CN101949549A - Flow control method of combustion system - Google Patents

Abstract

The invention discloses a combustion system flow control method, in particular to a combustion system flow control method used in the heating section of a galvanizing or continuous annealing unit. The invention provides a combustion system flow control method capable of quickly reaching a steady state in the combustion system, comprising the following steps: A, first measuring the opening degrees of the gas flow regulating valve and the air flow regulating valve when the temperature and pressure are stable; B, Before burning, set the opening of the gas flow regulating valve and the air flow regulating valve to 80%-100% of the opening when the temperature and pressure are stable, so that the gas burns at this opening; C. Combustion and Run the PID control system. According to the change of load and working conditions, the PID control system uses the gas flow regulating valve and the air flow regulating valve to increase or decrease the fuel and air flow, adjust the temperature and the temperature deviation, so that the whole combustion process can achieve Stable combustion.

Description

Combustion system flow control method

technical field

The invention relates to a combustion system flow control method, in particular to a combustion system flow control method used in the heating section of a galvanizing or continuous annealing unit.

Background technique

In the combustion system, PID (proportional-integral-differential controller) is usually used for control. The PID controller adjusts the deviation of the entire control system according to the PID control principle, so that the actual value of the controlled variable is in line with the process requirements. The predetermined value is the same. Although the PID controller can keep the actual value consistent with the process value in the long-term operation, it is difficult to quickly reach the predetermined process value at the beginning. For example, the combustion system in the heating section of the galvanizing or continuous annealing unit, the diameter of the gas and air pipes is usually between 100mm and 200mm according to the capacity of the heating section, and the mixed combustion must be slightly under-oxygen combustion to meet the requirements for the surface quality of the strip, and the adjustment and control should be done as much as possible. It is possible to ensure that the flow is stable, the fluctuation is small, and the target value of the flow setting is quickly reached. In fact, gas and air flow regulating valves are usually controlled by conventional PID, the flow rate is adjusted from 0M ³ /H to the flow rate set by the process, and the opening of the valve is adjusted from 0% to the required opening through PID adjustment. The adjustment is slow, and at the same time, the valve adjustment is unstable in the small flow range, which leads to unstable and insufficient combustion during the adjustment process, low safety of the combustion system, and affects product quality.

Contents of the invention

The technical problem to be solved by the present invention is to provide a flow control method of the combustion system that can make the combustion system reach a steady state quickly.

The combustion system flow control method that the present invention solves its technical problem adopts, comprises the following steps:

A. First measure the opening of the gas flow regulating valve and the air flow regulating valve when the temperature and pressure are stable;

B. Before combustion, set the opening of the gas flow regulating valve and the air flow regulating valve to 80%-100% of the opening when the temperature and pressure are stable, so that the gas can burn at this opening;

C. Carry out combustion and run the PID control system. The PID control system uses the gas flow regulating valve and the air flow regulating valve to increase or decrease the fuel and air flow, adjust the temperature and the temperature deviation that occurs according to the change of the load and working conditions, so that Make the whole combustion process achieve stable combustion.

Further, in step B, the openings of the gas flow regulating valve and the air flow regulating valve are set to 100% of the openings when the temperature and pressure are stable.

Specifically, in step B, the openings of the gas flow regulating valve and the air flow regulating valve are set to 93.3% of the openings when the temperature and pressure are stable.

Further, in the step B, the flue gas flow regulating valve and the air flow regulating valve are adjusted through a PLC control system.

The beneficial effects of the present invention are: before performing PID control, first give the combustion system flow regulating valve a pre-opening degree, and then perform PID control on the basis of this opening degree, which enables the combustion system to quickly Get the required gas flow, so as to quickly reach the roughly required process conditions. At this time, the PID controller uses its own advantages to control the flow for a long time, so that the entire combustion system is stable. In this way, unfavorable conditions such as unstable and insufficient combustion and low safety of the combustion system at the initial stage of combustion are avoided, and the product quality is improved.

