JP2731794B2 - High performance overfire air system for NOx control - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Cross-Reference of Related Applications This application is cross-referenced with the following patent applications filed and assigned with this application: Hellwell Todd David, Glacier John and Marker Tony
United States patent application filed under the name of Michael Scott entitled "Collective Combustion Combustion System" (C88045)
0).

BACKGROUND OF THE INVENTION The present invention relates to horn-combustion fossil fuel fired furnaces, and more particularly, to an overfire air system for reducing NOx emissions from horn-burned pulverized coal combustion furnaces.

Pulverized coal has been favorably suspended and burned in furnaces for a long time by the angle combustion method. According to this angular combustion method,
Fuel and air are introduced into the furnace from the four corners of the furnace such that they are directed tangentially to an imaginary circle in the center of the furnace. This type of combustion method has many benefits, such as good mixing of fuel and air, stable flame conditions, and long residence time of the combustion gases in the furnace. There is.

Recently, it has become increasingly important to minimize air pollution as much as possible. To this end, many pollution control officials in the United States hope that the United States Congress will pass comprehensive air emission reduction legislation by the end of the 1990s. And the main purpose of such a law is, first,
It will mandate a retrofit of NOx and SOx control for existing fossil fuel burners.

With particular reference to the NOx problem, nitrogen oxides form during the combustion of fossil fuels in the form of two separate substances called thermal NOx and fuel NOx. Thermal NOx
Arise from the thermal fixation of molecular nitrogen and oxygen in the combustion air. The rate of thermal NOx formation is extremely affected by the local flame temperature and, to a lesser extent, the local concentration of oxygen. In practice, all thermal NOx is produced in areas of the flame where the temperature is high.

Fuel NOx, on the other hand, results from the oxidation of organically bound nitrogen of nitrogen in fossil fuels such as coal and heavy oil. The rate of fuel NOx production is generally strongly influenced by the rate of mixing of the fuel and air streams, especially by local oxygen concentrations. However, the flue gas NOx concentration due to nitrogen in the fuel is typically only a small part of the level generated from complete oxidation of all nitrogen in the fuel, for example, 20-60%. From the foregoing, it will be readily apparent that total NOx production is a function of both local oxygen concentration and maximum flame temperature.

Continuing with the description, several improvements have been made to the standard angle combustion technology. These improvements are mainly due to good NO
It has been made to achieve reduced x emissions. Part 1
One improvement is described in US Patent Application No. 786,427 (October 11, 1985).
Dated and assigned to the same assignee as the present application,
And entitled "Control System and Method for Operating a Combustion Pulverized Coal Furnace", which has now been abandoned). According to the technique of this U.S. patent application, pulverized coal and air are introduced from a number of lower burner heights and directed tangentially to an imaginary circle in the center of the furnace and additional pulverized coal and air are added. Are introduced tangentially to the imaginary circle from a number of upper burner heights but in a direction opposite to the direction of introduction of the pulverized coal and air. As a result of utilizing such a technique, good mixing of the fuel and air is achieved, which results in a conventional combustor (as is well known to those skilled in the art, typically 20-30
% Of excess air). And, reducing excess air helps to minimize the production of NOx, a major source of air pollution from coal-fired furnaces, as described above. Also,
Reduction of excess air also results in increased efficiency of the coal fired furnace.

Combustion techniques that have been modified to reduce NOx by the aforementioned U.S. patent application, however, have several disadvantages. That is, gases rotating in opposing directions in the furnace cancel each other out, so that the gas flows somewhat straighter through the upper portion of the furnace, thereby reducing turbulence and mixing above the furnace and leaving the furnace. The amount of unburned carbon particles emitted increases. In addition, slag and unburned carbon may adhere to the furnace wall. And, due to the adhesion of the slag and unburned carbon to the furnace wall, the heat transfer efficiency to the water cooling tube lining the furnace wall decreases, the necessity of soot blowing increases, and the life of the water cooling tube is shortened. Become.

Second, another improvement for NOx reduction was found in U.S. Pat.
No. 01, issued on Dec. 29, 1987 and assigned to the same assignee as the present application, and disclosed in the specification of "Low Excess Air Dull Combustion System". According to the technique of this U.S. Pat. No. 4,715,301, pulverized coal is suspended and burned in a furnace with good mixing with air, as in the previously abandoned U.S. Pat. Also, all of the aforementioned benefits associated with an angled combustion furnace are obtained by forming a swirling rotating fireball in the furnace. The furnace wall is protected by a shroud of air, which reduces slacking on the furnace wall. This is achieved by the following method.

That is, coal and primary air are introduced into the furnace from a first level, and auxiliary air at least twice the amount of primary air is introduced into the furnace immediately above or immediately above said first level. The second below
From the height, the primary air is introduced in a direction opposite to the direction in which the primary air is directed tangentially to the imaginary circle, and one of the plurality of first heights and second heights is set to one. So that it is above the other. By introducing a large amount of auxiliary air into the furnace at a high speed, a swirl is created in the furnace in the direction of the auxiliary air introduction. For this reason, the fuel introduced so as to rotate in the direction opposite to the rotating direction of the spiral of the furnace is urged to change its direction with respect to the direction of the total furnace gas after entering the furnace. Thus, tremendous turbulent mixing of fuel and air is produced by this method. This increased mixing also reduces the need to introduce excess air from a higher height in the furnace. Also, due to this increased mixing,
The carbon conversion is increased, which improves the overall heat release rate of the furnace, while at the same time reducing slacking and fouling above the furnace. Furthermore, auxiliary air is introduced tangentially to an imaginary circle having a diameter greater than the diameter of the imaginary circle into which fuel is introduced, thereby forming a layer of air adjacent to the furnace wall. Also, overfire air, which forms substantially all of the excess air supplied to the furnace, is introduced into the furnace from a height that is substantially higher than all the introduction heights of primary air and auxiliary air. In this case, the overfire air is directed tangentially to an imaginary circle in the center of the furnace, but in a direction opposite to the direction of introduction of the auxiliary air.

Second, yet another improvement to burn pulverized coal as a fuel with low NOx emissions is disclosed in U.S. Pat. No. 4,669,398.
No. 5,985,878, issued June 2, 1987, and entitled "Pulverized Fuel Combustion Device". In accordance with the teachings of U.S. Pat. No. 4,669,398, a pulverized fuel combustion device is characterized by comprising a first pulverized fuel injection compartment, a second pulverized fuel injection compartment, and an auxiliary air compartment as described below. . In the above-mentioned first pulverized fuel injection compartment, the total amount of the consumed primary air and secondary air is supplied to the furnace so as to be mixed with the primary air to burn the pulverized coal. Less than air volume. Further, in the second pulverized fuel injection compartment, the total amount of the primary air and the secondary air is substantially equal to the theoretical air amount required to burn the pulverized coal by being supplied so as to be mixed with the primary air. Or, preferably, the theoretical air volume is also somewhat less. Further, the auxiliary air compartment injects auxiliary air into the furnace. And these three compartments are arranged close to each other.

In such a pulverized fuel combustion device, the gaseous mixture of the primary air and the fuel injected by the first and second pulverized fuel injection compartments is mixed at a ratio that reduces the generation of NOx. . Furthermore, a mixture of primary air and pulverized fuel from the second pulverized fuel injection compartment (it is difficult to ignite stably by itself) is a mixture that is easy to ignite from the first pulverized fuel injection compartment. Can be used to ensure proper ignition and combustion. Therefore, according to the pulverized fuel combustion device, the pulverized fuel can be burned with stable ignition and low NOx generation.

