SYSTEM AND METHOD FOR MONITORING AND CONTROLLING FURNACE - Patent application

Abstract

The present invention discloses a furnace monitoring and / or control system. The system includes a thermal imaging device located at a distance from the exterior of the furnace and generating field signals of the furnace, a signal processing unit configured and programmed to receive these field signals and generate a temperature map of the exterior of the furnace, and means for displaying the temperature map of the exterior of the furnace. The system may further include an analysis unit configured and programmed to generate control signals based on the received field signals or the temperature map, and a furnace controller configured to receive these control signals, apply the control signals, and control the furnace. The present invention also describes a method for controlling the operation of a furnace using the above-described system.

Description

[Technical Field]

[0001] The present invention relates to a method and system for monitoring or controlling furnace operation, and more particularly to monitoring or controlling furnace operation using thermal imaging techniques. [Background technology]

[0002] Various industries (eg, steel, aluminum, and glass) all rely on furnaces for manufacturing processes.

[0003] It is known in the art to monitor the physical integrity of furnaces, and particularly the refractory materials of the furnace construction.

[0004] US 2013 / 120738 A1 relates to a metal box or container lined with refractory material and designed to hold material at high temperatures such as those used in industrial applications (e.g., gasification processes in chemical and power production, electric arc furnaces (EAF), basic oxygen furnaces (BOF), ladle furnaces, blast furnaces, degassing furnaces, and argon oxygen decarburization (AOD) furnaces in the steel industry). It is known from US 2013 / 120738 A1 to monitor the integrity of such containers protected by refractory material using a first radiation detector configured to measure the external surface temperature of the container and a first radiation source configured to measure the thickness of the refractory material, whereby a central controller displays the measured values ​​of the external surface temperature of the container and the measured values ​​of the thickness of the refractory material to a user.

[0005] U.S. Patent Application Publication No. 2017 / 131033 discloses a system for assessing and monitoring the condition of materials forming parts of an asset (e.g., a refractory furnace). The system operates to identify defects and measure erosion profiles and thicknesses of different materials, including refractory materials, in industrial furnaces using radio frequency signals. The system includes a software management subsystem configured to implement signal processing techniques, process collected data, generate reports, visualize conditions, estimate remaining operational life, determine the level of penetration of molten material into the surrounding layers of the furnace, and enable a user to monitor the condition of the furnace both locally and remotely.

[0006] U.S. Patent Application Publication No. 2014 / 123758 discloses a system and method for acoustically monitoring the structural integrity and physical deformation of a metallurgical furnace, including during furnace operation. Acoustic sensors (and optionally other sensors) are mounted in the furnace. Acoustic emission events generated in the furnace are analyzed to identify conditions that exceed one or more thresholds. The location of the acoustic emission may be identified and reported. An output signal may be generated in response to the acoustic emission. The location of the acoustic emission may be used to identify the location of a potential fault in the furnace.

[0007] Thus, the purpose of the above-described method and system is to monitor the structural integrity of a furnace.

[0008] Furnaces are prone to inefficiencies and failures due to a number of reasons. Examples include coking involving the furnace interior, underheating and overheating, combustor misalignment, and product leaks. Additionally, process conditions significantly affect furnace performance. If these failures or suboptimal conditions are not corrected, they can cause quality problems, energy waste, and even the shutdown of the entire process line.

[0009] For this reason, it is further known to monitor the operation of the furnace.

[0010] U.S. Patent Application Publication No. 2017 / 261264 discloses a fault diagnosis method for an electric magnesia furnace, including: 1) deploying six cameras; 2) capturing video information using the six cameras during furnace operation, transmitting the video information to a control center, and then analyzing the video information using a chip in the control center. The chip uses a multi-view-based fault diagnosis method. The method includes: 2-1) comparing the difference between two consecutive frame histograms for shot segmentation; 2-2) calculating a set of characteristic values ​​for each shot captured in step 2-1, and then calculating color, texture, and motion vector information; 2-3) evaluating shot importance through entropy; 2-4) clustering shots together by calculating similarity; 2-5) generating and optimizing a multi-view video summary using a multi-objective optimization model; and 2-6) performing fault detection and diagnosis. 3) displaying the results of the fault detection and diagnosis on a host computer interface in the control center.

