A control method for preventing excessive nitrogen oxide emissions in flue gas from the all-oxygen sintering process in steel rolling furnaces.

Abstract

A control method for preventing excessive nitrogen oxide emissions in flue gas from the all-oxygen sintering process of a steel rolling furnace, belonging to the field of nitrogen oxide emission reduction technology for heating furnaces, includes the following steps: determining the initial time intervals Δt for cooling and heating. 11 , Δt 12 Detect furnace section temperature deviation; if the actual furnace section temperature is higher than the set furnace temperature, meeting the cooling conditions, first reduce the oxygen flow rate by a limited amount, and wait for the time interval Δt. 11 Then, adjust the gas flow rate according to the set oxygen-fuel ratio r. If the actual furnace temperature is lower than the set furnace temperature, and the heating conditions are met, first increase the gas flow rate by a limited amount, and wait for the time interval Δt. 12 Then, the oxygen flow rate is adjusted according to the set oxygen-fuel ratio limit r. This invention addresses the problem of excessive nitrogen oxides (NOx) in all-oxygen sintering steel heating furnaces. This method ensures that there is always an appropriate amount of fuel gas consumed and input into the furnace when adjusting the furnace temperature.

Description

Technical Field

[0001] This invention belongs to the field of nitrogen oxide emission reduction technology for heating furnaces, specifically relating to a control method for preventing excessive nitrogen oxide emissions in flue gas from the all-oxygen sintering process of steel rolling heating furnaces. Background Technology

[0002] Currently, the temperature control of heating furnaces commonly used in China mostly employs dual-cross-limiting control technology. A key feature of this control technology is its combustion air adjustment priority strategy, which prioritizes increasing the amount of combustion air during heating and decreasing the amount of fuel gas during cooling, aiming to ensure complete combustion of the input fuel gas.

[0003] With the widespread adoption of oxy-fuel steelmaking technology, the high oxidizing power of pure oxygen has made the problem of excessive nitrogen oxides (NOx) increasingly prominent. Even when natural gas is used as the main heating material, excessive NOx still exists, thus becoming a major problem hindering the production of heating furnaces.

[0004] In addition, analysis of a large amount of actual production process information revealed that although nitrogen (N2) is an inert gas, high-purity oxygen can still generate a large amount of nitrogen oxides (NOx) if there are no other combustible gases in the furnace. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a method for controlling excessive nitrogen oxide emissions in the oxy-fuel process of steel rolling furnaces, comprising the following steps:

[0006] S1: Determine the initial time intervals for cooling and heating, respectively, Δt. 11 , Δt 12 ;

[0007] S2: Detects temperature deviation in the furnace section;

[0008] Let the oxygen-fuel ratio be r; the time intervals for cooling and heating under reverse double-cross limiting control are Δt and Δt, respectively. 11 , Δt 12 The waiting time from the start of cross-adjustment to detection is Δt2(p), where p is the furnace section number where the billet is located. This is used to select different waiting times; the farther the furnace section is from the nitrogen oxide detection point, the longer the waiting time. The nitrogen oxide emission limit target value is NOx. t The actual emission value of nitrogen oxides is NOx. a ; make

[0009] ε≤NOx a -NOx t ≤0, (1).

[0010] Furthermore, step S2 also includes the following steps:

[0011] S3: If the actual furnace section temperature is higher than the set furnace temperature, and the cooling conditions are met, first reduce the oxygen flow rate by a limited amount, and wait for the time interval Δt. 11 Then, adjust the gas flow rate according to the set oxygen-fuel ratio limit r.

[0012] Furthermore, it also includes the following steps:

[0013] S4: If the gas flow rate is reduced, wait for Δt2(p) and then detect nitrogen oxides (NOx); if the target deviation of nitrogen oxides (NOx) is... a -NOx t If the value is less than the critical value ε, and ε≤0, for any fixed value, then the decrease is Δt. 11 If the target deviation for nitrogen oxides (NOx) is (NOx a -NOx t If ) is greater than 0, then increase Δt. 11 Return to execute S2.

[0014] Furthermore, in step S4, the optimal time interval Δt is generated. 11opt As given by formula (2), when the temperature drops...

[0015] ε≤minΔ t11 =Δt 11opt (NOx a -NOx t )≤0 (2).

[0016] Furthermore, step S2 also includes the following steps:

[0017] S5: If the actual furnace section temperature is lower than the set furnace temperature, and the heating conditions are met, first increase the gas flow rate by a limited amount, and wait for the time interval Δt. 12 Then, adjust the oxygen flow rate according to the set oxygen-fuel ratio limit r.

