JP2020118357A - Oxygen ratio control system - Google Patents

Abstract

To provide an oxygen ratio control system which can prevent an oxygen ratio of an air-fuel mixture from being largely disordered from a prescribed value when adjusting an opening of a flow rate regulation valve so that the oxygen ratio of the air-fuel mixture reaches the prescribed value.SOLUTION: An oxygen ratio control system comprises fuel gas supply means 2 having a fuel gas flow rate regulation valve 5, combustion air supply means 10 having a combustion air flow rate regulation valve 13, and a control device 25. The control device 25 comprises: an opening calculation part 26 for calculating target openings of the fuel gas flow rate regulation valve 5 whose oxygen ratio reaches a prescribed value, and the combustion air flow rate regulation valve 13; and a regulation valve control part 28 for controlling motions of the fuel gas flow rate regulation valve 5 and the combustion air flow rate regulation valve 13 so that opening times from prescribed openings up to the respective target openings coincide with one another.SELECTED DRAWING: Figure 1

Description

The present invention relates to an oxygen ratio control system that is attached to a combustion device that burns an air-fuel mixture and controls the oxygen ratio of the air-fuel mixture.

Conventionally, various methods of adjusting the oxygen ratio of the air-fuel mixture supplied to a combustion device such as a burner that combusts the air-fuel mixture have been proposed. As one of them, fuel gas or combustion air supplied to the combustion device has been proposed. There is a method of adjusting the supply flow rate of oxygen, etc. by a flow rate adjusting valve.

For example, Patent Document 1 discloses a composite tubular flame burner including a fuel flow rate control valve capable of controlling the flow rate of fuel gas supplied to the burner and an air flow rate control valve capable of controlling the flow rate of oxygen-containing gas. In the composite tubular flame burner, the flow rate of each gas can be changed by appropriately selecting and adjusting the openings of the fuel flow rate adjusting valve and the air flow rate adjusting valve, and the oxygen ratio contained in the air-fuel mixture can be adjusted. It is like this.

JP, 2014-1910, A

However, when the flow rate of the gas supplied to the combustion equipment is adjusted by the flow rate adjusting valve, the flow rate characteristics (flow rate according to the opening) differ for each flow rate adjusting valve, and the target opening degree is reached for each flow rate adjusting valve. The following problems occur due to the difference in the time required to do so.

For example, when the target opening degrees of the two flow rate adjusting valves are so different that the oxygen ratio of the air-fuel mixture of two certain gas species becomes a predetermined value, these two flow rate adjusting valves are set to the same target opening degree. When the opening operation is performed on one side, one of the flow rate adjusting valves may reach the target opening degree and the other flow rate adjusting valve may not reach the target opening degree. In this case, one gas is supplied at a predetermined flow rate, but the other gas is not yet supplied at a predetermined flow rate. Therefore, until the other flow rate adjusting valve reaches the target opening, one gas is excessively supplied and the oxygen ratio of the air-fuel mixture is largely disturbed from the predetermined value. When there is a difference in the flow rate characteristic of each regulating valve, the oxygen ratio may be disturbed more greatly than the predetermined value. Such a problem may similarly occur when performing oxygen enrichment in which oxygen is supplied in addition to combustion air.

Therefore, for example, when the temperature inside the heating furnace is raised using a combustion device, oxygen is supplied during the temperature rise even though a plurality of gases are supplied so that the oxygen ratio of the mixture becomes a predetermined value. The ratio is greatly disturbed from a predetermined value, and as a result, there arises a problem that a change in the temperature inside the furnace adversely affects the processed material and accelerates the deterioration rate of the equipment itself.

The present invention has been made in view of the above circumstances, and when adjusting the opening of the flow rate adjusting valve so that the oxygen ratio of the air-fuel mixture becomes a predetermined value, the oxygen ratio of the air-fuel mixture becomes larger than the predetermined value. It is an object of the present invention to provide an oxygen ratio control system capable of suppressing disturbance.

