WO2016199291A1 - Process for producing reduced iron - Google Patents

Abstract

A process for producing reduced iron by reducing an iron oxide with a reducing gas in a reducing furnace (1), characterized in that a furnace top gas (T) discharged when producing the reduced iron in the reducing furnace (1) is cooled with a medium other than water and thereafter with water.

Description

Method for producing reduced iron

The present invention relates to a method for producing reduced iron in which reduced iron is produced by reducing iron oxide using a reducing gas.

Conventionally, as described in Patent Document 1, a manufacturing method is known in which reduced iron is produced by reducing iron oxide using a reducing gas inside a vertical reduction furnace called a shaft furnace.

In this system, a raw material gas such as natural gas, which is a raw material of the reducing gas, is passed through the catalyst tube of the reformer and receives heat generated by the combustion of the fuel gas inside the combustion chamber of the reformer, and is modified. Quality. Thereby, the reducing gas containing hydrogen, carbon monoxide, etc. is produced | generated. The reducing gas is introduced into the reduction furnace and reduces iron oxide contained in the pellets supplied from the upper part of the reduction furnace. Thereby, reduced iron in which iron oxide is reduced is produced. Reduced iron is sequentially discharged from the lower outlet of the reduction furnace. The top gas discharged after the above-described reduction of iron oxide is performed inside the reduction furnace is introduced into a wet dust collecting cooler for the top gas and collected and cooled. Part of the gas after dust collection and cooling is sent to the combustion chamber of the reformer and reused as fuel gas. A cooling gas separately introduced into the reduction furnace is circulated in the lower part of the reduction furnace. The cooling gas extracted during the circulation is collected and cooled by a wet dust collecting cooler for cooling gas. The cooled gas is returned to the inside of the reduction furnace, and the reduced iron is cooled in the lower part of the reduction furnace.

In this system, a large amount of water is used to collect and cool the gas in the wet dust collector cooler for the top gas and the cooling gas wet dust collector. The water used in these devices is generally collected in a water storage section such as a pit, and then cooled by evaporating a part of the water in a cooling tower or the like, and then returned to these devices again. Recycled and reused inside the system. Therefore, the water used in these devices removes all the heat load received from the gas by the cooling tower. The amount of water consumed in this system is mostly occupied by the amount of water evaporated in the cooling tower and the accompanying blowdown water. Here, blowdown water is discharged outside the water circulation system in order to prevent the concentration of ionic components such as calcium contained in the water due to the evaporation of water inside the cooling tower from being concentrated. It is water. When the concentration of the ionic component is high, this water is deposited as a solid in a cooling tower or other equipment in the system. Therefore, it is necessary to discharge the blowdown water from the cooling tower and control the ion concentration before the solid matter is deposited.

In the above system, the water used in the above equipment for cooling the gas removes all the heat load received from the gas at the cooling tower C, so the amount of evaporated water and blowdown water in the cooling tower are reduced. Difficult to do. As a result, there is a problem that it is difficult to reduce water consumption in the entire system.

In the reduced iron production system as described above, in which raw gas such as natural gas is used, it is often installed in an area where natural gas is produced. Since it is sometimes difficult to secure water in these areas, reducing water consumption of the system is an important issue.

US Pat. No. 5,437,708

An object of the present invention is to provide a method for producing reduced iron capable of reducing water consumption.

The reduced iron production method according to the first aspect of the present invention is a reduced iron production method for producing reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace, wherein When the reduced iron is produced, the exhaust gas outside the furnace is cooled with a medium other than water, and then the exhaust gas outside the furnace cooled by the medium is cooled with water. And

A method for producing reduced iron according to a second aspect of the present invention is a method for producing reduced iron by producing reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace, Water droplets of such a size that water for adjusting the exhaust gas outside the furnace when producing reduced iron remains in the inside of the reduction furnace without being completely evaporated in the upper space of the reduction furnace It sprays so that it may disperse | distribute to the iron oxide inside the said reduction furnace by the diameter.

A method for producing reduced iron according to a third aspect of the present invention is a method for producing reduced iron by producing reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace, As a fuel gas for extracting a part of the exhaust gas outside the furnace before cooling it with water when producing reduced iron, and heating the raw material gas that is the raw material of the reducing gas to produce the reducing gas The remaining exhaust gas outside the furnace is cooled with water.

The method for producing reduced iron according to the fourth aspect of the present invention is a method for producing reduced iron by producing reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace, wherein the reducing gas is Of the generated exhaust gas of the reformer, the reduced iron production facility or the seal gas used for preventing oxidation of the reduced iron is cooled with a medium other than water, and then the seal gas cooled with the medium is cooled. And cooling with water.

The method for producing reduced iron according to the fifth aspect of the present invention is a method for producing reduced iron by producing reduced iron by reducing iron oxide using a reducing gas inside the reduction furnace, A lower part and a discharge part of the reduced iron are protected with a refractory, and the reduced iron is cooled by the cooling gas by introducing and circulating a cooling gas cooled with water into the reduction furnace. Is discharged from the reduction furnace, or the reduced iron is discharged from the reduction furnace in a high-temperature state without introducing the cooling gas into the reduction furnace.

It is a system configuration figure of a reduced iron manufacturing system used for a manufacturing method of reduced iron concerning a 1st embodiment of the present invention. It is a system block diagram of the reduced iron manufacturing system used for the manufacturing method of reduced iron to the modification of 1st Embodiment of this invention. It is a system block diagram of the reduced iron manufacturing system used for the manufacturing method of reduced iron to 2nd Embodiment of this invention. It is a system block diagram of the reduced iron manufacturing system used for the manufacturing method of reduced iron in 3rd Embodiment of this invention. It is a graph which shows the ratio which compared the thermal load in each part of the reduced iron manufacturing system in each embodiment of this invention with the thermal load in the case of the system of a comparative example. It is a graph which shows the ratio which compared the thermal load of the whole reduced iron manufacturing system in each embodiment of this invention with the thermal load in the case of the system of a comparative example. It is a graph which shows the ratio which compared the amount of replenishment water of the reduced iron manufacturing system in each embodiment of this invention with the amount of replenishment water in the case of the system of a comparative example. It is a graph which shows the supplementary water reduction rate in the various characteristics of the manufacturing method of the reduced iron of this invention. It is a system block diagram of the reduced iron manufacturing system as a comparative example of this invention.

Hereinafter, embodiments of the method for producing reduced iron of the present invention will be described in more detail with reference to the drawings.

(First embodiment)
FIG. 1 shows a system configuration diagram of a reduced iron production system used in the first embodiment of the method for producing reduced iron of the present invention.

The reduced iron production system shown in FIG. 1 generates a reducing gas D by reforming a reducing gas 1 and a feed gas H that is a mixed gas of a raw material gas G1 such as natural gas and a process gas Q described later. A reformer (reformer) 2 for reducing the exhaust gas discharged from the reduction furnace 1 when the reduced iron R is produced inside the reduction furnace 1, that is, the furnace top gas T is collected with water using dust. After mixing the furnace top gas wet dust collector 4 to be cooled, the raw material gas G1 and a part of the furnace top gas T (that is, the process gas Q), the feed gas H that is a mixed gas sent to the reformer 2 is preheated. Produced by the preheater 3, the seal gas cooler 5 for producing the seal gas S by cooling the combustion exhaust gas discharged from the reformer 2 in a state where the oxygen component is controlled to be low, and the reformer 2. Cool part of the reducing gas D To comprise a reducing gas cooler 6, a cooling gas wet dust collector 7 for dust collection and cooling the gas to circulate in the lower part of the reduction furnace 1. In addition, a pellet feeding unit 22 is provided inside the reduction furnace 1.

