Fossil fuel-based carbon is widely used in iron and steelmaking in a number of forms, and the replacement of these materials with renewable carbon derived from biomass is seen as offering the greatest potential to reduce the greenhouse gas footprint of steel production. Life cycle assessment methodology has been used to estimate the greenhouse gas footprint of charcoal production from biomass, as well as the potential reductions in greenhouse gas emissions from the use of charcoal from biomass in the integrated, mini-mill/EAF and direct smelting steelmaking routes. The results indicated that the use of charcoal in the integrated steelmaking route in likely applications and substitution rates has the potential to reduce the greenhouse gas footprint of steel by 0.69-1.21 t CO2e/t steel (or 31-57%) without any charcoal production by-product (bio-oil and electricity) credits, and by 0.91-1.61 t CO2e/t steel (42-74%) with these by-product credits included. The corresponding reductions for the mini-mill/EAF and direct smelting routes were 0.028-0.056 t CO2e/t steel (5.5-11%) and 0.34-1.70 t CO2e/t steel (16-80%) without by-product credits, and 0.037-0.075 t CO2e/t steel (7.3-14.7%) and 0.45-2.25 t CO2e/t steel (21-106%) with by-product credits respectively. However, the magnitude of the by-product credits depends on the by-product yields in the charcoal retort, which in turn are dependent on a number of factors, in particular, the nature of the pyrolysis process (fast or slow) and the biomass feed composition.Estimates of the potential plantation areas available to grow the biomass required to produce charcoal for steelmaking purposes in a sustainable manner, together with estimates of sources of biomass residues suggest that it is possible that an appreciable amount of the world's steel production can utilise charcoal in place of coal or coke over the coming decades. However, transportation is expected to be a significant issue affecting the cost of charcoal delivered to steel plants in all biomass source scenarios. Other issues such as technical aspects of charcoal use in steelmaking and economics will also play a significant role in the uptake of charcoal from biomass as a source of renewable carbon for iron and steelmaking.

The substitution of charcoal as an alternative fuel to coke breeze in a simulated Japanese Steel Mills (JSM) sinter blend was investigated. Compared with coke breeze, higher mix moisture contents were required for the sinter mixture containing charcoal to achieve optimum granulation. The green granules formed from the sinter mixture containing charcoal were clearly less dense and formed a less compacted green bed as evidenced by the packing density. To achieve return fines balance, fuel addition had to be increased from 3.62 to 4.17% (on a dry mixture basis) as the substitution of charcoal increased from 0 to 50%. However, at 100% subsitution, the sinter mixture failed to achieve balance even at a very high fuel addition level of 4.7%. Compared with the sinter fired with coke breeze, the sinter from the mixtures containing up to 50% charcoal was marginally weaker in terms of sinter yield, tumble strength (TI) and reduction disintegration (RDI). The reasons for weaker sinter are discussed. Fuel rate increased considerably with charcoal substitution due to increased fuel addition and decreased sinter yield. However, increasing fuel rate did not lead to a reduction of sintering productivity. In contrast, the sintering speed and productivity were maintained as the charcoal substitution rate increased from 0 to 25% and then increased considerably with further increase in charcoal substitution rate. The emission mechanisms of the CO, CO2, SO2 and NOX and H2O gases during sintering are clearly quite different. CO, CO2 and NOx emission was observed over the entire sintering process and varied slightly as the sintering process progressed. However, the SO2 and H2O emissions were observed only towards the completion of the sintering process. Both the CO and CO2 concentrations in the waste gas increased with the increasing substitution of charcoal for coke breeze; however the concentrations of SO2 and NOX in the waste gas decreased.

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The replacement of coal-based fuels by renewable fuels such as charcoal is an attractive way to reduce net greenhouse gas emissions from the integrated steelmaking route. Our previous studies have indicated that the potential for savings in net CO2 emissions ranges from 32 to 58 percent, with use as a BF tuyere injectant being the largest application. The current study considered the combustibility of four types of charcoal in comparison with PCI coal under simulated BF raceway conditions. The major findings were that burnouts under standard conditions (air-cooled coaxial lance, O/C = 2.0) were comparable or better than that of the high volatile matter PCI coal studied, and a comparison with the trend line for burnout with injectant volatile matter previously established for coals, indicated that the hardwood charcoals studied had burnouts 40% (abs) higher than those of equivalent coals, and the softwood charcoal studied was higher again. A study of the effects of oxygen enrichment indicated that small increases were effective, and particularly so for the least combustible charcoal. Overall, the burnout results indicated that higherthan-coal injection rates should be possible in industrial practice, and in combination with the previous heat and mass balance results, they indicated the potential for increased BF productivity. The brief study of the combustion of coal-charcoal mixtures indicated good combustibility and predictable burnouts. The microscopic examination of both the charcoal injectants and their combustion chars indicated that there was significant fragmentation of the charcoals during combustion, boosting their already high surface areas and combustibility.

a b s t r a c tCharcoal produced from sustainably grown biomass can be used to reduce the net CO 2 emissions from iron and steel making operations. However careful control of pyrolysis conditions is required to produce charcoal with the necessary properties to optimise substitution for coal and coke in specific applications. The density of charcoal is an important property to control in order to minimise transport and handling costs as well as control of charcoal reactivity and strength.In this work the density of charcoal has been increased through compression of Blackbutt wood chips during pyrolysis. The true density of charcoal prepared under compression of 0.5 MPa and at a heating rate of 2 C/min was found to increase with pyrolysis temperature, especially at temperatures higher than 450 C. This increase in true density is likely to be due to restructuring of the graphitic structure at high temperatures. The true density of charcoal was found to be independent of compressive pressure during pyrolysis (0.056e4.0 MPa). The porosity of charcoal increased linearly with pyrolysis temperature and ranged from 0.24 at 300 C to about 0.46 at 700 C. The apparent density of charcoal prepared under a compressive pressure of 0.5 MPa was about 1000 kg/m 3 and had minimum between 400 and 600 C. This is similar to the apparent density of metallurgical coke. The results suggest that specially prepared charcoal could be a viable substitute for coal and coke in steelmaking applications which require a dense carbon product.