Optimisation of grinding in Danish pellet mill industry

The primary issue with the current project was to eliminate the difference in capacity and specific consumption when grinding with hammer mills. It is a well known problem in the Danish pet food, seed and fertilizing industry that the capacity varies, depending on the direction and rotation of the grinding mill. Furthermore, the project included an analysis and chart overview on the energy balance for the complete grinding process. Lastly, a solution to the problem of differences in consumption was constructed where a solution of double milling was suggested. The first grind would be performed on a smaller mill before entering the hammer mill. The energy balance showed that 74 percent of the electrical energy consumption used in the grinding process was turned into heat in the flour. The remaining 26% are lost in the electrical motor and the hammer mill itself. It was not possible to decide upon how much energy was needed to finely sort the corn for the flour according to the desired structure. However, tests with roller mills have shown that the heat loss in the flour can be halved. In practice, smaller quantities of rolled corn must be used when producing pellets. The structure of the flour from a roller mill is not the same as the structure of the flour from a hammer mill. Therefore potential savings on the energy balance can not be indicated. The project developed and produced a new feeding device for the hammer mill. Comparable tests on the operation of the hammer mill have been made with both the original and the new feeding device.