CN112013543A - Flameless combustion and heat recovery device and application - Google Patents

Flameless combustion and heat recovery device and application Download PDF

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Publication number
CN112013543A
CN112013543A CN202010800651.4A CN202010800651A CN112013543A CN 112013543 A CN112013543 A CN 112013543A CN 202010800651 A CN202010800651 A CN 202010800651A CN 112013543 A CN112013543 A CN 112013543A
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China
Prior art keywords
piece
hearth body
circulation piece
inner circulation
internal circulation
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Granted
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CN202010800651.4A
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CN112013543B (en
Inventor
王飞飞
李鹏飞
米建春
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H8/00—Fluid heaters characterised by means for extracting latent heat from flue gases by means of condensation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H9/00—Details
    • F24H9/0005—Details for water heaters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H9/00—Details
    • F24H9/0005—Details for water heaters
    • F24H9/0036—Dispositions against condensation of combustion products
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H9/00—Details
    • F24H9/18—Arrangement or mounting of grates or heating means
    • F24H9/1809—Arrangement or mounting of grates or heating means for water heaters
    • F24H9/1832—Arrangement or mounting of combustion heating means, e.g. grates or burners
    • F24H9/1836—Arrangement or mounting of combustion heating means, e.g. grates or burners using fluid fuel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)

Abstract

The invention discloses a flameless combustion and heat recovery device and application. The device comprises: the device comprises a hearth body, a burner arranged at the inlet end of the hearth body, an internal circulation piece arranged in the hearth body, an annular cavity formed between the internal circulation piece and the hearth body, and a condensation heat exchange piece arranged on the internal circulation piece and/or the hearth body; the inner circulation piece is a cylinder with one open end and one closed end, the open end of the inner circulation piece faces the inlet end of the hearth body, and a preset interval is reserved between the open end of the inner circulation piece and the inlet end of the hearth body, so that fuel and oxidant sprayed from the burner enter the inner circulation piece to be subjected to flameless combustion, and combustion flue gas flows out of the open end of the inner circulation piece and is exhausted from the outlet end of the hearth body after passing through the annular cavity; the condensation heat exchange piece is used for recovering heat in the combustion flue gas. The inventionNot only can ensure the establishment of stable flameless combustion in the furnace, but also can realize low NOxThe high-efficiency heat recovery is realized while the discharge amount is reduced.

Description

Flameless combustion and heat recovery device and application
Technical Field
The invention belongs to the field of industrial hot water gas-fired boilers and flameless combustion, and particularly relates to a flameless combustion and heat recovery device and application.
Background
Implementation of coal-to-gas engineering, and related regulations on NOxThe regulation of emissions presents new challenges to the development of clean burning technologies and burners. The flameless combustion is volume combustion, has NO obvious flame front and local high temperature in the combustion process, and can convert NO into NOxThe discharge amount is reduced to an extremely low level, so that the technology is very suitable for application in the fields of industrial boilers and the like. The power density of industrial boilers is relatively high, typically at MW/m3The increase in grade and power will tend to cause heat build-up in the furnace and an increase in average temperature, which will result in NOxThe increase of the discharge capacity requires the heat in the furnace to be dissipated so as to reduce the average temperature in the furnace. In actual industrial system, like gas boiler, the quick scattering and disappearing can be realized through the water-cooling wall to the heat of burning in the stove, but, flameless burning need build suitable thermal environment in the stove in order to maintain stably, if directly be applied to industrial boiler with flameless burning to realize the heat through the water-cooling wall and scatter and disappear fast, then arouse the problem such as burning unstability very likely.
Therefore, in an actual industrial system, when the heat loss in the boiler is too much, such as the water wall in the boiler is getting a lot of heat, the thermal environment required by the flameless combustion cannot be guaranteed, thereby causing flameout instability of the flameless combustion, and when the heat loss in the boiler is too little, the local high temperature and NO can be causedxThe emissions increase. As such, flameless combustion has not been widely popularized in the industrial boiler field.
