PAH mixture removal from hot gas by porous carbons.: From model compounds to real conditions

This paper reports an investigation of the abatement of polycyclic aromatic hydrocarbon (PAH) emissions using different carbonaceous materials as adsorbents. PAH model compounds (naphthalene and phenanthrene) were initially used to obtain a deeper understanding of the complex process of PAH adsorption in industrial hot gas cleaning systems. First, the adsorption of binary mixtures of these compounds was carried out at the laboratory scale in an experimental rig specially designed for this purpose, where gas-phase fluorescence is used for detection. Experimental conditions, mainly in terms of temperature and contaminant concentration, close to those observed in flue gases from energy generation systems were applied. The PAH adsorption process was analyzed in terms of experimentally obtained breakthrough curves. After the detection parameters had been optimized, the influence of the structural and chemical properties of the activated carbon was studied. It was found that the higher the adsorbent porosity, the higher the breakthrough time of both PAHs, with the microporosity and the micropore size distribution being the main factors controlling the adsorption process. Moreover, several naphthalene/phenanthrene binary mixtures were studied to assess the effect of the inlet concentration on PAH adsorption. It was observed that the presence of a second PAH in the inlet gas stream reduces the adsorbent efficiency and that, in general, the higher the naphthalene concentration, the lower the adsorbent efficiency. Finally, the conclusions obtained from model compounds were checked under real conditions.