Improved Ethylene Cracking Furnace Control with Modern Process Mass Spectrometers

Whereas process mass spectrometers have been used as an alternative (lower cost) solution to multiple process gas chromatograph installations for many years, their use has been somewhat limited by their complexity - both real and perceived. The latest generation of process mass spectrometers has been designed to dramatically reduce the complexity by means of fault-tolerant design and automated setup but questions remain as to the value provided by the faster and more complete analysis that they provide.

This paper discusses the use of a magnetic sector mass spectrometer for the purpose of improving the operation of the ethylene naphtha cracking furnaces at the Braskem olefins unit located in Camaçari, Bahia, Brazil. Gas composition data was collected with two-minute resolution from the effluent of four furnaces each monitored over a complete de-coke to de-coke campaign. The effects of coke buildup and feedstock variation on the kinetic cracking severity of the furnaces are assessed and the implications for improved furnace control are discussed.