Also, a pulverized fuel combustion device constructed in accordance with the teachings of the above-mentioned U.S. Pat.No. 4,669,398 provides an additional compartment for injecting an inert fluid into the space provided between the three compartments described above for each compartment. It is characterized in that one is arranged. Thus, the gaseous mixture of primary air and pulverized fuel is such that the inert fluid is one of the inert fluid ejection compartments.
Forming the curtain from the two injections so that they do not interfere with each other, thereby minimizing the production of NOx from the gaseous mixture injected from the first and second pulverized fuel injection compartments Can be.
Also, the mixture of primary air and pulverized fuel from the first pulverized fuel injection compartment and the auxiliary air from the auxiliary air compartment are separated from each other by a curtain of another inert fluid from the other inert fluid injection compartment. Interference is prevented. As a result, the mixture of the primary air and the pulverized fuel can be burned without changing the mixture ratio, thereby preventing an increase in NOx generation.

Next, another improvement in which pulverized coal was burned as fuel with simultaneous reduction of NOx and SOx emissions was reported in U.S. Pat. No. 4,426,939 (patent issued Jan. 24, 1984). And assigned to the same assignee as the present application, and is disclosed in the specification entitled "Methods for Reducing NOx and SOx Emissions." No. 4,426,
According to the teaching of 939, pulverized coal is burned in a furnace in such a way as to reduce the maximum temperature in the furnace and maintain good flame stability and complete combustion of the fuel. Such a method is accomplished as follows.

That is, the pulverized coal is transported toward the furnace by an air flow. During this transport, the stream is split into two parts, one of which is a fuel-rich part (fuel-rich part)
And the other part is a part with low fuel (poor fuel part). Then, the fuel-rich portion is introduced into the first zone in the furnace. Air is also introduced into this first zone in an amount insufficient to support all complete combustion of the fuel in the fuel-rich portion. On the other hand, the lean fuel portion is introduced into a second zone in the furnace. Also, the air in this second area,
Excess air is introduced in such an amount that it is more than required to burn all of the fuel in the furnace. Finally, the coal is introduced into the furnace at the same time as the fuel, which minimizes the maximum temperature in the furnace and minimizes the production of NOx and SOx in the combustion gases.

The combustion systems constructed in accordance with one of the previously abandoned U.S. patent applications and the three patented U.S. patents described above have been demonstrated to work for their respective purposes. Nevertheless, it has nevertheless been apparent in the past that there is a need for improving these combustion systems. In particular, a need has emerged in the past to provide a new and improved combustion system, a feature that would benefit from the incorporation of a high performance overfire air system. The basic reason for using overfire air is to provide a more effective method for controlling NOx in fog-fired fossil fuel fired furnaces. Overfire air is introduced tangentially to an imaginary circle in the center of the furnace through a plurality of additional air compartments called overfire air ports. These additional air compartments are designed as vertical extensions of the wind box provided at each corner of the fog-fired fossil fuel furnace.

The theory that overfire air can reduce NOx emissions is as follows. By using the overfire air, generation of NOx due to both fixing of nitrogen in the atmosphere (thermal NOx) and oxidation of nitrogen in fuel (fuel NOx) is suppressed. The use of overfire air reduces the total oxygen available in the primary flame region. And, as a result of the decrease in total oxygen, the nitrogen in the fuel, rather than the nitrogen oxides, due to the lack of oxygen in this primary flame zone and the intense competition with the carbonaceous material for available oxygen It undergoes a recombination reaction that forms molecular nitrogen (N ₂ ). As a result, NOx production through nitrogen in fuel conversion is greatly reduced. Similarly, the effect of overfire air causes a decrease in thermal NOx through temperature that depends on the Zeldbitch mechanism. Heat generation during the early stage combustion of the primary flame region is somewhat reduced and delayed due to the reduced oxygen environment with ideally completed combustion near the overfire air port. Increasing the furnace volume and spreading heat generation through the furnace can result in a lower maximum combustion temperature, thereby reducing the production of thermal NOx.

The overfire air, according to typical applications, is one of a single fixed height at the top of the wind box, referred to as tightly coupled overfire air, or a higher height, referred to as separate overfire air. Introduced through two closely assembled ports. Experimental tests have shown that by introducing a portion of the overfire air through a tightly coupled overfire air port and another portion of the overfire air through a separate overfire air port, the NOx from fossil fuel combustion can be reduced. It is shown that it can be reduced considerably. Furthermore, empirical tests have shown that there is the best distribution of overfire air between the tightly coupled overfire air port and the isolated overfire air port. For example, in the case of bituminous coal,
The best distribution is obtained with one third of the overfire air flowing through the tightly coupled overfire air port and two thirds of the overfire air flowing through the separate overfire air port.

In addition to the foregoing, the manner in which the overfire air is introduced into the furnace in a well-controlled manner to mix with the furnace gas is also important to maximize overfire air efficiency. Test data indicates that the improvement in NOx emissions can be achieved by the following methods. That is, overfire air is injected from each corner of the furnace through two, three or more compartments, where each compartment provides a portion of the total overfire air flow at a different combustion angle.
By introducing a horizontal “spray” or “fan” distribution of air over the planar area of the furnace, NOx emissions are reduced as compared to other patterns of overfire air injection into the furnace. Can be improved.

Also, by using such an overfire air injection pattern, a more uniform flame pattern is created on the vertical exit surface of the furnace, thereby improving the condition of the furnace exit. That is, all angular combustion fossil fuel fired furnaces have non-uniform flow patterns in the convection passage due to the low tangential furnace flow pattern. And, due to this non-uniform flow pattern, the flow on one side is greater than the flow on the other side, resulting in a steam temperature imbalance. In contrast, as mentioned above, a horizontal "spray" of overfire air over the planar area of the furnace
Alternatively, the aforementioned steam temperature imbalance is reduced by introducing overfire air into the furnace in a spray pattern that provides a "fan-shaped" distribution.

Finally, an improvement in mixing the overfire air with the furnace gas is to introduce the overfire air at a high moment. To achieve this high overfire air moment, the overfire air must be at a speed well above those typically used in conventional combustion systems, for example, 30-45 m / sec (100-150 ft / sec). At a speed of 60 to 90 m / sec (200 to 300 ft / sec). In order to obtain such a high speed of the overfire air, it is necessary to use a boost fan.

Summarizing the foregoing, the prior art on a new and improved combustion system incorporating a high performance overfire air system that is particularly suitable for use in connection with fog-fueled fossil fuel fired furnaces. When a high-performance overfire air system is used in a fossil fuel combustion furnace, NOx
There is a need to be able to achieve a level of release that is at least as low as, if not better than, the level currently established as a standard prescribed by United States law. It is. Also, in this case, a high performance overfire air system can be incorporated into the combustion system without providing any additional equipment, catalyst, or increasing fuel costs for operation of the combustion system. Is preferred. Further, in this case, it is fully compatible with other types of NOx emission reduction systems used to further reduce NOx, such as limestone injection systems, reburning systems and selective catalytic reduction (SCR) systems, thus providing high performance. Preferably, an overfire air system can be incorporated into the combustion system. Furthermore, even when applied to new combustion systems,
Preferably, or even an application to an existing combustion system, it should be equally adaptable so that a high performance overfire air system can be incorporated into the combustion system.

Accordingly, it is an object of the present invention to provide a new and improved high performance overfire air system for NOx control designed for use in combustion systems of the type used in fossil fuel fired furnaces. .

