Nitrogen oxide reburning reduction nozzle and reduction method

Abstract

The invention provides a nitrogen oxide (NOx) reburning reduction nozzle and a reduction method. The NOx reburning reduction nozzle comprises a biomass conveying pipe which is communicated with an annular buffering cavity so as to convey biomass to the annular buffering cavity; biomass enters the annular cavity after passing through the annular buffer chamber, and the annular cavity is used for conducting annular self-excitation pulsation reburning reduction on biomass fuel near the wall face of the hearth. The first spray pipe is used for spraying biomass into the deep part of the hearth; and the second spray pipe is used for spraying the biomass into the middle position of the hearth. By means of the technical scheme, the annular cavity enables biomass fuel to generate annular self-excitation pulsation, meanwhile, the multi-stage spray pipe is utilized, the NOx reburning reduction efficiency of a boiler rear burning area is remarkably improved, meanwhile, circulating flue gas is used for conveying powdery biomass, and the annular self-excitation pulsation combustion device can be suitable for a circulating fluidized bed boiler and a pulverized coal boiler at the same time, especially for the NOx emission reduction situation under the oxygen-enriched combustion working condition. And the emission of pollutants can be effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nitrogen oxide reburning reduction, and particularly relates to a nitrogen oxide reburning reduction nozzle and a reduction method. BACKGROUND

[0002] With the continuous development of circulating fluidized bed (CFB) boiler technology, it has become an important clean combustion method for large coal-fired units in China due to its wide fuel adaptability, high combustion efficiency, and low pollutant emission. The World Energy Statistics Yearbook points out that the power industry is still the main field of coal consumption. However, a large amount of pollutants such as NO x (nitrogen oxides) are generated during coal combustion, so under the condition that coal still occupies the main position of energy consumption, how to realize efficient and low-pollution utilization of coal resources has become an important research direction in the energy field.

[0003] In order to realize low-nitrogen combustion of CFB oxygen-enriched combustion boiler, it is necessary to control the emission of NO x . In order to achieve this goal, researchers have widely explored various optimization schemes of operating and structural parameters, including adjusting the initial coal powder temperature, equivalence ratio, fuel / oxidant grading ratio, and oxygen concentration distribution, to improve the combustion conditions and NO x generation mechanism. Reburning technology, also known as fuel staging or in-furnace reduction technology, is one of the most effective measures among many in-furnace methods for reducing NO x emission. Reburning technology can ensure good combustion conditions in the early stage of fuel combustion, and the establishment of the reburning zone has little to do with the main combustion zone coal, which can solve the problem that other low-NO x combustion technologies have poor effects when burning low-volatile coal. Recirculated flue gas under oxygen-enriched combustion conditions can be used as a transport gas for reburning reduction, which can enhance the reduction effect. The combination of reburning reduction technology and oxygen-enriched combustion technology can simultaneously achieve CO2 and NO x emission reduction.

[0004] At present, there are related schemes about reducing boiler NO x emission, such as the prior art discloses a method for reburning and reducing NO x by adjusting coal powder with active gas, but there is no specific device or equipment that can reduce NO x emission, therefore, it is urgent to develop a specific device that can adapt to an oxygen-rich atmosphere, use CO2 or recirculated flue gas to transport powdered biomass as a reducing agent for NO x reburning reduction technology, so as to achieve efficient, economical and environmentally friendly NO x control effect in the post-combustion zone. SUMMARY

[0005] In view of the above defects or improvement needs of the prior art, the present application provides a nitrogen oxide reburning reduction nozzle and a reduction method, wherein the features of oxygen-enriched combustion and multi-stage staged reduction are combined, the arrangement forms of key structures such as an annular cavity, a first nozzle, and a second nozzle are introduced, multi-stage injection, CO2 delivery, a Venturi tube drainage, and annular self-excited pulsating reburning reduction technology are introduced in the post-combustion region, so that the pulverized biomass can be efficiently reburned in an oxygen-enriched atmosphere to reduce the emission of nitrogen oxides x The reburning reduction reaction significantly reduces the emission of nitrogen oxides, and the structure is simple, and is suitable for low-nitrogen transformation and application scenarios of circulating fluidized bed boilers and pulverized coal boilers.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0007] In a first aspect, the present application provides a nitrogen oxide reburning reduction nozzle, comprising:

[0008] A first nozzle having a first injection hole formed along an axis inside the first nozzle;

[0009] A second nozzle having a second injection hole formed inside the second nozzle and located on both sides of the first nozzle;

[0010] An annular cavity arranged around the second nozzle;

[0011] An annular buffer cavity arranged at one end of the annular cavity;

[0012] A biomass delivery pipe arranged at an end of the annular buffer cavity away from the annular cavity, the biomass delivery pipe having a delivery hole formed along an axis inside the biomass delivery pipe, the delivery hole being in communication with the annular buffer cavity;

[0013] A Venturi tube in communication with an end of the first nozzle away from the biomass delivery pipe;

[0014] Wherein, the annular buffer cavity has a perforated plate arranged near one side of the annular cavity, the perforated plate has a through hole formed therein, the inner wall of the through hole is inclined, and the diameter of the end of the through hole near the annular cavity is smaller than the diameter of the end of the through hole near the biomass delivery pipe; and the through hole is in communication with the annular cavity.

[0015] The annular cavity has an annular bluff body coaxially arranged away from one side of the annular buffer cavity, and the side wall of the annular bluff body gradually increases in thickness from the side wall near the annular buffer cavity to the side wall away from the annular buffer cavity;

[0016] The annular cavity has an open end near the annular bluff body;

[0017] The Venturi tube comprises a converging section, a throat section and a diverging section in sequence, wherein the converging section is communicated with the first nozzle at one end away from the throat section, the inner diameter of the converging section gradually decreases from the end close to the first nozzle to the end away from the first nozzle, the diverging section gradually increases in inner diameter from the end close to the throat section to the end away from the throat section, and a draft tube is arranged on the throat section.

[0018] Preferably, the included angle between the inner wall of the through hole and the axis of the through hole is 45°-75°.

[0019] Preferably, the projection of the side wall of the annular blunt body on a vertical plane is an isosceles triangle, the base length of the isosceles triangle is 0.1-0.3 of the width of the annular cavity, and the height of the isosceles triangle is 0.3-0.5 of the length of the annular cavity.

