JP4831582B2 - Combustion device with CO sensor - Google Patents

Description

  The present invention relates to a main heat exchanger that recovers sensible heat in burner flue gas, a sub heat exchanger that recovers latent heat in flue gas that has passed through the main heat exchanger, and CO (monoxide) in the flue gas. The present invention relates to a combustion apparatus with a CO sensor comprising a CO sensor for detecting a carbon) concentration.

  Conventionally, as this type of combustion apparatus, a CO sensor that detects the CO concentration in the combustion exhaust gas downstream of the auxiliary heat exchanger is known (for example, see Patent Document 1).

  The CO sensor includes a cylindrical sensor main body in which a CO detection unit is built, and a gas introduction unit formed of a porous material that guides combustion exhaust gas to the detection unit is provided on one axial end surface of the sensor main body. The reason why the gas introduction part is formed of a porous material instead of a simple opening is to protect the detection part. The detection unit is provided with a detection element that carries an oxidation catalyst and a comparison element that does not carry an oxidation catalyst. The detection element and the comparison element are incorporated in a resistance bridge circuit.

  When the CO sensor is used, the detection element and the comparison element are heated to a predetermined operating temperature (about 200 ° C.) by energization. When CO contacts the detection element in this state, an oxidation reaction of CO by the catalyst occurs. Then, the electrical resistance increases due to the temperature rise of the detection element due to the heat of oxidation reaction, and this resistance change breaks the resistance balance with the comparison element on the resistance bridge circuit, and the output voltage of the CO sensor changes. Based on this, the CO concentration is detected.

  However, the sensitivity of the CO sensor has temperature dependence, and even if the CO concentration is the same, the sensor output varies greatly depending on the temperature of the combustion exhaust gas. Since the temperature of the flue gas upstream of the auxiliary heat exchanger varies in a wide range of about 60 to 250 ° C. depending on the burner combustion amount, the CO concentration in the flue gas upstream of the auxiliary heat exchanger is changed to CO. When detecting with a sensor, it is necessary to perform temperature compensation. On the other hand, the temperature of the combustion exhaust gas on the downstream side of the auxiliary heat exchanger becomes considerably low due to the latent heat recovery in the auxiliary heat exchanger, and even if it changes, it falls within a narrow range of about 30 to 60 ° C. Therefore, when the CO concentration in the combustion exhaust gas downstream of the auxiliary heat exchanger is detected by the CO sensor as in the above-mentioned conventional example, temperature compensation is not required, and the CO concentration is accurately detected by the CO sensor with a simple structure. it can.

However, the combustion exhaust gas downstream of the auxiliary heat exchanger has a low temperature and a relative humidity of nearly 100%. Therefore, in the above conventional example, moisture in the combustion exhaust gas is likely to condense on the CO sensor. And since the combustion product dissolves in the dew condensation water, the combustion product is deposited by repeating the condensation of the CO sensor and the subsequent drying, and the gas introduction part of the CO sensor is clogged with the precipitate, thereby reducing the CO concentration. It may become impossible to detect.
Japanese Patent No. 3744621

  In view of the above points, an object of the present invention is to provide a combustion apparatus with a CO sensor that prevents condensation on the CO sensor and can accurately detect the CO concentration over a long period of time.

The present invention includes a main heat exchanger that recovers sensible heat in the combustion exhaust gas of a burner, a sub heat exchanger that recovers latent heat in the combustion exhaust gas that has passed through the main heat exchanger, and a downstream side of the sub heat exchanger. A combustion apparatus with a CO sensor comprising a CO sensor for detecting the CO concentration in combustion exhaust gas, the CO sensor comprising a cylindrical sensor body incorporating a CO detection part, and a porous material for guiding combustion exhaust gas to the detection part in in one and a forming gas introducing portion, the portion of the sensor body axially spaced from the detection unit, is formed a gas inlet which flue gas flows Rutotomoni, the portion excluding the gas inlet of the sensor body A gas introduction part is provided in the sensor body so as to divide the inner space of the sensor body into an inner chamber that houses the detection part and an outer chamber that communicates with the gas inlet, and downstream of the auxiliary heat exchanger. The gas inlet is below the exhaust passage Or wherein the CO sensor is disposed in a posture facing obliquely downward.

