Application Note

Vapor and liquid flow control for aseptic packages

One of our customers, a manufacturer of food packaging equipment, was looking for a solution to supply hydrogen peroxide in into their aseptic sterilization process of food packaging. As a solution, Bronkhorst supplied multiple vapor-generating systems consisting of liquid flow controllers, gas flow controllers and a temperature-controlled mixing and evaporation device

Food products are often sterilized as a final step in the process. In aseptic sterilization the foods have been sterilized outside the packaging. This can be done by steam sterilization. After that, the foods are placed in the aseptic packages that have been sterilized previously in a separate way. The last step is sealing the packages under sterile conditions.

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Flow control in aseptic process

For this application a compact liquid flow controller is needed to control a low flow of hydrogen peroxide solution (flows of ca. 1 kg/h), to inject into a formed packaging. PET bottles, cartons or pouches, and caps need to be sterilized separately. After the sterilization step, the remaining hydrogen peroxide will be removed by using air drying. 

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Important topics

  • High-performance decontamination
  • Low H2O2 concentration for low H2O2 consumption 
  • Stable gas, vapor and liquid flows with good process control

Vapor solution for aseptic packages

The solution consists of two Bronkhorst vapor-generating systems (CEM - Controlled Evaporation and Mixing systems) - one side for PET bottles, cartons or pouches and another side for caps. The hydrogen peroxide (35% H2O2 in water) is injected as a vapor for better concentration control. The vapor condenses at the inside surfaces of the packaging, where the H2O2 in the liquid phase performs its sterilizing action. In a subsequent drying step, the condensate is removed using hot air supplied by a gas mass flow controller, after which the dry and aseptically sterilized packaging is ready to be filled with liquid or cream.

The vapor-generating CEM systems each consist of a liquid mass flow controller (thermal LIQUI-FLOW or Coriolis-based mini CORI-FLOW), a EL-FLOW Select mass flow controller for air as a carrier gas (and for drying afterwards), and a temperature-controlled mixing and evaporation device. 
The hydrogen peroxide is dosed accurately in the range of 200 (for caps) to 2000 (for cartons and pouches) g/h of H2O2 solution, and the flow of drying air is typically around 100 l/min. The liquid, gas and temperature controllers communicate easily with PLC’s for an optimum integration in the customer’s systems. 

Flow meters used for aseptic packages

Due to its robust configuration with direct through-flow measurement, the thermal LIQUI-FLOW requires minor mounting precautions to be able to operate inside the customer’s systems. At this time, more than 100 vapor-generating solutions (CEM) have been installed worldwide on aseptic sterilization systems.

Alternative: Coriolis based liquid flow controllers

As an alternative, use of the mini CORI-FLOW flow controller has the advantage that - in addition to its medium-independent mass flow - the density of the dosed medium is measured. As hydrogen peroxide will eventually decompose into water and oxygen, the physical properties of the dosed H2O2 solution are not constant over time. Therefore, this device is able to monitor the concentration and, hence, the quality of the hydrogen peroxide dosing. 

Due to the fact that hydrogen peroxide is injected in a controlled way so that not too much will be supplied, the costs of this sterilizing agent are reduced. Using this solution, the aseptic sterilization process is well-monitored and traceable, contributing to the extension of the shelf-life of food products.

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Flow control for aseptic packages

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