燃用高灰分、低热值劣质烟煤层燃锅炉特点分析

分析了高灰分、低热值劣质烟煤的燃烧特点,详尽介绍了燃劣质烟煤的层燃燃烧方式的选取;锅炉整体布置;辅机选取;运行调整.     

燃用劣质煤锅炉的设计与选配经验

分析了高灰分、低热值劣质烟煤的燃烧特点,介绍了燃劣质烟煤的层燃燃烧方式的选取、锅炉整体布置、辅机选取、运行调整等。     

劣质烟煤在层燃炉上的高效燃烧

分析高灰份、低热值劣质烟煤的燃烧特点,燃劣质烟煤的层燃燃烧方式的选取、锅炉整体布置、辅机选取、运行调整.     

劣质烟煤燃烧问题的讨论

根据1976年底召开的电站锅炉燃烧技术会议上的介绍和讨论,本文综述了各单位几年来燃烧劣质烟煤的经验。劣质烟煤的特点是水份多、灰份高和热值低,因此对燃用这种煤的锅炉设备也提出了一些特殊要求。文中着重综述了炉膛热负荷、燃烧器的形式和布置、切圆直径、一二次风比例、三次风等问题。     

低NOX燃烧技术及其在我国燃煤电站锅炉中的应用

针对我国以煤为主的电力状况，对我国电站锅炉目前采用的低氧燃烧、空气分级和燃料分级燃烧的各影响因素进行了分析和总结，根据采用某些低NOx燃烧技术后尚不能使燃用低挥发份无烟煤、贫煤和劣质烟煤的电站锅炉NOx排放达到国家标准要求的事实，指出了进一步进行降低燃用以上煤种NOx排放水平的空气分级和燃料分级燃烧技术研究的必要。图2参12     

淮北电厂1号炉燃用淮北劣质烟煤的经验

淮北电厂1号炉为上海锅炉厂SG-220-100-1型烟煤锅炉。为了适应燃用劣质烟煤,曾在该炉上进行了燃烧调整试验。在试验基础上刘一、二次风的配比作了一些改进,同时对直吹式煤粉管道的布置和防止堵粉等问题进行了探讨。通过上述运行调整,该炉目前已能安全经济运行。     

富集型燃烧器在单独燃用合山劣质烟煤锅炉上的应用

合山劣质烟煤是我国燃烧特性最差的一种动力用煤.现有燃烧器在合山电厂400 t/h的4号煤粉炉上单独燃用合山煤时,出现燃烧稳定性较差、燃烧效率低等问题.采用稳燃性能优异的富集型燃烧器对下两排一次风燃烧器实施改造,并针对合山煤高灰高硫特点采取一些防范措施.改造后,锅炉单独燃用合山煤时燃烧稳定,飞灰含碳量和大渣含碳量均小于3 %,锅炉效率大幅度地提高了近10 %,达到90 %,炉内受热面和燃烧器没有出现严重的结渣和明显的高温腐蚀.     

“双前拱”燃烧技术在层燃链条锅炉上的应用

“双前拱”是一种新型的锅炉炉拱，它使煤得到更充分的燃烧，火焰温度提高约２００℃，锅炉效率提高１０％以上，节煤效果显著。采用该炉拱后，锅炉还可以正常燃用劣质烟煤，甚至无烟煤，有利于开发利用煤炭资源。     

往复炉排热水锅炉的研究与试验

介绍燃用劣质烟煤的往复炉排锅炉的结构设计特点及其性能试验结果。     

300 MW CFB锅炉分离器中心筒固定方式存在问题分析及改进措施

循环流化床锅炉是近几十年迅速发展起来的一项高效、低污染的燃烧技术。它具有接近或达到同容量煤粉炉的燃烧效率;燃料适应性强,不仅可以燃用烟煤等优质煤,而且可燃用各种劣质燃料;负荷调节比宽,在25%负荷下仍能稳定燃烧;低温燃烧使NO_x生成量少,可用石灰石作脱硫添加剂低成本实现炉内脱硫;灰渣便于综合利用等优势,是国际上公认的商业化程度最好的洁净煤技术之一。由于其独特的优点是大型流化床锅炉得以很快发展。对于流化床锅炉来说,分离器是锅炉的主要部件,分离效果直接影响其安全经济运行。     

Components,formulations, solutions,evaluation, and application of comprehensive combustion models

