CN113154874A - Heating furnace low NOx combustion control method based on gas fuel - Google Patents
Heating furnace low NOx combustion control method based on gas fuel Download PDFInfo
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- CN113154874A CN113154874A CN202110401508.2A CN202110401508A CN113154874A CN 113154874 A CN113154874 A CN 113154874A CN 202110401508 A CN202110401508 A CN 202110401508A CN 113154874 A CN113154874 A CN 113154874A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
- F27B9/30—Details, accessories, or equipment peculiar to furnaces of these types
- F27B9/40—Arrangements of controlling or monitoring devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
- F27B9/04—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity adapted for treating the charge in vacuum or special atmosphere
- F27B9/045—Furnaces with controlled atmosphere
Abstract
The invention relates to a heating furnace low NOx combustion control method based on gas fuel, 1) controlling the furnace atmosphere of a soaking zone to be a weak oxidizing atmosphere, so that the fuel is completely combusted in the soaking zone, and the flue gas does not contain CO; 2) controlling the atmosphere of the hearth of each heating section in the high-temperature section to be reducing atmosphere, so that the CO content in the flue gas entering the low-temperature heating section from the high-temperature section is 3-10%; 3) controlling the atmosphere of a hearth of a heating section to be reducing atmosphere, so that the content of CO in the flue gas of the low-temperature heating section is not more than 1.5%; 4) and an air nozzle is additionally arranged in the preheating section, when the content of CO in the flue gas in the preheating section is more than 1%, the air nozzle is opened to burn the residual CO, and the air nozzle is closed until the content of CO is 0, so that the air excess coefficient of the preheating section is ensured to be more than 1.2. The invention reduces the generation of flue gas NOx at the high-temperature section, and simultaneously burns the residual fuel through the low-temperature section, thereby improving the heat absorption efficiency of the billet.
Description
Technical Field
The invention relates to the technical field of thermal energy conservation, in particular to a heating furnace low NOx combustion control method based on gas fuel.
Background
NOx, one of the major pollutants to be controlled, is the main pollution source causing acid rain and photochemical smog, and causes great harm to human health, various crops and ecological environment. With the implementation of a new environmental protection method, the requirements on the gas emission of the steel enterprises are more and more strict, and according to the ultra-low emission standard of the steel enterprises, the indexes of NOx of a heating furnace and a heat treatment furnace in a steel rolling process are as low as 150mg/Nm3。
The NOx in the steel industry mainly comes from the fuel combustion process, which mainly comprises the combustion of coal, the combustion of coke, the combustion of fuel oil and the combustion of industrial secondary gas, and N in the fuel under the high-temperature condition+、N2N in combustion air2NO and N are generated under the action of high temperature2O、NO2And a small amount of N2O3、N2O4、N2O5. The solid fuel has more N compounds, the generated flue gas is seriously influenced by fuel nitrogen, the generation amount of NOx is higher, the flue gas denitration treatment is generally needed at the later stage, the fuel nitrogen is reduced to a lower level through a fine desulfurization process in the industrial gas preparation process, and the low-level requirement of the NOx can be realized only by controlling the generation of thermal nitrogen in the combustion process.
Patent CN201811208892.9 a mix formula flameless burning low NOx burner entirely, discloses that be equipped with the combustion net inside lining that extends towards the combustion cylinder inboard in the combustor, and the one side of combustion net inside lining towards the combustion cylinder outside is equipped with the combustion net. Set up the combustion net on the combustion net inside lining, when making the premixed gas of air and natural gas pass through the combustion net, can be even pass from the combustion net, make premixed gas evenly burn on the surface of combustion net, avoid the combustion cylinder to produce local high temperature, guarantee the normal operating of combustor. Flame is dispersed by a combustion net, the existing air gas is preheated to a certain temperature, the structure of the flame does not depend on mixing and only depends on flow velocity, and the mode cannot effectively reduce the concentrated combustion of the flame.
