CN113757646B - Flue gas recycling combustion system for injecting natural gas and oxygen by using venturi tube - Google Patents
Flue gas recycling combustion system for injecting natural gas and oxygen by using venturi tube Download PDFInfo
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- CN113757646B CN113757646B CN202110931485.6A CN202110931485A CN113757646B CN 113757646 B CN113757646 B CN 113757646B CN 202110931485 A CN202110931485 A CN 202110931485A CN 113757646 B CN113757646 B CN 113757646B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C9/00—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber
- F23C9/06—Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber for completing combustion
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/02—Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone
- F23D14/04—Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone induction type, e.g. Bunsen burner
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/46—Details, e.g. noise reduction means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/46—Details, e.g. noise reduction means
- F23D14/60—Devices for simultaneous control of gas and combustion air
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/46—Details, e.g. noise reduction means
- F23D14/70—Baffles or like flow-disturbing devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L7/00—Supplying non-combustible liquids or gases, other than air, to the fire, e.g. oxygen, steam
- F23L7/007—Supplying oxygen or oxygen-enriched air
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N1/00—Regulating fuel supply
- F23N1/02—Regulating fuel supply conjointly with air supply
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/18—Systems for controlling combustion using detectors sensitive to rate of flow of air or fuel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D2207/00—Ignition devices associated with burner
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/18—Systems for controlling combustion using detectors sensitive to rate of flow of air or fuel
- F23N2005/181—Systems for controlling combustion using detectors sensitive to rate of flow of air or fuel using detectors sensitive to rate of flow of air
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/18—Systems for controlling combustion using detectors sensitive to rate of flow of air or fuel
- F23N2005/185—Systems for controlling combustion using detectors sensitive to rate of flow of air or fuel using detectors sensitive to rate of flow of fuel
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- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/32—Direct CO2 mitigation
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- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
Abstract
The invention relates to a flue gas recycling combustion system for injecting natural gas and oxygen by using a Venturi tube, which comprises an oxygen gas cylinder, an oxygen flow meter, an oxygen control valve, an oxygen injection Venturi tube, a natural gas cylinder, a natural gas flow meter, a natural gas control valve, a natural gas injection Venturi tube, a combustion chamber, a gas turbine, a mainstream flue gas flow meter, a flue gas control valve, a cooling device, an induced draft fan, a circulating flue gas flow regulating valve, an oxygen conveying pipeline group, a natural gas conveying pipeline group, a flue gas circulating pipeline group and a smoke exhaust pipeline group. The oxygen supply pipeline and the natural gas supply pipeline provide oxygen and natural gas for the system, and the oxygen and the natural gas are sent into the combustion chamber to be combusted and work is done in the turbine. One part of the smoke generated after the steam turbine works passes through the smoke exhaust pipeline group; the other part of the oxygen and the natural gas are led back into the system by the air inducing machine after passing through the cooling device, injected and mixed by the Venturi tube, and finally sent into the combustion chamber to realize high-temperature low-oxygen combustion.
Description
Technical Field
The invention relates to the field of natural gas power generation, in particular to a flue gas recycling combustion system for injecting natural gas and oxygen by using a Venturi tube.
Background
Environmental problems in China are more and more severe, and haze becomes a great threat to public health. Research shows that nitrogen oxides are one of the important causes of haze, and the control of the emission of NOx is an important measure for controlling haze weather. In a traditional natural gas system, natural gas is often used as a main fuel, but a main pollutant in flue gas after natural gas combustion is NOx, and the situation that NOx is discharged during natural gas combustion to cause pollution is receiving more and more attention. In the context of both policy and market environments, how to reduce NOx emissions is an urgent technical problem to be solved.
Among the Nox generated during the operation of the natural gas boiler, thermal Nox generated by the combustion of natural gas accounts for 95% or more of the total amount. NOx is mainly Nitric Oxide (NO), nitrogen dioxide (NO) 2 ) Wherein NO is about 95%. Research has shown that reducing the oxygen concentration by flue gas recirculation and reducing the temperature in the combustion zone are both effective in reducing the concentration of flue gas nitrogen oxides. Therefore, a flue gas recycling combustion system using a venturi to inject natural gas and oxygen becomes the focus of research in the field.
