Determining of accurracy of drawing, preparation and analysis of biofuels samples and fuels of waste origin

Increase of biofuels and solid secondary fuels part as sources of energy in a fuel-energy balance inputs to improvement of utilization efficiency, and to saving energetic raw materials resources, as well as to reduction of quantity of produced wastes. In Poland, biomass and solid secondary fuels are burned with a coal as energetic mixture, more and more often. Therefore, there exists a need of detailed procedures study with range of drawing and preparing of biofuel samples and the whole secondary fuels. In these procedures, a differentiation of this fuels with regard to qualities, grain size distribution, concentration should be considered. In the paper, guidelines were presented related to the way of sampling for physical-chemical tests and defining of drawing samples accurracy. To optimize the way of biomass or solid secondary fuels sampling procedure, the tests of grain size distribution, size and number of primary samples impact onto the accurracy of sampling procedure were conducted. On the basis of results obtained, it was found that in the case of most solid biofuels and solid secondary fuels, an optimum number of primary samples, which have to be drawn from a party up to 1000 t, should be 36, as minimum. In the case of mixtures of solid secondary fuels, one should draw 54 primary samples, as minimum. In the case of biofuels, which characterize with law qualitative differentiation (chips, sawdust), it will be sufficient to draw primary samples af mass no lesser than 1.5 kg. Mixed primary samples of solid secondary fuels should have mass of minimum 3 kg. For sawdusts and mixtures of different kind of secondary fuels, the best results were obtained at size reduction below 1 mm. In the case of PET bottle wastes and wood-chips, in view of their homogeneity under regard of content ash, the sufficient size reduction is the grain size distribution below 2 mm.