Efficiency of Biomass Use for Blast Furnace Injection

Abstract

Numerous studies and available experience proved the feasibility and benefits of the biomass usage in various metallurgical applications, particularly, by its injection into the blast furnace (BF). This contribution focuses on three aspects, which could increase the economic efficiency of this technology. The first one is related to the thermal treatment of biomass. Woody biomass were pyrolysed using a laboratory pyrolysis plant under different conditions resulting in various amounts and properties of solid, liquid and gaseous constituents. Co-injection of the produced charcoal and biogas into the BF was proposed. Mathematical modelling using the experimental data of mentioned biomass product characteristics was undertaken to examine the effect of this technology on the BF operation results. The second aspect is related to the optimisation of grain size and size distribution of injected solid biomass products. Tests using a laboratory injection rig allowed for recommendation of the coarser grinding of charcoal than that for fossil coal applied for the BF injection. This could lead to the additional energy and cost saving. The third aspect concerns the improvement of the BF control. It is proposed a new BASE 1 method for the BF thermal state control by adaption of the pyrolysis parameters while injecting pyrolysed biomass and coupling the blast furnace with a pyrolysis reactor.

Process Concept for the Dry Recovery of Thermal Energy of Liquid Ferrous Slags

“…The ecological, political, and social pressure to decarbonize steelmaking and foster circular economy give these technologies a second life. New approaches lead such a trend, like the BASE method [19]. The BASE method couples blast furnace with a pyrolysis reactor and shows that by interlinking of processes, like the presented slag heat recovery for the utilization of biomass in iron and steelmaking can become reality.…”

Multi-Step Recycling of BF Slag Heat via Biomass for CO2 Mitigation

“…Table 4 demonstrates the theoretical impact of partially replacing 5% of 350 kg coke per tonne hot metal with TB and additionally injecting it to PC (+17.5 kg TB /t HM ) together with biogas injection of, e.g., 100 m 3 /t HM . Typical oxygen content in the blast due to TB are 25%, and combined biogas injection is between 30 and 40%, resulting in a flame temperature around 2117 • C [18]. The presented exemplary coke-replacement rates with TB and biogas of Table 4 are independent of mass and energy balances and need further investigation with case studies.…”

“…Torrefying biomass and injecting it as a pulverised coal (PC) alternative into the enhanced blast furnaces is an option to partially replace the specific consumption of coke. Furthermore, the coke consumption can be lowered with the injection of biogas as syngas [18] partially replacing or in addition to the hot blast, which is only carrying sensible heat. Such biogas injection and its effects can be compared to BF top gas recycling [24][25][26][27].…”

“…The presented exemplary coke-replacement rates with TB and biogas of Table 4 are independent of mass and energy balances and need further investigation with case studies. The considered TB [18] has a moisture content of 2.3 wt.%, ash content of 0.6 wt.%, volatile matter of 6.0 wt.%, and a carbon value (C fix ) of 88.3 wt.%. The considered biogas has H 2 of 35.7 vol.%, CO of 37.1 vol.%, CO 2 of 9.7 vol.%, H 2 O of 4.0 vol.%, N 2 of 13.5 vol.%, and no CH 4 [18].…”

“…Depending on the process temperature, three categories of pyrolysis are defined: lowtemperatures pyrolysis at <500 • C, mid-temperature pyrolysis at 500-800 • C, and hightemperature pyrolysis at >800 • C. Torrefaction is low-temperature pyrolysis at <320 • C and produces solid, liquid, and gaseous products. Depending on the processing speed, slow, fast, and flash pyrolysis are distinguished and result in different ratios and yields of solid, liquid, and gaseous products [18].…”