JP2012031470A - Method of reforming exhaust gas generated from arc furnace, reforming device, and method of manufacturing reformed gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a method of reforming an exhaust gas generated from an arc furnace, capable of simultaneously achieving both carburetion of the exhaust gas generated from the arc furnace and emission reduction of carbon dioxide, as well as a reforming device and a method of advantageously manufacturing a carbureted gas from such exhaust gas generated from the arc furnace.SOLUTION: The method of reforming an exhaust gas generated from an arc furnace includes the steps of: directing the exhaust gas generated from an arc furnace to a combustion chamber of an exhaust gas recovery equipment for combustion; and adding a reducing agent to hot combustion exhaust gas ejected from the combustion chamber to conduct a reforming reaction between carbon dioxide included in the combustion exhaust gas and a reducing agent. The method is thus effective for the carburetion of the gas and reduction of a generated amount of carbon dioxide. The reforming device and the method of manufacturing the reformed carbureted gas are also provided.

Description

  The present invention relates to an arc furnace generated exhaust gas reforming method, reformer, and reformed gas manufacturing method, and in particular, is performed between carbon dioxide gas contained in the arc furnace generated exhaust gas and an externally supplied reducing agent. The present invention proposes a technique that is effective for reforming by increasing the thermal energy of the exhaust gas and reducing the amount of carbon dioxide emission by the reforming reaction.

  In recent years, reducing carbon dioxide emissions has become an urgent issue in order to protect the global environment and prevent global warming. In particular, at steelworks, reducing carbon dioxide emissions has become the most important issue as it relates to the survival of companies. Conventionally, various proposals have been made for this purpose, but a full-fledged carbon dioxide reduction technology has not yet been completed.

  In general, an arc furnace in a steelworks, for example, an arc furnace for steelmaking, is operated to inject oxygen gas or add carbon material together with oxygen gas for the purpose of improving productivity and reducing power consumption. . At that time, high-temperature exhaust gas containing carbon dioxide gas is generated from the arc furnace. From the viewpoint of utilizing the sensible heat of such high-temperature exhaust gas, it is common to recover waste heat by supplying this to a boiler and generating low-pressure steam. However, the utility value of low-pressure steam at steelworks is low, so that such exhaust gas is normally diffused into the atmosphere without being effectively used.

By the way, it is known that various hydrocarbons such as methane and oxygen-containing compounds such as methanol and dimethyl ether react with carbon dioxide gas or steam to be reformed to carbon monoxide or hydrogen. As a waste heat recovery technique using this reaction, Patent Document 1 discloses a gas and / or liquid containing hydrocarbons in a high-temperature exhaust gas containing carbon dioxide and / or steam generated from a refining facility such as a converter. Has been disclosed in which a reforming reaction of the following formula (1) is caused to occur and carbon monoxide and hydrogen in the exhaust gas are increased to increase the latent heat of the exhaust gas. .
CH ₄ + CO ₂ → 2CO + 2H ₂ (1)

  Further, in Patent Document 2, methane and water vapor are added to an exhaust gas generated from a converter at a gas temperature of 1300 ° C. or higher to cause a water gas reaction of the following formula (2), and in the exhaust gas A method and apparatus for increasing the amount of carbon monoxide and hydrogen are disclosed.

CH ₄ + H ₂ O → CO + 3H ₂ (2)

However, in the method disclosed in this document 2, the reaction that occurs due to the addition of water vapor is only CO and H ₂ , and the reforming reaction involving carbon dioxide does not occur, so that it does not contribute to the reduction of CO ₂ at all. There is.

JP 2000-212615 A JP-A-2-11715

  As can be seen from the above, conventionally, the reforming and recovery of converter exhaust gas has been the mainstream, and the exhaust gas generated from the arc furnace is used to reduce the latent heat content of the exhaust gas by utilizing the sensible heat of this gas. There is no known technique for increasing heat (accumulating the endothermic component of the above formula (1) in the form of combustion heat of the reaction product), and at least in this field, energy is wasted. It is the actual situation.

  By the way, the components of the exhaust gas generated from the converter and the exhaust gas generated from the arc furnace are greatly different. Therefore, the above-mentioned conventional reforming technology can be immediately applied to the exhaust gas reforming processing technology of the arc furnace. Can not. For example, the converter exhaust gas contains a lot of carbon monoxide, but in the case of the exhaust gas discharged from the arc furnace, most of it is nitrogen, and the carbon monoxide is only about 10% by volume or less.

