JP2588282B2 - Industrial furnace combustion control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a combustion control method for maintaining a good combustion state of an industrial furnace such as a boiler.

(Prior art) This year, in the furnace of a combustion device, NO
_In order to reduce _x , various burners are used, for example, a combustion system such as a two-stage combustion system, an exhaust gas mixing system, and a flame division system. Any of these methods lowers the combustion temperature or lowers the air supply amount, or a combination of these methods, and is a so-called thermal which is likely to occur at a high temperature and an excessive air supply amount.
It is intended to suppress NO _x. There are also so-called fuel NO _x which produces nitrogen compounds contained in the addition in the fuel cause, as reduction method of the fuel NO _x, there is a combustion at a low oxygen partial pressure is desirable. To reduce these thermal NO _x and fuel NO _x ,
In Japanese Patent Publication No. 61-1903, a burner is arranged in a furnace in stages,
First, in the lower stage, for example, the air ratio is 0.7 or less, that is, strong reduction combustion is performed in an extreme fuel excess state where the average oxygen concentration in the total supplied air amount is 17% or less. Then, in the middle stage, the air supply amount (air ratio 0.8 About 0.9), and finally, in the upper stage, a shortage of air is supplied, and combustion is performed according to a theoretical amount to be consumed for complete combustion of unburned components. In order to perform the multi-stage combustion described in the above publication in the furnace, it is necessary to appropriately supply combustion air to each burner.

In the conventional combustion device, the combustion air first passes through the common duct, and then is separately introduced into the burner combustion duct, and is supplied to each burner disposed near the opening in the duct furnace. In order to check the state of the combustion air, an oxygen sensor was provided in the common duct, and the oxygen concentration at only a representative point was measured.

(Problems to be Solved by the Invention) However, if the representative point is measured in the common duct, the multi-stage combustion cannot be performed with the appropriate air supply amount as described above, that is, the optimal combustion for each burner (combustion) management) is not performed, the reduction of the NO _x in the combustion exhaust gas was not performed effectively.

An object of the present invention is to provide a combustion control method for an industrial furnace that can detect the state of combustion air supplied to each burner and manage the combustion of each burner.

(Means for Solving the Problems) The combustion control method of the present invention relates to a multistage combustion type industrial furnace of an exhaust gas recirculation system, which is provided in individual ducts for guiding combustion air to each burner and flows into the combustion air. A valve means for adjusting the supply amount and a base end provided with an oxygen sensor and a flow rate sensor having a hot-wire type air sensing element provided in a protruding state in an individual duct between each valve means and each burner are integrated. A combustion air analyzer configured to measure oxygen concentration and flow rate of combustion air in each of the individual ducts, and using the measured values to determine the combustion state of each burner of an industrial furnace. Is feedforward controlled.

(Operation) According to the present invention, since the combustion air analyzer for measuring the oxygen concentration and the air flow rate of the combustion air in each duct is provided between the burner and the valve member of each duct,
The amount of air supplied to each burner can be detected,
It is possible to feed forward control the combustion state of each burner, and it is possible to adjust the combustion balance between the burners by correcting the variation in the combustion that has conventionally occurred due to the different air flow rates in each duct. As a result of matching the combustion balance, NO generated by combustion
_x can be significantly reduced.

(Example) An example of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic diagram of an industrial combustion furnace. 1 is a furnace,
Numeral 3 designates a separate duct which introduces combustion air into the furnace 1 and supplies combustion air to each burner and which is partitioned into each chamber.
Denotes valve members for limiting the flow rate of the combustion air flowing into the separate duct 3. In the furnace 1, burners provided so as to protrude from the separate duct 3 to the furnace 1 are arranged in two stages, four in each stage. The lower burner 7 is a reduction burner, and the upper burner 9 is a main burner.
NO port 11 is formed on the upper furnace wall of these burners,
These are configured to perform two-stage combustion.

Further, a common duct 13 for supplying combustion air to the separate duct 3 is provided. The common duct 13 is supplied to the air having an oxygen concentration of, for example, 20.6% sent from the air blower 15 through the air heater 17 to the exhaust gas recirculation path. For example, combustion air having an oxygen concentration of 17% is supplied by mixing a part of the combustion exhaust gas having an oxygen concentration of 2%, which is sent through 19. This is generally called an exhaust gas recirculation system. further,
A combustion air analyzer 21 is inserted into each separate duct 3 at a position between each burner and each valve member, penetrating the pipe wall of each duct.

