Currently, online analytical instruments usually have two sampling and analysis methods. One is the extractive process analysis system, and the other is the in-situ online analysis system. The two sampling analysis methods have their own advantages and disadvantages. The extractive process analysis system has the following three advantages over the in-situ online analyzer system:
Changes in working conditions do not affect real-time measurement and analysis results.
Changes in working conditions usually result in changes in the temperature, pressure, and medium of the process gas. The in-line in-situ online analyzer system needs to be compensated according to the actual temperature, pressure, humidity and other parameters of the working condition, which will cause measurement errors. The extractive process analysis system through the pretreatment system controls the process gas constant temperature, pressure regulation, steady flow, dust removal, dehumidification, etc., so that the process gas always maintains the ideal analysis state required by the online analysis instrument, so the measurement results are not affected by the working conditions. Change impact.
The abnormal state of the installation position affects the measurement and life of the online analysis instrument.
The in-situ online oxygen analyzer system is directly installed on the process pipeline of the chemical plant, and the chemical pipeline is usually accompanied by various abnormal conditions that are not conducive to online analysis, such as: different intensities and continuous vibration; strong electromagnetic Disturbance; high temperature roasting of chemical pipelines, seasonal climate changes, etc. The existence of these abnormal conditions for a long time will have a serious impact on the measurement results, and will seriously affect the service life of the high-precision online analyzer. The extractive process analysis system is usually installed in the instrument cabinet far away from the chemical pipeline, or installed in the analysis room, and it is less or not affected by these abnormal conditions.
Purge nitrogen must be continuously introduced.
In-line in-situ online analyzer system, in order to prevent dust, water vapor, corrosive substances and other impurities in the process pipeline from polluting the instrument glass window, a nitrogen purge system is usually used. The nitrogen purging system requires clean nitrogen to be purged continuously for 24 hours, and the nitrogen consumption is large. Insufficient nitrogen pressure or flow will cause pollution of the instrument glass window, affect the light transmittance, and thus affect the analysis results.
If the purge gas contains the measured component, it will seriously affect the measurement and analysis, especially when performing low-concentration detection.