Numerical Investigation of the Combustion Characteristics and Nitric Oxide Formation in a Municipal Waste Incinerator

Numerical analysis has been carried out to investigate the combustion and NO formation and distribution characteristics using a beta probability density function (PDF) method in a three-dimensional municipal waste incinerator by considering the turbulent reacting flow with thermal radiation. For numerical calculation, the multiblock method is adopted to simulate a complex geometry. The program developed has been validated with a commercial program. Considering not only thermal NO but also prompt NO, parametric studies for excess air ratio, secondary air injection, and radiation have been undertaken. By increasing the primary air supply, higher excess air ratio lowers the temperature inside the incinerator so that the amount of NO formation is reduced. When the secondary air injection is considered, more secondary air injection does not always reduce NO formation because of another factor, the equivalence ratio. Additionally, in order to simulate the real situation in an incinerator, nongray gas radiation should be introduced, since including the radiation effect results in lower NO formation because of radiative heat loss.     

An equilibrium model for predicting flue-gas composition of an incinerator

The composition of an incinerator flue gas depends characteristically on the operating parameters such as combustion temperature, fractional excess air value, and moisture content of the waste material. An a priori knowledge of the influence of these parameters on the flue-gas composition helps to carry out the combustion process efficiently by appropriately selecting their values. A simple chemical equilibrium model is proposed to predict the flue-gas composition from an incinerator at different operating temperatures, excess air values, and moisture contents of the combusting material. The predicitions are supposed to establish the upper limit of the chemical species concentrations in the flue gas and hence the model is considered as an appropriate one for selecting the pollution control equipment and in estimating the upper limit of environmental contamination. The model-based computations predict that at a given temperature and moisture content, the increase in excess air decreases the concentrations of carbon monoxide, carbon dioxide, water, and hydrogen in the flue gas while it increases that of oxygen. Similarly, the proportion of nitrogen dioxide, nitrogen, sulfur dioxide and sulfur trioxide decreases while that of nitric oxide increases. At a given excess air and moisture content, the increase in temperature decreases the concentrations of carbon monoxide and hydrogen and increases of carbon dioxide and water due to better combustion. Similarly, the increase in temperature also augments the concentrations of nitric oxide, nitrogen dioxide and sulfur dioxide while it decreases that of nitrogen and sulfur trioxide. Similar trends are observed at different levels of moisture content.     

Effect of secondary air supply rate on the combustion of volatile gas in a controlled‐air incinerator

Experiments have been carried out to study the effect of secondary air supply rate on the combustion of volatile gas in a controlled‐air incinerator. The secondary air supply was varied at flow rates of 0.56, 1.026, 1.73 Nm³/min. The waste in this study was categorized into three types: namely those containing low, medium and high combustible matter. The significant results of the experimental investigation shown that increasing secondary air supply rate reduces the chamber temperature in both chambers and strong effect on CO reduction for waste with high combustible content. NO formation increases slightly as secondary air supply increases and SO₂ formation depends on the sulfur content in the waste and insensitive to secondary air for the range of flow rate tested. Copyright © 2005 John Wiley & Sons, Ltd.     

市政污泥流化床掺烧生物质的NO与SO2排放特性研究

为了探究市政污泥燃烧过程中的气态污染物排放特性,在30 kW鼓泡流化床实验台上进行了市政污泥的燃烧实验,研究燃烧温度、二次风率、秸秆掺混比等参数对气态污染物排放特性的影响。结果表明：燃烧温度的升高会显著提高NO与SO₂的排放;提高二次风率使NO排放浓度减少,SO₂排放浓度增加;由于生物质中较低的N、S含量以及生物质与污泥燃烧的协同作用,污泥掺烧生物质能够有效地减少NO与SO₂的排放;秸秆占比由0提升至40%,NO由289 mg/m³下降至140 mg/m³,而SO₂排放浓度也从3 949 mg/m³下降至1 725 mg/m³;污泥掺烧秸秆时,NO与SO₂的整体排放特性与污泥单独焚烧相似,掺烧秸秆能够加快整体的燃烧速率,并加强燃烧气氛的氧化性,进而影响气态污染物的排放。     

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.     

