JPH0387513A - Method for controlling combustion in industrial furnace - Google Patents

Abstract

PURPOSE:To considerably reduce NOX generated by combustion by measuring the oxygen concentration of the air for combustion and the velocity of the flow by means of a device for analyzing air for combustion provided between a burner and a valve for regulating the supply of air for combustion. CONSTITUTION:Into each of separate ducts 3 at a position between the burner and the valve, a device 21 for analyzing air for combustion is inserted through the duct wall. The device 21 for analyzing air for combustion is equipped with a probe for an oxygen sensor for measuring the oxygen concentration of the air for combustion, a gaseous object for the measurement, and with a probe for a flow-rate sensor for measuring the quantity of the flow of the gaseous object for the measurement. The oxygen sensor 45 outputs a voltage correspond ing to the oxygen concentration of the air for combustion; the voltage is processed by an O2-computing element 121 and supplied to a Wet/Dry conversion device 125 whereby the measurement value determined in terms of a concentra tion of wet oxygen containing moisture is converted to a value in terms of a concentration of dry oxygen containing no moisture. The dry air value thus obtained is outputted to a control device, which executes a feed-forward control according to the dry air value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a combustion control method for maintaining a good combustion state in an industrial furnace such as a boiler.

(Conventional technology) This year, NO in combustion exhaust gas was
, combustion methods such as a two-stage combustion method, an exhaust gas mixture method, and a flame split method are being implemented using various burners. All of these methods reduce the combustion temperature, reduce the air supply amount, or combine these methods, and reduce so-called thermal NO. This is to suppress the In addition, there is also so-called fuel NO, which is generated due to nitrogen compounds contained in fuel, and combustion under a low oxygen partial pressure is considered desirable as a method for reducing fuel NO. In order to reduce these thermal NO and fuel NO, JP-A-61-1903 discloses that burners are arranged in stages in the furnace, and first, in the lower stage, the air ratio is set to 0.7 or less, that is, the Strong reductive combustion is performed in an extreme fuel excess state where the average oxygen concentration in the total air amount is 17% or less, and then in the middle stage, the air supply amount (air ratio 0.8 to 0
．． 9) to perform combustion, and finally in the upper stage,
A method is described in which a deficit air is supplied and the combustion is carried out with the stoichiometric amount to be consumed for complete combustion of the unburned matter. In order to perform the multistage combustion described in the above publication in a furnace, it is necessary to appropriately supply combustion air to each burner.

In conventional combustion equipment, combustion air first passes through a common duct, then is introduced into individual burner combustion ducts, and is supplied to each burner arranged near the opening in the duct furnace. To check the condition of combustion air,
An oxygen sensor was placed in the common duct and the oxygen concentration was measured only at its representative points.

(Problem to be solved by the invention) However, if the representative point is measured within the common duct, it is not possible to perform multi-stage combustion with an appropriate air supply amount as described above. management) was not carried out, and the reduction of Nl]H in the combustion exhaust gas could not be carried out 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 control the combustion of each burner.

(Means for Solving the Problems) The combustion control method of the present invention is provided in each duct that guides combustion air to each burner in an industrial/industrial furnace using an exhaust gas recirculation method. and a combustion air analyzer projecting within a respective duct between each of the valve means and each of the burners;
The combustion air analyzer measures the oxygen concentration and flow velocity in the combustion air, and feedforward control of combustion in the furnace of an industrial furnace is performed based on the measured values.

(Function) According to the present invention, a combustion air analyzer that measures the oxygen concentration and air flow rate of combustion air in each duct is provided between the burner and valve member of each duct, so that the air is supplied to each burner. Therefore, it is possible to perform feedforward control of the combustion state of each burner. Furthermore, it is possible to correct the combustion variations that conventionally occurred due to different air flow rates in each duct, and to control the combustion state between burners. The combustion balance can be matched. As a result of matching this combustion balance, NO generated by combustion
, can be significantly reduced.

<Example) Embodiments of the present invention will be described based on the drawings.

