CO2 gasification of industrial cokes and characterization of cokes produced in laboratory

Abstract

Metallurgical coke is an important raw material for iron making in a blast furnace. Two significant criteria for selecting high quality coke are Coke Reactivity Index (CRI) and Coke Strength after Reaction with carbon dioxide (CSR). CSR and CRI tests are expensive, labor-intensive and time-consuming. Meanwhile, CSR has linear inverse relation with CRI. Hence, research for coke quality can be focused on coke reactivity with CO2, which depicts the CRI. Part of this study aims at analyzing coke gasification with carbon dioxide of industrially manufactured coke. Thermo-gravimetric analysis of cokes was conducted by heating the cokes to a certain temperature and soaking in CO2. Using non-isothermal methods, the kinetic parameters, such as activation energy and pre-exponential constant, were calculated during the heating period in CO2. Conversions during the soaking period were also obtained from TGA and were correlated with CRI of the cokes. Another part of study was concentrated on production of cokes in laboratory. Different bituminous, coking coals and a sub-bituminous coal were used for coal carbonization, which was conducted in a horizontal tube furnace by heating samples in an inert atmosphere at different heating rates. Samples were also produced by addition of two binders, asphaltene and ash free coal, in bituminous and sub-bituminous coal and the effect of the binders on the carbonization products were studied. In this study, the CO2 reactivity of the cokes was detected by using Thermo-Gravimetric Analysis (TGA); the samples were heated to 1100˚C in an inert atmosphere and soaked at 1100 ˚C in CO2 for two hours. Total porosity of the cokes was determined by using image stitching of thin sections in digital microscopy at 250X magnification, followed by image processing in MATLAB. Raman spectroscopy was carried out to observe the spectra radiated from the coke samples, which gave two distinct peaks, indicative of graphitic carbon and disoriented carbon; extent of graphitization was calculated using the area under the peaks.