ABSTRACT

Several studies have been conducted to decrease the cost of sorbents used for the control of mercury emissions. Thus far, several sorbents with low surface areas have been reported to exhibit promising mercury removal capacities. However, based on the results reported, it is difficult to understand the mechanisms of adsorption and oxidization of elemental mercury on sorbents with low surface areas compared to those with higher surface areas. Three types of materials with different surface areas were evaluated herein for use as carbon sorbents for the adsorption of elemental mercury: (1) coal, (2) sewage sludge, and (3) unburned carbon. The respective raw sorbents and FeCl₃-impreganted congeners were evaluated. Each sorbent was tested in a fixed-bed reactor system under two simulated flue gas conditions (1) without and (2) with 20 ppm hydrogen chloride (HCl). The injection of HCl increased the mercury adsorption efficiency of all tested sorbents by decreasing the emission of elemental mercury. Doping the sorbent with FeCl₃ increased the mercury adsorption efficiency during the earlier test period under both simulated flue gas conditions (without and with HCl). FeCl₃-impregnated activated carbon and FeCl₃-impregnated unburned carbon emitted large amounts of oxidized mercury during the later test periods.

Implications: We tested three types of sorbents to investigate the mercury adsorption characteristics of sorbents with low surface area. The mercury adsorption test was conducted by varying the raw material of the sorbent, chemical impregnation of the sorbent and the simulated flue gas composition. We found that HCl in simulated flue gas increased the mercury adsorption efficiency of both the raw and FeCl₃-impregnated sorbents by decreasing the emission of elemental mercury.

摘要

已经进行了几项研究以降低用于控制汞排放的吸附剂的成本。迄今为止，已经报道了几种具有低表面积的吸附剂表现出有希望的汞去除能力。然而，根据报告的结果，与具有较高表面积的吸附剂相比，难以理解具有低表面积的吸附剂对元素汞的吸附和氧化机制。本文评估了三种具有不同表面积的材料用作吸附元素汞的碳吸附剂：(1) 煤，(2) 污水污泥，和 (3) 未燃烧的碳。各自的原始吸附剂和 FeCl ₃- 对浸渍的同类物进行了评估。每种吸附剂在固定床反应器系统中在两种模拟烟道气条件 (1) 没有和 (2) 有 20 ppm 氯化氢 (HCl) 下进行测试。HCl 的注入通过减少元素汞的排放来提高所有测试吸附剂的汞吸附效率。在早期测试期间，在两种模拟烟道气条件下（没有和有 HCl），用 FeCl ₃掺杂吸附剂提高了汞吸附效率。FeCl ₃浸渍活性炭和FeCl ₃浸渍未燃烧碳在后期测试期间排放大量氧化汞。

启示：我们测试了三种类型的吸附剂，以研究低表面积吸附剂的汞吸附特性。通过改变吸附剂的原料、吸附剂的化学浸渍和模拟烟气成分来进行汞吸附试验。我们发现模拟烟道气中的 HCl通过减少元素汞的排放来提高原始吸附剂和 FeCl ₃浸渍吸附剂的汞吸附效率。