JP5617667B2 - Method for reforming combined arc melting furnace exhaust gas and combined arc melting furnace - Google Patents

Description

  The present invention relates to a method for reforming exhaust gas generated when a cold iron source such as iron scrap or directly reduced iron is melted in a complex arc melting furnace having a shaft-shaped preheating chamber, and a complex arc melting used in the method. It relates to the furnace.

  In recent years, cold iron sources such as iron scrap have been conventionally regenerated as molten steel after being melted and refined using various arc furnaces. However, since a large amount of electric power is required to melt the cold iron source by the arc furnace, in recent years, the cold iron source is generated by the high-temperature exhaust gas generated from the melting chamber of the arc furnace for the purpose of reducing the power consumption. There has been proposed a new method for melting while preheating.

  As a typical example, Patent Document 1 proposes a composite arc melting furnace including a melting chamber and a shaft-type preheating chamber for introducing exhaust gas generated in the melting chamber. In the operation of this combined arc melting furnace, the iron scrap to be charged exists between the preheating chamber and the melting chamber, and the iron scrap is heated and melted by arc heat in the melting chamber. This is a method for melting iron scrap, characterized in that molten steel is discharged when at least one heat of molten metal has accumulated.

  Further, in Patent Document 2, in using high-temperature exhaust gas generated from an arc melting furnace, a gas containing hydrocarbons and / or a high-temperature exhaust gas containing carbon dioxide and / or steam generated from a refining facility such as a converter and / or Alternatively, there is disclosed a method for so-called “heat increase” in which a liquid is supplied to induce a reforming reaction and carbon monoxide and hydrogen in the exhaust gas are increased to increase the latent heat content of the exhaust gas.

JP-A-10-292990 JP 2000-212615 A

However, in the method disclosed in Patent Document 1, since the exhaust gas generated in the melting chamber is discharged without being burned, there remains a problem in terms of effective use of the exhaust gas. Further, in the method disclosed in Patent Document 2, when the reforming reaction shown in the following formula (1) is performed by blowing natural gas (hydrocarbon) into the converter exhaust gas, the completion temperature of the reaction is 800 ° C. If it is lower than the range, the production of carbon becomes remarkable, which causes the deposition of carbon, dust and the like in the exhaust gas recovery facility, and there is a problem in that the reforming reaction efficiency is lowered and the conversion rate of carbon dioxide is lowered.
CH ₄ + CO ₂ → 2CO + 2H ₂ (1)

  The present invention is a technology developed in view of the above-described circumstances of the prior art, and the object is to occur when a cold iron source is melted using a composite arc melting furnace. To propose a composite arc melting furnace exhaust gas reforming method and a composite arc melting furnace capable of reforming exhaust gas without causing deposition of carbon, dust, etc., and increasing the latent heat of the exhaust gas. is there.

  By the way, it is known that ammonia gas reacts with carbon monoxide and carbon dioxide to be reformed into various hydrocarbons, oxygen-containing compounds such as methanol and dimethyl ether, and the like. Examples of chemical reaction formulas are shown in the following formulas (2) and (3).

2NH ₃ + CO → CH ₄ + H ₂ O + N ₂ (2)
4NH ₃ + CO ₂ → 2H ₂ + 2H ₂ O + 2N ₂ + CH ₄ (3)

According to the research by the inventors, in a laboratory test in which ammonia gas (NH ₃ ) was blown into a mixed gas of CO and CO ₂ , the reforming reaction of the formula (2) was performed under a low temperature condition of 400 ° C. or less. On the other hand, under the high temperature condition of 600 ° C. or higher, the result that the reforming reaction of the formula (3) proceeds is obtained.

The present invention is a technique that pays attention to the reforming reaction between ammonia gas and CO and CO ₂ contained in the exhaust gas. That is, in the present invention, instead of introducing a gas and / or a liquid containing hydrocarbon as proposed in Patent Document 2, ammonia gas is introduced, and the ammonia gas and exhaust gas components (CO, CO ₂₎ are introduced. ), The heat generated at this time is used for preheating the cold iron source, and hydrogen and hydrocarbons in the exhaust gas are increased. The present invention proposes a method for reforming exhaust gas generated from a combined arc melting furnace in which the latent heat of exhaust gas is increased (heat increase) and a melting furnace therefor.

