Temperature measuring system for ovens

Abstract

A method for measuring furnace temperatures, wherein the method comprises: Obtained (300) radiation measurements from several areas of interest (114) using multiple thermal imaging cameras (150); Measuring (302) a surface temperature using a radiation measurement obtained from an area of ​​interest selected (402) from the several areas of interest, with: Determine (408) an effective background radiation affecting the selected area of ​​interest using radiation measurements obtained from areas of interest other than the selected area of ​​interest; Determine (410) a compensated radiation by removing the effective background radiation from the radiation measurement obtained from the selected area of ​​interest; Correcting (412) the compensated radiation with respect to an atmospheric emission, wherein the correction with respect to the atmospheric emission is determined on the basis of properties of a flame front traversed for the radiation measurement of the selected area of ​​interest, wherein the properties of the flame front include a length of the flame front traversed; and Converting (414) the corrected compensated radiation into the measured surface temperature.

Description

BACKGROUND

[0001] The availability of local temperature measurements from within a furnace or furnace system, such as a reforming furnace, can be essential for the operation of the furnace. Such temperature measurements can be obtained using radiation thermometry. However, the accuracy of the radiation thermometry measurements can be adversely affected by the conditions within the furnace.

[0002] WO 2004 / 069 547 A2 discloses a device for thermal imaging of target surfaces.

[0003] US 4 432 657 A discloses a pyrometer method for measuring the slab temperature in a reheating furnace.

[0004] The present invention aims to provide an improved method for measuring furnace temperatures.

[0005] This problem is solved by the subject matter of the independent claims.

[0006] Embodiments are defined by the dependent claims.

[0007] When the term "embodiment" refers hereinafter to unclaimed combinations of features, this term should be understood to refer to examples that provide a context for understanding the present invention. OVERVIEW

[0008] Generally, one aspect of the invention relates to a method for measuring furnace temperatures. The method comprises obtaining radiation measurements from a plurality of regions of interest (ROIs) using a plurality of thermal imaging cameras, and measuring a surface temperature using a radiation measurement obtained from a ROI selected from the plurality of ROIs. Measuring the surface temperature comprises determining an effective background radiation affecting the selected ROI using radiation measurements obtained from ROIs different from the selected ROI, obtaining compensated radiation by removing the effective background radiation from the radiation measurement obtained from the selected ROI, and converting the compensated radiation into the measured surface temperature.

[0009] Generally, one aspect of the present invention relates to a non-transitory computer-readable medium containing instructions for measuring surface temperatures. The instructions include the functionality of obtaining radiation measurements from a plurality of regions of interest (ROIs) using a plurality of thermal imaging cameras and measuring a surface temperature using a radiation measurement obtained from an ROI selected from the plurality of ROIs. Measuring the surface temperature includes determining an effective background radiation affecting the selected ROI using radiation measurements obtained from ROIs other than the selected ROI, obtaining a compensated radiation by removing the effective background radiation from the radiation measurement obtained from the selected ROI, andobtained from the selected ROI, and converting the compensated radiation into the measured surface temperature.

[0010] Generally, in one aspect, the invention relates to a system for measuring furnace temperatures. The system comprises a plurality of thermal imaging cameras and a processing unit. The processing unit is configured to obtain radiation measurements from a plurality of regions of interest (ROIs) using the plurality of thermal imaging cameras and to measure a surface temperature using a radiation measurement obtained from an ROI selected from the plurality of ROIs. Measuring the surface temperature comprises determining an effective background radiation influencing the selected ROI, wherein radiation measurementsUsing radiation measurements obtained from ROIs other than the selected ROI, obtaining a compensated radiation by removing the effective background radiation from the radiation measurement obtained from the selected ROI, and converting the compensated radiation into the measured surface temperature. SHORT DESCRIPTION OF DRAWINGS Fig. 1A-1C show temperature measurement systems for measuring temperatures inside a furnace according to one or more embodiments of the invention. Fig. 2-4 show a flowchart according to one or more embodiments of the invention. Fig. 5 shows a computer system according to one or more embodiments of the invention. DETAILED DESCRIPTION

[0011] Specific embodiments of the invention will now be described in detail with reference to the accompanying figures. For consistency, like elements are designated by like reference numerals throughout the various figures.

[0012] Throughout the application, ordinal numbers (e.g., first, second, third, etc.) are used as an adjective for an element (that is, for each noun in the application). The use of ordinal numbers is not intended to imply or create a particular order of the elements, nor is it intended to limit any element to a single element unless explicitly disclosed, such as through the use of the terms "before," "after," "only," and other such terms. The use of ordinal numbers is intended solely to distinguish the elements. For example, a first element is different from a second element, and the first element may include more than one element and may follow (or precede) the second element in an order of elements.

[0013] In the following description of the Fig. 1A-5, any component described with respect to one figure in various embodiments of the invention may be equivalent to one or more like-named components described in connection with another figure. For brevity, descriptions of these components are not repeated with respect to each figure. Thus, all embodiments of the components of each figure are incorporated by reference and should be understood as optionally present within any other figure that includes one or more like-named components. Further, in accordance with various embodiments of the invention, any description of the components of a figure should be understood as an optional embodiment that may be implemented in addition to, in conjunction with, or in place of the embodiments described in connection with a corresponding like-named component in another figure.

