JPS64602B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the field of clean combustion and exhaust gas purification of hot air heating systems, particularly indoor open type hot air heating systems.

Conventional indoor open-air heating systems used Bunsen burners as burners, which had the disadvantage of high _NOx values. Therefore, indoor open-air heating systems that use premixing such as a bunk burner to reduce _NOx are also being developed.

However, because the heat capacity of the ceramic plate that forms the flame nozzle in the sybank burner is large, it takes a long time to reach stable sintering upon ignition, the airflow has a negative effect on combustion, and TDR cannot be achieved. In addition, although it is possible to reduce _NOx , it has the disadvantage of a high proportion of _NO2 , which is said to have an adverse effect on the human body.

On the other hand, in order to make the combustion exhaust gas cleaner, an oxidation catalyst has been proposed in the combustion exhaust gas passage to oxidize intermediate products such as CO and HC, but the oxidation catalyst has certain temperature conditions. If the amount of oxygen in the catalyst atmosphere was above a certain level, the effect on the characteristics could be ignored, so the installation conditions were as follows:
Although considerations have been made regarding catalyst performance, such as temperature, and combustion performance, such as ventilation resistance, little consideration has been given to means of reducing NO ₂ in combustion gas to NO.

The purpose of the present invention is to achieve low _NOx by enabling low-load combustion using premixed surface combustion, and to effectively reduce _NOx , especially _NO2 , in combustion exhaust gas to reduce exhaust gas. This relates to a hot air heating device that not only purifies the air but also provides TDR.

An embodiment of the present invention will be described above based on FIG. 1.

FIG. 1 is a side sectional view showing the principle of the hot air heating device of the present invention.

In the figure, 1 is the casing of the hot air heating device, 2 is the burner that performs premixed surface combustion, and the gas nozzle 3
A primary air port 4, a mixing pipe 5, and
A mixture chamber 6, a flame port 8 made of wire mesh or the like on the inside of the combustion tube 7, an outer tube 9 of the combustion tube 7 made of a metal plate, and a combustion chamber with a sealed structure to prevent the inflow of secondary air. It consists of 10.

A transition metal reduction catalyst 12 having approximately the same diameter as the exhaust pipe 11 is provided in the exhaust gas passage downstream of the combustion chamber 10 via an exhaust pipe 11 having a smaller diameter than the outer cylinder 9 .

When the air sucked from the suction port 14 by the blower 13 passes through the guide plate 15 which has the same diameter or more as the outer cylinder 9, it sucks combustion gas and causes the air to flow through the outer cylinder 9 of the combustion cylinder 7.
Air is blown from the outlet 17 through the hot air passage 16 on the outer periphery of the air. Note that the blower 13, the exhaust guide 15, and the reduction catalyst 12 are arranged to face each other so that the hot air flows into the reduction catalyst 12.
It is designed to prevent air from blowing onto the surface.

18 is a gas valve, 19 is a governor, and control circuit 2
0, the spark plug 21 discharges and ignites, and the output of the combustion detection element 22 is detected to control combustion. When the combustion amount is large, the air volume is also large, and when the combustion amount is small, the air volume is also controlled. It has a control function that makes it small.

In the above configuration, the gas ejected from the gas nozzle 3 sucks air necessary for combustion as primary air from the primary air port 4, and is guided to the mixture chamber 6 while being mixed in the mixing pipe 5. The air-fuel mixture is ejected into the combustion chamber 10 from a flame port 8 made of a wire mesh or the like, and at the same time is discharged and ignited by a spark plug 21, and surface combustion occurs in the flame port 8.

Since the flame port 8 is formed of wire mesh or the like, its heat capacity is small, and since the outer cylinder 9 of the combustion tube 7 is formed of a metal plate, the amount of heat passing through as radiant heat from the flame port 8 to the outside is small. Therefore, during low load combustion,
In other words, when the combustion amount was small, the airflow amount was small, so
There is little cooling from the outer periphery of the outer cylinder 9, and the flame mouth temperature that maintains good combustion is maintained.

On the other hand, during high-load combustion, that is, when the combustion amount is large, the temperature of the outer cylinder 9 of the combustion tube 7 increases;
Since the outer periphery of the tube is a hot air passage and the amount of air blown is large, the outer tube 9 can be cooled and the flame opening 8 can be prevented from becoming abnormally hot, thereby preventing backfire. There isn't.

Furthermore, a reduction catalyst 12 made of a transition metal such as stainless steel, molybdenum steel, or iron-chromium steel is placed in the exhaust gas passage downstream of the combustion chamber 10 at approximately 500°C to 700°C.
Since the exhaust pipe 11 is provided in the high temperature range of the exhaust pipe 11 with a diameter smaller than that of the outer cylinder 9, NO ₂ in the exhaust gas is reduced to NO. Furthermore, the exhaust pipe 11 having a smaller diameter than the outer cylinder 9, the reduction catalyst 12, and the guide plate 15 having the same diameter as the outer cylinder 9 produce the following effects.