Disclosure of Invention
In order to solve the problems in the prior art, the concentration of Nox in the flue gas discharged by the system is reduced through flue gas recirculation, and the flue gas recycling combustion system for injecting natural gas and oxygen by using the venturi tube is provided.
In order to achieve the purpose, the invention adopts the technical scheme that:
the system comprises an oxygen gas cylinder 1, an oxygen flow meter 2, an oxygen flow control valve 3, an oxygen injection venturi tube 4, a natural gas cylinder 5, a natural gas flow meter 6, a natural gas flow control valve 7, a natural gas injection venturi tube 8, a combustion chamber 9, a gas turbine 10, a discharged flue gas flow meter 11, a discharged flue gas flow control valve 12, a cooling device 13, an induced draft fan 14, a circulating flue gas flow regulating valve 15, an oxygen conveying pipeline group 16, a natural gas conveying pipeline group 17, a flue gas circulating pipeline group 18 and a smoke exhaust pipeline group 19; wherein the combustion chamber 9 includes a safety valve 91, a viewing hole 92, and an igniter 93; oxygen delivery conduit set 16 includes oxygen delivery conduit a161, oxygen delivery conduit b162, and oxygen delivery conduit c163; the natural gas transportation pipeline group 17 includes a natural gas transportation pipeline a171, a natural gas transportation pipeline b172, and a natural gas transportation pipeline c173; the flue gas circulating pipeline group 18 comprises a flue gas circulating pipeline a181, a flue gas circulating pipeline b182, a flue gas circulating pipeline c183, a flue gas circulating pipeline d184, a flue gas circulating pipeline e185, flue gas circulating pipelines f186 and 192, a flue gas circulating pipeline g187 and a flue gas circulating pipeline h188; the smoke exhaust pipeline group 19 comprises a smoke exhaust pipeline a191, a smoke exhaust pipeline b192 and a smoke exhaust pipeline c193; in the oxygen transmission pipeline, an oxygen gas cylinder 1, an oxygen transmission pipeline a161, an oxygen flowmeter 2, an oxygen transmission pipeline b162, an oxygen flow control valve 3 and an oxygen transmission pipeline c163 are connected in sequence and then are connected into an oxygen injection venturi tube 4; in a natural gas transmission pipeline, a natural gas cylinder 5, a natural gas transmission pipeline a171, a natural gas flow meter 6, a natural gas transmission pipeline b172, a natural gas flow control valve 7 and a natural gas transmission pipeline c173 are connected in sequence and then connected to a natural gas injection venturi tube 8; in the flue gas combustion circulation main path, an induced draft fan 14, a circulating flue gas flow regulating valve 15, an oxygen injection venturi tube 4, a natural gas injection venturi tube 8, a combustion chamber 9, a gas turbine 10 and a cooling device 13 are sequentially connected, and the cooling device 13 is connected with the induced draft fan 14; in the exhaust flue gas pipeline, a flue gas exhaust pipeline a191, an exhaust flue gas flowmeter 11, a flue gas exhaust pipeline b192, an exhaust flue gas flow control valve 12 and a flue gas exhaust pipeline c193 are connected in sequence.
The oxygen gas bottle 1 is connected with an oxygen flow meter 2 through an oxygen conveying pipeline a161, the oxygen flow meter 2 is connected with an oxygen flow control valve 3 through an oxygen conveying pipeline b162, and the oxygen flow control valve 3 is communicated with an oxygen injection venturi tube 4 through an oxygen conveying pipeline c 163.
The natural gas bottle 5 is connected with the natural gas flowmeter 6 through a natural gas conveying pipeline a171, the natural gas flowmeter 6 is connected with the natural gas flow control valve 7 through a natural gas conveying pipeline b172, and the natural gas flow control valve 7 is communicated with the natural gas injection venturi tube 8 through a natural gas conveying pipeline c 173.
