Advantages and disadvantages of the decimation sampling method
The advantages and disadvantages of the decimation sampling method are as follows: the decimation sampling method is divided into two types: direct extraction sampling method and dilution extraction sampling method. (1) Direct extraction sampling method analysis process: the flue gas is pumped by the diaphragm pump, and is filtered by the sampling probe for coarse dust removal, heating and heat preservation pipeline transmission, and then sent to the analysis after condensing and dehumidifying, fine dust removal, flow regulation and other pretreatment steps. The instrument is analyzed.
Advantages: 1 dry basis measurement, can directly measure the content of pollutants in dry flue gas; 2 because the soot and water vapor have been removed from the sample gas, the analyzer has high measurement accuracy.
Disadvantages: the sample needs to be transported with heat insulation (temperature is maintained between 140~160 °C); 2 samples need to be pre-treated by dehumidification and water removal; 3 there is possibility of acid condensation in high sulfur, and the sampling and pretreatment parts should be prevented. Corrosion; 4 sample system needs frequent maintenance; 5 sample flow rate is large (generally ≥ 2L / min). The filter is easy to block, need to be back-purged regularly.
(2) Dilution extraction sampling method analysis process: the flue gas is pumped by the jet pump, and the flue gas is diluted with a certain dilution ratio with clean air to reduce the concentration of gaseous pollutants, and the diluted flue gas is introduced into the analyzer for analysis. The method is extended from the ambient air quality monitoring method to the monitoring of pollution sources. The analyzer has a small measuring range and therefore needs to be diluted.
Advantages: 1 no need for heat tracing pipeline; 2 simple pretreatment system, no dehumidification and dust removal equipment; 3 small amount of flue gas is extracted (generally 0.5L/min), probe filter is small, not easy to block; 4 sample system maintenance Small amount; 5 to avoid measurement errors caused by water-soluble gases (SO 2 , CO 2 ).
Disadvantages: 1 wet basis measurement, measuring the content of pollutants in the wet flue gas, need to increase the humidity measurement (or assuming the moisture content of the flue gas), the content of the wet flue gas is corrected to the content of the dry flue gas, thereby calculating the emission It adds a potential source of error; ② need some way to correct the changes in pressure and temperature conditions; ③ a larger amount of dilution air, to ensure measurement accuracy, the need for dilution air purification treatment to remove SO 2, NO x, CO 2 , CO and water vapor (water vapor dew point as low as -38 ° C); 4 dilution ratio must be precisely controlled, the dilution ratio error should not be greater than ± 1%; 5 often need to antifreeze the sampling pipeline and heat the sampling probe; 6 Calibration gas must be passed from the dilution probe to ensure calibration accuracy.
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