By making the reduction catalyst 12 smaller in diameter, the amount of exhaust gas passing through per unit area of the catalyst 12 increases, so the catalyst 12 can be stably maintained at a high temperature of 500°C to 700°C even during low load combustion. can. Therefore, the ring element effect can be reliably expected even under high and low loads.

The guide plate 15, which has the same diameter as the outer cylinder 9, can completely prevent the air induced by the blower 13 from flowing into the surface of the catalyst 12, which has a smaller diameter than the guide plate 15. Catalyst 12
At the top, indoor air and exhaust gas do not mix. As a result, reoxidation of NO on the catalyst 12 can be prevented and the ring element effect can be maintained.

Since the catalyst 12 is maintained at a high temperature even during low-load combustion, the radiant heat from the catalyst 12 makes it possible to achieve a higher temperature inside the combustion chamber 10 than in the case where the catalyst 12 is not present. Since no air flows into the combustion chamber 12, no air flows into the combustion chamber 10, and the flame is not disturbed. These make it possible to stabilize the flame during low-load combustion and significantly suppress the generation of CO.

The combustion chamber 10 has a sealed structure that prevents air from entering, which prevents disturbance of the combustion gas in the combustion chamber 10 by the blower 13 and enables uniform combustion, which prevents deterioration of combustibility and prevents auxiliary air from entering as bypass air. Since the O ₂ concentration in the combustion exhaust gas passing through the reduction catalyst 12 is lowered, there is less oxidation of NO to NO ₂ , and the efficiency of converting NO ₂ to NO is improved, achieving low NO ₂ . be done.

FIG. 2 is a sectional view of a main part showing another embodiment of the exhaust stack, in which a shows the exhaust pipe 11' having a truncated conical shape and whose diameter becomes smaller in the direction of flow of exhaust gas, and b shows the exhaust pipe 11'. This is an embodiment in which the tip of the outer tube 9 of the combustion tube is made small in diameter and serves as an exhaust tube 11''.

The functions and effects of these embodiments are almost the same as those of the embodiment shown in FIG.

As is clear from the above description, according to the present invention, the combustion chamber 10 has a sealed structure that prevents the inflow of secondary air, and the exhaust pipe 11 and the reduction catalyst 12 are made smaller in diameter than the outer pipe 9, so that the ring-forming effect of air blowing is achieved. This prevents the oxidation of NO to NO ₂ , and also increases the ring element effect from NO ₂ to NO, achieving low NO ₂ .

Furthermore, by forming the combustion tube 7 outer tube 9 of the premixed surface combustion burner with a metal plate, low-load combustion is possible, low _NOx is achieved, and the combustion amount can be varied as a hot air heating device. It is possible.

In addition, the air guides between the reduction catalyst and the blower are placed facing each other to prevent air from hitting the reduction catalyst, which reduces the NO ₂ ringing effect and reduces the oxidation of NO to NO ₂ due to air blowing, which is unique to hot air systems. It is possible to prevent combustion from worsening due to the influence of air blowing.

Furthermore, by forming the combustion outer cylinder with a metal plate and controlling the amount of air blown depending on the amount of combustion, it is possible to keep the air ratio constant and expand the combustion range.

[Brief explanation of drawings]

FIG. 1 is a sectional side view showing one embodiment of the hot air heating device of the present invention, and FIG. 2 is a sectional view of essential parts showing another embodiment of the exhaust stack. 2... Burner, 7... Combustion cylinder, 8... Burner port,
9...Outer cylinder, 10...Combustion chamber, 11...Exhaust pipe,
12...Reduction catalyst, 13...Blower, 16...Hot air passage, 20...Control circuit.

Claims (1)

[Claims] 1 A cylindrical combustion tube made of a metal plate A combustion tube that has a burner that performs premixed surface combustion with a flame port formed with a wire mesh or the like on the inside of the outer cylinder and a hot air blower, and is installed facing a blower guide. The outer periphery of the outer cylinder is a hot air passage, and the combustion chamber has a sealed structure to prevent the inflow of secondary air.A transition metal-based reduction catalyst is provided in the combustion gas passage downstream of the combustion chamber, and the reduction catalyst has a diameter smaller than that of the outer cylinder. A control circuit is provided which is disposed at approximately the same diameter as the exhaust pipe through the exhaust pipe, and is provided facing each other in the order of the blower and the blow guide reduction catalyst, and also controls the blowing amount to be large or small depending on the size of the combustion amount. A warm air heating system is installed.