In this work, slow pyrolysis of sawdust of Eucalyptus pilularis biomass and ternary molten carbonate eutectic [Li2CO3, 43.5%; Na2CO3, 31.5%; and K2CO3, 25% (mole percentage)] in thermogravimetric analysis at three different temperatures, 600, 750, and 900 °C, was studied. These salts affect the slow pyrolysis process, including changes in the volatile release mechanism and the morphology of remnant char material. The initial results show that, in the presence of molten carbonate, biomass particles make bubble-shaped larger particles, which result in less volatile emissions and more char residue. It is suggested that the ternary eutectic has a chemical diluent and catalytic role, particularly in the case of higher salt doping. Results from scanning electron microscopy images give strong evidence that molten carbonates capture volatiles inside swelling carbon particles, which causes the generation of various sizes of pores as well as char-making reactions, and at a higher temperature, the bubble-shaped particles will rupture. Swelling of this nature has previously only been observed clearly in coal precursors; however, this is the first observation in a biomass-based system. Also, at a temperature above 750 °C, decomposition of molten carbonate generates CO2 and carbon/carbonate gasification produces CO as well as a more “activated” biochar.

This study deals with the modification of chars derived from different biomass samples (woody biomass, cellulose and lignin). Chars are formed during slow pyrolysis on addition of alkali ternary eutectic...

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The impact of N2 and CO2 atmospheres on the interaction between Eucalyptus pilularis biomass and a ternary molten carbonate eutectic (Li2CO3: Na2CO3: K2CO3) has been investigated at 600 °C and 900 °C. For lower temperature conversion under CO2, prevention of volatile release in the eutectic treated biomass is slightly higher than under N2 injection; however, similar bubble-shaped morphology of the remnant char is observed under both carrier gases. By increasing the temperature to 900 °C under CO2, the reverse Boudouard reaction begins to consume carbon fuel, while molten carbonate gasification also accelerates the reaction to a lower temperature set point (shifted from ~735 °C to ~640 °C). The mass loss of carbonate under CO2 and N2 at 900 °C is 0 (negligible) and 18 wt.%, respectively. In the absence of carbon particles, the decomposition of carbonate to M2O (l) and CO2 (g), as well as molten salt vaporization, are the sole potential routes of weight loss in an inert gas. Previous observations of biomass and eutectic mixture thermochemical conversion under N2 have suggested carbon/carbonate gasification is dominant at elevated temperatures, with production of CO expected. However, analysis of gas chromatography (GC) suggests that carbon/carbonate gasification is the weaker pathway by producing only 7 vol.% of CO, compared with molten carbonate decomposition with 27 vol.% CO2 emission for this system.