Explosion Hazards in Ethylene Producing and Processing Plants
Because of its reactivity, symmetry and simple structure, ethylene, also known as ethene, is the most fundamental and most used building block in the chemical industry. Most of the ethylene in the world is made by cracking natural gas liquids or oil cuts. Steam crackers consist of many different unit operations that comprise several technologies, including: fired heaters, cold boxes, reactors, very large and high kinetic mechanical equipment and distillation units. Since so many different unit operations are combined in a single facility, it represents a major investment to its owners. Failure modes of steam crackers include tube failure, reactor runaways, heater explosions, low temperature brittle breakage, high temperature failures, mechanical impacts and failures caused by vibration. These constitute a significant safety risk to the people working in them. History has shown that vapour cloud explosions (VCEs) constitute a major risk to ethylene plants. Worldwide, on average two major ethylene incidents haen each year in ethylene handling facilities; most of these involve vapour releases, fires and/or explosions. The extent of the damage, which would occur if a vapour cloud were ignited, is a key consideration in the design of ethylene processing facilities, in the routing of pipelines, and in the development of emergency response procedures. Explosion hazards need to be considered for the layout of the plants, the design of control buildings, the determination of separation distances (e.g., from cooling towers) and the location of temporary facilities such as trailers. The question of where to locate trailers on a ethylene processing site has become a major issue of contention (in North America) since the refinery explosion at Texas City in 2005. A consensus is building that industry practices based on a minimum performance are no longer acceptable. For example, the first American Petroleum Institute (API) draft of Management of Hazards Associated with Location of Process Plant Portable Buildings API RP 753 (2006) was considered woefully inadequate (by some newspapers). This issue is very important to ethylene producers (and users) because the VCE hazards need to be managed differently while at the same time the treatment of ethylene, as the cause of a VCE, is changing. For many years it has been assumed that explosion modeling of vapour clouds, including ethylene clouds, on the basis of deflagrative combustion was a sufficiently safe and conservative approach. However, over the last couple of years it has become evident that ethylene is more insidious than previously thought In 2003 Baker et al. published a paper about a set of large-scale unconfined vapor cloud explosion tests involving ethylene-air mixtures in a congested environment where presumably a deflagration to detonation transition (DDT) occurred. At about the same time TNO (2005) observed unexpectedly high overpressures effects while studying the interaction effects of two adjacent confined areas on a burning ethylene-air cloud. TNO interpreted these donor-acceptor results as a strong indication that ethylene-air mixture detonated locally. In order to manage new requirements and demands, pro-active ethylene producers have to adopt design processes based on more realistic event modeling and building protection.
ethylene ethene flame propagation explosion deflagration trailers dispersion PES
Jan C. A. WINDHORST
NOVA Chemicals, P.O. Box 5006, Red Deer, Alberta T4N 6A1, CanadaWEC, 83 Dobler Ave., Red Deer, Alberta T4R 1X3, Canada
国际会议
西安
英文
831-835
2007-10-23（万方平台首次上网日期，不代表论文的发表时间）