Numerical modelling of flow and transport processes in a calciner for cement production

Controlling the calcination process in industrial cement kilns is of particular importance because it affects fuel consumption, pollutant emission and the final cement quality. Therefore, understanding the mechanisms of flow and transport phenomena in the calciner is important for efficient cement production. The main physico-chemical processes taking place in the calciner are coal combustion and the strongly endothermic calcination reaction of the raw materials. In this paper a numerical model and a parametric study are presented of the flow and transport processes taking place in an industrial calciner. The numerical model is based on the solution of the Navier-Stokes equations for the gas flow, and on Lagrangean dynamics for the discrete particles. All necessary mathematical models were developed and incorporated into a computational fluid dynamics model with the influence of turbulence simulated by a two-equation (k-ε) model. Distributions of fluid velocities, temperatures and concentrations of the reactants and products as well as the trajectories of particles and their interaction with the gas phase are calculated. The results of the present parametric study allow estimations to be made and conclusions to be drawn that help in the optimization of a given calciner.     

“CHCT”催化剂在水泥煅烧中的催化作用探讨

“CHCT”催化剂在水泥熟料煅烧过程中通过对煤炭的催化燃烧进而促进固相反应、液相反应、熟料急冷 ,使用该催化剂可降低水泥生产成本、增加企业经济效益     

Burnability of cement raw materials at rapid calcination conditions

Cement raw materials (clay, limestone and pyrite cinders) were mixed, pressed into pellets, burnt at high temperatures, cooled and the resulting clinkers analysed for free CaO content. The effect of the following parameters and their interactions on the free CaO was studied: top temperature of burning (in three levels: 1300, 1350, 1400°C), soaking time at top temperature (in three levels: 5, 30 and in some cases 60 min), method of heating (in two levels: rapid and normal), method of cooling (in two levels, rapid and slow), lime saturation factor of the mix, LSF (in three levels, 0.95, 0.85, 0.76). Experiments were planned to enable a statistical evaluation (calculation of error variance at various levels of significance). Rapid calcination improves the burnability of cement raw materials, as contrasted to normal calcination. This indicates that rapid calcination enables the use of lower calcination temperatures. A long soaking at top temperature is unnecessary in case of rapid calcination. The free CaO content of the clinker is affected primarily by the LSF of the mix and the top temperature of firing; all other parameters are less effective.     

分解炉内煤矸石悬浮煅烧的数值模拟

煤矸石制备水泥辅助胶凝材料的应用研究对水泥行业的节能减排与大宗固废的高值利用均具有重要意义。本文以河北某地不同矿区的6种煤矸石为原料，采用XRD，热重等方法分析判断其化学成分和矿物组成，通过静态煅烧实验研究了其煅烧活化条件，并通过胶砂实验测定其胶凝活性。结果表明，煅烧温度和时间会影响产品的胶凝活性，煤矸石经过适当的热处理后，可用作辅助胶凝材料替代部分水泥熟料，在实现煤矸石资源化利用的同时，也为水泥工业碳减排提供了新路径。但煤矸石成分复杂，活化煅烧需要注意煅烧制度。采用CPFD（Computational Particle Fluid Dynamics）数值模拟方法模拟了分解炉内煤矸石传热、传质及化学反应，分析了不同工况下分解炉内气固两相流场。结果表明：入炉空气的温度较低时无法点燃煤矸石中的可燃组分，通过高温烟气点火和分级司料可有效解决这一问题。     

萤石尾矿作矿化剂在水泥熟料煅烧中的应用研究

通过利用萤石尾矿作为水泥熟料生产的替代原料,组织开展了水泥窑熟料煅烧试验。试验数据分析显示,在熟料煅烧过程中,萤石尾矿中CaF2掺入可明显提高生料易烧性,促进碳酸盐的分解,降低熟料煤耗,提高熟料强度,同时试验发现伴随萤石尾矿的掺加,窑系统氮氧化物排放下降,萤石尾矿催化提高窑系统脱硝效率,降低氨水用量,有利于降低企业脱硝成本。     