Patent document CN203758260U discloses a furnace of a gas industrial boiler, which solves the problem of unstable combustion in a combustion furnace. However, in the application process of the furnace pipe, the combustion reaction intensity in the furnace is increased, and the combustion heat dissipation rate in the furnace pipe is difficult to control, so that pollutants (such as NO) are generatedx) The discharge amount is too high, and the application value is relatively low. Therefore, how to simultaneously realize high-efficiency utilization of heat and low NOxEmissions are important issues that must be addressed before applying flameless combustion technology to heat-dominated industries, such as industrial boilersAnd (5) problems are solved.
Disclosure of Invention
In view of the above defects or improvement needs of the prior art, the present invention provides a flameless combustion and heat recovery device and an application thereof, and aims to provide an internal circulation member in a boiler and combine a condensation heat exchange member with the boiler, so as to realize stable flameless combustion and high efficiency heat recovery. Thereby solving NO in the existing boilerxThe discharge amount is high, and the heat can not be efficiently recovered when the flameless combustion technology is directly adopted.
To achieve the above object, according to one aspect of the present invention, there is provided a flameless combustion and heat recovery apparatus, comprising: the device comprises a hearth body, a burner arranged at the inlet end of the hearth body, an internal circulation piece arranged in the hearth body, an annular cavity formed between the internal circulation piece and the hearth body, and a condensation heat exchange piece arranged on the internal circulation piece and/or the hearth body;
the inner circulation piece is a cylinder with one open end and one closed end, the open end of the inner circulation piece faces the inlet end of the hearth body, and a preset interval is reserved between the open end of the inner circulation piece and the inlet end of the hearth body, so that fuel and oxidant sprayed from a burner enter the inner circulation piece to be subjected to flameless combustion, and combustion flue gas flows out of the open end of the inner circulation piece, passes through the annular cavity and is discharged from the outlet end of the hearth body; the condensation heat exchange piece is used for recovering heat in the combustion flue gas.
Preferably, the material of the internal circulation piece has a thermal conductivity of 0.01-5W/m.K.
Preferably, the setting position of the condensation heat exchange member is determined by the heat conductivity coefficient of the material of the inner circulation member; when the heat conductivity coefficient of the material of the internal circulation piece is 0.01-1W/m.K, the condensation heat exchange piece is arranged on the internal circulation piece or on the internal circulation piece and the hearth body simultaneously; when the heat conductivity coefficient of the material of the internal circulation piece is 1-5W/m.K, the condensation heat exchange piece is arranged on the hearth body.
Preferably, the internal circulation piece is in a straight cylinder shape or a non-straight cylinder shape; when the inner circulation piece is in a non-straight cylinder shape, the inner circulation piece gradually expands or gradually shrinks from the open end to the closed end of the inner circulation piece according to a preset angle.
Preferably, the preset angle is greater than 0 ° and less than or equal to 15 °.
Preferably, the length ratio of the internal circulation piece to the hearth body is (0.3-0.9): 1, the ratio of the hydraulic diameter of the internal circulation piece to the hydraulic diameter of the hearth body is (0.3-0.9): 1.
preferably, the preset distance is 1% -15% of the length of the hearth body.
Preferably, the burner includes both a flame burner and a flameless burner, and the burner is disposed at the symmetrical center or the asymmetrical center of the inlet end of the furnace body.
Preferably, the inner circulation piece and the cross section of the hearth body are independently selected from circular or regular polygon.
According to another aspect of the present invention there is provided a use of the apparatus described above, the use comprising the steps of: (1) forming stable flamed combustion in the inner circulation piece by using a flamed combustor; when the average temperature of the flue gas in the internal circulation piece rises to 600-800 ℃, closing the flamed combustor, and simultaneously opening the flameless combustor to form flameless combustion; (2) the flow rate of the condensing medium in the condensing heat exchange member is controlled so that the average temperature of the flameless combustion in the inner circulation member is 900-1300 ℃.
