煤的热天平燃烧反应动力学特性的研究

采用热天平获得同一种煤在不同升温速率下的TG、DTG曲线,可求出燃烧速率、燃烧温度随燃烬度的变化曲线,根据两个不同升温速率下的数据,可计算出化学动力学参数活化能和指前因子随燃烬度的变化曲线。根据实验数据计算得到四个煤种的反应动力学参数随燃烬度变化的曲线,并预测其中一种煤在第三个升温速率下的燃烧速率随燃烬度的变化曲线,计算结果与实验结果符合较好。用此模型预测了在不同的恒定温度下试验煤种的煤粉燃烧速率随燃烬度的变化趋势。     

加福无烟煤粉燃烬过程的微结构研究

一、引言 福建加福无烟煤着火与燃烬非常困难,为世界上最难烧的煤种之一。燃烧加福煤粉煤锅炉的飞灰含碳量甚高,一般超过30％。为了系统地探讨加福煤燃烬困难的原因,我们在一维粉煤试验炉上做燃烬试验,并对取样颗粒进行微结构研究。图1算出了一维炉取样口位置。共做四个工况,其中Ⅰ属正常工况,Ⅱ为缺氧工况,Ⅲ和Ⅳ分别为低温和高温(延长高温区)工况。由图看出:(1)热力工况对加福煤粉的燃烬有影响。低温和缺氧对燃烬不利;提高炉内平均温度水平(扩大高温区)将降低飞灰含碳量。(2)总的说加     

煤粉在四角切向燃烧煤粉锅炉炉膛内的燃烧行为

本文对煤粉在四角切向燃烧煤粉锅炉炉膛内的燃烧行为进行了数值研究。在计算中,将煤岩学对煤进行分类研究的思路引入燃烧学,对煤粉中所含不同煤岩类别的煤粒分别进行了研究。结果表明,煤粉中的部分难燃组分在炉膛内未能燃烬;炉膛出口处颗粒的浓度存在较明显的偏差,右侧浓度较大,未燃成分较多;煤粉的未燃烬及浓度偏差对四角切向燃烧煤粉锅炉的局部超温爆管现象有直接的影响,且三次风的影响更为严重。     

压力对煤粒燃烬时间影响的研究

一、前言近年来国内外均在发展煤的加压燃烧技术。但是加压条件下煤的燃烧特性可供参考的数据很少,国内还是一片空白。本文介绍了一种加压燃烧炉的研制、调试和实验方法;测定了不同压力下煤粒燃烧过程中的温度变化曲线(T-t);得到了压力对煤的燃烬时间的影响规律;用煤粒表面扩散燃烧模型计算了不同压力下煤粒的燃烬时间,计算结果与实验结果符合得很好。     

单头部双级旋流器燃烧室流场PIV测量

利用粒子图像测速(PIV)测量技术对单头部双级旋流器燃烧室紊流流场进行了测量,试验研究主燃孔射流与旋流器旋转射流之间相互作用,结果表明:不同旋流器几何参数(如:叶片安装角)和主燃孔布置对轴向和径向气流速度分布及回流区结构的影响都较大,为了得到一个满意的气动特性和中心回流区,选择合理的主燃孔布局比旋流数更为重要.     

热刺激下不同结构引信的响应机理

为了掌握引信在泄压结构作用下的响应特性,通过自行设计的引信泄压装置,开展了烤燃条件下泄压装置对引信响应剧烈程度的影响研究。试验结果表明,慢速烤燃和快速烤燃条件下,泄压结构均可以有效降低引信响应时刻的内部压力,降低引信在烤燃条件下的响应烈度,但是引信在慢速烤燃和快速烤燃条件下的响应情况存在一定差异。通过数值模拟对引信的响应情况进一步分析,结果表明:慢速烤燃条件下,引信点火点位于传爆药柱中心;快速烤燃条件下,引信点火点位于传爆药底部。点火位置不同使得传爆药的压力释放过程不同,慢速烤燃通过中心点火形成从中心至泄压孔的排气通道来释放内部压力,快速烤燃泄压孔释放部分压力后,剩余压力导致底部端盖被冲破。     

