JP2010071616A - Waste heat recovering method of reduction furnace for manufacturing metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of efficiently recovering waste heat of high temperature from the waste heat generated in cooling a plurality of reduction furnaces for manufacturing metal. <P>SOLUTION: In this method of recovering waste heat generated in the plurality of reduction furnaces for manufacturing metal by reducing metallic chloride, the waste heat generated from the plurality of reduction furnaces is integrated and recycled. The reduction furnace is operated by a batch method in which an operation process includes a temperature rising process, a steady operation process and a cooling process, and only the waste heat of a temperature higher than a waste heat recovery lower limit temperature of the reduction furnaces in the steady operation process or the cooling process, is integrated and recycled. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and apparatus for efficiently recovering waste heat generated in a reduction furnace for metal production.

  Sponge titanium is produced by reacting titanium tetrachloride and molten magnesium at a high temperature using a stainless steel reaction vessel as a reduction furnace. Since the reaction between titanium tetrachloride and molten magnesium is an exothermic reaction, air is blown onto the surface corresponding to the reaction portion of the reaction vessel to forcibly cool it.

  Although the melting point of metallic titanium is in the vicinity of 1670 ° C., it is known that it melts by forming a eutectic with iron in the vicinity of 1050 ° C. Therefore, it is important to control the temperature of the reaction vessel below the eutectic point in order to stably produce the reaction vessel without melting.

  In many cases, the air used for cooling the reaction vessel is discharged into the atmosphere while being heated in the reaction vessel. Since the air used for the cooling is heated to about 300 to 400 ° C., it seems to have an undesirable effect on global warming.

  In addition, the titanium sponge production reaction in the reaction vessel is a batch operation in which a series of steps are repeated, and specifically comprises a heating temperature raising step, a steady operation, and a cooling step, and is used for cooling the reaction vessel. The temperature of the exhausted air is not constant and changes with time depending on the above-described process in which the reaction vessel is placed.

  Therefore, it is difficult to stably use air that has been used to cool the reaction vessel and heated to a high temperature (hereinafter sometimes referred to as “waste heat”), and it is also possible to arrange the reaction vessels in parallel. When the reaction is carried out, the operation of each furnace is independent because each is a batch operation, and the waste heat recovered individually from each furnace is small, making it difficult to enjoy the benefits of recovery. .

  Thus, a technique for efficiently utilizing the waste heat used in the reduction furnace for producing sponge titanium is desired.

  In this regard, many techniques are known that utilize waste gas and waste heat generated in a reactor. For example, a technology is disclosed in which waste gas released from a dual converter is apparently continuously recovered by switching a valve attached to a waste gas passage of the converter. (For example, refer to Patent Document 1). However, there is no description regarding a technique for efficiently recovering waste heat discharged from two or more independent converters in an efficient manner.

  Further, a method is disclosed in which waste gas from a metallurgical furnace is collected to generate steam, the steam is guided to a gas turbine, and power is generated by the gas turbine (see, for example, Patent Document 2). However, there is no description regarding a method for stably recovering heat from waste gas generated in the metallurgical furnace.

  Furthermore, a technique for obtaining cold water by guiding low-temperature waste heat recovered in a metallurgical furnace to an absorption refrigerator is also disclosed (for example, see Patent Document 3). However, there is no description regarding a method for stably recovering the waste heat.

Japanese Patent Publication No. 06-063014 JP 05-340501 A JP 9-125126 A

  As described above, the technology for efficiently recovering the waste heat recovered from the metallurgical furnace or smelting furnace seems to be widely known. However, the waste heat of the reduction furnaces in different operating states can be recovered stably. There is no literature about the technology to do.

  An object of the present invention is to provide a method for efficiently recovering waste heat at a high temperature among waste heat generated when cooling a plurality of reduction furnaces for metal production.

  As a result of extensive studies in view of such circumstances, it has been found that by using waste heat generated from a plurality of reduction furnaces for metal production, waste heat with a stable calorific value can be recovered. It came to complete.

