The brief introduction about TDLAS in methane detection

How to detect gas

Methane is a kind of flammable and explosive gas, which is the main component of natural gas, gas and biogas. Gas is the primary disaster in coal mine safety. Natural gas used in daily life is also a potential safety hazard. According to the "2021 National Gas Accident Analysis Report" issued by the Safety Management Working Committee of China City Gas Association, a total of 455 natural gas accidents occurred. At present, commonly used methane gas sensors are divided into electrical and optical categories. Electrical methane gas sensors are based on catalytic combustion elements, semiconductor gas sensors, electrochemical sensors, etc. This type of electrical gas sensor is highly sensitive and suitable for many types of combustible gases, but the most fatal weakness is the need for electricity, which can prduce sparks, poisoning, and often need to be calibrated. The other type is TDLAS. The laser scanning remote sensor device uses laser spectral absorption technology to measure gas leakage at a distance of up to 100m. The device has fast response speed, high sensitivity, high detection accuracy, good gas selectivity, and strong ability to resist interference from other gases or water vapor.

What’s TDLAS

Tunable diode laser absorption spectroscopy (TDLAS, sometimes referred to as TDLS, TLS or TLAS is a technique for measuring the concentration of certain species such as methane, water vapor and many more, in a gaseous mixture using tunable diode lasers and laser absorption spectrometry. The advantage of TDLAS over other techniques for concentration measurement is its ability to achieve very low detection limits (of the order of ppb). Apart from concentration, it is also possible to determine the temperature, pressure, velocity and mass flux of the gas under observation. TDLAS is by far the most common laser based absorption technique for quantitative assessments of species in gas phase.

The advantage of TDLAS technology

The laser scanning gas detector has strong environmental adaptability, no oxygen environment, long life, no poisoning, no need for standard calibration. However, the laser gimbal host must be placed in the station, which requires power and is not intrinsically safe. In order to distinguish the host from the station with methane gas, a methane gas monitoring device was developed by using optical fiber to transmit laser. The laser emitted by the monitoring host away from the methane gas is transmitted to the gas monitoring point through the optical fiber, and the optical fiber collimator in the optical fiber gas box is used to expand the beam into the air for a certain distance to interact with the methane gas. The rest of the laser is coupled into the fiber and transmitted back to the monitoring host via another fiber collimator in the fiber airbox. The device uses the TDLAS principle to analyze and process the returned laser to obtain the concentration of methane gas [6]. In this paper, the principle, composition and network of the fiber laser gas monitoring device are introduced, and the practical application is given. Fiber laser methane gas monitoring device can be widely used in gas stations, petroleum and petrochemical, oil refineries, chemical plants, metallurgy, electric power industry and other places that may produce methane gas. The device can be flexibly networked to meet the field requirements, and the methane detection limit is 100ppm and the quantitative range is 100000ppm.

BLV BL-CH4 Drone Methane Detector is a drone based sensor which use TDLAS technology. This is a very high accuracy and high efficiency way of detecting CH4.

If you want to know more details, please feel free to contact us.