Description of drawings

Fig. 1 is the schematic diagram of equipment used in the present invention;

Fig. 2 is the valve opening-time graph when only using PID control system in embodiment one;

Fig. 3 is the fuel gas flow-time graph when only using PID control system in embodiment one;

Fig. 4 is the valve opening-time graph when embodiment two and only use PID control system;

Fig. 5 is the gas flow-time graph when embodiment two and only use PID control system;

Fig. 6 is the valve opening-time graph when embodiment three and only use PID control system;

Fig. 7 is the gas flow-time graph when embodiment three and only use PID control system;

Parts, parts and numbers in the figure: gas source 1, air source 2, PID control system 3, gas flow regulating valve 4, cut-off valve 5, air flow regulating valve 6, burner 7.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing.

As shown in Figure 1, the present invention comprises the following steps:

A. First measure the opening of the gas flow regulating valve 4 and the air flow regulating valve 6 when the temperature and pressure are stable; the opening when the temperature and pressure are stable here is the opening required by the process, the process conditions and the production environment related to the product.

B. Before combustion, set the openings of the gas flow regulating valve 4 and the air flow regulating valve 6 to 80%-100% of the openings when the temperature and pressure are stable.

C. Carry out combustion and run the PID control system 3. The PID control system 3 uses the gas flow regulating valve 4 and the air flow regulating valve 6 to increase or decrease the fuel and air flow according to the change of the load and working conditions, adjust the temperature and the occurrence of Temperature deviation, so that the entire combustion process can achieve stable combustion. At the beginning of combustion, the entire system is close to a stable combustion state, so after running the PID control system 3, it can quickly reach a stable combustion state.

In order to facilitate the control of the gas flow regulating valve 4 and the air flow regulating valve 6, in step B, the flue gas flow regulating valve and the air flow regulating valve 6 are adjusted by the PLC control system. When setting the pre-opening degree, the required pre-opening degree can be quickly and accurately achieved by using the PLC control system. It is beneficial to improve the efficiency and stabilize the combustion system.

Embodiment one

Taking the galvanized combustion system as an example, the pipe diameter of the gas flow regulating valve 4 is 100mm; the pipe diameter of the air flow regulating valve 6 is 400mm; when the temperature and pressure are stable, the opening of the gas flow regulating valve 4 and the air flow regulating valve 6 Both are 25%, the gas flow rate under this opening is 200M ³ /H, and the air flow rate is 800M ³ /H. Control the combustion system as follows:

A. Adjust the opening of the gas flow regulating valve 4 and the air flow regulating valve 6 to 25% before combustion, and the gas flow regulating valve 4 and the air flow regulating valve 6 in this process are controlled by the PLC control system.

B. Carry out combustion and run the PID control system 3. The PID control system 3 uses the gas flow regulating valve 4 and the air flow regulating valve 6 to increase or decrease the fuel and air flow according to the change of the load and working conditions, adjust the temperature and the occurrence of Temperature deviation, so that the entire combustion process can achieve stable combustion. The PID control system 3 controls the gas flow regulating valve 4 and the air flow regulating valve 6 according to a conventional process.

The comparison of the opening changes of the gas flow regulating valve 4 and the air flow regulating valve 6 between the combustion system using the method of this embodiment and the combustion system using only the PID control system 3 is shown in Figure 2. The combustion system with the opening degree and PID control system 3 reaches a steady state in about 5 seconds, that is, the opening degree is 25%, while the combustion system only using the PID control system 3 reaches a stable opening degree in about 26 seconds. The changes in gas flow caused by this are shown in Figure 3. The gas flow of the combustion system using the preset opening and PID control system 3 reaches a stable value of 200M ³ /H in about 7 seconds, while the combustion system using only PID control system 3 in The gas flow reaches a stable value in about 27 seconds. The stability of the gas flow indicates the stability of the entire process parameters. According to the adjustment scheme of this embodiment, the steady state can be reached 20 seconds earlier, which avoids unstable and insufficient combustion at the beginning, reduces combustion fluctuations, and improves combustion safety. Since the time of the unstable state is greatly shortened, the quality of the product is improved.

Embodiment two

Taking the combustion system in the heating section of the continuous retreat unit as an example, the diameter of the gas flow regulating valve 4 is 100mm; the pipe diameter of the air flow regulating valve 6 is 400mm; when the temperature and pressure are stable, the gas flow regulating valve 4 and the air flow regulating valve 6 The opening degree of each is 20%, the gas flow rate under this opening degree is 150M ³ /H, and the air flow rate is 600M ³ /H. Control the combustion system as follows:

A. Adjust the opening of the gas flow regulating valve 4 and the air flow regulating valve 6 to 16% before combustion, which is 80% of the opening in stability. control system control.

