高温热解过程中新疆高碱煤中钙的演变

以新疆准东地区高碱煤(五彩湾煤和天池能源煤)为实验煤种,通过萃取法研究煤中钙的存在形式及其在热解过程中的演变规律。研究表明,本实验中两种高碱煤中钙主要为醋酸铵溶钙和盐酸溶钙,其中天池能源煤含有较多的水溶钙。1 500℃热解后天池能源煤焦炭中水溶钙的含量明显较高,主要是因为天池能源煤中本身存在一定量的硫化钙,在高温热解的过程中保存在焦炭中;五彩湾煤焦炭中的醋酸铵溶钙含量高于其它煤种,主要是因为五彩湾煤中硅铝的含量较少导致部分钙仍以氧化钙的形式存在于焦炭中。高温热解过程中,煤焦中钙均以较为稳定的形式存在,随着热解温度的上升,焦炭中钙的含量呈上升趋势。1 200℃时焦炭中的钙主要以硬石膏和氧化钙等醋酸铵溶钙为主;1 200~1 400℃硫酸钙分解,导致水溶钙小幅上升,但整体依然以醋酸铵溶钙为主,此时的醋酸铵溶钙主要以氧化钙形式存在;1 400~1 500℃氧化钙与硅、铝等物质反应使醋酸铵溶钙转化为盐酸溶钙。

Calcium transformation during the high-temperature pyrolysis process of high-alkali coal from Xinjiang

The existence forms of calcium contained in the high-alkali coal from Xinjiang，China and the calcium transformation during the high-temperature pyrolysis process were investigated using extraction method.The results show that the calcium contained in high-alkali coal mainly exists in the form of ammonium acetate soluble calcium and hydrochloric soluble calcium，while there is some water soluble calcium contained in Tianchi Energy coal.The water soluble calcium in Tianchi Energy coke prepared at 1 500 ℃ is apparently high because CaS contains in Tianchi energy coal and CaS is still left in the coke.The ammonium acetate soluble calcium in Wucaiwan coke prepared at 1 500 ℃ is apparently higher than that in the cokes from other coals because the content of silicon and aluminum in Wucaiwan coal is low and a part of CaO is still left in the coke.With the increase of pyrolysis temperature，the calcium content of the resulted coke increase.The calcium contained in the coke prepared at 1 200 ℃ mainly exists in the form of ammonium acetate soluble calcium species including anhydrite and quicklime and others.In the case of the coke prepared under the temperature range of 1 200-1 400 ℃，the contained anhydrite decomposition leads to a slightly increase of water soluble calcium，however，the calcium still mainly exists in the form of ammonium acetate soluble calcium as CaO.When the pyrolysis temperature increases from 1 400 ℃ to 1 500 ℃，the chemical reaction between CaO and silicon and aluminum makes ammonium acetate soluble calcium be transformed into hydrochloric soluble calcium.