长石与石灰石釉料调配的始熔温度研究

通过改变长石与石灰石的相对含量并考虑不同品种的长石进行釉料的调配，获得了钾长石-石灰石、钾钠长石-石灰石、钠长石-石灰石3个系列共18种釉施于白胎上。通过不断改变还原结束温度对所制釉料制品进行烧制，观察各烧成制品的釉色变化，推算出釉的始熔温度，进而对钾长石、钾钠长石、钠长石与石灰石调配的始熔温度的变化规律进行分析和讨论。     

提高预均化配料效果的几个措施

我公司2000t／d熟料生产线，采用石灰石、黏土、粉煤灰和铁矿石4组分配料。石灰石通过窄轨铁路送人厂内，粉煤灰、黏土通过汽车运至厂内。生料配料采用矩形堆场预均化配料方式，预均化采用石灰石、黏土和粉煤灰3组分配料或采用石灰石、黏土配料或采用石灰石、粉煤灰配料。生料配料站由混合料（预均化堆场的料）、铁矿石和校正料（石灰石）组成，配比由中控室操作。     

采用高镁石灰石配料改善生料易烧性的探讨

HR25001／d预分解窑水泥生产线于2002年投产，原采用石灰石、页岩、砂岩和硫酸渣4组分配料，石灰石氧化钙含量基本在54％以上，品位较高，杂质含量较少，结构致密，易烧性反而不好。加之页岩和砂岩结晶硅含量较多，生料易烧性较差，熟料质量一直不理想。另外几个石灰石矿均毗邻风景区，出于保护环境的原因近年来开采量被严格限制。为了改善生料的易烧性并打破石灰石供应的瓶颈，厂部决定采用邻近价格较低但氧化镁含量较高的黑石灰石进行部分替代，考虑到过高的氧化镁可能会对煅烧工况和熟料质量产生较大影响，决定先组织试生产，并特地选择在窑系统中修后进行，以避免干扰。     

采用高镁石灰石配料改善生料易烧性的探讨

HR厂为2000t／d新型干法回转窑，2002年底投产，原采用石灰石、页岩、砂岩和硫酸渣4组分配料，石灰石氧化钙含量基本在54％以上，品位较高，杂质含量较少，结构致密，易烧性反而不好，加之页岩和砂岩结晶硅含量较多，生料易烧性较差，熟料质量一直不理想；加之几个石灰石矿均毗邻风景区，出于保护环境的原因近年来开采量被严格限制，为了改善生料的易烧性并打破石灰石供应的瓶颈，厂部决定采用邻近价格较低但氧化镁含量较高的黑石灰石进行部分替代。考虑到过高的氧化镁可能会对窑的煅烧和熟料质量产生较大影响，决定先组织试生产，并特地选择在窑系统中修后进行，以避免干扰。     

湿法烟气脱硫喷雾吸收塔设计概要

对石灰石-石膏法烟气脱硫工艺中喷雾吸收塔结构、反应机理及内件配置进行了分析介绍，根据已有的工程设计经验，给出了喷雾吸收塔的设计参数，并讨论了设计中应考虑的主要问题。     

水泥熟料与第二组分混合粉磨特性研究

研究了水泥熟料与石灰石、矿渣、火山灰等材料以及立窑熟料与回转窑熟料双组分物料的分别与混合粉磨特性。通过测定分别与混合磨产物的粒度分布、比表面积和筛余值,以及熟料与石灰石混合粉磨产物各粒级范围两组分的相对含量,分析了易磨性不同的两组分物料之间的相互作用,揭示了混合粉磨过程中常发生选择性粉磨,一组分物料可能对另一组分物料的粉磨起促进或阻碍作用。恰当利用这种相互作用可以改善双组分物料易磨性,从而促进了整体的粉磨过程,并改善水泥粒度分布与性能。     

石灰石活化分解的研究

以某水泥厂不同产地（A矿山石灰石和B矿山石灰石）的石灰石为原料，用XRD、TG-DTA测试方法对其相关特性进行了分析；并运用石灰石分解的相边界反应收缩圆柱体反应机理，对其进行了石灰石分解活化能计算分析。结果显示A矿山石灰石较B矿山石灰石的活化能低、易分解。     

脱硫灰中主要组分对石灰石脱硫活性的影响研究

研究脱硫灰中主要组分对石灰石脱硫活性的影响具有重要意义。选择表观溶解速率常数k作为石灰石脱硫活性的评价指标,使用瑞士万通902智能电位滴定仪,分析了脱硫灰中Si O2、Al2O3、Fe2O3、Ca SO3与Mg O等五中组分对石灰石脱硫活性的影响。结果表明,在实验浓度范围内Si O2、Ca SO3、Al2O3等均促进了石灰石的溶解,其对石灰石脱硫活性的影响程度大小顺序为Ca SO3Al2O3Si O2;而Mg O对石灰石的溶解主要起抑制作用;Fe2O3对石灰石脱硫活性的影响与其浓度有关;当脱硫灰与石灰石掺合作脱硫剂时,应综合考虑脱硫灰中各组分的含量及其对石灰石溶出的影响,选择适宜的脱硫灰和石灰石掺合比。     

