Hot blast stove combustion control system and method based on coal gas components and flue gas residual oxygen amount

Abstract

The invention belongs to the technical field of hot-blast stove combustion control, and mainly relates to a hot-blast stove combustion control system and method based on coal gas components and flue gas residual oxygen content, the control system comprises a controller and a hot-blast stove, and the hot-blast stove is communicated with a gas supply mechanism, a combustion-supporting mechanism, a cold air mechanism and a smoke exhaust mechanism; a coal gas branch pipe adjusting valve is arranged between the hot-blast stove and the air supply mechanism, an air branch pipe adjusting valve is arranged between the hot-blast stove and the combustion-supporting mechanism, a cold air valve is arranged between the hot-blast stove and the cold air mechanism, a hot air valve is arranged between the hot-blast stove and the air supply mechanism, and a flue valve is arranged between the hot-blast stove and the smoke exhaust mechanism; a gas analysis mechanism is arranged between the hot-blast stove and the gas supply mechanism, and a detection mechanism is further arranged between the hot-blast stove and the smoke exhaust mechanism. The coal gas and the air are fully combusted through real-time calculation and accurate allocation of the required combustion-supporting air consumption, meanwhile, manual work is replaced with an automatic control mode, the labor intensity of workers and coal gas consumption can be reduced, and the air supply temperature of the hot blast stove can be increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of combustion control of hot blast stoves, and mainly relates to a combustion control system and method for hot blast stoves based on gas composition and residual oxygen content in flue gas. Background Art

[0002] In order to improve energy utilization efficiency and reduce production costs, the combustion process of hot blast stoves requires a relatively high combustion efficiency. This means that the fuel needs to be burned as completely as possible to reduce the generation of incomplete combustion products and make full use of the chemical energy of the fuel.

[0003] However, the combustion process of hot blast stoves has characteristics such as multi-variables, non-linearity, large time delay, and time-varying. It is necessary to operate the hot blast stove frequently. Coupled with the frequent changes in gas pressure and gas composition, when burning the stove manually, the gas flow rate and air flow rate cannot be adjusted in time, making it difficult to meet the control requirements for the arch top temperature and exhaust gas temperature, and will cause environmental protection data such as CO, SO 2 and NO x to often exceed the standard. And adding desulfurization and denitration equipment will greatly increase production costs. Summary of the Invention

[0004] The present invention provides a combustion control system and method for hot blast stoves based on gas composition and residual oxygen content in flue gas to solve the problem that the gas in the hot blast stove cannot be fully burned in the prior art.

[0005] To solve the above problems, the present invention adopts the following technical solutions: A combustion control system for hot blast stoves based on gas composition and residual oxygen content in flue gas includes a controller and a hot blast stove. The hot blast stove is respectively connected to a gas supply mechanism, a combustion-supporting mechanism, a cold air mechanism, and a smoke exhaust mechanism; A gas branch pipe regulating valve is provided between the hot blast stove and the gas supply mechanism to adjust the actual gas flow rate supplied by the gas supply mechanism to the hot blast stove. An air branch pipe regulating valve is provided between the hot blast stove and the combustion-supporting mechanism to adjust the air consumption supplied by the combustion-supporting mechanism to the hot blast stove. A cold air valve is provided between the hot blast stove and the cold air mechanism to adjust the cold air consumption supplied by the cold air mechanism to the hot blast stove. A hot air valve is also provided between the hot blast stove and the gas supply mechanism to control the hot air supplied by the hot blast stove to the gas supply mechanism. A flue gas valve is provided between the hot blast stove and the smoke exhaust mechanism to control the flue gas discharged from the hot blast stove; A gas analysis mechanism is also provided between the hot blast stove and the gas supply mechanism. The gas analysis mechanism is used to detect the content of each component in the gas to determine the calorific value of the gas. A detection mechanism is also provided between the hot blast stove and the smoke exhaust mechanism. The detection mechanism is used to detect the residual oxygen content in the flue gas; The controller is respectively connected to a temperature detection component, a gas branch pipe regulating valve, an air branch pipe regulating valve, a cold air valve, a hot air valve, a flue gas valve, a gas analysis mechanism, and a detection mechanism to control their operations.

[0006] It has the following beneficial effects: By calculating and accurately allocating the required amount of combustion-supporting air in real time, it is possible to achieve operation with a low excess air coefficient and respond promptly to fluctuations in the gas composition and pressure without modifying the structure of the hot blast stove, enabling the full combustion of gas and air, achieving the control effect of suppressing the generation of nitrogen oxides. At the same time, replacing manual operation with automatic control can reduce the labor intensity of personnel and gas consumption, and increase the hot blast temperature of the hot blast stove.

