Laser Gas Detector LGD F200


Courtesy of Axetris Ag

Laser gas detection with innovative, easy-to-integrate OEM modules

Diode Laser based gas detection gains increased interest in the industry as it offers significant benefits in terms of selectivity, stability and low maintenance. Axetris provides innovative gas detector modules as basis for extractive process control systems and for continuous emission monitoring systems (CEMS). The technology increases] performance, reliability and cost effectiveness - or simply enables new applications for OEM customers.

Laser Gas Detection (LGD), based on Tuneable Diode Laser Spectrometry (TDLS), provides a solution to many gas detection challenges in emission monitoring and process control. The technology offers unique advantages like precise optical, contact-less measurements, excellent target gas selectivity and sub ppm-level detectivity.

Today, laser based gas analysers have high component cost and require typically a rather complex design with very accurate control of the laser light inside the analyser to achieve the required sensitivities. The high material cost for the optical and optoelectronic components and the related high R&D and engineering effort have so far hindered a wide distribution of the TDLS technology into mainstream applications and limited it to mainly high-end environmental and emission monitoring applications.

Axetris has developed a laser gas OEM analyser module for gases such as NH3, H20, CH4, C02 and HCI, which enables companies without detailed laser spectroscopic expertise and without high initial investments to benefit from the advantages of this seminal gas detection technology.

The sensor module concept has been kept very simple to control the cost of the module and to enhance its robustness. It requires only the conditioned gas and electrical supply as input and delivers directly the gas concentration as output. The performance is achieved at short absorption length in a compact module by sophisticated high level optical system design and a proprietary detection algorithm based on technology-enhanced Tuneable Diode Laser Spectroscopy. The spectroscopic information is collected by modulating the wavelength of a narrow bandwidth near-infrared diode laser across the absorption line of the target gas. Subsequent data processing in the integrated electronics leads to a high-resolution concentration measurement.

The OEM analyser module features a flow-through sample cell with a typical gas flow of 3 l/min and a cell volume of only 15 ml. This allows a rapid gas exchange and thus very fast response times. The cell has been modular designed in two configurations, one for measurements at ambient gas temperature and one for applications which require a hot measurement of the gas where the cell is usually heated to 190 °C. The latter is especially of interest for water soluble target gases in combustion processes with high water concentrations in the gas matrix.

The high sensitivity and the large dynamic range of the detection technology enable measurement from sub-ppm level to high percentage concentration without physical adaptation of the device. The design of the LGD F200 enables a tailor made application fit for a range of gases and applications. Achieving the best performance and low cost of ownership, the detector is being applied in applications as listed below.

LGD F200 applications
NH3 Slip in SCR process control
The hot wet ammonia slip measurement in a high water background in the exhaust gas of combustion process with Selective Catalytic Reduction (SCR) technology as used on automotive test beds and fossil fired power plants. In power plants, the ammonia slip is measured downstream the SCR catalyst to control the DeNOx process. An integrated water measurement is precise enough to allow a dry basis or standard condition correction to the measurement which is required for many regulations.

HCI Environmental Compliance Monitoring
The extractive set-up allows for simple zero and span gas testing in compliance with legal regulations as for example in continuous monitoring of HCI in waste incineration furnaces.

NH3 Livestock Climate Control
Improving health and growth of livestock the NH3 must be monitored. Therefore the indoor air quality has to be regulated to comply with the animal welfare and productivity requirements. The LGD F200 technology can play an important role thanks to the low cross sensitivity (selectivity) to enhance the NH3 concentration in the livestock and monitor the exhaust air quality.

'Axetris has developed a laser gas OEM analyser module for gases such as NH3,

H20, CH4, C02 and HCI'
CH4 Landfill and Environmental monitoring
A popular issue of methane landfill, waste water - greenhouse gas (GHG) and underwater GHG research can be addressed with the LGD F200. The technology offers a real time monitoring with very high dynamic range required and the selective measurement of methane.

CH4 Leak-search
The exact and reliable city gas search is an important mobile monitoring system to avoid methane losses due to defective pipework The short response time and the accuracy in combination with low maintenance and rugged design characterize the LGD F200 for the low power consumption application.
'the design of the LGD F200 enables a tailor made application fit for a range of gases and applications. Offering the best performance and low cost of ownership'

C02 and NH3 for Contamination of Natural Gas
Measurement at the point of production, distribution or point of use of natural gas supplies are ideal applications for the LGD F200.

Summary and outlook
The LGD is a perfect tool and cost effective solution for OEM integrators active in emission monitoring or process control and allows for simple integration due to its self-contained and stand-alone system design. The modular and intelligent design enables the future considerations of additional gases and development and adaptations of new detection algorithm.

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