Drying & Stabilisation Line — Equipment Specification
1. Process Objective
Reduce moisture content of flaxseed (from harvest-wet 14–18 % down to ≤ 8 % storage moisture) while maintaining seed viability (germination ≥ 85 % for whole seed) and preventing oxidative rancidity. The line also stabilises partially-processed fractions (press cake, gum cake) prior to storage or further processing. Four independent drying technologies provide operational flexibility and allow matching energy efficiency to product state. This station is designated CCP-4 (Critical Control Point — Moisture & Temperature Control).
2. Equipment Configuration & Flow Diagram
Wet Flaxseed / Intermediate Product
│
├───→ [ Fluidised Bed Dryer ] ───→ (Whole seed, 60–90 °C, 3 MT/hr)
│ │
│ ▼
├───→ [ Microwave Dryer ] ───→ (Germination-sensitive seed, 40–60 °C, 1 MT/hr)
│ │
│ ▼
├───→ [ Steam Tube Rotary Dryer ] ───→ (Press cake / bulk, 70–100 °C, 2 MT/hr)
│ │
│ ▼
└───→ [ Infrared Dryer ] ───→ (Gum cake / thin-layer, 50–80 °C, 0.5 MT/hr)
│
▼
[ Tempering / Cooling Bins ]
│
▼
Dry Product (≤ 8 % moisture)
│
▼
[ Storage Silos / Bag-off ]
3. Equipment Specifications
3.1 Fluidised Bed Dryer (FBD)
| Parameter |
Value |
| Type |
Continuous vibratory fluidised bed |
| Rated capacity |
3 MT/hr (whole flaxseed) |
| Inlet moisture |
≤ 18 % (w/w) |
| Outlet moisture |
≤ 8 % (target 7.0–7.5 %) |
| Inlet air temperature |
60 – 90 °C (adjustable) |
| Outlet air temperature |
40 – 55 °C |
| Air volume |
15 000 – 20 000 m³/hr |
| Bed area |
2.4 m × 0.8 m (1.92 m²) |
| Bed depth |
50 – 150 mm |
| Plenum pressure |
1.5 – 3.0 kPa |
| Vibration amplitude |
2 – 5 mm (variable) |
| Vibration frequency |
50 Hz (eccentric drive) |
| Material |
SS304 (contact), carbon steel (plenum) |
| Heat source |
Steam-to-air heat exchanger (3 bar(g)) |
| Dust control |
Cyclone + bag filter (99.5 % capture) |
| Exhaust fan |
15 kW, backward-curved |
| Residence time |
8 – 15 min |
3.2 Microwave Dryer
| Parameter |
Value |
| Type |
Continuous belt, multi-mode MW cavity |
| Rated capacity |
1 MT/hr (whole flaxseed) |
| Inlet moisture |
≤ 16 % (w/w) |
| Outlet moisture |
≤ 8 % (target 7.0–7.5 %) |
| Product temperature |
40 – 60 °C (gentle drying) |
| MW frequency |
915 MHz ± 25 MHz |
| Total MW power |
75 kW (6 × 12.5 kW magnetrons) |
| Applicator cavity |
SS304, 4 m × 1.2 m belt |
| Belt width |
1 000 mm |
| Belt speed |
0.5 – 5 m/min (VFD) |
| Penetration depth |
30 – 60 mm (flaxseed bed) |
| Energy consumption |
≤ 0.35 kWh / kg H₂O removed |
| Control |
IR pyrometer feedback → MW power modulation |
| Safety |
Interlock doors, microwave leakage < 5 mW/cm² |
| Cooling |
Magnetron cooling: deionised water loop, 60 L/min |
| Material |
SS304 chamber, PTFE belt |
| Dust control |
Integrated HEPA exhaust |
3.3 Steam Tube Rotary Dryer
| Parameter |
Value |
| Type |
Indirect rotary, steam tube bundle |
| Rated capacity |
2 MT/hr (press cake / bulk) |
| Inlet moisture |
≤ 22 % (w/w) |
| Outlet moisture |
≤ 8 % (target 6–8 %) |
| Product temperature |
70 – 100 °C |
| Steam tube pressure |
4 bar(g) saturated (144 °C) |
| Tube bundle area |
50 m² (SS304 tubes) |
| Shell diameter |
1 800 mm |
| Shell length |