Figure 1 shows a schematic diagram of an industrial combustion furnace. 1 is the furnace, 3
5 shows a separate duct that introduces combustion air into the furnace 1, supplies combustion air to each burner, and is partitioned into each chamber, and 5 shows a valve member that limits the flow rate of the combustion air flowing into the separate duct 3. . Furnace 1 has separate duct 3
Burners protruding from the furnace 1 are arranged in two stages, with four burners in each stage. The lower burner 7 is a reduction burner, and the upper burner 9 is a main burner. NO bows 11 are formed on the upper furnace walls of these burners, and are configured to perform two-stage combustion.

Further, a common duct 13 is provided to supply combustion air to the separate duct 3.
For example, air with an oxygen concentration of 20.6% sent from the near blower 15 via the air heater 17 is mixed with a portion of the combustion exhaust gas with an oxygen concentration of 2%, sent through the exhaust gas recirculation path 19. 17% combustion air is provided. This is commonly referred to as exhaust gas recirculation. Further, a combustion air analyzer 21 is inserted into each separate duct 3 at a position between each burner and each valve member by 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 Figure 2, the gas to be measured, combustion air (hereinafter referred to as “
"Gas to be measured." An oxygen sensor probe 31 that measures the oxygen concentration of These probes 31 and 33 are integrated at their base end portions, that is, at the terminal box 39, and a mounting flange 41 formed on the terminal box 39 and a wall side flange 4 provided on the wall portion 35.
3 are screwed together to maintain the inserted state of the probes 31 and 33.

As shown in detail in the cross-sectional and side views of FIGS. 3(a) and 3(b), an oxygen sensor 45 in the form of a cylinder with a bottom is mounted on the tip side of the probe 31 for the oxygen sensor, for example, if it is incinerated. Sensor fastener 47 airtightly fixed by scattering method
The probe jig 5 of the probe 31 is attached to the probe 31 by screws etc.
3 is screwed on. Further, around the oxygen sensor 45 mounted in this manner, a heater holder 51 containing a built-in heater 49 (these constitute a heater unit) is fitted into the sensor fastener 47 from the inside, and is integrally bonded with cement. is fixed. Therefore, the oxygen sensor 45, the sensor clasp 47, the heater 49, and the heater holder 51 (ie, the heater unit) are integrated to constitute 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 etc., the probe jig 53 has
The filter holder 55 is fitted, and this filter holder 55 is
A filter 57 is fitted into the opening provided in the opening, and the filter 57 is fixed by screwing a pressing jig 59 having an opening in the center. By the way, a step is provided on the outer periphery of the outer corner of the filter holder 55 on the side that abuts the sensor fastener 47, and a gas passage 60 is formed between the step of the filter holder 55 and the probe jig 53. do. Furthermore, the calibration gas introduction pipe 61 of this filter holder 55
A gas inlet/outlet 69 leading to the internal space 67 is provided to coincide with the opening 63 on the outlet side of the filter holder 5.
A gas outlet 69 is provided at a position of the probe jig 53 that is substantially opposite to the opposite side of the gas inlet/outlet 69 of the probe jig 53. Therefore, a communication space is formed from the internal space 67 to the gas space to be measured. Therefore, the gas to be measured or the calibration gas introduced into the internal space 67 can be quickly discharged to the outside.

For 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 portion of the gas is replaced by gas diffusion and thermal convection due to the difference in concentration of the gas to be measured. and reaches the measurement electrode provided deep inside the oxygen sensor 45. Other gases to be measured are discharged to the outside through a gas inlet/outlet 65, a gas passage 60, and a gas outlet 69, as shown in the figure. Therefore, since this oxygen sensor 45 is provided with a gas flow path from the inflow to the outflow of the gas to be measured, the gas to be measured is quickly introduced into the internal space, and moreover, almost all of the gas to be measured is introduced into the internal space. By performing gas replacement while maintaining an equilibrium state, the responsiveness of the oxygen sensor 45 can be maintained high and protection against thermal shock can be provided at the same time.

Similarly, when introducing a calibration gas to calibrate the output of the oxygen sensor, the calibration gas first passes through the calibration gas introduction tube 61 arranged outside the probe 31, passes through the opening 63 and the gas inlet/outlet 65. The internal 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 blocked. A part of the calibration gas filling the internal space 67 reaches the deep part of the oxygen sensor 45 after being replaced by gas diffusion and gas convection due to the difference in gas concentration.
Contact the measuring electrode. Other calibration gases can be used in the internal space 6.
7 is discharged from the gas outlet 69 via the gas passage 60 when the pressure becomes negative with respect to the pressure of the gas atmosphere to be measured.

