A method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide

Abstract

The present application provides a method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide, which relates to the field of metallurgy. The method comprises: determining a baking process curve according to the use status of the ladle; opening a gas valve group for providing gas, an oxygen valve group for providing oxygen, and a carbon dioxide dilution gas valve group for providing carbon dioxide dilution gas; igniting and feedback of the ignition status by an infrared imager, and after confirming that the ignition is successful, the gas valve group, the oxygen valve group, and the carbon dioxide dilution gas valve group are opened to a set flow rate to start baking the ladle; online detection of the nitrogen oxide content in the flue gas and the ladle baking temperature, and dynamic adjustment of the flow rate of the gas valve group, the oxygen valve group, and the carbon dioxide dilution gas valve group. The method provided in the present application can significantly improve the flue gas radiation capacity and reduce the generation of thermal NOX in the flue gas, and has a significant effect on reducing NOX emissions during the ladle baking process.

Description

Technical Field

[0001] The present application relates to the field of metallurgy, and in particular to a method for reducing nitrogen oxide emissions from ladle baking by utilizing carbon dioxide. Background Art

[0002] The preheating effect of the ladle in the steel production process directly affects the normal progress of the production process and the cleanliness of the molten steel. At present, the ladle baking is mainly based on gas and air combustion mode. Due to the high flame combustion temperature, the NOx content in the flue gas is generally higher than 500ppm / Nm 3 , resulting in disorderly emission of NOX during the ladle baking process, causing a harsh environment in the ladle baking area.

[0003] The steel industry emits significant amounts of CO2 during its production processes, accounting for approximately 16% of total CO2 emissions. The flue gas from the steel industry's combustion processes contains relatively high levels of CO2, and the flue gas generally retains residual heat. Further purification can produce high-concentration CO2 gas. Utilizing CO2 as a resource has become a pressing issue for the steel industry.

[0004] In view of this, this application is hereby filed. Summary of the Invention

[0005] The purpose of this application is to provide a method for reducing nitrogen oxide emissions from ladle baking by utilizing carbon dioxide, so as to solve the above-mentioned problem.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] A method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide, comprising:

[0008] Determine the baking process curve according to the use status of the ladle;

[0009] Open the gas valve group for providing fuel gas, the oxygen valve group for providing oxygen, and the carbon dioxide diluent valve group for providing carbon dioxide diluent;

[0010] Ignition is started and the ignition status is fed back by the infrared imager. After confirming that the ignition is successful, the gas valve group, the oxygen valve group and the carbon dioxide dilution gas valve group are opened to the set flow rate to start baking the ladle;

[0011] The nitrogen oxide content in the baking flue gas and the ladle baking temperature are detected online, and the flow rates of the gas valve group, the oxygen valve group, and the carbon dioxide dilution gas valve group are dynamically adjusted. The specific adjustment rules include:

[0012] When the ladle baking temperature is lower than the set value, the flow rates of the gas valve group and the oxygen valve group are increased, and the flow rate of the carbon dioxide dilution gas valve group is reduced; when the ladle baking temperature is higher than the set value, the flow rates of the gas valve group and the oxygen valve group are reduced, and the flow rate of the carbon dioxide dilution gas valve group is increased;

[0013] Increasing the flow rates of gas and oxygen improves combustion efficiency and heating, thereby raising the temperature inside the ladle. Reducing the flow rate of carbon dioxide diluent reduces the dilution effect, maintaining gas and oxygen concentrations, and thus helping to increase combustion temperature. The goal of this adjustment method is to ensure that the baking temperature inside the ladle remains stable near the set value to meet the baking process requirements and product quality standards.

[0014] When the nitrogen oxide content in the baking flue gas is higher than 1000ppm, the flow rates of the carbon dioxide dilution valve group and the oxygen valve group are adjusted so that the volume proportion of oxygen in the combustion-supporting gas is not less than 25%, and pure carbon dioxide gas or carbon dioxide-rich flue gas with a carbon dioxide volume proportion of not less than 20% is used as the carbon dioxide dilution gas; when the nitrogen oxide content in the baking flue gas is greater than 300ppm and less than or equal to 1000ppm, the flow rates of the carbon dioxide dilution valve group and the oxygen valve group are adjusted so that the volume proportion of oxygen in the combustion-supporting gas is not less than 60%, and pure carbon dioxide gas or carbon dioxide-rich flue gas with a carbon dioxide volume proportion of not less than 40% is used as the carbon dioxide dilution gas; when the nitrogen oxide content in the baking flue gas is greater than 100pp m, when the nitrogen oxide content in the baking flue gas is less than or equal to 300ppm, adjust the flow rates of the carbon dioxide dilution valve group and the oxygen valve group so that the volume proportion of oxygen in the supporting combustion gas is not less than 70%, and use pure carbon dioxide gas or carbon dioxide-rich flue gas with a carbon dioxide volume proportion of not less than 60% as the carbon dioxide dilution gas, and at the same time control the temperature of the carbon dioxide-rich flue gas to be not less than 50°C; when the nitrogen oxide content in the baking flue gas is less than or equal to 100ppm, adjust the flow rates of the carbon dioxide dilution valve group and the oxygen valve group so that the volume proportion of oxygen in the supporting combustion gas is not less than 90%, and use pure carbon dioxide gas or carbon dioxide-rich flue gas with a carbon dioxide volume proportion of not less than 80% as the carbon dioxide dilution gas, and at the same time control the temperature of the carbon dioxide-rich flue gas to be not less than 50°C;

[0015] After the set baking time and temperature are reached, the gas valve group, the oxygen valve group and the carbon dioxide dilution gas valve group are closed in sequence to complete the ladle baking.