[0011] Other methods for monitoring furnace operation include temperature detection and infrared imaging. Sensors or infrared cameras are placed inside the furnace or near the observation port and measure a single point or a very limited area inside the furnace. As a result, operators cannot obtain an overview and form a direct correlation between processing steps and furnace performance. U.S. Patent Application Publication No. 2017 / 261262 discloses a common and specific information-based fault diagnosis device for an EFMF (electric magnesium fusion furnace) that uses six cameras to perform video information. Three cameras are positioned relative to the three electrodes on the surface layer of the EFMF and are aimed at the electrodes of the EFMF to monitor for furnace-generated faults. The remaining cameras are positioned symmetrically around the furnace body at a 120-degree angle and are aimed at the furnace body to monitor for the occurrence of furnace leaks. A control center connected to the six cameras collects and analyzes the video information acquired by the six cameras. The analyzed data is displayed on a host computer interface in the control center. Therefore, six cameras are applied to monitor the furnace surface and furnace body according to the multi-view concept, so as to successfully detect, diagnose and identify furnace-generated faults and furnace leakage faults through the extracted common and special information. Temperature detection and thermal imaging are not mentioned. Summary of the Invention [Means for solving the problem]

[0012] It is an object of the present invention to provide a system and method based on thermal imaging technology, particularly infrared (IR) cameras, that allows for global data collection and monitoring of an entire furnace over time. Appropriate control algorithms can be applied to process the collected data and generate control signals that can then be fed to a furnace controller to optimize furnace performance. Improved furnace control offers the potential for significant energy savings and reductions in emissions, particularly nitrogen oxides. The entire system is designed to be rugged, easy to install, and relatively transparent to the furnace operator.

[0013] In one aspect, the present invention discloses a furnace monitoring system including a thermal imaging device positioned at a distance from the exterior of the furnace and generating field signals of the furnace, the monitoring system further including a signal processing unit configured and programmed to receive these field signals and generate a temperature map of the exterior of the furnace, and a human machine interface (HMI) for displaying the temperature map locally or remotely.

[0014] In another embodiment, the thermal imaging device comprises a CCD (charge coupled device) camera.

[0015] According to the invention, the temperature map is divided into several zones corresponding to different components of the furnace, selected from the group comprising one or more combustors, inlets, outlets, flue gas paths, or a combination of at least two of these components.

[0016] In another aspect, the present invention discloses a furnace control system including a thermal imaging device positioned at a distance from the exterior of the furnace and generating field signals of the furnace, the furnace control system further including a signal processing unit configured and programmed to receive these field signals and generate a temperature map of the exterior of the furnace, an HMI configured and programmed to display the temperature map locally or remotely, an analysis unit configured and programmed to generate control signals based on the received field signals or the generated temperature map, and a furnace controller configured to receive these control signals, apply the control signals, and control the furnace.

[0017] In another aspect, the present invention discloses a method for controlling operation of a furnace using the furnace control system described above, the method comprising: generating a field signal external to the furnace over a range of time using a thermal imaging device; transmitting the field signals to a signal processing unit and generating a temperature map of the exterior of the furnace over a range of time using the signal processing unit; displaying the temperature map locally or remotely by an HMI; applying, by an analysis unit, a control algorithm to the received field signals or the generated temperature map to generate a control signal; controlling operation of the furnace with a furnace controller using the generated control signal; Includes.

[0018] For the above-described method, the time range includes multiple operating steps of the described furnace. Examples of such possible operating steps include charging the furnace through a charging port, discharging the furnace through a discharging port, heating the charge material without a phase change of the charge material, causing the supplied heat to melt the solid charge material, refining the melt in the furnace, etc.

[0019] In the present invention, a thermal imaging device, particularly an infrared camera, is placed outside the furnace at a distance from the furnace. Thus, the present invention eliminates the need for expensive heat-resistant materials or cooling accessories for the imaging device. Once properly positioned, the thermal imaging device and corresponding signal processing unit generate a thermal profile or temperature map of the furnace over time. The thermal profile or temperature map is divided into different zones, focusing on selected components of the furnace. This improves imaging sensitivity.