It is another object of the present invention to provide a high performance overfire air system for NOx control, designed for use in combustion systems of the type used in fuzzy combustion fossil fuel fired furnaces. .

Still another object of the present invention is to use NOx emissions in a combustion system of the type used in fuzzy-fueled fossil-fired furnaces, where the emission of NOx is below the level currently established as a standard prescribed by U.S. law. It is an object of the present invention to provide a high performance overfire air system for NOx control, which can be reduced at least to a level, if not better, at that level.

Still another object of the present invention is a multi-stage overfire, comprising a tightly coupled overfire air compartment and a separate overfire air compartment, for use in a combustion system of the type used in fog-fired fossil fuel fired furnaces. It is to provide a high performance overfire air system for NOx control, which incorporates the use of an air compartment.

Yet another object of the present invention is to provide a system for use in combustion systems of the type used in fog-fired fossil fuel-fired furnaces, wherein the space between the tightly coupled overfire air compartment and the separate overfire air compartment is provided. A high performance overfire air system for NOx control, characterized in that the best possible distribution of overfire air is obtained.

Yet another object of the present invention is to design for use in a combustion system of the type used in fog-fired fossil fuel fired furnaces and incorporate the use of multi-angle overfire air introduction patterns. It is to provide a high performance overfire air system for NOx control.

Yet another object of the present invention is to provide a total combustion of overfire air which is designed for use in a combustion system of the type used in fuzzy combustion fossil fuel fired furnaces and according to a multi-angle overfire air introduction pattern. High performance overfire for NOx control, characterized in that a part of the flow is introduced at different angles and a horizontal "spray" or "fan" distribution of the overfire air over the planar area of the furnace It is to provide an air system.

Yet another object of the present invention is to provide overfire air to a furnace designed to be used in a combustion system of the type used in fuzzy-fueled fossil fuel-fired furnaces, and to use overfire air in furnaces in conventional combustion systems. An object of the present invention is to provide a high performance overfire air system for NOx control, which is introduced at a sufficiently high speed.

Yet another object of the present invention is to provide additional equipment, catalysts, or fuel costs for operation, designed for use in combustion systems of the type used in fog-fired fossil fuel fired furnaces. It is to provide a high-performance overfire air system for NOx control, which does not need to be increased.

Still another object of the present invention is to provide another NOx emission reduction type designed to be used in a combustion system of the type used in fuzzy combustion fossil fuel fired furnaces and used to further reduce NOx emissions. Systems, such as limestone injection systems, reburn systems, and selective catalytic reduction (SC)
R) NOx, fully compatible with the system
It is to provide a high performance overfire air system for control.

Still another object of the present invention is to provide a combustion system of the type used in fuzzy fuel-fired furnaces with a combustor, to be applied to new combustion systems or to use existing combustion systems. An object of the present invention is to provide a high performance overfire air system for NOx control, characterized in that it can be adapted very equally, even if it is applied to air pollution.

According to one aspect of the present invention, there is provided a combustion system of a type that is particularly suitable for use in a fossil fuel fired furnace provided with a burner section. A high performance overfire air system for NOx control is provided. And, this high performance overfire air system includes a multi-stage overfire air compartment. These multi-level overfire air compartments consist of at least one tightly coupled overfire air compartment and three separate overfire air compartments. A tightly coupled overfire air compartment is mounted at the top of the wind box in the burner area of the furnace. Also, a tightly coupled overfire air nozzle is mounted in the tightly coupled overfire air compartment.

On the other hand, the three separate overfire air compartments are spaced from the plurality of tightly coupled overfire air compartments and from the wind box in the burner section of the furnace so as to be in line with the tightly coupled overfire air compartments. Is also mounted at an upper height. Also, the three separate overfire air nozzles extend at different combustion angles, so that the overfire air emitted from these separate overfire air nozzles can be sprayed horizontally or "sprayed" or over a planar area of the burner section of the furnace. The three separate overfire air nozzles are mounted on the three separate overfire air conversions to establish a "fan" distribution.

Also, an overfire air supply is connected to both the tightly coupled overfire air nozzle and the plurality of separate overfire air nozzles to provide a predetermined best distribution of overfire air between both nozzles. Thus, overfire air is supplied to both of these nozzles. The overfire air supply also feeds the overfire air into the burner area of the furnace through the three separate overfire air nozzles at a rate higher than that previously used to introduce overfire air into the furnace. Feed at a sufficiently high rate.

Next, in accordance with another aspect of the present invention, there is provided a combustion system of a type that is particularly suitable for use in a fossil fuel fired furnace provided with a burner section, A method is provided for operating a high performance overfire air system for NOx control. And this
The method of operating the high performance overfire air system for NOx control consists of introducing tightly coupled overfire air into the furnace burner area from the top of the wind box and blowing separated overfire air into the furnace burner area. Introducing from a height above the box. In this case, the introduction of the tightly coupled overfire air from the top height of the wind box and the introduction of the separated overfire air from a height above the wind box are determined by a predetermined overrun between them. According to the best distribution of fire air. Also, the overfire air introduced into the furnace burner section from a height above the wind box may distribute the horizontal "spray" or "fan" distribution of overfire air over the planar area of the furnace burner section. Introduced to establish. Further, the overfire air introduced into the burner area of the furnace from a height above the wind box is at a rate sufficiently higher than the rate previously used to introduce overfire air into the furnace. Is introduced into the burner area.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical cross-sectional view schematically illustrating a fossil fuel combustion furnace with a high performance overfire air system for NOx control configured in accordance with the present invention.

FIG. 2 is a front view of a combustion system of the type used in fuzzy combustion fossil fuel combustion furnaces, showing one embodiment of a high performance overfire air system for NOx control configured in accordance with the present invention.

FIG. 3 shows a high performance overfire air system for NOx control constructed in accordance with the present invention, with the distribution between the tightly coupled overfire air and the separated overfire air pre-determined and used for NOx. It is a graph which shows an effect.

FIG. 4 is a plan view showing a horizontal "spray" or "fan" distribution pattern of overfire air using a high performance overfire air system constructed in accordance with the present invention.

FIG. 5 uses a high performance overfire air system constructed in accordance with the present invention, with the overfire air being distributed according to the horizontal "spray" or "fan" distribution pattern shown in FIG. 6 is a graph showing the effect on NOx when the operation is performed.

FIG. 6 is a graph showing the effect on NOx when a high performance overfire air system constructed in accordance with the present invention is used with overfire air being introduced into the furnace at a high velocity.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, and in particular to FIG. 1, there is depicted a fossil fuel fired furnace generally indicated by the reference numeral 10. A detailed description of the fossil fuel fired furnace 10 illustrated in FIG. 1 need not be provided here, as the structure and mode of operation of the fossil fuel fired furnace itself is well known to those skilled in the art. Think. Rather, indicated generally by the reference numeral 14 in FIG.
For the purpose of gaining an understanding of a fossil fuel fired furnace 10 that can be associated with a combustion system indicated generally at 12 in FIG. 1, comprising a sophisticated overfire air system constructed in accordance with the present invention. Because of the combustion system 12 and the high performance overfire air system 14 described above,
(This high performance overfire air system 14, according to the present invention, can be installed in the furnace 10 as part of the combustion system 12, and when installed in the combustion system 12,
It may be sufficient to simply describe here some components of the fossil fuel-fired furnace 10 that cooperate with the fossil fuel-fired furnace 10 (which serve to reduce NOx emissions from the fossil fuel-fired furnace 10). For a detailed description of the components and operating modes of the fossil fuel-fired furnace 10 not described herein, refer to the prior art, for example, patented on January 12, 1988 to FJE Berti. Reference may be made to US Pat. No. 4,719,587, assigned to the same assignee as the present application.