[0007] Furthermore, there are multiple hot blast stoves, and all of the multiple hot blast stoves are connected to the gas supply mechanism, combustion-supporting mechanism, cold air mechanism, and smoke exhaust mechanism; The gas supply mechanism is connected to a main gas pipe, and the main gas pipe is respectively connected to multiple hot blast stoves through multiple gas branch pipes. The gas branch pipe regulating valve is arranged on the gas branch pipe, and the gas analysis mechanism is arranged on the main gas pipe; A main gas pipe regulating valve is arranged on the main gas pipe to regulate the total amount of gas supplied by the main gas pipe to multiple hot blast stoves.

[0008] It has the following beneficial effects: By arranging multiple hot blast stoves, when one of the hot blast stoves needs to be overhauled, maintained, or has a temporary fault, the other several hot blast stoves can continue to operate, ensuring the continuous supply of hot blast, avoiding heat supply interruption caused by the failure of a single hot blast stove, and ensuring that the production process is not affected; Multiple hot blast stoves operating in parallel can make the hot blast temperature more stable through reasonable adjustment. Even if there are certain changes in the combustion condition or heat exchange efficiency of a certain hot blast stove, the stable outlet hot blast temperature can be maintained by adjusting the operating parameters of the other several hot blast stoves, which is beneficial to improving product quality; According to different requirements of the production process, the operating states of multiple hot blast stoves can be flexibly adjusted. When the heat supply demand is low, the load of some hot blast stoves can be appropriately reduced or one of the hot blast stoves can be stopped to reduce energy consumption; when the heat supply demand is high, multiple hot blast stoves can be operated simultaneously to meet the production needs. This flexible adjustment method can enable the hot blast stove system to better adapt to different production conditions and improve energy utilization efficiency.

[0009] Furthermore, the combustion-supporting mechanism is connected to a main combustion-supporting pipe, and the main combustion-supporting pipe is respectively connected to multiple hot blast stoves through multiple combustion-supporting branch pipes. The air branch pipe regulating valve is arranged on the combustion-supporting branch pipe.

[0010] Furthermore, the cold air mechanism is connected to a main cold air pipe, and the main cold air pipe is respectively connected to multiple hot blast stoves through multiple cold air branch pipes. The cold air valve is arranged on the cold air branch pipe.

[0011] Further, the smoke exhaust mechanism is connected to a main smoke exhaust pipe, and the main smoke exhaust pipe is respectively connected to a plurality of hot blast stoves through a plurality of smoke exhaust branch pipes. The flue gas valve and the detection mechanism are arranged on the cold air branch pipe.

[0012] A combustion control method for a hot blast stove based on gas composition and residual oxygen content in flue gas is applied to the combustion control system of the hot blast stove based on gas composition and residual oxygen content in flue gas, and includes the following steps: Firing process: Open the regulating valve of the gas branch pipe, the regulating valve of the air branch pipe, and the flue gas valve, close the hot air valve and the cold air valve. The blast furnace gas and air are mixed and burned, and the generated flue gas stores heat in the hot blast stove. The flue gas is discharged through the flue gas valve. Soaking process: Close the regulating valve of the gas branch pipe, the regulating valve of the air branch pipe, the flue gas valve, the hot air valve, and the cold air valve. Air supply process: Open the cold air valve and the hot air valve, close the regulating valve of the gas branch pipe, the regulating valve of the air branch pipe, and the flue gas valve. After the cold air is heated by the hot blast stove, hot air is supplied to the air supply mechanism through the hot air valve.

[0013] Further, the firing process is divided into four stages: ignition stage, rapid top temperature rise stage, flue gas temperature control stage, and furnace closing stage. Ignition stage: First, control the initial opening of the regulating valve of the air branch pipe to be 20%-30%. When the opening of the regulating valve of the air branch pipe decreases to 15%, then control the opening of the regulating valve of the gas branch pipe to be 15%. After that, continuously decrease the opening of the regulating valve of the gas branch pipe, while the opening of the regulating valve of the air branch pipe remains at 15%. When the opening of the regulating valve of the gas branch pipe reaches 10%, the ignition ends. Rapid top temperature rise stage: After the ignition ends, enter the rapid top temperature rise stage to quickly burn the arch top of the hot blast stove to the set value. At this time, calculate the set gas flow rate based on the initial gas heat set value. Through the PID control of the controller, with the set gas flow rate as the target value, control the opening of the regulating valve of the gas branch pipe to determine the actual gas flow rate. The set air consumption value is adjusted based on the residual oxygen content in the flue gas measured by the detection mechanism on the basis of the theoretical air consumption. Flue gas temperature control stage: Calculate the flue gas temperature rise rate in real time, smooth the flue gas temperature rise curve through the mean filtering method, multiply it by the remaining firing time and add the current flue gas temperature to obtain the predicted flue gas temperature at the end of firing. Subtract the set flue gas temperature to get the flue gas temperature difference value, and adjust the set gas flow rate according to the difference value so that the set flue gas temperature is exactly reached at the end of firing. The set air consumption value is adjusted on the basis of the theoretical air consumption. Compare the set arch top temperature with the actual arch top temperature to adjust the set range of the residual oxygen content in the flue gas. Further, adjust the set air consumption value according to the residual oxygen content in the flue gas. Furnace closing stage: When the flue gas temperature reaches the set value or the firing time reaches the set time, close the furnace.

