Utilizing biomass and waste for power production—a decade of contributing to the understanding, interpretation and analysis of deposits and corrosion products

Through the years, Danish utilities have gained significant knowledge on how to minimize or even avoid ash deposition problems in utility boilers, firing a worldwide suite of high-volatile bituminous coals. In the early 1990s, the Danish Government decided on a 20% reduction in the CO₂-emission before the year 2005, based on the 1988-level. Biomass is considered CO₂-neutral due to its short time of regeneration, compared to fossil fuels. Thus, the Danish power producers are enjoined to burn 1.0 Mtonnes of straw, 0.2 Mtonnes of wood chips and 0.2 Mtonnes of straw/wood chips (free choice) every year beyond year 2005. As a consequence of this, the CHEC Research Centre, Department of Chemical Engineering, Technical University of Denmark, being partly funded by the Danish power utilities, has during the last decade, investigated ash and deposit formation, and corrosion, in utility boilers fired with coal, petcoke, orimulsion, and different types of biomass (straw (barley, rape and wheat), wood (beech, spruce, fibreboard, bark and waste wood), shea nuts, olive stones, etc.). A number of reviews of these full-scale measuring campaigns have been provided in the open literature. Recently, a project on the formation of ash and deposits in waste incinerators has been initiated.This paper summarizes our findings, including recent activities on: (1) deposit formation during coal-wheat straw co-firing in suspension-fired boilers; (2) a pilot-scale study of ash and deposit formation in the Sandia Multi-Fuel Combustor (MFC); (3) a full-scale measuring campaign dealing with the effect of co-firing of biomass on the ash and deposit formation; (4) a full-scale measuring campaign addressing low-temperature corrosion of tubes in the air pre-heater of a straw-fired utility boiler; (5) a lab-scale study of the corrosion of superheater materials in straw-fired utility boilers, and, finally; (6) a fundamental study on ash and deposit formation in municipal solid waste incinerators. The paper provides insight into the experience gained on ash, deposit and corrosion formation in thermal fuel conversion systems fired with solid non-fossil fuels, and focuses attention on how these results fit into our current understanding of this subject. A complete and updated list of references covering our research activities within this area during the last decade is provided. In addition, a brief overview of current and future research activities is provided.     

水泥生产线篦冷机料层厚度新型控制技术

新型干法水泥窑第三代篦冷机熟料料层厚度控制是保证水泥成品质量的重要环节。使用安装在篦冷机本体上的料层测厚仪,直接测量出篦冷机熟料的料层厚度,通过自动控制系统对篦冷机的料层厚度进行直接控制,以保证篦冷机内部热工参数的稳定,提高和稳定水泥产品的质量和产量。     

同兴垃圾发电厂DCS控制系统

重庆同兴垃圾发电厂采用的是德国马丁公司(原法国阿尔斯通公司)的逆推式炉排焚烧技术。本文叙述了焚烧技术的工艺流程、DCS控制系统的硬件构成及功能。以全厂集中操作与各工段分散控制相结合的系统运行模式,实现了垃圾焚烧发电厂整体生产过程的监控和低成本运行,提高了垃圾焚烧发电机组的自动化和管理水平。     

LBTF5000型充气梁篦式冷却机工艺技术概要

LBTF5000型充气梁篦式冷却机是在其系列产品广泛应用的基础上设计的用于5000t/d至5500t/d的熟料冷却设备、设计采用了高阻力篦板、厚料层、均匀分风、脉冲供风等工艺技术，其篦床分区更适合规模大型化的特点，并提出了供风参数取值的依据，该设备的保证性能指标已达到国内外同类产品的先进水平。     

Study of the transient release of water vapor from a fuel bed of wet biomass in a reciprocating-grate furnace