That is, the present invention provides a cold iron source that sequentially descends the preheating chamber by means of an arc melting furnace comprising a melting chamber and a shaft-shaped preheating chamber that stands on the top and communicates with the melting chamber. In the combined arc melting furnace that is preheated using the high-temperature exhaust gas generated in step 1 and that is subsequently guided to the melting chamber and arc-melted, the cold iron source exists across the preheating chamber and the upper portion of the melting chamber The carbon material which is an auxiliary heat source is blown into the melting chamber, while the ammonia gas is blown into the preheating chamber, so that the ammonia gas and 600 ° C. or more at the hot water surface in the melting chamber of the preheating chamber. It led to the reforming reaction between carbon dioxide in the flue gas, reforming side of the composite arc melting furnace generation exhaust gas, characterized in that increasing the hydrogen concentration and the hydrocarbon gas concentration in the exhaust gas It is.

In the above-described method for reforming the combined arc melting furnace exhaust gas,
(1) The exhaust gas generated in the melting chamber contains at least 5% carbon dioxide,
(2) The ammonia gas is blown from an ammonia gas introduction port provided at one or a plurality of locations in a region from the position of the molten metal surface in the melting chamber of the preheating chamber to the upper end position of the deposition layer of the cold iron source in the upper portion of the preheating chamber. that,
(3 ) The temperature of the exhaust gas generated from the melting chamber is 400 ° C. or less at the upper end position of the cold iron source in the upper part of the preheating chamber, and reforming of the ammonia gas and carbon monoxide in the exhaust gas at that position Guiding the reaction to increase the concentration of hydrocarbon gas in the exhaust gas,
( 4 ) The amount of ammonia gas blown is 5 to 25% of the amount of exhaust gas generated from the dissolution chamber,
( 5 ) The amount of the carbon material blown is 5 kg / t or more with respect to the cold iron source in the melting chamber,
Is a more preferable solution.

Further, in the present invention, an arc electrode and a melting chamber for arc melting of the cold iron source, and a cold iron source that is installed above the melting chamber, communicates with the melting chamber, is charged and filled. An auxiliary heat source supply means and an oxygen supply means for supplying an auxiliary heat source to the melting chamber, and a deposited layer of a cold iron source above the preheating chamber from the position of the hot water surface in the melting chamber of the preheating chamber. in the region up to the upper end position, and one or ammonia gas inlet at a plurality of locations, have a, a gas recovery system for recovering the exhaust gas generated in the melting chamber, at the melt surface position of the dissolution chamber of the preheating chamber And recovering exhaust gas with increased hydrogen concentration and hydrocarbon-based gas concentration by introducing a reforming reaction between ammonia gas blown from the ammonia gas inlet and carbon dioxide in the exhaust gas at 600 ° C. or higher. The To propose a complex arc melting furnace for the butterflies.

According to the present invention configured as described above, when producing a molten steel by melting a cold iron source, the carbonaceous material is supplied as an auxiliary heat source in the melting chamber, thereby melting the cold iron source in the melting chamber. Can be promoted more. However, this causes not only unburned CO but also CO ₂ to be generated in the exhaust gas generated when the cold iron source is dissolved. In the present invention, ammonia (NH ₃ ) gas is introduced into the preheating chamber for modification. The exhaust gas component (CO, CO _2, etc.) can be reformed to H ₂ or hydrocarbon by causing a quality reaction. Therefore, according to the present invention, it is possible to effectively use the thermal energy of the exhaust gas without causing the deposition of carbon or dust, and at the same time, it is possible to increase the heat of the exhaust gas. The exhaust gas whose temperature has been increased in this way can be effectively used for an energy source for operating various facilities in the steelworks, or for recovering exhaust heat by a boiler.

It is a schematic sectional drawing which shows one Embodiment of the composite arc melting furnace of this invention.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a longitudinal section showing an example of a combined arc melting furnace used in the present invention.