萤石尾矿作矿化剂在水泥熟料煅烧中的应用研究

通过利用萤石尾矿作为水泥熟料生产的替代原料,组织开展了水泥窑熟料煅烧试验。试验数据分析显示,在熟料煅烧过程中,萤石尾矿中CaF2掺入可明显提高生料易烧性,促进碳酸盐的分解,降低熟料煤耗,提高熟料强度,同时试验发现伴随萤石尾矿的掺加,窑系统氮氧化物排放下降,萤石尾矿催化提高窑系统脱硝效率,降低氨水用量,有利于降低企业脱硝成本。     

水泥熟料岩相分析在水泥生产中的作用

预分解窑与湿法窑的工艺差异,其熟料的微观结构能够明显反映;熟料的晶体结构取决于工艺过程,并能判断操作水平的高低;从分解炉结渣的微观结构可以准确地找出原燃材料存在的问题。也就是说,水泥生产过程中的不良环节均能从熟料岩相结构中反映出来。     

水泥窑低氮煅烧自适应控制系统的设计与研发

水泥回转窑系统是连续进出料的高温热工设备,它的热工参数离散,是一个多变量、非线性、强干扰、大滞后的复杂系统。使用传统的机理建模和常规的控制方法,烧成系统污染物排放勉强能够达到环保国标要求,但要进一步降低氮氧化物排放极其困难。利用Elman神经网络进行建模,通过分析及预处理变量数据,优化多维模糊规则表,控制低氮燃烧器,基于理论分析及系统设计,形成一套水泥炉窑低氮煅烧自适应控制系统。试验结果表明,系统对多变量的预测误差低于6%,且实现连续稳定运行近100天。     

利用水泥窑协同处置危废对熟料煅烧的影响

利用水泥窑协同处置固废、危废是一种循环利用废弃物的方式。水泥厂利用水泥窑协同处置浆渣、废液、无机淤泥等危险废弃物,根据废弃物特性不同选择不同的加入点对熟料煅烧影响各不相同,本文探讨了危废加入窑系统后对熟料煅烧的影响。结果表明,根据危废热值、水分、有害成分等含量的差异选择不同的加入点可以有效降低煤耗和氨水消耗;通过浆渣入口的调整可以降低危废对窑工况和熟料煅烧的影响;对危废喂料量及有害成分的控制可以满足水泥质量要求的同时减少危废对熟料煅烧的影响。     

AOS生产反应机理描述及相关工艺计算

简述了α-烯基磺酸盐(AOS)的特性,通过对AOS磺化反应机理的分析,就反应过程物料组成及相关控制指标进行了理论计算,提供了一系列理论数据,阐述了AOS生产工艺控制关键点。     

C_4烷烃混合热裂解反应机理的数值模拟

通过对蒸汽热裂解反应机理实验研究困难的分析,提出了将Materials studio模拟和Aspen Plus模拟计算相结合的烃类热裂解自由基反应机理的理论研究方法。并用该理论方法对正丁烷和异丁烷及其混合物的相互作用机理进行了研究。结果表明:正丁烷热裂解主要是1-C4H9·中β-C—C键发生的断裂生成乙烯,由2-C4H9·断β-C—C键生成丙烯;异丁烷热裂解主要是i-C4H9·中β-C—C键的断裂生成丙烯。采用与文献[1]同样的原料数据进行模拟,并与该文献中混合C4烷烃热裂解的实验数据进行了对比,说明该理论方法计算得到的结果与实验结果吻合较好。     

Thermodynamic modelling of the hydration of Portland cement

A thermodynamic model is developed and applied to calculate the composition of the pore solution and the hydrate assemblage during the hydration of an OPC. The calculated hydration rates of the individual clinker phases are used as time dependent input. The modelled data compare well with the measured composition of pore solutions gained from OPC as well as with TGA and semi-quantitative XRD data. The thermodynamic calculations indicate that in the presence of small amounts of calcite typically included in OPC cements, C-S-H, portlandite, ettringite and calcium monocarbonates are the main hydration products. The thermodynamic model presented in this paper helps to understand the interactions between the different components and the environment and to predict the influence of changes in cement composition on the hydrate assemblage.     

