# Influence of Coal-Fired Fly Ash on Measurement Error of NO2 Electrochemical Sensors

## TL;DR

This study shows that coal-fired fly ash causes NO2 sensors to become inaccurate and fail faster due to reduced gas diffusion.

## Contribution

The study identifies coal-fired fly ash deposition as a novel cause of sensor inaccuracy and reduced lifespan in NO2 electrochemical sensors.

## Key findings

- Measurement errors of NO2 sensors ranged from 8.015% to 30.35% after 30 days of fly ash exposure.
- Fly ash reduces the gas diffusion area and coefficient, increasing sensor error.
- Fly ash deposition is linked to inaccurate measurements and shorter sensor lifespans.

## Abstract

To overcome the limitations of NO2 electrochemical sensors, including their inaccurate measurements and short working life, when used around coal-fired power plants, we investigated the influence of coal-fired fly ash deposition on the measurement error of NO2 electrochemical sensors through experimental tests. The morphological characteristics and pellet diameter distribution of coal-fired fly ash pellets were determined via scanning electron microscopy. The sedimentation velocity of coal-fired fly ash pellets in the air was determined through theoretical calculations of aerodynamics and hydrodynamics. Additionally, the effect of the deposition of coal-fired fly ash on the measurement error of NO2 electrochemical sensors was determined through experimental tests. The test results show that the minimum and maximum measurement errors of the NO2 electrochemical gas sensor were 8.015% and 30.35%, respectively, after a deposition duration of 30 days with 30 mg/m3 coal-fired fly ash. This demonstrates that coal-fired fly ash deposition is the cause of the inaccurate measurements and short working life of these sensors. Coal-fired fly ash causes a decrease in the gas diffusion area of the sensor and the diffusion coefficient, thus increasing the sensor measurement error.