Modification of ash flow properties of coal rich in calcium and iron by coal gangue addition

Flow property of coal ash and slag is an important parameter for slag tapping of entrained flow gasifier.The viscosity of slag with high contents of calcium and iron exhibits the behavior of a crystalline slag,of which viscosity sharply increases when temperature is lowered than temperature of critical viscosity(Tcv).The fluctuation in temperature near the Tcv can cause an accumulation of slag inside the gasifier.In order to prevent slag blockage,it is necessary to adjust the ash composition by additive to modify the flow property of coal rich in calcium and iron.Main components of coal gangue are Al2O3 and SiO2,which is a potential additive to modify the ash flow properties of these coals.In this work,we inves-tigated the ash flow properties of a typical coal rich in calcium and iron by adding coal gangue with dif-ferent SiO2/Al2O3 ratio.The results showed that the ash fusion temperatures (AFTs) firstly decreased,and then increased with increasing amount of coal gangue addition.Chemical composition of coal ash rich in calcium and iron moved from gehlenite primary phase to anorthite,quartz and corundum primary phases.The slags with coal gangue addition behaved as a glassy slag,of which the viscosity gradually increased as temperature decreased.Besides,a high SiO2/Al2O3 ratio of coal gangue was beneficial to modify the slag viscosity behavior.Addition of coal gangue with a high SiO2/Al2O3 ratio impeded forma-tion of crystalline phases during cooling.This work demonstrated that coal gangue addition was an effec-tive way to improve the ash flow properties of the coal rich in calcium and iron for the entrained flow gasifier.     

煤矸石的化工应用

综述了煤矸石在化工应用中的研究情况,利用煤矸石生产化工产品技术可行,且原料来源广泛。     

Multiple linear equation of pore structure and coal–oxygen diffusion on low temperature oxidation process of lignite

This work aimed at studying the feasibility of calculating the coal–oxygen diffusion properties during the low temperature oxidation process of lignite so as to predict its spontaneous combustion process. Coal samples were oxidized in air ambient under different temperatures. Scanning Electron Microscope was used to indicate the surface morphology changes of oxidization. Then, based on fractal theory and flow characteristics, the fractal dimension of gas diffusion in the pore ways was calculated under different temperature. Considering pore size distribution, connectivity distribution and Fick diffusion mechanisms, the relationship between the gas diffusivity change with pore area fractal dimension and porosity was investigated, and multiple linear equation of the coal–oxygen diffusion coefficients and pore parameters was obtained. Comparison between the experimental data and model prediction verifies the validity of the model. The research provides a theoretical basis for the prediction model of coal–oxygen diffusion law.     

Modeling changes of fractal pore structures in coal pyrolysis

Coal pyrolysis processes are numerically investigated in mathematically produced coal pore models which simulate real coal pores in the parameters of the porosity and fractal dimension. The simulations include FG-DVC chemical reaction model, gas molecular diffusion in pores, energy conservation model and coal swelling model. Numerical results are verified by experimental results qualitatively, and they revealed that both the porosity and volatile contents of the parent coal can affect the fractal dimension of the final char pores after pyrolysis linearly. A formula to predict the fractal dimension of char pores from its parent coal properties is obtained by curve fitting in numerous results.     

Research on cementitious behavior and mechanism of pozzolanic cement with coal gangue

In this paper, the mechanical property of coal gangue in the activatory process is studied by using the method of orthogonal experiment, and then the micromechanism of various coal gangues is determined by modern test methods such as scanning electron microscope (SEM) and nuclear magnetic resonance (NMR). The experiment can approve those results: when proper amount of gypsum and fluorite were taken as for mineralizer in the course of calcinations of added-calcium coal gangue, much micropore can appear in microstructure and it can be in more molten state; spectrum peak of ²⁹Si in this kind of coal gangue is not only in splitting decomposition, but also in broadening; the mechanical property of coal gangue calcined with calcium is in accordance with microstructure.     

同煤塔山矿煤矸石制烧结砖工艺技术及应用

简述了同煤集团研究石炭系煤矸石综合利用的途径及制烧结砖技术的背景,详细介绍了以全煤矸石为原料,应用双级真空硬塑挤压、一次码烧、全自动生产工艺技术建设2．4亿块／a烧结砖工程项目一期工程1．2亿块／a生产线的设计要点及设备选型。煤矸石制砖项目是集团公司塔山工业园区重要循环产业链之一,促进了园区产业结构的优化,进一步增强了企业的综合经济实力。     

