JPS605645B2 - Low NOx type heat treatment furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low N○× type heat treatment furnace capable of reducing the emission of N○× (nitrogen oxides) in order to prevent pollution.

BACKGROUND OF THE INVENTION Conventionally, a continuous loft hearth furnace as shown in FIG. 1 has been widely used for heat treatment of metallic strip materials.

That is, this heat treatment furnace is provided with a subheating chamber 2, a heating chamber 3, and a cooling chamber 4 in the order of the traveling direction of the object 1 to be heated, and burns fuel with a burner 5 in the heating chamber 3 to heat the object 1 to a predetermined position. 6 indicates a flue provided at the front of the preheating chamber 2. Combustion gas generated in the heating chamber 3 is guided to the preheating chamber 2 and heats the object 1 to be heated, and the heat exchanger 7 installed in the flue 6 recovers the amount of heat in the exhaust gas. In this way, although the conventional heat treatment furnace has already taken into consideration the effective use of thermal energy,
No consideration was given to the treatment of the waste, and it was released into the atmosphere as is, causing air pollution. Therefore, the present invention aims to provide a low N○× type heat treatment furnace that can suppress NO emissions without impairing the effective use of heat. The catalyst layer divides the ripening chamber into a primary heating chamber on the flue side and a secondary heating chamber on the heating chamber side. Air is introduced into the preheating chamber, and if the component of the atmospheric gas in the heating chamber is oxidizing, reducing gas or fuel is introduced into the secondary preheating chamber at the same time as the air is introduced into the primary preheating chamber. be.

Next, one embodiment of the present invention will be described with reference to FIGS. 2 to 4.

Note that in these embodiment figures, the same reference numerals as in FIG. 1 indicate the same parts. In the present invention, the preheating chamber 2 is located approximately in the middle of the preheating chamber 2.
A partition wall 8 is provided that divides the heating chamber into a primary heating chamber 2a on the flue 6 side and a secondary preheating chamber 2b on the heating chamber 3 side, and a catalyst layer 9 of nickel, chrome, etc. is provided on the inner periphery of the partition wall 8. 10 is heating chamber 3
11 is an analyzer that measures the concentration of unburned components (C○, ratio) in the sampled atmospheric gas; 12 measures the 02 concentration in the sampled atmospheric gas. 13 is an air supply pipe that supplies air to the primary preheating chamber 2a, 14 is a throttle valve provided in the air supply pipe 13, and 15 is a flammable gas such as C○, Day 2, etc. in the secondary preheating chamber 2b. 16 is the gas supply pipe 15 for supplying a reducing gas or a hydrocarbon fuel such as natural gas, methane, or kerosene;
This is a throttle valve installed in the

When the object to be heated 1 is subjected to so-called bright heat treatment in a non-oxidized state, as is well known, the heating chamber 3 is heated with a burner 5 to supply fuel at an air-fuel ratio of 0.
．． It is filled with a reducing atmosphere gas containing 0.5 to 4.0% of unburned matter such as C○, Day 2, etc., which is caused by incomplete combustion at 95 degrees Celsius and a lack of air for combustion. Therefore, in this case, the analyzer 11 detects CO, and the analyzer 12 detects 02
is not detected at all. Therefore, this reducing atmospheric gas is first led to the secondary preheating chamber 2b, and is subjected to the child heat of the object to be heated 1.
Next, by passing through the catalyst layer 9, the NOx contained in this atmospheric gas is caused to react with C○, reducing the NO concentration. Air is introduced to completely combust the remaining unburned matter such as C○, 2, etc., and the combustion heat generated at this time is also used for preheating the object to be heated 1 in the primary preheating chamber 2a. Furthermore, depending on the material of the object 1, it is not necessarily necessary to heat treat it in a non-oxidized state; Every time)
02 remains in the atmospheric gas. Therefore, the analyzer 11 hardly detects C○, Day 2, and the analyzer 12
detects 02. Therefore, this oxidizing atmospheric gas is first led to the secondary heat chamber 2b, where it is supplied to the heat of the object 1 to be heated, and at the same time, reducing gas such as C○, Day 2, etc. is supplied from the gas supply pipe 15. is introduced, and its C○, Q and NO wide form the catalyst layer 9.
reacts as it passes through, reducing the concentration of N○ skin. In addition, if hydrocarbon fuel such as natural gas, methane, or kerosene is introduced, this fuel will remain in the atmospheric gas at zero.
The combustion reaction with 2 produces CO and 2, and this C
O, Day 2, and N○x react with each other when they pass through the catalyst layer 9, thereby reducing the N○x concentration. In the primary preheating chamber 2a, air is introduced from the air supply pipe 13 in the same way as described above to completely burn the remaining CO, Q, etc., and the combustion heat is used to preheat the object to be heated 1. Note that when the unburned gas reburns in the primary heat chamber 2a, the temperature of the atmospheric gas is already lower than that in the heating chamber 3, so this combustion in the secondary heat chamber 2a generates N○× again. There's no way I'll let you do that. Similarly, by the time the atmospheric gas in the heating chamber 3 reaches the catalyst layer 9, the temperature of the atmospheric gas has already been lowered to some extent due to contact with the object to be heated 1, so overheating of the catalyst layer 9 is prevented. Ru. By applying conventional technology, the throttle valve 14 of the air supply pipe 13 and the throttle valve 16 of the gas supply pipe 15 can be configured so that their relative values are automatically adjusted based on commands from the analyzers 11 and 12, respectively. can be achieved, in which case the throttle valve 14 is adjusted proportionally to the C0, day 2 concentration indicated by the analyzer 11.
In addition, the opening degree of the throttle valve 16 is increased in proportion to the 02 concentration indicated by the analyzer 12 to increase the amount of gas supplied. Low N○ of the present invention
As explained in the above embodiments, the x-type heat treatment furnace can
The generated N○× is converted into C○ by the catalyst layer in the subheating chamber.
As a result of this reaction, N○k changes from the conventional 1'2
Since the heat energy can be reduced to 1 to 1'3, even if it is emitted into the atmosphere, the degree of pollution is suppressed within an acceptable range, which is useful for pollution prevention, and the thermal energy is effectively recovered to the heated object in the preheating chamber. It has many excellent effects such as good thermal efficiency.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a conventional heat treatment furnace, FIG. 2 is a vertical cross-sectional view of a low N○× type heat treatment furnace showing an embodiment of the present invention, and FIG.
The figure is an
FIG. 1... Heated object, 2... Child heating chamber, 2a.
...Primary heating chamber, 2b...Secondary preheating chamber,
3... Heating chamber, 5... Burner, 6... Flue, 9... Catalyst layer, 11, 12... Analyzer, 13... ...Air supply pipe 15...Gas supply pipe. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A preheating chamber is formed to which the atmospheric gas in the heating chamber is guided, and the preheating chamber is divided into a primary preheating chamber on the flue side and a secondary preheating chamber on the heating chamber side by a catalyst layer provided in the preheating chamber. If the component of the atmospheric gas in the heating chamber is reducing, air is introduced into the primary preheating chamber, and if the component of the atmospheric gas in the heating chamber is oxidizing, air is introduced into the primary preheating chamber at the same time as the secondary preheating chamber. A low NOx type heat treatment furnace characterized in that a reducing gas or fuel is introduced into a sub-preheating chamber.