Next, a specific embodiment of the combustion air analyzer according to the present invention will be described below with reference to FIG.

In FIG. 2, an oxygen sensor probe 31 for measuring the oxygen concentration of combustion air (hereinafter, referred to as a "gas to be measured") as a gas to be measured, and a flow sensor probe for measuring the flow rate of the gas to be measured. 33, for example, are inserted into openings 37 formed in the wall 35 of each separate duct 3, and these probes 31, 33 are integrated at their base end, that is, a terminal box 39, and formed in this terminal box 39. Mounting flange 41,
A wall-side flange 43 provided on the wall portion 35 is screwed together to maintain the insertion state of the probes 31, 33.

As shown in detail in FIGS. 3 (a) and 3 (b) in a sectional view and a side view, on the tip side of the oxygen sensor probe 31, for example, a bottomed cylindrical oxygen sensor 45 is fired. It is screwed to the probe jig 53 of the probe 31 by a screw or the like via a sensor retainer 47 airtightly fixed by a fitting method. Around the oxygen sensor 45 attached in this way, a heater holder 51 containing a heater 49 (which constitutes a heater unit) is fitted into the sensor holder 47 from the inside, and is integrally formed by cement bonding. It is fixed to. Therefore, the oxygen sensor 45, the sensor attachment 47, the heater 49, and the heater holder 51 (that is, the heater unit) have an integral structure to form the sensor unit 52.

On the side of the oxygen sensor 45 exposed to the gas to be measured,
In order to prevent the inflow of dust and the like, a filter holder 55 is fitted to the probe jig 53, and a filter 57 is inserted into an opening provided in the filter holder 55.
Is fixed by screwing a pressing jig 59 having an opening at the center. By the way, a step is provided on the outer peripheral portion of the outer corner on the side where the filter holder 55 abuts on the sensor fastener 47, and the step of the filter holder 55 and the probe jig are provided.
A gas passage 60 is formed between 53. Further, a gas inlet / outlet 69 communicating with the internal space 67 is provided so as to coincide with the opening 63 on the outlet side of the calibration gas introduction pipe 61 of the filter holder 55, and a portion of the filter holder 55 opposite to the gas inlet / outlet 69 is provided. A gas outlet 69 is provided at a position of the probe jig 53 that is substantially opposed. Therefore, a communication space from the internal space 67 to the measured gas space is formed. Therefore, the gas to be measured or the calibration gas introduced into the internal space 67 can be quickly discharged to the outside.

With respect to the oxygen sensor having such a predetermined shape, the gas to be measured passes through the filter 57 and is introduced into the internal space 67, and a part of the gas is subjected to gas replacement due to gas diffusion and thermal convection due to the concentration difference of the gas to be measured. The measurement is performed, and reaches the measurement electrode provided deep inside the oxygen sensor 45. Other measured gases are
As shown in the figure, the gas is discharged to the outside through the gas inlet / outlet 65, the gas passage 60, and the gas outlet 69. Therefore, the oxygen sensor 45 is provided with a gas flow path from the inflow to the outflow of the gas to be measured, so that the gas to be measured is quickly introduced into the internal space, and almost no gas is supplied to the measurement electrode of the oxygen sensor. By performing the gas replacement while maintaining the equilibrium state, it is possible to simultaneously protect the thermal shock while keeping the responsiveness of the oxygen sensor 45 high.

Similarly, at the time of introducing a calibration gas for calibrating the output of the oxygen sensor, first, the calibration gas passes through a calibration gas introduction pipe 61 arranged outside the probe 31, passes through an opening 63 and a gas inlet / outlet 65. The interior space 67 is filled. At this time, since the internal space 67 is in a positive pressure state, the inflow of the gas to be measured is prevented. A part of the calibration gas filled in the internal space 67 reaches the deep portion of the oxygen sensor 45 after gas replacement is performed by gas diffusion and gas convection due to a gas concentration difference, and comes into contact with the measurement electrode. The other calibration gas is discharged from the gas outlet 69 through the gas passage 60 when the internal space 67 becomes a negative pressure with respect to the pressure of the gas atmosphere to be measured. Therefore, the calibration gas does not directly hit the measurement electrode of the oxygen sensor 45 when the calibration gas is introduced, that is, does not rapidly cool, and the temperature of the oxygen sensor between the measurement of the gas to be measured and the introduction of the calibration gas. Enables highly accurate calibration with little change.