用煤矸石制备Al2O3-SiC复相粉体的研究

以煤矸石和碳质材料(工业炭黑、活性炭、无烟煤)为主要原料,在流动氩气中碳热还原制备了A l2O3-SiC复相粉体,研究了碳过量数、碳源、反应温度、保温时间、成型压力、添加剂种类及数量等工艺参数对制备的A l2O3-SiC复相粉体的相组成和显微结构的影响。结果表明,反应温度、保温时间及氯化物添加剂对煤矸石碳热还原反应有显著影响。通过优化工艺,以煤矸石为基料,加入适量炭黑,在1 550℃3 h下制备出了w(A l2O3)=58%、w(SiC)=42%的复相粉体,其粒度d50≤5μm;加入适量添加剂,可降低合成温度50℃。     

煤矸石作为替代原料在我公司水泥生产中的应用

我公司不断探寻新型低成本可替代原料。粉煤灰为粉状物料且水分较高,容易堵下料口,造成下料困难,经过多次实验发现,煤矸石与湿粉煤灰成分相近,其为块状物料,易于输送,价格较湿粉煤灰更为低廉,具有较高的资源替代性。煤矸石可替代现有的铝质校正材料湿粉煤灰进行生料配料。使用煤矸石配料能减少煤的配入量,使系统实物煤耗降低约0.5 kg/t;煤矸石到厂价格较湿粉煤灰价格便宜20元/t左右,可有效降低生料配料成本,具有较好的经济效益。煤矸石中硫含量较高且波动较大,可能造成烧成系统结皮、尾气硫超标等,使用时应加强煅烧工艺控制,并做好硫排放控制措施。     

Characterization of porous structure of coal char from a single devolatilized coal particle: Coal combustion in a fluidized bed

The combustion characteristics of coal char are highly dependent on initial pore structure of devolatilized char as well as on the structural evolution during the combustion of char. The development of pore structure also throws light on the mechanism of the combustion process. In the present work evolution of pore structure of partially burnt coal char of Indian origin has been investigated experimentally in a batch-fluidized bed and analyzed. The BET surface area, micropore surface area and porosity of char at various levels of carbon burn-off have been determined. Experimental specific surface area has been found to agree well with theoretical prediction using random pore model. Modified random pore model is used to determine the active surface area. Char combustion mechanism based on shrinking unreacted core and shrinking reacted core models are delineated during the course of reaction at various bed temperatures. This is substantiated with the proportional representation of ash and carbon matrix in scanning electron microscope images. It is also concluded that in the present investigation the mean pore size is much smaller and hence the Knudsen diffusion predominates. Analysis based on similar experimental observations and models for pore structure evolution to investigate char combustion reaction regime has not been reported in literature.     

煤矸石的资源化利用

介绍了煤矸石的基本组成及对水体,土壤,大气等的危害。介绍了几种煤矸石利用的主要途径及新的利用途径,并进行了经济技术分析,提出煤矸石资源化利用的建议。     

煤矸石对硬化水泥浆体结构形成的影响

通过对硬化水泥浆体物理力学性能的检测,结合XRD和SEM分析,研究了不同掺量的煤矸石对硬化水泥浆体水化性能的影响。结果表明:随着煤矸石掺量的增加,水泥的标准稠度用水量增加,凝结时间缩短,抗压强度降低,熟料矿物的水化速率提高,水泥-煤矸石体系的水化速率降低。煤矸石掺量不同,水化模式亦不同。     

Diffusional effect of pores on the densification in microgravity liquid phase sintered FE-CU alloys

OLiPSE-02 Fe-Cu samples, which were liquid phase sintered under 10 m 5 torr in microgravity for 20, 30, 60, and 330 min for each composition, were analyzed in this article. The compositions of the samples are 80% Fe/Cu, 70% Fe/Cu, 60% Fe/Cu, and 50% Fe/Cu by volume. The experimental results of distortion and densification were presented. During the microgravity processing, liquid ejection occured for the long duration samples with compositions 70% Fe/Cu and 60% Fe/Cu. Measurements of the weights and dimensions of all the beads were made and their distributions were presented. One of the beads that are about the average weight and size from the 70% Fe/Cu long duration sample was chosen to be mounted, polished, etched, and analyzed under an optical microscope. The iron in the bead appeared as iron grains and its grain size was smaller than that in the mother sample with the same composition. Discussions of the bead and its iron grain formations are provided.     

Effect of porosity and hexagonality on the infrared transmission of spark plasma sintered ZnS ceramics

Tailoring phase transition and microstructural evolution during sintering is crucial for the fabrication of ZnS ceramics transparent to infrared (IR) radiation. Herein, we have described the phase transition, microstructure, and related IR transmission of spark-plasma-sintered ZnS ceramics in terms of sintering temperature and pressure. The pore characteristics of spark-plasma-sintered ZnS ceramics were evaluated using Mie scattering theory. Changes in hexagonality and residual pore characteristics of the microstructure affected IR transmission of the sintered specimens. High temperature and pressure condition of SPS were found to increase excessive hexagonal phase (>20%), mainly contributing to a transmittance decay in the range 2–4 μm.     

