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 exists 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, continuous flow of CO2, creating ideal conditions for capture before it enters 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 for emissions, pricing mechanisms for carbon, and incentives to drive development. In the US, the Section 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 2030–2050 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 (GC) 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.
Process Gas Chromatography
A process 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 GC is its ability separate complex gas mixtures into individual components in a single measurement.
Understanding the chemical composition of a gas is important for several reasons, including maintaining product quality, optimizing operating parameters, protecting workers near the process area, and ensuring regulatory compliance.
A GC analyzer works by sampling a small amount of gas from a pipeline or process stream and then injecting it into a flow of carrier gas. This mixture moves through a column filled with a stationary-phase material. Each component interacts with the stationary phase differently, causing it to move through a GC 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 a 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, an analyzer typically tracks CO2, O2, N2, and SOx. When analyzing gas during blue hydrogen or syngas production, it would likely follow H2, CO, CH4, and CO2 to ensure CO2 removal is effective. In both industrial off-gas and chemical looping systems, there could be many additional hydrocarbons and contaminates 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 GC 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,” said Al Kania, business development 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.
Accurate Measurements Guide Decisions
Process GC 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.
In addition, using accurate measurements of the chemical composition of the feedstock, operators can make knowledgeable decisions about the effectiveness of the carbon capture process and identify opportunities to optimize 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 ensure that 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 GCs 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,” said Kania.
Accurate GC readings play an important role in minimizing operational and safety-related risks from hydrogen sulfide (H2S) breakthroughs and oxygen (O2) ingress.
By maintaining accuracy and reliability, GC instruments provide timely and reliable information on the changes in the gas mixture, enabling operators to act before issues escalate.
GC Design and 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 and should be rated for use in corrosive and potentially explosive atmospheres where hazardous gases may be present.
Kania says the MAXUM II utilizes real-time diagnostics to predict component wear, drift, or failure before it disrupts operations.
Measurement accuracy are also be affected by changes in gas composition as operations scale from pilot to full 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 gas composition to drift over time,” said 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 laboratory analysis.
“Instead of waiting hours for laboratory results, inline analyzers allow operators to observe changes in gas composition as they occur,” said 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.
For facilities like steel mills, cement plants, and pulp and paper mills, the most widely deployed technology is amine-based chemical absorption systems installed on flue gas streams. In this approach the exhaust gas is passed through a large absorber tower containing a liquid solvent that chemically binds with CO2.
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 that has a liquid solvent in it which reacts with CO2 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 capture methods 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,” explained 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 processers continue to increase their CCUS investments, measuring, validating, and controlling the gas streams will become increasingly important for both 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 GC is a foundational technology that enables the precise, continuous monitoring of complex gas streams.
