Hot-blast stove heat supply system capable of reducing nitrogen oxide emission and heat supply method thereof

Abstract

The hot-blast stove heat supply system comprises a hot-blast stove body and a fan, the hot-blast stove body is connected with a combustion-supporting air inlet pipe, the fan is arranged at an air inlet of the combustion-supporting air inlet pipe, a hot air outlet of the hot-blast stove body is connected with an air inlet of a vertical mill, and a hot air outlet of the vertical mill is connected with an air outlet of the vertical mill. An air outlet of the vertical mill is connected with an inlet of the main dust collector, an outlet of the main dust collector is divided into a discharge branch and a circulation branch, the circulation branch is connected with an air inlet of the vertical mill, and the circulation branch is further connected with an inlet of the fan through a circulation air pipe. The system has the advantages of being low in investment cost and easy and convenient to operate and maintain by improving the pipeline structure.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hot blast stove heating, and particularly relates to a hot blast stove heating system with reduced nitrogen oxide emission and a heating method thereof. BACKGROUND

[0002] Generally, the nitrogen oxide emission generated by the hot blast stove will exceed the NOx emission limit value (300 mg / m 3 ).

[0003] The current technical route for controlling nitrogen oxide (NOx) emission of the hot blast stove system mainly includes combustion control and post-combustion control.

[0004] Combustion control: the core is to use a low-nitrogen burner. However, this technology not only has high equipment cost, but more importantly, it has poor adaptability to coke oven gas, and it is difficult to meet the stable denitration demand under such fuel conditions.

[0005] Post-combustion control: mainly relies on denitration technologies such as selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR). Although this method is effective, it requires additional investment in the construction of a denitration device, and continuously consumes expensive catalysts or reducing agents, resulting in a significant increase in operating costs.

[0006] For the hot blast stove system that has not been equipped with a low-nitrogen burner or a post-end denitration device, it is urgent to explore an innovative process measure or equipment. SUMMARY

[0007] The purpose of the present application is to solve the above-mentioned problems in the prior art, and to provide a hot blast stove heating system with reduced nitrogen oxide emission and a heating method thereof. The device has the advantages of low investment cost and simple operation and maintenance.

[0008] One of the purposes of the present application is to provide a hot blast stove heating system with reduced nitrogen oxide emission, which comprises a hot blast stove body and a fan. The hot blast stove body is connected with a combustion-supporting air inlet pipe. The air inlet of the combustion-supporting air inlet pipe is connected with the fan. The hot air outlet of the hot blast stove body is connected with the air inlet of a vertical mill. The air outlet of the vertical mill is connected with the inlet of a main dust collector. The outlet of the main dust collector is divided into an exhaust branch and a circulation branch. The circulation branch is connected with the air inlet of the vertical mill. The circulation branch is also connected with the air inlet of the fan through a circulating air pipe.

[0009] As a preferred solution, it further comprises a fresh air supplement pipe connected with the air inlet of the fan, which is used to supplement fresh air into the fan to provide oxygen required for combustion.

[0010] As a preferred scheme, the combustion-supporting air inlet pipe is divided into two branches, and the two branches are connected with the hot blast stove body respectively, one branch is connected with the air inlet of the hot blast stove body and is provided with an air valve I for controlling air volume, and the other branch is connected with the air distribution inlet of the hot blast stove body and is provided with an air valve II for controlling air volume.

[0011] As a preferred scheme, the circulating air pipe is provided with an air valve III for controlling air volume.

[0012] As a preferred scheme, the fresh air supplement pipe is connected at the air inlet side of the air valve III, and the fresh air supplement pipe is provided with an air valve IV for controlling air volume.

[0013] As a preferred scheme, the outlet end of the hot blast stove body is provided with a temperature-control cold air pipe, and the temperature-control cold air pipe is provided with a temperature-control cold air valve, which is used for supplementing low-temperature cold air to the hot air outlet of the hot blast stove body, so as to reduce the hot air outlet temperature of the hot blast stove body.

