Periodic Reporting for period 1 - ReMFra (REcovering Metals and Mineral FRAction from steelmaking residues)
Berichtszeitraum: 2022-12-01 bis 2024-05-31
Each year the EU steel sector generates several million tons of metal and mineral containing residues that are currently largely under-exploited and are often sent to landfills with an enormous waste of resources that could replace virgin materials. ReMFra main objective is the development and validation of highly efficient pyrometallurgic melting and reduction demonstration plant at relevant industrial scale for recovering metals and minerals contained in a wide range of steelmaking residues.The ReMFra process will allow to valorise steelmaking residues, such as filter dust, scale, sludge and slags, to obtain pig iron, iron rich oxides, a highly concentrated zinc oxide and an inert slag. ReMFra comprises two main parts to be developed, improved and tested at industrial scale: Plasma Reactor and RecoDust. The first will be dedicated to recover the coarse residues (scale, sludge, slag), while the second will focus on fine-grained dusts. The project will allow the improvement of iron yield using recovered pig iron instead of new pig iron and replacing the iron ore with the iron rich oxide. The recovery of concentrated ZnO and inert slag as by-products will provide a significant source of income and will contribute to the overall carbon neutrality. To reach the full circularity, the process foresees the use, as reducing agent, of secondary carbon sources (i.e. waste plastics). Energy recovery solutions will also be integrated in the metal recovery process starting from enabling the use of molten pig iron.
The proposed innovation is to achieve a high recycling rate of these residues (>80%) with a metal recovery efficiency greater than 90% and a mineral recovery efficiency greater than 90%, contributing to the achievement of the European Green Deal goals, with reference to circular economy and reduction of CO2 emissions. The outstanding performances of the proposed solution will be demonstrated through the implementation of the achieved advances at industrial test scale.
The proposed innovation is to achieve a high recycling rate of these residues (>80%) with a metal recovery efficiency greater than 90% and a mineral recovery efficiency greater than 90%, contributing to the achievement of the European Green Deal goals, with reference to circular economy and reduction of CO2 emissions. The outstanding performances of the proposed solution will be demonstrated through the implementation of the achieved advances at industrial test scale.
During the first reporting period all the activities foreseen and planned as part of WP2 "Residue classification and use cases requirements" and WP3 "ReMFra process and plant design"
In particular, within WP2, the possible clusters of residues streams based on chemical and physical characteristics were identified, considering possibility to maximize the recovery of metal fraction. For each cluster the most suitable treatment and valorisation technology between Plasma and RecoDust, was indicated.
Following the classification of the residues the mass and energy balance for the Plasma reactor were developed based on the following assumptions:
The distribution of the different chemical species between metal bath, slag and dust has been defined on the basis of literature data and previous experimental activities and industrial tests
The metal bath shall have the 3% of carbon content. The coal used for reduction has 10% of ash content
Different recipes were investigated and the mass and energy balance were calculated based on the developed model of the Plasma Reactor.
The same approach was applied to the RecoDust process under the following assumptions/process requirements:
Before used in the demo plant, the input materials need to be dried (moisture <0.5%) and sieved (the grain size limit for the installed transport system is 400 μm).
The solid residues are injected pneumatically into the Flash-Reactor.
The system consists of the storage tank, the feeders for natural gas and nitrogen, the exhaust air, and the pneumatic conveying line to the burner.
The maximum grain size depends on the grain size distribution as tests with each feedstock provide crucial information on the pneumatic conveying ability.
For the RecoDust process, the RecoDust slag (RDS) must be liquid at the operating temperature. The Flash-Reactor's temperature is limited to 1800°C by the refractory material (Al2O3 and Cr2O3), so the RDS melting point should be below 1550°C.
The RecoDust pilot plant is designed for the use of BOFD with a ZnO content of 16.4 wt.-% and an iron content of 43.6 wt.%.
Disruptive substances, like Sulphur, must be limited since the RecoDust pilot plant is not designed for it.
Finally, for the RecoDust process the following operational parameters were developed:
The heat balance considers the heat of the under stoichiometric combustion, the chemical reactions and the heat losses of the Flash-Reactor.
The air excess ratio of the burner is between 0.7 and 0.9. In this area the process heat is provided as well as the required amount of reducing agents namely carbon monoxide and hydrogen.
The quantity of reducing agents CO and H2 must be matched with the quantity of ZnO of the feedstock.
In summary, there are opposing effects about dezincification and specific energy consumption:
Higher air excess ratios result in lower specific energy consumption.
The higher the zinc content in the feedstock, the lower the air excess ratio must be for a sufficient dezincification.
As part of the WP3 the main achievement consisted in:
For the Plasma Reactor - The Key findings of the deliverables are the optimal binder composition and mechanical characteristics for storage and handling were identified, thermogravimetric tests provided insights into the reduction kinetics and exothermic effects of the briquettes, IBLU polymer exhibited a lower reducing capacity compared to anthracite, the mechanical properties of the briquettes were adequate for storage and handling, the efficiency of the IBLU polymer as a reducing agent was lower compared to anthracite needed optimization of the briquette recipes.
