Development of a Real-Time,In-SituParticle Sizing Technique: Real-Time Light Transmission Spectroscopy (RTLTS)

Abstract

We developed an improved particle measurement spectroscopic technique, real-time laser transmission spectroscopy (RTLTS), to detect the number-weighted distribution of particles in real time. The measurement system used a deuterium-tungsten lamp for the light source and a spectrometer as the detector. The operating wavelength range was 300-810 nm. To obtain a physically reasonable number concentration from the experimental results, a sequential regularization method was used during the calculations. To verify the feasibility and reliability of RTLTS, the number-weighted distribution of polystyrene particle suspensions was determined over diameters ranging from 0.005 to 2.000 μm in 0.005-μm increments. The measured concentration error was 0.67-32.67%. A mean diameter of the smallest particle we had detected was 0.09 μm, with a 16% oversizing. The measurable concentration range was ∼10 8 #/cc to ∼10 11 #/cc for 0.895-μm-diameter particles. The measurable concentration range could be adjusted simply by changing the system configuration. This technique is available for both waterborne and airborne particles.

Real-time light transmission spectroscopy (RTLTS): A real-time and in situ particle size distribution measurement for fractal-like diesel exhaust particles

“…In accordance with previous research (Yoon et al, 2013), Mieplot 4.3 software by Laven (2011) was used for the extinction cross-section matrix (σ) simulation. The refractive index is a wavelength-dependent property, and so wavelengthdependent refractive indices should be used.…”

“…Sequential regularization for solving ill-posed problems was conducted in a similar manner as that used in previous research (Yoon et al, 2013). Regularization leads to the regularized solution n R by combining the residual norm and the side constraint.…”

“…As has been discussed previously (Yoon et al, 2013), the diameter resolution of the measurement was altered to a logarithmic scale. The measurement target diameter range was 10-550 nm, which was divided into 100log-scaled steps.…”

“…The light extinction phenomenon per particle is dependent on the wavelength of light and the particle diameter and concentration. The light extinction coefficient for a polydispersed particle at a specific wavelength λ i can be expressed as follows (Li et al, 2010;Yoon et al, 2013):…”

“…To address these issues, we developed a real-time particle-size distribution measurement technique based on the realtime light-transmission spectroscopy (RTLTS) method of Yoon et al (2013). The theoretical background of this technique uses the light extinction spectrum, in which light transmission through a particle suspension is measured as a function of wavelength for particle sizing and density measurements.…”