生活垃圾焚烧发电锅炉的稳定燃烧控制与调整

垃圾焚烧发电锅炉的稳定燃烧控制与调整是运行中的重点和难点。如何实现稳定燃烧提高垃圾燃烧热效率是垃圾发电产业的研究课题之一。本文以某炉排层燃垃圾焚烧发电锅炉为例,从垃圾燃料特性、垃圾料层厚度、一次风和二次风等方面阐述垃圾发电锅炉的稳定燃烧控制与调整,为垃圾焚烧发电锅炉的优化运行提供参考。     

天然气塔式同轴分级燃烧室掺氢燃烧特性 数值模拟研究

为了解天然气掺氢对贫预混燃气轮机性能的影响,采用Chemkm-pro研究了燃料的化学反应动力学 特性,对比了不同当量比、掺氢比下的绝热火焰温度、层流火焰传播速度及点火延迟时间,结果表明掺氢能缩 短燃料点火延迟时间,增加绝热火焰温度及提高火焰传播速度。进一步以天然气塔式同轴分级燃烧室为研 究对象,研究了掺氢比对燃烧室燃烧场分布及燃烧效率、总压损失系数、温度分布不均匀度、一氧化碳及氮氧 化物排放量等性能参数的影响。结果表明,随着掺氢比的增加,燃烧效率上升,总压损失系数增加,温度分布 不均匀度下降,一氧化碳排放量下降,氮氧化物排放量增加。掺氢比在35%时燃烧室发生回火。在30% ~ 35%掺氢比范围内,燃烧室性能参数变化较大。其中,总压损失系数增幅为24. 74%,温度分布不均匀度降幅 为31.11%,氮氧化物排放量增幅为416.12%。     

城市生活垃圾_MSW_与煤混烧过程中气体污染物的排放

人者在0．2MW循环流化床上进行了城市生活垃圾与煤混烧实验。在线测量了NOx,NO,N2O,SO4,HCl和Cl2排放浓度,探讨了城市生活垃圾与煤掺煤比（R）和温度对气体污染物排放的影响。实验结果显示,在混烧过程中,随拉圾加入量的增加,NOx,NO,N2O和SO4排放量减少,Cl2排放浓度啬 。当掺烧比R不变,温度增加时,NOx,NO排放量增加,N2O排放减少,SO2,HCl和Cl2排放浓度基本不变,飞灰和底渣中二恶英含量减少。     

Co-firing of Thai lignite and municipal solid waste (MSW) in a fluidised bed: Effect of MSW moisture content

Co-firing investigation of a high-moisture-content municipal solid waste (MSW) with Thai lignite have been performed in a laboratory-scale fluidised bed to study the effects of MSW moisture content on the combustion and emission characteristics of major gaseous pollutants. In this study the comparison of 35%- and 60%-moisture MSWs were tested. The results show that the bed temperature in the case of 35%-moisture content is higher than for in case of 60%-moisture content due to the difference of physical properties of the fuel. The combustion efficiency for the case of 35%-moisture MSW is higher than that for 60%-moisture MSW due to higher bed temperature at lower waste moisture content. The synergistic effect of the co-firing of lignite with MSW reduces the emission of CO leading to increase in combustion efficiency. CO concentration for the case of 35%-moisture content is generally lower, and is much less sensitive to the level of excess air. Both the concentration values of SO₂ and the fuel-S converted are lower for lower moisture content waste, particularly at high mass fraction of waste. The fuel mixture with low-moisture in waste gives higher fuel-N conversion to NO whereas the fuel-N conversion to N₂O is higher for higher moisture content waste, particularly at high excess air.     

Investigating the impact and reaction pathway of toluene on a SOFC running on syngas

The integration of solid oxide fuel cells (SOFCs) with gasification systems have theoretically been shown to have a great potential to provide highly efficient distributed generation energy systems that can be fuelled by biomass including municipal solid waste. The syngas produced from the gasification of carbonaceous material is rich in hydrogen, carbon monoxide and methane that can fuel SOFCs. However, other constituents such as tar can cause catalyst deactivation, and blockage of the diffusion pathways. This work examines the impact of increasing concentrations of toluene as a model tar in a typical syngas composition fed to a NiO-GDC/TZ3Y/8YSZ/LSM–LSM SOFC membrane electrode assembly operating at 850°C and atmospheric pressure. Results suggest that up to 20 g/Nm³ of toluene and a low fuel utilisation factor (c.a. 17%) does not negatively impact cell performance and rather acts to increase the available hydrogen by undergoing reformation. At these conditions carbon deposition does occur, detected through EDS analysis, but serves to decrease the ASR rather than degrade the cell.     

