Summary

Danisco in Zundert, the Netherlands, freezes fresh vegetables. The process of freezing leafy vegetables includes blanching, to stop the enzyme reactions in the product. Dropping the hot vegetables (95°C) into a tub filled with ice water (4°C) stops the blanching process. The final temperature of the product and liquid is around 22°C. The effluent (35 m³ per hour) is reused for washing fresh vegetables and the cooled product is then frozen in a freezing tunnel.
The cooling process has been redesigned, which saves energy for freezing and production of ice water. The final product temperature is lower (4°C) and the cooling water temperature is higher (53°C), which makes heat recovery feasible. The amount of ice water has been reduced by 67%, reducing the cost of ground water and the costs of discharging the effluent into the sewage treatment system.
The transport system makes it possible to change the single cooling temperature phase into multiple (more effective) cooling stages.
The total project costs amount to € 233,000, with energy savings (520,000 kWh and 185,000 m³ of natural gas) of € 65,000 per year. Additional savings are made on ground water reduction and effluent treatment, totalling € 28,000 per year. The payback period is approximately 2.5 years.
Similar applications can be found in the vegetable and fruit processing industries.