垃圾衍生燃料热重法的燃烧特性

采用热重技术对由垃圾可燃物制备的垃圾衍生燃料(RDF)的燃烧特性进行了实验研究，并由微分热重曲线计算了它们燃烧反应的动力学参数．研究结果表明，草木类RDF存在二次着火现象，织物、塑料及混合原料RDF只存在固碳着火点．草木类RDF最易着火燃烧并且燃烧最猛烈但持续时间很短，塑料类RDF最耐烧，混合原料RDF的燃烧反应较平稳并且持续时间较长，易于实现稳定的燃烧．RDF的燃烧过程可由几个一级反应来描述．混合原料RDF中的各组成原料的燃烧相互影响，其燃烧特性不能由各组成原料燃烧特性简单叠加而成，各种原料RDF燃烧的难易程度可用表观活化能来表征。     

城市生活垃圾制备的RDF的热工性能研究

针对城市生活垃圾组分波动大、水分含量高、可燃物热值低且不稳定等特点,通过物理和化学改性,制备出热值相对稳定的垃圾衍生燃料(RDF);采用TG-DSC-MS分析法对加入改性剂的RDF的部分热工性能进行了研究。结果表明,通过物理方法降低RDF的自由水可以有效地提高RDF的热值,采用化学方法可以转化RDF中水分的赋存形式,达到降低自由水含量的目的 ,但并不一定能提高其热值;过量去湿剂的使用还会导致热值的显著降低,化学去湿剂与固态可燃物的综合运用可以有效调控RDF的热值。RDF的燃烧有4个失重阶段,第1阶段为失水过程,第2和第3两个阶段分别为RDF中的纤维物和聚合物两类物质的燃烧过程,第4阶段为RDF中固定碳的燃烧以及燃烧过程产物的高温分解过程。     

制鞋废料与木粉混合制备RDF的燃烧性能研究

为实现制鞋废料的能源化利用,文章探索了不同比例的木粉与制鞋废料混合制备的垃圾衍生燃料(RDF)的燃烧性能。对RDF颗粒进行工业分析、元素分析、热重分析及高低位热值检测,研究结果表明:随着制鞋废料掺混量的增加,RDF颗粒中的挥发分逐渐升高,热值逐渐增大,但当制鞋废料掺比超过20%时,RDF颗粒难于成型且松散易碎;制鞋废料的掺比越大,RDF颗粒的着火点就越高,制鞋废料的掺入还会导致RDF颗粒的最大失重温度上升,最大失重速率提高。     

生物油热解及燃烧特性分析

对由木粉热解所得的生物油样品分别进行了氮气与氧气气氛下不同升温速率的热重分析试验.结果表明:生物油的热解分为两个阶段,第一阶段为生物油中低沸点有机物的挥发以及各组分间反应生成各类产物的过程,第二阶段为各种重组分的裂解过程;生物油的燃烧分为3个阶段,即前期的挥发与裂解和最后焦炭的燃烧过程.提高升温速率使氮气气氛中生物油样品的初始失重温度、失重峰值温度及对应的最大失重速率均有所增大,且在较高升温速率(20℃min)下,较少含炭残余物形成.随升温速率升高,生物油着火温度提高,最终失重率无变化.最后根据热重数据对热解与燃烧各段反应进行了动力学拟合.     

污泥热解油的燃烧特性及动力学模型

利用热重分析(TG)对污泥热解油的燃烧特性进行了研究,污泥热解油的燃烧过程分为两个阶段.第1阶段为轻质有机物挥发后与氧发生均相燃烧,第2阶段为难挥发有机物与氧发生非均相燃烧,其中第1阶段燃烧反应是其失重的主要原因.分析了升温速率对燃烧特性的影响,发现增大升温速率有利于燃烧.对燃烧过程中烟气的排放规律进行了红外分析(FTIR),从另一角度印证了热重分析的结果.根据热重曲线建立动力学模型,分别对不同升温速率下燃烧过程的两个阶段进行动力学参数计算.活化能的变化趋势再次表明提高升温速率有利于污泥热解油的燃烧.     

污水污泥热解和燃烧特性的实验研究

采用热分析的方法研究了2种污泥的热解和燃烧特性。实验结果表明,热解和燃烧都可以划分为3个阶段。第1阶段是水分析出阶段。第2个阶段是污泥失重的主要阶段,燃烧失重是由于有机物的分解燃烧和固定碳的燃烧引起,热解失重是由于有机物的分解引起。第3阶段中,燃烧过程失重主要是无机物引起,热解过程失重是由于无机物和残余有机物引起。在燃烧和热解主要阶段(第2阶段)内,污泥燃烧的反应速率总体上大于热解的反应速率。污泥热解和燃烧在第2和第3阶段是放热过程。     

基于TG-FTIR的造纸污泥热转化特性研究

目前对有机工业污泥在不同热转化过程中的反应特性和产物性质缺少系统对比研究.利用热重和红外光谱联用方法(TG-FTIR)对高挥发分造纸污泥在不同热转化过程中的反应特性进行了研究.氮气、空气和CO2气氛分别对应热解、燃烧和气化反应.3种热转化过程在400℃前的热失重和反应特性相似,主要为水分和挥发分析出的热分解反应.500...     