[0018] Furthermore, it also includes the following steps:

[0019] S6: If the oxygen flow rate is initially increased, wait for Δt2(p) before detecting nitrogen oxides (NOx); if the target deviation of nitrogen oxides (NOx) is... a -NOx t If the value is less than the critical value ε, then reduce Δt. 12 If the target deviation (NOx) a -NOx t If ) is greater than 0, then increase Δt. 12 Return to execute S2.

[0020] Furthermore, step S6 is used to generate the optimal time interval Δt. 12optAs given by formula (3), when the temperature rises...

[0021] ε≤minΔ t12 =Δt 12opt (NOx a -NOx t )≤0 (3).

[0022] The beneficial effects of this invention are as follows: This invention addresses the problem of excessive nitrogen oxides (NOx) in all-oxygen sintering furnaces. The method ensures that there is always an appropriate amount of fuel gas digesting and inputting oxygen into the furnace section when adjusting the furnace temperature. Attached Figure Description

[0023] Figure 1 This is a flowchart of the nitrogen oxide control and prediction process for the heating furnace of the present invention. Detailed Implementation

[0024] To make the technical means and objectives of this invention easier to understand, the invention is further described below with reference to specific embodiments. A method for controlling excessive nitrogen oxide emissions in flue gas from an all-oxygen sintering process in a steel rolling furnace is described below. Figure 1 As shown, it includes the following steps:

[0025] S1: Determine the initial time intervals for cooling and heating, respectively, Δt. 11 , Δt 12 ;

[0026] S2: Detects temperature deviation in the furnace section;

[0027] S3: If the actual furnace section temperature is higher than the set furnace temperature, and the cooling conditions are met, first reduce the oxygen flow rate by a limited amount, and wait for the time interval Δt. 11 Then, adjust the gas flow rate according to the set oxygen-fuel ratio limit r.

[0028] S4: If the gas flow rate is initially reduced, wait for a time Δt2(p) before detecting nitrogen oxides (NOx). If the target deviation of nitrogen oxides (NOx) is... a -NOx t If the value is less than the critical value ε, then reduce Δt. 11 If the target deviation for nitrogen oxides (NOx) is (NOx a -NOx t If ) is greater than 0, then increase Δt. 11 .

[0029] S5: If the actual furnace section temperature is lower than the set furnace temperature, and the heating conditions are met, first increase the gas flow rate by a limited amount, and wait for the time interval Δt. 12 Then, adjust the oxygen flow rate according to the set oxygen-fuel ratio limit r.

[0030] S6: If the oxygen flow rate is initially increased, after a waiting time Δt2(p), nitrogen oxides (NOx) are detected. If the target deviation of nitrogen oxides (NOx) is... a -NOx t If the value is less than the critical value ε, then reduce Δt. 12 If the target deviation (NOx) a -NOx t If ) is greater than 0, then increase Δt. 12 .

[0031] S7: Return to execute S2.

[0032] Step S4 is used to generate the optimal time interval Δt 11opt It is given by formula (2).

[0033] Step S6 is used to generate the optimal time interval Δt 12opt It is given by formula (3).

[0034] Let the oxygen-fuel ratio be r; the time intervals for cooling and heating under reverse double-cross limiting control are Δt and Δt, respectively. 11 , Δt 12 The waiting time from the start of cross-adjustment to detection is Δt2(p); the target value for nitrogen oxide emissions is NOx. t The actual emission value of nitrogen oxides is NOx. a Therefore, when the temperature drops or rises, the time interval Δt is adjusted. 11 or Δt 12 , making

[0035] ε≤NOx a -NOx t ≤0, (1)

[0036] When the temperature drops

[0037]

[0038] Or when the temperature rises

[0039]

[0040] This invention addresses the problem of excessive nitrogen oxides (NOx) in oxy-fuel steelmaking furnaces by proposing a control method to prevent NOx exceedances in flue gas. This method ensures that a suitable amount of fuel gas is always supplied to the furnace section for oxygen digestion during furnace temperature adjustment. The implementation method is as follows:

[0041] If it is necessary to lower the furnace section temperature, first reduce the oxygen flow rate; after Δt 11After a cooling waiting interval, the gas flow rate is adjusted according to the set oxygen-fuel ratio r. The system then waits for Δt2(p) (the detection waiting time, where p is the furnace section number where the billet is located; different waiting times are selected, with longer waiting times for furnace sections farther from the NOx detection point) before starting NOx detection. If the target deviation of NOx is... a -NOx t If the value is less than the critical value ε (ε≤0, any constant value), then decrease Δt. 11 The aim is to reduce excess gas input; if the target deviation (NOx) a -NOx t If ) is greater than 0, then increase Δt. 11 The aim is to reduce nitrogen oxide emissions and ensure that flue gas meets emission standards.

