KR20200118493A - Flame image analysis for furnace combustion control - Google Patents

Abstract

The operation of the furnace combustion control system is responsive to image analysis, and correlation of the flame produced by combustion in the furnace, outside or within the furnace, to correlate the image with the carbon monoxide content of the flame. It is controlled by adjustment of the flow of oxygen and/or fuel into the furnace.

Description

Flame image analysis for furnace combustion control

The present invention is intended to control and/or reduce the emission of carbon monoxide from the furnace, in which the material is heated and the heating can cause the formation of carbon monoxide (a furnace is a closed chamber such as a combustion chamber in which fuel and gaseous oxidants are burned. Means space) for the operation of the combustion control system.

The operation of the material being heated in the furnace can lead to the formation of carbon monoxide in the furnace. The mechanisms by which carbon monoxide can be formed include incomplete combustion of fuel in the furnace; Incomplete combustion of combustible materials when the material to be heated in the furnace is also intended to be burned; And/or conversion of the carbonaceous material present in or on the material to be heated. Examples of such transformations include pyrolysis and/or incomplete combustion of carbonaceous materials.

When carbon monoxide is formed in the furnace, the release of carbon monoxide out of the furnace is usually undesirable. Various techniques exist for the removal of carbon monoxide from gaseous offgas leaving the furnace, such as absorption of carbon monoxide into an absorbent, or addition of reactants that react with carbon monoxide to the offgas. Such techniques present problems such as cost and difficulty of implementation and control.

The present invention provides an efficient method for avoiding the emission of carbon monoxide from the furnace. The invention also provides an efficient method for controlling the operation of a furnace to achieve improved efficiency and production rates.

One aspect of the present invention is a method of heating a material in a furnace, the method

(A) A material containing carbonaceous substances in a furnace having a flue is heated using heat generated by combustion of fuel and gaseous oxidizer supplied into the furnace in the furnace, and derived from carbonaceous substances. Producing carbon monoxide that is formed in the furnace, a flame that can extend out of the furnace from the flue;

(B) Flame from images of the flame taken outside or inside the furnace by a digital camera located outside the furnace, by electronically expressing at least one parameter corresponding to the intensity of the flame and corresponding to the concentration of carbon monoxide in the flame. Characterizing the concentration of carbon monoxide in the flame and determining the characterized concentration of carbon monoxide in the flame from predetermined correlations of actual concentrations of carbon monoxide in the flame for the expressed values of the at least one parameter;

(C) comparing the characterized concentration of carbon monoxide in the flame as characterized according to step (B) with a pre-established threshold concentration value for said concentration;

(D) When the characterized concentration of carbon monoxide in the flame exceeds the pre-established threshold concentration value, in the furnace, continuing to characterize the concentration of carbon monoxide in the flame from images of the flame taken by a digital camera outside the furnace. The amount of oxygen, the amount of fuel, or both oxygen and fuel supplied into the furnace available to react to reduce the characterized concentration of carbon monoxide in the flame for a predetermined length of time below a pre-established threshold concentration value. Adjusting to an effective amount or amounts.

Another aspect of the present invention is a method of heating the material in the furnace, the method

(A) A material containing a carbonaceous material in a furnace having a flue is heated by using heat generated by combustion in the furnace of fuel and gaseous oxidant supplied into the furnace, thereby reducing carbon monoxide derived from the carbonaceous material. Generating-a flame is formed in the furnace that can extend out of the furnace from the flue;

(B) By electronically expressing at least one parameter corresponding to the intensity of the flame and corresponding to the concentration of carbon monoxide in the flame, from images of the flame taken outside the furnace or inside the furnace by a digital camera located outside the furnace. Characterizing the concentration of carbon monoxide in the flame and determining the characterized concentration of carbon monoxide in the flame from predetermined correlations of actual concentrations of carbon monoxide in the flame for expressed values of at least one parameter;

(C) comparing the characterized concentration of carbon monoxide in the flame as characterized according to step (B) with a pre-established threshold concentration value for said concentration;

(D) When the characterized concentration of carbon monoxide in the flame exceeds the pre-established threshold concentration value, carbon monoxide in the furnace, while continuing to characterize the concentration of carbon monoxide in the flame from images of the flame taken by a digital camera outside the furnace. Adjusting the amount of oxygen supplied into the furnace available to react with the amount effective to lower the characterized concentration of carbon monoxide in the flame below a pre-established threshold concentration value for a predetermined length of time.

