Mass Balance of Biocarbon Electrodes Obtained by Experimental Bench Production

Abstract

Biocarbon electrodes (BCE) for specialty applications were produced, bench scale, from biomass. The pyrolysis of wood logs at 1000°C yielded charcoal and volatile by-products which were condensed and later distilled to recover the biopitch, utilized as the binding agent. The biocoke was ground and mixed with the binder to obtain the bio-electrode paste. The green electrode was molded at 60 MPa and 150°C. Heat treatments include calcination at 1000°C followed by graphitization at 2700°C. The physical properties of BCE showed microcrystallite dimensions of L_c = 124 Å and L_a = 565 Å, electrical resistivities of 10^‒4Ω.m and the mechanical measurements yielded a Young’s modulus near 3.0 GPa, rupture strength of 50 MPa and a thermal expansion coefficient of 6.10^‒6°C^‒1. The mass balance of the manufacture process indicates 31% of biocoke, 45% of condensed and 24% of volatile materials. The vacuum distillation of condensed fractions resulted in 11.2% of biopitch. Mixing and molding of biocoke with biopitch paste produced the green electrode which was calcined and finally, graphitized. Ultimately, the heat treatment process yields 28.9% of graphitized BCE.