Computational Analysis of The Performance of Shaft Furnaces with Partial Replacement of The Burden with Self-Reducing Pellets Containing Biomass

Elisa Pinto Da Rocha,José Adilson De Castro,Leonardo Silva,Rayla De Souza Caldas

doi:10.1590/1980-5373-mr-2019-0533

Elisa Pinto Da Rocha, José Adilson De Castro + Show 2 more

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https://doi.org/10.1590/1980-5373-mr-2019-0533

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Abstract

The shaft furnace knowed Midrex™ is used for the production of direct reduced iron with the use of reformed gas. Another process based on shaft reactors is the Tecnored process, which exhibits the great advantage of using self-reducing agglomerates. Therefore, it was proposed a combination of the shaft furnace for direct reduction with self-reducing pellet burden. In addition, with the aim of improving the furnace efficiency and reducing the need for reformed gas, the injection of natural gas and oxygen into the bustle region is proposed. Thus, it is possible exploit the advantages of direct reduction involving high amounts of hydrogen and faster reactions of the self-reducing process to decrease the CO2 emission, compared to that of blast furnace. The energy profile, productivity, and carbon emission of the traditional shaft furnace were compared with the simulated results after partial replacement of the burden with self-reducing pellets containing fines of elephant grass charcoal. The simulation results for a combination of 15% of self-reducing pellets in the burden with 2.5% oxygen and natural gas injection were the best among the scenarios simulated, with the productivity being 2.7 ton/m3 day and the decrease in the amount of reformed gas being 10%.

Highlights

The shaft furnace used in direct reduction processes has some advantages, such as lower energy demand due the absence of metal melting, the use of different sources of reducing agents, the use of reformed gas as a reducing agent in the fuel option, and the produced sponge iron exhibiting a lower carbon concentration when compared with that of pig iron, which can demand less refining operations
The shaft furnace is a continuous flow reactor that is charged with iron ore pellets and lump iron ores that descend by gravity while they are reduced to iron by the reducing gas in counter-current flow
Previous investigations of the behavior of the shaft furnace charged with pellets and using reformed reducing gas were performed by using computational simulations, and the results suggested the possibility of reaching around 93% of the metallization degree . 8-10 a large amount of reducing gas is required, and hydrogen reduction is efficient only at high temperatures

Summary

Introduction

The shaft furnace used in direct reduction processes has some advantages, such as lower energy demand due the absence of metal melting, the use of different sources of reducing agents, the use of reformed gas as a reducing agent in the fuel option, and the produced sponge iron exhibiting a lower carbon concentration when compared with that of pig iron, which can demand less refining operations. It was proposed rate equations that represent the new raw material used in the model, based on previous experimental studies 18 and for DRI pellets with composition considered in previous works [10, 11, 19] It was developed simulation scenarios based on a reference case involving actual operation and those based on partial substitution of the charge with SRP (self reduced pellet)

Materials and Methods

Calculation

Results and Discussion

Conclusion