The present study investigates how sudden changes in fuel moisture affected the combustion characteristics of the fuel bed in a 4-MW reciprocating-grate furnace. The moisture content of the fuel fed to the furnace was monitored online using a near-infrared spectroscopy device, and the water vapor concentration in the flue gas was measured continuously. To obtain experimental data on fuel-bed conditions, the temperature and gas composition in the bed were measured using a probe. A simplified drying model was developed using the measured gas composition values as inputs. The model was then used to estimate the drying rate and to simulate the extent of the drying zone along the grate. Measurements indicated that a change in the moisture content of the fuel fed to the furnace was detected as a change in water vapor concentration in the flue gas with a delay of about 2 h. The model predicted that a portion of wet fuel would need about 2 h to become dry, in line with the measured time delay of the water vapor concentration change in the flue gas. Overall, there was good alignment between the measured and simulated results, supporting the validity of the model and the assumed mechanisms.     

提高φ3.2×3.1m格子型球磨机处理量节能降耗的试验研究

在矿石硬度、给矿粒度、钢球配比、磨矿浓度及溢流细度等参数相同的条件下，通过增加钢球装填量和缩小出料口进行提高磨机处理量的试验研究。试验表明，适当缩小出料口，处理量明显增加，而钢球消耗和负荷确明显减少和降低。     

带式烧结机台车篦条有限元分析

基于有限元法,运用ANSYS软件对带式烧结机台车上的篦条进行了温度场和应力场分析,得到了高温时篦条的应力分布场,指出了烧结机工作时篦条受力的关键部位和薄弱环节,并提出了篦条设计时应注意的问题和改进方向.     

120万t链算机-回转窑投产达产实践

介绍了莱钢第一条120万t／a链算机一回转窑氧化球团生产线投产后,采取各种措施,加强生产组织、摸索优化操作控制参数、完善工艺、整改设备缺陷,提前实现了达产目标,转鼓指数达到94％,平均抗压强度达到2100N／个以上,为高炉冶炼提供了优质的原料。     

Discrete element analysis of experiments on mixing and stoking of monodisperse spheres on a grate

Understanding the details of the mixing and stoking process on grate firing systems is crucial for the optimization of the combustion process in waste or biomass incineration plants. The Discrete Element Method (DEM) can help to obtain further information on the mixing process within a bed of fuel particles. Especially the influence of a change in operational parameters can be examined avoiding large experimental effort. In the current paper five simulations for a generic grate are compared with the corresponding experiments. The experiments were carried out throughout an anterior parameter study on mixing and stoking on a grate [Sudbrock F.; Simsek E.; Wirtz S.; Scherer V.: “An experimental analysis of the influence of operational parameters on mixing and stoking of a monodisperse granulate on a grate”, Powder Technology 198, Issue 1, 29-37, 2010] [19]. The system considered is equipped with vertically moving bars which induce stoking. In a first approach monodisperse plastic spheres are used. The grate is encased by a transparent polycarbonate housing which provides optical access to the movement of the particles in the wall planes. The mixing process is measured and quantified by image analysis of the front wall of the grate. The mixing behaviour of the particle assembly observed in experiments and simulation appears to be very similar indicating that DEM is able to predict the particle mixing in the bed. In order to quantify the visual observations the mixing behaviour has been evaluated by different mixing parameters. They are compared in dependence of the number of strokes of the grate bars. A good agreement between measurements and simulations could be observed.     

粗颗粒浮选机的研制与应用

粗颗粒浮选机是一种既能选别常规粒级、又能选别较粗粒级的全粒级充气机械搅拌式浮选机,特别适用于选别含有粗粒级的有色、黑色、非金属矿物,对一般硫化矿物的入选粒度上限可达０４ｍｍ（３５％－００７４ｍｍ）,该机的特征和技术关键在于采用了新式叶轮—定子系统、独特的槽体结构和产生悬浮层的格子板,在它们的联合作用下获得了叶轮在低转速下粗粒矿物在槽体中部的悬浮层和细粒矿物经两侧至槽体底部的流体大循环,使深槽浮选机浅槽化,创造了粗、细粒矿物向气泡附着及良好的升浮条件,从而解决了粗粒矿物浮选易沉槽和不易获得较高选别指标的技术难题。