DCS控制系统的三种应用结构

我公司目前具备4×5　000t/d的生产能力，由于厂区易于获取石灰石，在厂内还建有一座小型的石灰石粉磨站，把经过破碎的石灰石研磨成细粉供应给燃煤发电厂做脱硫用。公司根据设备投资成本、设备运行状况分别在水泥生产线、余热发电和石灰石粉磨站采用了不同结构的DCS控制系统。本文对其应用情况进行总结。     

我厂原燃料质量及均化情况述评

在新型干法水泥生产中，采用均化技术，努力提高人窑生料合格率及燃料质量是保证回转窑热工制度稳定和熟料质量的有效手段。我厂设有两条2000t／d新型干法水泥生产线，采用石灰石、粘土、铁粉、砂岩4组分配料，并在生料及燃料制备的全过程中都不同程度地采用了一定的均化措施，本文拟就我厂原、燃料质量及均化情况谈一些看法，供参考。1石灰石质员及均化情况我厂石灰石矿山各勘探线的CaO平均在引．13％～51．66％波动，二级品CaO在48．24％～51．11％范围内波动。在B级储量范围内，各勘探线的Caop标准偏差为0．98％～3．54％，不均匀系数…     

Rheological characterization of cement pastes with functional filler particles

Cement pastes were studied using conventional rheological methods. The effect of different types of functional fillers on the rheological properties and hydration rate of the pastes was analysed. The fillers were found to have varying chemistry and therefore surface properties. Porous titania particles raised the cohesive energy of the paste significantly already at low additions. Limestone particles raised the cohesive energy somewhat, but clearly less than titania. The zeta potential of the particles was found to somewhat affect the rheology. Reaction rates of the pastes were measured using oscillatory rheological measurement with constant amplitude and frequency. Titania particles were found to accelerate the hydration rate more than limestone particles. Of the limestone particles pure calcite increased the reaction rate more than dolomitic limestone. When the limestone particles were modified to provide C–S–H nucleation sites the cohesive energy was raised and the reaction rate was further increased.     

Comparison of the morphology of alkali–silica gel formed in limestones in concrete affected by the so-called alkali–carbonate reaction (ACR) and alkali–silica reaction (ASR)

The morphology of alkali–silica gel formed in dolomitic limestone affected by the so-called alkali–carbonate reaction (ACR) is compared to that formed in a siliceous limestone affected by alkali–silica reaction (ASR). The particle of dolomitic limestone was extracted from the experimental sidewalk in Kingston, Ontario, Canada that was badly cracked due to ACR. The siliceous limestone particle was extracted from a core taken from a highway structure in Quebec, affected by ASR. Both cores exhibited marked reaction rims around limestone particles. The aggregate particles were polished and given a light gold coating in preparation for examination in a scanning electron microscope. The gel in the ACR aggregate formed stringers between the calcite crystals in the matrix of the rock, whereas gel in ASR concrete formed a thick layer on top of the calcite crystals, that are of the same size as in the ACR aggregate.     

DYNAMIC SOLIDS MIXING BETWEEN COAL AND LIMESTONE IN A GAS-SOLID FLUIDIZED BED

Dynamic characteristics of solids mixing between coal and limestone were studied. Experiments were carried out in a 0.203 m diameter cold fluidized bed with coal and limestone of different sizes as the fluidized particles. Experimental parameters examined included operation time, air flow rate, bed height, initial bed setup, relative particle size and relative amount of the two particles. The coal concentration profile was analyzed through bed sectioning, and a mixing index was used to describe the profile. The observed results were presented graphically and in correlation forms. The steady state results were also compared with those available in the literature.     

Effect of aggregate size on transition zone properties at the portland cement paste interface

Structural features of the transition zone between granular aggregate and portland cement paste were studied. Two types of aggregates were used, quartz and limestone. The transition zones are structurally characterized by a parameter referred to as “interfacial excess conductance” based on electrical conductivity methods. The experimental results indicate that the transition zone between quartz particles and portland cement paste is always less dense than bulk paste, regardless of the aggregate size, and that the thickness of this transition zone decreases with the decreasing of the aggregate size. The same general features occur for the transition zone between larger limestone particles and portland cement paste. A transition zone denser than bulk paste occurs, however, for much smaller limestone particles due possibly to chemical interaction between the limestone particles and portland cement paste.     