[0020] Preferably, the length of the Venturi tube is 0.2-0.3 of the length of the first nozzle;

[0021] The length of the converging section is 0.25-0.4 of the length of the Venturi tube, and the half-cone angle of the converging section is 12°-20°;

[0022] The length of the throat section is 0.1-0.2 of the length of the Venturi tube, and the ratio of the inner diameter of the throat section to the diameter of the first nozzle is (0.3-0.5):1;

[0023] The length of the diverging section is 0.4-0.6 of the length of the Venturi tube, and the half-cone angle of the diverging section is 5°-10°.

[0024] Preferably, the ratio of the length of the annular cavity to the length of the first nozzle is (0.15-0.3):1;

[0025] The ratio of the length of the annular buffer cavity to the length of the first nozzle is (0.1-0.2):1;

[0026] The ratio of the length of the biomass conveying pipe to the length of the first nozzle is (0.2-0.4):1;

[0027] The ratio of the width of the annular cavity to the diameter of the first nozzle is (3-5):1;

[0028] The ratio of the width of the annular buffer cavity to the width of the annular cavity is (0.5-0.7):1;

[0029] The ratio of the diameter of the conveying hole to the width of the annular cavity is (0.1-0.2):1, and the ratio of the diameter of the second nozzle to the diameter of the first nozzle is (0.5-0.8):1;

[0030] The ratio of the length of the second nozzle to the length of the first nozzle is (0.5-0.8):1.

[0031] Preferably, the ratio of the outer circumference of the annular cavity to the width is (4-8):1;

[0032] The ratio of the outer circumference of the annular cavity to the width is (4-8):1;

[0033] The ratio of the area of the through hole near the side of the annular cavity to the cross-sectional area of the annular cavity is 1:(4-25).

[0034] Preferably, the ratio of the inner diameter of the drainage tube to the inner diameter of the throat of the Venturi nozzle is (0.4-0.6):1;

[0035] The ratio of the length of the drainage tube to the inner diameter is (1.5-3):1.

[0036] In a second aspect, the present application also provides a method for reburning and reducing nitrogen oxides, comprising the following steps:

[0037] The reburning and reducing nozzle for nitrogen oxides is installed on one side of the boiler; wherein, when installed, the side of the annular cavity close to the orifice plate is attached to the side wall of the boiler, the annular cavity is connected to the inside of the boiler, and the first nozzle and the second nozzle both extend into the boiler;

[0038] The biomass fuel passes through the first nozzle and the Venturi nozzle into the boiler, in the Venturi nozzle, the biomass fuel is premixed with the flue gas in the furnace of the boiler, is partially pyrolyzed, is sprayed into the furnace, and then reacts with the nitrogen oxides in the furnace through reburning and reduction;

[0039] The biomass fuel passes through the second nozzle into the furnace, is mixed with the flue gas, and then reacts with the nitrogen oxides in the furnace through reburning and reduction;

[0040] The biomass fuel is transported into the annular buffer chamber through the biomass delivery tube, enters the annular cavity, and then oscillates in the annular cavity through self-excited pressure pulsation and is mixed with the flue gas, and finally enters the furnace through the annular blunt body to further strengthen the self-excited pulsation, and then reacts with the nitrogen oxides through reburning and reduction.

[0041] Preferably, the transport speed of the biomass fuel is 5-30 m / s;

[0042] If the boiler is a circulating fluidized bed boiler, the recommended reburning and reduction reaction temperature is 1050-1150 K;

[0043] If the boiler is a pulverized coal boiler, the recommended reburning and reduction reaction temperature is 1300-1400 K.

[0044] Preferably, the biomass fuel is transported into the combustion boiler through CO2 or flue gas.

[0045] The nitrogen oxide reburning reduction nozzle and the reduction method have the following beneficial effects relative to the prior art:

[0046] 1、The nitrogen oxide reburning reduction nozzle of the application, an annular cavity is arranged on the periphery of the nozzle, the annular cavity causes the biomass fuel to generate annular self-excited pulsation, and a multi-stage nozzle formed by the first nozzle and the second nozzle significantly improves the NO x Reduction efficiency in the post-combustion area of the boiler, and the use of the circulating flue gas to transport the powdered biomass can be simultaneously applied to the circulating fluidized bed boiler and the pulverized coal boiler, especially under the oxygen-enriched combustion condition of NO x X emission reduction, which can effectively reduce the emission of pollutants;

[0047] 2、The NO x X reburning reduction nozzle of the application generates periodic pressure fluctuation through the annular cavity to establish a stable self-excited pulsation flow field in the post-combustion area, significantly strengthens the disturbance mixing and mass transfer process of the biomass powder, the flue gas and NO x X, and thus effectively improves the reburning reaction rate of NO x X;

[0048] 3、The multi-stage injection structure composed of the annular self-excited pulsation injection area, the injection area formed by the second nozzle and the Venturi tube injection area realizes the spatial and chemical grading supply of the fuel, effectively prolongs the reburning reaction residence time, builds a progressive reduction atmosphere, and significantly improves the conversion efficiency of NO x X to N2. Compared with the conventional single-stage circular straight injection nozzle, under the same reburning condition, the NO x X reduction rate is increased from about 31% to 54% to 39% to 66%, and the denitrogenation efficiency is increased by about 8% to 12%. The application uses the CO2-enriched circulating flue gas as the biomass transport medium, avoids the exogenous N2 induced by air transport to generate NO x X, forms a local rich reduction atmosphere in the injection area, promotes the rapid pyrolysis of the biomass to generate CO, CH4 and H2 reducing gases, further strengthens the chemical reduction reaction of NO x X under the oxygen-enriched combustion environment, and realizes higher and more stable denitrogenation efficiency;

[0049] 4、The nozzle structure of the application is compact and has high modularity, can be directly applied to the oxygen-enriched combustion boiler without modifying the original air supply system, and can flexibly adjust the injection angle and arrangement mode according to the hearth structure, realizes the collaborative and efficient reduction of NO and N2O, suppresses the generation and emission of NO x X, has the advantages of high-efficiency denitrogenation, good combustion stability and safe and reliable operation, and is suitable for the low-NO x X emission modification and the popularization of the biomass reburning denitrogenation technology under the oxygen-enriched combustion condition. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description only show some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

[0051] Figure 1 For the NO x Structure diagram of the reburning injection nozzle;

[0052] Figure 2 For the NO Figure 1 Sectional view of the middle A-A surface;

[0053] Figure 3 For the NO x Structure diagram of the reburning injection nozzle installed on the boiler;

[0054] Figure 4 For the NO x Structure diagram of the reburning injection nozzle installed on the side wall of the boiler;

[0055] Figure 5 For the sectional view of the conventional single-stage direct injection reburning nozzle in Comparative Example 1. DETAILED DESCRIPTION

[0056] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of protection of the present application.

