JPH0611106A - Combustion method in heating furnace - Google Patents

Abstract

PURPOSE:To reduce the unit requirement of fuel in a heating furnace and improve the efficiency of recoverying a carbonic acid gas by utilizing oxygen which is generated at the time of the generation of hydrogen required for the synthetic reaction of an organic compound, and performing combustion under an oxygen-enriched state. CONSTITUTION:The hydrogen generation side of an electrolyzing device 6 for water is connected to an organic compound synthesizing device 13. Further, the oxygen generation side of the electrolyzing device 6 for water is connected to an air pipeline 7 for feeding combustion air to a burner 2 via an oxygen pipeline 8, and oxygen-enriched air is fed to the burner 2. A material 4 to be heated is charged into a heating furnace 1. On the other hand, a carbon- containing fuel, which generates a carbonic acid gas by combustion, and an organic compound are supplied to the burner 2, whereby combustion is performed under an oxygen-enriched state. In this way, the unit requirement of fuel in the heating furnace can be reduced, and the concentrations of the carbonic acid gas and steam contained in a combustion gas become high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion method for a heating furnace which heats a heat target such as a slab or billet to a predetermined target temperature.

[0002]

2. Description of the Related Art Carbon dioxide (CO ₂ ) generated by the combustion of carbon-containing fuel in steel heating furnaces, power generation boilers, etc. is one of the substances causing global warming. This carbon dioxide immobilization method includes a biological immobilization method utilizing photosynthesis of plants, algae / fungi, marine organisms, etc., as well as chemical synthesis by organic chemical synthesis, polymer synthesis, photocatalyst, catalytic hydrogenation method, etc. There are various immobilization methods.

Of these, the catalytic hydrogenation method has a large ability to immobilize carbon dioxide gas per unit time and unit area and is capable of treating a large amount of carbon dioxide gas, such as methane (CH ₄ ), ethane (C ₂ H _{2 6} ), including lower hydrocarbons such as ethylene (C ₂ H ₄ ) to higher hydrocarbons such as oil and wax, and alcohols such as methanol (CH ₃ OH) and ethanol (C ₂ H ₆ O). A wide range of organic compounds can be synthesized.

As a combustion method of a heating furnace utilizing this catalytic hydrogenation method, for example, as described in "Chemical Engineering", June 1990, pages 47 to 49, an electrolyzer 6 is used. Water to electrolyze oxygen (O ₂ )
And hydrogen (H ₂ ) are generated, and from this hydrogen and the concentrated carbon dioxide gas separated by the carbon dioxide gas separator 10 from the exhaust gas discharged from the heating furnace 1, an organic compound fuel is produced by the organic compound synthesizer 13. There is one that is synthesized and burns this organic compound to heat the object to be heated (see FIG. 2). This method aims at synthesizing and reusing a fuel of an organic compound such as methanol from concentrated carbon dioxide gas and hydrogen in exhaust gas, and oxygen is used outside the system as a chemical raw material or the like.

[0005]

However, in this conventional heating furnace combustion method, since oxygen generated by electrolysis of water is used outside the system, oxygen-rich combustion is performed in the heating furnace in the system. There is a problem that the amount of exhaust gas, that is, the amount of heat loss of exhaust gas, is larger than that in the case of carrying out, and therefore the unit fuel consumption of the heating furnace is high. In addition to this, because of the air combustion, the carbon dioxide concentration in the combustion gas is low compared to the oxygen enriched combustion,
There was a problem that the efficiency of carbon dioxide recovery in the carbon dioxide separator was low and the carbon dioxide separator was large.

The present invention has been devised in order to improve the above problems of the prior art, and its main purpose is to:
It is an object of the present invention to provide a combustion furnace combustion method capable of reducing the fuel consumption rate of the heating furnace and improving the recovery efficiency of carbon dioxide gas.

[0007]

According to the present invention, such an object is obtained by electrolyzing water to generate oxygen and hydrogen, and synthesizing an organic compound from hydrogen and concentrated carbon dioxide gas in exhaust gas. In the combustion method of the heating furnace in which the organic compound is burned with the carbon-containing fuel to heat the object to be heated, the oxygen-enriched combustion is performed by mixing oxygen with the combustion air of the burner. It is achieved by providing a combustion method for a heating furnace. In particular, it is advisable to circulate and supply a part of the exhaust gas after sensible heat recovery to the burner.

