JPS59127648A - Preparation of gas containing oxygen in low concentration - Google Patents

Abstract

PURPOSE:To prepare atmospheric gas containing oxygen in low concn., by passing a gaseous mixture of reducing fuel and oxygen-containing stock gas through an oxidizing catalyst while controlling the flow amounts of both components to perform catalytic combustion. CONSTITUTION:Reducing fuel 1 such as H or CO and stock gas 2 containing oxygen in predetermined concn. are introduced into a mixer 5 respectively through a flow controller 3 and a stock gas flow amount controller 4 and, after mixing, the gaseous mixture is introduced into an oxidizing catalyst zone 6 prepared by supporting a catalyst metal such as platinum or rhodium by a carrier to subject the reducing fuel 1 to catalytic combustion. On the other hand, the oxygen concn. in the formed combustion exhaust gas is detected by a detector 7 and the obtained signal is connected to the fuel flow amount controller 3 of the reducing fuel 1 and the stock gas flow amount controller 4 through a controller 8. Therefore, atmospheric gas containing a constant amount of oxygen can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an atmospheric gas containing a low concentration of oxygen, and more specifically, the present invention relates to a method for producing an atmospheric gas containing a low concentration of oxygen.
The present invention relates to a method for producing a low oxygen concentration gas containing oxygen at a substantially constant concentration of 0 U Oppm or less.

BACKGROUND ART Conventionally, in firing furnaces that process metals and the like that dislike the presence of oxygen, and in firing furnaces that handle electronic parts and the like, a gas containing no oxygen at all or a low oxygen concentration gas containing only a small amount of oxygen is indispensable.

Generally speaking, the low oxygen concentration gas used in such an atmosphere firing furnace is obtained by supplying an inert gas such as nitrogen gas from a gas cylinder, using a gas obtained by decomposing ammonia gas, or using gas such as liquid nitrogen gas. Methods such as using a gas obtained by oxidation are known.

However, since large scale gases of this kind are used in industrial large-scale atmosphere firing furnaces, they have the drawback that maintenance and management of these gases requires a great deal of effort and is extremely expensive.

The present invention relates to a method for producing a high-purity, low-oxygen-containing gas in large quantities at low cost, which solves the above-mentioned drawbacks of the conventional methods. -Carbon oxide” n'2n T Cn
H2n+2 (however, n≦4) reduced fuel consisting of at least one citron is catalytically combusted in the presence of a raw material gas containing oxygen at a predetermined concentration, the oxygen concentration in the gas produced by the catalytic combustion is detected, and the detected value is The method is characterized in that the amount of reduced fuel is controlled accordingly, or the flow rate of raw material waste is controlled while supplying a constant amount of reduced fuel, so that a constant amount of ambient air waste is generated when the oxygen concentration is low. This is a method for producing scum with cumulative concentration.

In addition, catalytic combustion in the present invention refers to passing a mixture of oxygen-containing raw material gas such as air and reduced fuel through an oxidation catalyst,
This refers to the combustion of reduced fuel through catalytic action.

Section 14 shows a specific example of a more favorable configuration of the present invention.・Explain based on diagrams.

Reducing fuel such as H, Co or CnH2n l CnH
At least one of the W source materials 1 such as methane gas, ethane gas, propane gas, and butane gas represented by 2n+4 (where n≦4), etc., and a raw material gas 2 preferably containing several percent of oxygen are adjusted in fuel flow rate. 3 and the raw material gas stream # Wbit 4 are introduced into the mixer 5 and mixed, and then platinum, rhodium, and nickel.

A catalytic metal such as cobalt, iron, or copper is introduced into an oxidation catalyst zone 6 supported on a preferably ceramic catalyst carrier in the form of a honeycomb, pellet, plate, etc., and the reduced fuel 1 is catalytically combusted. Then, the oxygen concentration in the combustion exhaust gas generated by the catalytic fuel gε is detected by a solid-state gas detector or other oxygen concentration detector 7. Then, the exhaust gas 1 detected by the oxygen concentration detector 7. .

An electric signal corresponding to the oxygen concentration in the gas is connected to the fuel flow rate controller 8 of the reduced fuel 1 and the raw material gas flow rate controller 4 through the regulator 8.

And oxygen # in the combustion exhaust gas generated by catalytic combustion
7.1 Controller 8 so that the oxygen concentration approximately matches the desired oxygen concentration.
By controlling the flow rate of the reduced fuel l with the fuel flow rate controller 8 or by keeping the flow rate of the reduced fuel constant and controlling the flow rate of the raw material gas with the raw material gas flow rate controller 4, it is possible to reduce the flow rate to 500 ppm, preferably 500 ppm. This is a method for producing a low-purple-containing scum by producing an atmospheric gas containing a substantially constant acid concentration as described below.

