Alternative Thermal Processing of Coal – Pilot Extruded Coke and Supercapacitor Demonstration

This project focussed on two manufacturing technologies (extrusion, direct casting) for the shaped heating of coal. It followed on from project C34064 with two specific aims:

• To retrofit a high temperature furnace to the existing pilot extruder unit and produce extruded coke products for CSR evaluation; and
• To construct a supercapacitor demonstration unit using coal-derived carbon tiles for energy storage evaluation.

A number of key findings were made and are detailed in the report.

Thermally extruded cokes:

• Extruded coke quality was measured between 65-73% CSR, similar to commercially produced coke from the same coal;
• Extruded coke blends of 10% bio-additives measured between 64-65% CSR, which appear to be some of the highest coke strengths for the biomass addition within the published literature;
• The system appeared to be sufficiently versatile to prepare semi-cokes from a PCI coal (5 ddpm fluidity) for iron ore sintering and in the preparation of biochar. Further work is needed to optimise the pretreatment of bio-liquids, though this is more related to the feedstock (molasses) rather than the system;

Supercapacitor demonstration:

• The activation of larger amounts of carbon tiles in air produced significant over-heating and specific methods were developed to control the level of exposure with periodic nitrogen purges for thermal equilibration;
• The electrical charge/discharge cycling of the supercapacitor cells resulted in severe electrodeposition of the copper wires onto the opposite electrode (cathode); despite every effort at protecting the metal surfaces. Other metals deposits and crystal grains were also observed on the carbon surfaces;
• The electrolyte (after supercapacitor testing) was found to contain a number of dissolved metals believed to be sourced from the coal, and a precipitate containing a range of different crystal grains. This suggested that the supercapacitor cells would benefit from “pre-conditioning” to electrically leach these metals out. Of the metals tested, 8 appear on Australia's critical mineral list and this may prove to be a novel route for further critical mineral recovery.