The temperature effect and system equilibrium of preparing powdered activated coke sorbent in a rapid carbonization-activation two-step process

Abstract

ABSTRACT In this study, a rapid carbonization-activation two-step process for preparing powdered activated coke (PAC) sorbent is proposed. Shengli lignite is utilized as the feedstock to prepare PACs through this process, employing various combinations of carbonization and activation temperatures. The pore structure, surface functional groups, yield and SO2 adsorption properties of the PACs are comprehensively analyzed. Additionally, Aspen Plus software is employed to calculate the system equilibrium of this process. Results demonstrate that the performance of the prepared PAC is predominantly influenced by the activation temperature. Despite variations in carbonization temperature, consistent performance and yield are achieved as long as the activation temperature remains constant. Through the experimental design, the optimum combination of carbonization temperature and activation temperature of the two-step process is optimized, that is, the carbonization temperature is 750°C, and the activation temperature is 950°C. The SBET of the PAC prepared under optimal condition is 550 m2/g, and its SO2 adsorption capacity is 116.58 mg/g, which are both higher than that of the other ACs. The system equilibrium indicates that the optimal parameters for PAC preparation can be achieved by employing a water and air spray technique between the combustion zone and activation zone, with a water spray rate of 1.70 (kg/kg coal for combustion) and an air spray rate of 2.75 (kg/kg coal for combustion). In addition, the maintenance of system equilibrium necessitates the combustion of a certain amount of gas to elevate the temperature through the injection of a specific quantity of air into the carbonization step, with an air spray rate set at 11.00 (kg/kg coal for combustion).