Characteristic configuration of the oxygen ratio control system according to the present invention to achieve the above object,
An oxygen ratio control system, which is attached to a combustion device for burning an air-fuel mixture containing at least fuel gas and combustion air, and which controls an oxygen ratio of the air-fuel mixture,
A fuel gas flow rate adjusting valve for adjusting the supply flow rate, and a fuel gas supply means for supplying the fuel gas to the combustion device,
Combustion air flow rate adjusting valve for adjusting the supply flow rate, the combustion air supply means for supplying the combustion air to the combustion equipment,
And a control means,
The control means is
An opening degree calculation unit that calculates each target opening degree of the fuel gas flow rate adjustment valve and the combustion air flow rate adjustment valve where the oxygen ratio is a predetermined value,
It is provided with an adjustment valve control unit that controls the operations of the fuel gas flow rate adjustment valve and the combustion air flow rate adjustment valve so that the opening times from a predetermined opening degree to each of the target opening degrees are the same. is there.

According to the above characteristic configuration, when the fuel gas and the combustion air are supplied to the combustion equipment, the target opening of the fuel gas flow rate adjusting valve and the target opening of the combustion air flow rate adjusting valve are set so that the oxygen ratio becomes a predetermined value. Is calculated by the opening degree calculation unit, and the operation of each flow rate adjustment valve is controlled by the adjustment valve control unit so that the opening time of each flow rate adjustment valve from the predetermined opening to the respective target opening becomes the same. By doing so, for example, even if the target opening of the fuel gas flow rate adjusting valve where the oxygen ratio becomes a predetermined value is smaller than the target opening of the combustion air flow rate adjusting valve, the fuel gas flow rate adjustment is performed. The valve and the combustion air flow rate adjusting valve can reach each target opening at the same timing.

Therefore, when adjusting the openings of the fuel gas flow rate adjusting valve and the combustion air flow rate adjusting valve to adjust the oxygen ratio of the air-fuel mixture to a predetermined value, the fuel gas and combustion air It is possible to suppress the occurrence of the problem that one of the flow rates becomes extremely large compared to the other, and the oxygen ratio is greatly disturbed from a predetermined value.

In the present application, the "oxygen ratio" is the ratio of the supplied oxygen amount to the theoretical oxygen amount.

Further, a further characteristic configuration of the oxygen ratio control system according to the present invention has an oxygen flow rate adjusting valve for adjusting the supply flow rate, and further comprises oxygen supply means for supplying oxygen to the combustion equipment,
The opening degree calculation unit further calculates a target opening degree of the oxygen flow rate adjusting valve where the oxygen ratio is a predetermined value,
The adjustment valve control unit operates the fuel gas flow rate adjustment valve, the combustion air flow rate adjustment valve, and the oxygen flow rate adjustment valve so that the opening times from a predetermined opening to each of the target openings are the same. Is in the point of controlling.

In the above characteristic configuration, when the fuel gas, the combustion air and oxygen are supplied to the combustion equipment, the target opening of the fuel gas flow rate adjusting valve and the target opening of the combustion air flow rate adjusting valve are set so that the oxygen ratio becomes a predetermined value. Degree, and the target opening degree of the oxygen flow rate adjusting valve is calculated by the opening degree calculating unit, and the adjusting valve is adjusted so that each flow rate adjusting valve has the same opening time from the predetermined opening degree to the respective target opening degree. The controller controls the operation of each flow rate adjusting valve. As a result, even when the target opening of each fuel adjusting valve where the oxygen ratio becomes a predetermined value is different, all of the fuel adjusting valves can reach each target opening at the same timing.

Therefore, while adjusting the openings of the fuel gas flow rate control valve, the combustion air flow rate control valve, and the oxygen flow rate control valve so that the oxygen ratio of the mixture becomes a predetermined value, the fuel gas, It is possible to suppress the problem that the flow rate of any one or two gases of combustion air and oxygen becomes extremely large as compared with the flow rates of other gases, and the oxygen ratio is greatly disturbed from a predetermined value.

By the way, the combustion air supplied to the combustion equipment may be preheated, for example, when it is used to raise the temperature in the heating furnace to a predetermined target temperature by the combustion equipment. The differential pressure before and after the combustion air flow rate adjusting valve changes depending on the temperature of the combustion air, and if the differential pressure changes, the flow rate corresponding to the opening degree of the combustion air flow rate adjusting valve also changes. Therefore, the target opening of the combustion air flow rate adjusting valve is calculated so that a predetermined oxygen ratio is obtained at a certain temperature, and the combustion air flow rate adjusting valve is operated so as to reach the calculated target opening. Then, although the target opening is finally reached, excess or deficiency of the combustion air may occur and the oxygen ratio may be disturbed from the predetermined value. Therefore, in order to suppress the disturbance of the oxygen ratio from the predetermined value as much as possible, it is preferable to correct the target opening degree of the combustion air flow rate adjusting valve according to the temperature of the combustion air.