[0057] Those skilled in the art can understand that, unless specifically stated otherwise, the singular forms "one", "a", "said" and "the" used herein also include the plural forms. It should be further understood that the phrase "comprising" used in the specification of the present application means that the features, integers, steps, operations, elements and / or components exist, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we say that an element is "connected" to another element, it can be directly connected to the other element, or there can be intermediate elements. In addition, "connected" used herein can include wireless connection. The phrase "and / or" used herein includes all or any single unit and all combinations of the associated listed items.

[0058] In the present application, unless specifically stated and limited otherwise, a first feature is "on" or "under" a second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature is "over", "above" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the first feature is higher in horizontal height than the second feature. The first feature is "under", "below" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the first feature is lower in horizontal height than the second feature.

[0059] It should be understood that although the terms first, second, etc. can be employed in this disclosure to describe various information, such information should not be limited to these terms. These terms are only used to differentiate one piece of information from another piece of information of the same type.

[0060] The embodiment of the present application provides a nitrogen oxide (NO x ) reburning reduction nozzle, as shown in the figure, comprising: Figures 1-2

[0061] A first nozzle 4, a first injection hole is arranged in the first nozzle 4 along an axis;

[0062] A second nozzle 3, the second nozzle 3 is arranged on the outer periphery of the first nozzle 4, and a second injection hole 31 is arranged in the second nozzle 3 and located on both sides of the first nozzle 4;

[0063] A ring cavity 2, the ring cavity 2 is arranged on the outer periphery of the second nozzle 3;

[0064] A ring buffer cavity 7, the ring buffer cavity 7 is arranged at one end of the ring cavity 2;

[0065] A biomass conveying pipe 1, the biomass conveying pipe 1 is arranged at the end of the ring buffer cavity 7 away from the ring cavity 2, a conveying hole is arranged in the biomass conveying pipe 1 along an axis, and the conveying hole is in communication with the ring buffer cavity;

[0066] A Venturi tube 8, the Venturi tube 8 is arranged at the end of the first nozzle 4 away from the biomass conveying pipe 1;

[0067] The ring buffer cavity 7 is provided with a hole plate 5 close to the ring cavity, a through hole 51 is arranged on the hole plate 5, the inner wall of the through hole 51 is arranged in an inclined manner, the diameter of the end of the through hole 51 close to the ring cavity is smaller than the diameter of the end of the through hole 51 close to the biomass conveying pipe, and the through hole 51 is in communication with the ring cavity 2;

[0068] The ring cavity 2 is hollow (an annular cavity is arranged inside), a ring blunt body 6 is coaxially arranged in the ring cavity 2 away from the ring buffer cavity 7, and the side wall of the ring blunt body gradually increases in thickness from the side wall close to the ring buffer cavity to the side wall away from the ring buffer cavity;

[0069] ​The annular cavity 2 is open at one end close to the annular blunt body.

[0070] The Venturi tube 8 comprises a converging section 81, a throat section 82 and a diverging section 83 in sequence, wherein the converging section 81 is communicated with the first nozzle 4 at one end away from the throat section 82, the inner diameter of the converging section 81 gradually decreases from one end close to the first nozzle 4 to one end away from the first nozzle 4, and the inner diameter of the diverging section 83 gradually increases from one end close to the throat section 82 to one end away from the throat section 82; the throat section 82 is communicated with the draft tube 10, and the axis of the draft tube 10 is perpendicular to the axis of the Venturi tube 8.

[0071] The NO of the application x The re-combustion reduction nozzle comprises a first nozzle 4, a second nozzle 3, an annular cavity 2, an annular buffer cavity 7, a biomass delivery pipe 1 and a Venturi tube 8; wherein the first nozzle 4 is in the shape of a cylinder, and a first nozzle hole is formed in the first nozzle 4 along the axial direction; the second nozzle 3 is sleeved on the outer periphery of the first nozzle 4, and a second nozzle hole 31 is formed in the second nozzle 3 and located on both sides of the first nozzle 4, and the second nozzle hole 31 is parallel to the first nozzle hole; the annular cavity 2 is sleeved on the outer periphery of the second nozzle 3, one end of the annular cavity 2 is provided with the annular buffer cavity 7, the annular buffer cavity 7 is coaxially sleeved on the outer periphery of the second nozzle 3, and one end of the annular buffer cavity 7 is communicated with the biomass delivery pipe 1; the biomass delivery pipe 1 is in the shape of a cylinder, and a delivery hole is formed in the biomass delivery pipe 1 along the axial direction, and the delivery hole is communicated with the annular buffer cavity; a perforated plate 5 is arranged in the annular buffer cavity 7 close to the annular cavity, a through hole 51 is formed in the perforated plate 5, the inner wall of the through hole 51 is arranged in an inclined manner, the diameter of one end of the through hole 51 close to the annular cavity is smaller than the diameter of one end of the through hole 51 close to the biomass delivery pipe, that is, the diameter of one end of the through hole 51 close to the biomass delivery pipe 1 is larger, and the diameter of one end of the through hole 51 close to the annular cavity 2 is smaller; the annular blunt body 6 is coaxially arranged in the annular cavity 2 away from the annular buffer cavity 7, that is, the axis of the annular blunt body 6 is the same as the axis of the annular cavity 2, and the thickness of the side wall of the annular plate gradually increases from the direction close to the annular buffer cavity to the direction away from the annular buffer cavity, that is, the thickness of one end of the annular plate close to the biomass delivery pipe 1 is small, and the thickness of one end of the annular plate away from the biomass delivery pipe 1 is large.