1 is a schematic diagram showing how the present invention can be implemented on a furnace apparatus.
2 is a chart showing the sequence of steps of the present invention.

The present invention is useful for heating any material that can be heated in a furnace. Examples of such materials include finished products as well as ferrous metals such as iron and steel, including scrap, as well as iron ores and other compounds. Further examples include finished products as well as non-ferrous metals, such as aluminum and copper, and ores and other compounds thereof, including scrap. Heating of any such materials is employed to prepare them for further chemical and/or physical treatment.

The invention is also useful for heating materials in which some or all of the materials are melted. In such an operation, the material may include any of the metals, metal oxides and other metal compounds described above. Other examples include products that are melted together in a glass making furnace to form molten glass; Such materials include pieces of recycled glass known as cullets, and raw materials known as batches that are melted together to make the glass, such materials are typically sodium oxide, potassium oxide, and silicates of sodium and potassium. Includes. Another example of such an operation is a cement kiln, where raw materials, typically comprising lime or limestone, and silica and/or aluminosilicate (clay) and other desired additives are heated together so that they melt and react with each other. To form the compounds that make up the cement.

The invention is also useful for heating materials, such as incinerators, in which some or all of the materials must be burned. Materials that can be heated in the practice of this aspect of the invention include all combustible products, such as carbonaceous fuels, and solid waste.

Any of the materials treated according to the present invention have the property that they contain some carbonaceous material, so heating the material can cause carbon monoxide to form in the furnace from the carbonaceous material. The carbonaceous material present may be an organic compound present in the material being heated and/or may include some or all of the material that is heated and then burned in the furnace. For example, scraps comprising aluminum, copper, iron and/or steel may have carbonaceous materials such as paints or other organic coatings, organic foods and/or human waste thereon. A cullet present in the glassmaking material may retain on it organic matter, which is a residue of food or other organic matter that was present on the cullet before it was recycled as a cullet.

The carbon monoxide formed in the furnace is caused by incomplete combustion of the fuel in the furnace; Incomplete combustion of combustible materials when the material to be heated in the furnace is also intended to be burned; And/or transformation of the carbonaceous material in or on the material to be heated, examples of such transformations including pyrolysis or incomplete combustion of the carbonaceous material, to be produced by any one or more of several possible mechanisms. I can. Just as carbon monoxide emissions from a furnace are undesirable irrespective of the source of carbon monoxide, the present invention is useful irrespective of the source or mechanism by which carbon monoxide, which is at risk of being released from the furnace, is formed therefrom.

1, a furnace 1 is shown in cross section. The furnace shown has a shape that is typical of a furnace that can be rotated about a horizontal axis in the embodiment shown in Fig. 1, but the invention can also be practiced with furnaces of any other type and shape. In the furnace 1, the material to be heated is marked with 2. The material 2 is heated by the heat from the flame 4 formed in the furnace by combustion of the fuel 13 and the oxidant 12 in the burner 11. Suitable fuel 13 may be any combustible carbonaceous material, preferred examples of which include methane, natural gas, and atomized fuel oil. Suitable oxidizing agents supplied at 12 include oxygen, such as air, oxygen-rich air, and any gaseous product containing a stream having an oxygen content of at least 50% by volume, preferably at least 90% by volume. Streams with such elevated oxygen content are commercially available from any of several suppliers of atmospheric gas. While one flame 4 is shown, a furnace in which the present invention may be practiced may comprise more than one burner 11 and more than one flame 4.

The furnace 1 comprises at least one flue 6 through which gaseous products can exit the furnace 1. The gaseous products leaving the flue 6 include gaseous products of combustion between the oxidizer 12 and the fuel 13, such as carbon dioxide and water vapor, and may contain volatile organic compounds (VOC) and may contain carbon monoxide. In a practical application of the invention, if only one flue 6 is present, the flame 15 can extend from the outlet 7 of the flue 6. If more than one flue 6 is present, there may be a flame 15 extending from at least one outlet 7 of at least one flue 6. Carbon monoxide may be present in flame 15 and may or may not be completely burned in flame 15.

