1360 m³ Fireproof Tobacco Leaf Cold Storage of Jiangxi Tobacco Research Institute

1. High-Fire-Rating Thermal Insulation Enclosure System

Panels: All 150 mm thick Class B1 polyurethane double-sided color steel sandwich panels are adopted. The core material has an oxygen index of ≥30% with Class B1 flame retardant combustion performance and fire integrity exceeding 45 minutes, complying with the separation requirements for single-layer cold storage firewalls specified in GB 50072-2010.

Air Tightness and Cold Bridge Breakage: Panels are joined with eccentric hook locks. All vertical and horizontal inner joints are filled with food-grade neutral silicone sealant to eliminate condensation caused by cold bridges. The cold storage door is fitted with three heating wires for anti-freeze door frames to avoid ice formation at the opening section.

Floor Insulation: Two staggered layers of 100 mm Class B1 extruded polystyrene (XPS) boards are laid, covered with 6 mm patterned aluminum plates. The floor bears forklift loads while providing bottom thermal insulation.

2. Dual-Loop Redundant Refrigeration System by GEA Germany

To guarantee absolute safety of research samples, GEA Germany semi-hermetic piston air-cooled condensing units with one operational and one standby unit are selected. Detailed configurations are as follows:

Temperature Difference Suppression & Moisture Loss Prevention: A 20% overcapacity margin is reserved for air cooler selection. The evaporation temperature is set at -4°C, significantly higher than the conventional -8°C. The air supply and return temperature difference is controlled within 2.5 K, maintaining relative humidity of 60%–65% RH inside the warehouse. Without additional humidifiers, the monthly weight loss rate of tobacco leaves is kept below 0.2%.

3. Intelligent Precision Temperature Control & Data Traceability

Control Core: Siemens S7-1200 PLC paired with a 7-inch touch screen, integrated with 4 four-wire Pt100 platinum resistance sensors with metrological accuracy of ±0.1°C, installed at the air return outlet, air supply outlet, warehouse center and top hot zone.

Temperature Control Strategy: The sensor at the warehouse center serves as the main control point with built-in PID auto-tuning algorithm. The system enforces limits on compressor startup intervals and defrost trigger conditions. Actual steady-state temperature fluctuation ≤±0.3°C, and temperature rise during defrost is less than 0.8°C.

Remote Management & Alarms: The system connects to the institute’s BMS via Ethernet for real-time operating condition viewing on mobile devices. A three-tier alarm system is activated for abnormal temperature rise: on-site audible & visual alerts, SMS notification and mobile App push, with a 48-hour data black box backup function.

4. Fire Protection & Food-Grade Sanitary Structure

Integrated Fire Safety: Arc Fault Detection Devices (AFDD) are installed on power supply circuits of air coolers. Explosion-proof LED lights are used for warehouse lighting with fully sealed junction boxes. Combined smoke and heat detectors are mounted under inner ceiling panels; signals are directly transmitted to the building fire control room and interlocked to shut down the refrigeration system.

Food-Grade Contact Surface Control: The inner wall is lined with 0.8 mm thick 304-2B stainless steel, and patterned aluminum floor plates are integrally welded. All three internal corners are finished with food-grade epoxy putty into R80 circular arcs to eliminate dust accumulation dead zones. Test reports complying with FDA standards are provided for all sealants and cable sheaths, meeting clean background requirements for tobacco heavy metal and nitrosamine analytical experiments.

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