  According to the present invention, since the gas inlet faces downward or obliquely downward, hot air generated by energization heating of the detection unit is likely to stay in the inner chamber and the outer chamber. Then, the sensor body and the gas inlet are heated by the hot air, and the relative humidity of the combustion exhaust gas flowing in from the gas inlet is reduced due to the mixing of the hot air in the outer chamber, so that the moisture in the combustion exhaust gas becomes the inner surface of the sensor body. Condensation at the gas inlet is prevented. As a result, clogging of the gas introduction part due to precipitation of combustion products is prevented, and the CO concentration can be detected with high accuracy over a long period of time.

  Here, the gas inlet may be formed on one end surface in the axial direction of the sensor main body, or may be formed on one side in the circumferential direction of the peripheral surface portion near one end in the axial direction of the sensor main body. When the gas inlet is formed on one axial end surface of the sensor body, the CO sensor is arranged in a vertical posture or an inclined posture with the gas inlet on the lower side in the exhaust passage downstream of the auxiliary heat exchanger. The above effects can be obtained. When the gas inlet is formed on one side in the circumferential direction near the one end of the sensor body in the axial direction, the gas inlet is directed horizontally to the exhaust passage on the downstream side of the auxiliary heat exchanger. By arranging the CO sensor in a posture, the above-described effects can be obtained.

  FIG. 1 shows a combustion apparatus comprising a hot water supply heat source machine. This combustion apparatus includes a combustion housing 2 in which a burner 1 is built. Combustion air is supplied to the combustion housing 2 from below by a combustion fan 3. A main heat exchanger 4 that recovers sensible heat in the combustion exhaust gas of the burner 1 is disposed in the upper part of the combustion housing 2. The main heat exchanger 4 includes a large number of heat absorption fins 4a and a plurality of heat absorption tubes 4b penetrating through the heat absorption fins 4a. These heat absorption tubes 4b are connected in series to form a series of heat exchange channels, and the water flowing through the heat exchange channels absorbs the sensible heat in the combustion exhaust gas and is heated.

  Above the combustion casing 2 is provided an exhaust casing 5 through which the combustion exhaust gas that has passed through the main heat exchanger 4 flows in via an outlet 2a provided at the rear upper surface of the combustion casing 2. An auxiliary heat exchanger 6 that recovers latent heat in the combustion exhaust gas is disposed in the exhaust casing 5. The auxiliary heat exchanger 6 includes a plurality of heat absorption tubes 6 a that are provided horizontally in the exhaust casing 5. Then, cold water is allowed to flow through these heat absorption tubes 6a so that moisture in the combustion exhaust gas is condensed on the outer surface of the heat absorption tubes 6a. Thereby, the water which flows into the auxiliary heat exchanger 6 absorbs latent heat and is heated. The water heated by the auxiliary heat exchanger 6 is sent to the main heat exchanger 4.

  An exhaust cover 7 is provided so as to cover the exhaust casing 5 from the front side to the upper side. Between the exhaust cover 7 and the exhaust casing 5, an exhaust passage 8 extending from the front side to the upper side of the exhaust casing 5 is defined. The combustion exhaust gas that has passed through the auxiliary heat exchanger 6 flows into the exhaust passage 8 from the outlet 5a at the lower front of the exhaust housing 5 and is discharged out of the machine from the exhaust port 7a provided on the upper surface of the exhaust cover 7. ing.

  A CO sensor 9 is disposed in the exhaust passage 8. As shown in FIG. 2, the CO sensor 9 includes a cylindrical sensor body 91 formed of a metal having excellent corrosion resistance such as stainless steel, and a CO detection unit 92 is built in the sensor body 91. The detection unit 92 includes a detection element 92a that carries an oxidation catalyst incorporated in the resistance bridge circuit, a comparison element 92b that also does not carry an oxidation catalyst incorporated in the resistance bridge circuit, and a partition 92c between the elements 92a and 92b. Is provided. In the figure, 92d is a terminal pin for each element 92a, 92b.

  The detection element 92a and the comparison element 92b are always energized, and both elements 92a and 92b are heated to a predetermined operating temperature (about 200 ° C.). When combustion exhaust gas containing CO in this state comes into contact with the detection element 92a, an oxidation reaction of CO occurs on the detection element 92a, and the electric resistance of the detection element 92a changes due to this reaction heat. This resistance change breaks the resistance balance with the comparison element 92b in the resistance bridge circuit, and the output voltage of the CO sensor 9 changes. Based on this voltage change, the CO concentration in the combustion exhaust gas is detected. When the detected CO concentration becomes equal to or higher than a predetermined reference value, safety control is executed to reduce the combustion amount of the burner 1 or stop the combustion.

