HTST pasteurization (72–75 ℃ / 15 s) is the core process of fresh-milk production. This project supplied SAMIT sanitary-grade three-stage plate heat exchangers for a 200 t/d fresh-milk line of a North China dairy group, paired with a fully automatic CIP (Clean-in-Place) system.
1. Project Background
Customer
A well-known North China dairy group; newly built 200 t/d fresh pasteurized-milk line, required to meet EU hygiene standards.
Process Requirements
Raw milk 4 ℃ → preheat 65 ℃ → pasteurize 75 ℃ × 15 s → cool 4 ℃ → aseptic filling.
Key Constraints
- Ra ≤ 0.4 μm, dead-leg-free design
- FDA / 3-A / cGMP certification
- Daily automatic CIP
2. Technical Solution
The SAMIT S-series sanitary plate heat exchanger was adopted, arranged in three stages for heat recovery. Plates are 316L stainless steel, electropolished to Ra 0.38 μm; seals are FDA-compliant EPDM, and all end-plate ports use tri-clamp fittings.
| Stage | Function | Hot Side (Milk) | Cold Side | Area |
|---|---|---|---|---|
| Preheat (Heat Recovery) | Cold milk ↔ freshly pasteurized hot milk | 75 → 20 ℃ | 4 → 65 ℃ | 32 m² |
| Pasteurization | Heated by hot water to pasteurization temp. | 65 → 75 ℃ | 78 → 73 ℃ hot water | 6 m² |
| Cooling | Chilled water cools heat-recovered milk to 4 ℃ | 20 → 4 ℃ | 1.5 → 6 ℃ chilled water | 12 m² |
| Total | Three-stage heat-recovery rate 92% | 50 m² | ||
3. Process Flow
4. Implementation
- Equipment supply: 1 set of sanitary PHE + 1 CIP (Clean-in-Place) system + 1 automation control cabinet.
- Key quality: All wetted parts electropolished to Ra 0.38 μm; gaskets supplied with FDA 21 CFR 177.2600 compliance certificate; the whole unit passed 3-A certification.
- Installation & commissioning: 30-day on-site installation + 7-day performance test; pasteurization-stage temperature accuracy ±0.3 ℃.
Differentiated design: The corner-port gaskets of SAMIT sanitary PHEs feature a "leak-off groove"; should a gasket fail, the medium drains visibly through the groove, preventing cold/hot milk cross-mixing and batch contamination. This is a safety feature absent from ordinary industrial-grade PHEs.
5. Operating Results
Energy Saving
92% heat-recovery rate; saves 1800 t/year of steam, equivalent to 165 t of standard coal.
Product Quality
Pasteurization temperature accuracy ±0.3 ℃; total plate count ≤ 5000 CFU/mL, better than the national standard.
Hygiene Performance
Post-CIP microbial test 0 CFU/mL; plates still bright as new after a 3-year opening inspection.
6. Lessons Learned
The core of dairy pasteurization is the heat-recovery rate. Every 1-percentage-point increase saves 50,000–80,000 RMB/year in steam cost (at 200 t/d scale). The SAMIT three-stage design reaches 92% heat recovery — industry-leading. We advise dairies not to look only at first cost when selecting, but to focus on the 5-year total cost (including steam consumption and spare parts).