  That is, the present invention is a method for recovering waste heat generated in a plurality of reduction furnaces that produce metal by reducing metal chloride, and integrates and reuses waste heat generated from a plurality of reduction furnaces. It is characterized by.

  Moreover, this invention makes it a preferable aspect to integrate and utilize only the waste heat more than a waste heat recovery minimum temperature among the waste heat generated from the said reduction furnace.

  Furthermore, the present invention selects a reduction furnace in which the waste heat temperature is first expected to fall below the lower limit of the waste heat recovery temperature among the reduction furnaces belonging to the operation furnace group in which the waste heat is controlled to a constant amount. Among the reduction furnaces belonging to the outage furnace group, it is preferable to select a reduction furnace that first exceeds the lower limit of the waste heat recovery temperature.

  This invention makes it a preferable aspect to supply the waste heat collect | recovered by the said method to an absorption refrigerating machine via a vapor | steam, and to obtain cold water. Furthermore, the waste heat recovered by the method described above is preferably supplied to a heat exchanger to obtain hot air.

  By implementing the present invention having the above-described features, it is possible to efficiently recover the waste heat generated in the reduction furnace for metal production.

According to the present invention, it is possible to stably recover waste heat generated when cooling a reduction furnace for metal production such as sponge titanium. By introducing the waste heat to the absorption chiller, the operating number of the cooling compressor can be reduced, and as a result, the power consumption can be reduced. In addition, the amount of high-temperature waste heat released into the atmosphere can be reduced. In addition, the waste gas is not combustion gas but electrothermally heated air, does not include moisture and CO ₂ generated by combustion, and has the effect of suppressing corrosion of equipment and reducing the environmental load. As a result, it is possible to reduce the amount of CO ₂ that is a cause of global warming and to reduce the amount of heat released to the atmosphere.

The best embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of a reduction furnace for metal production according to the present invention. In this embodiment, a reduction furnace M for metal production in which titanium sponge is produced by magnesium reduction of titanium tetrachloride is shown.

Prior to the start of the reduction reaction of the titanium sponge in the temperature raising step , the reaction vessel 1 is inserted into the reduction furnace 3 and then the heater 2 built in the reduction furnace 3 is energized while the inside of the reaction vessel 1 is in an inert gas atmosphere. The temperature of the reaction vessel 1 is raised to the reaction start temperature of titanium tetrachloride and molten magnesium. This process is called a temperature raising process.

After the temperature of the steady operation step reaction vessel 1 reaches the reaction start temperature, titanium tetrachloride is dropped onto the surface of the molten magnesium previously charged in the reaction vessel 1 after the temperature is stabilized. On the surface of the molten magnesium bath charged in the reaction vessel 1, titanium tetrachloride reacts with the molten magnesium to produce sponge titanium.

  Since the reaction between titanium tetrachloride and molten magnesium is an exothermic reaction, when the reaction is started, a portion of the reaction vessel 1 near the surface where the reaction between titanium tetrachloride and magnesium proceeds (hereinafter “reaction”). In some cases, the reaction heat is generated intensively. If this state is left as it is, the temperature of the reaction part may exceed the eutectic point of titanium metal and iron (near 1050 ° C.) and the reaction vessel may be melted.

  Therefore, in the on-site equipment, as shown in FIG. 1, cooling air is sent from the outside to a portion corresponding to the reaction zone of the reaction vessel 1 to suppress overheating of the reaction zone. As a result, the temperature of the reduction furnace corresponding to the steady operation in FIG. 2 is controlled in the range of 900 ° C. to 1050 ° C. In the present invention, the above state is called a steady operation process.

Cooling step After the above-described reaction is continued and a predetermined amount of sponge titanium is produced in the reaction vessel 1, the dropping of titanium tetrachloride into the reaction vessel 1 is terminated and the heater 2 of the reduction furnace 3 is turned off, The reaction vessel 1 is cooled to near room temperature. In the present invention, the above process is called a cooling process.

