Patent ID: 7906012

Claim:
A method to extend run-length of a primary fractionator in an ethylene plant by reducing fouling and froth/foam formation and by reducing its column pressure drop, comprising the steps of: (a) feeding cracked gas to the primary fractionator, wherein: (i) the primary fractionator is experiencing severe fouling in a rectification section thereof; (ii) wherein severe fouling is a result of very rapid deposition of one or more fouling compounds selected from the group consisting of polymers of styrene, indene, di-vinylbenzene, alpha-methylstyrene, indenes, naphthalene, higher ring compounds and combinations thereof; (iii) wherein the severe fouling has been caused not only on upper tray surfaces, but also beneath tray surfaces resulting in increased column pressure drop along with its diminished operational efficiencies; and (iv) wherein the severe fouling due to very rapid deposition of fouling species also results in increased and excessive froth/foam formation, which in-turn results in further and very rapid increase in column pressure drop and thereby further reduced fractional efficiencies of the column as indicated by at least one of liquid-gas contact ratio, feed rate, reflux rate, product top temperature, gasoline end point or pressure differential; wherein, the process is characterized by: (b) essentially adding, continuously or periodically, an antifoulant-antifoaming agent to the primary fractionator reflux in an amount effective to reduce the deposits of fouling compounds and to reduce the froth/foam formation in the rectification section of the primary fractionators by injecting antifoulant-antifoaming agent along with reflux stream, wherein: (i) the antifoulant-antifoaming agent is polysiloxane; and (ii) the addition of antifoulant-antifoaming agent in above manner results in reduction of fouling by reducing deposits of fouling compounds and in reduction of froth/foam formation, and in reduction of column pressure drop as observed by change of colour of gasoline from brownish colour to its normal yellowish green colour and by improved operational efficiencies as indicated by at least one of liquid-gas contact ratio, feed rate, reflux rate, product top temperature, gasoline end point or pressure differential; and thereby (iii) results in extension of the run-length of the primary fractionator.