[0016] When the nitrogen oxide content is high (greater than 1000ppm): the oxygen ratio is not less than 25%: ensure that there is sufficient oxygen in the combustion to enhance the oxidation reaction and reduce the formation of nitrogen oxides. Use flue gas rich in carbon dioxide (carbon dioxide volume ratio is not less than 20%): by adding carbon dioxide diluent gas, dilute the nitrogen oxides in the combustion products, reduce their concentration and emissions;

[0017] When the nitrogen oxide content is moderate (greater than 300ppm and less than or equal to 1000ppm): the oxygen ratio is not less than 60%: continue to ensure sufficient oxygen in combustion to control the formation of nitrogen oxides and reduce emissions. Use flue gas rich in carbon dioxide (carbon dioxide volume ratio is not less than 40%): also dilute the nitrogen oxides in the flue gas by adding carbon dioxide;

[0018] When the nitrogen oxide content is low to medium (greater than 100ppm and less than or equal to 300ppm): the oxygen ratio is not less than 70% to ensure combustion efficiency and control nitrogen oxide emissions. Use flue gas rich in carbon dioxide (carbon dioxide volume ratio is not less than 60%) to maintain the effect of carbon dioxide dilution of flue gas and control emissions;

[0019] When the nitrogen oxide content is low (less than or equal to 100ppm): the oxygen ratio is not less than 90% to ensure optimal combustion conditions and reduce all opportunities for the formation of nitrogen oxides. Use flue gas rich in carbon dioxide (carbon dioxide volume ratio is not less than 80%): continue to dilute the flue gas by adding carbon dioxide to minimize the concentration and emission of nitrogen oxides.

[0020] The purpose of this adjustment is to maximize the control and reduction of nitrogen oxide emissions during the baking process, by adjusting the fuel gas and oxygen ratio and using carbon dioxide-rich flue gas as a diluent gas, to meet environmental protection standards and ensure the effectiveness and quality of the production process.

[0021] Preferably, the usage status includes minor repair, medium repair and major repair.

[0022] Preferably, the baking process curve is a curve showing the relationship between baking time and baking temperature.

[0023] Preferably, the fuel gas includes one or more of blast furnace gas, converter gas, coke oven gas and natural gas.

[0024] Preferably, the flow rate of the gas is 100-8000Nm 3 / h, the flow rate of oxygen is 50-6000Nm 3 / h, the flow rate of the carbon dioxide diluent is not greater than 10000Nm 3 / h.

[0025] The gas flow rate is determined by the different sizes of ladles, and the oxygen flow rate is calculated from the gas flow rate. Excessive carbon dioxide dilution gas will take away too much heat, resulting in energy waste.

[0026] Optionally, the gas flow rate can be 100Nm 3 / h、500Nm 3 / h、1000Nm 3 / h、2000Nm 3 / h、3000Nm 3 / h、4000Nm 3 / h、5000Nm 3 / h、6000Nm 3 / h、7000Nm 3 / h、8000Nm 3 / h or 100-8000Nm 3 / h, the oxygen flow rate can be 50Nm 3 / h、100Nm 3 / h、500Nm 3 / h、1000Nm 3 / h、2000Nm 3 / h、3000Nm 3 / h、4000Nm 3 / h、5000Nm 3 / h、6000Nm 3 / h or 50-6000Nm 3 / h, the flow rate of the carbon dioxide diluent can be 50Nm 3 / h、100Nm 3 / h、500Nm 3 / h、1000Nm 3 / h、2000Nm 3 / h、3000Nm 3 / h、4000Nm 3 / h、5000Nm 3 / h、6000Nm 3 / h、7000Nm 3 / h、8000Nm 3 / h、9000Nm 3 / h、10000Nm 3 / h or not more than 10000Nm 3 Any value of / h.

[0027] Preferably, before ignition, the flow rates of all valve groups are opened to 60%-80% of the process setting flow rates.

[0028] Optionally, before ignition, the flow rates of all valve groups are opened to 60%, 70%, 80% or any value between 60% and 80% of the process setting flow rate.

[0029] Preheating and preparation stage: Before ignition, the ladle needs to be preheated and prepared. Setting the valve group flow rate between 60% and 80% of the process setting flow rate can gradually increase the furnace temperature, preheat the equipment and baking chamber, and prepare for the subsequent baking process.