In addition, in the prior art using the sensible heat of the carbon dioxide-containing exhaust gas generated from a converter, a smelting reduction furnace, etc., the carbon dioxide reaction efficiency is reduced, or SiO ₂ or Al _{2 is} contained in the exhaust gas treatment system pipeline. There has been a problem that non-combustion components such as O ₃ are deposited, and carbon dioxide gas is not involved in the reaction, which is ineffective in increasing the exhaust gas heat and reducing carbon dioxide emission.

  Therefore, an object of the present invention is to provide an arc furnace-generated exhaust gas reforming method, a reforming apparatus, and such an arc furnace-generated exhaust gas that can simultaneously increase the heat of the arc furnace-generated exhaust gas and reduce carbon dioxide emissions. The present invention proposes a method for efficiently producing the reformed gas.

  In order to overcome the above-mentioned problems of the prior art, increase the heat of the arc furnace generated exhaust gas, reduce the amount of carbon dioxide emission, and efficiently produce the reformed gas, the present invention firstly, Carbon dioxide containing exhaust gas discharged from the arc furnace is introduced into the combustion tower of the exhaust gas treatment section and burned, and it is included in the combustion exhaust gas by adding a reducing agent to the high temperature combustion exhaust gas discharged from the combustion tower. The present invention proposes a method for reforming exhaust gas generated by an arc furnace, characterized in that the reforming reaction of carbon dioxide gas and a reducing agent is guided to reform the combustion exhaust gas.

In the modification method of the present invention,
(1) blowing air between the arc furnace and the combustion tower;
(2) The addition of the reducing agent is performed when the concentration of carbon dioxide in the flue gas discharged from the combustion tower is 10% by volume or more and the concentration of carbon monoxide is 10% by volume or less.
(3) completing the reforming reaction when the combustion exhaust gas temperature is 800 ° C. or higher;
(4) The arc furnace is an electric furnace of a type in which carbon material and oxygen are blown into the furnace and burned.
(5) The reducing agent uses at least one fossil resource compound selected from natural gas, liquefied petroleum gas, methane, ethane, light naphtha, raffinate, methanol, ethanol, dimethyl ether and diethyl ether,
(6) The reducing agent is a non-fossil resource-based organic compound,
Is a more preferable solution.

Secondly, in the present invention, the carbon dioxide-containing exhaust gas discharged from the arc furnace is introduced into the exhaust gas recovery facility and a reducing agent is added, thereby leading to a reforming reaction by the carbon dioxide gas and the reducing agent contained in the exhaust gas. An apparatus for reforming the exhaust gas,
An arc furnace generated exhaust gas recovery facility is configured with an exhaust gas processing unit, a dust recovery unit, an exhaust gas recovery / discharge unit, and a calculation control unit, and the exhaust gas processing unit combusts the arc furnace generated exhaust gas to raise the temperature, A reducing agent blowing device, a temperature measuring device, a concentration measuring device, and a cooling tower for lowering the temperature of the exhaust gas heated by the reforming reaction are arranged at the downstream side of the combustion tower, Provides an apparatus for reforming an exhaust gas generated by an arc furnace, which is provided with a flow rate control device that controls the amount of addition of a reducing agent that operates according to the output from the temperature measurement device and the output from the concentration measurement device. .

In the above reformer of the present invention,
(1) The dust recovery unit is a gas flow meter, a blower and a dust collector disposed along a dust collection duct.
(2) The exhaust gas recovery / discharge unit operates according to the output of the CO gas and CO ₂ gas concentration by the concentration measuring device, and is provided with a gas flow path switching valve for selecting a flare or a flow path to the gas holder. That
(3) The concentration measuring device is a gas analyzer disposed downstream of the combustion tower in the exhaust gas recovery facility,
(4) The temperature measuring device is a thermometer disposed on the downstream side of the combustion tower in the exhaust gas recovery facility,
(5) The reducing agent blowing device is installed at one or more locations downstream of the combustion tower in the exhaust gas recovery facility,
Provides a more suitable solution.

