Claims
- 1. An improved purging process for controlling back-flow migration of air into a flare system through which a flare gas is caused to be destroyed, the process comprising:
- flowing purge gas through the flare system in a sufficient amount to substantially prevent air migration into the exit port through which the purge gas is exhausted to the atmosphere;
- sensing the flow rate of the flare gas being passed through the flare system;
- reducing the flow of purge gas to permit substantial air migration to occur, said reduction of purge gas being for a selected interval of time and the amount of reduction being a predetermined amount in response to the sensed flare gas flow rate; and
- re-establishing the full flow of purge gas at the end of the interval such that only a predetermined amount of migration air has occurred to prevent harmful conditions from occurring as a result of the air migration.
- 2. The process of claim 1 wherein the step of reducing the flow of purge gas comprises ceasing the purge gas flow when the sensed flare gas flow rate is greater than a first predetermined flare gas flow rate.
- 3. The process of claim 2 wherein the step of reducing the flow of purge gas comprises decreasing the purge gas flow when the sensed flare gas flow is less than the first predetermined flow rate and greater than a second predetermined flow rate, the rate of purge gas flow being determined by said decreasing of same such that the flow rate of flare gas and purge gas is at least equal to the first predetermined flow rate.
- 4. The process of claim 3 wherein the step of reducing the flow of purge gas comprises complete cessation of purge gas flow when the sensed purge gas flow rate is equal to or less than the second predetermined flare gas flow rate.
- 5. The process of claim 4 wherein the control of the purge gas is effected by a timing device which reduces the flow of purge gas at the predetermined intervals.
- 6. The process of claim 5 wherein the control of purge gas is effected by an oxygen analyzer means for measuring the oxygen content in the flare system and for re-establishing the flow of purge gas when the oxygen content in the flare system exceeds predetermined values of oxygen content of the gas mixture in the flare system.
- 7. The process of claim 6 wherein the control of purge gas is effected by a timing device which reduces the flow of purge gas at predetermined intervals.
- 8. The process of claim 7 wherein the control of purge gas is effected by a sensor device which senses a predetermined condition in the flare stack and which re-establishes full flow of purge gas when the predetermined condition is sensed.
- 9. The process of claim 8 wherein the sensor device is a temperature sensor and the predetermined condition is a predetermined temperature.
- 10. The process of claim 8 wherein the sensor device is a vacuum sensor and the predetermined condition is a predetermined pressure.
- 11. An improved purging process for controlling the rate of back flow migration of air into a flare system through which a flare gas is caused to flow, the process comprising:
- flowing purge gas through the flare system in a sufficient amount to substantially prevent air migration into the exit port through which the purge gas is exhausted to the atmosphere;
- ceasing the flow of purge gas to permit substantial air migration to occur, said ceasing of purge gas being for a selected cessation interval of time;
- sensing the flow rate of the flare gas during the cessation interval of time during which the purge gas has been ceased;
- starting a partial flow of purge gas during the selected interval of time when the sensed flare gas flow rate is less than a first flare gas flow rate; and
- re-establishing the full flow of purge gas at the end of the cessation interval of time such that only a predetermined amount of migration air has occurred to prevent harmful conditions from occurring as a result of the air migration.
- 12. An improved purging process for controlling the rate of back flow migration of air into a flare system through which a flare gas is caused to flow, the process comprising:
- flowing purge gas through the flare system in a sufficient amount to substantially prevent air migration into the exit port through which the purge gas is exhausted to the atmosphere;
- ceasing the flow of purge gas to permit substantial air migration to occur, said ceasing of purge gas being for a selected cessation interval of time;
- sensing the flow rate of the flare gas during the cessation interval of time during which the purge gas has been ceased;
- starting a partial flow of purge gas during the selected interval of time when the sensed flare gas flow rate is in a transition range defined as being between a first flare gas flow rate and a second flare gas flow rate, the cessation of purge gas continuing if the sensed purge gas flow rate is either side of said transition range, the partial flow of purge gas being sufficient to effect a total flow of purge gas and flare gas at a rate above the transition range; and
- re-establishing the full flow of purge gas at the end of the cessation interval of time such that only a predetermined amount of migration air has occurred to prevent harmful conditions from occurring as a result of the air migration.
- 13. The process of claim 12 wherein the cessation of the purge gas is effected by a timing device which ceases the flow of purge gas at the predetermined intervals.
- 14. The process of claim 12 wherein the cessation of purge gas is effected by an oxygen analyzer means for measuring the oxygen content in the flare system and for re-establishing the flow of purge gas when the oxygen content in the flare system exceeds predetermined values of oxygen content of the gas mixture in the flare system.
- 15. The process of claim 14 wherein the cessation of purge gas is effected by a timing device which ceases the flow of purge gas at predetermined intervals of time.
- 16. The process of claim 12 wherein the cessation of purge gas is effected by a sensor device which senses a predetermined condition in the flare stack and which reestablishes full flow of purge gas when the predetermined condition is sensed.
- 17. The process of claim 16 wherein the sensor device is a temperature sensor and the predetermined condition is a predetermined temperature.
- 18. The process of claim 16 wherein the sensor device is a vacuum sensor and the predetermined condition is a predetermined pressure.
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part to U.S. application Ser. No. 623,845, entitled PURGING PROCESS, filed June 23, 1984 and now U.S. Pat. No. 4,559,006.
US Referenced Citations (8)
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
623845 |
Jun 1984 |
|