Mars - Pet food industry

Mars aims to make all their production processes "sustainable in a generation" by eliminating fossil fuel energy and greenhouse gas emissions, minimizing impact on water quality and availability and mitigating the impacts of waste by 2040. For the pet food production more than 50 similar drying lines are currently using fossil fuel as energy carrier. In 2014, Mars made a significant step towards achieving carbon neutral operation by acquiring a massive 118 turbine wind farm that provides renewable electricity. High temperature heat pumps and MVR can use this renewable electricity to supply the necessary drying energy for the production, hereby substituting fossil fuel by 100%. The technology can be implemented and used in other processes, since steam is used in other operations as energy carrier. A further advantage of superheated steam drying is the possibility to reduce pollution, since the condensed steam can be treated in a conventional waste water treatment.

Process description:

An open loop heat pump will be integrated in a superheated steam dryer for pet food by Mars in Verden, Germany. Kibbles (raw material) from the extruder are fed into the drying chamber and transported through a superheated steam atmosphere by belts. The drying chamber is open at the bottom and steam pressure is, therefore, close to ambient pressure. The product is dried due to the evaporation of its moisture in the superheated steam atmosphere, which then adds vapor to the drying system. The superheated steam in the drying chamber is cooled down from around 150-160 °C (inlet) to 110 °C (outlet) during the drying process, but the superheated condition is sustained, i.e. there is no condensation in the system. The dryer is a prototype with a capacity of 500 kW. The heat pump demonstrator will fully substitute the initial natural gas heating system. For full-scale industrial application the system must be scaled up to a capacity of 1200 kW. The specific energy consumption of the current system is between 800 and 900 kWh per ton of removed water. It will be lowered substantially to 200 kWh/t by the open loop heat pump.

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