Study on particle loss in high-temperature flue gas sampling during fuel conversion

Abstract

The sampling accuracy for high-temperature flue gas is limited by the particle deposition on the sampling tube wall, which is important for the study of fuel conversion. Herein, deposition of 0.1–10 μm particles in 300–1000 K flue gas in the sampling tube is numerically investigated, and the corresponding particle loss is quantified by theoretical modeling. Saffman lift force and thermophoretic force dominate the particle deposition in the isothermal and cooling sections of the tube, respectively. Along the tube, the cumulative deposition rate is negligible in the isothermal section and increases rapidly and then gradually reaches the terminal deposition rate in the cooling section. The terminal deposition rate increases with the flue gas temperature, which can be up to 40.77% and 24.62% for 0.1 μm and 10 μm particles in 1000 K flue gas, respectively. A formula of the terminal deposition rate is proposed as a function of the flue gas temperature, which predicts the numerical results with an error less than 5%. The normalized profiles of the cumulative deposition rate under different sampling condition coincide, and a distribution function related to the flow Reynolds number is proposed. Based on the above formula and function, a model is presented which well predict the particle loss in the sampling tube with different lengths.