Automatic optimization combustion control system of blast furnace hot blast stove

Abstract

The invention relates to the technical field of blast furnace hot blast stove control systems, in particular to a blast furnace hot blast stove automatic optimization combustion control system which comprises vault temperature control, flue temperature control, air-fuel ratio optimization and control and realization of PID control theory controlled by a Siemens PID module. The system controls the gas flow in real time to be matched with the air-fuel ratio to adjust the air flow, the defect of manual furnace burning is completely avoided, the furnace burning consistency is very good, and the actual vault and flue temperature can always reach the set value when the set furnace burning time is reached. An optimized classic control mode is adopted, full-automatic furnace control is achieved through multi-section PID, and perfect automatic optimization combustion control is achieved by controlling the gas amount, the air amount and the air-fuel ratio through tests and repeated parameter adjustment.

Description

Technical Field

[0001] The invention relates to the technical field of blast furnace hot blast stove control systems, in particular to an automatic optimization combustion control system for a blast furnace hot blast stove. Background Art

[0002] Based on three aspects of the background, first, the widespread use of automatic optimization combustion systems for blast furnace hot blast stoves today; second, the development of automatic optimization combustion for blast furnace hot blast stoves, especially in blast furnace ironmaking systems in metallurgical systems, automatic optimization combustion systems for blast furnace hot blast stoves are most widely used; third, the application of automatic optimization combustion for blast furnace hot blast stoves in energy conservation and emission reduction; the technological development is not yet mature, especially in optimizing combustion and energy conservation and emission reduction.

[0003] At present, the automatic combustion system of hot blast furnace is more and more widely used in blast furnace ironmaking production system, playing an important role in optimizing combustion control and energy saving, emission reduction and environmental protection. With the development of automatic optimization combustion of hot blast furnace, more and more automatic optimization combustion systems of hot blast furnace are being developed. The most basic function of the automatic optimization combustion system of hot blast furnace is to control and optimize combustion, minimize energy consumption and exhaust gas pollutant emissions as much as possible, complete the optimization combustion on time within the specified time, and greatly reduce the labor intensity of operators.

[0004] The wide application of automatic optimization combustion system for hot blast furnace is also an important background of the present invention. The automatic optimization combustion system for hot blast furnace is a production process control and automatic adjustment system based on PLC (programmable logic controller) control. It can realize real-time optimization combustion by collecting signal data such as temperature and flow on site and controlling gas regulating valve and air regulating valve.

[0005] Therefore, the current blast furnace hot blast stove control system has the following problems: Since the hot blast stove automatic optimization combustion system has very high requirements, it must reach the specified temperature within the specified time with the least energy consumption and the least pollutant emissions. How to effectively optimize combustion becomes the key. With the improvement of computer CPU computing speed, real-time calculation and adjustment are becoming stronger and stronger, making it possible for the hot blast stove automatic combustion system to be adjusted through real-time calculation.

[0006] Most of the existing automatic optimization combustion systems for hot blast furnaces are controlled by the heating curve expert optimization system. The optimization process not only wastes energy but also causes air pollution. In addition, the heating curve of the expert system has too many human factors and is difficult to adapt to the site with greatly changing conditions, and the set parameters are not easy to adjust. In view of this, we propose an automatic optimization combustion control system for hot blast furnaces. Summary of the invention

