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The Basic Principles and Characteristics of Several Types of Gas Analyzers (3)

The Basic Principles and Characteristics of Several Types of Gas Analyzers (3)


7. Oxygen analyzer (according to the principle: oxidation drill, paramagnetic)

(1) The basic principle of oxidation drill analyzer

The basic principle of cobalt oxide analyzer for measuring oxygen content: attach porous platinum electrodes (also known as platinum black) to both sides of a piece of cobalt oxide, and keep them at high temperature. If the oxygen content in the gas on both sides is different, an electromotive force will appear between the two electrodes. This electromotive force is generated due to the different oxygen concentration of the gas on both sides of the solid electrolyte, so it is called the oxygen concentration difference potential, and the size of the oxygen concentration difference potential can be calculated by the Nernst formula.

Advantage:
It is generally used for flue discharge or combustion control. The sampling probe is resistant to high temperature and corrosion. The installation method is direct insertion or extraction. It has the characteristics of simple structure, good stability, high sensitivity, fast response, etc. The output signal is convenient for signal transmission and processing, and the accuracy is relatively high.

(2) Basic principle of paramagnetic analyzer

Paramagnetic oxygen analyzers are generally divided into three types: magnetomechanical, magnetic pressure and oxygen thermomagnetic convection analyzers. The paramagnetic oxygen analyzer uses the paramagnetism of oxygen molecules to guide the measured gas to the built-in magnetic field. Oxygen molecules move in accordance with the magnetic field in the magnetic field and generate thrust on the suspended dumbbell ball. The oxygen content in the measured gas is obtained by measuring the deviation of the dumbbell ball.

Advantages: fast response speed, high measurement accuracy, often used for precise process control.

8. Laser gas analyzer

(1) Basic principles of dust semiconductor laser gas analyzer

DLAS (Diode Laser Absorption Spectroscopy) technology is essentially a spectral absorption technology, which obtains the concentration of gas by analyzing the selective absorption of laser light by gas.

The difference between it and the traditional infrared spectrum absorption technology is that the spectrum width of the semiconductor laser is much smaller than the broadening of the gas absorption line. Therefore, DLAS technology is a high-resolution spectral absorption technology. The light intensity attenuation of the semiconductor laser passing through the measured gas can be obtained by the Lambert-Beer law expression. The relational expression indicates that the higher the gas concentration, The greater the attenuation of light. Therefore, the gas concentration can be measured by measuring the attenuation of the gas to the laser.

Advantage:
The response measurement time can be reduced to 1 second, there is no cross-interference of other gases, no sampling is required, on-site measurement can be performed, and very low detection limits (ppb and low ppm) can be carried out.

(2) Basic principles of Raman laser gas analyzer

The core part of the laser gas analyzer RLGA is a laser detection device in which the HeNe laser can emit a safe low-power single-wave laser into a gas test cavity. Because the laser energy is weak, the inside of the device is continuously reflected by the mirrors at both ends of the detection cavity, which magnifies the energy by about 1000 times. The photon collides with gas molecules and scatters to produce a spectrum that is different from the laser spectrum, and the spectra scattered by different molecules are specifically different, which is "Raman scattering spectrum".

The inner wall of the detection cavity is equipped with 8 optical filters and photoelectric sensors to absorb and detect the specific spectral frequencies of different molecules, so as to obtain the content of 8 different gas components to be measured. According to this principle, the content of each gas to be measured is obtained by direct measurement without any derivative calculation; the detection accuracy of RLGA is higher; the reaction speed is faster.

Advantages:
-Can detect almost all industrial process gases online (more than 100 types of measurable gases)
-The sample gas adopts the extraction type. After entering the analysis chamber, one analyzer can measure 8 gases at the same time, which is suitable for the measurement of complex mixed gases
-All measured values are directly measured, no derivative calculation is required
-The detection interval is 50 milliseconds, and the response time can be as low as 1 second
-The detection range of any gas is not limited. The same analyzer can measure several ppm offline, 30% or 100% online
-Integrated automatic gas continuous sampling system and calibration system
-Integrated fully automatic back blow and back flush system
-Integrated detection point pressure and temperature tracking system
-Small size, easy to install and operate (only the size of household microwave oven)
-Standard digital OPC signal output (including gas detection results, pressure, temperature, charge, and analyzer status and other parameters)
-Maintenance is simple, only need to clean the surface of the optics and replace the filter and desiccant regularly (cycle of six months)
-long lasting;


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