Research of efficiency of lignite chemical modification and steam-gas activation combining for sorbents preparation*

The paper presents the results of research for sorbents preparation when combining the processes of chemical modification and steam-gas activation of lignite from the Kharanorsk deposit (Zabaikalsky Krai). The experimental studies were carried out by two ways of activation methods combination: parallel and successive exposure on feedstock. The lignite processed by chemical reagent (KOH) was exposed to steam during the whole period of thermolysis under the parallel action. Under successive exposure, the thermolysis was performed in two stages - first without steam supply, then with steam-gas activation. In the work the optimal parameters of the process of combining the chemical and steam-gas lignite activation methods were determined and the quality of the generated sorbents was studied. The efficiency of combined activation was estimated by comparing the sorption characteristics of the samples with the results obtained during chemical and steam-gas activation as autonomous processes and with the requirements to these characteristics of industrially produced active carbon grades. Combined activation of lignite allowed to increase the value of iodine adsorption activity in comparison with autonomous steam-gas activation by 1.8-2 times, chemical activation - by 2.7-10 %. The obtained values of iodine adsorption activity at combination of chemical modification and steam-gas activation exceed the value of 100 % (1000 mg/g) that meets the requirements to high quality industrially produced active carbons of SKT-0 grade.