JP2015178913A - Slag heat recovering device, slag heat recovering method, and heat generating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for recovering heat as high-temperature water from high-temperature slag generated in refining metal.SOLUTION: A slag heat recovering device 250 is composed of a charging portion 22 for high-temperature slag 21, a water tank portion 23 for reserving water, a slag discharging portion 210, and a heat exchanging portion 25. The charging portion 22 is inclined, the discharging portion 210 has a screw conveyor 29, and the heat exchanging portion 25 is disposed at an upper part in the vertical direction, of the water tank portion 23. The high-temperature slag 21 has a temperature of 800°C or more, and its grain size is 2-8 mm. The charging portion 22 has an inclined face of an inclination angle of 20-55 degrees. The high-temperature slag 21 is charged into water along the inclined face, the slag 28 after cooling is discharged, and steam 24 generated in charging the slag 21 into the water is recovered and made to exchange heat with water 27C to obtain hot water 27.

Description

  The present invention relates to a slag heat recovery device and a slag heat recovery method, and more particularly to an apparatus and method for recovering thermal energy from high temperature slag of 800 ° C. or higher to produce high temperature water of 90 ° C. or higher.

  In a blast furnace or electric furnace in a metal smelting process such as steel or nickel, molten metal and molten slag as a by-product are generated by a reduction reaction, and the temperature of the slag is in a high temperature state close to 1500 ° C (steel and steel). (In the case of ferronickel), it is discharged into the atmosphere with enormous heat energy. Considering recent energy saving trends and rising fossil fuel prices, it is desirable to recover the thermal energy and use it as a heat source for low-temperature heat demand. If high-temperature water of 90 ° C or higher can be produced by heat recovery, it can be used for a wide range of applications such as heating, cooling, hot water supply, and power generation. Heat recovery from high-temperature slag is an economical measure. Very useful.

  A number of methods for recovering heat from slag have been proposed centering on blast furnace slag. For example, (a) a method of recovering heat in the form of high-temperature water by directly contacting steam obtained from molten slag with water (Patent Document) 1) and (b) a slag sensible heat recovery method (see Patent Document 2) that produces high-temperature gas of 500 ° C. or higher by directly contacting high-temperature slag with gas. Among these methods, the method (a) generates steam by bringing slag and water into direct contact with each other, makes the steam and water directly contact with each other to form hot water of 90 to 95 ° C., and uses the hot water as a heat source to exchange heat with water. It is a method to make it. The method (b) is a technique that uses equipment for replacing the hot gas with hot water in addition to the hot gas generator of 500 ° C. or higher.

JP-A-5-296673 JP 2012-1418 A

  In the method (a), the temperature of the recovered water does not exceed 90 ° C. Furthermore, even if it is decided to directly use the 90-95 ° C. hot water obtained first, it is unavoidable that the pulverized slag 2 disclosed here is mixed with fine slag powder. Fine powder will also enter the heat exchanger 8, making it difficult to reuse and not practical.

  In addition, in the method (b), in addition to the high temperature gas generator of 500 ° C. or higher as described above, equipment for replacing the high temperature gas with hot water is required. However, the capital investment is huge and it is difficult to use it. As described above, although various methods for recovering thermal energy of high-temperature slag have been studied, all have problems such as the temperature of hot water obtained by heat recovery, mixing of fine slag powder, and equipment costs, and there is much room for improvement. It was a thing.

  The problem to be solved by the present invention is to solve the problems such as low temperature of hot water obtained by heat recovery in the prior art, mixing of slag fine powder, equipment cost, etc., especially from high temperature slag of 800 ° C. or higher. It is to provide a slag heat recovery device, a slag heat recovery method and a heat production method capable of recovering water and obtaining high temperature water of 90 ° C. or higher.

  As a result of examining the above problems, the inventor of the present application can solve the problem by a heat recovery apparatus configured by a slag discharge unit and a slag heat exchange unit provided with an inclined charging unit, a water tank unit, a screw conveyor for charging high-temperature slag. The present invention has been found, and the present invention has been completed based on this. That is, the invention claimed in the present application, or at least the disclosed invention, as means for solving the above-described problems is as follows.