  FIG. 2 shows the temperature change of the reaction vessel 1 in the temperature raising step, the steady operation step, and the cooling step. In the present invention, among the steps described above, the waste heat at which the temperature of the reaction vessel 1 is equal to or higher than a predetermined temperature (hereinafter sometimes referred to as “waste heat recovery lower limit temperature”) is selectively recovered. This is a preferred embodiment.

  For example, as shown in FIG. 3, the above-described aspect is provided when the waste heat supplied to the reduction furnace 3 and cooled by heating the reaction vessel 1 is discharged to the outside from an outlet provided in the reduction furnace 3. The automatic valve 10 can selectively supply waste heat at or above the lower limit of the waste heat recovery temperature to the waste heat recovery device.

  In this invention, it is preferable to set the waste-heat recovery minimum temperature in the range of 300 to 400 degreeC. By setting the waste heat recovery lower limit temperature in the temperature range as described above, it is possible to supply waste heat with a stable amount of heat to the waste heat recovery device.

  In the present invention, the reduction furnace M for metal production is a batch type as described above, and therefore, by operating each of the plurality of reduction furnaces M for metal production while shifting the process, the entire factory is apparently continuous. Sponge titanium is manufactured.

  Therefore, in this invention, it is preferable to integrate and utilize the waste heat discharged | emitted from the reduction furnace M for each metal manufacture in one place. As a result, the processes of the individual metal production reducing furnaces M individually follow the steps of temperature increase, steady operation and cooling, but the waste heat discharged from each metal production reducing furnace M is in one place. By integrating, the waste heat whose amount of heat is smoothed can be supplied to the waste heat recovery device.

  In the present invention, as shown in FIG. 4, the reduction furnace M for metal production in which the temperature of the waste heat discharged from each reduction furnace M for metal production is equal to or higher than the lower limit of the waste heat recovery temperature is classified as an operation furnace group. In addition, after completion of the cooling process, the sponge titanium produced through the vacuum separation process is extracted, and further, the maintenance of the reaction vessel 1 is completed, and the metal production reducing furnace M is classified into a dormant furnace group. Thus, it is preferable to control the integration method of the waste heat discharged from each metal production reducing furnace M.

  In the present invention, a reduction furnace (corresponding to reduction furnace A in FIG. 4) is selected from among the reduction furnaces belonging to the operating furnace group, where the waste heat temperature is expected to first fall below the lower limit of the waste heat recovery temperature. And it is preferable to control so that the automatic valve 10 shown in FIG. 3 attached to the reduction furnace is closed immediately before the waste heat temperature falls below the lower limit. On the other hand, among the reduction furnaces belonging to the resting furnace group, a reduction furnace (corresponding to reduction furnace D in FIG. 4) whose waste heat temperature first exceeded the lower limit of the waste heat recovery temperature is selected and installed in the reduction furnace. It is preferable to control the automatic valve 10 shown in FIG.

  The reduction furnace belonging to the operating furnace group for which waste heat recovery has been stopped is managed as a shutdown furnace group, and the reduction furnace belonging to the shutdown furnace group for which waste heat recovery has been started is transferred to an operation furnace group for management. Is preferred.

  The individual reducing furnaces belonging to the outage furnace and the individual reducing furnaces belonging to the operating furnace group are individually displayed in correspondence with individual batch symbols such as A, B, C, and D as shown in FIG. Preferably, the temperature profile of the reduction furnace is displayed on the monitor screen.

  By using such a display in combination with individual controls, it is possible for the site manager to operate while grasping the movement of the individual reducing furnaces and the state of waste heat recovery.

  In addition, by performing group management of the reduction furnace as described above, there is an effect that it is possible to perform control related to waste heat recovery in accordance with the maintenance situation and operation state of the reduction furnace at the site.

