Investigations on the chemical looping with oxygen uncoupling process using Indian coal and copper oxide oxygen carrier

Abstract

In this study, the effectiveness of CuO as an oxygen carrier (OC) in chemical looping with oxygen uncoupling (CLOU) process was investigated using three Indian coals with varying origin and nature. The thermogravimetric analysis (TGA) experiments were performed with coal to OC mass-ratio of 1:20, 1:30, and 1:40 at varying temperatures of 800, 850, 900, 950 °C. The mass loss profiles of coal/CuO indicated that the CLOU combustion reaction was the most suitable with a mass ratio of 1:30 and at 850 °C. Multicyclic combustion-reoxidation performance (for 45 h) also showed sufficiently good repeatability with minor agglomeration. Besides, the kinetic triplet, such as apparent activation energy (Ea), pre-exponential factor (A), and kinetic model function, g(x), were estimated for reactions in the pyrolysis and combustion zones applying the Coats and Redfern model on the TGA mass loss data. From mathematical model fitting, it was found that the three-dimensional Jander-diffusion model provides an excellent fit to the experimental data for the selected temperature zones, and the combustion reaction kinetics is likely to be a diffusion dominated process. The estimated apparent activation energies for three coals studied in this work were in the range of 38.3–60.1 kJ/mol and 102.6–129.0 kJ/mol in the temperature zone of 400–600 °C and 600–950 °C, respectively. The findings of the present study suggest first-time that the Indian coal-based CLOU process using CuO OC is promising, and the derived kinetic information will be useful for CLOU reactor design using Indian coal and CuO OC.