Products > Process > Laser Gas Analyzer

OVERVIEW

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.


GASDETECTION LIMITMEASUREMENT RANGE
O20.01%Vol0-1%Vol, 0-100%Vol
CO0.5PPm0-50ppm, 0-100%Vol
CO21.5ppm0-150ppm, 0-100% Vol
H2O0.3ppm0-30ppm, 0-100%Vol
NH30.1ppm0-10ppm, 0-100%Vol
HCL0.2ppm0-50ppm, 0-100ppm
HF0.1ppm0-10ppm, 0-1,000ppm
H2S0.01ppm0-50ppm, 0-100%Vol
CH410ppm0-200ppm, 0-100%Vol
C2H20.1ppm0-10ppm, 0-100%Vol
C2H40.6ppm0-60ppm, 0-100%Vol
HCN0.3ppm0-30ppm, 0-10,000ppm
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.


CONFIGURATION

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.

MEASURING PRINCIPLE

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.


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Measuring Principle Diagram

TECHNOLOGY COMPARISON


ITEMLGA LASER SYSTEMCONVENTIOAL ONLINE ANALYSIS
AdaptabilityApplicable to high temperature, pressure moisture, dust density and   corrosionApplicable to constant temperature, pressure and dust free
MeasurementIn-situ, continuous/real-time measurement; sample gas evacuation   freeWith sample conditioning system, discontinuous measurement
Response timeFast, only limited by electronics response, less than 1secSlow, limited by gas sampling, transport, and instrument electronics   response 20+sec
AccuracyAverage concentration along the optical path; no cross interference   from other gas species, dust, and gas parameter fluctuationsGas 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
ReliabilityNo moving parts, highly reliableMany moving parts, low reliability
Calibration&MaintenanceCalibration:<2times/year Maintenance:<2times/yearCalibration:2-3times/month                                                    Maintenance: frequent
Operation costsNo spare parts, only cost of electricityLots of spare parts, around 20% of the equipment cost per year

TECHNICAL PRINCIPLE

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.


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“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. 


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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.