Effect of waste serpentine on the properties of basic insulating refractories

Basic insulating refractories were fabricated by the pressing route using dead-burned magnesia, pure calcined alumina, expanded perlite, and calcined waste serpentine as starting raw materials in four compositions from F1 to F4. Periclase and forsterite were major phases in F1 and F2 compositions, while spinel was also detected in the XRD patterns of F3 and F4 samples. Quantitative phase analysis showed that F4 sample sintered at 1450?°C has the highest forsterite content among all other samples. On the other hand, it has lower thermal conductivity compared to F1 to F3, and even lower than aluminosilicate IFBs with the same bulk density. It is concluded that forsterite is a highly insulating material, compared to periclase, corundum, periclase-spinel, aluminosilicates, such as mullite, etc.     

一种航空液冷机箱集成制造工艺技术

文中以一种兼有“蛇形水道”和“深孔水道”的航空液冷机箱作为实例,进行集成制造工艺研究.从工艺方法选择、材料选择及工艺流程三个方面进行论述,确定水道和机箱成形工艺方案.对总体工艺方案、水道成形工艺方案、机箱成形工艺方案等方面中的关键工艺技术进行了详细分析,针对研制过程中出现的问题,提出了具体有效的解决方案.通过对研制结果的分析,验证了上述工艺方案的可行性.     

Enhancement of pentlandite surface magnetism and implications for its separation from serpentine via magnetic separation

The magnetism of pentlandite surface was enhanced through the selective precipitation of micro-fine magnetite fractions on pentlandite surfaces. This was achieved through adjustment of slurry pH and addition of surfactants. The results showed that at pH 8.8 with the addition of 100 g/t sodium hexametaphosphate, 4.5 L/t oleic acid, and 4.5 L/t kerosene, significant amount of fine magnetite particles adhered to the pentlandite surface, while trace amount of coating was found on serpentine surfaces. Thus, the magnetism of pentlandite was enhanced and pentlandite was well separated from serpentine by magnetic separation under the magnetic field intensity of 200 kA/m. Scanning electron microscopy (SEM) and zeta potential measurement were performed to characterize changes of mineral surface properties. Calculations of the extended Derjaguin–Landau–Verwey–Ocerbeek (EDLVO) theory indicated that, in the presence of surfactants the total interaction energy between magnetite and pentlandite became stronger than that between magnetite and serpentine. This enabled the selective adhesion of magnetite particles to pentlandite surfaces, thereby enhancing its magnetism.     

白云石和蛇纹石对烧结矿质量及显微结构的影响

白云石和蛇纹石对烧结矿质量及显微结构影响的研究结果表明:配加白云石提高烧结矿的MgO含量,烧结矿转鼓强度降低,而配加蛇纹石提高烧结矿的MgO含量时,转鼓强度提高.配加白云石后,烧结矿矿物组成主要为铁酸钙与骸晶状赤铁矿,骸晶状赤铁矿周围有大量以玻璃质物相存在的硅酸盐矿物,且有大量微细裂纹;烧结矿孔隙率大,气孔为大孔薄壁结构,所以烧结矿强度低.配加蛇纹石后,烧结矿矿物组成主要为磁铁矿和铁酸钙,钙铁橄榄石矿物增多变大,气孔为中孔厚壁结构,所以烧结矿的质量得以改善.     

塔式炉蛇形管受热面工艺研究

本文通过对几种结构形式的蛇形管受热面进行工艺研究,阐述了670MW超临界机组用塔式锅炉蛇形管受热面的关键制造工艺。     

生物质热风炉换热器传热性能数值分析及实验研究

以生物质热风炉为研究对象,搭建生物质热风炉实验台,控制空气入口速度为12～20 m/s,开展相关测试实验。采用Realizable k-ε湍流模型,速度和压力的耦合采用SIMPLEC算法,利用FLUENT软件计算得到换热器温度、速度、压力分布,将模拟结果与实验测试结果进行比较,误差在2%以内。结果表明：随着壳程空气流速的逐渐增大,换热器的壳程温差ΔT、压降Δp逐渐升高;对流传热系数、总传热系数、传热量和换热器评价指标η也逐渐增大。随着雷诺数增大,努塞尔数和传热因子逐渐增大。     

小曲率蛇形微通道弯头处弹状流流动及传质特性的数值研究

采用CLSVOF（coupled level set and volume of fluid）方法,以空气和水为工作流体对小曲率矩形截面蛇形微通道内气液两相流动进行模拟研究。验证模型的合理性后,研究了曲率对弯通道内压降的影响,曲率及气相速度对弹状流气泡及液塞长度的综合影响;同时深入分析了弯管内气液两相流动的传质特性,包括不同曲率下气泡长度的变化,弯管内液侧体积传质系数与液膜体积传质系数的比较,曲率及气相速度对液相体积传质系数的影响。同时,对比了回转弯道与直微通道传质系数的差异,发现弯微通道可以强化传质。     

Evaporation heat transfer and pressure drop characteristics of R-290 (propane), R-600 (butane), and a mixture of R-290/R-600 in the three-lines serpentine small-tube bank

This paper reports an experimental investigation of heat-transfer and pressure-drop behavior of R-290, R-600, and R-290/R-600 in the three-lines serpentine small-diameter (2.46 mm) tube bank. Heat transfer coefficients and pressure drop characteristics are measured for a range of heat flux (5–21 kW/m²), mass flux (250–500 kg/m² s), equilibrium mass quality (0–0.86), and the fixed mixture composition ((R-290/R-600 (55 wt.%/45 wt.%)). The results show that the flow boiling heat transfer coefficients for R-290, R-600, and R-290/R-600 are 1.66–1.96-fold, 1.28–1.38-fold and 1.57–1.88-fold greater as compared with those for R-134a under equal heat and mass fluxes. Also, the two-phase flow frictional pressure drop for R-600, R-290/R-600 and R-290 are 1.41–1.60-fold, 1.32–1.50-fold and 1.22–1.40-fold smaller as compared with that for R-134a. A new heat transfer correlation was presented by using a superposition model to predict the experimental data for both pure refrigerants and refrigerant mixtures. Experimental results were compared with several correlations which predict the evaporative heat transfer, which are in good agreement with experimental data.     

蛇纹石/La复合粉体的制备及其摩擦性能

分别采用水溶液沉淀法和乙醇溶液沉淀法制备了蛇纹石/La复合粉体,并分别在120℃（脱除吸附水）和700℃（蛇纹石脱除羟基）对复合粉体进行了干燥和煅烧热处理。利用X射线衍射法、扫描电子显微镜、能谱分析表征了复合粉体的物相组成、微观形貌。利用MM-10W型多功能摩擦磨损试验机对复合粉体的摩擦性能进行了评价。结果表明：蛇纹石/La复合粉体中,La化合物呈纳米颗粒,并包覆在蛇纹石表面;700℃煅烧将导致蛇纹石/La复合粉体物相变化和摩擦性能变差;120℃干燥处理的蛇纹石/La复合粉体具有良好的减摩-抗磨性能,摩擦因数较未添加者降低22.48%以上。     

活化酸浸蛇纹石提取镁的实验研究

采用球磨和煅烧工艺对蛇纹石进行预处理, 破坏其晶体结构, 改善其物理化学特性, 并用不同无机酸进行浸取。通过实验确定最佳条件是: 在球磨机中球磨1 h后的矿粉, 700 ℃条件下恒温煅烧1 h, 然后用3 mol/L H₂SO₄在常温下搅拌1 h, 固液比为1∶15, MgO的浸出率可达到93%。