[0030] Temperature control during baking: Through gentle heating at the beginning, the transfer and distribution of heat can be effectively controlled to avoid uneven heat or excessive heating, thereby ensuring temperature control and uniformity of the steel during baking.

[0031] Energy conservation and optimization of fuel utilization: Controlling the valve group flow rate at a lower percentage can effectively save energy and optimize fuel utilization efficiency. In the initial stage, it is not necessary to reach full power combustion, which can reduce energy consumption and reduce production costs.

[0032] Protect equipment and extend service life: Gradually increasing the flow rate can reduce thermal stress on the equipment and extend its service life. A gentle warm-up process helps reduce thermal shock and thermal stress on the equipment, improving its stability and reliability.

[0033] The valve group flow rate during the ladle baking process is opened to 60% to 80% of the process setting flow rate in order to effectively preheat the equipment, control the temperature, save energy, and protect the equipment before baking begins, thereby ensuring that the entire baking process can proceed smoothly and achieve the expected production results.

[0034] Preferably, the carbon dioxide content in the carbon dioxide-rich flue gas is 1%-98%, and the temperature is 20-500°C.

[0035] When high-purity carbon dioxide gas is used as the carbon dioxide diluent gas, the carbon dioxide concentration is not less than 99%.

[0036] Optionally, the carbon dioxide content in the carbon dioxide-rich flue gas can be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98% or any value between 1% and 98%, and the temperature can be 20°C, 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C or any value between 20-500°C.

[0037] Preferably, the interval time when closing the gas valve group, the oxygen valve group and the carbon dioxide dilution gas valve group is less than or equal to 5 seconds.

[0038] Preferably, the infrared imager has the function of measuring point temperature, average temperature and maximum temperature of surface temperature.

[0039] Preferably, the ladle is of the 30-350 ton level.

[0040] Compared with the prior art, the advantages of this application include:

[0041] The present application provides a method for reducing nitrogen oxide emissions from ladle baking by utilizing carbon dioxide. CO2-rich flue gas or pure CO2 emitted during the steel production process is used as a combustion-supporting gas diluent in the ladle baking process. The strong radiation capacity of CO2 triatomics and the reduction of the flame temperature in the oxygen-rich / full-oxygen combustion process can greatly improve the radiation capacity of the flue gas, while ensuring the temperature and reducing the amount of thermal NOX generated in the flue gas. This has a significant effect on reducing NOX emissions during the ladle baking process, and provides support for green and energy-saving production in the steel industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0043] Figure 1 Schematic diagram of the equipment used in the method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide provided in an embodiment of the present application.

[0044] Reference numerals:

[0045] 1-Gas pipeline; 2-Oxygen pipeline; 3-CO2 / CO2 dilution gas pipeline; 4-Gas valve group; 5-Oxygen valve group; 6-CO2 / CO2 dilution gas valve group; 7-Burner; 8-Ladle cover; 9-Ladle; 10-Ignitor; 11-Infrared imager; 12-NOX online detector. DETAILED DESCRIPTION

[0046] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0047] like Figure 1As shown, the device for executing the method provided by this application in the embodiment is first introduced, as follows:

[0048] The equipment includes a gas pipeline 1, an oxygen pipeline 2, a CO2 / CO2 dilution gas pipeline 3, a gas valve group 4, an oxygen valve group 5, a CO2 / CO2 dilution gas valve group 6, a burner 7, a ladle cover 8, a ladle 9, an igniter 10, an infrared imager 11, and an online NOx detector 12. The gas pipeline 1 is connected to the gas valve group 4, the oxygen pipeline 2 is connected to the oxygen valve group 5, and the CO2 / CO2 dilution gas pipeline 3 is connected to the CO2 / CO2 dilution gas valve group 6. In an optional embodiment, the outlet of the CO2 / CO2 dilution gas valve group 6 is connected to the oxygen pipeline 2. The outlets of the gas valve group 4 and the oxygen valve group 5 are connected to the burner 7. The burner 7 passes through the ladle cover 8 and is ignited by an igniter 10 (illustrated only), providing a flame into the ladle 9 for preheating. Accordingly, the infrared imager 11 and the online NOx detector 12 pass through the ladle cover 8 to reach the ladle 9 and detect the temperature and nitrogen oxide content.

[0049] Example 1

[0050] This embodiment provides a method for reducing nitrogen oxide emissions during ladle baking using carbon dioxide. During the ladle baking process, fuel gas provided by a gas pipeline, oxygen provided by an oxygen pipeline, and CO2 or a CO2 mixture provided by a CO2 diluent pipeline are mixed through a burner, and combustion and ignition are performed using an igniter to initiate high-temperature baking of the ladle. The mixing ratio of fuel gas, oxygen, and CO2 diluent is dynamically adjusted based on regional temperature changes measured by an infrared imager and the display results of an online NOx detector. Because the addition of CO2 diluent reduces flame temperature, improves flue gas thermal radiation capacity, and reduces thermal NOx generation, efficient energy utilization is achieved during the ladle baking process, significantly reducing NOx generation during the baking process.