[0007] The object of the present invention is to provide a blast furnace hot blast stove automatic optimization combustion control system to solve the problems raised in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions: A blast furnace hot blast stove automatic optimization combustion control system, comprising: (1) Vault temperature control When the dome temperature exceeds the dome temperature setting value, the combustion control starts after a delay of a few seconds. Through the Siemens PID temperature control module, the gas and air flow rates are increased or decreased to raise or lower the temperature of the combustion chamber, thereby raising or lowering the dome temperature. When the dome temperature is lower than the setting value, the gas is increased and the air volume is reduced to raise the dome temperature. When the dome temperature is higher than the setting value, the reverse control is performed to keep the dome temperature within the required range until the furnace is burned. (2) Flue temperature control According to the set value of flue temperature and the set value of furnace burning time, the "required flue heating rate" is calculated, and the "actual flue heating rate" is calculated at the same time. The flue temperature rises slowly in the early stage of furnace burning, and rises faster in the later stage of furnace burning. The flue heating rate is not linear. The automatic control system calculates and compares the "required heating rate" and the "actual heating rate" in real time. When the "actual flue heating rate" is lower than the "should be heating rate", the gas and air flow rates are increased. When the "actual flue heating rate" is higher than the "required heating rate", the gas and air flow rates are reduced. When the flue temperature is higher than the set temperature, the burning begins to be reduced, and the gas and air flow rates are reduced to stabilize the flue temperature near the set value until the furnace burning is completed and air is supplied to the blast furnace. (3) Optimization and control of air-fuel ratio Using the best air-fuel ratio will cause the dome temperature to exceed the set value. In the early stage of furnace burning, the furnace should be burned according to the best air-fuel ratio. In the middle and late stages, the air-fuel ratio should be adjusted in real time according to the temperature change rate. (4) PID control theory and implementation of Siemens PID module control The FB41 module is used to regulate and control the gas flow and air flow, and the FB58 module is used to regulate and control the dome temperature and flue temperature. The dome temperature and flue temperature are also controlled by adjusting the gas flow and air flow. All controls are achieved by adjusting the opening of the gas regulating valve and the air regulating valve. Each hot air furnace is automatically controlled by two sets of FB41 modules and two sets of FB58 modules.

[0009] Preferably, the dome temperature is low when the furnace starts to burn, and it is required to heat up quickly to reach the dome temperature setting value. The initial value of the air-fuel ratio is set to the optimal value. This air-fuel ratio makes the dome temperature rise rapidly, especially when it is close to the dome temperature setting value, it can still keep rising. This value is used as the initial value of the air-fuel ratio. After repeated experiments, the optimal air-fuel ratio is found as the initial value for furnace burning.

[0010] Compared with the prior art, the invention has the following beneficial effects: the automatic optimization combustion control system of the blast furnace hot blast stove: Save gas: Through the big data collected by the computer and real-time adjustment of gas and air according to the set parameters, the air-fuel ratio can be accurately controlled to optimize the gas so that it can always burn fully. The heating rate can also ensure the full combustion of the gas, reducing the gas waste caused by human operation.

[0011] Reduce pollutant emissions: By controlling the vault temperature within a reasonable range and optimizing the flue temperature rise curve, energy waste and the generation of nitrogen oxides can be reduced.

[0012] High consistency: The required amount of gas and air is calculated and adjusted in real time according to the set firing time to ensure that the furnace can be fired within the specified time. The consistency is very good, neither over-burning nor under-burning. The firing time, dome temperature and flue temperature can be set arbitrarily within a certain range.

[0013] Not completely dependent on flow rate: multiple groups of optimized PID control algorithms are used to control the gas flow and air flow, but it is not completely dependent on the flow rate. The flow rate can be inaccurate but cannot fluctuate too much. There is a digital filtering algorithm.

[0014] Open and close the gas slowly: open the valve gradually when the furnace starts burning and close the valve gradually when the furnace ends to avoid drastic fluctuations in gas pressure.

[0015] Disturbance-free switching between manual and automatic modes: The entire furnace firing process does not require operator intervention. Manual intervention is possible in emergencies, and switching between manual and automatic modes does not disturb the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The working principle diagram of the FB41 module in the present invention; Figure 2 This is a working principle diagram of the FB58 module in the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The hot blast furnace can provide the blast furnace with the hot air required for ironmaking. It is generally composed of three (two burning and one sending) or four (two burning and two sending) hot blast furnaces, which rotate to provide hot air to the blast furnace uninterruptedly. The hot blast furnace is built with refractory materials and can withstand extremely high temperatures and temperature changes. During the combustion period of the hot blast furnace, the preheated blast furnace gas and preheated combustion air are burned in the combustion chamber. The hot gas generated by the combustion passes through the arch and enters the checkered bricks of the heat storage chamber. The heat is transferred to the checkered bricks through heat exchange, and the exhaust gas passes through the flue heat exchanger and is discharged from the chimney.

[0019] There are three working states of the hot blast stove: "air supply" or "combustion" or "stifling furnace"; Air supply: Cold air is blown into the hot blast furnace through a blower. The cold air exchanges heat with the heat in the checker bricks to generate hot air, which continuously supplies hot air to the blast furnace.

