Effect of Weathering of Coal and Organic Dusts on Their Spontaneous Ignition

Weathering of coal and other cellulosic dusts occur due to the process of wetting and subsequent drying, or by subjecting them to a temperature higher than the ambient temperature for prolonged time periods. The first type of weathering occurs in a wetted storage. The second type of weathering occurs when a dust processing unit stores and maintains the dust deposit at an elevated temperature. As a result of weathering, the physical and thermal properties of the dust may change. Therefore, the weathered dust sample is expected to ignite at a different hot plate temperature as compared to that of a fresh sample, when tested in a standard test method (ASTM E 2021). In this study, three dust samples namely, wheat flour, Pittsburgh seam coal and powder river basin coal, are tested. These dust samples are subjected to one or both types of weathering. Thermogravimetric analysis and standard ignition tests are carried out with both fresh and weathered dust samples. Estimation of the activation energies and reactivity, and measurement of the minimum surface temperature for the onset of ignition have been carried out for all the cases. The implications of the observed results on industrial safety related to combustible dust layers are discussed.     

封闭式大储量圆形煤场储煤自燃分析及处理

针对燃煤电厂发生多起封闭式大储量圆形煤场储煤自燃问题,如何防止和治理煤炭自燃迫在眉睫。分析认为,煤炭自燃的主要原因是煤场库存量大、煤炭挥发分高、堆煤氧化层增大和水分催化,而减少空气与煤的接触面,控制煤中的水分含量,做好通风散热等措施,是预防和治理圆形煤场储煤自燃的关键。为此,提出建立健全煤质管理档案、"先进先出,烧旧存新,定期置换"、控制煤炭自燃的供氧量、发现自燃征兆及时处理、严控自燃煤的入场堆存时间和处理煤炭自燃的策略等措施,提高煤场的安全运行和电厂的经济效益。     

Self-heating and Spontaneous Ignition of Fibreboard Insulating Panels

In recent years, several fires in Canada have been attributed to spontaneous ignition in insulating fibreboard panels. To investigate this claim, critical temperatures for the spontaneous ignition of 75, 190 and 305 mm cubes of fibreboard were measured in small-scale laboratory tests. Employing the Frank-Kamenetskii theory, it was then determined that the critical temperature for spontaneous ignition of 1.2 m cubical pallet of fibreboard is 104C and for a tractor trailer full of fibreboard is 89C. A test in which a dry, 305 mm cube of fibreboard was placed in a humid environment showed that absorption of water vapour by fibreboard is exothermic. For large quantities of fibreboard, such as found in tractor trailers and railway cars, adiabatic conditions may prevail near the centre of the load so that absorption of water vapour can result in centre temperatures in the order of 100C. This is sufficiently hot that oxidation within the load will commence and may result in spontaneous combustion. Recommendations on how spontaneous combustion can be avoided during the storage and transport of fibreboard panel products are also presented.     

自燃煤矸石活性研究

通过对铜川自燃煤矸石进行分拣、粉碎、过筛,利用X射线荧光光谱仪、等离子体发射光谱仪、X射线衍射（XRD）仪、同步热分析仪对铜川自燃煤矸石进行检测.研究了不同矿物以及成分对煤矸石活化性能的影响,并通过抗压强度法对自燃煤矸石活性进行了验证.结果表明：铜川煤矸石在自燃过程中形成的活性物为无定形SiO2,κ Al2O3和无定形Al2O3,其结晶度的高低决定了自燃煤矸石活性的高低,同时自燃过程中煤矸石的疏松程度也会影响其活性.通过测定Si4+,Al3+溶出量及利用XRD分析结晶度可以快速测定自燃煤矸石的活性.     

复配7504灭蝇药在垃圾堆场的试验应用

上海的生活垃圾主要在市郊几个生活垃圾填埋场集中处置,日产量已达到11000t。由于填埋场当日垃圾得不到及时覆盖,造成苍蝇泛滥成灾。自大面积、高密度灭蝇技术应用后,填埋场上蝇密度得到了有效控制。但是,随着城市发展和经济建设的要求,以敌敌畏为主要原料的灭蝇药物的使用范围正受到限制,在发达国家敌敌畏已禁止或有限制地使用。为与国际接轨,寻找敌敌畏的有效替代物,开发对人畜毒性低、环境污染轻的高效杀虫药物,以适应垃圾填埋场发展的需要,须积极开发新型药物。 先进国家使用的杀虫剂药物的毒性指标LD_(50)(致死中剂量)指标控制在500～5000mg/kg,并且有     

自燃煤矸石骨料在预拌混凝土中的应用研究

用自燃煤矸石取代天然砂石配制预拌混凝土,研究了自燃煤矸石骨料附加水及预湿时间对预拌自燃煤矸石骨料混凝土工作性和强度的影响,并在此基础上,研究了这种预拌混凝土的抗氯离子渗透性能和抗冻性能.结果表明:控制好自燃煤矸石骨料的附加水及预湿时间,在外加剂及掺合料的共同作用下,预拌自燃煤矸石骨料混凝土的坍落度、坍落度经时损失、强度等级、抗氯离子渗透性能及抗冻融性能均满足GB/T 14902—2003规定的质量标准.     