The system shown in FIG. 1 further includes a first dry dust collector 11, a second dry dust collector 12, a seal gas heat exchanger 13, and a seal as components closely related to the manufacturing method of the first embodiment. A gas temperature controller 14, a furnace top gas water sprayer 15, a seal gas water sprayer 16, and a furnace top gas heat exchanger 17 are provided.

The first dry dust collector 11 is a machine that collects relatively large foreign matters such as pellet fragments or pellets contained in the furnace top gas T without using water outside the reduction furnace 1. As the first dry dust collector 11, for example, an inversion dust collector (so-called dust catcher) that collects foreign matters by rapidly reversing the flow of the furnace top gas T is used.

The second dry dust collector 12 is a machine that further collects foreign matters contained in the furnace top gas T after passing through the first dry dust collector 11 without using water outside the reduction furnace 1. As the second dry dust collector 12, for example, a centrifugal dust collector (so-called cyclone dust collector) that collects foreign matters contained in the furnace top gas T using a centrifugal force is used. A portion of the furnace top gas T exiting the second dry dust collector 12 is extracted as the furnace top fuel gas F, passes through the pipe L2 to the seal gas heat exchanger 13, and the remaining furnace top gas T is supplied to the pipe. It goes to the top gas heat exchanger 17 through L1.

The seal gas heat exchanger 13 exchanges heat between the seal gas S and the top fuel gas F before being introduced into the seal gas cooler 5. As a result, the seal gas S is cooled, and at the same time, the top fuel gas F is preheated before being introduced into the reformer 2.

The seal gas temperature adjuster 14 adjusts the temperature of the seal gas S before being introduced into the seal gas heat exchanger 13. Specifically, the seal gas temperature regulator 14 adjusts the temperature so that the seal gas S is cooled by the water SW sprayed from the seal gas water sprayer 16 so that the seal gas heat exchanger 13 is not damaged. The

The furnace top gas water sprayer 15 controls the temperature of the furnace top gas T by spraying water on the furnace top gas T inside the reduction furnace 1. As a result, the furnace top gas T is adjusted to a temperature that does not damage equipment on the downstream side of the reduction furnace 1 (for example, the furnace top gas heat exchanger 17).

The furnace top gas heat exchanger 17 is installed on the upstream side of the furnace top gas wet dust collector 4. The furnace top gas heat exchanger 17 is generated when the furnace top gas T before being introduced into the furnace top gas wet dust collector 4 and the furnace top gas T is collected and cooled by the furnace top gas wet dust collector 4. Exchange heat with the process gas Q. Thereby, the furnace top gas T is cooled before being introduced into the furnace top gas wet dust collector 4, and at the same time, the process gas Q is preheated before being introduced into the reformer 2 via the preheater 3.

In the system shown in FIG. 1, a reducing gas D is generated as follows, and reduced iron R is produced using the reducing gas D. The raw material gas G1 supplied from the supply port P1 and the process gas Q are mixed to become a feed gas H. The feed gas H is introduced into the portion 3 a of the preheater 3 and preheated by heat exchange with the exhaust gas E generated from the combustion chamber 2 b of the reformer 2. The preheated feed gas H passes through the catalyst tube 2a of the reformer 2. At this time, the feed gas H passing through the catalyst tube 2a is reformed by receiving heat generated by combustion of the fuel gas G2 such as natural gas (mainly methane) in the combustion chamber 2b. Thereby, the reducing gas D containing hydrogen, carbon monoxide, etc. is produced | generated. The reducing gas D is introduced into the reduction furnace 1 and reduces iron oxide, which is the main component of the pellet P supplied from the upper part of the reduction furnace 1. Thereby, reduced iron R in which iron oxide is reduced is produced. The reduced iron R is sequentially discharged from the lower discharge port of the reduction furnace 1. The pellets P containing the reduced iron R are fed by the pellet feeder 22 such as a Baden feeder and are uniformly lowered in the reduction furnace 1.

The furnace top gas T discharged after producing the reduced iron R in the reduction furnace 1 is introduced into the furnace top gas wet dust collector 4 and is subjected to a dust collection process using water and a cooling process. The gas whose temperature and moisture have been adjusted by collecting and cooling with water is compressed as a process gas Q by the process gas compressor 8 and then mixed with the raw material gas G1 into the feed gas H. Thus, it is sent to the catalyst tube 2a of the reformer 2 via the preheater 3, and is reused as the raw material of the reducing gas.

Further, in this system, the air A sent to the combustion chamber 2b of the reformer 2 is sent to the portion 3b of the preheater 3 by the compressor 9 to exchange heat with the exhaust gas E from the combustion chamber 2b. And then sent to the combustion chamber 2b.

A part of the exhaust gas generated from the combustion chamber 2b of the reformer 2 is controlled in oxygen concentration, and after being cooled with water in the seal gas cooler 5, the equipment constituting the reduced iron production system is oxidized. Used as a seal gas S for preventing or preventing reoxidation of the reduced iron R.

The temperature of the reducing gas D traveling from the reformer 2 to the reduction furnace 1 is adjusted by cooling a part thereof with water in the reducing gas cooler 6.

In the lower part of the reduction furnace 1, the gas inside the reduction furnace 1 is partially extracted, and is collected and cooled by using a cooling gas wet dust collector 7 with water. The cooled gas is sent into the reduction furnace 1 by the compressor 10 and circulated and used to cool the reduced iron P in the lower part of the reduction furnace 1.

In this system, water is used for cooling the gas in the furnace top gas wet dust collector 4, the seal gas cooler 5, the reducing gas cooler 6, and the cooling gas wet dust collector 7. Water used in these devices is collected in a water storage section such as a pit, and after cooling by evaporating a part of the water in the cooling tower C, it is returned to these devices and circulated inside the system. And reused.

The manufacturing method of the first embodiment is roughly divided into the following four features.

(1) The first feature is that the furnace top gas T is cooled with a medium other than water, and then the furnace top gas T cooled with the medium is cooled with water. Specifically, in the furnace top gas heat exchanger 17 on the upstream side of the furnace top gas wet dust collector 4 in FIG. 1, the furnace top gas T is cooled by the process gas Q, and then the furnace top gas cooled by the process gas Q is used. The furnace top gas T is cooled using water in the furnace top gas wet dust collector 4.

Since the top gas T discharged from the reduction furnace 1 during the production of the reduced iron R has a high temperature and a large flow rate, all the heat of the top gas T is cooled with water for cooling in the top gas wet dust collector 4. If it tries to cool, the heat load to water will be large and the consumption of water will increase. Therefore, in this feature (1), before the furnace top gas T is cooled with water in the furnace top gas wet dust collector 4, the furnace top gas T is preliminarily treated with the process gas Q in the furnace top gas heat exchanger 17. Cooling is performed, and a part of the heat of the furnace top gas T is absorbed by the process gas Q. Thereafter, in the furnace top gas wet dust collector 4, the furnace top gas T cooled with the process gas Q is cooled using water. For example, the furnace top gas T is cooled to a temperature that can be reused as the process gas Q in the system. Thereby, the heat load which the water used for cooling receives from the said furnace top gas reduces. As a result, when the water is cooled and reused by the cooling tower C or the like, the amount of evaporated water and blowdown water are reduced, so that the water consumption of the entire reduced iron production system can be reduced.

(2) The second feature is that the temperature of the furnace top gas T is controlled by spraying water TW onto the furnace top gas T inside the reduction furnace 1.