That is, a further characteristic configuration of the oxygen ratio control system according to the present invention is that the control unit corrects the target opening of the combustion air flow rate adjusting valve according to the temperature of the combustion air. The point is that it has a section.

According to the above characteristic configuration, the opening degree correction unit can correct the target opening degree of the combustion air flow rate adjustment valve calculated by the opening degree calculation unit to the target opening degree according to the temperature of the combustion air. ..

Therefore, by operating the combustion air flow rate adjusting valve so that the target opening degree according to the temperature of the combustion air is reached, excess or deficiency of the combustion air is less likely to occur, and the oxygen ratio of the air-fuel mixture has a predetermined value. It is possible to suppress a large disturbance from.

By the way, when the fuel gas and the combustion air are supplied to the combustion equipment so that the oxygen ratio of the air-fuel mixture becomes a predetermined value, or the oxygen ratio of the air-fuel mixture of the fuel gas, the combustion air and the oxygen is predetermined. The degree to which the oxygen ratio of the air-fuel mixture is disturbed from a predetermined value when it is supplied to the combustion device so as to have a value of is changed by the opening of each flow rate adjusting valve at the time when the opening operation is started. That is, for example, when the opening degree of one flow rate adjusting valve at the start of the opening operation is 40% and the opening degree of the other flow rate adjusting valve at the start of the opening operation is 0%, Although the corresponding gas is being supplied at the predetermined flow rate, the time during which the gas corresponding to the other flow rate adjusting valve is not yet supplied at the predetermined flow rate becomes long, and as a result, The oxygen ratio of the air-fuel mixture will be greatly disturbed from the predetermined value. Therefore, from the viewpoint of suppressing the oxygen ratio of the air-fuel mixture from being greatly disturbed from the predetermined value, it is preferable that the opening degree of each flow rate adjusting valve at the start of the opening operation is 0%.

That is, as a further characteristic configuration of the oxygen ratio control system according to the present invention, the adjustment valve control unit operates the flow rate adjustment valves so that the opening times from 0% to the target opening degrees are the same. Is in the point of controlling.

According to the above characteristic configuration, when the fuel gas and the combustion air are supplied to the combustion device, or when the fuel gas, the combustion air and oxygen are supplied to the combustion device, each flow rate control valve is 0%. Since the operation of each flow rate adjusting valve can be controlled by the adjusting valve control unit so that the opening time from reaching to each target opening becomes the same, there is a problem that the oxygen ratio of the air-fuel mixture is greatly disturbed from a predetermined value. The generation can be further suppressed.

It is a figure showing the schematic structure of the oxygen ratio control system concerning an embodiment. It is a graph which shows the flow characteristic of a fuel gas flow control valve. It is a graph which shows the flow characteristic of the combustion air flow control valve. It is a graph which shows the flow characteristic of an oxygen flow control valve. It is a figure for demonstrating the aspect which adjusts an oxygen ratio. It is a figure for demonstrating the aspect which adjusts an oxygen ratio. It is a figure for demonstrating the aspect which adjusts an oxygen ratio.

Hereinafter, an oxygen ratio control system according to an embodiment of the present invention will be described with reference to the drawings. In addition, in the present embodiment, a case where the burner (combustion device) for heating the inside of the heating furnace is attached will be described as an example.

As shown in FIG. 1, the oxygen ratio control system 1 according to the present embodiment is a fuel for supplying a fuel gas (13A) to a burner B provided inside and outside one of a plurality of furnace walls in a heating furnace R. A gas supply unit 2, a combustion air supply unit 10 for supplying combustion air to the burner B, an oxygen supply unit 20 for supplying oxygen to the burner B, and a control device (control unit) 25 are provided.

Incidentally, in the present embodiment, the burner B is provided with a pilot burner B1 for ignition, and the fuel gas and the combustion air are supplied to the pilot burner B1. Further, in the present embodiment, the inside of the heating furnace R can be heated by burning the mixture of the supplied fuel gas, combustion air, and oxygen in the burner B, and the temperature inside the heating furnace R can be increased. Can be measured by the in-furnace thermometer T.

