| Popis: |
The contribution deals with the preparation of small-diameter briquettes on the basis of desintegrated phyto-materials and the admixture of coal and coke. The phyto-materials are classified as a dry biomass that can be, on the one hand, the wastes from wood-working industry,(sawdust, chips, bark, etc.) or dried mass from the plant production and, on the other hand, the mass of quick-growing plants cultivated on special plantations. In present time this renewable energy resource attracts attention by its heating value ranging from 10 to 16 MJ.kg-1 (EkoWATT, 2001), a low ash content of 0.5 6.5 % and by a low sulphur content in a water free sample of 0.05 0.12 %.As a phyto-material the spruce sawdusts having a grain size of 2 mm were used. The admixture of brown coal, hard coal and coke with a grain size of 0.040 mm was added to the sawdust and in such way prepared mixtures were subjected to briquetting with the aim to obtain small-diameter briquettes. The influence of admixtures amount on the density, and the suitable briquetting press have been studied. A saleability of briquettes on the basis of phyto-materials is conditioned by their density that must be higher than 1,000 kg.m-3. Thus, an adding of denser material with a relatively high calorific value would enable to attain the required density as well as to retain and/or to improve the main utility properties, i.e. calorific value and ash content.The adding evinces itself in an enhancement of briquetting press, but also density of obtained briquettes is often much higher that required by the market. It was showed that in the case of clear spruce sawdust the density of 1,059 kg.m-3 under the briquetting press of 250 MPa can be attained. According to other results, an admixture of brown coal is not very favourable because briquetting press exceeds the value of 300 MPa. As to hard coal adding, the presses under 250 MPa were achieved at the content of 25 30 %. The density of these briquettes ranges from 1,050 1,085 kg.m-3. The best results have been obtained by adding coke. The briquetting press lower than 250 MPa has already been attained at the coke content of 15 %. The further increase of the coke content up to 30 % resulted in the briquetting press of 185 MPa. The density of briquettes with the admixture of coke was from 1,037 to 1,063 kg.m-3. |