Development and application of comprehensive, multidimensional, computational combustion models are increasing at a significant pace across the world. While once confined to specialized research computer codes, these combustion models are becoming more readily accessible as features in commercially available computational fluid dynamics (CFD) computer codes. Simulations made with such computer codes offer great potential for use in analyzing, designing, retrofitting, and optimizing the performance of fossil-fuel combustion and conversion systems.The purpose of this paper is to provide an overview of comprehensive combustion modeling technology as applied to fossil-fuel combustion processes. This overview is divided into three main parts. First, a brief review of the state-of-the-art of the various components or submodels that are required in a comprehensive combustion model is presented. These submodels embody mathematical and numerical representations of the fundamental principles that characterize the physico-chemical phenomena of interest. The submodel review is limited to those required for characterizing non-premixed, gaseous and pulverized coal gasification and combustion processes. A summary of the submodels that are available in representative computer codes is also presented.Second, the kinds of data required to evaluate and validate the predictions of comprehensive combustion codes are considered. To be viewed with confidence, code simulations must have been rigorously evaluated and validated by comparison with appropriate experimental data, preferably from a variety of combustor geometries at various geometric scales. Three sets of validation data are discussed in detail. Two sets are from the highly instrumented, pilot-scale combustor called the controlled profile reactor (CPR) (one natural gas-fired and one coal-fired), and the other set is for a full-scale, corner-fired 85 MW_e utility boiler.Third, representative applications of comprehensive combustion models are summarized, and three sets of model simulations are compared with experimental data. The model simulations for the three test cases were made using two commonly used, CFD-based computer codes with comprehensive combustion model features, PCGC-3 and FLUENT 4.4. In addition to the standard version of FLUENT, predictions were also made with a version of FLUENT incorporating advanced submodels for coal reactions and NO pollutant formation.     

Oxy-fuel combustion of pulverized coal: Characterization,fundamentals, stabilization and CFD modeling

Oxy-fuel combustion has generated significant interest since it was proposed as a carbon capture technology for newly built and retrofitted coal-fired power plants. Research, development and demonstration of oxy-fuel combustion technologies has been advancing in recent years; however, there are still fundamental issues and technological challenges that must be addressed before this technology can reach its full potential, especially in the areas of combustion in oxygen-carbon dioxide environments and potentially at elevated pressures. This paper presents a technical review of oxy-coal combustion covering the most recent experimental and simulation studies, and numerical models for sub-processes are also used to examine the differences between combustion in an oxidizing stream diluted by nitrogen and carbon dioxide. The evolution of this technology from its original inception for high temperature processes to its current form for carbon capture is introduced, followed by a discussion of various oxy-fuel systems proposed for carbon capture. Of all these oxy-fuel systems, recent research has primarily focused on atmospheric air-like oxy-fuel combustion in a CO₂-rich environment. Distinct heat and mass transfer, as well as reaction kinetics, have been reported in this environment because of the difference between the physical and chemical properties of CO₂ and N₂, which in turn changes the flame characteristics. By tracing the physical and chemical processes that coal particles experience during combustion, the characteristics of oxy-fuel combustion are reviewed in the context of heat and mass transfer, fuel delivery and injection, coal particle heating and moisture evaporation, devolatilization and ignition, char oxidation and gasification, as well as pollutants formation. Operation under elevated pressures has also been proposed for oxy-coal combustion systems in order to improve the overall energy efficiency. The potential impact of elevated pressures on oxy-fuel combustion is discussed when applicable. Narrower flammable regimes and lower laminar burning velocity under oxy-fuel combustion conditions may lead to new stability challenges in operating oxy-coal burners. Recent research on stabilization of oxy-fuel combustion is reviewed, and some guiding principles for retrofit are summarized. Distinct characteristics in oxy-coal combustion necessitate modifications of CFD sub-models because the approximations and assumptions for air-fuel combustion may no longer be valid. Advances in sub-models for turbulent flow, heat transfer and reactions in oxy-coal combustion simulations, and the results obtained using CFD are reviewed. Based on the review, research needs in this combustion technology are suggested.     