Draught fan 14 passes through flue gas circulating line a181 and connects circulation flue gas flow control valve 15, circulation flue gas flow control valve 15 connects oxygen through flue gas circulating line b182 and draws and penetrate venturi 4, oxygen draws and penetrates venturi 4 and connect the natural gas through flue gas circulating line c183 and draw and penetrate venturi 8, natural gas draws and penetrates venturi 8 and connect combustion chamber 9 through flue gas circulating line d184, combustion chamber 9 passes through flue gas circulating line e185 and connects gas turbine 10, gas turbine 10 exports and links to each other with flue gas circulating line f 186's one end, and two branches are divided into to flue gas circulating line f 186's other one end, be smoke exhaust pipe a191 and flue gas circulating line g187 respectively: the smoke exhaust pipeline a191 is communicated with a smoke exhaust flowmeter 11, the smoke exhaust flowmeter 11 is connected with a smoke exhaust flow control valve 12 through a smoke exhaust pipeline b192, the smoke exhaust flow control valve 12 is communicated with a smoke exhaust pipeline c193, and the other end of the smoke exhaust pipeline c193 is connected with the atmosphere to form a smoke exhaust pipeline; the flue gas circulating pipeline g187 is communicated with the cooling device 13 and is connected with a flue gas circulating pipeline h188, and the flue gas circulating pipeline h188 is connected with the induced draft fan 14.
The oxygen injection venturi tube 4 and the natural gas injection venturi tube 8 adopt venturi tubes with the same specification, and mainly comprise a reducing section 41, a throat section 42, an injection hole 43 and a gradually expanding section 44; the tapered section 41 is a hollow conical cone, the outer diameter of the tapered section is reduced from 180mm to 140mm, the inner diameter of the tapered section is reduced from 160mm to 120mm, and the length of the tapered section is 180mm; the throat section 42 is a hollow cylinder with an inner diameter of 120mm, an outer diameter of 140mm and a length of 100mm; the divergent section 44 is a hollow conical cone, the outer diameter is divergent to 180mm from 140mm, the inner diameter is divergent to 160mm from 120mm, and the length is 180mm; the injection hole 43 is arranged in the middle of the throat section 42, the inner diameter is 60mm, the length is 80mm, and the axis of the injection hole 43 is vertical to the axis of the throat section 42; the axes of the tapered section 41, the throat section 42 and the diverging section 44 are collinear.
The combustion chamber is provided with a safety valve 91, an observation hole 92 and an igniter 93, and the safety valve 91 is positioned in the middle of the outer flame tube; the viewing port 92 is located in the middle of the outer flame tube and extends into the inner flame tube, and the igniter 93 is located in the middle of the swirler.
When the combustion system works, in the initial stage of ignition and operation, in order to ensure timely ignition of natural gas, smoke gas recirculation needs to be stopped, a circulating smoke gas flow regulating valve 15 is closed firstly, a discharged smoke gas flow control valve 12 is opened later, an oxygen flow control valve 3 and a natural gas flow control valve 7 are opened in sequence, and the opening degree of the oxygen flow control valve 3 and the opening degree of the natural gas flow control valve 7 are optimally combined to ensure that the natural gas and the oxygen are ignited timely; in a normal working stage, in order to reduce NOx emission, the oxygen concentration is reduced and the temperature of a combustion area is reduced through flue gas recirculation, the opening degree of a valve 12 of a discharged flue gas flow control valve is reduced, then a circulating flue gas flow regulating valve 15 is partially opened as required, the opening degrees of an oxygen flow control valve 3 and a natural gas flow control valve 7 are regulated according to the combustion condition in a combustion chamber 9 and actual requirements, and in a normal working interval, the valve opening degree of the flue gas flow control valve 12, the opening degree of the circulating flue gas flow regulating valve 15, the opening degree of the oxygen flow control valve 3 and the opening degree of the natural gas flow control valve 7 are optimally combined to ensure the low emission of NOx; when the system is closed, the natural gas flow control valve 7 is closed firstly, then the oxygen flow control valve 3 is closed, then the valve opening degree of the circulating flue gas flow control valve 15 is increased, then the discharged flue gas flow control valve 12 is closed, a flue gas purging system is adopted, after a certain time, the discharged flue gas flow control valve 12 is opened, meanwhile, the circulating flue gas flow control valve 15 is closed, and the system stops working.