Still referring to FIG. 1 of the drawings, the fossil fuel fired furnace 10 illustrated in FIG. 1 includes a burner section generally indicated by reference numeral 16. As will be described in more detail below in connection with a description of the structure and mode of operation of the combustion system 12 and the high performance overfire air system 14, within the burner section 16 of the fossil fuel fired furnace 10 are known by those skilled in the art. Combustion of fossil fuel and air is initiated by well-known methods. The hot gas generated from the combustion of the fossil fuel and the air flows upward in the fossil fuel combustion furnace 10. While the hot gas flows upward through the fossil fuel fired furnace 10, the hot gas is piped (not shown for clarity in the drawings) in a manner well known to those skilled in the art. Gives heat to the fluid flowing through it. The tubes described above are arranged on all four walls of the fossil fuel fired furnace 10 according to conventional methods. The hot gas then flows through a horizontal passage of the fossil fuel combustion furnace 10, generally indicated by reference numeral 18, followed by the back of the fossil fuel combustion furnace 10, generally indicated by reference numeral 20. Proceeds to the gas path and exits the fossil fuel combustion furnace 10. Both the horizontal passage 18 and the back gas passage 20 generally accommodate other heat exchange surfaces (not shown) for generating and superheating steam in a manner well known to those skilled in the art. . The steam is then allowed to flow to a turbine (not shown), which generally constitutes one component of a turbine / generator (not shown), whereby the steam is passed through the turbine and the turbine in a known manner. It provides the driving force for driving an associated generator (not shown), from which electricity is generated.

Combustion system 12 and smart overfire air system 14 (this overfire air system is, according to the present invention, designed to be used as part of a combustion system, such as the combustion system 12 described above, and includes a combustion system such as the combustion system described above. 12 together with a furnace designed in the form of a fossil fuel-fired furnace 10 shown in FIG. Please refer to FIG. 1 and FIG. In particular, the high performance overfire air system 14 is designed for use in a combustion system, such as the combustion system 12 described above. And, when the combustion system 12 is used in a furnace, such as the fossil fuel combustion furnace 10 of FIG. 1 of the drawings, the high performance overfire air system 14 operates to reduce NOx emissions from the fossil fuel combustion furnace 10.

Referring first to the combustion system 12, the combustion system 12, as best understood by reference to FIGS. 1 and 2 of the drawings, has a housing, preferably a reference numeral in FIGS. Includes a housing in the form of a wind box, indicated by 22. The wind box 22 is mounted to the burner section 16 of the fossil fuel fired furnace 10 by any suitable mounting means (not shown) known in the art, in a manner well known to those skilled in the art. The longitudinal axis extends in a substantially parallel relationship to the longitudinal axis of the fossil fuel fired furnace 10.

Continuing with the description of the combustion system 12, according to the configuration illustrated in FIGS. 1 and 2 of the drawings, a first air compartment, indicated by reference numeral 24 in FIG. Is provided at the lower end. And
An air nozzle, indicated by reference numeral 26, is mounted in the air compartment 24 by any suitable mounting means known in the art (not shown). Figure 1 of the drawing
An air supply, schematically depicted in FIG. 1 and generally indicated by the reference numeral 28, is connected to the air nozzle 26 in a manner to be described in detail below. This causes the air supply 28 to supply air to the air nozzle 26 and then through this air nozzle 26 to the burner area of the fossil fuel combustion furnace 10.
Supply air to 16. For this purpose, an air supply device
28 includes a fan indicated by reference numeral 30 in FIG. 1 of the drawing and an air duct indicated by reference numeral 32. These air ducts 32 are connected, on the one hand, to the fan 30 and, on the other hand, to the air nozzle 26 (see FIG. 2), as indicated diagrammatically by the reference numeral 34 in FIG. (Not shown) in fluid flow connection.

With further reference to wind box 22, according to the configuration of combustion system 12 illustrated herein, a first fuel compartment, indicated generally by reference numeral 36 in FIG.
A lower portion of the wind box 22 is provided so as to be positioned in a substantially side-by-side relationship with the air compartment 24 described above. A first fuel nozzle, indicated by reference numeral 38 in FIG. 2 of the drawings, is mounted to the fuel compartment 36 by any suitable mounting means known in the art (not shown). A fuel supply, schematically depicted in FIG. 1 of the drawings and generally indicated by reference numeral 40, is connected to a fuel nozzle 38 in a manner described in greater detail below. As a result, the fuel supply device 40 supplies the fuel to the fuel nozzle 38.
To the burner section 16 of the fossil fuel fired furnace 10 through the fuel nozzle 38. That is,
The fuel supply 40 includes a pulverizer, designated by reference numeral 42 in FIG. 1 of the drawings, and a fuel duct, designated by reference numeral 44. In the crusher 42, the fossil fuel to be burned in the fossil fuel combustion furnace 10 is crushed in a manner well known to those skilled in the art. Also, the fuel duct 44 has separate valves and controls on the one hand to the pulverizer 42 and on the other hand to the fuel nozzle 38 (see FIG. 2) as shown diagrammatically by reference numeral 46 in FIG. 1 of the drawings. It is connected in fluid flow relation through a vessel (not shown). As can be seen with reference to FIG. 1 of the drawing, the pulverizer 42 is connected to the fan 30 and air is supplied from the fan 30 to the pulverizer 42 again.
Is supplied to the fuel nozzles 38 by air flow through the fuel duct 44 in a manner well known to those skilled in the art.

In addition to the air compartment 24 and the fuel compartment 36 described above, the wind box 22 is also provided with a second air compartment, indicated generally by the reference numeral 48 in FIG. The air compartment 48 is provided within the wind box 22 so as to be best understood with reference to FIG. 2 of the drawings, in a substantially juxtaposed relationship over the fuel compartment 36. The air nozzle, indicated by reference numeral 50 in FIG. 2 of the drawings, is mounted in air compartment 48 by any suitable mounting means known in the art (not shown). This air nozzle 50 is connected to the air supply device 28 described above by an air duct.
Connected through 32. As can be best understood with reference to FIG. 1 of the drawings, the air duct 32 is connected to the fan 30 on the one hand and the air nozzle 50 (as shown diagrammatically by the reference numeral 52 in FIG. 1 on the other hand). FIG.
) Is connected in fluid flow relation through separate valves and controllers (not shown). This causes the air supply 28 to supply air to the air nozzle 50 and then to the burner section 16 of the fossil fuel combustion furnace 10 through the air nozzle 50 in a similar manner as described above in connection with the air nozzle 26. Supply.

Continuing with the description of the combustion system 12, according to the illustrated embodiment, a second fuel compartment, generally indicated by reference numeral 54 in FIG. It is provided to be positioned in a substantially side-by-side relationship above the air compartment 48. A second reference numeral generally indicated by reference numeral 56 in FIG.
The fuel nozzles are mounted in the fuel compartment 54 by suitable mounting means (not shown) known in the art. The fuel nozzle 56 is connected to the fuel supply device 40 described above.
Through a fuel duct 44. As best understood with reference to FIG. 1 of the drawings, the fuel duct 44
On the one hand a pulverizer 42, in which the fossil fuel to be burned in the fossil fuel combustion furnace 10 is pulverized by methods well known to those skilled in the art, and on the other hand, The fuel nozzle 56 (see FIG. 2) is connected in fluid flow relation through a separate valve and controller (not shown) as shown schematically by reference numeral 58 in FIG. 1 of the drawings. This causes the fuel supply 40 to supply fuel to the fuel nozzle 56 in a manner similar to that described above in connection with the fuel nozzle 38, and then through the fuel nozzle 56 to the burner section 16 of the fossil fuel combustion furnace 10.
Supply fuel to The same description as described above is again repeated here, but as can be seen with reference to FIG. 1 of the drawings, the crusher 42 is connected to the fan 30 and
Air is also supplied from the fan 30 to the crusher 42, whereby fuel supplied from the crusher 42 to the fuel compartment 54 is passed through the fuel duct 44 by airflow in a manner well known to those skilled in the art. Be transported.