[1] A charging part that is a supply port for slag generated in metal smelting, a water tank part that is connected to the charging part and that is a destination of slag, a discharge part for discharging slag that is connected to the water tank part, and A slag heat recovery device comprising a heat exchanging section, wherein the charging section is provided with an inclination, and the discharge section is provided with a continuous discharge means for continuously discharging the slag after heat recovery. The slag heat recovery device is characterized in that the heat exchange unit recovers heat from steam or hot water generated in the water tank unit.
[2] The slag heat recovery device according to [1], wherein water is used as a medium in the heat exchange unit to obtain hot water of 90 ° C. or higher.

  [3] In order to make the amount of slag stored in the water tank portion substantially constant, adjusting means for adjusting the slag supply amount in the charging portion and the discharge amount in the discharge portion is provided, The slag heat recovery device according to [1] or [2].

[4] The slag heat recovery device according to any one of [1] to [3], wherein the slope provided in the charging portion has an inclination angle of 20 ° to 55 °.
[5] The slag heat recovery device according to any one of [1] to [4], wherein the heat exchange unit is provided above the water tank unit.

[6] The slag heat recovery device according to any one of [1] to [4], wherein at least a part of the heat exchange unit is provided in the water tank unit.
[7] The slag heat recovery device according to [5] or [6], wherein an exhaust structure for preventing an explosion due to steam generated from the water tank is provided.

[8] Using the slag heat recovery device according to any one of [1] to [7], slag is introduced into the water tank part from the introduction part, and steam or hot water generated thereby and the heat exchange part in the heat exchange part A slag heat recovery method for recovering heat by exchanging heat with a medium.
[9] The slag heat recovery method according to [8], wherein the slag to be fed satisfies at least one of the following conditions (A) and (B).
(A) 800 ° C or more (B) Particle size 8mm or less

[10] The slag heat recovery device to be used has a structure in which the heat exchanging section uses water as a medium and is provided above the water tank section, and the water level stored in the water tank section-the heat exchanging section When the distance is 30 mm or more and 50 mm or less, the amount of water supplied into the heat exchange unit is 5 liters / min or less, and the slag temperature at the time of charging is 800 ° C. or more, it is possible to generate hot water of 90 ° C. or more. The slag heat recovery method according to [8] or [9], which is characterized.
[11] A heat production method that uses slag generated in metal smelting, throws the slag into water, and exchanges heat between the steam or hot water generated thereby and the heat exchange medium. The method for producing heat from slag, wherein the slag satisfies at least one of the following conditions (A) and (B):
(A) 800 ° C or more (B) Particle size 8mm or less

  Since the slag heat recovery device, the slag heat recovery method, and the heat production method of the present invention are configured as described above, according to this, the low hot water temperature obtained, which is a problem of the prior art, the slag fine powder Mixing and high equipment costs can be eliminated.

  In particular, the thermal energy can be recovered from high-temperature slag of 800 ° C. or higher, and high-temperature water of 90 ° C. or higher can be obtained from normal temperature water. In addition to being usable for heating, hot water supply, and power generation, cold water can be created by using a heat pump, so it can also be used for cooling and is an invention that can be applied to many purposes.

It is explanatory drawing which shows notionally the basic composition of this invention slag heat recovery apparatus. It is explanatory drawing which shows the Example of this invention slag heat recovery apparatus. It is explanatory drawing which shows notionally another basic composition of this invention slag heat recovery apparatus.

The present invention will be described in further detail.
FIG. 1 is an explanatory view conceptually showing the basic structure of the slag heat recovery apparatus of the present invention. As shown in the figure, the slag heat recovery device 50 is connected to the charging unit 2 that is a supply port of slag generated in metal smelting, the water tank unit 3 that is connected to the charging unit 2 and that is the destination of slag, and the water tank unit 3. The slag discharge unit 10 and the heat exchange unit 5 are provided, the charging unit 2 is inclined, and the discharge unit 10 has a screw for continuously discharging the slag after heat recovery. The main configuration is that a conveyor or other continuous discharge means 9 is provided.

  With this configuration, in the present slag heat recovery device 50, the high-temperature slag generated in metal smelting is supplied from the charging unit 2, and slides down the inclined surface of the charging unit 2 and enters the water tank unit 3 connected thereto. As a result, steam and hot water are generated in the water tank section 3, and the heat of these steam or hot water is recovered by the heat exchange section 5, and the slag after the heat recovery is stored in the water tank section by the continuous discharge means 9 of the discharge section 10. 3 is discharged.