[0014] As a preferred scheme, the circulating branch is provided with a circulating air valve, and the inlet of the circulating air pipe is connected at the air inlet side of the circulating air valve.

[0015] As a preferred scheme, the exhaust branch is connected with a chimney.

[0016] The second object of the present application is to provide a heat supply method of the hot blast stove heat supply system with reduced nitrogen oxide emission, which comprises the following steps: the hot air generated by the hot blast stove body enters the vertical mill, and the material in the vertical mill is dried; the exhaust air of the vertical mill is de-dusted by the main dust collector, and the de-dusted air flow enters the main exhaust fan and is divided into a circulating branch and an exhaust branch, wherein the exhaust branch is discharged into the chimney, and the circulating branch is partially combined with the exhaust air of the hot blast stove body and then re-introduced into the vertical mill, and the other part of the circulating branch is introduced into the air fan inlet, the outlet of the air fan is divided into combustion-supporting air and distribution air, the combustion-supporting air directly enters the hot blast stove burner of the hot blast stove body through the air inlet via the air valve I, the distribution air directly enters the furnace interlayer of the hot blast stove body through the air distribution inlet via the air valve II, and then enters the furnace from the bottom after preheating to perform air distribution, so as to adjust the exhaust air temperature of the hot air outlet of the hot blast stove body, thereby achieving the required air volume and temperature for drying in the vertical mill.

[0017] As a preferred scheme, the external cold air is supplemented into the circulating air pipe through the fresh air supplement pipe, and the proportion of the circulating air and the external cold air is adjusted through the air valve IV.

[0018] Advantages Firstly, this solution improves the hot blast stove heating system by connecting the circulation branch between the main dust collector and the vertical mill to the inlet of the blower via a circulating air duct. This introduces the circulating air from the grinding system into the hot blast stove body, using the circulating air as the source of combustion air and distribution air. Since the circulating air temperature is typically 80~95℃, while the outside air temperature is typically -20~35℃, the circulating air temperature is higher than the outside air temperature, which helps improve fuel combustion efficiency, reduce fuel consumption, and achieve energy conservation and emission reduction. Furthermore, the circulating air has a lower oxygen content than fresh air, which helps control the furnace temperature to ≤800℃, thus blocking the thermal NOx formation pathway at its source. The hot blast stove heating system using this scheme can effectively reduce NOx emissions from the heating system. Compared with using low-NOx burners, the required equipment cost is lower, and it can be used for various fuel types, including coke oven gas. Compared with post-combustion NOx emission control methods such as selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR), it does not require investment in the construction of denitrification equipment and continuous consumption of expensive catalysts or reducing agents, resulting in lower construction and operating costs.

[0019] Secondly, in this scheme, the bottom air inlet of the hot blast stove body is equipped with air valve I, and the side air outlet of the hot blast stove body is equipped with air valve II. By cooperating with air valve I and air valve II, for example by adjusting the opening of air valve II and / or increasing the opening of air valve I, the air volume required for combustion at the bottom air inlet of the hot blast stove body can be increased, forcibly elongating and dispersing the high-temperature flame, reducing the accumulation of high temperature, thereby reducing the amount of NOx generated.

[0020] Thirdly, this scheme optimizes the hot blast stove heating method. By utilizing a heating system with the aforementioned specific structure, it suppresses local NOx surges by using excess combustion air and blocks NOx formation pathways by reducing oxygen concentration in the combustion zone and the oxygen content in flue gas emissions. These multiple measures work together to achieve NOx emission reduction and compliance with emission standards. This approach not only effectively reduces NOx emissions from the heating system but also offers advantages such as low investment costs and simple operation and maintenance, thus achieving a win-win situation for both environmental and socio-economic benefits. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a process flow diagram of the hot air furnace heating system of the present invention; Figure 2This is a schematic diagram of the pipe connection of the hot blast stove body in one embodiment of the present invention. Figure 1 ; Figure 3 This is a schematic diagram of the pipe connection of the hot blast stove body in one embodiment of the present invention. Figure 2 ; The diagram is labeled as follows: 1. Hot air furnace body; 2. Air valve I; 3. Air valve II; 4. Air valve III; 5. Air valve IV; 6. Circulating air valve; 7. Fan; 8. Temperature-controlled cold air valve; 9. Vertical mill; 10. Main dust collector; 11. Main exhaust fan; 12. Chimney; 13. Outlet air valve; 100. Combustion air inlet pipe; 101. Air inlet; 102. Air distribution port; 200. Circulating pipeline; 300. Fresh air supply pipe; 400. Circulating branch; 500. Exhaust branch; 600. Temperature-controlled cold air pipe; 700. Hot air outlet pipe. Detailed Implementation

