燃煤PM10在高梯度磁场中的捕集

根据高梯度磁分离原理,在考虑磁场、流场、布朗扩散和惯性作用的情况下,建立了高梯度磁场捕集燃煤可吸入颗粒物的模型,计算了颗粒捕集效率,并将计算结果与试验结果进行对比分析。结果发现,在0.023~9.3μm的粒径范围内,颗粒捕集效率计算值与试验值呈现的趋势基本一致,1~9.3μm的颗粒计算值与试验值吻合较好,误差在5%以内。较高的颗粒磁化强度、磁场强度以及较长的停留时间均有利于颗粒在磁场中的捕集,布朗扩散对于dp<1μm的颗粒捕集效率有较大促进作用,而惯性作用对颗粒捕集效率影响微弱。研究表明,采用高梯度磁场捕集燃煤可吸入颗粒物是一种有效可行的方法。     

燃煤飞灰中可吸入颗粒物在磁场中聚并收尘试验研究

针对燃煤电站锅炉飞灰这种弱磁性可吸入颗粒物,将由专门研制的气溶胶发生器产生的气溶胶(PM10)颗粒按照粒径大小分为12等级,利用低压电称冲击器ELPI测试在不同磁感应强度下各级颗粒浓度的变化,考察磁场对颗粒磁聚并的影响.结果表明,燃煤飞灰这种弱磁性粉尘在磁场中有一定的聚并作用,对其中PM2.5的颗粒聚并的效果更明显.     

太阳能辅助燃煤碳捕集发电机组的变工况热力性能研究

通过对比3种燃煤碳捕集发电方案,确立了一新型太阳能辅助燃煤碳捕集发电系统,利用热力学和(火用)分析模型对集成系统的热力性能和(火用)性能进行评估,基于外部燃料(火用)贡献度模型,分析了变工况对系统产品和再沸器产品贡献度的影响。结果表明：提高机组负荷和工质的初参数有利于改善集成系统的热经济性和(火用)效率;随着主蒸汽压力的降低,锅炉燃煤(火用)和二次再热燃煤(火用)对系统产品的贡献度逐渐升高,而一次再热燃煤(火用)对系统产品的贡献度逐渐降低;随着主蒸汽温度的升高,锅炉燃煤(火用)对系统产品的贡献度逐渐升高,而一、二次再热燃煤(火用)对系统产品贡献度逐渐降低;提高负荷有利于提高一、二次再热燃煤(火用)对系统产品的贡献度和碳捕集与封存压缩余热(火用)对再沸器产品的贡献度。     

燃煤PM10在磁场中聚并脱除理论与实验研究

提出了燃煤可吸入颗粒物在均匀磁场中的二元碰撞聚并模型,模型通过直接跟踪在磁偶极子力、气体曳力、布朗力和重力作用下做相对运动的粒子,根据粒子的相对运动轨迹确定燃煤细微飞灰粒子间的聚并系数。在数值计算获得聚并系数的基础上,应用求解粒子聚并动力学方程的区域算法,计算了东胜烟煤燃烧产生的飞灰细微粒子在均匀磁场中的聚并脱除效率,并与实验进行了比较。结果表明,在0.098～9.314μm粒径范围内,0.576～3.758μm粒径的飞灰粒子聚并脱除效率最高;总脱除效率随外磁场强度、颗粒质量浓度以及粒子在磁场中停留时间的增加而增大,粒子饱和磁化时,总脱除效率达到最大值;实验结果与数值模拟结果相一致。模型预测结果表明,当颗粒质量浓度为40 g/m3时,燃煤飞灰细微粒子的总脱除效率可达52%。     

各种除尘技术性能比较及袋式除尘器在我国的应用前景

针对我国以煤为主要发电用燃料的格局,燃煤锅炉所释放的粉尘占到总排放量的60%这一事实,在分析比较各种除尘技术性能基础上,得出由于静电除尘器本身对微细粒子的捕集能力有限,加之我国燃煤锅炉所产生飞灰性质差别较大影响了静电除尘器的除尘效率,从而导致电厂烟尘排放浓度超标的实际情况,结合袋式除尘器能有效捕集对人体危害大的5 μm以下的细微颗粒的优点,建议燃煤电厂锅炉安装使用袋式除尘器来捕集这些细微颗粒.     

