Study On Optical Measurement For Particle Size Distribution Of Silica Particles In Water

In order to reduce environmental pollution and improve drinking water quality,the types and contents of suspended particles are attracting more and more attention.Optical measurement and inversion of particle size distribution of suspended particles has become the focus of world. Silica suspended particle is the main component of suspended matter in atmosphere and water,high-precision measurement and inversion of the particle size distribution is essential to resolve air pollution and purify water quality. This thesis researches the optical measurement and inversion of silica suspended particles with different particle sizes based on Mie scattering theory, and the researches are as follow.(1) The influence of refractive index on the scattering intensity is analyzed by choosing the angle scattering method with high accuracy and sensitivity. The research shows that the influences of different refractive index can be neglected when the scattering angle is small (? = 0 ?0.25rad). The original signal detected by spectrometer is seriously affected by noise. The denoising effect is significant when the denoising factor is 200 based on the wavelet transform method.(2) Choosing the Smoothing Chahine Iteration Algorithm as the main method of particle size inversion after comparing the complexity as well as advantages and disadvantages of several non-independent mode algorithms and independent mode algorithms. The scattering coefficient of silica suspended particles with different particle size 2 ?m, 5 ?m and the 1:1 mixing ratio at different scattering angles and different wavelengths was measured according to the change of concentration. The result shows that the scattering coefficient has the highest resolution with change of concentration when the scattering angle is 15 degree and the wavelength range is 450.03~625.16 nm.(3) According to the experimental results, the thesis compares the relationship between scattering coefficient and wavelength of silica suspended particles with the sum of two particle sizes and the 1:1 mixing ratio at different concentrations. It is concluded that the same coefficient in the fitting equation is basically the same as the multiple at same concentration. The linear correlation is strong and the inversion error is small. The thesis compares the theoretical and experimental values of particle size distribution of silica suspended particles, and it can be determined that the real time inversion accuracy is high with suitable wavelength range (450.03 nm, 475.03 nm, 500.01 nm).