[0023] The present invention will now be described in detail through exemplary embodiments. However, it should be understood that, without further description, elements, structures, and features in one embodiment may be advantageously incorporated into other embodiments.

[0024] It should be noted that, unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "a," "an," or "the," and similar words used in the specification and claims of this patent application do not express a limitation of quantity, but rather indicate the presence of at least one. Terms such as "comprising" or "including" indicate that the elements or objects preceding "comprising" encompass the elements or objects listed following "comprising" or "including" and their equivalents, but do not exclude other elements or objects having the same function.

[0025] As shown in the figure, this embodiment provides a hot blast stove heating system for reducing nitrogen oxide emissions, including a hot blast stove body 1 and a blower 7. The hot blast stove body 1 includes an air inlet 101 at the bottom and an air distribution port 102 on the side. The air inlet 101 and the air distribution port 102 are respectively connected to the outlet of the blower 7 through pipelines. A circulation branch 400 is also provided between the main dust collector 10 and the vertical mill 9. The inlet of the blower 7 is connected to the circulation branch 400 through a circulation duct 200, thereby reintroducing the circulating air discharged from the main dust collector 10 into the hot blast stove body 1. At the same time, a fresh air supply duct 300 is also connected to the inlet side of the blower 7 for supplying fresh air to the hot blast stove body 1. A certain amount of outside air is added to the blast furnace body 1 to supplement the oxygen required for combustion. In this scheme, the inlet side of the blower 7 is replaced by the replacement of the original complete supply of fresh outside air with the supply of circulating air discharged from the main dust collector 10 and introduced into the vertical mill 9. The other part is supplemented with a small amount of fresh outside air. The purpose of this design is to draw about 90°C circulating air from the circulation branch 400 of the grinding system through the new pipeline as the air supply source for the hot blast furnace body 1. By using low oxygen circulating air to replace the full oxygen air mixing, the oxygen concentration in the combustion zone and the oxygen content in the flue gas emissions can be reduced. By reducing the oxygen content, the furnace temperature can be controlled to a certain extent to prevent it from overheating.

[0026] In this embodiment, approximately 90°C circulating air is drawn from the circulating air duct of the grinding system through a newly added pipeline as the air supply source for the hot blast stove body 1. In principle, the air intake valve III4 is opened at 100%, and the air valve IV5 is opened at 0~20% to mix in cold air in order to provide the oxygen required for combustion. The inlet of the blower 7 is connected to the outlet of the air valve III4, which is used to divide the air supply of the hot blast stove body 1 into two paths through the blower 7. One path goes directly into the hot blast stove burner through the pipeline and air valve I2, and the other path goes directly into the furnace jacket through the pipeline and air valve II3. After preheating, it enters the furnace from the bottom for air distribution to regulate the exhaust temperature of the hot air outlet.

[0027] In this invention, the hot air outlet of the hot blast furnace body 1 is connected to the air inlet of the vertical mill 9 via a hot air outlet pipe 700. The gas exiting the vertical mill 9 is dedusted by the main dust collector 10 and then discharged by the main exhaust fan 11, which divides into two branches: a circulation branch 400 and an exhaust branch 500. The exhaust branch 500 is discharged into the atmosphere via a chimney 12, while the circulation branch 400 mixes with the hot air prepared by the hot blast furnace body 1 to form circulating air that returns to the vertical mill 9. An outlet air valve 13 for controlling the air volume and opening / closing is also provided on the hot air outlet pipe 700.