Specifically, the water droplet diameter of the water of such a size that the water TW for adjusting the temperature of the furnace top gas T remains inside the reduction furnace 1 without being completely evaporated in the upper space of the reduction furnace 1. Then, spraying is performed so that the iron oxide is dispersed in the central portion of the reduction furnace 1.

According to this feature, it is possible to adjust the temperature of the top gas T inside the reduction furnace 1 using the water TW, and at the same time, even when the water TW contains an ionic component. Since the water TW does not completely evaporate and remains in the iron oxide, it is dispersed in the iron oxide, so that the ionic component can be attached to the iron oxide and removed outside the water circulation system. That is, by spraying the water TW by controlling the water droplet diameter of the water TW so that the water TW does not completely evaporate in the upper space of the reduction furnace 1 and adheres to the pellets, calcium contained in the water TW, An ionic component such as magnesium or sodium can be removed by adhering to the pellet. For this reason, since it is possible to reuse the blow-down water containing the ionic component that has been discarded until now for the temperature control of the furnace top gas, it is possible to reduce the consumption of water. Further, since the water TW is sprayed so as to be dispersed in the iron oxide, it is avoided that the inside of the reducing furnace 1 is excessively cooled, so that the reduction reaction of iron oxide in the inside of the reducing furnace 1 is not affected.

In the above feature (2), since the temperature of the top gas T is adjusted by spraying water TW in the upper space of the reduction furnace 1, abnormalities (for example, pellets inside the reduction furnace 1 inside the reduction furnace 1). Even if the temperature of the furnace top gas T rises due to the occurrence of a state where it does not descend (so-called shelf suspension, etc.), the furnace top gas T cooled to an appropriate temperature by the water is reduced downstream of the reduction furnace 1. (For example, the top gas heat exchanger 17). Therefore, damage due to temperature fluctuation of the furnace top gas T can be prevented. Alternatively, it is not necessary to manufacture the device using an expensive material such as an alloy in order to improve the heat resistance of the device.

Furthermore, by dispersing the water TW sprayed inside the reduction furnace 1 into pellets and then evaporating it, it is possible to remove ion components contained in the water TW and reduce blowdown water. Since the water vapor generated when the water TW evaporates inside the reduction furnace 1 is condensed and recovered by the top gas wet dust collector 4 on the downstream side of the reduction furnace 1, the water consumption of the entire system is not increased.

(3) A third feature is that a furnace for extracting a part of the furnace top gas T before cooling it with water and heating the feed gas H that is a mixed gas of the source gas G1 and the process gas Q It is used as the top fuel gas F, and the remaining furnace top gas T is cooled with water. Specifically, the furnace top gas T is branched at the outlet of the second dry dust collector 12, a part of the furnace top gas T is extracted as the furnace top fuel gas F and sent to the combustion chamber 2b of the reformer 2, The remaining furnace top gas T is cooled with water in the furnace top gas wet dust collector 4.

According to this feature, a part of the furnace top gas T is used as a feed gas H (mixed gas of the raw material gas G1 and the process gas Q) as a raw material of the reducing gas in order to generate the reducing gas D in the reformer 2. ) Is sent to the combustion chamber 2b of the reformer 2 to be used as the furnace top fuel gas F for heating, and extracted in advance without cooling with water. Therefore, it becomes possible to reduce the quantity of the furnace top gas T cooled using water by the furnace top gas wet dust collector 4, and the heat load which the water used for cooling receives from the said furnace top gas T reduces. As a result, when the water is cooled and reused by the cooling tower C or the like, the amount of evaporated water and blowdown water are reduced, so that the water consumption of the entire reduced iron production system can be reduced. In addition, the gas used as the raw material of the reducing gas is only required to contain at least the raw material gas G1, and may be only the raw material gas G1.

(4) A fourth feature is that the seal gas S is cooled with a medium other than water, and then the seal gas S cooled with the medium is cooled with water. Specifically, the seal gas S is cooled by the furnace top fuel gas F in the seal gas heat exchanger 13, and then the seal gas S cooled by the furnace top fuel gas F is used by the seal gas cooler 5 using water. Cooling.

According to this feature, before the seal gas S is cooled with water in the seal gas cooler 5, the seal gas heat exchanger 13 is cooled in advance with the furnace fuel gas F in advance, and the heat of the seal gas S is reduced. Part is absorbed in the furnace top fuel gas F, and then the seal gas S cooled by the furnace top fuel gas F is cooled with water. Thereby, the heat load which the water used for cooling receives from the said seal gas reduces. As a result, when the water is cooled and reused by the cooling tower C or the like, the amount of evaporated water and blowdown water are reduced, so that the water consumption of the entire reduced iron production system can be reduced.

Further, the manufacturing method of the first embodiment further has the following features associated with the above four features (1) to (4).

That is, in the above manufacturing method, the temperature of the furnace top gas T is adjusted using water in the reduction furnace 1 before the furnace top gas T is cooled with a medium other than water. Specifically, in the reduction furnace 1 upstream of the furnace top gas heat exchanger 17, water TW is sprayed from the furnace top gas water sprayer 15 to the furnace top gas T to control the temperature of the furnace top gas. When the furnace top gas T discharged from the reduction furnace 1 becomes excessively hot, a furnace top gas heat exchanger 17 that exchanges heat between the furnace top gas T and a medium other than water is used. In order to avoid such damage, the temperature of the furnace top gas T must be controlled by spraying water on the furnace top gas T before cooling it with a medium other than water. Thus, it is possible to preliminarily cool the furnace top gas T to a temperature that avoids damage to equipment such as the heat exchanger. Thereby, the furnace top gas T can be cooled stably without fear of damage in the furnace top gas heat exchanger 17.

In the above manufacturing method, before the top gas T is cooled with a medium other than water, the top gas T is dedusted. Specifically, dust removal of the furnace top gas T is performed by the first and second dry dust collectors 11 and 12 on the upstream side of the furnace top gas heat exchanger 17.

According to this feature, the dust contained in the furnace top gas T discharged from the reduction furnace 1 is removed in advance before cooling the furnace top gas T, whereby heat is generated between the furnace top gas T and a medium other than water. It is possible to avoid the possibility that equipment such as the top gas heat exchanger 17 that performs the exchange is worn or blocked by dust.

In the above manufacturing method, the process gas Q having the same component as that of the furnace top gas T is used for cooling the furnace top gas T. Therefore, when heat is exchanged between these gases, the equipment should be damaged. However, there is no problem even if these gases are mixed.

In addition, you may use the air which has a pressure lower than the pressure of the furnace top gas T as media other than said water. In this case, air having a pressure lower than the pressure of the furnace top gas T is used for cooling the furnace top gas T in the furnace top gas heat exchanger 17 before performing the cooling process with water in the furnace top gas wet dust collector 4. Thereby, the heat load which the water used for cooling receives from the said furnace top gas T is reduced. As a result, it is possible to reduce water consumption. In addition, since the cooling air has a pressure lower than the pressure of the furnace top gas T, the partition wall between these gases in the furnace top gas heat exchanger 17 in which heat exchange between the air and the furnace top gas T is performed. Even if the gas is damaged, there is no inconvenience because air does not flow into the path on the furnace top gas T side.

Further, as the medium other than the water, both the process gas Q and air having a pressure lower than the pressure of the furnace top gas T are used. The furnace top gas T is cooled with the process gas Q, and then air It may be cooled by. In this case, both the process gas Q and the air having a pressure lower than the pressure of the furnace top gas T are used for cooling the furnace top gas T before cooling with water, so that the water used for cooling can be used in the furnace. The heat load received from the top gas T is reduced. As a result, it is possible to reduce water consumption. Since the temperature of the process gas Q is usually higher than the temperature of the air, the furnace top gas T can be efficiently cooled stepwise by cooling the furnace top gas T with the process gas Q and then cooling with air. is there.