Drawings
FIG. 1 is a schematic flow chart of a flue gas recirculation combustion system according to an embodiment of the present invention
FIG. 2 is a three-dimensional view of a combustion chamber provided in accordance with an embodiment of the present invention
FIG. 3 is a three-dimensional view of an oxygen injection venturi in accordance with an embodiment of the present invention
FIG. 4 is a three-dimensional view of a natural gas injection venturi according to an embodiment of the present invention
Detailed Description
As shown in fig. 1, the flue gas recycling combustion system using a venturi tube to inject natural gas and oxygen of the present invention comprises an oxygen gas cylinder 1, an oxygen flow meter 2, an oxygen flow control valve 3, an oxygen injection venturi tube 4, a natural gas cylinder 5, a natural gas flow meter 6, a natural gas flow control valve 7, a natural gas injection venturi tube 8, a combustion chamber 9, a gas turbine 10, a discharged flue gas flow meter 11, a discharged flue gas flow control valve 12, a cooling device 13, an induced draft fan 14, a circulating flue gas flow control valve 15, an oxygen delivery pipeline group 16, a natural gas delivery pipeline group 17, a flue gas circulating pipeline group 18, and a smoke exhaust pipeline group 19; wherein the combustion chamber 9 includes a safety valve 91, a viewing hole 92, and an igniter 93; oxygen delivery conduit set 16 includes oxygen delivery conduit a161, oxygen delivery conduit b162, and oxygen delivery conduit c163; the natural gas transportation pipeline group 17 includes a natural gas transportation pipeline a171, a natural gas transportation pipeline b172, and a natural gas transportation pipeline c173; the flue gas circulating pipeline group 18 comprises a flue gas circulating pipeline a181, a flue gas circulating pipeline b182, a flue gas circulating pipeline c183, a flue gas circulating pipeline d184, a flue gas circulating pipeline e185, a flue gas circulating pipeline f186, a smoke exhaust pipeline a191, a flue gas circulating pipeline g187 and a flue gas circulating pipeline h188; the smoke exhaust duct group 19 includes a smoke exhaust duct b192 and a smoke exhaust duct 193.
The whole flue gas circulation system comprises four main pipelines: the system comprises an oxygen supply pipeline, a natural gas supply pipeline, a flue gas combustion circulation main pipeline and a flue gas discharge pipeline. The oxygen supply line includes: the oxygen injection device comprises an oxygen gas cylinder 1, an oxygen flow control valve 2, an oxygen flow meter 3, an oxygen injection venturi tube 4 and an oxygen delivery pipeline group 16; the oxygen gas bottle 1 is connected with the oxygen flow meter 2 through an oxygen conveying pipeline a161, the oxygen flow meter 2 is connected with the oxygen flow control valve 3 through an oxygen conveying pipeline b162, and the oxygen flow control valve 3 is communicated with the oxygen injection venturi tube 4 through an oxygen conveying pipeline c163 and is connected into the smoke circulating pipeline group 18 to convey oxygen into the system. The natural gas supply line includes: the natural gas injection device comprises a natural gas bottle 5, a natural gas flowmeter 6, a natural gas flow control valve 7, a natural gas injection venturi tube 8 and a natural gas conveying pipeline group 17; natural gas bottle 5, connect natural gas flowmeter 6 through natural gas pipeline a171, natural gas flowmeter 6 passes through natural gas pipeline b172 natural gas flow control valve 7, natural gas flow control valve 7 through drawing venturi 8 intercommunication with natural gas pipeline c173 with the natural gas, finally insert in flue gas circulation pipe group 18, carry the natural gas in to the system. The flue gas combustion circulation main road comprises: the system comprises a combustion chamber 9, a gas turbine 10, a cooling device 13, an induced draft fan 14, a circulating flue gas flow regulating valve 15 and a flue gas circulating pipeline group 18. The induced draft fan 14 is connected with a circulating flue gas flow regulating valve 15 through a flue gas circulating pipeline a181, the circulating flue gas flow regulating valve 15 is connected with an oxygen injection venturi tube 4 through a flue gas