[0014] It has the following beneficial effects: Through the coordinated action of the proportional (P), integral (I), and derivative (D) links of the controller, the PID of the controller can accurately adjust the supply volume of hot blast stove gas according to the deviation between the set value and the actual value. The proportional link can quickly respond to the deviation, the integral link can eliminate the steady-state error, and the derivative link can predict the change trend of the error and make adjustments in advance, so that the gas and air can burn fully, achieving the control effect of suppressing the generation of nitrogen oxides.

[0015] Further, in the stage of rapid top temperature rise, the method for adjusting the set value of air consumption is that when the residual oxygen content value exceeds the upper limit of the set residual oxygen content range, the set value of air consumption is reduced based on the theoretical air consumption according to the deviation; when the residual oxygen content value is lower than the lower limit of the set residual oxygen content range, the set value of air consumption is increased based on the theoretical air consumption according to the deviation; When the stage of rapid top temperature rise lasts for 10 minutes or the arch top temperature reaches within ±10°C of the set value, it enters the flue gas temperature control stage.

[0016] It has the following beneficial effects: It enables the gas and air to burn fully, achieving the control effect of suppressing the generation of nitrogen oxides.

[0017] Further, in the furnace closing stage, first record the opening of the gas branch pipe regulating valve before furnace closing, and divide it by the number of adjustments to obtain the opening value of each closing of the gas branch pipe regulating valve; Keep the air-fuel ratio before furnace closing unchanged, and adjust the opening of the air branch pipe regulating valve so that the gas precedes the air; After each action of the gas branch pipe regulating valve, delay for 5 seconds before performing the next furnace closing action. When the opening of the gas branch pipe regulating valve is less than or equal to 5, close the gas branch pipe regulating valve, and then delay for 3 seconds to close the air branch pipe regulating valve.

[0018] It has the following beneficial effects: It can avoid the adverse effects caused by the imbalance of the air-fuel ratio and flow rate fluctuations on another hot blast stove in the burning state, and avoid the situation of exceeding environmental protection data standards.

[0019] Further, the formula for calculating the theoretical air consumption is:

[0020] The formula for calculating the gas heat is:

[0021] Where: M 1 ——The theoretical air consumption, M 2 ——The actual gas flow rate, a——The excess air coefficient, between 1.2 and 1.5, Q —— actual gas heat h 1 —— proportion of CO in the gas measured by the gas analysis mechanism h 2 —— proportion of H 2 in the gas measured by the gas analysis mechanism h 3 —— proportion of CH 4 in the gas measured by the gas analysis mechanism h 4 —— proportion of O 2 in the gas measured by the gas analysis mechanism h 5 —— calorific value of the gas measured by the gas analysis mechanism; The calculation formula for the flue gas temperature rise rate is:

[0022] The calculation formula for predicting the flue gas temperature is:

[0023] Where: V —— flue gas temperature rise rate, unit: °C / min TE 0 —— current flue gas temperature TE n —— flue gas temperature n seconds ago TE YC —— predicted flue gas temperature Ti SP —— set furnace burning time, unit: min Ti —— actual furnace burning time, unit: min. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] By referring to the drawings and reading the following detailed description, the above and other objects, features, and advantages of the exemplary embodiments of the present invention will become easily understandable. In the drawings, several embodiments of the present invention are shown in an exemplary rather than restrictive manner, and the same or corresponding reference numerals represent the same or corresponding parts, where: Figure 1 is the structural diagram of the hot blast stove system; Figure 2 is the block diagram of the hot blast stove gas main pipe pressure control system; Figure 3 is the block diagram of the hot blast stove combustion-supporting main pipe pressure control system; Figure 4 is the block diagram of the hot blast stove exhaust fan frequency control system; Figure 5 is the flowchart of the hot blast stove burning process control; Figure 6 It is the block diagram of the hot blast stove flue gas temperature control system; Figure 7 It is the block diagram of the hot blast stove arch top temperature control system.