The furnace 1 may include a sight port 10 in the wall of the furnace, through which the flame 4 inside the furnace 1 can be observed from outside the furnace 1.

According to the present invention, the camera 21 is located outside the furnace 1. The camera 21 includes an aperture 22 through which the camera 21 receives an image. In one embodiment of the invention, the camera 21 is positioned relative to the furnace 1 such that the aperture 22 of the camera 21 faces toward the flame 15. In another embodiment of the present invention, the camera 21 has the aperture 22 of the camera 21 aligned with the sight port 10, so that the camera 21 captures an image of the flame 4 inside the furnace 1 It is positioned relative to the furnace 1 so that it can be received.

The camera 21 is a digital camera, which means that the camera 21 detects one or more characteristics of the object (in this case, the detected characteristic includes at least the intensity of the flame toward which the camera 21 is directed), and the detection It means that the image corresponding to the specified characteristics is electronically expressed in digital form. Digital cameras with this capability are commercially available. These may be standalone units, or they may be part of an equipment item that also has additional functional capabilities (eg, telephony, time recording, etc.).

Still referring to FIG. 1, the control device 25 controls the flow rate of the oxidizer 12 and the fuel 13 to the burner 11 (or to the multiple burners if more than one burner 11 is present). do. Optionally but preferably, a lance 27 is provided to release supplemental oxidant into the furnace 1 when additional oxidant has to be put into the furnace 1. The flow of oxidant through the lance 27 is controlled by a control device 29. The oxidizing agent that can be introduced into the furnace 1 through the lance 27 may be air, oxygen-rich air, or a higher purity oxidizing agent with an oxygen content of at least 50% by volume and even at least 90% by volume. The oxygen content of the oxidizing agent supplied into the furnace 1 through the lance 27 may be the same or different with respect to the oxygen content of the oxidizing agent 12 supplied into the furnace 1.

In FIG. 1, block 23 refers to a complete system that performs the sequence of steps presented as 31, 33 and 35 in FIG. 2. The system may exist in one integrated device, or the components performing certain steps may be physically separated from other components and connected to each other by suitable cables or by cableless wireless connections. Some or all of the components may be included in the camera 21. However, for ease of function and due to the possibility that the camera 21 can be placed in an environment that can be hot and dusty and thus potentially harsh on a component such as a processor, the camera 21 can be physically removed from other components. Separated into, the camera 21 is preferably connected by cable or wireless connection to a component that performs step 31 at least first following acquisition of the image by the camera 21. As can be seen in Figure 1, the system 23 is connected to the camera 21 to receive input from the camera 21, the system 23 is the control device 25 and (if present) the control device ( 29), and provides signals to the control devices 25, 29.

In operation, combustion is carried out inside the furnace 1 in the presence of the material 2 in the furnace 1. A flame is formed in the furnace, which can appear as a flame 15 extending from the opening 7 of the flue 6. In one embodiment of the present invention, the camera 21 faces the flame 15 and an image of the flame 15 is received through the aperture 22. In another embodiment of the present invention, the camera 21 faces toward the furnace 1, so that an image of the flame 4 inside the furnace 1 is received at the aperture 22 through the sight port 10. The flames 15 or 4 can be very bright, so the aperture 22 and exposure must be adjusted to prevent focal blooming of the image. In some situations, it may be desirable to be able to dynamically adjust the exposure of an image so that an appropriate resolution is achieved when the image is very dark. In most situations, such dynamic adjustment is not necessary. The view factor and resolution of the camera image should be such that the image size is at least 50 x 50 pixels, preferably at least 300 x 300 pixels. One skilled in the art can readily determine the appropriate image resolution and image view factor for a given distance of camera 21 from flame 15 or 4 and for a given size of flame 15 or 4. Camera 21 generates a digital electronic image of flame 15 or flame 4 based on at least one parameter of the flame, such as the intensity of flame 15 or flame 4. The electronic image is electronically transmitted by the camera 21 to the device performing step 31.

In step 31, the signal corresponding to the image of the flame 15 or 4 represents the intensity of the flame or various intensities, and one or more values which may include various values over the area of the flame within the field of view of the camera 21 Is converted to Intensities are detected and expressed digitally to produce an array of values corresponding to the detected intensities. The detected intensity parameter also corresponds to the concentration of carbon monoxide present in the flame.

