Utilizing proprietary technologies of Tunable Diode Laser Absorption Spectroscopy (TDLAS), FPI delivers the LGA system to satisfy in-situ measurements with high accuracy, fast response, strong reliability and virtually maintenance free.
The LGA system is applicable to almost all industrial process, especially well proven in harsh conditions in combination of high temperature, pressure, dust, corrosives and contaminants.
Leveraging an installed base of over 6,000 units, the LGA system has been extensively used for combustion and safety control, process optimization, energy recovery, scientific research as well as environment monitoring. To date, these units have been employed in metallurgy, refinery, petrochemical, natural gas, power plant, waste incineration, cement and other situations where gas measurement is needed.
|GAS||DETECTION LIMIT||MEASUREMENT RANGE|
|CO2||1.5ppm||0-150ppm, 0-100% Vol|
|NOTE: Listed are detection limits specified for 1m optical path at 20℃, 1 bar abs. Dual Gas CO+CO2, HCL+H2O are available for particular applications. Other gases and detailed measurement ranges may be available or customizable on request.|
The transmitter portion of the LGA system consists mainly of diode laser, laser driver and HMI modules, realizing diode laser driving, spectrum data processing and human-machine interface. The receiver unit of the analyzer is composed of a photoelectric sensor, signal processing and purge control modules, is capable of signal processing and anti-explosion control.
The laser beam from the transmitter unit passes across the stack or duct work and is absorbed by the measured gas. The attenuated light is then detected by the photoelectric sensor in the receiver unit, and the resulting signal is sent back to the transmitter unit and analyzed to yield gas concentration.
Measuring Principle Diagram
|ITEM||LGA LASER SYSTEM||CONVENTIOAL ONLINE ANALYSIS|
|Adaptability||Applicable to high temperature, pressure moisture, dust density and corrosion||Applicable to constant temperature, pressure and dust free|
|Measurement||In-situ, continuous/real-time measurement; sample gas evacuation free||With sample conditioning system, discontinuous measurement|
|Response time||Fast, only limited by electronics response, less than 1sec||Slow, limited by gas sampling, transport, and instrument electronics response 20+sec|
|Accuracy||Average concentration along the optical path; no cross interference from other gas species, dust, and gas parameter fluctuations||Gas concentration at the tip of the sampling probe only, affected by gas influence and absorption, and leaked during gas sampling and transport; cross interference from other gas species, dust, and gas parameter fluctuations; gas information lost due to dissolution, absorption, and leakage|
|Reliability||No moving parts, highly reliable||Many moving parts, low reliability|
|Calibration&Maintenance||Calibration:<2times/year Maintenance:<2times/year||Calibration:2-3times/month Maintenance: frequent|
|Operation costs||No spare parts, only cost of electricity||Lots of spare parts, around 20% of the equipment cost per year|
No Cross Interference
The laser spectrum features excellent monochromaticity with spectral width down to 0.001nm, which is much narrower than spectral width of other light sources. By utilizing the ‘Single-line’ spectroscopy, a well-targeted laser spectrum can be sorted out to cover only the measuring gas without overlapping spectrum of all background gases.
“Single-line spectrum” mearsurement
No Effects from Dust, Moisture and Window Contamination
TDLAS gas analyzers use a laser spectral scanning technique. The unit
periodically scans the gas under test with a modulation frequency range larger than the gas absorption spectral line-width such that, within one scan period, there are two distinctive areas. Area I is uneffected by the gas absorption and gives Td, whereas Area II is effected and gives Tgd.
The transmittance of the gas under test is then calculated accurately by Tg=Tgd/Td. The interference from dust and optical window contamination is, therefore, automatically screened out.
Automatic Temperature & Pressure Compensation
When gas temperature and pressure under measurement changes, the width and height of the absorption waveform change, which effects the accuracy of the measurement. By having 4-20mA process temperature and pressure input, the LGA system automatically compensates for them with a proprietary algorithm to ensure measurement accuracy.