JP2001152313A - Atmospheric gas generator and method for high-temperature rapid carburizing - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To stably generate a metamorphic gas containing high concentration of carbon monoxide, which is suitable as a high-temperature rapid carburizing atmosphere gas, while suppressing soot generation and avoiding the danger of explosion. The present invention provides an atmosphere gas generating apparatus and method for high-temperature rapid carburizing that can be performed. SOLUTION: A raw material mixed gas obtained by mixing a hydrocarbon and a source gas such as carbon dioxide and oxygen is introduced into a nickel catalyst layer, and a high-temperature rapid carburizing atmosphere gas containing carbon monoxide and hydrogen is generated by a catalytic reaction. In the apparatus, an oxygen jetting portion for jetting oxygen is provided in the middle of the nickel catalyst layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for generating an atmospheric gas for rapid carburizing at high temperature, and more particularly, to an atmospheric gas for carburizing having a composition capable of effectively performing high-temperature rapid carburizing treatment of steel parts and the like. And a method for generating the same.

[0002]

2. Description of the Related Art As a method for generating an atmosphere gas for carburization containing carbon monoxide and hydrogen, after mixing a paraffinic hydrocarbon such as LNG or LPG with air, the mixed gas (raw material mixed gas) is heated to a high temperature. An air mixing method has been widely used, in which a gas is introduced into a shift furnace having a retained nickel catalyst layer and a catalytic reaction (shift reaction) between oxygen and hydrocarbons in the air is performed to obtain a shift gas containing carbon monoxide and hydrogen. Used.

[0003] However, since about 79% (volume%, the same applies hereinafter) of nitrogen is present in air used as an oxygen source, the concentration of carbon monoxide and hydrogen in the resulting metamorphic gas may not exceed a certain level. For example, the limit of the concentration of carbon monoxide when methane is used is 20%, and that of butane is 23.5%.

On the other hand, in carburizing treatment, in particular, high-temperature rapid carburizing treatment, when the concentration of carbon monoxide is low, a stable carburizing atmosphere is unlikely to be formed in the furnace due to gas equilibrium at high temperature. Is required to be high. In addition, increasing the concentration of carbon monoxide, for example, when carburizing a component having a hole, it is possible to sufficiently carburize deep into the hole, or carburize while stacking fine components and carrying a belt. In this case, there is an advantage that the stacking thickness of the components on the belt can be increased.

On the other hand, as a source gas to be mixed with hydrocarbons,
By performing the shift reaction using carbon dioxide or oxygen instead of air, the concentration of carbon monoxide in the shift gas can be increased. Theoretically, if a methane and oxygen are subjected to a conversion reaction at a molar ratio of 2: 1, 2 moles of carbon monoxide and 4 moles of hydrogen are generated, so that the carbon monoxide concentration is about 33.3.
%, And a converted gas having a hydrogen concentration of about 66.7% is obtained. Similarly, when methane and carbon dioxide react at a 1: 1 molar ratio, 2 moles of carbon monoxide and 2 moles of hydrogen are produced, and the concentration of both becomes 50%. In the case of butane, 4 moles of carbon monoxide and 5 moles of hydrogen are generated by the reaction with 2 moles of oxygen, and 8 moles of carbon monoxide and 5 moles are formed by the reaction with 4 moles of carbon dioxide. Of hydrogen is produced.

[0006]

However, if carbon monoxide or oxygen is used to generate a high concentration of carbon monoxide, soot generated in the shift furnace becomes a serious problem.
For example, when carbon dioxide is used as a source gas, since the metamorphic reaction is an endothermic reaction, the supply of heat from a heater that heats the nickel catalyst layer to a predetermined temperature is partially insufficient, and one of the nickel catalyst layers is supplied. When the temperature decreases in the part, the reaction does not proceed sufficiently in that part, and soot is generated. When a large amount of soot is generated in the shift furnace in this way,
The operation of the apparatus cannot be continued because the nickel catalyst layer is clogged.