[0014] In general, embodiments of the invention relate to a system and method for measuring temperatures from image data using radiation thermometry. More specifically, accurate temperature measurements of a region of interest (ROI) can be obtained by correcting thermal radiation data obtained from one or more thermal imaging cameras for various factors that would otherwise adversely affect the accuracy of the temperature measurement. These factors include, but are not limited to, background radiation, such as radiation from other heat sources reflected from the ROI, atmospheric attenuation, amplifying effects from flames, the geometric configuration of the environment in which the measurements are obtained, and the emissivity of the ROI being measured.The procedures used to correct these factors are described in detail below.

[0015] In one or more embodiments of the invention, the corrections may be performed in real time or near real time, resulting in accurate temperature measurements even in dynamically changing environments.

[0016] The corrections can be performed for multiple ROIs within the field of view of the thermal imaging camera or can be performed for multiple ROIs within fields of view of multiple cameras according to one or more embodiments of the invention. Although the corrections are performed for different ROIs, separately for each ROI, dependencies between ROIs can be taken into account, as described below.

[0017] Fig. 1A-1C show temperature measurement systems (100) according to one or more embodiments of the invention. Fig. 1A shows a top view of an illustrative furnace or furnace system (102) and thermal imaging cameras (150). Fig. 1B shows a side view into the furnace (102). Fig. The view shown in Figure 1B is an example of a view obtained by a thermal imaging camera (150) through a side door (110) into the furnace (102). A thermal imaging camera (150) positioned to capture images from inside the furnace may obtain such a view. Fig. Figure 1C shows a top view as a detail of the illustrative oven of the Fig. 1A. The furnace may, for example, be a reforming furnace of a steam reformer used to produce hydrogen and / or other industrial gases and fuels. The interior of the furnace (102) may be enclosed by a group of furnace walls (104). A group of reforming tubes (108) may pass through the interior of the furnace. Fig. 1A and Fig. 1B, the reforming tubes (108) pass through the furnace, starting from the floor (112) to the ceiling (not shown) of the furnace (102) in a vertical direction. Alternatively or additionally, reforming tubes (108) may pass through the furnace in any other orientation, for example, horizontally. A catalytic reaction may take place in the reforming tubes (108). This catalytic reaction may, for example, be a reaction of a combination of steam and hydrocarbons to form hydrogen and carbon monoxide, and further to more hydrogen and carbon dioxide. The reaction may be based on an external heat source. In one embodiment of the invention, the external heat source is provided by heating the reforming tubes (108) by combustion of oil or gas, for example, natural gas, within the furnace (102). The furnace may be top-fired, wall-fired, and / or bottom-fired by burners (106).

[0018] The reforming tubes (108) may be metal tubes. These metal tubes may be subjected to high temperatures and / or high pressures. Depending on the type of reforming process being performed, temperatures may be in the range of 1000°C and pressures may reach 100 bar. Under these conditions, the reforming tubes (108) may be subject to aging. Aging may be accelerated if hot spots exist on the walls of the reforming tubes. To extend the service life of the reforming tubes and to avoid the risk of possible complete failures, it is desirable to control the furnace to avoid hot spots, for example, by making local adjustments to the fuel flow to the burners. It may therefore be necessary to measure temperatures inside the furnace (102).In order to detect hot spots in the walls of the reforming tubes, it may be desirable to obtain surface temperatures of the reforming tubes. In one embodiment of the invention, regions of interest (ROIs) (114) from which temperature measurements are to be obtained therefore include several (many) regions on the surface of the reforming tubes. Furthermore, temperature measurements can be obtained from the furnace walls (104), the furnace floor (112), the furnace ceiling (not shown), etc. ROIs (114) can be arranged on almost any target object in and / or on the furnace (102). Those skilled in the art will recognize that, although in . Fig. 1A-1C, the temperature measurement system (100) is shown as being used to measure temperatures in a reforming furnace, the systems and methods may also be used in a different type of furnace, even in non-furnace environments, without departing from the invention.

[0019] In the continuation of the explanation of the Fig. 1, the temperature measurement system (100) used to measure surface temperatures in the furnace (102) comprises thermal imaging cameras (150). The thermal imaging cameras can be positioned and oriented such that one or more regions of interest (ROIs) (114) lie within the field of view of the thermal imaging cameras. Multiple cameras can be used to reach all desired ROIs (114) in the furnace (102). The one or more thermal imaging cameras (150) can be arranged outside the furnace (102) and can obtain a view into the interior of the furnace through an access or a port in one of the furnace walls (104). The Fig. The illustrative furnace shown in Figure 1A is provided with viewing doors (110). A camera (150) mounted outside the furnace can obtain a view into the interior of the furnace through one of the viewing doors (110). Depending on the position of the ROIs (114), several viewing doors (110) can be provided with cameras (150). According to one embodiment of the invention, a viewing door (110) can be provided with a lens in the region of a bore that can be cooled. Furthermore, further measures can be provided to mechanically and thermally protect the thermal imaging cameras (150). For example, a control system can automatically retract a thermal imaging camera and / or a lens if the cooling of the camera is impaired.