集成碳捕集及太阳能系统的燃煤发电机组的环境评估

采用Eco-Indicator 99方法作为环境指标评价方法,对传统燃煤机组(方案一)、燃煤碳捕集发电系统(方案二)及太阳能辅助燃煤碳捕集发电系统(方案三)进行了■环境分析及全生命周期评估,并对比了3种方案的■环境指标。结果表明：3种方案中系统■效率大小为方案三>方案一>方案二;因碳捕集与封存(CCS)系统对功率产生了惩罚,而太阳能对机组功率有所补偿,使得电力比环境影响排序为方案二>方案一>方案三;CCS系统的电耗导致系统净功率有所下降,因此3种方案生产1 kW·h电力产生的环境影响为方案二>方案三>方案一;■环境指标分析中,只有锅炉产生污染物且在环境影响中占主导地位,可通过降低污染物产生来减少环境影响,而对于锅炉、小汽轮机等设备,还可通过提高■效率来降低环境影响。     

静电增强湿式除尘器捕集可吸入颗粒物的定量描述

湿式重力喷淋除尘器一般对可吸入颗粒物的除尘效率较差,而借助静电力,则有望改善湿式除尘器对细微颗粒的除尘效果.首先介绍了静电增强湿式除尘器的捕集机制,包括布朗扩散、拦截、惯性碰撞和静电捕集;然后利用事件驱动常体积法描述了典型火电厂中三峰分布的烟尘颗粒群的尺度分布函数的动力学演变过程,以此量化静电增强湿式除尘器的除尘过程.结果表明,典型的传统湿式重力喷淋除尘器对PM的分级除尘效率在5%以上;如果液滴荷电,有望使得该除尘器对PM的分级除尘效率达到70%以上;如果颗粒荷电,PM的分级除尘效率将在25%以上;在液滴和颗粒同时荷上相反电荷的静电增强湿式除尘器中,PM的分级除尘效率接近100%.     

静电增强湿式除尘器的优化运行

利用颗粒和液滴间的静电吸引力可以大幅度提高传统湿式重力喷淋除尘器的除尘性能.着重分析液滴荷电而颗粒不荷电的湿式除尘器的工作状况,阐述了布朗扩散、拦截、惯性碰撞和静电捕集等4种除尘机理.介绍了典型工况中该除尘器烟尘颗粒度分布,并通过分析捕集速率(沉积核)的方式对该除尘器的运行优化进行了分析.结果表明:含尘气流输运速度越大,液滴喷射速度越小;液滴几何尺度越小,液滴荷质比越高;液气比越大,越有利于可吸入颗粒物的高效脱除.     

太阳能辅助碳捕集的660MW燃煤电站出力变化研究

为研究碳捕集对燃煤机组出力的影响,建立了仿真模型,分析了燃煤机组加装碳捕集装置后的系统性能变化。系统分为常规方案和太阳能辅助方案,常规方案抽取机组中压缸排汽为碳捕集装置供能,太阳能辅助方案采用太阳能完全替代抽汽,以提升燃煤电站性能。以660 MW燃煤机组为研究对象,分析了碳捕集改造对燃煤电站性能的影响,并将太阳能辅助对机组性能的提升作用与常规方案进行了对比。结果表明：与原燃煤机组相比,常规方案下机组最大出力由666.70 MW下降到466.31 MW,供电效率由42.79%下降到30.69%;太阳能辅助方案下,机组出力可以达到604.30～608.06 MW,说明碳捕集会对燃煤电站的最大出力造成较大影响,而利用太阳能辅助碳捕集基本能完全恢复机组的做功能力。     

载体配比及灰分对DPF压降及内部流场的影响

基于D30 TCI柴油机耦合氧化催化器(DOC)和柴油机颗粒捕集器(DPF)的试验台架,对3种不同结构DPF开展压降特性试验.并构建了DPF一维仿真模型及三维1/4孔道模型,研究了载体配比、载体孔密度对DPF压降及捕集特性的影响及载体配比及灰分沉积对DPF孔道内部气流运动及颗粒沉积特性的影响.结果表明:同一 DPF配比...     

