what are the key components of a complete pulse protein dry fractionation processing plant

Dry fractionation is a fully water-free, chemical-free mechanical process for producing pulse protein concentrates (42–65% crude protein) from peas, faba beans, lentils, chickpeas. The full plant is split into 6 core functional sections: Raw Material Pre-Cleaning & Dehulling, Ultra-Fine Milling, Dynamic Air Classification (Primary + Multi-Stage Polishing), Optional Electrostatic Polishing, Powder Post-Processing, Central Air/Dust & Explosion Safety, PLC Automation & Online Analytics.

1. Raw Material Pre-Treatment & Dehulling Section (Mandatory Front-End)

Purpose: Remove hull fiber, stones, metal and impurities to raise baseline protein content and eliminate separation interference in downstream classification

Core Equipment & Components

1. Raw Silo & Feeding System
   Storage silos, level sensors, loss-in-weight variable screw feeders, pneumatic conveying lines for uniform, stable feed rate.
2. Cleaning Module
   • Vibrating grading sieve: Remove oversized pods, clods, broken foreign matter
   • Gravity destoner: Separate heavy sand/stones
   • Magnetic separator: Extract ferrous metal fragments to protect milling equipment
   • Color sorter (optional high-grade food line): Remove discolored, damaged pulses
3. Tempering Conditioning Unit
   Low-moisture steam/mist spray to adjust pulse moisture to 8–11% to embrittle hulls without softening cotyledons.
4. Dry Dehuller Core Machine
   Differential-speed corrugated cracking rollers to split seeds and detach seed coats.
5. Static Zig-Zag Air Classifier (Hull Separator)
   Fixed baffle inertial air separation to separate lightweight hull fiber (by-product) from dense dehulled cotyledons.
6. Recirculation Sieve Buffer Bin
   Recycle partially dehulled mixed seeds back to dehuller; store clean hull-free cotyledons before milling.

2. Ultra-Fine Milling Section (Cell Liberation Core)

Purpose: Mechanically rupture pulse cell walls to liberate discrete tiny protein bodies (1–3 μm) and intact starch granules (20–40 μm), generating flour with target D50 = 13–25 μm for optimal aerodynamic sorting
Two industrial milling options (large plants use standalone pin mills; small lines use integrated ACM mills):

A. Standalone Pin Mill System (2–10 t/h large-scale production standard)

• Variable-frequency pin rotor + ceramic coated stator pin discs (80–120 m/s tip speed)
• Water-cooled grinding chamber to control powder temperature <45°C and prevent protein thermal denaturation
• Closed negative-pressure air transport inlet/outlet
• Cold auxiliary airflow for de-agglomeration of sticky protein particles

B. ACM Air Classifying Mill (Integrated grinding + primary classification, <2 t/h small/lab lines)

Combines impact grinding + built-in dynamic classifier wheel in one unit, reduces equipment footprint.

Supporting Milling Auxiliaries

• Variable-speed metering feeder to stabilize mill loading
• Cyclone pre-collector for milled flour intermediate storage
• Anti-static, explosion-proof sealed conveying pipelines

3. Dynamic Air Classification Fractionation Section (Protein Enrichment Core)

Separates milled flour into protein-rich fine fraction and starch-rich coarse fraction by balancing rotor centrifugal force and air drag force. Split into primary bulk separation and optional secondary polishing stage for high-purity protein (>58%)

3.1 Primary Dynamic Air Classifier (Standard for All Plants)

1. Core dynamic classifier host
   • Adjustable-speed classifier wheel (rotor, 0–10,200 RPM): Defines cut-point (10–22 μm)
   • Dual independent discharge outlets: fine protein stream / coarse starch stream
   • Secondary trimming air circuit to wash starch micro-fines off wheel blades
2. Dual cyclone recovery collectors
   • Fine cyclone: Capture crude protein concentrate (45–53% protein)
   • Coarse cyclone: Collect intact starch granules (recycled back to pin mill for re-liberation)
3. Variable-frequency main centrifugal blower: Regulates system air velocity to tune cut-point
4. Closed-loop recirculation piping for mixed middling agglomerates (unseparated cell clusters) returned to pin mill