The fuel gas supply means 2 includes a fuel gas supply unit 3 for supplying a fuel gas, a main fuel gas supply passage 4 having one end connected to the fuel gas supply unit 3 and the other end connected to a fuel injection unit B2 of the burner B, and A fuel gas flow rate adjusting valve 5 that is provided in the main fuel gas supply path 4 and adjusts the supply flow rate of the fuel gas supplied to the burner B is provided.

Further, the fuel gas supply means 2 is provided with a sub fuel gas supply path 6 which is branched from the fuel gas supply section 3 and the fuel gas flow rate adjusting valve 5 in the main fuel gas supply path 4 and which is connected to the pilot burner B1. The auxiliary fuel gas supply passage 6 is provided with an adjusting valve 7 for adjusting the supply flow rate of the fuel gas to the pilot burner B1.

The combustion air supply means 10 includes a supply air blower 11 for supplying combustion air, and a main combustion air supply passage 12 having one end connected to the supply air blower 11 and the other end connected to the burner B. The main combustion air supply passage 12 is composed of a first main combustion air supply passage 12a and a second main combustion air supply passage 12b connected so as to bypass the first main combustion air supply passage 12a. Further, in the first main combustion air supply passage 12a, a combustion air flow rate adjusting valve 13 for adjusting the supply flow rate of the combustion air supplied to the burner B in order from the air supply blower 11 side, a first main combustion air supply valve 12a A heat exchanger 14 for heating the combustion air flowing in the air supply passage 12a and an air thermometer 15 for measuring the temperature of the combustion air flowing in the main combustion air supply passage 12 are provided. An adjusting valve 16 for adjusting the flow rate of the combustion air flowing downstream of the heat exchanger 14 is provided between the combustion air flow rate adjusting valve 13 and the heat exchanger 14.

The second main combustion air supply passage 12b has one end connected between the combustion air flow rate adjusting valve 13 and the adjustment valve 16 and the other end between the heat exchanger 14 and the air thermometer 15. An adjusting valve 17 for adjusting the flow rate of the combustion air flowing downstream through the second main combustion air supply passage 12b is provided in the second main combustion air supply passage 12b.

In the combustion air supply means 10, the combustion air flowing through the first main combustion air supply passage 12a is heated by the heat exchanger 14 using the high temperature exhaust gas discharged from the heating furnace R as a heating medium. The combustion air flowing through the second main combustion air supply passage 12b is supplied to the burner B without being heated by the heat exchanger 14, while being supplied to the burner B. Therefore, the amount of combustion air flowing through the first main combustion air supply passage 12a and the amount of combustion air flowing through the second main combustion air supply passage 12b are adjusted, that is, the adjustment valves 16 and 17 are opened. By adjusting the degree, the temperature of the combustion air supplied to the burner B can be adjusted.

Further, the combustion air supply means 10 is branched from between the air supply blower 11 and the combustion air flow rate adjusting valve 13 in the main combustion air supply passage 12, and is connected to the pilot burner B1 as the auxiliary combustion air supply passage 18. The auxiliary combustion air supply passage 18 is provided with an adjusting valve 19 for adjusting the supply flow rate of the combustion air to the pilot burner B1.

The oxygen supply means 20 is an oxygen supply unit 21 for supplying oxygen, one end of which is connected to the oxygen supply unit 21, and the other end of which is connected between the burner B in the main combustion air supply passage 12 and the thermometer 15. The channel 22 and the oxygen supply channel 22 are provided with an oxygen flow rate adjusting valve 23 that adjusts the supply flow rate of oxygen supplied to the burner B.

The control device 25 controls the fuel gas flow rate adjusting valve 5 and the combustion air flow rate in which the air ratio and/or the oxygen enrichment ratio of the air-fuel mixture have a predetermined value (in other words, the oxygen ratio of the air-fuel mixture has a predetermined value). The target opening degree of the combustion air flow rate adjusting valve 13 is set in accordance with the opening degree calculating unit 26 that calculates the target opening degree of each of the adjustment valve 13 and the oxygen flow rate adjusting valve 23, and the temperature of the combustion air supplied to the burner B. The operations of the fuel gas flow rate adjusting valve 5, the combustion air flow rate adjusting valve 13, and the oxygen flow rate adjusting valve 23 are controlled so that the opening degree correction unit 27 for correction and the opening time from 0% to each target temperature are the same. The adjusting valve control unit 28 is provided. Further, the control device 25 includes an operating unit 29 for the operator to input a target temperature in the heating furnace R, an air ratio/oxygen enrichment ratio according to the target temperature input from the operating unit 29, and the combustion for supply. A condition determining unit 30 for determining the temperature of the air, a communication unit including a communicator capable of transmitting and receiving data to and from the burner B, the flow rate adjusting valves 5, 13, 23, the thermometers 15 and T, etc. by wire or wireless (not shown). Have). The air ratio is the supply amount of the mixed gas of combustion air and oxygen with respect to the theoretical air amount, and the oxygen enrichment ratio is the oxygen concentration of the mixed gas of combustion air and oxygen.