燃煤可吸入颗粒物声波团聚效果的实验研究和数值分析

1引言我国是燃煤大国,每年燃煤产生的一次和二次颗粒物数量巨大。排放到空气中的颗粒物不仅降低了大气的能见度,影响环境和气候,而且危害人体健康,使致病率和死亡率上升。可吸入颗粒物(<10μm)是目前我国城市大气环境的主要污染物,尤其是空气动力学直径小于2.5μm的颗粒物(PM2.     

A particulate model of solid waste incineration in a fluidized bed combining combustion and heavy metal vaporization

This study aims to develop a particulate model combining solid waste particle combustion and heavy metal vaporization from burning particles during MSW incineration in a fluidized bed. The original approach for this model combines an asymptotic combustion model for the carbonaceous solid combustion and a shrinking core model to describe the heavy metal vaporization. A parametric study is presented. The global metal vaporization process is strongly influenced by temperature. Internal mass transfer controls the metal vaporization rate at low temperatures. At high temperatures, the chemical reactions associated with particle combustion control the metal vaporization rate. A comparison between the simulation results and experimental data obtained with a laboratory-scale fluid bed incinerator and Cd-spiked particles shows that the heavy metal vaporization is correctly predicted by the model. The predictions are better at higher temperatures because of the temperature gradient inside the particle. Future development of the model will take this into account.     

Coal combustion and its pollution control in China

Coal combustion will continue to be a major component of energy production in the foreseeable future, owing to its abundance in China. A primary challenge will be to seek ways to utilize the coal resources in an environmentally acceptable manner. This paper presents the coal combustion scenario and its related air pollution in China. Some commonly used technologies for removing the pollutants from coal combustion had been introduced after comparison of its utilization efficiency, engineering investment-, and operation expense. In order to cost-effectively reduce the pollutant emission, it is necessary to enhance the coal utilization efficiency by implementing large-scale advanced technologies and increasing the coal-washing rate. There is dire need for indigenously developed techniques for the pollution control to reduce the engineering cost. The development of low-cost, low water-consuming flue gas desulfurization technologies, low-cost technologies for reducing NO_x emission, and low-cost advanced technologies for inhalable particle emission control, must be predominantly paid attention.     

Effects of particle sizes on transport phenomena in single char combustion

A one-dimensional char combustion model including pore structure effects is used to numerically investigate single char particle combustion for several different types of char samples. Previously, it is expected that small char particles have less combustion time. However, the present work shows that this is true only if the combustion time is defined as that needed for a char particle diameter diminished below a certain value. If the combustion time is defined as time needed for the carbon conversion ratio higher than a certain value, there are optimal particle sizes in a limited combustion period. Just reducing the char particle sizes may not get high carbon conversion ratios. It has also been found that, in general, the larger particles have higher temperatures at the exterior surfaces.     

Particle emissions of direct injection internal combustion engine fed with a hydrogen-rich reformate

Thermochemical Recuperation is a promising waste heat recovery method that enables utilization of the engine waste heat together with onboard hydrogen production resulting in a significant improvement in thermal efficiency and a massive reduction in gaseous pollutants emission. However, an unexpectedly high particle emission level as compared to the gasoline-fed engine was measured despite the combustion of a hydrocarbon-free hydrogen-rich methanol steam reforming (MSR) products, containing 75% mol. H₂ and 25% mol. CO₂. In the existing literature, this phenomenon has not described yet.In this reported study, experiments are performed to investigate reasons of the elevated particle emissions by a direct injection spark ignition engine fed with MSR reformate, and results are compared with a baseline engine fed with gasoline at the same engine loads and speeds. Results of particle number concentration and size distribution measurements show that the total particle number concentration emission of engine fed with MSR reformate is 170% higher compared to gasoline. A direct experimental comparison between the port and the direct reformate injection performed on the same engine shows an increase in particles formation with a direct injection method. Based on these findings, several hypotheses are presented attributing to excessive lubricant involvement in the combustion process. The peculiarities specific for direct reformate injection that could result to the enhanced particles formation are jet – lubricated wall interaction, lubricant vapor entrainment into the reformate jet and shorter flame quenching distance of hydrogen compared to gasoline.     