With further reference to wind box 22, according to the illustrated embodiment, wind box 22 is also provided with a third air compartment, indicated generally by reference numeral 60 in FIG. Have been. This air compartment 60 is, as best understood with reference to FIG.
Within the fuel compartment 54 in a substantially side-by-side relationship. The air nozzle, indicated by reference numeral 62 in FIG. 2 of the drawings, is mounted in air compartment 60 by any suitable mounting means known in the art (not shown). This air nozzle 62
The above-mentioned air supply device 28 is connected through an air duct 32. As can best be understood with reference to FIG. 1 of the drawings, the air duct 32 is connected to the fan 30 on the one hand and the air nozzle 62 (as shown diagrammatically by the reference numeral 64 in FIG. 1 on the other hand). 2) in fluid flow connection through separate valves and controllers (not shown). This allows the air supply 28 to be operated in a manner similar to that described above with respect to the air nozzles 26 and 50.
Air is supplied to the air nozzle 62 and then this air nozzle
Air is supplied through 62 to the burner section 16 of the fossil fuel fired furnace 10.

In addition to the configuration described above, the combustion system 12 may further include, according to the embodiment illustrated in FIGS.
A third fuel compartment, indicated generally by reference numeral 66 in FIG. The fuel compartment 66 is provided in the wind box 22 so as to be positioned substantially above the air compartment 60. A third fuel nozzle, indicated by reference numeral 68 in FIG. 2 of the drawings, is mounted within the fuel compartment 66 by any suitable mounting means known in the art (not shown). The fuel nozzle 68 is connected to the fuel supply device described above.
It is connected to 40 through a fuel duct 44. Figure 1 of the drawing
See the fuel duct 44 for best understanding
On the one hand to a crusher 42, in which the fossil fuel to be burned in the fossil fuel combustion furnace 10 is crushed by methods well known to those skilled in the art. On the other hand, FIG.
Are connected in fluid flow relation to the fuel nozzle 68 (see FIG. 2) through separate valves and controllers (not shown) as shown diagrammatically. This allows the fuel supply device 40 to supply fuel to the fuel nozzle 68 in a manner similar to that described above with respect to the fuel nozzles 38 and 56,
The fuel is then supplied to the burner section 16 of the fossil fuel combustion furnace 10 through the fuel nozzle 68. As mentioned above, and as best seen with reference to FIG. 1 of the drawings, the crusher 42 is connected to the fan
The fuel supplied to the fuel compartment 66 is also transported through the fuel duct 44 by air flow in a manner well known to those skilled in the art.

Continuing with the description of the combustion system 12, according to the embodiment illustrated in FIGS. 1 and 2 of the drawings, the wind box 22 is indicated generally by the reference numeral 72 in FIG. 2 of the drawings. A fourth air compartment is provided. The fourth air compartment 72 is provided in the wind box 22 so as to be positioned substantially above the fuel compartment 66. A fourth air nozzle, indicated by reference numeral 74 in FIG. 2 of the drawings, is mounted within air compartment 72 by any suitable mounting means known in the art (not shown). This air nozzle 74
Is connected to the above-described air supply device 28 through an air duct 32. As best understood with reference to FIG. 1 of the drawings, the air duct 32 on the one hand
On the other hand, an air nozzle 74 (see FIG. 2), as shown schematically by reference numeral 76 in FIG.
Connected in fluid flow relation through separate valves and controllers (not shown). Accordingly, the air supply device 28
In a manner similar to that described above in connection with the air nozzles 26, 50 and 62, air is supplied to the air nozzle 74 and then through the air nozzle 74 to the burner section of the fossil fuel combustion furnace 10.
Supply air to 16.

Also, according to the illustrated embodiment of the combustion system 12, a fourth fuel compartment, generally indicated by reference numeral 78 in FIG. Are provided so as to be substantially aligned with each other. A fourth fuel nozzle, indicated by reference numeral 80 in FIG. 2 of the drawings, is mounted within fuel compartment 78 by any suitable mounting means known in the art (not shown). The fuel nozzle 80 is connected to the above-described fuel supply device 40 through the fuel duct 44. As can best be understood with reference to FIG.
(In this crusher, the fossil fuel to be burned in the fossil fuel combustion furnace 10 has been crushed by methods well known to those skilled in the art) and, on the other hand, in FIG. 1 of the drawings. The fuel nozzle 80 (see FIG. 2) is connected in fluid flow relationship through a separate valve and controller (not shown), as indicated schematically by reference numeral 82. As a result, the fuel supply device 40
In a manner similar to that described above in connection with 8,56 and 68,
Fuel is supplied to the fuel nozzle 80 and then this fuel nozzle
The fuel is supplied to the burner section 16 of the fossil fuel combustion furnace 10 through 80. As mentioned above, and as best seen with reference to FIG. 1 of the drawings, the crusher 42 is connected to the fan 30 and air is supplied from the fan 30 to the crusher 42 as well, thereby Fuel supplied from the machine 42 to the fuel compartment 78 is transported through the fuel duct 44 by airflow in a manner well known to those skilled in the art.

Next, the configuration of the high performance overfire air system 14 according to the present invention and the manner in which the high performance overfire air system 14 according to the present invention forms part of a combustion system, for example the combustion system 12 described above, will be described. I do.

For this description, reference is made in particular to the drawings, FIGS. Thus, as best understood with reference to FIGS. 1 and 2, the high performance overfire air system 14 according to the preferred embodiment of the present invention is generally shown in FIG. Includes a pair of tightly coupled overfire air compartments as shown. These tightly coupled overfire air compartments 84 and 86, according to a preferred embodiment of the present invention, are located in the upper portion of the wind box 22 of the combustion system 12 in a substantially side-by-side relationship with the air compartment 78 described above. It is provided to be. Then, in FIG.
A pair of tightly coupled overfire air nozzles, indicated by 90 and 90, are located within a pair of tightly coupled overfire air compartments 84 and 86.
The overfire air nozzle 90, which is mounted in the overfire air compartment 84, is mounted in the overfire air compartment 86 by any suitable mounting means (not shown) known in the art. Tightly coupled overfire air nozzles 88 and 90
Are connected to the above-described air supply device 28 through the air duct 32, respectively. As best understood with reference to FIG. 1 of the drawings, the air duct 32 has a fan
Separate valves and controls (not shown) at 30 and, on the other hand, at the tightly coupled overfire air nozzles 88 and 90 as shown diagrammatically by reference numeral 92 in FIG.
Connected through. Thereby, the air supply device 28
Supplies air to each of the tightly coupled overfire air nozzles 88 and 90 and then supplies air to the burner section 16 of the fossil fuel fired furnace 10 through these overfire air nozzles 88 and 90.