Further, in the above manufacturing method, when a part of the top gas T discharged from the reduction furnace 1 is extracted and used as the top fuel gas F, the extracted top gas T is used as a fuel gas when generating the reducing gas. It is heated in advance by exchanging heat with the exhaust gas generated by the combustion of this, and then used as the furnace top fuel gas F. Specifically, in the seal gas heat exchanger 13, the top fuel gas F is preheated by the heat of the seal gas S exiting from the reformer 2, and then sent to the combustion chamber 2 b of the reformer 2. According to this feature, the extracted top gas T is heated in advance by exchanging heat with the seal gas S, which is an exhaust gas generated by the combustion of the fuel gas when reducing gas is generated. As a result, when the furnace top gas T is reused as the furnace top fuel gas F, the amount of heat at the time of combustion increases, and the amount of fuel gas used can be reduced. Moreover, since the seal gas S is cooled by taking heat away from the furnace top gas T, it becomes possible to reduce the heat load on the water used in the seal gas cooler 5 that cools the seal gas S. It is possible to reduce water consumption.

In the above manufacturing method, the temperature of the seal gas S is adjusted using the water SW before the seal gas S is cooled with a medium other than water. Specifically, the seal gas S is cooled by spraying water W in the seal gas temperature regulator 14 on the upstream side of the seal gas heat exchanger 13. When the seal gas S becomes excessively hot, equipment such as the seal gas heat exchanger 13 for exchanging heat between the seal gas S and a medium other than water may be damaged. Therefore, in the above feature, before the seal gas S is cooled with a medium other than water, the temperature of the seal gas S is adjusted in advance using water, thereby avoiding damage to equipment such as the seal gas heat exchanger 13. It is possible to preliminarily cool the sealing gas S to a temperature at which it can be performed. Thereby, it is possible to cool the seal gas S stably without fear of damage in the seal gas heat exchanger 13.

In the above manufacturing method, a gas having a low oxygen concentration (that is, a gas having an oxygen concentration of 3% or less) is used as a medium other than water for cooling the seal gas S. For example, nitrogen or an inert gas having an oxygen concentration of 2% or less is used. Specifically, the top fuel gas F is used as the medium. According to this feature, since the seal gas S is cooled using a gas having a low oxygen concentration as a medium, these in the seal gas heat exchanger 13 in which heat exchange between the gas having a low oxygen concentration and the seal gas S is performed. There is no inconvenience even if the partition walls between the gases are damaged. In particular, when the furnace top fuel gas F is used as a medium, the amount of heat at the time of combustion of the furnace top fuel gas F increases by preheating the furnace top fuel gas F by exchanging heat with the seal gas S. . Therefore, the fuel gas (specifically, the outside of the system) used for heating the feed gas H (mixed gas of the raw material gas G1 and the process gas Q) that is the raw material of the reducing gas in order to generate the reducing gas. It is possible to reduce the amount of fuel gas G2) supplied from the vehicle.

Note that nitrogen gas may be used as long as the gas has a low oxygen concentration. In this case, even if the partition between these gases in the seal gas heat exchanger 13 in which heat exchange between the nitrogen gas and the seal gas S is performed is damaged and these gases are mixed, the seal gas S is prevented from being oxidized. There is no inconvenience.

Further, as another example of the gas having a low oxygen concentration, the process gas Q may be used. In this case, it is possible to improve the thermal efficiency of the entire process by heating the process gas Q with the sealing gas S in advance to heat it.

In the above manufacturing method, the reversible first dry dust collector 11 is installed on the upstream side of the centrifugal second dry dust collector 12 such as a cyclone dust collector, and the first dry dust collector 11 relatively contains the furnace top gas T. By removing the large foreign matter, it is possible to eliminate the problem that the centrifugal second dry dust collector 12 is worn by the foreign matter.

In the above manufacturing method, the temperature of the furnace top gas T is kept constant, and iron oxide having a large particle size is primarily removed by the first dry dust collector 11 and the second dry dust collector 12 to thereby provide downstream equipment (furnace top gas). The safety of the heat exchanger 17 and the like is improved. As a result, the device can be manufactured at a low cost with a simple structure.

(Modification of the first embodiment)
In addition, although the reduced iron manufacturing system used for the manufacturing method of said 1st Embodiment is provided with the furnace top gas heat exchanger 17, this invention is not limited to this. For example, you may abbreviate | omit the top gas heat exchanger 17 like the reduced iron manufacturing system of the modification of 1st Embodiment shown by FIG. Also in this case, the reduced iron production system shown in FIG. 2 has the above-described features (2) to (4) and features associated therewith, and it is possible to achieve the effects of these features. .

(Second Embodiment)
The system block diagram of the reduced iron manufacturing system used for 2nd Embodiment of the manufacturing method of the reduced iron of this invention is shown by FIG. The reduced iron production system shown in FIG. 3 is different from the reduced iron production system of the first embodiment shown in FIG. 1 in that the preheater 3 has a portion 3c, and the seal gas heat exchanger 13 in FIG. And the point that the top fuel gas F is preheated from the top gas wet dust collector 4 in the portion 3c of the preheater 3 and then introduced into the combustion chamber 2b of the reformer 2. The other configuration of the reduced iron production system shown in FIG. 3 is the same as that of the reduced iron production system of the first embodiment shown in FIG.

The reduced iron production system shown in FIG. 3 also has the above-described features (1) to (2) and features associated therewith, and it is possible to achieve the effects of these features.

In the manufacturing method of the second embodiment, as in the first embodiment, the furnace top gas T is adjusted in temperature by the water TW sprayed from the furnace top gas water sprayer 15 inside the reduction furnace 1, and then The top gas T is removed by the first dry dust collector 11 and the second dry dust collector 12.

In the manufacturing method of the second embodiment, all the dust-removed furnace top gas T is cooled by the process gas Q through the furnace top gas heat exchanger 17 installed on the upstream side of the furnace top gas wet dust collector 4, and the furnace top gas T is cooled. Part of the heat of the gas T is taken away by the process gas Q. Thereafter, the furnace top gas T after being cooled by the process gas Q is collected and cooled by the furnace top gas wet dust collector 4. Therefore, the heat load in the furnace top gas wet dust collector 4 can be reduced.

Further, the furnace top gas T is dust-removed by the first and second dry dust collectors 11 and 12 and further collected and cooled by the furnace top gas wet dust collector 4 and then reused as the process gas Q. By cooling the furnace top gas T with the process gas Q boosted by the process gas compressor 8, it is possible to reduce the thermal load of water used in the entire system. Further, since the process gas Q is preheated by receiving heat when the furnace top gas T is cooled, there is room for heat recovery of the exhaust gas of the reformer 2 and further reduction of the fuel gas G2 such as natural gas. Is possible.

Conventionally, heat recovery of the furnace top gas T has been studied, but there have been the following problems (i) to (iv) or problems.

(I) The moisture needs to be controlled for reforming of the reduction process (reforming carbon dioxide and steam gas).

(Ii) The furnace top gas T is accompanied by a large amount of foreign matter such as iron oxide, and in some cases, may be accompanied by large foreign matter such as pellets, so that the foreign matter is blocked by the boiler or heat exchanger. Wear is a problem.

(Iii) When a boiler was used, cooling water for cooling the steam after use was required, and the effect of reducing water consumption was limited.

(Iv) If a heat exchanger is used to cool the top gas T with air, if the heat exchanger is damaged, the air is mixed into the process gas or the top fuel gas F, thereby It is difficult to actually employ air cooling because there is a danger.