Feasibility study on the controlled hydriding combustion synthesis of Mg–La–Ni ternary hydrogen storage composite

The feasibility of using the controlled hydriding combustion synthesis (CHCS) under a high magnetic field to prepare the Mg–La–Ni ternary hydrogen storage alloys was studied. Comparison was made between the conventional hydriding combustion synthesis (HCS) and the CHCS. The influence of a high magnetic field on the physicochemical properties (thermodynamic and kinetic characteristics, hydrogen absorption/desorption (A/D) properties, thermal behavior, phase composition and morphology) of the Mg–La–Ni composite was analyzed and the results suggested that a high magnetic field can change the microstructure and phase compositions, decrease the hydriding/dehydriding (H/D) temperature and the particle size of the composite, and increase the H/D rates. Based on this study, the lower-temperature metal hydrides prepared by CHCS seem to be technically feasible for lab-scale and it could represent a possible and attractive alternative to prepare the hydrogen storage materials.     

Numerical studies on the combustion properties of char particle clusters

Particle clustering is an important phenomenon in dense particle–gas two-phase flow. One of the key problems worth studying is the reacting properties of particle clusters in coal particle combustion process in the dense particle region. In this paper, a two-dimensional mathematical model for the char cluster combustion in airflow field is established. This char cluster consists of several individual particles. The comprehensive model includes mass, momentum, and energy conservation equations for both gas and particle phases. Detailed results regarding velocity vector, mass component, and temperature distributions inside and around the cluster are obtained. The micro-scale mass and heat transfer occurred inside and around the char cluster are revealed. By contrastively studying the stable combustion of char particle clusters consisting of different particles, the combustion properties of char clusters in various particle concentrations are presented and discussed.     

An electrical network for the numerical solution of transient mhd couette flow of a dusty fluid: Effects of variable properties and hall current

The Network Simulation Method (NSM) has been used to study the variations with velocity of suction, hall effect, Reynolds and Hartmann number, particle concentration and Eckert number on the unsteady MHD Couette Flow and heat transfer of a dusty and electrically conducting fluid between parallel plates in the presence of an external uniform magnetic field and uniform suction and injection. The solutions are obtained with the network model proposed and the electric circuit simulation program PSpice. The fluid is acted upon by a constant pressure gradient and an external uniform magnetic field is applied perpendicular to the plates. Due to the presence of uniform suction and injection, the Hall Effect is not dismissed. The NSM is applied to solve the steady-state and transient problems of flow and heat transfer for both the fluid and dust particles. This method requires only discretization of the spatial co-ordinates, while time remains a real continuous variable. Velocity and temperature are studied for different values of the viscosity and magnetic field parameters and for different particle concentrations and upper wall velocities.     

外加磁场对磁流化床烟气脱硫过程的影响

研究了磁流化床脱硫过程中外加磁场对流化状态、脱硫效率和脱硫产物特性的影响,并分析了磁场强化脱硫的机理.结果表明:随着磁场的增强,磁流化床经历了3个阶段.在鼓泡流化状态下,床层压降不稳定,脱硫效率低;在磁稳流化状态下,床层压降小,脱硫效率快速提高;在磁聚状态下,床层压降较大,脱硫效率提高.兼顾脱硫效率和能源消耗两方面的要求,在磁稳流化状态下进行烟气脱硫是适宜的.此外,对脱硫产物微观形貌和化合物成分的分析表明:磁场改变了铁磁颗粒表面脱硫产物的附着方式,并促进了S(IV)的氧化,提高了SO2的吸收速率,从而提高了磁流化床的脱硫效率.     

小型卧式燃煤热风炉内流动与传热过程的数值模拟及实验

为了研究第三挡板长度对热风炉燃烧性能的影响,以热风炉燃烧室为研究对象,利用FLUENT软件对其进行了数值模拟,模拟分析了燃烧室内的温度分布、速度分布及颗粒物浓度分布等情况,最后搭建了试验台对数值模型进行了验证。结果表明：燃烧室温度模拟值与实验值的相对误差在10%以内;燃烧高温区位于第一挡板和第二挡板顶部之间的区域;大部分颗粒物集中在炉排底部附近,随着烟气绕挡板流动,颗粒物浓度逐渐降低;热风炉燃烧室内第三挡板长度为270mm时,可以减少炉膛出口处颗粒物的排放,使燃烧更充分。