  The heat exchange unit 5 is supplied with a heat medium from the heat medium supply unit 30, transfers the recovered heat to the heat medium, and supplies the heat to the heat supply unit 40. That is, in the present slag heat recovery device 50, the slag is supplied from the input unit 2 to the water tank unit 3, and heat is exchanged between the steam or hot water generated thereby and the medium in the heat exchange unit 5, thereby recovering heat. (Thermal production) is performed.

  In the slag heat recovery device 50 of the present invention, the medium used for the heat exchange unit 5 can be used without limitation as long as it is a fluid suitable for the heat medium. Water has a sufficient function as a heat medium and has sufficient practicality, and is an optimal medium for the present invention. In this apparatus 50, warm water of 90 ° C. or higher can be obtained using normal temperature water. Therefore, the following description is limited to the case where water is used as a medium.

  In the present slag heat recovery apparatus 50, the reason why the charging section 2 is inclined is to efficiently input high temperature slag into the water tank section using gravity, but the angle of the inclined surface is 20 ° or more and 55 ° or less. Is desirable. If it is less than 20 °, slag having a particle size of 2 to 8 mm, which is the optimum size of slag particles described later, does not efficiently fall, so that hot water of 90 ° C. or higher cannot be obtained. Moreover, if it exceeds 55 degrees, slag will be thrown into the water of the water tank part 3 vigorously, water will jump out and it will be dangerous, and the amount of water in the water tank part 3 will decrease temporarily, This is not preferable because the amount of steam necessary for the production is not obtained.

  As the continuous discharge means 9 of the discharge unit 10, a screw conveyor is optimal. This is because it is the most reliable for discharging slag continuously and the apparatus configuration can be made compact. However, it is not excluded from the present invention to use a continuous discharge device such as a belt conveyor or a bucket conveyor instead of the screw conveyor.

  The heat exchange part 5 of the slag heat recovery device 50 can be provided above the water tank part 3. In this case, even if it is not directly above the water tank unit 3 but obliquely above, it corresponds to “upward”, but it is most desirable to be positioned above the water tank unit 3 in the vertical direction. Since the steam generated from the water tank part 3 rises vertically upward, the heat exchange part 3 receives this directly by circulating the inside by placing the heat exchange part 5 above the water tank part 3, particularly in the vertical direction. The medium to be used, that is, water, can efficiently take heat away.

  In the case of such a configuration, it is recommended to provide an exhaust structure for preventing explosion due to water vapor generated from the water tank section 3. Specifically, a gap for releasing the steam may be provided between the heat exchange unit 5 and the water tank unit 3. However, the exhaust structure is not limited to this. For example, the exhaust structure may be an open / close door that is normally closed and opens only when the pressure rises due to the steam and allows the steam to escape to the outside. Further, a separate heat exchange unit may be additionally installed at the exhaust structure, and heat recovery from the steam escaping to the outside may be performed.

  It is recommended that the slag used in the apparatus 50 satisfy at least one of the conditions (A) 800 ° C. or higher, (B) particle size 8 mm or less. The recommended lower limit of the temperature is 800 ° C. The temperature of the molten slag discharged from steel and nickel smelting is about 1500 ° C. In the case of copper smelting, it is about 1200 ° C. This is because the temperature is easy and the heat energy is large. The temperature is based on the surface temperature, and may be a value obtained by measuring the slag immediately before being introduced into the heat recovery apparatus with a contact type or a radiation thermometer with adjusted emissivity.

  The reason why the recommended particle size is 8 mm or less is that when the particle size exceeds 8 mm, the specific surface area decreases and the heat recovery efficiency decreases. The particle size range can be further limited to 2 mm or more and 8 mm or less. This is because a slag having a particle size of less than 2 mm is too fine to form a lump in the charging unit 2 and does not always slide smoothly, and may not necessarily drain well from the water in the water tank unit 3. is there.

  FIG. 2 is an explanatory view showing an embodiment of the slag heat recovery apparatus of the present invention. In the present slag heat recovery apparatus 250, a high-temperature slag 21 that is a solidified slag and is 800 ° C. or higher is used. This is continuously or intermittently inserted into the input unit 22. The input part 22 is comprised from the inlet and the slope which slides down, and can be comprised from the raw material which a heat distortion and high temperature oxidation do not produce easily with a steel material, a refractory brick, etc. Due to the inclination of the charging unit 22, the slag 21 falls downward due to gravity, enters the water tank unit 23 where water is accumulated with a constant amount of water, raises the temperature of the water, and changes it to steam.