In the present invention, thirdly, from the carbon dioxide containing exhaust gas discharged from the arc furnace, a reducing agent is added to the exhaust gas, and the reformed gas is reacted by reacting the carbon dioxide gas and the reducing agent contained in the exhaust gas. In the manufacturing method,
The reducing agent is added to the exhaust gas when the oxygen concentration in the exhaust gas is 1% by volume or less, and the reaction for reforming is completed when the exhaust gas temperature is 800 ° C. or higher. Proposes a method for producing reformed gas from arc furnace generated exhaust gas

In the above production method of the present invention,
(1) The arc furnace is an electric furnace of a type in which carbon material and oxygen are blown into the furnace and burned.
(2) The carbon dioxide-containing exhaust gas is introduced into the combustion tower and burned in advance prior to the addition of the reducing agent.
(3) The reducing agent uses at least one fossil resource compound selected from natural gas, liquefied petroleum gas, methane, ethane, light naphtha, raffinate, methanol, ethanol, dimethyl ether and diethyl ether.
(4) The reducing agent is a non-fossil resource-based organic compound,
Is a more preferable solution.

(1) According to the present invention, it is possible to increase the heat of the exhaust gas discharged from the arc furnace. In particular, since the reducing agent is added after the exhaust gas is first combusted, the carbon dioxide reforming reaction is efficient. It proceeds well and does not cause precipitation or deposition of non-combustion components such as SiO ₂ . Therefore, it is possible to simultaneously achieve an increase in the heat generated by the arc furnace generated exhaust gas and a reduction in the discharge of carbon dioxide.
(2) Further, according to the present invention, the installation of the combustion tower and the cooling tower can suppress the generation of harmful substances such as dioxin as well as the improvement of the carbon dioxide gas reforming reaction efficiency.
(3) Further, according to the present invention, the reducing agent is added on the downstream side of the combustion tower where the temperature and components of the treated exhaust gas can be easily controlled. The reaction time can be easily controlled, and stable reforming operation of the arc furnace generated exhaust gas can be performed.
(4) Also, according to the present invention, the reformed gas whose heat is increased (having high thermal energy) from the arc furnace generated exhaust gas is efficiently and economically produced without causing an increase in the amount of carbon dioxide gas generated. be able to.
(5) Further, according to the present invention, it is economical because a reforming reaction uses a substance that is produced in large quantities at a low cost as a fuel or a chemical raw material at present or in the future as a reducing agent.
(6) Furthermore, according to the present invention, non-fossil resource-based organic compounds such as bioethanol and biodiesel can be used as a reducing agent for the reforming reaction, which greatly contributes to the reduction of carbon dioxide emissions. it can.

It is an approximate line figure of the modification processing flow of the arc furnace generated exhaust gas explaining the present invention. It is sectional drawing which shows the outline of an arc furnace and an exhaust system.

  The present invention basically achieves efficient heat increase of the arc furnace-generated exhaust gas and reduction of carbon dioxide emission simultaneously by the reforming reaction using carbon dioxide gas contained in the arc furnace-generated exhaust gas. The present invention relates to a reforming technique of arc furnace generated exhaust gas.

That is, the exhaust gas generated from the top of the furnace lid of an electric furnace for steelmaking of the type in which oxygen is blown together with various carbon materials is 10% by volume or more of CO ₂ , 10% by volume or less of CO, It contains about 50 to 75% by volume of nitrogen and 10% by volume or less of oxygen, and the temperature is about 600 ° C. In the present invention, first, the exhaust gas generated from the arc furnace (hereinafter referred to as “off-gas”) is introduced into a combustion tower, which will be described later, and burned to rise to a high-temperature off-gas of about 800 ° C. or higher, preferably 900 ° C. or higher. Warm up. In the present invention, the reason for increasing the temperature of the off gas in the combustion tower is that it is effective for promoting the reforming reaction of the above formula (1) and reducing harmful substances such as dioxins in the off gas. is there.

  In reforming the off-gas, the present invention uses an exhaust gas recovery facility comprising an exhaust gas treatment unit, a dust recovery unit, an exhaust gas recovery / discharge unit, and an arithmetic control unit that are attached to the arc furnace, A predetermined treatment as described in detail below is performed to produce a reformed gas with increased heat.

  That is, the off-gas generated from the arc furnace is first heated in the combustion tower of the exhaust gas treatment section, and then a reducing agent (natural gas or the like) is added. At this time, the carbon dioxide gas and the reducing agent in the off-gas cause a reforming reaction represented by the above formula (1). In the present invention, the addition of the reducing agent is started when the concentration of carbon dioxide in the off-gas is 10% by volume or more and the concentration of carbon monoxide is 10% by volume or less. This condition is arranged in the exhaust gas treatment unit. It adjusts in the installed secondary air adjustment pipe and the combustion tower. In addition, in the present invention, at least one of the addition amount, the addition timing, and the addition position of the reducing agent is set so that the reforming reaction due to the addition of the reducing agent is completed at a temperature of 800 ° C. or higher. Control based on output. By such treatment, the off-gas is reliably heated and the amount of carbon dioxide emission is reduced.