宏观煤岩分类及燃烧反应动力学参数

本文将神木、西山煤用重液分离法分为亮煤、暗煤和无机矿物质三种宏观煤岩类别并进行了燃烬实验。实验结果表明，显微组分存在形式的不同导致厂其在各宏观煤者类别中纯度的较大差异；宏观煤岩类别间燃烧反应动力学参数的明显差异要求对原有的将煤粉视为物理、化学性质均匀的颗粒的燃烧模型进行改进。     

可溶性碳纳米管Z扫描实验研究

以可溶性碳纳米管为研究对象,进行了Z扫描实验.实验中通过改变样品的参量,研究了材料在不同浓度和不同厚度下的Z扫描曲线特性;实验分别在532nm和1064nm的激光下进行,并分别进行了开孔和闭孔实验.材料的闭孔 Z扫描曲线没有明显的峰谷对称结构,而开孔Z扫描曲线呈现关于原点对称的单一谷形状,表明样品存在较强的非线性吸收效应,非线性吸收可能是其主要的光限幅机理.     

燃用天然气合成油增压柴油机特性研究

在一台增压中冷柴油机上分别燃用常规柴油与代用燃料天然气合成油(GTL),供油提前角分别设为上止点前9°和12°CA,对比研究了燃用这两种燃料的柴油机动力性、经济性、燃烧和排放特性.与柴油相比,燃用GTL的柴油机有效功率和转矩不变,有效燃油油耗率降低,有效热效率相当;GTL的最高燃烧压力和放热率峰值均略低,GTL的着火时刻、缸压和放热率峰值出现时刻均略晚,燃烧持续期略长;与柴油相比,在试验工况下GTL平均降低了16.6%HC、14.5%CO、15.7%碳烟和15.1%NOx排放.试验结果显示GTL是一种有潜力的低排放代用燃料.     

煤粉预燃室内气体湍流交换系数的实验和数据整理

一、引言 旋流式煤粉预燃室作为一种新型粉煤燃烧器,在降低电站锅炉点火用油,提高煤粉锅炉的低负荷稳燃性能等方面发挥了显著的怍用.旋流式煤粉预燃室合理地组织了旋转射流、环形射流,有其独特的结构和配风方式,其稳燃机理尚不完全清楚.本文作者则在预燃室冷态流动模型上用温度示踪方法试验研究了有根部风的改进型预燃室内气流的混合过程,并用三孔测速探针测量了筒内八个断面上的轴向和切向速度分布,对预燃室内部     

Multifractality analysis of crack images from indirect thermal drying of thin-film dewatered sludge

Crack formation is inevitable during sludge drying because of the existence of uneven thermal stress. Experiments have been conducted to study crack pattern formation in thin film sludge. Crack images show that the thinner the sewage sludge film, the more even the crack distribution. The crack changes from a flaky texture to a banded structure with increasing thickness. Multifractal methods are proposed to analyze the crack image of four different thicknesses of dried sludge. Several parameters are conducted for quantification of the crack image and the results indicate that the width of spectra increases with thicker sludge film, that is to say, nonunifromity of crack distribution increases with increasing thickness, which proves that the multifractal method is sensitive enough to quantify the crack distribution and can be seen as a new approach for the changing research of crack images of sewage sludge drying.     

