JP2001152314A - 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: An apparatus for introducing a mixed gas of a hydrocarbon and a source gas such as carbon dioxide and oxygen into a nickel catalyst layer and generating a carburizing atmosphere gas containing carbon monoxide and hydrogen by a catalytic reaction. , A hydrocarbon introduction part for introducing hydrocarbon 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.

Accordingly, the present invention provides a modified gas containing a high concentration of carbon monoxide, which is suitable as an atmosphere gas for rapid carburization at high temperatures, while suppressing the generation of soot and avoiding the danger of explosion when using oxygen. It is an object of the present invention to provide an atmosphere gas generating apparatus and method for high-temperature rapid carburizing that can be stably generated.

[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 a device for introducing into the catalyst layer and generating a carburizing atmosphere gas containing carbon monoxide and hydrogen by a catalytic reaction, a hydrocarbon introduction section for introducing hydrocarbon is provided in the middle of the nickel catalyst layer. And

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 containing at least a part of the nickel catalyst layer, at least a part of the hydrocarbon is mixed.

[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 the hydrocarbon supplied from the hydrocarbon supply source 11 with the carbon dioxide supplied from the carbon dioxide supply source 12, and a carbon supply supplied from the hydrocarbon supply source 11. A second gas mixer 16 for mixing hydrogen and carbon dioxide supplied from a carbon dioxide supply source 12 and / or nitrogen supplied from a nitrogen supply source 14, and the first gas mixer 1
5 is provided with a preheater 17 for preheating the raw material mixed gas mixed at 5 to a predetermined temperature, a shift furnace 18 having a nickel catalyst layer, and a cooler 19 for rapidly cooling the shift gas. An oxygen introducing section 21 for introducing and mixing oxygen supplied from an oxygen supply source 13 into a path 20 of a preheated raw material mixed gas leading to a preheating raw material mixed gas, and a hydrocarbon-containing mixed gas mixed by the second gas mixer 16 Hydrocarbon introduction section 22 introduced from the middle of the nickel catalyst layer in 18
And

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 mixed gas composed of a predetermined amount of hydrocarbon and carbon dioxide mixed by the first gas mixer 15 is preheated to a predetermined temperature by a preheater 17,
After oxygen is introduced and mixed from the oxygen introduction part 21, this raw material mixed gas is introduced into the nickel catalyst layer in the shift furnace 18, and further, a predetermined amount of carbonized gas introduced from the hydrocarbon introduction part 22 in the middle of the nickel catalyst layer. Hydrogen and carbon dioxide are mixed, and a metamorphic gas containing carbon monoxide and hydrogen is generated by these metamorphic reactions. The generated metamorphic gas is
After being rapidly cooled by the cooler 19, it is sent 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.

As described above, the hydrocarbon as the raw material is mixed with carbon dioxide, and is introduced into the nickel catalyst layer in the form of a mixed raw material gas mixed with oxygen through the preheater 17; A predetermined amount is divided and supplied to a path for introducing into the catalyst layer from the hydrocarbon introduction section 22 provided on the way.

By dividing and supplying hydrocarbons in this manner, the amount of hydrocarbons in the mixed raw material gas flowing into the nickel catalyst layer maintained at a high temperature can be made smaller than usual. Therefore, the amount of carbon generated by the rapid thermal decomposition of hydrocarbons when flowing into the nickel catalyst layer can be reduced, so that the generated carbon can be quickly reacted with carbon dioxide and oxygen. Moreover, in the atmosphere gas on the upstream side of the nickel catalyst layer, the supplied oxygen or the oxygen generated by the thermal decomposition of carbon dioxide is in an excessive state, so that even if soot is generated, It can be quickly removed by reacting with oxygen.

The hydrocarbon introduced from the hydrocarbon introduction part 22 in the middle of the nickel catalyst layer quickly reacts with excess carbon dioxide and oxygen flowing in the nickel catalyst layer to generate carbon monoxide and hydrogen.

Since a small amount of hydrocarbons are reacted in two steps in the nickel catalyst layer in this manner, a temperature drop due to an endothermic reaction can be suppressed, so that the shift reaction can be reliably performed. Thus, the generation of soot can be suppressed and a stable shift reaction can be performed.

The introduction of hydrocarbons from the hydrocarbon introduction section 22 suppresses a sudden reaction near the hydrocarbon introduction section,
In order to suppress the generation of soot, it is preferable to dilute the hydrocarbon with carbon dioxide or nitrogen. The dilution ratio of hydrocarbons, that is, the mixing ratio with carbon dioxide and nitrogen, depends on the type of raw material,
It can be set according to the amount of gas flowing through the nickel catalyst layer, the amount introduced from the hydrocarbon introduction unit 22, the reaction state in the nickel catalyst layer, and the like. Further, as the gas for diluting the hydrocarbon, an appropriate gas can be used as long as it does not affect the shift reaction or the shift gas generated.
More than one type can be used.