On the other hand, a constant-temperature hot-wire flow velocity sensor (hereinafter abbreviated as "flow velocity sensor") 71 for measuring the flow velocity of the gas to be measured is provided on the tip side of the probe 33, as shown in FIG. This flow rate sensor 71 is a wind sensor 73 for measuring the flow rate.
And a wind temperature element 75 for temperature compensation, and a mesh (mesh) filter 72 is provided in a portion of the probe 33 corresponding to the flow velocity sensor 71, so that dust and the like can be introduced into the probe 33. The gas to be measured is introduced while eliminating the inflow. By the way, the principle of the wind sensing element will be described. When a gas to be measured hits a heated sensor portion, which is arranged in a gas flow to be measured and a resistance wire as a sensor is heated, the resistance wire is cooled. The temperature drops. The amount of heat deprived at this time is related to the flow velocity, and the relation between the flow velocity U (m / s) and the amount of heat dissipated H is expressed by King's equation.

H = (a + b · U ^{1 / m} ) (T−Ta) (1) where H: heat dissipation a, b, m: constant determined by fluid, etc. U: flow velocity T: heated object (that is, temperature of hot wire) Ta: Temperature of surrounding fluid However, in the constant-temperature hot-wire flow velocity sensor, the same amount of heat as the amount of heat dissipated is supplied by current, the amount of heat dissipated and the amount of heat supplied are always kept constant, and the resistance temperature is kept constant. Therefore, the flow velocity can be obtained by measuring the amount of supplied heat. Therefore, when a bridge circuit having a hot wire on one side is formed, and the resistance of this hot wire is R _H and the current flowing through the hot wire is I _H , the supplied heat quantity Q is as follows: Q = I _H ² · R _H (2) At this time, the amount of heat dissipated H and the amount of heat Q supplied are balanced, so that if H = Q, then I _H ² · R _H = (a + b · U ^{1 / m} ) (T−Ta) (3) Therefore, I _H −T if the relationship and Ta are known, by measuring the current value I _H, it can be determined velocity U. However, in order to obtain Ta, the temperature of the gas to be measured is measured using the air temperature element 75.

The feature of this hot-wire type air-sensing element 73 is that it is not affected by the pressure, viscosity, etc. of the fluid as compared with other differential pressure type flow measurement, Karman vortex flow measurement, and flows into an industrial furnace such as a boiler. The combustion air is particularly effective because the draft pressure is large. Also, this format is structurally small,
This is convenient because the weight can be reduced.

As described above, the probe 31 having the oxygen sensor 45 and the probe 33 having the flow rate sensor 71 are integrated at the base end thereof, and are close to the tip side of each probe so as not to hinder each other's operation. With the arrangement, the oxygen concentration in the burner combustion air and the combustion air flow rate (that is, the oxygen flow rate) can be continuously measured at substantially the same installation point.

Next, as a modified example of the mounting structure of the oxygen sensor 45 to the tip of the probe 11, as shown in a sectional view of a main part of FIG. A metal cylindrical sensor support tube 85 is inserted, and the sensor support tube 85 includes an outward flange 87 and a frustoconical portion 89, and is provided on the frustoconical portion 89. A cylindrical oxygen sensor 91 with a bottom is fitted into the opening 90 with its bottom facing the flange side.

Further, a cylindrical gas introduction pipe 95 having an outward flange 93 is inserted into the sensor support pipe 85 from the outside, and the sensor support pipe 85 and the gas introduction pipe 95 are connected to the outward flanges 87 and 93. Can be fixed to the probe 11 by screwing it to the inward flange 83 with a bolt or the like in the area of. By the way, a calibration gas introduction pipe 84 that penetrates the inward flange 83 and the outward flange 87 is provided, and the calibration ass passes through a gap formed between the sensor support pipe 85 and the gas introduction pipe 95 to be measured. To be sent to Note that a porous ceramic filter 99 for dust removal is bonded to the flange-side opening 97 of the measured gas introduction pipe 95 by means such as alumina cement.

