| Popis: |
Based on the concept of industrial ecology, this study investigated the interaction between hydrogen sulfide and carbonaceous surfaces, and the application of the resulting sulfur impregnated material for vapor phase mercury control. A fixed bed reactor system was used to study adsorption and oxidation of hydrogen sulfide and mercury uptake by carbonaceous materials. The carbon surface chemistry was characterized using state of the art techniques before and after sulfur impregnation. Adsorption of hydrogen sulfide onto carbonaceous surfaces at low temperatures and under dry and anoxic conditions included both reversible and irreversible components. Reversible adsorption was affected mainly by pore structure and pore filling is likely the dominating mechanism. On the other hand, hydrogen sulfide retention (or irreversible adsorption) was affected by surface chemistry. Retention of hydrogen sulfide occurred through strong and possibly dissociative surface interactions. The retained amount of hydrogen sulfide increased with an increase in the surface area. The retained amount of H2S correlates well with the density of basic surface groups, especially those derived from basic oxygen containing surface groups. Therefore, hydrogen sulfide retention was enhanced by surface treatments, such as heat treatment and ammonia treatment. Sulfurization at temperatures between 200-800 ¢ªC resulted in high sulfur content and very stable sulfur forms such as organic sulfur. Higher temperatures also led to more uniform sulfur distribution inside the sorbent pores. Uptake of hydrogen sulfide under these conditions occurs as a result of substitution of the surface oxygen or active carbon atoms. The most effective mercury sorbents were produced by the reaction between H2S and carbonaceous surface at 600 ¡ÆC. The presence of H2S during the cooling process increased the amount of relatively unstable species like elemental sulfur, and sorbents produced under these conditions also showed effective mercury uptake. It was found that sulfur forms are important parameters affecting mercury uptake; the amounts of elemental sulfur, thiophene, and sulfate showed good correlation with mercury uptake capacity, with active elemental sulfur species being the most effective. |
