Devolatilization Kinetics of Different Types of Bio-Coals Using Thermogravimetric Analysis

Asmaa A El-Tawil,Lena Sundqvist Ökvist,Bo Björkman,Hesham M Ahmed

doi:10.3390/met9020168

Asmaa A El-Tawil, Lena Sundqvist Ökvist + Show 2 more

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https://doi.org/10.3390/met9020168

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Abstract

The interest of the steel industry in utilizing bio-coal (pre-treated biomass) as CO2-neutral carbon in iron-making is increasing due to the need to reduce fossil CO2 emission. In order to select a suitable bio-coal to be contained in agglomerates with iron oxide, the current study aims at investigating the thermal devolatilization of different bio-coals. A thermogravimetric analyzer (TGA) equipped with a quadrupole mass spectrometer (QMS) was used to monitor the weight loss and off-gases during non-isothermal tests with bio-coals having different contents of volatile matter. The samples were heated in an inert atmosphere to 1200 °C at three different heating rates: 5, 10, and 15 °C/min. H2, CO, and hydrocarbons that may contribute to the reduction of iron oxide if contained in the self-reducing composite were detected by QMS. To explore the devolatilization behavior for different materials, the thermogravimetric data were evaluated by using the Kissinger– Akahira–Sonuse (KAS) iso-conversional model. The activation energy was determined as a function of the conversion degree. Bio-coals with both low and high volatile content could produce reducing gases that can contribute to the reduction of iron oxide in bio-agglomerates and hot metal quality in the sustained blast furnace process. However, bio-coals containing significant amounts of CaO and K2O enhanced the devolatilization and released the volatiles at lower temperature.

Highlights

IntroductionThe blast furnace (BF) is the most widely used technology for producing hot metal for steelmaking
The blast furnace (BF) is the most widely used technology for producing hot metal for steelmaking.In the BF, iron oxide is reduced to metallic iron by fossil carbon resources
Bio-coal volatile content will release volatiles a comparatively high temperature, Bio-coalwith witha low a low volatile content will the release the at volatiles at a comparatively high ensuring that the generated reducing gases can contribute to the reduction in the agglomerates temperature, ensuring that the generated reducing gases can contribute to the reduction inwith the iron oxide

Summary

Introduction

The blast furnace (BF) is the most widely used technology for producing hot metal for steelmaking. In the BF, iron oxide is reduced to metallic iron by fossil carbon resources (coke, coal, oil, natural gas, etc.). The reducing conditions in the furnace are created by top-charged (coke) and tuyere-injected (pulverized coal, oil, etc.) reducing agents [1]. The total consumption of coke is about 300 kg/t hot metal [1,2] depending on the amount of auxiliary reducing agents [3]. The steel industry aims to reduce coke consumption and minimize CO2 emissions by improving the energy efficiency of the process and by investigating the use of carbon-neutral materials such as bio-coal (pre-treated biomass) to substitute part of the fossil sources. CO2 emitted for every ton of steel produced was on average

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