[0020] The thermal imaging camera can be any type of radiation thermometer that measures radiant power in a certain spectral range. For example, the thermal imaging camera can be a CCD camera, with each pixel providing a radiation measurement, or it can be a pyrometer that provides only a single radiation measurement. The incident thermal radiation can be recorded from areas within the field of view of the camera system, including the ROIs (108). An ROI can be represented by one or more pixels of the thermal imaging camera (150). An ROI within the field of view can be defined during installation of the system. During installation, an operator can select a group of pixels corresponding to a specific area in the furnace, for example, the surface of a reforming tube, and can then assign it to an ROI.For example, an image displaying the measured thermal radiation values ​​can be presented to the operator, and the operator can mark ROIs, for example, by placing rectangles, circles, and the like in the displayed image. Pixels located within a marked area can then be considered to form a ROI. Thus, measurements of incident radiation obtained from these individual pixels can be processed as measurements belonging to the ROI, as shown in . Fig. 3, and they can be used as measurements of the thermal radiation of the ROI. A separate thermal radiation value can be obtained for each pixel of the thermal imaging camera. The incident radiation received by the thermal imaging camera can be thermal radiation restricted to a range of wavelengths, for example, infrared thermal radiation at a wavelength of 3.9 µm and / or 850 nm. Those skilled in the art will recognize that any wavelength can be selected based on application criteria. In particular, a wavelength can be selected to account for known atmospheric conditions in the furnace. For example, the wavelength can be selected to avoid wavelengths known to exhibit water vapor absorption effects when the furnace atmosphere contains a significant amount of water vapor.Similarly, a wavelength can be selected to reduce flame amplification effects when measurements are taken through a region of the furnace in which burners are installed.

[0021] Analog or digital signals corresponding to the intensity of the detected incident radiation can be obtained for each pixel of the thermal imaging system. The analog or digital signals can be fed to a processing unit (160) in which the temperature measurement is carried out according to an embodiment of the invention.

[0022] In one or more embodiments of the invention, the thermal imaging camera (150) and the processing unit (160) are calibrated so that the temperature is measured accurately, making the following simplifying assumptions: (i) The thermal imaging camera responds only to a single wavelength. Consequently, a monochromatic approximation, which indicates that the signal obtained by the thermal imaging camera in response to the incident radiation is proportional to the spectral radiance of the affected region of interest (ROI), can be used, and (ii) the measured ROI is considered to be a blackbody. Using these assumptions, a measured temperature T m from the measured signal of the thermal imaging camera S m can be calculated using the following function: Tm≈−c2λ ln sm, where c2 = 0.014388 mK is the second radiation constant used in Planck's law. Consequently, the unit of temperature resulting from the application of equation (1) is Kelvin. Equation (1) is a result of using the Wien approximation to Planck's law.

[0023] Furthermore, the function Sm≈e−c2λTm used to calculate the measured signal of the thermal imaging camera from the measured temperature.

[0024] In equations (1) and (2) the measured temperature T m only agrees with the actual temperature of a target body if the target body is a blackbody. For a non-blackbody, the measured temperature T m deviate from the actual temperature of the measured target body. The measured temperature T mAccording to one embodiment of the invention, the radiation temperature is therefore a radiation temperature. The radiation temperature can be understood as the temperature of a black body with the same spectral radiation as the actually measured body. Therefore, the radiation temperature T m often deviate from the actual temperature of the target body, since target bodies are typically not black bodies.

[0025] Continuing the explanation of the Fig. 1A-1C, the processing unit (160) according to an embodiment of the invention is a computing device configured to carry out at least one of the steps of the methods described in Fig. 2-4. The processing unit (160) may, for example, correct the signals obtained from a thermal imaging camera from a region of interest for background radiation, atmospheric absorption, the geometric configuration of the environment in which measurements are taken, and the emissivity of the region of interest being measured, as described below.

[0026] The Fig. The furnace detail shown in Figure 1C illustrates how background radiation can affect the measurement of a temperature in a region of interest (114) on the surface of a reforming tube (108). The thermal imaging camera (150) receives radiation from the region of interest (solid arrow) directed from the region of interest to the thermal imaging camera. However, the reforming tube (108) is subject to the influence of background radiation from other surfaces in the furnace, as indicated by the dashed arrows. Fig. 1C, the source of this background radiation is the furnace wall (104). In general, any type of object, including, but not limited to, other reforming tubes, a floor, a ceiling, and / or a flame, can emit background radiation to the reforming tube. Fig. 1C can detect any surface in a semicircle in front of the ROI, that is, in the angular range -90° < Θ in < 90°, as shown by the dotted line in Fig. 1c, can be considered as background radiation directed toward the ROI. In the general case of 3D environments, any surface in a hemisphere in front of the ROI can be considered as an area emitting background radiation toward the ROI.

[0027] Since the reforming tube may reflect background radiation, the radiation signal received by the thermal imaging camera from the ROI may contain the reflected background radiation. The radiation signal received by the thermal imaging camera must therefore be adjusted for the reflected background radiation in order to obtain an accurate measurement of the temperature in the ROI according to one or more embodiments of the invention. Compensation may be performed by estimating the background radiation to which the ROI is exposed and by removing this estimated radiation component, as described in detail below with reference to Fig. 4. These steps can be performed by the processing unit (160).

