JPS61256111A - Surface combustion burner and heat exchanger utilizing this burner - Google Patents

Abstract

PURPOSE:To prevent backfire and make it possible to provide always and stably surface combustion regardless of the variation in supply amount of a premixing gas by providing a metal net through which the premixing gas passes at the downstream side of a mixing chamber where a combustion gas and air are mixed and mounting a cooling pipe through which a cooling fluid passes and which cools the metal net. CONSTITUTION:A metal net 10 is provided at the downstream side of a mixing chamber 9, and a cooling pipe 11 is fixed on to the net. The metal net 10 is cooled by a cooling pipe 11 through which a cooling fluid passes to maintain a premixing gas passing through the net meshed at a temperature below the ignition temperature. When the amount of the premixing gas being supplied is made small and the supply rate is lowered in order to lower the combustion temperature at the burner A, the position of ignition in the combustion chamber 12 is gradually moved toward the premixing chamber 9, but since the premixing gas temperature is maintained at a temperature below the ignition temperature, the premixing gas passing through the metal net 10 does not ignite. Consequently there is no ignition of the premixing gas in the mixing chamber 9 and backfire is, therefore, prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is capable of burning a premixed gas made by mixing a combustion gas and air after passing through a cooling section, thereby reducing the temperature by turndown or the like. To prevent a flashback phenomenon from occurring even when the supply pressure of the supplied premixed gas decreases.

[Conventional technology]

A conventional surface combustion burner is shown in FIG. That is, a combustion gas supply pipe 1 and a combustion air supply pipe 2 are connected to a mixing chamber 4 formed at the bottom of the frame 3, where the combustion gas and combustion air are mixed. The premixed gas passes through the ventilation panel 5 on the upper side of the downstream side of the mixing chamber 4 and rises, and near the upper surface of this ventilation panel 5, the premixed gas forms a planar shape and burns. do.

[Problem that the invention seeks to solve]

However, in such conventional surface combustion burners, when a large turndown is performed to reduce the flame size, the flow rate of the supplied premixed gas decreases, so the combustion position moves upstream. As a result, there is a risk of an explosion occurring inside the mixing chamber 4, etc. Furthermore, even if the turndown is proper, if the ventilation holes in the ventilation panel 5'1 are not uniform, the degree of red heat on the top surface of the ventilation panel 5 will not be uniform, making it easy to cause backfire.

Furthermore, the connection between the ventilation panel 5 and the frame 3 is required to be tight, and once a backfire occurs, the impact of the explosion often causes cracks in the ventilation panel 5, and these cracks cause further backfire. This creates a vicious cycle, and as a result, there is a problem that the burner becomes unusable in a short period of time.

This invention was made by focusing on the problems of the prior art, and aims to prevent the flashback and maintain a stable surface shape at all times regardless of changes in the amount of premixed gas supplied. The purpose is to enable the combustion of all types of fuel.

[Means for solving problems]

The first invention is to arrange a wire mesh through which a premixed gas passes on the downstream side of a mixing chamber that mixes combustion gas and air, and a cooling fluid passes through the wire mesh to cool the wire mesh. A cooling pipe is attached and a combustion chamber is further formed downstream of the wire mesh to constitute a surface combustion burner.

Moreover, the second invention arranges a wire mesh through which the premixed gas passes on the downstream side of the mixing chamber where combustion gas and air are mixed,
A cooling pipe for cooling the wire mesh through which a cooling fluid passes is attached to the wire mesh, and a combustion chamber is further formed on the downstream side of the wire mesh to constitute a surface combustion burner. A heat exchange device is constructed by arranging a finned corrugated tube through which a fluid to be heated passes, with a porous object in between, on the downstream side.

[Effect]

A premixed gas obtained by mixing combustion gas and air in the mixing chamber is supplied to the combustion space through a wire mesh and is combusted there. The wire mesh is cooled by cooling tubes through which a cooling fluid passes to maintain the premixed gas passing through the wire at a temperature below the ignition temperature. Therefore, in order to lower the combustion temperature of the burner, by reducing the amount of premixed gas supplied and slowing down its supply speed, the ignition position, which used to be in the combustion chamber, gradually moved toward the mixing chamber. However, since the premixed gas passing through the wire mesh is maintained below the ignition temperature as described above, the premixed gas passing through the wire mesh does not ignite. Therefore, since the premixed gas is not ignited in the mixing chamber, there is no risk of flashback occurring. Note that depending on the arrangement of the cooling pipe, the premixed gas is also cooled by this cooling pipe.