  The installation part of the CO sensor 9 is surrounded by a sensor cover 10. As shown in FIG. 3, the sensor cover 10 includes a pair of side plate portions 10a and 10a and a baffle plate portion 10b between the side plate portions 10a and 10a, and the baffle plate portion 10b leads to the installation portion of the CO sensor 9. The flow of the combustion exhaust gas is restricted so that the combustion exhaust gas gently flows into the CO sensor 9.

  By the way, the sensitivity of the CO sensor 9 has temperature dependency, and temperature compensation is required when the temperature of the combustion exhaust gas changes over a wide range. Here, the temperature of the combustion exhaust gas on the downstream side of the auxiliary heat exchanger 6 becomes considerably low due to the latent heat recovery in the auxiliary heat exchanger 6, and even if it changes, it falls within a narrow range of about 30 to 60 ° C. Therefore, when the CO sensor 9 is provided in the exhaust passage 8 on the downstream side of the auxiliary heat exchanger 6 as in this embodiment, there is an advantage that the CO concentration in the combustion exhaust gas can be accurately detected without performing temperature compensation. On the other hand, the combustion exhaust gas on the downstream side of the auxiliary heat exchanger 6 has a low temperature and a relative humidity of nearly 100%, and moisture in the combustion exhaust gas is likely to condense on the CO sensor 9.

  Therefore, in the present embodiment, a gas inlet 93 into which combustion exhaust gas flows is formed in a portion of the sensor main body 91 that is separated from the detection unit 92 in the axial direction. The sensor body 91 is formed of a porous material such as a mesh so as to partition the internal space of the sensor body 91 into an inner chamber 91 a that houses the detection unit 92 and an outer chamber 91 b that communicates with the gas inlet 93. A gas introduction unit 94 is provided so that the combustion exhaust gas flowing in from the gas inlet 93 is guided to the detection unit 92 via the outer chamber 91 b and the gas introduction unit 94. More specifically, one end surface in the axial direction of the sensor main body 91 is opened to serve as a gas inlet 93, and the gas inlet 93 is positioned in the sensor main body 91 between the detection unit 92 and the gas inlet 93. 94 is provided.

  The CO sensor 9 is disposed in the exhaust passage 8 on the downstream side of the auxiliary heat exchanger 6 in a vertical posture with the gas inlet 93 on the lower side. According to this, since the gas inlet 93 faces downward, hot air generated by energization heating of the detection element 92a and the comparison element 92b is likely to stay in the inner chamber 91a and the outer chamber 91b. And the sensor main body 91 and the gas introduction part 94 are heated by this hot air, and the relative humidity of the combustion exhaust gas flowing in from the gas inlet 93 decreases due to the mixing of the hot air in the outer chamber 91b, and the moisture in the combustion exhaust gas Is prevented from condensing on the inner surface of the sensor main body 91 and the gas introduction portion 94. As a result, clogging of the gas introduction part 94 due to precipitation of combustion products contained in the combustion exhaust gas is prevented, and the CO concentration can be detected with high accuracy over a long period of time.

  By the way, in this embodiment, the CO sensor 9 is arranged in a vertical posture. However, even if the CO sensor 9 is arranged in an inclined posture in which the gas inlet 93 faces obliquely downward, a practically sufficient dew condensation prevention function is obtained. It is done. However, when the CO sensor 9 is arranged in a horizontal posture, hot air easily flows out from the gas inlet 93, and a sufficient dew condensation prevention function cannot be obtained.

  Next, a second embodiment in which a sufficient dew condensation preventing function can be obtained even when the CO sensor 9 is disposed in a horizontal posture will be described with reference to FIG. The basic structure of the CO sensor 9 of the second embodiment is the same as that of the first embodiment, and the same members and parts as those of the first embodiment are denoted by the same reference numerals as above. Yes.

  The difference of the CO sensor 9 of the second embodiment from that of the first embodiment is that the one end surface in the axial direction of the sensor body 91 is closed and the circumferential surface portion of the sensor body 91 near the one end in the axial direction is the same in the circumferential direction. A gas inlet 93 is formed on the side, and a gas inlet 94 is provided in the sensor body 91 adjacent to the gas inlet 93.