Combustion synthesis of zero-, one-, two- and three-dimensional nanostructures: Current trends and future perspectives

The combustion phenomenon is characterized by rapid self-sustaining reactions, which can occur in the solid, liquid, or gas phase. Specific types of these reactions are used to produce valuable materials by different combustion synthesis (CS) routes. In this article, all three CS approaches, i.e. solid-phase, solution, and gas-phase flame, are reviewed to demonstrate their attractiveness for fabrication of zero-, one-, two-, and three-dimensional nanostructures of a large variety of inorganic compounds. The review involves five sections. First, a brief classification of combustion synthesis methods is given along with the scope of the article. Second, the state of art in the field of solid-phase combustion synthesis is described. Special attention is paid to the relationships between combustion parameters and structure/properties of the produced nanomaterials. The third and fourth sections describe details for controlling material structures through solution combustion synthesis and gas-phase flame synthesis, respectively. A variety of properties (e.g., thermal, electronic, electrochemical, and catalytic) associated with different types of CS nanoscale materials are discussed. The conclusion focuses on the most promising directions for future research in the field of advanced nanomaterial combustion synthesis.     

Evolution,challenges and path forward for low temperature combustion engines

Universal concerns about degradation in ambient environment, stringent emission legislations, depletion of petroleum reserves, security of fuel supply and global warming have motivated research and development of engines operating on alternative combustion concepts, which also have capability of using renewable as well as conventional fuels. Low temperature combustion (LTC) is an advanced combustion concept for internal combustion (IC) engines, which has attracted global attention in recent years. LTC concept is different from the conventional spark ignition (SI) combustion as well as compression ignition (CI) diffusion combustion concepts. LTC technology offers prominent benefits in terms of simultaneous reduction of both oxides of nitrogen (NO_x) and particulate matter (PM), in addition to reduction in specific fuel consumption (SFC). However, controlling ignition timing and combustion rate are primary challenges to be tackled before LTC technology can be implemented in automotive engines commercially. This review covers fundamental aspects of development of LTC engines and its evolution, historical background and origin of LTC concept, encompassing LTC principle, its advantages, challenges and prospects. Detailed insights into preparation of homogeneous charge by external and internal measures for mineral diesel and gasoline like fuels are covered. Fuel requirements and fuel induction system design aspect for LTC engines are also discussed. Combustion characteristics of LTC engines including combustion chemistry, heat release rate (HRR), combustion duration, knock characteristics, high load limit, fuel conversion efficiencies and combustion instability are summarized. Emission characteristics are reviewed along with insights into PM and NO_x emissions from LTC engines. Finally, different strategies for controlling combustion rate and combustion timings for gasoline and mineral diesel like fuels are discussed, showing the way forward for this technology in future towards its commercialization.     

The ignition,oxidation, and combustion of kerosene: A review of experimental and kinetic modeling

For modeling the combustion of aviation fuels, consisting of very complex hydrocarbon mixtures, it is often necessary to use less complex surrogate mixtures. The various surrogates used to represent kerosene and the available kinetic data for the ignition, oxidation, and combustion of kerosene and surrogate mixtures are reviewed. Recent achievements in chemical kinetic modeling of kerosene combustion using model-fuels of variable complexity are also presented.     

The effect of equivalence ratio,temperature and pressure on the combustion characteristics of hydrogen-air pre-mixture with turbulent jet induced by pre-chamber sparkplug

The pre-chamber sparkplug mode can increase the combustion velocity because it can induce the turbulent jet into the cylinder. Higher combustion velocity can increase the brake thermal efficiency and decrease the knock tendency for hydrogen engines. To explore the effect of pre-chamber sparkplug mode on the combustion characteristics of the hydrogen-air mixture, different equivalence ratios, initial pressures and temperatures were selected to study in a constant volume combustion chamber working with pre-chamber sparkplug mode and normal sparkplug mode. The results showed that the pre-chamber sparkplug mode can accelerate the combustion velocity, increase maximum combustion pressure and decrease the combustion duration at all initial conditions. The maximum combustion pressure of pre-chamber sparkplug mode occurred at the equivalence ratio of 1.0 while it occurred at the equivalence ratio of 1.2 with normal sparkplug mode, which means pre-chamber sparkplug mode can increase the higher brake thermal efficiency and power. The combustion intensity of pre-chamber sparkplug mode was bigger than 1 and the biggest value occurred at the equivalence ratio of 0.6. Moreover, the combustion intensity of pre-chamber sparkplug mode was higher with lean equivalence ratios than that of rich equivalence ratios. Increasing the initial pressure can increase maximum combustion pressure and combustion velocity obviously for pre-chamber sparkplug mode, which was different from the normal sparkplug mode. The initial temperatures had little impact on the combustion intensity. These results showed the pre-chamber sparkplug mode was more suitable to be used in the boosting hydrogen engines to improve the performance.     

