锅炉飞灰含碳量高的原因分析及降低措施

锅炉飞灰含碳量是影响锅炉运行效率的重要因素,对机组总体性能也有着很大的影响.对锅炉飞灰含碳量的成因进行分析,并提出改善措施,有利于指导运行人员及时进行锅炉燃烧和制粉系统的调整,提高锅炉燃烧效率及控制水平,降低发电煤耗,提高竞价上网能力.     

大型复杂结构件抛丸改进方案

为解决某大型焊接结构件抛丸时工件上面大量堆积钢丸并可能导致安全事故的问题,从改变工件吊挂状态和在工件上增加漏丸工艺孔两方面入手,令工件可安全地在已有抛丸线上进行自动除锈.     

特殊工业粉尘地区复合绝缘子腐蚀失效过程研究

硅橡胶复合绝缘子因其优异的憎水性及憎水迁移性而具备较好的防污闪能力,往往作为应对污闪事故的首选方案。但在部分特殊工业粉尘地区,复合绝缘子在短时间运行后会出现爬电及蚀损现象,并发展为绝缘失效。为研究特殊工业粉尘地区复合绝缘子的腐蚀失效过程,测试了某特殊工业园区内运行的复合绝缘子的表面污秽度及污秽成分、污闪电压梯度、憎水性能及微观性能,并分析了其腐蚀失效过程。主要结论如下:绝缘子表面等值盐密为0.1~0.2 mg/cm²,其污秽成分与化工污源类似;存在自然污秽时绝缘子表面憎水性良好,但其憎水性的减弱、恢复及迁移特性均不能满足运行要求;绝缘失效的起因是电晕放电导致憎水性降低,进而导致伞裙电蚀损,最后发展为绝缘失效。     

Importance of Low-Temperature Melt-Mixing on the Construction of Stereocomplex Crystallites with Superior Nucleation Efficiency in Asymmetric Poly(l-lactide)/Poly(d-lactide) Blends

The nucleation efficiency (NE) of stereocomplex crystallites (SCs) formed in asymmetric poly(L-lactide)/poly(D-lactide) (PLLA/PDLA) blends is generally unsatisfactory because the competition between stereocomplexation and chain mixing involved in the melt-mixing process can cause low formation efficiency and even severe aggregation of SCs. Herein, it is attempted to achieve high-efficient formation of finely dispersed SCs particles by designing a unique melt-mixing procedure, where the mixing of PLLA with 0.75 wt% PDLA is first performed at elevated temperatures (far above the melting temperature of SCs) to allow the homogeneous mixing of PLLA/PDLA chains and then at a low temperature (slightly above that of homocrystallites) to permit the full stereocomplexation of the premixed chains. It is found that the SCs formed in the blends exhibit unexpectedly low NEs (e.g., 54.5%), much inferior to that (73.6%) in the counterpart without undergoing premixing. This is because the introduction of premixing leads to a remarkable deterioration in the amount of SCs particles formed, despite decreased particle size, highlighting that the direct mixing at low temperatures of 170–180 °C (about 20–30 °C lower than that used in common melt-processing of PLA) is more effective for the construction of SCs with superior NE. The mechanisms for these striking findings are discussed.     

Stereocomplex Crystallization Induced Significant Improvement in Transparency and Stiffness–Toughness Performance of Core-Shell Rubber Nanoparticles Toughened Poly(l-lactide) Blends

Toughening modification of poly(l -lactide) (PLLA) with rubber particles is often realized at the cost of transparency, mechanical strength, and modulus because high rubber loadings are generally required for toughening. In this work, a promising strategy to simultaneously improve the transparency and stiffness–toughness performance of poly(butyl acrylate)-poly(methyl methacrylate) (BAMMA) core-shell rubber nanoparticles toughened PLLA blends by utilizing the stereocomplex (SC) crystallization between PLLA and poly(d -lactide) (PDLA) is devised. The results reveal that the construction of SC crystallites in PLLA matrix via melt-mixing PLLA/BAMMA blends with PDLA can prevent BAMMA nanoparticles from aggregation and promote them to form network-like structure at lower contents. As a result, not only higher toughening efficiency with less rubber contents but also superior transparency is achieved in the PLLA/PDLA/BAMMA blends as compared with the PLLA/BAMMA ones where large aggregated BAMMA clusters are formed. Moreover, the outstanding reinforcement of SC crystallites network for PLLA can impart an enhanced tensile strength and modulus to PLLA/PDLA/BAMMA blends, thus improving the stiffness–toughness performance of PLLA/PDLA/BAMMA blends to a higher degree. This work demonstrates that SC crystallization is a promising solution to solve the contradiction between transparency and mechanical properties and then obtain superior comprehensive performances in rubber toughened PLLA blends.     

