Ethylene furnace radiant coil decoking method
AssigneeLummus Technology Inc.
InventorsStephen De Haan, Barbara Stancato, Brian K. Sullivan, Charles E. Nagy, Frank McCarthy
Life of this patent
Estimating the term…
Abstract
Methods are provided for decoking the radiant coils in an ethylene cracking plant. The decoking process is controlled by monitoring the coil outlet temperature to control the rate of burning of coke in the radiant coils. Air flow rates, steam flow rates and coil outlet temperatures are controlled during the decoking process to prevent tube damage, minimize decoking time and maximize coke removal.
Claims14
A method for decoking the radiant coils in an ethylene furnace comprising the steps of:
- (a) providing a flow of steam and firing burners in the furnace to heat the radiant coils to achieve a predetermined average coil outlet temperature;
- (b) while maintaining the steam flow rate and furnace burner firing rate constant, providing air flow to the radiant coils and adjusting the flow rate of the air to achieve a first predetermined change in the coil outlet temperature in the radiant coils;
- and
- (c) while maintaining the steam flow rate and furnace burner firing rate constant, providing air flow to the radiant coils and adjusting the flow rate of the air to achieve a second predetermined change in the coil outlet temperature in the radiant coils to a decoking temperature.
A method for decoking the radiant coils in an ethylene furnace comprising the steps of:
- (a) providing a flow of steam and firing burners in the furnace to heat the radiant coils to achieve a predetermined average coil outlet temperature and maintaining the radiant coils at the predetermined average coil outlet temperature for a predetermined period of time;
- (b) while maintaining the steam flow rate and furnace burner firing rate constant, providing air flow to the radiant coils and adjusting the flow rate of the air to achieve a first predetermined change in the coil outlet temperature in the radiant coils;
- (c) maintaining the radiant coils at the coil outlet temperature achieved in step (b) for a predetermined period of time;
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- (d) while maintaining the steam flow rate and furnace burner firing rate constant, adjusting the air flow rate until the coil outlet temperature in the radiant coils to achieve a second predetermined change in the coil outlet temperature in the radiant coils to a decoking temperature, such that the decoking temperature is about 20° C. to 80° C. above the average coil outlet temperature in the radiant coils achieved in step (a).
A method for decoking the radiant coils in an ethylene furnace comprising the steps of:
- (a) providing a flow of steam and firing burners in the furnace to heat the radiant coils to achieve an average coil outlet temperature of about 830° C. and maintaining the radiant coils at the average coil temperature of about 830° C. for about one hour;
- (b) while maintaining the steam flow rate and furnace burner firing rate constant, providing air flow to the radiant coils and adjusting the flow rate of the air to achieve a coil outlet temperature in the radiant coil of about 850° C.;
- (c) maintaining the coil outlet temperature in the radiant coil at about 850° C. for a period of about one hour;
- (d) while maintaining the steam flow rate and furnace burner firing rate constant, adjusting the air flow rate until the coil outlet temperature in the radiant coil increases to about 870° C.;
- (e) determining the stoichiometric minimum quantity of air required to raise the coil outlet temperature to 870° C. and comparing this rate to the actual air flow rate to determine if spalled coke is present;
- and,
- (f) using this comparison to further adjust the air rate and burner firing rate.
Dependencies are inferred from the claim text.