Patent Application
20140016126
This disclosure relates generally to inventory management systems. More specifically, this disclosure relates to a servo gauge that uses Raman spectroscopy for storage tank applications.
Liquid natural gas (LNG) is routinely stored in large storage tanks. The value of liquid natural gas is often based on its “heat content,” which is a measure of the amount of heat that is released when the liquid natural gas is burned. Conventional storage tanks often include level-temperature-density (LTD) gauges, which can be used to estimate the heat content of liquid natural gas in the storage tanks. However, conventional LTD gauges often estimate the temperature and density of liquid natural gas within a tank, and those values are then used to estimate the chemical composition of the liquid natural gas within the tank. This process can create relatively large errors in the heat content measurements, such as errors of up to 5% or even more. Depending on whether the heat content is overestimated or underestimated, these errors can result in significant monetary losses for either the buyer or the seller of the liquid natural gas.
This disclosure provides a servo gauge that uses Raman spectroscopy for storage tank applications.
In a first embodiment, an apparatus includes a servo gauge. The servo gauge includes a displacer configured to be raised and lowered within material in a tank. The servo gauge also includes at least one light source configured to illuminate a sample of the material at the displacer. The servo gauge further includes at least one detector configured to measure radiation that has interacted with the sample of the material at the displacer. In addition, the servo gauge includes an analyzer configured to perform Raman spectroscopy analysis of measurements from the at least one detector and identify at least one characteristic of the material.
In a second embodiment, a method includes positioning a displacer of a servo gauge within material in a tank. The method also includes illuminating a sample of the material at the displacer and measuring radiation that has interacted with the sample of the material at the displacer. The method further includes performing Raman spectroscopy analysis of the measured radiation to identify at least one characteristic of the material.
In a third embodiment, a non-transitory computer readable medium embodies a computer program. The computer program includes computer readable program code for receiving measurements of radiation that has interacted with a sample of material in a tank at a displacer of a servo gauge positioned within the tank. The computer program also includes computer readable program code for performing Raman spectroscopy analysis of the measurements to identify at least one characteristic of the material.
Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.
For a more complete understanding of this disclosure, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
A servo gauge 106 facilitates analysis of the material 104 stored in the tank 102. For example, the servo gauge 106 could be used to identify the chemical composition of the material 104 in the tank 102 using Raman spectroscopy. The servo gauge 106 includes a displacer 108 that is physically raised and lowered within the tank 102. The displacer 108 sinks within the material 104 in the tank 102, and the displacer 108 supports the use of Raman spectroscopy for analyzing the material 104 at different levels within the tank 102. The servo gauge 106 can also be used to perform other functions, such as determining the level of the material 104 in the tank 102.
A connector 107 couples the displacer 108 to the main housing of the servo gauge 106. The connector 107 can be moved by the servo gauge 106 to control the raising and lowering of the displacer 108. For example, the connector 107 could be wound around a drum in the servo gauge 106, and the servo gauge 106 could rotate the drum to raise or lower the displacer 108.
The servo gauge 106 includes any suitable structure for analyzing a material in a tank using Raman spectroscopy. The connector 107 includes any suitable structure for connecting a displacer to another portion of a servo gauge. The connector 107 could, for example, include a fiber optic cable for transporting laser light or other illumination to and from the displacer 108. The displacer 108 includes any suitable structure that is moved within a tank and that samples material in a tank.
The determined characteristic(s) of the material 104 in the tank 102 can be provided from the servo gauge 106 to a monitoring system 110 over a wired or wireless link. The monitoring system 110 can use the determined characteristic(s) of the material 104 in any suitable manner. For example, the monitoring system 110 could notify personnel associated with the tank 102, such as by displaying the determined characteristic(s) on a display 112 or by transmitting the determined characteristic(s) to a wireless or other user device 114.
In one aspect of operation, the servo gauge 106 can raise and lower the displacer 108 so that the displacer 108 reaches different locations within the material 104 in the tank 102. At one or more locations, the servo gauge 106 analyzes the material 104 in the tank 102 using Raman spectroscopy. During the analysis, for example, the servo gauge 106 can determine the chemical composition of the material 104. The chemical composition or information based on the chemical composition (such as heat content) could then be provided to an external device or system, such as the monitoring system 110.
The servo gauge 106 can repeat this analysis of the material 104 at various heights within the tank 102. For example, this process could be repeated at a set number of specific locations within the tank 102, at a number of locations separated by a specified step distance within the tank 102, or continuously through the entire height of the material 104 in the tank 102.