[0072] The biomass delivery pipe 1 is communicated with the annular cavity 2, and is used for spraying the powdered biomass fuel into the annular cavity 2; a perforated plate 5 is arranged at the outlet end of the biomass delivery pipe 1, and the inner wall of the through hole 51 is arranged in an inclined manner, so that the powdered biomass is prevented from being accumulated at the edge of the through hole 51 to cause blockage, and the tapered nozzle formed by the through hole 51 helps to improve the velocity gradient of the jet flow, so that the jet flow is more likely to generate self-excited pulsation after entering the annular cavity 2; the annular cavity 2 is arranged in a self-excited pulsation structure, and the powdered biomass fuel is sprayed from the perforated plate, and periodic pressure fluctuation is generated in the annular cavity 2 under the action of the conveying gas flow, so that the self-excited pulsation phenomenon occurs, and the powdered biomass fuel finally passes through the annular bluff body 6 to further strengthen the self-excited pulsation, so that the structure can form a strong disturbance zone near the furnace wall surface, strengthen the mixing of the powdered biomass fuel and nitrogen oxides such as NO in the flue gas, and form a first self-excited pulsation reduction zone.

[0073] The second nozzle 3 is arranged around the outer periphery of the first nozzle 4, and is used for spraying the powdered biomass into the middle region of the furnace to form a second reduction zone; the first nozzle 4 is located at the center of the nozzle, and the spraying direction is perpendicular to the furnace wall surface, and is used for spraying the powdered biomass into the deep high-temperature zone of the furnace to form a third reduction zone; the central jet flow and the intermediate jet flow are gradually mixed in the furnace, so that the reduction gas is fully reacted with nitrogen oxides such as NO and N2O in different temperature layers, and the NO x The reburning reduction efficiency is improved.

[0074] The annular buffer cavity 7 is used for temporarily storing, stabilizing pressure and flow homogenizing the powdered biomass from the biomass delivery pipe 1, so that the instantaneous particle concentration and velocity fluctuation are buffered;

[0075] The Venturi tube 8 comprises a converging portion 81, a throat portion 82 and a diverging portion 83 which are sequentially communicated, wherein the converging portion 81 is communicated with the first nozzle 4 at the end away from the throat portion 82, the inner diameter of the converging portion 81 gradually decreases from the end close to the first nozzle 4 to the end away from the first nozzle 4, and the inner diameter of the diverging portion 83 gradually increases from the end close to the throat portion 82 to the end away from the throat portion 82; the drainage pipe 10 is arranged on the throat portion 82 in communication, and the axis of the drainage pipe 10 is perpendicular to the axis of the Venturi tube 8;

[0076] The reburning biomass powder enters the biomass delivery pipe, the first nozzle, and the second nozzle simultaneously. The biomass fuel entering the first nozzle is injected into the furnace through the Venturi tube. The biomass fuel first passes through the contraction section 81 in the Venturi tube to form a negative pressure, and the flue gas in the furnace is sucked into the throat section 82 through the drainage pipe 10, so that the flue gas in the furnace is mixed with the biomass powder in advance and pyrolysis releases reducing gas. Then, the biomass powder, the flue gas, and the reducing gas are further mixed in the gradually expanding section 83 and are injected into the furnace. After the biomass powder entering the second nozzle is injected into the furnace, it further drives the biomass powder and volatile matter sprayed from the annular cavity to mix with the flue gas, and the biomass powder itself pyrolysis releases reducing gas to reduce NO x .

[0077] In some embodiments, the included angle between the inner wall of the through hole 51 and the axis of the through hole 51 is 45°-75°.

[0078] In some embodiments, the projection of the side wall of the annular bluff body 6 on the vertical plane is an isosceles triangle, the length of the base of the isosceles triangle is 0.1-0.3 times the width of the annular cavity (the length of the base of the isosceles triangle is 0.5 times the width of the annular cavity), and the height of the isosceles triangle is 0.3-0.5 times the length of the annular cavity.

[0079] In some embodiments, to further improve the mixing effect of flow disturbance and fuel, the cross section of the annular cavity 2 can be designed as a variable cross section flow channel structure, that is, the cross section is expanded or reduced to strengthen the turbulent flow, and the mixing of reburning fuel and NO x is further strengthened. This structure can produce secondary pressure wave reflection during injection, form a stronger annular self-excited pulsation frequency, and thus enhance the flow disturbance in the near-wall region and the reburning reduction reaction activity.

[0080] In some embodiments, the first nozzle 4 is connected to the end of the biomass delivery pipe 1 and is provided with a Venturi tube 8, and the length of the Venturi tube is 0.2-0.3 times the length of the first nozzle;

[0081] The length of the contraction section 81 is 0.25-0.4 times the total length of the Venturi tube, the half-cone angle of the contraction section 81 is 12°-20°, and the cross section of the contraction section 81 is conical, and the included angle between the side of the cone and the axis of the cone is the half-cone angle;

[0082] The length of the throat section 82 is 0.1-0.2 times the total length of the Venturi tube, and the ratio of the inner diameter of the throat section 82 (the inner diameter of the throat section 82 is the same, that is, the throat section 82 is a cylindrical shape with the same diameter) to the diameter of the first nozzle is (0.3-0.5):1;

[0083] The length of the gradually expanding section 83 is 0.4-0.6 times the total length of the Venturi tube, the half-cone angle of the gradually expanding section 83 is 5°-10°, and the cross section of the gradually expanding section 83 is conical, and the included angle between the side of the cone and the axis of the cone is the half-cone angle.

[0084] In some embodiments, the ratio of the length of the annular cavity 2 to the length of the first nozzle 4 is (0.15~0.3):1;

[0085] The ratio of the length of the annular buffer cavity 7 to the length of the first nozzle 4 is (0.1~0.2):1;

[0086] The ratio of the length of the biomass delivery pipe 1 to the length of the first nozzle 4 is (0.2~0.4):1;

[0087] The ratio of the width of the annular cavity 2 to the diameter of the first nozzle is (3~5):1;

[0088] The ratio of the width of the annular buffer cavity 7 to the width of the annular cavity 2 is (0.5~7):1;

[0089] The ratio of the diameter of the delivery hole to the width of the annular cavity 2 is (0.1~0.2):1; the ratio of the diameter of the second nozzle to the diameter of the first nozzle is (0.5~0.8):1;

[0090] The ratio of the length of the second nozzle 3 to the length of the first nozzle 4 is (0.5~0.8):1.

