灰分变化对城市固体垃圾燃烧过程的影响

为了更好地了解层燃垃圾焚烧炉的燃烧过程,建立了固定床垃圾焚烧层燃炉热态试验台.模拟的城市固体垃圾由蔬菜、纸板和细沙按一定的比例组成.通过物料中灰分含量的变化,对固定床层内温度、火焰传播速度、气氛浓度和床层重量变化进行了实验研究.结果表明:随着灰分含量的增加,物料燃烧的速度和火焰锋面的传播速度一直是降低的;CO2、CO的平均排放速度减小;NO的平均排放速度先增大后降低.     

木质生物质层燃燃烧特性实验研究

搭建单元体炉层燃燃烧实验台,以松木为原料,对木质生物质的层燃特性进行研究。通过控制炉排给风量,对层燃的床层温度变化过程、床料失重情况以及床层析出气氛测定,研究木质生物质的层燃燃烧特性及相关规律。结果显示炉排给风量对木质生物质层燃的床层温度分布等燃烧特性有较为显著的影响。     

生物质层燃实验台的设计与实验

研究小型层燃炉燃烧实验系统,设计并搭建了生物质多功能实验台,可进行层燃燃烧、室燃燃烧及配风等实验的模拟.同时对水稻秸秆和玉米芯燃料层燃燃烧过程进行了研究,分析了风量对生物质燃料层燃燃烧的影响.研究表明:对床层内部分布的热电偶的温度和整个燃烧过程中床层上方的气体浓度变化进行分析,燃烧过程的温度变化曲线与床层上方气体浓度变...     

煤和生物质床层燃烧氮氧化物生成规律的对比研究

为揭示和评估燃料特性对床层燃烧过程中氮氧化物生成规律的影响,选取了燃煤与生物质成型颗粒这两种代表性燃料,在单元体炉试验台上模拟层燃反应过程,并测定了床层表面和内部的温度及气氛.结果表明:无论燃煤还是生物质,床层内部的氮氧化物浓度峰值都显著高于床层表面,证实了炭层对氮氧化物优良的还原作用.生物质与燃煤相比火焰锋面处的氮氧...     

高水分城市固体垃圾床层燃烧的数值模拟研究

本文针对运动炉排上的高水分垃圾床层燃烧过程,用计算流体动力学的方法进行了数值模拟.数值模拟结果与热态试验结果体现了一致性,两种结果分布趋势吻合良好.通过数值计算结果的分析比较,研究了高水分垃圾燃烧床层固相水分变化、温度变化的规律.研究了不同一次风温、一次风率对高水分垃圾燃料床层干燥和燃烧的影响.     

基于床层下降的链条炉数值模型与计算

建立了考虑床层下降的链条锅炉二维稳态层燃数值模型,通过求解床层高度控制方程得到床层高度沿炉排前进方向变化的分布,利用动网格技术实现床层高度的下降。对比层燃模型和单元体炉实验结果,实验测得燃烧后床层高度为30 mm,改进后模型预测值为26.9 mm,表明改进后的模型可以更准确地预测床层高度、床层燃烧温度、气体产物分布,提高了层燃数值模型的计算精度。     

水分变化对固定床内模拟城市固体垃圾燃烧的影响

实验研究了焚烧过程中固定床内温度、烟气成分浓度、火焰传播速度和质量燃烧速率的变化规律.实验结果表明:在物料燃烧稳定阶段,火焰传播速度几乎是恒定的,并且随着水分含量的增加,质量燃烧速率和火焰传播速度降低;NO的浓度变化曲线一般存在两个峰值;水分较高物料燃烧时,CO和NO的平均排放浓度较低;火焰的长度与水分含量成反比.     

典型生物质燃料层燃燃烧特性的试验研究

在小型单元体炉中进行了不同形状尺寸及种类的生物质燃料的层燃燃烧试验.采用着火锋面传播速率及着火锋面温度研究了生物质燃料在同一给风量条件下的层燃燃烧特性,并分析了不同给风量对层燃燃烧的影响.结果表明:尺寸较小的燃料颗粒,完全燃尽需要的时间较长,燃烧过程中床层温度较高,而经过压缩的成型生物质燃料,燃烧稳定性好,适合层燃燃烧;对于不同种类的生物质,挥发分含量越高,其燃尽时间越短,灰分含量越高,燃烧稳定性越差;着火锋面传播速率与着火锋面温度都随着给风量的增加而提高.     