In general, the above technical solutions conceived by the present invention include at least the following advantageous effects compared to the prior art.
(1) The internal circulation piece is arranged in the boiler, the condensation heat exchange piece is combined with the boiler, the high-temperature environment required by flameless combustion in the internal circulation piece can be ensured, the effective utilization of combustion heat can be realized, and NO is reducedxThe utilization rate of the heat of the combustion reaction of the whole device is maximized while the emission is realized, and the device is suitable for applying a flameless combustion technology in industries such as industrial boilers and the like which mainly use the heat. Solves the problem of NO in the prior artxThe discharge amount is high, and the heat of the flameless combustion device is difficult to efficiently recover.
(2) The arrangement position of the condensation heat exchange member is determined according to the material heat conductivity coefficient of the inner circulation member, so that stable flameless combustion and efficient heat recovery can be realized more accurately and effectively. When the material thermal conductivity coefficient of the internal circulation piece is relatively small, the internal temperature of the internal circulation piece is very high, and at the moment, the condensation heat exchange piece is arranged on the internal circulation piece to extract heat and reduce the temperature, and the graded recovery of heat is realized. When the material coefficient of heat conductivity of inner loop spare is great relatively, the inner loop spare internal temperature can be through self heat conduction to the ring chamber, at this moment, only need set up condensation heat transfer spare on the furnace body, in heat recovery, guarantee flameless combustion's stability in the inner loop spare.
(3) Through optimizing various geometric parameters of the inner circulation piece, the inner circulation piece can be guaranteed to form an effective high-temperature environment and a large-scale backflow space, meanwhile, the smoke can be fully released in the annular cavity, the flowing resistance is moderate, and the safety and the stability of the whole device are improved.
Drawings
FIG. 1 is a schematic structural diagram of a flameless combustion and heat recovery apparatus according to an embodiment of the present invention;
FIG. 2 is a graph showing the maximum temperature in the inner circulation member and NO in the case where the condensation heat exchange member is not provided in the flameless combustion and heat recovery apparatus according to the embodiment of the present inventionxThe impact of emissions;
FIG. 3 is a schematic structural diagram of a flameless combustion and heat recovery device according to an embodiment of the present invention, wherein a condensing heat exchange member is disposed on an inner circulation member;
FIG. 4 is a schematic structural diagram of a condensing heat exchanger disposed on a furnace body of the flameless combustion and heat recovery apparatus according to the embodiment of the present invention;
FIG. 5 is a schematic view showing a structure in which an inner circulation member of the flameless combustion and heat recovery apparatus according to the embodiment of the present invention is gradually expanded in a non-straight tubular shape;
FIG. 6 is a schematic view of a non-straight-cylindrical tapered inner circulation member of the flameless combustion and heat recovery apparatus according to the embodiment of the present invention;
FIG. 7 shows an internal circulation of the flameless combustion and heat recovery apparatus according to the embodiment of the present inventionThe configuration of the ring member is such as to provide maximum temperature and NO in the inner circulation memberxThe impact of emissions;
FIG. 8 is a schematic cross-sectional view taken at A-A of the flameless combustion and heat recovery apparatus of FIG. 1;
FIG. 9 is a view showing the arrangement position of the burner in the flameless combustion and heat recovery apparatus according to the embodiment of the present invention with respect to the maximum temperature in the inner circulation member and NOxThe effect of emissions.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:
1-a hearth body; 2-a burner; 3-an internal circulation piece; 4-ring cavity; 5-condensation heat transfer; 6-inner chamber;
101-an inlet end of the furnace body; 102-an outlet end of the furnace body; 301-open end of the inner circulation member.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
An embodiment of the present invention provides a flameless combustion and heat recovery apparatus, referring to fig. 1, comprising: the hearth comprises a hearth body 1, a combustor 2 arranged at an inlet end 101 of the hearth body, an inner circulation piece 3 arranged inside the hearth body 1, a ring cavity 4 formed between the inner circulation piece 3 and the hearth body 1, and a condensation heat exchange piece 5 arranged on the inner circulation piece 3 and/or the hearth body 1. The inner circulation piece 3 is a cylinder with one open end and one closed end, the open end 301 of the inner circulation piece faces the inlet end 101 of the hearth body, and a preset interval is reserved between the open end and the inlet end 101 of the hearth body, so that fuel and oxidant sprayed from the burner 2 enter the inner circulation piece 3 for flameless combustion, and combustion flue gas flows out of the open end 301 of the inner circulation piece, passes through the annular cavity 4 and is discharged from the outlet end 102 of the hearth body; the condensation heat exchange piece 5 is used for recovering heat in the combustion flue gas.