[0020] Combustion: Preheated blast furnace gas and preheated combustion air are burned in the combustion chamber. The combustion exhaust gas passes through the vault and enters the checker bricks in the regenerator, where the heat is transferred to the checker bricks.

[0021] Smoldering furnace: waiting for air to be supplied and combustion to begin.

[0022] Among them, the combustion process is the most critical, and achieving automatic optimized combustion is the key to ensuring normal production of the blast furnace and energy conservation and emission reduction.

[0023] The hot air furnace is fired within a set time by adjusting the amount of gas and air to make the dome temperature and flue temperature reach the specified value, and the dome and flue temperatures are maintained until the air supply or the furnace combustion stops to complete the firing.

[0024] Manual furnace burning is to manually adjust the air regulating valve and gas regulating valve to control the heating speed of the dome temperature and flue temperature so that they reach the specified temperature within the specified time. The operation method is to open the air regulating valve first and then open the gas regulating valve. The valve opening and gas air flow rate are given a fixed value based on previous experience. According to the change of the dome temperature, the gas regulating valve and the air regulating valve are adjusted to make the dome temperature and flue temperature reach the expected value and remain stable. Due to the adjustment based on experience, it is inevitable that the dome temperature and flue temperature cannot stably reach the predetermined value within the predetermined time. Sometimes the gas air pressure is also unstable. In the end, the dome and flue temperatures are either high or low, which is difficult to control. Due to the inability to burn stably, a lot of gas is wasted.

[0025] In the early days, automatic burning of hot blast furnaces was generally an expert system, which converted manual burning experience into computer control data to achieve combustion control. Now there are many kinds of automatic burning control methods. All controls are designed to reduce the workload of operators, reduce unreasonable consumption of gas, and achieve stable hot air supply to the blast furnace.

[0026] The arch is close to the combustion chamber of the hot blast furnace, and the flue is far away from the combustion chamber. The combustion intensity (determined by the amount of gas and air) affects the temperatures of both places. How to ensure that the arch temperature and the flue temperature are within the set firing time and reach the temperature required to supply air to the blast furnace has become a difficulty in automatic firing.

[0027] The system of the present invention controls the gas flow in real time and adjusts the air flow in coordination with the air-fuel ratio, completely avoiding the defects of manual furnace burning. The furnace burning consistency is very good. When the set furnace burning time is reached, the actual vault and flue temperature also reach the set value. The optimized classic control method is adopted, and the multi-stage PID realizes the full-automatic furnace burning control. By controlling the gas volume, air volume and air-fuel ratio, after testing and repeated adjustment of parameters, perfect automatic optimization combustion control is realized.

[0028] Specifically, the present invention provides a blast furnace hot blast stove automatic optimization combustion control system, comprising: (1) Vault temperature control The dome temperature is the key to ensuring the air supply temperature to the blast furnace. Controlling the appropriate dome temperature can reduce combustion energy consumption. Maintaining the dome temperature within a stable range is conducive to continuous air supply to the blast furnace.

[0029] The air-fuel ratio is the ratio of air to fuel during combustion. When the furnace starts burning, the dome temperature is low, and it is required to heat up quickly to reach the dome temperature setting value. The initial value of the air-fuel ratio is set to the optimal value. This air-fuel ratio makes the dome temperature rise rapidly, especially when it is close to the dome temperature setting value, it can still rise. This value is used as the initial value of the air-fuel ratio. After repeated tests, the optimal air-fuel ratio is found as the initial value of the furnace burning. Since the gas used for combustion is basically stable, the initial value of the air-fuel ratio does not need to be adjusted in real time according to the temperature rise.

[0030] After a period of time, the dome temperature can reach the set value. When the dome temperature exceeds the dome temperature set value, the combustion control will be started after a delay of a few seconds. Through the Siemens PID temperature control module, the gas and air flow rates are increased or decreased to increase or decrease the temperature of the combustion chamber, thereby increasing or decreasing the dome temperature. When the dome temperature is lower than the set value, the gas is increased and the air volume is reduced to increase the dome temperature. When the dome temperature is higher than the set value, reverse control is performed to keep the dome temperature within the required range until the end of the furnace burning.