circulating pipeline b182, the oxygen injection venturi tube 4 is connected with a natural gas injection venturi tube 8 through a flue gas circulating pipeline c183, the natural gas injection venturi tube 8 is connected with the combustion chamber 9 through a flue gas circulating pipeline d184, the combustion chamber 9 is connected with the gas turbine 10 through a flue gas circulating pipeline e185, the outlet of the gas turbine 10 is connected with a flue gas circulating pipeline f186, the flue gas circulating pipeline f186 is divided into two branch pipelines which are a flue gas exhaust pipeline a191 and a flue gas circulating pipeline g187, wherein the flue gas exhaust pipeline a191 is communicated with a flue gas exhaust flowmeter 11 and leads to a flue gas exhaust pipeline, and the flue gas circulating pipeline g187 is communicated with a cooling device 13 and belongs to one part of a flue gas combustion circulating main; the cooling device 13 is connected with the induced draft fan 14 through a flue gas circulation pipeline h188 to form complete flue gas circulation. The flue gas discharge line comprises: the flue gas discharge device comprises a flue gas discharge flowmeter 11, a flue gas discharge flow control valve 12 and a flue gas discharge pipeline group 19, wherein the flue gas discharge flowmeter 11, the flue gas discharge flow control valve 12 and the flue gas discharge pipeline group 19 are used for controlling the flow of the flue gas discharge by adjusting the opening degree of the flue gas discharge flow control valve 12, a flue gas discharge pipeline b192 is communicated with the flue gas discharge flowmeter 11 and the flue gas discharge flow control valve 12, and a flue gas discharge pipeline 193 is communicated with the flue gas discharge flow control valve 12 and the outside, so that the flue gas discharge is realized.
As shown in fig. 2, the bottom of the outer flame tube 94 is connected to the side wall of the inner flame tube 95, wall cooling holes 97 are provided on the side wall of the inner flame tube 95 and communicate with the outer flame tube 94 through the wall cooling holes 97, and the wall cooling holes are circular holes and are distributed in 45-degree rows around the wall. The wall surface of the inner flame tube 95 is provided with a middle cooling hole 98 which is positioned below the wall surface cooling hole 97, and the middle cooling hole is a circular hole and is distributed at 45 degrees around the wall surface. The lower cooling holes 99 are located at the outlet section of the lower part of the inner flame tube 95 which is gradually reduced, and the lower cooling holes are circular holes and distributed at 45 degrees around the wall surface. A swirler 96 is located at the upper portion of the inner liner 95 with swirler vanes distributed 90 degrees around the swirler. The igniter 93 is located at the lower part of the swirler 96, the observation hole 92 is located at the middle part of the outer flame tube 94 and extends into the inner flame tube 95 to observe the gas combustion condition, and the safety valve 91 is located at the middle part of the outer flame tube 94 and automatically opens when the internal pressure of the combustion chamber rises to exceed a specified value, so as to prevent explosion.
The oxygen injection venturi 4 as shown in figure 3 comprises a convergent section 41, a throat section 42, a divergent section 44 and an injection orifice 43. The tapered section 41 is a hollow conical cone, the outer diameter of the tapered section is reduced from 180mm to 140mm, the inner diameter of the tapered section is reduced from 160mm to 120mm, and the length of the tapered section is 180mm; the throat section 42 is a hollow cylinder with an inner diameter of 120mm, an outer diameter of 140mm and a length of 100mm; the divergent section 44 is a hollow conical cone, the outer diameter is divergent to 180mm from 140mm, the inner diameter is divergent to 160mm from 120mm, and the length is 180mm; the injection hole 43 is arranged in the middle of the throat section 42, the inner diameter is 60mm, the depth is 80mm, and the axis of the injection hole 43 is vertical to the axis of the throat section 42; the axes of the tapered section 41, the throat section 42 and the diverging section 44 are collinear.
