Solid fuel production with torrefaction from vineyard pruning waste

The objective of this study is to convert the waste biomass obtained after pruning procedure into a usable solid fuel by means of torrefaction. To this end, pruning waste was subjected to torrefaction procedure in fixed bed system. The effects of parameters as temperature, processing time and N2 and O2 concentration in carrier gas on the product and features of solid product were examined. Torrefaction procedure was performed under carrier gas environment of nitrogen-air mixture which composed of four different oxygen concentrations from 0% to 21% O2 at 220, 250 and 280 ˚C temperatures and 0, 10, 20, 40 and 60 minute processing times. In order to determine the features of solid products and compare them with raw biomass, proximate, elemental, FTIR, TGA and DTA analysis were conducted and high heating values were determined. The study aimed to convert the waste biomass obtained at the end of vine pruning procedure into a usable solid fuel through torrefaction it was observed that the product yields were most affected by yields temperature and that as the temperature increased yields solid product decreased while yields liquid and gas product increased. It was also observed that processing time was effective on large-size samples. A comparison of the torrefaction procedures in air and nitrogen environment showed that the amount of solid product was higher under air environment whereas the amounts of liquid and gas products were higher under nitrogen environment. It was found out that the increased procedure temperature raised fixed carbon ratio of solid product and that under slight torrefaction conditions O2 concentration did not affect the composition of the solid product. It was determined that in nitrogen environment and under strong torrefaction conditions H/C and O/C ratios approached to the peat and lignite zone in the Van Krevelen diagram. In addition, it was found out that increased procedure temperature and high heating value reduced energy efficiency. It was concluded that 79.73% of energy of the biomass torrefied at 280ᴼC was preserved and it would be appropriate to conduct the torrefaction of waste vine shoots at this temperature as the high heating value approached to coal. It was found out that the functional groups of solid product obtained in inert environment were affected by increased working temperature. TGA and DTA curves of torrefied biomasses obtained for raw biomass and nitrogen environment and at 250 and 280ᴼC temperature showed that torrefaction temperature was effective on the lignocellulosic structure and that with higher torrefaction temperature a solid product with higher lignin content could be obtained. TGA-DTA curves of solid products obtained in inert and oxidative environment showed that the efficiency of torrefaction performed in oxidative environment was lower than the inert environment.