Further, according to the invention of the heat exchange device, in addition to the function of the burner, it has the following function. That is, the combustion gas combusted in the combustion chamber of the burner heats the porous object to make it red-hot, and the exhaust gas passes through the porous object and heats the finned corrugated tube before being discharged. On the other hand, unburned gas that has not been combusted in the combustion chamber is combusted while passing through the porous object, which also causes the porous object to become red hot. Since the finned corrugated tube is heated by the exhaust gas and also by the radiant heat of the red-hot porous object, the fluid passing through the corrugated tube is heated efficiently (heat exchanged and heated).

Furthermore, since the porous body is constantly heated during combustion of combustion gas, the premixed gas supplied to the combustion chamber through the wire mesh is completely combusted within the combustion chamber and the porous body. Further, even during so-called high-load combustion in which the supply pressure of the premixed gas is increased, a phenomenon in which the flame is blown away (blow-off phenomenon) does not occur.

〔Example〕

1 to 3 show an embodiment, in which FIGS. 1 and 2 show a heat exchange device, and FIG. 3 shows a burner of the heat exchange device.

6 is a frame, to the bottom of which a combustion gas supply pipe 7 and a combustion air supply pipe 8 are connected, and at the bottom of the frame 6 a mixing pipe for mixing combustion gas and air. A chamber 9 is formed. A wire mesh 10 is arranged on the upper side, which is the downstream side of the mixing chamber 9, and a cooling pipe 11 is fixed to this gold N410. In this embodiment, the cooling pipe 11 is made of a flexible pipe and is fixed to the frame 6, and a wire mesh 10 is fixedly supported on the cooling pipe 11 by means such as welding. Water is allowed to pass through the cooling pipe 11 as a cooling fluid.

Note that it is also possible to use a gas as this fluid, and as the cooling pipe 11, it is also possible to use a large number of parallel pipes instead of a coiled pipe. Furthermore, depending on the conditions such as the structure of the wire mesh 10 and the size of the mesh, a plurality of wire meshes 10 may be used in a stacked manner, and the dimensions and intervals of the cooling pipework 1 may be appropriately changed to allow the wire mesh 10 to pass through the wire mesh 10. The design shall be such that the premixed gas has a temperature below the ignition temperature at this passage point.

A combustion chamber 12 is formed on the upper side of the wire mesh 10 on the downstream side. This combustion chamber 12 is a planar space formed above the wire mesh 10, and its height is not very large.

Thus, the mixing chamber 9, the wire mesh 10, the cooling pipe 11, and the combustion chamber 12
The burner A is constructed by the following.

The frame 6 is extended upward, and a porous object 13 is fixed inside the frame 6 on the upper side, which is the downstream side of the combustion chamber 12. The porous material body 3 is made of a heat-resistant material, such as ceramics, metallurgy, and asbestos, and allows gas to pass upward, which is the downstream direction. A finned flexible pipe 14 is arranged on the upper side, which is the downstream side, of the porous body 13, and a fluid to be heated 2, for example, water, is passed through this. 14a is a fin of the finned flexible tube 14.

The burner A, the porous body 13, and the finned flexible tube 14 constitute the heat exchange device of this embodiment.

The premixed gas, which is a mixture of combustion gas and air sufficiently in the mixing chamber 9, passes through the mesh of gold M410 cooled by the cooling pipe 11, and is cooled in this passage. It is supplied to the combustion chamber 12 and becomes combustion gas. This combustion gas always burns in a planar shape in the combustion chamber 12 to heat the porous object 13 by ignition by a separately prepared ignition device or by the heat of the already combusted gas.

Further, even if there is unburned gas, it is burned while passing upward through the porous body 13, and this also heats the porous body 13 and makes it red-hot.