As shown in fig. 3, when the circulating gas passes through the tapered section 41 of the oxygen injection venturi tube 4, the flow cross section is reduced, the flow rate is increased, and the pressure is reduced, when the circulating flue gas enters the throat section 42, the gas flow rate is increased to the highest and the pressure is reduced to the lowest, the backflow gas forms a low-pressure area in the throat section 42, the oxygen is injected through the injection hole 43, when the oxygen enters the oxygen injection venturi tube, the mixed oxygen is mixed into the circulating flue gas, the circulating flue gas enters the tapered section 44, the mixed gas is reduced in speed and increased in pressure, and the mixed gas enters the pipeline system. Then the mixed gas of the oxygen and the circulating flue gas enters a natural gas injection venturi tube 8, the natural gas is injected into the natural gas injection venturi tube in the same way, and the mixed gas is fully mixed with the mixed gas and then enters a pipeline system.
In the initial stage of ignition and operation, the circulation flue gas flow rate control valve 15 is first closed, the exhaust flue gas flow rate control valve 12 is then opened, and the oxygen flow rate control valve 3 and the natural gas flow rate control valve 7 are then opened in this order. At the moment, the flow of smoke in the pipeline is insufficient, oxygen is conveyed to the system through the self pressure difference of the oxygen gas bottle 1, the oxygen flows through the natural gas injection venturi tube 8 to form a low-pressure area at the throat section 82, the natural gas in the natural gas bottle 5 is injected into an injection port of the natural gas injection venturi tube 8 under pressure and mixed with mixed smoke of main stream smoke and the oxygen, and then the mixed smoke passes through the swirler 96 from the combustion chamber inlet 910 along the main gas pipeline and enters the inner flame tube 95 to be combusted after being ignited by the igniter 93. At the moment, the oxygen content entering the combustion chamber is higher, the proportion is higher, the combustion speed can be accelerated, the complete combustion is promoted, and the combustion efficiency is improved; a large amount of gas generated by combustion finally becomes flue gas after doing work, and at the moment, the part of flue gas is completely discharged out of the atmosphere by closing the circulating flue gas flow regulating valve 15 and opening the flue gas flow control valve 12.
Under the normal working state, the circulating flue gas flow regulating valve 15 is partially opened at first, and then the opening degree of the discharged flue gas flow control valve 12 is partially reduced, so that part of the flue gas enters the flue gas circulating system for flue gas recirculation. So on the one hand can heat the mist that gets into the combustion chamber, reduces the oxygen concentration in the mist on the one hand, can realize high temperature low oxygen burning step by step, reduces the nitrogen oxide concentration in the flue gas. When the flue gas flow in the flue gas circulation pipeline is large enough to ensure that the oxygen concentration in the mixed gas sent into the combustion chamber is low enough, the opening degree of the discharged flue gas flow control valve 12 can be increased, part of flue gas generated by combustion work is discharged, and meanwhile, the opening degree of the circulation flue gas flow control valve 15 is reduced, so that the dynamic balance between the flue gas flow in the flue gas circulation pipeline and the discharged flue gas flow is realized on the whole. In the working state, the smoke in the smoke circulating pipeline flows through the oxygen injection Venturi tube 4 to form a low-pressure area at the throat opening section 42, and the oxygen in the oxygen cylinder 1 is injected into the injection opening of the oxygen injection Venturi tube 4 under pressure and mixed into the mainstream smoke; the mixed flue gas of the mainstream smoke and the oxygen flows through the natural gas injection venturi tube 8 to form a low-pressure area at the throat section 82, the natural gas in the natural gas cylinder 5 is injected into the injection port of the natural gas injection venturi tube 8 under pressure and mixed into the mixed flue gas of the mainstream smoke and the oxygen, then the mixed gas passes through the swirler 96 from the combustion chamber inlet 910 along the main gas pipeline, is ignited by the igniter 93 and then enters the inner flame tube 95 for combustion, the combustion condition can be observed through the observation hole 92 during combustion, the completely combusted gas flows out of the combustion chamber through the combustion chamber outlet 911 and enters the gas turbine 10 for doing work, part of exhaust gas which completes doing work enters the exhaust smoke pipeline, and then flows through the exhaust smoke flow meter 11 and the exhaust smoke flow control valve 12 in sequence and then is discharged into the atmosphere; the other part of the exhaust gas still flows through the cooling device 13 in the flue gas combustion circulation main path and is led back by the induced draft fan 14, and the mixed gas mixed with the oxygen and the natural gas continuously participates in circulation.
