school energy&environment

Treatment, transport and storage

The market requires coal to have a high quality and purity. The coal extracted from mines contains a mixture of fractions of different sizes, sometimes containing rocks or compost. Therefore a preparation stage is needed, called “beneficiation” and the raw coal is divided into a series of clean, uniform and classified products, ready to be sold. In some cases raw coal has a high quality that satisfies consumers’ needs. In these cases the “beneficiation” is not necessary and the coal can be simply broken into pieces and sieved in order to obtain a specific product.
A good preparation of coal before its combustion increases the homogeneity and efficiency of this combustible, reduces transport costs and its displacement inside the plant produces less dust and reduces the emission of sulphur oxides.
Once coal has been extracted, it is necessary to transport it to the plants where it will be used. For short distances, trucks will be used, while for longer distances trains, barges and ships will be employed. Recently coal pipes have been tested: the mineral is pumped after being transformed into dust and mixed with water. Preventive measures are taken at any stage during transport and storage, in order to reduce any environmental impact. For example, the superficial flow of contaminated water is limited by the design of storage equipment and all waters are carefully treated before being re-used and disposed of. The dusts can be controlled by using water spray and compacting the coal to be stored.
Road or sea transport systems can be used to transport the coal from the storage place to combustion sites. However, more than 60% of the coal used to produce energy is consumed at 50 km from the extraction mine.