Further, as described above, the raw material mixed gas is preheated by the preheater 17 and then introduced into the nickel catalyst layer, whereby the temperature drop of the nickel catalyst layer can be more reliably suppressed. 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 position of the hydrocarbon introduction section 22 may be set in a stable state where there is almost no generation of soot in the nickel catalyst layer. Positioning may be performed according to conditions.

As shown in the system diagram of the main part of FIG.
A plurality of shift converters 181 and 182 may be installed in series, and a path 24 for introducing a hydrocarbon or a gas obtained by diluting a hydrocarbon with nitrogen or the like may be provided in a path 23 therebetween.
3, a plurality of nickel catalyst layers 25a and 25b may be provided in the shift furnace 18 and a path 27 for introducing hydrocarbons may be provided in a path 26 therebetween.

The combination of the hydrocarbon as the raw material and the source gas such as carbon dioxide and oxygen is optional. A preferable raw material combination is, for example, 0.33 mol of carbon dioxide, oxygen with respect to 1 mol of methane. 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. Can be introduced from the oxygen introduction part 21 and mixed. In addition, an oxygen-containing gas such as air can be introduced from the oxygen introduction unit 21.

The supply amount of hydrocarbons from the hydrocarbon introduction part 22 can be appropriately set according to the progress of the reaction in the nickel catalyst layer, etc. It should be set to a predetermined amount, it may be determined according to the type of hydrocarbon, the mixed amount of carbon dioxide and oxygen of the source gas, etc., and the amount of hydrocarbon supply may be adjusted according to the operating conditions. Good. Further, it is possible to use different types of hydrocarbons.

The hydrocarbon introduction section 22 can be provided at a plurality of positions according to the reaction conditions. The hydrocarbon introduction section 22 may be formed so as to be movable in the gas flow direction in the nickel catalyst layer. it can.

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, the operating conditions, and the like, and may be omitted.

FIG. 4 is a sectional view showing a specific example of the shape of the nickel layer portion in the shift furnace. This metamorphic furnace has a double tube structure in which an inner cylinder 32 for leading out a modified gas is disposed coaxially inside an outer cylinder 31 having a bottomed cylindrical body. In between, 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.

A hydrocarbon inlet pipe 40 provided with a plurality of outlets 22 serving as a hydrocarbon inlet on the lower side surface is provided with a cover 37.
And is arranged along the inner cylinder 32 through the refractory material 38, and in the nickel catalyst layer 33 in consideration of thermal expansion and contraction between the inner cylinder 32 and the hydrocarbon introduction pipe 40. It is slidably fastened by a plurality of stop rings 41.

The length of the hydrocarbon 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 the reaction is stable and there is almost no possibility that soot is generated. The supply direction and the supply speed of the hydrocarbon from the jet port 22 should be set so that the hydrocarbon can be 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 hydrocarbon introduction pipes 40 may be provided around the inner cylinder 32.
In addition, it is also possible to provide a plurality of ejection ports 22 for ejecting a predetermined amount of hydrocarbons in the longitudinal direction of one hydrocarbon introduction pipe 40, and to arrange the hydrocarbon introduction pipe 40 in the axial direction. It is also possible to provide it movably.

[0038]

As described above, according to the present invention,
Since part of the hydrocarbon is introduced from the middle of the nickel catalyst layer, the denaturation reaction in the nickel catalyst layer can be performed in a stable state, and the temperature decrease accompanying the denaturation reaction can be suppressed. Occurrence can 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 system diagram of a main part showing another embodiment of the atmospheric gas generator for high-temperature rapid carburizing of the present invention.

FIG. 3 is a system diagram of a main part showing still another embodiment.

FIG. 4 is a cross-sectional view showing a specific example of the shape of a nickel catalyst layer in a shift furnace.

[Explanation of symbols]

11: hydrocarbon source, 12: carbon dioxide source, 13
... Oxygen supply source, 14 ... Nitrogen 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: hydrocarbon introduction part, 31 ...
Outer cylinder, 32 inner cylinder, 33 nickel catalyst layer, 34 flange, 35 mixed gas introduction pipe, 36 inflow chamber, 37 cover, 38 refractory material, 39 catalyst retention plate, 40 hydrocarbon introduction Tube, 41 ... retaining 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 a high temperature, wherein a hydrocarbon introduction section for introducing a hydrocarbon is provided in the middle of the nickel catalyst layer. 2. A method for introducing a mixed gas of a mixture of hydrocarbons, carbon dioxide and oxygen into a nickel catalyst layer and generating a carburizing atmosphere gas containing carbon monoxide and hydrogen by a catalytic reaction. At least a part of the mixture is mixed in the middle of the nickel catalyst layer.