8 000 mm |
| Rotary speed |
4 – 12 rpm (VFD) |
| Fill volume |
15 – 20 % of shell |
| Residence time |
20 – 40 min |
| Drive motor |
22 kW, helical gearbox |
| Trunnion bearings |
Split roller, grease-lubricated |
| Sweep gas |
N₂ purge at 100 Nm³/hr (O₂ ≤ 3 %) |
| Material |
SS304 shell, SS304 tubes, carbon steel jacket |
| Dust control |
Gravity settling + bag filter |
| Specific steam consumption |
1.3 – 1.5 kg steam / kg H₂O removed |
3.4 Infrared Dryer (IR)
| Parameter |
Value |
| Type |
Medium-wave IR + hot air (hybrid) |
| Rated capacity |
0.5 MT/hr (gum cake, thin layer) |
| Inlet moisture |
≤ 60 % (w/w, gum cake / thin-layer) |
| Outlet moisture |
≤ 8 % |
| Product temperature |
50 – 80 °C |
| IR emitter type |
Medium-wave carbon-fibre (2–4 µm) |
| Total installed power |
45 kW (9 × 5 kW emitters) |
| Emitter surface temp |
650 – 850 °C |
| Conveyor belt |
PTFE-coated mesh, 800 mm wide |
| Belt speed |
0.2 – 3 m/min |
| Product layer |
5 – 20 mm |
| Hot air supplement |
50 – 70 °C, 2 000 m³/hr |
| Energy consumption |
≤ 1.1 kWh / kg H₂O removed |
| Control |
Zoned PID (3 zones); pyrometer per zone |
| Material |
SS304 chamber + reflectors |
| Exhaust |
Integrated condensing scrubber (odour control) |
4. Technology Comparison Table
| Criterion |
Fluidised Bed |
Microwave |
Steam Tube Rotary |
IR Hybrid |
| Primary product |
Whole seed |
Germination-sensitive |
Press cake / bulk |
Gum cake / thin layer |
| Throughput (MT/hr) |
3.0 |
1.0 |
2.0 |
0.5 |
| Product temp. range |
55 – 75 °C |
40 – 60 °C |
70 – 100 °C |
50 – 80 °C |
| Best moisture reduction |
10 % pt |
8 % pt |
14 % pt |
52 % pt (gum cake) |
| Energy efficiency |
★★★★ (low λ) |
★★★★ (volumetric) |
★★★★ (indirect) |
★★★ (thin layer only) |
| Gentleness / viability |
★★★ |
★★★★★ (lowest T) |
★★ |
★★★ |
| Capital cost |
Medium |
High |
Medium-high |
Low |
| Operating cost |
Low |
Medium (electricity) |
Low (steam) |
Medium-high (electric) |
| Footprint (m²) |
12 |
18 |
30 |
8 |
| CIP / cleaning ease |
★★★★ |
★★★ |
★★ |
★★★★★ |
| Dust explosion risk |
Moderate |
Low (low T) |
Low (N₂ sweep) |
Low |
| ATEX zone (if any) |
Zone 22 (dust) |
None if T < 60 °C |
Zone 22 (dust) |
Zone 22 (dust) |
| Metric |
Target |
Monitoring Method |
| Final moisture (all products) |
≤ 8 % (w/w) |
Online NIR + oven check (hourly) |
| Germination rate (whole seed) |
≥ 85 % (Microwave path) |
Germination test (daily) |
| Peroxide value (seed oil) |
≤ 2.0 meq O₂/kg |
AOCS Cd 8-53 (weekly) |
| FBD outlet temp (CCP-4 limit) |
≤ 90 °C |
In-line RTD |
| MW product temp (CCP-4 limit) |
≤ 60 °C |
IR pyrometer |
| Rotary product temp (CCP-4) |
≤ 100 °C |
Contact RTD on discharge |
| IR product temp (CCP-4) |
≤ 80 °C |
Pyrometer per zone |
| Drying uniformity (all) |
ΔMC ≤ 1.5 % across batch |
Grab samples (5 per lot) |
| Volumetric throughput accuracy |
± 5 % |
Load cell / belt scale |
| O₂ in rotary sweep gas |
≤ 3 % |
In-line O₂ analyser |
6. HACCP — CCP-4 Integration
| CCP |
Hazard |
Critical Limit |
Monitoring |
Corrective Action |
| 4a |
Product temp. exceeded → oxidative rancidity, nutrient loss |
Per dryer limits (see §5) |
Continuous temp. logging |