  The CO sensor 9 according to the second embodiment is disposed in the exhaust passage 8 on the downstream side of the auxiliary heat exchanger 6 in a horizontal posture with the gas inlet 93 facing downward. Even in this case, similarly to the first embodiment, hot air generated by energization heating of the detection element 92a and the comparison element 92b is likely to stay in the inner chamber 91a and the outer chamber 91b. Therefore, as in the first embodiment, the function of preventing condensation on the inner surface of the sensor main body 91 and the gas introduction part 94 is obtained, and clogging of the gas introduction part 94 due to precipitation of combustion products is prevented. Thus, the CO concentration can be accurately detected over a long period of time.

  In addition, in 2nd Embodiment, although the formation range of the gas inflow port 93 is limited to the surrounding surface part of the sensor main body 91, gas flow over a part of axial direction one end surface from the surrounding surface part of the sensor main body 9 is carried out. It is also possible to form the inlet 93. In this case, when the CO sensor 9 is disposed in a horizontal posture, it is desirable that the opening portion of the gas inlet at the shaft end of the sensor body 9 is located below the detection element 92a.

  Moreover, in 2nd Embodiment, although the gas introduction part 94 is arrange | positioned with the attitude | position orthogonal to the axis line of the sensor main body 91, it is not restricted to this. That is, as in the third embodiment shown in FIG. 5, the gas introduction portion 94 is obliquely crossed with the axis of the sensor main body 91 so as to straddle the portion adjacent to the gas inlet 93 and the shaft end of the sensor main body 91. It is also possible to arrange in a posture.

  Moreover, although the said embodiment applies this invention to the combustion apparatus which consists of a heat source apparatus for hot-water supply, other than a heat source apparatus provided with a sensible heat recovery type main heat exchanger and a latent heat recovery type sub heat exchanger The present invention can be widely applied as a combustion apparatus with a CO sensor.

Sectional drawing of the combustion apparatus of 1st Embodiment of this invention. The expanded sectional view of the important section of the combustion device of a 1st embodiment. The perspective view of the sensor cover with which the combustion apparatus of 1st Embodiment is equipped. The expanded sectional view of the important section of the combustion device of a 2nd embodiment. The expanded sectional view of the important section of the combustion device of a 3rd embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Burner, 4 ... Main heat exchanger, 6 ... Sub heat exchanger, 8 ... Exhaust passage, 9 ... CO sensor, 91 ... Sensor main body, 92 ... Detection part, 93 ... Gas inflow port, 94 ... Gas introduction part.

Claims (3)

A main heat exchanger that recovers sensible heat in the combustion exhaust gas of the burner, a sub heat exchanger that recovers latent heat in the combustion exhaust gas that has passed through the main heat exchanger, and a combustion heat exhaust gas downstream of the sub heat exchanger A combustion apparatus with a CO sensor comprising a CO sensor for detecting the CO concentration,
The CO sensor includes a cylindrical sensor body having a built-in CO detection unit, and a gas introduction unit formed of a porous material that guides combustion exhaust gas to the detection unit.
The portion of the sensor body axially spaced from the detector, Rutotomoni is formed a gas inlet which flue gas flows, the portion excluding the gas inlet of the sensor body is closed,
In the sensor body, a gas introduction part is provided so as to partition the internal space of the sensor body into an inner chamber that houses the detection part and an outer chamber that communicates with the gas inlet,
A combustion apparatus with a CO sensor, characterized in that a CO sensor is disposed in an exhaust passage on the downstream side of the auxiliary heat exchanger so that the gas inflow port faces downward or obliquely downward.   The gas inlet is formed on one end surface in the axial direction of the sensor body, and the CO sensor is disposed in an exhaust passage on the downstream side of the auxiliary heat exchanger in a vertical posture or an inclined posture with the gas inlet facing downward. The combustion apparatus with a CO sensor according to claim 1.   A horizontal posture in which the gas inlet is formed on one side in the circumferential direction near the one end of the sensor body in the axial direction, and the gas inlet is directed downward in the exhaust passage on the downstream side of the auxiliary heat exchanger. 2. The combustion apparatus with a CO sensor according to claim 1, wherein the CO sensor is disposed.

Images