JPS62225803A - Burner - Google Patents

Abstract

PURPOSE:To suppress the formation of NOx and decompose it with a simple constitution and reduce the NO2 content by supplying a reducing fuel such as exceesively high concentra tion fuel around a pre-mixture flame and constituting in a combustion exhaust gas passage a thermal insulation chamber which maintains substantially a constant temperature. CONSTITUTION:A pre-mixture fuel with a mixing ratio larger than a stoichiometric mixture ratio (air ratio>1) is supplied to a burner 2 to form a pre-mixture flame 19 which is a main flame. When a little amount of a reducing gas is supplied to a portion around the flame 19 from an auxiliary fuel inlet opening 9, a reducing flame 20 is formed which encloses the flame 19. With this a large proportion of NOx is decomposed into N2 and O2, and also to form a little amount of CO and an unburned composition. The combustion exhaust gas which was formed at a combustion section ascends to heat resistant bodies 13 and it also raises the temperature of a thermal insulation chamber 14 and constitutes with the aid of the circumferential heat insulation constitution a thermal insulation space of substantially uniform temperature. The small amount of NOx and CO and unburned composition which where formed in the combustion section ascend with the exhaust gas and enter the thermal insulation chamber 14 and three the unburned composition oxidation is promoted and finally it disappears. At the same time most of the NO2 in the NOx is changed into NO2 by thermal dissociation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a gas or petroleum fuel combustor, particularly to an improvement of a combustor for an indoor open type heating appliance, and is intended to make exhaust gas cleaner.

BACKGROUND OF THE INVENTION Recent combustors of this type have been designed to produce cleaner exhaust gases with lower NOx emissions. The main means for this purpose is to lower the flame temperature, and there is a surface combustion type burner shown in this example (FIG. 3). Also, a catalyst is installed in the exhaust gas passage.
or oxidizing unburned matter (for example, JP-A-56-1108)
(No. 15 Publication) Also, a ring element has been proposed, but the former is currently in practical use, but the latter has not yet been put into practical use. Furthermore, NOx reduction often promotes an increase in Go.

Problems to be Solved by the Invention Although efforts have been made to reduce NOx as described above, this is still not sufficient and there is a risk of increased Co generation. Also, epidemiologically, NOx
It is said that NO2 in the air has several times more harmful effects than NO, and as NOx becomes lower, the ratio of NO2 increases, sometimes reaching 6.
Since NO2 occupies the range of 0 to 90 degrees, there are concerns about its impact on the human body in closed spaces such as indoors.

The present invention solves this problem by reducing NOx, (I
The purpose is to reduce ltCO conversion and NO2 generation in exhaust gas.

Means for Solving the Problems In order to solve the above problems, the combustor of the present invention supplies cyclic fuel such as rich fuel (fuel with a stoichiometric air ratio or higher) around the premixed flame, and A heat retention chamber (space) that maintains a substantially constant temperature is configured in this combustion exhaust gas passage.

Effect of the present invention With the above-described configuration, the NOx generated by the premixed flame with low NOx generation is refluxed into N2 and 02 with the surrounding cyclogenic fuel, and the incompletely combusted portion generated here is transferred to the heat retention space. is completely oxidized and the N in the remaining NOx
Low NOx and low Co by thermally dissociating O2 with NOK
1 to achieve low NO2.

Example Embodiments of the present invention will be described below with reference to the blackened drawings.

FIG. 1 is a side sectional view showing the principle of an indoor open type warm air heater using the combustor of the present invention, FIG. FIG. 1 is a perspective view of the burner portion of the combustor.

1 is a casing of a hot air heater, 2 is a rod-shaped burner with a semicircular cross section, and is composed of a primary air port 4 provided opposite a gas nozzle 3, a mixing pipe 5, a mixture chamber 6, and a wire mesh. The flame port 7 forms a surface combustion type burner.

Reference numeral 8 denotes a combustion chamber through which the flame hole 7 of the burner 2 can be seen from below. A plurality of auxiliary fuel ports 9 are provided in the auxiliary fuel chamber 10 at positions around and below the flame hole portion 7 of the burner. This auxiliary fuel chamber is separated from the burner 2 by a fuel supply circuit (not shown). Reference numeral 11 denotes an exhaust gas passage provided at the outlet of the combustion chamber 9, and a plurality of heat-resistant bodies 13 made of heat-resistant ceramic or metal and having a large number of through holes 12 are disposed in the exhaust gas passage 11 with gaps provided. Shig
The 1% room is 14. In this example, / Nicum-shaped heat resistant body 1
Two pieces of 3 are placed with a gap between them.