Therefore, when the calibration gas is introduced, the measurement electrode of the oxygen sensor 45 is not directly hit by the calibration gas, that is, the measurement electrode is not rapidly cooled.
Furthermore, there is little temperature change in the oxygen sensor between the measurement of the gas to be measured and the introduction of the calibration gas, making highly accurate calibration possible.

On the other hand, on the tip side of the probe 33, as shown in FIG. 4, a constant temperature deformable hot wire flow rate sensor (hereinafter abbreviated as "flow rate sensor J") 71 for measuring the flow rate of the gas to be measured is provided. The flow rate sensor 71 has a bad air element 73 for measuring the flow rate and an air temperature element 75 for temperature compensation, and a mesh filter 72 is provided in the portion of the probe 33 corresponding to the flow rate sensor 71. established,
The gas to be measured is introduced while preventing dust and the like from flowing into the probe 33. By the way, to explain the principle of the bad air element, when the sensor part is placed in the flow of the gas to be measured and is heated by passing a current through the resistance wire as the sensor part, when the gas to be measured hits the sensor part, the resistance wire is cooled down. Its temperature drops. The amount of heat taken away at this time is related to the flow velocity, and the relationship between the flow velocity U (m/s) and the amount of heat dissipated H at this time is K
It is expressed by the formula ing.

tl=(a+b−υ1/′″) (T−Ta)
(1) Here, H: Amount of heat dissipated a, b, +n: Constant determined by the fluid, etc. U: Flow velocity T: Heated object (i.e. temperature of the hot wire) Ta: Temperature of the surrounding fluid However, in a constant temperature type hot wire flow velocity sensor, The same amount of heat as the amount of heat dissipated is supplied by electric 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 rate can be determined by measuring the amount of heat supplied. Therefore, a bridge circuit with a hot wire on one side is constructed, the resistance of this hot wire is R1+, and the current flowing through the hot wire is 1.
．． Then, the amount of heat supplied Q is as follows: Q=In2 ・R, (2) At this time, the amount of heat dissipated H and the amount of heat supplied Q are balanced, so if we set H=Q, 1) 1" ・R, = (a+b -U”')(T-
Ta) (3) Therefore, h T relation and T
If a is known, by measuring the current value IH,
The flow velocity U can be determined. 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 bad wind element 73 is that it is not affected by fluid pressure, viscosity, etc. compared to other differential pressure type flow rate measurement and Karman vortex flow rate measurement, and it is This is particularly effective in the case of commercial air because the draft pressure is large. Further, this type is convenient because it can be made smaller and lighter in terms of structure.

As described above, the probe 31 having the oxygen sensor 45 and the probe 33 having the flow rate sensor 71 are integrated at their proximal ends, and are placed close to each other at the distal ends of the probes so as not to interfere with each other's operations. Because it is placed
The oxygen concentration in the burner combustion air and the combustion air flow rate (ie, oxygen flow rate) can be continuously measured at approximately the same installation point.

Next, as a modification of the mounting structure of the oxygen sensor 45 to the tip of the probe 11, as shown in the cross-sectional view of the main part in FIG. A cylindrical sensor support tube 85 made of metal is inserted, and this sensor support tube 85 has an outward flange 87;
A cylindrical oxygen sensor 91 with a bottom is fitted into an opening 90 provided in the truncated conical portion 89 with its bottom facing the flange side. .

Furthermore, a cylindrical gas-to-be-measured introduction pipe 95 having an outward flange 93 is inserted into the sensor support pipe 85 from the outside,
The sensor support tube 85 and the measured gas introduction tube 95 can be fixed to the probe 11 by screwing them to the inward flange 83 with bolts or the like in the areas of their outward flanges 87 and 93. By the way, a calibration gas introduction pipe 84 is provided that penetrates the inward flange 83 and the outward 7 flange 87, and the calibration gas passes through the gap formed between the sensor support pipe 85 and the gas to be measured introduction pipe 95 to the oxygen sensor. I have it sent to 91. In addition, in the flange side port 97 of the gas introduction pipe 95 to be measured,
A porous ceramic filter 99 for dust removal is adhered by means such as alumina cement.