However, in the manufacturing method of the second embodiment, water TW is sprayed onto the furnace top gas T inside the reduction furnace 1 to regulate the temperature of the furnace top gas T, and further upstream of the furnace top gas heat exchanger 17. , The first and second dry dust collectors 11 and 12 perform the dust removal of the furnace top gas T in advance, so that the risk of damage to equipment such as the furnace top gas heat exchanger 17 is greatly reduced.

Further, in the furnace top gas heat exchanger 17, heat exchange is performed between the furnace top gas T and the process gas Q having the same component, so that the furnace top gas heat exchanger 17 is damaged and these gases are mixed. The risk of explosion is avoided even if it is done.

When the furnace top gas heat exchanger 17 uses air to cool the furnace top gas T, the outlet on the air side is opened to the atmosphere so that the system can be shut down in the system (ie, the furnace top gas T Since the path through which the gas passes is a positive pressure, it is possible to prevent air from mixing in the path of the top gas T and to avoid the risk of explosion.

(Third embodiment)
The system block diagram of the reduced iron manufacturing system used for 3rd Embodiment of the manufacturing method of the reduced iron of this invention is shown by FIG. Compared with the reduced iron production system of the first embodiment shown in FIG. 1, the reduced iron production system shown in FIG. 4 has a lower part of the reduction furnace 1 and a discharge portion of reduced iron protected by a refractory 21. And the point that the pellet feeder 22 is protected by the refractory 23. The other configuration of the reduced iron production system shown in FIG. 3 is the same as that of the reduced iron production system of the first embodiment shown in FIG.

The pellet feeder 22 is a device for uniformly lowering pellets containing reduced iron inside the reduction furnace 1, and is, for example, a Baden feeder.

The refractories 21 and 23 are made of a material having fire resistance that can withstand the temperature (for example, about 600 ° C.) of the reduced iron R immediately after being generated inside the reduction furnace 1, and are, for example, castable refractories.

In the manufacturing method of the third embodiment, the reduced iron R discharge part and the pellet feed part 22 in the reduction furnace 1 are protected by the refractories 21 and 23 and cooled in the cooling gas wet dust collector 7 using water. After introducing the gas into the reduction furnace 1 and cooling the reduced iron R with the cooling gas, the reduced iron R is discharged from the reduction furnace 1 or in a state where the cooling gas is not introduced into the reduction furnace 1. One of R is discharged from the reduction furnace 1 in a high heat state.

Here, “when the cooling gas is not introduced into the reduction furnace 1 and the reduced iron R is discharged from the reduction furnace 1 in a high heat state” means that the operation of the cooling gas wet dust collector 7 and the compressor 10 is stopped. In addition, both the case of removing the cooling gas wet dust collector 7 and the compressor 10 are included.

Since the reduced iron R immediately after being manufactured inside the reduction furnace 1 is in a high temperature state (for example, about 600 ° C.), the lower part in the reduction furnace 1, the discharge part of the reduced iron R, and the pellet feeding part 22 are connected to the refractory 21. , 23 is protected from the heat of the reduced iron R, and if necessary, a cooling gas cooled with water is circulated in the lower part of the reduction furnace 1 and the reduced iron R is cooled by the cooling gas, and then the reduction is performed. Either the iron R is discharged from the reduction furnace 1 or the reduced iron is discharged from the reduction furnace 1 in a high heat state without introducing the cooling gas into the reduction furnace 1. Thereby, compared with the case where reduced iron is always cooled with the cooling gas cooled using water in the cooling gas wet-type dust collector 7, the thermal load of the water for cooling a cooling gas reduces. As a result, when the water is cooled and reused by the cooling tower C or the like, the amount of evaporated water and blowdown water are reduced, so that the water consumption of the entire reduced iron production system can be reduced.

In addition, when the reduced iron is always cooled using the cooling gas, the cooling gas is subjected to dry dust collection upstream of the cooling gas wet dust collector 7 and the cooling gas and the process gas Q, etc. The heat load of water can be reduced by performing heat exchange and pre-cooling.

The reduced iron production system shown in FIG. 4 also has the above-described features (1) to (4) and features associated therewith, and it is possible to achieve the effects of these features.

Reduced iron that produces reduced iron by reducing iron oxide using a reducing gas such as hydrogen or carbon monoxide produced by reforming natural gas inside the reduction furnace 1 as in the above manufacturing method In the manufacturing method (so-called Midrex (registered trademark) method), there are currently roughly divided into three systems, namely, a CDRI (Cold DRI) system that cools and discharges reduced iron (DRI) in the reduction furnace 1, and There are an HDRI (Hot DRI) system that discharges reduced iron while it is hot, and an HBI (Hot Briquetting Iron) system that agitates Hot DRI with a briquette machine and cools it.

Most of the early plants applying the Midrex method are the above-mentioned CDRI system, and the DRI in the furnace is cooled by introducing seal gas, natural gas, or process gas into the furnace as a cooling gas. The

In the manufacturing method of the third embodiment, the DRI discharge system can be configured to discharge HDRI (that is, a structure in which the discharge portion is protected by a refractory), and the cooling system for cooling the cooling gas can be operated or stopped. By doing so, it is normally used as an HDRI system, and is used as a CDRI system as needed.

Thus, normally, when the HDRI is discharged, the circulation of the cooling gas can be stopped, and the load of the cooling water system for cooling the cooling gas can be eliminated.

At the same time, after the HDRI is discharged from the reduction furnace 1, it is put into the electric furnace at a high temperature of, for example, 600 ° C., thereby greatly reducing the electric consumption in the electric furnace (for example, reduction of 100 w / t-steel) It is possible to make it. Moreover, since the melting time of HDRI can be shortened, the productivity in the electric furnace is greatly improved.

Further, in the system shown in FIG. 4, a pellet feeding unit 22 (so-called Baden feeder) for making the pellets uniformly effective is installed inside the reduction furnace 1. Although this equipment is conventionally protected by cooling water, in the manufacturing method described above, since the pellet feeder 22 is protected by the refractory 23, it is possible to reduce the heat load of the equipment cooling water system. In the conventional CDRI system, the reduction in the thermal load of the equipment cooling water is offset by an increase in the thermal load of the cooling gas system (that is, the cooling gas wet dust collector 7), and the refractory 23 that protects the pellet feeder 22 is protected. There was no merit of using. However, in the manufacturing method of the third embodiment, the discharge part of the reduction furnace 1 is covered with the refractory 21 and the pellet feeding part 22 is covered with the refractory 23, thereby enabling both CDRI and HDRI to be discharged. A hot conversion mechanism is configured. By adopting this hot conversion mechanism, the thermal load in the cooling gas wet dust collector 7 is greatly reduced. Further, by protecting the pellet feeder 22 with the refractory 23, the thermal load of the equipment cooling water is also reduced, so that the thermal load of the circulating water can be reduced.

(Comprehensive description about the effect of the said embodiment)
As a comparative example of the present invention, a reduced iron production system employing a conventional Midrex process includes a reducing furnace 1, a reformer 2, a preheater 3, and a furnace top gas wet as shown in FIG. A dust collector 4, a seal gas cooler 5, a reducing gas cooler 6, and a cooling gas wet dust collector 7 are provided. Since these components are common to the components of the system shown in FIG. Further, the system shown in FIG. 9 is different from the system shown in FIG. 1 in that the furnace top fuel gas F is introduced from the furnace top gas wet dust collector 4 to the reformer 2.

