Contribution of Filtration and Coalescence to Steam Cracking Furnace Productivity and Emissions Control

Sylvie Balouet, T. H. Wines, and Thierry Darde, EEPC HSE Conference, Vienna, October 14-15, 2004

Hydrocarbon streams feeding ethylene steam cracking furnaces often contain significant levels of corrosion products, water, and salts. This is especially true when naphtha is supplied by marine vessels. In these cases, high efficiency liquid–liquid coalescers and filters are recommended to condition the inlet feed stream. Contaminants in the inlet hydrocarbons can adversely affect ethylene production in a number of ways. Sodium and iron oxides are known to be coke promoters and their presence can reduce the run time of the ethylene furnaces before de-coking is required, and in some instances reduce the life of the furnace tubes by as much as one third. Unscheduled or frequent de-coking cycles lead to a loss in ethylene production, shortened furnace tube life, and create higher maintenance costs. Frequent de-coking will also result in particulate release to the atmosphere and can create environmental concerns over excessive emissions. Fouling of flow meters and control valves can lead to difficulty in maintaining the optimum furnace temperature and steam/hydrocarbon feed ratio. This can lead to poor yield of ethylene by the cracker and undesirable by-products. Installation experience on crackers using high efficiency liquid–liquid coalescers and/or filters is presented at four ethylene plants located in Benelux, Germany, China and Australia. These case histories encompass ethylene plants that have naphtha feed supplied by marine transport, plants that use naphtha from refineries, and an ethylene plant that operates an ethane gas cracker. High efficiency liquid–liquid coalescers and filters were found to optimize ethylene plants for upgrades and expansions of existing crackers. They can provide a solution for increasing the refinery/cracker synergy allowing the use of more contaminated feeds including Light Cat-cracked Naphtha (LCN / FCC gasoline) as well as the use of marine transported naphtha.
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