In addition, in the example shown in FIG. 1, the number of the oxidation catalyst zone 6 is one, or the oxygen concentration contained in the raw material gas is 11%.
or above, or if the raw material gas is air, the oxygen concentration is 5
However, when reducing fuel is added to the oxygen gas, the oxygen concentration may increase upstream of the catalyst, making it impossible to control the oxygen concentration. It is desirable to reduce the oxygen concentration in stages by using a multi-stage catalyst.As shown in Fig. 2, multiple oxidation catalyst zones 6 are arranged in series, and the combustion of fuel is repeated in stages to reduce the oxygen concentration in the gas. Makoto, finally the predetermined r-jl! It is preferable that the total c element concentration be the same.

In addition, in this case, as shown clearly, various flow rate adjustments are made in total 3,
4 and 5 are similarly provided, and the reducing fuel and raw material gas are connected to the first stage. In addition, as shown in Figure 2, it is extremely effective to preheat the raw material waste by exchanging heat with the high-temperature waste obtained by catalytic combustion and the raw material waste containing oxygen in a heat exchanger 9. It is. In addition, in this 5e specification, if the reducing fuel added to the raw material gas is a hydrocarbon fuel expressed as CnH2n+2 or CnH2n (however, n≦4), if the number of carbon atoms exceeds 4, the oxygen concentration in the raw material gas will be 1゛. It becomes difficult to control the amount of reducing fuel added in response to fluctuations in oxygen concentration, making it difficult to produce gas with a stable oxygen concentration.

Further, as the raw material waste in the present invention, waste gas discharged through regular burner combustion, including G1 whole gas, can be used. However, burner combustion exhaust gas contains a large amount of sulfur oxide, and when dealing with a large amount of gas, problems may arise in public buildings. stomach.

In addition, if the raw material gas contains dust, dust, etc., the produced gas according to the present invention also contains these dusts.

If the furnace is used as a sintering furnace for electronic parts, etc., which requires a clean atmosphere free of dust and dirt, remove dust and dirt from the raw material gas in advance. It is desirable to leave it there. Furthermore, even if the raw material gas contains C12 and C12, it is desirable to remove them in advance depending on the intended use of the produced gas.

In addition, in order to catalytically burn the reduced fuel, the temperature of the mixed gas of the inflowing raw material gas and reduced fuel must be at least 20".
It is preferable that the temperature is higher than C. Therefore, as shown in Fig. 2, the heat of the catalytically burned exhaust gas is recovered by the heat exchanger 9, and this heat is used to preheat the oxygen-containing raw material gas that flows into the combustion catalyst. By utilizing it, the thermal efficiency in the dregs production method of the present invention can be increased.

Next, a non-inventive embodiment will be described.

Air preheated to 800°C is used as a raw material gas, and methane gas and propane gas are used as reducing fuels, respectively, and the mixture passes through two oxidation catalysts arranged in series as shown in Figure 2. This caused catalytic combustion.

The catalyst used in this case was an oxidation catalyst prepared by impregnating a honeycomb-shaped mullite carrier with an alumina layer of 50 μm thick and impregnated with 2% Asahi Arashi platinum. The gas flow rate Sv in the catalyst zone was set to 2×10”/Hr.

In addition, the oxygen concentration in the combustion gas at each °C catalyst is detected by a magnetic dumbbell oxygen detector 7, and reducing fuel is supplied to the catalyst at the same stage so that the acid concentration in the combustion gas is 10.5%. The flow rate is controlled by the air flow controller 8 of the first catalyst zone 6, and then the reduction fuel is supplied to the second stage so as to maintain the oxygen concentration in the combustion gas at 200 ppm in the second stage catalyst. The mixture was controlled by the second flow rate controller 3 so as to be mixed in the mixture 5 of the catalyst zone 6. The results of examining the oxygen concentration and stability of the obtained manufactured casta were similar to those of the first case.

, Example 2 As in Example 1, two catalytic reaction zones 6.6 were arranged in series, and a raw material gas consisting of air preheated to ao o "c, a certain amount of propane gas as a reducing fuel, and catalytic combustion was carried out while controlling the flow rate of the raw material gas. In this case, the same catalyst as in Example 1 was used as the catalyst.
11N17g of propane gas is added to the air through a screw meter that can be changed in the range of ~a o Nm8/u□, and the mixture is passed through the front catalyst zone using a grinder.
Next, 17g of propane gas was added to this combustion gas and catalytically burned from the rear catalyst zone 6, and the oxygen concentration in the combustion gas was measured using a magnetic dumbbell oxygen detector. The oxygen concentration was detected at 200p.
The raw material gas weight was changed by changing the opening degree of the raw material gas flow rate controller in front of the catalyst zone in the latter stage so that the raw material gas weight became pm. The results of examining the oxygen concentration and stability of the gas produced in this manner are shown in Table 2.