[0028] The processing unit (160) can, for example, be connected to industrial monitoring and control systems, such as via the Open Process Control (OPC) interoperability standard for industrial automation. An output of the processing unit (160) obtained by executing one or more of the methods described below can therefore be used to monitor and control the furnace (102) and / or to generally improve process behavior. The processing unit (160) can include a function to generate alarm messages when temperature windows specified for monitored ROIs are exceeded. Furthermore, the processing unit (160) can include the function to archive temperature data obtained from the ROIs.The archived temperature data may include thermal radiation values ​​recorded by a thermal imaging camera and / or temperature measurement data calculated using one or more of the methods described below. Furthermore, the processing unit may include a visualization unit for displaying the thermal radiation values ​​and / or the measured temperatures to an operator using, for example, a textual representation or graphical representation, such as a heat map.

[0029] In one embodiment of the invention, the processing unit (160) is a computing system similar to that used in Fig. 5 is described.

[0030] Those skilled in the art will recognize that although the temperature measurement system described above is presented in the context of a reforming furnace, temperature measurement systems may be used in other scenarios without departing from the invention. For example, temperature measurement systems according to one or more embodiments of the invention may be used to monitor and / or control boilers and other types of furnaces, such as bakeout furnaces, reheat furnaces, bake ovens, and the like. Furthermore, a temperature measurement system may be scaled as needed or desired. For example, all regions of interest (ROIs) in a small furnace with a simple geometry may be captured by a single thermal imaging camera. Therefore, a basic temperature measurement system may have only a single thermal imaging camera. In contrast, a large furnace with a complex geometry may require many cameras to capture all ROIs.Therefore, a larger temperature measurement system can be based on image data from a network of many thermal imaging cameras.

[0031] Fig. 2-4 show flow diagrams according to one or more embodiments of the technique. Fig. 2 shows a method for configuring the temperature measurement system to perform temperature measurements. Fig. 3 and Fig. 4 show methods for performing temperature measurement according to one or more embodiments of the invention.

[0032] Although the various steps in the flowcharts are illustrated and described sequentially, those skilled in the art will recognize that some or all of the steps may be performed in different orders, combined, or omitted, and that some or all of the steps may be performed simultaneously. In one embodiment of the technique, the steps described in Fig. 2-4 shown steps in parallel with any other steps shown in Fig. 2-4 are performed without deviating from the technique.

[0033] Fig. 2 shows a method for configuring the temperature measurement system to perform temperature measurements. Fig. 2 can be performed once during the installation of the temperature measurement system. Alternatively, one or more of the steps described in Fig. 2 are carried out regularly, for example, when the Fig. 3 and Fig. 4 described procedures.

[0034] According to Fig. 2, in step 200, the one or more thermal imaging cameras are calibrated. The calibration is performed by measuring a blackbody (a blackbody cavity) at a known temperature point or points. The gain of the one or more thermal imaging cameras can then be adjusted so that the radiation temperature(s) indicated by the one or more cameras match the one or more blackbody temperatures. The calibration in step 200 can be performed inside the furnace after the cameras have been installed, for example, when a reference body is installed inside the furnace or outside the furnace prior to the cameras' installation.

[0035] In step 202, possible effects of atmospheric absorption and / or emission in the furnace are determined. Atmospheric absorption may occur if the atmosphere between the region of interest (ROI) being measured and the camera is absorbing at the wavelength used to perform the measurements. The degree of absorption may depend on the concentration of the gases causing the absorption and may depend on the distance between the ROI and the camera. The absorption may be determined based on measurements or based on known properties of the furnace atmosphere. A determination based on measurements of absorption may, for example, be performed by measuring the radiation of an ROI into the furnace from different distances.The difference in the obtained radiation temperatures (lower radiation temperature for greater distance; higher radiation temperature for smaller distance) can be used to determine the atmospheric attenuation, assuming a specific relationship between distance and atmospheric absorption. This relationship can be assumed to be linear. Alternatively, the attenuation can be modulated if the furnace atmosphere is well understood. For example, it may be known that the furnace atmosphere contains a certain level of water vapor, which causes a certain attenuation of the radiation over a certain distance at the wavelength used for the measurements. An absorption coefficient can be used to quantify the attenuation effect determined in step 202.

[0036] Similarly, atmospheric emissions can affect measurement accuracy. Emission effects can occur, for example, if the atmosphere between the ROI being measured and the camera contains a flame. A flame can exhibit a characteristic spectral emission spectrum. If this spectrum overlaps with the wavelength used to perform the measurements, the measured ROI temperature may be magnified due to the radiation emitted by the flames. Therefore, measurements performed through flames may require compensation for the atmospheric emissions caused by the flames. The amplifying effect of flames can be measured or modeled based on known properties of the furnace atmosphere.A measurement-based gain estimation can be performed, for example, by measuring the same ROI in the furnace from different distances. The difference in the obtained radiation temperatures (higher measured radiation temperature for greater distance; lower measured radiation temperature for smaller distance) can be used to estimate the atmospheric emissions, assuming a specific dependence between distance and atmospheric emissions. This dependence can be assumed to be linear, for example. Alternatively, the atmospheric emissions can be modeled based on known absorption properties, for example for the fuel being burned. The model-based estimation can be performed in real time if the parameters specified in . Fig. 3 and Fig. 4. In one embodiment of the invention, the width of the traversed flame front may be taken into account when a flame front lies between a camera and a region of interest (ROI) measured by the camera, and the fuel flow to the burners belonging to the flame front may be metered such that, based on the fuel flow and the type of fuel, the atmospheric conditions in the flame region and the corresponding atmospheric emissions can be modeled, thus enabling dynamically correctable compensation with respect to the atmospheric emissions. An emission coefficient may be used to quantify the emission effect determined in step 202.