[0051] The method provided in this embodiment is used for baking a 120t pure oxygen ladle. The ladle is in overhaul state, the baking time is set to 58h, the baking temperature is set to 1050℃, the fuel gas is converter gas (the composition is shown in Table 1 below), and the calorific value of the gas is 1450kcal / Nm 3 , the design baking flow is 500-1500Nm 3 / h, the supporting fuel is oxygen and CO2, and the designed oxygen flow rate is 200-800Nm 3 / h, designed CO2 flow rate is 0-1000Nm 3 / h, CO2 concentration and temperature are 99% and 25℃ respectively.

[0052] Based on the ladle status, set the baking curve as:

[0053] In the 0-1h interval, the ladle baking temperature is set to 200°C;

[0054] In the 1h-3h range, the ladle baking temperature is set to 400℃;

[0055] In the 3h-7h range, the ladle baking temperature is set at 800℃;

[0056] In the 7h-58h range, the ladle baking temperature is set to 1050℃.

[0057] Table 1 Converter gas composition

[0058] CO / vol% <![CDATA[CO2 / vol%]]> <![CDATA[N2 / vol% <!-- 4 -->]]> 48 23 29

[0059] The gas valve group, oxygen valve group and CO2 valve group are opened simultaneously through the computer system, and the flow of all valve groups is opened to 60%-100% of the process setting flow.

[0060] At the start of the baking phase, the igniter starts to ignite, and the infrared imager provides feedback on the ignition status. After confirming that the ignition is successful, the gas valve group, oxygen valve group, and CO2 dilution gas valve group are opened to the set flow rate to start baking:

[0061] In the 0-1h interval, the average NOX content in the flue gas is 350ppm, and the converter gas flow rate is 500Nm 3 / h, oxygen flow rate is 220Nm 3 / h, CO2 flow rate is 140Nm 3 / h;

[0062] In the 1h-3h interval, the average NOx content in the flue gas is 80ppm, and the converter gas flow rate is 1000Nm 3 / h, oxygen flow rate is 440Nm 3 / h, CO2 flow rate is 50Nm 3 / h;

[0063] In the 3h-7h period, the average NOx content in the flue gas was 40ppm, and the converter gas flow rate was 1200Nm 3 / h, oxygen flow rate is 530Nm 3 / h, CO2 flow rate is 50Nm 3 / h;

[0064] In the 7h-58h period, the average NOx content in the flue gas was 18ppm, and the converter gas flow rate was 1200Nm 3 / h, oxygen flow rate is 530Nm 3 / h, CO2 flow rate is 55Nm 3 / h.

[0065] The infrared imager displays the temperature changes in the ladle, and the NOX online detector detects the NOX content in the flue gas online. The ladle temperature rise curve basically coincides with the set temperature curve. When the deviation between the actual temperature rise curve and the set temperature curve during the baking process reaches 5°C, the flow rate of the fuel gas and the auxiliary fuel gas is dynamically adjusted, and the fuel gas flow rate is adjusted to ±80Nm 3 / h, so that the temperature deviation between the actual heating curve of the ladle and the set heating curve is ≤3℃.

[0066] After testing, during the baking process, the average NOX content in the flue gas was 350ppm in the 0-1h interval; the average NOX content in the flue gas was 80ppm in the 1h-3h interval; the average NOX content in the flue gas was 40ppm in the 3h-7h interval; and the average NOX content in the flue gas was 18ppm in the 7h-58h interval, which met the NOX emission standards of the steel industry and solved the hidden danger of disorderly NOX emissions from the ladle.

[0067] According to the ladle status and baking mode settings, the infrared imager displays the temperature changes in the ladle. When the set baking time and temperature are reached, the temperature is fed back to the ladle baking system.

[0068] The system dynamically controls the closing of the gas valve group first, and then the oxygen valve group and the CO2 dilution gas valve group. The closing interval is ≤5s to complete a ladle pure oxygen baking process.

[0069] Example 2

[0070] The method provided in this embodiment is used for baking a 120t pure oxygen ladle. The ladle is in normal state, the baking time is set to 18h, the baking temperature is set to 1050℃, the fuel gas is converter gas (the composition is shown in Table 1 below), and the calorific value of the gas is 1513kcal / Nm 3 , the design baking flow is 500-1500Nm 3 / h, the supporting fuel is oxygen and carbon dioxide diluent containing carbon dioxide, and the designed oxygen flow rate is 200-800Nm 3 / h, the designed converter gas flow rate is 0-5000Nm 3 / h, the CO2 concentration and temperature in the converter gas are 21% and 25℃ respectively.

[0071] Based on the ladle status, set the baking curve as:

[0072] In the 0-1h interval, the ladle baking temperature is set to 200°C;

[0073] In the 1h-3h range, the ladle baking temperature is set to 400℃;

[0074] In the 3h-6h range, the ladle baking temperature is set at 800℃;

[0075] In the 6h-18h range, the ladle baking temperature is set to 1050℃.