[0007] On the other hand, when oxygen is used, there is no problem of temperature drop because the metamorphic reaction is an exothermic reaction, but since the mixed gas of hydrocarbon and oxygen is within the explosive limit mixing ratio, only oxygen is used as the oxygen source. Using it as a source causes a great problem in terms of safety.

Thus, even if it is known that the use of carbon dioxide or oxygen as a source gas instead of air can produce a modified gas containing a high concentration of carbon monoxide, the actual apparatus In practice, the importance of safety and stability has been emphasized, and in fact, an air addition method using air as a source gas has been adopted.

[0009] Therefore, the present invention provides a method for removing soot generated in a nickel catalyst layer as carbon monoxide, and at the same time, avoiding the danger of explosion, while increasing the carbon monoxide suitable as a high-temperature rapid carburizing atmosphere gas. It is an object of the present invention to provide an atmosphere gas generating apparatus and method for high-temperature rapid carburizing that can stably generate a metamorphic gas containing a concentration.

[0010]

In order to achieve the above object, an atmosphere gas generating apparatus for high-speed and rapid carburizing according to the present invention is characterized in that a raw material mixed gas obtained by mixing a hydrocarbon and a source gas such as carbon dioxide and oxygen is mixed with nickel. In an apparatus for introducing into a catalyst layer and generating a carburizing atmosphere gas containing carbon monoxide and hydrogen by a catalytic reaction, an oxygen ejection section for ejecting oxygen is provided in the middle of the nickel catalyst layer. .

Further, in the method for generating an atmospheric gas for high-temperature rapid carburizing according to the present invention, a raw material mixed gas obtained by mixing hydrocarbon, carbon dioxide and oxygen is introduced into a nickel catalyst layer, and carbon monoxide and hydrogen are separated by a catalytic reaction. In the method for generating a carburizing atmosphere gas including, in the middle of the nickel catalyst layer,
It is characterized by mixing oxygen.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram showing one embodiment of an atmospheric gas generator for high-temperature rapid carburizing according to the present invention. This high-temperature rapid carburizing atmosphere gas generator uses a hydrocarbon as a raw material and carbon dioxide and oxygen as a source gas, and includes a hydrocarbon supply source 11, a carbon dioxide supply source 12, an oxygen supply source 13, A nitrogen supply source 14, a first gas mixer 15 for mixing hydrocarbons supplied from the hydrocarbon supply source 11 with carbon dioxide supplied from the carbon dioxide supply source 12, and oxygen supplied from the oxygen supply source 13. A second method of mixing carbon dioxide supplied from the carbon dioxide supply source 12 and / or nitrogen supplied from the nitrogen supply source 14
A gas mixer 16, a preheater 17 for preheating the raw material mixed gas mixed by the first gas mixer 15 to a predetermined temperature,
A shift furnace 18 having a nickel catalyst layer and a cooler 19 for rapidly cooling the shift gas are provided.
An oxygen introduction unit 21 for introducing and mixing oxygen supplied from the oxygen supply source 13 into a path 20 of a preheated raw material mixed gas from the furnace to the shift furnace 18, and oxygen and carbon dioxide mixed by the second gas mixer 16. And / or an oxygen jetting part 22 for jetting a mixed gas with nitrogen from the middle of the nickel catalyst layer in the shift furnace 18.

The preheater 17 has a heater 17a and a thermometer 17b for preheating the raw material mixed gas to a predetermined temperature.
Provided in the shift furnace 18 are a heater 18 a for heating the nickel catalyst layer to a predetermined temperature and a thermometer 1.
8b are provided. Note that, as the shift furnace 18, a shift furnace basically similar to the shift furnace based on the conventional air mixing method can be used.
It is 1100 ° C., usually about 1050 ° C.