Further, the control device 25 includes various control units (not shown) that control the operation of the burner B and the opening/closing of the adjusting valves 7, 16, 17, 19, and adjust the opening degree of the adjusting valve 7. By adjusting the supply flow rate of the fuel gas to the pilot burner B1, switching the start/stop of the supply, and adjusting the opening degree of the adjusting valve 16, the supply flow rate of the combustion air to the pilot burner B1 is adjusted or supplied. It is possible to adjust the temperature of the combustion air to be supplied to the burner B by switching the start/stop of the above, or adjusting the opening of the adjusting valves 16 and 17.

The opening degree calculation unit 26 first calculates Cv according to the following formula 1 or formula 2 based on the supply flow rates of the fuel gas, the combustion air, and the oxygen at which the air ratio and/or the oxygen enrichment ratio of the mixture become predetermined values. Calculate the value. In Formula 1 and Formula 2, Q _G is the flow rate [m ³ /h] of the gas in the standard state (15° C., 0.1013 MPa), G _G is the specific gravity of the gas when air is 1, and t Is the temperature of the fluid [° C.], P ₁ is the absolute pressure [MPa] on the primary side (upstream side of the flow rate adjusting valves 5, 13, 23), and P ₂ is the secondary side (flow rate adjusting valves 5, 13, 23). 23 (downstream side) is an absolute pressure [MPa]. When P ₂ >(P ₁ /2), the Cv value can be calculated by Expression 1, and when P ₂ ≦(P ₁ /2), the Cv value can be calculated by Expression 2.

Then, based on the calculated Cv value, the target opening degree is calculated from the relationship (flow rate characteristic) between the Cv value and the opening degree regarding the fuel gas flow rate adjusting valve 5, the combustion air flow rate adjusting valve 13 and the oxygen flow rate adjusting valve 23. .. As an example, FIG. 2 shows a graph of the flow rate characteristics of the fuel gas flow rate adjusting valve 5, FIG. 3 showing the combustion air flow rate adjusting valve 13, and FIG. 4 showing the oxygen flow rate adjusting valve 23.

By the way, the differential pressure before and after the combustion air flow rate adjusting valve 13 varies depending on the temperature of the combustion air, and if the differential pressure changes, the actual flow rate will change even if the opening degree of the combustion air flow rate adjusting valve 13 is the same. Therefore, it is preferable that the target opening degree of the combustion air flow rate adjusting valve 13 considers the temperature of the combustion air supplied to the burner B.

Therefore, the opening degree correction unit 27 refers to the coefficient table in which the opening degree correction coefficients according to the temperature of the combustion air are summarized, and the opening degree corresponding to the temperature of the combustion air determined by the condition determination unit 30. The correction coefficient is extracted, and the target opening degree of the combustion air flow rate adjusting valve 13 calculated by the opening degree calculation unit 26 is multiplied by the correction coefficient to correct the target opening degree in consideration of the temperature of the combustion air. To do. The coefficient table can be created, for example, by conducting an experiment in advance and based on the result. When the temperature of the combustion air is 50°C, the opening correction coefficient is 1.00 or 100°C. For example, when the temperature of the combustion air increases by 50° C., the opening degree correction coefficient increases by 0.10, such as 1.10 when the temperature is 1.10 and when the temperature is 150° C. is 1.20.

The adjustment valve control unit 28 determines the time (open time) from when the opening degree of the fuel gas flow rate adjustment valve 5 reaches the target opening degree calculated by the opening degree calculation unit 26 (open time), and the combustion air flow rate adjustment valve. The time (opening time) from when the opening degree of 13 reaches 0% to the target opening degree corrected by the opening degree correction unit 27, and when the opening degree of the oxygen flow rate adjusting valve 23 changes from 0% to the opening degree calculation unit 26. The operations of the fuel gas flow rate adjusting valve 5, the combustion air flow rate adjusting valve 13, and the oxygen flow rate adjusting valve 23 are controlled so that the time (opening time) until reaching the calculated target opening is all the same time. To do. As such a control method, the operating speed (for example, a constant operating speed) of each flow rate adjusting valve 5, 13, 23 is determined so that the target opening is reached in a predetermined time, and the determined operating speed is determined. The method of operating the flow rate adjusting valves 5, 13, 23 can be exemplified by.