  As shown in the figure, the composite arc melting furnace 1 used in the present invention comprises a melting chamber 2 and a shaft-type preheating chamber 3 standing upward from a part of the upper portion thereof, and the inside thereof is lined with a refractory material. Yes. The melting chamber 2 has a furnace bottom electrode 6 at the bottom, and has the shaft-shaped preheating chamber 3 and the water-cooled furnace wall 4 communicating with the melting chamber 2 at the top. A furnace lid 5 is provided so as to cover the opening. The furnace lid 5 has a water cooling structure that can be opened and closed, and is provided with a graphite upper electrode 7 that moves up and down toward the melting chamber 2. The upper electrode 7 and the furnace bottom electrode 6 are energized by a DC power source (not shown) through a cold iron source in the furnace so that an arc 19 can be generated therebetween. It has become.

Further, an oxygen blowing lance 8 and a carbonaceous material blowing lance 9 are attached to the furnace lid 5, and oxygen for assisting the dissolution of the cold iron source 15 is supplied from the oxygen blowing lance 8, Auxiliary heat sources such as coke, char, coal, charcoal, graphite, biomass charcoal powder, or a carbon material made of a mixture thereof are blown from the blowing lance 9 through air or nitrogen. As a result, the generated exhaust gas always contains unburned components (CO gas), carbon dioxide (CO ₂ ), and the like.

  Above the preheating chamber 3, there is provided a bottom-opening type supply bucket 13 suspended from the traveling carriage 24, and this supply bucket 13 can be opened and closed provided at the top of the preheating chamber 3. A cold iron source (for example, iron scrap) 15 can be charged into the preheating chamber 3 via the supply port 20.

  In the composite arc melting furnace configured as described above, the cold iron source 15 charged in the preheating chamber 3 is preheated while descending sequentially with time, and eventually reaches the melting chamber 2 and then the upper part. When the cold iron source 15 is melted by the heat of the arc 19 generated from the electrode 7, high-temperature exhaust gas is generated in the melting chamber 2. The exhaust gas is sucked into the duct 21 through the preheating chamber 3 by a blower 42 and a dust collector 43 provided upstream of the duct 21 provided above the preheating chamber 3. In this process, the exhaust gas is cooled in the preheating chamber 3. The iron source 15 is preheated by the heat of the high temperature exhaust gas. Note that the preheated cold iron source 15 in the preheating chamber 3 falls freely according to the speed of melting in the melting chamber 2 and sequentially or intermittently moves into the melting chamber 2.

In the present invention, when the cold iron source 15 is melted by the heat of the arc 19 in the melting chamber 2 as described above, the carbon material is supplied into the melting chamber 2 through the carbon material blowing lance 9 and burned. Thus, in the process in which the melting of the cold iron source 15 in the melting chamber 2 is promoted and the high-temperature exhaust gas generated in the melting chamber 2 is sucked into the duct 21 through the preheating chamber 3, the preheating chamber 3 It is characterized in that a reforming reaction is caused between ammonia gas blown into the interior and CO and CO ₂ in the exhaust gas rising in the preheating chamber 3.

According to such a configuration, in particular, ammonia gas blown into the preheating chamber 3 and CO and CO ₂ gas contained in the high-temperature (about 400 to 1000 ° C.) exhaust gas generated in the dissolution chamber 2 Since the reforming reaction shown in the above formula (2) or (3) occurs depending on the temperature of the exhaust gas, hydrocarbons, H _2, etc. in the exhaust gas increase, thereby increasing the latent heat of the exhaust gas. become able to.

The exhaust gas composition generated from the melting chamber _{2, CO: 2~8%, CO} 2: 5~15%, O 2: 1~15%, N 2: 50~80%, H 2 O: 0~5%, H ₂ is about 0 to 3%, and CO and CO ₂ among them react with ammonia gas in the preheating chamber 3 to cause the above reforming reaction.

  The reaction of the above formula (2), that is, the reaction between CO and ammonia gas in the exhaust gas proceeds preferentially under a low temperature condition of 400 ° C. or lower, resulting in an increase in the amount of hydrocarbon gas in the exhaust gas. The exhaust gas latent heat can be increased. Moreover, since this reaction is an exothermic reaction, the reaction heat can be used for preheating the cold iron source in the preheating chamber 3.