Table 2 Example 3 1 to 11 in which propane gas was burned with a normal gas burner
Exhaust gas containing VOI% oxygen and having a temperature of 300"C is used as a raw material gas, and hydrogen, carbon oxide, methane, ethylene, propane, and butylene are used as reducing fuel.

Butane was separately added to each layer, and alumina was supported on a mullite carrier formed into a honeycomb shape with a layer thickness of 50 μm.
5V-200001/)i
catalytic combustion was carried out. Then, the oxygen concentration in the exhaust gas after catalyst/combustion, that is, the oxygen concentration in the manufactured gas, was detected using a Mi air dumbbell type oxygen detector, and the oxygen concentration was determined to be 300 ppm.
Table 8 shows the results of examining the oxygen concentration and stability of the produced gas obtained by controlling the Tonkyu fuel supply unit using a flow wind F8 meter so as to maintain the same temperature. As a comparative example, a normal gas volume regulator was used and the combustion ratio of propane gas and air was set to 1.
The oxygen concentration in the exhaust gas obtained when combustion was performed at a low oxygen concentration was also measured.

Table 3 1.0 Hydrogen 300 4]
,〇 -Carbon oxide 8004 1.0 Methane 300
41.0 Propane 30
08 1.0 Butylene 3003 1.0 Butane 300
35-7 - carbon oxide 300
85~7 Ethylene 3006 5~7 Propane 8006 10~11 Propane 'a o o 1
0. Example 4 Propane gas is burned in a normal gas burner, and the oxygen concentration in the exhaust gas is 1. The temperature preheated by heat exchange which changes periodically from VOZ% to avoz% is aoo
The exhaust gas of ``c'' was used as a raw material gas, and was passed through a probe belt containing one combustion catalyst as shown in Figure 1, and fed to the catalyst so that the cumulative concentration in the produced gas after catalytic combustion was 200 ppm. The results of controlling the amount of propane gas and examining the oxygen concentration and stability in the produced gas are shown in Table 4.Here, the same 2 coul% platinum catalyst as in Example 3 was used as the catalyst. S.V.
-20000141 was used. Oxygen concentration was measured using a porcelain dumbbell oxygen detector, and propane gas was supplied using a meter linked to the oxygen detector.

4th table 1 2oo
105 200
830 2 (+0
As explained above, according to the present invention, an atmospheric gas having a low oxygen concentration and a stable oxygen concentration can be easily and inexpensively produced.

The gas turbidly produced by Muen-Ying can be used as an inert gas to create the atmosphere in various firing furnaces, etc., and maintenance is easier compared to the conventional method of supplying gas from gas cylinders. It is an industrially extremely effective gas production method because it can stably supply a large amount of low-grade gas with a simple system.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the flow of one example of the gas production method of the present invention, and FIG. 2 is an explanatory diagram showing the flow of a different specific example of the present invention. ■... Reducing fuel, 2... Enriched raw material gas, 3...
Reduction l) Fuel flow controller, 4... Raw material gas flow rate regulator, 5... Mixer, 6... Oxidation catalyst W&band, 7... Oxygen concentration detector, 8... Regulator , 9... Heat exchange gain.

Claims (1)

[Claims] 1. In a method for producing an atmospheric gas containing low concentration of oxygen, hydrogen, -carbon oxide I CnH2111CnHsn+
g <where n≦4) is catalytically combusted in the presence of a raw material gas containing oxygen at a predetermined concentration, the oxygen concentration in the gas produced by the catalytic combustion is detected, and according to the detected value. Then, the amount of the reducing fuel is controlled so that the oxygen concentration is in a low concentration and approximately constant range, or the source gas principle is controlled while supplying a certain amount of the reducing fuel,
A method for producing a gas containing a low oxygen concentration, which is characterized by generating atmospheric scum with a substantially constant oxygen concentration within a predetermined range. 2. The method for producing a low-oxygen-containing gas according to claim 1, wherein the reduced fuel and raw material gas are passed through a plurality of combustion catalyst zones arranged in series. 8. A method for producing a gas containing low oxygen concentration according to claim 1 or 2, wherein the raw material gas containing oxygen is preheated by heat exchange with gas obtained by catalytic combustion.