[0020] Because field signals and temperature maps are generated over a range of time during continuous furnace operation, heat leaks, hot spots, or other anomalies associated with particular components or operational steps are readily visible to the operator, either locally or remotely. For example, field signal and temperature map zones corresponding to inlet or outlet and outlet points, respectively, reveal the sequence and frequency of inlet and outlet operations, and the duration of each of these processing steps. Such information not only helps the operator monitor the physical condition of the furnace and furnace components and prevent catastrophic failures, but can also help the operator optimize furnace operation, thereby further enabling the processing performed in the furnace.

[0021] Additionally, information obtained from the field signals and / or temperature maps may be input to an analysis unit to generate control signals that are supplied to a furnace controller that controls the furnace.

[0022] The control algorithms applied by the analysis unit may be or have been developed by mathematical calculations or simulations of historical (ie, pre-collected) operating data.

[0023] In summary, the present invention provides an economical, near real-time method for monitoring, optimizing, and controlling furnace operation, so that preventative maintenance can be performed, if necessary, to avoid costly, unplanned breakdowns or shutdowns.

[0024] The accompanying drawings are to be understood as examples of the present invention and do not in any way limit the scope of the invention. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic diagram showing components of a furnace monitoring and control system. [Figure 2] 1 is a flow chart illustrating the steps of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] In FIG. 1, the reference symbols indicate the following features: 1—furnace, 2—CCD camera, 3—signal processing unit, 4—analysis unit, 5—furnace controller, 6—combustor, 7—inlet, 8—outlet, 9—flue gas path.

[0027] In an exemplary embodiment, a thermal imager using multiple infrared wavelengths is used to obtain fast and accurate temperature mapping of the entire furnace during furnace operation. For example, the thermal imager includes a CCD camera that sends a field signal to a beam splitter. One beam should be used to optically focus the camera, and the other beam should be sent to a signal processing unit (e.g., a computer containing data processing software).

[0028] In this context, a "field signal" refers to a mapping of a parameter over a two- or three-dimensional region or zone of interest, as opposed to a fixed-time or "spot" signal that measures the parameter at only individual points.

[0029] A CCD camera is positioned to capture signals from all areas of interest, including the combustor, all observation, inlet and outlet ports, and the flue gas path. The collected infrared field signals can be digitally processed into an artificial color temperature map (different colors indicate different temperatures) and stored or displayed on a monitor. The monitor or other display means may be located near the furnace or away from the furnace in a remote area.

[0030] The measurement field of the CCD camera is divided into different zones corresponding to selected components of the furnace (e.g., the inlet, outlet, combustor, observation port for observing the combustor, and flue gas path). According to an embodiment of the present invention, only field signals from zones corresponding to such selected components are collected and processed by the signal processing unit. In this way, data sensitivity and data processing speed can be increased, and the resulting temperature map is clearer to the operator.

[0031] An operator observing the furnace temperature map, either locally or remotely, can compare the measured temperature with the furnace's setpoint temperature, corresponding to standard or desired furnace operation, and adjust operating parameters according to the operator's experience or established protocol. For example, accurate temperature measurements can be obtained by comparing pixel intensities at two different infrared wavelengths. Near-infrared wavelengths between 700 and 800 nm may be used.

[0032] In addition to or instead of manual control by an operator, digitally processed field signals or temperature maps are sent to an analysis unit. Software based on embedded control algorithms can run locally or remotely in the analysis unit, e.g., on a cloud-based server, to generate control signals capable of performing a variety of functions. The control algorithm may generate control signals, among other things, to minimize the difference between the field temperature setpoint and the measured field temperature. The software allows for data storage and historical information review. The control signals are sent to a furnace controller that controls the furnace in a closed-loop or open-loop manner to maintain operating parameters within safety or control limits, automatically tune operating parameters to preset values, or rapidly respond to warning signs. To do so, the analysis unit may compare actual data values, alarm or warning thresholds, determine whether an alarm is desirable or necessary, and may further analyze the combination of sensor data against theoretical and / or experimental databases to determine whether another condition exists that requires maintenance intervention or attention. Such analysis and warnings may be performed by a cloud computing system. The alarm may be provided through any standard method, including the use of lights or audible warnings, in the control room, combustor, flow control skid, or any other convenient location. The furnace controller may be a primary or auxiliary controller configured to receive control signals to assist in furnace control.

