Effect of high temperature on reduction-controlling reaction rate of agricultural waste chars and coke with steelmaking slag

Abstract

Agricultural wastes generated from palm and coconut shells could be renewable carbon sources in steelmaking by providing the solution to environmental problems and reducing the gas emission. By applying these wastes as carbon reductant at steelmaking’s temperature, the determination of the reduction-controlling reaction rate is necessary. Thus, the present study aims to provide an understanding of the effect of high temperature (1823 K) on the reduction-controlling reaction rate of palm and coconut chars that reacted with steelmaking slag. Palm and coconut shells were pyrolyzed at 723 K under nitrogen inert for char conversion. The char has a porous structure and contains high volatile matter that is more chemically active in the system reaction compared to coke. All carbonaceous materials including coke as a control carbon mixed with steelmaking slag using an infrared (IR) gas analyzer to measure the amounts of carbon dioxide (CO2) and carbon monoxide (CO) gases produced after reduction. The reaction rate of palm and coconut chars after reaction with steelmaking slag was lower (0.93721 × 10−5 and 0.30563 × 10−5 mol cm−2 s−1) than that of coke (2.16283 × 10−5 mol cm−2 s−1) due to lower fixed carbon content that retards the reaction rate. The reaction using palm and coconut chars approached faster the equilibrium of the carbon solution-loss reaction (C + CO2 → 2CO) and Boudouard equilibrium where the reaction reached the equilibrium value of 1.0 than coke due to higher CO generation. The results found that agricultural waste char is used as a carbon reductant in iron oxide reduction of steelmaking slag in a cleaner and sustainable production of iron due to their better properties such as volatile matter and porous structure.