[0008]

By doing so, since oxygen generated by electrolysis of water is used for combustion of the burner, the amount of combustion gas is reduced and the concentration of carbon dioxide gas in the combustion gas is increased. Therefore, the heat loss of exhaust gas is reduced, the fuel consumption rate of the heating furnace is reduced, the recovery efficiency of carbon dioxide gas in the carbon dioxide gas separation device is improved, and the emission amount of carbon dioxide gas to the atmosphere is reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a system flow chart of a combustion method for a heating furnace showing an embodiment of the present invention.

In FIG. 1, a heating furnace 1 made of a refractory wall is provided with a burner 2 and a flue 3 for discharging combustion gas, and a heated object 4 such as a slab or a billet is provided. It is arranged in this heating furnace 1 so that it can be heated.

The burner 2 is provided with a fuel pipe 5a for supplying a carbon-containing fuel such as heavy oil, kerosene, LPG, coke oven gas which burns to generate carbon dioxide gas, and a fuel pipe 5b for supplying an organic compound described later. It is connected.

Further, the oxygen generating side of the water electrolyzer 6 is connected to an air pipe 7 for supplying combustion air to the burner 2 via an oxygen pipe 8 to supply oxygen-enriched air to the burner 2. It is supposed to be supplied.

Exhaust gas exhaust heat recovery device 9, carbon dioxide gas separation device 10 and chimney 11 are provided in the flue 3 through which the combustion gas flows.
They are connected and arranged in this order. In addition to this, the outlet of the exhaust heat recovery device 9 is connected to the burner 2 via the exhaust gas pipe 12, and the low temperature exhaust gas after the exhaust heat recovery device 9 is circulated and supplied to the burner 2.

The hydrogen generation side of the water electrolyzer 6 is connected to the organic compound synthesizer 13 via a hydrogen pipe 14. The organic compound synthesizer 13 is connected to the carbon dioxide gas separator 10 via a carbon dioxide gas pipe 15.

Each pipe has a blower, a booster,
Although a valve and the like are provided, they are not shown here.

Next, the operation function of the above embodiment will be described.

First, the objects to be heated 4 are charged into the heating furnace 1 in batch or continuously.

On the other hand, a carbon-containing fuel that burns to generate carbon dioxide and an organic compound are supplied to the burner 2 through the respective fuel pipes 5a and 5b to perform oxygen-rich combustion. As a result, the nitrogen (N ₂ ) content in the oxygen-enriched air is reduced, and the amount of combustion exhaust gas is reduced. Therefore, the fuel consumption rate of the heating furnace 1 decreases, and the carbon dioxide gas and steam in the combustion gas become high in concentration, the gas radioactivity in the heating furnace 1 increases, and the radiative heat transfer amount of the object to be heated 4 increases. .

In addition to this, a part of the low-temperature exhaust gas after the exhaust heat recovery device 9 is circulated in the burner 2 and exhaust gas diluted combustion is performed. As a result, the combustion gas amount of the burner 2 increases and the high flame temperature at the time of oxygen-enriched combustion decreases, so that the object to be heated is uniformly soft-heated, and the generation of nitrogen oxides is suppressed.

The combustion gas, which has heated the object to be heated 4, flows out as an exhaust gas from the flue 3, but after the sensible heat of the exhaust gas is recovered by the exhaust heat recovery device 9, it becomes a low temperature exhaust gas. Is recirculated and supplied to the burner 2 via the exhaust gas pipe 12. And the remaining exhaust gas, physical absorption method, chemical absorption method,
After the carbon dioxide gas is separated by the carbon dioxide gas separation device 10 such as a membrane separation method, it is discharged into the atmosphere from the chimney 11 as an exhaust gas containing a low concentration of carbon dioxide gas.

Although not shown in FIG. 1, the heat recovered by the exhaust heat recovery device 9 is used for preheating combustion air or for generating steam.

On the other hand, electrolysis of water (reaction formula: 2H ₂ O → 2H ₂ + O) is performed by the electrolysis device 6 using electric energy such as nuclear power generation and solar power generation that does not generate carbon dioxide gas.
₂ ) is performed and oxygen and hydrogen are generated.

This oxygen is supplied to the air pipe 7 through the oxygen pipe 8 and is supplied to the burner 2 as oxygen-enriched air for oxygen-enriched combustion.

Further, hydrogen is supplied to the organic compound synthesizer 13 together with the carbon dioxide gas concentrated in the carbon dioxide gas separator 10. Here, organic compounds such as methane, ethane, and methanol are synthesized by the catalytic hydrogenation method. In particular, methanol is the most economical because it consumes less hydrogen than the synthesis of other organic compounds.

In the synthetic reaction of this kind of organic compound,
Generally, a catalyst and a constant temperature and pressure are required. For example, in a synthesis reaction of methanol using Cu—ZnO—La ₂ O ₃ as a catalyst (reaction formula: CO ₂ + 3H ₂ → CH ₃ OH).
+ H ₂ O), 300 ° C., 110 atm reaction conditions, the conversion of carbon dioxide gas is about 30%, and methanol of 99.9% purity can be synthesized.