[0037] In step 204, the emissivity ε of the surface in the one or more ROI(s) is determined. Various methods can be used to evaluate the emissivity of an ROI to be measured. For example, the emissivity can be determined from the literature based on the material and surface properties in the ROI. Alternatively, the emissivity can be measured. Emissivity measurements can be performed once, for example, when the temperature measurement system is installed, or they can be performed regularly during the operation of the temperature measurement system.In one embodiment of the invention, the emissivity is determined based on a thermal radiation measurement obtained from the ROI and on a thermal radiation measurement obtained from a reference body with known emissivity, for example, a blackbody known to have the same temperature as the target surface in the ROI. Based on the difference between the measured thermal radiation of the blackbody and the measured thermal radiation of the ROI, a gain factor can be determined in the ROI that corrects the difference in the radiation received from the blackbody and the target surface. The inverse of the gain factor is used as the emissivity of the target body in the ROI.Alternatively or additionally, a temperature sensor, such as a thermocouple, installed near the ROI may serve as a temperature reference for determining emissivity in the ROI. If the emissivity is determined regularly, step 204 may be performed as part of the [process] described in . Fig. 4 described procedure.

[0038] Fig. Figure 3 shows a method for measuring a temperature using thermal radiation measurements obtained from one or more thermal imaging cameras according to an embodiment of the invention. Fig. 3 can be executed once to obtain one or more temperature measurements. Alternatively, the method can be executed repeatedly to obtain repeated updated temperature measurements. In one embodiment of the invention, the method can be used to continuously obtain temperature measurements in real time or near real time, ie, immediately after the radiation measurements have been performed.

[0039] In step 300, thermal radiation measurements are obtained from regions of interest (ROIs) within the furnace. A thermal radiation value may be provided per pixel. Thus, multiple thermal radiation measurements for a single ROI may be received simultaneously. Furthermore, repeated measurements may be performed over a time interval. In one embodiment of the invention, the measurements are taken to obtain a single thermal radiation measurement per ROI. Averaging may be performed over multiple pixels of the ROI and / or over time. Spatial averaging may consider measurements obtained from all pixels of the ROI, or it may only consider measurements from a subset of the pixels. When measurements are taken to detect hot spots, spatial averaging may not be performed.Temporal averaging can be performed over a time interval that includes multiple measurements. For example, thermal radiation values ​​can be averaged from several consecutive recorded camera images, for example, over one second or several seconds, to reduce the effect of short-term temperature fluctuations.

[0040] Spatial and / or temporal averaging may be performed for thermal radiation measurements. If the measurements provided by the one or more thermal imaging cameras are radiation temperatures, the radiation temperatures may be converted to thermal radiation values ​​using equation (2) before averaging is performed. Subsequently, equation (1) may be used to convert the thermal radiation value to a radiation temperature if necessary. Step 300 may be performed for several or all ROIs in the furnace, resulting in a set of radiation temperature measurements and / or thermal radiation measurements.

[0041] In step 302, measurements for the surface temperatures in the regions of interest (ROIs) are obtained from the thermal radiation measurements according to one or more embodiments of the invention. The thermal radiation measurements determined in step 300 are corrected for environmental effects, and temperature measurements for the ROIs are derived from the corrected thermal radiation measurements. The corrections performed in step 302 may include, but are not limited to, corrections for the emissivities of the surfaces in the ROIs, corrections for atmospheric absorption and / or emission effects in the furnace, and corrections to reduce the effect of background radiation originating from other regions in the furnace and reflected by the ROIs. The details of step 302 are described in Fig. 4 described.

[0042] In step 304, the temperature measurements obtained for the ROIs are returned. These temperature measurements, or measurements, are understood, after the corrections performed in step 302, to accurately represent surface temperatures in the ROIs. The temperature measurements are communicated to a user and can be displayed, for example, in a table and / or in a graphical visualization, such as a heat map. Furthermore, the temperature measurements can be archived, for example, on a hard drive. The temperature measurements can also be used to control the operation of the furnace. In areas where excessive heat is detected, adjustments can be made to decrease the fuel flow to the one or more burners, and in areas where temperatures are determined to be too low, the fuel flow to the one or more burners can be increased.

[0043] Fig. Figure 4 shows a method for measuring surface temperatures in the regions of interest (ROIs) from the thermal radiation measurements obtained from these ROIs. According to one or more embodiments of the invention, the measurement provides a correction for environmental effects that would otherwise cause uncorrected radiation temperatures to deviate from the actual surface temperatures in the ROIs. To perform a correction of a single thermal radiation measurement obtained from a specific ROI, measurements from other ROIs within the furnace can be used as a basis, as described below.

[0044] In step 400, a ROI for which a surface temperature is to be measured is selected. Many ROIs may be monitored in a furnace according to an embodiment of the invention. For example, the operator of the reforming furnace may wish to determine the surface temperatures of all reforming tubes. Consequently, at least one ROI is located on each of the reforming tubes, and additionally on walls, the floor, the ceiling, the flame fronts, and the like. A selected ROI may therefore be one of the ROIs located on one of the reforming tubes.

