Torrefaction of beech wood pellet and combustion behavior of torrefied pellets

Use of renewable sources is still a crucial option for energy supply in view of environmental consequences of fossil fuel-dependent industry. Today, only 10% of world's energy needs have been met by biomass sources. This is lower than expectations considering vast interest on biomass energy and necessitates more practical approaches to substitute fossil fuel usage. Torrefaction is a promising technique to obtain coal-like solids which can be incorporated into today's power systems. In this study, torrefaction of pellets prepared from beech wood sawdust and combustion behavior of torrefied pellets were investigated. For this purpose, the wood pellets were subjected to torrefaction in the fixed bed system. The effect of process parameters such as temperature and processing time on product yield and solid product properties were examined. The torreaction was carried out at 220, 260 and 300 ° C for 10, 20, 40 and 60 minutes at each temperature. The solid product obtained at the end of the process was burned in the fixed bed combustion system and the effect of the furnace initial temperature on combustion behavior was investigated. In addition, proximate, elemental, TGA and DTG analyzes of the torrefied product were performed. In the study carried out with the aim of converting beech wood pellet into a usable solid fuel by torrefaction process, it was concluded that the procedure temperature was more effective on the solid product yield than the processing time. It was determined that the increased procedure temperature increased fixed carbon content of the solid product and decreased the volatile content of the solid product. With the increase in the process temperature, the carbon content of torrefied solids increased while oxygen content decreased. TGA and DTG analyzes showed that hemicellulose was completely degraded in solid products obtained from moderate and severe torrefaction. The combustion behavior of torrefied pellets in the fixed bed combustion system was investigated and it was observed that the ignition times of the torrefied pellets were shortened. It was determined that volatile combustion times of torrefied pellets were shortened with torrefaction temperature and processing time. There was no relationship between volatile combustion time and volatile combustion rate. The carbon combustion time was found to be prolonged by an increase in the fixed carbon content in the torrefied product. It was concluded that volatile combustion period and carbon combustion period were affected by the furnace initial temperature. It was found that the CO2 and NO emissions determined during the volatile combustion period of the raw and torrefied solids were reduced due to the leaving of volatile components from the structure depending on the severity of torrefaction.