Definition
Dry wet particle size meter is an analytical instrument used to measure the particle size and distribution of particulate materials. It disperses the sample through different dispersion media (dry air or liquid) and measures the particle population using optical or physical principles. The instrument plays a fundamental role in product quality control and process optimization in many industrial and scientific research fields.
Principle
The core measurement principle of a dry wet particle size meter is usually based on laser diffraction or dynamic light scattering. Laser diffraction method According to the theory of Flanghefei diffraction or Mie scattering, the particles produce a diffraction pattern related to particle size under the irradiation of a laser beam, and the particle size distribution is calculated by detecting the light intensity of the angular distribution and using the inverse algorithm. The dynamic light scattering method estimates particle size by analyzing the fluctuations in light intensity caused by the Brownian motion of particles in liquids. Both methods rely on appropriate physical models and algorithms for data processing.
For laser diffraction, its basic relationship can be expressed as:
I(θ) ∝ ∫ N(D) · f(D,θ, m) dD
where I(θ) is the light intensity at the scattering angle θ, N(D) is the particle size distribution function, and f is the scattering function related to the particle size D and the relative refractive index m.
Measurement method
Dry measurement usually uses air as the dispersion medium, and the sample is fed into the dispersion chamber through the injector, and passes through the measurement area after being fully dispersed under the action of compressed air. This method is suitable for dry, fluid and non-agglomerating powder samples, and is relatively easy to operate, without subsequent cleaning, but it is necessary to pay attention to the possible effects of ambient humidity and static electricity.
Wet measurements disperse the sample in a suitable liquid medium (such as water or organic solvent) and pump it into the measurement cell after agitation or ultrasonication to ensure that the particles are evenly dispersed and suspended. The wet method can effectively disperse most agglomerated particles, which is suitable for samples that are easily soluble in air or require a stable liquid environment, but the compatibility of the sample with the medium and the subsequent cleaning steps need to be considered.
Influencing factors
The accuracy of the measurement results is influenced by several factors. Sample preparation is a key part: the dry method needs to control the injection speed and disperse air pressure to avoid fragmentation or agglomeration; The wet method requires the selection of appropriate dispersants, ultrasonic intensity and time. The accurate input of optical parameter settings, such as particle refractive index and absorption coefficient, has a significant impact on the laser diffraction results. Instrument calibration status, background measurement, and optical cleanliness are also the basis for ensuring data reliability. In addition, sample representativeness, concentration range, and measurement time need to be optimized according to specific instrument requirements.
Application:
Dry wet particle size meters are widely used in many industrial and scientific research fields. In the ceramics and building materials industry, it is used to monitor the particle size of raw material powders and finished products to ensure sintering performance and strength. In the field of coatings and inks, the particle size distribution affects the hiding power, leveling and stability of the product. In metal powder metallurgy, particle size is directly related to billet density and sintering shrinkage. In the chemical industry, the particle size of catalysts, fillers and polymer particles is an important parameter for process control. In addition, it can be used in environmental monitoring to analyze the particle size distribution of atmospheric dust or water treatment flocs.
Selection
The selection of a dry wet particle size meter requires a comprehensive consideration of the measurement needs and sample characteristics. First, the routine measurement state should be clarified: for samples that are easily soluble in liquids, need to be stored dry, or are tested quickly in large quantities, the dry system may be more suitable; Wet systems tend to be advantageous for cases where agglomeration is easi, characterization is required in process liquids, or where sample volumes are limited. The measurement range and accuracy need to cover the particle size distribution of the target particles and confirm that the instrument complies with relevant industry standards (e.g., ISO 13320). Operational complexity, maintenance requirements, and the analytical capabilities of the data software are also considerations when selecting a model. It is recommended to evaluate the actual performance and suitability of the instrument through representative sample testing.