On the other hand, the reaction of the above formula (3), that is, the reaction between CO _{2 in} the exhaust gas and ammonia gas preferentially proceeds under a high temperature condition of 600 ° C. or higher. Since this reaction is an endothermic reaction, the sensible heat of the exhaust gas is lost during the reforming reaction. However, the reaction increases the amount of hydrogen and hydrocarbon-based gas and can increase the latent heat of the exhaust gas. There are quality benefits. In order to promote the reaction according to the formula (3), it is preferable that at least 5% of CO ₂ is contained in the exhaust gas generated from the dissolution chamber 2.

  As described above, since the reactions of the above formulas (2) and (3) selectively proceed according to the temperature of the exhaust gas passing through the preheating chamber 3, the ammonia gas blowing position is selected according to the purpose of use of the exhaust gas. Preferably, for example, when the preheating of the cold iron source is important, ammonia gas is blown into the vicinity of the upper position of the deposition layer of the cold iron source 15 in the preheating chamber 3 where the exhaust gas temperature is low. On the other hand, when priority is given to increasing the exhaust gas latent heat, ammonia gas is blown into the vicinity of the hot water surface in the melting chamber 2 of the preheating chamber 3 where the exhaust gas temperature is high, and the above (3 It is preferable to cause the reaction of formula (1) to occur preferentially.

In the present invention, ammonia gas is blown from an ammonia gas inlet 25 provided on the side wall of the preheating chamber 3. In this case, the ammonia introduction port 25 is connected to one or more in the circumferential direction and the vertical direction of the side wall in the region from the molten metal surface position in the melting chamber 2 to the upper end position of the deposition layer of the cold iron source 15 in the preheating chamber 3. It is preferable to provide at a location. According to this, each reaction of CO and CO ₂ in the exhaust gas generated from the melting chamber 2 and ammonia gas can be surely performed at each position, and the ammonia inlets 25 are provided at a plurality of locations. This is because the temperature of the cold iron source 15 in the preheating chamber 3 does not deviate.

The exhaust gas that has finished the reforming reaction with ammonia gas in the preheating chamber 3 as described above is sucked by the blower 42, cooled by the cooling tower 40 through the duct 21, and then collected by the dust collector 43 including a bag filter. After collecting dust, the gas is discharged from the flare 45 to the atmosphere via the gas flow rate switching valve 44 or collected in the gas holder, and then sent to various facilities in the ironworks to be effectively used as fuel. A gas analyzer or a gas flow meter is preferably installed upstream of the cooling tower 40. In the gas analyzer, the concentrations of CO, CO ₂ , O ₂ , H ₂ , and CH ₄ gas in the exhaust gas are adjusted. Measure and continuously measure the flow rate of the exhaust gas with the gas flow meter.

  Incidentally, the bottom of the melting chamber 2 on the side opposite to the preheating chamber 3 is closed by a door 22 and has a steel outlet 11 filled with stuffed sand or mud agent on the inside thereof. The side wall is provided with an outlet 12 which is closed by a door 23 and which is filled with stuffed sand or mud agent.

  A burner 10 is attached to the furnace lid 5 located above the steel outlet 11. By this burner 10, fossil fuel such as heavy oil, kerosene, pulverized coal, propane gas, natural gas, biomass fuel, and the like are burned in the melting chamber 2 with air, oxygen, or oxygen-enriched air to produce steel. The temperature of molten steel can be raised.

Hereinafter, a procedure for melting the cold iron source in the DC arc furnace 1 will be described.
First, the cold iron source 15 is charged into the preheating chamber 3 from the supply bucket 13. The charged cold iron source 15 passes through the preheating chamber 3 and is first charged into the melting chamber 2 and then gradually filled into the preheating chamber 3. In order to uniformly charge the cold iron source 15 into the melting chamber 2, the cold iron source 15 is placed in the melting chamber 2 on the side opposite to the side directly connected to the preheating chamber 3 with the furnace lid 5 opened. It can also be charged. Further, hot metal may be charged into the melting chamber 2 when the cold iron source 15 is charged. According to this, the amount of electric power used can be significantly reduced by the heat of the hot metal. The hot metal is charged into the melting chamber 2 through a ladle for supply (not shown) and a hot metal (not shown) connected to the melting chamber 2.