钢纤维增强自燃煤矸石轻集料混凝土试验研究

针对煤矸石占用大量耕地并对矿区生态环境造成的污染问题,参照国标,对辽宁省阜新市高德矿排放的自燃煤矸石进行了化学组成、耐久性及有害物质含量、物理力学性能的检测,发现其各项指标均满足国家对轻集料标准的要求.为此,将自燃煤矸石破碎作轻粗集料、钢纤维作增强材料,设计了5组钢纤维掺量的混凝土试件,进行了拌和物工作性及均质性,硬化后抗压强度、劈拉强度和抗折强度的试验,并且以试验结果为样本,建立了钢纤维掺量与混凝土强度之间的定量关系式.研究结果表明,当钢纤维掺量小于2%(体积分数)时,随钢纤维掺量增加,自燃煤矸石轻集料混凝土的抗压?劈拉和抗折强度都有不同程度的提高,其中以抗折强度的增长最为显著.另外,对上述现象进行了机理分析.     

A Parametric Study on the Inception and Evolution of Underground Coal Fires Based on a Lab-Scale Experimental Setup

Fire Technology - The tendency of self-ignition of coal is the root cause of underground coal fires (UCFs). A parametric study is carried out on a lab-scale experimental setup developed based on...     

煤粉燃烧器点火系统的比较优化

当前,在国际市场上沥青混合料搅拌所用热源设备大多是燃油燃烧器。由于我国煤碳资源比较丰富,国内中小型设备多数选用燃煤燃烧器,同燃油燃烧器相比较,燃煤燃烧器更符合我国国情,从经济上更占有优势。     

煤场大型网架安装施工实例

湖南华菱涟钢焦化煤场网架纵轴长420m,两连跨宽111m;跨间居中安装两条纵向通长的皮带运输机和斗轮堆取料机;网架开始安装时,场内已经有50%左右的地面已经堆煤,皮带运输机和斗轮堆取料机已经投入生产;本文针对煤场安装与生产同步进行时这一比较特殊施工环境,如何组织施工,采用什么样的施工工法,作了比较详细的介绍。该施工工法经实践证明,适应于大型煤场的网架安装。     

面向对象方法在参数化设计中的应用初探

面向对象是当前程序设计的重要方法,也是描述现实问题的有效思想,通过对面向对象在参数化建筑设计中的两个应用实例的介绍,进而阐释其优势及应用潜力。     

A Parametric Study on the Time-to-Failure of Wood Framed Walls in Fire

A model has been developed for predicting the time-to-failure of gypsum board clad wood framed walls exposed to fire. This model was developed for designing wood framed walls in accordance with new performance-based building fire codes being introduced around the world. The model has been used to undertake a parametric study of the effects of a wide range of variables on the time-to-failure due to structural collapse. The study found that the most dominant variables in building construction in descending order of importance are depth and breadth of stud sections, fire temperature, thickness of gypsum board, elastic modulus of wood in compression, enthalpy of gypsum board (that is the product density and specific heat) and vertical load. Variations in the thermal properties of wood do not dominate the influences affecting the time-to-failure. The study supports the component additive method for estimating the fire resistance of walls.     

腹板纵向加劲肋的参数研究

采用有限元数值模拟方法,对处于平面内弯曲的腹板纵向加劲肋的最佳位置和尺寸进行研究。分析对象为具有各种不同纵横比的平板,提出计算最小次弯矩的公式,并将其与AASHTO推荐的计算方法对比。结果显示,腹板加劲肋的最佳位置主要取决于其相对抗挠刚度。     

参数化地域建筑创作方法研究

参数化设计为地域建筑的设计提供了全新的视角,引导地域化建筑创作的方法与实践发生着前所未有的转变。通过对当前参数化建筑设计领域与地域化相关实践与理论的分析,认为参数化地域建筑创作方法包括三方面内容：自然要素的参数化生成、传统材料与建造技术的参数化创新、地域文化要素的参数化转译。     

大倾角煤层回采巷道非对称锚网索支护与实践

根据淮南矿区大倾角(25°～45°)煤层开采地质和技术条件,采用物理模拟综合分析了大倾角煤层回采巷道围岩结构特征及采用锚杆支护时的围岩变形、破坏、应力演化等力学特征,揭示了大倾角煤层回采巷道围岩力学特征非对称演化机理.研究表明,实体煤回采巷道应重点支护顶板和高帮,而留小煤柱回采巷道应重点支护顶板和低帮.基于巷道围岩力学特征的非对称性,提出并实施了大倾角煤层实体煤回采巷道和留小煤柱回采巷道的非对称锚网索支护方法.工程应用表明,非对称锚网索支护能适应大倾角煤层回采巷道围岩结构和力学特征,有效控制巷道围岩变形.     

水箱冷冲模具图形参数化的研究

按照计算机辅助设计系统中汽车水箱冷冲模具图形参数化的基本要求,对在ＡｕｔｏＣＡＤ平台上实现图形参数化所涉及的编程技术进行研究,提出实现参数化图形的方法。     

大直径混凝土筒仓仓壁温度应力参数分析

内外温差对仓壁配筋设计影响较大,起控制作用的环向弯矩可按等效环向力考虑。参数分析结果表明温度作用与内外温差、弹性模量、仓壁厚度等参数呈线性变化关系,且温度作用与贮料荷载作用下最大环向力比值随筒仓直径的增加应呈下降趋势。     

预应力混凝土圆形筒仓工程实践

本文以一贮煤仓为例,对无粘结预应力技术在大型煤仓中的应用进行了较详细的介绍,并对该类工程的设计与施工提出了建议。