The condensation heat exchange member 5 can be, for example, a water-cooled wall, the water-cooled wall can be arranged in a way that the water-cooled wall is paved on the inner circulation member 3 and/or the inner wall surface of the hearth body 1 according to a common way in the prior art, and an inlet and an outlet of a heat exchange medium (such as water) are arranged on the water-cooled wall. In a possible way of embodiment of the invention, the material of the inner circulation member 3 has a thermal conductivity of 0.01-5W/m.k. The internal circulation member 3 is preferably a clay refractory brick, a mullite brick, alumina, high alumina brick, or the like, which has a small thermal conductivity in the range of 0.01 to 5W/m.K.
And the setting position of the condensation heat exchange member 5 is determined by the heat conductivity coefficient of the material of the internal circulation member 3; wherein, when the material heat conductivity coefficient of the internal circulation piece 3 is 0.01-1W/m.K, the condensation heat exchange piece 5 is arranged on the internal circulation piece 3 or on the internal circulation piece 3 and the hearth body 1 simultaneously. When the heat conductivity coefficient of the material of the internal circulation piece 3 is 1-5W/m.K, the condensation heat exchange piece 5 is arranged on the hearth body 1.
Referring to FIG. 2, FIG. 2 shows the material thermal conductivity of the inner circulation member of the flameless combustion and heat recovery apparatus without the provision of the condensing heat transfer member against the maximum temperature in the inner circulation member and NOxThe effect of emissions. It can be seen that the too low thermal conductivity will cause the heat in the inner chamber to be hard to dissipate, so it is necessary to extract heat through the water wall of the inner wall to reduce the temperature and NO in the furnacexAnd (4) discharging. And when the thermal conductivity coefficient of the material of the inner circulation piece is more than 5W/m.K, the combustion is extinguished.
Specifically, referring to fig. 3, the inner wall of the inner circulation member 3 forms an inner chamber 6 which is open at one end, and when the thermal conductivity of the material of the inner circulation member 3 is relatively small (0.01-1W/m · K), the average temperature in the inner chamber 6 of the inner circulation member 3 is high, at this time, the condensation heat exchange member 5 is provided on the inner circulation member 3, for example, a water cooling wall is provided on the inner wall of the inner circulation member 3. Part of the heat can be extracted, and the average combustion temperature in the inner chamber 6 can be controlled at 900-1300 ℃ by adjusting the water flow velocity in the water-cooling wall. ByIn NOxThe generation of NO is sensitive to temperature, and when the temperature exceeds about 1450 ℃, NO is generatedxMass production begins. Therefore, the embodiment of the invention controls the average combustion temperature in the inner chamber 6 to be 1000-1300 ℃ through the condensation heat exchange piece 5 arranged on the inner circulation piece 3, and can realize the reduction of NOxThe discharge amount, and the heat recovery can be realized by the heat extracted by the condensation heat exchange member 5.