Continuing with the description of the high performance overfire air system 14, according to a preferred embodiment of the present invention, the high performance overfire air system 14 further includes a plurality of separate overfire air compartments. The plurality of separate overfire air compartments are spaced apart above a pair of tightly coupled overfire air compartments 84 and 86 and are suitably mounted in a known manner so as to be substantially aligned with the longitudinal axis of wind box 22. It is attached by means (not shown). Also, the plurality of separate overfire air compartments described above, in accordance with a preferred embodiment of the present invention, have respective reference numerals in FIG.
Includes three compartments, generally indicated by 94, 96 and 98. A plurality of separate overfire air nozzles, indicated by reference numerals 100, 102 and 104, respectively, in FIG. 2 of the drawings, include overfire air nozzles 100 in a plurality of separate overfire air compartments 94, 96 and 98. The overfire air nozzle 102 is vertically (slope) and horizontal (sway) within the overfire air compartment 96 so that it can be mounted for both vertical (slope) and horizontal (sway) movement in the air compartment 94. ), So that the overfire air nozzle 104 can be mounted so that both movements are possible.
It is mounted by any suitable mounting means (not shown) known in the art so that it can be mounted so that both vertical (inclined) and horizontal (yaw) movements can be made within the same. Each of the plurality of separate overfire air nozzles 100, 102 and 104 includes:
The above-mentioned air supply device 28 is connected through an air duct 32. As best understood with reference to FIG. 1 of the drawings, the air duct 32 has a separate overfire as shown schematically by the reference numeral 106 on the one hand to the fan 30 and on the other hand to FIG. Air nozzle 10
Each of 0, 102 and 104 (see FIG. 2) is connected through a separate valve and controller (not shown). This allows
An air supply 28 supplies air to each of the separate overfire air nozzles 100, 102, and 104, and then supplies air to the burner section 16 of the fossil fuel fired furnace 10 through these overfire air nozzles.

Next, the high performance overfire air system 14 described above, constructed in accordance with the present invention, and the high performance overfire air system 14 for the purpose of achieving a reduction in NOx emissions from a furnace, e.g. The mode of operation with the combustion system 12 designed to be used will be briefly described. The above fossil fuel combustion furnace 10
In addition, both a combustion system 12 and a high performance overfire air system 14 associated with the combustion system 12 are installed.

Referring to the mode of operation of the combustion system 12 constructed in accordance with the embodiment illustrated in FIGS. 1 and 2 of the drawings, air and fossil fuels are provided in a wind box 22 and alternately positioned in the air compartments above and below. And the burner area of the fossil fuel fired furnace 10 through the fuel compartment
Introduced in 16. That is, according to the embodiment of the combustion system 12 illustrated here, air is supplied to the air compartment 2.
Burner area 1 of fossil fuel fired furnace 10 through 4, 48, 60 and 72
6 and fossil fuels are introduced into the burner section 16 of the fossil fuel combustion furnace 10 through fossil fuel compartments 36, 54, 66 and 78. And fossil fuels introduced into the burner section 16 of the fossil fuel fired furnace 10 through the fossil fuel compartments 36, 54, 66 and 78 by methods well known to those skilled in the art;
The air compartments 24, 48, 60 and
Combustion with air introduced through 72 is started. Hot gas generated from the combustion of fossil fuel and air in the burner section 16 of the fossil fuel combustion furnace 10 flows upward through the fossil fuel combustion furnace 10 in a known manner. While the hot gas flows upwardly through the fossil fuel fired furnace 10, the hot gas provides heat to the fluid flowing through the tubes (not shown) in a manner well known to those skilled in the art. The tubes are arranged on all four walls of the fossil fuel furnace 10 according to known methods. The hot gas then flows through the horizontal passage 18 of the fossil fuel combustion furnace 10 and subsequently proceeds to the back gas passage 20 of the fossil fuel combustion furnace 10 where the fossil fuel combustion furnace 10
Exit 10. Each of the horizontal passage 18 and the back gas passage 20 generally contains another heat exchange surface (not shown) for generating and superheating steam in a manner well known to those skilled in the art. . The steam is then allowed to flow to a turbine (not shown), which generally constitutes one component of a turbine / generator (not shown), whereby the steam is passed through the turbine and the turbine in a known manner. It provides the driving force for driving an associated generator (not shown), from which electricity is generated.

Next, the operation mode of the high performance overfire air system 14 will be described. The purpose of configuring and using this high performance overfire air system 14 is to reduce the rate of NOx production by both atmospheric nitrogen fixation (thermal NO) and fuel nitrogen (fuel NOx). is there. This is achieved by reducing the total oxygen available in the primary flame zone. To this end, according to the mode of operation of the high performance overfire air system 14, the overfire air is at one of the single fixed height positions of the burner section 16 of the fossil fuel combustion furnace 10 at the top of the wind box 22. Introduced through one or two closely assembled compartments, and through one or more additional compartments located higher up. It is commonly referred to in the art as a tightly coupled overfire air compartment. The closely assembled compartments described above are shown in FIG.
And 86. Also, the higher located compartments, generally referred to in the art as separate overfire air compartments, are designated by reference numerals 94, 96 and 98 in FIG. 2 of the drawings.

One feature of the high performance overfire air system 14 according to the present invention is as follows. That is, a portion of the overfire air enters the burner section 16 of the fossil fuel fired furnace 10 through the tightly coupled overfire air compartments 84 and 86 and another portion of the overfire air passes through the separate overfire air compartments 94, 96 and 98. This provides the best predetermined distribution of overfire air between the tightly coupled overfire air and the separate overfire air. The benefits arising from utilizing this best distribution of overfire air may best be understood with reference to FIG. 3 of the drawings. FIG. 3 illustrates the use of a high performance overfire air system constructed in accordance with the present invention and having a predetermined distribution of overfire air between the tightly coupled overfire air and the separate overfire air. 5 is a graph showing an effect on NOx. And, the line indicated by reference numeral 108 in FIG. 3 indicates that when a furnace, such as the fossil fuel combustion furnace 10 described above, is operated with a combustion system such as the combustion system 12 described above, the base of NOx ppm levels from the furnace is measured. Represents a line plot. Also, the line indicated by reference numeral 110 in FIG. 3 indicates that when a furnace, such as the fossil fuel combustion furnace 10 described above, is operated with a combustion system, such as the combustion system 14 described above, at 0% overfire air, NOx released from the furnace
Represents a plot of ppm levels. In addition, FIG.
The line indicated by the arrow indicates that the furnace, e.g.
1 represents a plot of the NOx ppm levels released from a furnace when operated to introduce all of the% overfire air into the furnace as tightly coupled overfire air. Still further, the line indicated by reference numeral 114 in FIG. 3 indicates that the furnace, such as the fossil fuel fired furnace 10 described above, has 20% overfire air and separates all of the 20% overfire air. 1 represents a plot of the NOx ppm levels emitted from a furnace when operated to enter the furnace as air.

Still referring to FIG. 3, the point indicated by reference numeral 116 is that the furnace, e.g., the fossil fuel fired furnace 10 described above, combines a high performance overfire air system 14 constructed in accordance with the present invention with an associated combustion system 12. Operated with 20% overfire air, this 20% overfire air, according to the best distribution, its 9% overfire air is also 11% as tightly coupled overfire air
NOx pp released from the furnace when each overfire air is introduced as separate overfire air
Represents an m-level plot. Therefore, the following can be easily understood from the above description with reference to FIG.

1) The use of overfire air results in a reduction in NOx ppm levels compared to not using overfire air.

2) Use the same amount of overfire air and tightly couple all overfire air by using overfire air and introducing all of the overfire air as separate overfire air. NOx ppm compared to when introduced as
A further reduction of the level occurs.