  In this way, the heated off-gas, that is, the reformed off-gas, is used (combusted) as various heat sources in the steel works, for example, so that carbon dioxide gas is finally discharged, but in the steel works. The amount of auxiliary fuel used, such as heavy oil, can be reduced by an amount corresponding to the increase in heat, and carbon dioxide gas can be reduced accordingly.

  FIG. 1 is a flowchart showing an outline of an arc furnace generated exhaust gas recovery facility for explaining an embodiment of the present invention. This exhaust gas recovery facility includes an exhaust gas processing unit 200, a dust recovery unit 300, an exhaust gas recovery / discharge unit 400, and an arithmetic control unit 500 that are disposed on the downstream side of the arc furnace 100.

  As schematically shown in FIG. 2, the arc furnace 100 is an electric furnace of an arc melting type in which a raw material is bucketed by turning a furnace lid, and a furnace body 101 in which an iron source is charged, A detachable furnace lid 102 that closes the opening at the top of the furnace body 101 is provided. From the upper side of the furnace lid 102, one DC arc electrode 103 that passes through the furnace lid and is vertically inserted into the furnace body 101 is disposed.

  The furnace body 101 is provided with an oxygen blowing lance 104 for supplying an oxygen gas and a carbon blowing lance 105 for supplying a carbon material, which are inserted from the side wall into the furnace. From the lance 105, carbon material made of coke, char, coal, charcoal, graphite, biomass charcoal, or a mixture thereof is blown into the furnace main body 101 using air, nitrogen, or the like as a carrier gas. Separately from this furnace body 101, a burner 106 is disposed, from which air or oxygen or oxygen-enriched air is supplied together with fossil fuels such as heavy oil, kerosene, propane gas, natural gas, Burn in the furnace body 101. The burner 106 is attached as necessary.

The exhaust gas discharged from the arc furnace 100 described above, that is, off-gas, is first sent to the exhaust gas processing unit 200. In the exhaust gas treatment unit 200, an elbow-shaped dust collection duct 203, smoke absorption dust 204 connected to its extension position, and a combustion tower 201 disposed downstream of the smoke absorption dust 204 are arranged as upstream equipment. Further, on the downstream side of the combustion tower 201, a thermometer 210, a reducing agent blowing nozzle 216, and a gas analyzer 208 are connected via a reforming reaction duct 206 connected to the cooling tower 202 described later. Are arranged respectively. The gas analyzer 208 can measure the concentration of CO gas, CO ₂ gas, and O ₂ gas in the exhaust gas.

  In the exhaust gas treatment unit 200, air (secondary air) is blown from a secondary air adjustment pipe 205 installed in the smoke absorption duct 204 in order to burn off gas. Next, the off-gas that has been subjected to the addition of secondary air enters the combustion tower 201 through the smoke absorption duct 204, where it burns in contact with the combustible gas contained in the off-gas, and rises to a temperature of 800 ° C. or higher. Is done. The off-gas heated by the combustion in the combustion tower 201 is then subjected to a reforming process in contact with a reducing agent in the reforming reaction duct 206.

  The reformed off-gas that has undergone the reforming reaction is then sent out to the dust recovery unit 300, but before that, first, a cooling process is performed in the cooling tower 202.

  In general, since iron scrap charged in the steelmaking arc furnace 100 contains chlorine, the reformed off-gas that has been reformed in the exhaust gas treatment unit 200 is harmful as a chlorine compound. Dioxins may be included and must be removed. Specifically, first, the CO in the off-gas is burned in the combustion tower 201 so that the chlorine content in the exhaust gas decomposes rapidly even if dioxins and the like form, so that the dioxins are decomposed at 800 ° C. or higher. The temperature is raised to On the other hand, the reformed off-gas subjected to the reforming process is then led to the cooling tower 202 through the reforming reaction duct 206, where it is rapidly cooled to a temperature of 250 ° C. or lower. This is because the recombination of harmful substances such as dioxins is prevented by rapidly cooling the reformed off gas. As a result, the concentration of harmful substances such as dioxins in the reformed off gas can be finally reduced to a regulated value or less.