污泥吸附剂的制备及其光谱性能研究

以城市和石化污水厂生化活性污泥及剩余污泥为原料,采用热解法制备烟气脱硫吸附剂,并与商品活性炭对比进行了孔结构、扫描电镜、X射线衍射、热分析及元素分析性质表征,利用傅里叶红外光谱法研究污泥吸附剂在SO₂-O₂-N₂及SO₂-O₂-H₂O_(g)-N₂体系的吸附机理。结果表明城市污水厂剩余污泥制备的吸附剂脱硫性能较好,其次为石化活性污泥,生化活性污泥吸附剂脱硫性能较差,剩余污泥制备的吸附剂脱硫率略低于商品活性炭。SO₂-O₂-N₂体系吸附机理主要为物理吸附,SO₂-O₂-H₂O_(g)-N₂体系SO₂发生了催化氧化,以化学吸附为主。吸附过程中起吸附作用的主要是微孔结构。     

城市下水污泥和煤/LPG在循环流化床上的混烧试验研究

在高6000 mm、直径300mm的循环流化床上进行了含水率为79％的湿污泥与煤／石油液化气(LPG)的混烧试验。试验结果表明:无论用煤还是LPG作为辅助燃料,试验都能在设定的工况条件下稳定运行;向炉内加入石灰石的量达到钙硫摩尔比为3．4∶1时,二氧化硫和氯化氢的排放达标,脱硫效率和脱氯效率分别为75％和94％;在试验中, 烟气中NOx排放、烟气中汞含量和二恶英类排放都不超标;试验产生的飞灰含碳量低,飞灰中痕量元素的浸出毒性不超标;计算表明,如果利用余热干燥污泥和预热空气可有效地减少辅助燃料的消耗量。     

Assessment of sonotrode and tube reactors for ultrasonic pre-treatment of two different sewage sludge types

The effectiveness of tube and sonotrode reactors for the sonication of sewage sludge under identical conditions was compared for the first time. Despite the considerable structural differences, sonication with each ultrasonic reactor led to an accelerated degradation rate and an increased methane production within the first five days for the majority of the sewage sludge samples tested. On closer examination, however, it becomes clear that the investigated sonication systems are not equally suitable for the substrates considered. While the use of a sonotrode proved to be particularly advantageous for the treatment of waste activated sludge (+25% methane yield at 300 kJ/kg_TS), the use of a 2-inch tube reactor achieved the highest enhancement for low-intensity sonication in digested sludge (+22% methane yield at 300 kJ/kg_TS). With increasing energy input, more chemical oxygen demand was solubilized, but this did not result in an increase in methane yield for all samples. Sonication of waste activated sludge led to a significant reduction in viscosity of up to 50%, and a reduction of up to 60% was observed after sonication of digested sludge with low energy inputs. The study, therefore, demonstrates that the choice of the most suitable sonication system essentially depends on the properties of the sludge to be sonicated.     

Tube reactors as a novel ultrasonication system for trouble-free treatment of sludges

The performance of a novel low-maintenance tube reactor for ultrasonic treatment of sludge has been evaluated. The effects of sonication on the release of soluble chemical oxygen demand (sCOD) and anaerobic digestibility of raw and digested sewage sludge as well as agricultural sludge were studied. Results suggest that solubilization and digestibility is dependent on both type of sludge and the energy input. Digested and raw sludge showed high degree of solubilization, however, methane production was only increased for digested sludge. Agricultural sludge was not significantly affected by ultrasonic treatment neither concerning sCOD release nor methane production. The configuration of the ultrasonic system (serial vs. parallel operation) did not show a significant difference in both sCOD release and methane production. However, parallel operation tends to perform better for digested sludge, while serial operation tends to perform better for raw sludge. The strongest effect was observed for the treatment of digested sludge by increasing the methane production by more than 60%, although with a very intensive energy input of more than 5,000 kJ per kg total solids. Hence, tube reactors seem to be an attractive alternative to sonotrode-based systems achieving similar performance at low maintenance with great potential especially for digested sludge.     

