STEAM-ACTIVATED CARBONS FROM A BITUMINOUS COAL IN A CONTINUOUS MULTISTAGE FLUIDIZED-BED PILOT-PLANT

A vertical three-stage fluidized bed pilot plant, with downcomers, was designed and built in order to study the continuous process of the pr oduction of activated carbons from a high-volatile bituminous coal fro m the Puertollano basin (Spain), by steam activation. The pilot plant can operate with a production of up to 40 kg per day. Very good activa ted carbons were produced at the selected operating conditions. The ef fect of the following operating conditions on the reactivity and adsor ption characteristics of the activated carbons was analyzed: (1) carbo nization conditions (one- and two-step activation), (2) activation tem perature (800-850 degrees C), and (3) steam gas velocity (1.5-3 times the minimum fluidization velocity). Carbonization conditions considera bly affect the reactivity of the chars obtained; the faster the carbon ization process, the higher the reactivity. Nevertheless, the effect o f this variable on the development of porosity is not very relevant, a nd consequently the direct activation process is an attractive alterna tive to the two-step (carbonization and activation) process. On the ot her hand, both temperature and steam flow rate (affecting the reaction rate) have a marked effect on the development of porosity. Copyright (C) 1996 Elsevier Science Ltd