In step 33, the detected intensity parameter is compared with a pre-established correlation of the intensity parameter to the actual concentration of carbon monoxide in the flame. Pre-established correlations are achieved by simultaneously measuring the concentration of carbon monoxide in the flame through gas sampling using a gas sampling probe followed by analysis of the sampled gas, or through established techniques such as continuous emission monitoring, and detected by camera 21. By observing the values of the expressed parameters derived in step 31 from the intensity-based values as described, and recording the measured concentrations and parameter values together, where they can be read together, for example in a computer or in a created catalog. Can be established. In this way, each intensity parameter expressed by the system corresponds to the actual concentration value of carbon monoxide in the flame. Determination of the existing correlation between the expressed parameter and the measured carbon monoxide concentration may have already been carried out during the initial setup of the system in the furnace, and usually does not need to be repeated in a given furnace each time the furnace is running. However, the operator may find that it is desirable to establish a new set of correlations for different furnaces as well as for a given furnace in situations where the conditions under which a given furnace should be operated will be quite different.

The system described herein can be used to achieve any of several methods of controlling furnace operation. One such method is to control carbon monoxide emissions by controlling the oxygen supply to the furnace, which is now described:

The operation of the furnace will have a pre-established value for the concentration of carbon monoxide in the flame, so values of carbon monoxide concentration exceeding that value are unacceptable and must be lowered. Typical values of excess carbon monoxide may range from 3% by volume to 30% by volume, but the value may vary depending on the location, the nature of the material 2 heated in the furnace 1, or other conditions. The pre-established value is any value of importance to the operator, such as values indicating an excessive risk of environmental damage, or indicating a risk violation of applicable environmental regulations, or indicating an undesirable imbalance between the economic and thermodynamic conditions in the furnace. Is based on a factor or group of factors.

In step 33, a pre-established value for the concentration of carbon monoxide in the flame (which may also be referred to as a threshold or set point) is stored, and a detected intensity parameter corresponding to the carbon monoxide concentration in the flame at any one point in time is stored. It is compared with a pre-established threshold. The comparison may be performed at any desired rate, but preferably the comparison is performed at a rate of once every 2 to 5 seconds. Preferably the comparison is carried out automatically by means of a suitably programmed controller.

If the detected and processed intensity parameter corresponds to the actual carbon monoxide concentration in the flame above a pre-established threshold, the system performs an action resulting in additional oxygen being provided in the furnace 1. In FIG. 2, this action is represented in step 33 as generating a signal that activates the combustion control system 35 to allow additional oxygen to be present in the furnace 1. The additional oxygen will react with the carbon monoxide present in the furnace, so less carbon monoxide leaves the furnace 1 through the flue 6 in the flame 15 or elsewhere. By any of several modes, additional oxygen may be provided into the furnace 1 to react with the detected excess carbon monoxide. For example, one such mode is the control system 35 of oxygen 12 supplied into the furnace 1 through the burner 11 without increasing the flow rate of the fuel 13 into the furnace 1. It is to increase the amount. Another possible mode is supplemental oxidant, or an increased amount of supplemental oxygen, via supplementary supply line 29 (shown in FIG. 1), also without increasing the flow rate of fuel 13 into furnace 1. Is to supply. Another possible mode is to reduce the amount of fuel 13 supplied into the furnace 1 without reducing the amount of oxygen 12 or supplemental oxygen 27 supplied into the furnace 1. Or, any combination of these modes can be implemented simultaneously.

A preferred embodiment is to provide supplemental oxygen 27 so that the operator does not have to adjust the stoichiometric ratio of the oxidizer and fuel supplied through one or more burners 11. The make-up supply line 27 is preferably into an area where carbon monoxide is not particularly desirable, or in a relatively higher amount, such as in the vicinity of the area where the interior of the furnace 1 connects with the upstream end of the flue 6. It should be positioned to supply the oxidizing agent into the area within the furnace where carbon monoxide may be present.

The provision of additional oxygen continues until the detected and processed value indicative of the carbon monoxide concentration in the flame is reduced to a value below the previously established threshold. If desired, the additional oxygen should be less than the pre-established threshold, as below the pre-established threshold 0.5% to 2%, in order to minimize the number of times the provision of additional oxygen has to be stopped after the start of Should be served until.

