JP2839296B2 - Exhaust gas treatment equipment for gas nitriding furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the invention]

(Field of Industrial Application) The present invention relates to an exhaust gas treatment apparatus for a gas nitriding furnace used for decomposing and treating exhaust gas containing ammonia gas discharged from a nitriding furnace. (Prior art) For the purpose of improving wear resistance and fatigue strength, the gas nitriding method applied to gears, shafts, etc. includes a pure nitriding method using hydrogen gas at the time of ammonia gas and nitrogen gas; Nitrogen gas, and RX gas, C as carbon supply gas
There is a gas nitrocarburizing method using O ₂ gas and CO gas. In any of these gas nitriding methods, since ammonia gas is used, ammonia gas remains in the exhaust gas and cannot be discharged as it is due to problems such as pollution, so that the exhaust gas needs to be treated. Conventionally, such exhaust gas treatment involves introducing the exhaust gas into a combustion type in which the exhaust gas containing ammonia gas is burned in a combustion cylinder equipped with a gas burner, or into a cracking furnace containing a catalyst having the same structure as an AX gas generating furnace. Then, a decomposition furnace method of decomposing ammonia gas into nitrogen gas and hydrogen gas has been used. (Problems to be Solved by the Invention) However, the combustion method is simple, but when the amount of ammonia gas in the exhaust gas or the component amount of hydrogen gas generated by decomposition of the ammonia gas is small, the exhaust gas is difficult to burn, and the Odor is generated by the ammonia gas of the combustion, which is a problem. Further, since the burner is constantly burning, the fuel cost increases and unattended operation is not possible, and the high heat of the burner deteriorates the working environment. On the other hand, in the decomposition furnace system, regardless of the concentration of ammonia gas or hydrogen gas in the exhaust gas, it is possible to always decompose ammonia gas stably, and the problem of odor as described above is solved. Separately, an expensive cracking furnace must be installed. Furthermore, when treating the exhaust gas containing CO ₂ and CO gas discharged in the gas nitrocarburizing method by this method, when the piping between the nitriding furnace and the cracking furnace cools, ammonia carbonate precipitates and the piping There is also the problem of clogging. As described above, both the combustion method and the decomposition furnace method have problems and have problems to be solved. (Object of the Invention) The present invention has been made in order to solve the above-mentioned problems of the conventional exhaust gas treatment apparatus, and the object thereof is that the installation space is small and the apparatus can be easily attached to a nitriding furnace. In addition, an object of the present invention is to provide an exhaust gas treatment apparatus for a gas nitriding furnace capable of completely decomposing exhaust gas containing ammonia gas discharged from the nitriding furnace regardless of the ammonia gas concentration.

