Two-dimensional modelling of deposits formation on platen superheaters in pulverized coal boilers

The 1D modeling of deposits formation is not able to describe properly the gas and particles flow in the vicinity of heat transfer tubes in boilers. Especially, the recirculation zones in the down-stream side of tubes are not possible to reproduce by the 1D models. Known applications of the CFD codes to deposition modelling were able to reproduce only the rate of particles deposition on surfaces, while for practical reasons the most important information is the shape and size of deposits, because it enables prediction of heat transfer abatement with boiler operation time. Paper presents 2D modelling of deposits on platen superheaters in pulverized coal boilers. Particularly, the observed in industrial boilers bridging of the tubes spacing was reproduced by the model in which the particle size dependence of the ash sticking probability was proposed. It has been demonstrated that the ash particles size play important role in the deposits growth mechanism.     

Investigations on fouling rate in convective bundles of coal-fired boilers in relation to optimization of sootblower operation

The article deals with results of full-scale investigations on fouling in convective bundles of chosen types of coal-fired boilers. The boilers tested were: conventional pulverized-coal fired two-pass boilers (two types), a single-pass subcritical (a tower shape) boiler and CFB boiler. Mechanisms of deposit formation and basics of deposit modeling are shortly discussed. An own approach to predict build-up of loose powdery sediments was developed on the basis of the results of full-scale measurements. The correlation for maximum fouling time was obtained by statistical processing of measurement data and is applied in optimization of sootblower system operation. The obtained correlation depends on the following variables: geometric properties of the bundle, fly ash size distribution and basic parameters of the flue gases—all of them are easily accessible in boiler operation.     

基于支持向量机与高斯分布估计的低NOx排放

燃烧优化的核心在于建立有效而快速的建模工具及寻优算法,以便于在线应用。为了研究新方法的适用性以及克服常用算法的缺点,本文利用支持向量回归建立了大型四角切圆燃烧电站锅炉NO_x排放特性模型。利用大量的热态实炉试验NO_x排放数据对模型进行了训练和验证。结果表明,支持向量回归模型能获得较神经网络模型更加准确的预测结果,相对于神经网络,支持向量回归能更好处理大样本量数据的非线性问题。随后,采用一种基于高斯概率密度 (GPDD)的分布估计优化算法对NO_x排放模型进行了寻优。研究发现,与遗传算法相比,GPDD具有更好的寻优能力与更快的收敛速度。结合支持向量回归与高斯概率密度分布(GPDD)算法能有效降低燃煤锅炉NO_x排放量,不到1 min的优化时间便于在线应用。研究结论可为该算法在实际电厂中推广应用提供参考依据。     

Kinetic Modeling of Large‐Scale Reaction Systems

This review gives a brief account of basic ideas underlying approaches to analysis and modeling of large‐scale reaction systems. The emphasis is on model simplification and mechanism/dimension reduction via heuristic concepts and formal mathematical techniques. Among the key topics discussed are: top‐down and bottom‐up modeling approaches, graph/matrix representation of chemical reactions, mechanistic vs. pathways models, quantitative structure‐reactivity relationships, mathematical reduction of dimensionality, high‐fidelity surrogate models, continuum approximation, lumping of nonlinear kinetics, overall behavior/kinetics of many reactions, effect of pore diffusion, steady state multiplicity and stability. Some common features of dimension reduction methodologies are noted. Areas where further work will be valuable are identified.     

An optimal filter based MPC for systems with arbitrary disturbances

In this study, a linear model predictive control (MPC) approach with optimal filters is proposed for handling unmeasured disturbances with arbitrary statistics. Two types of optimal filters are introduced into the framework of MPC to relax the assumption of integrated white noise model in existing approaches. The introduced filters are globally optimal for linear systems with unmeasured disturbances that have unknown statistics. This enables the proposed MPC to better handle disturbances without access to disturbance statistics. As a result, the effort required for disturbance modeling can be alleviated. The proposed MPC can achieve offset-free control in the presence of asymptotically constant unmeasured disturbances. Simulation results demonstrate that the proposed approach can provide an improved disturbance õrejection performance over conventional approaches when applied to the control of systems with unmeasured disturbances that have arbitrary statistics.     