[0045] In step 402, the surrounding surfaces to be considered in the subsequently performed surface temperature measurement are determined. A surrounding surface may be a surface of another object of the reforming furnace. In one embodiment of the invention, the radiation from surrounding surfaces influences the radiation temperature measurement obtained from the ROI. In general, only surfaces in a hemisphere in front of the ROI are considered in step 402, as previously described with reference to Fig. 1C. Consequently, the surrounding surfaces determined in step 402 may be specific to the ROI selected in step 400. For example, in a scenario where an ROI located on a reforming tube faces only a wall, a floor, and a ceiling, only the wall, floor, and ceiling may need to be considered surrounding surfaces. All other surfaces in the furnace may be ignored, regardless of whether ROIs are located thereon or not. In contrast, in another scenario where an ROI located on a reforming tube additionally faces a segment of a second wall, an adjacent reforming tube, and a dirty flame (e.g., a flame that produces a significant amount of soot), all of these surfaces are considered surrounding surfaces.

[0046] In step 404, an average radiance is determined for each of the surrounding surfaces to be considered. The average radiance of a surrounding surface may be determined based on a radiance measurement obtained from a region of interest located on the surrounding surface. When multiple regions of interest are located on a single surface, an average radiance may be determined by calculating the mean of the radiances obtained from the regions of interest. Different regions of interest may be weighted differently and / or one or more of the regions of interest may be completely ignored when determining the average radiance.

[0047] In step 406, a geometric view factor is determined for each of the surrounding surfaces to be considered. In general, a geometric view factor for a specific surrounding surface can be understood as a weight applied to the corresponding mean radiation obtained in step 404. Using the geometric view factor obtained in step 406 and the mean radiations determined in step 404, a weighted radiation mean can be calculated as described in step 408. A geometric view factor can be determined using the following surface integral over the i-th surrounding surface A i be determined: gi=1π∬AicosΘindωin, where g i is the geometric view factor of the i-th surrounding surface. A small element of an area dA on the surface A i is at the angle Θ in arranged. Θ inis, as previously mentioned with reference to Fig. 1C, the angle between the considered surface element and the normal of the target surface of the measurement location. dA intersects the small angle dω in at the measurement position. The geometric visibility factors of all surrounding surfaces considered add up to 1.

[0048] In equation (3), an isotropically scattering surface is assumed in the ROI, i.e., a surface that reflects radiation equally in all directions. If this assumption is not justified, angular dependencies can be considered if necessary. These angular dependencies can be described using a bidirectional reflectivity distribution function (BRDF), where reflectivity is a function of the polar angle and the azimuthal angle describing an incident radiation, and a polar angle and azimuthal angle specifying the direction of the reflected radiation. For surfaces that do not scatter completely isotropically, the BDRF must be considered in the geometric view factor equation.

[0049] In step 408, the effective background radiation is determined. According to one embodiment of the invention, the effective background radiation is a weighted sum of the average radiation of the surrounding surfaces to be considered, which is determined in step 404. The weighting is performed using the geometric visibility factors obtained in step 406. Consequently: Sb=∑i=1Ngi Ssi where S b is the signal of the effective background radiation, N is the number of surrounding surfaces considered and Ss i is the signal of the mean radiation of the i-th surrounding surface.

[0050] In step 410, the effective background radiation signal is removed from the radiation measured in the ROI using Ss=Sm−(1−ε)Sbε, where S sis the radiation signal received from the ROI on the surface of the selected reforming tube after subtracting the reflected background radiation, and where ε is the emissivity of the surface in the ROI. Consequently, according to one or more embodiments of the invention, S s the radiation emitted by the reforming tube due to the temperature of the reforming tube in the ROI.

[0051] In step 412, a correction is performed for the effects of atmospheric absorption and / or emission. The correction may be performed by dividing the compensated radiation signal by the absorption and / or emission coefficient determined in step 202. Step 412 may be performed to account for atmospheric effects that would otherwise result in erroneous temperature readings. More specifically, the atmospheric absorption correction accounts for effects that would result in lower temperature readings, whereas the atmospheric gain correction accounts for effects that would result in elevated temperature readings.As previously described in step 202, the correction may take into account the composition of the atmosphere, the distance between the ROI and the camera, and may dynamically provide updates based on predicted atmospheric changes, for example, based on the type of burner fuel, the length of the flame front traversed in a measurement, the fuel flow to the burner, and the like.

[0052] In step 414, the compensated radiation signal is converted to a surface temperature. Equation (1) can be used for the conversion. Steps 410-414 can be performed on the averaged radiation signal obtained from the entire selected ROI. Alternatively or additionally, steps 410-414 can be performed for a radiation signal obtained from a single pixel or separately from multiple pixels within the selected ROI. Performing these steps on individual pixel measurements can enable the determination of a surface temperature with high spatial resolution, for example, to detect local hot spots on the surface of the reforming tubes.

[0053] In step 416, a determination is made as to whether additional ROIs remain for which a surface temperature measurement is to be obtained. Such ROIs may, for example, be located on other reforming tubes. If a determination is made that additional ROIs remain, the method may return to step 400. If no additional ROIs remain, the method may terminate.