  Next, while feeding a direct current between the furnace bottom electrode 6 and the upper electrode 7 in the melting chamber 2, the upper electrode 7 was moved up and down, and was inserted between the furnace bottom electrode 6 and the upper electrode 7 or charged. An arc 19 is generated between the cold iron source 15 and the upper electrode 7, and the cold iron source 15 is melted by the heat of the arc 19. At this time, it is preferable to generate the molten slag 18 by melting the flux. This is because the molten metal 17 produced by the molten slag 18 can be kept warm. When the production amount of the molten slag 18 is too large, the molten slag 18 may be discharged from the outlet 12 during operation.

  After the furnace bottom electrode 6 and the upper electrode 7 are energized, when the oxygen blowing lance 8 and the carbonaceous material blowing lance 9 can be inserted into the melting chamber 2, oxygen is supplied from the oxygen blowing lance 8 to supply a cold iron source 15 To help dissolve. On the other hand, carbon material is blown into the molten slag 18 as an auxiliary heat source from the carbon material blowing lance 9 in order to reduce the power consumption.

The amount of oxygen blown from the oxygen blowing lance 8 is preferably 15 Nm ³ or more per ton of the molten metal 17 staying in the melting chamber 2 between the start of melting and the tapping. This is because when the amount of oxygen blown is less than 15 Nm ³ per ton of molten metal, the effect of reducing the power consumption rate by melting the cold iron source 15 or oxidizing the carbonaceous material is small.

  Further, the amount of carbon material blown by the carbon material blowing lance 9 into the melting chamber 2 may be equal to or more than the chemical equivalent amount of oxygen blown from the oxygen blowing lance 8. Preferably, it is 5 kg / t or more. This is because if the carbon content of the carbon material is smaller than the oxygen gas to be blown, the molten metal 17 is excessively oxidized or the carbon concentration is lowered.

The carbon material dissolved in the molten metal 17 or the carbon material suspended in the molten slag 18 reacts with oxygen blown from the oxygen blowing lance 8 to be decarburized to become CO gas, and its reaction heat is an auxiliary heat source. This will contribute to the reduction of power consumption. Moreover, since the molten slag 18 is expanded by forming with the CO gas as the reaction product, the tip of the upper electrode 7 is buried in the molten slag 18. Therefore, the arc 19 generated from the upper electrode 7 is wrapped by the molten slag 18, and the heat deposition efficiency of the arc 19 is increased. Moreover, the high-temperature CO gas generated in a large amount and the CO ₂ gas generated by burning this CO gas efficiently preheat the cold iron source 15 in the preheating chamber 3.

CO and CO ₂ in a large amount of high-temperature exhaust gas generated when the cold iron source 15 is melted as described above are supplied to the preheating chamber 3 and then the ammonia gas inlet provided on the side wall of the preheating chamber 3. It reacts with the ammonia gas blown from 25 and is reformed into hydrocarbon and H ₂ as shown in the above formulas (2) and (3).

  The amount of ammonia gas blown into the preheating chamber 3 is 5 to 25%, preferably 8 to 18%, of the exhaust gas flow rate generated from the melting chamber 2. This is because when the amount of ammonia gas blown is less than 5% of the exhaust gas flow rate, the reforming reaction does not occur sufficiently due to the shortage of the ammonia gas amount, whereas when it exceeds 25%, the ammonia gas amount becomes excessive, It is because it emits in an unreacted state and the problem of odor occurs.

  Since the cold iron source 15 in the preheating chamber 3 falls freely into the melting chamber 2 according to the amount of the cold iron source 15 in the melting chamber 2 and decreases, this decrease is preheated from the supply bucket 13. The cold iron source 15 is sequentially charged into the chamber 3 to make up for it. The charging of the cold iron source 15 into the preheating chamber 3 is continuous or intermittent so that the cold iron source 15 can be maintained (continuously) across the preheating chamber 3 and the melting chamber 2. To do. At that time, it is preferable that a cold iron source of 50 mass% or more of the amount of hot water discharged remains in the preheating chamber 3 and the melting chamber 2. This is because the high-temperature exhaust gas generated from the melting chamber 2 is effectively used for preheating the cold iron source.

