The imbibition ability of extinguishant is an important factor influencing the extinguishing effect for smoldering fire in pulverized coals. The coal particle size, bulk compactness, and aqueous solution properties si...The imbibition ability of extinguishant is an important factor influencing the extinguishing effect for smoldering fire in pulverized coals. The coal particle size, bulk compactness, and aqueous solution properties significantly affect the imbibition ability of extinguishment. This work aims to reveal the influence of the properties of pulverized coals and aqueous solution on the imbibition ability of extinguishant for smoldering fire through experiments and capillary theories. The imbibition height and rate were adopted to evaluate the imbibition ability of extinguishment. The results showed that a relatively small bulk compactness and a fine coal particle size negatively influenced the extinguishing process dominantly because of its high surface energy and low wettability. An additive was used to adjust the properties of aqueous solution. The liquid with a larger surface tension, a smaller contact angle, and a lower viscosity induced a better imbibition ability of extinguishment.展开更多
自燃修复(self-sustaining treatment for active remediation,STAR)技术是一种新近发展起来的并对修复非水相液体(NAPLs)污染包气带具有较好应用前景的修复方法。该技术与固体物质的阴燃类似,是没有火焰的缓慢燃烧。有机污染物附着在...自燃修复(self-sustaining treatment for active remediation,STAR)技术是一种新近发展起来的并对修复非水相液体(NAPLs)污染包气带具有较好应用前景的修复方法。该技术与固体物质的阴燃类似,是没有火焰的缓慢燃烧。有机污染物附着在土壤含水层介质固体表面,依靠异相氧化燃烧,产生的热量可以维持污染物的持续燃烧,不需要热量的持续输入。为了探讨高浓度有机污染土壤STAR修复技术的影响因素,缩短煤焦油加热时间,减少二次污染的产生。通过一维模拟柱分别开展了污染物浓度、空气流速、含水率对煤焦油维持阴燃的影响。研究表明:当污染物浓度在80 000~110 000 mg·kg-1时,煤焦油可以维持阴燃;当浓度低于80 000 mg·kg-1时,煤焦油不能维持阴燃;随着煤焦油浓度的增大峰值温度出现所需时间越来越短,平均峰值温度越来越大,平均燃烧传播速度越来越小;空气流速在2~10 cm·s-1范围内时煤焦油均可维持阴燃,且随着空气流速的增大峰值温度出现所需时间越来越短,平均燃烧传播速度与空气流速间近似呈线性增长关系;含水率的增大对煤焦油维持阴燃没有影响,且随着含水率的增大峰值温度出现所需时间越来越长,平均峰值温度和平均燃烧传播速度均有所降低。与污染物浓度和空气流速相比,含水率对加热时间的影响最大。因此,在含水率变化的情况下,应重点关注煤焦油副产物苯、甲苯、二甲苯、萘等有毒有害气体的产生。展开更多
基金supported by the Key Technical Research Plan of Ministry of Public Security (No. 2017JSYJA13)Independent Innovation Fund of Tianjin University (No. 1706)
文摘The imbibition ability of extinguishant is an important factor influencing the extinguishing effect for smoldering fire in pulverized coals. The coal particle size, bulk compactness, and aqueous solution properties significantly affect the imbibition ability of extinguishment. This work aims to reveal the influence of the properties of pulverized coals and aqueous solution on the imbibition ability of extinguishant for smoldering fire through experiments and capillary theories. The imbibition height and rate were adopted to evaluate the imbibition ability of extinguishment. The results showed that a relatively small bulk compactness and a fine coal particle size negatively influenced the extinguishing process dominantly because of its high surface energy and low wettability. An additive was used to adjust the properties of aqueous solution. The liquid with a larger surface tension, a smaller contact angle, and a lower viscosity induced a better imbibition ability of extinguishment.
文摘为研究地下煤火的蔓延特性,根据真实煤火背景设计搭建了煤火阴燃的实验装置.采用加热棒进行强制点火,并根据工况需要改变实验装置的通风条件,揭示了自然通风下煤火阴燃过程中温度分布和质量损失的变化规律.结果表明:点火过程表面裂隙的发育具有随机性,导致点火阶段不可重复.水平方向上,上、中层峰值温度稳定在590℃和540℃,传播速度为0.274 mm/min和0.261 mm/min.根据升温速率和加速度曲线将煤-氧反应过程分为吸附热控制区、水分蒸发控制区、氧化控制区、热解控制区和氧化-热解反应竞争区5个区间.将质量损失分为4个阶段,随着反应的进行,质量损失速率不断减小.侧边通风增大边界处氧气浓度,氧气从侧面沿水平方向进入煤层有一个渗透距离,大约为6 cm.
