Application of eLAS-200 laser gas analyzer & gas analysis system


Application of eLAS-200 laser gas analyzer & gas analysis system
I. TDLAS Working Principle
A basic TDLAS setup consists of tunable diode laser light source, transmitting (i.e. beam shaping) optics, optically accessible absorbing medium, receiving optics and detectors. The emission wavelength of the tunable diode laser, viz. VCSEL, DFB, etc., is tuned over the characteristic absorption lines of a species in the gas in the path of the laser beam. This causes a reduction of the measured signal intensity, which can be detected by a photodiode, and then used to determine the gas concentration and other properties as described later

II. eLAS Series Features
2.1 High selectivity
TDLAS is a high resolution spectral technique. the measurement is free from interference from other gases, and this property has obvious advantages over other analytical methods.
2.2Universal property
TDLAS technology can effectively measure all active molecules absorbed in the near infrared region, and basically cover the main  analytical gases.
2.3Strong Applicability
TDLAS technology has the advantages of high speed and high sensitivity.
In practical applications, the time resolution can reach MS magnitude,
The sensitivity is up to ppb.

III.eLAS-200 Introduction

The eLAS-200 laser gas analyzer / system uses the principle of TDLAS to measure the specific gas concentration in the process gas component. The gas analyzer has many advantages, such as high sensitivity, fast response, free from background gas interference and non-contact optical measurement. It can be applied to many fields such as gas emission monitoring and process control.

Moreover, according to the characteristics of HCL laser, the effective optical path of the reflecting pool of the analyzer reaches 1-3 meters, and the sensitivity of the analyzer is consistent with that of the analyzer, which greatly improves the compatibility with other systems.

IV.eLAS-200 gas analysis System performance parameter








Response time



0-10ppm, 50ppm,0-1000ppm





≤ ±1%FS

Functional parameter



Power Supply

AC110-2200V/47-63Hz  3

Digital Output


Analog output

4-20mA the maximum load of 900Ω

Relay output

Load capacity: AC/DC 24V/1A; concentration exceeding limit alarm, transmission abnormal alarm, laser temperature abnormal alarm

Environment parameter

 Optical path

1-3 meters

Gas sample temperature


Gas sampling pressure

Atmospheric pressure±5kPa

Environmental pressure


Sampling velocity


Ambient temperature






V.eLAS-200 Laser Gas Analysis System

eLAS-200 HCL laser gas analysis system uses the whole process of high temperature combined heat extraction to monitor HCL gas in sample gas.

The system consists of a sampling unit, a transmission unit, a preprocessing unit, a control unit, and an analysis unit. The analysis unit uses TDLAS technology.

VI.eLAS-300 system consists of

VII.Sampling flow chart of eLAS-200 system
The sample gas through sampling probe, the heating tube to the pretreatment unit, the pretreatment unit comprises a normally closed type high temperature valve SV1, precision filter, jet pump, the SV1 valve is used to cut off gas in the sampling, the precision filter for further purification of the sample gas, dust removal in the sample gas, jet pump is used to provide dynamic sample gas transmission, the system controlled by PLC sampling and purging actual automatic cycle. All the gas flow through the components and pipes are placed in the constant temperature heating box to prevent the pipeline from being blocked by ammonia salt, and to reduce the loss of gas samples.

VIII.eLAS series in Waste Incineration Power Plant Application
One waste incineration power generation capacity of 6MW in East south Asia, they use of SNCR technology denitration, HCL testing equipment installed in the chimney 35 meters platform, sampling distance  less than 5 meters.Another waste incineration site under construction was hoping to install a HCL system before and after processing, with HCL 300PPM gas analyzer .

Customer bought a HCL gas analyzer, with customers own CEMS system and pretreatment, simultaneous measurement of SO2, NOX,O2

1. in order to ensure HCL emissions, in 2016, the waste incineration power generation purchased a set of eLAS-200 online HCL analyzer use;

2. At the beginning of first  week, the data is normal and third party inspection data similar (according to the right picture);

3. In a few days, HCL data has been shown to zero, unable to get valid data. The examination found that the gas path inside the instrument was polluted. After the pipeline is polluted or corroded, it is easier to absorb the sampling gas . (as in the right picture below)
4. After cleaning, the instrument is re connected with N2 and standard gas, and the test value is completely normal

IX.Improper gas pretreatment system problems analysis
1.Optical mirror and cell of eLas-200 gas analyzer were polluted by particles looking like rustiness from metal oxidation. The metal gas inlet connector after the gas pre-treatment unit had the same oxidation
>> This is why the gas analyzer couldn’t be calibrated successfully and had no readings because the optical light intensity was too weak and the light couldn’t be transmitted.


2) Sampling distance is about 70 meters while nominal value of HCl is a few ppm.

>> Because HCl is a highly reactive gas, it was totally adsorbed by material along such a distance.

3)Solenoid valves inside the cabinet and a piece of the sampling pipe are not heated

>> There is a high probability that the un-heated parts are generating cold points resulting in moisture condensation and formation of acid water; the remaining gaseous HCl will be absorbed into this liquid and the analyzer will have no reading.

4)Stainless steel pipes are used inside the cabinet for connecting the solenoid valves;

>> PFA tubing is generally preferred when sampling highly reactive gases as HCl to avoid gas adsorption by the material.

5)The heated pump is placed before the gas analyzer.

1. In order to complete the acceptance as soon as possible, purchased the eLAS-200 complete set of analysis system . The eLas-200 is installed on the platform of stack which is less than 5 meter from sampling point, with IP65 metal enclosure. (the following figure is to analyze the data transmitted to the CEMS human-machine interface, the HCL concentration is 6PPM, and the field HCL concentration is maintained at 5-15PPM.

2. The third party testing machine: Gasmet  FT-IR gas analyser, with hot wet sampling system . Sampling from the similar sampling point of CEMS system, via heated tube down to gas analyzer transport car.

3.  The comparison results are shown below. Gasmet, FT-IR,  and eLAS-200 HCL test trends

4. Measurement comparison analysis

The diagram trends were almost the same between Gasmet T-IR gas analyzer  and eLas-200  HCL  value, especially after 15p.m., the reading trends were going the same (From 13pm to 15pm, eLas-300 HCL value was lower than Gasmet FT-IR gas analyzer, we checked system gas flow, check liquid moisture, and increased system  heated temperature to 180 ℃ from 160 ℃;

Finally eLas-300 HCL gas analysis system passed the third party testing and working very good.