Inside the probe 11, a stainless steel support fitting 101 inserted from the base end side of the probe extends coaxially with the probe 11, and a reference gas is diffused between the support fitting 101 and the probe 11 by diffusion. I am trying to get in. Further, a temperature detecting means 103 for measuring the temperature near the oxygen sensor, for example, a thermocouple or the like is attached to the support fitting 101 by a mounting fitting 105. Further, a heater support tube 115 having an annular heater 113 is connected to a distal end of the support fitting 101 via a joining flange 109. On the inner wall of the heater support tube 115, an electric contact 117 is provided via an insulator 118.The contact 117 can be constituted by a contact terminal and a concave ring holding the contact terminal. it can. With such a configuration, the oxygen sensor is
When it is inserted into the oxygen sensor, it can be electrically connected to an electrode provided on a predetermined outer surface of the oxygen sensor.

The apparatus configured as described above has the measured gas introduction pipe 95 and the sensor support pipe 85 in a state where all the parts are attached.
And a cylindrical gap is formed between the gap and the calibration gas introduction pipe extending through the sensor support pipe 85 and extending into the gap.
The gas is guided from the gas outlet of 84, and the gas is blown from the outer periphery to the base side of the detection cell toward the tip side. Further, since the gap has a large surface area, the gap efficiently transfers heat to the calibration gas from the heater 113 located in the vicinity of the gap with the cell support tube 85 and the tube wall of the heater support tube 115 therebetween. Therefore, it is possible to reduce rapid cooling of the detection cell, that is, disturbance of the temperature adjustment due to spraying the calibration gas having a large temperature difference from the measured gas to the detection cell.

Next, a processing circuit of the measured value in the combustion air analyzer 21 will be described.

In the block diagram shown in FIG.
An output voltage corresponding to the oxygen concentration of the combustion air is supplied from the oxygen sensor 45 to the O ₂ calculator 121 connected to the oxygen sensor 45, where the oxygen sensor 45 is controlled and the relationship between the output voltage and the oxygen concentration is controlled. Are linearized, calibrated, and pressure-corrected. Processed output voltage in O ₂ calculator 121, Wet / Dry connected to O ₂ calculator 121
It is supplied to the converter 125, where a process of converting the measured value of the wet oxygen concentration containing moisture into the measured value of the dry oxygen concentration containing no moisture is performed. The measured value of the dry air is output to a controller (not shown), and the controller performs feedforward control based on this value. This Wet /
The data necessary for the operation of the dry converter 125 is supplied from the input terminals O and F to the air ratio calculator 129 and the mixture ratio calculator 127.
And is input to the Wet / Dry converter 125.

Further, the flow velocity U (m / s) is obtained from the current I _H and the temperature Ta measured by the wind sensor 73 and the air temperature element 75 according to the equation (3), and the data is used to calculate the mass flow rate connected to these elements. Output to the device 133. In the calculator 133, the flow rate U (m / s) is converted into the mass flow rate m (kg / S) based on the data from the input terminals A, P, and t. at 137, based on data from the 1 / [rho ₀ calculator 135, the mass flow rate m conversion from (kg / s) to the volumetric flow rate F (m ³ / s) is performed, the control device via the output transducer Output to

Next, each circuit will be described in detail.
Performs an operation based on the following principle. When the fuel is a gaseous fuel, various gas components (%) in the gaseous fuel are
_{2%, CO%, H 2} %, CH 4%, C 4 H 10%, C 5 H 12%, N 2%, O 2
% And H ₂ O%, the theoretical air amount A ₀ (N _m ³ / N _m ³ ) And the volume of each component of the exhaust gas after combustion is GCO ₂ = (CO ₂ + CO + Σm · C _m H _n ) / 100 (5) The volume G (N _m ³ / N _m ³ ) of the wet (water-containing) exhaust gas is as follows: G = GCO ₂ + GH ₂ O + GO ₂ + GN ₂ = GK1 + μ × A ₀ (9) The air ratio μ is obtained from the equations (7) and (9). (However, O _2ECW : oxygen concentration in combustion exhaust gas) is required. That is, the air ratio μ is determined from the data on each composition of the fuel and the wet oxygen concentration in the combustion exhaust gas. Therefore, data relating to the oxygen concentration of the combustion exhaust gas from the oxygen sensor 25 is input from the input terminal O, data relating to the composition of the fuel is input from the input terminal F, and the air ratio calculator 12
Within 9 the air ratio μ is determined.

The concentration of each component other than O ₂ in the flue gas is It can be calculated as follows. The above calculation is also performed by the air ratio calculator.

In addition, when the fuel is a solid or liquid fuel, the concentration of each component in the fuel exhaust gas can be calculated in the same manner as in the case of the gaseous fuel.

