Conveying of coarse crystalline materials can abrade bends, degrade through impact or settle when transport conditions change. Their conveying duty should be based on representative particle data and a route that reflects the installed geometry.
This feasibility approach is relevant to mineral salts, crystalline chemicals, granulated ingredients and other free-flowing products whose particle integrity or abrasion potential matters.
Confirm the Material Grade
The design basis should include particle-size distribution rather than mean size alone. Record particle density, bulk density, shape, moisture, hardness, friability, abrasiveness and fines content. Large angular crystals can respond very differently from rounded granules of similar size.
Product variability also matters. A screening fraction, supplier change or recycled fines can alter minimum transport behavior and filter loading. Representative test material should cover the credible production range rather than an ideal laboratory batch.
Establish the Defensible Flow Mode
Many coarse products with limited air retention are conveyed in dilute suspension, but this should be confirmed through testing or relevant production data. Increasing supply pressure does not automatically create dense phase. If the material cannot form stable low-velocity plugs or an aerated bed, lowering airflow may simply cause deposition and blockage.
The project should identify a repeatable stable boundary by reducing airflow in controlled steps during a representative trial. Pressure fluctuation, incomplete delivery and material retained in the line are important warning signs. The operating setpoint then remains above that boundary by a margin reflecting product and ambient variation.
Control the Velocity Consequences
The velocity needed to suspend coarse particles can create high impact energy at bends, diverter valves and receiver entries. A single-bore positive-pressure line also experiences gas expansion downstream, so the highest actual velocity may occur near the discharge.
The route should be as direct as practical, and bend selection should balance pressure, wear and particle damage. A stepped-bore line may limit excessive downstream velocity if the post-step sections remain stable and clear reliably. Any improvement should be demonstrated rather than assumed.
Match the Feeder and Pipeline
Coarse crystals can bridge over small openings, chip in tight clearances or damage rotary-valve components. The feeder must deliver the required mass without unacceptable crushing or leakage. Nominal displacement should be corrected for real pocket filling, bulk density and pressure conditions.
Oversized particles, agglomerates or foreign objects should be addressed upstream because they can jam the feeder or create a pipeline obstruction. Screens, magnets or other protective measures depend on the material and process hazard assessment.
Build the Complete Air and Pressure Duty
Airflow is set by the material-specific transport requirement and pipeline bore. Total differential pressure includes inlet filter and silencer, air piping, feeder leakage, material acceleration, straight pipe, vertical lift, bends, valves, receiver and the clean-to-fouled filter range.
Normal and maximum credible points should be evaluated at consistent blower-inlet conditions. High volume at modest pressure may fit a roots blower well, while a route with excessive pressure or velocity may require bore, route or material-rate changes before equipment selection.
Verify Product Quality and Equipment Limits
Trials should compare particle-size distribution and fines before and after conveying when commercial quality can be affected. Inspect high-impact components for wear and monitor receiver dust load. The selected airflow should move product reliably without an unnecessary velocity surplus.
For coarse crystalline solids, the practical selection window comes from representative transport evidence and acceptable wear. State the material grade, particle distribution and receiver conditions alongside the final flow and pressure point.
Glossary
Coarse crystal: Relatively large, solid particle with an ordered structure and potentially brittle edges.
Dilute suspension: Conveying state in which particles are substantially supported and transported by the gas stream.
Fines fraction: Proportion of material below a defined small-particle size limit.
Impact-sensitive product: Bulk solid whose commercial or process quality can be damaged by collision energy.
Particle inertia: Resistance of a particle to changes in velocity or direction.
Screening fraction: Particle-size range produced or retained by a classification screen.
Suspension boundary: Lowest demonstrated gas condition that maintains acceptable dilute-phase movement.