Inside the probe 11, a stainless steel support fitting 101 inserted from the proximal end of the probe extends concentrically with the probe 11, and the reference gas is diffused between the support fitting 101 and the probe 11. We are trying to get an influx of people.

Further, a temperature detection means 103 for measuring the temperature near the oxygen sensor, such as a thermocouple, is attached to the support fitting 101 by a mounting fitting 105. In addition, support metal fittings 1
A heater support tube 115 having an annular heater 113 is connected to the tip of the heater support tube 115 via a joining flange 109. An electrical contact 117 is provided on the inner wall of the heater support tube 115 via an insulator 118, and the contact 117 can be composed of a contact terminal and a concave ring that holds the contact terminal. . With such a configuration, when the oxygen sensor is inserted into the contactor 117, it can be electrically connected to an electrode provided on a predetermined outer surface of the oxygen sensor.

The device configured in this manner has the gas to be measured inlet pipe 95 and the sensor support pipe 8 when all its parts are attached.
A cylindrical gap is formed between the sensor support tube 85 and the gas outlet of the calibration gas introduction tube 84 that extends into the gap through the sensor support tube 85. Gas is blown out from the outer periphery of the base toward the tip. Furthermore, since the surface area of this gap itself is large, heat is efficiently transferred from the heater 113 located near the gap across the tube walls of the cell support tube 85 and the heater support tube 115 to the calibration gas. Therefore, it is possible to reduce the rapid cooling of the detection cell, that is, the disturbance in temperature control caused by spraying the calibration gas having a large temperature difference with the gas to be measured onto the detection cell.

Next, a measurement value processing circuit in the combustion air analyzer 21 will be explained.

In the block diagram shown in FIG.
The output voltage corresponding to the oxygen concentration of the combustion air is connected to the oxygen sensor 45 from the oxygen sensor 45.
There, the oxygen sensor 45 is controlled, and various processes such as linearizing the relationship between output voltage and oxygen concentration, calibrating, and correcting the pressure are performed. 0□Arithmetic unit 1
The output voltage processed in 21 is
The oxygen is supplied to the Wet/Dry converter 125 connected to 1, where a process is performed to convert the measured value of the wet oxygen concentration containing water into the measured value of the dry oxygen concentration that does not contain water. This measured value of dry air is output to a control device (not shown), and the control device performs feedforward control based on this value. This Wet/Dry converter 12
The data necessary for the operation in step 5 is provided at the input terminals O and F.
From there, it is input to the Wet/Dry converter 125 via the air ratio calculator 129 and the mixture ratio calculator 127.

Also, the current 1. measured in the bad wind element 73 and the wind temperature element 75 is shown. and temperature Ta to flow velocity IJ (m/s)
is obtained from equation (3), and the data is output to the mass flow rate calculator 133 connected to these elements. This calculator 133 calculates the mass flow rate M (k
g/S) is performed, and the next stage volumetric flow rate calculator 13
7, the mass flow rate M (kg/s) is converted into a volumetric flow rate (m'/S) based on the data from the l/ρ0 calculator 135, and is output to the control device via the output converter. be done.

Next, to explain each circuit in detail, the air ratio calculator 129
performs calculations based on the following principle. When the fuel is gaseous fuel, the various gas components (%) in the gaseous fuel are CO□
%, C0%, 02%, CH, %, C, H,, %, C5H
12%, N2%, 0°%, 820%, the theoretical air amount Aa (N, 3/N, 3)i;! , ...(4) The volume of each component of the exhaust gas after combustion is GCO, = (
CO2+CO+ Σm −C,H,,)/100
-(5) GHzO= (L +820+ Σ C, It,,)/100 ... (6) GO2= ・A ・(μ ml) ... (7) Volume of exhaust gas G (N ,'/N,')
is G=GCO2+GH20+G口a"GNz=GKl+
μXA Q - (9) Air ratio μ is (7
), from equation (9) (where 0°ECIT: oxygen concentration in combustion exhaust gas)
is required. That is, the air ratio μ is determined from data regarding each composition of the fuel and the wet oxygen concentration in the combustion exhaust gas.