The device and the method for reducing the generation of nitrogen oxides in the coke oven extract the waste gas in a waste gas channel of the coke oven and force the waste gas to be sent into an air channel of the coke oven to be mixed with air; the oxygen content of the air is diluted with the exhaust gas. The invention can obviously reduce the concentration of nitrogen oxides in waste gas and the absolute discharge amount of the nitrogen oxides without changing the internal structure of the coke oven, and improve the ambient atmospheric environment of enterprises. Reducing the oxygen content of the air can reduce the formation of thermal NOx, but because of O2The reduction in (b) may result in insufficient combustion, reduced fuel efficiency and increased energy losses.
Patent CN201811155404.2 discloses a radiant tube emission system and method for reducing nitrogen oxide emission, and discloses a method for reducing NO in a combustion processXReduction of NO by catalytic reactionXCombined two-stage reduction of NO in flue gasXContent of NOXThe content can be reduced to an extremely low level, and the equipment cost is greatly reduced. The NOx content is reduced in a catalytic mode, the NOx content is similar to that of post-treatment, meanwhile, the modification cost of the combustor is high, and the energy cost is greatly improved.
By combining the analysis and retrieval results of related patents, the reduction of the NOx content in gas combustion mainly needs to reduce the oxygen content in a high-temperature area and reduce a concentrated high-temperature area, and meanwhile, the production cost and the furnace and kiln efficiency must be considered. For a steel rolling heating furnace, a heating area is divided into three or more heating sections of high, medium and low temperature, and the generation condition of NOx can be completely controlled by adopting a reasonable control method, so that low NOx combustion is realized.
Disclosure of Invention
The invention aims to provide a heating furnace low NOx combustion control method based on gas fuel, which reduces the generation of flue gas NOx and reduces the consumption of fuel.
In order to achieve the purpose, the invention adopts the following technical scheme:
a low NOx combustion control method of a heating furnace based on gas fuel controls the atmosphere of each combustion section of the heating furnace to ensure that the residual fuel in a high-temperature section is combusted secondarily in a low-temperature heating section, and the method comprises the following specific steps:
1) controlling the furnace atmosphere of the soaking section to be a weak oxidizing atmosphere, wherein the air surplus coefficient of the soaking section is 1.05-1.2, the coal gas heat load accounts for 10-20% of the total heat load of the heating furnace, and the furnace pressure is 0-10 Pa; the fuel is completely combusted in the soaking section, and the flue gas does not contain CO;
2) controlling the atmosphere of a hearth of each heating section in the high-temperature section to be a reducing atmosphere, controlling the air excess coefficient of a first heating section adjacent to the soaking section to be not less than 0.6, sequentially increasing the air excess coefficient of each heating section by 0.1-0.2 along the traveling direction of flue gas, wherein the coal gas heat load of the high-temperature section accounts for 60-80% of the total load of the heating furnace, the coal gas heat loads of the heating sections in the sections are evenly distributed, and the pressure of the hearth of the high-temperature section is 10-20 Pa, so that the CO content in the flue gas entering the low-temperature heating section from the high-temperature section is 3-10%;
3) controlling the atmosphere of a hearth of a heating section to be a reducing atmosphere, wherein the air excess coefficient is 0.9-1.1, the coal gas heat load accounts for 10% -20% of the total heat load of the heating furnace, and the hearth pressure is 10-20 Pa; the CO content in the flue gas of the low-temperature heating section is not more than 1.5 percent;
4) and an air nozzle is additionally arranged in the preheating section, when the content of CO in the flue gas of the preheating section is more than 1%, the air nozzle is opened to burn the residual CO, and the air nozzle is closed until the content of CO is 0, so that the air excess coefficient of the preheating section is more than 1.2, and the pressure of a hearth is 0-10 Pa.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the atmosphere of each section of the heating furnace is reasonably controlled, the generation of flue gas NOx in a high-temperature section is reduced, and meanwhile, the residual fuel is combusted through a low-temperature section, so that the heat absorption efficiency of the billet is improved, the incomplete combustion loss of the heating furnace is reduced, and the energy-saving and environment-friendly combustion control technology of the heating furnace is realized.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a graph of NOx generation for different air excess coefficients a.
In the figure: smoke component detection points (1-5) and an air nozzle (6).
Detailed Description
The following further describes embodiments of the present invention with reference to the accompanying drawings:
as shown in figure 1, the heating furnace comprises a preheating section, a heating section, a second heating section, a third heating section and a soaking section, and smoke component detection points (1-4) are arranged among the combustion sections. An air nozzle 5 is arranged on the top of the preheating section.