Referring to fig. 1, when the material thermal conductivity of the internal circulation member 3 is relatively small (0.01-1W/m · K), the average temperature in the inner chamber 6 of the internal circulation member 3 is high, and at this time, the condensation heat exchange member 5 may be provided on both the internal circulation member 3 and the furnace body 1, for example, water cooling walls may be provided on the inner wall of the internal circulation member 3 and on the inner wall of the furnace body 1. In this way, the average temperature in the inner chamber 6 is reduced, i.e. a portion of the heat is extracted, by the water walls on the inner wall of the inner circulation member 3. Meanwhile, the heat of the flue gas entering the annular cavity 4 is recovered through the water-cooled wall on the inner wall of the hearth body 1, and NO is reducedxAnd meanwhile, the graded utilization and the maximum utilization rate of heat are realized. By adopting the manner of arranging the condensation heat exchange member, the heat extraction rate of the flameless combustion and heat recovery device provided by the embodiment of the invention can reach 90 percent at most, wherein the outer chamber is about 60 percent, and the inner chamber is about 30 percent (here, the heat extraction rate is the ratio of heat extraction to input power). And when flameless combustion is realized in the prior art, the heat extraction rate of the hearth system is about 50 percent at most.
Referring to fig. 4, when the thermal conductivity of the material of the internal circulation member 3 is relatively large (1-5W/m · K), the condensation heat exchange member 5 is disposed on the furnace body 1. Because the material coefficient of heat conductivity of the inner circulation piece 3 is higher, a part of heat in the inner chamber 6 can be conducted through the inner circulation piece 3 and directly enters the annular cavity 4, and after the flue gas enters the annular cavity 4, the rest of the heat of the flue gas can be extracted through the water-cooled wall of the hearth body 1.
When the thermal conductivity of the material of the internal circulation member 3 is equal to 1W/m · K, the condensation heat exchange member 5 may be disposed on the internal circulation member 3 or both the internal circulation member 3 and the furnace body 1, or the condensation heat exchange member 5 may be disposed on the furnace body 1.
Referring to fig. 1, 5 and 6, in a possible way of the embodiment of the present invention, the internal circulation member 3 is a straight cylinder or a non-straight cylinder; when the inner circulation member 3 is in a non-straight cylinder shape, the inner circulation member gradually expands or gradually contracts from the open end 301 to the closed end according to a preset angle. The preset angle is greater than 0 ° and less than or equal to 15 °. Referring to fig. 5, the inner circulation member 3 is arranged in such a manner as to be gradually expanded from the open end 301 to the closed end thereof, and referring to fig. 6, the inner circulation member 3 is arranged in such a manner as to be gradually reduced from the open end 301 to the closed end thereof. Preferably, the inner circulation member 3 is gradually expanded from the open end 301 to the closed end by 15 °, and the NO can be maximally reduced by the gradual expansion by 15 °xThe amount of discharge of (c).
Referring to FIG. 7, it is shown that the inner circulation member 3 of the embodiment of the present invention is gradually adjusted in angle from the inner circulation member 3 arranged in a 15 degree tapered manner to the inner circulation member 3 arranged in a straight cylindrical manner (from-15 degree to 0 degree as shown in FIG. 7), and is gradually adjusted in angle from the inner circulation member 3 arranged in a straight cylindrical manner to the inner circulation member 3 arranged in a 15 degree tapered manner (from 0 degree to 15 degree as shown in FIG. 7), for NOxThe amount of emissions and the maximum temperature within the internal circulation. In the figure 7, the length of the hearth body is 1.2m, the hydraulic diameter of the hearth body is 0.3m, the length of the internal circulation piece is 1m, and the hydraulic diameter of the internal circulation piece is 0.25 m.