[0042] If it is necessary to increase the furnace section temperature, first increase the gas flow rate, then at intervals Δt 12 After a (heating waiting interval) time, oxygen flow adjustment is initiated. After oxygen flow adjustment begins, the system waits for Δt2(p) (the detection waiting time, where p is the furnace section number where the billet is located; different waiting times are selected, with longer waiting times for furnace sections farther from the NOx detection point) before starting NOx detection. If the NOx target deviation (NOx...) is... a -NOx t If the value is less than the critical value ε, then reduce Δt. 12 The aim is to reduce excess fuel input. If the target deviation (NOx) a -NOx t If ) is greater than 0, then increase Δt. 12 The aim is to reduce nitrogen oxide emissions and ensure that flue gas meets emission standards.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling excessive nitrogen oxide emissions in flue gas from an oxygen-fired steelmaking furnace, characterized in that: Includes the following steps: S1: Determine the initial time intervals for cooling and heating, respectively, Δt. 11 , Δt 12 ; S2: Detects temperature deviation in the furnace section; Let the oxygen-fuel ratio be r; the time intervals for cooling and heating under reverse double-cross limiting control are Δt and Δt, respectively. 11 Δt 12 The waiting time from the start of cross-adjustment to detection is Δt2(p), where p is the furnace section number where the billet is located. This is used to select different waiting times; the farther the furnace section is from the nitrogen oxide detection point, the longer the waiting time. The nitrogen oxide emission limit target value is NOx. t The actual emission value of nitrogen oxides is NOx. a ; Make ε≤NOx a -NOx t ≤0, (1); Step S2 further includes the following steps: S3: If the actual furnace section temperature is higher than the set furnace temperature, and the cooling conditions are met, first reduce the oxygen flow rate by a limited amount, and wait for the time interval Δt. 11 Then, adjust the gas flow rate according to the set oxygen-fuel ratio r limit; Step S2 further includes the following steps: S4: If the actual furnace section temperature is lower than the set furnace temperature, and the heating conditions are met, first increase the gas flow rate by a limited amount, and wait for the time interval Δt. 12 Then, adjust the oxygen flow rate according to the set oxygen-fuel ratio limit r.

2. The control method for preventing excessive nitrogen oxide emissions in flue gas from the all-oxygen sintering process of a steel rolling furnace as described in claim 1, characterized in that, It also includes the following steps: S5: If the gas flow rate is reduced, wait for Δt2(p) and then detect nitrogen oxides (NOx); if the target deviation of nitrogen oxides (NOx) is... a -NOx t If the value is less than the critical value ε, and ε≤0, for any fixed value, then the decrease is Δt. 11 If the target deviation for nitrogen oxides (NOx) is (NOx a -NOx t If ) is greater than 0, then increase Δt. 11 Return to execute S2.

3. The control method for preventing excessive nitrogen oxide emissions in flue gas from the all-oxygen sintering process of a steel rolling furnace as described in claim 2, characterized in that, Step S5 is used to generate the optimal time interval Δt 11opt As given by formula (2), when the temperature drops... ε≤minΔ t11 =Δt 11opt (NOx a -NOx t )≤0 (2)。 4. The control method for preventing excessive nitrogen oxide emissions in flue gas from the all-oxygen sintering process of a steel rolling furnace as described in claim 1, characterized in that, It also includes the following steps: S6: If the oxygen flow rate is initially increased, wait for Δt2(p) before detecting nitrogen oxides (NOx); if the target deviation of nitrogen oxides (NOx) is... a -NOx t If the value is less than the critical value ε, then reduce Δt. 12 If the target deviation (NOx) a -NOx t If ) is greater than 0, then increase Δt. 12 Return to execute S2.

5. The control method for preventing excessive nitrogen oxide emissions in flue gas from the all-oxygen sintering process of a steel rolling furnace as described in claim 4, characterized in that, Step S6 is used to generate the optimal time interval Δt 12opt As given by formula (3), when the temperature rises... ε≤minΔ t12 =Δt 12opt (NOx a -NOx t )≤0 (3)。

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