[0031] (2) Flue temperature control The flue temperature must reach the set value when the furnace is fired. The flue temperature should not be too high or too low. If it is too high, it is easy to cause damage to the hot blast furnace grate (equipment), and if it is too low, the air supply duration cannot be guaranteed. A reasonable value needs to be set according to the process requirements, and a reasonable furnace firing completion time needs to be set according to the furnace change time to ensure that the flue temperature reaches the set value when the furnace is changed.

[0032] The whole process of furnace burning is to calculate the "required heating rate of the flue" and the "actual heating rate of the flue" according to the set value of flue temperature and the set value of furnace burning time. The flue temperature rises slowly in the early stage of furnace burning, and rises faster in the later stage of furnace burning. The flue heating rate is not linear. The automatic control system calculates and compares the "required heating rate" and the "actual heating rate" in real time. When the "actual heating rate of the flue" is lower than the "should be heating rate", the gas and air flow rates are increased. When the "actual heating rate of the flue" is higher than the "required heating rate", the gas and air flow rates are reduced. When the flue temperature is greater than the set temperature, the burning begins to be reduced, and the gas and air flow rates are reduced to stabilize the flue temperature near the set value until the furnace burning is completed and air is supplied to the blast furnace.

[0033] (3) Optimization and control of air-fuel ratio Theoretically, the optimal air-fuel ratio is conducive to combustion temperature rise. Using the optimal air-fuel ratio, the dome temperature will exceed the set value. The furnace should be burned according to the optimal air-fuel ratio in the initial stage of burning. In the middle and late stages, the air-fuel ratio should be adjusted in real time according to the temperature change rate to achieve the purpose of optimizing combustion and saving gas. The air-fuel ratio has a certain range. It can neither make the temperature too high or too low nor cause incomplete combustion to produce CO1. The upper and lower limits of the air-fuel ratio are set to ensure reasonable combustion.

[0034] (4) PID control theory and implementation of Siemens PID module control PID regulation is a commonly used classic regulation method, which is proportional integral differential regulation. It performs PID operation on the deviation between the set value and the measured value, sums these values ​​and outputs them, and uses the output value to control the device action. After the device is activated, the deviation between the set value and the measured value can be reduced. P is proportional, I is integral, and D is differential.

[0035] When compiling the regulation program, the present invention selects two PID modules provided by Siemens PLC, FB41 module conventional continuous control module and FB58 module continuous temperature control module for regulation and control.

[0036] like Figure 1 and Figure 2 As shown in the figure: PV_IN measurement value: input value of the controlled object on site SP_INT set value: the value you want to control MAN manual value: output value given in manual mode (valve position given) MAN_ON manual automatic switch: when it is zero, it will be put into automatic DEADB_W Deadband: Deviation within this range is not adjusted GAIN ratio: proportional gain value TI integration: integration time TD Differential: Differential Time LMN output value: output value of PID module (valve position setting).

[0037] The present invention uses FB41 module to regulate and control gas flow and air flow, and uses FB58 module to regulate and control dome temperature and flue temperature. The dome temperature and flue temperature are also controlled by regulating gas flow and air flow. All controls are achieved by adjusting the opening of the gas regulating valve and the air regulating valve. The entire hot blast stove automatic burning system is a rather complex cascade regulation system (cascade regulation is a set of PID output controlling another set of PID given). Each hot blast stove uses two sets of FB41 modules and two sets of FB58 modules to achieve automatic control.

[0038] These two PIDs are similar. The default condition of the FB41 module is that there is no differential and only PI regulation. The FB58 module is an excellent function block for temperature control. Temperature control is the most difficult of all controls, especially combustion control. The temperature hysteresis is very large and difficult to stabilize. The control effect of the FB58 module is good.

[0039] The setting requirements of PID adjustment parameters are very high. To stabilize the controlled object within the required range, the valve cannot be operated frequently, which can easily damage the valve. The FB58 module has a self-tuning function, but due to the high requirements of the hot air furnace, this function cannot be used. You can only manually adjust the parameters to stabilize the controlled parameters and prevent the valve from operating frequently. The four modifiable parameters on the screen are: proportional, integral, differential and dead zone.