It can be seen that by providing the inner circulation member with a gradual expansion of 15 deg., the maximum temperature within the inner circulation member is relatively minimal (about 1650 deg.C), and NO is relatively lowxThe discharge was relatively minimal (about 7.2ppm) and the maximum temperature in the inner circulation member was relatively highest (about 1780 ℃ C.) with the inner circulation member arranged in a 15 ℃ tapering manner, NOxThe emissions were also relatively maximum (about 10.3 ppm). The use of the 15 degree taper enables a 25% reduction in NO to be achieved relative to the 15 degree taper of the inner circulation member 3 (FIG. 6) of the embodiment of the inventionxAnd (5) discharging. The inner circulation member 3, NO is arranged from a manner of gradually reducing at 15 degrees to a manner of being in a straight cylinder shapexDischargingGradually lowered, and the inner circulation member 3 is disposed from a straight cylindrical form to a form gradually expanded by 15 DEG, NOxThe emissions gradually decrease. The above dimensions are only one possible form, and this trend still exists when the dimensions of the hearth and the internal circulation member are changed.
In addition, the length ratio of the internal circulation piece 3 to the hearth body 1 is (0.3-0.9): 1, the ratio of the hydraulic diameter of the internal circulation piece 3 to the hydraulic diameter of the hearth body 1 is (0.3-0.9): 1. if these two ratios are too small, so that the inner chamber 6 is too small, this will result in too short a residence time of the fumes in the entire device, despite the NOxThe emission of (2) is reduced, but the maximum heat extraction rate of the whole device cannot reach 90%. If the two ratios are too large, the inner chamber 6 is too large, which is equivalent to fully extruding the hearth space, thereby reducing the heat exchange probability of the annular cavity 4, and also being incapable of ensuring that the maximum heat extraction rate of the whole device cannot reach 90%.
The preset distance between the open end 301 of the internal circulation piece and the inlet end 101 of the hearth body is 1-15% of the length of the hearth body 1. The length of the hearth body 1 is indicated by L in fig. 1, and the length of the inner circulation member 3 is also indicated by L in fig. 1. If the value of the preset distance is too small, the retention time of the flue gas in the internal circulation piece 3 is too long, and high temperature and more NO are easily formedxAnd the resistance of the hearth is increased; if the predetermined distance is too large, the residence time of the flue gas in the inner circulation member 3 is too short, despite NOxThe combustion is unstable, and the maximum heat extraction rate of a hearth system cannot reach 90 percent.
Referring to fig. 8, the inner circulation member 3 is selected from a circle or a regular polygon independently of the cross section of the furnace body 1. In fig. 8 (a), the cross section of the hearth body 1 is a regular quadrangle, and the cross section of the inner circulation member 3 is a circle. In fig. 8 (b), the cross section of the hearth body 1 is a regular quadrangle, and the cross section of the inner circulation member 3 is a regular triangle. In fig. 8 (c), the cross sections of the hearth body 1 and the inner circulation member 3 are both square. In fig. 8 (d), the cross section of the hearth body 1 is a regular quadrangle, and the cross section of the inner circulation member 3 is a regular pentagon. In fig. 8 (e), the hearth body 1 and the inner circulation member 3 are both circular in cross section. In FIG. 8 (f), the cross section of the hearth body 1 is circular, and the cross section of the inner circulation member 3 is regular triangle. In FIG. 8 (g), the cross section of the hearth body 1 is circular, and the cross section of the inner circulation member 3 is square. In fig. 8 (h), the cross section of the hearth body 1 is circular, and the cross section of the inner circulation member 3 is regular pentagon. Wherein, the regular quadrilateral furnace body 1 and the inner circulation piece 3 can form stronger flue gas entrainment in the furnace relative to the circular and polygonal furnace body 1 and the inner circulation piece 3, thereby reducing the temperature in the furnace and the generation amount of NOx. Compared with the hearth body 1 and the internal circulation piece 3 with other shapes, the hearth body 1 and the internal circulation piece 3 with the square shape can reduce the NOx emission by about 15 percent.
