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E-mail
531172201@qq.com
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Phone
13560799601
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Address
5th Floor, Building 6, Longbi Industrial Zone, Bantian Street, Longgang District, Shenzhen
Shenzhen Dongri Yingneng Technology Co., Ltd
531172201@qq.com
13560799601
5th Floor, Building 6, Longbi Industrial Zone, Bantian Street, Longgang District, Shenzhen
For the flammability measurement of VOC (volatile organic compound) pipeline gases, the infrared principle (NDIR) is usually superior to the catalytic combustion principle and is a more recommended choice.
Firstly, we need to understand the most crucial point:
Catalytic combustion principleWhat is being measured FlammabilityorExplosion riskIt detects the total heat generated by the oxidation reaction (combustion) of all combustible gases on the sensor and converts it into a reading of "% LEL" (lower explosive limit). itCannot distinguishWhat kind of gas is burning.
Infrared principleWhat is being measuredSpecific gas concentrationIt detects infrared radiation through the absorption characteristics of specific gases and can accurately measure itSpecific VOC gasesThe concentration is usually measured in ppm or% vol. Through algorithms, it can beconversionUse% LEL to indicate explosion risk.
| feature | Catalytic combustion principle | Infrared principle |
|---|---|---|
| Measurement object | All combustible gases (overall flammability) | Specific VOC gases (with clear targets) |
| principle | Gas burns without flame on the catalyst surface, causing a change in resistance | Gas absorption of specific wavelength infrared light |
| advantage | -Low cost -Reacts with non-polar molecules such as hydrogen -Mature technology and wide application |
-highly selectiveNot affected by interference from other gases -Not poisoned or inhibitedLong lifespan -No combustion risk -Fast response speed and good stability |
| shortcoming | -Easy to be poisoned/inhibitedSilicon, sulfur, lead, halogens, etc. can damage the sensor -Oxygen is required to work (not suitable for hypoxic environments) -Relatively low accuracy, susceptible to environmental factors -The lifespan of the sensor is limited and needs to be replaced regularly |
-relatively high cost -Yes, that's rightHydrogen (H ₂), Acetylene (C ₂ H ₂)Equisymmetric structured non-polar molecules have no response or weak response |
The gas composition in VOC pipelines is complex and typically involves the following challenges:
Risk of poisoning：
Many VOC gases in industrial processes already contain or are accompanied by themSilanes, sulfides (such as H ₂ S), halogenated hydrocarbons (such as chlorobenzene, dichloromethane), phosphatesWait.
These substances will irreversibly poison the catalyst of the catalytic combustion sensor, leading to a decrease in its sensitivityProviding incorrect low readings poses a significant safety hazard.
Hypoxic environment：
The gas inside the pipeline may be inHypoxia or enrichment state(For example, in an inert gas protected reactor). Catalytic combustion sensors require at least~10% oxygen to function properly, otherwise they cannot detect.
High concentration environment
The concentration of VOCs in pipelines may be very high, even exceeding 100% LEL. Long term exposure to high concentrations of combustible gases can "burn" catalytic combustion sensors and shorten their lifespan.
infrared sensorAvoiding the above issues:
It is not affected by poisoning because it is based on optical principles and does not undergo chemical reactions with gases.
It doesn't need oxygen.
It can withstand high concentrations of gases (depending on the design).
| scene | Recommendation principle | reason |
|---|---|---|
| Most VOC pipeline monitoring(Benzene, toluene, xylene, ketones, alcohols, alkanes, etc.) | Infrared principle | Anti poisoning, long lifespan, high precision, safety and reliability are the choices for long-term stable operation. |
| Known gas components are simple, clean, non-toxic substances, and have limited budget | Catalytic combustion principle | Low cost, able to meet basic explosion-proof monitoring needs. But close attention should be paid to the risk of poisoning and lifespan. |
| The gas contains hydrogen (H ₂) or acetylene (C ₂ H ₂) | Catalytic combustion principleorInfrared+catalytic composite type | Infrared is not sensitive to these two gases. The principle of catalytic combustion must be used. |
| The gas composition is complex and varied, and includes gases that can be measured by both catalysis and infrared spectroscopy | Infrared principle | The high selectivity of infrared can avoid interference from other gases and provide more accurate readings of the target gas. |
| Require safety and maintenance quantity | Infrared principle | There is no risk of sudden death of sensors, and the maintenance cycle is long. |
Overall, for VOC pipeline inspection, investing in an infrared based gas detector is a wiser, safer, and more economical choice in the long run, unless the budget is very tight or the target gas is hydrogen.