Reference numeral 15 denotes a heat insulating body that heats at least the periphery of the heat retention chamber 14, and the exhaust gas passage including the combustion chamber 8 may have a heat insulating structure. Reference numeral 16 denotes a blower, which mixes indoor air sucked through a suction/outlet port 17 with exhaust gas discharged from an exhaust gas passage 11, and blows the mixture into the room through an outlet port 18 as warm air.

19 is a premixed flame, and 20 is an annular flame formed around the outer periphery of the premixed flame 19.

In the above configuration, premixed fuel with a stoichiometric mixing ratio or higher (air ratio>1) is supplied to the burner 2, and the premixed flame 1 that forms the main flame
Form 9. In general, the flame reaches a high temperature of around 2000°C and has a large amount of H200ppm in a partially premixed Bunsen flame.
NOx (reaching above) is generated. Although the present invention uses a fully premixed surface combustion burner, it produces around 20 ppm of NOx, most of which is emitted as NO2.

Therefore, in the present invention, when a small amount of cyclic gas, in this example, fuel gas in an amount of about 1,710 times that of the main flame, is supplied from the auxiliary fuel port 9 to the vicinity of the premixed flame 190 forming the main flame, the flame 1
An annular flame 20 is formed so as to surround 9. This decomposes most of the NOx into N2 and O2, and also produces small amounts of CO and unburned matter. That is, although NOxFi is drastically reduced, unburned components mainly consisting of CO are generated. The combustion exhaust gas generated in the combustion section rises and heats the heat resistor 13, increasing the temperature of the heat retention chamber 14, and changing the surrounding insulation structure to approximately equal to -
This constitutes a heat retention space. At this time, in this example, the heat resistor 13 has a diameter of the hole on the outlet side of the heat retention chamber 14 smaller than the diameter of the hole on the inlet side, thereby increasing thermal interference between the heat resistors and raising the temperature of the heat retention chamber. A small amount of NOx, CO, and unburned components generated in the combustion section are discharged together with the exhaust gas and enter the heat retention chamber 14, where the oxidation of the unburned components is promoted in the approximately uniform heat retention chamber, resulting in almost unburned components. minutes disappear.

At the same time, most of the NO2 in NOx becomes NO due to thermal dissociation.
Changes to That is, generation of No is almost non-existent at temperatures below 1400°C, and thermal dissociation of NO2 into No is promoted at temperatures above 400-500°C. Further, the oxidation of CO is promoted in the temperature range of 500 to 1000°C. These changes are greatly influenced by residence time and temperature; higher temperatures are faster for removing NO2 and CO, and the longer the residence time, the greater the amount of change. From these, the temperature of the heat retention chamber should be 500°C or more, preferably 600°C.
Although a large capacity is desired at temperatures between C and 800 degrees Celsius, if it is a household combustor, it is sufficient if the heat resistor gap H is approximately 20 to 80. Furthermore, it is more effective if the heat resistant body 12 supports an oxidation catalyst.

What is important here is that by making the main flame a self-contained combustion type, the combustion flame itself can reduce NOx, and even if ring gas is supplied to the surrounding area, the main flame itself will not elongate.
The reason is that only the ring region is expanded to ensure the NOx decomposition region. Low NOx generation by the main burner and a small amount of ring source gas provide a sufficient ring source light region, which reduces the generation of co and reduces the load on the downstream heat storage chamber. Note that depending on the combustion amount and stoichiometric mixture ratio, it may be necessary to supply secondary air to the upper part of the combustion chamber or the heat retention chamber.

The clean exhaust gas leaving the heat retention chamber 14 is mixed into the air flow and discharged into the room.

Effects of the Invention As described above, the combustor of the present invention has a simple configuration and can reduce NO.
This results in a combustor that suppresses and decomposes the generation of NOx, reduces the NO2 content in this NOx, and greatly improves the safety of exhaust gas for the human body.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of a combustor used in a hot-air heater showing an embodiment of the present invention, Fig. 2 is a partial sectional view of the combustor shown in Fig. 1, and Fig. 3 is a partial sectional view of the combustor shown in Fig. 1. FIG. 3 is a perspective view showing the F111j component of the combustor. 2... ・Nokuna, 9-... Auxiliary fuel port, 11...
Exhaust passage, 12... Through hole, 13... Heat resistant body, 14
... Heat retention chamber (heat retention space), 19... Main flame.

Claims (2)

[Claims] (1) A burner that forms a main flame, an auxiliary fuel port arranged around this burner to form a combustion section, and a heat retention chamber that forms a substantially constant temperature range in the exhaust gas passage downstream of this combustion section. and a combustor that supplies air-excess fuel to the burner and supplies ring source gas to the auxiliary fuel port. (2) A combustor according to claim 1, in which at least two heat-resistant bodies having through holes are disposed in the exhaust gas passage with a gap therebetween to form a heat retention chamber.