  The water tank 23 is provided with a water pipe so that water that has evaporated by the introduction of the high-temperature slag 21 can be replenished, and a float and a liquid level sensor 212 are attached to keep the amount of water constant. The amount of the replenishing water 211 to be replenished is controlled by sending a signal from the liquid level sensor 212, and replenishment from the water pipe to the water tank unit 23 is performed. In addition, what is necessary is just to make the water tank part 23 from stainless steel or FRP, for example, in order to prevent corrosion. In addition, it is good also as providing the appropriate automatic conveyance means for conveying slag to the screw conveyor 29 automatically also in the water tank part 23. FIG.

  The steam 24 generated in the water tank unit 23 is in contact with the heat exchange unit 25 installed above, and heats the water 27 </ b> C flowing in the heat exchange unit 25. The heat energy possessed by the high-temperature steam is efficiently taken in by the heat exchanging unit 25 and transmitted to the water 27C flowing through the inside, whereby the temperature can be changed to high-temperature water (hot water) 27H of 90 ° C. or higher.

  Inside the heat exchanging section 25, there are provided a port for supplying water from the outside, a water pipe provided so as to stay for a longer time and exchange heat, and an outlet for the water. Steam directly touches the lower part of the heat exchanging section 25, and the water flowing inside takes the heat and is discharged as hot water from the outlet. Therefore, since the material of the heat exchanging portion 25 is required to have high thermal conductivity and high corrosion resistance, it is desirable to use gold, silver, copper, aluminum or an alloy thereof.

  A gap 26 for releasing steam is provided between the heat exchange unit 25 and the water tank unit 23. Thereby, a steam explosion etc. can be prevented.

  The slag 28 after the heat exchange is discharged to the outside by a screw conveyor 29 inserted and installed in the water tank 23 and stocked. Here, the screw conveyor 29 and the stock portion that collects the slag cooled by heat are combined to form the discharge unit 210. In addition, since water accumulates in the portion where the slag is accumulated, it is desirable to use a material having high corrosion resistance, such as stainless steel or FRP.

  The apparatus 250 may be configured to include an adjusting unit that adjusts the slag supply amount in the input unit 22 and the discharge amount in the discharge unit 210 so that the slag amount stored in the water tank unit 23 is substantially constant. Thereby, the quantity of the slag 21 thrown into the water tank unit 23 becomes constant, and the temperature of the generated steam 24 and the water 27H heated by heat exchange can be made constant. That is, the amount of heat recovery can be adjusted by adjusting the amount of slag input and the amount discharged by the screw conveyor.

  In this apparatus 250, makeup water 211 is supplied from the outside into the water tank section 23, and the amount of water is controlled to be substantially constant by attaching a float or a liquid level sensor 212.

  In this apparatus 250, the distance between the water surface of the water stored in the water tank 23 and the heat exchange part is 30 mm or more and 50 mm or less, the supply amount of water 27C into the heat exchange part 25 is 5 liters / min or less, and the slag temperature at the time of charging By setting the temperature to 800 ° C. or higher, hot water of 90 ° C. or higher can be obtained.

  FIG. 3 is an explanatory view conceptually showing another basic configuration of the slag heat recovery apparatus of the present invention. As shown in the figure, the slag heat recovery device 350 may be configured so that at least a part of the heat exchanging unit 35 is located in the water tank unit 33. That is, the slag heat recovery apparatus of the present invention is not necessarily limited to the configuration in which the heat exchange unit is installed away from the water vertically above the water tank unit as shown in FIG. In addition, it is possible to adopt a configuration in which the water tank 33 is installed and immersed in water.

  Rather, it can be said that efficiency is higher in terms of heat transfer when heat is recovered from water that is liquid than vapor that is gas. Even in this case, since water vapor can be generated from the water tank section 33, it is recommended to provide an appropriate exhaust structure for preventing explosion.

EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to this Example.
<1. Device>
A slag heat recovery device having the structure shown in FIG. 2 was manufactured. SUS304 stainless steel was basically used, and only the input part was reinforced with refractory bricks. The heat exchange part used the aluminum alloy. Tap water was used as the water flowing in the water tank and heat exchanger. The temperature of tap water was 15-20 ° C. A liquid level sensor was installed in the water tank to control the amount of water to be constant. Note the volume of the water tank is 0.07 m ^3, water volume in the water tank was set to 0.05 m ^3.

