JPS58129106A - Combustion device - Google Patents

Abstract

PURPOSE:To achieve low NOx and low NO2 combustion and sharply detect incomplete combustion state by carrying out complete pre-mixing surface combustion in a hermetic combustion chamber in which the flow-in of secondary air to the combudtion surface, and poviding an oxygen concentration sensor in opposite to the combustion surface. CONSTITUTION:A gas nozzle 2 is provided in opposite to a mixing pipe inlet 3 of a burner 1, and gas injected from the gas nozzle 2 is introdued through the mixing pipe inlet 3 to a gaseous mixture chamber 4 as a gaeous mixture together with air necessary for the combustion by an ejector effect of the gaseous flow and comes to have a uniform pressure and surface combustion is carried out at flame ports 5 having a number of small holes such as wire nets. A reduction catalyst 9 consisting of a transient metal or the like is provided at a combustion gas passage 8 provided at the rear stream of the combustion chamber 7. An oxygen concentration sensor 11 consisting of an ignition plug 10, SnO2, TiO2 and the like is provided in opposition to the wire net flame ports 5 within the combustion chamber 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to clean exhaust gas and improve safety of combustion appliances, particularly indoor open type heating appliances.

Conventionally, many household combustion appliances have used Bunsen burners, which had the disadvantage of high NOx emissions. Therefore, many heating appliances such as stoves use a Schwank burner to reduce NOx (nitrogen oxides).

However, since the heat capacity of the ceramic plate that forms the flame opening of the burner is large, it takes a long time to reach stable combustion. Airflow tends to have a negative effect on combustion. Although the NOx value is low, the proportion of NO2, which has been shown to have an adverse effect on the human body, is high;
It had the disadvantage that it did not provide O2. Therefore, many indoor open type hot air heaters use Bunsen burners, and although proposals have been made to reduce NOx using Bunsen burners, the NOx value is 30 to 60p.
t compared to a conventional Bunsen burner at about pm, 4. y
However, it is not completely satisfactory.

Furthermore, for molded equipment that is used for long periods of time, such as heating equipment, there is a need for a safety device that detects incomplete combustion that occurs when the oxygen concentration drops or the primary air vent becomes clogged, and stops combustion.
A safety device using an oxygen sensor such as a two-sensor sensor has been proposed, but it has the disadvantage that the safety device is activated after the combustion condition has deteriorated.

The present invention improves the above-mentioned drawbacks and provides low Not and NO2
The present invention relates to a combustion device that achieves combustion and has a safety device that sensitively detects incomplete combustion.

The present invention uses a burner that is composed of a flame nozzle and a combustion chamber with many small holes and performs completely premixed surface combustion to achieve low NO.
By creating a sealed structure that prevents the inflow of secondary air into the combustion chamber, the oxidation of NO to HCh is prevented.

The installation of an oxygen concentration sensor such as Ti0z makes it possible to sensitively detect incomplete combustion, and a transition metal-based reduction catalyst is installed in the exhaust gas passage downstream of the combustion chamber to reduce [02] in the combustion gas. This is intended to reduce HO2 by reducing it to NO.

FIG. 1 shows an embodiment in which the present invention is applied to a gas stove.

In the figure, 1 is a burner that performs premixed surface combustion, and a gas nozzle 2 is provided facing the mixing tube 3 of the burner 1, and the gas δ ejected from the gas nozzle 2 is combusted by the ejector effect of the gas flow. The mixture is guided as a mixture from the mixing tube 3 to the mixture chamber 4 together with the air required for this, and the pressure is equalized and surface combustion occurs in the flame port 5 having a large number of small holes such as a wire mesh.

The outer cylinder 6 of the burner 1 is made of heat-resistant glass, and transmits and radiates the radiant heat of the red-hot wire gauze opening 6. Reference numeral 7 denotes a combustion chamber, which has a sealed structure to prevent secondary air from flowing into the combustion surface. 8 is a combustion gas passage downstream of the combustion chamber 7, and a reduction catalyst 9 made of a transition metal or the like is provided in the passage. In the combustion chamber 7, an oxygen concentration sensor 11 made of a 10°5 nOz spark plug, Ti02, etc. is provided opposite the wire mesh flame port 5. 12 is a gas valve, and 13 is a control circuit for operating an ignition or safety device.

According to this embodiment, the burner 1 performs uniform premixed surface combustion, and the wire mesh flame port 6 can prevent the generation of localized high temperature areas, so that low NOx is achieved, and the combustion chamber 7
Since the combustion chamber has a closed combustion chamber structure that prevents secondary air from flowing into the combustion chamber, oxidation of NO to NO2 by the secondary air can be prevented.

