Protecting stainless steel surfaces using ppm levels of sulfur compounds during ethylene production

世界上每年生产的乙烯超过1亿吨，是石化工业生产的最大化学原料之一。在北美，由乙烯获得的主要产品是广泛使用的聚乙烯，NOVA化学公司在加拿大的阿尔伯塔经营着世界上最大的乙烯和聚乙烯联合体。 乙烯是通过各种烃的高温蒸汽裂化生产的，优选乙烷。不幸的是，焦炭（碳的固体形式）作为副产品生产，这降低了生产效率，通过更高的能量使用增加了生产成本，并且不可避免地导致工厂停工以去除焦炭并更换高温腐蚀损坏的金属基础设施。特别是，不锈钢管的金属粉尘可导致高压气体管线的灾难性故障。在工业中已知的是，烃进料中低水平的各种硫物质可以降低焦炭积聚和金属粉化随时间的严重性，但是保护水平高度依赖于硫物质的量和类型，以及烃进料的组成和其在炉的热区中保持的时间长度。在与NOVA的合作中，我们将通过进行一系列新的研究来更好地了解这些因素之间的关系，这些研究近似于钢在500- 1000 oC的不同停留时间下暴露于乙烷，蒸汽和硫物种的热区。在加拿大合格人才稀缺的领域培训学生的过程中，这些信息将用于通过精确选择正确的硫种类和最佳浓度/条件来生成解决方案，从而最大限度地减少焦化和钢铁腐蚀。这项研究将在依赖于暴露于高温碳氢化合物反应的金属（如钢）的各种加拿大工业中产生重大影响，无论是在制定预防措施方面，还是在各种领域的技术培训方面，包括气态碳氢化合物动力学，表面反应，金属腐蚀以及表面和材料表征。

With well over 100 million tonnes produced annually in the world, ethylene is one of the largest chemical feedstocks produced by the petrochemical industry. In North America, a primary product obtained from ethylene is the widely used polyethylene, and NOVA Chemicals Corporation operates the largest ethylene and polyethylene complexes in the world in Alberta, Canada. Ethylene is produced by high temperature steam cracking of a variety of hydrocarbons, with ethane being preferred. Unfortunately, coke (solid forms of carbon) is produced as a bi-product, which decreases production efficiency, increases production costs through higher energy use, and inevitably leads to plant down-time to remove coke and replace high temperature corrosion damaged metal infrastructure. In particular, metal dusting of stainless steel tubing can lead to catastrophic failure of high pressure gas lines. It is known in the industry that low levels of a variety of sulfur species in the hydrocarbon feed can reduce the severity of coke build-up and metal dusting over time, but the level of protection is highly dependent on the amount and type of sulfur species, as well as the composition of the hydrocarbon feed and the length of time it remains in the hot zone of the furnace. In collaboration with NOVA, we will develop a significantly better understanding of the relationship between these factors by performing a series of novel studies that approximates the hot zone exposure of the steel to ethane, steam, and sulfur species with varied residence times at 500-1000oC. In the course of training students in a field where qualified people in Canada are scarce, this information will be used to generate solutions through precise selection of the right sulfur species and optimum concentration/conditions such that coking and steel corrosion is minimized. This research will have significant ramifications in a wide variety of Canadian industries that rely on metals such as steel that are exposed to high temperature hydrocarbon reactions, both in terms of developing preventative measures, as well as technical training in a variety of areas including gaseous hydrocarbon kinetics, surface reactions, metal corrosion and surface and material characterization.