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

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.

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:
• generating a time derivative by calculating a derivative of the plurality of temperature measurements with respect to time;
• applying a transform to the time derivative to generate a complex spectrum;
• and
• determining an amplitude and a phase of the complex spectrum, wherein the amplitude and the phase of the complex spectrum indicate a coking deposit proximal the sensor location.

A system for detecting coking in a wash bed of a vacuum pipe still, comprising:

• a sensing cable including an optical fiber sensor array aligned with a heating element disposed in the wash bed, the optical fiber sensor array having a plurality of sensor locations;
• an optical signal interrogator coupled with the optical fiber sensor array and adapted to receive a signal from each of the plurality of sensor locations and configured to measure a first temperature profile of the sensing cable at the plurality of sensor locations within the vacuum pipe still;
• a control unit, coupled with the heating element and the optical signal interrogator, configured to determine 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;
• and
• an excitation source coupled with the heating element and configured to propagate 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;
• wherein the optical signal interrogator is configured to measure, over time, 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
• wherein the 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.

A system for detecting coking in a wash bed of a vacuum pipe still, comprising:

• a sensing cable including an optical fiber sensor array aligned with a heating element disposed in the wash bed, the optical fiber sensor array having a plurality of sensor locations;
• an optical signal interrogator coupled with the optical fiber sensor array and adapted to receive a signal from each of the plurality of sensor locations and configured to measure a first temperature profile of the sensing cable at the plurality of sensor locations, wherein the optical signal interrogator is configured, for each of the plurality of sensor locations, to measure a plurality of temperatures over a period of time upon arrival of the heat pulse at the sensor location;
• a control unit, coupled with the heating element and the optical signal interrogator, configured to determine 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;
• and
• an excitation source coupled with the heating element and configured to propagate 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;
• wherein the optical signal interrogator is configured to measure, over time, 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
• wherein the 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, wherein the control unit is configured, for each temperature profile, to perform 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.

A system for detecting coking in a wash bed of a vacuum pipe still, comprising:

• a sensing cable including an optical fiber sensor array aligned with a heating element disposed in the wash bed, the optical fiber sensor array having a plurality of sensor locations;
• an optical signal interrogator coupled with the optical fiber sensor array and adapted to receive a signal from each of the plurality of sensor locations and configured to measure a first temperature profile of the sensing cable at the plurality of sensor locations, wherein the optical signal interrogator is configured, for each of the plurality of sensor locations, to measure a plurality of temperatures over a period of time upon arrival of the heat pulse at the sensor location;
• a control unit, coupled with the heating element and the optical signal interrogator, configured to determine 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;
• and
• an excitation source coupled with the heating element and configured to propagate 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;
• wherein the optical signal interrogator is configured to measure, over time, 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
• wherein the 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, wherein the control unit is configured, for each temperature profile, to:
• generate a time derivative by calculating a derivative of the plurality of temperature measurements with respect to time;
• apply a transform to the time derivative to generate a complex spectrum;
• and
• determine an amplitude and a phase of the complex spectrum, wherein the amplitude and the phase of the complex spectrum indicate a coking deposit proximal the sensor location.

A method for detecting coking and flow maldistribution in a catalyst bed of a hydroprocessing reactor, comprising:

• providing within a catalyst bed of a hydroprocessing reactor 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 catalyst bed 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;
• detecting a misdistribution condition in the catalyst 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;
• and
• detecting coking within the catalyst bed 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.

A system for detecting coking and flow maldistribution in a catalyst bed of a hydroprocessing reactor, comprising:

• a sensing cable including an optical fiber sensor array aligned with a heating element disposed within a catalyst bed of a hydroprocessing reactor, the optical fiber sensor array having a plurality of sensor locations;
• an optical signal interrogator coupled with the optical fiber sensor array and adapted to receive a signal from each of the plurality of sensor locations and configured to measure a first temperature profile of the sensing cable at the plurality of sensor locations;
• a control unit, coupled with the heating element and the optical signal interrogator, configured to determine a flow distribution of fluids within the catalyst bed 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;
• and
• an excitation source coupled with the heating element and configured to propagate 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;
• wherein the optical signal interrogator is configured to measure, over time, 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
• wherein the 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,
• wherein the control unit is configured to detect a misdistribution condition in the catalyst 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.