The information obtained by or from the servo gauge 106 could be used in any suitable manner. For example, the chemical composition can be used in various ways, such as to calculate the heat content of liquid natural gas stored in the tank 102. Among other things, this enables liquid natural gas storage owners/operators to accurately measure the chemical composition of stored liquid natural gas. With that information, the actual heat content (and thus the actual commercial value) of the liquid natural gas can be more accurately assessed. Moreover, this information could be used to support other functions, such as safety-related functions. As a specific example, this information can be used to determine whether liquid natural gas in the tank 102 is undergoing stratification. These functions can generate results that are far more accurate than the results obtainable using conventional level-temperature-density (LTD) gauges.
Although
The drive compartment 204 includes a drive train 210, which imparts rotation to the drum 208 via a shaft 212. For example, the drive train 210 or shaft 212 could generate a magnetic field, and magnet coupling can be used to convey torque between the shaft 212 and the drum 208. In these embodiments, no direct connection may be needed between the drum compartment 202 and the drive compartment 204. However, other techniques for causing rotation of the drum 208 could be used, such as when the shaft 212 is physically connected to the drum 208. The drive train 210 includes any suitable structure for imparting rotation to a drum. In particular embodiments, the drive train 210 includes a stepper motor that causes the drum 208 to rotate in specified steps, meaning the drum 208 does not rotate freely but in defined amounts or “steps.” In other embodiments, the drive train 210 can rotate the drum 208 freely.
The drive compartment 204 may optionally include a measuring unit 214, which could be used to determine the level of material 104 in the tank 102. The measuring unit 214 could use any suitable technique to identify the level of material 104 in the tank 102. For example, the weight of the displacer 108 could vary depending on whether the displacer 108 is contacting the material 104. The measuring unit 214 could therefore use the torque on the drum 208 to detect when the displacer 108 comes into contact with the material 104. The measuring unit 214 includes any suitable structure for measuring a level of material in a tank.
A controller 216 controls the overall operation of the servo gauge 106. For example, the controller 216 could control the raising and lowering of the displacer 108. The controller 216 could also detect a mechanical fault with the servo gauge 106, such as by using measured torques from the measuring unit 214. The controller 216 includes any suitable structure for controlling operation of a servo gauge, such as at least one microprocessor, microcontroller, field programmable gate array (FPGA), digital signal processor (DSP), or other processing or control device.
In this example, the servo gauge 106 further includes a user interface 218 and a network interface 220. The user interface 218 facilitates communication between the servo gauge 106 and an operator or other personnel. The user interface 218 could provide data from an operator to the controller 216, such as a command to raise or lower the displacer 108. The user interface 218 could also allow the personnel to review measurement data generated by the servo gauge 106. The user interface 218 includes any suitable interface for interacting with one or more users, such as a keypad or keyboard and a display.
The network interface 220 facilitates the communication of data to or from the servo gauge 106. For example, the network interface 220 could receive measurements from the servo gauge 106 and transmit the measurements to one or more external destinations (such as the monitoring system 110). The network interface 220 includes any suitable structure supporting wired or wireless communications, such as an Ethernet interface, an RF transceiver, or other wired or wireless interface.
The power supply compartment 206 includes a power supply 222, which provides operating power to various components of the servo gauge 106. The power supply 222 includes any suitable structure for providing power, such as a battery, fuel cell, or solar cell.
As noted above, the servo gauge 106 includes various components supporting Raman spectroscopy to determine one or more characteristics of the material 104 in the tank 102. As shown in
The detector 226 measures radiation that has interacted with the sample of the material 104. For example, the detector 226 could measure the intensity of light that has interacted with the sample of the material 104 at various wavelengths. The detector 226 includes any suitable structure for measuring light that passes through or otherwise interacts with a sample of material. In particular embodiments, the detector 226 includes a photodetector, spectrometer, or other detection device.
The analyzer 228 analyzes measurements from the detector 226 to identify the chemical composition or other characteristic(s) of the sample of the material 104. For example, the analyzer 228 can analyze the measurements from the detector 226 to identify the inelastic or Raman scattering of light caused by the material 104. This information can then be used to identify the composition of the material 104. The analyzer 228 can use any suitable Raman spectroscopy technique for analyzing the material 104 that are known in the art. The analyzer 228 includes any suitable structure for implementing Raman spectroscopy analysis. In this example, the analyzer 228 includes at least one processing device 230, such as at least one microprocessor, microcontroller, FPGA, DSP, or other processing or control device. The analyzer 228 also includes at least one memory device 232 storing instructions and data used, generated, or collected by the processing device(s) 230. The analyzer 228 further includes at least one interface 234 facilitating communication with external devices or systems, such as the controller 216, user interface 218, or network interface 220.
