maintaining the quality of products, optimizing operating parameters, protecting people working near the process area and complying with regulations.
The analyzer works by sampling a small amount of gas from a pipeline or process stream and injecting it into a flow of carrier gas. This mixture then moves through a column filled with a stationary phase material. Each component interacts with the stationary phase differently, causing it to move through the column at a distinct rate. As each separated component reaches the end of the column, it enters the detector, where it is identified and quantified. The detector’s signal is processed by the computer to determine the concentration of each component in the sample.
In carbon capture processes, large amounts of flue or process gases enter a capture unit. Therefore, it is imperative to be able to accurately separate and quantify the major components in the gas. However, one of the biggest obstacles in this regard is that different processing plants generate different gas mixes while operating under different pressures, temperatures and impurity levels.
For flue gas analysis from a power plant, the analyzer typically tracks CO2, oxygen (O2), nitrogen, sulfur oxide. When analyzing the gas during blue hydrogen or syngas production, it would likely follow hydrogen, carbon monoxide, methane, CO2 to ensure the CO2 removal is effective. In both industrial off-gas and chemical looping systems, there could be many additional hydrocarbons and contaminants present that need to be measured and tracked.
Because of these factors, analytical equipment needs to be versatile. However, many plants use online analyzers that detect only one compound or element, so several are needed for more complex streams.
“The strength of gas chromatography lies in its ability to measure multiple components within a gas stream simultaneously, unlike individual gas analyzers that are limited to detecting a single component at a time,” says Al Kania, business development manager at Valmet, a global provider of technologies, automation and services for process industries. Valmet’s process GC, MAXUM II, has a large installed base across process industries globally.
Industrial-grade products like the MAXUM II are designed to operate across a temperature range of -20 C to -100 C and should be rated for use in corrosive and potentially explosive atmospheres where hazardous gases may be present.
Accurate Measurements Guide Decisions
Process gas chromatograph systems must deliver a level of accuracy that supports effective CCUS implementation. Reliable, high-precision measurements enable operators to accurately determine system composition, providing a dependable foundation for all downstream decisions.
With detailed compositional information, operators can effectively evaluate the performance of carbon capture processes and make informed adjustments to improve absorption and stripping efficiency. Accurately measured process parameters provide the confidence needed by operators to make educated decisions regarding the actual chemistry of the system.
Additionally, using accurate measurements of the chemical composition of the feedstock, operators can make knowledgeable decisions as to the effectiveness of the carbon capture process and identify opportunities to optimize both the absorption and stripping processes.
The accurate identification and quantification of each component present in the gas stream is critical in managing amine degradation during CO2 absorption, mitigating corrosion risks through effective control of corrosive conditions, operating compressors and pipelines safely at or below their design limits and ultimately ensuring that the captured CO2 meets the specified standards of purity for transportation and storage.
Validated laboratory-grade compositional data is also necessary to meet many of the reporting requirements for regulatory purposes related to carbon sequestration and to qualify for available tax incentives.
“Many reporting frameworks require validated, laboratory-grade quality for process compositional data,” said Kania. “Process GCs are the established analytical method capable of meeting these requirements.”
Guarding Against Analytical Drift
Although advanced analyzers like gas chromatographs are sophisticated, small measurement inaccuracies can lead to higher operational expenses or cause the control system to make unnecessary adjustments to the process.
This gradual shift in accuracy — known as analytical drift — is caused by variables such as temperature, detector deterioration, contaminants and electronic stability issues. Analytical drift may occur even when the analyzer is regularly calibrated.
“If an instrument experiences analytical drift, it may report CO2 concentrations that are either higher or lower than actual values. This can lead the system to incorrectly adjust absorber or regeneration conditions, resulting in increased energy consumption or reduced capture efficiency,” says Kania.
Accurate GC readings play an important role in minimizing operational and safety-related risks from hydrogen sulfide breakthroughs and O2 ingress.
By maintaining their accuracy and reliability, GC instruments provide timely and reliable information on changes to the gas mixture so operators can take actions before the situation escalates.
GC Design & Construction
The design and construction of the process GC is also a factor in controlling drift. Industrial-grade products are designed to operate across a temperature range of -20 C to -100 C (-4 F to -148 F) and should be rated for use in corrosive and potentially explosive atmospheres where hazardous gases may be present.
Other factors that can affect measurement accuracy are the changes that occur in gas composition when a pilot-scale operation transitions to full-scale production.
“At the pilot stage, the gas composition may appear consistent. Once the process is scaled up, small variations in temperature, reaction efficiency or material flow can cause the gas composition to drift over time,” says Kania.
If these changes are not detected promptly, the plant may continue producing gas that falls outside the required purity specifications. This is where the advantages of real-time monitoring far outweigh periodic sampling and analysis in a laboratory.
“Instead of waiting hours for laboratory results, inline analyzers allow operators to observe changes in gas composition as they occur,” says Kania.
Advancing CCUS initiatives
According to Kania, processors producing significant amounts of CO2 are regularly approached by major energy companies, which develop and operate CCUS projects — often in partnership with specialized technology providers.
Carbon capture systems come in several types and are typically installed on industrial exhaust streams to remove CO2 before it is emitted, often as modular units that can be retrofitted onto existing plants. Most industrial-scale facilities such as steel mills, cement plants, and pulp and paper plants deploy chemical absorption systems that use amine solvents to remove CO2 from their flue gas streams. The process works by passing the flue gas through an absorber tower containing a liquid solvent, which reacts with carbon dioxide to form a compound.
The amines react specifically with CO2 while allowing nitrogen, oxygen and all other gases to be removed from the absorber. The CO2-rich liquid is then heated in a regeneration column, releasing the CO2 into a compressed gas stream. The solvent is then recirculated to the top of the absorber.
Another type of gas purification for removing CO2 is physical absorption, also known as solvent absorption. In this method, the gas being purified is contacted with a solvent that will absorb the CO2.
Various other carbon capturemethods separate CO2 by using different mechanisms to improve efficiency and purity. Given the diverse process configurations, projects often prioritize the flexibility of a single instrument platform.
“With configurable detectors, one analyzer can perform a wide range of analytical measurements across multiple points in the CCUS value chain, minimizing the need for separate instruments and reducing long-term maintenance demands,” said Kania.
A Foundational Tool for CCUS
Today, CCUS has evolved from an ambitious concept into an actual engineering solution to meet ambitious decarbonization goals.
As processors continue to increase their CCUS investments, measuring, validating and controlling the gas streams will become increasingly important for operational efficiency, as well as regulatory reporting requirements, verification of stored CO2 and integrity of long-term storage.
In environments characterized by extremely high concentrations of CO2, trace contaminants and the need for uninterrupted operation, process gas chromatography is a foundational technology that enables the precise, continuous monitoring of complex gas streams.
Images courtesy of Valmet