We successfully developed and tested briquette recipes for the pre-treatment process in the Plasma demo. The results highlighted the potential and limitations of using IBLU polymer as a substitute for anthracite, with further optimization needed to enhance metal yield and carburization. The findings from this task provide a solid foundation for the subsequent tasks in the ReMFra project, contributing to the overall goal of improving the efficiency and sustainability of steel-plant residue processing.
For the RecoDust, K1-MET investigated four different feedstocks, which were (i) fine BOF dust from vaS, (ii) EAF Dust from Tenaris, (iii) BOF dust from thyssenkrupp Steel Europe (tkSE), and (iv) microgranules (particle size 1.1mm) from Tata Steel. Sieving and drying were done to quantify the pre-processing efforts to assure sufficient quality (dry, free-floating, grain size ~400µm) for the RecoDust process. Subsequently, heating microscope tests were done.
Finally the final result of WP3 was the design of the flash reactor for the RecoDust plant adapted pneumatic dust conveying system using natural gas as fuel, the design of the flash reactor to assure a high quality of the iron-rich product and of the Crude Zinc Oxide.
For the Plasma reactor the main WP3 achievement was the the basic and detailed design of the adaptation of the DALMINE’s Ladle Furnace to facilitate the smelting reduction of steel-plant residues in the Plasma Reactor.
In particular, within WP2, the possible clusters of residues streams based on chemical and physical characteristics were identified, considering possibility to maximize the recovery of metal fraction. For each cluster the most suitable treatment and valorisation technology between Plasma and RecoDust, was indicated.
Following the classification of the residues the mass and energy balance for the Plasma reactor were developed based on the following assumptions:
The distribution of the different chemical species between metal bath, slag and dust has been defined on the basis of literature data and previous experimental activities and industrial tests
The metal bath shall have the 3% of carbon content. The coal used for reduction has 10% of ash content
Different recipes were investigated and the mass and energy balance were calculated based on the developed model of the Plasma Reactor.
The same approach was applied to the RecoDust process under the following assumptions/process requirements:
Before used in the demo plant, the input materials need to be dried (moisture <0.5%) and sieved (the grain size limit for the installed transport system is 400 μm).
The solid residues are injected pneumatically into the Flash-Reactor.
The system consists of the storage tank, the feeders for natural gas and nitrogen, the exhaust air, and the pneumatic conveying line to the burner.
The maximum grain size depends on the grain size distribution as tests with each feedstock provide crucial information on the pneumatic conveying ability.
For the RecoDust process, the RecoDust slag (RDS) must be liquid at the operating temperature. The Flash-Reactor's temperature is limited to 1800°C by the refractory material (Al2O3 and Cr2O3), so the RDS melting point should be below 1550°C.
The RecoDust pilot plant is designed for the use of BOFD with a ZnO content of 16.4 wt.-% and an iron content of 43.6 wt.%.
Disruptive substances, like Sulphur, must be limited since the RecoDust pilot plant is not designed for it.
Finally, for the RecoDust process the following operational parameters were developed:
The heat balance considers the heat of the under stoichiometric combustion, the chemical reactions and the heat losses of the Flash-Reactor.
The air excess ratio of the burner is between 0.7 and 0.9. In this area the process heat is provided as well as the required amount of reducing agents namely carbon monoxide and hydrogen.
The quantity of reducing agents CO and H2 must be matched with the quantity of ZnO of the feedstock.
In summary, there are opposing effects about dezincification and specific energy consumption:
Higher air excess ratios result in lower specific energy consumption.
The higher the zinc content in the feedstock, the lower the air excess ratio must be for a sufficient dezincification.
As part of the WP3 the main achievement consisted in:
For the Plasma Reactor - The Key findings of the deliverables are the optimal binder composition and mechanical characteristics for storage and handling were identified, thermogravimetric tests provided insights into the reduction kinetics and exothermic effects of the briquettes, IBLU polymer exhibited a lower reducing capacity compared to anthracite, the mechanical properties of the briquettes were adequate for storage and handling, the efficiency of the IBLU polymer as a reducing agent was lower compared to anthracite needed optimization of the briquette recipes.
We successfully developed and tested briquette recipes for the pre-treatment process in the Plasma demo. The results highlighted the potential and limitations of using IBLU polymer as a substitute for anthracite, with further optimization needed to enhance metal yield and carburization. The findings from this task provide a solid foundation for the subsequent tasks in the ReMFra project, contributing to the overall goal of improving the efficiency and sustainability of steel-plant residue processing.
For the RecoDust, K1-MET investigated four different feedstocks, which were (i) fine BOF dust from vaS, (ii) EAF Dust from Tenaris, (iii) BOF dust from thyssenkrupp Steel Europe (tkSE), and (iv) microgranules (particle size 1.1mm) from Tata Steel. Sieving and drying were done to quantify the pre-processing efforts to assure sufficient quality (dry, free-floating, grain size ~400µm) for the RecoDust process. Subsequently, heating microscope tests were done.
Finally the final result of WP3 was the design of the flash reactor for the RecoDust plant adapted pneumatic dust conveying system using natural gas as fuel, the design of the flash reactor to assure a high quality of the iron-rich product and of the Crude Zinc Oxide.
For the Plasma reactor the main WP3 achievement was the the basic and detailed design of the adaptation of the DALMINE’s Ladle Furnace to facilitate the smelting reduction of steel-plant residues in the Plasma Reactor.
This topic will be developed in the next reporting periods