三维建模在精细油藏描述中的应用研究

储层三维建模是精细油藏描述的核心,随着油田的开发和计算机水平发展,油藏的研究要求更高的定量化,储层的描述要求更加精细,建立精度较高的储层三维模型非常有意义。储层建模工作分为油藏构造建模,沉积微相建模和油藏属性建摸三步。文中讨论了这三种模型,并以靖安油田某区块为例说明了在油藏研究中的应用状况。     

美国燃煤工业锅炉技术

介绍了美国工业锅炉的基本情况和主要的燃煤工业锅炉技术,分析了锅炉专用煤的要求及燃煤工业锅炉的污染控制技术。分析发现,美国的燃煤工业锅炉运行年代长,通过不断技术改造使锅炉保持较高的运行效率;美国对不同类型锅炉的煤质有专门规定,以保证锅炉高效率燃烧和低污染排放。美国燃煤锅炉采用各种污染物减排措施,保证了污染物达标排放。     

废热锅炉特殊工况可操作性分析

就合成氨装置中斜置式火管型废热锅炉在两种特殊工况下的可操作性进行了分析,指出该废热锅炉在两种工况下不可操作的原因是：不能满足结构强度和材料高温性能的要求,以及高温气体对设备材料的腐蚀等因素造成的。     

Nonlinear model based control of two-product reactive distillation column

Nonlinear feedback control scheme for reactive distillation column has been proposed. The proposed control scheme is derived in the framework of Nonlinear Internal Model Control. The product compositions and liquid and vapor flow rates in sections of the reactive distillation column are estimated from selected tray temperature measurements by an observer. The control scheme is applied to an example reactive distillation column in which two products are produced in a single column and the reversible reaction A+B=C+D occurs. The relative volatilities are favorable for reactive distillation so that the reactants are intermediate boilers between the light product C and the heavy product D. Ideal physical properties, kinetics, and vapor-liquid equilibrium are also assumed. It is shown that the proposed control scheme keeps tight product composition control.     

Heat transfer in the rotary ash cooler with residual char combustion considered

In circulating fluidized-bed (CFB) boilers, some residual char is left in the ash when the ash is drained into the rotary ash cooler (RAC). The residue char will combust in the RAC given oxygen is present. It is important to understand and predict the influence of residual char combustion on the heat transfer process in the RAC in order to avoid slagging and fouling inside the RAC. In this paper, an improved heat transfer model of the RAC was developed in which the residual char combustion process was considered. Based on the analysis, the shrinking sphere model was selected to describe the residual char combustion. The improved model was validated by the final ash temperature and cooling water temperature data measured from a few RACs equipped with the coal fired CFB boilers with different steam output. The predictions of the improved model agree well with the field measurement data, within an error range of ± 10%. The simulation results also show that the heat released from residual char combustion counts for about 60-80% of the total heat released by ash in the inlet section of the RAC, and the influence of residual char combustion decreases rapidly along the ash flow. The final ash temperature increases accordingly with the increase of inlet carbon content, and decreases with the increases of residual char size. As particle size is larger than 3 mm, the final ash temperature changes little at a given carbon content due to a low mass burning rate. It is suggested that combustion of residual char should be considered when the inlet carbon content is over 2.5%; otherwise, the combustion of residual char in the RAC could be neglected.     

Coal research in Newcastle—past, present and future

Coal research, particularly in the area of coal utilization, has flourished in the University of Newcastle for last several decades. There have been significant developments in the area of furnace modeling and heat transfer—modeling of radiative heat transfer in pulverized coal fired boilers and aerodynamic modeling of swirl burners, blast furnace raceways, coal combustion—kinetics of devolatilisation, combustion and gasification, mineral and ash reactions—thermal behaviour of different minerals, ash formation and their implications on ash deposition and thermal performance. There have been some investigations into in situ gasification, NO_x formation and cofiring with biomass as well. Coal characterization—for organic and inorganic matter and ash has been a strong activity in the past few years.This paper presents a comprehensive review of these activities summarizing the key achievements in each area. The paper also describes possible directions and drivers for future coal research in the current environment.     

