Friedrich-Alexander-University Erlangen-Nürnberg, Germany
Drying of pasta is a process with high cost of energy. In Europe, it is allowed to have a residual moisture content of 13% in dry pasta. Due to the inhomogeneous drying process, the industry dries the pasta down to 8% residual moisture. The inhomogeneous drying is visible all over the conveyor belt; the wet spots have a diameter of 10 cm.
The idea is to detect these spots with NIR measurement instrumentation to dry with local adaptive nozzles. First, it has to be known, which maximum air speed is possible, without flying pasta in the dryer. With these results, numerical simulations were done to investigate the main airflow through the pasta layer. Based on the first simulations, simulations were done to design the local adaptive nozzles.
To validate the numerical simulations a bench-scaled pasta dryer was build up. This dryer has near infrared (NIR) sensors and the designed nozzles. The main airflow, the humidity and the airflow through the nozzles can be controlled.
The experimental results confirm the numerical results; the airflow above the nozzles in the area of the pasta is 0.5 m/s higher than the main airflow. In this area, the drying is faster than in the rest of the dryer and parts with higher humidity can dry to the level of the pasta on the conveyor belt.
With NIR sensors, the humidity of the pasta can be measured and the nozzles can be regulated. This technology can reduce the inhomogeneous humidity on a conveyor belt. Less inhomogeneous humidity of the pasta reduces power which is needed to overdry the pasta.