[0054] Although the various steps in the flowchart are illustrated and described sequentially, those skilled in the art will recognize that some or all of the steps may be performed in different orders, that they may be combined or omitted, and that some or all of the steps may be performed in parallel. In one embodiment of the invention, the Fig. 2 steps shown parallel to some others in Fig. 2 without departing from the invention.

[0055] Embodiments of the invention may enable accurate measurements of temperatures. Methods and systems according to one or more embodiments of the invention are particularly suitable for demanding environments, such as the interior of furnaces, e.g., furnaces for reforming, annealing, metal or glass production, and the like, where measuring the temperature of an object may be complicated by factors including the emissivity of the object, flame effects, reflection from components, atmospheric effects, and the geometry of the furnace, among others. The temperature measurements may be performed for a single or many regions of interest at any one time or simultaneously.

[0056] A temperature measurement system according to one or more embodiments of the invention can be used for real-time monitoring or real-time control of temperatures in industrial applications involving reformers, boilers, and the like. In a reforming furnace, the furnace temperature can be controlled based on the determined temperature measurements to optimize processes within the reforming furnace. In particular, the temperature measurements can be used to minimize fluctuations in the temperatures of the reforming tube wall, thereby potentially avoiding unfavorable hot spots, and can be used to operate the reformer at a higher reforming temperature without exceeding the maximum allowable temperature of the reforming tube wall.As a result, the lifetime of the reforming tubes can be increased, while the operating point of the reformer can be improved at the same time, resulting in, for example, increased reformer output, shorter preheating times, and the like.

[0057] The system according to one or more embodiments of the invention is based on one or more thermal imaging cameras that simultaneously acquire data from all regions of interest (ROIs) in the furnace. Measurement accuracy can be increased because the method does not require manual targeting of a region of interest with a handheld pyrometer. Since radiation measurements are available immediately and simultaneously from all ROIs, reliable temperature measurements can be obtained even in environments where dynamically varying temperatures in the furnace do not allow temperature measurements based on sequentially obtained radiation measurements. Furthermore, since the system does not require the opening of the furnace doors to perform a radiation measurement, disturbances to the furnace atmosphere associated with opening furnace doors are avoided.

[0058] Temperature sensing solutions according to one or more embodiments of the invention may be more cost-effective and accurate compared to manually performed conventional temperature measurements, may achieve coverage of more areas of interest, and may be performed more frequently (e.g., quickly and continuously) in an automated manner, while reducing risks to personnel.

[0059] Embodiments of the invention may be implemented in virtually any type of computing system, regardless of the platform used. For example, the computing system may be one or more mobile devices (e.g., a wearable computer, a smart phone, a personal digital assistant, a tablet computer, or other mobile device), desktop computers, server computers, slots in a server rack, or any other type of computing device or devices that have at least the minimum processing power, memory, and input and output devices to carry out one or more embodiments of the invention. For example, as described in Fig.5, the computing system or computer system (500) may include one or more computer processors (502), an associated memory (504) (e.g., random access memory (RAM), cache memory, flash memory, and the like), one or more storage devices (506) (e.g., a hard drive, an optical drive such as a compact disk (CD) drive or a digital versatility disk (DVD) drive, a flash memory stick, etc.), and numerous other elements and functions. The one or more computer processors (502) may be an integrated circuit for executing instructions. For example, the one or more computer processors may be one or more cores or micro-cores of a processor.The computing system (500) may further include one or more input devices (510), such as a touchscreen, a keyboard, a mouse, a microphone, a touch-sensitive pad, an electronic pen, or any other type of input device. The computing system (500) may further include one or more output devices (508), such as a screen (e.g., a liquid crystal display (LCD), a plasma display, a touchscreen, a cathode ray tube (CRT) monitor, or other display device), a printer, external memory, or other output device. One or more of the output devices may be the same as or different from the one or more input devices.The computing system (500) may be connected to a network (512) (e.g., a local area network (LAN), a wide area network (WAN), such as the Internet, a cellular network, or another type of network) via a network interface connection (not shown). The one or more input and output devices may be connected locally or remotely (e.g., via the network (512)) to the one or more computer processors (502), the memory (504), and the one or more storage devices (506). There are different types of computing systems, and the aforementioned input and output devices may take other forms.

[0060] Software instructions in the form of computer-readable program code for implementing embodiments of the invention may be stored, in whole or in part, temporarily or permanently on a non-transitory computer-readable medium, such as a CD, DVD, storage device, floppy disk, tape, flash memory, physical memory, or other computer-readable storage medium. In particular, the software instructions may correspond to computer-readable program code that, when executed by one or more processors, is configured to implement embodiments of the invention.

[0061] Furthermore, one or more elements of the aforementioned computing system (500) may be located at a remote location and connected to the other elements via a network (512). Furthermore, one or more embodiments of the invention may be implemented on a distributed system having multiple nodes, wherein each portion of the invention may be located at a different node within the distributed system. In one embodiment of the invention, the node corresponds to a dedicated computing device. Alternatively, the node may correspond to a computer processor with associated physical memory. Alternatively, the node may correspond to a computer processor or a micro-core of a computer processor with shared memory and / or resources.