生物质成型燃料层燃NO排放特性研究

在层燃单元体炉上研究了生物质成型燃料的NO排放特性,采用热电偶和烟气分析仪对生物质成型燃料层燃过程中床层温度和表面气氛进行监测,分析了生物质成型燃料的燃烧特性和NO排放特性。试验结果表明,生物质成型燃料层燃分为火焰传播段和焦炭燃尽段。NO主要在火焰传播段生成,而在焦炭燃尽段,由于焦炭的还原作用,NO排放量逐渐降低,此外,NO排放总量随着一次风量的增加先减小后变大。     

生物质层燃燃烧过程中的影响因素分析

针对生物质层燃燃烧过程,综述了生物质燃料物理性质、供风以及炉排运动形式对层燃燃烧过程影响的研究进展;归纳了颗粒粒度大小、密度和全水分对燃烧过程的影响,操作因素中风量分配、风速、空气预热对燃烧的影响和不同炉排运动对料床上颗粒混合状况和燃烧的影响。当前,层燃燃烧过程的影响因素分析,多数都是基于固定床或者移动炉排开展的实验,对于由炉排运动引起的燃烧过程中料床上颗粒混合、颗粒粒度大小分布、孔隙率、料床厚度不均匀性等规律的研究,还处于初始阶段。     

Pyrolytic oil from fixed bed pyrolysis of municipal solid waste and its characterization

Municipal solid waste, in the form of paper waste, has been converted into liquid oil by a fixed bed pyrolysis process. Favorable properties for pyrolysis conversion such as high volatile content, elemental composition, and thermochemical behavior of the waste were investigated by characterization study. The waste paper feedstock was pyrolyzed in an externally heated 7 cm diameter, 38 cm high fixed bed reactor with nitrogen as a carrier gas. The pyrolysis oil was collected in a series of condenser and ice-cooled collectors. The char was separately collected while the gas was flared. The effect of process conditions, like fixed bed reactor temperature, feedstock size and effect of running time on the product yields, was studied. The composition of the oil was determined at a bed temperature of 450 °C, at which the liquid yield was maximum. The liquid product was analyzed for physical, elemental and chemical composition using Fourier transform infra-red (FTIR) spectroscopy.     

Waste heat utilization in a ceramic industry

The scope for energy conservation in a ceramic factory was studied. It was found that the sensible heat of the flue gas from kilns could be used to heat the casting shop. A pebble bed waste heat regenerator was chosen to collect the sensible heat of the flue gas. Experiments were performed on a pilot plant scale pebble bed to study its characteristics using a flue gas stream whose temperature and composition were similar to the factory conditions. The results of the heating cycle showed that 14 500 kcal h⁻¹ of heat can be collected from flue gas in a 0·126 m³ bed. This information was used to design a complete retrofit system. Financial analysis of the proposed project showed that it has a pay-back period of 15 months. © 1997 by John Wiley & Sons, Ltd.     

Development of a low-temperature two-stage fluidized bed incinerator for controlling heavy-metal emission in flue gases

This study develops a low-temperature two-stage fluidized bed system for treating municipal solid waste. This new system can decrease the emission of heavy metals, has low construction costs, and can save energy owing to its lower operating temperature. To confirm the treatment efficiency of this system, the combustion efficiency and heavy-metal emission were determined. An artificial waste containing heavy metals (chromium, lead, and cadmium) was used in this study. The tested parameters included first-stage temperature and system gas velocity. Results obtained using a thermogravimetric analyzer with a differential scanning calorimeter indicated that the first-stage temperature should be controlled to at least 400 °C. Although, a large amount of carbon monoxide was emitted after the first stage, it was efficiently consumed in the second. Loss of the ignition values of ash residues were between 0.005% and 0.166%, and they exhibited a negative correlation with temperature and gas velocity. Furthermore, the emission concentration of heavy metals in the two-stage system was lower than that of the traditional one-stage fluidized bed system. The heavy-metal emissions can be decreased by between 16% and 82% using the low-temperature operating process, silica sand adsorption, and the filtration of the secondary stage.     

Glycerol steam reforming in a bench scale continuous flow heat recovery reactor

In the present study glycerol was successfully gasified using a diesel engine waste heat recovery system obtaining hydrogen and methane rich gaseous products. The reforming reactor was equipped with a vaporization pre-chamber to ensure uniform reactants distribution and a fixed reaction bed, being mounted in countercurrent flow configuration with the engine combustion gases stream. Accordingly, the reactions were conducted at gradually increased temperature conditions; starting at around 300 °C in the top section of the reaction bed and finishing in a controlled outlet bed temperature of 600–800 °C. When compared to homogeneous temperature reactors, the configuration used here produced a syngas of higher methane and ethylene contents. With regards to the reactor performance, syngas lower heat values of more than 22 MJ/kg were achieved with glycerol feed concentrations within 50–70% and outlet bed temperatures above 700 °C, corresponding to cold gas efficiencies of around 85%. The present results indicate that glycerin can be utilized as a syngas feedstock for steam reforming processes based on waste heat recovery.     