[0076] Table 2 Converter gas composition

[0077] CO / vol% <![CDATA[CO2 / vol%]]> <![CDATA[N2 / vol%]]> 50 21 29

[0078] The gas valve group, oxygen valve group and CO2 valve group are opened simultaneously through the computer system, and the flow of all valve groups is opened to 60%-100% of the process setting flow.

[0079] At the start of the baking phase, the igniter starts to ignite, and the infrared imager provides feedback on the ignition status. After confirming that the ignition is successful, the gas valve group, oxygen valve group, and CO2 dilution gas valve group are opened to the set flow rate to start baking:

[0080] In the 0-1h interval, the average NOX content in the flue gas is 350ppm, and the converter gas flow rate is 500Nm 3 / h, oxygen flow rate is 220Nm 3 / h, CO2 mixer flow rate is 140Nm 3 / h, the carbon dioxide content in the carbon dioxide diluent is 50%;

[0081] In the 1h-3h interval, the average NOX content in the flue gas is 150ppm, and the converter gas flow rate is 1000Nm 3 / h, oxygen flow rate is 440Nm 3 / h, CO2 mixer flow rate is 180Nm 3 / h, the carbon dioxide content in the carbon dioxide diluent is 60%;

[0082] In the 3h-6h interval, the average NOx content in the flue gas was 75ppm, and the converter gas flow rate was 1200Nm 3 / h, oxygen flow rate is 530Nm 3 / h, CO2 mixer flow rate is 50Nm 3 / h, the carbon dioxide content in the carbon dioxide diluent is 70%;

[0083] In the 6h-18h period, the average NOx content in the flue gas was 43ppm, and the converter gas flow rate was 1200Nm 3 / h, oxygen flow rate is 530Nm 3 / h, CO2 mixer flow rate is 55Nm 3 / h, the carbon dioxide content in the carbon dioxide dilution gas is 80%.

[0084] The infrared imager displays the temperature changes in the ladle, and the NOX online detector detects the NOX content in the flue gas online. The ladle temperature rise curve basically coincides with the set temperature curve. When the deviation between the actual temperature rise curve and the set temperature curve during the baking process reaches 5°C, the flow rate of the fuel gas and the auxiliary fuel gas is dynamically adjusted, and the fuel gas flow rate is adjusted to ±80Nm 3 / h, so that the temperature deviation between the actual heating curve of the ladle and the set heating curve is ≤3℃.

[0085] After testing, during the baking process, the average NOX content in the flue gas was 350ppm in the 0-1h interval; the average NOX content in the flue gas was 150ppm in the 1h-3h interval; the average NOX content in the flue gas was 75ppm in the 3h-6h interval; and the average NOX content in the flue gas was 43ppm in the 6h-18h interval, which met the NOX emission standards of the steel industry and solved the hidden danger of disorderly NOX emissions from the ladle.

[0086] According to the ladle status and baking mode settings, the infrared imager displays the temperature changes in the ladle. When the set baking time and temperature are reached, the temperature is fed back to the ladle baking system.

[0087] The system dynamically controls the closing of the gas valve group first, and then the oxygen valve group and the CO2 dilution gas valve group. The closing interval is ≤5s to complete a ladle pure oxygen baking process.

[0088] Example 3

[0089] The method provided in this embodiment is used for baking a 300t pure oxygen ladle. The ladle is in normal state, the baking time is set to 18h, the baking temperature is set to 1050℃, the fuel gas is converter gas (the composition is shown in Table 1 below), and the calorific value of the gas is 1392kcal / Nm 3 , the design baking flow is 1500-4000Nm 3 / h, the supporting fuel is oxygen and CO2, and the designed oxygen flow rate is 200-800Nm 3 / h, designed CO2 flow rate is 0-2500Nm 3 / h, CO2 concentration and temperature are 99% and 25℃ respectively.

[0090] Based on the ladle status, set the baking curve as:

[0091] In the 0-1h interval, the ladle baking temperature is set to 200°C;

[0092] In the 1h-3h range, the ladle baking temperature is set to 400℃;

[0093] In the 3h-6h range, the ladle baking temperature is set at 800℃;

[0094] In the 6h-18h range, the ladle baking temperature is set to 1050℃.

[0095] Table 3 Converter gas composition

[0096] CO / vol% <![CDATA[CO2 / vol%]]> <![CDATA[N2 / vol%]]> 46 25 29

[0097] The gas valve group, oxygen valve group and CO2 valve group are opened simultaneously through the computer system, and the flow of all valve groups is opened to 60%-100% of the process setting flow.