Claims

[1] A method for measuring furnace temperatures, the method comprising: Obtaining (300) radiation measurements from a plurality of areas of interest (114) using a plurality of thermal imaging cameras (150); Measuring (302) a surface temperature using a radiation measurement obtained from a region of interest selected from the plurality of regions of interest (402), comprising: determining (408) an effective background radiation affecting the selected region of interest using radiation measurements obtained from regions of interest other than the selected region of interest; determining (410) a compensated radiation by removing the effective background radiation from the radiation measurement obtained from the selected region of interest; Correcting (412) the compensated radiation with respect to an atmospheric emission, wherein the correction with respect to the atmospheric emission is determined based on properties of a flame front traversed for the radiation measurement of the selected region of interest, wherein the properties of the flame front include a length of the traversed flame front; and Converting (414) the corrected compensated radiation into the measured surface temperature. [2] The method of claim 1, wherein each of the plurality of regions of interest is a surface region on a reforming tube (108), a wall (104), a floor (112), a ceiling, and / or the flame front. [3] The method of claim 1, wherein the radiation measurement value obtained from the selected region of interest is obtained from a plurality of pixels in the region of interest, averaging spatially and / or temporally. [4] The method of claim 1, wherein the radiation measurement value obtained from the selected region of interest is obtained from a single pixel in the region of interest. [5] The method of claim 1, wherein a thermal imaging camera of the plurality of thermal imaging cameras obtains radiation measurements from a plurality of regions of interest that are a subset of the plurality of regions of interest. [6] The method of claim 1, wherein the radiation measurements are obtained simultaneously; and wherein the surface temperature is measured in real time. [7] The method of claim 1, wherein determining the effective background radiation for the selected region of interest comprises: Selecting surrounding surfaces that add reflected radiation to the radiation measurement obtained from the selected area of ​​interest, wherein each of the surrounding surfaces comprises at least one region of interest of the plurality of regions of interest; Determining average radiations of the surrounding surfaces based on radiation measurements from the at least one region of interest on each of the surrounding surfaces; Determining a weighted average of the mean radiations of the surrounding surfaces, where the weighted average is the effective background radiation. [8] The method of claim 7, wherein the weighted average is determined based on geometric visibility factors of the surrounding surfaces. [9] The method of claim 1, further comprising: Correcting the radiation measurement value obtained from the selected region of interest with respect to an emissivity of the selected region of interest. [10] The method of claim 9, wherein the emissivity is determined by comparing the radiation measurement value obtained from the selected region of interest with a radiation measurement value obtained from a reference body with known emissivity, wherein a temperature of the reference body with the known emissivity is identical to a temperature of the region of interest. [11] The method of claim 1, further comprising: Correcting the compensated radiation with respect to atmospheric absorption. [12] The method of claim 1, wherein the flame front properties include: a type of fuel supplied to a burner (106) that generates the flame front; and / or a fuel flow to the burner that creates the flame front. [13] The method of claim 12, wherein the atmospheric emission correction is dynamically updated based on the fuel flow to the combustor. [14] The method of claim 1, further comprising: Adjusting the measured surface temperature to match a reference surface temperature. [15] A non-transitory computer-readable medium storing instructions for measuring oven temperatures, the instructions including a function to: Obtaining radiation measurements from multiple areas of interest using multiple thermal imaging cameras; Measuring a surface temperature using a radiation measurement obtained from a region of interest selected from the plurality of regions of interest, comprising: Determining an effective background radiation affecting the selected region of interest using radiation measurements obtained from regions of interest other than the selected region of interest; Determining a compensated radiation for removing the effective background radiation from the radiation measurement obtained from the selected region of interest; and Correcting the compensated radiation with respect to an atmospheric emission, wherein the correction with respect to the atmospheric emission is determined on the basis of properties of a flame front traversed for the radiation measurement of the selected region of interest, wherein the properties of the flame front include a length of the traversed flame front; and Converting the corrected compensated radiation into the measured surface temperature. [16] The non-transitory computer-readable medium of claim 15, wherein the radiation measurements are obtained simultaneously; and wherein the surface temperature is measured in real time. [17] The non-transitory computer-readable medium of claim 15, wherein the instructions further comprise a function to: Correcting the compensated radiation with respect to atmospheric absorption, where the properties of the flame front include: a type of fuel supplied to a burner that creates the flame front; and / or a fuel flow to the burner that creates the flame front. [18] A system (100) for measuring furnace temperatures, comprising: several thermal imaging cameras; a processing unit configured to: To obtain radiation measurements from multiple areas of interest using multiple thermal imaging cameras; to measure a surface temperature using a radiation measurement obtained from a region of interest selected from the plurality of regions of interest, comprising: Determining an effective background radiation affecting the selected region of interest using radiation measurements obtained from regions of interest other than the selected region of interest; Determining a compensated radiation by removing the effective background radiation from the radiation measurement obtained from the selected region of interest, wherein the processing unit is further configured to: to correct the compensated radiation with respect to an atmospheric emission, wherein the correction with respect to the atmospheric emission is determined on the basis of properties of a flame front traversed for the radiation measurement of the selected region of interest, wherein the properties of the flame front include a length of the traversed flame front; and Converting the corrected compensated radiation into the measured surface temperature. [19] The system according to claim 18, wherein the radiation measurements are obtained simultaneously; and where the surface temperature is measured in real time. [20] The system of claim 18, wherein the processing unit is further configured to: to correct the compensated radiation with respect to atmospheric absorption, where the properties of the flame front include: a type of fuel supplied to a burner that creates the flame front; and / or a fuel flow to the burner that creates the flame front.

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