Mercury Release during Thermal Treatment of Two Coal Gangues and Two Coal Slimes under N₂ and in Air

Abstract

The mercury release from coal gangue and coal slime has attracted wide interest, because of the utilization of coal gangue and coal slime in some power plants. In order to develop the Hg control technology, it is necessary to gain the information on the Hg release during thermal treatment of coal gangue and coal slime. This paper presents a study about Hg release during thermal treatment of two coal gangues and coal slimes under air and N2 atmosphere through the online atomic fluorescence spectroscopy aided with the Ontario Hydro Method. The result shows that the release profiles of Hg for the two coal gangues and two coal slimes are similar under the same atmosphere, respectively. Most of the Hg is released at <650 °C under a N2 atmosphere and at<500–550 °C under air for all of the samples. The release ratio of Hg2+ is much lower than that of Hg0 for each sample. The release ratio of Hg0 released under N2 is more than that under air. Because of the high volatility of Hg, the release ratio of total Hg is much higher than the corresponding volatile yield in any case investigated in this study. Meanwhile, the Hg0 release profiles for the samples show two or three peaks under N2 atmosphere, suggesting that different modes of occurrence of mercury are presented in the coal gangues and coal slimes.

Preparation of Poly Aluminum-Ferric Chloride (PAFC) Coagulant by Extracting Aluminum and Iron Ions from High Iron Content Coal Gangue

“…During high temperature calcination, the crystalline structure of kaolinite is destroyed [ 38 ] and the following reactions occur: Al 2 Si 2 O 5 (OH) 4 (kaolinite) → Al 2 O 3 ·2SiO 2 (metakaolin) + 2H 2 O ↑ …”

Effect of the Coal Preparation Process on Mercury Flows and Emissions in Coal Combustion Systems

“…Therefore, technologies such as the adsorption method and dust shuttling can be applied in cement kiln coprocessing plants in priority to improve their Hg control effect . Plants can also reduce the Hg burden in the wastes through technologies such as waste thermal treatment to reduce their Hg input burden . Currently, the required maximum value of Hg input to waste codisposal cement kiln is 0.23 mg Hg/kg cement clinker produced .…”

“…The higher Hg content of coal gangue and the lower synergic Hg removal efficiency of APCDs in coal gangue-fired power plants jointly resulted in this phenomenon. Therefore, additional Hg removal in coal gangue-fired power plants may require the use of special Hg removal technologies (e.g., adsorption method) or source alternative technologies (e.g., thermal pretreatment), which are without wide application in China currently . Compared to different emission statuses between coal-fired power plants and coal gangue-fired power plants, these two types of power plants have been following the same emission limit of 30 μg/Nm 3 in China over the past decade .…”

Preparation of NaA Zeolite from High Iron and Quartz Contents Coal Gangue by Acid Leaching—Alkali Melting Activation and Hydrothermal Synthesis

“…Coal gangue is the main discharged waste of the coal industry [1,2]. The arbitrary stacking of it seriously influences the safety of the ecological environment [3,4].…”