Method for measuring reactor bed level from active acoustic measurement and analysis

• US 20090282910A1
• Filed: 05/08/2009
• Published: 11/19/2009
• Est. Priority Date: 05/13/2008
• Status: Active Grant

• Current Assignee: ExxonMobil Research & Engineering Company (Exxon Mobil Corporation)
• Original Assignee: ExxonMobil Research & Engineering Company (Exxon Mobil Corporation)
• Inventors: Bitar, Jormarie, Song, Limin, Disko, Mark M., Lobo, Julio D.
• Granted Patent: US 8,850,881 B2
• Time in Patent Office: Days
• US Class Current: 73/290.V
• CPC Class Codes: G01F 23/296 Acoustic waves
• CPC Class Codes: G01F 23/2966 making use of acoustical resonance or standing waves

Abstract

The present invention is a non-intrusive method to determine the fluid level in a vessel. In a preferred embodiment, the vessel is a delayed coker drum in a refinery. Waves are generated in the vessel from an outside source. For wall vibration generated in the frequency range of 1-20,000 Hz, accelerometers on the exterior wall of the vessel measures the frequency of the vibration modes of the vessel. The fluid level can be related to the frequency of the vibration mode.

Claims

1. A method to determine the fill level of material inside a vessel comprising relating a shift of the natural frequencies of wall vibrations to fill level wherein a relationship between frequency shift of wall vibrations and fill level is determined by

a) inducing vibration on the wall in said vessel from an external source,

b) measuring the vibration signals on the wall of said vessel as a function of frequency,

c) relating frequency to the fill level.

2. The method of claim 1 wherein said wall vibration from the external source is generated with a broad band of frequencies in said vessel.

3. The method of claim 2 wherein the frequencies in the said vessel is determined from the vibration signals measured on the exterior wall when the vessel contains different levels of material.

4. The method of claim 1 wherein said external source is a dynamic actuator.

5. The method of claim 4 wherein said dynamic actuator is a periodic pneumatic impactor, an electromatic dynamic shaker, or a prezoelectric dynamic actuator.

6. The method of claim 4 wherein said external source is mounted on the exterior surface of the wall of the vessel and located so as to produce an optimal vibration signal.

7. The method of claim 1 wherein said frequency range is 1-2000 Hz.

8. The method of claim 1 wherein said fill level is related to the frequency of a preselected vibration mode.

9. The method of claim 8 wherein the vibration mode is the first vibration mode and associated frequency is the first dominant peak in the frequency spectrum.

10. The method of claim 1 further comprising an analytical model to relate to frequency of the vibration signals to the fill level.

11. The method of claim 1 wherein the step of measuring the vibration signals by accelerometers placed at positions on the exterior of the vessel will give optimum results.

12. The method of claim 1 wherein said measuring of the vibration signals is performed by measuring attenuation of wall vibrations.

14. The method of claim 12 wherein the relation between the frequency shift and fill level, and the relation between attenuation and fill level are combined to provide performance of fill level measurement.

13. A method to determine the fill level of material inside a vessel comprising relating attenuation of wall vibrations to fill level wherein a relationship between the attenuation of wall vibrations and fill level is determined by

a) inducing vibration on the wall in said vessel from an external source,

b) measuring the vibration signals on the exterior wall of said vessel as a function of frequency,

c) selecting a vibration mode

d) relating amplitude of vibration mode to the fill level.