[0028] In a typical embodiment of the present invention, the hot blast stove body 1 is supplied with air via a blower 7 and two separate paths. The combustion air inlet pipe 100 at the outlet of the blower 7 is divided into two branches. One branch is connected to the air inlet 101 of the hot blast stove body 1 and is equipped with a damper I2 for controlling the air volume. The other branch is connected to the air distribution port 102 of the hot blast stove body 1 and is equipped with a damper II3 for controlling the air volume. By adjusting the opening of dampers I2 and II3, the air volume of the two pipelines can be controlled. One path of air enters the hot blast stove burner of the hot blast stove body 1 directly after passing through damper I2, thereby elongating and dispersing the high-temperature flame at the moment of coke oven gas combustion, reducing high-temperature accumulation, and thus reducing the amount of NOx generated. The other path of air enters the furnace jacket of the hot blast stove body 1 directly through the pipeline and damper II3 for air distribution, so as to achieve the appropriate air volume and temperature required for drying in the vertical mill 9. This scheme regulates the airflow of two branches by installing air valves I2 and II3 on ​​the two outlets of the blower 7. For example, by increasing the opening of air valve I2, the combustion air of the hot blast stove is increased to 2 to 2.5 times the required combustion airflow, forcibly elongating and dispersing the high-temperature flame, reducing high-temperature accumulation, and thus reducing the amount of NOx generated. In actual operation, excessive opening of air valve I2 can cause pipeline vibration. Therefore, air valve I2 can be opened to the maximum opening that does not cause pipeline vibration (for example, an opening between 50% and 100%), and then the airflow is controlled by reducing the opening of air valve II3. This indirect method increases the airflow on the side of air valve I2. The temperature-controlled cold air duct 600 is connected to the hot air outlet of the hot blast stove body 1. The temperature-controlled cold air duct 600 is equipped with a temperature-controlled cold air valve 8. When the outlet air temperature of the hot blast stove body 1 is too high, the temperature-controlled cold air valve 8 mixes cold air into the outlet flue gas so that the exhaust air temperature of the furnace body reaches about 400°C. After the system is running stably, nitrogen oxides are detected at the flue gas detection port on chimney 12.

[0029] In this embodiment, the circulating air duct 200 is equipped with an air valve III4 for controlling the air volume. The fresh air supply duct 300 is equipped with an air valve IV5 for controlling the air volume. The fresh air supply duct 300 is connected to the air inlet side of the air valve III4. By setting the air valve IV5 in the fresh air supply duct 300, the ratio of circulating air to cold air can be adjusted. The purpose of extracting circulating air as the air source for the hot blast stove is to reduce the oxygen content in the flue gas at the outlet of the hot blast stove. Using low-oxygen circulating air from the grinding system to replace the external all-oxygen air changes the combustion conditions inside the hot blast stove body 1 without affecting the combustion of the hot blast stove. This can directly reduce the total amount of NOx generated and significantly reduce the oxygen content at the outlet of the chimney 12, eliminating the artificially high emission conversion value. Thus, a dual reduction in the absolute concentration and conversion concentration of NOx in the flue gas is achieved simultaneously.

[0030] According to the "Emission Standard of Air Pollutants for Cement Industry" GB4915-2013, for the exhaust gas of drying equipment using an independent heat source, the oxygen content in the exhaust gas should be tested simultaneously. The measured atmospheric pollutant emission concentration should be converted into the baseline emission concentration under the baseline oxygen content state according to the following formula, and this should be used as the basis for judging whether the emission meets the standard.

[0031] In the formula: C 基 —Baseline emission concentration of air pollutants, mg / m³ 3 ; C 实 —Measured atmospheric pollutant emission concentration, mg / m³ 3 ; O 基 —Baseline oxygen content percentage: 10% for exhaust gas from cement kilns and kiln tail waste heat utilization systems, and 8% for exhaust gas from drying equipment using independent heat sources. O 实 —The measured percentage of oxygen content in exhaust gas.