When the system is shut down, firstly close natural gas flow control valve 7 and then close oxygen flow control valve 3, then increase the 15 valve apertures of circulation flue gas flow control valve, then close exhaust flue gas flow control valve 12, the purpose is to reduce the flue gas emission gradually, fully consume oxygen and natural gas in the pipeline, wash the pipeline simultaneously, open exhaust flue gas flow control valve 12 and close circulation flue gas flow control valve 15, exhaust flue gas after a certain time.
In summary, the low pressure generated by the flue gas in the venturi tube is mainly used for ejecting the oxygen and the natural gas, the oxygen and the natural gas are fully mixed and then enter the combustion chamber for combustion, the oxygen-enriched combustion state is realized at the initial stage of system operation, and then the high-temperature low-oxygen combustion state can be realized, so that the combustion efficiency is improved, and the concentration of nitrogen oxides in the flue gas is reduced; the mixing proportion of the oxygen and the natural gas is controlled through the injection mixing effect of the venturi tube, so that the sufficient mixing of the oxygen and the natural gas can be promoted, the local overheating is avoided, and the generation of nitrogen oxides is reduced. The flue gas is adopted to preheat the natural gas and the oxygen, and no additional pipeline and heat exchange equipment are needed to be arranged, so that the overall economy of the system is improved.
Claims (5)
1. The utility model provides an utilize venturi to draw flue gas cyclic utilization combustion system who penetrates natural gas and oxygen which characterized in that: the device comprises an oxygen gas cylinder (1), an oxygen flow meter (2), an oxygen flow control valve (3), an oxygen injection Venturi tube (4), a natural gas cylinder (5), a natural gas flow meter (6), a natural gas flow control valve (7), a natural gas injection Venturi tube (8), a combustion chamber (9), a gas turbine (10), a discharged flue gas flow meter (11), a discharged flue gas flow control valve (12), a cooling device (13), an induced draft fan (14), a circulating flue gas flow regulating valve (15), an oxygen conveying pipeline group (16), a natural gas conveying pipeline group (17), a flue gas circulating pipeline group (18) and a smoke exhaust pipeline group (19); wherein the combustion chamber (9) comprises a safety valve (91), an observation hole (92) and an igniter (93); the oxygen conveying pipeline group (16) comprises an oxygen conveying pipeline a (161), an oxygen conveying pipeline b (162) and an oxygen conveying pipeline c (163); the natural gas conveying pipeline group (17) comprises a natural gas conveying pipeline a (171), a natural gas conveying pipeline b (172) and a natural gas conveying pipeline c (173); the smoke circulating pipeline group (18) comprises a smoke circulating pipeline a (181), a smoke circulating pipeline b (182), a smoke circulating pipeline c (183), a smoke circulating pipeline d (184), a smoke circulating pipeline e (185), a smoke circulating pipeline f (186), a smoke circulating pipeline g (187) and a smoke circulating pipeline h (188); the smoke exhaust pipeline group (19) comprises a smoke exhaust pipeline a (191), a smoke exhaust pipeline b (192) and a smoke exhaust pipeline c (193); in the oxygen transmission pipeline, an oxygen gas cylinder (1), an oxygen transmission pipeline a (161), an oxygen flow meter (2), an oxygen transmission pipeline b (162), an oxygen flow control valve (3) and an oxygen transmission pipeline c (163) are connected in sequence and then are connected into an oxygen injection venturi tube (4); in a natural gas transmission pipeline, a natural gas cylinder (5), a natural gas transmission pipeline a (171), a natural gas flowmeter (6), a natural gas transmission pipeline b (172), a natural gas flow control valve (7) and a natural gas transmission pipeline c (173) are connected in sequence and then are connected into a natural gas injection venturi tube (8); in the flue gas combustion circulation main path, an induced draft fan (14), a circulating flue gas flow regulating valve (15), an oxygen injection venturi tube (4), a natural gas injection venturi tube (8), a combustion chamber (9), a gas turbine (10) and a cooling device (13) are sequentially connected, and the cooling device (13) is connected with the induced draft fan (14); in the flue gas exhaust pipeline, a flue gas exhaust pipeline a (191), a flue gas exhaust flowmeter (11), a flue gas exhaust pipeline b (192), a flue gas exhaust flow control valve (12) and a flue gas exhaust pipeline c (193) are connected in sequence.
