GAS DETECTION


ecologically responsible ways of operating. Reducing carbon emissions to the atmosphere


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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, Servomex looks 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


nternational 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


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 analyser 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


analysers 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 desulfurisation, 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


How to clean up your act


26 wInter 2021 | IndustrIal complIance


of greenhouse gases – CO2, CH4 and nitrous oxide (N2O) – that can be emitted. NOx, SOx, and CO are also seen as key pollutants.


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