Cement, Energy and Environment

subsequent analysis, sample quantities of only a few grams are required which have to be ground to a size of 0.2- 1mm to ensure representativeness and facilitate the release of the properties to be determined. In addition to these requirements, the material properties must not be altered during the grinding process, i.e. there must be no contamination and the volatile components have to be preserved. Sampling Residual waste is a very heterogeneous mixture of solids. Unsorted, it may contain a variety of plastics, cellulose, ceramics and metals , singly or combined, with different breaking properties. On-site sampling methods, such as those specified for pourable bulk materials, can hardly be applied here in view of the composition of the substances involved. Automatic sampling tools, like chute or shovel samplers, do not fulfil their purpose in this case. That is why sampling from a waste heap or a waste transport consignment is largely a manual process. The laboratory sample must be prepared in such a way that its qualitative composition comes as close as possible to the total quantity to be evaluated. A labofaj~ry sample normally consists of a defined number of individual samples. The number and quantity of the individual samples to be taken depends on the total quantity of waste, its homogeneity and the maximum "grain size" contained. Already during on-site sampling, care should be taken to ensure that metallic parts are sorted out, because they represent a special problem for further mechanical processing, especially for the crushing devices involved. The removed metal parts are assessed separately. Pre-crushing The complete laboratory sample, consisting of individual samples, is mixed and subjected to an initial crushing process, as far as possible in air-dry condition. This is done in the SM 300 heavy-duty cutting mill , which is ideal for the pre– crushing of such heterogeneous mixtures with different breaking properties. With the cutting rotor's tangential cut and its high-powered drive, textile and leather parts, plastic caps and ductile metal cans are cut up just as effectively as abrasive electronic scrap and nonmetallic car-shredding parts. The cutting tools consist of hardened steel and hard metal (tungsten carbide). Even so, there are limits to this cutting mechanism, namely when steel and iron parts are involved. Therefore , the use of a magnetic separator should be considered before material is fed into the mill. The final fineness is mainly determined by replaceable bottoms sieves with defined aperture sizes. Experience shows that, with aperture sizes of 4 or 6 mm, it is already possible to achieve an adequate homogeneous mixture from which representative sub- samples can be taken for analysis or further processing. The latter here means the fine grinding of a representative sub– sample to the required analytical fineness. This depends on the subsequent analytical procedure, which is often described in relevant standards or regulations. Sample division Pourable, dry bulk materials are reduced in a representative fashion in sample dividers with a rotating dividing crown or laboratory rotating tube dividers to the required quantity according to DIN 51701 . These dividers provide reliable and reproducible results. If the material is not "pourable", then a sample splitter of appropriate size can be a suitable alternative. Random sampling is not advisable due to the high error rate. When selecting a suitable sample splitter, attention should be paid to the maximum opening of the dividing segments. It should be at least three times Rt'hl h pl.uwt.ny b.tll mill l'fv\ 100 ( r'v\ (It•!\) ,lfl(f '>fv\ )l)(} llt'.!Vy cfutv cutt111:~ n1tll \helm·:\ 52