Configuration of the Invention

(Means for Solving the Problems) An exhaust gas treatment apparatus for a gas nitriding furnace according to the present invention is provided between a cylindrical heat insulator whose outside is covered with a metal sheath and a heating element provided inside the cylindrical heat insulator. A reaction tube having an ammonia decomposition catalyst and having a reaction tube penetrated through the furnace wall is provided. On one side of the reaction tube in the cylinder axis direction, an intake port opening into the furnace is provided, and a reaction tube in the cylinder axis direction of the reaction tube is provided. On the other side, an exhaust port that opens to the outside of the furnace is provided, and the configuration of such an exhaust gas treatment apparatus for a gas nitriding furnace is a means for solving the above-described conventional problems. Features. (Operation) The exhaust gas treatment apparatus for a gas nitriding furnace according to the present invention is attached with a tubular reaction tube provided with a heat insulator, a catalyst for decomposing ammonia, and a heating element penetrating the furnace wall. Therefore, the exhaust gas introduced into the reaction tube by convection from the heating element from the intake port provided on one side of the reaction tube and opened inside the furnace is heated to a high temperature by the heating element,
Ammonia gas in the exhaust gas is decomposed by the action of the ammonia decomposition catalyst into hydrogen gas of nitrogen gas.
The gas is discharged from the furnace through an exhaust port provided on the other side of the reaction tube. At this time, since the reaction tube is directly attached to the nitriding furnace, gas piping is unnecessary, heat loss is small, installation is simple, and heating by the heating element in the reaction tube is achieved by effectively utilizing the furnace temperature. Is reduced. (Examples) Hereinafter, the present invention will be described specifically with reference to examples. FIG. 1 is a longitudinal sectional view showing an embodiment of an exhaust gas treatment apparatus for a gas nitriding furnace according to the present invention. The exhaust gas treatment apparatus 1 for a gas nitriding furnace shown in FIG. A heat generating element, which will be described later,
5. By inserting the reaction tube 4 containing the ammonia decomposition catalyst 9, the heat insulator 10, and the like, a part of the reaction tube 4 is attached in a state of protruding into the furnace. The reaction tube 4 has an inside of the reaction tube 4 of 800 to 1000
A radiant tube heater 5 which is a heating element which is heated and held at about 0 ° C .;
And a heat insulator 6 for supporting the same. The circumference of the radiant tube heater 5 and the heat insulator 6 is covered with a radiant tube 7 made of heat-resistant steel, in this embodiment, SUS310S stainless steel. In this embodiment, the basket-shaped shelves 8 are mounted in five steps. And the shelf 8
Inside the catalyst for ammonia decomposition (in this embodiment) 9
Is charged. A cylindrical heat insulator 10 is further provided around a perforated metal shelf 8 containing the ammonia decomposition catalyst 9.
And a gas passage is formed between the radiant tube 7 and a thermocouple 11 made of chromel-alumel or platinum-platinum rhodium for temperature control in this passage on the right side in the drawing. Has been installed. The heat insulator 10 maintains the temperature in the reaction tube 4 attached to the gas nitriding furnace 2 which is normally maintained at about 500 to 650 ° C. at 800 to 1000 ° C. suitable for decomposing ammonia gas. The heat is insulated so that the internal temperature of the reaction tube 4 of 800 to 1000 ° C. does not adversely affect the nitriding treatment. The outer periphery of the heat insulator 10 is covered with a skin 12 also made of SUS 310S stainless steel, and reinforces the reaction tube 4. Further, at the bottom of the reaction tube 4, there is provided an exhaust gas intake hole 13 that penetrates the outer shell 12 and the heat insulating material 1 and opens to the outside of the furnace.
An exhaust port 14 that opens outside the furnace is provided. Further, a water cooling jacket 15 and a water distribution pipe 15a for cooling the outer part of the upper part of the reaction tube 4 are provided on the outside of the reaction tube 4 and at the attachment portion to the gas nitriding furnace 2.
A heater terminal 16 for supplying power to the radiant tube heater 5 is provided at an upper end of the radiant tube 7, and these are covered by a terminal cover 17. An exhaust gas treatment device 1 for a gas nitriding furnace having the above-described structure includes:
Power is supplied to the radiant tube heater 5 by temperature control using the thermocouple 11, and the inside of the reaction tube 4 is maintained at a temperature in the range of 800 to 1000 ° C. suitable for decomposing ammonia gas. Then, the exhaust gas in the gas nitriding furnace 2 is introduced into the inside of the reaction tube 4 from the intake port 13 provided at the bottom of the reaction tube 4 by the convection generated by the heater 5 controlled to the temperature range. The ammonia gas in the exhaust gas is heated while rising in the direction of the arrow shown in FIG. 2, and is decomposed into hydrogen gas and nitrogen gas by the catalytic action of the ammonia decomposition catalyst 9 heated to the temperature,
The gas is discharged from the exhaust port 14 to the outside of the furnace. At this time, since the decomposition of the ammonia gas in the exhaust gas is due to the catalytic action, it can be completely decomposed into hydrogen gas and nitrogen gas regardless of the content. The reaction tube 4 is set at a nitriding temperature of 50.
Since it is arranged directly inside the furnace of the nitriding furnace 2 maintained at 0 to 650 ° C., the heating power for heating the heater 5 can be reduced, and the exhaust gas contains CO ₂ gas or CO gas. Even in the case of the gas nitrocarburizing method, there is no precipitation of ammonium carbonate or the like, and the adverse effects due to this are eliminated. Furthermore, the exhaust gas treatment device 1 is compactly assembled as described above, so that the installation space is small and can be easily installed in an existing gas nitriding furnace, and is suitable for unmanned operation.

As described above, the exhaust gas treatment apparatus for a gas nitriding furnace according to the present invention includes a cylindrical heat insulator whose outside is covered with a metal sheath and a heating element provided inside the cylindrical heat insulator. A reaction tube provided with a catalyst for decomposing ammonia therebetween and having a reaction tube penetrated through the furnace wall, an intake port opening into the furnace is provided on one side of the reaction tube in the cylinder axis direction, and a cylinder shaft of the reaction tube is provided. On the other side of the direction, an exhaust port that opens to the outside of the furnace is provided, so that it can be easily attached to an existing nitriding furnace, and the ammonia gas in the exhaust gas of the nitriding furnace can be converted to an ammonia concentration. It has an extremely excellent effect that it can be completely decomposed regardless of the above.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view for explaining one embodiment of an exhaust gas treatment apparatus for a gas nitriding furnace according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Gas-nitriding furnace exhaust gas treatment apparatus, 2 ... Gas-nitriding furnace, 2a ... Furnace wall, 4 ... Reaction tube, 5 ... Radiant tube heater (heating element), 9 ... Ammonia decomposition catalyst, 10 …… Cylindrical insulator, 12… Outer skin, 13 …… Inlet, 14 …… Exhaust.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F27D 17/00 B01D 53/36

Claims (1)

(57) [Claims] 1. A reaction tube provided with a catalyst for decomposing ammonia and penetrating through a furnace wall between a cylindrical heat insulator whose outside is covered with a metal outer skin and a heating element provided inside the cylindrical heat insulator. In addition, it is preferable that an intake port that opens into the furnace is provided on one side of the reaction tube in the cylinder axis direction, and an exhaust port that opens outside the furnace is provided on the other side of the reaction tube in the cylinder axis direction. Characteristic exhaust gas treatment equipment for gas nitriding furnace.