Measuring principle

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.

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 Tgd and Td. 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.

By having 4-20mA process temperature and pressure input, the LGA system automatically compensates for them with a proprietary algorithm to ensure measurement accuracy.

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Technology Comparison

Item	LGA Laser System	Conventional  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
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

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LGA-4100

• Cross stack, fast response < 1s
• No gas sampling, no cross interference
• No zero drift, diverse optical length (0.5-20m)
• Reliable in all harsh conditions: high temperature & pressure, dust density, moisture and corrosion
• ATEX certified

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LGA-4500

• Low detection limit, no cross interference
• Online calibration, no zero drift
• Reliable in all harsh conditions: high temperature & pressure, dust density, moisture and corrosion
• ATEX certified

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Technical Data

Model	LGA-4100/LGA-4500/LGA-4500IC
Technical   Principle	TDLAS
Installation   type	Cross    duct/Extractive
GAS	DETECTION  LIMIT	MEASUREMENT  RANGE
NH3	0.1ppm	0-10ppm,    0-100%
HCL	0.2ppm	0-50ppm,    0-100ppm
HF	0.1ppm	0-10ppm,    0-1,000ppm
H2S	0.1ppm	0-50ppm,    0-100%
Repeatability	≤  ±1%F.S.
Linearity	≤  ±1%F.S.
Span drift	≤  ±1%F.S./6 months
Response time(T90)	<  1s
Warm-up time	≤  15min
Optical path length	0.5-20m
Flue gas temperature	max.  1500℃
Flue gas pressure	0.8  to 4 bar   abs.
Analog outputs	2  outputs 4-20mA, max. load 750Ω, electrically isolated
Relay outputs	3  outputs 24V DC/1A
Analog inputs	2  inputs 4-20mA, for gas temp. & pres. compensation
Communications	RS485  (or Bluetooth, RS232 or GPRS )
ATEX  certified	Ex  d op is pxIIC T5 Gb

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