[0032] Among them, C 基 Corresponding to the NOx conversion concentration in this scheme, C 实 This corresponds to the absolute concentration of NOx measured in this scheme.

[0033] This solution takes the exhaust gas from a drying equipment using an independent heat source as an example. By changing the combustion conditions inside the hot air furnace, NO can be suppressed. x The generation path directly reduces NO x The total amount generated, thereby reducing NO in flue gas x Actual concentration C 实 On the other hand, by optimizing combustion air distribution, the oxygen content (O2) in the exhaust gas at the chimney outlet can be significantly reduced. 实 According to the conversion formula specified in GB4915-2013, when O 实 When the value decreases, the denominator in the formula increases, and in C... 实 Given the inherent decrease, the converted concentration C 基 It will further decrease, thereby eliminating the effect of O 实 The problem of excessively high emission conversion values ​​will ultimately lead to the simultaneous achievement of NO2 in flue gas. x absolute concentration C 实 With converted concentration C 基 Double reduction.

[0034] This embodiment also provides a heating method using the above-mentioned hot blast stove heating system for reducing nitrogen oxide emissions, comprising the following steps: hot air generated by the hot blast stove body 1 enters the vertical mill 9 to dry the material inside the vertical mill 9; the exhaust air from the vertical mill 9 is removed by the main dust collector 10, and the dust-removed airflow enters the main exhaust fan 11 and is divided into a circulation branch 400 and an exhaust branch 500, wherein the exhaust branch 500 enters the chimney 12 for external discharge, and a portion of the exhaust air from the circulation branch 400 merges with the hot air discharged from the hot blast stove body 1 and then re-exposes the exhaust air. The newly introduced vertical mill 9, along with another part of the exhaust air from the circulation branch 400, enters the inlet of the blower 7. The outlet of the blower 7 is divided into two paths: combustion air and distribution air. The combustion air enters the hot blast stove burner of the hot blast stove body 1 directly through the air inlet 101 via the air valve I2. The distribution air enters the furnace jacket of the hot blast stove body 1 directly through the air distribution port 102 via the air valve II3. After preheating, it enters the furnace from the bottom for distribution air, which is used to adjust the exhaust air temperature of the hot air outlet of the hot blast stove body 1, thereby achieving the required air volume and temperature for drying by the vertical mill 9.

[0035] In this heating method, outside cold air is supplied to the circulating air duct 200 through the fresh air supply duct 300. Air valve IV5 is used to adjust the ratio of circulating air to cold air, thereby supplying a certain amount of outside air to the hot blast stove body 1 to supplement the oxygen required for combustion. Cold air is supplied to the hot blast stove outlet through the temperature-controlled cold air duct 600. The temperature-controlled cold air valve 8 is used to control the exhaust air temperature to approximately 400℃. The combustion air volume is adjusted by the coordinated use of air valves I2 and II3.

[0036] This invention, when the heating system is running, strictly controls the temperature inside the hot blast stove to not exceed 800°C by adjusting the fuel consumption, the blower's air volume, the cold air distribution volume, and the circulating air volume, thereby reducing NOx formation inside the stove through temperature control. Compared with existing technologies, this solution requires lower costs and is applicable to various fuel types, especially coke oven gas, compared to combustion-based NOx emission control methods using low-NOx burners. Furthermore, compared to post-combustion NOx emission control methods using selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR) technologies, it eliminates the need for investment in denitrification equipment and the continuous consumption of expensive catalysts or reducing agents, resulting in lower construction and operating costs.