Next, in the oxygen ratio control system 1 according to the present embodiment, regarding the process of adjusting the oxygen enrichment rate to a predetermined value, as shown in FIG. 5, the target temperature of the heating furnace R input by the operation unit 29 is set. Accordingly, while maintaining the air ratio of the air-fuel mixture at the theoretical air ratio λs, the oxygen enrichment rate is increased from a specific oxygen enrichment rate H ₁ to the oxygen enrichment rate H ₂ , and the combustion is performed at a predetermined temperature. An example of changing the state of supplying air to the burner B will be described. The openings of the flow rate adjusting valves 5, 13, 23 in FIG. 5 are examples.

In this case, first, in the opening degree calculation unit 26, the fuel gas necessary for supplying the burner B with the oxygen enrichment rate H ₂ while keeping the air ratio of the mixture at the theoretical air ratio λs Based on the supply flow rates of air and oxygen, the Cv value was calculated for each flow rate adjusting valve 5, 13, 23, and each flow rate adjustment was performed based on the calculated Cv value and the flow rate characteristic graphs shown in FIGS. 2 to 4. The target opening degree of the valves 5, 13, 23 is calculated.

Then, in the opening degree correction unit 27, the temperature of the combustion air supplied to the burner B is set to the target opening degree of the combustion air flow rate adjusting valve 13 calculated by the opening degree calculation unit 26 (the target input to the operation unit 29. By multiplying the opening degree correction coefficient corresponding to the temperature of the combustion air determined by the condition determining unit 30 according to the temperature, the target opening degree in which the temperature of the supplied combustion air is taken into consideration is corrected. Thereafter, the adjusting valve control unit 28 determines the operating speed of each of the flow rate adjusting valves 5, 13, 23 so that each of the flow rate adjusting valves 5, 13, 23 reaches the target opening degree from 0% in a predetermined time. To do.

After that, the adjusting valve control unit 28 determines that the flow rate adjusting valves 5, 13, and 23 are at 0% to a target opening degree (fuel gas flow rate adjusting valve 5 is 70% in FIG. 5) at a predetermined time (for example, 8 seconds). The operating speed of each flow rate adjusting valve 5, 13, 23 is determined so that the air flow rate adjusting valve 13 reaches 80% and the oxygen flow rate adjusting valve 23 reaches 60%. Thereafter, the flow rate adjusting valves 5, 13, which are in the open state (in FIG. 5, the fuel gas flow rate adjusting valve 5 is 70%, the combustion air flow rate adjusting valve 13 is 70%, and the oxygen flow rate adjusting valve 23 is 50%). 23 is closed (the opening is 0%), and the flow rate adjusting valves 5, 13, and 23 are operated so as to reach the respective target openings at the determined operation speed. That is, the opening operation of each of the flow rate adjusting valves 5, 13, 23 is started simultaneously from the state where the opening degree is 0%, and each of the flow rate adjusting valves 5, 13, 23 is made to reach each target opening degree in the same predetermined time.

This allows all of the flow rate adjusting valves 5, 13, 23 to reach the target opening degree at the same timing, although the target opening degree of each of the flow rate adjusting valves 5, 13, 23 is different.

Therefore, according to the oxygen ratio control system 1 of the present embodiment, when the air ratio or the oxygen enrichment ratio of the air-fuel mixture is adjusted to a predetermined value, the fuel gas, the combustion air, and the The flow rate of any one or two gases of oxygen becomes extremely large compared to the flow rates of other gases, and the air ratio or the oxygen enrichment ratio is largely disturbed from a predetermined value, in other words, the oxygen ratio is a predetermined value. Therefore, it is possible to suppress the occurrence of the problem of large disturbance.