[0091] The ratio of the outer circumference of the annular cavity 2 to the width is (4~8):1;

[0092] The ratio of the outer circumference of the annular buffer cavity 7 to the width is (4~8):1;

[0093] The ratio of the area of the through hole near the side of the annular cavity to the cross-sectional area of the annular cavity is 1:(4~25);

[0094] The ratio of the inner diameter of the drainage pipe to the inner diameter of the throat of the Venturi nozzle is (0.4~0.6):1;

[0095] The ratio of the length of the drainage pipe to the inner diameter is (1.5~3):1.

[0096] Specifically, the length of the annular cavity 2 is the length of the annular cavity 2 in the left-right direction, Figure 1 the width of the annular cavity 2 is the height of the annular cavity 2 in the up-down direction, i.e. the distance between the wall surface of the annular cavity 2 in contact with the second nozzle 3 and the outermost wall surface; Figure 1 the length of the annular buffer cavity 7 is the length of the annular buffer cavity 7 in the left-right direction, Figure 1 the width of the annular buffer cavity 7 is the height of the annular buffer cavity 7 in the up-down direction, i.e. the distance between the wall surface of the annular buffer cavity 7 in contact with the first nozzle 4 and the outermost wall surface; Figure 1The height of the middle annular buffer cavity 7 in the up-down direction, that is, in the radial direction; the outer circumference of the annular cavity 2 refers to: the cross section of the annular cavity 2 is a concentric circle, and the circumference corresponding to the outer circle is the outer circumference of the annular cavity 2; the outer circumference of the annular buffer cavity 7 refers to: the cross section of the annular buffer cavity 7 is a concentric circle, and the circumference corresponding to the outermost circle; the calculation method of the cross-sectional area of the annular cavity is: the cross section of the annular cavity is a concentric circle, wherein the inner circle radius r1 and the outer circle radius r2, and the cross-sectional area of the annular cavity is π(r2 2 - r1 2 )。

[0097] The above parameter configuration can balance the injection momentum and mixing efficiency, so as to ensure the high-efficiency reduction of NO x and the uniformity of the furnace temperature field.

[0098] The nozzle of the application is arranged in the post-combustion zone, can be used in cooperation with the oxygen-enriched combustion system, and realizes low nitrogen emission under high oxygen concentration. Compared with the traditional selective non-catalytic reduction method (SNCR) or the single-stage ordinary reburning nozzle structure, the application does not need to introduce ammonia reducing agent, avoids the generation of NO x induced by the exogenous N2 brought by air delivery; simultaneously, through the annular self-excited pulsation reinforced mixing and multi-stage injection distribution, the synergistic high-efficiency reduction of NO and N2O is realized, the generation and emission of NO x are inhibited, and the combustion stability is significantly improved.

[0099] The application sets the annular cavity at the periphery of the nozzle, establishes a stable self-excited pulsation flow field in the post-combustion zone through periodic pressure fluctuation, significantly strengthens the disturbed mixing and mass transfer process of biomass powder, flue gas and NO x , and thus effectively improves the reburning reduction reaction efficiency of NO x .

[0100] The application adopts the multi-stage injection structure composed of the annular self-excited pulsation injection zone, the injection zone formed by the second nozzle and the Venturi tube injection zone, realizes the spatial grading and chemical grading supply of fuel, effectively prolongs the reburning reaction residence time and builds a progressive reduction atmosphere, and thus the conversion efficiency of NO x to N2 is significantly improved. Compared with the conventional single-stage circular straight injection nozzle, under the same reburning working condition, the NO x reduction rate is increased from about 31% to 54% to 39% to 66%, and the denitrification efficiency is increased by about 8% to 12%.

[0101] The application uses CO2-enriched circulating flue gas as the biomass delivery medium, avoids the generation of NO xThe local reducing atmosphere is formed in the injection area, and the rapid pyrolysis of the biomass is promoted to generate CO, CH4 and H2 reducing gases, so that the chemical reduction reaction of NO x is further strengthened in the oxygen-enriched combustion environment, and higher and more stable denitration efficiency is achieved compared with the NO x reburning reduction in the air atmosphere.

[0102] The nozzle structure is compact and has high modularization, can be directly applied to the oxygen-enriched combustion boiler without modifying the original air supply system, and can flexibly adjust the injection angle and arrangement mode according to the hearth structure, has the advantages of high-efficiency denitration, good combustion stability, safe and reliable operation and the like, and is suitable for low-NO x x emission transformation and biomass reburning denitration technology popularization under the oxygen-enriched combustion condition.

[0103] Based on the same inventive concept, the application also provides a NO x reburning reduction method, comprising the following steps:

[0104] The NO x reburning reduction nozzle is installed on one side of the combustion boiler (specifically, the reburning zone in the hearth); wherein, when installed, the side of the annular cavity close to the orifice plate is attached to the side wall of the boiler, the annular cavity is located in the hearth of the boiler, the annular cavity is communicated with the hearth, the first nozzle, the second nozzle and the Venturi tube all extend into the boiler;

[0105] The biomass fuel enters the boiler through the first nozzle and the Venturi tube, in the Venturi tube, the biomass fuel is premixed with the flue gas in the hearth first, and then the reducing gas (CO, H2, CH4 and the like) is generated after part of the pyrolysis, and then injected into the hearth, and then the reburning reduction reaction with NO x occurs in the hearth;

[0106] The biomass fuel enters the hearth through the second nozzle at the same time, mixes with the flue gas, and the reburning reduction reaction with NO x occurs;

[0107] The biomass fuel is transported into the buffer chamber through the biomass conveying pipe at the same time, and then enters the annular self-excited pulsating cavity, and then the self-excited pulsation occurs in the cavity, and then the self-excited pulsation is further intensified through the annular bluff body, and then mixes with the boiler flue gas, and finally enters the combustion boiler, and then the reburning reduction reaction with NO x occurs.