Therefore, data regarding the oxygen concentration of the combustion exhaust gas from the oxygen sensor 45 is input from the input terminal O, data regarding the composition of the fuel is input from the input terminal F, and the air ratio μ is calculated in the air ratio calculator 129. It will be done.

Further, the concentration of each component other than 0□ in the combustion exhaust gas can be calculated as shown in U. The above calculations are also performed by the air ratio calculator.

Note that even when the fuel is 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 gaseous fuel.

Further, the mixture ratio calculator 127 performs calculations based on the following principle.

In the exhaust gas recirculation system, the combustion exhaust gas is
3> Intake, air OA from near blower (i113
), and if the mixing ratio at this time is M, -
The amount of air mixed with humans 01B is Qwn = OA + Mouth EC (m3)... (16) The oxygen concentration in the combustion air at this time is 02wBw (%
), the following equation is obtained from the balance of income and expenditure of 0□ before and after mixing.

Ow,・021! I! =20.6・OA+02ε
Cw・0. ! .

...(17) However, 0□I! ell: Because of the oxygen concentration in the combustion exhaust gas, substituting and rearranging equations (16) and (17), the mixture ratio M becomes, and the mixture ratio M is determined from the oxygen concentration in the combustion exhaust gas and the oxygen concentration in the combustion air. It will be done. Therefore, the mixture ratio calculator 127 contains the oxygen concentration 0 obtained by the oxygen sensor 45.
2. . Oxygen concentration port 2w is input through the input terminal ○ and obtained by the oxygen sensor 45! Iv is input through the 02 calculator 121, and the mixture ratio M is calculated.

The wet10ry converter 125 in the next stage performs calculations to convert wet gas, which is gas from which moisture (H2O) contained in the combustion exhaust gas has not been removed, into dry gas, which is gas from which most of the moisture has been removed. It is a circuit. To explain the principle below, first, wet oxygen concentration 02w++w
(%) is the dry oxygen concentration of 0□1. If D (%), (%) is obtained from equation (19) as follows. That is, 1llet/Dry converter 125
Now, the oxygen concentration in the combustion exhaust gas manually input from the input terminal ○ is 02I:. , the moisture concentration H20icw in the combustion exhaust gas calculated by the air ratio calculator 129 and the mixture ratio calculator 12
From the mixture ratio M calculated in step 7, dry oxygen concentration 02+11B
Processing to calculate D is performed. This dry oxygen concentration o2w
sn is output to the control device and used for control.

On the other hand, in the flow velocity/temperature compensation calculator 131, the bad air element 73
From the current I□ measured by the air temperature element 75 and the fluid temperature Ta, the flow velocity U (+n/5
ec) is processed.

The mass flow rate calculator 137 at the next stage converts the gas flow rate into a mass flow rate, and thus processes are performed based on the principle shown below. First, the mass flow rate m (kg/5ec) is m = U-A
- ρ However, U: duct flow velocity (m/5ec) A: duct cross-sectional area (m') ρ: gas density (kg/m3) By the way, the gas density ρ (kg/m3) is expressed as. Therefore, the data of the duct cross-sectional area A (m''), the duct internal pressure P (sHg), and the duct internal gas temperature 1 (℃) are obtained from the input terminals A, P, and t, respectively, and then 1/ρ
. Gas standard density ρ from the calculator 135. (kg/Nm')
The receiver receives the relevant data and performs arithmetic processing according to equation (21).

Note that the l/ρ0 calculator 135 first calculates CO□ and N20°N2 other than the oxygen concentration 02yaw from the mixture ratio M calculated by the mixture ratio calculator 127 in order to calculate each component of the combustion air.

1+ M Next, from each composition, the standard density ρ of the gas. Find (kg/Nyo3).

ρo 4.429 ・02W11-”1.965・C
[12WBW+0.804 ・N20 wBW+1
．． 251·N2waw /100... (24) Therefore, from the oxygen concentration 0□Ecw in the fuel exhaust gas obtained from the oxygen sensor 45 and the mixture ratio M obtained from the mixture ratio calculator 127, the standard density of gas ρo (kg/ Nm3) is calculated. The standard density ρ of this gas. (kg/Nm3) is manually input to the mass flow rate calculator 133 and volume flow rate calculator 137.