In the system shown in FIG. 9, the following gas (a) to (d) are used in the top gas wet dust collector 4, the cooling gas wet dust collector 7, the reducing gas cooler 6, and the seal gas heat exchanger 5. Considering the thermal load received by the circulating water for cooling and the circulating water used for cooling other equipment, that is, the thermal load of the equipment cooling water of (e) below, As an example, the heat load ratio of cooling water used by circulating inside the system is
(A) Top gas: 54.3%
(B) Cooling gas: 19.1%
(C) Reducing gas: 13.6%
(D) Seal gas: 6.3%
(E) Equipment cooling water: 6.7%
It is.

When the manufacturing method of the first to third embodiments is adopted, the heat load in each device and the entire system is shown in the case where the comparative example (that is, the manufacturing method using the system of FIG. 9) is 100%. Reduced as shown in graphs 5-6. Further, regarding the amount of replenishment water for replenishing the reduced amount of cooling water used in circulation, as shown in the graph of FIG. Reduced compared to the amount of makeup water.

From the above graphs of FIGS. 5 to 7, the effects of the following embodiments can be seen.

(I) By carrying out the manufacturing method of the first embodiment, there is no need to cool the top fuel gas F in the top gas wet dust collector 4, so the heat load in the top gas wet dust collector 4 is a comparative example. It is reduced to about 67% compared with the manufacturing method.

At the same time, by spraying blowdown water as water TW in the upper space of the reduction furnace 1, it is possible to reduce the amount of blowdown water equal to the amount of the water TW.

Further, since the sealing gas S is cooled by the sealing gas heat exchanger 13, the thermal load of the sealing gas cooler 5 is reduced to about 66% as compared with the manufacturing method of the comparative example.

If a high-temperature reducing gas (that is, reformed gas) is directly introduced into the reduction furnace 1 without passing through the reducing gas cooler 6, the heat load in the reducing gas cooler 6 can be reduced to zero. .

Due to the above effects, the overall heat load is about 66% of the manufacturing method of the comparative example, and the amount of makeup water is reduced to about 62% of the manufacturing method of the comparative example.

Furthermore, the fuel gas G2 such as natural gas can be reduced by sending the top gas T to the reformer 2 as the top fuel gas F in a high temperature state.

Further, a furnace top gas heat exchanger 17 is provided on the upstream side of the furnace top gas wet dust collector 4, and heat recovery is performed in advance from the furnace top gas T by the furnace top gas heat exchanger 17. 4 can be reduced to 37% of the manufacturing method of the comparative example. The total heat load is about 50% of the manufacturing method of the comparative example. The amount of makeup water is reduced to 42% of the comparative example.

Similarly, when the heat load of the cooling gas wet dust collector 7 is reduced, the amount of makeup water is also reduced.

In the case of the modification of the first embodiment (that is, the system without the top gas heat exchanger 17 shown in FIG. 2), the absence of the top gas heat exchanger 17 leads to the case of the first embodiment. 5, the heat load in the top gas wet dust collector 4 shown in FIG. 5 is increased to 67%, and the overall heat load shown in FIG. 6 is also increased to 66%. The replenishment shown in FIG. The amount of water also increases to 62%. However, the modified example of the first embodiment is improved in comparison with the comparative example.

(II) By performing the manufacturing method of the second embodiment, the temperature of the furnace top gas T at the inlet of the furnace top gas wet dust collector 4 is up to 150 ° C. compared to 380 ° C. in the case of the manufacturing method of the comparative example. descend. The heat load is reduced to 53% as compared with the manufacturing method of the comparative example. Similarly to the first embodiment, if the manufacturing method is carried out without using the reducing gas cooler 6, the heat load on the reducing gas cooler 6 can be reduced to zero.

Due to the above effects, the overall heat load is reduced to about 61% of the manufacturing method of the comparative example, and the amount of makeup water is reduced to about 52% of the manufacturing method of the comparative example.

Similarly, when the heat load of the cooling gas wet dust collector 7 is reduced, the amount of makeup water is also reduced.

(III) By implementing the manufacturing method of the third embodiment, in addition to the effects of the first embodiment, the thermal load is reduced to 0% by not stopping the operation of the cooling gas wet dust collector 7. Can do. Moreover, since the thermal load of the pellet feeder 22 can be reduced to 0 out of the thermal load of the equipment cooling water, the thermal load of the equipment cooling water in the entire system is reduced to 55% compared to the manufacturing method of the comparative example. can do.

Due to the above effects, the overall heat load is 28% of the manufacturing method of the comparative example, and the amount of makeup water is reduced to 17%.

Next, compared with the makeup water for replenishing the cooling water used in the system in the production method of the comparative example, the individual characteristics (test number No. 1) of the reduced iron production method of the first to third embodiments are compared. The results of examining the reduction rate of makeup water in 1 to 14) are shown in Table 1 and the graph of FIG. From these Table 1 and the graph of FIG. It can be seen that in all features 1 to 14, the amount of makeup water is reduced. In Table 1, “TGS” means the furnace top gas wet dust collector 4, and “SGcooler” means the seal gas cooler 5.

Here, test numbers 1 to 14 correspond to the following features.
Test No. 1: The top gas T is cooled with a medium other than water (for example, the process gas Q), and then the top gas T cooled with the medium is cooled with water.
No. 2: Before cooling the furnace top gas T with a medium other than water, the furnace top gas T is temperature-controlled using water TW.
No. 3: The water TW for adjusting the temperature of the furnace top gas T is reduced within the reduction furnace 1 with the water droplet size of the water in such a size that the water TW remains in the upper space of the reduction furnace 1 without being completely evaporated. It sprays so that it may disperse | distribute to the iron oxide inside the furnace 1. FIG.
No. 4: Prior to cooling the top gas T with a medium other than water, the top gas T is dedusted.
No. 5: A part of the furnace top gas T discharged when producing reduced iron in the reduction furnace 1 is extracted and used as the furnace top fuel gas F, and the remaining furnace top gas T is cooled with water.
No. 6: The extracted top gas T is heated in advance by exchanging heat with exhaust gas (for example, seal gas S) generated by the combustion of the fuel gas when reducing gas is generated. Use.
No. 7: The top gas T is primarily cooled with a medium other than water (for example, process gas Q), and then the top gas T cooled with the medium is directly cooled with water so as to have a predetermined moisture content.
No. 8: As a medium other than water for cooling the furnace top gas T, the process gas Q generated by cooling the furnace top gas T using water is used.
No. 9: As a medium other than water for cooling the furnace top gas T, air having a pressure lower than the pressure of the furnace top gas T is used.
No. 10: As a medium other than water for cooling the furnace top gas T, both the process gas Q and air having a pressure lower than the pressure of the furnace top gas T are used, and the furnace top gas T is cooled by the process gas Q. And then cooled by the air.
No. 11: The seal gas S is cooled with a medium other than water (for example, the furnace fuel gas F), and then the seal gas S is cooled with water.
No. 12: Before cooling the seal gas S with a medium other than water (for example, the furnace fuel gas F), the temperature of the seal gas S is adjusted using water.
No. 13: Furnace top fuel gas is used as a medium other than water.
No. 14: The discharge part of the reduced iron in the reduction furnace 1 is protected by the refractory 21 and the reduced iron is discharged from the reduction furnace 1 in a high heat state without introducing the cooling gas into the reduction furnace 1.

(Other embodiments)
As an example of cooling water reduction other than the above manufacturing method, for example, a wet dust collector is installed between the preheater 3 and the chimney (not shown), and the supersaturation contained in the exhaust gas E discharged from the preheater 3 is used. The water vapor content may be recovered by this wet dust collector and reused for replenishing cooling water.

The steam released from the cooling tower C may be recovered by indirect cooling and reused.

The water may be cooled using an air fin cooler instead of the cooling tower C.