[0108] In some embodiments, the biomass fuel first passes through the contraction section 81 in the Venturi tube to form a negative pressure, and the flue gas in the furnace is sucked into the throat section 82 through the draft tube 10, so that the flue gas in the furnace is mixed with the biomass powder in advance and pyrolysis to release reducing gas, and then the biomass powder, the flue gas and the reducing gas are further mixed in the diverging section 83 and sprayed into the furnace. After the biomass powder entering the second injection pipe is sprayed into the furnace, it further drives the biomass powder and volatile matter sprayed from the annular cavity to mix with the flue gas, while the biomass powder itself pyrolysis releases reducing gas to reduce NO x .

[0109] In some embodiments, after the biomass powder entering the second injection pipe is sprayed into the furnace, it further drives the biomass powder and volatile matter sprayed from the annular cavity to mix with the flue gas, while the biomass powder itself pyrolysis releases reducing gas to reduce NO x .

[0110] Specifically, during the operation of the nozzle, the biomass fuel is first sprayed into the annular buffer cavity 7 through the biomass delivery pipe 1, then enters the annular cavity 2 through the perforated plate 5, and finally passes through the annular bluff body 6 to form a strong annular self-excited pulsating combustion zone near the side wall of the combustion boiler. In this area, the main pyrolysis reaction of biomass fuel occurs, producing CO, H2, CH4 and other reducing gases, which provide the basis for the subsequent reburning reduction of nitrogen and oxygen gases such as NO x .

[0111] At the same time, part of the powdered biomass fuel is sprayed into the middle position of the boiler furnace through the second injection pipe 3, driving the reducing gas generated by the pyrolysis of the front end, the biomass and NO x to fully mix and form a main reburning reduction reaction zone in the middle position. At this time, the reducing gases such as CO, CH4 and H2 react with NO x to generate N2, achieving efficient decomposition and conversion of NO x .

[0112] At the same time, the biomass enters the first injection pipe 4 and is pre-mixed with the flue gas in the Venturi tube 8, and finally is sprayed into the deep part of the furnace; this area has high temperature and strong turbulence, and further strengthens the reburning reduction reaction between the reducing gas and NO x . Through this three-stage injection method, a multi-stage reaction structure of "near-wall annular self-excited pulsation, middle-layer reduction, and deep-layer strengthening" is formed, effectively prolonging the reburning reduction path of NO x .

[0113] In some embodiments, the biomass fuel is transported into the boiler by flue gas or CO2, and the fuel transport medium of the nozzle of the present application is circulating flue gas (the flue gas is the flue gas generated in the boiler, which is used as a carrier gas to transport the biomass fuel into the furnace, and the reaction generates new flue gas, which is used as a carrier gas to transport the biomass fuel again, and so on, to generate circulating flue gas) or CO2. In order to ensure the residence time of the reburning fuel in the reburning section, the transport speed is 5 m / s to 30 m / s, which is used to sequentially send the powdered biomass fuel into each nozzle. Using CO2 transport can avoid the participation of air and prevent the generation of thermal NO caused by exogenous nitrogen, and CO2 can participate in the carbon reaction to generate CO at high temperature, further enhancing the local reducing atmosphere.

[0114] The particle size of the biomass fuel is less than 200 μm, and the biomass fuel can be selected from biomass powders such as peanut shells, poplar, rice straws, corn stalks, and pine wood.

[0115] In some embodiments, if the boiler is a circulating fluidized bed boiler, the recommended reburning reduction temperature is 1050 K to 1150 K, and if the boiler is a pulverized coal boiler, the recommended reburning reduction temperature is 1300 K to 1400 K.

[0116] Further, referring to Figure 3 the NO x The reburning reduction nozzle is installed on one side of the boiler 20, Figures 3-4 the NO x The installation position of the reburning reduction nozzle is that the annular cavity is attached to the side wall of the combustion boiler on the side close to the orifice plate during installation, the annular cavity is located in the furnace of the boiler and is connected to the furnace, the first nozzle, the second nozzle, and the Venturi tube all extend into the combustion boiler, the flue gas generated by the reaction is discharged through the smoke exhaust bin and is used as a carrier gas to transport the biomass fuel again, and so on, to generate circulating flue gas.

[0117] The following further illustrates the NO x reburning reduction nozzle and reduction method. This part further illustrates the content of the present application in combination with specific embodiments, but should not be understood as a limitation of the present application. If not specifically stated, the technical means used in the embodiments are conventional means familiar to those skilled in the art. Unless specifically stated, the reagents, methods, and equipment used in the present application are conventional reagents, methods, and equipment in the art.

[0118] Example 1

[0119] The present embodiment provides a NO x reburning reduction method, which comprises the following steps:

[0120] The present embodiment provides a NO Figures 1-2 reburning reduction nozzle; x

[0121] ​An included angle between the inner wall of the through hole and the axis of the through hole is 60°;

[0122] The projection of the side wall of the annular bluff body on the vertical plane is an isosceles triangle, the length of the base of the isosceles triangle is 0.2 of the width of the annular cavity, the length of the base of the isosceles triangle is 0.5 of the width of the annular cavity, and the height of the isosceles triangle is 0.4 of the length of the annular cavity;

[0123] The length of the Venturi tube is 0.25 of the length of the first nozzle;

[0124] The length of the contraction part is 0.3 of the total length of the Venturi tube, and the half cone angle of the contraction part is 15°;

[0125] The length of the throat part is 0.15 of the total length of the Venturi tube, and the ratio of the inner diameter of the throat part to the diameter of the first nozzle is 0.4:1;

[0126] The length of the gradual expansion part is 0.55 of the total length of the Venturi tube, and the half cone angle of the gradual expansion part is 10°;

[0127] The ratio of the length of the annular cavity to the length of the first nozzle is 0.2:1;

[0128] The ratio of the length of the annular buffer cavity to the length of the first nozzle is 0.1:1;

[0129] The ratio of the length of the biomass conveying pipe to the length of the first nozzle is 0.3:1;

[0130] The ratio of the width of the annular cavity to the diameter of the first nozzle is 4:1;

[0131] The ratio of the width of the annular buffer cavity to the width of the annular cavity is 0.6:1;

