CN110906359B - Combustion device capable of adjusting secondary air temperature and use method - Google Patents
Combustion device capable of adjusting secondary air temperature and use method Download PDFInfo
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- CN110906359B CN110906359B CN201911126634.0A CN201911126634A CN110906359B CN 110906359 B CN110906359 B CN 110906359B CN 201911126634 A CN201911126634 A CN 201911126634A CN 110906359 B CN110906359 B CN 110906359B
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- secondary air
- air
- bypass
- pipe
- temperature
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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
- F23L15/00—Heating of air supplied for combustion
- F23L15/04—Arrangements of recuperators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N3/00—Regulating air supply or draught
- F23N3/005—Regulating air supply or draught using electrical or electromechanical means
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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 combustion device capable of adjusting secondary air temperature and a control method, belonging to the technical field of clean and efficient utilization of coal; the combustion device comprises a secondary air inlet pipe, an air preheater, a secondary air outlet pipe, a bypass air pipe, a gate valve and an adjusting valve; according to the invention, by adding the secondary air duct bypass and additionally arranging the gate valve and the regulating valve on the bypass air duct, under the condition of not changing the total secondary air flow, the secondary air temperature is regulated by regulating the flow of secondary air cold air of the bypass, so that the burnout of carbon in the combustor is enhanced, and meanwhile, the content of gases such as CO and the like in a reducing atmosphere is reduced, and the technical problem of high-temperature corrosion of the surface of a pipe in the low-nitrogen combustor adopting a secondary air form at present is solved.
Description
Technical Field
The invention relates to a combustion device capable of adjusting secondary air temperature and a using method thereof, belonging to the technical field of clean and efficient utilization of coal.
Background
At present, the main air supply forms of coal-fired units in China are divided into a primary air form and a secondary air form, and a few of the units adopt a tertiary air form. The main stream coal-fired unit boilers of 300MW, 600MW and 1000MW grades take primary air and secondary air as main parts and do not contain a tertiary air form. The primary air is used for carrying qualified pulverized coal to enter a hearth, and the secondary air is used for supplying air required by combustion. In order to improve the combustion efficiency of the pulverized coal, designed primary air and secondary air are heated by an air preheater before entering a hearth, and are heated to more than 300 ℃ from normal temperature.
For primary air, the primary air has the function of heating raw coal, when coal powder is carried away from a coal mill, in order to ensure the safety (no fire and no deflagration) of coal powder airflow, the outlet temperature of the coal mill is not suitable to be too high (for example, the outlet of the coal mill for grinding lignite is not suitable to exceed 75 ℃), in the design, a detailed guidance suggestion is given by related national standard regulations, so that one path of bypass cold air (not passing through an air preheater) must be considered in the design, and the section of cold air is mixed with the primary air passing through the air preheater at the outlet of the air preheater so as to adjust the temperature of the primary air entering the coal mill.
For secondary air, all current designs are considered to be without bypass, mainly for two reasons: firstly, the secondary air is combustion-supporting air, and the higher the temperature is, the higher the combustion efficiency in the hearth is; secondly, the secondary air volume accounts for 60% -75% of all air volume, the air exchanges heat with flue gas after passing through the air preheater, the exhaust gas temperature of the air preheater is reduced, the more the air volume passes through the air preheater, the larger the flue gas temperature reduction amplitude is, and the higher the thermal efficiency of the boiler is.
The above is the mainstream design mode of the air supply of the coal-fired unit at present. However, after the low-nitrogen burners of the coal-fired unit boiler which are common nationwide are transformed and put into operation for several years, the high-temperature corrosion of the water-cooled wall of the hearth is found to be serious at present, and the heat-engine plant has to replace the corroded water-cooled wall pipe in a large area during the overhaul period. This is because: the combustion principle of the low-nitrogen combustor is to reduce the oxygen content of a combustor area (the combustor is positioned in a water-cooled wall), reduce the oxygen content of a main combustion area, perform oxygen-poor combustion on pulverized coal, reduce NOx in the main combustion area in a reducing atmosphere, and arrange over the main combustion area overfire air (a part of secondary air) to burn off the pulverized coal which is not combusted in the main combustion area. The low-nitrogen combustion mode is the current main flow mode, although NOx generated by a hearth is reduced, high-temperature corrosion is formed on the surface of a water-cooled wall pipe near a main combustion zone due to the reducing atmosphere of the main combustion zone, so that the thinning of the pipe is accelerated, and the service life of the pipe is influenced.