降低矸石带煤率的方法

中国目前入选原煤中60%左右是跳汰洗选。在跳汰选煤过程中,影响跳汰机分选效率的因素有入料原煤特性,跳汰机风阀周期特性(跳汰频率及进、排气时间),矸石段、中煤段排料情况,各室顶水情况,风压、水压等,并且诸因素间相互制约,再加上人为因素的影响,既兼顾精煤质量又提高分选效率非常困难。以济三煤矿选煤厂BATAC跳汰机为例,通过改善风量与水量的配比,改造跳汰机筛板,稳定床层的同时,保证了精煤灰分,矸石带煤率由原先的6%降至5%以下,提高了精煤回收率,为选煤厂带来明显的经济效益。     

煅烧高铝煤矸石-矿渣-水玻璃系地聚合物材料的研究

根据地聚合物合成原理，采用煅烧高铝煤矸石-磨细矿渣-水玻璃系合成地聚合物类材料。深入研究了高铝煤矸石-矿渣-水玻璃系统材料的制备、性能的测试评价、水化硬化机理和最优制备工艺参数选择。材料中矿渣对早期强度起主要作用，煅烧高铝煤矸石对后期强度贡献较大。在矿渣和高铝煤矸石质量比处于合理状态时，材料各龄期强度均较优。高铝煤矸石类地聚合物材料的抗压强度随水玻璃模数的减小而增大，随水玻璃掺量的增大而增大，随液胶比的减小而增大。水玻璃模数为1．049，矿渣与煅烧高铝煤矸石的配比为4：6，激发剂掺量为22％，液胶比为0．35时，复合材料28d抗压强度达到了41．7MPa。     

Hydration of cement and pore structure of concrete cured in tropical environment

This paper presents the results of an experimental study on the effect of curing on the degree of cement hydration and capillary porosity of concrete in a tropical environment. It provides basic information for the estimation of w/c of hardened concrete using petrographic methods. Concrete with w/c ratios of 0.30 to 0.70 with an increment of 0.05 was investigated. The concrete was cured at 20 and 35 °C and exposed to various durations of moist curing. The results indicated that the concrete cured at 20 °C water for 28 days had a higher degree of cement hydration and lower capillary porosity than did the concrete cured in water of the same temperature for 7 days followed by exposure to outdoor air for 21 days, but had an opposite trend compared to the concrete cured in 35 °C water for 7 days followed by exposure to outdoor air. However, the differences on the degree of cement hydration and capillary porosity for the concrete cured in these different conditions were not significant.     

Evolution of pore structure and active surface areas of coal and char during hydrogenation

A Belgian coal (Beringen) has been used in a fundamental study of the changes in pore structure and active surface area during hydrogenation. The coal was devolatilized under N₂ and then hydrogenated at constant temperature up to various conversion yields. Reactivities of the chars were determined by isothermal thermogravimetric analysis. Changes in total surface area, calculated from CO₂ adsorption isotherms at 298 K, and in macropore distribution, obtained by mercury penetration, were found to lead to the same conclusion. In the first reaction stage, the preponderant phenomenon was the opening of previously closed micropores, induced by the material consumed by the reaction. This stopped completely when conversion yield exceeded 55 wt% when the maximum surface area was observed. Then removal of material from pore walls became predominant, pores were enlarged and pore walls disappeared gradually with increasing hydrogenation yields. Oxygen chemisorption capacities were measured at 383 K and 0.1 MPa air to give a relative indication of the concentration of carbon active sites. Active surface area results were compared to total surface area values and correlated with reaction rates.     

分光光度法测定煤矸石中的微量铜

研究了三苯胺萃取分离干扰离子后 ,Cu与 DPC-CPB-OP的显色反应体系测定煤矸石中的微量铜 ,结果满意。关键词 :分光光度法 ;二苯碳酰二肼 ;煤矸石 ;铜     

Modeling of pore structure evolution within the fiber bundle during chemical vapor infiltration process

Taking into account the gas diffusion parallel and perpendicular to the bundle axis, a two-dimensional model combining the non-conservative level set method and the steady-state diffusion equation is presented for evolving pore structure in the bundle cross-section. Parametric studies have been conducted to determine the sensitivity of residual porosity within the bundle to the structure parameters. Sheldon and Besmann's approach is revised and more realistic approximated expressions depicting the accessible and total porosity evolution inside the bundle are given. Such expression can serve as useful estimate of pore structure evolution for modeling the CVI process.     

南堡1-5区东一段储层微观孔隙结构特征研究

应用物性分析、薄片观察、扫描电镜、常规压汞等方法,对南堡1-5区东一段储层特征及孔隙结构进行了研究。研究结果表明,储层孔隙类型有粒间溶孔、粒内溶孔、晶间微孔、铸模孔,以粒间溶孔为主要类型;喉道类型以点状、缩颈型喉道为主;孔隙结构以中孔-中喉道型为主,其次是中孔-大喉道型、中孔-小喉道型。