[0025] Explanation of the reference numerals in the drawings: 1. Hot blast stove; 2. Gas branch pipe regulating valve; 3. Air branch pipe regulating valve; 4. Hot air valve; 5. Gas analysis mechanism; 6. Cold air valve; 7. Flue gas valve; 8. Detection mechanism; 9. Gas main pipe regulating valve; 10. Combustion-supporting mechanism; 11. Smoke exhaust mechanism. Specific embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Those skilled in the art should know that the embodiments described below are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

[0027] The following specifically introduces various non-limiting embodiments of the present invention. The number of any element in the drawings is for illustration rather than limitation, and any naming is only for distinction and does not have any limiting meaning. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0028] Embodiment of the control system As Figure 1 shown, the combustion control system of the hot blast stove 1 based on the gas composition and the residual oxygen content in the flue gas includes three hot blast stoves 1 operating in parallel, adopting an operation system of two burning and one feeding. Each hot blast stove 1 is equipped with a gas branch pipe regulating valve 2, an air branch pipe regulating valve 3, a hot air valve 4, a cold air valve 6, a flue gas valve 7 and a detection mechanism 8 for detecting the residual oxygen content in the flue gas. The gas from the gas supply mechanism (blast furnace) is detected for the gas composition by the gas analysis mechanism 5 and then supplied to the three hot blast stoves 1 through the gas main pipe regulating valve 9. The combustion-supporting mechanism 10 (combustion-supporting fan) has a frequency modulation function and supplies air to the three hot blast stoves 1. The smoke exhaust mechanism 11 (smoke exhaust fan) has a frequency modulation function and extracts and discharges the flue gas generated by the hot blast stove 1.

[0029] Specifically, the combustion control system of the hot blast stove 1 based on the gas composition and the residual oxygen content in the flue gas includes a controller and three hot blast stoves 1. The three hot blast stoves 1 are all connected to a gas supply mechanism, a combustion-supporting mechanism 10, a cold air mechanism and a smoke exhaust mechanism 11. Among them, the controller has a PID unit.

[0030] The gas branch pipe regulating valve 2 is arranged between the hot blast stove 1 and the gas supply mechanism to adjust the actual gas flow supplied by the gas supply mechanism to the hot blast stove 1. The air branch pipe regulating valve 3 is arranged between the hot blast stove 1 and the combustion-supporting mechanism 10 to adjust the air consumption supplied by the combustion-supporting mechanism 10 to the hot blast stove 1. The cold air valve 6 is arranged between the hot blast stove 1 and the cold air mechanism to adjust the cold air consumption supplied by the cold air mechanism to the hot blast stove 1. The hot air valve 4 is arranged between the hot blast stove 1 and the gas supply mechanism to control the hot air supplied by the hot blast stove 1 to the gas supply mechanism. The flue gas valve 7 is arranged between the hot blast stove 1 and the flue gas exhaust mechanism 11 to control the flue gas discharged from the hot blast stove 1.

[0031] In this embodiment, a gas analysis mechanism 5 is further arranged between the hot blast stove 1 and the gas supply mechanism. The gas analysis mechanism 5 is used to detect the content of each component in the gas to determine the calorific value of the gas. The detection mechanism 8 (zirconia analyzer) is arranged between the hot blast stove 1 and the flue gas exhaust mechanism 11. The detection mechanism 8 is used to detect the residual oxygen content in the flue gas.

[0032] The controller is respectively connected to the temperature detection component, the gas branch pipe regulating valve 2, the air branch pipe regulating valve 3, the cold air valve 6, the hot air valve 4, the flue gas valve 7, the gas analysis mechanism 5 and the detection mechanism 8 to control their operations.

[0033] By calculating and accurately allocating the required combustion-supporting air consumption in real time, without modifying the structure of the hot blast stove 1, the operation with a low excess air coefficient can be realized and the timely response to the fluctuations of the gas composition and pressure can be achieved, enabling the full combustion of the gas and air, achieving the control effect of suppressing the generation of nitrogen oxides. At the same time, replacing manual operation with an automatic control method can reduce the labor intensity of personnel and gas consumption and increase the air supply temperature of the hot blast stove 1.

[0034] In this embodiment, the zirconia analyzer is an instrument that measures the oxygen content using the principle of the concentration difference cell of zirconia solid electrolyte. Zirconia is a solid electrolyte with oxygen ion conduction characteristics. At high temperatures (generally heated to 600 - 800 °C), when the oxygen partial pressures on both sides of the zirconia are different, oxygen ions will migrate from the side with high oxygen partial pressure through the zirconia electrolyte to the side with low oxygen partial pressure, thus generating a potential difference between the two sides, and this potential difference is also called the concentration difference potential. The zirconia analyzer consists of a detection element and a transmitter. The core component in the detection element is the zirconia probe, which is composed of a zirconia ceramic tube, internal and external electrodes, and a heating element, etc. The zirconia ceramic tube is the channel for oxygen ion conduction, the internal and external electrodes are used to lead out the potential difference signal, and the heating element ensures that the zirconia operates at a suitable working temperature. The transmitter amplifies, converts, and processes the potential difference signal measured by the detection element, and finally outputs the oxygen content measurement value in the form of a digital or analog signal. It may also have a temperature compensation function to eliminate the influence of temperature changes on the measurement results. Some transmitters also have a communication interface to transmit the measurement data to the upper computer or control system.