Steps 31, 33, and 35 may be performed in suitably programmed controllers connected to each other by a suitable cable or by a wireless connection. Instead, they can all reside in one piece of hardware.

As shown, the system described herein also provides a supply of oxygen (oxidant), fuel, or both oxygen and fuel to achieve the desired combustion characteristics within the furnace or to perform control of the furnace operation from start-up. By adjusting, it can be used to perform other methods of controlling the operation of the furnace. In this embodiment of the present invention, one set point or more than one set point (typically in one burner, or in each of several burners if the furnace has multiple burners) corresponding to the fuel flow rate and oxygen flow rate of the furnace 3 to 10 set points) are pre-established in the controller.

In these embodiments, image analysis parameters are received in step 33 and compared to user-defined control level set points which also pre-set the flow values to be used for the burner and oxidant lance for each level. This last part is communicated with the furnace combustion control unit PLC. The user can also select other process parameters such as timers to activate/deactivate the control level. The user at this stage also allows the operator to select the language to be displayed on the ball control panel, and also select other variables to be controlled. The controller 33 collects data from the camera and associated software, processes this data with user input (limits, oxygen flow set point, natural gas flow set point, delay time), reduces CO emissions and reduces furnace output. Dynamically adjust the process to increase

The user selects the control variable and selects the start limit, stop limit, and "off-delay" values (each arbitrary number required, typically 1-10 each, and a number of "on-delay" values (typically 1 to 5)) are set. The user also sets the oxygen flow set point and the burner natural gas flow set point for each corresponding limit. When the initial start limit is exceeded by more than the on delay time, the software sets the corresponding oxygen flow set point and natural gas flow set point. Setpoints are processed in the same order as limits are exceeded. Once the control variable falls below the interruption limit and the off delay timer is complete, the above-described level is set.

When the control variable falls below all interrupt limits and the final off delay is complete, the oxygen set point is set to zero and the burner fuel set point returns to normal control.

When the furnace door is open, the oxygen set point is set to zero and the burner fuel set point returns to normal control.

The systems and methods described herein enable the operator to realize benefits in the operation of the furnace, such as more efficient operation in terms of fuel consumption and reduced cycle times. By monitoring the carbon monoxide content of the flame (and by doing so in real time, this is how the present invention can be used), the operator supplies oxygen and/or fuel to the furnace so that the heat of combustion of carbon monoxide can be retained and used advantageously in the furnace. The rate can be adjusted, thereby enabling the operator to achieve the same degree of heating and/or melting of the material in the furnace within a shorter cycle time, and the operator heating and/or heating with less fuel consumption per unit of heated material. Or it may be possible to achieve melting.

The present invention is an advantageous method for controlling carbon monoxide emissions from the furnace and for controlling the overall furnace operation, for various reasons. One reason is that the implementation of the method of the invention for an operating furnace does not require a continuous direct measurement of the concentration of carbon monoxide in the flame. Another reason is that the present invention detects parameters that characterize carbon monoxide in flames rather than flue gases or exhaust gases, which measurements tend to be more variable and less reliable. In addition, the method of the present invention does not measure the temperature of the flame, and is not based on measuring the difference in flame temperature, and is therefore more reliable and less susceptible to temperature fluctuations in the flame. Instead, the method of the invention is based on the correlation of image parameters corresponding to the carbon monoxide concentration in the flame, which is believed to be a novel and efficient mode of operation.

Other advantages include reduced demands on maintenance of the equipment used; Little or no furnace downtime and lower installation costs for installation of a system carrying out the invention; And for adjusting the oxygen supply, the fuel supply, or both the oxygen supply and the fuel supply, when the system detects a condition that requires an increase or other change in the amount of oxygen and/or the amount of fuel supplied into the furnace. It will include faster response times.