In the apparatus shown in this embodiment, a raw material gas mixture comprising hydrocarbons and carbon dioxide mixed by a first gas mixer 15 is preheated to a predetermined temperature by a preheater 17, and oxygen is introduced from an oxygen introduction unit 21. After mixing, this raw material mixed gas is introduced into the nickel catalyst layer in the shift furnace 18, and further, oxygen or a mixed gas of oxygen, carbon dioxide, and / or nitrogen jetted from the oxygen jetting part 22 in the middle of the nickel catalyst layer. Are mixed, and a shift gas containing carbon monoxide and hydrogen is generated by these shift reactions. The generated transformed gas is rapidly cooled by the cooler 19 and then sent out to a carburizing furnace or the like as a carburizing atmosphere gas.

In addition, various devices such as a pressure reducing valve, a pressure gauge, a flow meter, a flow regulating valve, a solenoid valve, a check valve and the like can be provided in each path as needed. Further, a plurality of heaters may be arranged in consideration of controllability. Further, a path for supplying another gas, for example, nitrogen or air for performing concentration adjustment or the like may be provided.

The preheater 17 is for preheating a raw material mixture gas composed of hydrocarbons and carbon dioxide to a temperature lower than the thermal decomposition temperature of hydrocarbons. The preheating temperature at this time is as high as possible. It is preferable to set it, but when it reaches the thermal decomposition temperature, hydrocarbons are decomposed into carbon and hydrogen or carbon and hydrogen and methane, and the carbon generated by decomposition becomes so-called soot in the path. It will adhere or flow into the nickel catalyst layer to cause clogging. Therefore, when the hydrocarbon is methane, it is preheated to 623 ° C or lower, preferably 600 ° C or lower, for propane, 423 ° C or lower, preferably 400 ° C or lower, and for butane, it is preheated to 463 ° C or lower, preferably 420 ° C or lower. It is desirable.

In the preheater 17, it is preferable to preheat gas containing no oxygen, as shown in this embodiment. That is, when preheating is performed in a state containing oxygen, oxygen and hydrocarbons react (combustion reaction) in the preheater, and the generated reaction heat may damage the preheater 17 and the pipe (path 20). . However, when the amount of oxygen is sufficiently small, it is also possible to preheat in a state containing oxygen.

The oxygen introduced from the oxygen introducing section 21 is not only used as a source gas but also reacts with a part of the hydrocarbons in the preheated raw material mixture gas derived from the preheater 17 by a combustion reaction. It also has the effect of further raising the temperature of the preheated raw material mixed gas, so that the temperature of the raw material mixed gas flowing into the nickel catalyst layer in the shift furnace 18 is sufficiently raised.

The oxygen spouted from the oxygen spouting portion 22 in the middle of the nickel catalyst layer into the catalyst layer is for removing soot generated in the nickel catalyst layer,
By reacting with soot, ie, carbon, to generate carbon monoxide or carbon dioxide, it has an action of removing soot from the inside of the catalyst layer.

Therefore, the position of the oxygen jetting portion 22 is set so as to jet oxygen to a portion where soot is easily generated and a portion where temperature is easily lowered in the nickel catalyst layer. Positioning is performed according to various conditions such as the type of raw material, mixing ratio, and heating temperature.

As described above, by spouting and mixing oxygen at a predetermined position in the middle of the nickel catalyst layer, the generated soot can be quickly removed, and the temperature of the soot-producing portion can be reduced by the heat generated by the reaction with the soot. Reduction can be prevented, and generation of soot itself can be suppressed. Further, this oxygen also functions as a part of the oxygen source, and becomes a raw material for finally generating carbon monoxide by a catalytic reaction with soot.

