混凝土碳化研究综述

混凝土碳化作用研究是混凝土耐久性研究的重要部分。碳化会降低混凝土的碱性,破坏钢筋表面的钝化膜,从而使混凝土对钢筋的保护作用减弱。本文从碳化机理、影响碳化的因素、碳化区的划分以及碳化对钢筋混凝土性能的影响几方面介绍了碳化对混凝土的影响。     

低钙硅酸盐矿物碳化硬化性能研究进展EI北大核心CSCD

低钙硅酸盐矿物在一定湿度下能够与二氧化碳发生反应,反应产物能够迅速凝结、硬化形成致密的硬化体。为了更好地研究和利用低钙硅酸盐矿物的碳化硬化性能,综述了低钙硅酸盐矿物的碳化反应过程、碳化硬化机理等方面的研究进展。低钙硅酸盐矿物碳化形成的碳酸钙晶体和高度聚合的非晶态二氧化硅凝胶是硬化体强度增长的主要来源,并且低钙硅酸盐矿物组成、结构及其与胶凝性能的关系,碳化反应及硬化机理,碳化硬化体的结构和耐久性等方面需要进一步系统研究。     

纳米碳酸钙碳化过程中“四膜模型”的研究

在双膜理论基础上,探讨建立了纳米碳酸钙碳化过程的“四膜模型”;用“四膜模型”来解释超细碳酸钙生产过程中碳化前期、中期、末期及过度碳化等各阶段的动力学区域和碳化机理,解释碳化过程中包裹返碱现象发生的规律和预防机理,都取得了理想的效果.     

石灰碳化煤球碳化机理及新工艺探讨

对石灰颗粒,单个煤球的碳化过程,以新观点解释了煤球碳化机理,研究了成型压力与煤球质量、碳化速率及预干燥的关系。提出低压成型,高料层低温碳化及后补强期的新工艺。     

型煤“三大要素”浅谈

型煤作为煤炭的深加工产品，在煤资源的充分利用方面，已显示出它独有的可行性与节能性。从早期碳化煤球与目前广泛应用的腐植酸煤棒、煤球的比较来看，碳化煤球制作工艺复杂、成本高，对煤炭利用的热效率低，特别是碳化煤球降低了原煤的固定碳含量，直接影响了其工业价值。而腐植酸煤球，虽然其工业燃烧指标要优于碳化煤球，但在制作过程中，人们由于忽视了制作型煤的“三大要素”，     

低钙硅酸盐矿物碳化硬化性能研究进展

低钙硅酸盐矿物在一定湿度下能够与二氧化碳发生反应,反应产物能够迅速凝结、硬化形成致密的硬化体。为了更好地研究和利用低钙硅酸盐矿物的碳化硬化性能,综述了低钙硅酸盐矿物的碳化反应过程、碳化硬化机理等方面的研究进展。低钙硅酸盐矿物碳化形成的碳酸钙晶体和高度聚合的非晶态二氧化硅凝胶是硬化体强度增长的主要来源,并且低钙硅酸盐矿物组成、结构及其与胶凝性能的关系,碳化反应及硬化机理,碳化硬化体的结构和耐久性等方面需要进一步系统研究。     

煤热解机理研究新进展

本文综述了国内外在煤热解机理方面研究的新进展。主要包括新近有关煤热解气、液产品的形成和逸出机理，煤热解过程中表征特性参数的理论与模型（如大分子网络模型、ＦＧ－ＤＶＣ模型和交联理论），在此基础上提出煤热解机理研究的建议和看法。     

两种煤沥青碳化的自由基历程研究

通过对煤沥青及其碳化产物的ESR研究,表明煤沥青碳化初期反应经历了自由基历程,发现中间相阶段脱氢缩聚使得稳定自由基大量生成,半焦阶段导电电子的产生使得碳化产物的ESR谱线异常增宽,中间相阶段碳化产物的自由基浓度增加与其分子量的增大是一致的,而碳化产物的ESR线宽大小在某种程度上可以反映分子的“流动性”,同时比较了两种煤沥青碳化产物的电子物性差异。     

超细碳酸钙的合成与形状控制

采用气体分布板控制碳化速度,通过加入不同形状的控制剂,合成了链状、片状、立方体状、纺锤状、球形、针状六种不同形状的超细碳酸钙．研究了碳化过程中的粘度变化及机理和碳化速率对碳酸钙晶体成核生长过程的影响．基本实现了链状碳酸钙的粒度控制．     