[Another embodiment]
[1] In the above embodiment, the oxygen enrichment rate is increased while the air ratio of the air-fuel mixture is kept at the theoretical air ratio λs in accordance with the target temperature of the heating furnace R input by the operation unit 29, and the burner is Although the case where the state of supplying the combustion air heated to B is changed has been illustrated, for example, as shown in FIG. 6, the air of the air-fuel mixture is changed according to the target temperature of the heating furnace R input by the operation unit 29. The oxygen enrichment rate may be increased from the oxygen enrichment rate H ₁ to the oxygen enrichment rate H ₂ while maintaining the ratio at the theoretical air ratio λs, and the combustion air may be normal temperature.
In this case, first, in the opening degree calculation unit 26, the fuel gas necessary for supplying the burner B with the oxygen enrichment rate H ₂ while keeping the air ratio of the mixture at the theoretical air ratio λs Based on the supply flow rates of air and oxygen, Cv values were calculated for the respective flow rate adjusting valves 5, 13, 23, and based on the calculated Cv values and the flow rate characteristic graphs shown in FIGS. The target opening degrees of 5, 13, and 23 are calculated.
Next, in the adjusting valve control unit 28, the flow rate adjusting valves 5, 13 and 23 are set to the target opening degree in a predetermined time (for example, 8 seconds) (in FIG. 6, the fuel gas flow rate adjusting valve 5 is 70%, the combustion air flow rate is 70%). The operation speed of each flow rate adjusting valve 5, 13, 23 is determined so that the adjusting valve 13 reaches 60% and the oxygen flow rate adjusting valve 23 reaches 60%. Thereafter, the flow rate adjusting valves 5, 13, which are in the open state (70% for the fuel gas flow rate adjusting valve 5, 70% for the combustion air flow rate adjusting valve 13 and 50% for the oxygen flow rate adjusting valve 23 in FIG. 6), 23 is closed (the opening is 0%), and the flow rate adjusting valves 5, 13, 23 are operated at the determined operation speed.
This allows all of the flow rate adjusting valves 5, 13, 23 to reach the target opening degree at the same timing, although the target opening degree of each of the flow rate adjusting valves 5, 13, 23 is different.

[2] In the above embodiment, for example, as shown in FIG. 7, the air ratio of the air-fuel mixture is set to the theoretical air ratio λs and the oxygen enrichment is performed in accordance with the target temperature of the heating furnace R input by the operation unit 29. In some cases, the combustion air heated to a predetermined temperature may be supplied to the burner B without combustion (oxygen enrichment rate 0%).
In this case, first, in the opening degree calculation unit 26, based on the supply flow rates of the fuel gas and the combustion air necessary to supply the burner B so that the air ratio of the air-fuel mixture becomes the theoretical air ratio λs, The Cv value is calculated for the flow rate adjusting valves 5 and 13, and the target opening degree of each flow rate adjusting valve 5 and 13 is calculated based on the calculated Cv value and the graphs of the flow rate characteristics shown in FIGS. 2 and 3.
Then, in the opening degree correction unit 27, the temperature of the combustion air supplied to the burner B is set to the target opening degree of the combustion air flow rate adjusting valve 13 calculated by the opening degree calculation unit 26 (the target input to the operation unit 29. By multiplying the opening degree correction coefficient corresponding to the temperature of the combustion air determined by the condition determining unit 30 according to the temperature, the target opening degree in which the temperature of the supplied combustion air is taken into consideration is corrected.
After that, in the adjusting valve control unit 28, the flow rate adjusting valves 5 and 13 are set to the target opening degree in a predetermined time (for example, 8 seconds) (in FIG. 7, the fuel gas flow rate adjusting valve 5 is 70%, and the combustion air flow rate is adjusted). The operation speed of each flow rate adjusting valve 5, 13 is determined so that the valve 13 reaches 90%. Thereafter, the flow rate adjusting valves 5 and 13 that are in the open state (70% for the fuel gas flow rate adjusting valve 5 and 80% for the combustion air flow rate adjusting valve 13 in FIG. 7) are closed (the opening is 0%). Then, the flow rate adjusting valves 5 and 13 are operated at the determined operation speed.
This allows all of the flow rate adjusting valves 5 and 13 to reach the target opening degree at the same timing, although the target opening degrees of the flow rate adjusting valves 5 and 13 are different.

[3] In the above-described embodiment, the oxygen supply means 20 is provided, but the oxygen supply means 20 may not be provided.

[4] In the above embodiment, the opening correction unit 27 that corrects the target opening of the combustion air flow rate adjustment valve 13 is provided, but a configuration that does not include the opening correction unit 27 is adopted. Is also good.

