iPURSE 2019

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https://ir.lib.pdn.ac.lk/handle/20.500.14444/37

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Browsing iPURSE 2019 by Author "Alahakoon, A. M. Y. W."

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    Paddy husk pyrolysis in a small scale down draft double chamber (DDDC) pyrolyser: heat of pyrolysis
    (University of Peradeniya, Sri Lanka, 2019-09-12) Alahakoon, A. M. Y. W.; Nilmalgoda, E. P. R. H. H. W.; Karunarathna, A. K.; Dharmakeerthi, R. S.
    Conversion of biomass wastes into energy rich resources by thermochemical treatment methods like pyrolysis has been identified as one of the most sustainable solution for energy and resource recovery. Understanding the thermal behavior of these thermochemical processes is very important in developing energy efficient pyrolysis technologies. The heat of pyrolysis can be described as the energy released or absorbed during the chemical conversion of biomass into pyrolysis products. In the absence of micro-scale thermogravimetric analysis, the stoichiometric method with the use of macromolecular conversions can alternatively be used in finding the heat of pyrolysis. In this research, an overall stoichiometric equation was developed for producing biochar from the pyrolysis of rice husk. The stoichiometric equation was developed using experimental and literature data while the heat of pyrolysis was calculated by the difference of total Higher Heating Values (HHV) (kJ/mol) of pyrolysis products and biomass inputs. Subsequently, heat of pyrolysis for paddy husk in a small scale down draft double chamber (DDDC) pyrolyser unit was estimated. The mean compositional formulas for paddy husk and biochar were found with the help of elemental analysis in literature and the syngas composition was estimated experimentally using a Gasboard 3100P syngas analyzer. The remaining mass was estimated as the tar fraction derived during the thermal decomposition. The developed stoichiometric equation for reaction of 1mol (CH₁.₅₅₆O₀.₆₁₇) of paddy husk yields biochar (CH₀.₂₆O₀.₁₃₄), H₂, CO, CH₄, C₂H₄, CO₂, H₂O and tar (CH₀.₈₀₁O₀.₃₇₅) in the molar ratios of 0.516, 0.017, 0.051, 0.009, 0.0004, 0.033, 0.285, 0.389, respectively. Calculated heat of pyrolysis was +31.64 kJ/molfeed at an average pyrolysis temperature of 823 K. This positive energy value indicated that the pyrolysis of paddy husk in the used DDDC reactor was an endothermic reaction requiring an external energy supply to initiate and continue the pyrolysis process.
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    Thermo-pyrolysis conversion of sewage sludge into biochar and its characterization
    (University of Peradeniya, 2019-09-12) Gamagedara, K. Y. B.; Alahakoon, A. M. Y. W.; Karunarathna, A. K.; Kirindage, K. G. I. S.; Attanayake, C. P.
    This research was conducted to evaluate and compare the quality of sewage sludge (SS) biochar produced by pyrolysis, in a laboratory scale reactor inside a muffle furnace and field scale Double Chamber Reactor (DCR). Small samples of (140 g) SS collected from a municipal sewage treatment facility was pyrolysed in a muffle furnace at different temperatures (250, 300, 350, 400, 450, 500, 550 °C) for two residence times (30 and 60 minutes) at a constant heating rate (10 °C/ minute). In field scale research, DCR reactor was fed with 12.5 kg of air dried SS and pyrolysed at 750 °C for 3 hours. It was observed that raw SS particles remained after pyrolysed at any temperatures between 250 and 550 °C for 30 minutes, and even for 60 minutes at lower temperature of 250 °C. The biochar produced by said heat treatment for 60 minutes were analyzed by International Biochar Initiative guidelines and leaching toxicity was assessed using Toxicity Characteristic Leaching Procedure (TCLP). Results showed that biochar recovery decreases with increasing pyrolysis temperature. Fixed carbon and ash content of biochar increased with increasing pyrolysis temperature while volatile solids decrease with increasing pyrolysis temperature. TCLP showed that conversion of SS to biochar reduced leaching potential of N, P, K, Ca, Mg, Mn and Pb by 77%, 79%, 7%, 1%, 55%, 23% and 68% when SS pyrolysis temperature increased from 300 to 550 °C. In the DCR reactor, leaching potentials of the same elements were comparable or even less than the biochar made at 550 °C in laboratory scale reactor. Further, it was observed that SS contained excessive amount of calcium due to lime (Ca(OH)₂) addition to septic tanks for maintaining pH. The results revealed that pyrolysis convertion of SS to biochar at elevated temperatures reduce the leaching potential of nutrients and metals.