  Furthermore, after the reaction of the operating furnace group has proceeded for a predetermined time, in the reducing furnace belonging to the operating furnace group, the waste heat recovery of the reducing furnace that has cut the lower limit of the waste heat recovery temperature is stopped, and Among the reduction furnaces to which it belongs, it is preferable to recover the waste heat of the reduction furnace that first exceeded the lower limit of the waste heat recovery temperature.

  By following the waste heat recovery method as described above, it is possible to further smooth and recover compared to a case where the heat amounts of waste heat discharged from a plurality of reduction furnaces M for metal production are simply integrated. It is what you play.

As the moisture in the air used for cooling the reduction furnace M for metal production of the present invention, it is preferable to use air of 50 g / m ³ or less. The air can be used as it is.

  The waste heat recovered by the method of the present invention can be recovered once, for example, in the form of steam through a heat exchanger, and the recovered steam is guided to an absorption refrigerator to produce cold water. The cold water can be used for an air conditioner for heat countermeasures at an operation site. As a result, the power used by the compressor for operating the air conditioner can be effectively reduced.

Also, the cold water. It can be used for refrigeration equipment necessary for the production process of titanium tetrachloride. As a result, the power of the compressor of the refrigeration equipment can be effectively reduced. As a result, there is an effect that the amount of CO ₂ generated by the combustion of fossil energy used for producing electric power can be suppressed.

Furthermore, the amount of moisture in the air which constitutes the waste heat recovered by the present invention is below the saturation vapor content in the air at that temperature, also a general refining waste gas containing CO and CO ₂ On the other hand, the waste heat according to the present invention uses air as a medium, and therefore has a feature that it is high-quality air with less CO ₂ or CO content than the smelting exhaust gas.

For this reason, the amount of carbon dioxide produced by the reaction of water in the air that constitutes the waste heat and CO ₂ is very small, and there is almost no influence of corrosion on the heat exchangers and piping. In winter, the waste heat can be directly supplied to a heat exchanger to be used as a heat source for heating.

As described above, in the present invention, the waste heat can be efficiently recovered and used as a refrigerant as well as directly as a heat medium, and as a result, the amount of CO ₂ released into the atmosphere. There is an effect that can be effectively suppressed.

In addition, since the waste heat medium according to the present invention is not combustion gas but air, it does not contain moisture or CO ₂ newly generated by gas combustion, suppresses corrosion of equipment, and has an effect of reducing environmental load. It is what you play.

  In addition, since the high-temperature waste heat itself released into the atmosphere can be reduced, the result is that it can contribute to the prevention of global warming.

[Example 1]
Operating Conditions 1) Reduction furnace for metal production M: Reduction furnace for titanium sponge production 2) Number of operating units: 15 3) Batch size: 7t / furnace 4) Waste heat recovery temperature lower limit: 300 ° C
5) Collection method: Simple integration method (corresponding to claims 1 to 3)

  The waste heat generated from the reduction furnace M was recovered according to the method corresponding to claim 1 using 15 reduction furnaces M for metal production shown in FIG. As a result, 54% of the total waste heat discharged from the reduction furnace M could be recovered. Further, the recovered heat amount (electric power amount) was 64 kWh per furnace.

[Example 2]
Operating Conditions 1) Reduction furnace for metal production M: Reduction furnace for titanium sponge production 2) Number of operating units: 15 3) Batch size: 7t / furnace 4) Waste heat recovery temperature lower limit: 300 ° C
5) Collection method: Priority selection method (corresponding to claims 5 to 6)

  As shown in FIG. 4, the reduction furnace M for metal production is classified into an operation furnace group and a dormant furnace group, and the reduction of the waste heat temperature from the operation furnace group is expected to first fall below the lower limit of the waste heat recovery temperature. In addition to selecting a furnace, among the reduction furnaces belonging to the outage furnace group, the reduction furnace with the hot air temperature first exceeding the lower limit of the waste heat recovery temperature was preferentially selected to recover the waste heat discharged from the reduction furnace. . As a result, an improvement effect of 141% in the amount of heat recovered per furnace of the reduction furnace M for metal production was recognized as compared with Example 1.