[0035] The zirconia material itself has good chemical stability and thermal stability. As long as appropriate operating conditions are maintained, the instrument can operate stably for a long time, reducing the need for frequent calibration and maintenance.

[0036] Specifically, the gas supply mechanism is connected to a main gas pipe. The main gas pipe is respectively connected to multiple hot blast stoves 1 through multiple gas branch pipes. A gas branch pipe regulating valve 2 is provided on the gas branch pipe, and a gas analysis mechanism 5 is provided on the main gas pipe. A main gas pipe regulating valve 9 is provided on the main gas pipe to regulate the total gas consumption supplied by the main gas pipe to the multiple hot blast stoves 1. As Figure 2 shown, a first pressure sensor is provided on the main gas pipe. The first pressure sensor is electrically connected to the controller. The first pressure sensor feeds back the pressure in the main gas pipe to the controller, and the controller controls the main gas pipe regulating valve 9 to perform pressure regulation.

[0037] In this embodiment, by arranging multiple hot blast stoves 1, when one of the hot blast stoves 1 needs to be repaired, maintained or has a temporary failure, several other hot blast stoves 1 can continue to operate, ensuring the continuous supply of hot air, avoiding heat supply interruption caused by the failure of a single hot blast stove 1, and ensuring that the production process is not affected.

[0038] In this embodiment, the multiple hot blast stoves 1 operating in parallel can be reasonably adjusted to make the hot air temperature more stable. Even if there are certain changes in the combustion condition or heat exchange efficiency of a certain hot blast stove 1, the stable outlet hot air temperature can be maintained by adjusting the operating parameters of several other hot blast stoves 1, which is beneficial to improving product quality.

[0039] According to different requirements of the production process, the operating states of the multiple hot blast stoves 1 can be flexibly adjusted. When the heat supply demand is low, the load of some hot blast stoves 1 can be appropriately reduced or one of the hot blast stoves 1 can be stopped to reduce energy consumption; when the heat supply demand is high, multiple hot blast stoves 1 can be operated simultaneously to meet the production needs. This flexible adjustment method enables the hot blast stove 1 system to better adapt to different production conditions and improve energy utilization efficiency.

[0040] Specifically, the combustion-supporting mechanism 10 is connected to a main combustion-supporting pipe. The main combustion-supporting pipe is respectively connected to multiple hot blast stoves 1 through multiple combustion-supporting branch pipes. An air branch pipe regulating valve 3 is provided on the combustion-supporting branch pipe. As Figure 3 shown, a second pressure sensor is provided on the main combustion-supporting pipe. The second pressure sensor is electrically connected to the controller. The second pressure sensor feeds back the pressure in the main combustion-supporting pipe to the controller, and the controller controls the combustion-supporting fan to perform pressure regulation.

[0041] The cold air mechanism is connected to a main cold air pipe. The main cold air pipe is respectively connected to multiple hot blast stoves 1 through multiple cold air branch pipes. A cold air valve 6 is provided on the cold air branch pipe.

[0042] The smoke exhaust mechanism 11 is connected to a main smoke exhaust pipe, and the main smoke exhaust pipe is respectively connected to multiple hot blast stoves 1 through multiple smoke exhaust branch pipes. The flue gas valve 7 and the detection mechanism 8 are arranged on the cold air branch pipe. As Figure 4 shown, the frequency of the smoke exhaust fan is determined by the air branch pipe flow rate and the gas branch pipe flow rate.

[0043] Embodiment of the control method A combustion control method for a hot blast stove 1 based on gas composition and residual oxygen content in flue gas is applied to a combustion control system for a hot blast stove 1 based on gas composition and residual oxygen content in flue gas, and includes the following steps: Firing process: Open the gas branch pipe regulating valve 2, the air branch pipe regulating valve 3, and the flue gas valve 7, close the hot air valve 4 and the cold air valve 6. The blast furnace gas and air are mixed and burned, and the generated flue gas stores heat in the hot blast stove 1, and the flue gas is discharged through the flue gas valve 7.

[0044] Soaking process: Close the gas branch pipe regulating valve 2, the air branch pipe regulating valve 3, the flue gas valve 7, the hot air valve 4, and the cold air valve 6.

[0045] Air supply process: Open the cold air valve 6 and the hot air valve 4, close the gas branch pipe regulating valve 2, the air branch pipe regulating valve 3, and the flue gas valve 7. After the cold air is heated by the hot blast stove 1, hot air is supplied to the air supply mechanism through the hot air valve 4.

[0046] In this embodiment, as Figure 5 shown, the firing process is divided into four stages: ignition stage, rapid top temperature rise stage, flue gas temperature control stage, and furnace closing stage.