Furthermore, transition metal-based materials have the effect of promoting the reduction of NO2 to NO in the high temperature range of SOO to 800'C, and a reduction catalyst 9 made of a transition metal-based material is installed in the combustion gas passage 8. It is installed at a position where the effective temperature is 8. On the other hand, NOx in combustion exhaust gas is NOx in terms of combustion.
However, as the temperature decreases, oxidation progresses to NO2 and the proportion of NO2 in NOx increases, but when it comes into contact with the reduction catalyst 9, the reduction from NO2 to NO is promoted and the proportion of NO2 in NOx decreases. Thus, low NOZ is achieved.

Furthermore, the reduction catalyst 9 provided in the combustion gas passage 8 equalizes the pressure within the combustion chamber 7, achieving more uniform surface combustion and making it possible to further reduce the generation of harmful gases such as 00.

Furthermore, an oxygen concentration sensor 11 such as 8nOz or Ti0z is installed opposite the combustion surface in the sealed combustion chamber 7 that prevents the inflow of secondary air, so that it can prevent the atmospheric oxygen concentration from decreasing, the primary air port clogging, and the exhaust gas. It can detect deterioration in combustion conditions due to blockages, etc., and prevents the inflow of secondary air, so deterioration in combustibility and changes in the characteristics of the sensor are synchronized, which is better than when using conventional sensors of this type. Fig. 2 shows an embodiment in which the present invention is applied to an open hot air heater.

In the figure, the same components as those in FIG. 1 are labeled with the same page numbers.

In the figure, 6' is an outer cylinder of the burner 1 made of sheet metal, 14 is a pressure regulator that keeps the gas pressure constant, and 16 is a second gas valve that controls the amount of combustion. 16 is a blower, and exhaust guide 1
Due to this, the air directly hits the combustion gas, which may have an adverse effect on combustion.
It is provided so as not to reduce the reduction effect. 1
Reference numeral 8 denotes a hot air passage around the outer circumference of the outer cylinder 6' of the burner 1, and the shape 1 position of the hot air passage 18, exhaust guide 17, and exhaust pipe 8 is set so as to suck combustion gas into hot air. , 19 is the main body casing of the open hot air heater.

In this embodiment, the outer cylinder 6' of the burner 1 is made of sheet metal because the outer periphery of the outer cylinder 6' is used as the hot air passage 18, so there is no need to collect radiant heat, and as a result, the radiant heat is reduced. Since the combustion surface temperature rises, constant combustion can be achieved even under low load. Furthermore, uniform combustion due to equalization of the internal pressure of the combustion chamber 7 by the reduction catalyst 9 enables stable combustion even under low load, making it possible to further reduce NOx, and
It also becomes possible to achieve a high TDR (Turn Down Ratio).

In this embodiment, basically, the same effects as in the embodiment shown in FIG. 1 can be obtained.

As explained above in the embodiments, according to the present invention, the following effects can be obtained.

■ Low NO thanks to fully premixed surface combustion in a sealed combustion chamber that prevents secondary air from entering the combustion surface! .

Low NO2 is achieved - ■ A transition metal-based reduction catalyst is installed in the exhaust gas passage to reduce NO2.
Since 2 is reduced to NO, a further reduction in NOZ can be achieved, and the reduction catalyst equalizes the pressure in the combustion chamber, allowing for more uniform combustion, which enables stable combustion during low-load combustion. Lower NOx can be achieved.

■ , 8nO facing the combustion surface where there is no inflow of secondary air.
2. Equipped with an oxygen concentration sensor such as Ti 02, so when the atmospheric oxygen concentration decreases or the primary air port becomes clogged.

A safety device has become possible that can acutely detect incomplete combustion conditions such as when the exhaust is blocked.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the principle of construction of a stoff showing one embodiment of the present invention, and FIG. 2 is a cross-sectional view of the principle of construction of an open hot air heater showing another embodiment 911. 1...burner, 6...flame port, 7...
... Combustion chamber, 8... Combustion gas passage, 9...
...Reduction catalyst, 11...Oxygen concentration sensor. Name of agent: Patent attorney Toshi Nakao (1 person)
IS1 Figure 2 q Fence (2

Claims (1)

[Claims] A burner that performs premixed surface combustion is configured by a flame port having a large number of small holes such as a wire mesh and a combustion chamber, and the combustion chamber has a sealed structure that prevents secondary air from flowing into the combustion surface, The combustion device further includes an oxygen concentration sensor provided in the combustion chamber, and a transition metal-based reduction catalyst provided in a combustion gas passage downstream of the combustion chamber.