回转窑内传热及燃烧过程的数值模拟

运用流体模拟软件Fluent和Matlab分别对碳素煅烧回转窑内气体空间和物料料层内的传热过程进行了研究,预测了窑内烟气、窑内壁和料层的温度分布。结果表明,窑内的高温区域主要集中在挥发分大量燃烧的区段上;二、三次冷空气的引入均会使窑内烟气温度明显下降,但对料层温度影响不显著。将窑外壁的计算结果与其实际测试结果进行了比较,两者吻合较好,说明该模拟方法的适用性,从而为碳素回转窑的优化设计和经济运行提供了指导和依据。     

Design of an indirect heat rotary kiln gasifier

A non-ordinary type of solid fuel gasification reactor, which was under development for the few past decades and it is briefly described as indirect heat rotary kiln gasifier, seems to be capable of sufficiently satisfying the incorporated gasification needs in the most challenging contemporary power technologies using solid fuels, like IGCC and CLC combustion. The design of such a gasifier emerges in this work, while the focus is mostly on the presentation of the relevant theoretical model. Moreover, model predictions are compared and optimized with respect to experimental data that were acquired in a pilot scale gasification unit including the suggested type of gasifier. Comparisons showed successful predictions of such a marginal error that could be characterized as quite sufficient for a primary model validation. However, the model flexibility to a wide variety of different solid fuels, rotary kiln configurations and operating conditions has to be verified by assessment of further experimental results.     

水泥回转窑筒体表面余热吸收式制冷技术研究

水泥生产是一个高耗能的行业,回转窑筒体表面的余热损失可达输入能量的10%。通过在回转窑表面布置集热罩,可得到平均温度为100℃的热水。这些热水用于溴化锂吸收式制冷机组,可以得到制冷量1516 kW,相较于普通空调和电动压缩机制冷技术,采用溴化锂吸收式制冷技术回收回转窑表面余热进行制冷每年夏天可以节省20万元左右电费。     

回转窑系统热工标定的准备工作及经验

<正>1标定目的标定回转窑的实际产量;通过测量和计算有关数据,可以对窑系统进行一次综合评价,比较其运行参数与设计值以及国内外同类型窑先进值之间的差别,通过分析原因,找出窑系统存在的问题,为系统进一     

余热发电回转窑节能提产技术改造

我公司原有2条500t／d带余热发电干法中空窑生产线，为2台3000kW汽轮发电机提供400℃过热蒸汽进行发电，发电量基本可以满足生产需要。随着科学技术的不断发展和原煤及燃油价格的大幅上涨，余热发电中空窑日益显得技术落后，生产成本居高不下。于是公司于2001年决定对2号窑进行全面的提产改造，将原来的干法中空窑改造为新型的预分解窑，同时局部改造余热锅炉，取得了良好的效果。     

Convective heat transfer coefficient for the side-wall in a fixed bed

Fixed beds are widely used in the chemical and process industry due to their relatively simple yet effective performance. Determining the radial heat transfer at the wall in a fixed bed is crucial to predict the performance of columns. Heat transfer parameters often need to be obtained experimentally. Various Nusselt ${\mathrm{Nu}}_w$ versus Reynolds ${Re}_p$ correlations in literature show considerable scatter and discrepancies. The tube-to-particle diameter ratio $\frac{D_{\mathrm{t}}}{D_{\mathrm{p}}}$ and boundary conditions on the particle surface have been understood to affect heat transfer near the wall by virtue of influence on the near-wall porosity and mixing. In this work, a fixed bed consisting of mono-disperse particles is generated via gravity-forced sedimentation modelling utilizing the discrete element method for a $\frac{D_{\mathrm{t}}}{D_{\mathrm{p}}}$ ratio of 3.3. The system is meshed and imported in a computational fluid dynamics (CFD) solver. Fluid inlet velocity is varied to get ${Re}_p\in \left[1,1500\right]$ corresponding to the laminar and turbulent flow regimes. The particles are treated as boundaries with Dirichlet, Neumann, and Robin boundary conditions applied for the closure of energy balance. Another set of simulations is run with particles modelled as solids with varying thermal conductivities ($k_s/k_f$). The heat flux and volume-averaged fluid temperature calculated during post-processing are used to determine the wall heat transfer coefficient and, subsequently, the wall Nu number. Fifteen ${\mathrm{Nu}}_w$ versus ${Re}_p$ correlations are compiled and analyzed. A new semi-empirical correlation for the wall Nusselt number has been developed for a fixed bed packed with monodisperse spheres for $\frac{D_t}{D_p}=3.3$ and results compared with data published in literature. Additionally, the impact of buoyancy effect on the wall Nusselt number has been studied.     

Convective heat transfer in channels with high wall ribs

The features of the convective heat transfer intensified by the turbulization caused by high ribs are experimentally studied using laboratory tube-in-tube heat exchangers.     

回转窑筒体段节的更换

0前言江西万年青水泥股份有限公司(以下简称我公司)现有4台2 500 t/d干法回转窑生产线,是一家大型干法水泥企业。生产中窑筒体,特别是窑口段节时常会被烧损变形,严重时就必须更换新筒节。对于新型干法回转窑来说,一是其系统产量大,对窑口筒体材料磨损加剧,容易造成窑口筒体的过     

R410A的流动沸腾换热性能

引言 氟氯烃在制冷空调行业的大量使用和排放,已经造成大气臭氧层的破环.根据1992年"蒙特利尔议定书"的规定,在制冷与空调工业中广泛采用的氯氟碳化合物(CFCs)制冷剂将被禁用.近年来,人们努力在寻找对环境无危害或危害小的制冷工质,并对这些工质的热力学性能进行深入的研究分析.随着禁止时间的迫近,有关R22替代物以及相应的冷冻机油的研究正在加紧进行.目前国际上呼声最高的HFC(氢氟化烷烃)类替代物有R407C和R410A.     

应用流体旋转法的多种强化传热方式

概述了应用流体旋转法强化管内单相流的几种强化传热方式及强化传热的机理；并利用分析，从经济用能方面比较了这几种强化传热方式，得出椭圆断面厚壁螺旋管在损失率最小的情况下，其流动工况较高，达到了强化传热的目的。     

回转窑窑口筒休的更换

对于新型干法窑来讲,其窑口具有如下特点:①窑口热流量大,冷却带很短甚至没有,窑口环境十分恶劣(出窑熟料1300℃～1400℃,二次风温1000℃～1200℃);②产量大,窑口材料磨损加剧,容易造成窑口筒体的过热变形;③筒体温度高,热膨胀大,材料强度衰减严重;④操作稍有不慎,窑头容易出现正压.因此,其窑口筒体的寿命相对较短.我厂拥有两条RSP型预分解窑(规格φ4×60m),运行近10年已更换过4次窑口筒体.现把我们的做法做一下简单总结,以期能成为引玉之砖.     

回转窑筒体散热计算方法探讨

通过回转窑内气体辐射换热和耐火砖、窑皮的导热及窑筒体与环境之间的对流换热的研究,给出了回转窑筒体散热计算模型,基于该模型研究了窑筒体温度与耐火砖、窑皮厚度的关系。按此计算模型,估算5500t/d熟料线回转窑的筒体散热量与实际标定结果相近。