Further, the mixing ratio calculator 127 performs calculation based on the following principle.

In the exhaust gas recirculation method, the combustion exhaust gas is Q _EC (m ³ )
Uptake, when mixed with air Q _A (m ³⁾ from air blower, when the mixing ratio at this time is M, If mixed air quantity Q _WB is an oxygen concentration of the combustion air of _{Q WB = Q A + Q EC} (m 3) ... (16) In this case Q _2WBW (%) and, mixed before and after the O ₂ balance The following equation is obtained from the relation.

Q _WB · O _2WBW = 20.6 · Q _A + O _2ECM · Q _EC … (17) where O _2ECW : Oxygen concentration in the combustion exhaust gas. Therefore, the mixing ratio M is The mixing ratio M is obtained from the oxygen concentration in the combustion exhaust gas and the oxygen concentration in the combustion air. Therefore, the oxygen concentration O _2ECW obtained by the oxygen sensor 25 is input to the mixing ratio calculator 127 via the input terminal O, and the oxygen concentration O _2WBW obtained by the oxygen sensor 45 is input to the mixing ratio calculator 127 via the O ₂ calculator 121. ,
The calculation of the mixture ratio M is performed.

The next-stage Wet / Dry converter 125 converts the humid gas, which is a gas from which the moisture (H ₂ O) contained in the flue gas has not been removed,
This is a circuit that performs a calculation for calculating a dry gas, which is a gas from which water is almost removed. The principle is explained below. First, when the wet oxygen concentration is O _2WBW (%) and the dry oxygen concentration is O _2WBD (%), From equation (19) From equations (20) and (21), the oxygen concentration in dry gas O _2WBD
(%) Is required. That is, in the Wet / Dry converter 125, the oxygen concentration O 2 _ECW in the flue gas input from the input terminal O and the moisture concentration H ₂ O in the flue gas calculated by the air ratio calculator 129
A process of calculating the dry oxygen concentration O _2WBD from the _ECW and the mixture ratio M calculated by the mixture ratio calculator 127 is performed. This dry oxygen concentration _O2WBD is output to the control device and used for control.

On the other hand, the flow velocity / temperature compensation calculator 131 calculates the flow velocity U (m / sec) in the duct from the current I _H and the fluid temperature Ta measured by the wind sensing element 73 and the wind temperature element 75 according to the equation (3). You.

In the mass flow calculator 133 at the next stage, in order to convert the gas flow rate into the mass flow rate, processing is performed based on the following principle. First, the mass flow rate m (kg / sec) is as follows: m = U · A · ρ, where U: flow velocity in the duct (m / sec) A: duct cross-sectional area (m ² ) ρ: gas density (kg / m ³ ) The gas density ρ (kg / m ³ ) Indicated by Therefore, the data of the duct cross-sectional area A (m ² ), the duct pressure P (mmHg), and the duct gas temperature t (° C.) are received from the input terminals A, P, t, respectively, and 1 / ρ
_The data relating to the gas standard density ρ ₀ (kg / Nm ³ ) is received from the ₀ calculator 135, and a calculation process according to m = U · A · ρ is performed.

In 1 / [rho ₀ calculator 135, first to calculate the components of the combustion air, the mixture ratio calculator 127 CO ₂ from the mixing ratio M calculated other than oxygen concentration O _2WBW in, H ₂ O, N ₂ Ask for.

Next, from these compositions, the standard density ρ _{0 of the} gas (kg / N _m ³ )
Ask for.

ρ ₀ = 1.429 · O _{2WBW +} 1.965 · CO _{2WBW +} 0.804 · H ₂ O _WBW + 1.251 · N _2WBW / 100 (24) Therefore, the oxygen concentration O _2ECW in the fuel exhaust gas obtained from the oxygen sensor 25 and From the mixture ratio M obtained by the mixture ratio calculator 127, the standard density ρ ₀ (kg / Nm ³ ) of the gas is calculated. The standard density ρ ₀ (kg / Nm ³ ) of this gas is input to the mass flow calculator 133 and the volume flow calculator 137.

Further, in the volume flow rate calculator 137, the volume flow rate F (m ³ / se
c) In order given, the mass flow rate computation unit 133 obtained in the mass flow m (kg / sec), the arithmetic processing [rho ₀ obtained in 1 / [rho ₀ calculator 135 is divided is made therein, the air The flow rate is output.

