APPLICATION OF THE ELUSIEVE PROCESS TO THE CLASSIFICATION OF MEAT AND BONE MEAL PARTICLES

Meat and bone meal (MBM), a product of the rendering industry, comprises a mixture of two particle types. The utility and value of MBM would increase if the two particle types could be separated economically. Past efforts at classification of MBM particles have achieved limited success. In the present research, a classification method originally developed for distiller's dried grains is applied with modifications to MBM In this process, known in the literature as elusieving, a mixture of particles is screened into multiple fractions, and each fraction is processed separately using airstream classification units. In the present research, the MBM was treated with an anti-caking agent prior to processing. The screen opening sizes were chosen to isolate the smallest particles, which are very high in ash, and divide the remaining material into thirds. Each fraction was run through an air classification unit at multiple airspeeds, and the proximate compositions of the materials collected from the units were determined These results were used to determine the optimal separation of particle types that would be achieved if each fraction were classified at the ideal airspeed. Unprocessed MBM with an ash content of 26.1%, dry basis, was fractionated into one stream with ash content reduced to 19.8% (42.0% of total mass) and another with ash content increased to 34.4% (58.0% of original mass). A concept named ash shift is defined and used to compare the separations produced by different methods. The ash shift results from elusieve processing (25.7%) are shown to be superior to the ash shift achievable through screening (7.4%) or airstream classification (17.7%) alone. The appropriateness and limitations of the elusieve process for classifying MBM particles are discussed.