工业锅炉除垢技术现状与展望

工业锅炉数量约占我国锅炉总量的96％以上。定期除垢是确保锅炉安全经济运行的方式之一。论述了目前工业锅炉常用的3种除垢技术,比较了它们的使用条件和优缺点,并对除垢技术未来的发展进行了展望。     

Fuzzy cognitive approach of a molecular distillation process

Takagi-Sugeno fuzzy model is presented as an alternative modeling tool for the molecular distillation process of heavy liquid petroleum residues. A nonlinear phenomenological model formed by partial differential equations involving temperature and composition is regarded as a virtual working plant for the generation of data required to build the fuzzy models. Furthermore, experimental data from the molecular distillation process of an atmospheric residue 673.15 K upward (673.15 K+) at different operating conditions were used to develop the fuzzy representations. In this work, the system was simulated through the development of software in Fortran 90/95 and the numerical solution by using the finite-difference method. In the fuzzy approaches, the distillation temperature and the feed flow rate are the input variables, while the liquid interface temperature, the film thickness, the concentration profiles, and the distillate flow rate were considered as the output responses. The fuzzy models obtained were compared with the results generated from the phenomenological model, showing an excellent agreement.     

130t/h循环流化床锅炉返料器异常的分析与处理

循环流化床锅炉的物料循环系统是实现燃料煤完全燃烧的关键环节,也是循环流化床锅炉的特性之一,它主要由旋风分离器、立管和返料器组成,其中返料器工作的正常与否,直接制约着锅炉燃烧是否稳定,并影响着锅炉的长周期安全运行。     

论锅炉化学清洗中的安全及防护

针对锅炉化学清洗过程中遇到的一些实际问题 ,对锅炉化学清洗的工作程序与要点进行了探讨 ,并对锅炉的化学清洗问题提出了一些建议     

循环流化床锅炉输运系统设计

介绍了燃料制备及冷却除渣系统 ,该系统为循环流化床锅炉提供了合格的燃料并连续自动地排除灰渣 ,确保了锅炉安全稳定的运行     

Application of scaling and sensitivity analysis for tumor–immune model reduction

Mathematical modeling plays a facilitating role in comprehending tumor growth and its interaction with the immune system. However, there are some hindrances in modeling these phenomena. Firstly, the complexity of the tumor–immune model increases with the inclusion of dynamics of different types of immune cells. In this work, complexity is considered in terms of number of parameters and differences in the order of magnitude of their values. We have assumed that the model structure accurately represents the actual tumor–immune interactions. This may result in non-identifiability, imprecise measurement/estimation of the parameters. Secondly, very few parameters in the model will significantly influence the evolution of state variables and it is important for us to know these sensitive parameters.In this work, a recent and elaborate tumor–immune model is considered and its reduced parametric representation is obtained through a systematic scaling approach without any loss in its predictive ability. The advantage of scaling approach is quantified using theoretical identifiability analysis and by evaluating the condition number of the Fisher information matrix. Then, global sensitivity analysis is applied on the reduced model to identify the key parameters affecting the tumor progression. Such model reduction and parameter analysis may be necessary in order to increase the possibility of bringing model based approaches to standard medical practice and patient care.     

搪瓷釜的使用维护与常用修补方法

介绍搪瓷釜的使用维护要点，简单介绍目前国内外常用的搪瓷釜修补方法，从用、管、修相结合出发来延长搪瓷釜的使用寿命。     

头台油田肇261西块储层建模研究

在储层精细地质研究的基础上,将已有的成果结合petrel软件,进行储层建模研究,建立研究区的构造模型、相模型和属性模型.对于研究区的地质构造以及砂体连通性有更深入的认识,对调整注采关系和数值模拟有重要意义.     

小型锅炉脱硫改造技术研究

锅炉尾气治理是当今环保部门对锅炉使用或剔除的重要指标之一.新建锅炉均必须有尾气净化设施,而旧有锅炉则必须要进行脱硫技术改造.但由于受场地限制,很多小型锅炉改造困难,而湿法脱硫采用喷淋是设施占地庞大的主要原因.针对小型锅炉存在的问题,介绍了气液直接接触脱硫技术,它可以在较小的空间完成尾气治理,满足改造要求.