Boron Nitride Nanosheets Strengthened PVA/Borax Hydrogels with Highly Efficient Self-Healing and Rapid pH-Driven Shape Memory Effect

Self-healing hydrogels often possess poor mechanical properties which largely limits their applications in many fields. In this work, boron nitride nanosheets are introduced into a network of the poly(vinyl alcohol)/borax (PVA/borax) hydrogels to enhance the mechanical properties of the hydrogel without compromising the self-healing abilities. The obtained hydrogels exhibit excellent mechanical properties with a tensile strength of 0.410 ± 0.007 MPa, an elongation at break of 1712%, a Young's Modulus of 0.860 ± 0.023 MPa, and a toughness of 3.860 ± 0.075 MJ m⁻³. In addition, the self-healing efficiency of the hydrogels is higher than 90% within 10 min at room temperature. Benefiting from the excellent self-healing properties, the shapeability of the hydrogel fragments is observed using different molds. In addition, the hydrogels display rapid pH-driven shape memory effects and can recover to their original shape within 260 s. Overall, this work provides a new approach to hydrogels with integrated excellent mechanical properties, self-healing abilities, and rapid pH-driven shape memory effects.     

GCr15SiMn轴承钢中大尺寸TiN生成与控制

 以西宁特钢EAF→LF→VD→IC工艺路线生产GCr15SiMn轴承钢为研究背景,采用矿物解离分析仪、夹杂物自动分析系统、化学分析及X射线荧光光谱仪等检测手段与热力学计算相结合的方法,研究了铸锭中大尺寸TiN夹杂物的析出机理,分析了冶炼阶段钢液中钛含量增加的原因,并提出了相应的改进工艺。通过对轴承钢中残余钛、氮含量的热力学计算,发现大尺寸TiN主要是在凝固过程中析出和长大,降低冶炼过程中钛含量是控制TiN生成的主要途径。对原工艺冶炼过程钛含量变化进行分析,钢液中钛增量主要发生在EAF出钢→LF结束阶段,其中52%钛增量来自于炉渣。为了避免炉渣中钛进入钢液,借助于七元炉渣CaO-SiO₂-MgO-FeO-Al₂O₃-MnO-TiO₂与钢液之间平衡的钛分配比(LTi)模型,计算了铝含量和炉渣中CaO含量对LTi 的影响,预测了最佳的平衡炉渣成分。结果表明,适当降低铝含量和炉渣中CaO含量可以提高渣-钢之间的钛分配比,降低钢液的钛含量;当铝质量分数为0.015%～0.025%、CaO质量分数为50%～55%时,其他炉渣组元的最佳成分(质量分数)为18%～24% Al₂O₃和12%～17% SiO₂。此外,定量描述了不同LTi条件下EAF下渣量与LF终点钛含量的关系。最后,采用“低炉渣碱度、低铝含量以及严格控制电炉下渣量”的改进措施进行了优化试验,优化后冶炼终点钛质量分数可控制在小于0.002 0%,铸锭TiN平均数密度可由原工艺的2.09个/mm2降低至0.73个/mm2,且TiN尺寸几乎都小于10 μm。     

核级FeCrAl包壳材料研究进展

摘要：日本福岛核电站泄漏事故暴露了锆合金易与水蒸气反应造成爆炸的缺陷,又将人们的视线拉回了各项性能较为均衡的FeCrAl合金。FeCrAl合金较锆合金具有更好的耐腐蚀性能,更能满足核反应堆高温水蒸气环境下的工作条件。为进一步保障核反应堆安全性,各国学者对FeCrAl合金的性能进行了大量研究。基于此,综述了FeCrAl合金腐蚀机制及其在高温蒸汽和高温水环境中的腐蚀行为;探讨了合金元素（稀土、Ti、Zr、Nb和Mo）、变形和热处理对合金力学性能的影响;总结了FeCrAl合金辐照性能和焊接性能的研究进展。最后指出了核级FeCrAl合金在研究中存在的不足及未来重点发展方向,为今后其他学者在该领域的研究提供参考。     

节能降碳的蓄热式加热炉烟气反吹关键技术

摘要：蓄热式加热工艺是大型钢铁企业轧钢工序普遍采用的加热技术,但该工艺高频率换向蓄热燃烧导致公共管道内的燃气交替排入大气造成环境污染和能源浪费,使其成为钢铁生产流程中少有未进行污染物治理的生产工序。基于消除蓄热式加热炉热工制度缺陷,系统介绍了蓄热式加热炉烟气反吹扫技术及与之匹配的加热炉烟气反吹安全联锁与防爆技术、烟气反吹工艺设计与时序调控技术。该成果应用于某钢铁企业蓄热式加热炉（160t/h）建设国内首套换向残留燃气反吹技术示范线,该加热炉燃气放散体积分数由9.0%降低至0.208%,CO放散减排率达92%以上,轧钢燃气耗量节约4.38%。其后承建多家钢铁企业19条蓄热式轧钢加热炉烟气反吹改造工程,均取得较好效果,节能、环保及社会效益显著,同时减少碳氧化物的排放量,助力国家实现双碳目标。     

Cu基形状记忆合金干滑动磨损研究

对Cu基形状记忆合金CuZnAl进行了干滑动磨损,采用扫描电镜观察磨损表面及磨屑.结果表明,CuZnAl合金的磨损过程受塑性变形控制,粘着与转移磨损和剥离磨损是材料失重的两种主要机制.电镜薄膜拉伸时显微裂纹尖端发生了应力诱发马氏体相变.用显微裂纹钝化作用的马氏体择优取向机制和应力诱发马氏体相变机制阐述了这种软基体高变形能力材料的耐磨本质。