As described above, the oxygen concentration output obtained through each circuit from the sensor unit 52 and the air flow rate output obtained through each circuit from the flow rate sensor 71 are used to feed-forward control the valve members and the like, and the combustion air supply amount can be adjusted, is performed appropriately staged combustion, it is possible to reduce the NO _x in the combustion exhaust gas as a result.

(Effects of the Invention) As is clear from the above description, the present invention provides a combustion air analyzer for measuring the oxygen concentration and the air flow rate of combustion air in each duct connected to the combustion burner, and a supply air amount. By providing a valve member to adjust, the combustion state of each burner can be feed-forward controlled.Moreover, since the control which was conventionally performed based on the theoretical oxygen amount is performed based on the actual supply oxygen amount, it is more precise. The combustion balance between the burners can be matched, the control of the flame temperature (heat curve and heat distribution) becomes more accurate, and the supplied oxygen amount can be made relatively low, so that these effects are synergistic. Accordingly, NO _x generated by combustion can be significantly reduced. Also,
In the initial stage of combustion at the time of starting the industrial furnace, it is possible to optimize combustion.

[Brief description of the drawings]

1 is an overall schematic view showing a combustion apparatus according to an embodiment of the present invention, FIG. 2 is a side view showing an air analyzer for combustion according to the present invention, and FIGS. FIG. 4 is a side view and a plan view showing the internal structure of the flow rate sensor. FIG. 5 is a sectional view showing a modification of the mounting structure of the oxygen sensor. FIG. 2 is a block diagram showing an internal processing circuit of the combustion air analyzer. 1 Furnace 3 Separate duct 5 Valve member 7 Burner 9 Burner 11 NO port 13 Common duct 15 Air blower 17 Air heater 18 Exhaust gas Circulation path 21 ... Combustion air analyzer 23 ... Saver, 25 ... Oxygen sensor 31 ... Oxygen sensor probe 33 ... Flow sensor probe 35 ... Wall, 37 ... Opening 39 ... Terminal Box, 41 Mounting flange 43 Wall flange 45 Oxygen sensor 47 Sensor bracket 49 Heater 51 Heater holder 52 Sensor unit 53 Probe jig 55 … Filter holder 57… Filter 59… Pressing jig 60… Gas passage 61… Calibration gas introduction pipe 63… Opening 65… Gas inlet 67… Internal space 69… Gas Outlet 71: Flow velocity sensor, 72: Filter 73: Sensitive element, 75: Air temperature element 83: Inward flow 84, Calibration gas inlet tube 85 Sensor support tube 87 Outward flange 89 Conical cone 90 Opening 91 Oxygen sensor 93 Outward flange 95 … Measurement gas introduction pipe 99… Ceramic filter 101… Support metal fittings 103… Temperature detecting means 105… Mounting metal fittings 109… Connection flange 113… Heater 115… Heater support pipe 117… contactors, 118 ...... insulator 121 ...... O ₂ calculator, 123 ...... temperature controller 125 ...... Wet / Dry converter 127 ...... mixing ratio computing unit 129 ...... air ratio calculator 131 ...... velocity / temperature compensation calculator 133 ...... mass flow calculator 135 ...... 1 / ρ ₀ calculator, 137 ...... volume flow calculator

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toru Kodachi 24-18 Shinkaicho, Mizuho-ku, Nagoya-shi, Aichi Prefecture Newly-opened house 402 (72) Inventor Katsuhiko Kimura 2--21, Osu, Naka-ku, Nagoya-shi, Aichi 14 ( 72) Inventor Hiroshi Yamada 49-3 Tsurugazawa, Narumi-cho, Midori-ku, Nagoya-shi, Aichi (56) References Japanese Patent Application Laid-Open No. 58-145820 (JP, A) Japanese Utility Model Application Sho 58-132360 (JP, U)

Claims (1)

(57) [Claims] In a multistage combustion type industrial furnace of an exhaust gas recirculation type, valve means are provided in individual ducts for guiding combustion air to each burner, and adjust a supply amount of combustion air flowing into the respective ducts. A combustion air analyzer integrally comprising a means and a base end provided with an oxygen sensor and a flow rate sensor having a hot-wire type air-sensing element provided in a protruding state in individual ducts between the respective burners, An industrial furnace characterized in that the combustion air analyzer measures the oxygen concentration and flow rate in the combustion air in the individual ducts, and feeds forward the combustion state of each burner of the industrial furnace based on the measured values. Combustion control method.