Tunnel Pasteurizer Product

Overview

A tunnel pasteurizer is a continuous conveyorized system that applies thermal treatment to filled bottles in a temperature-controlled tunnel. The design is straightforward: bottles move along a Bottle Conveyor through three thermal zones. The first applies hot water via the Hot Water Spray Zones to raise the product temperature to pasteurization levels (160–180°F). A holding zone maintains this temperature. The final zone cools bottles with Recovery and Cooling Spray to prevent package stress. A Hot Water Tank and Heat Exchanger supply and maintain hot water, while a Control Panel regulates all sequences.

How it works

Empty bottles arrive filled with product. They are placed into Bottle Carriers on the Bottle Conveyor. The Drive Motor moves the chain at a preset speed: typically 1–2 meters per minute, giving each bottle 25–50 minutes of cumulative thermal treatment.

As bottles enter the first hot spray zone, the Spray Pump circulates water from the Hot Water Tank through the Spray Nozzles at the spray header. The water, maintained at 170–180°F by the Tank Heater (powered by steam from a boiler or electric resistance), sprays onto the bottles from multiple angles (top, bottom, and sides). The heat penetrates the glass and transfers into the product inside. The PLC monitors the actual temperature at each zone using the Zone Temperature Probe and adjusts the spray flow by opening or closing the Spray Solenoid Valve to maintain setpoint.

In the holding zone (typically the middle section of the tunnel), bottles remain at peak temperature for the required hold time (15–30 minutes, depending on product type and regulatory requirements). This sustained temperature is lethal to most pathogens and spoilage organisms.

As bottles reach the final cooling sections, the Cool Spray Solenoid opens, and cool water (50–60°F, drawn from municipal supply or a secondary tank) sprays onto the bottles via the Cool Spray Nozzles. This rapid thermal shock cools the bottles quickly, reducing stress on the glass and package. The cooling water is partially preheated by a Cool Water Recovery Loop heat exchanger that captures waste heat from the tunnel drainage—improving energy efficiency.

All drainage water collects in the Drainage Sump, which pumps it back to the main tank (hot side) or to waste, depending on quality and recovery efficiency target. The Agitator Paddle in the main tank continuously mixes the water, preventing thermal stratification (cold pockets at the bottom that would reduce heating effectiveness).

The Heat Exchanger is the core heating device. It transfers energy from steam (or hot water from an external boiler) to the pasteurization water. As the tank water loses heat to evaporation and spray, the PLC in the Control Panel opens the steam inlet, and the heat exchanger replenishes the tank temperature. Once setpoint is reached, a modulating steam trap or throttle valve reduces flow.

The HMI Touchscreen on the control panel allows operators to set:

• Tunnel speed: 0.5–2 m/min (longer residence time = stronger thermal effect, but lower throughput).
• Hot zone temperature: typically 170–180°F.
• Hold time duration: baked into speed and zone length.
• Cool zone temperature: typically 50–60°F.

The PLC monitors the Flow Meter and Pressure Transmitter to ensure spray nozzles are not clogged and pressure is stable. If flow or pressure drops below setpoint, the Alarm Horn sounds and the PLC logs the event for compliance records.

Key features

• Continuous operation: No batch holding; bottles move steadily through at the desired thermal profile.
• Scalability: Tunnel length and speed adjust throughput; larger bottles or slower speeds = longer dwell.
• Energy recovery: Cool-water preheating recovers 70–85% of thermal energy, significantly reducing steam/electric consumption.
• Regulatory compliance: Hold time and temperature are logged automatically, providing proof for regulatory bodies.
• Reduced glass stress: Gradual heating and cooling in hot and cool zones minimize thermal shock fractures.
• Sanitization: High-temperature spray inherently cleans the bottle exterior during pasteurization.