Improvement of fuel qualities of solid fuel biochars by washing treatment

Raw biomass washing prior to pyrolysis treatment has been employed to mitigate the ash-related problems encountered during resultant biochar combustion. However, wide-spread application of this approach is limited by high energy consumption and low washing efficiency. In the present study, the biochar washing instead of raw biomass washing was attempted to overcome aforementioned problems, and fuel qualities of washed biochars were investigated for the first time. The results showed that major ash forming metals can be efficiently removed by all tested washing agents (de-ionized water (DW), acetic acid (AA) and citric acid (CA)), especially for acid washing agents AA and CA. As a consequence, the ash content of the biochars decreased, and the slagging and fouling issues were dramatically mitigated. Due to metal removal, the washed biochars exhibited improved combustion properties, especially for the biochars derived from agricultural biomass. In addition, noticeable decreases in nitrogen and sulfur contents were observed following washing treatment, suggesting the additional benefit of reducing emissions of nitrogen and sulfur pollutants during washed biochar combustion. Compared to raw biomass washing prior to pyrolysis, the significantly increased washing efficiency and fuel quality and decreased hydrophilicity of the biochars indicate that pyrolysis combined with subsequent biochar washing is more suitable to produce solid fuel biochars with high fuel quality from different source of waste biomass. (C) 2015 Elsevier B.V. All rights reserved.

[1]  Marek Pronobis,et al.  Evaluation of the influence of biomass co-combustion on boiler furnace slagging by means of fusibility correlations , 2005 .

[2]  D. Che,et al.  Effect of water washing on fuel properties, pyrolysis and combustion characteristics, and ash fusibility of biomass , 2013 .

[3]  Rajasekhar Balasubramanian,et al.  A comparative study of nitrogen conversion during pyrolysis of coconut fiber, its corresponding biochar and their blends with lignite. , 2014, Bioresource technology.

[4]  S. Staggenborg,et al.  Washing sorghum biomass with water to improve its quality for combustion , 2014 .

[5]  Kj Krzysztof Ptasinski,et al.  Biomass upgrading by torrefaction for the production of biofuels: A review , 2011 .

[6]  Bryan M. Jenkins,et al.  On the properties of washed straw , 1996 .

[7]  Zbigniew Hubicki,et al.  Kinetic and adsorptive characterization of biochar in metal ions removal , 2012 .

[8]  Yuncong C. Li,et al.  Characteristics and mechanisms of hexavalent chromium removal by biochar from sugar beet tailing. , 2011, Journal of hazardous materials.

[9]  Jenny M. Jones,et al.  Commodity Fuels from Biomass through Pretreatment and Torrefaction: Effects of Mineral Content on Torrefied Fuel Characteristics and Quality , 2012 .

[10]  K. Khilar,et al.  Influence of mineral matter on biomass pyrolysis characteristics , 1995 .

[11]  Peter Arendt Jensen,et al.  Removal of K and Cl by leaching of straw char , 2001 .

[12]  S. Mekhilef,et al.  A review on biomass as a fuel for boilers , 2011 .

[13]  Zhengang Liu,et al.  A comparison of thermal behaviors of raw biomass, pyrolytic biochar and their blends with lignite. , 2013, Bioresource technology.

[14]  S. Mani,et al.  Impact of torrefaction on the grindability and fuel characteristics of forest biomass. , 2011, Bioresource technology.

[15]  S. Kent Hoekman,et al.  Hydrothermal Carbonization (HTC) of Lignocellulosic Biomass , 2011 .

[16]  X. Bi,et al.  Overview and some issues related to co‐firing biomass and coal , 2008 .

[17]  U. Jäglid,et al.  The effects of fuel washing techniques on alkali release from biomass , 2002 .

[18]  Fu-Shen Zhang,et al.  Characterization and application of chars produced from pinewood pyrolysis and hydrothermal treatment , 2010 .

[19]  Zhengang Liu,et al.  Upgrading of waste biomass by hydrothermal carbonization (HTC) and low temperature pyrolysis (LTP): A comparative evaluation , 2014 .

[20]  N. Said,et al.  Effect of water washing on the thermal behavior of rice straw. , 2013, Waste management.

[21]  Peter Arendt Jensen,et al.  Pretreatment of straw for power production by pyrolysis and char wash , 2001 .

[22]  Rajasekhar Balasubramanian,et al.  Preparation and characterization of fuel pellets from woody biomass, agro-residues and their corresponding hydrochars , 2014 .

[23]  Bryce J. Stokes,et al.  Biomass as Feedstock for A Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply , 2005 .

[24]  P. Jansens,et al.  Biomass combustion in fluidized bed boilers: Potential problems and remedies , 2009 .

[25]  S. Vassilev,et al.  An overview of the organic and inorganic phase composition of biomass , 2012 .

[26]  Bryan M. Jenkins,et al.  Influence of leaching pretreatment on fuel properties of biomass , 2014 .

[27]  Hongwei Wu,et al.  Biochar as a Fuel: 1. Properties and Grindability of Biochars Produced from the Pyrolysis of Mallee Wood under Slow-Heating Conditions , 2009 .