燃煤过程中水蒸气对砷释放特性的影响

为了研究水蒸气对煤燃烧过程中砷释放特性的影响,在800~1 300℃下对庆华煤进行燃烧试验,并结合XRD分析了水蒸气对砷释放的作用机理。气氛中有水蒸气时,可以明显加快煤的失重;相同温度下,气氛中存在水蒸气时,煤中砷的逃逸有一定的增加,随着水蒸气浓度的增加,逃逸率增加趋势放缓;随着温度的增加,水蒸气对砷的逃逸率的提升效果减弱。在水蒸气气氛下灰的矿物质组成结构发生变化,石膏等硫酸盐增多,主要是水蒸气促进了石膏的形成,缩减了高活性CaO的停留时间,抑制了CaO对砷的捕捉,造成砷吸附率降低,逃逸率增加。

Effect of steam on arsenic volatile characteristics during coal combustion

The combustion experiments of Qinghua coal were conducted on a customized isothemal thermogravimetric to study the effect of water on release characteristics of arsenic.Besides,XRD analysis was also used to make a further research on the mechanism of the effect of steam on release characteristics of arsenic.Results show that the presence of steam can accelerate the combustion rate of coal.At a certain temperature,the volatilization ratio of arsenic in steam atmosphere is larger than that without steam,and with the increase of steam concentration,the increase of arsenic volatilization ratio slow down.With the increase of temperature,volatilization ratio of arsenicincreased gradually,but the positive effect of steam on volatilization ratio of arsenic begins to weaken.Compared with air atmosphere,mineral compositionsin ash changed under the steam atmosphere,such as gypsum and other sulfate.It is mainly because the steam promoted the formation of gypsum and inhibited the formation of arsenate via avoiding the reaction between CaO and arsenic,resulting in the increase of arsenic volatilization ratio.