  As described above, if the off-gas discharged from the combustion tower 201 has a carbon dioxide concentration of 10% by volume or more, a carbon monoxide concentration of 10% by volume or less, and a temperature of 800 ° C. or more, the reducing agent blowing is performed. The reducing agent for the reforming reaction can be added from the inlet 216. In the present invention, the temperature of the off-gas is continuously measured by the thermometer 210, and the amount of reducing agent and / or the amount of blowing-in of the reducing agent is so blown that the reforming reaction is completed at a temperature of 800 ° C. or higher. Change the (injection) position as necessary.

  In the present invention, the reason why the concentration of carbon dioxide in the off gas is 10% by volume or more with respect to the timing of blowing the reducing agent is that a heat increase effect by reforming cannot be obtained (corresponding to Comparative Example 4). In addition, the reason why the concentration of carbon monoxide is 10% by volume or less is that a heat increase effect by reforming cannot be obtained (corresponding to Comparative Example 3).

  Further, in the present invention, the reducing agent is used so that the reforming reaction of the reformed off gas, that is, the reformed off gas in a state of being heated as the latent heat of the reaction product is completed at a temperature of 800 ° C. or higher. It is necessary to adjust the addition amount and / or the blowing position thereof. The reason for setting the off-gas temperature at the completion of the reforming reaction to 800 ° C. or higher is that when the off-gas temperature at the completion of the reforming reaction is lower than 800 ° C., the conversion rate of carbon dioxide gas decreases, the heat increase effect and the carbon dioxide gas reduction This is because both effects are reduced.

  Here, the above-mentioned “completion of the reforming reaction” means that the reaction between the added reducing agent such as methane and the carbon dioxide in the exhaust gas has progressed to an approximate equilibrium in the atmosphere. In theory, an infinite residence time is required for the reaction to proceed to complete equilibrium, and an approximate equilibrium cannot be defined precisely. Therefore, in the present invention, when the amount of hydrogen gas increases more than twice that before the reforming process with respect to the hydrogen gas concentration in the exhaust gas before reforming, it is defined as “completion of reforming reaction”.

  The reducing agent that can be used in the present invention includes at least one fossil resource-based compound selected from natural gas, liquefied petroleum gas, methane, ethane, light naphtha, raffinate, methanol, ethanol, dimethyl ether, diethyl ether, and the like. preferable. Of these, natural gas, liquefied petroleum gas, light naphtha, raffinate, and dimethyl ether are preferable because they are highly reactive with carbon dioxide gas, inexpensive, and easily available in large quantities.

  Further, as the reducing agent, a non-fossil resource-based organic compound may be used together with or in place of the fossil resource-based compound. Use of non-fossil resource-based organic compounds is preferable because the reforming reaction is performed by a carbon-neutral reducing agent in addition to the increase in off-gas generated by the carbon dioxide reforming reaction, which can greatly contribute to the reduction of carbon dioxide emissions. Examples of the non-fossil resource-based organic compound include bioethanol, biodiesel, or a mixture thereof.

  In addition, when using a reducing agent that is a gas at room temperature, such as natural gas or liquefied petroleum gas, a nozzle suitable for gas blowing may be used, and the nozzle shape and the number of nozzles are not particularly limited. In addition, in the case of a reducing agent that is liquid at room temperature, such as raffinate, bioethanol, and biodiesel, it may be injected by spraying it in the form of a mist, or it may be injected after being vaporized. When supplying in mist form, the droplet diameter should just be an efficient contact with a carbon dioxide gas, Preferably it is 0.01-1000 micrometers, More preferably, it is 0.1-100 micrometers.

  Furthermore, when using a liquefied gas such as dimethyl ether or a liquefied gas of a non-fossil resource-based organic compound as a reducing agent, it may be vaporized in advance and injected as a gas. Or you may vaporize within a nozzle and supply. When the reducing material supplied in liquid is vaporized in the vicinity of the nozzle or in the nozzle, the nozzle itself is cooled by the heat of vaporization, which is preferable from the viewpoint of protecting the nozzle.

  The reformed off gas whose temperature has dropped via the cooling tower 202 is then sent to the dust recovery unit 300. The dust collection unit 300 includes a dust collection duct 302, a gas flow meter 303, and a dust collector 301 including a bag filter. The dust collector 301 is connected to the downstream side of the dust collection duct 302, and the gas flow meter 303 allows the reformed off-gas. Can be continuously measured. The dust in the reformed off gas supplied through the dust collection duct 302 is collected and collected by the dust collector 301. The dust collection duct 302 is provided with a direct blower 304.

