磷渣低热水泥熟料的配制与烧成

以普通配料与磷渣配料相对比,以实验数据为依据,探讨了磷渣低热水泥熟料的矿物组成及率值对熟料性能的影响,分析了磷渣配料对生料易烧性及熟料性能的影响。     

利用高掺量磷渣煅烧优质水泥熟料的研究

采用磷渣为原料烧制优质水泥熟料.通过差热分析研究磷渣配料煅烧熟料的形成机理,利用金相显微镜对烧制的熟料进行岩相结构分析,观察其矿物形貌,用X射线衍射分析研究熟料的矿物组成和水泥水化产物组成.实验结果表明,利用高掺量磷渣配料可以显著改善生料的易烧性,加快熟料矿物的形成,并且矿物生长良好,早期强度较高.磷渣掺量为18%或21%时,所生产的熟料的游离CaO含量小于1.0%,C3S含量大于63%.     

磷-氟-钢渣复合添加剂对水泥熟料烧成的影响

磷(P)或氟(F)的阴离子团可以促进硅酸盐水泥熟料的烧成,因此,利用P与F的复合效应,并引入钢渣做晶种,分析晶种与阴离子的复合对硅酸盐水泥熟料形成规律所产生的影响.结果表明:磷渣、钢渣与萤石的三元复合体系对熟料中游离氧化钙含量的改善作用明显优于单掺磷渣或钢渣与萤石二元复合体系的.当煅烧温度提高至1350℃或1450℃时,三元复合体系仍明显改善了生料的易烧性.三元复合体系可改善液相的粘度与矿物的形貌,促进3CaO·SiO2的形成和生长发育.热分析表明:与空白样相比,磷渣、钢渣与萤石的三元复合体系将碳酸盐分解峰值温度、反应起始温度和反应结束温度分别降低了50,15℃和55℃.     

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。     

磷渣在水泥生料配料中的机理及应用

1 前言 我省磷化工企业在制取黄磷时,以10:1的比例产生大量磷渣,仅瓮福磷矿和开阳磷矿两处的年排放量就达200万t以上,堆集如山形成环境污染。然而它却是水泥生产中优于粘土、石灰石,并部分代替它们作原材料、代替萤石作矿化剂的好原料,起到节能降耗作用,并烧制出优质熟料,提高水泥质量。现就粒化电炉磷渣(以下简称“磷渣”)在水泥生料中的配料机理及其应用进行探讨。     

掺杂对高C3S水泥熟料烧成及C3S形成动力学的影响

利用铁尾矿作为作硅铝质原料进行生料配料(熟料率值KH =0.97,SM =2.5,IM =1.5),其中C3S含量超过70％.在此空白生料的基础上分别掺入氟、硫和氟硫复合阴离子,各试样分别在1300℃,1350℃,1400℃和1450℃下煅烧30 min,然后测定熟料中f-CaO的含量,并计算C3S的形成活化能.通过差热分析和XRD分析,研究高C3S熟料的烧成过程.结果表明:氟、硫的掺入能够显著改善生料的易烧性,大幅降低C3S的活化能,促进熟料的烧成.单掺时硫比氟的效果要好,氟硫复掺比单掺效果好.生料的差热分析表明,氟、硫能够使石灰石的分解温度降低10 ～20℃,同时能促进熟料的液相烧结.在1450℃时复掺氟硫熟料的主要矿相是C3S,还有少量的C2S,C3A和C4AF,表明高C3S水泥熟料已经烧成.     

用磷渣代替熟料晶种的探讨

巴东县三峡水泥厂生料磨为Φ2.2×6.5m,采用微机配料系统,煅烧设备为Φ3.0×10m塔盘式机立窑,成球采用预加水微机控制系统,生料采用复合矿化剂,但由于萤石来自于四川省彭水,路途远,价格也较高,为了降低生产成本,试用来源充足、价格低、运输方便的磷渣作非熟料晶种,取得了很好的经济效果。 依据结晶学中诱导原理,在生料中加入     

钴离子对水泥熟料烧成作用的研究

为探讨掺入钴离子对硅酸盐水泥熟料易烧性和矿物结构的影响，进行了系列试验研究。试验以空白生料为基准，分别掺入0．5％，1％，2％的Co2O3，煅烧至1250，1300，1350，1400，1450℃，利用化学分析、XRD、SEM、高温显微分析等方法，探讨了Co2O3掺入对熟料烧成和矿相性能的影响情况。结果表明：（1）掺入Co2O3能改善硅酸盐水泥生料的易烧性，且掺量越大，易烧性越好；（2）掺入Co2O3可以降低熟料反应相中液相生成温度，降低液相的粘度，促进C2S矿物的形成。     

磷渣晶种的节能分析

0 引言 中国建筑材料科学研究院发明的“添加晶种水泥立窑煅烧技术”,已在全国各地水泥企业广泛应用,其经济效益十分明显。但实施该项技术,需要挑选优质熟料返回生料配料。这样费时且成本高。为此本厂尝试用磷渣代替熟料晶种配料,在Φ2.84×10m机立窑生产线上煅烧水泥熟料取得良好效果。 1 工业分析     