[0132] The ratio of the diameter of the conveying hole to the width of the annular cavity is 0.2:1;

[0133] The ratio of the diameter of the second nozzle to the diameter of the first nozzle is 0.6:1;

[0134] The ratio of the length of the second nozzle to the length of the first nozzle is 0.6:1;

[0135] The ratio of the outer circumference of the annular cavity to the width is 8:1;

[0136] The ratio of the outer circumference of the annular buffer cavity to the width is 5:1;

[0137] The ratio of the area of the through hole close to the side of the annular cavity to the cross-sectional area of the annular cavity is 1:20;

[0138] The ratio of the inner diameter of the drainage tube to the inner diameter of the throat part of the Venturi nozzle is 0.5:1;

[0139] The ratio of the length of the drainage tube to the inner diameter is 2:1;

[0140] According to the present application Figure 4 as shown, the NO x The reburning nozzle is installed on one side of the combustion boiler; wherein, when installed, the annular cavity is attached to the side wall of the combustion boiler near the side of the orifice plate, the annular cavity is connected to the inside of the combustion boiler, the first nozzle, the second nozzle and the Venturi tube all extend into the combustion boiler; the length of the annular cavity is 0.1m, the width of the annular cavity is 80mm, the first nozzle extends into the combustion boiler by 0.5m, the second nozzle extends into the combustion boiler by 0.3m, and the diameter of the first orifice is 20mm;

[0141] The biomass fuel enters the boiler through the first nozzle and the Venturi tube, in the Venturi tube, the biomass fuel is premixed with the flue gas in the hearth of the boiler first, is partially pyrolyzed and then sprayed into the hearth, and then reacts with the NO x in the hearth to generate reburning reduction reaction;

[0142] The biomass fuel enters the hearth through the second nozzle at the same time, mixes with the flue gas, and then reacts with the NO x in the hearth to generate reburning reduction reaction;

[0143] The biomass fuel is transported into the annular buffer cavity through the biomass delivery pipe, oscillates in the annular cavity and mixes with the flue gas, and then enters the hearth through the annular bluff body to react with the NO x to generate reburning reduction reaction;

[0144] Wherein, the reference NO x concentration before the main fuel in the combustion boiler enters the reburning section is 100 mg / Nm 3 The biomass fuel is selected as pine biomass powder with an average particle size of 160 μm, and the delivery medium is CO2-rich circulating flue gas;

[0145] The biomass powder is delivered by CO2-rich circulating flue gas as carrier gas at a delivery speed of 15m / s, enters the buffer chamber 7 after stable pressure, enters the annular cavity 2 through the orifice plate 5, and forms a first-stage annular self-excited pulsating pyrolysis zone in the nozzle near-wall area; at the same time, part of the biomass is sprayed into the middle part of the hearth through the second nozzle 3 to form a second-stage main reburning reduction zone; the remaining biomass is sprayed into the deep part of the hearth through the first nozzle 4 and the Venturi tube 8 to form a third-stage deep intensive reduction zone, thereby constructing a multi-stage reburning reaction path of “near-wall pyrolysis—middle-layer main reduction—deep intensive compensation”.

[0146] By adjusting the biomass reburning fuel, the system is tested under different operating conditions in turn, and the system continuously and stably operates for not less than 8h under each operating condition, and the nozzle does not appear to be blocked, backfired and coked and other adverse phenomena. The measured NO x concentration at the outlet of the boiler is 61 mg / Nm 334mg / Nm 3 , NO x The reduction rate is 39%~66%.

[0147] During the test, the temperature field distribution of the furnace is uniform, no local high-temperature hot spot appears, and the combustion stability is good, indicating that the nozzle of the present application will not adversely affect the main combustion condition under the condition of high denitration efficiency.

[0148] Comparative Example 1

[0149] The nozzle provided by the present comparative example is a conventional single-stage direct injection type reburning nozzle, and a sectional view thereof is shown in Figure 5 , which comprises a nozzle pipe 11 and a third injection hole 12 opened along the nozzle pipe axis, and four fourth injection holes 13 opened outside the third injection hole 12 and arranged circumferentially along the third injection hole 12, the diameters of the third injection hole 12 and the fourth injection hole 13 are both 15mm;

[0150] The nozzle in Comparative Example 1 is installed on one side of the boiler, the nozzle pipe 11 is inserted into the combustion boiler by 0.3m, the biomass reburning fuel is taken as the carrier gas by CO2 enrichment circulating flue gas, the conveying speed is 15m / s, and enters the furnace through the third injection hole 12 and the fourth injection hole 13. Under the condition that other process parameters are the same as in Example 1, the system is tested for reburning operation. The results show that under the same reburning condition, using the conventional single-stage circular direct injection type reburning nozzle, the NO x concentration at the outlet of the boiler is 69mg / Nm 3 ~46mg / Nm 3 , and the NO x concentration is reduced to a certain extent, and the reduction rate is about 31%~54%. However, compared with the present application, the denitration effect of the conventional direct injection type reburning nozzle still has a significant gap.

[0151] In summary, compared with the conventional single-stage circular direct injection type reburning nozzle, the NO x reduction rate of the nozzle of the present application is increased by 8%~12% under the same reburning condition, and the improvement is stable and repeatable, indicating that the present application has more excellent engineering application effect in NO x reburning reduction. And under the condition of oxygen-enriched combustion, there is no need to introduce ammonia reducing agent, avoiding the problems of ammonia escape, corrosion and secondary pollution in SNCR process.

[0152] Further long-term test results show that the nozzle structure is complete, the annular self-excited pulsation cavity and the nozzle of each stage are not blocked or significantly worn, and no abnormal slagging phenomenon is observed in the furnace, indicating that the nozzle of the present application has good long-term operation stability and engineering application reliability, and is suitable for low-NO x x emission retrofit engineering under the condition of oxygen-enriched combustion of circulating fluidized bed boiler and pulverized coal boiler.

[0153] It can be understood that any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations of the technical features in the above-described embodiments are described, however, as long as the combination of the technical features does not exist contradictory, it should be considered within the scope of the present disclosure.