[0098] At the start of the baking phase, the igniter starts to ignite, and the infrared imager provides feedback on the ignition status. After confirming that the ignition is successful, the gas valve group, oxygen valve group, and CO2 dilution gas valve group are opened to the set flow rate to start baking:

[0099] In the 0-1h interval, the average NOx content in the flue gas was 370ppm, and the converter gas flow rate was 1500Nm 3 / h, oxygen flow rate is 660Nm 3 / h, CO2 mixer flow rate is 440Nm 3 / h;

[0100] In the 1h-3h interval, the average NOx content in the flue gas was 110ppm, and the converter gas flow rate was 2500Nm 3 / h, oxygen flow rate is 1100Nm 3 / h, CO2 mixer flow rate is 470Nm 3 / h;

[0101] In the 3h-6h interval, the average NOx content in the flue gas is 50ppm, and the converter gas flow rate is 3000Nm 3 / h, oxygen flow rate is 1325Nm 3 / h, CO2 mixer flow rate is 100Nm 3 / h;

[0102] In the 6h-18h period, the average NOx content in the flue gas was 27ppm, and the converter gas flow rate was 3000Nm 3 / h, oxygen flow rate is 1325Nm 3 / h, CO2 mixer flow rate is 140Nm 3 / h.

[0103] The infrared imager displays the temperature changes in the ladle, and the NOX online detector detects the NOX content in the flue gas online. The ladle temperature rise curve basically coincides with the set temperature curve. When the deviation between the actual temperature rise curve and the set temperature curve during the baking process reaches 5°C, the flow rate of the fuel gas and the auxiliary fuel gas is dynamically adjusted, and the fuel gas flow rate is adjusted to ±80Nm 3 / h, so that the temperature deviation between the actual heating curve of the ladle and the set heating curve is ≤3℃.

[0104] After testing, during the baking process, the average NOX content in the flue gas was 370ppm in the 0-1h interval; the average NOX content in the flue gas was 110ppm in the 1h-3h interval; the average NOX content in the flue gas was 50ppm in the 3h-6h interval; and the average NOX content in the flue gas was 27ppm in the 6h-18h interval, which met the NOX emission standards of the steel industry and solved the hidden danger of disorderly NOX emissions from the ladle.

[0105] According to the ladle status and baking mode settings, the infrared imager displays the temperature changes in the ladle. When the set baking time and temperature are reached, the temperature is fed back to the ladle baking system.

[0106] The system dynamically controls the closing of the gas valve group first, and then the oxygen valve group and the CO2 dilution gas valve group. The closing interval is ≤5s to complete a ladle pure oxygen baking process.

[0107] Comparative Example 1

[0108] The method provided in this comparative example is used for baking a 120t pure oxygen ladle. The ladle is in overhaul state, the baking time is set to 58h, the baking temperature is set to 1050℃, the fuel gas is converter gas (the composition is shown in Table 1 below), and the calorific value of the gas is 1331kcal / Nm 3 , the design baking flow is 500-1500Nm 3 / h, the supporting fuel is air, and the designed air flow rate is 1000-4000Nm 3 / h.

[0109] Based on the ladle status, set the baking curve as:

[0110] In the 0-1h interval, the ladle baking temperature is set to 200°C;

[0111] In the 1h-3h range, the ladle baking temperature is set to 400℃;

[0112] In the 3h-7h range, the ladle baking temperature is set at 800℃;

[0113] In the 7h-58h range, the ladle baking temperature is set to 1050℃.

[0114] Table 4 Converter gas composition

[0115] CO / vol% <![CDATA[CO2 / vol%]]> <![CDATA[N2 / vol%]]> 44 27 29

[0116] The gas valve group and oxygen valve group are opened simultaneously through the computer system, and the flow of all valve groups is opened to 60%-100% of the process setting flow.

[0117] At the start of the baking phase, the igniter starts to ignite, and the infrared imager provides feedback on the ignition status. After confirming that the ignition is successful, the gas valve group and the oxygen valve group are opened to the set flow rate to start baking:

[0118] In the 0-1h interval, the average NOX content in the flue gas is 350ppm, and the converter gas flow rate is 500Nm 3 / h, air flow rate is 1100Nm 3 / h;

[0119] In the 1h-3h interval, the average NOx content in the flue gas is 450ppm, and the converter gas flow rate is 1000Nm 3 / h, air flow rate is 2200Nm 3 / h;

[0120] In the 3h-7h interval, the average NOX content in the flue gas is 500ppm, and the converter gas flow rate is 1200Nm 3 / h, air flow rate is 2650Nm 3 / h;

[0121] In the 7h-58h period, the average NOx content in the flue gas was 650ppm, and the converter gas flow rate was 1200Nm 3 / h, air flow rate is 2650Nm 3 / h.

[0122] The infrared imager displays the temperature changes in the ladle, and the NOX online detector detects the NOX content in the flue gas online. The ladle temperature rise curve basically coincides with the set temperature curve. When the deviation between the actual temperature rise curve and the set temperature curve during the baking process reaches 5°C, the flow rate of the fuel gas and the auxiliary fuel gas is dynamically adjusted, and the fuel gas flow rate is adjusted to ±80Nm 3 / h, so that the temperature deviation between the actual heating curve of the ladle and the set heating curve is ≤3℃.