The control parameters of each combustion section of the heating furnace are shown in the following table:
example 1:
the designed output of a rail beam heating furnace of a certain large-scale factory is 120t/h, the product mainly comprises large-scale section steel, heavy rail steel and deformed steel, the blank is a large-scale square blank of 380mm multiplied by 280mm, the length of the heating furnace is 35m, and the hot charging rate is more than 70%. The heating structure comprises a preheating section, a first heating section, a second heating section, a third heating section and a soaking section, the heating furnace is in an intensified heating state for a long time due to the short length of the heating furnace, the temperature of the second heating section is set to be more than 1350 ℃, the temperature of the soaking section is set to be more than 1300 ℃, the NOx in exhaust smoke exceeds the standard due to the high temperature of the heating furnace, and the NOx reaches 350mg/Nm3Above, the simultaneous combustion rate reaches 1.25GJ/t (above 700 ℃ in hot charging).
The control method of the rail beam heating furnace is improved, and the thermal load of the gas in the soaking zone is set to be 2500-2800 Nm3H, air-fuel ratio 2: 1, the air excess coefficient is 1.05, the hearth pressure is 5Pa, and a smoke detection point 1 detects that the smoke does not contain CO.
Three heating section coal gas thermal load 7000 ~ 7200Nm3H, air-fuel ratio 1.65: 1, the air excess coefficient is 0.75, the hearth pressure is 15Pa, and the CO content in the flue gas is 6 percent detected by a detection point 2.
The thermal load of the gas in the two heating sections is 6000-6500 Nm3H, air-fuel ratio 1.8: 1, the air excess coefficient is 0.85, the hearth pressure is 15Pa, and the CO content in the flue gas is 3.5 percent detected by a detection point 3.
A heating section with a gas thermal load of 1500-2000 Nm3H, air-fuel ratio 2.2: 1, the air excess coefficient is 1.2, and the furnace pressure is 5 Pa. And 4, detecting that the smoke does not contain CO by using the detection point.
When the CO at the detection point 4 is zero, the preheating section closes the air nozzle and no excess air is supplied.
The unit consumption reaches 1.12GJ/t under the condition of unchanged yield, and the NOx is reduced to 200mg/Nm3The following.
Example 2:
the design output of a slab heating furnace of a certain hot rolling plant is 250t/h, the product mainly comprises hot rolling strip steel, silicon steel and the like, the slab is a large slab with the thickness of 10000mm multiplied by 1280mm multiplied by 230mm, the length of the heating furnace is 45m, and the hot charging rate is more than 30%. The heating structure comprises a preheating section, a first heating section, a second heating section, a third heating section and a soaking section, and because the heating furnace has low heat loading rate and high heating temperature, the temperature of the heating section is set to be more than 1320 ℃, and the temperature of the soaking section is set to be more than 1280 ℃, the NOx in exhaust smoke exceeds the standard due to the high temperature of the heating furnace, and reaches 320mg/Nm3Meanwhile, the burn-up reaches 1.42GJ/t (cold charging).
The control method of the improved slab heating furnace sets the load of a soaking section at 6000-6500 Nm3H, air-fuel ratio 2: 1, the surplus coefficient is 1.05, the hearth pressure is 7Pa, and the smoke detection point 1 detects that the smoke does not contain CO.
Load 17000-17200 Nm of three heating sections3H, air-fuel ratio 1.34: 1, the excess coefficient is 0.71, the hearth pressure is 20Pa, and the content of CO in the flue gas is 7.2 percent detected by a detection point 2.
Load of two heating sections 14000-15000 Nm3H, air-fuel ratio 1.56: 1, the excess coefficient is 0.81, the hearth pressure is 15Pa, and the content of CO in the flue gas is 4.5 percent detected by a detection point 3.
A load of 4000-5000 Nm in a heating section3H, air-fuel ratio 2.0: 1, the excess coefficient is 1.08, and the furnace pressure is 5 Pa. And 4, detecting the content of CO in the smoke by using a detection point to be 1.3 percent.
