Chen Yuanyuan, Shen Shaobo, Gu Jinlang, Zhang Zhen, Li Na
School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, China.
ACS Omega. 2020 Oct 13;5(42):27278-27286. doi: 10.1021/acsomega.0c03486. eCollection 2020 Oct 27.
Reducing chlorine corrosion to metals at high temperatures is a big problem for many industrial processes. Some high Ni alloys such as Hastelloy C-276 (Ni > 50 wt %) have been widely used for this purpose. Chlorine and chlorides often coexisted in many industrial processes at high temperatures, such as some industrial incinerators and metallurgical furnaces. Thus, a comprehensive experimental investigation regarding the effect of NaCl on the chlorination corrosion of metallic nickel powder by chlorine at a high temperature was performed. It was more convenient to investigate the intrinsic chlorination mechanisms and kinetics of metallic Ni if Ni powder was used instead of a Ni plate. It was found that there existed a critical chlorination temperature of 450 °C for relative safe use of Ni-based alloy in the presence NaCl. The Ni chlorination in the presence of NaCl was increased with increasing temperature and reached a maximum of 97% at 700 °C, which was about 21% higher than that in the absence of NaCl. An anhydrous NiCl was initially formed at about 700 °C during the chlorination process and then immediately reacted with NaCl to form a novel eutectic complex with a flaky shape, a melting point of 585 °C, and a simplified molecular formula of NiNaCl based on X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electronic microscopy (SEM), and chemical analysis with inductively coupled plasma atomic emission spectroscopy (ICP-AES). As a result, only the complex of NiNaCl and NaCl was left in the chlorinated product. At 700 °C, the chlorinated product evaporated only in the form of complex NiNaCl instead of individual NiCl or NaCl. The chlorination mechanisms of metallic Ni at a high temperature, for example, 700 °C, in the presence of NaCl were as follows. Step 1: Formation of initial chlorinated solid product NiCl (mp 1001 °C) at a high temperature; step 2: The NiCl reacted with solid additive NaCl (mp 801 °C) to form a final liquid product NiNaCl (mp 585 °C); step 3: External Cl(g) was dissolved in the liquid product layer; step 4: The chlorine dissolved in the liquid product of NiNaCl reacted with the unreacted Ni core. The external Cl(g) passed through the liquid product NiNaCl layer faster than the solid product NiCl layer formed in the absence of NaCl. This resulted in 21% more chlorination corrosion of metallic Ni powder with NaCl addition than that without NaCl addition.
在许多工业过程中，降低高温下氯气对金属的腐蚀是一个大问题。一些高镍合金，如哈氏合金C - 276（镍含量> 50 wt%）已被广泛用于此目的。在许多高温工业过程中，如一些工业焚烧炉和冶金炉中，氯和氯化物常常共存。因此，针对氯化钠对金属镍粉在高温下被氯气氯化腐蚀的影响进行了全面的实验研究。如果使用镍粉而非镍板来研究金属镍的内在氯化机理和动力学，会更加方便。研究发现，在存在氯化钠的情况下，镍基合金相对安全使用存在一个450℃的临界氯化温度。在有氯化钠存在时，镍的氯化程度随温度升高而增加，在700℃时达到最大值97%，比无氯化钠时高出约21%。在氯化过程中，约700℃时最初形成无水氯化镍，然后立即与氯化钠反应形成一种新型片状共晶复合物，其熔点为585℃，基于X射线衍射（XRD）、差示热分析（DTA）、扫描电子显微镜（SEM）以及电感耦合等离子体原子发射光谱（ICP - AES）化学分析，其简化分子式为NiNaCl。结果，氯化产物中仅留下NiNaCl和NaCl的复合物。在700℃时，氯化产物仅以复合NiNaCl的形式蒸发，而非单个的NiCl或NaCl。金属镍在高温（例如700℃）下在有氯化钠存在时的氯化机理如下。步骤1：在高温下形成初始氯化固体产物NiCl（熔点1001℃）；步骤2：NiCl与固体添加剂NaCl（熔点801℃）反应形成最终液体产物NiNaCl（熔点585℃）；步骤3：外部Cl(g)溶解在液体产物层中；步骤4：溶解在NiNaCl液体产物中的氯与未反应的镍核反应。外部Cl(g)穿过液体产物NiNaCl层的速度比在无氯化钠时形成的固体产物NiCl层快。这导致添加氯化钠时金属镍粉的氯化腐蚀比不添加氯化钠时多21%。
