Aiming at solving the problems of inaccurate measurement and short service life of SO_2 electrochemical gas sensor in monitoring air pollutants around thermal power plants

by taking the fly ash from a gangue-fired power plant in Shuozhou

Shanxi Province as the research object

and based on the analysis of the morphological characteristics of fly ash

the settling speed of fly ash and the amount of deposition at different times were obtained through theoretical calculation

and the influence of fly ash on the measurement error of SO_2 sensor was tested by experiments. The results show that

the diameter distribution range of the fly ash is 4～10 μm

the settling velocity of the fly ash is 2.25×10-3 m/s and the deposition amount in one day is 1.55 mg. The deposition time of fly ash will affect the measurement error of the sensor

the longer the deposition time

the greater the measurement deviation of the sensor. The reason is that the deposition of fly ash leads to the reduction of gas diffusion area s and diffusion coefficient K of the electrochemical sensor. Under the condition of fly ash deposition

the greater the gas mass concentration

the faster the gas reaches the working electrode area

the higher the effective SO_2 concentration detected in the limited response time

and the smaller the measurement error of the sensor. When the SO_2 electrochemical sensor is used in the environment with a large amount of fly ash

it is recommended to install a filter membrane with pore diameter less than 4 μm to prevent dust and clean the deposited fly ash regularly.