Preparation of amorphous coal-based activated coke via a two-step process of carbonization and steam activation

Abstract

The coal-based activated coke (AC) is suitable for desulfurization and denitrification in coal-fired power plants. However, the current studies on millimeter-sized amorphous AC are limited. To evaluate the preparation parameters of millimeter-sized amorphous AC, two typical middle-low rank coal samples, Fugu coal and Datong coal, are selected as the raw materials. The effects of carbonization/activation parameter, particle size and steam flow rate on the yield and pore structure of AC are studied. Samples are analyzed by the synchronous thermal analyzer and the fully automatic rapid specific surface and porosity analyzer. The results show that carbonization and the long-time steam activation at a low temperature can make the internal pores of samples fully developed, significantly increasing the specific surface area and pore volume. The coke yield, specific surface area and mesoporous proportion of Fugu AC obtained by activation at 700 °C for 3 h are 60.95 %, 429.54 m2/g and 29.60 %, respectively. The corresponding values of Datong AC obtained at 850 °C for 3 h are 53.19 %, 892.20 m2/g and 23.01 %, separately. Both of Fugu AC and Datong AC belong to the hierarchical porous AC. The influence of particle sizes on the performance of AC at the millimeter level is within the acceptable range. Therefore, the same carbonization and activation parameters can be chosen to prepare Fugu AC and Datong AC with different particle sizes, respectively. The water vapor flow rate has a significant effect on the pore structure of AC. There is a moderate flow rate (0.03 mL min−1 at this study’s experimental conditions) for preparing the hierarchical porous amorphous AC. The study shows that it is feasible to prepare the amorphous AC with the hierarchical pore structure by employing the millimeter-sized medium–low rank coal particles. The AC could be applied for the pollutants removal in the coal-fired power plants.