Pneumatic conveying design: the material throughput (capacity) of a pneumatic conveying system primarily depends on which of the following?

Introduction:
Pneumatic conveying is widely used for powders and granules in chemical, food, and cement plants. Capacity prediction requires understanding how material properties, air conditions, and pipeline geometry interact to determine solids loading and pressure drop.

Given Data / Assumptions:

• Steady dilute or dense phase conveying.
• Air as the conveying gas.
• Fixed blower/compressor performance curve and pipeline route.

Concept / Approach:
Throughput depends on both the driving force (air pressure/vacuum) and the resistances (friction in bends and straight runs) as well as the material’s conveyability (bulk density, particle size, cohesiveness). Larger diameters reduce gas velocity for a given volumetric flow, affecting saltation and pickup conditions. Bulk density alters solids loading ratio at the same volumetric feed.

Step-by-Step Solution:
Relate blower capacity and line resistance to available pressure drop.Note that diameter and routing (bends, vertical lifts) change frictional losses.Incorporate material factors (bulk density) into solids loading and pickup velocity.Therefore, capacity depends on all listed factors.

Verification / Alternative check:
Empirical design charts (e.g., Zenz–Othmer) and vendor software require inputs for material properties, air conditions, and pipeline geometry, confirming multi-factor dependence.

Why Other Options Are Wrong:

• Any single-factor choice ignores the coupled nature of pressure drop and minimum conveying velocity.
• “None” contradicts well-established design practice.

Common Pitfalls:
Oversizing air velocity (causing attrition) or undersizing (leading to plugging); forgetting that elbows drastically increase pressure drop.

Final Answer:
All (a), (b) and (c)