垃圾焚烧炉二次配风优化数值研究

为研究焚烧炉二次助燃风的作用,以某厂生活垃圾焚烧炉为研究对象,建立了生活垃圾焚烧炉的三维数值模型,采用计算流体力学软件FLIC和FLUENT对炉排上的固相燃烧和炉膛内的气相燃烧过程进行了耦合模拟。结果表明:当焚烧炉不设置二次助燃风时,烟气在喉口和一次烟道内混合不均匀,可燃成分会沿后拱形成贴壁流,使得炉壁局部热负荷较高,易发生烧损现象,燃烧的不均匀也对污染物的消减不利;当在炉膛两侧设置二次风,尤其是旋流二次风时,流场得到较好的组织,可使喉口区域形成多个旋流区,二次燃烧效果比较好,并且湍动能、烟气路径长度和停留时间都较优,有利于可燃成份的充分燃烧和污染物的消减。     

Effect of concentration of bed materials on combustion efficiency during incineration

The concentration of bed materials in a fluidized bed incinerator influences the reaction time, mass and heat transfer efficiency. These parameters significantly affect the combustion efficiency and the generation of pollutants in the waste incineration. This research studied the effect of concentration of bed materials on combustion efficiency during waste incineration. The size of bed materials, combustion temperature, and excess air factor were controlled to assess the concentration of carbon monoxide. The pressure drop was measured to evaluate the bed expansion and calculate the concentration of bed materials. Experimental results indicated that the concentration of carbon monoxide did not decrease with the decrease of residence time and increase of excess air factor. With higher heat transfer efficiency, the combustion time could be reduced and the combustion efficiency would be improved. The concentration of carbon monoxide at 700 °C was higher than that at 800 and 900 °C. The influence of heat transfer efficiency on combustion efficiency was significant as the operating temperature was higher than 700 °C. The concentration of carbon monoxide decreased with increasing static bed height. In addition, the size of bed materials affected the mixing and heat transfer efficiency in the sand bed. According to the result of experiment, the best particle size of bed materials was 770 μm.     

Performance,emission and combustion characteristics of a variable compression ratio engine using methyl esters of waste cooking oil and diesel blends

The performance, emission and combustion characteristics of a single cylinder four stroke variable compression ratio multi fuel engine when fueled with waste cooking oil methyl ester and its 20%, 40%, 60% and 80% blends with diesel (on a volume basis) are investigated and compared with standard diesel. The suitability of waste cooking oil methyl ester as a biofuel has been established in this study. Bio diesel produced from waste sun flower oil by transesterification process has been used in this study. Experiment has been conducted at a fixed engine speed of 1500 rpm, 50% load and at compression ratios of 18:1, 19:1, 20:1, 21:1 and 22:1. The impact of compression ratio on fuel consumption, combustion pressures and exhaust gas emissions has been investigated and presented. Optimum compression ratio which gives best performance has been identified. The results indicate longer ignition delay, maximum rate of pressure rise, lower heat release rate and higher mass fraction burnt at higher compression ratio for waste cooking oil methyl ester when compared to that of diesel. The brake thermal efficiency at 50% load for waste cooking oil methyl ester blends and diesel has been calculated and the blend B40 is found to give maximum thermal efficiency. The blends when used as fuel results in reduction of carbon monoxide, hydrocarbon and increase in nitrogen oxides emissions.     

混煤农药废液流化床焚烧的排放特性研究

报道了采用流化床焚烧高浓度混煤农药废液时,床温对不同混煤比例农药废液燃烧效率、CO排放水平的影响,并研究了N2O生成与NO、CO的关联性.试验研究表明,不同混煤比例的农药废液焚烧效果各不相同;N2O的生成与NO、CO存在一定的关联性.     