By supplying this organic compound as a fuel to the burner 2 and using it as an auxiliary fuel for the carbon-containing fuel, the amount of the carbon-containing fuel used is reduced. As a result, the amount of fuel used in the heating furnace is reduced and the amount of carbon dioxide gas emitted is reduced, which is useful for suppressing global warming.

Next, the results obtained by trial calculation of the effect of the present invention will be illustrated.

Fuel consumption rate is 400 × 10 ³ Kcal /
t, a coke oven gas-exclusive steel material heating furnace having an exhaust gas heat loss of 100 × 10 ³ Kcal / t is used as a base condition for trial calculation,
Air combustion by conventional methanol synthesis (O ₂ = 21%)
And a case of using the methanol synthesis of the present technology and oxygen-rich combustion (O ₂ = 50%) in combination.
The effect of reducing the fuel consumption rate of the heating furnace, the amount of coke oven gas used, and the amount of carbon dioxide released into the atmosphere was calculated.

The coke oven gas was burned at a theoretical oxygen ratio of 1.0, and the amount of methanol synthesized was the same between the prior art and the present invention.

The fuel characteristics of the coke oven gas and methanol used in the trial calculation are shown in Table 1, and the trial calculation results are shown in Table 2.

[0032]

[Table 1]

[0033]

[Table 2]

As a result, according to the prior art, it was found that the fuel consumption rate was at the same level as the base condition of the trial calculation, and the amount of coke oven gas and carbon dioxide released into the atmosphere could be reduced to about 28%.

On the other hand, according to the technique of the present invention, the fuel consumption rate can be reduced to about 87%, and the amount of coke oven gas and carbon dioxide released into the atmosphere can be reduced to about 16% based on the base calculation conditions. Was given. That is, it can be seen that an extremely great effect can be obtained in reducing the fuel consumption rate of the heating furnace and the amount of carbon dioxide released into the atmosphere as compared with the conventional technique.

In this example, liquid methanol was used at room temperature and atmospheric pressure in consideration of economy in synthesizing organic compounds and ease of handling as a fuel, but methane, ethane, Of course, it is also possible to synthesize other organic compounds such as ethanol and use them as fuels, or to provide a storage tank for oxygen, hydrogen, organic compound fuels, etc. in the middle of the piping for load fluctuation adjustment. It goes without saying that various changes can be made without departing from the scope of the present invention.

[0037]

As is apparent from the above description, according to the combustion furnace combustion method of the present invention, oxygen-enriched combustion is performed by utilizing oxygen generated during hydrogen production necessary for the synthesis reaction of organic compounds. Therefore, the amount of combustion gas is reduced, the concentration of carbon dioxide is increased, the heat transfer amount of the object to be heated is promoted, the heat loss of exhaust gas is reduced, and the fuel consumption rate of the heating furnace can be reduced. Since the concentration of carbon dioxide in the exhaust gas is high, the efficiency of carbon dioxide recovery in the carbon dioxide separator is high, and therefore the amount of carbon dioxide released into the atmosphere is reduced, and global warming can be suppressed. Since the heating furnace for the object to be heated, the electrolyzer for water, and the organic compound synthesizer are configured as an integrated system, operation management of the device is easy. And so on.

[Brief description of drawings]

FIG. 1 is a system flow diagram of a combustion furnace combustion method according to an embodiment of the present invention.

FIG. 2 is a system flow diagram of a combustion method for a heating furnace according to the related art.

[Explanation of symbols]

 1 Heating Furnace 2 Burner 3 Flue 4 Heated Material 5a ・ 5b Fuel Pipe 6 Electrolyzer 7 Air Pipe 8 Oxygen Pipe 9 Exhaust Heat Recovery Device 10 Carbon Dioxide Separator 11 Chimney 12 Exhaust Gas Pipe 13 Organic Compound Synthesizer 14 Hydrogen Pipe 15 Carbon dioxide piping

Claims (2)

[Claims] 1. Electrolysis of water to generate oxygen and hydrogen, an organic compound is synthesized from the hydrogen and concentrated carbon dioxide gas in the exhaust gas, and the organic compound is burned with a carbon-containing fuel to be heated. In the method for combustion in a heating furnace for heating, the oxygen-enriched combustion is performed by mixing the oxygen with the combustion air of the burner. 2. The method for combustion in a heating furnace according to claim 1, wherein a part of the exhaust gas after sensible heat recovery is circulated and supplied to the burner.