碳酸锂气液固三相反应结晶过程研究

碳酸锂的气液固三相反应结晶过程包含碳酸锂碳化反应和碳酸氢锂溶液的热析分解两个过程。首先对于碳化过程,考察了碳酸锂碳化转化率和反应速率的影响因素;建立并求解构建碳化微观机理模型,进而确定了碳酸锂碳化过程为气体传质控制。对于热析分解过程,研究了碳酸锂晶体产品的粒度分布、晶体形貌和聚结程度等与反应物浓度、温度、搅拌、晶种以及外场等因素的关系,尤其是在超声结晶条件下能够获得形貌完整且不聚结的碳酸锂棒状晶体。最后,揭示了碳酸锂的结垢机理,并基于实验验证提出了光滑表面、介稳区控制和晶种添加等方案可有效抑制结垢。     

炼焦机理和焦炭质量预测的研究进展

综述了煤的热塑性、炼焦机理和焦炭质量预测的研究进展。煤的化学结构如煤中镜质组的烷基侧链和移动氢的含量决定了煤的热塑性,核磁共振、质子磁共振热分析、拉曼光谱和电子顺磁共振谱等从分子水平解释煤的热塑性、配合煤的相互作用和炼焦机理。塑性成焦机理认为,良好的氢传递和分子重排是炼焦中获得优质焦炭的重要条件,塑性成分在焦炭光学组织形成中非常关键,改变加热速率可使煤的光学组织形成机理改变。碱度指数（modified basicity index,MBI）、复合焦势（composite coking potential,CCP）和组合煤指数（combined coal index,CCI）等参数可精确地预测焦炭反应后强度和焦炭反应性。矿物质对焦炭强度的影响是研究热点,控制焦炭的裂纹和尺寸是未来焦炭质量的要求。     

煤炭化过程中结焦压力的产生机理

论述了结焦压力的产生机理,从实际现象到内在本质,深入到炭化过程中煤大分子结构变化、脱挥发分速率、半焦及焦炭结构等多方面探讨了压力产生的来源与主要影响因素,并指出炭化室中心焦炭形成时会产生最大膨胀压力．最后提到了已有的一些鉴别危险结焦煤并预测其可能产生的结焦压力的一些方法．     

焦炉石墨生成规律研究

使用实验室模拟装置考察了4种煤在不同条件下的石墨生长情况。研究了水分、温度及炼焦煤的其它性质对石墨生成速度的影响。结果表明,石墨的沉积过程可以分为3个阶段。石墨沉积量在原料煤水分为7%时取得最小值。所用煤源的挥发分越高,同样条件下产生的石墨量越多;较高的硫含量导致石墨沉积量增大;煤中的氧促进沉积碳的生成。     

无烟煤与焦煤复配制备型焦的炭化过程研究

对比研究了无烟煤、焦煤和复配型煤在炭化过程中的化学组成与性质变化;采用热天平(TG)和傅立叶变换红外光谱仪(FTIR)对炭化过程中无烟煤、焦煤和复配型煤的气体释放和热失重情况及表面官能团进行了测试分析;采用X射线光电子能谱仪(XPS)对无烟煤型焦、焦煤型焦和复配型焦的碳、氧元素的化学状态进行了表征。结果表明:在低温阶段复配型煤的炭化是无烟煤和焦煤炭化的线性叠加,在高温阶段无烟煤和焦煤炭化存在协同效应,使得复配型煤释放更多的气体,失重大于两者失重的线性叠加;复配型煤在炭化过程中表面官能团的变化趋势与无烟煤和焦煤单独炭化时表面官能团的变化趋势一致,但由于两者的协同作用,复配型煤的碳元素氧化程度更高,易于生成更多的C—O基团。     

单种强黏结性肥煤的配煤实验及黏结指数变化分析

将半焦、焦粉、主焦煤以不同的比例,配入新疆焦煤集团强黏结性肥煤中,进行黏结性实验,实验结果表明,焦煤和经低温干馏处理过的半焦在配入比例5%以内时,配合煤的黏结指数并未遵循低于最高黏结指数的一般规律;不同温度干馏的半焦其配合煤的黏结指数不同。通过实验验证,强黏结性的肥煤对无黏结性的半焦会产生非常强的黏结性,这对于动力煤的半焦的配煤炼焦具有一定的实践意义。     

