JPH01250745A - Analyzing apparatus of air for burning - Google Patents

Abstract

PURPOSE:To detect the quantity of supply of air for burning which is supplied to each burner, by providing probes having an oxygen sensor and a flow sensor being disposed in an offset manner from the oxygen sensor in relation to a flow of gas to be measured and being in direct contact with the gas to be measured, respectively. CONSTITUTION:A probe 31 for an O2 sensor measuring the concentration of O2 of air for burning, which is a gas to be measured, and a probe 33 for a flow sensor measuring a flow velocity of the gas to be measured are inserted into an opening 37 formed in the wall part 35 of each separate duct, for instance, and the probes 31 and 33 are made integral by a terminal 39. Thereby the probe 31 having the O2 sensor 45 and the probe 33 having the sensor 71 are made integral in a base end part thereof and, in addition, the sensors are disposed in proximity to each other on the fore end sides of the respective probes 31 and 33 so that they do not disturb the respective operations. Therefore, the concentration of O2 in the air for burning of a burner (the gas to be measured) and the flow rate of the burning air (i.e. the flow rate of O2) can be measured continuously at the same point of disposition.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a combustion engine that measures the amount of combustion air supplied to the combustion chamber of an industrial furnace in order to control the combustion state of an industrial furnace such as a boiler. The present invention relates to a commercial air analysis device.

(Conventional technology) This year, NO in combustion exhaust gas was
In order to reduce All of these methods reduce the combustion temperature, reduce the air supply, or combine these methods, and reduce the so-called thermal N sleep that tends to occur in conditions of high temperature and excessive air supply. It is something to suppress. In addition, there is also so-called fuel NO, which is generated due to nitrogen compounds contained in fuel, and combustion under low oxygen partial pressure is considered desirable as a method for reducing fuel NO. In order to reduce these thermal NO and fuel N emissions, Japanese Patent Application Laid-Open No. 1903/1983 discloses that burners are arranged in stages in the furnace, and first in the lower stage, the air ratio is reduced to 0.
．． 7 or less, that is, the average oxygen concentration in the total amount of air supplied is 17
% or less, strong reductive combustion is performed in an extreme fuel surplus state, then combustion is performed in the middle stage by controlling the amount of air supplied (air ratio approximately 0.8 to 0.9), and finally in the upper stage, the insufficient amount of air is removed. A method is described in which the combustion is carried out with the stoichiometric amount being supplied and 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. combustion management) could not be carried out, and NO8 in the combustion exhaust gas could not be effectively reduced.

An object of the present invention is to provide a combustion air analyzer capable of detecting the amount of combustion air supplied to each burner.

(Means for Solving the Problems) The combustion air analyzer of the present invention is inserted through the wall of a duct partitioned into each chamber for supplying combustion air to the burner of an industrial furnace. Combustion characterized by comprising a probe having an oxygen sensor attached to the tip side thereof, and a flow rate sensor also located at the tip side and offset from the oxygen sensor with respect to the gas flow to be measured, with which the gas to be measured comes into direct contact. This is an air analyzer for air use.

(Function) The present invention is based on the fact that in order to optimize the combustion in the furnace of an industrial furnace, it is necessary to measure the amount of combustion air supplied in each duct leading to the burner. If we focus only on the oxygen that is brought into combustion out of this amount of supplied air, we can first determine the amount of supplied air by detecting the oxygen concentration contained in the combustion air and its flow rate. In view of the above requirements, in the present invention, a probe having an oxygen sensor and a flow rate sensor is inserted and arranged so as to measure a representative point within each duct. Moreover, in order to prevent the oxygen sensor from interfering with the operation of the flow rate sensor, they are placed at different levels (offset arrangement) with respect to the gas flow to be measured. Therefore, the oxygen concentration in the combustion air and the combustion air flow rate can be measured continuously by wiping at the same installation point. Furthermore, since both sensors of the probe are small, the diameter of the probe can be made relatively small.

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

Figure 1 shows a schematic diagram of an industrial combustion furnace. ■ 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 ports 11 are formed in 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, combustion air (hereinafter referred to as
An oxygen sensor probe 31 that measures the oxygen concentration of a gas (hereinafter referred to as "measured gas") and a flow rate sensor probe 33 that similarly measures the flow rate of the measured gas are formed, for example, on the wall portion 35 of each separate duct 3. These probes 31 and 33 are integrated at their base ends, that is, the terminal box 39, and a mounting flange 41 formed on the terminal box 39 and a wall side flange provided on the wall 45 are inserted into the opening 37. 4
3 are screwed together to maintain the inserted state of the probes 31 and 33.

Probe 3 for the oxygen sensor, as shown in detail in FIG.
1, an oxygen sensor 45 having a cylindrical shape with a bottom, for example, is screwed onto the probe jig 53 of the probe 31 with a screw or the like via a sensor clasp 47 which is airtightly fixed by, for example, a boundary method. ing.