[0033] Using the furnace monitoring and control system described above, external furnace and load field temperature data can be generated essentially in real time and acquired or stored over time, including various processing steps. A mathematical model or simulation is constructed based on historical data for more optimal operating conditions. Field control is performed by comparison with an optimization database. Field control works in conjunction with traditional controllers to make adjustments, mitigate hot spots and instabilities, and optimize combustion performance. Field control consists of minimizing the difference between a set of field setpoints and actual field measurements, rather than matching setpoints to a limited number of measurements.

[0034] The field signals and the resulting temperature map can not only monitor the safe operation of the furnace and determine whether maintenance intervention is required, but also may be used to optimize furnace operation.

[0035] For example, the control algorithm may determine necessary adjustments to the air-fuel ratio, the burn rate for all or part of the combustor, the sequence and frequency of insertions and ejections, and the time intervals for each process step.

[0036] For example, field signals corresponding to a combustor or observation port for the combustor can verify proper operation of the combustor of interest in near real time, and based on the field signals corresponding to the combustor or observation port, or the corresponding zones in the generated temperature map, any malfunctions (e.g., flame extinguishing or flame misalignment) or areas for optimization (e.g., increasing or decreasing the firing rate to obtain a desired temperature profile within the furnace) can be identified.

[0037] The field signals corresponding to the charging port can be observed in near real time based on the corresponding zone of the field signals or generated temperature map corresponding to the charging port, whether the charging port is open or closed, whether the open port is fully open or the closed port is fully closed, and the time the charging port is open. It can also be observed via these field signals or generated temperature map whether material (charge material) is being fed into the furnace through the charging port and whether the charging port remains open for much longer than the time required to feed the charge material due to its effect on the thermal image of the furnace.

[0038] Similarly, the field signals corresponding to the outlets can be used to monitor in near real time whether the outlets are open or closed, whether closure is complete, and how long the outlets remain open. It can also be used to monitor whether material is being effectively ejected through the outlets, including whether there is a time lapse between the opening of the outlets and the start of material being ejected, and / or whether there is a time lapse between the end of ejection and the closing of the outlet.

[0039] The time that a furnace throat, particularly a charge or discharge throat, remains open during a production cycle is an important factor with respect to furnace performance. In fact, open throats can cause significant heat loss and the ingress of significant amounts of unheated nitrogen-containing ambient air. Therefore, keeping the duration of open throats to a minimum significantly improves furnace efficiency.

[0040] The field signals corresponding to the flue gas path and the corresponding zones of the temperature map produced may provide a near real-time indication of the level of heat loss through the flue gas path. Furthermore, if the flue gas path includes a post-combustion zone in which combustibles present in the flue gas are burned with an oxidizer, the field signals corresponding to the post-combustion zone in the flue gas path and the corresponding zones of the temperature map may provide a near real-time indication of (changes in) the level of combustibles in the flue gases discharged from the furnace.

[0041] Thus, the field signals produced by the thermal imaging device and the temperature map produced by the signal processing unit provide important information regarding the operation of the furnace, any anomalies and opportunities to improve the efficiency of furnace operation in near real time.

