Method for detecting non-anode effect CF4

Abstract

The invention discloses a method for detecting non-anode effect CF4, which comprises a sampling point which is obtained by sampling electrolytic tank flue gas on a gas pipe of the electrolytic tank, a tank cover plate of the electrolytic tank is kept in a sealed state, the gas collection efficiency of the flue gas in the electrolytic tank is not less than 90%, a detection device spectral analysis sensitizing zone is corrected, therefore the volume concentration of the CF4 spectral analysis sensitizing zone is in 0-1ppmv scope; the dust in flue gas is removed before the flue gas is introduced in the detection device, a drying agent is used for absorbing the moisture in flue gas; the detection device is started, the zero point of the device is calibrated, and the flue gas flux in the detection device is regulated, voltage change and anodic current density change of the electrolytic tank are monitored, when the voltage of the electrolytic tank exceeds normal operation voltage by 50 millivolts or anodic current density exceeds normal operation current density by 0.5A / cm<2>, the detection is started, and the volume concentration of CF4 is recorded. The method of the invention can detect the non-anode effect CF4 with extreme low concentration and reach the purpose of quantitative analysis of the non-anode effect CF4.

Description

[0001] technical field [0002] The invention belongs to the field of electrolytic aluminum greenhouse gas emission reduction, in particular to a non-anode effect CF 4 detection method. Background technique [0003] In the production process of electrolytic aluminum, the electrolytic reaction in normal production is the carbon thermal reduction reaction of alumina to generate aluminum and emit CO 2 . But during the "anode effect" of the electrolyzer, the electrolyzer produces two fluorocarbons: carbon tetrafluoride (CF 4 ) and dicarbon hexafluoride (C 2 f 6 ), collectively referred to as perfluorocarbons (PFCs). Its formation reaction is as follows: [0004] Na 3 AlF 6 +3 / 4C=3 / 4CF 4 +Al+3NaF (E=2.55V) [0005] Na 3 AlF 6 +C=1 / 2C 2 f 6 +Al+3NaF (E=2.68V) [0006] CF 4 and C 2 f 6 The lifetimes of the two compounds are as high as 50,000 years and 10,000 years respectively, and they have extremely high global warming potential (GWP), which belongs to strong gr...

AI Technical Summary

Problems solved by technology

However, non-anode effect CF cannot be detected with existing PFC detection methods 4 The main problems are: (1) The CF used in the existing PFC detection method 4 The sensitivity range of spectral analysis is 10-100ppmv, and the detection equipment cannot identify the extremely low concentration of non-anode effect CF 4 Spectrum; (2) The sampling points of the existing PFC detection method include the flue gas of multiple electrolyzers, which dilutes the non-anode effect CF 4 The concentration makes it difficult for the detection equipment to detect the non-anode effect CF 4 (3) The moisture in the flue gas seriously interferes with the spectral analysis of the detection equipment, and the moisture stays in the optical path for a long time, which affects the detection accuracy of the equipment, causes the minimum detection limit of the equipment to drift positively, and is easy to ignore low-concentration CF 4 spectrum

[0009] The domestic and foreign patent literature has been searched, and there is no reference to non-anode effect CF 4 Report on detection method

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