  The reformed off-gas thus dedusted is then sent to the exhaust gas recovery / discharge unit 400. The exhaust gas recovery / discharge unit 400 is provided with an exhaust gas recovery duct 402, a blower 404, a gas flow rate switching valve 403, and a flare 401. The reformed off-gas from which dust has been removed flare through the gas flow rate switching valve 403. The gas is discharged from 401 to the atmosphere or discharged to a gas holder (not shown).

  In carrying out the above-described reforming method of the arc furnace generated exhaust gas, the present invention introduces carbon dioxide contained in the exhaust gas by introducing the carbon dioxide containing exhaust gas discharged from the arc furnace to the exhaust gas recovery facility and adding a reducing agent. An apparatus that guides a reforming reaction between a gas and a reducing agent to reform the exhaust gas is used. This apparatus is composed of an exhaust gas treatment unit, a dust recovery unit, an exhaust gas recovery / discharge unit, and an arithmetic control unit arranged on the downstream side of the arc furnace. Combustion tower that raises temperature by burning generated exhaust gas, reducing agent injection device, temperature measurement device, concentration measurement device, and temperature of exhaust gas increased by reforming reaction, arranged downstream of the combustion tower A cooling tower is provided, and the arithmetic control unit is provided with a flow rate control device that controls the amount of reducing agent added that is activated by the output from the temperature measuring device and the output from the concentration measuring device. It is characterized by.

  In the reformer, a gas analyzer 208 disposed on the downstream side of the combustion tower 201 is used as the concentration measuring device disposed in the exhaust gas treatment unit 200. Further, as the measuring device, a thermometer 210 disposed on the downstream side of the combustion tower 201 is used.

  The dust recovery unit 300 has a configuration in which a gas flow meter 303, a blower 304, and a dust collector 301 are sequentially arranged along the dust collection duct 302 from upstream.

The exhaust gas recovery / discharge unit operates according to the output of the CO gas concentration and the CO ₂ gas concentration by the gas analyzer 208, and selects a flow path to the flare 401 or a gas holder (not shown). It is a part formed by arranging.

  A configuration example of the arithmetic control unit 500 is indicated by a dotted line in FIG. In this illustrated example, there is only one flow rate control valve 502 for supplying the reducing agent, which includes a gas analyzer 208 for measuring carbon dioxide concentration and carbon monoxide concentration, and a thermometer for measuring temperature. The control is performed by one or both outputs of 210, but the control may be performed separately using two control valves (not shown) via the arithmetic unit 501. Further, the gas flow path switching valve 403 is controlled by the output of the gas analyzer 208, and at the same time, another control valve is installed on the downstream side of the switching valve, and the control is performed by the output of the thermometer 210. Good.

  Now, in the present invention, a high-temperature carbon dioxide-containing exhaust gas discharged from an arc furnace, that is, by adding a reducing agent to the off-gas and reacting the carbon dioxide and the reducing agent contained in the off-gas, thereby increasing the heat. A modified off-gas can be produced. In this modified offgas production method, the addition of the reducing agent into the offgas is such that the concentration of carbon dioxide in the offgas heated to 800 ° C. or higher discharged from the combustion tower 201 is 10% by volume or more. When the carbon concentration is 10% by volume or less and the reforming reaction is completed when the off-gas temperature is 800 ° C. or higher, the heat increase rate is 9 (corresponding to the present invention 2) or more. A reformed gas having the indicated amount of heat can be produced.

  Here, the reformed off gas produced by reforming the arc furnace generated exhaust gas means an increased heat gas generated by the completion of the reaction between the carbon dioxide gas in the exhaust gas and the reducing agent. “Completion of the reforming reaction” is as defined above. That is, in the operation of the arc furnace, the gas whose hydrogen gas amount has increased to more than twice that before the reforming treatment is used as the reforming off gas.

  In the present invention, the reason for defining “reformed off-gas” in this way is that the carbon dioxide gas concentration is decreased by the above-described reforming reaction, while the hydrogen and carbon monoxide concentrations are increased. The combustion heat of the gas is increased by about 5 to 30%, but the combustion heat generally indicates a calculated value from the gas composition, not the actual measurement value. The “reformation off gas” was defined by the change in the above.

  In the above description, an example of a DC arc electric furnace is shown as the arc furnace. However, it goes without saying that the above-described technique of the present invention can also be applied to an AC arc electric furnace in which three arc electrodes are arranged. Absent. Further, the present invention can be applied to a structure in which a gas blowing plug for blowing a stirring gas into the bottom of an AC arc electric furnace is provided.