[0037] In this invention, by using excessive combustion air to suppress local NOx surges, replacing full-oxygen air with low-oxygen circulating air to reduce oxygen concentration in the combustion zone and oxygen content in flue gas emissions, and strictly controlling the furnace temperature to ≤800℃, the path of thermal NOx formation is blocked at the source. Through the combined use of these measures, NOx emission reduction and compliance with emission standards are achieved. The air supply source for the hot blast stove body 1 is the circulating air duct of the grinding system, replacing outside atmospheric air as the source of combustion air and distribution air. Since the circulating air temperature is typically 80~95℃, while outside atmospheric air is typically -20~35℃, the circulating air temperature is higher than that of outside atmospheric air, which helps improve fuel combustion efficiency, reduce fuel consumption, and achieve energy conservation and emission reduction.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A hot blast stove heating system for reducing nitrogen oxide emissions, characterized in that: The device includes a hot blast furnace body and a blower. The hot blast furnace body is connected to a combustion air inlet pipe, and the inlet of the combustion air inlet pipe is connected to the blower. The hot air outlet of the hot blast furnace body is connected to the air inlet of the vertical mill, and the air outlet of the vertical mill is connected to the inlet of the main dust collector. The outlet of the main dust collector is divided into a discharge branch and a circulation branch. The circulation branch is connected to the air inlet of the vertical mill and is also connected to the inlet of the blower through a circulation duct.

2. The hot blast stove heating system for reducing nitrogen oxide emissions according to claim 1, characterized in that: It also includes a fresh air supply duct, which is connected to the air inlet of the fan and is used to supply fresh air to the fan to provide the oxygen required for combustion.

3. The hot blast stove heating system for reducing nitrogen oxide emissions according to claim 1, characterized in that: The combustion air inlet pipe is divided into two branches, and the two branches are respectively connected to the hot blast stove body. One branch is connected to the air inlet of the hot blast stove body and is equipped with air valve I for controlling the air volume. The other branch is connected to the air distribution port of the hot blast stove body and is equipped with air valve II for controlling the air volume.

4. A hot blast stove heating system for reducing nitrogen oxide emissions according to claim 1, characterized in that: The circulating air duct is equipped with an air valve Ⅲ for controlling the air volume.

5. A hot blast stove heating system for reducing nitrogen oxide emissions according to claim 2, characterized in that: The fresh air supply pipe is connected to the air inlet side of the air valve III; the fresh air supply pipe is equipped with an air valve IV for controlling the air volume.

6. A hot blast stove heating system for reducing nitrogen oxide emissions according to claim 2, characterized in that: A temperature-controlled cold air pipe is installed at the outlet end of the hot air furnace body, and a temperature-controlled cold air valve is installed on the temperature-controlled cold air pipe to supplement low-temperature cold air into the hot air outlet of the hot air furnace body, so as to reduce the hot air discharge temperature of the hot air furnace body.

7. A hot blast stove heating system for reducing nitrogen oxide emissions according to claim 2, characterized in that: A circulation air valve is installed on the circulation branch; the inlet of the circulation air duct is connected to the air inlet side of the circulation air valve.

8. A hot blast stove heating system for reducing nitrogen oxide emissions according to claim 1, characterized in that: The discharge branch is connected to the chimney.

9. A heating method using a hot blast stove heating system for reducing nitrogen oxide emissions as described in any one of claims 1-8, characterized in that, The process includes the following steps: Hot air generated by the hot blast stove body enters the vertical mill to dry the material inside; the exhaust air from the vertical mill is dusted by the main dust collector, and the dust-removed airflow enters the main exhaust fan and is divided into a circulation branch and an exhaust branch. The exhaust branch enters the chimney for external discharge, and part of the exhaust air from the circulation branch merges with the hot air discharged from the hot blast stove body and is reintroduced into the vertical mill. At the same time, another part of the exhaust air from the circulation branch enters the fan inlet. The fan outlet is divided into two paths: combustion air and distribution air. The combustion air enters the hot blast stove burner of the hot blast stove body directly through the air inlet via air valve I, and the distribution air enters the furnace jacket of the hot blast stove body directly through the distribution port via air valve II. After preheating, the distribution air enters the furnace from the bottom for distribution, which is used to adjust the exhaust air temperature of the hot air outlet of the hot blast stove body, thereby achieving the required air volume and temperature for drying in the vertical mill.

10. A heating method for a hot blast stove heating system for reducing nitrogen oxide emissions according to claim 9, characterized in that, Outside cold air is supplied to the circulating air duct through the fresh air supply duct, and the ratio of circulating air to outside cold air is adjusted by the air valve IV.

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