Abstract
This study investigated the isothermal gasification reactivity of biomass char (BC) and coal char (CC) blended at mass ratios of 1:3, 1:1, and 3:1 via isothermal thermogravimetric analysis (TGA) at 900, 950, and 1000°C under CO2. With an increase in BC blending ratio, there were an increase in gasification rate and a shortening of gasification time. This could be attributed to the high specific surface area of BC and the high uniformity of carbon structures in CC when compared to those in BC. Three representative gas-solid kinetic models, namely, the volumetric model (VM), grain model (GM), and random pore model (RPM), were applied to describe the reaction behavior of the char. Among them, the RPM model was considered the best model to describe the reactivity of the char gasification reaction. The activation energy of BC and CC isothermal gasification as determined using the RPM model was found to be 126.7 kJ/mol and 210.2 kJ/mol, respectively. The activation energy was minimum (123.1 kJ/mol) for the BC blending ratio of 75%. Synergistic effect manifested at all mass ratios of the blended char, which increased with the gasification temperature.
Highlights
Gas-based shaft furnace direct reduction technology has developed rapidly worldwide owing to its unique advantages, including quicker reduction, flexible product quality, highly automatic, low energy consumption, and low environmental impact [1]
The scanning electron microscope (SEM) images of biomass char (BC) and coal char (CC) presented in Fig. 1 indicate that the BC particles have a loose lamellar structure with thin walls, which is probably the broken honeycomb structure after the loss of substantial volatiles in biomass
The specific surface area of BC is 73.2 m2/g, while that of the CC char is much lower (7.07 m2/g). This results in the lower reactivity of CC compared to that of the BC, which is in accordance with the study reported by Yuan et al [8,18] that the specific surface area has a great influence on the gasification reactivity
Summary
In order to develop the kinetic model of char gasification, the gasification reaction rate (r) was considered by the following rate equation [17]:. Three models were implemented to interpret the experimental results, namely, VM, GM, and RPM, as they have a theoretical basis and involve fewer parameters. These models give different formulations of the term f (X). The RPM considers the overlapping of pore surfaces, which results in the reduction of surface area available for the reaction [16]. The RPM contains two parameters, ψ , which is related to the initial pore structure of the char sample (X = 0) and the reaction rate constant, k. Where dX d t exp,i is the experimental data, dX d t model,i is the value calculated by the model, and n is the number of data points
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: International Journal of Minerals, Metallurgy, and Materials
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
