Critical Process Measurement for CCS: Part Two

Analytical Techniques and Instrumentation

Part One of this series introduced the processes that are critical to the success and safety of Carbon Capture and Storage (CCS) operations. This second instalment investigates the analytical techniques that engineers can use to verify the purity of captured CO₂, detect trace contaminants, and prevent corrosive or hazardous reactions throughout the capture, transport, and geological injection phases.

Real-time data from gas chromatographs and moisture and oxygen analyzers ensures compliance with stringent environmental and safety regulations; it also enables process optimization, risk mitigation, and early leak detection. In the following sections, we will explore the key analytical methods integral to CCS, detailing how each technology functions and contributes to maintaining the structural integrity of infrastructure, safeguarding subsurface storage sites, and ultimately supporting the reliable, long-term sequestration of carbon dioxide.

Analytical Techniques

Gas Chromatography (GC)

Gas chromatography is used to measure the purity of CO₂ by separating and quantifying trace impurities. A gas chromatograph operates by injecting a gas sample into a column, where different components separate based on their interaction with the column material. A detector then quantifies these components, providing a detailed composition analysis. These instruments are essential in the Carbon Capture and Storage (CCS) process, providing precise analysis and quantification of gas compositions.

In CCS, CO₂ is separated from other gases in industrial processes or power plants. The GC plays a key role in ensuring that the captured CO₂ meets required purity standards by analyzing the gas streams. This real-time analysis allows operators to optimize the efficiency of the capture process.

After capture, CO₂ is transported and injected into geological formations for storage, and the GC is instrumental in monitoring the gas composition before and after injection to ensure purity and detect any potential leaks or unintended reactions.

The accuracy provided by GC measurements enables regulatory compliance, as it ensures the CCS process adheres to environmental standards and legal requirements. Additionally, the GC contributes to risk management and establishing safety protocols by detecting potential contaminants or unexpected gases that could compromise the storage site's integrity or safety, thereby supporting the overall reliability of the CCS process.

Oxygen Analyzers

Oxygen analyzers can be employed to measure O₂ content in the CO₂ stream, using electrochemical or thermo-paramagnetic sensors. Oxygen levels in the production processes can be at percentage levels, but dried CO₂ injected into wells is typically kept very low (<40 ppmV). This is important to avoid corrosion and to prevent reactions with the geological formations that could undermine the integrity of the storage site. The analyzers provide continuous, real-time monitoring to ensure oxygen levels remain within specified limits, to prevent oxidative reactions and corrosion. The sensors selected must be compatible for use in CO₂ and protected from high O₂ concentrations. Due to H₂S and other contaminants, a scrubber may be required to ensure a representative measurement and prolonged sensor life.

Moisture Analyzers

Accurate moisture content readings are fundamental to maintaining the quality and safety of the gas being transported and stored. Inaccurate measurements can lead to several issues, including corrosion, freezing, or hydrate formation in pipelines, which can cause blockages or damage to the infrastructure.

Many industries, especially those dealing with gas transportation and storage, are subject to stringent regulations and standards. These often require measurement instruments – such as moisture analyzers – to be calibrated against traceable national standards to ensure consistency and reliability. Compliance with these regulations helps avoid legal and financial penalties and ensures the operations meet industry best practices.

Summary

Precise analytical instrumentation lies at the heart of a safe, efficient, and compliant CCS workflow. From the high-resolution separations of gas chromatography to the vigilant, continuous oversight of oxygen and moisture analyzers, these techniques work together to verify CO₂ purity, detect insidious contaminants, and guard against corrosion or hydrate formation. By delivering real-time insights, they empower operators to fine-tune capture performance, preempt operational risks, and demonstrate adherence to stringent regulatory – and ultimately societal – expectations.

In Part Three, we will examine the benefits of enhanced process control in CCS.