[0154] The above are only preferred embodiments of the present application, and only the technical principles of the present application are specifically described, and these descriptions are only for the purpose of explaining the principles of the present application, and cannot be interpreted in any way as a limitation on the scope of protection of the present application. Based on the explanation here, any modification, equivalent replacement and improvement made within the spirit and principle of the present application, and other specific embodiments of the present application which can be easily thought by those skilled in the art without creative labor, should be included in the protection scope of the present application.

Claims

1. A nitrogen oxide reburning reduction nozzle, characterized in that, include: The first nozzle has a first spray hole opened along the axis inside; The second nozzle is sleeved on the outer periphery of the first nozzle, and second nozzle holes are opened inside the second nozzle and on both sides of the first nozzle. An annular cavity is fitted around the outer periphery of the second nozzle; An annular buffer cavity is disposed at one end of the annular cavity; A biomass conveying pipe is disposed at one end of the annular buffer cavity away from the annular cavity. A conveying hole is provided inside the biomass conveying pipe along the axis, and the conveying hole communicates with the annular buffer cavity. A venturi tube, which is connected to the end of the first nozzle furthest from the biomass delivery pipe; The annular buffer cavity has a perforated plate on the side near the annular cavity, and a through hole is formed on the perforated plate. The inner wall of the through hole is inclined, and the diameter of the end of the through hole near the annular cavity is smaller than the diameter of the end near the biomass conveying pipe. The through hole communicates with the annular cavity. An annular blunt body is coaxially provided on the side away from the annular buffer cavity inside the annular cavity, and the sidewall thickness of the annular blunt body gradually increases from the direction close to the annular buffer cavity to the direction away from the annular buffer cavity; The annular cavity is open at one end near the annular blunt body; The venturi tube includes a constriction section, a throat, and a diverging section connected in sequence. The end of the constriction section away from the throat is connected to the first nozzle. The inner diameter of the constriction section gradually decreases from the end near the first nozzle to the end away from the first nozzle, and the inner diameter of the diverging section gradually increases from the end near the throat to the end away from the throat. A drainage tube is connected to the throat.

2. The nitrogen oxide reburning reduction nozzle as described in claim 1, characterized in that, The angle between the inner wall of the through hole and the axis of the through hole is 45°~75°.

3. The nitrogen oxide reburning reduction nozzle as described in claim 1, characterized in that, The projection of the sidewall of the annular blunt body onto the vertical plane is an isosceles triangle, the base of which is 0.1 to 0.3 times the width of the annular cavity, and the height of which is 0.3 to 0.5 times the length of the annular cavity.

4. The nitrogen oxide reburning reduction nozzle as described in claim 1, characterized in that, The length of the venturi tube is 0.2 to 0.3 times the length of the first nozzle; The length of the contraction section is 0.25 to 0.4 times the length of the venturi tube, and the semi-cone angle of the contraction section is 12° to 20°. The length of the throat is 0.1 to 0.2 times the length of the venturi tube, and the ratio of the inner diameter of the throat to the diameter of the first nozzle is (0.3 to 0.5):

1. The length of the expanding section is 0.4 to 0.6 times the length of the venturi tube, and the semi-cone angle of the expanding section is 5° to 10°.

5. The nitrogen oxide reburning reduction nozzle as described in claim 1, characterized in that, The ratio of the length of the annular cavity to the length of the first nozzle is (0.15~0.3):1; The ratio of the length of the annular buffer cavity to the length of the first nozzle is (0.1~0.2):1; The ratio of the length of the biomass delivery pipe to the length of the first nozzle is (0.2~0.4):1; The ratio of the width of the annular cavity to the diameter of the first nozzle is (3~5):1; The ratio of the width of the annular buffer cavity to the width of the annular cavity is (0.5~0.7):1; The ratio of the diameter of the conveying hole to the width of the annular cavity is (0.1~0.2):1; the ratio of the diameter of the second spray hole to the diameter of the first spray hole is (0.5~0.8):1; The ratio of the length of the second nozzle to the length of the first nozzle is (0.5~0.8):

1.

6. The nitrogen oxide reburning reduction nozzle as described in claim 1, characterized in that, The ratio of the outer circumference of the annular cavity to its width is (4~8):1; The ratio of the outer perimeter to the width of the annular buffer cavity is (4~8):1; The ratio of the area of ​​the through hole near the annular cavity to the cross-sectional area of ​​the annular cavity is 1:(4~25).

7. The nitrogen oxide reburning reduction nozzle as described in claim 1, characterized in that, The ratio of the inner diameter of the drainage tube to the inner diameter of the venturi nozzle throat is (0.4~0.6):1; The ratio of the length to the inner diameter of the drainage tube is (1.5~3):

1.

8. A method for re-burning and reducing nitrogen oxides, characterized in that, Includes the following steps: The nitrogen oxide reburning and reduction nozzle as described in any one of claims 1 to 8 is installed on one side of the boiler; wherein, during installation, the side of the annular cavity near the orifice plate is attached to the side wall of the boiler, the annular cavity is connected to the interior of the boiler, and the first nozzle and the second nozzle both extend into the boiler. Biomass fuel enters the boiler through the first nozzle and the venturi tube. In the venturi tube, the biomass fuel is first premixed with the flue gas in the boiler furnace, partially pyrolyzed and then injected into the furnace, where it undergoes a re-burning reduction reaction with nitrogen oxides in the furnace. Biomass fuel enters the furnace through the second nozzle, mixes with the flue gas, and then undergoes a re-burning reduction reaction with nitrogen oxides in the furnace. Biomass fuel is simultaneously transported through a biomass conveying pipe to a buffer chamber, and then enters an annular cavity. In the annular cavity, self-excited pressure pulsation occurs and it mixes with flue gas. Finally, it enters the furnace through an annular bluff body and undergoes a re-burning reduction reaction with nitrogen oxides.

9. The nitrogen oxide re-burning reduction method as described in claim 8, characterized in that, The biomass fuel is transported at a speed of 5~30m / s; If the boiler is a circulating fluidized bed boiler, the recommended reburning reduction reaction temperature is 1050~1150K; If the boiler is a pulverized coal boiler, the recommended reburning reduction reaction temperature is 1300~1400K.

10. The nitrogen oxide re-burning reduction method as described in claim 8, characterized in that, Biomass fuel is delivered to the boiler via CO2 or flue gas.

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