Reaction kinetics of fluidised bed gasification of Jordanian oil shales

Trying to achieve the optimal utilisation of oil shale resources, and the production of a more environmentally acceptable fuel, as well as a solid waste with a low a sulphur content, thereby reducing acidic leachates, has led to this investigation. In this article, the influences of the bed temperature and the choice of fluidising gas on the quality and quantity of the produced fuel gas, using a continuous feed fluidised bed reactor, were investigated. The composition and calorific value of the generated gas were determined. There was a nearly linear increase in the amount of fuel gas produced as a function of temperature, reaching ∼350 kg per 10³ kg of dry raw shale and the gross calorific value ranged from 15 to 23 MJ·kg⁻¹ with CO and H₂ being the major constituents. Subsequent experiments were carried out, employing a thermogravimetric analyser under similar conditions as applied to the fluidised bed reactor. Gasification of the investigated shales complied with first-order kinetics within the limits of experimental error and the activation energy and temperature at which maximum reactivity rate occurred decreased slightly as the shale particle size was reduced.     

Characteristics of oxygen-blown gasification for combustible waste in a fixed-bed gasifier

With increasing environmental considerations and stricter regulations, gasification of waste is considered to be a more attractive technology than conventional incineration for energy recovery as well as material recycling. The experiment for combustible waste mixed with plastic and cellulosic materials was performed in a fixed-bed gasifier to investigate the gasification behaviour with the operating conditions. Waste pelletized to a diameter of 2–3 cm and 5 cm length, was gasified in the temperature range 1100–1450 °C. The composition of H₂ was in the range 30–40% and CO 15–30% depending upon the oxygen/waste ratio. Gasification of waste due to the thermoplastic property of the mixed-plastic melting and thermal cracking shows a prominent difference from that of coal or coke. It was desirable to maintain the top temperature at 400 °C to ensure the mass transfer and uniform reaction throughout the packed bed. As the bed height was increased, the formation of H₂ and CO was increased, whilst the CO₂ decreased by the char-CO₂ reaction and plastic cracking. From the experimental results, the cold gas efficiency was around 61% and the heating values of product the gases were in the range of 2800–3200 kcal/Nm³.     

Hydrogen-rich gas production by steam gasification of municipal solid waste (MSW) using NiO supported on modified dolomite

NiO on modified dolomite (NiO/MD) catalysts were developed for hydrogen-rich gas production from steam gasification of municipal solid waste (MSW). The catalysts were prepared through deposition-precipitation method and characterized by various characterization methods. The activity of NiO/MD on the steam gasification of MSW was investigated in a lab-scale fixed bed. The results indicated that the catalysts could significantly eliminate the tar in the gas production and increase the hydrogen yield. In addition, higher temperature contributed to higher hydrogen production and gas yield, meanwhile, the optimal ratio of steam to MSW (S/M) was found to be 1.23. In the experimental conditions, the NiO/MD catalysts showed a good performance over a long lifetime test.     

废塑料流化床焚烧及排放特性的试验研究

在一内径40mm、高500mm小型电加热流化床焚烧炉上对废塑料的燃烧特性，包括燃烧效率、挥发份析出特性及烟黑的生成进行了试验，分析了主要气体污染物（SO2、NO、HCl)的排放特性及运行条件（过剩空气率、床温及水份等参数）对废塑料燃烧和排放的影响。     

Effect of particle size on pyrolysis of single-component municipal solid waste in fixed bed reactor

According to the differences in components, three representative components (plastic, kitchen garbage and wood) in municipal solid waste (MSW) were pyrolyzed in a fixed bed reactor to evaluate the influence of particle size on pyrolysis performance of single-component municipal solid waste (MSW). The bed temperature was set at 800°C and each sample was separated into three different size fractions (0–5 mm, 5–10 mm and 10–20 mm). The results show for all the samples particle size has an effect on pyrolysis product yields and composition: smaller particle size results in higher gas yield with less tar and char; the decrease of particle size can increase H₂ and CO contents of gas, as well as the ash and carbon element contents in the char. And the influence is the much more significant for sample with higher fixed carbon and ash contents, such as kitchen garbage, and less for sample with higher volatile content, plastic in the test.