[0123] After testing, during the baking process, the average NOX content in the flue gas was 350ppm in the 0-1h interval; the average NOX content in the flue gas was 450ppm in the 1h-3h interval; the average NOX content in the flue gas was 500ppm in the 3h-7h interval; and the average NOX content in the flue gas was 650ppm in the 7h-58h interval, which is far below the NOX emission standards of the steel industry, and there is a serious risk of disorderly NOX emissions from the ladle.

[0124] According to the ladle status and baking mode settings, the infrared imager displays the temperature changes in the ladle. When the set baking time and temperature are reached, the temperature is fed back to the ladle baking system.

[0125] The system dynamically controls the closing of the gas valve group first, and then the oxygen valve group and the CO2 dilution gas valve group. The closing interval is ≤5s to complete a ladle pure oxygen baking process.

[0126] Comparative Example 2

[0127] The method provided in this comparative example is used for baking a 120t pure oxygen ladle. The ladle is in normal condition, the baking time is set to 58h, the baking temperature is set to 1050℃, the fuel gas is converter gas (the composition is shown in Table 1 below), and the calorific value of the gas is 1450kcal / Nm 3 , the design baking flow is 500-1500Nm 3 / h, the supporting fuel is oxygen and CO2 diluent containing CO2, and the designed oxygen flow rate is 200-800Nm 3 / h, designed CO2 flow rate is 0-100Nm 3 / h, CO2 concentration and temperature are 99% and 25℃ respectively.

[0128] Based on the ladle status, set the baking curve as:

[0129] In the 0-1h interval, the ladle baking temperature is set to 200°C;

[0130] In the 1h-3h range, the ladle baking temperature is set to 400℃;

[0131] In the 3h-6h range, the ladle baking temperature is set at 800℃;

[0132] In the 6h-18h range, the ladle baking temperature is set to 1050℃.

[0133] Table 5 Converter gas composition

[0134] CO / vol% <![CDATA[CO2 / vol%]]> <![CDATA[N2 / vol%]]> 48 23 29

[0135] The gas valve group, oxygen valve group and CO2 valve group are opened simultaneously through the computer system, and the flow of all valve groups is opened to 60%-100% of the process setting flow.

[0136] At the start of the baking phase, the igniter starts to ignite, and the infrared imager provides feedback on the ignition status. After confirming that the ignition is successful, the gas valve group, oxygen valve group, and CO2 dilution gas valve group are opened to the set flow rate to start baking:

[0137] In the 0-1h interval, the average NOX content in the flue gas is 350ppm, and the converter gas flow rate is 500Nm 3 / h, oxygen flow rate is 220Nm 3 / h, CO2 mixer flow rate is 220Nm 3 / h, the carbon dioxide content in the carbon dioxide diluent is 20%;

[0138] In the 1h-3h interval, the average NOX content in the flue gas is 350ppm, and the converter gas flow rate is 1000Nm 3 / h, oxygen flow rate is 440Nm 3 / h, CO2 mixer flow rate is 290Nm 3 / h, the carbon dioxide content in the carbon dioxide diluent is 20%;

[0139] In the 3h-6h interval, the average NOx content in the flue gas is 350ppm, and the converter gas flow rate is 1200Nm 3 / h, oxygen flow rate is 530Nm 3 / h, CO2 mixer flow rate is 130Nm 3 / h, the carbon dioxide content in the carbon dioxide diluent is 20%;

[0140] In the 6h-18h period, the average NOx content in the flue gas was 350ppm, and the converter gas flow rate was 1200Nm 3 / h, oxygen flow rate is 530Nm 3 / h, CO2 mixer flow rate is 350Nm 3 / h, the carbon dioxide content in the carbon dioxide dilution gas is 20%.

[0141] The infrared imager displays the temperature changes in the ladle, and the NOX online detector detects the NOX content in the flue gas online. The ladle temperature rise curve basically coincides with the set temperature curve. When the deviation between the actual temperature rise curve and the set temperature curve during the baking process reaches 5°C, the flow rate of the fuel gas and the auxiliary fuel gas is dynamically adjusted, and the fuel gas flow rate is adjusted to ±80Nm 3 / h, so that the temperature deviation between the actual heating curve of the ladle and the set heating curve is ≤3℃.

[0142] After testing, during the baking process, the average NOX content in the flue gas was 350ppm in the 0-1h interval; the average NOX content in the flue gas was 300ppm in the 1h-3h interval; the average NOX content in the flue gas was 200ppm in the 3h-6h interval; and the average NOX content in the flue gas was 100ppm in the 6h-18h interval, which is far below the NOX emission standards of the steel industry, and there is a serious risk of disorderly NOX emissions from the ladle.

[0143] According to the ladle status and baking mode settings, the infrared imager displays the temperature changes in the ladle. When the set baking time and temperature are reached, the temperature is fed back to the ladle baking system.

[0144] The system dynamically controls the closing of the gas valve group first, and then the oxygen valve group and the CO2 dilution gas valve group. The closing interval is ≤5s to complete a ladle pure oxygen baking process.

