Title:
Wet Torrefaction of Norwegian Biomass Fuels
Author(s):
Bach, Q.V., Tran, K.-Q., Skreiberg, Ø.
Document(s):
Paper
Abstract:
Wet torrefaction of biomass for bioenergy applications involves the use of hot compressed water as reaction environment to improve the fuel properties of the biomass materials, which among others includes increased heating values and better grindability. The process may be defined as hydrothermal pyrolysis of biomass fuels within the temperature window of 200–260 °C. Compared with dry torrefaction, wet torrefaction is capable of upgrading biomass fuels with very high moisture contents without the need of pre¬drying the feedstock, which is a highly energy sensitive step. In addition, hydrothermal media can wash part of the ash out of the biomass and offer a cleaner fuel. In the present work, wet torrefaction for typical Norwegian biomass fuels was experimentally studied within the temperature window of 175¬225oC, using a 250mL reactor from Parr Instrument series 4650. Two types of Norwegian biomass fuels were used as feedstock, Norway spruce softwood and birch softwood. Effects of process parameters such as reaction temperature, holding time, and feedstock size on the yield and fuel properties of solid products were investigated. Effect trends similar to that of dry torrefaction were observed. Feedstock particle size also has effects on the yield and probably the properties. However, the effects of this factor may be overwhelmed when wet torrefaction is carried in the conditions of longer reaction time and/or higher reaction temperature. In addition, the reduction in specific grinding energy of wet torrefied biomass can be up to 26 times compared with the raw materials. More interestingly, the ash content of torrefied biomass significantly decreases by wet torrefaction. This opens up a possibility to produce cleaner solid fuels via WT, with regard to inorganic impurities. It appears that wet torrefaction produces less solid product than dry torrefaction in the conditions of the same reaction temperature and time, but the fuel properties is much better. In the conditions to produce the same solid product yield, wet torrefaction offers solid fuels with significantly higher heating values. The difference in the HHV increase within the tested conditions varied within 0.9¬21%.
Keywords:
wet torrefaction, hydrothermal pretreatment, wet biomass, fuel upgrading, fuel washing
Topic:
R&D on Processes for Solid, Liquid and Gaseous Fuels from Biomass
Subtopic:
Advanced solid biofuels
Event:
20th European Biomass Conference and Exhibition
Session:
3DV.4.15
Pages:
1755 - 1763
ISBN:
978-88-89407-54-7
Paper DOI:
10.5071/20thEUBCE2012-3DV.4.15
Price:
FREE