<2. Conditions (Part 1)>
Slag was introduced at 15 kg / min, and the rotational speed of the screw conveyor was adjusted so that almost the same amount was discharged. The heat recovery effect under each condition of the temperature and particle size of the slag at the time of charging into the slag heat recovery device and the inclination angle at the time of charging was evaluated by measuring the maximum water temperature after recovery. The slag temperature at the time of charging (slag charging temperature) was measured by measuring the slag surface radiation temperature, the slag particle size was measured by screening the slag after discharge, and the water temperature after heat recovery was measured by a thermistor thermometer. Table 1 shows the conditions and measurement results in each example and comparative example.

  Examples 1-4 are examples based on the present invention. In any case, the slag charging temperature is 800 ° C. or more, the slag particle size is 2 to 8 mm, the tilting angle of the charging part is 20 to 55 degrees, and is within the range defined by the present invention. Was able to achieve the target of 90 ° C. or higher.

  In Comparative Example 1, since the slag charging temperature was less than 800 ° C, the amount of recovered heat was small, and the water temperature after heat recovery did not reach 90 ° C.

  In Comparative Example 2, since the slag particle size was less than 2 mm and was too fine, a lump was formed at the charging portion 22 and did not slide smoothly. For this reason, the slag is cooled by the charging unit 22, and the water temperature after heat recovery cannot be set to 90 ° C. or higher.

  In Comparative Example 3, since the slag particle size exceeds 8 mm, the specific surface area is small, heat recovery takes time and heat recovery efficiency is reduced, and furthermore, the volume per slag particle is large. Combined with the decrease in the slag density in the water tank 23, the water temperature after heat recovery did not reach 90 ° C.

  In Comparative Example 4, the tilt angle of the charging unit 22 is less than 20 degrees, and the slag having a particle size of 2 to 8 mm has not dropped efficiently, and has cooled down by the charging unit 22, so the water temperature after heat recovery is It did not reach 90 ° C.

  In Comparative Example 5, since the inclination angle of the charging unit 22 exceeds 55 degrees, the slag was poured into the water of the water tank unit 23 vigorously, and the water jumped out of the gap 26 and was dangerous. Furthermore, since the amount of water in the water tank portion 23 temporarily decreases, a sufficient amount of water vapor cannot be obtained, and the amount of additional replenishment water at room temperature increases, making it difficult to raise the water temperature. In particular, the water temperature after heat recovery did not reach 90 ° C.

<3. Conditions (Part 2)>
2. As a result of this experiment, it was possible to demonstrate part of the conditions for obtaining high-temperature water of 90 ° C. or higher, and further confirmation experiments were carried out based on these results. That is, in a state where the particle size is 2 to 8 mm and 800 to 1000 ° C. is used, and the inclination angle of the charging unit 22 is 45 degrees, the slag charging amount (charging speed), the distance between the water tank unit 23 and the heat exchange unit 25 The heat recovery effect under each condition of the amount of cooling water in the heat exchanger serving as the heat exchanger 25 was evaluated by measuring the maximum water temperature after recovery. Table 2 shows the conditions and measurement results in each example and comparative example.

  Examples 5-8 are examples based on this invention, and all are 30-50 mm in distance with the water tank part 23, the amount of cooling water is 4-5 liters / min, and within the range of the conditions prescribed | regulated by this invention. Therefore, the water temperature after heat recovery was able to achieve the target of 90 ° C or higher. In this experiment, 12-18 kg / min was suitable as a slag input amount (input speed) condition for obtaining sufficient heat recovery.

  In Comparative Example 6, the amount of slag input was less than 7 kg / min, but the amount of generated heat was small, and the water temperature after heat recovery did not reach 90 ° C. It is thought that the input amount was too small.

  In Comparative Example 7, because the distance to the water tank unit 23 is less than 30 mm, the slag also collides with the heat exchange unit 25 together with the steam 24, and the heat exchange unit 25 is damaged, so heat exchange is not performed efficiently. The water temperature after heat recovery did not reach 90 ° C. Further, the gap 26 is reduced, and water vapor is rapidly discharged, which is dangerous.