[0040] It is not difficult to see from the above content that the blast furnace hot blast stove automatic optimization combustion control system of this embodiment: Save gas: Through the big data collected by the computer and real-time adjustment of gas and air according to the set parameters, the air-fuel ratio can be accurately controlled to optimize the gas so that it can always burn fully. The heating rate can also ensure the full combustion of the gas, reducing the gas waste caused by human operation.

[0041] Reduce pollutant emissions: By controlling the vault temperature within a reasonable range and optimizing the flue temperature rise curve, energy waste and the generation of nitrogen oxides can be reduced.

[0042] High consistency: The required amount of gas and air is calculated and adjusted in real time according to the set firing time to ensure that the furnace can be fired within the specified time. The consistency is very good, neither over-burning nor under-burning. The firing time, dome temperature and flue temperature can be set arbitrarily within a certain range.

[0043] Not completely dependent on flow rate: multiple groups of optimized PID control algorithms are used to control the gas flow and air flow, but it is not completely dependent on the flow rate. The flow rate can be inaccurate but cannot fluctuate too much. There is a digital filtering algorithm.

[0044] Open and close the gas slowly: open the valve gradually when the furnace starts burning and close the valve gradually when the furnace ends to avoid drastic fluctuations in gas pressure.

[0045] Disturbance-free switching between manual and automatic modes: The entire furnace firing process does not require operator intervention. Manual intervention is possible in emergencies, and switching between manual and automatic modes does not disturb the production process.

[0046] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A blast furnace hot blast stove automatic optimization combustion control system, comprising: (1) Vault temperature control When the dome temperature exceeds the dome temperature setting value, the combustion control starts after a delay of a few seconds. Through the Siemens PID temperature control module, the gas and air flow rates are increased or decreased to raise or lower the temperature of the combustion chamber, thereby raising or lowering the dome temperature. When the dome temperature is lower than the setting value, the gas is increased and the air volume is reduced to raise the dome temperature. When the dome temperature is higher than the setting value, the reverse control is performed to keep the dome temperature within the required range until the furnace is burned. (2) Flue temperature control According to the set value of flue temperature and the set value of furnace burning time, the "required flue heating rate" is calculated, and the "actual flue heating rate" is calculated at the same time. The flue temperature rises slowly in the early stage of furnace burning, and rises quickly in the later stage of furnace burning. The flue heating rate is not linear. The automatic control system calculates and compares the "required heating rate" and the "actual heating rate" in real time. When the "actual flue heating rate" is lower than the "should heating rate", the gas and air flow rates are increased. When the "actual flue heating rate" is higher than the "required heating rate", the gas and air flow rates are reduced. When the flue temperature is higher than the set temperature, the burning begins to be reduced, and the gas and air flow rates are reduced to stabilize the flue temperature near the set value until the furnace burning is completed and air is supplied to the blast furnace. (3) Optimization and control of air-fuel ratio Using the best air-fuel ratio will cause the dome temperature to exceed the set value. In the early stage of furnace burning, the furnace should be burned according to the best air-fuel ratio. In the middle and late stages, the air-fuel ratio should be adjusted in real time according to the temperature change rate. (4) PID control theory and implementation of Siemens PID module control The FB41 module is used to regulate and control the gas flow and air flow, and the FB58 module is used to regulate and control the dome temperature and flue temperature. The dome temperature and flue temperature are also controlled by adjusting the gas flow and air flow. All controls are achieved by adjusting the opening of the gas regulating valve and the air regulating valve. Each hot air furnace is automatically controlled by two sets of FB41 modules and two sets of FB58 modules.

2. The automatic optimization combustion control system for hot blast stoves in blast furnaces according to claim 1 is characterized in that: When the furnace starts to burn, the dome temperature is low, and it is required to heat up quickly to reach the dome temperature setting value. The initial value of the air-fuel ratio is set to the optimal value. This air-fuel ratio makes the dome temperature rise rapidly, especially when it is close to the dome temperature setting value, it can still keep rising. This value is used as the initial value of the air-fuel ratio. After repeated experiments, the optimal air-fuel ratio is found as the initial value of the furnace burning.

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