Dry-Powder Laser Diffraction Particle Size Analyzer

What is the Dry-Powder Laser Diffraction Particle Size Analyzer?

A laser diffraction analyzer that disperses powders in a compressed-air stream without liquid. It suits free-flowing, solvent-sensitive or water-reactive materials and gives fast measurements in routine production control. It is best matched to particles from a few micrometres upward and to laboratories handling large sample volumes.

Overview

The dry variant feeds powder through a vibrating chute into a venturi disperser where compressed air at an adjustable pressure, typically 0.5 to 4 bar, breaks up loose agglomerates before the aerosol crosses the laser beam. Extraction by a vacuum unit prevents contamination of the laboratory. Because no solvent is involved, it suits water-soluble, hygroscopic or reactive powders and eliminates dispersant disposal. Dispersion pressure must be optimised by a pressure titration so that agglomerates are broken without attriting the primary particles. Sample mass is typically 1 to 50 g, larger than wet methods, which improves sampling representativeness for coarse powders. The lower size limit is commonly around 0.5 µm, and cohesive fine powders below 5 µm may disperse incompletely. Cleaning is fast, with brush and air purge between samples.

How does it work?

Laser diffraction analyzers pass a laser beam through a dispersed sample; particles scatter light at angles inversely related to their size, and a detector array records the angular intensity pattern. The Mie or Fraunhofer model converts this pattern into a volume-based size distribution. Dynamic light scattering instead measures intensity fluctuations caused by Brownian motion, and the Stokes–Einstein equation converts the diffusion coefficient into a hydrodynamic diameter. Dynamic image analysis captures particle silhouettes with a high-speed camera and reports size and shape descriptors directly. Sedimentation methods apply Stokes' law to settling velocity under gravity or centrifugal force. Key components include the light source, sample dispersion unit (wet or dry), detector array or correlator, and software with optical-property databases.

What are the key features?

• Venturi disperser with pressure adjustable from 0.5 to 4 bar
• Vibrating feeder with controlled feed rate and obscuration feedback
• Integrated vacuum extraction to capture the dispersed aerosol
• No liquid dispersant, removing solvent cost and disposal
• Pressure titration tool for method development
• Rapid cleaning between samples by air purge

What are the technical specifications?

A typical dry-powder laser diffraction particle size analyzer configuration offers measuring range of 0.5–3500 µm, measurement principle of Laser diffraction, dry aerosol, dispersion pressure of 0.5–4 bar (compressed air), air consumption of ≈ 20–60 L/min at 2 bar, sample quantity of 1–50 g and feed system of Vibrating chute with feedback. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Dry-Powder Laser Diffraction Particle Size Analyzer is used in lactose and inhalation powder control, cement, sand and mineral aggregates, metal and additive manufacturing powders, fertiliser and granulated chemicals and coffee, flour and food powders. Across the wider Particle Size Analyzers class, laboratories also deploy it for pharmaceutical powder and inhaler development, battery cathode and anode materials and ceramics and cement.

Which standards and certifications apply?

Relevant standards and methods include ISO 13320, USP <429>, ISO 13322-1, ISO 13322-2, ISO 22412, GB/T 19077 and Ph. Eur. 2.9.31. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Particle size results depend heavily on sampling and dispersion, so representative sub-sampling, a documented dispersion protocol and sonication or pressure settings must be validated for each material. Install the instrument on a vibration-free bench away from direct sunlight, and keep the optical bench clean; check background and alignment before each session. Verify performance periodically with certified reference materials such as polystyrene latex or glass beads, following ISO 13320 acceptance criteria. Replace dispersant and clean the cell to avoid carry-over. Enter refractive index and absorption values correctly, because they strongly influence Mie results. Regulated laboratories should perform IQ/OQ/PQ and use audit-trail-enabled software.

How do I select the right Dry-Powder Laser Diffraction Particle Size Analyzer?

Select the dry variant for free-flowing powders of a few micrometres to millimetres where solvents are undesirable, such as hygroscopic, water-reactive or large-volume production samples. Specify the expected D10–D90 range, powder cohesiveness, available compressed-air quality and whether vacuum extraction is acceptable. Fine cohesive powders below 5 µm are usually better measured with the wet variant.

How does it compare with other Particle Size Analyzers variants?

Start from the expected size range and sample state. Laser diffraction covers roughly 0.1 to 3500 µm and suits most powders and suspensions; dynamic light scattering is preferred below about 1 µm; dynamic image analysis is chosen when shape matters or when a few oversize particles must be detected; centrifugal sedimentation resolves narrow multimodal distributions of fine particles. Next decide between wet and dry dispersion: dry dispersion avoids solvents and suits free-flowing powders, while wet dispersion gives better deagglomeration of cohesive or fine materials. Check whether the method must follow ISO 13320 or USP <429>, and whether 21 CFR Part 11 audit trails are needed. Also consider sample volume, automation, cleaning time between samples and the availability of validated SOP templates.