[0042] As a result, objectives (e.g., increased thermal efficiency, reduced nitrogen oxide emissions, elimination of hot spots, and prevention of shutdowns) are achieved. In all embodiments, signals are transmitted via wires or a network (e.g., the Internet, an intranet, a local area network (LAN), and a wide area network (WAN)) via wired and / or wireless communication. The data processing unit may include a local or cloud-based server that can store and retrieve data. FIG. 1 illustrates a furnace monitoring and control system of the present invention. The exemplary furnace 1 includes a furnace body, a combustor 6, an insertion or charging port 7, a discharge port 8, and a flue gas path 9. While only one combustor is shown in the drawing, a furnace may include multiple combustors, and all or some (preferably all) of these combustors may be monitored using the furnace monitoring or control system of the present invention. The insertion port 7 is opened to feed raw materials into the furnace and closed after the feed is complete. Similarly, the discharge port 8 is opened and closed to remove products from the furnace. The opening durations of the inlet and outlet ports, their relative order, and the time intervals between steps affect the energy efficiency of furnace performance. At least one thermal imaging device, in this case a CCD camera 2, is placed at a predetermined location outside the furnace so that measurements can be taken of selected components of the furnace. Because the signals are collected over the entire field and not concentrated at a few distinct points, they are called field signals. These field signals are transmitted to a signal processing unit 3 via a wired or wireless network. The signal processing unit 3 converts the field signals into a temperature map, which is displayed via an integrated display device or sent to a remote display device (HMI), such as a mobile phone, for viewing by an operator. If more control functions are desired, the temperature map or raw field signals are fed to an analysis unit 4, which utilizes control algorithms to generate control signals based on comparison of the data to ideal operating conditions. The analysis unit 4 can be a standalone computer or be combined with the signal processing unit 3 into a single device. The control signals are then transmitted to a furnace controller 5, facilitating control of the furnace's operation.Typically, furnace controller 5 relies on signals from other sensors to implement primary control, with the signal primarily captured by the thermal imager serving as a source of auxiliary control.

[0043] The steps for monitoring and controlling the furnace are summarized in the flow chart of FIG.

[0044] Although the present invention has been described in detail with reference to specific embodiments, it will be understood that those skilled in the art can use variations and modifications of the described embodiments, and therefore, these variations and modifications also fall within the spirit and scope of the present invention as defined by the appended claims and equivalents of the claims.

Claims

1. 1. A furnace monitoring system for monitoring a furnace (1) over a range of time during furnace operation, comprising: a) a thermal imaging device (2) located outside the furnace (1) at a distance from the exterior of the furnace (1) and generating a field signal of the furnace (1); b) a signal processing unit (3) configured and programmed to receive the field signals and generate a temperature map of the exterior of the furnace (1); c) means (4) for displaying said temperature map locally or remotely; Including, - said furnace monitoring system is a system for monitoring said furnace (1) over a range of time during furnace operation, the generated temperature map is divided into several zones corresponding to different components of the furnace, selected from the combustor (6), the observation port for observing the combustor, the inlet (7), the outlet (8) and the flue gas channel (9); the generated temperature map is generated only in some zones corresponding to different components of the furnace, selected from the combustor (6), the observation port for combustor observation, the inlet (7), the outlet (8) and the flue gas channel (9); A furnace monitoring system comprising:

2. 2. A furnace monitoring system according to claim 1, comprising an infrared CCD camera (2) positioned at a distance from the exterior of the furnace (1) and generating a temperature map of the exterior of the furnace (1), said temperature map being capable of being observed locally or remotely.

3. 10. A furnace control system for controlling operation of a furnace over a range of time, comprising the furnace monitoring system of claim 1, d) an analysis unit (4) configured and programmed to generate a control signal based on the received field signal or the generated temperature map; e) a furnace controller (5) configured to receive said control signal, apply said control signal and control said furnace (1); a furnace control system further comprising:

4. 4. A method of controlling the operation of a furnace (1) over a range of time using the furnace control system of claim 3, comprising the steps of: a) generating field signals external to the furnace (1) over said range of time during furnace operation using a thermal imaging device (2); b) transmitting said field signals to a signal processing unit (3) to generate, over said range of time, a temperature map of the exterior of said furnace (1) divided into several zones corresponding to different components of said furnace (1) selected from the combustor (6), the inlet (7), the outlet (8) and the flue gas duct (9), and displaying said temperature map locally or remotely; c) applying a control algorithm to the received field signals or the generated temperature map using an analysis unit (4) to generate a control signal; d) controlling the operation of the furnace (1) with a furnace controller (5) using the generated control signal; A method comprising:

5. 5. The method according to claim 4, wherein steps a) and b) are performed by a CCD camera (2).

6. 5. The method of claim 4, wherein only field signals from zones corresponding to selected components of the furnace (1) are processed by the signal processing unit (3).

7. The method of claim 4 , wherein the algorithm runs on a cloud-based server.

8. 5. The method of claim 4, wherein the range of time includes multiple operating steps of the furnace (1).

9. 9. The method according to claim 8, wherein the multiple operating steps include feeding raw materials into the furnace (1) through the inlet (7) and discharging residue from the outlet (8).

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