[0047] Ignition stage: First, control the initial opening of the air branch pipe regulating valve 3 to be 20%-30%. When the opening of the air branch pipe regulating valve 3 decreases to 15%, then control the opening of the gas branch pipe regulating valve 2 to be 15%. After that, continuously decrease the opening of the gas branch pipe regulating valve 2, while the opening of the air branch pipe regulating valve 3 remains at 15%. When the opening of the gas branch pipe regulating valve 2 reaches 10%, the ignition ends.

[0048] Rapid top temperature rise stage: After the ignition ends, enter the rapid top temperature rise stage to quickly burn the arch top of the hot blast stove 1 to the set value. At this time, according to the initial gas heat set value Q SP calculate the set gas flow rate M SP =Q SP / h 5 , through the PID control of the controller, with the set gas flow rate M SP as the target value, control the opening of the gas branch pipe regulating valve 2, so as to determine the actual gas flow rate M 2 , and at the same time make the actual gas flow rate close to the set gas flow rate M SP . The air consumption set value is at the theoretical air consumption M 1On this basis, the air usage setting value is adjusted according to the residual oxygen content in the flue gas measured by the detection mechanism 8. In this embodiment, the initial gas heat setting value Q SP It needs to be determined based on actual needs.

[0049] In the stage of rapid temperature rise, the air consumption setting value is adjusted according to the deviation in the theoretical air consumption M when the residual oxygen value exceeds the upper limit of the residual oxygen setting range. 1 When the residual oxygen value is lower than the lower limit of the set residual oxygen setting range, the theoretical air consumption M is increased according to the deviation. 1 On this basis, increase the air usage setting value to enable the gas and air to burn fully and achieve the control effect of inhibiting the generation of nitrogen oxides.

[0050] When the rapid rise stage of top temperature lasts for 10 minutes or the dome temperature reaches within ±10℃ of the set value, the smoke temperature control stage begins.

[0051] The theoretical air consumption calculation formula is:

[0052] The formula for calculating the heat of gas is:

[0053] in: M 1 ——Theoretical air consumption, M 2 ——Actual gas flow, a——excess air coefficient, between 1.2-1.5, Q——actual gas heat, h 1 ——The gas analysis agency measured the proportion of CO in the gas, h 2 ——Gas analysis agency measured H in coal gas 2 Proportion, h 3 ——The gas analysis agency measured CH 4 Proportion, h 4 ——Gas analysis agency measured O in coal gas 2 Proportion, h 5 ——The calorific value of coal gas is measured by the gas analysis agency.

[0054] Smoke temperature control stage: Calculate the real-time smoke temperature rising rate, smooth the smoke temperature rising curve through the mean filtering method, multiply it by the remaining furnace burning time and then add the current smoke temperature to obtain the predicted smoke temperature at the end of furnace burning. Subtract the set smoke temperature from it to get the smoke temperature difference value, and adjust the set value of gas flow according to the difference value so that the set smoke temperature is exactly reached at the end of furnace burning. The current smoke temperature can be detected in real time by the first temperature sensor, and the first temperature sensor is installed on the corresponding smoke exhaust branch pipe. As Figure 6 shown, the first temperature sensor is electrically connected to the controller, and the first temperature sensor feeds back the smoke temperature to the controller, and the controller adjusts the smoke temperature.

[0055] The set value of air consumption is adjusted on the basis of the theoretical air consumption M 1 . Compare the set arch top temperature with the actual arch top temperature, adjust the set range of residual oxygen in the flue gas, and further adjust the set value of air consumption according to the residual oxygen in the flue gas. The actual arch top temperature can be detected in real time by the second temperature sensor, and the second temperature sensor is installed on the corresponding hot blast stove 1. As Figure 7 shown, the second temperature sensor is electrically connected to the controller, and the second temperature sensor feeds back the arch top temperature to the controller, and the controller adjusts the arch top temperature.

[0056] Among them, the calculation formula for the smoke temperature rising rate is:

[0057] The calculation formula for the predicted smoke temperature is:

[0058] Among them: V - Smoke temperature rising rate, unit: ℃ / min, TE 0 - Current smoke temperature, TE n - Smoke temperature n seconds ago, TE YC - Predicted smoke temperature, Ti SP - Set furnace burning time, unit: min, Ti - Actual furnace burning time, unit: min.

[0059] Furnace closing stage: When the flue gas temperature reaches the set value or the furnace burning time reaches the set time, the furnace is closed. In the furnace closing stage, first record the opening of the gas branch pipe regulating valve 2 before the furnace is closed, and divide it by the number of adjustments to obtain the opening value of the gas branch pipe regulating valve 2 each time it is closed. Keep the air-fuel ratio unchanged before furnace closing, and adjust the opening of the air branch pipe regulating valve 3 so that the gas precedes the air. Each time the gas branch pipe regulating valve 2 is actuated, there is a delay of 5 seconds before the next furnace closing action. When the opening of the gas branch pipe regulating valve 2 is less than or equal to 5, the gas branch pipe regulating valve 2 is closed, and then the air branch pipe regulating valve 3 is closed after a delay of 3 seconds. The furnace closing stage can avoid the adverse effects of air-fuel ratio imbalance and flow fluctuation on another hot blast furnace 1 that is in the furnace burning state, and avoid the situation where environmental protection data exceeds the standard.

