Wet Sample Dilution

Wet sample dilution

Wet process streams often contain particle concentrations that are far too high for direct laser diffraction measurement. Without proper dilution, excessive optical attenuation and multiple scattering effects can make accurate PSD analysis impossible. Sample dilution is therefore one of the most important parts of any online wet particle sizing system. The objective is to reduce the concentration to an optimal measurement range while still preserving the true particle size distribution of the original process stream.

The dilution stage must achieve a careful balance. If the sample concentration remains too high, the laser beam becomes excessively attenuated and detector signals become distorted due to multiple scattering. If the sample is over-diluted, the scattering signal becomes too weak and noisy. Xoptix wet systems are specifically designed to maintain the optimal loading conditions required for stable and reproducible online PSD measurement.

Unlike laboratory systems where dilution is performed manually by an operator, industrial online systems must dilute the sample continuously and automatically under changing process conditions. Flowrate, solids concentration, pressure, and slurry properties may vary significantly during operation. Xoptix dilution systems are therefore engineered for fully automatic operation with stable dilution performance over long periods of continuous industrial use.

The overall methodology of wet online PSD measurement consists of four key stages: sample extraction, sample dilution, PSD measurement, and sample recycle or disposal. The dilution stage acts as the critical link between process sampling and optical measurement, ensuring that the slurry entering the wet flow cell is always within the correct concentration range for reliable laser diffraction analysis.

Xoptix offers multiple dilution technologies depending on the process requirements and slurry characteristics. One solution is the four-way valve sampling system, where the slurry sample is extracted from the process line using a peristaltic pump or sampling valve and diluted inside a dedicated dilution tank before entering the wet measurement cell.

The four-way valve dilution system can include multiple supporting components such as stirrers, ultrasonic probes, level sensors, pinch valves, and ball valves. Stirrers help maintain homogeneous suspension of particles, while optional ultrasonic probes can assist in dispersing agglomerates within the slurry. These additional features help ensure stable and representative PSD measurement even for difficult materials.

A second and more advanced approach is the Variable Stage Dilution System (VSDS). In this system, the sample enters a dedicated multi-stage dilution device where precise dilution ratios can be achieved automatically using multiple parallel dilution channels. This allows very flexible and highly controlled concentration adjustment for challenging wet process applications.

The VSDS technology allows several selectable dilution stages, enabling the system to handle wide variations in slurry concentration while maintaining stable optical loading conditions inside the wet flow cell. Different dilution ratios can be selected depending on the process conditions, allowing the analyser to remain operational even when the incoming process stream changes significantly during plant operation.

Because many industrial slurry systems operate under elevated pressures, Xoptix dilution solutions may also include pressure reduction vessels and carefully controlled hydraulic layouts. These components ensure safe and stable sample handling while protecting the measurement system from excessive process pressure or unstable hydraulic conditions.

Xoptix's expertise in wet sample handling is supported by proprietary technology developed specifically for industrial online particle size measurement. The company holds patents in the field of sample dilution systems, covering innovative methods for achieving stable, representative, and repeatable dilution of concentrated process slurries. These patented technologies form the foundation of Xoptix dilution solutions.

After dilution and measurement, the sample can either be returned back to the process or discharged to waste depending on the application requirements. In minerals processing or other large-scale slurry operations, returning the sample to the process minimizes material loss. In applications where contamination control or hygiene is critical, the measured sample can instead be safely disposed of after analysis.

An important design target in Xoptix wet systems is achieving approximately 10% sample loading inside the wet flow cell. This operating range typically provides sufficient scattering signal for accurate PSD measurement while avoiding excessive attenuation and multiple scattering errors. Maintaining this balance continuously under real industrial conditions is one of the key advantages of Xoptix’s dedicated dilution technologies.

The ability to design reliable online dilution systems requires combined expertise in slurry handling, hydraulic engineering, particle sizing, and industrial automation. Xoptix develops complete integrated wet PSD systems where sampling, dilution, measurement, and process integration are engineered together as one fully optimized solution rather than as separate individual components.