煤和煤矸石及其燃烧产物中稀土元素赋存形态研究

Occurrence forms of rare earth elements in coal and coal gangue and their combustion products

针对中国三个典型电厂的煤和煤矸石及其燃烧产物(渣和飞灰),采用逐级提取-电感耦合等离子体质谱法测定各级提取物的稀土元素浓度,进而研究煤和煤矸石及其燃烧产物中稀土元素的赋存规律。结果表明,煤和煤矸石中,稀土元素主要以酸溶态、硅酸盐&铝硅酸盐态赋存,煤矸石中分别占42.54%和45.62%,褐煤中分别占32.85%和57.13%,烟煤中分别占18.10%和75.46%;而煤和煤矸石燃烧产物中,稀土元素主要赋存在硅酸盐&铝硅酸盐态中,占稀土元素总量的80%左右;燃烧过程中,煤矸石、褐煤和烟煤中其他各形态(水溶态、离子交换态、酸溶态、硫化物结合态和有机物结合态)稀土元素分别有36%、23%和5%转变到燃烧产物中的硅酸盐&铝硅酸盐态。同一赋存形态中,各稀土元素在不同原料中的占比不同,但稀土元素从La到Lu,在不同原料中的变化特性相同;渣和飞灰中,因飞灰在烟气中暴露时间更长,导致同一赋存形态中,稀土元素从La到Lu,在渣和飞灰中的变化特性不同。

Distribution of rare earth elements(REEs)in six speciations extracted from coal and coal gangue and their combustion products(slag and fly ash)generated by three different power plants in China were determined by sequential extraction procedure combined with inductively coupled plasma mass spectrometry method.The results show that the REEs mainly occurred as acid soluble and silicate&aluminosilicate fraction,e.g.,approximately 42.54%and 45.62%in coal gangue,32.85%and 57.13%in lignite,and 18.10%and 75.46%in bituminous coal,respectively.However,REEs in the combustion products were mainly presented in silicate&aluminosilicate fraction regardless of coal or coal gangue,reaching up to approximately 80%of the total REEs content.During combustion,around 36%,23%,and 5%from the other five fractions(water soluble,ion-exchangeable,acid soluble,organic,and sulfide)were transformed to silicate&aluminosilicate fraction from coal gangue,lignite,and bituminous coal,respectively.In the case of coal or coal gangue,the amount of each REEs in the same extracted fraction was different,but the distribution trend of REEs from La to Lu in each fraction was followed in the same rule.In the case of slag and fly ash generated from coal or coal gangue,distribution of REEs from La to Lu in each fraction showed the different trend between fly ash and slag.This was due to the fly ash exposed in flue gas system was much longer than the time for slag formation.