As shown in figure 1, the pulverized coal is burnt at high temperature to generate CO content2Content and pulverized coal surface O2Schematic representation of the content variations. The main mechanism responsible for this phenomenon is that at high temperatures, the combustion of pulverized coal produces a significant amount of CO.
The combustion of coal powder, mainly the combustion of carbon particles, is the key of the high-efficiency combustion of coal, and the primary reaction is as follows:
C+O→CO2,2C+O2→2CO
whereas the secondary reaction can only be carried out at high temperatures:
C+CO2→2CO,2CO+O2→2CO2
as can be seen from the above reaction and FIG. 1, at high temperature, much CO is generated on the surface of carbon, and at this time, in the low-nitrogen combustion mode, the oxygen content in the main combustion zone is further reduced, so that the CO is not completely combusted, and the existence of CO causes Fe in the coal ash particles2O3Is reduced into FeO, which is a strong solvent, so that the ash melting point of the coal ash is reduced by about 200 ℃. Otherwise, under a reducing atmosphere, H2The generated content of S is increased, the gas and the fused ash particles attach to the surface of the water-cooled wall pipe and react with metal to weaken the thickness of the pipe step by step and form high-temperature corrosion on the surface of the pipe。
Disclosure of Invention
The invention aims to solve the technical problem of high-temperature corrosion of the surface of a pipe in the existing low-nitrogen combustor in a secondary air mode.
In order to solve the problems, the technical scheme adopted by the invention is to provide a combustion device capable of adjusting the temperature of secondary air, which comprises a secondary air inlet pipe, an air preheater, a secondary air outlet pipe, a bypass air pipe and an adjusting valve; the secondary air inlet pipe is connected with an air preheater, and the air preheater is provided with a secondary air outlet pipe; one end of the bypass air pipe is connected with the secondary air inlet pipe, and the other end of the bypass air pipe is connected with the secondary air outlet pipe; the bypass air pipe is provided with a regulating valve.
Preferably, a gate valve is arranged in the bypass air pipe.
The invention also provides a using method of the combustion device capable of adjusting the temperature of the secondary air, which is characterized by comprising the following steps of:
step 1: and collecting and counting various data of the operation load of the coal-fired unit.
Step 2: and carrying out data acquisition and statistics on the total secondary air quantity and temperature required by the coal-fired unit.
And step 3: and carrying out data acquisition and statistics on the secondary air bypass air quantity required by the coal burner group.
And 4, step 4: and (3) analyzing according to the statistical results of the step (1), the step (2) and the step (3), wherein the air volume of the bypass air is used as a target value, the unit load is used as a feedforward value, the mixed secondary air temperature is used as a feedback value, and a regulating valve of a bypass secondary air duct is used as an actuating mechanism for operation control.
And 5: on the premise that the total secondary air flow is not changed, the secondary air quantity coming out of the bypass part can be adjusted according to the adjusting valve, so that the total secondary air temperature after mixing is changed.
Step 6: gradually closing the regulating valve of the bypass secondary air duct along with the reduction of the load of the unit; or the regulating valve of the bypass is opened gradually as the unit load increases to a high load. If the bypass is not put into use, the bypass can be directly closed by a gate valve.
The invention aims to provide a combustion device for relieving high-temperature corrosion and a using method thereof. The principle is as follows: the CO is generated greatly mainly in a high-temperature stage (high load), and the amount of CO generated by the boiler in middle and low furnace temperature (middle and low load) stages is not large. The secondary air temperature can be reduced under high load, and the original design can be maintained under medium and low load. The mechanism involved is that after the temperature of the secondary air is reduced, the air density of the secondary air is increased, when the secondary air quantity is unchanged, the momentum of the secondary air is increased, the penetration strength of the secondary air is improved, the secondary air can penetrate through the surfaces of CO and carbon particles, and CO and H are further removed2S, burning out, and reducing the content of reducing gas; secondly, at high temperature, the combustion speed is influenced by oxygen diffusion, and how to better diffuse air to the surface of carbon is very important; finally, the surface temperature of the carbon particles is higher than the ambient smoke temperature when the carbon particles are burnt, and the air temperature is properly reduced when the carbon particles are in high load, so that the surface temperature of the carbon particles can be reduced, and the melting strength of ash formed by the particles is relieved.