The preheating stage was started with an air nozzle to feed 8800Nm3The pressure of the furnace chamber is 10 Pa. And 5, detecting that the smoke does not contain CO by using a detection point.
The unit consumption reaches 1.33GJ/t under the condition of unchanged yield, and the NOx is reduced to 220mg/Nm3The following.
It will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the principles of the invention, and these modifications and variations also fall within the scope of the invention as defined in the appended claims. The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and their concepts should be equivalent or changed within the technical scope of the present invention.
Claims (4)
1. A low NOx combustion control method of a heating furnace based on gas fuel is characterized in that the atmosphere of each combustion section of the heating furnace is controlled, so that the residual fuel in a high-temperature section is combusted secondarily in a low-temperature heating section, and the method comprises the following specific steps:
1) controlling the furnace atmosphere of the soaking section to be a weak oxidizing atmosphere, wherein the air surplus coefficient of the soaking section is 1.05-1.2, the coal gas heat load accounts for 10-20% of the total heat load of the heating furnace, and the furnace pressure is 0-10 Pa; the fuel is completely combusted in the soaking section, and the flue gas does not contain CO;
2) controlling the atmosphere of a hearth of each heating section in the high-temperature section to be a reducing atmosphere, controlling the air excess coefficient of a first heating section adjacent to the soaking section to be not less than 0.6, sequentially increasing the air excess coefficient of each heating section by 0.1-0.2 along the traveling direction of flue gas, wherein the coal gas heat load of the high-temperature section accounts for 60-80% of the total load of the heating furnace, the coal gas heat loads of the heating sections in the sections are evenly distributed, and the pressure of the hearth of the high-temperature section is 10-20 Pa, so that the CO content in the flue gas entering the low-temperature heating section from the high-temperature section is 3-10%;
3) controlling the atmosphere of a hearth of a heating section to be a reducing atmosphere, wherein the air excess coefficient is 0.9-1.1, the coal gas heat load accounts for 10% -20% of the total heat load of the heating furnace, and the hearth pressure is 10-20 Pa; the CO content in the flue gas of the low-temperature heating section is not more than 1.5 percent;
4) and an air nozzle is additionally arranged in the preheating section, when the content of CO in the flue gas of the preheating section is more than 1%, the air nozzle is opened to burn the residual CO, and the air nozzle is closed until the content of CO is 0, so that the air excess coefficient of the preheating section is more than 1.2, and the pressure of a hearth is 0-10 Pa.
2. The low NOx combustion control method for the gas fuel-based heating furnace according to claim 1, wherein the air excess coefficient of the soaking zone in the step 1) is 1.05-1.1, and the hearth pressure is 5-10 Pa.
3. The low NOx combustion control method of the gas fuel-based heating furnace according to claim 1, wherein in the step 2), the air excess coefficient of a first heating section adjacent to the high temperature section and the soaking section is 0.6-0.8, and the hearth pressure is 15-20 Pa.
4. The low NOx combustion control method of a gas fuel-based heating furnace according to claim 1, wherein the air excess coefficient of the first heating section in the step 3) is 1.0 to 1.1, and the furnace pressure is 5 to 10 Pa.
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| TWI797831B (en) * | 2021-11-12 | 2023-04-01 | 中國鋼鐵股份有限公司 | Method for designing control parameters of furnace |
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| CN110793032A (en) * | 2019-09-30 | 2020-02-14 | 鞍钢股份有限公司 | Oxygen-enriched combustion system of heating furnace and control method thereof |
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| CN111412755A (en) * | 2020-03-03 | 2020-07-14 | 首钢京唐钢铁联合有限责任公司 | Method for reducing emission concentration of nitric oxide in steel rolling heating furnace |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101561224A (en) * | 2009-05-15 | 2009-10-21 | 首钢总公司 | Method for controlling combustion atmosphere in large-scale walking beam type plate blank heating furnace |
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| CN110793032A (en) * | 2019-09-30 | 2020-02-14 | 鞍钢股份有限公司 | Oxygen-enriched combustion system of heating furnace and control method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| TWI797831B (en) * | 2021-11-12 | 2023-04-01 | 中國鋼鐵股份有限公司 | Method for designing control parameters of furnace |
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