In the embodiment of the present invention, the burner 2 includes both a flame burner and a flameless burner. Namely, the burner 2 is a combination of a flame burner and a flameless burner; the flame burner is used for stabilizing flame at the initial stage, and can adopt a rotational flow flame stabilizer, a slotted bluff body flame stabilizer or a non-slotted bluff body flame stabilizer; the flameless combustor is used in stable flameless combustion stage, and may be non-premixed, premixed or direct jet nozzle to ensure the high speed jetting of fuel and air into the inner cavity to form flameless combustion. The fuel injected into the apparatus provided by the embodiment of the present invention through the burner 2 may be natural gas, ethane, propane, hydrogen, low heating value synthesis gas, or other gaseous fuel, and the oxidant may be air, a mixture of oxygen and inert gas, or a mixture of air and inert gas.
The burner 2 is disposed at the symmetric center or the asymmetric center of the inlet end 101 of the furnace body, and the inlet end 101 of the furnace body is a baffle. The burners 2 are preferably arranged at the asymmetric center of the inlet end 101 of the furnace body, which results in a stronger entrainment rate of flue gas in the furnace than at its symmetric center, thereby reducing the average temperature in the furnace.
Referring to FIG. 9, it is shown that in an embodiment of the invention burners are provided at the symmetric center and the asymmetric center of the inlet end 101 of the furnace body for NOxThe amount of emissions and the maximum temperature within the internal circulation. Wherein, the length of the hearth body in the figure 7 is 1.2m, and the hydraulic diameter of the hearth body0.3m, the length of the internal circulation piece is 1m, and the hydraulic diameter of the internal circulation piece is 0.25 m. The internal circulation piece is arranged in a straight cylinder shape. It can be seen that locating the burner at the asymmetric center of the inlet end 101 of the furnace body reduces the NO by about 50% over locating it at the symmetric centerxAnd (4) discharging the amount. The maximum temperature in the internal circulation member also has to be significantly reduced. The above dimensions are only one possible form, and this trend still exists when the dimensions of the hearth and the internal circulation member are changed.
Another embodiment of the present invention provides a use of the apparatus as described above, the use comprising the steps of: (1) forming stable flamed combustion in the inner circulation piece by using a flamed combustor; gradually closing the flamed combustor and simultaneously gradually opening the flameless combustor to form flameless combustion after the average temperature of the flue gas in the internal circulation piece is increased to 600-800 ℃; (2) the flow rate of the condensing medium in the condensing heat exchange member is controlled so that the average temperature of the flameless combustion in the inner circulation member is 900-1300 ℃.
Specifically, in the initial stage, the fluid flow in the water-cooled wall of the hearth body 1 is slowed down, so that the heat loss of the hearth body 4 is reduced, stable flame combustion is formed in the inner chamber 6 by adopting a flame burner, the inner chamber 6 is preheated, in the process, the combustion power can be gradually increased, the combustion mainly occurs in the inner chamber 6, and the flue gas enters the annular cavity 4 through a gap between the open end 301 of the inner circulating piece and the inlet end 101 of the hearth body and then flows out through the outlet end 102 of the hearth body. When the average temperature of the flue gas in the internal circulation piece 3 rises to 600-800 ℃, gradually closing the flameless burner, simultaneously gradually opening the flameless burner, and enabling the inner chamber 6 to generate large-scale entrainment through high-speed jet flow to form flameless combustion so as to realize the switching of combustion modes.
When the heat conductivity coefficient of the material of the internal circulation piece 3 is relatively large (1-5W/m.K), the temperature in the inner chamber 6 is relatively high, the flow rate control of flowing water in the water cooling wall on the internal circulation piece 3 is conducted (for example, an inlet and outlet valve of the water cooling wall is controlled), a part of heat is properly extracted, the combustion temperature in the inner chamber is controlled to be 900-1300 ℃, and after flue gas enters the annular cavity 4, the heat can be extracted through the water cooling wall on the hearth body 1, so that the graded utilization and the maximum utilization rate of the heat are realized. The heat diffusion can also be carried out through the wall surface of the hearth body 1, namely, the water-cooled wall can also not be arranged on the hearth body 1.