The above mechanism corresponds to the basic formula:
m2w2/m1w1＝ρ2w2/ρ1w2
m is above2、m1Secondary air and primary air volume; w is a2、w1Is the velocity of the secondary air and the primary air; rho2And ρ1Is the corresponding air density. When the air temperature is reduced, the air density is increased, and if the quality of the secondary air is kept unchanged, the speed and momentum of the secondary air are improved. By combining the above mechanisms, it is known that burnout of carbon is enhanced and the content of gas such as CO in a reducing atmosphere is relieved.
Compared with the prior art, the invention has the following beneficial effects:
by adding the secondary air duct bypass and additionally arranging the gate valve and the regulating valve on the bypass air duct, the flow of secondary air cold air from the bypass can be regulated. Along with the adjustment of the flow, after secondary air cold air from the bypass and secondary air hot air from a main secondary air channel outlet of the air preheater are converged, the effect of adjusting the air temperature is achieved, and meanwhile, the total secondary air flow is not changed. The total flow of the secondary air is constant, the temperature of the air is adjustable, the burnout of carbon in the burner is enhanced, the content of gases such as CO and the like in a reducing atmosphere is reduced, and the technical problem of high-temperature corrosion of the surface of a pipe in the low-nitrogen burner adopting the secondary air mode at present is solved.
Drawings
FIG. 1 shows the content of CO, generated by burning coal dust at high temperature2Content and pulverized coal surface O2Schematic representation of the content variations.
An X axis: indicating distance from coal surface
Y-axis: volume percent representing different gas contents
FIG. 2 is a schematic view of the structure of a combustion apparatus capable of adjusting the temperature of secondary air according to the present invention.
Reference numerals: 1. secondary air inlet pipe 2, air preheater 3, secondary air outlet pipe 4, bypass air pipe 5, gate valve 6 and regulating valve
Detailed Description
In order to make the invention more comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings:
as shown in FIG. 1, it can be seen that CO is generated on the surface of carbon at high temperature, and at this time, in the low-nitrogen combustion mode, the oxygen content in the main combustion zone is further reduced, so that CO is not completely combusted, and the existence of CO causes Fe in the inside of the coal ash particles2O3Reduced to FeO, a strong solvent, which lowers the ash melting point of the coal ash by about 200 ℃, and H in a reducing atmosphere2The generated content of S is increased, the gas and the fused ash particles attach to the surface of the water-cooled wall pipe and chemically react with metal, the thickness of the pipe is weakened step by step, and high-temperature corrosion on the surface of the pipe is formed.
As shown in fig. 2, the invention provides a combustion device capable of adjusting the temperature of secondary air to slow down high-temperature corrosion, which comprises a secondary air inlet pipe 1, an air preheater 2, a secondary air outlet pipe 3, a bypass air pipe 4, a gate valve 5 and an adjusting valve 6; the secondary air inlet pipe 1 is connected with the air preheater 2, secondary air-cooled air enters the air preheater 2 and is heated into hot air after heat exchange, and the hot air is discharged from a secondary air outlet pipe 3 connected with the air preheater 2; one end of the added bypass air pipe 4 is connected with the secondary air inlet pipe 1, and the other end of the bypass air pipe 4 is connected with the secondary air outlet pipe 3; the bypass air pipe 4 is provided with a gate valve 5 and a regulating valve 6.
The invention provides a low-air-temperature combustion technology aiming at the problems that the surface of a water-cooling wall pipe is easy to corrode under high temperature and the like, in a main secondary air wind path, a method of shunting secondary air cold wind by a bypass wind pipe is adopted, so that the total secondary air flow is not changed, and the secondary air quantity from the bypass wind pipe part can be adjusted by an adjusting valve 6, thereby changing the mixed total secondary air temperature. Gradually closing the regulating valve 6 of the secondary air path of the bypass air pipe along with the reduction of the load of the unit; and as the unit load increases to a high load, the regulating valve 6 of the bypass air pipe is opened gradually. If the bypass duct is not put into use, the bypass duct can be directly closed by the gate valve 5 to return to the original design.
The invention provides a using method of a combustion device capable of adjusting secondary air temperature, which comprises the following steps:
step 1: and collecting and counting various data of the operation load of the coal-fired unit.
