LOW-COST ADSORBENTS FOR LOW-TEMPERATURE CLEANING OF FLUE-GASES

The adsorption capacity with regard to SO2 of chars prepared from a lo w-grade coal has been evaluated at typical conditions of flue gas (pre sence of oxygen and water vapour and linear gas velocity of 0.12 m s(- 1)) at an inlet concentration of 2 g SO2 m(-3). The flue gases have be en simulated, varying the water vapour and oxygen contents as well as the adsorption temperature which was varied between 80 degrees C and 1 50 degrees C. The study has focused on the influence of several proces s variables as well as the intrinsic features of the chars, such as th eir porous texture, on the SO2 adsorption capacity of the chars. Under the conditions studied, the positive effect of water vapour in the ab sence of oxygen has been observed. This effect can be explained by the intervention of oxygen functionalities in chars. Here two effects ove rlap: the oxygen present in chars and their surface chemistry as well as the porous structure available. Temperature is also an important pa rameter in the SO2 adsorption efficiency. A minimum surface area is re quired for the temperature effect to be observed; otherwise the cataly tic oxidation of SO2 to SO3 and subsequent storage of H2SO4 takes plac e to a very small extent and the negative effect of temperature increa se to 150 degrees C is not appreciable. (C) 1998 Elsevier Science Ltd. All rights reserved.