The porous body 13 allows the combustion exhaust gas to pass upward therein, thereby exchanging heat with the fluid within the porous body 13 through the finned corrugated pipe 14, thereby heating the fluid. On the other hand, the radiant heat of the porous body 13 heated and red-hot by the combustion also heats the fluid in the finned plumber 4.

In this way, the fluid passing through the finned corrugated tube 14 is efficiently heated by both the combustion exhaust gas and the radiant heat of the porous body 13.

Further, since the porous body 13 is constantly heated during combustion of the combustion gas, the supplied premixed gas is completely combusted, which also improves the heat exchange efficiency.

Further, under normal conditions, the combustion occurs in the combustion chamber 12 between the wire mesh 10 and the porous object 13.

On the other hand, during high-load combustion when the supply pressure of the premixed gas increases, the porous object 13 is heated to a higher temperature and the flame propagation speed is faster, so even if the flow rate of the premixed gas is high, Since the flame propagation velocity and the flow velocity of the premixed gas are balanced in opposite directions and burn at the same position, it is also possible to prevent the flame from blowing off (blow-off phenomenon).

On the other hand, the wire mesh 10 is cooled by a cooling pipe 11 through which a cooling fluid passes, and maintains the premixed gas passing through the mesh at a temperature lower than the ignition temperature. Therefore, in order to lower the combustion temperature of burner A, by reducing the amount of premixed gas supplied and decreasing its supply speed, the position of ignition that was performed in combustion chamber 12 gradually shifts to mixing chamber 9. However, since the premixed gas passing through the wire mesh 10 is maintained lower than the ignition temperature as described above, the premixed gas passing through the wire mesh 10 is not ignited. For this reason, the mixing chamber 9
Since the premixed gas is not ignited inside the tank, there is no risk of flashback occurring. Note that the premixed gas is supplied to the cooling pipe 11.
It is also cooled by

In addition, in this embodiment, the cooling pipe 11 and the finned serpentine pipe 14 are
Although water is passed through each separately, it is also possible to connect the outlet of the cooling pipe 11 to the inlet of the finned corrugated pipe 14.

〔Effect of the invention〕

As explained above, according to the present invention, since the metal mesh cooled by the cooling pipe is interposed between the mixing chamber and the combustion chamber, the premixed gas is lower than the ignition temperature at the mesh position of the wire mesh. It's getting lower. Therefore, if the supply speed of the premixed gas is reduced, the ignition position that was taking place in the combustion chamber will gradually move toward the mixing chamber, but the premixed gas passing through the wire mesh will reach the ignition temperature as described above. Since it is kept lower, the premixed gas passing through the wire mesh will not ignite. Therefore, since the premixed gas is not ignited in the mixing chamber, there is no risk of flashback occurring.

Further, according to the heat exchange device of the present invention, in addition to the above-mentioned effects, it is possible to prevent the flame from blowing off (blow-off phenomenon) even during high-load combustion when the supply pressure of the premixed gas increases. It also has the effect of contributing to the prevention of incomplete combustion.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the present invention, FIG. 2 is a sectional view taken along line nn of FIG. 1, FIG. 3 is a perspective view showing the burner of this invention, and FIG. It is a half sectional view showing a conventional example. A... Burner, 6... Frame, 7... Gas supply pipe,
8... Air supply pipe, 9... Mixing chamber, 10... Wire mesh, 11... Cooling pipe, 12... Combustion chamber, 13...
Porous object, work 4...Finned corrugated pipe.

Claims (2)

[Claims] (1) A wire mesh through which the premixed gas passes is placed downstream of the mixing chamber that mixes gas and air to create a premixed gas, and a cooling fluid passes through the wire mesh to cool the wire mesh. A surface combustion burner characterized in that a cooling pipe is attached and a combustion chamber is further formed on the downstream side of the wire mesh. (2) A wire mesh through which the premixed gas passes is placed downstream of the mixing chamber that mixes gas and air to create a premixed gas, and a cooling fluid passes through the wire mesh to cool the wire mesh. A cooling pipe is attached, and a combustion chamber is further formed on the downstream side of the wire mesh to constitute a surface combustion burner, and the fluid to be heated passes through the porous object on the downstream side of the combustion chamber of the surface combustion burner. A heat exchange device characterized by having a finned serpentine tube arranged therein.