3) Use the same amount of overfire air, but by introducing this overfire air into the furnace as tightly coupled overfire air and separate overfire air according to the best distribution, for example as illustrated in FIG. By introducing 20% overfire air into the furnace and best distributing 9% of it as tightly coupled overfire air and 11% of it as separate overfire air,
Even further reductions in x ppm levels occur.

And the best distribution ratio of overfire air between the tightly coupled overfire air and the separated overfire air will vary depending on the type of coal. For example, in the case of bituminous coal, experiments show that the best distribution ratio is to distribute 1/3 of the overfire air as tightly coupled overfire air and 2/3 as separate overfire air. I understand.

Next, a second feature of the high performance overfire air system 14 in accordance with the present invention is that separated overfire air enters the burner section 16 of the fossil fuel fired furnace 10 with three from each of the four corner sections of the furnace. Introduced through the compartments, where each compartment introduces a portion of the total flow of separated overfire air at a different combustion angle, which moves the air nozzles 100, 102 and 104 vertically (tilted) and / or horizontally (pieces). By shaking)
It is intended to achieve a horizontal "spray" or "fan" distribution of the separated overfire air over the planar area of the furnace. This distinct state of horizontal "spray" or "fan" distribution of the separated overfire air over the planar area of the burner section 16 of this fossil fuel fired furnace 10 is depicted in FIG. 4 of the drawings. As can be best seen with reference to FIG. 4, the separated overfire air is supplied to the burner section 16 of the fossil fuel fired furnace 10 in accordance with the present invention.
The four corners of the furnace, namely 10 in FIG.
Introduced from each corner indicated by a, 10b, 10c and 10d respectively. In accordance with the present invention, this introduction of the separated overfire air takes place through the three separate overfire air compartments 94, 96 and 98 shown in FIG.

Although not shown in FIG. 4, the fossil fuel combustion furnace 10
The four corner sections 10a, 10b, 10c and 10d have separate overfire air compartments 94, 96 and 98, respectively. Further, in the burner section 16 of the fossil fuel combustion furnace 10,
From each of the four corners 10a, 10b, 10c and 10d of the furnace,
Separated overfire air introduced through separate overfire air compartments 94, 96 and 98 provided in these sections is introduced at different combustion angles indicated by reference numerals 118, 120 and 122 in FIG. 4, respectively. For ease of reference, in FIG. 4, the same reference numerals, that is, 118, 120 and 122 are used in relation to each of the four corner portions 10a, 10b, 10c and 10d of the fossil fuel combustion furnace 10. .

Further, as best understood with reference to FIG. 4 of the drawings, the burner section 16 of the fossil fuel fired furnace 10 at different combustion angles indicated by reference numerals 118, 120 and 122 in FIG.
The separation overfire air is introduced such that a horizontal "spray" or "fan" distribution of the separation overfire air occurs over the planar area of the furnace. That is, as shown in FIG. 4, the separated overfire air introduced into the burner section 16 of the fossil fuel fired furnace 10 at each of the different combustion angles 118, 120, and 122, respectively, is referenced 124, 126, respectively.
And 128. And
These passages 124, 126 and 128 collectively create a distribution pattern in the form of a horizontal "spray" or "fan" distribution pattern, as best seen with reference to FIG. Also, as can be seen from FIG.
The distribution pattern of the separated overfire air introduced from each of the corners 10 a, 10 b, 10 c and 10 d of the 10 substantially overlaps each other at the center of the burner section 16 of the fossil fuel fired furnace 10.

The benefits gained by introducing the separated overfire air from the separated overfire air compartments 94, 96 and 98 into the burner section 16 of the fossil fuel fired furnace 10 at different combustion angles are illustrated in FIG. 5 of the drawings. And is best understood. FIG. 5 is constructed in accordance with the present invention;
FIG. 5 is a graph showing the effect on NOx when using a high performance overfire air system where overfire air is distributed according to the horizontal “spray” or “fan” distribution pattern shown in FIG.

In FIG. 5, the point indicated by reference numeral 130 is a furnace, such as the fossil fuel combustion furnace 10 described above, which is operated together with a combustion system such as the combustion system 12 described above, and is introduced through a separate overfire air compartment. All of the separated overfire air into the burner section 16 of the fossil fuel combustion furnace 10 at the same combustion angle, ie, +
At an angle of 15 °, this introduces separated overfire air through the fuel compartments 38, 54, 66, 78 and the air compartments 24, 48, 60, 72 into the burner section 16 of the fossil fuel fired furnace 10, respectively. FIG. 4 shows a plot of NOx ppm levels from the furnace when introduced co-rotating for fuel and air.

Also, the point indicated by reference numeral 132 in FIG. 5 is that the furnace, such as the fossil fuel combustion furnace 10 described above, operates with a combustion system, such as the combustion system 12 described above, and the separation introduced through a separation overfire air compartment. All of the overfire air is introduced into the burner section 16 of the fossil fuel fired furnace 10 at the same combustion angle, i.e., an angle of -15 °, thereby separating the separated overfire air into the combustion compartments 38, 54, 66, 78 and the air. Compartment 24,
4 represents a plot of NOx ppm levels from the fossil fuel-fired furnace 10 when introduced counter-rotating, with respect to fuel and air being introduced into the burner section 16 of the furnace 10 through 48, 60, 72, respectively.

Still referring to FIG. 5, what is indicated by reference numeral 134 in FIG. 5 is that the furnace, e.g., the high performance overfire air system 14 associated with the fossil fuel combustion furnace 10 constructed in accordance with the present invention, and the combustion system 14 Operating together, all of the separated overfire air is introduced at different fuel angles through each of the separated overfire air compartments 94, 96 and 98, thereby providing a horizontal "overfire" for the separated overfire air shown in FIG. Sprayed or fan shaped
Distribution on the flat area of the furnace,
FIG. 4 represents a plot of NOx ppm levels from the furnace. According to the preferred embodiment of the present invention, the different firing angles implemented for the aforementioned purposes for the separate overfire air compartments 94, 96 and 98 are + 15 °, 0 ° and -15 °. Therefore, from the description above with reference to FIG.
The following will be readily apparent.

1) All of the separated overfire air is introduced through the separated overfire air compartment at the same combustion angle of -15 °, and the separated overfire air is injected into the fuel compartments 38,54,66,78 and the air compartments 24,48,6.
Burner section 16 of fossil fuel combustion furnace 10 through 0,72 respectively
Introducing counter-rotation with respect to the fuel and air being introduced to the
At the same angle of 15 °, it is introduced through a separate overfire air compartment and all of the separated overfire air is passed through the fuel compartments 38, 54, 66, 78 and the air compartments 24, 48, 60 and 72, respectively, into the fossil fuel combustion furnace 10. With respect to the fuel and air introduced into the burner section 16 of the
Greater reductions in x ppm levels occur.

2) All of the separated overfire air is introduced through separate overfire air compartments 94, 96 and 98 at different combustion angles of + 15 °, 0 ° and -15, and FIG.
Ensuring that the horizontal "spray" or "fan" distribution of the separated overfire air over the flat area of the furnace as shown in, makes all of the separated overfire air -15 °.
At the same combustion angle, through a separate overfire air compartment, and separate overfire air is passed through the fuel compartments 38, 44, 66, 78 and the air compartments 24, 48, 60, 72, respectively, to the burner section of the fossil fuel combustion furnace 10. With respect to fuel and air introduced at 16, a greater reduction in NOx ppm levels occurs as compared to introducing counter-rotation.