浅谈核电站工程用水泥的生产

介绍了根据核电站建设用水泥的品质要求,通过制订合理的配料方案,选择适合的原、燃料,以及加强对生产过程的控制,终于生产出合格的核电站建设用水泥。     

含磷石灰岩矿的特征及其对水泥生产的影响

简要地分析了磷酸盐矿物的地质特征和结构特征,并详细分析了安哥拉罗安达水泥厂含磷石灰岩矿床的化学组成、磷和氟含量及其矿物特征和形貌。在此基础上,重点试验研究了P2O5对水泥生产和熟料性能的影响情况。试验结果初步显示:(1)含磷高的原料对熟料的烧成和产品性能影响很大,因P2O5既会影响水泥熟料矿物C3S的形成,还会阻碍水泥的早期水化,严重影响水泥的凝结和硬化过程;(2)熟料中当w(P2O5)2.0%时可以制备性能满足要求的水泥,在生产控制中要严格控制生料中w(P2O5)1.0%[石灰石中w(P2O5)0.8%]为宜;(3)在含磷熟料中,适量F-的存在[w(F-)0.35%]能降低P2O5的负影响。     

磷石膏制水泥缓凝剂净化工艺

磷石膏制水泥缓凝剂是其综合利用的重要方法之一。分析了磷石膏中各类杂质对水泥缓凝剂性能的不利影响,介绍了磷石膏净化过程的几种工艺方法:物理水洗法、化学预处理法和干燥煅烧法,分析其净化效果。推荐针对不同杂质含量的磷石膏采用不同的净化组合工艺。     

Numerical modelling for rotational moulding with non-isothermal heating

Abstract

In the rotational moulding process, the internal air temperature has been widely recognised as a tool to predict an optimum cycle time. This paper presents a new numerical approach to predict the internal air temperature in a two-dimensional (2-D) static model without requiring the consideration of the tumbling motion of polymer powder. The initial non-isothermal heating of the static model is actually formed by two changeable plastic beds (stagnant and mixing beds), which represent the actual stagnant and mixing pools inside a rotating mould respectively. In the numerical approach, the lumped-parameter system and coincident node technique are proposed to incorporate with the Galerkin Finite Element Method in order to account for the complex thermal interaction of the internal air. It helps to overcome the difficulty of multidimensional static models in predicting an accurate internal air temperature during the heating stage of rotationally powdery plastic. Importantly, the predicted temperature profiles of the internal air, oven times for different part thicknesses and process conditions accord with the available experimental results.     

Effect of calcination temperature on use of high-boron-content waste for low-temperature wall tile production

The effects of the calcination temperature on raw-colemanite-waste properties and calcined waste content on wall tile production were investigated. Waste containing 11.24% B₂O₃ calcined between 500 and 800°C was added to wall tile granules in various ratios (0–100 wt.%) to produce a low-temperature-sintered wall tile by adding the maximum content of boron waste, as determined through optimal calcination. The low-temperature (850–1000°C) sinterability of the samples and the effect of the calcined colemanite-waste content on the wall tile properties were investigated. The samples were characterised using X-ray fluorescence, X-ray powder diffraction, differential thermal analysis, thermogravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and colourimetry. The waste calcined at 800°C exhibited a substantially different phase distribution, bond structure, morphology, and colour. The wall tile produced using 40 wt.% colemanite waste calcined at 800°C and subsequently sintered at 950°C exhibited the optimal properties. The linear firing shrinkage, water absorption, and flexural strength of the optimised wall tile were 0.88%, 16.04%, and 36.07 MPa, respectively. The optimised wall tile exhibited major albite, quartz, and diopside phases and 64% higher strength. The sample calcined at 800°C showed that high colemanite-waste content could be incorporated into ceramic bodies.     

磷渣用于水泥熟料生产的试验

磷渣是电热法生产黄磷时排出的一种具有潜在活性的低熔点工业废渣。在水泥熟料烧成过程中掺入磷渣能降低熟料烧成热耗、改善熟料矿物组成、提高熟料性能,但在实际使用过程中,会引起结皮加速、烧成工况波动等问题。在生产试验过程中,磷渣掺入量由1%~3%逐渐增加,通过生料配料调整、烧成系统精细控制,最终达到改善生料易烧性、降低熟料热耗、提高熟料质量的目标。