  The operation was carried out by charging 147 tons of iron scrap as a charge in a 150 t DC arc electric furnace. In this operation, 85 t of ordinary iron scrap was initially charged in the electric furnace, and the energization conditions and burner / oxygen lance / carbon material blowing conditions shown in Table 1 were used.

Arc melting, the oxygen flow rate from the burner: 60~70m ³ / min, the oxygen flow rate from the oxygen lance: 100~120m ³ / min, was carried out in the carbonaceous material blowing amount 60～100Kg / min conditions. The melting time was 14 minutes for melting 1 and 27 minutes for melting 2, and steel was extracted after refining for 12 minutes. During the operation of the arc furnace, the gas analysis and the exhaust gas temperature were measured in the exhaust gas treatment section of the exhaust gas recovery facility, and the reducing agent was injected into the temperature rising off gas in the reforming reaction duct. For this reforming treatment, natural gas was added as a reducing agent at a flow rate equal to the CO ₂ flow rate. Since the natural gas had a CH ₄ content of 92% by volume, it was assumed that the molar ratio of CO ₂ to CH ₄ could be approximately 1: 1.

  The results in this arc furnace operation example are shown in Table 2 in comparison with Examples 1-3 and Comparative Examples 1-4. However, the total calorific value of off-gas shown in this table includes the calorific value of natural gas added as a reducing agent.

In Invention Example 1, the heat of combustion of reforming the previous off-gas was the 270kcal / Nm ^3, the post-modification with 1350kcal / Nm ^3, were fivefold heat off-gas volume criterion. Since the off-gas flow rate is also 1.43 times, it was found that the amount of heat increase was very large. The true heat increase rate, which is the ratio of the total calorific value when considering the calorific value of natural gas added as a reducing agent, was 25%.
Invention Example 2 is an example having the same temperature as Invention Example 1, but having a different gas composition. The true heat increase rate in Invention Example 2 was 9%.
Invention Example 3 is an example having the same gas composition as Invention Example 2, but different in temperature. The true heat increase rate in Invention Example 3 was 11%.

On the other hand, in the comparative example, the true heat increase rate is not changed or is reduced. That is, the comparative example 1 is an example in which a reducing gas is injected at the time of scrap charging after the melting 1. That is, the charging of the scrap is a condition deviating from the scope of the present invention because the temperature is lowered because the furnace lid is opened. Further, in this example, no burner or charcoal material is blown, and a large amount of air enters the furnace, so that the gas composition is also outside the scope of the present invention. Since CO ₂ is detected even after reforming, it is considered that the reforming reaction does not occur sufficiently under such conditions.

Next, Comparative Example 2 is a condition where the temperature deviates from the scope of the present invention. Since CO ₂ is detected even after reforming, it is considered that the reforming reaction does not occur sufficiently under such conditions. Comparative Example 3 is a condition in which the CO gas concentration is out of the scope of the present invention. Although the reforming reaction has occurred, the true heat increase rate is reduced. Comparative Example 4 is a condition in which the CO gas 2 concentration is out of the scope of the present invention. Although the reforming reaction has occurred, the true heat increase rate has not changed.

  The technique of the present invention is effective not only as an arc furnace for steelmaking but also as an exhaust gas reforming recovery technique for other metal melting arc furnaces for generating direct current and alternating current that generate high-temperature exhaust gas.

100 arc furnace 101 furnace body 102 furnace lid
103 Electrode 104 Oxygen blowing lance
105 Carbon material blowing lance 106 Burner 200 Exhaust gas treatment unit 201 Combustion tower
202 Cooling tower 203 Dust collection duct 204 Smoke absorption duct 205 Secondary air adjustment pipe 206 Reforming reaction duct
208 Gas Analyzer 210 Thermometer 216 Reducing Agent Blow 300 Dust Recovery Unit 301 Dust Collector 302 Dust Collection Duct 303 Gas Flow Meter 304 Blower 400 Exhaust Gas Recovery / Discharge Unit 401 Flare 402 Exhaust Gas Recovery Duct 403 Gas Channel Switching Valve
404 Blower 500 Arithmetic Control Unit 501 Arithmetic Device
502 Flow control valve

Claims (18)

