NORDIC FOCUS
Process Industries Finland ) said in a recent report : “ The key question is : could green steel production be the solution for more sustainable society and the future ? What does green steel actually mean ? Is it just a way to greenwash the industry , or is there really CO 2-free technology available for producing steel ?”
The steel industry is responsible for roughly 7 % of total global CO 2 emissions , yet it is an incredibly important material used in a wide range of applications in infrastructure , transportation , energy and clean energy technologies as well as in many manufacturing industries .
The outright replacement of steel is almost impossible , so there is a high demand to convert steel making into a more sustainable process , the authors said .
The traditional method of producing steel using coal and other fossil fuels releases large amounts of carbon dioxide and other greenhouse gases into the atmosphere , contributing to climate change . The traditional steelmaking process also results in significant secondary environmental pollution , including air and water pollution .
The main challenge in implementing green steelmaking is not just in developing new technologies and the cost associated with them , but the ability to offer commercial-scale production with these new technologies . This also comes with significant energy requirements to power the processes , as well as the ability to source quality ores – which are in short supply on a global basis .
“ Overall , the solution for green steelmaking conversion requires a multi-faceted approach that involves technological advancements , policy changes and industry collaboration to create sustainable and eco-friendly steel production processes ,” the authors said .
The dialogue around the production of green steel has emerged as a focal point in recent years within the steel sector , with much of this tending to feature technology suppliers and producers asserting the superior techno-economic feasibility of their respective solutions for green steel production . Yet , determining the optimal technology route is not a straightforward process , according to the authors . Decisionmaking must consider an array of key factors that influence the chosen process flowsheet .
The production process flowsheet development has many factors , but AFRY ’ s experts have identified five major considerations in the development phase : 1 . Availability , type , and cost of iron ore or concentrate ( s ) and scrap : the composition of the feed material can determine whether the Electric Arc Furnace ( EAF ) or Open Slag Bath Furnace ( OSBF ) coupled with Basic Oxygen
Furnace ( BOF ) is chosen for the steelmaking process . For instance , if the feed material composition includes direct reduced iron ( DRI ) grade concentrate , which produces low furnace slag volumes , the EAF is preferred . On the other hand , if the feed material consists of BF-grade concentrate , which produces high slag volumes that is also a better by-product compared with EAF slag , the OSBF + BOF may be a better option . The valorization of steelmaking slag is becoming increasingly important as primary ore deposits become depleted and slag volumes increase . Slag valorization should be considered in the plant concept as landfilling is not an option in many permitting processes . Also , if significant amounts of scrap is used as feedstock , the EAF furnace is required as the OSBF + BOF combination is unable to process large scrap volumes .
2 . Availability of green electricity : when mitigating CO 2 emissions with the use of hydrogen in the iron reduction process ( direct reduced iron ( DRI ) production ), the grid needs to be green enough to justify the use of hydrogen and to lower Scope 2 emissions . In circumstances where electricity predominantly derives from fossil sources , it may prove advantageous to employ a combination of hydrogen and natural gas as the primary reducing agents . The substitution of the conventional blast furnace route with the DR process , even when using a mixture of natural gas and hydrogen , can result in significant CO 2 emission reductions . Post commissioning , the proportion of hydrogen can be progressively increased , contingent on its availability . The achievement of net-zero CO 2 emissions is feasible with the exclusive use of hydrogen , however , it warrants noting that if carbon is completely omitted in DRI production , the feed DRI to the smelting process does not contain any carbon . Steelmaking requires some carbon in the feed mix to reach the required product qualities . This carbon can be introduced via bio-carbon ( biogasbiochar ) sources .
3 . Hydrogen production : the selection between hydrogen production methods – Alkaline Water Electrolysis , Polymer Electrolyte Membrane and Solid Oxide Electrolyser Cell ( SOEC ) – depends on multiple factors , such as required efficiency , scale of production , required purity of hydrogen and availability of resources such as water and steam ( for SOEC ). The tradeoff between initial capital expenditure and sustaining capital expenditure should also influence the decision-making process for selecting the hydrogen production method . Also , hydrogen storage needs to be considered .
4 . Natural gas supply : when using natural gas in significant quantities , the design of the supply route and logistics requires a high level of precision and thought . This encompasses considerations of sourcing locations , transport infrastructure , storage facilities and delivery mechanisms . Additionally , the reliability of the supply chain , potential risks including geopolitical factors , and emergency contingency plans are all critical elements to consider in the design process .
5 . Existing steel mill versus greenfield steel mill : if the green steel investment is considered a replacement of traditional blast furnaces in an integrated steel mill , the implications for existing production need to be carefully studied . Ongoing production cannot be impeded during the implementation phase . For a greenfield project , the integrated mini-mill approach – which can encompass all processes from hydrogen production and feed handling to the production of the finished cold rolled
Illustration showing the Direct Reduced Iron ( 100 % hydrogen ) + Electric Arc Furnace route in green steelmaking
18 International Mining | JUNE 2023