[0145] The method provided in this application applies CO2 or CO2-rich flue gas to the oxygen-enriched / pure oxygen ladle baking process, and dynamically adjusts the flow rate and mixing ratio of the fuel gas and the supporting gas based on different baking processes and NOX control conditions to achieve the reduction of NOX emissions in the ladle baking process. At the same time, it utilizes the CO2 emitted by the steel industry as a resource, and promotes the development of NOX control technology in the oxygen-enriched / full oxygen ladle baking process.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide, characterized in that: include: Determine the baking process curve according to the use status of the ladle; Open the gas valve group for providing fuel gas, the oxygen valve group for providing oxygen, and the carbon dioxide diluent valve group for providing carbon dioxide diluent; Ignition is started and the ignition status is fed back by the infrared imager. After confirming that the ignition is successful, the gas valve group, the oxygen valve group and the carbon dioxide dilution gas valve group are opened to the set flow rate to start baking the ladle; The nitrogen oxide content in the baking flue gas and the ladle baking temperature are detected online, and the flow rates of the gas valve group, the oxygen valve group, and the carbon dioxide dilution gas valve group are dynamically adjusted. The specific adjustment rules include: When the ladle baking temperature is lower than the set value, the flow rates of the gas valve group and the oxygen valve group are increased, and the flow rate of the carbon dioxide dilution gas valve group is reduced; when the ladle baking temperature is higher than the set value, the flow rates of the gas valve group and the oxygen valve group are reduced, and the flow rate of the carbon dioxide dilution gas valve group is increased; When the nitrogen oxide content in the baking flue gas is higher than 1000ppm, the flow rates of the carbon dioxide dilution valve group and the oxygen valve group are adjusted so that the volume proportion of oxygen in the combustion-supporting gas is not less than 25%, and pure carbon dioxide gas or carbon dioxide-rich flue gas with a carbon dioxide volume proportion of not less than 20% is used as the carbon dioxide dilution gas; when the nitrogen oxide content in the baking flue gas is greater than 300ppm and less than or equal to 1000ppm, the flow rates of the carbon dioxide dilution valve group and the oxygen valve group are adjusted so that the volume proportion of oxygen in the combustion-supporting gas is not less than 60%, and pure carbon dioxide gas or carbon dioxide-rich flue gas with a carbon dioxide volume proportion of not less than 40% is used as the carbon dioxide dilution gas; when the nitrogen oxide content in the baking flue gas is greater than 100pp m, when the nitrogen oxide content in the baking flue gas is less than or equal to 300ppm, adjust the flow rates of the carbon dioxide dilution valve group and the oxygen valve group so that the volume proportion of oxygen in the supporting combustion gas is not less than 70%, and use pure carbon dioxide gas or carbon dioxide-rich flue gas with a carbon dioxide volume proportion of not less than 60% as the carbon dioxide dilution gas, and at the same time control the temperature of the carbon dioxide-rich flue gas to be not less than 50°C; when the nitrogen oxide content in the baking flue gas is less than or equal to 100ppm, adjust the flow rates of the carbon dioxide dilution valve group and the oxygen valve group so that the volume proportion of oxygen in the supporting combustion gas is not less than 90%, and use pure carbon dioxide gas or carbon dioxide-rich flue gas with a carbon dioxide volume proportion of not less than 80% as the carbon dioxide dilution gas, and at the same time control the temperature of the carbon dioxide-rich flue gas to be not less than 50°C; After the set baking time and temperature are reached, the gas valve group, the oxygen valve group and the carbon dioxide dilution gas valve group are closed in sequence to complete the ladle baking.

2. The method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide according to claim 1, characterized in that: The usage status includes minor repair, medium repair and major repair.

3. The method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide according to claim 1, characterized in that: The baking process curve is a curve of the relationship between baking time and baking temperature.

4. The method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide according to claim 1, characterized in that: The fuel gas includes one or more of blast furnace gas, converter gas, coke oven gas and natural gas.

5. The method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide according to claim 1, characterized in that: The gas flow rate is 100-8000Nm 3 / h, the flow rate of oxygen is 50-6000Nm 3 / h, the flow rate of the carbon dioxide diluent is not greater than 10000Nm 3 / h.

6. The method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide according to claim 1, characterized in that: Before ignition, all valve group flows are opened to 60%-80% of the process set flow.

7. The method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide according to claim 1, characterized in that: The carbon dioxide content in the carbon dioxide-rich flue gas is 1%-98%, and the temperature is 20-500°C.

8. The method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide according to claim 1, characterized in that: When closing the gas valve group, the oxygen valve group and the carbon dioxide dilution gas valve group, the interval time is less than or equal to 5s.

9. The method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide according to claim 1, characterized in that: The infrared imager has the function of measuring point temperature, average temperature and maximum temperature of surface temperature.

10. The method for reducing nitrogen oxide emissions from ladle baking using carbon dioxide according to any one of claims 1 to 9, characterized in that: The ladle is of the 30-350 ton level.

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