  Carbon dioxide containing exhaust gas discharged from the arc furnace is introduced into the combustion tower of the exhaust gas treatment section and burned. A method for reforming an exhaust gas generated by an arc furnace, wherein a reforming reaction by a carbon dioxide gas and a reducing agent is guided to reform the combustion exhaust gas. The method for reforming an exhaust gas generated by an arc furnace according to claim 1, wherein air is blown between the arc furnace and the combustion tower. The reducing agent is added when the concentration of carbon dioxide in the combustion exhaust gas discharged from the combustion tower is 10% by volume or more and the concentration of carbon monoxide is 10% by volume or less. The method for reforming exhaust gas generated in the arc furnace according to 2. The method for reforming an arc furnace generated exhaust gas according to any one of claims 1 to 3, wherein the reforming reaction is completed when the combustion exhaust gas temperature is 800 ° C or higher. The method for reforming an arc furnace generated exhaust gas according to any one of claims 1 to 4, wherein the arc furnace is an electric furnace of a type in which carbon material and oxygen are blown into the furnace and burned. The reducing agent uses at least one fossil resource compound selected from natural gas, liquefied petroleum gas, methane, ethane, light naphtha, raffinate, methanol, ethanol, dimethyl ether, and diethyl ether. Item 6. A method for reforming an arc furnace generated exhaust gas according to any one of Items 1 to 5. The method for reforming exhaust gas generated in an arc furnace according to any one of claims 1 to 6, wherein the reducing agent is a non-fossil resource-based organic compound. By introducing the carbon dioxide-containing exhaust gas discharged from the arc furnace to the exhaust gas recovery facility and adding a reducing agent, the reforming reaction by the carbon dioxide gas and the reducing agent contained in the exhaust gas is guided to reform the exhaust gas. A device for performing
An arc furnace generated exhaust gas recovery facility is configured with an exhaust gas processing unit, a dust recovery unit, an exhaust gas recovery / discharge unit, and a calculation control unit, and the exhaust gas processing unit combusts the arc furnace generated exhaust gas to raise the temperature, A reducing agent blowing device, a temperature measuring device, a concentration measuring device, and a cooling tower for lowering the temperature of the exhaust gas heated by the reforming reaction are arranged at the downstream side of the combustion tower, Is a reformer for an arc furnace generated exhaust gas, which is provided with a flow rate control device that controls the amount of addition of the reducing agent that operates according to the output from the temperature measuring device and the output from the concentration measuring device.   The apparatus for reforming an exhaust gas generated in an arc furnace according to claim 8, wherein the dust recovery unit is provided with a gas flow meter, a blower, and a dust collector along a dust collection duct. The exhaust gas recovery / discharge unit is provided with a gas flow path switching valve that operates according to the output of the CO gas and CO ₂ gas concentration by the concentration measuring device and selects the flow path to the flare or gas holder. An apparatus for reforming exhaust gas generated by an arc furnace according to claim 8 or 9. 9. The apparatus for reforming exhaust gas generated in an arc furnace according to claim 8, wherein the concentration measuring device is a gas analyzer disposed downstream of the combustion tower in the exhaust gas recovery facility.   The said temperature measurement apparatus is a thermometer arrange | positioned in the downstream of the combustion tower in exhaust gas recovery equipment, The reformer of the arc furnace generated exhaust gas of Claim 8 characterized by the above-mentioned.   The apparatus for reforming exhaust gas generated in a metallurgical furnace according to claim 8, wherein the reducing agent blowing device is installed at one or more locations downstream of the combustion tower in the exhaust gas recovery facility. In the method for producing the reformed gas by adding a reducing agent to the exhaust gas from the carbon dioxide-containing exhaust gas discharged from the arc furnace and reacting the carbon dioxide gas and the reducing agent contained in the exhaust gas,
The reducing agent is added to the exhaust gas when the oxygen concentration in the exhaust gas is 1% by volume or less, and the reaction for reforming is completed when the exhaust gas temperature is 800 ° C. or higher. A method for producing reformed gas from arc furnace generated exhaust gas. 15. The method for producing a reformed gas from an arc furnace generated exhaust gas according to claim 14, wherein the arc furnace is an electric furnace of a type in which carbon material and oxygen are blown into the furnace and burned. The method for producing a reformed gas from an arc furnace-generated exhaust gas according to claim 14 or 15, wherein the carbon dioxide-containing exhaust gas is introduced into a combustion tower and burned in advance prior to addition of a reducing agent. The reducing agent uses at least one fossil resource compound selected from natural gas, liquefied petroleum gas, methane, ethane, light naphtha, raffinate, methanol, ethanol, dimethyl ether, and diethyl ether. Item 17. A method for producing a reformed gas from an arc furnace generated exhaust gas according to any one of Items 14 to 16. The method for producing a reformed gas from the arc furnace generated exhaust gas according to any one of claims 14 to 17, wherein the reducing agent is a non-fossil resource-based organic compound.

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