A hot-flow model analysis of the MSW incinerator

A hot-flow model incinerator was constructed to simulate the combustion chamber of mass-burn municipal solid waste (MSW) incinerator. Experiments using the reduced scale simplified model were designed to reproduce the physical processes. The Current study focuses on the gas phase mixing and the subsequent oxidative destruction of incomplete combustion products. Excessive carbon monoxide is generated by operating the gas burner under fuel-rich conditions, and is supplied into the furnace chamber as a hot gas stream, where fresh air is provided by the secondary air injection. Mixing is quantified by measuring the local gas concentrations (CO and O₂) and temperatures since the destruction rate of CO is controlled by oxygen availability and chemical kinetic rates. The degree of mixing is monitored while the design alternatives of the secondary air injection pattern are systematically adjusted. This effect of the secondary air injection schemes on the degree of mixing are observed, and the measurements of temperature fluctuation with fine-wire thermocouples are performed for the quantitative evaluation of mixing. The results agree well with the plausible scenario of mixing and provide a better understanding of the mixing process. The hot flow accompanying chemical reactions in the model incinerator is also analysed numerically using the computational fluid dynamics codes to bolster the understanding of the experimental results. The modelling results compare reasonably well with experimental data. This comparison helps to cross-check the results. © 1997 John Wiley & Sons, Ltd.     

内旋流流化床燃烧系统设计研究

根据垃圾的热值和物理成分分析,结合流化床布风的冷态实验结果,对内旋流流化床燃烧系统进行了研究,设计出热态试验装置并成功地进行了生活垃圾焚烧试验。     

EVT垃圾焚烧系统燃烧设备

本文从垃圾料系统,焚烧炉排型式和燃烧调整等方面,介绍德国ＥＶＴ公司的垃圾焚烧系统燃烧设备,分析了燃烧设备的特点。     

城市垃圾典型组分燃烧特性研究

本文首先分析了垃圾燃烧存在的问题,再介绍垃圾燃烧特性的热重分析原理和燃烧特性参数的确定方法.对十种工况的垃圾燃烧进行分析,通过试验得出各组分的TGA和DTGA曲线及其燃烧特征参数.经研究发现混合组分垃圾的燃烧过程具有分步性,其活化能低于单组分垃圾,比单一组分垃圾更易燃烧;混合垃圾的燃烧特性并没有发生显著变化,可以近似用...     

Comparative performance and emission studies when using olive oil as a fuel supplement in DI and IDI diesel engines

An experimental study is conducted to evaluate and compare the use of a diesel fuel supplement, specifically a 25/75% and a 50/50% blend of waste olive oil and commercial diesel fuel, in a four-stroke, DI (Direct Injection) diesel engine and in a four-stroke, IDI (Indirect Injection) diesel engine having a swirl-combustion chamber. The influence of the blends (diesel fuel+olive oil), for a large range of loads, has been examined on fuel consumption, maximum pressure, exhaust temperature, exhaust smokiness and exhaust-gas emissions such as nitrogen oxides (NO_x), hydrocarbons (HC) and carbon monoxide (CO). The differences in the measured performance and exhaust-emission parameters, from the baseline operation of either engine, are determined and compared. The study shows, for both the DI and IDI engines, a small penalty in specific fuel consumption, a moderate increase in exhaust smokiness and essentially unaltered maximum pressures and exhaust temperatures when using the blends. Also, for both the IDI and DI engines when using the blends, the study shows moderate decreases in emitted nitrogen oxides and increases in hydrocarbons as well as negligible increases in emitted carbon monoxide. Theoretical aspects of diesel engine combustion are used to aid the interpretation of the observed engines' behaviour.     

柴油机富氧燃烧排放特性的试验研究

介绍了在S195柴油机上进行富氧燃烧的试验，对柴油机排放特性进行了比较与分析，目的是通过试验研究，找到在富氧条件下同时降低碳烟和NOx排放的方法。研究结果表明，增加进气氧的质量分数，碳烟排放大幅度下降，HC和CO也趋于下降，但NOx排放显增加；推迟供油提前角，可以使NOx排放降低，但碳烟有上升趋势，HC和CO排放增加。所以，采用富氧燃烧时必须同时推迟供油提前角，才能获得较低的排放量组合。