Cr对水泥熟料矿物生成及水泥早期水化产物形成影响的研究

用化学试剂Cr(NO3)3代替工业废物中的Cr,对含Cr水泥熟料的矿物生成及水化进行了研究。研究结果表明,Cr可以提高熟料相中C2S的含量,在水泥水化初期促进了钙矾石的增长,同时有新的水化产物结晶相生成。     

铬渣作水泥原料及混合材的试验研究

研究了铬渣对水泥生料易烧性、熟料烧成液相出现温度及熟料物理性能的影响;同时还研究了利用铬渣作为水泥混合材对水泥物理性能的影响。结果表明:在水泥生料中加入适量铬渣,可有效改善生料易烧性,并使熟料烧成液相出现温度降低50℃左右,有利于提高水泥熟料强度;铬渣可作为水泥混合材使用,且效果比粉煤灰及火山灰好。     

珠江水泥厂配料方案及其水泥特性的研究

分析了广东省内几家新型干法水泥厂的熟料成分及水泥性能,并着重研究了“粤秀”牌水泥配制混凝土时具有优良性能的原因。研究表明:即使同是新型干法窑生产的熟料,其矿物组成、物理性能及其与减水剂相容性仍存在着较大的差异;磨制成水泥后,由于受熟料矿物组成及水泥颗粒组成的影响,在配制混凝土时性能差异更大。故若要提高新型干法窑水泥在配制混凝土时的性能,应重视熟料的矿物组成,优化水泥的颗粒级配,改善水泥与减水剂的相容性,而不应单一重视熟料的物理性能。     

Improvement of Al3+ ion conductivity by F doping of (Al0.2Zr0.8)4/3.8NbP3O12 solid electrolyte for mixed potential NH3 sensors

New Al³⁺ ion conducting solid electrolytes (Al_0.2Zr_0.8)_4/3.8NbP₃O_12-xF_2x(0?≤x?≤?0.4) with Nasicon-structure are successfully prepared by solid state reaction method. The influences of the doped F^- content on the properties of the (Al_0.2Zr_0.8)_4/3.8NbP₃O_12-xF_2x samples are investigated using X-ray powder diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The results show that F^- doping can effectively improve the sinterability and the total conductivity of the (Al_0.2Zr_0.8)_4/3.8NbP₃O_12-xF_2x samples. Among the solids series, (Al_0.2Zr_0.8)_4/3.8NbP₃O_11.7F_0.6 shows the highest conductivity of 1.53?×?10^?3 S?cm^?1at 500?°C, which is approximately 7.9 times higher than that of the undoped (Al_0.2Zr_0.8)_4/3.8NbP₃O₁₂. The ion transference number of the samples is higher than 0.99 at 300–700?°C. On the basis of the promising properties, a mixed-potential type NH₃ sensor based on (Al_0.2Zr_0.8)_4/3.8NbP₃O_11.7F_0.6 electrolyte and In₂O₃ sensing electrode has been developed. The sensing performance of the sensor is evaluated. The mixed-potential type sensor can work at relatively low temperatures of 200–350?°C and an excellent sensitivity of 99.71?mV/decade at 250?°C is obtained. The sensor also displays excellent stability and reproducibility, accompanied by low cross-sensitivities to CO₂, CH₄ and H_2.     

Mechanical and dielectric properties of 3D printed highly porous ceramics fabricated via stable and durable gel ink

A novel, efficient, versatile strategy was carried out to fabricate highly porous ceramic parts based on the combination of strong colloidal gel ink fabricated with high boiling point organic solvents and DIW technique. The preparation and optimization of inks and the effect of heating temperature on the phase composition, microstructure, mechanical properties and dielectric properties of ceramic parts were systematically investigated. The strong colloidal ink exhibits excellent ambient stability and printability. The sintering temperatures bring about the evolution of phases, structural mechanical properties and dielectric properties of ceramic parts. Ultimately, Si₂N₂O single wall ceramic parts with a frame density of 1.07?1.14 g/cm³ and an apparent porosity of 53.13 ± 1.29% were successful fabricated. The dielectric constant and dielectric loss of Si₂N₂O sample (1650℃) are only 4.24 and 0.0049, respectively. This strategy provides a reference for in-situ synthesis of high-performance porous ceramic components based on the DIW.     