Alternatively, the blowdown water may be reused using a reverse osmosis membrane.

The specific embodiments described above mainly include inventions having the following configurations.

The reduced iron production method according to the first aspect of the present embodiment is a reduced iron production method for producing reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace, Cooling the out-of-core exhaust gas with a medium other than water when manufacturing the reduced iron, and then cooling the out-of-core exhaust gas cooled with the medium using water. Features.

According to such a feature, since the out-of-core exhaust gas discharged from the reduction furnace at the time of manufacturing reduced iron has a high temperature and a large flow rate, an attempt is made to cool all the heat of the out-of-core exhaust gas with cooling water. If so, the heat load on the water is large, and the amount of water consumption increases. Therefore, in the present embodiment, the exhaust gas outside the furnace is cooled beforehand with a medium other than water before being cooled with water, and a part of the heat of the exhaust gas outside the furnace is absorbed by a medium other than water, and then In addition, the out-of-core exhaust gas cooled with the medium is cooled with water. Thereby, the heat load which the water used for cooling receives from the said exhaust gas outside a furnace reduces. As a result, when the water is cooled and reused by a cooling tower or the like, the amount of evaporated water and blowdown water are reduced, so that it is possible to reduce the amount of water consumed by the reduced iron production system as a whole.

Before cooling the out-of-furnace exhaust gas with a medium other than the water, it is preferable to adjust the temperature of the out-of-furnace exhaust gas using water in the reduction furnace.

If the exhaust gas discharged from the reduction furnace becomes too hot, equipment such as a heat exchanger that exchanges heat between the exhaust gas and the medium other than water will be damaged. There is a fear. Therefore, before cooling the out-of-furnace exhaust gas with a medium other than water, the temperature of the out-of-furnace exhaust gas is adjusted with water in advance, so that damage to equipment such as a heat exchanger can be avoided. It is possible to precool the exhaust gas. Thereby, it is possible to cool the out-of-furnace exhaust gas stably without fear of damage in the heat exchanger.

In addition, it is preferable to perform dust removal of the exhaust gas outside the furnace before cooling the exhaust gas outside the furnace with a medium other than the water.

According to such a feature, the dust contained in the exhaust gas discharged from the reduction furnace is removed in advance before cooling the exhaust gas, thereby exchanging heat between the exhaust gas and the medium other than water. It is possible to avoid the possibility that a device such as a heat exchanger that wears out is worn or blocked by dust.

In addition, it is preferable that a process gas whose temperature and moisture are adjusted by cooling the out-of-furnace exhaust gas using the water is used as the medium.

According to this feature, the process gas generated by cooling the exhaust gas outside the furnace with water is used for cooling the exhaust gas before the cooling, so that the water used for cooling is The heat load received from the exhaust gas outside the furnace is reduced. As a result, it is possible to reduce water consumption. In addition, since process gases having the same components as the exhaust gas outside the furnace are used for cooling the exhaust gas outside the furnace, when heat exchange is performed between these gases, the equipment is damaged by any chance. There is no inconvenience even if they are mixed.

Further, it is preferable that air having a pressure lower than the pressure of the exhaust gas outside the furnace is used as the medium.

According to this feature, by using air having a pressure lower than the pressure of the out-of-core exhaust gas for cooling the out-of-core exhaust gas before performing the cooling treatment with water, the water used for cooling is discharged from the out-of-core exhaust. The heat load received from the gas is reduced. As a result, it is possible to reduce water consumption. In addition, since the cooling air has a pressure lower than the pressure of the exhaust gas outside the furnace, the partition wall between these gases in the heat exchanger in which heat exchange between the air and the exhaust gas outside the furnace is damaged is damaged. However, there is no inconvenience because air does not flow into the path outside the furnace exhaust gas.

Further, as the medium, both a process gas whose temperature is adjusted and moisture-adjusted by cooling the outside exhaust gas using water and air having a pressure lower than the pressure of the outside exhaust gas are used, It is preferable that the exhaust gas outside the furnace is cooled with the process gas and then cooled with the air.

According to such a feature, both the process gas and the air having a pressure lower than the pressure of the out-of-core exhaust gas are used for cooling the out-of-core exhaust gas before the cooling with water, so that the water used for cooling is reduced. The heat load received from the out-of-furnace exhaust gas is reduced. As a result, it is possible to reduce water consumption. Since the temperature of the process gas is usually higher than the temperature of air, it is possible to efficiently cool the out-of-core exhaust gas stepwise by cooling the out-of-core exhaust gas with the process gas and then cooling with air.

A method for producing reduced iron according to a second aspect of the present embodiment is a method for producing reduced iron by producing reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace, wherein the reduction furnace The water for adjusting the temperature of the exhaust gas discharged outside the furnace when producing reduced iron at the inside of the reduction furnace is left in the upper space of the reduction furnace without being completely evaporated in the interior of the reduction furnace. It sprays so that it may disperse | distribute to the iron oxide inside the said reduction furnace with the water droplet diameter.

According to such a feature, it is possible to adjust the temperature of the exhaust gas outside the reduction furnace using water inside the reduction furnace, and at the same time, even when the water contains ionic components, the water is completely removed. Therefore, the ionic component can be attached to the iron oxide and removed outside the water circulation system. For this reason, since it is possible to reuse the blowdown water containing the ionic component that has been discarded until now for the temperature control of the exhaust gas outside the furnace, it is possible to reduce the amount of water consumption. . Further, since water is sprayed so as to be dispersed in iron oxide, it is avoided that the inside of the reduction furnace is excessively cooled, so that the reduction reaction of iron oxide inside the reduction furnace is not affected.

A method for producing reduced iron according to a third aspect of the present embodiment is a method for producing reduced iron by producing reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace, wherein the reduction furnace In order to heat a raw material gas that is a raw material of the reducing gas in order to extract a part of the out-of-core exhaust gas that is discharged when producing reduced iron with water before cooling with water and to generate the reducing gas The remaining exhaust gas outside the furnace is cooled with water.

According to such a feature, a part of the exhaust gas outside the furnace is not cooled with water because it is used as a fuel gas for heating a raw material gas that is a raw material of the reducing gas in order to generate a reducing gas. Therefore, it is possible to reduce the amount of out-of-core exhaust gas cooled by water, and the heat load that the water used for cooling receives from the out-of-core exhaust gas is reduced. As a result, when the water is cooled and reused by a cooling tower or the like, the amount of evaporated water and blowdown water are reduced, so that it is possible to reduce the amount of water consumed by the reduced iron production system as a whole.

Further, it is preferable that the extracted exhaust gas outside the furnace is heated in advance by exchanging heat with the exhaust gas generated by the combustion of the fuel gas when the reducing gas is generated, and then used as the fuel gas. .

According to such a feature, the extracted exhaust gas outside the furnace is heated in advance by exchanging heat with the exhaust gas generated by the combustion of the fuel gas when the reducing gas is generated. As a result, when the out-of-furnace exhaust gas is reused as fuel gas, the amount of heat during combustion increases, and the amount of fuel gas used can be reduced. In addition, since the exhaust gas is cooled by taking heat away from the out-of-furnace exhaust gas, it is possible to reduce the heat load on the water used in the cooler for cooling the exhaust gas, and water consumption. It is possible to reduce the amount.

The method for producing reduced iron according to the fourth aspect of the present embodiment is a method for producing reduced iron by producing reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace, wherein the reducing gas Of the combustion exhaust gas of the reformer that produces the reduced iron manufacturing equipment or the sealing gas used for preventing oxidation of the reduced iron is cooled with a medium other than water, and then the sealing gas cooled with the medium Is cooled with water.