B. Carry out combustion and run the PID control system 3. The PID control system 3 uses the gas flow regulating valve 4 and the air flow regulating valve 6 to increase or decrease the fuel and air flow according to the change of the load and working conditions, adjust the temperature and the occurrence of Temperature deviation, so that the entire combustion process can achieve stable combustion. The PID control system 3 controls the gas flow regulating valve 4 and the air flow regulating valve 6 according to a conventional process.

See Figure 4 for a comparison of the openings of the gas flow regulating valve 4 and the air flow regulating valve 6 between this embodiment and the combustion system using only the PID control system 3, and Figure 5 for the comparison of the gas flow changes. In this embodiment, the opening reaches a steady state in about 4 seconds, and the gas flow reaches a steady state in about 5 seconds. However, the opening of the combustion system using only the PID control system 3 reaches a steady state in 15 seconds, and the gas flow reaches a steady state in 17 seconds. According to the adjustment scheme of this embodiment, the steady state can be reached 12 seconds earlier.

Embodiment three

Taking the combustion system in the heating section of the continuous retreat unit as an example, the diameter of the gas flow regulating valve 4 is 80mm; the pipe diameter of the air flow regulating valve 6 is 300mm; when the temperature and pressure are stable, the gas flow regulating valve 4 and the air flow regulating valve 6 The opening degree of each is 30%, the gas flow rate under this opening degree is 120M ³ /H, and the air flow rate is 480M ³ /H. Control the combustion system as follows:

A. Adjust the opening of the gas flow regulating valve 4 and the air flow regulating valve 6 to 28% before combustion, which is 93.3% of the opening in stability. The gas flow regulating valve 4 and air flow regulating valve 6 in this process are passed through PLC control system control.

B. Carry out combustion and run the PID control system 3. The PID control system 3 uses the gas flow regulating valve 4 and the air flow regulating valve 6 to increase or decrease the fuel and air flow according to the change of the load and working conditions, adjust the temperature and the occurrence of Temperature deviation, so that the entire combustion process can achieve stable combustion. The PID control system 3 controls the gas flow regulating valve 4 and the air flow regulating valve 6 according to a conventional process.

See Figure 6 for a comparison of openings of the gas flow regulating valve 4 and air flow regulating valve 6 between this embodiment and the combustion system using only the PID control system 3 , and see Figure 7 for the comparison of gas flow changes. In this embodiment, the opening reaches a steady state in about 4 seconds, and the gas flow reaches a steady state in about 5 seconds. However, the opening of the combustion system using only the PID control system 3 reaches a steady state in 32 seconds, and the gas flow reaches a steady state in 33 seconds. According to the adjustment scheme of this embodiment, the steady state can be reached 28 seconds earlier.

Claims (4)

1. combustion system flow control methods may further comprise the steps:

A, the aperture of gas flow control valve and air flow rate adjustment valve when at first recording temperature and pressure and stablize;

B, before burning, the 80%-100% of aperture made combustion gas burn under this aperture when the aperture of gas flow control valve and air flow rate adjustment valve was set to temperature and pressure and stablizes;

C, burn and move the PID control system, the PID control system is according to the variation of load and operating mode, utilize gas flow control valve and air flow rate adjustment valve that fuel and air mass flow are increased or reduces, adjust the temperature deviation of temperature and appearance, thereby make whole combustion process reach smooth combustion.

2. combustion system flow control methods as claimed in claim 1 is characterized in that: in the B step, when the aperture of gas flow control valve and air flow rate adjustment valve is set to temperature and pressure and stablizes 100% of aperture.

3. combustion system flow control methods as claimed in claim 1 is characterized in that: in the B step, when the aperture of gas flow control valve and air flow rate adjustment valve is set to temperature and pressure and stablizes 93.3% of aperture.

4. as claim 1,2 or 3 described combustion system flow control methods, it is characterized in that: in the B step, flue gas flow control valve and air flow rate adjustment valve are regulated by the PLC control system.

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