Use of limestone obtained from waste of the mussel cannery industry for the production of mortars

Various types of cement−SiO₂−CaCO₃ mortar were prepared by replacing quarry limestone aggregate with limestone obtained as a by-product from waste of the mussel cannery industry. The CaCO₃ aggregate consists mainly of elongated prismatic particles less than 4 μm long rather than of the rounded particles of smaller size (2-6 μm) obtained with quarry limestone. The mechanical and structural properties of the mortars were found to be influenced by aggregate morphology. Setting of the different types of mortar after variable curing times was evaluated by scanning electron microscopy (SEM), thermogravimetric analysis (TG) and mercury intrusion porosimetry (MIP) techniques. Mortars with a high content in mussel shell limestone exhibited a more packed microstructure, which facilitates setting of cement and results in improved mortar strength. The enhanced mechanical properties of the new mortars allow the cement content in the final mortar composition to be decreased and production costs to be reduced as a result.     

Electron microscopy and phase analysis of fly ash from pressurized fluidized bed combustion

The characterization of the typical fly ashes from pressurized fluidized bed combustion system (PFBC) in Japan and Europe was carried out by electron microscopy and phase analysis using energy-dispersive X-ray spectroscopy (EDX). The purity of limestone as in-bed sulfur removal sorbent influences the desulfurization reaction. The high-purity limestone yielded both hydroxyl ellestadite and anhydrite in Japanese PFBC ashes, while dolomite-rich limestone yielded anhydrite in European PFBC ashes. When the high-purity limestone was used, hydroxyl ellestadite particles were observed as the independent particles or the rim around limestone particles. The Al₂O₃ content in the glassy phase was inversely proportional to the CaO content in the glassy phase, suggesting that the glassy phases were formed from metakaoline and calcite as end members. Since hydroxyl ellestadite, glassy phase and metakaoline are reactive under hydrothermal conditions, PFBC ashes are expected to be used as raw materials for autoclaved products.     

Improvement of CO2 capture performance of calcium-based absorbent modified with palygorskite

Limestone can be used for CO₂ capture and sequestration (CCS) in flue gas effectively. However, its CCS capability will dramatically decline after several cycles due to the surface "sintering". In this work, the limestone was modified with palygorskite to reduce sintering phenomenon between the absorbent particles during the CCS process and the carbonation rate of the limestone can be enhanced effectively. Palygorskite is a natural mineral with nano-fibrous structure which can reduce the mutual contact of limestone particles during the CCS process. The results were detected by TGA, SEM,MIP, FTIR and particle size analyzer respectively. The best CO₂ capture performance of modified absorbent was 13.11% improvement with only 5 wt% palygorskite added during the CCS process after 15 cycles compared with natural absorbent. It was found that excellent microscopic structures of absorbent modified with palygorskite was created, and the surface sintering was postponed leading to CO₂ capture performance enhanced under the same conditions.     

Limestone filler cement in low w/c concrete: A rational use of energy

The effect of limestone filler (up to 20%) on the degree of hydration, the volume of hydration products, and the optimal replacement of limestone filler in cement pastes at different w/cm ratios (0.25-0.50) were investigated by using a quadratic statistical model. The results show an increase in the degree of hydration in very low w/cm ratio paste when the limestone filler content is increased. However, the largest volume of hydration products occurs for high w/cm ratio pastes, for which the available space also increases with the limestone filler content. Finally, for a given cement, the optimum limestone filler content for different w/cm ratios can be obtained by using the gel-space ratio concept.In addition, concrete mixtures (w/cm=0.30 and 0.34) were made to determine the compressive strength. The results have shown that concretes containing limestone filler cements present a small reduction of strength at 28 days improving the hydration of clinker particles in the system. The strength of concrete depends on the gel-space ratio, which takes into account all of the effects produced by limestone filler addition: the increase of the degree of hydration, the dilution, and the increase of the effective w/c ratio.     

The behaviour of petrographic constituents of hard coals in coking process and structure of the cokes obtained

The behaviour in the coking process of the main petrographic constituents - vitrinites, exinites, micrinites and fusinites - separated from hard coals of different rank (from flame coal to anthracite), and the differences in structure of the obtained cokes were examined and discussed.     

Calculation of the hindered settling velocity of a bimodal mixture of solid particles of arbitrary shape in a Newtonian fluid

A method for calculating the settling velocity of a bimodal mixture of particles of arbitrary shape is proposed. The method uses the concept of effective particle diameter, which characterizes the particle shape, volume, and midsection area. The method takes into account the contact interaction between particles of different sizes due to their collisions. The calculation results are compared with experimental data on settling of bimodal mixtures of limestone particles of arbitrary shape.