3.2 Secondary Polishing Dynamic Classifier (Premium High-Purity Upgrade)

Takes crude fine protein from primary stage and tightens cut-point to 10–16 μm to filter contaminating fragmented starch micro-fines:

• Independent high-speed classifier wheel, low airflow operation
• Secondary coarse reject stream (starch fines) recycled to primary classifier (avoids regrinding and extra starch fragmentation)
• Final output: 58–65% high-purity food-grade protein concentrate

4. Optional Tribo-Electrostatic Separation Module (Yield & Purity Booster)

Installed post two-stage air classification to solve the air classification limitation: inability to separate same-size protein and starch micro-fines

• Tribo-charging tube (Teflon lining): Creates differential electrostatic charge (protein = positive, starch = negative)
• High-voltage parallel-plate electrode separation chamber (3–9 kV DC)
• Dual collection hoppers: high-purity protein stream + starch waste stream
• Middling mixed agglomerate recycle line back to primary classification
  Benefit: Raises total protein recovery by 8–18% while lifting purity by 5–10%.

5. Powder Post-Processing & Packaging Section

Refine, stabilize and package finished protein concentrate and starch/fiber co-products

1. Powder Cooling Buffer Silos
   Water-jacketed cooling bins with slow agitation to eliminate heat, static agglomeration and bridging
2. Vibratory Fine Sifter
   Remove minor soft agglomerates to guarantee smooth, free-flowing protein powder
3. Independent Storage Silos
   • High-protein concentrate silo (optional nitrogen blanketing for anti-oxidation)
   • Starch co-product silo
   • Hull fiber by-product silo
4. Automatic Packaging Line
   Loss-in-weight filling machines for 25kg valve bags / bulk 1-ton jumbo bags
   Metal detector, weight check station, heat sealer, dust recovery hoods

6. Central Air Circulation, Dust Collection & Explosion Safety System (Plant-Wide Mandatory)

All processing stages run under full negative pressure to eliminate fugitive dust and meet food safety standards

1. Pulse Baghouse Dust Collectors
   Food-grade anti-static PTFE-laminated filter bags for mill, classifier, packaging stations
2. Circulating cold air exchange unit: Recover waste air, cool milling/classification chambers to protect protein functionality
3. Full Explosion Protection System (required for combustible organic dust)
   • Static grounding for all metal equipment and pipelines
   • Flame arrestors, isolation dampers on all recirculation ducts
   • Rupture vent panels + flameless venting devices
   • Spark detection & inert nitrogen extinguishing system (large industrial plants)
   • Over-temperature interlock safety shutdowns

7. PLC Automation, Control & Online Analytical Instruments

1. Central PLC HMI Control Cabinet
   Full linkage of all variable-speed drives: dehull rollers, pin mill rotor, classifier wheel speed, blower air velocity, feed rate. Real-time parameter trending, auto-tune, remote monitoring.
2. Online Real-Time Testing Sensors
   • Laser particle size analyzer: Continuous D50/D90 monitoring of milled flour
   • NIR near-infrared sensor: Instant crude protein measurement of fine concentrate, auto-adjusts classifier wheel speed
   • Moisture/temperature transmitters for raw pulses and finished powder
3. Auxiliary control components: Pneumatic discharge valves, level switches, frequency inverters, emergency stop interlocks

Full Integrated Process Flow Summary

Raw pulse storage → Pre-cleaning + tempering → Roller dehuller + static hull air separation → Dehulled cotyledon buffer silo → Pin mill ultra-fine grinding → Primary dynamic air classification (crude protein + starch recycle) → Optional secondary polishing classifier / electrostatic separation → Powder cooling + sieving → Finished product silos → Automatic packaging

Key Equipment Function Overview Table