生物质与皮革废渣混合成型燃料燃烧特性研究

本文利用热重分析的方法研究玉米秆和皮革废渣混合成型燃料的燃烧特性。通过绘制不同混合比例、不同升温速率的燃烧特性TG-DTG曲线,分析燃烧特并获得最佳混合比例。对比成型燃料与粉末的燃烧特性。通过本例来推断生物质和工业废弃物的燃烧规律。实验结果表明:玉米秆有一个失重高峰,皮革废渣有三个。玉米秆燃烧分为加热、快速失重、缓慢失重三个阶段。皮革燃烧过程较为复杂。随着混合物中玉米秆质量分数增加,燃烧速度增加。成型后燃料的密度增加,热值增加,TG-DTG曲线超前。升温速率增加,燃烧时间缩短,燃烧速率最大值增加,但失重率降低。     

氯化钾催化纤维素热裂解动力学研究

在差示热重分析仪上对生物质中最常见的金属元素钾的氯盐对纤维素热裂解动力学的催化效果进行了研究。试验发现氯化钾的存在影响到热失重初始阶段活性纤维素的生成过程，导致了热重曲线向低温侧移动，并且提高了焦炭的产率。结合Broido-Shafizadeh模型，对纤维素热解过程的催化作用机理进行探讨，发现纯纤维素主失重阶段呈现出连续反应模式，分别对应于活性纤维素和挥发分的生成过程，并随反应温度的提高两者依次成为整体失重过程的控制因素。钾盐的参与由于强烈催化了活性纤维素的生成反应，将控制反应转移到消耗过程的一对竞争反应中，分别对应于焦炭和挥发份的生成。对比纯纤维素的失重动力学参数，氯化钾对活性纤维素消耗过程中挥发份的生成反应和炭化反应均有强烈的催化效果。     

污水污泥的燃烧特性

通过对几种污泥样品热重分析,研究污泥的燃烧特性,根据燃烧实验所得的热失重曲线,对几种污泥的燃烧过程进行了分析。对实验数据进行了处理,采用Phadnis法和微分法相结合的方法确定了燃烧反应机理并求出了反应动力常数Ａ和Ｅ,在燃烧的不同阶段,总反应速率控制因素不同。     

垃圾衍生燃料炭化物燃烧特性分析

利用热分析方法研究垃圾衍生燃料(RDF)和垃圾衍生燃料炭化物(cRDF)的燃烧特性,分析RDF和cRDF的燃烧TG-DTG曲线,得出RDF和cRDF的着火温度、燃烧特性指数和燃烧动力学参数等燃烧特性.研究表明,cRDF发热量比RDF高34%～43%,但由于挥发分含量较低,燃烧性能不及RDF,因此cRDF作为燃料时应和其它燃料配合使用,以改善其着火性能.     

垃圾衍生燃料(RDF)流化床燃烧过程中NOx的产生

对RDF(Refuse Derived Fuel)在流化床中进行燃烧反应,并在不同的工况下污染物NOx生成进行了实验研究。结果表明：污染物NOx的产生与RDF本身的成分组成、燃烧温度、过量空气系数、二次风有密切联系；二次风的通入,过量空气系数保持在1.1都能降低NOx的产生。     

Jet flames of a refuse derived fuel

This paper is concerned with combustion of a refuse derived fuel in a small-scale flame. The objective is to provide a direct comparison of the RDF flame properties with properties of pulverized coal flames fired under similar boundary conditions. Measurements of temperature, gas composition (O₂, CO₂, CO, NO) and burnout have demonstrated fundamental differences between the coal flames and the RDF flames. The pulverized coals ignite in the close vicinity of the burner and most of the combustion is completed within the first 300 ms. Despite the high volatile content of the RDF, its combustion extends far into the furnace and after 1.8 s residence time only a 94% burnout has been achieved. This effect has been attributed not only to the larger particle size of fluffy RDF particles but also to differences in RDF volatiles if compared to coal volatiles. Substantial amounts of oily tars have been observed in the RDF flames even though the flame temperatures exceeded 1300 °C. The presence of these tars has enhanced the slagging propensity of RDF flames and rapidly growing deposits of high carbon content have been observed.     