Reduce heat input / increase feed rate; inspect product quality |
| 4b |
Moisture > 8 % → mould growth during storage |
Outlet MC ≤ 8 % (w/w) |
Online NIR (every 2 min) |
Re-circulate batch; increase residence time or temp. |
| 4c |
O₂ ingress in rotary dryer → fire / auto-oxidation |
Sweep gas O₂ ≤ 3 % |
O₂ analyser (continuous) |
Increase N₂ purge; check seals; emergency stop |
| 4d |
Dust explosion (FBD, rotary) |
Housekeeping; ATEX-rated equipment |
Visual + pressure sensors |
Automatic deluge; shut down air; evacuate |
7. Maintenance Schedule
| Component |
Frequency |
Activity |
| FBD air distribution plate |
Weekly |
Inspect holes for blockage; clean with compressed air |
| FBD bag filter |
Monthly |
Pulse-jet cleaning check; replace bags annually |
| Microwave magnetrons |
2 000 hr |
Replace cathode if power < 85 % nominal |
| Microwave belt |
Monthly |
Clean PTFE surface; check tracking |
| Rotary dryer tube bundle |
Quarterly |
Ultrasonic thickness check; sweep for leaks |
| Rotary trunnion bearings |
500 hr |
Grease re-charge; check alignment |
| Rotary steam traps |
Monthly |
Verify condensate removal; rebuild if passing steam |
| IR emitters |
1 000 hr |
Replace carbon-fibre elements (9×) |
| IR conveyor mesh |
200 hr |
Clean with hot water; check for tears |
| All dust collection systems |
Monthly |
Inspect ductwork; clean cyclone; empty drums |
| N₂/O₂ analysers |
Quarterly |
Calibrate with certified gas |
8. Spare Parts Inventory (Minimum Stock)
| Part |
Qty |
Supplier Reference |
| FBD air distribution plate |
1 |
FBD-192-ADP (OEM) |
| FBD bag filter elements (set) |
12 |
FBD-BAG-20 |
| Microwave magnetron (12.5 kW) |
2 |
MW-915-12.5 (OEM) |
| Rotary dryer steam trap |
3 |
RD-ST-25 (Spirax Sarco) |
| Rotary trunnion bearing |
1 |
RD-SRB-1800 |
| IR carbon-fibre emitter (5 kW) |
3 |
IR-CF-5K |
| IR pyrometer sensor |
2 |
IR-PYRO-MW |
| N₂ analyser sensor cell |
1 |
O2-SENSOR-ZR |
| Vibration isolator (FBD) |
4 |
FBD-VIB-MNT |
9. Utility Requirements
| Utility |
Connection |
Peak Demand |
| Electrical |
400 V, 3-phase, 50 Hz |
140 kVA (MW peak) |
| Steam |
4 bar(g) saturated |
1 200 kg/hr (rotary + FBD) |
| Natural gas |
n/a (all steam or electric) |
— |
| Cooling water |
30 °C supply, ΔT 10 °C |
5 m³/hr (MW magnetron cooling) |
| N₂ |
4 bar(g), 99.9 % |
150 Nm³/hr (rotary sweep) |
| Compressed air |
6 bar(g), oil-free |
20 Nm³/hr (FBD pulse-jet) |
| Drainage |
Standard |
2 m³/hr (condensate) |
10. Safety & Compliance
- ATEX Zone 22: FBD outlet, rotary dryer discharge, dust collection hoppers — combustible dust rated equipment.
- Microwave leakage: Annual survey per IEC 62311 — limit 5 mW/cm² at 5 cm.
- Rotary dryer N₂ purge: Interlocked — if O₂ > 3 % or N₂ flow < 50 Nm³/hr, heat shuts down automatically.
- Hot surface guarding: All dryers have insulated cladding + hazard warning labels (> 60 °C surfaces guarded).
- LOTO: Lockout for rotary dryer tube bundle access, microwave magnetron maintenance, FBD bed access.
- PPE: Heat-resistant gloves for product sampling; hearing protection in FBD/rotary area (> 85 dB(A)).
Document Owner: Process Engineering Manager
Revision: 1.0
Date: 2026-07-20
CCP-4 Validated: Production Manager / HACCP Team