The role of gas analysis in clean air strategies to reduce carbon emissions

International action on the climate, such as the 2016 Paris Agreement, has increased awareness of the effect of greenhouse gases, driving industrial plant operators to reduce emissions and find more ecologically responsible ways of operating.

Reducing carbon emissions to the atmosphere has become an area of growing importance for operators. Sensitivity towards the issue has been raised by the introduction of increasingly stringent environmental regulations.

Gas analysis delivers an effective solution for these efforts, supporting measurement of harmful emissions, and by improving efficiency to ensure fewer emissions are generated in the first place.

In this article, we’ll look at three main process areas that support a clean air strategy: combustion efficiency, gas clean-up (including carbon capture processes), and emissions monitoring.

Combustion control solutions

Combustion reactions mix fuel with oxygen in a fired heater to generate heat energy for a process. They typically need a significant amount of fuel, create potential safety hazards, and generate harmful emissions including carbon dioxide (CO₂).

Running fired heaters with high excess air – as happened before gas analyzer technology – avoids creating unsafe conditions that could lead to an explosion, but is highly inefficient, increasing fuel consumption.

Excess oxygen (O₂) also combines with nitrogen and sulfur in the fuel to produce unwanted emissions such as oxides of nitrogen (NOx) and sulfur (SOx).

Accurate measurement of O₂ and combustibles such as carbon monoxide (CO) helps to optimise the ratio between the air and fuel creates a more efficient reaction.

Controlling combustion in this way benefits plants looking to meet environmental standards requirements. Fuel consumption is reduced, resulting in fewer emissions, a reduction in NOx, SOx and CO, and a decrease in CO₂.

Zirconia-based sensing technology is long established as a solution for O₂ monitoring in combustion, with reliable, accurate results and a fast response to changing conditions. Tunable Diode Laser (TDL) technology provides an even faster measurement, particularly for CO, and gives an average measurement across the measurement path, rather than the result at a single point. However, since TDL sensing is highly specific to the gas being measured, separate analyzers are required for O₂ and CO.

Gas analysis also supports greater process efficiency in many other applications. An efficient process reaction reduces the amount of harmful emissions likely to be generated.

Gas clean-up and carbon capture

Gas analysis is important in gas cleaning, the removal of harmful substances from process gases that might otherwise be emitted by the plant.

Typical examples of gas clean-up processes include DeNOx (ammonia slip) treatment, flue gas desulfurization, and carbon capture and storage (CCS).

Capturing and storing CO₂ ensures it is not released into the atmosphere. This results in a cleaner environment, and allows the CO₂ to be used in other processes. Three different methods exist: pre-combustion, oxyfuel, and post-combustion CCS.

Post-combustion CCS takes place when CO₂ is removed from the flue gas after fossil fuels have been burned. Oxyfuel CCS produces a flue gas consisting almost entirely of CO₂ and steam by reacting the fuel source with almost pure O₂ – this means flue gas can be stored/sequestered without significant pretreatment.

Both these methods can be used in new plants, or retrofitted to existing ones.

A third method, pre-combustion CCS, is performed before burning the fuel, and converts the fuel into a mixture of hydrogen and CO₂. This is difficult to retrofit, so is better for newly built facilities.

Whichever method is used, the captured CO₂ is then compressed into a liquid and transported for storage.

As countries look to meet their responsibilities under Paris Agreement carbon reduction targets, the use of industrial-level CCS is likely to grow significantly, as is the requirement for accurate gas analysis to support the processes.

Monitoring emissions

Reducing carbon emissions has been a key issue for many countries in recent years, with legislation limiting the amounts of greenhouse gases – CO₂, CH₄ and nitrous oxide (N₂O) – that can be emitted. NOx, SOx, and CO are also seen as key pollutants.

Monitoring flue gas emissions helps determine the process efficiency and protect the environment, and demonstrates that plant operators are complying with the necessary regulations.

To ensure compliance, a continuous emissions monitoring system (CEMS) is required to measure all the necessary components of the flue gas. This must be capable of offering the highest sensitivity and accuracy when dealing with multiple measurements for pollutants.

Any gas analysis system must also meet MCERTS and QAL1 certifications to comply with regulatory criteria.

Cleaner energy sources

Cleaner energy sources, such as hydrogen, are becoming increasingly attractive to many industries – hydrogen gas (H₂) does not contain carbon, so cannot form CO₂ as a byproduct of combustion.

Plants that produce hydrogen are ramping up output to meet increased demand. The purity of the hydrogen they produce affects its quality as a fuel, and this is where gas analysis again plays a major role.

Depending on the manufacturing method, the most common contaminants will be O₂, CO and CO₂. All three of these can be monitored by gas analyzers to ensure product purity.

A cleaner future

Whether it is used to ensure more efficient processes, to support the safe removal of pollutants, or to monitor the remaining emissions that are output to the atmosphere, gas analysis plays an essential role in cleaner plant and refinery operations.

Additionally, it is certain that gas analysis technology will be essential to the production of current and future cleaner energy sources.

A wide range of sensing technologies is needed to achieve all the necessary goals of a clean air strategy in order to ensure the best-fit and most cost-effective solution for each application.

By combining all three stages of the clean air strategy outlined here, plants and refineries can fully address the impact of their operations on the wider environment, and contribute fully to the creation of a world with cleaner air.

Find out more about the three-stage clean air strategy at servomex.com