Furthermore, the volumetric flow rate calculator 137 calculates the volumetric flow rate P (m
”/5ec) is given by F=m ・ - (25) ρ0, the mass flow rate M (kg/5ec) obtained by the mass flow rate calculator 133 is given by 1/ρ. ρ0 obtained by the calculator 135 Arithmetic processing is performed within it to divide the air flow rate, and the air flow rate is output.

As described above, based on the oxygen concentration output obtained from the oxygen sensor 52 via each circuit and the air flow rate output obtained from the flow rate sensor 71 via each circuit, the valve member etc. are feed forward controlled to provide combustion air. The supply amount can be adjusted, multistage combustion can be performed appropriately, and as a result, NOi in the combustion exhaust gas can be reduced.

(Effects of the Invention) As is clear from the above description, the present invention provides a combustion air analyzer that measures the oxygen concentration and air flow rate of combustion air and a supply air amount in each duct connected to a combustion burner. Because it is equipped with a valve member to adjust, the combustion state of each burner can be controlled in a feedforward manner.Moreover, control that was conventionally performed based on the theoretical amount of oxygen is now performed based on the actual amount of supplied oxygen, making it more precise. The combustion balance between burners can be matched, the flame temperature (heat curve and heat distribution) can be controlled more precisely, and the amount of oxygen supplied can be relatively low, so these effects are synergistic. In addition to this, it is possible to significantly reduce NO generated by combustion.
Optimum combustion is possible at the initial stage of combustion when starting up an industrial furnace.

[Brief explanation of drawings]

Fig. 1 is an overall schematic diagram showing a combustion device according to an embodiment of the present invention, Fig. 2 is a side view showing a combustion air analyzer of the present invention, and Figs. 3 (a) and (b) are diagrams of an oxygen sensor. 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 modified example of the mounting structure of the oxygen sensor; FIG. 6 is a cross-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 boat 13...Common duct 15...Air blower 17...Air heater
19... Exhaust gas recirculation path 21... Combustion air analyzer 23... Energy saver 25... Oxygen sensor 31
...Oxygen sensor probe 33...Flow rate sensor probe 35...Wall portion 37...Opening 39...
Terminal box 41...Mounting flange 43...Wall side flange 45...Oxygen sensor 47...Sensor fastener 49...Heater 51...Heater holder
52...Sensor unit 53...Probe jig
55... Filter holder 57... Filter
59...Press jig 60...Gas passage 61
...Calibration gas introduction pipe 63...Opening part 65
...Gas inlet/outlet 67...Internal space 69...
- Gas discharge lower 1...flow velocity sensor 72...filter 73...bad air element 75...air temperature element 83...inward flange 84...calibration gas introduction pipe 85...sensor support tube 87... outward flange 89... truncated conical portion 90... opening 91... oxygen sensor 93
...Outward flange 95...Measurement gas introduction pipe 9
9...Ceramic filter 101...Support fitting 103...Temperature detection means 105...Mounting fitting 109...Joining flange 113...Heater 115...Heater support tube 117...Electrical contact Child 118...Insulator 12
1...02 Arithmetic unit 123...Temperature controller 125
-Wet/Dry converter 127...Mixing ratio calculator 129...Air ratio calculator 131...Flow velocity/temperature compensation calculator 133...Mass flow calculator 135...1/ρ. Calculator 137...Volume flow rate calculator Fig. 3 (b) 5 3 Fig. 5 Fig. 6

Claims (1)

[Claims] 1. In an industrial furnace of exhaust gas recirculation type, a valve means provided in each duct that guides combustion air to each burner to adjust the amount of incoming combustion air supplied, and a valve means between each valve means and each burner. Each duct is equipped with a combustion air analyzer installed in a protruding state, and the combustion air analyzer measures the oxygen concentration and flow velocity in the combustion air, and the measured values are used to determine the temperature inside the furnace of an industrial furnace. A combustion control method for an industrial furnace characterized by feedforward control of combustion.