Flowmeters eliminate cleaning
Shell Chemicals, at Moerdijk, the Netherlands, operates one of Europe's largest ethylene plants, where Emerson's Vortex 8800CD dual-vortex flowmeters improved plant steam-measurement reliability. The meters provided two flow measurements on the main steam lines: one for plant process control and a separate measurement for the plant safety instrumented system.
Shell found that vortex metering delivered more reliable steam-flow measurement, increasing plant uptime. Furthermore, plant operators have a better, more accurate steam-flow measurement, allowing production optimization.
Shell's naphtha-cracker process mixes accurate proportions of light distillate feed-stock (LDF)—such as naphtha or ethane—and steam, heating them to a high temperature in a furnace, cracking the LDF into basic feedstocks like ethylene, and also creating some carbon and coke deposits, that recirculate with process water.
To remove these deposits and assure measurement reliability, a monthly cleaning schedule had been established for each flowmeter.
Engineers conducted a three-month trial with a Rosemount 8800CD on one furnace line. Thereafter all 20 furnaces were scheduled to be equipped with the dual-vortex measurement systems. The first eight furnaces have now operated for over two years, without flowmeter removal for cleaning.
For more information, visit www.GoToEmerson.com .
—Richard Phelps, senior editor, Control Engineering,