Claims (14)

As a method of heating a material in a furnace,
(A) A material containing a carbonaceous material in a furnace having a flue is heated using heat generated by combustion in the furnace of fuel and gaseous oxidizer supplied into the furnace, and the carbonaceous material Producing carbon monoxide derived from material, wherein a flame is formed in the furnace that can extend out of the furnace from the flue;
(B) by electronically expressing at least one parameter corresponding to the intensity of the flame and corresponding to the concentration of carbon monoxide in the flame, photographed outside the furnace or inside the furnace by a digital camera located outside the furnace Characterizing the concentration of carbon monoxide in the flame from images of the flame, and determining the characterized concentration of carbon monoxide in the flame from predetermined correlations of actual concentrations of carbon monoxide in the flame for expressed values of the at least one parameter. Determining;
(C) comparing the characterized concentration of carbon monoxide in the flame as characterized according to step (B) to a pre-established threshold concentration value for the concentration;
(D) when the characterized concentration of carbon monoxide in the flame exceeds the pre-established threshold concentration value, continuing the concentration of carbon monoxide in the flame from images of the flame taken by the digital camera outside the furnace While characterizing, the amount of oxygen supplied into the furnace available to react within the furnace, the amount of fuel, or both amounts of oxygen and fuel, determine the characterized concentration of carbon monoxide in the flame for a predetermined length of time. Adjusting to an amount or amounts effective to lower below the pre-established threshold concentration value. The method of claim 1 wherein the material comprises a metal. The method of claim 1, wherein in step (A) at least a portion of the material being heated is burned. The method of claim 1, wherein in step (A) at least a portion of the material being heated is melted. The method according to claim 1, wherein in step (D), adjusting the amount of oxygen in the furnace available to react in the furnace comprises the amount of oxygen supplied into the furnace compared to the amount of the fuel supplied into the furnace. The method comprising the step of increasing the amount. The method according to claim 1, wherein in step (D), adjusting the amount of oxygen in the furnace available to react in the furnace comprises the amount of the fuel supplied into the furnace compared to the amount of oxygen supplied into the furnace. Reducing the amount. The method of claim 1, wherein the flame extends out of the furnace from the flue, and images are taken by the digital camera of the flame extending out of the furnace from the flue. The method of claim 1, wherein images are taken by the digital camera of the flame inside the furnace. The method of claim 1, comprising adjusting the amount of oxygen supplied into the furnace when the characterized concentration of carbon monoxide in the flame exceeds the pre-established concentration value. The method of claim 1, comprising adjusting the amount of fuel supplied into the furnace when the characterized concentration of carbon monoxide in the flame exceeds the pre-established concentration value. The method of claim 1, comprising adjusting the amount of oxygen and the amount of fuel supplied into the furnace when the characterized concentration of carbon monoxide in the flame exceeds the pre-established concentration value. A method according to claim 1 for heating the material in the furnace, comprising:
(A) A material containing a carbonaceous material in a furnace having a flue is heated using heat generated by combustion in the furnace of fuel and gaseous oxidant supplied into the furnace, and derived from the carbonaceous material. Generating carbon monoxide to be formed in the furnace, a flame capable of extending out of the furnace from the flue;
(B) by electronically expressing at least one parameter corresponding to the intensity of the flame and corresponding to the concentration of carbon monoxide in the flame, photographed outside the furnace or inside the furnace by a digital camera located outside the furnace Characterizing the concentration of carbon monoxide in the flame from images of the flame, and determining the characterized concentration of carbon monoxide in the flame from predetermined correlations of actual concentrations of carbon monoxide in the flame for expressed values of the at least one parameter. Determining;
(C) comparing the characterized concentration of carbon monoxide in the flame as characterized according to step (B) to a pre-established threshold concentration value for the concentration;
(D) when the characterized concentration of carbon monoxide in the flame exceeds the pre-established threshold concentration value, continuing the concentration of carbon monoxide in the flame from images of the flame taken by the digital camera outside the furnace While characterizing, the amount of oxygen supplied into the furnace available to react with carbon monoxide in the furnace is effective in lowering the characterized concentration of carbon monoxide in the flame below the pre-established threshold concentration value for a predetermined length of time. Adjusting to an amount. The method of claim 12, wherein in step (D), adjusting the amount of oxygen in the furnace available to react with carbon monoxide in the furnace is oxygen supplied into the furnace compared to the amount of the fuel supplied into the furnace. The method comprising the step of increasing the amount of. The method of claim 12, wherein in step (D), adjusting the amount of oxygen in the furnace available to react with carbon monoxide in the furnace is the fuel supplied into the furnace compared to the amount of oxygen supplied into the furnace. Reducing the amount of.

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