Wind field reconstruction for the dispersion modeling of accidental chemical spills on complex geometry

Chemical spills on complex geometry are difficult to model due to the uneven concentration distribution caused by air flow over ground obstacles. Computational fluid dynamics (CFD) is one of the powerful tools to estimate the building-resolving wind flow as well as pollutant dispersion. However, it takes too much time and requires enormous computational power in emergency situations. As a time demanding task, the estimation of the chemical spill consequence for emergency response requires abundant wind field information. In this paper, a comprehensive wind field reconstruction framework is proposed, providing the ability of parameter tuning for best reconstruction accuracy. The core of the framework is a data regression model built on principal component analysis (PCA) and extreme learning machine (ELM). To improve the accuracy, the wind field estimation from the regression model is further revised from local wind observations. The optimal placement of anemometers is provided based on the maximum projection on minimum eigenspace (MPME) algorithm. The fire dynamic simulator (FDS) generates high-resolution data of wind flow over complex geometries for the framework to be implemented. The reconstructed wind field is evaluated against simulation data and an overall reconstruction error of 9% is achieved. When used in real case, the error increases to around 12% since no convergence check is available. With parameter tuning abilities, the proposed framework provides an efficient way of reconstructing the wind flow in congested areas.     

Engineering an ultrathin amorphous TiO2 layer for boosting the weatherability of TiO2 pigment with high lightening power

TiO₂ pigments are typically coated with inert layers to suppress the photocatalytic activity and improve the weatherability. However, the traditional inert layers have a lower refractive index compared to TiO₂, and therefore reduce the lightening power of TiO₂. In the present work, a uniform, amorphous, 2.9-nm-thick TiO₂ protective layer was deposited onto the surface of anatase TiO₂ pigments according to pulsed chemical vapor deposition at room temperature, with TiCl₄ as titanium precursor. Amorphous TiO₂ coating layers exhibited poor photocatalytic activity, leading to a boosted weatherability. Similarly, this coating method is also effective for TiO₂ coating with amorphous SiO₂ and SnO₂ layers. However, the lightening power of amorphous TiO₂ layer is higher than those of amorphous SiO₂ and SnO₂ layers. According to the measurements of photoluminescence lifetime, surface photocurrent density, charge-transfer resistance, and electron spin resonance spectroscopy, it is revealed that the amorphous layer can prevent the migration of photogenerated electrons and holes onto the surface, decreasing the densities of surface electron and hole, and thereby suppress the photocatalytic activity.     

Synthesis of ZrCx with controlled carbon stoichiometry by low temperature solid state reaction

Zirconium carbide (ZrC_x) powders were synthesized at temperatures between 1300℃ and 2000℃ by solid state reaction of zirconium hydride (ZrH₂) and carbon black. Crystal structure, lattice parameters, and grain sizes of the as-synthesized ZrC_x powders were characterized for two different starting ZrH₂:C ratios of 1:0.60 and 1:0.98. Powders with stoichiometry approaching ZrC_0.98 were synthesized at temperatures as low as 1600℃ whereas ZrC_x powders synthesized at lower temperatures had lower carbon contents regardless of the starting ZrH₂:C ratio. Crystallite sizes as small as about 50 nm were obtained due to the low synthesis temperature. Oxygen dissolved into the ZrC_x lattice when carbon vacancies were present. Neutron diffraction analysis was used to determine that carbon stoichiometry increased and dissolved oxygen content decreased as synthesis temperature increased.     

Structural,infrared reflectivity spectra and microwave dielectric properties of the Li7Ti3O9F ceramic

A cubic rock salt structured ceramic, Li₇Ti₃O₉F, was fabricated via the conventional solid-state reaction route. The synthesis conditions, sintering characteristics, and microwave dielectric properties of Li₇Ti₃O₉F ceramics were investigated by X-ray diffraction (XRD), thermal dilatometer, Scanning Electron Microscopy (SEM) accompanied with EDS mapping, and microwave resonant measurements. Rietveld refinement, selected area electron diffraction (SAED) pattern and high-resolution transmission electron microscopy (HRTEM) confirmed that Li₇Ti₃O₉F adopts a cubic rock-salt structure. The ceramic sintered at 950?°C presented the optimal microwave properties of ε_r?=?22.5, Q×f?=?88,200?GHz, and τ_f?=??24.2?ppm/^oC. Moreover, good chemical compatibility with Ag was verified through cofiring at 950?°C for 2?h. These results confirm a large potential for Li₇Ti₃O₉F ceramic to be utilized as substrates in the low temperature cofired ceramic (LTCC) technology. This work provides the possibility to exploit low-temperature-firing ceramics through solid solution between oxides and fluorides.     

Excellent optical transparency of potassium-sodium niobate-based lead-free relaxor ceramics induced by fine grains

Here we report a lead-free multifunctional material (1-x)(K_0.5Na_0.5)NbO₃-xBa(Mg_1/3Nb_2/3)O₃ prepared by pressure-less sintering procedure. X-ray diffraction indicates a gradual crystal structure transformation with increasing x. Microstructural observation demonstrates that the addition of Ba(Mg_1/3Nb_2/3)O₃ additive reduces the size of grains with clear grain boundary, which is favorable for a high optical transmittance. The relaxor characteristics of the ceramics could lead to further enhancement of the transparency, owing to the low defects and weak light scattering. Notably, the ceramics with 0.04 ≤ x ≤ 0.06 all show good transparency over 70% in visible region and 80% in infrared region.