高氧化钙煤灰渣特性的探讨

本文论述了高氧化钙的煤炭资源和灰渣特性，通过实验讨论了添加氧化钙对酸性煤灰降低灰熔融温度和灰粘度的作用与影响。

电感耦合等离子体发射光谱法快速测定白云石、石灰石中高含量氧化钙

建立电感耦合等离子体发射光谱法测定白云石、石灰石中高含量氧化钙。样品经10 mL盐酸溶液(1∶1)、1.5 mL浓硝酸溶解后,设定测试功率为1 150 W,分析谱线波长为373.6 nm,氩气流量为0.7 L/min,辅助气流量为0.5L/min,氩气压力为0.2 MPa,观测高度为13 mm,泵转速为50 r/min,采用等离子体原子发射光谱法进行测定。钙的质量浓度在0~10.0μg/L范围内与信号强度线性良好,相关系数为0.999 9,方法检出限为3.2μg/L。采用所建方法分别测定白云石和石灰石标准样品,测定结果的相对标准偏差分别为0.28%~0.31%、0.19%~0.25%(n=6),测定平均值与标准值的相对误差分别为0.20%~0.48%、0.18%~0.22%。分别用所建方法与GB/T 3286.1—2012方法测定白云石、石灰石样品,测定结果的相对误差分别为0.26%~0.29%、0.34%~0.48%。该方法满足白云石、石灰石中高含量氧化钙的测定要求。

高游离氧化钙水泥的显微结构与膨胀机理研究

运用扫描电子显微镜 (SEM)研究了高游离氧化钙 (f- Ca O)水泥的水化及其在水泥石中氢氧化钙的分布和显微结构特征。讨论了水化早期和后期 Ca(OH) 2 晶体的结晶特性及界面结合关系 ,指出了熟料中成大堆分布的 f- Ca O晶体缓慢水化导致 Ca(OH) 2

Effect of Calcium Oxide Additive on the Performance of Iron Oxide Sorbent for High-Temperature Coal Gas Desulfurization

The effect of calcium oxide additive in iron oxide sorbent for hot gas desulfurization was investigated by XRD and TPR techniques.XRD characterization showed that CaO was highly dispersed after the calcination of sorbents.Calcium sulfate formed in the desulfurization was decomposed and regenerated to CaO by reacting with CO before the next sulfidation process.Calcium participated in every sulfidation/regeneration cycle and contributed to the enhancement of sulfur capacity.The TPR results showed that the reduction temperature of the sorbent increased with the increase of the content of calcium.Calcium played a role of retarding reduction.Therefore,the addition of calcium oxide additive will benefit the utilization of iron oxide sorbent in strongly reducing atmospheres.

Carbon Dioxide Captured from Flue Gas by Modified Ca-based Sorbents in Fixed-bed Reactor at High Temperature

Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors： calcium hydroxide, calcium carbonate, calcium acetate monohydrate and calcium oxide. The CO2 absorption capacity of those sorbents was investigated in a fixed-bed reactor in the temperature range of 350-650 ℃. It was found that all of those sorbents showed higher capacity for CO2 absorption when the operating temperature higher than 450 ℃. The CaAc2-CaO sorbent showed the highest CO2 absorption capacity of 299 mg.g-1. The mor- phology of those sorbents was examined by scanning electron microscope （SEM）, and the changes of composition before and after carbonation were also determined by X-ray diffraction （XRD）. Results indicated that those sorbents have the similar chemical compositions and crystalline phases before carbonation reaction [mainly Ca（OH）2], and CaCO3 is the main component after carbonation reaction. The SEM morphology shows clearly that the sorbent pores were filled with reaction products after carbonation reaction, and became much denser than before. The N2 adsorption-desorption isotherms indicated that the CaAc2-CaO and CaCO3-CaO sorbents have higher specific surface area. lar2er oore volume and anoropriate pore size distribution than that of CaO-CaO and Ca（OH）2-CaO.

Influence of CaO-based expansive agent,superabsorbent polymers and curing temperature on pore structure evolution of early-age cement paste

Cracks easily generate in concrete at early age owing to the shrinkage deformation.CaO-based expansion agent(CEA)and superabsorbent polymers(SAP)have been extensively used for the mitigation of concrete shrinkage.The macroscopic properties of concrete are highly determined by the microstructure.In this study,the influence of CEA and SAP addition on the pore structure evolution of cement paste under different curing temperatures was evaluated via low-field nuclear magnetic resonance spectroscopy.Test results indicated that,in cement paste,a higher CEA content led to a higher porosity and a larger most probable pore diameter(MPPD).Meanwhile,SAP addition increased the porosity and MPPD of CEA cement paste at early age but decreased them after 7 d,and a higher SAP content always brought a higher porosity and MPPD.Furthermore,the addition of SAP led to a lower porosity and MPPD of CEA cement paste than that of plain cement paste after 14 d.Moreover,the porosity and MPPD of CEA cement paste decreased first and subsequently increased as the curing temperature raised.

新阳煤矿高钙煤矸石热活化特性研究

采用热重分析法、电导率法、pH值法及ICP-AES离子浓度检测对新阳煤矿高氧化钙含量煤矸石热分解过程及不同温度热激发后煤矸石的活化特征进行了系统的分析研究。结果表明:活化过程中煤矸石物相变化经历了4个阶段:即吸附水挥发阶段、失重稳定阶段、有机碳质等挥发阶段和煤矸石结构水挥发、矿物分解阶段;随活化温度的升高,电导率值、活性离子浓度均呈下降的趋势,而溶液pH呈相反的变化规律;溶液pH测试实验表明:高氧化钙煤矸石在蒸馏水中溶解时形成一种高pH、强碱强极性溶解环境。

HCl Dry Removal with Modified Ca-Based Sorbents at Moderate to High Temperatures

Modified Ca-based sorbents were obtained by adding sodium alkali into Ca(OH)2 and CaCO3. Reactive properties of modified Ca-based sorbents with acidic gases were investigated through reacting with gaseous HC1 at 450-760℃, and SEM and XRD technologies were adopted to get information on the reaction mechanism. Experimental data showed that HC1 dry removal efficiencies increased with temperature before 700℃ for all of the investigated sorbents, and there existed improved sorbents that corresponded to the highest removal efficiencies under the similar conditions. SEM photographs exhibited morphology difference between original and improved sorbents both before and after the reaction; and displayed that improved sorbents formed more porous product layers than original sorbents especially at higher temperature when product sintering became heavier, which is favorable to HC1 dry removal. XRD analysis showed that (1) improved Ca(OH)2 and CaCO3 were less crystalline than original lime and limestone; (2) the reaction product species of improved Ca(OH)2 changed with reaction temperature, while for original Ca(OH)2 the same product species appeared for all of the tested temperatures; and (3) for improved CaCO3, the only product at lower temperatures was CaCl2.2H2O and more product species were produced when temperature was higher than 650℃, but no CaCl2.Ca(OH)2.H2O formed at 700℃, while for the case of original CaCO3, the undesired CaCl2.Ca(OH)2.H2O appeared at 700℃. Presently, reaction temperature interval of 650-700℃ is recommended for improved Ca(OH2) to get the highest efficiency, for improved CaCO3 reaction at higher temperature deserves further investigation to make a good choice.