Technical Market Support » Metallurgical Coal
Steel production accounts for approximately 7% of global greenhouse gas emissions. Including biomass in coal blends for coke production is considered an ideal approach to decarbonization as changes to key infrastructure such as blast furnaces and coke ovens are not required. Raw and heat-treated biomass addition to coke however, results in significant quality degradation, even in low concentrations.
Glucose, a sugar, is a mineral-free, plant derived compound that melts at 146°C and pyrolyzes to form aromatized carbon molecules. It presents a scalable source of biomass as it can be synthesized from the acid hydrolysis of any cellulosic material including agricultural, forestry and textile waste streams. Due to the absence of mineral matter, a coking coal blend with sugar may reduce the ash content of the produced coke.
As part of this project, a prospective biomass blending program was conducted to determine the impact glucose addition has on coke quality formed from three Bowen Basin coals. Additional blends were prepared by combining dextrose monohydrate with coke breeze, lignosulphonate and torrefied prickly acacia. These additives are low-value or waste products that could provide additional sources of fixed carbon. A total of 20 small scale coking blends were tested under ALS's standard coking conditions.
A minor increase in coke reactivity but a significant drop in coke strength was found with the addition of 20% dextrose monohydrate to the 173-C and C173-C-001. Doubling the dextrose monohydrate content to 40% produced relatively minor further deterioration in coke quality. A blend comprising 60% C173-C-001 and 40% dextrose monohydrate produced a coke CSR of 29.9 with 10.6% of the fixed carbon attributable to biomass. This blend ratio was repeated with additional coal crushing and compaction to 1100 kg/m3 for a maximum CSR achieved of 35.6.
Coke was able to be produced from the C174-C-001 with a sugar content of 20% producing a CSR of 10.0. This suggests the sugar acted as binder during carbonization, allowing inert coal particles to form into a coke matrix.