[0060] The PID controller can accurately adjust the gas supply of the hot blast furnace 1 according to the deviation between the setting and the actual through the synergistic effect of the three links of proportion (P), integration (I) and differentiation (D). The proportional link can respond to the deviation quickly, the integral link can eliminate the steady-state error, and the differential link can predict the error change trend and make adjustments in advance, so that the gas and air can be fully burned, achieving the control effect of inhibiting the formation of nitrogen oxides.

Claims

1. A hot blast stove combustion control system based on coal gas composition and flue gas residual oxygen content, characterized in that: It includes a controller and a hot air furnace, wherein the hot air furnace is respectively connected with an air supply mechanism, a combustion-supporting mechanism, a cold air mechanism and a smoke exhaust mechanism; A gas branch pipe regulating valve is provided between the hot blast stove and the gas supply mechanism to regulate the actual gas flow supplied by the gas supply mechanism to the hot blast stove; an air branch pipe regulating valve is provided between the hot blast stove and the combustion-supporting mechanism to regulate the amount of air supplied by the combustion-supporting mechanism to the hot blast stove; a cold air valve is provided between the hot blast stove and the cold air mechanism to regulate the amount of cold air supplied by the cold air mechanism to the hot blast stove; a hot air valve is further provided between the hot blast stove and the gas supply mechanism to control the hot air supplied by the hot blast stove to the gas supply mechanism; a flue valve is provided between the hot blast stove and the smoke exhaust mechanism to control the exhaust of smoke from the hot blast stove; A gas analysis mechanism is also provided between the hot blast furnace and the gas supply mechanism, and the gas analysis mechanism is used to detect the content of each component in the coal gas to determine the calorific value of the coal gas. A detection mechanism is also provided between the hot blast furnace and the smoke exhaust mechanism, and the detection mechanism is used to detect the residual oxygen content in the smoke; The controller is respectively connected to the temperature detection component, the gas branch pipe regulating valve, the air branch pipe regulating valve, the cold air valve, the hot air valve, the flue valve, the gas analysis mechanism and the detection mechanism to control their operation.

2. The hot blast stove combustion control system based on gas composition and flue gas residual oxygen content according to claim 1 is characterized in that: There are multiple hot blast furnaces, and the multiple hot blast furnaces are all connected with the air supply mechanism, the combustion-supporting mechanism, the cold air mechanism and the smoke exhaust mechanism; The gas supply mechanism is connected to a gas main pipe, and the gas main pipe is connected to a plurality of hot blast furnaces through a plurality of gas branch pipes, the gas branch pipe regulating valve is arranged on the gas branch pipe, and the gas analysis mechanism is arranged on the gas main pipe; The gas main pipe is provided with a gas main regulating valve to adjust the total amount of gas supplied by the gas main pipe to the multiple hot blast furnaces.

3. The hot blast stove combustion control system based on gas composition and flue gas residual oxygen content according to claim 2 is characterized in that: The combustion-supporting mechanism is connected to a combustion-supporting main pipe, and the combustion-supporting main pipe is respectively connected to a plurality of hot blast furnaces through a plurality of combustion-supporting branch pipes, and the air branch pipe regulating valve is arranged on the combustion-supporting branch pipe.

4. The hot blast stove combustion control system based on coal gas composition and flue gas residual oxygen content according to claim 2 is characterized in that: The cold air mechanism is connected with a cold air main pipe, and the cold air main pipe is connected with a plurality of hot air furnaces through a plurality of cold air branch pipes respectively, and the cold air valve is arranged on the cold air branch pipes.

5. The hot blast stove combustion control system based on coal gas composition and flue gas residual oxygen content according to claim 2, characterized in that: The smoke exhaust mechanism is connected to a smoke exhaust main pipe, and the smoke exhaust main pipe is respectively connected to a plurality of hot air furnaces through a plurality of smoke exhaust branch pipes, and the flue valve and the detection mechanism are arranged on the cold air branch pipes.