When the heat conductivity coefficient of the material of the inner circulation piece 3 is relatively small (0.01-1W/m.K), part of heat in the inner chamber 6 can directly enter the annular cavity 4 through the wall surface of the inner circulation piece 3, and after the flue gas enters the annular cavity 4, the heat can be extracted through the water-cooled wall on the hearth body 1. The flow speed of flowing water in the water-cooled wall on the hearth body 1 is controlled, so that the combustion temperature in the inner chamber is 900-1300 ℃.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A flameless combustion and heat recovery apparatus, comprising: the device comprises a hearth body (1), a combustor (2) arranged at an inlet end (101) of the hearth body, an internal circulation piece (3) arranged in the hearth body (1), an annular cavity (4) formed between the internal circulation piece (3) and the hearth body (1), and a condensation heat exchange piece (5) arranged on the internal circulation piece (3) and/or the hearth body (1);
the inner circulation piece (3) is a cylinder with one open end and one closed end, the open end (301) of the inner circulation piece faces the inlet end (101) of the hearth body, a preset distance is reserved between the open end and the inlet end (101) of the hearth body, so that fuel and oxidant sprayed from the burner (2) enter the inner circulation piece (3) to be subjected to flameless combustion, and combustion flue gas flows out of the open end (301) of the inner circulation piece, passes through the annular cavity (4) and is discharged from the outlet end (102) of the hearth body; the condensation heat exchange piece (5) is used for recovering heat in the combustion flue gas.
2. The device according to claim 1, characterized in that the material of the inner circulation member (3) has a thermal conductivity of 0.01-5W/m-K.
3. The apparatus according to claim 1, wherein the position of the condensation heat exchange member (5) is determined by the thermal conductivity of the material of the internal circulation member (3); when the heat conductivity coefficient of the material of the internal circulation piece (3) is 0.01-1W/m.K, the condensation heat exchange piece (5) is arranged on the internal circulation piece (3) or simultaneously arranged on the internal circulation piece (3) and the hearth body (1); when the material heat conductivity coefficient of the internal circulation piece (3) is 1-5W/m.K, the condensation heat exchange piece (5) is arranged on the hearth body (1).
4. The device according to claim 1, characterized in that the internal circulation member (3) is of a straight or non-straight cylindrical shape; when the inner circulation piece (3) is in a non-straight cylinder shape, the inner circulation piece gradually expands or gradually shrinks from the open end (301) to the closed end of the inner circulation piece according to a preset angle.
5. The device according to claim 4, characterized in that said preset angle is greater than 0 ° and less than or equal to 15 °.
6. The apparatus according to claim 1, characterized in that the ratio of the length of the internal circulation member (3) to the furnace body (1) is (0.3-0.9): 1, the ratio of the hydraulic diameter of the inner circulation piece (3) to the hydraulic diameter of the hearth body (1) is (0.3-0.9): 1.
7. the apparatus according to claim 1, characterized in that the preset spacing is 1-15% of the length of the furnace body (1).
8. The apparatus according to claim 1, characterized in that the burners (2) comprise both a flame burner and a flameless burner, the burners (2) being arranged at the symmetrical or asymmetrical center of the inlet end (101) of the furnace body.
9. The apparatus according to claim 1, characterized in that the inner circulation member (3) is selected from circular or regular polygon shape independently of the cross section of the furnace body (1).
10. Use of the device according to any of claims 1-9, characterized in that the use comprises the following steps:
(1) forming stable flamed combustion in the inner circulation piece by using a flamed combustor; when the average temperature of the flue gas in the internal circulation piece rises to 600-800 ℃, closing the flamed combustor, and simultaneously opening the flameless combustor to form flameless combustion;
(2) the flow rate of the condensing medium in the condensing heat exchange member is controlled so that the average temperature of the flameless combustion in the inner circulation member is 900-1300 ℃.
CN202010800651.4A 2020-08-11 2020-08-11 Flameless combustion and heat recovery device and application Expired - Fee Related CN112013543B (en)

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