  In Comparative Example 8, since the distance to the water tank unit 23 exceeded 50 mm, the heat exchange unit 25 was not heated by the steam 24, and the water temperature after heat recovery did not reach 90 ° C.

  In Comparative Example 9, the amount of cooling water exceeded 5 liters / min, and the amount of water was too large, so heat could not be efficiently recovered from the heat exchanging unit 25, and the water temperature after heat recovery did not reach 90 ° C.

  In Comparative Example 10, since the amount of slag input exceeded 18 kg / min, the slag was vigorously charged into the water in the water tank 23, and the water jumped out of the gap 26 and was dangerous. Furthermore, since the amount of water in the water tank portion 23 temporarily decreases, a sufficient amount of water vapor cannot be obtained, and the amount of additional replenishment water at room temperature increases, making it difficult to raise the water temperature. In particular, the water temperature after heat recovery did not reach 90 ° C.

  According to the slag heat recovery device, the slag heat recovery method, and the heat production method of the present invention, high temperature water can be obtained by recovering the thermal energy of the high temperature slag. This invention can be applied to various uses such as heating, hot water supply, power generation, and cooling, and is a highly practical invention. Therefore, the invention is highly useful in metal refining, energy, air conditioning equipment, environment and other related industrial fields.

2, 22, 32 ... charging unit 3, 23, 33 ... water tank unit 5, 25, 35 ... heat exchange unit 9, 39 ... continuous discharging means 10, 210, 310 ... discharging unit 21 ... high temperature slag 24 ... steam 26 ... Steam escape clearance 27C ... Water 27H ... Hot water (hot water)
28 ... Slag 29 after heat exchange ... Screw conveyor 211 ... Makeup water 212 ... Liquid level sensor 30, 330 ... Heat medium supply unit 40, 340 ... Heat supply unit 50, 250, 350 ... Slag heat recovery device

Claims (11)

An input part that is a supply port for slag generated in metal smelting, a water tank part that is connected to the input part and that is a destination of slag, a discharge part for discharging slag that is connected to the water tank part, and a heat exchange part The slag heat recovery device is composed of a slant in the charging part, and the discharge part is provided with continuous discharge means for continuously discharging the slag after heat recovery The slag heat recovery device is characterized in that the heat exchange unit recovers heat from steam or hot water generated in the water tank unit. The slag heat recovery apparatus according to claim 1, wherein the heat exchange unit uses water as a medium to obtain hot water of 90 ° C. or higher. The adjusting means is provided for adjusting the slag supply amount in the charging portion and the discharge amount in the discharge portion so that the slag amount stored in the water tank portion is substantially constant. 2. The slag heat recovery device according to 2. The slag heat recovery apparatus according to any one of claims 1 to 3, wherein the slope provided in the charging portion has an inclination angle of 20 ° to 55 °. The slag heat recovery device according to any one of claims 1 to 4, wherein the heat exchange part is provided above the water tank part. The slag heat recovery device according to any one of claims 1 to 4, wherein at least a part of the heat exchange part is provided in the water tank part. The slag heat recovery apparatus according to claim 5 or 6, further comprising an exhaust structure for preventing an explosion caused by steam generated from the water tank section. The slag heat recovery device according to any one of claims 1 to 7, wherein slag is introduced into the water tank part from the introduction part, and between the generated steam or hot water and the medium in the heat exchange part. A slag heat recovery method that recovers heat by heat exchange. The slag heat recovery method according to claim 8, wherein the slag to be fed satisfies at least one of the following conditions (A) and (B).
(A) 800 ° C or more (B) Particle size 8mm or less The slag heat recovery device to be used has a structure in which the heat exchanging section uses water as a medium and is provided above the water tank section, and sets the distance between the water surface stored in the water tank section and the heat exchange section. 30 mm or more and 50 mm or less, when the amount of water supplied into the heat exchange section is 5 liters / min or less and the slag temperature at the time of charging is 800 ° C. or more, hot water of 90 ° C. or more can be generated. The slag heat recovery method according to claim 8 or 9. A heat production method that uses slag generated in metal smelting, throws the slag into water, and performs heat exchange between the steam or hot water generated thereby and the heat exchange medium, and the slag used is at least A method for producing heat from slag, which satisfies any of the following conditions (A) and (B):
(A) 800 ° C or more (B) Particle size 8mm or less

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