Method and system for detecting coking growth and maldistribution in refinery equipment

Patent metadata

Field	Value
Publication number	US-9880035-B2
Application number	US-201414226939-A
Country	US
Kind code	B2
Filing date	Mar 27, 2014
Priority date	Mar 28, 2013
Publication date	Jan 30, 2018
Grant date	Jan 30, 2018

Abstract

Systems and methods for detecting coking in a wash bed of a vacuum pipe still with a sensing cable including an optical fiber sensor array aligned with a heating element disposed in the vessel. An optical signal interrogator is configured to measure a first temperature profile at a plurality of sensor locations to determine a flow distribution. An excitation source is configured to propagate at least one heat pulse through the heating element and the optical signal interrogator is configured to measure a second temperature profile corresponding to the heat pulse at the sensor locations. A control unit is configured to detect coking by determining one or more properties of the media exposed to the sensing cable at each of the plurality of sensor locations based on the second temperature profile corresponding thereto.

First claim

What is claimed is:

1. A method for detecting coking in a wash bed of a vacuum pipe still, comprising:
providing within a vacuum pipe still a sensing cable including an optical fiber sensor array aligned with a heating element;
measuring a first temperature profile of the sensing cable at a plurality of sensor locations within the vacuum pipe still;
determining a flow distribution of fluids within the vacuum pipe still by identifying a first set of sensor locations of the sensing cable exposed to vapor and a second set of sensor locations of the sensing cable exposed to liquid based on the first temperature profile;
propagating at least one heat pulse through the heating element along at least a portion of the sensing cable to affect an exchange of thermal energy between the heating element and media, including the fluids, exposed to the sensing cable;
measuring, over time, at least a second temperature profile of the sensing cable corresponding to the heat pulse at each of the plurality of sensor locations of the optical fiber sensor array; and
detecting coking by determining one or more properties of the media exposed to the sensing cable at each of the plurality of sensor locations based on the second temperature profile corresponding thereto.

2. The method of claim 1 , wherein measuring the first temperature profile and the second temperature profile includes measuring using fiber Bragg grating array based sensing, Raman scattering based sensing, Rayleigh scattering based sensing, or Brillioun scattering based sensing.

3. The method of claim 1 , wherein the heating element includes a resistive heating element and wherein propagating the at least one heat pulse includes applying an electrical pulse with a predetermined frequency and predetermined waveform.

4. The method of claim 1 , wherein propagating at least one heat pulse through the heating element includes propagating the at least one heat pulse through a heating element aligned adjacent to the optical fiber sensor array.

5. The method of claim 1 , wherein propagating at least one heat pulse through the heating element includes propagating the at least one heat pulse through a heating element disposed concentrically with the optical fiber sensor array.

6. The method of claim 1 , wherein the heating element includes a thermoelectric device and wherein propagating at least one heat pulse through the heating element includes propagating cooling pulse.

7. The method of claim 1 , wherein measuring the first temperature profile includes passively measuring a temperature at each sensor location.

8. The method of claim 1 , wherein measuring the first temperature profile further includes propagating a heat pulse through the heating element along at least a portion of the sensing cable and, for each sensor location, measuring at least a heating temperature measurement during propagation of the heat pulse over the sensor location, a peak temperature measurement, and a cooling temperature measurement after propagation of the heat pulse over the sensor.

9. The method of claim 8 , wherein determining the flow distribution of the fluids includes calculating a difference in the heating temperature measurement, the peak temperature measurement, the cooling temperature measurement, or combination thereof, between sensor locations, wherein the difference indicates a change in fluid characteristic proximal at least one of the plurality of sensor locations if the difference exceeds a predetermined threshold.

10. The method of claim 1 , wherein the media includes a coking deposit.

11. The method of claim 1 , wherein determining the flow distribution of the fluids within the vacuum pipe still further includes detecting a misdistribution condition in the wash bed by monitoring the second temperature profile corresponding to each of the plurality of sensor locations, and comparing the monitored temperature profiles to predetermined temperature profiles corresponding to a desired operation condition.

12. The method of claim 1 , wherein determining the flow of the fluids within the vacuum pipe still further includes detecting a misdistribution condition in the wash bed by monitoring the second temperature profile corresponding to each of the plurality of sensor locations and at least a third temperature profile corresponding to each of the plurality of sensor locations, and comparing the second and third temperature profiles to detect a change in operation condition.

13. The method of claim 1 , wherein the sensing cable is disposed in a grid configuration within the wash bed, the method further comprising generating a multi-dimensional flow distribution based on the first temperature profile corresponding to each sensor location.

14. The method of claim 1 , wherein the sensing cable further includes a plurality of sensing cables, wherein each of the plurality of sensing cables is disposed within different layers of the wash bed, and wherein the control unit is further configured to generate a multi-dimensional flow distribution based on the first temperature profile corresponding to each sensor location.

15. The method of claim 1 , wherein the vacuum pipe still has an operating temperature between cryogenic temperatures and approximately 1000° C., wherein the sensing cable has a diameter of less than 2 mm, and wherein the optical signal interrogator is configured to measure the temperature profile at a spatial resolution less than 1 mm.

16. A method for detecting coking in a wash bed of a vacuum pipe still, comprising:
providing within a vacuum pipe still a sensing cable including an optical fiber sensor array aligned with a heating element;
measuring a first temperature profile of the sensing cable at a plurality of sensor locations;
determining a flow distribution of fluids within the vacuum pipe still by identifying a first set of sensor locations of the sensing cable exposed to vapor and a second set of sensor locations of the sensing cable exposed to liquid based on the first temperature profile;
propagating at least one heat pulse through the heating element along at least a portion of the sensing cable to affect an exchange of thermal energy between the heating element and media, including the fluids, exposed to the sensing cable;
measuring, over time, at least a second temperature profile of the sensing cable corresponding to the heat pulse at each of the plurality of sensor locations of the optical fiber sensor array, wherein measuring the second temperature profile corresponding to the heat pulse at each of the plurality of sensor locations includes, for each sensor location, measuring a plurality of temperatures over a period of time upon arrival the heat pulse at the sensor location; and
detecting coking by determining one or more properties of the media exposed to the sensing cable at each of the plurality of sensor locations based on the second temperature profile corresponding thereto, wherein detecting coking includes, for each temperature profile, performing a regression of the plurality of temperatures over a logarithm of corresponding measurement times for a predetermined time window in the period of time to generate a slope and an intercept of the regression, wherein the slope and the intercept indicate a coking deposit proximal the sensor location.

17. The method of claim 16 , wherein the predetermined time window includes a time window during a heating stage, the heating stage corresponding to a period of time during propagation of the heat pulse over the sensor location or a time window during a cooling stage, the cooling sta

Assignees

• Zhang Yibing
• Song Limin
• Keiser Geoff
• Hergenrother Michael Louis
• Stober Berne K
• Kalamaras Patricia H
• Umansky Benjamin Santiago
• Exxonmobil Res & Eng Co

Inventors

• Zhang Yibing
• Song Limin
• Keiser Geoff
• Hergenrother Michael Louis
• Stober Berne K
• Kalamaras Patricia H
• Umansky Benjamin Santiago

Classifications

• G01K11/32

  using changes in transmittance, scattering or luminescence in optical fibres · CPC title

• B01J8/001

  Controlling catalytic processes (B01J8/1809 takes precedence) · CPC title

• B01J2219/00247

  Fouling of the reactor or the process equipment · CPC title

• B01D3/04

  pipe stills · CPC title

• B01J2208/00424

  Peltier cooling elements · CPC title