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. Fixed. Therefore, the oxygen sensor 45, the sensor fastener 47, the heater 49, and the heater holder 51 (i.e., the heater unit) are integrated into the sensor unit 5.
2.

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 matches 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 65 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 exhaust port 69 is provided at a position of the probe jig 53 that substantially faces the opposite side of the gas inlet/outlet port 65 of No. 5. 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 are 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 type flow rate sensor (hereinafter abbreviated as "flow rate sensor") 71 for measuring the flow rate of the gas to be measured is provided. This flow rate sensor 71 has a wind sensing element 73 for measuring the flow rate and an air temperature element 75 for temperature compensation, and a mesh filter is provided in the portion of the probe 33 corresponding to the flow rate sensor 71. 72 is provided,
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 wind sensing 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 serving as the sensor part, when the gas to be measured hits the sensor part, the resistance wire is cooled down. The temperature will drop. 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 expressed by King's equation.

H-(a+b-U "l')(T-Ta)
(1) Here, H: Amount of heat dissipated a, b, m: 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 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. For this reason, a bridge circuit with a hot wire on one side is constructed, and the resistance of this hot wire is set to RI (the current flowing through the hot wire is set to 1 s).
t, the amount of heat supplied Q is Q"IN' ・R
=Q, then 1,"Rn = (a+b' [J
"'" )(T-Ta) (3) Therefore, 1. If the -T relationship and Ta are known, the flow velocity U can be determined by measuring the current value. 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 wind sensing 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 not affected by fluid pressure, viscosity, etc. when flowing into an industrial furnace such as a boiler. This is particularly effective in the case of combustion air, since the draft pressure is high. 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, the 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 31, as shown in the cross-sectional view of the main part in FIG. A metal cylindrical cell support tube 85 is inserted, the cell support tube 85 having an outwardly facing flange 87 and a frusto-conical portion 89.
An oxygen sensor 91 having a cylindrical shape with a bottom is inserted into an opening 90 provided in the
is fitted 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 gas-to-be-measured introduction tube 95 can be fixed to the probe 31 by screwing them to the inward flange 83 with bolts or the like in the areas of their outward seven flanges 87 and 93. By the way, a calibration gas introduction pipe 84 is provided that passes through the right side of the inward flange 83 and the outward flange 87, so that the calibration gas flows into the cell support tube 8.
5 and the gas to be measured is fed to the oxygen sensor 91 through a gap formed between the gas inlet pipe 95 and the gas to be measured. In addition,
A porous ceramic filter 99 for dust removal is adhered to the flange-side port 97 of the gas inlet pipe 95 using alumina cement or the like.

Inside the probe 31, a stainless steel support fitting 101 inserted from the proximal end of the probe extends concentrically with the probe 31, and the reference gas is diffused between the support fitting 101 and the probe 31. 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. Furthermore, a heater support tube 115 having an annular heater 113 is connected to the tip of the support fitting 101 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.

(Effects) As is clear from the above description, the present invention provides a probe having an oxygen sensor and a flow rate sensor inserted into each duct leading to each burner of an industrial furnace such as a boiler.
The oxygen concentration in the combustion air and the combustion air flow rate can be continuously measured at approximately the same measurement point. Furthermore, since both of the sensors are small, the probe diameter can be made relatively small.

[Brief explanation of the drawing]

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 FIG. 3 is a sectional view showing the mounting structure of an oxygen sensor. FIG. 4 is a side view and a plan view showing the internal structure of the flow rate sensor, and FIG. 5 is a sectional view showing a modification of the oxygen sensor mounting structure. ■...Furnace 3...Separate duct 5
...Valve member 7...Burner 9...Burner 11...NO port 13...Common duct 15...Near blower 17...Air heater
19...Exhaust gas recirculation path 21...Combustion air analyzer 25...Oxygen sensor 31...Oxygen sensor probe 33...Flow rate sensor probe 35...Wall part 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...wind sensing element 75...air temperature element 83...inward flange 84...calibration gas introduction pipe 85...sensor support Pipe 87...Outward flange 89...Frost-conical portion 90...Opening 91...Oxygen sensor 93
...Outward flange 95...Measurement gas introduction pipe 9
9...Ceramic filter

Claims (1)

[Claims] 1. An oxygen sensor is inserted through the wall of a duct that is partitioned into each chamber to supply combustion air to the burner of an industrial furnace, and an oxygen sensor is attached to the tip of the duct, and a gas to be measured is attached to the tip of the duct. A combustion air analyzer comprising: a probe having a flow rate sensor that is offset from the oxygen sensor with respect to the flow and is in direct contact with the gas to be measured.