煤矸石山非控自燃热动力学特征及移热方法研究

发布时间：2018-02-08 13:08

  本文关键词： 煤自燃 煤矸石山 自然发火 热棒 移热降温 余热移除　出处：《西安科技大学》2017年博士论文　论文类型：学位论文

【摘要】：自燃煤矸石山是一种比较特殊的燃烧系统,具有易自燃、蓄热大、易复燃的特点。露天堆放的煤炭和煤矸石时常发生自燃,浪费资源、污染环境,严重的还会引发事故,造成巨大损失。常规治理手段主要从“隔氧”的角度来控制煤矸石山自燃,由于内部积聚的热量无法及时散除,随着时间推移多会发生复燃。本文基于“降温”的技术思路,提出自燃煤矸石山热棒深部移热降温理方法。从理论角度分析了煤矸石自燃热动力学过程及发火条件,研究风流渗透、水分等内外因与煤矸石山自燃特性之间的相互关系。公乌素煤矸石所含N、C、H元素、固定碳含量和比热容均低于公乌素煤;含水率、含灰分量、含硫量、热扩散系数和导热系数均高于公乌素煤。在相同的温度梯度下,煤矸石内部温度变化传播更迅速、温度扩散能力更大,比公乌素煤传导的能量更多。相同的热量加热下,煤矸石升温更快,更易自燃。煤矸石综合燃烧指数S_n(V_(ad)+FC_(ad))/A_(ad)呈正相关,拟合系数R~2=0.9759,煤矸石含挥发分和固定碳含量越高、灰分越低,其综合燃烧性能越好。综合燃烧指数S_n.点燃指数Di和燃尽指数Dh与FC_(ad)/V_(ad)呈正相关,线性拟合相关系数分别为R~2=0.8429、0.9258、0.9972,在充分供氧燃烧条件下,燃料比越大,煤矸石的燃尽性能越好。耗氧速率、CO浓度和产生率、第三火灾系数R~3可作为预报煤矸石自燃的主要指标,CO_2和CH_4浓度及产生率、第一火灾系数R1第二火灾系数R~2作为辅助指标。将煤矸石的热失重过程划分为脱附、氧化剂裂解、燃烧和热活化及相变4个阶段,得到了对应阶段失重率和特征温度参数。采用Achar微分法和Coats-Redfern积分法联合求解了煤矸石非控自燃动力学参数和机理函数。热棒影响煤堆内部温度场热行为的实验研究表明,试验期内单根热棒对煤堆的最大降温幅度为33.4℃,降温率39.6%;双根热棒作用下煤堆内出现了“马鞍”状温度场分布。推导了热棒在煤堆中的降温半径数学关系式,计算得到80 h热棒的散热量分别为1.0865、2.1680和3.3649 MJ。模拟验证了热棒对煤堆内部温度场的影响及分布规律。研究表明,热棒对煤堆的降温效果与距离成负相关,与自燃煤堆内部热源功率成正相关。热棒对煤堆的蓄冷降温能力随时间持续增加。另外,本文确定了热棒现场实施安装工艺,建立了热棒远程无线安全运行监测系统,研究了工业试验现场热棒轴向温度、煤矸石山水平、垂直温度分布特征和日温度变化特征,基于热棒在煤堆中热周转过程,推导并计算了评价、判断热棒移热降温效果的散热量等量化标准。本文的研究可为热棒技术在煤矸石自燃防灭火领域的大范围推广应用提供基础和指导。
[Abstract]:The spontaneous combustion coal gangue mountain is a kind of relatively special combustion system, which has the characteristics of easy spontaneous combustion, large heat storage and easy re-burning. Spontaneous combustion of coal and coal gangue stored in the open air often occurs, waste resources, pollute the environment, and serious accidents occur. This paper is based on the technical thinking of "cooling down", because the internal heat accumulation can not be dissipated in time, and more and more reburning will occur over time, and this article is based on the technical thinking of "cooling down", which is mainly from the angle of "oxygen insulation", because the internal heat accumulation can not be dissipated in time. This paper puts forward a method of heat transfer and cooling mechanism in the deep part of spontaneous combustion gangue mountain heat rod, analyzes the thermal dynamic process and combustion conditions of spontaneous combustion of coal gangue from a theoretical point of view, and studies the permeation of air flow. The relationship between internal and external water content and spontaneous combustion characteristics of coal gangue. The fixed carbon content and specific heat capacity of gangue coal gangue are lower than those of gongwusu coal, the moisture content, ash content and sulfur content are lower than those of gongwusu coal. The thermal diffusion coefficient and thermal conductivity coefficient are both higher than those of Gongwusu coal. At the same temperature gradient, the internal temperature change of gangue propagates more rapidly, and the thermal diffusivity is larger than that of Gongwusu coal. Under the same heat heating, the thermal diffusivity of gangue is higher than that of gongwusu coal. The coal gangue heats up faster and is easier to self-ignite.; the comprehensive combustion index of coal gangue, Snn / V / D), has a positive correlation with FCU / A / A / A / D, and the fitting coefficient is 0.9759. The higher the volatile content and the fixed carbon content of coal gangue, the lower the ash content. The better the comprehensive combustion performance is, the better the comprehensive combustion index is: Sn.Ignition index Di and burnout index Dh are positively correlated with FCSAD / VSP / VSP, and the linear fitting correlation coefficients are RP20.84290.92580.9972, respectively. Under the condition of full oxygen combustion, the fuel ratio increases. The better the burnout performance of coal gangue is, the higher the oxygen consumption rate is, the CO concentration and production rate, and the third fire coefficient R3 can be used as the main index to predict the spontaneous combustion of coal gangue, such as CO-2 and CH_4 concentration and production rate. The first fire coefficient R1 and the second fire coefficient R2 are used as auxiliary indexes. The thermogravimetric process of coal gangue is divided into four stages: desorption, oxidant cracking, combustion and thermal activation and phase transition. The relative weightlessness rate and characteristic temperature parameters are obtained. The kinetic parameters and mechanism functions of uncontrolled spontaneous combustion of coal gangue are solved by Achar differential method and Coats-Redfern integral method. During the test period, the maximum cooling range of a single hot rod is 33.4 鈩，

本文编号：1495514