2. The flue gas recycling combustion system for injecting natural gas and oxygen by using the venturi tube as claimed in claim 1, characterized in that: draught fan (14), flue gas circulating line a (181), circulation flue gas flow control valve (15), flue gas circulating line b (182) and oxygen draw and penetrate venturi tube (4) and connect in order, oxygen draws and penetrates venturi tube (4), flue gas circulating line c (183), the natural gas draws and penetrates venturi tube (8), flue gas circulating line d (184), combustion chamber (9), flue gas circulating line e (185), gas turbine (10) and flue gas circulating line f (186) are connected in order, and two branches are divided into to the other one end of flue gas circulating line f (186), be smoke exhaust pipe a (191) and flue gas circulating line g (187) respectively: the smoke exhaust pipeline a (191), the smoke exhaust flowmeter (11), the smoke exhaust pipeline b (192), the smoke flow control valve (12) and the smoke exhaust pipeline c (193) are sequentially connected, and the other end of the smoke exhaust pipeline c (193) is connected with the atmosphere to form a smoke exhaust pipeline; the flue gas circulating pipeline g (187), the cooling device (13), the flue gas circulating pipeline h (188) and the induced draft fan (14) are connected in sequence.
3. The flue gas recycling combustion system for injecting natural gas and oxygen by using the venturi tube as claimed in claim 1, wherein: the oxygen injection Venturi tube (4) and the natural gas injection Venturi tube (8) adopt Venturi tubes with the same specification, and mainly comprise a reducing section (41), a throat section (42), an injection hole (43) and a gradually expanding section (44); the tapered section (41) is a hollow conical cone, the outer diameter of the tapered section is tapered from 180mm to 140mm, the inner diameter of the tapered section is tapered from 160mm to 120mm, and the length of the tapered section is 180mm; the throat section (42) is a hollow cylinder, the inner diameter is 120mm, the outer diameter is 140mm, and the length is 100mm; the divergent section (44) is a hollow conical cone, the outer diameter is divergent to 180mm from 140mm, the inner diameter is divergent to 160mm from 120mm, and the length is 180mm; the injection hole (43) is arranged in the middle of the throat section (42), the inner diameter is 60mm, the length is 80mm, and the axis of the injection hole (43) is vertical to the axis of the throat section (42); the axes of the tapered section (41), the throat section (42) and the diverging section (44) are located on the same straight line.
4. The flue gas recycling combustion system for injecting natural gas and oxygen by using the venturi tube as claimed in claim 1, characterized in that: the combustion chamber is provided with a safety valve (91), an observation hole (92) and an igniter (93), and the safety valve (91) is positioned in the middle of the outer flame tube; the observation hole (92) is positioned in the middle of the outer flame tube and extends into the inner flame tube, and the igniter (93) is positioned in the middle of the swirler.
5. The flue gas recycling combustion system for injecting natural gas and oxygen by using the venturi tube as claimed in claim 1, wherein: in the initial ignition and operation stage of the flue gas recycling combustion system, firstly, a circulating flue gas flow regulating valve (15) is closed, then, a discharged flue gas flow control valve (12) is opened, and then, an oxygen flow control valve (3) and a natural gas flow control valve (7) are opened in sequence; in the normal working stage, the valve opening of the discharged flue gas flow control valve (12) is reduced firstly, then the circulating flue gas flow regulating valve (15) is partially opened as required, and then the opening of the oxygen flow control valve (3) and the natural gas flow control valve (7) is regulated according to the combustion condition in the combustion chamber (9) and the actual requirement; when the system is closed, the natural gas flow control valve (7) is closed firstly, the oxygen flow control valve (3) is closed again, then the opening degree of the circulating flue gas flow control valve (15) is increased, the discharged flue gas flow control valve (12) is closed again, the discharged flue gas flow control valve (12) is opened after a certain time, the circulating flue gas flow control valve (15) is closed at the same time, and the system is closed.
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