  Although the case where the arc furnace 1 is a direct current type has been described above, the present invention can be applied without any problem even when an alternating current type arc furnace is used.

  In this embodiment, a DC-type composite with a furnace capacity of 180 tons comprising a melting chamber (furnace diameter 7.2 m, height 4 m) and a preheating chamber (width 3 m, length 5 m, height 7 m) shown in FIG. In an arc melting furnace, first, about 70 tons of normal-temperature iron scrap is charged into a preheating chamber of the furnace. Next, 70 tons of normal steel scrap was charged into the melting chamber, and an arc with a power capacity of up to 750 V and 130 KA was generated using a graphite upper electrode with a diameter of 30 inches to melt the iron scrap in the melting chamber. Started. During melting operation of iron scrap, ammonia gas is blown from the ammonia gas inlet provided on the side wall of the preheating chamber under the conditions shown in Table 1, and the preheating chamber lower end inlet (before the reforming reaction with ammonia gas) and upper end outlet position (ammonia gas) The gas analysis of the exhaust gas was measured after the reforming reaction), and the exhaust gas temperature was measured at the exhaust duct inlet at the top of the preheating chamber. The ammonia gas inlets were provided at three locations: A: the molten metal surface position in the melting chamber, C: the upper end position of the cold iron source in the upper part of the preheating chamber, and B: the intermediate position between A and C.

Further, in this example, immediately after energization, quick lime and fluorite were added into the melting chamber, and oxygen was blown from the oxygen blowing lance to 6000 Nm ³ / hr, and coke was blown from the carbonaceous material blowing lance at 80 kg / min. Quick lime and fluorite are heated to form molten slag, and then formed by blowing oxygen and coke, and used to guide the state in which the tip of the upper electrode is buried in the molten slag. At this time, the voltage was set to 550 V, and in the melting of iron scrap, the oxygen blowing rate was 30 Nm ³ / t, and the coke blowing rate was 30 kg / t.

The results of the present invention are shown in Table 1 together with comparative examples (Comparative Example 1: no ammonia gas blowing, Comparative Example 2: no coke (carbon material) blowing).
In this example, the ammonia gas inlet temperature when the ammonia gas was blown was 800 to 1300 ° C. for A, 500 to 800 ° C. for B, and 300 to 500 ° C. for C. Blowing amount of ammonia gas, the invention examples 1 to 5, 38 Nm ³ / min reasonable 7% of the exhaust gas flow rate, the invention Example 6 and Comparative Example 2 became 57 nm ³ / min is equivalent to 15%.

From the results of Table 1, in Invention Examples 1 to 6, by introducing ammonia gas into the preheating chamber and reacting with the exhaust gas for reforming, the iron scrap in the preheating chamber was efficiently preheated, It was confirmed that the unit could be reduced.
Further, in Invention Examples 1 to 6, the amount of hydrocarbons and H ₂ in the exhaust gas increased, whereas in Comparative Example 1 (when ammonia blowing was not performed), hydrocarbons were not detected in the exhaust gas, The amount of H ₂ was 3% or less. Further, in Comparative Example 2 (when no coke is blown), the amount of CO and CO ₂ in the exhaust gas generated from the melting chamber is small, so that a reforming reaction between CO and CO ₂ and ammonia gas occurs in the preheating chamber. Therefore, hydrocarbons were not detected in the exhaust gas, the amount of H ₂ was 3% or less, and the power consumption rate was also high.
In Invention Example 3, ammonia gas is blown from the position A where the exhaust gas temperature is the highest (800 to 1300 ° C.), whereby the reaction of the above formula (3) preferentially proceeds and a large amount of H ₂ is generated. Further, in Invention Example 5, when ammonia gas was blown from the C position where the exhaust gas temperature was low (300 to 500 ° C.), the reaction of the above formula (2) proceeded preferentially. Although the production of H ₂ was small, a large amount of CH ₄ could be generated instead.