Evolution of the nanostructure, fractal dimension and size of in-cylinder soot during diesel combustion process

The nanostructure, fractal dimension and size of in-cylinder soot during diesel combustion process have been investigated for a heavy-duty direct injection diesel engine, using a total cylinder sampling system followed by high-resolution transmission electron microscopy and Raman scattering spectrometry. Different structural organizations of in-cylinder soot are found depending upon the combustion phase. It is revealed that both the fringe tortuosity and separation distance decrease as combustion proceeds, while the mean fringe length increases distinctly from 1.00 to 2.13 nm, indicating the soot evolution toward a more graphitic structure during the combustion process. The fractal dimensions of aggregates are in a range of 1.20–1.74 at various crank angles under the applied engine operating conditions. As temperature and pressure increase, the fractal dimension decreases significantly to a minimum at the early diffusion combustion stage. The soot particles become more compact again as the fractal dimension increases during the subsequent combustion period. Primary particle sizes start small, go through a maximum in the early diffusion combustion phase and decline again as combustion proceeds.     

Combustion kinetic model uncertainty quantification,propagation and minimization

The current interest in the combustion chemistry of hydrocarbon fuels, including the various alcohol and biodiesel compounds, motivates this review of the methods and application of kinetic uncertainty quantification (UQ). Our intent is to provide a self-contained review about the mathematical principles and methods of uncertainty quantification and their application in highly complex, multi-parameter combustion chemistry problems. We begin by outlining the reasons why the kinetic uncertainty must be considered and treated as a part of the combustion chemistry development in order to make progress. This is followed by a brief discussion about the sources and classification of kinetic uncertainties and the meanings and definitions of model verification and validation. We discuss the histories of UQ studies with an emphasis on how the combustion community has a long tradition of UQ consideration through standard sensitivity analysis. Such efforts have motivated the advancements of UQ methods specifically tailored to combustion chemistry. They also led to the recent growing interests in applying UQ methods as a part of our recommended long-term solution to the chemical kinetic problem of combustion. We then review and classify the various UQ methods and illustrate their applications for problems involving forward uncertainty quantification and propagation, and as an inverse problem leading to model uncertainty constraining. For the inverse problem, the focus of discussion is in the use of methods originating from Bayes' Theorem. We show that, for combustion chemistry problems, while UQ alone cannot produce precise, individual rate parameters, it can be instrumental in measuring the progress of our understanding of combustion chemistry and in utilizing fundamental combustion property data beyond a simple “agree–disagree” statement. When treated as a Bayesian inference problem, UQ also aids the development of predictive kinetic models in two ways: the use of fundamental combustion property data, global or local, to provide a better constrained kinetic model, and along with forward kinetic uncertainty propagation, to yield estimates for the confidence of a model to make predictions outside of the thermodynamic regimes where the model has been tested. We provide several examples to illustrate the utility of the UQ methods discussed and to demonstrate that, in the field of combustion chemistry, further progress will be better achieved through a combination of fundamental studies of reaction rates through well-defined and designed experiments and ab initio theoretical calculations, and of analyses of global experimental measurements. These studies together must be supplemented by UQ analyses, in such a way that a measurable progress can be made over time.     

稻壳水热炭化学结构和燃烧特性及动力学分析

以稻壳为原料,利用水热碳化技术结合元素分析和热重法,考察水热反应强度对水热炭化学结构和燃烧特性及动力学的影响。结果表明：1）随着反应强度参数（lg R₀）的增大,水热炭整体挥发分和氧元素质量分数呈减少趋势,而C元素质量分数则逐渐增加,当水热反应强度lg R₀为4.90~6.19时,参数变化尤为显著,lg R₀为6.19时,C元素和O元素的质量分数分别为50.5%和21.3%,O/C和H/C原子比分别为0.32和1.21;2）相对于原料,水热炭的燃烧损失集中在固定碳和挥发分燃烧阶段,着火和燃尽温度均有小幅上升;3）当lg R₀由3.25增至6.49时,挥发分燃烧损失减小,固定碳燃烧损失增大,着火与燃尽温度呈整体向高温区转移的趋势,综合燃烧特性指数（S_N）呈先增加后减小的趋势;4）固定碳燃烧段活化能低于挥发分燃烧段,本次采用的动力学模型分析水热炭燃烧动力学结果可靠,相关系数（R²）均在0.92以上。