This bachelor project is written as the final step of the education as “Bachelor of Technology Management and Marine Engineering”. The project is written by Torben Harregaard Laursen, F15627 and Per Kristiansen, F15127 and is based on an internship at Aarhus University, Center for Biorefinery in Foulum, Denmark.
Center for Biorefinery is a scientist research platform where there already have been experimented with a pilot plant for extracting green protein from grass. During the internship, the focus has been on project planning of a new demo scale plant. The pilot plant can process an amount of up to 1 ton/h where the demo scale plant is planned to initially handle up to 10 ton/h and eventually up to 20 ton/h.
The demo scale plant is planned to be in service for processing grass from June 2019. The reason for building a demo scale plant is to get experience with a plant in a size that is reasonable for building all over Denmark.
The problem definition for this project is to determine the energy consumption for the heat treatment in the demo scale plant, and to asses means for optimizing this part of the process. Since it is a scientific plant, there has not been a lot of focus on the energy efficiency when designing the plant. Both due to a shortage in founding, but also due to the wish for a very flexible plant.
In the report there is a description on the plant layout, the streams of the materials and the heat exchange systems. There is special focus on using the waste heat from the brown juice to heat the green juice, as this is one of the big potentials for energy sawing. Another subject is cooling the green protein, this subject is chosen because of its special difficulties with cooling caused by the high viscosity.
During the writing off this report, there has been used different methods. The leader of The Biorefinery has been interviewed, there has been mail corresponded with the former leader and technicians from relevant companies. Experiments have been performed on the pilot plant, where data have been used to assess the performance of heat exchanging with biomass, and the validity of the known methods for calculating heat transferring, when used on biomass.
The pilot plant had a lot of issues with the heat exchanging of the green juice/ brown juice. During the internship it was discovered that the main problem was to little flow through the heat exchanger. This problem was solved by mounting a shunt system to get a higher flow, and data were collected and processed for different flow settings to determine the impact on heat transfer. It is revealed that the current heat exchangers are big enough to be used in the demo plant, although a larger heat exchanger could have the potential of reducing the energy consumption to less than half.
On the issue with cooling the green protein, there is no earlier experience from the pilot plant. There was bought a scraper heat exchanger for experimenting. Experiments made it clear that the heat exchanger is too small for the demo plant, but it is revealed that a scraper heat exchanger will be a reliable method to cool the green protein.
The conclusion is that there are good possibilities to make the plant more energy efficient.