According to such a feature, a medium other than water is used to cool a sealing gas used to protect reduced iron production equipment or reduced iron from oxygen in exhaust gas generated by combustion of fuel gas from water. In advance, a part of the heat of the seal gas is absorbed by a medium other than water, and then the seal gas cooled by the medium is cooled using water. Thereby, the heat load which the water used for cooling receives from the said seal gas reduces. As a result, when the water is cooled and reused by a cooling tower or the like, the amount of evaporated water and blowdown water are reduced, so that it is possible to reduce the amount of water consumed by the reduced iron production system as a whole.

Further, it is preferable to adjust the temperature of the sealing gas with water before cooling the sealing gas with the medium.

When the seal gas becomes excessively hot, equipment such as a heat exchanger for exchanging heat between the seal gas and a medium other than water may be damaged. Therefore, before cooling the seal gas with a medium other than water, preliminarily seal the seal gas to a temperature at which damage to equipment such as a heat exchanger can be avoided by adjusting the temperature of the seal gas with water in advance. Cooling is possible. As a result, the sealing gas can be cooled stably without fear of damage in the heat exchanger.

Further, it is preferable to use a gas having an oxygen concentration of 3% or less as the medium.

According to such a feature, since the sealing gas is cooled using a gas having a low oxygen concentration as a medium, a partition between these gases in the heat exchanger in which heat exchange between the gas having a low oxygen concentration and the sealing gas is performed. There is no inconvenience even if it is damaged.

The gas is preferably nitrogen gas.

According to such a feature, even if the partition between these gases in the heat exchanger in which heat exchange between the nitrogen gas and the seal gas is damaged and these gases are mixed, there is no problem in the antioxidant effect of the seal gas. No.

In addition, the gas is used to heat a raw material gas that is a raw material of the reducing gas in order to generate the reducing gas out of the exhaust gas discharged from the furnace when the reduced iron is produced in the reducing furnace. The out-of-core exhaust fuel gas used is preferred.

According to such a feature, the amount of heat at the time of combustion of the fuel gas discharged from the furnace rises by being heated in advance by exchanging the fuel gas discharged from the furnace with the seal gas. Therefore, it is possible to reduce the amount of fuel gas used to heat the raw material gas that is the raw material of the reducing gas in order to generate the reducing gas.

Further, it is preferable that the gas is a process gas whose temperature and moisture are adjusted by cooling with water of the out-of-furnace exhaust gas.

According to this feature, it is possible to improve the thermal efficiency of the entire process by heating in advance by exchanging the process gas with the seal gas.

The method for producing reduced iron according to the fifth aspect of the present embodiment is a method for producing reduced iron by producing reduced iron by reducing iron oxide using a reducing gas inside the reduction furnace, wherein the reduction furnace The lower part and the discharge part of the reduced iron are protected with a refractory, and the reduced iron is cooled by the cooling gas by introducing and circulating a cooling gas cooled with water into the reduction furnace. Either the iron is discharged from the reduction furnace, or the reduced iron is discharged from the reduction furnace in a high temperature state without introducing the cooling gas into the reduction furnace. .

Since the reduced iron immediately after being manufactured inside the reduction furnace is in a high temperature state, the lower part of the reduction furnace and the discharge part of the reduced iron are protected with a refractory, and cooled with water as necessary. The cooled cooling gas is circulated in the lower part of the reduction furnace, and after the reduced iron is cooled by the cooling gas, the reduced iron is discharged from the reduction furnace, or the cooling gas is not introduced into the reduction furnace. , One of discharging the reduced iron from the reduction furnace in a high heat state is selected. Thereby, compared with the case where reduced iron is always cooled with cooling gas, the heat load of the water for cooling cooling gas reduces. As a result, when the water is cooled and reused by a cooling tower or the like, the amount of evaporated water and blowdown water are reduced, so that it is possible to reduce the amount of water consumed by the reduced iron production system as a whole.

Claims (16)

A method for producing reduced iron that produces reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace,
When the reduced iron is produced in the reduction furnace, the exhaust gas outside the furnace is cooled with a medium other than water, and then the outside exhaust gas cooled by the medium is cooled with water. I do,
A method for producing reduced iron. Before cooling the outside exhaust gas with a medium other than the water, the outside exhaust gas is temperature-controlled using water in the reduction furnace.
The method for producing reduced iron according to claim 1. Before cooling the outside exhaust gas with a medium other than the water, dust removal of the outside exhaust gas is performed.
The manufacturing method of the reduced iron of Claim 1 or 2. As the medium, a process gas whose temperature is adjusted and moisture is adjusted by cooling the outside exhaust gas using the water is used.
The manufacturing method of the reduced iron of Claim 1 or 2. As the medium, air having a pressure lower than the pressure of the outside exhaust gas is used,
The manufacturing method of the reduced iron of Claim 1 or 2. As the medium, both a process gas whose temperature is adjusted and moisture-adjusted by cooling the outside exhaust gas using water, and air having a pressure lower than the pressure of the outside exhaust gas are used.
The out-of-furnace exhaust gas is cooled with the process gas and then cooled with the air;
The manufacturing method of the reduced iron of Claim 1 or 2. A method for producing reduced iron that produces reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace,
Water for adjusting the temperature of exhaust gas outside the furnace when producing reduced iron in the reducing furnace is large enough to remain inside the reducing furnace without being completely evaporated in the upper space of the reducing furnace. Spray so as to disperse the iron oxide inside the reduction furnace with the water droplet diameter.
A method for producing reduced iron. A method for producing reduced iron that produces reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace,
In order to heat a raw material gas that is a raw material of the reducing gas in order to extract a part of the out-of-furnace exhaust gas before cooling with water when producing reduced iron in the reducing furnace and generate the reducing gas The remaining exhaust gas from the furnace is cooled with water.
A method for producing reduced iron. The extracted exhaust gas outside the furnace is heated in advance by exchanging heat with the exhaust gas generated by the combustion of the fuel gas when the reducing gas is generated, and then used as the fuel gas.
A method for producing reduced iron according to claim 8. A method for producing reduced iron that produces reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace,
Cooling with a medium other than water the sealing gas used for reducing iron production equipment or reducing iron oxidation of the combustion exhaust gas of the reformer that generates the reducing gas,
Thereafter, the seal gas is cooled using water.
A method for producing reduced iron. The method for producing reduced iron according to claim 10, wherein the temperature of the sealing gas is adjusted with water before the sealing gas is cooled with the medium. As the medium, a gas having an oxygen concentration of 3% or less is used.
The method for producing reduced iron according to claim 10 or 11. The gas is nitrogen gas.
The method for producing reduced iron according to claim 12. The gas is used to heat a raw material gas that is a raw material of the reducing gas in order to generate the reducing gas out of the out-of-core exhaust gas discharged when the reduced iron is produced in the reducing furnace. The fuel gas discharged outside the furnace,
The method for producing reduced iron according to claim 12. The gas is a process gas whose temperature and moisture have been adjusted by being cooled with water out of the out-of-furnace exhaust gas.
The method for producing reduced iron according to claim 12. A method for producing reduced iron that produces reduced iron by reducing iron oxide using a reducing gas inside a reduction furnace,
The lower part of the reduction furnace and the discharge part of the reduced iron are protected with a refractory,
Cooling gas cooled with water is introduced into and circulated in the reduction furnace, and the reduced iron is discharged from the reduction furnace after cooling the reduced iron with the cooling gas, or the cooling gas is reduced in the reduction furnace. In a state where the reduced iron is not introduced into the furnace, the reduced iron is discharged from the reducing furnace while maintaining a high heat state.
A method for producing reduced iron.

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