In collaboration with ClearSign Technologies Corporation, Narion has incorporated a novel flame detecting methodology into several flame detection applications.
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Background
Flame detection sensors typically fall into one of three categories: optical, thermal, or electrical. The various sensors developed within these categories have their own pros and cons.
Optical techniques are the most widely used sensor for flame detection. They provide a quick response and are fairly robust. Optical sensors rely on the light emitted from a flame (natural chemiluminescence) measured at a specific range of wavelengths, either Ultraviolet, Visible, or Infrared. These sensors require an unobstructed line of sight of the flame, have limited viewing angle (solid angle) and have difficulty differentiating between flames, for example in multi-burner configurations.
The most common thermal technique is a thermocouple, which detects a flame by directly measuring the heat release (temperature) of the flame. This technique is slower than optical techniques and requires the sensor be in or near the flame; they can therefore have a rather short lifetime.
The most common electrical sensor is a flame rod. A flame rod detects a flame by exploiting the asymmetric conductivity property of a flame. In other words, a flame acts like an electrical rectifier when an AC signal is applied. Flame rods provide a robust flame presence signal and can differentiate between flames in multi-burner units. However, flame rods must be placed within the hot zone of the flame and can therefore have short lifetimes and poor reliability.
Electrical techniques for flame monitoring have been largely underdeveloped. While flame rods are the most developed electrical technique for flame detection other electrical techniques are rarely mentioned. The electrical characteristics of a flame can actually offer a lot more detail about the combustion process, more than simply flame presence. This is because the chemical ionization process of a flame depends on the operating conditions of the flame. Therefore, by measuring various electrical properties of the flame it becomes possible to characterize key flame characteristics, such as equivalence ratio, Wobbe index, Lean Blowout (LBO) and even the level of turbulence. This additional information can be used not only to detect the presence of a flame, but also to optimize the process of a burner and/or entire furnace system operation. Furthermore, these electrical measurements can be made using sensors located outside of the hot zone, therefore improving their lifetime as compared to a flame rod.
Applications
Industrial Process Burners – ClearSign EYETM
Industrial process burners are widely used throughout the Oil & Gas industry to provide heat for processes.
Publications
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