  The technology according to the present invention is useful as a method for effectively using the exhaust gas generated when a cold iron source such as iron scrap or directly reduced iron is melted by the exemplified composite arc melting furnace. It is possible to apply this concept to melting furnaces.

DESCRIPTION OF SYMBOLS 1 Arc furnace 2 Melting room 3 Preheating room 4 Furnace wall 5 Furnace lid 6 Furnace bottom electrode 7 Upper electrode 8 Oxygen blowing lance 9 Carbon material blowing lance 10 Burner 11 Outlet 12 Outlet 13 Supply bucket 15 Cold iron source 17 Molten metal 18 Molten slag 19 Arc 20 Supply port 21 Duct 22 Door 23 Door 24 Traveling carriage 25 Ammonia gas inlet 40 Cooling tower 42 Blower 43 Dust collector 44 Gas flow switching valve 45 Flare

Claims (7)

An arc melting furnace comprising a melting chamber and a shaft-shaped preheating chamber that stands upright and communicates with the melting chamber is used to generate a cold iron source that descends in the preheating chamber in order to generate hot exhaust gas generated in the melting chamber. In a combined arc melting furnace that is preheated and then led to the melting chamber to melt the arc,
Under the state where the cold iron source exists across the preheating chamber and the upper part of the melting chamber, while blowing the carbon material as an auxiliary heat source into the melting chamber, while blowing ammonia gas into the preheating chamber ,
The reforming reaction between the ammonia gas and carbon dioxide in the exhaust gas at 600 ° C. or higher is led at the molten metal surface position in the melting chamber of the preheating chamber to increase the hydrogen concentration and hydrocarbon gas concentration in the exhaust gas. A method for reforming exhaust gas generated from a combined arc melting furnace, characterized in that:   The method for reforming exhaust gas generated in a combined arc melting furnace according to claim 1, wherein the exhaust gas generated in the melting chamber contains at least 5% of carbon dioxide.   The ammonia gas is blown from one or a plurality of ammonia gas inlets in a region from the position of the molten metal surface in the melting chamber of the preheating chamber to the upper end position of the cold iron source deposition layer in the upper portion of the preheating chamber. The method for reforming exhaust gas generated from a combined arc melting furnace according to claim 1 or 2. The temperature of the exhaust gas generated from the melting chamber is 400 ° C. or less at the upper end position of the deposited layer of the cold iron source in the upper part of the preheating chamber, and at that position, the reforming reaction between the ammonia gas and carbon monoxide in the exhaust gas is led. The method for reforming exhaust gas generated in a combined arc melting furnace according to any one of claims 1 to 3 , wherein the concentration of hydrocarbon-based gas in the exhaust gas is increased. The method for reforming exhaust gas generated in a combined arc melting furnace according to any one of claims 1 to 4 , wherein the amount of ammonia gas blown is 5 to 25% of the amount of exhaust gas generated from the melting chamber. . The reforming of exhaust gas generated in a combined arc melting furnace according to any one of claims 1 to 5 , wherein the amount of carbon material blown is 5 kg / t or more with respect to the cold iron source in the melting chamber. Method. An arc electrode and melting chamber for arc melting of a cold iron source, and a shaft type preheating chamber which is provided above the melting chamber and communicates with the melting chamber and preheats the charged and filled cold iron source An auxiliary heat source supply means and an oxygen supply means for supplying an auxiliary heat source to the melting chamber, and a region from the position of the hot water surface in the melting chamber of the preheating chamber to the upper end position of the deposition layer of the cold iron source in the upper portion of the preheating chamber. , and 1 or ammonia gas inlet at a plurality of locations, have a, a gas recovery system for recovering the exhaust gas generated in the melting chamber, at the melt surface position of the dissolution chamber of the preheating chamber, the ammonia gas inlet and ammonia gas was blown from leading the reforming reaction between carbon dioxide in the flue gas of more than 600 ° C., and recovering the exhaust gas having increased hydrogen concentration and the hydrocarbon gas concentration composite ah Melting furnace.

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