The amount of oxygen ejected from the oxygen ejecting section 22 can be set according to the type of raw material, the amount of gas flowing through the nickel catalyst layer, and the like. It is preferable that oxygen is diluted with carbon dioxide or nitrogen, since the material or catalyst may be adversely affected. The oxygen dilution ratio, that is, the mixing ratio with carbon dioxide and nitrogen, is determined by the oxygen ejection unit 22.
Can be set in accordance with the amount of gas ejected from the catalyst, the reaction state in the nickel catalyst layer, and the like. At this time, if the amount of carbon dioxide is too large, an endothermic reaction may occur in the portion of the oxygen jetting part 22 to cause a decrease in temperature. The concentration of carbon and hydrogen will be low.

Further, as described above, by lowering the temperature of the nickel catalyst layer by suppressing the temperature of the nickel catalyst layer by introducing the raw material mixed gas into the nickel catalyst layer after preheating in the preheater 17. Further, by introducing oxygen from the oxygen introduction unit 21 to the raw material mixed gas before flowing into the nickel catalyst layer and causing a combustion reaction with a part of the hydrocarbon, the temperature of the gas flowing into the nickel catalyst layer can be further increased.

The combination of the hydrocarbon as the raw material and the source gas such as carbon dioxide and oxygen is arbitrary, and a preferable raw material combination is, for example, 0.33 mol of carbon dioxide, A combination of 0.335 mol or a combination of 0.5 mol of carbon dioxide and 0.25 mol of oxygen can be employed. Further, 1.4 moles of carbon dioxide and 0.8 moles of oxygen are used for 1 mole of propane.
Mole combination, carbon dioxide 1.2 moles, oxygen 0.
A combination of 9 moles can be used, and a combination of 1.8 moles of carbon dioxide and 1.1 moles of oxygen can be used for 1 mole of butane.

Further, it is also possible to use only oxygen as a source gas. For example, methane and oxygen are supplied at a molar ratio of 2: 1 and only methane is preheated to a predetermined temperature by a preheater 17, and oxygen is supplied. Can also be introduced and mixed from the oxygen introduction part 21 and the oxygen ejection part 22, respectively.

The amount of oxygen to be spouted from the oxygen spouting section 22 can be appropriately set according to the state of soot generation.
It should be set to a predetermined amount in accordance with the amount of oxygen introduced from the oxygen introduction unit 21 and may be determined according to the type of hydrocarbon, the mixed amount of carbon dioxide and oxygen, etc. May be adjustable in accordance with

When there are a plurality of locations where soot may be generated, a plurality of oxygen jetting portions 22 can be provided at appropriate positions. Further, the oxygen jetting part 22 can be formed so as to be movable in the gas flow direction in the nickel catalyst layer.

It should be noted that the preheater 17 and the oxygen introducing section 21 may be provided as necessary according to the type and mixing ratio of the raw materials, operating conditions, and the like, and may be omitted.

FIG. 2 is a sectional view showing a specific example of the shape of the nickel catalyst layer portion in the shift furnace. This metamorphic reactor is
It has a double-pipe structure in which an inner cylinder 32 for leading out a denatured gas is coaxially arranged inside an outer cylinder 31 having a bottomed cylindrical body, and between the outer cylinder 31 and the inner cylinder 32, A nickel catalyst layer 33 filled with a granular nickel catalyst is formed. Although not shown, a heater is arranged on the outer periphery of the outer cylinder 31, and a heat insulating material is further provided on the outer periphery.

At the upper end of the outer cylinder 31, a flange 34 having a through hole 34a corresponding to the diameter of the outer cylinder 31 is provided. An inflow chamber 36 for allowing gas to flow into the nickel catalyst layer 33 on average is provided. When oxygen is introduced from the oxygen introduction section 21, the inflow chamber 36 also serves as a combustion chamber in which hydrocarbons and oxygen react with each other. Therefore, the inflow chamber 36 is designed to withstand high temperatures. It is formed by a refractory material 38 filled in the cover 37.