[5] In the above embodiment, the target opening degree of the combustion air flow rate adjusting valve 13 calculated by the opening degree calculating section 26 is corrected according to the temperature of the combustion air determined by the condition determining section 30. However, it is not limited to this.
Even when the heated combustion air is supplied to the burner B, first, the opening degree of each flow rate adjusting valve 5, 13, 23 reaches each target opening degree calculated by the opening degree calculation unit 26 from 0%. The operation speeds of the flow rate adjusting valves 5, 13, 23 are determined so that all the opening times until are the same, and the operation of the flow rate adjusting valves 5, 13, 23 is started at the determined operation speed. After that, the temperature of the combustion air is measured by the air thermometer 15, and the opening degree correction unit 27 extracts the opening degree correction coefficient corresponding to the measured temperature of the combustion air from the coefficient table. The target opening degree of the combustion air flow rate adjusting valve 13 is corrected by multiplying the target opening degree of the combustion air flow rate adjusting valve 13 by the extracted opening degree correction coefficient. The adjustment valve control unit 28 changes the operation speed from that time so that the opening time until reaching the target opening is the same as the opening time until the other flow rate adjusting valves 5 and 23 reach the target opening. Is also good.

[6] In the above-described embodiment, the adjustment valve control unit 28 controls the opening degree of each flow rate adjusting valve 5, 13, 23 from 0% to reach each target opening degree calculated by the opening degree calculation unit 26. Although the operations of the flow rate adjusting valves 5, 13, 23 are controlled so that the time becomes the same, the present invention is not limited to this.
The adjustment valve control unit 28 adjusts the flow rate adjusting valves 5 and 13 so that the flow rate adjusting valves 5, 13, and 23 have the same opening time from the predetermined opening other than 0% to the target opening. , 13, 23 may be controlled.

In the present invention, the air ratio and/or the oxygen enrichment ratio of the air-fuel mixture have a predetermined value, in other words, when adjusting the opening of the flow rate adjusting valve so that the oxygen ratio has a predetermined value, It can be used for an oxygen ratio control system capable of suppressing the air ratio or oxygen enrichment ratio of the air-fuel mixture, that is, the oxygen ratio from being greatly disturbed from a predetermined value.

1 Oxygen ratio control system 2 Fuel gas supply means 5 Fuel gas flow rate control valve 10 Combustion air supply means 13 Combustion air flow rate control valve 20 Oxygen supply means 23 Oxygen flow rate control valve 25 Control device (control means)
26 Opening Calculation Section 27 Opening Correction Section 28 Adjusting Valve Control Section B Burner (Heating Equipment)

Claims (4)

An oxygen ratio control system, which is attached to a combustion device for burning an air-fuel mixture containing at least fuel gas and combustion air, and which controls an oxygen ratio of the air-fuel mixture,
A fuel gas flow rate adjusting valve for adjusting the supply flow rate, and a fuel gas supply means for supplying the fuel gas to the combustion device,
Combustion air flow rate adjusting valve for adjusting the supply flow rate, the combustion air supply means for supplying the combustion air to the combustion equipment,
And a control means,
The control means is
An opening degree calculation unit that calculates each target opening degree of the fuel gas flow rate adjustment valve and the combustion air flow rate adjustment valve where the oxygen ratio is a predetermined value,
An oxygen ratio including an adjusting valve control unit that controls the operations of the fuel gas flow rate adjusting valve and the combustion air flow rate adjusting valve so that the opening times from a predetermined opening degree to each of the target opening degrees are the same. Control system. Having an oxygen flow rate adjusting valve for adjusting the supply flow rate, further comprising an oxygen supply means for supplying oxygen to the combustion equipment,
The opening degree calculation unit further calculates a target opening degree of the oxygen flow rate adjusting valve where the oxygen ratio is a predetermined value,
The adjustment valve control unit operates the fuel gas flow rate adjustment valve, the combustion air flow rate adjustment valve, and the oxygen flow rate adjustment valve so that the opening times from a predetermined opening to each of the target openings are the same. The oxygen ratio control system according to claim 1, which controls the oxygen. The oxygen ratio control system according to claim 1, wherein the control unit includes an opening degree correction unit that corrects the target opening degree of the combustion air flow rate adjusting valve according to the temperature of the combustion air. .. The oxygen according to any one of claims 1 to 3, wherein the adjustment valve control unit controls the operation of each of the flow rate adjustment valves such that the opening time from 0% to each of the target opening amounts is the same. Ratio control system.

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