PRESSING-DRILL METHOD – A REPRESENTATIVE METHOD FOR TAKING ANALYSIS SAMPLES FROM RECYCLED MATERIALS

摘要

At Nordhausen University of Applied Sciences a new method – the ‘pressing-drill method’ – has been developed for sampling recycled materials. Proper sampling and analytical evaluation of waste as heterogeneous material are a concern for both producers and recyclers. To ensure economic and environmentally-friendly recycling of these materials, a very precise knowledge of their composition is necessary. With the conventional methods using dividing crosses and sample splitters, great deviations between the tested random samples could be observed. The development of the ‘pressing-drill method’ is based on the idea of the compression of the sample material into a geometrically defined shape (cylinder) and subsequent probability-proportional sampling by drilling samples directly out of the pressed body. The materials are compressed to transform them from a loose heap into a form enabling random selection of samples. Owing to the pressure applied during pressing, the material system has a compact material structure so that segregation caused by different material densities, wide particle size distribution and differences in geometry is avoided. Fluid contained in the sample is pressed trough small outlets in the mould. For a continuous and systematic application of the pressing-drill method, the Mini-Press-Cylinder supplements the geometry of the other cylinders for sampling. The Mini-P is designed for taking drilled material from a quantity of around 5 g for preparation of the analysis sample. The pressing-drill method is suitable for representative sampling of heterogeneous material systems with low bulk density, consisting of particles <40 mm in size. It has been proven that errors can be substantially reduced compared with the standard methods (dividing cross, sample splitters) used in common practice. The calorific or heating value and the total chlorine content were defined as the main parameters. The first results of tests on model mixes and real recycled material mixes confirm this approach.