Co-combustion of refuse derived fuel with Korean anthracite in a commercial circulating fluidized bed boiler

The effect of co-combustion of Refuse Derived Fuel (RDF) with Korean anthracite on the combustion and environmental performance was observed in the Tonghae commercial Circulating Fluidized Bed (CFB) boiler. High contents of oxygen and CaO in RDF reduced the amount of air required for combustion and the limestone flow rate for SO₂ capture in the CFB boiler, respectively. The temperature in the furnace exit increased slightly due to re-combustion of volatiles which resulted in limiting the co-combustion ratio of RDF for the CFB boiler to operate stably. With the increasing co-combustion ratio of RDF, the output voltages of electrostatic precipitator (EP), which consists of 2-channels and 5-stages collecting plates, decreased linearly. Eventually, stability of the EP could not be maintained above 5% of the RDF co-combustion ratio. The emissions of NO_x, HCl and dioxin during co-combustion did not change appreciably as compared to the case when Korean anthracite was burnt alone, which were also low enough to meet Korean emissions limits. On the other hand, chlorine contents in ashes emitted from the CFB boiler increased gradually with the increasing co-combustion ratio, which implied that most of chlorines were fixed by limestone.     

Imaging studies of in-cylinder HCCI combustion

An optically accessed, single cylinder engine operated in homogenous charge compression ignition (HCCI) mode with negative valve overlap (NVO) strategy was used to perform combustion processes diagnostics under premixed conditions corresponding to the low load regime of the HCCI operational envelope. The aforementioned processes analysis was conducted utilizing synchronized simultaneous combustion event crank-angle resolved images, acquired through piston crown window with in-cylinder pressure recording. This investigation was carried out for one-step ignition fuel—standard gasoline, fuel proceeding single-stage ignition process under conditions studied. The initial combustion stage is characterized by a maximum local reaction spreading velocity in the range of 40–55 m/s. The later combustion stage reveals values as high as 140 m/s in case of stoichiometric combustion. The mixture as well as combustion stages effects are pronounced in these observed analytical results.     

Numerical studies on heat coupling and configuration optimization in an industrial hydrogen production reformer

Steam methane reforming furnaces are the most important devices in the hydrogen production industry. The highly endothermic reaction system requires reaction tubes in the furnace to have a large heat transfer area and to be operated under high temperature and pressure conditions. In order to enhance heat transfer efficiency and protect reaction tubes, the controlling and optimization of the furnace structure have increasingly received more and more research attention. As known from the furnace structure, it is essential to couple the exothermic combustion with the endothermic reforming reactions due to the highly interactive nature of the two processes. Thus, in this paper, the combustion process in the furnace was numerically studied by using computational fluid dynamics (CFD) to model the combustion chamber, coupled with methane steam reforming reaction inside the reaction tubes, defined by a plug flow model. A set of combustion models were compared for the furnace chamber and a plug flow reaction model was employed for reforming reaction tubes, and then a heat coupling process was established. The predicted flue gas temperature distribution showed that the heat transfer in the furnace was not uniform, resulting in hot spots and heat losses on the tube wall. Therefore, structure optimization schemes were proposed. Optimization on arrangements of the tubes and the nozzles promoted the uniform distribution of flue-gas temperature and then improved heat transfer efficiency, thereby enhancing performance of the steam reforming process.     

固体废弃物燃烧过程气体成分EGA分析

利用EGA(即TGA-FTIR联用)技术,对油漆、污泥、RDF等燃烧过程中各阶段释放气体成分进行了分析,结果表明,EGA分析可以有效地表征固体废弃物在热解、气化和燃烧各个阶段的动态特征,如产物成分及相应的影响因素,对掌握研究废弃物焚烧过程的机理和建立相应的模型有重要意义.     

Thermogravimetric study of the decomposition of pelletized cellulose at 315°C–800°C

The thermal decomposition rate of pelletized cellulose cylinders in a laboratory furnace was studied to simulate the pyrolytic and combustive behavior of pelletized refuse-derived fuel (RDF). The decomposition rate was determined by measuring the mass-loss rate of three mass groups of cylinders at several fixed furnace temperatures over the range of 315°C–800°C and in both air and nitrogen atmospheres. The decomposition for all conditions tended to follow first-order reaction kinetics throughout the majority of the reaction and the rate of mass loss for cylinders in atmospheres of flowing air and nitrogen was found to be similar. The apparent Arrhenius activation energy ranged throughout the major course of the decomposition from 2.1 to 8.0 kcal/mol. A simple model is developed to describe the rate of weight loss. This study with cellulose cylinders as a model system aids the use of pelletized refuse-derived fuel (RDF) by providing information on the rate of fuel reaction in varying pyrolytic and combustive conditions.     

Combustion of niobium in hydrogen and nitrogen. Synthesis of niobium hydrides and hydridonitrides

This paper treats the combustion processes observed in the Nb–N–H system, and its application to the synthesis of niobium hydridonitrides. In particular the Self-Propagating high-temperature synthesis (SHS) process in Nb–H and Nb–N systems was studied. The combustion products were hydrides and nitrides, respectively. The determination of the main features of combustion process by obtaining binary compounds enabled to examine a ternary system including both N₂ and H₂ simultaneously. It was found that niobium combustion in the mixture of two reacting gases proceeded in three competetive ways, established earlier for IVA group metals. Various types of reaction occur depending on the partial pressure ratio.