[Example 3]
Cold water was produced from the waste heat recovered in Example 1 using an absorption refrigerator, and the cold water was used in an air conditioner for measures against heat. As a result, 60% of the power consumption of the air conditioner could be reduced.

[Comparative Example 1]
In Example 1, the waste heat exhausted from the reduction furnace M for producing metal was not recovered, but was entirely released into the atmosphere. As a result, 117 kWh of heat (electric energy) was released into the atmosphere from one furnace of the metal production reducing furnace M.

  ADVANTAGE OF THE INVENTION According to this invention, the waste heat discharge | released from the reduction furnace for metal manufacture can be collect | recovered effectively, and it can utilize effectively as a refrigerant | coolant or a heat carrier.

It is a schematic diagram which shows the reduction furnace for metal manufacture of this invention. It is a graph which shows the relationship between time and temperature in the reduction reaction of this invention. It is a schematic diagram which shows the cooling method of the reaction container of this invention. It is a schematic diagram which shows the waste-heat recovery method from the some reaction container of this invention.

Explanation of symbols

M ... reduction furnace for metal production, 1 ... reaction vessel, 2 ... heater, 3 ... reduction furnace, 10 ... automatic valve.

Claims (10)

  A method for recovering waste heat generated in a plurality of reduction furnaces for producing metal by reducing metal chloride, wherein the waste heat generated from the plurality of reduction furnaces is integrated and reused Waste heat recovery method for manufacturing reduction furnace.   The waste heat recovery method for a reduction furnace for metal production according to claim 1, wherein the operation process of the reduction furnace is operated in a batch system including a temperature raising process, a steady operation process, and a cooling process.   The waste of the reduction furnace for metal production according to claim 1 or 2, wherein, among the reduction furnaces in the steady operation process or the cooling process, only waste heat having a temperature equal to or higher than a minimum waste heat recovery temperature is integrated and used. Heat recovery method.   The plurality of reduction furnaces are controlled by being classified into an operation furnace group in which waste heat is controlled to a constant amount and a shutdown furnace group in an operation standby state of the reduction furnace. A waste heat recovery method for a reduction furnace for metal production according to claim 1.   Among the reduction furnaces belonging to the operating furnace group, a reduction furnace in which the waste heat temperature is first expected to be lower than the lower limit of the waste heat recovery temperature is selected, and waste heat recovery is performed in the reduction furnaces belonging to the shutdown furnace group. The waste heat recovery method for a reduction furnace for metal production according to claim 4, wherein a reduction furnace that first exceeds the lower temperature limit is selected.   Among the reduction furnaces belonging to the operating furnace group, stop the waste heat recovery of the reduction furnace that has fallen below the lower limit of the waste heat recovery temperature, and first reduce the lower limit of the waste heat recovery temperature among the reduction furnaces belonging to the shutdown furnace group. 6. The method for recovering waste heat of a reduction furnace for metal production according to claim 5, wherein recovery of the waste heat of the reduction furnace that has exceeded is started.   The waste heat recovery method for a reduction furnace for metal production according to any one of claims 1 to 6, wherein the reduction furnace is a reduction furnace for producing sponge titanium, sponge zirconium or sponge hafnium.   The waste heat recovery method for a reduction furnace for metal production according to any one of claims 1 to 7, wherein the waste heat medium is cooling air for a reduction furnace for metal production.   The waste heat recovery method of a reduction furnace for metal production according to any one of claims 1 to 8, wherein steam is obtained by supplying the integrated waste heat to a heat exchanger.   The waste heat recovery method for a reduction furnace for metal production according to any one of claims 1 to 8, wherein the integrated and recovered steam is supplied to an absorption refrigerator to obtain cold water.

Images