On the other hand, the lower end of the inner cylinder 32 is
, And the metamorphic gas generated in the nickel catalyst layer 33 passes through the through hole 39 a of the catalyst holding plate 39, and from the lower end opening 32 a of the inner cylinder 32 to the inner cylinder 32.
And flows out from the outlet 32b at the upper end of the inner cylinder penetrating the cover 37 and the refractory material 38, and is guided to the cooler 19.

An oxygen inlet pipe 40 provided with a plurality of oxygen outlets 22 on the lower side surface is provided along the inner cylinder 32 through the cover 37 and the refractory material 38. In consideration of the thermal expansion and contraction between the inner tube 32 and the oxygen introduction tube 40, the inner tube 32 is slidably fastened to the inner tube 32 by a plurality of stop rings 41.

As described above, the length of the oxygen introducing pipe 40, that is, the position of the jet port 22 in the nickel catalyst layer 33 is, as described above, a portion where soot is likely to be generated or slightly upstream thereof. Is set to In addition, the direction and speed at which oxygen is ejected from the ejection port 22 should be set so that the mixed gas can spread over the entire catalyst layer as much as possible.

Further, depending on conditions such as the gas flow rate in the nickel catalyst layer 33 and the amount of filled catalyst, a plurality of oxygen introduction pipes 40 can be provided around the inner cylinder 32. In addition, it is also possible to provide a plurality of injection ports 22 of a predetermined size in the longitudinal direction of one oxygen introduction pipe 40,
Further, it is also possible to provide the oxygen introduction pipe 40 so as to be movable in the axial direction. It should be noted that air may be used instead of the mixed gas of nitrogen and oxygen as the mixed gas ejected from the oxygen ejection section.

[0035]

As described above, according to the present invention,
Oxygen is ejected and mixed in the middle of the nickel catalyst layer, so that the soot generated in the nickel catalyst layer can be removed and the temperature decreases due to the heat generated during the reaction with the soot (carbon). Can be suppressed, so that generation of soot can also be suppressed. This makes it possible to use carbon dioxide or oxygen as a source gas to be mixed with the hydrocarbon, and to generate a modified gas having a high carbon monoxide concentration and an optimum composition as an atmosphere gas for high-temperature rapid carburizing.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of an atmosphere gas generating apparatus for high-temperature rapid carburizing of the present invention.

FIG. 2 is a cross-sectional view showing a specific example of the shape of a nickel catalyst layer in a shift furnace.

[Explanation of symbols]

14 nitrogen supply source, 11 hydrocarbon supply source, 12 carbon dioxide supply source, 13 oxygen supply source, 15 first gas mixer, 16 second gas mixer, 17 preheater, 18
Metamorphic furnace, 19: cooler, 20: path of preheated raw material mixed gas, 21: oxygen introduction part, 22: oxygen ejection part (ejection port),
31 ... outer cylinder, 32 ... inner cylinder, 33 ... nickel catalyst layer, 34
... Flange, 35 ... Mixed gas introduction pipe, 36 ... Inflow chamber, 3
7 ... cover, 38 ... refractory material, 39 ... catalyst holding plate, 40 ...
Oxygen introduction tube, 41 ... stop ring

Claims (2)

[Claims] 1. A raw material mixture gas obtained by mixing a hydrocarbon and a source gas such as carbon dioxide and oxygen is introduced into a nickel catalyst layer, and a carburizing atmosphere gas containing carbon monoxide and hydrogen is generated by a catalytic reaction. An apparatus for generating an atmosphere gas for rapid carburization at high temperature, characterized in that an oxygen jetting section for jetting oxygen is provided in the middle of the nickel catalyst layer. 2. A method according to claim 1, wherein a raw material mixed gas obtained by mixing hydrocarbon, carbon dioxide and oxygen is introduced into a nickel catalyst layer, and a carburizing atmosphere gas containing carbon monoxide and hydrogen is generated by a catalytic reaction. In the middle of the layer,
A method for generating an atmosphere gas for high-temperature rapid carburization, characterized by mixing oxygen.