Study on Modes of Occurrence of Mercury in Coals and Mercury Removal during Coal Preparation

摘要

Coal-combustion has become the most main source of mercury in atmosphere. For reducing pollution from the orign, the modes of occurrence of mercury of raw coal for four coal preparation plants (Tianzhuang, Laoshidan, Tuenlan, Tangshankuang) was investigated using float sink test and sequential chemical extraction Procedures(exchangeable (Hg), bound-sulfide (Hg), bound-organic (Hg) and residue (Hg)). The experimental results show that mercury in coal mainly occurs in bound-sulfide (77-97%), secondly is residue (2-20%), thirdly is exchangeable and bound-organic (less than 1.5%) in Tianzhuang, Laoshidan, Tuenlan. After coal preparation, the mercury content is removed in clean coal in varying degrees and about 65% can reduced; in Tangshankuang, that mercury in coal still mainly occurs in bound-sulfide(about 67%), most of which immerged in coal with micron or nanometer level grain., and bound organic is also relative higher (about 6%). After coal preparation, the mercury content is enriched in clean coal and only 20% can be removed by discharging gangue. In conclusion, the migration behavior and the removal effect of mercury during coal preparation process is different because of not only the existing form of mercury but also pyrite in coal