CFBC混烧城市污泥与煤:N2O和NO的排放

在0.15MWth CFBC试验台上混烧城市污泥与煤,当城市污泥的含水率和混烧率分别变化在30％～60％和25％～100％之间时,可以实现稳定燃烧。分析了炉膛温度和城市污泥混烧率对NO和N_oO生成浓度的影响。结果显示,在焚烧氮含量很高的城市污泥过程中,通过适当提高炉膛温度,可以控制N_2O的生成,但是NO的生成浓度主要与混烧率有关。     

The rate of gasification by CO2 of chars from waste

Three chars and an activated carbon were gasified by reaction with CO₂ in a fluidised bed of sand, at 800–1050 °C. The chars were produced from (i) dried sewage sludge, (ii) car tyres, and (iii) a bituminous coal. For the conditions used, the rate of CO₂ + C → 2CO was largely determined by chemical kinetics; there was a small effect from mass transfer for the most reactive char, derived from sewage sludge. The rate of CO formation, r, differed greatly for these chars, but was well described by:

The reactivity of a char depends on: (i) its pore structure, (ii) catalytic activity of the associated ash, and (iii) the activity of the char’s carbon. The sewage sludge char was the most reactive, on the basis of either BET area or mass by 2 orders of magnitude. The activated carbon had the lowest reactivity per unit BET surface area, indicating that the area in its micropores is comparatively unreactive.     

分析北京城市污泥中铅砷镉形态浓度的ICP-MS

城市污泥中重金属的难降解和高毒性限制了污泥的资源化利用.以北京G和Q污水处理厂的压滤出厂污泥为实验材料,采用BCR三步浸提法对污泥中铅砷镉Pb,As,Cd的三种形态进行提取,以HNO3-HClO4进行全量消解,利用ICP-MS检测Pb,As,Cd的全量和各形态的含量,从而为北京城市污泥的资源开发研究提供基础数据.实验结果表明,北京城市污泥中Pb和Cd含量比上世纪末明显降低:其中,G污泥中Pb,As,Cd的全量(干重)分别为19.60,37.96和1.34 mg·kg-1,而Q污泥中分别为19.58,23.46和2.30 mg·kg-1;两种污泥中Pb含量相差甚微,G污泥中As明显高于Q污泥,而Cd则显著低于后者;两种污泥中相应金属的三种形态的变化趋势基本一致:Pb与As以HAc酸溶态为主,H2O2可氧化态最少;而Cd主要以NH2OH-HCl可还原态存在,HAc酸溶态最少.三种重金属中生物毒性大的形态均占70%以上.     

The comparison of ultrasonic disintegration in laboratory and technical scale disintegrators

The study was aimed at finding the impact of the construction of two disintegration instruments (laboratory and technical scale) on the effects of ultrasonic disintegration. The tests were carried out on excess sewage sludge and an increase in soluble COD in the sludge after ultrasonic disintegration was determined. In both types of disintegrators, the sludge was subjected to ultrasounds at the same level of energy density, but the disintegration effects were about three times higher in the case of the technical module application.     

High-frequency ultrasound treatment of sludge: combined effect of surfactants removal and floc disintegration

Ultrasounds represent an effective technology in many research fields. In sewage sludge treatment, low-frequency ultrasound, particularly at 20 kHz, are widely used for sludge disintegration before the anaerobic digestion, while in the last years novel application of high-frequency ultrasound regards the decontamination of water and wastewater through sonochemical reactions. The innovative approach presented in this paper is the treatment of sewage sludge with ultrasound at 200 kHz for obtaining efficient sludge disintegration and the removal of the linear alkylbenzenesulphonates (LAS) at the same time. Results of the sonolysis experiments showed that native LAS degradation up to 40% can be achieved with low power input in less than 1 h. The degradation pattern was different for each LAS homologue (from C10 to C13), because of their physical-chemical properties, in particular as regards the alkyl chain length. This high-frequency ultrasound irradiation resulted effective also in terms of floc disintegration and soluble organic matter release, in particular for energy inputs higher than 30,000 kJ/kg TS. The disrupting effect of the 200 kHz treatment was also evaluated by microscope analyses and determination of the extracellular polymeric substances release in the liquid phase.