The various components 202-234 of the servo gauge 106 reside within a housing 236. The housing 236 protects the other components of the servo gauge 106 and can be mounted to the roof or other structure of a tank 102. The housing 236 includes any suitable structure for protecting other components of a servo gauge, such as a metal enclosure.
Note that various components shown as residing within the housing 236 could reside elsewhere. For example, the light source 224 and/or the detector 226 could reside within the displacer 108. As another example, the analyzer 228 could reside outside of the housing 236, such as in the monitoring system 110.
An example of an alternate arrangement of the servo gauge 106 is shown in
The electronics box 250 includes any suitable structure for housing one or more electronic components. While the electronics box 250 is shown here as being used with a single housing 236, the electronics box 250 could be coupled to multiple housings 236 of multiple servo gauges 106. When used with multiple servo gauges 106, the electronics box 250 could include multiple instances of the components 224-226 or 224-228, or the electronics box 250 could include a translation stage that allows light to be sent over and received from different optical fibers 252.
Although
A sample of the material at the displacer is illuminated at step 304. This could include, for example, the light source 224 generating visible, near infrared, near ultraviolet, or other radiation suitable for use with Raman spectroscopy. This could also include the light source 224 providing the radiation to the sample of material 104. The radiation could be provided in any suitable manner, such as by transporting the radiation from the light source 224 in the housing 236 to the displacer 108 over one or more optical fibers in the connector 107. Any suitable lenses or other optical devices could be used to provide the radiation to the material 104.
Radiation that has interacted with the sample of the material at the displacer is measured at step 306. This could include, for example, the detector 226 measuring the intensity of the illumination passing through the sample of material 104. Prior to measurement, the illumination passing through the sample could be transported over one or more optical fibers in the connector 107 to the detector 226 in the housing 236. Any suitable filters or other optical devices could be used to alter the radiation provided to the detector 226.
Raman spectroscopy analysis is performed using the measurements from the detector at step 308, and one or more characteristics of the sample of material are identified at step 310. The Raman spectroscopy analysis can, for example, analyze the inelastic scattering of light by the sample of material 104 to determine the composition of the sample. Various techniques for determining the composition of a material using Raman spectroscopy are known in the art and need not be described here. The characteristic(s) of the sample of material 104 can represent any suitable characteristic(s) and can vary depending on the type of material being analyzed. For liquid natural gas, one of the characteristics could be the heat content of the liquid natural gas at that location within the tank 102.
A determination is made whether another sample of the material in the tank is needed at step 312. This could include, for example, the servo gauge 106 determining whether samples of the material 104 have been analyzed over the entire range of the material's height in the tank 102. If not, the position of the displacer is changed at step 314. This could include, for example, the servo gauge 106 winding the connector 107 around the drum 208 to raise the displacer 108 by a specified distance in the tank 102. The process then returns to step 304 to analyze another sample of the material 104 in the tank. Note that analyzing the material 104 in a bottom-to-top direction is merely illustrative and that any random or organized pattern of sampling could be used.
The identified characteristic(s) of the material in the tank can be used in any suitable manner at step 316. For example, the heat content or other characteristic(s) of the material 104 could be displayed to an operator, used to calculate the market value of the material 104, or used to identify any stratification of the material 104. The identified characteristic(s) could be used in any other suitable way.
Although
In some embodiments, various functions described above are implemented or supported by a computer program that is formed from computer readable program code and that is embodied in a computer readable medium. The phrase “computer readable program code” includes any type of computer code, including source code, object code, and executable code. The phrase “computer readable medium” includes any type of medium capable of being accessed by a computer, such as read only memory (ROM), random access memory (RAM), a hard disk drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. A “non-transitory” computer readable medium excludes wired, wireless, optical, or other communication links that transport transitory electrical or other signals. A non-transitory computer readable medium includes media where data can be permanently stored and media where data can be stored and later overwritten, such as a rewritable optical disc or an erasable memory device.
It may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The terms “application” and “program” refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer code (including source code, object code, or executable code). The terms “transmit” and “receive,” as well as derivatives thereof, encompass both direct and indirect communication. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrase “associated with,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. For example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.
While this disclosure has described certain embodiments and generally associated methods, alterations and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure, as defined by the following claims.
This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/669,982 filed on Jul. 10, 2012, which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61669982 | Jul 2012 | US |