6. A hot blast stove combustion control method based on coal gas composition and flue gas residual oxygen content, characterized in that: The method is applied to a hot blast stove combustion control system based on coal gas composition and flue gas residual oxygen content as described in any one of claims 1 to 5, comprising the following steps: Furnace burning process: open the gas branch pipe regulating valve, air branch pipe regulating valve, flue valve, close the hot air valve, cold air valve, blast furnace gas and air are mixed and burned, the generated flue gas stores heat in the hot blast furnace, and the flue gas is discharged through the flue valve; Simmering process: close the gas branch pipe regulating valve, air branch pipe regulating valve, flue valve, hot air valve, and cold air valve; Air supply process: open the cold air valve and hot air valve, close the gas branch pipe regulating valve, air branch pipe regulating valve, and flue valve. After the cold air is heated by the hot air furnace, hot air is supplied to the air supply mechanism through the hot air valve.

7. The hot blast stove combustion control method based on coal gas composition and flue gas residual oxygen content according to claim 6, characterized in that: The furnace burning process is divided into four stages: furnace lighting stage, top temperature rapid rise stage, smoke temperature control stage, and furnace closing stage; Furnace lighting stage: First, control the initial opening of the air branch regulating valve to 20%-30%. When the opening of the air branch regulating valve is reduced to 15%, control the opening of the gas branch regulating valve to 15%. Then, continue to reduce the opening of the gas branch regulating valve, while the opening of the air branch regulating valve is maintained at 15%. When the opening of the gas branch regulating valve reaches 10%, the furnace lighting is completed. Top temperature rapid rise stage: After the furnace is lit, the top temperature rapid rise stage begins, so that the dome of the hot blast furnace quickly burns to the set value. At this time, the set gas flow is calculated based on the initial gas heat set value. Through the PID control of the controller, the set gas flow is used as the target value to control the opening of the gas branch pipe regulating valve to determine the actual gas flow. The air consumption set value is adjusted based on the theoretical air consumption and the residual oxygen content in the flue gas measured by the detection mechanism. Smoke temperature control stage: calculate the smoke temperature rise rate in real time, smooth the smoke temperature rise curve by the mean filter method, multiply it by the remaining furnace burning time and add it to the current smoke temperature to get the predicted smoke temperature at the end of furnace burning, subtract it from the set smoke temperature to get the smoke temperature difference, adjust the gas flow set value according to the difference, so that the set smoke temperature is just reached at the end of furnace burning; the air consumption set value is adjusted on the basis of the theoretical air consumption, and the set dome temperature is compared with the actual dome temperature to adjust the setting range of the residual oxygen in the smoke. Furthermore, the air consumption set value is adjusted according to the residual oxygen in the smoke; Furnace closing stage: When the flue gas temperature reaches the set value or the furnace burning time reaches the set time, the furnace is closed.

8. The hot blast stove combustion control method based on coal gas composition and flue gas residual oxygen content according to claim 7, characterized in that: In the stage of rapid rise of top temperature, the method of adjusting the air consumption setting value is to reduce the air consumption setting value based on the theoretical air consumption according to the deviation when the residual oxygen value exceeds the upper limit of the residual oxygen setting range; When the residual oxygen value is lower than the lower limit of the set residual oxygen setting range, the air usage setting value is increased based on the theoretical air usage according to the deviation; When the rapid rise stage of top temperature lasts for 10 minutes or the dome temperature reaches within ±10℃ of the set value, the smoke temperature control stage begins.

9. The hot blast stove combustion control method based on gas composition and flue gas residual oxygen content according to claim 7, characterized in that: During the furnace closing stage, the opening of the gas branch pipe regulating valve before the furnace closing is first recorded, and then divided by the number of adjustments to obtain the opening value of the gas branch pipe regulating valve each time it is closed; Keep the air-fuel ratio unchanged before shutting down the furnace, and adjust the opening of the air branch regulating valve so that the gas flows ahead of the air; Each time the gas branch regulating valve is actuated, there is a delay of 5 seconds before the next furnace closing action. When the opening of the gas branch regulating valve is less than or equal to 5, the gas branch regulating valve will be closed, and then the air branch regulating valve will be closed after a delay of 3 seconds.

10. The hot blast stove combustion control method based on gas composition and flue gas residual oxygen content according to claim 7, characterized in that: The theoretical air consumption calculation formula is: The formula for calculating the heat of gas is: in: M1——theoretical air consumption, M2——actual gas flow, a——excess air coefficient, between 1.2-1.5, Q——actual gas heat, h1——CO ratio in coal gas measured by gas analysis agency, h2——The proportion of H2 in coal gas measured by the gas analysis agency, h3——The proportion of CH4 in coal gas measured by the gas analysis agency, h4——The proportion of O2 in coal gas measured by the gas analysis agency, h5——Gas calorific value measured by gas analysis agency; The calculation formula for flue gas heating rate is: The calculation formula for predicting flue gas temperature is: in: V——Flue gas heating rate, unit: ℃ / min, TE0——Current flue gas temperature, TE n ——Flue gas temperature n seconds ago, TE YC - predict flue gas temperature, Ti SP ——Set the furnace burning time, unit min, Ti——actual furnace burning time, unit min.

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