Step 2: and carrying out data acquisition and statistics on the total secondary air quantity and temperature required by the coal-fired unit.
And step 3: and carrying out data acquisition and statistics on the secondary air bypass air quantity required by the coal burner group.
And 4, step 4: and (3) analyzing according to the statistical results of the step (1), the step (2) and the step (3), wherein the air volume of the bypass air is used as a target value, the unit load is used as a feedforward value, the mixed secondary air temperature is used as a feedback value, and a regulating valve of a bypass secondary air duct is used as an actuating mechanism for operation control.
And 5: on the premise that the total secondary air flow is not changed, the secondary air quantity coming out of the bypass part can be adjusted according to the adjusting valve, so that the total secondary air temperature after mixing is changed.
Step 6: gradually closing the regulating valve of the bypass secondary air duct along with the reduction of the load of the unit; or the regulating valve of the bypass is opened gradually as the unit load increases to a high load. If the bypass is not put into use, the bypass can be directly closed by a gate valve.
While the invention has been described with respect to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. Those skilled in the art can make various changes, modifications and equivalent arrangements, which are equivalent to the embodiments of the present invention, without departing from the spirit and scope of the present invention, and which may be made by utilizing the techniques disclosed above; meanwhile, any changes, modifications and variations of the above-described embodiments, which are equivalent to those of the technical spirit of the present invention, are within the scope of the technical solution of the present invention.
Claims (1)
1. A method for using a combustion device capable of adjusting the temperature of secondary air comprises a secondary air inlet pipe (1), an air preheater (2), a secondary air outlet pipe (3), a bypass air pipe (4) and an adjusting valve (6); the secondary air inlet pipe (1) is connected with the air preheater (2), and the air preheater (2) is provided with a secondary air outlet pipe (3); one end of the bypass air pipe (4) is connected with the secondary air inlet pipe (1), and the other end of the bypass air pipe (4) is connected with the secondary air outlet pipe (3); an adjusting valve (6) is arranged in the bypass air pipe (4); a gate valve (5) is arranged in the bypass air pipe (4); the method is characterized by comprising the following steps:
step 1: collecting and counting various data of the operation load of the coal-fired unit;
step 2: carrying out data acquisition and statistics on the total air quantity and temperature of secondary air hot air required by the coal-fired unit;
and step 3: carrying out data acquisition and statistics on secondary air bypass air quantity required by the coal burner group;
and 4, step 4: analyzing according to the statistical results of the step 1, the step 2 and the step 3, wherein the air volume of the bypass air is used as a target value, the unit load is used as a feedforward value, the mixed secondary air temperature is used as a feedback value, and a regulating valve of a bypass secondary air path is used as an actuating mechanism for operation control;
and 5: on the premise that the total secondary air flow is not changed, the secondary air quantity from the bypass part can be adjusted according to the adjusting valve, so that the total secondary air temperature after mixing is changed;
step 6: gradually closing the regulating valve of the bypass secondary air duct along with the reduction of the load of the unit; or the regulating valve of the bypass is opened gradually along with the increase of the unit load to a high load; if the bypass is not put into use, the bypass can be directly closed by a gate valve.
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| CN112050248A (en) * | 2020-09-10 | 2020-12-08 | 上海康恒环境股份有限公司 | Steam air preheater for household garbage incineration |
| CN112133942A (en) * | 2020-09-30 | 2020-12-25 | 上海海事大学 | Fuel cell of ship electric propulsion system and application thereof |
| CN113008042B (en) * | 2021-04-15 | 2023-04-18 | 新余钢铁股份有限公司 | Preheater protection structure for heating furnace and use method thereof |
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| CN109882879A (en) * | 2019-04-03 | 2019-06-14 | 华能国际电力股份有限公司玉环电厂 | A kind of full working scope denitrating flue gas and air preheater anti-blocking system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPS52101315A (en) * | 1976-02-23 | 1977-08-25 | Nissan Motor Co Ltd | The secondary air control equipment for exhaust gas system of internal combustion engine |
| JPH08145339A (en) * | 1994-11-22 | 1996-06-07 | Ishikawajima Harima Heavy Ind Co Ltd | Method and apparatus for controlling secondary air flow rate for combustion of coal fired boiler |
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