Decarbonisation Technology May 2022 Issue

is lost through the stack. Using a combustibles measurement, operators can reduce their excess oxygen reading to a safe range well before reaching the combustibles breakthrough point. The combustibles measurement provides the secondary reference point to allow operators to lower their combustion air levels at the burner thoughtfully. Together, flue gas analysis provides the excess oxygen reading and the combustibles measurement to safely optimise the combustion process. Role of process safety Finally, as its third critical role, flue gas analysis plays an important part in detecting unsafe conditions, using a combustibles detector and a hydrocarbons detector. As noted earlier, a combustibles detector measures the CO and Hâ‚‚ from normal incomplete combustion due to poor mixing at the burner. However, the combustibles measurement can also provide a safety measurement to detect and alert the onset of combustibles breakthrough. Using the combustibles measurement, operators have the ppm level visibility to monitor for CO breakthrough and insufficient levels of air at the burner. In addition, operators can also use a methane/ hydrocarbon catalytic detector to provide per cent-level measurements of methane, hydrocarbons, and also unburnt hydrogen in the flue gas. By itself, a combustibles detector does not run hot enough to measure methane and other small hydrocarbons. However, with a catalytic design similar to the combustibles detector, a hydrocarbon detector can be used instead to detect and signal high per cent levels of unburnt hydrocarbons in the flue gas, often as a result of fuel leaks at the burner, process tube leaks, and loss of flame during start-up and normal operation. Even when using high hydrogen fuels, the hydrocarbons detector will respond to any unburnt hydrogen present, and it can be used to detect these per cent-level unsafe conditions. The catalytic nature of the detector enables these measurements to include methane, hydrocarbons, and hydrogen in a single, combined, per cent-level value. The Ametek Thermox WDG-V analyser, shown in Figure 3 , is an example of a

combustion flue gas analyser that provides all three of these critical measurements in one sensor to ensure safe and efficient combustion control. Flue gas analysis for safe, efficient hydrogen combustion Overall, hydrogen will play an important role in reducing carbon emissions from scattered combustion point sources, especially in the existing installed base. Inherently, hydrogen is a much faster moving and burning molecule than methane, and special attention will be needed to transition to pure hydrogen as a fuel source or high hydrogen fuels. In the transition, flue gas analysis will continue to play an important role in the combustion burner setpoints, fuel efficiency, emission reduction, and process safety, especially when using hydrogen as a fuel source. Figure 3 The Thermox WDG-V is a combustion flue gas analyser capable of measuring excess oxygen, combustibles, and methane/ hydrocarbons in one unit

Tim Tallon


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