Second, the third feature of the high performance overfire air system 14 in accordance with the present invention is that the separated overfire air enters the burner section 16 of the fossil fuel fired furnace 10 at a rate higher than that used in conventional combustion systems. It is to be introduced at a sufficiently high speed, for example at a speed of 60-90 m / sec (200-300 ft / sec) compared to the conventional speed of 30-45 m / sec (100-150 ft / sec). The benefit gained by introducing the separation overfire air at such a high rate is illustrated in FIG.
Is best understood with reference to FIG. 6 is a graph showing the effect on NOx when using a high performance overfire air system configured in accordance with the present invention and introducing overfire air to the furnace at a high speed.

And, the line indicated by reference numeral 136 in FIG. 6 indicates that the furnace, for example, the fossil fuel combustion furnace 10 is operated with the combustion system, for example, the combustion system 12, and the overfire air is supplied at a low speed, i.e., the conventional combustion system. 4 shows a plot of NOx ppm levels from the furnace when introduced at a rate commonly used in FIG. Also, the line indicated by reference numeral 138 in FIG. 6 represents a furnace, such as the fossil fuel combustion furnace 10 described above, and a combustion system 14 associated with a high performance overfire air system 14 constructed in accordance with the present invention.
Operating along with the separation overfire air introduced into the burner section 16 of the fossil fuel fired furnace 10 through separation overfire air compartments 94, 96 and 98, sufficiently higher than the speed used in conventional combustion systems. In speed, for example, conventional speed 30-45m / sec (100-150ft / sec)
5 represents a plot of NOx ppm levels from the furnace when introduced at 60-90 m / sec (200-300 ft / sec).

Therefore, the following can be easily understood from the above description with reference to FIG. That is, all of the separated overfire air is delivered to the burner section 16 of the fossil fuel fired furnace 10 at a rate sufficiently higher than that used in conventional combustion systems.
Introducing through 94, 96 and 98 means that all of the overfire air is introduced at a lower speed, i.e. at a speed that is used in conventional combustion systems.
Greater reductions in ppm levels occur.

As described above, the present invention provides a new and improved high performance overfire air system for NOx control designed for use in combustion systems of the type used in fossil fuel fired furnaces. Is done. In addition, the present invention provides a high performance overfire air system for NOx control designed for use in combustion systems of the type used in fuzzy-fired fossil fuel fired furnaces. Further, in accordance with the present invention, NOx emissions are used in combustion systems of the type used in fuzzy-burning fossil fuel-fired furnaces, where NOx emissions are lower than currently determined as a standard limited by U.S. law. A high performance overfire air system for NOx control is provided that can be reduced, at least to a level at least equal, if not better.

Further, according to the present invention, it is used in a combustion system of a type used in a fossil fuel combustion furnace of a corner combustion type,
A high performance overfire air system for NOx control is provided that incorporates the use of a multi-stage overfire air compartment consisting of a tightly coupled overfire air compartment and a separate overfire air compartment. Further in accordance with the present invention, there is provided between a tightly coupled overfire air compartment and a separate overfire air compartment designed to be used in a combustion system of the type used in fog-fired fossil fuel fired furnaces. A high performance overfire air system for NOx control is provided, wherein the best predetermined distribution of overfire air is provided. Moreover, according to the present invention, it is designed to be used in a combustion system of the type used in fuzzy combustion fossil fuel fired furnaces and incorporates the use of multi-angle overfire air introduction patterns. A high performance overfire air system for NOx control is provided. In addition, according to the present invention, the total amount of overfire air is designed to be used in a combustion system of the type used in fuzzy-fired fossil fuel fired furnaces and according to a multi-angle overfire air introduction pattern. High performance overfire for NOx control, characterized in that a part of the flow is introduced at different angles and a horizontal "spray" or "fan" distribution of the overfire air over the planar area of the furnace An air system is provided.

Further, in accordance with the present invention, the overfire air is designed to be used in a combustion system of the type used in fuzzy-fueled fossil fuel fired furnaces, and overfire air is supplied to the furnace at a rate faster than that used in conventional combustion systems. A high performance overfire air system for NOx control, also introduced at a sufficiently high speed, is provided. Moreover, according to the present invention, it is designed to be used in a combustion system of the type used in fuzzy fuel-fired combustion furnaces, to provide additional equipment, catalysts or fuel costs for operation. There is provided a high performance overfire air system for NOx control, where no increase is required. Also, according to the present invention, there are other NOx emission reduction types designed to be used in combustion systems of the type used in fog-fired fossil fuel fired furnaces and used to further reduce NOx emissions. A high performance overfire air system for NOx control is provided that is fully compatible with systems such as limestone injection systems, reburn systems, and selective catalytic reduction (SCR) systems. Finally, according to the present invention, it is designed to be used in a combustion system of the type used in fuzzy combustion fossil fuel combustion furnaces, whether applied to new combustion systems or to existing combustion systems. A high performance overfire air system for NOx contact is provided, characterized in that it can be adapted very equally, even for applications to air.

While several embodiments of the present invention have been described in detail, it should be understood that variations thereof (some of which have been described) may be readily made by those skilled in the art. It is therefore contemplated that the appended claims will cover all such modifications as fall within the spirit and scope of the invention in addition to the modifications described above.

Claims (4)

(57) [Claims] 1. A furnace (10) having four corner portions (10a, 10b, 10c,
10d), the fossil fuel, the combustion supporting secondary air and the additional fossil fuel are each placed at a first height,
A wind box (22) for introducing into the burner area (16) of the furnace (10) from a second height above the height of the furnace and from a third height above the second height; At each of the four corners (10a, 10b, 10c, 10d) of the furnace (10) at a height above (22), overfire air is supplied from three different heights to the burner of the furnace (10). A method for operating fossil fuel fuel for NOx control in a configuration comprising three overfire air compartments (94,96,98) to be introduced into section (16), comprising: a. A burner section (10) in a furnace (10); F) introducing fossil fuel introduced through the wind box from the first level of the wind box (22) tangentially to the virtual circle in the center of the furnace at 16); b. Furnace (10) Combustion support secondary air introduced from the second height of the wind box (22) into the burner area (16) of the
Introduced tangentially to an imaginary circle in the center of the furnace; c. Introduced into the burner area (16) of the furnace (10) from the third height of the wind box (22) through said wind box Additional fossil fuel is introduced tangentially to the virtual circle in the center of the furnace; and d. Three overfire air compartments (94,96, 98), the overfire air introduced through the overfire air compartment from three different heights is introduced at different combustion angles, so that the overfire air falls on the planar area of the burner section (16) of the furnace (10). Establishing a horizontal "spray-like" or "fan-like" distribution of overfire air; a method for NOx controlled operation of a fossil fuel fired furnace. 2. Overfire air is passed into the burner section (16) of the furnace (10) through three overfire air compartments (94,96,98) to 60-90 m / sec (200-300 ft / ft).
2. The method for operating NOx control of a fossil fuel combustion furnace according to claim 1, wherein the introduction is performed at a speed in the range of (sec). 3. An additional overfire air is passed into the burner section (16) of the furnace (10) from a fourth height above a third height of the wind box (22) through the wind box. 2. The NOx control operation method for a fossil fuel combustion furnace according to claim 1, wherein the introduction is performed in a tangential direction with respect to an imaginary circle at the center of the inside. 4. A wind box (22) in the burner area (16) of the furnace (10).
More overfire air than the additional overfire air introduced through the wind box from the fourth height of the three overfire air compartments (94,96,98) into the burner section (16) of the furnace (10). 4. The fossil fuel combustion furnace according to claim 3, wherein
NOx control operation method.