配入无烟煤炼制优质冶金焦技术研究

在保证焦炭质量的前提下,最大限度的使用无烟煤进行炼焦。通过对原料煤分析,合理配入相应的1/3焦煤,肥煤和焦煤,通过捣固炼焦工艺,进行配煤炼焦试验,以生产达到一级冶金焦标准的优质焦炭。     

Optical anisotropy of carbonized coking- and caking-coal vitrains

The purpose of this work was to characterize in detail the optical anisotropy formed during carbonization of the range of coals used in the coking industry, the ultimate objective being to attain a better understanding of the coking process. Vitrains hand-picked from a series of coking and caking coals were carbonized to various temperatures between 380 and 1000 °C. The semicokes and cokes so produced were examined by polarized-light microscopy to determine the proportions of the different types of optical anisotropy developed during carbonization. The results demonstrated that coals normally grouped within one class of the coal classification system used by the National Coal Board can lead to cokes which are significantly different in terms of their optical anisotropy. The process of the anisotropic development during carbonization can be explained generally in terms of loss of volatile matter, variations in viscosity of the plastic mass, and distortion of ordered phases by the pressure of evolving gases. Differences in carbonization behaviour as judged by the coke anisotropy can be attributed to differences in the ‘molecular-structure’ of the parent coal. In this respect the oxygen in the coal is considered to be of primary significance.     

Structure in cokes from coals of different rank

A range of bituminous coals has been carbonized to 1273 K. Polished surfaces of the solid products, carbons or cokes, are examined for optical texture by optical microscopy. Fracture surfaces of the carbons are examined by scanning electron microscopy (SEM). The carbon from the lowest rank coal (NCB Code No. 702) is isotropic and fracture surfaces are featureless. Carbons from coals of ranks 602, 502 are optically isotropic but fracture surfaces are granular (size 0.1–0.2 μm), indicating small growth units of mesophase. In the carbon/coke from a 401 coal, the anisotropic optical texture and grain size are both ≈0.5–10 μm diameter. Coke from a coking coal (301a, 301b) has a layered structure extending in units of at least 20 μm diameter with sub-structures ~ 1.5 μm within the layers, indicating perhaps that the bedding anisotropy of these coals is not totally lost in the fluid phase of carbonization. The carbons from the higher rank coals have the bedding anisotropy of the parent coal. The combined techniques of optical microscopy and SEM (both before and after etching of the fracture surfaces of coke in chromic acid solution) reveal useful detail of structure in carbons/cokes and of the mechanism of carbonization of coking coals.     

A physicochemical study of carbonization phases,Part II: quenching experiments at the pilot scale

Previous experiments carried out on several carbonization phases showed a relationship between tar migration and the coking pressure. In the present study, tests analogous in principle to the previous ones were conducted at a pilot scale with 400 kg coal charges. Two coals were used: C28, which leads to no pressure (“safe”), and C19, which induces pressure (“dangerous”). N-methyl-2-pyrrolidinone (NMP) extractions from the carbonization phases of the two coals confirm that tar migration is dependent on the nature of the parent coal, i.e. whether “safe” or “dangerous”. In the case of dangerous coal, the impregnation of non-coked coal by tars has been evidenced. In relation to this phenomenon, increased coking pressure is likely to develop due to the enrichment of non-transformed coal by volatile matter, as well as to the drop in permeability of this phase. It is also suggested that heavy tars clog up the pores of the semi-coke of dangerous coals.     

Structure of the cokes obtained from the group components separated from coking coal vitrites by selective thermosolvolysis

The examination of the structure of cokes obtained from extracts separated from preheated vitrites of coking coals by progressive and continuous extraction with chloroform was carried out. The structural ordering (interplanar spacing and crystallite dimensions) of the cokes depends on the rank of the parent vitrites but it does not depend on the degree of extraction. The occurrence of optical anisotropy in cokes from the extracts is connected with both the rank of the parent vitrite and the degree of extraction. In the formation of the optical anisotropic structure during the carbonization of coking coal vitrites, the part of the extract which is of small size, which partially undergoes decomposition, is an important factor.