JP2009127093A - Method for treating high-temperature slag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating high-temperature slag, by which the slag can be efficiently recovered as valuables without producing strongly alkaline water in the treatment process and without requiring a long time for the treatment. <P>SOLUTION: The high-temperature slag containing CaO is subjected to primary cooling and subsequently transferred through a cooling device so as to be subjected to secondary cooling. The primary cooling is carried out by such a method that water is sprinkled onto the slag on a pit 2, and the secondary cooling is carried out using the cooling device 10 such as a rotary cooler. Both the primary cooling and the secondary cooling are carried out by means of water cooling in a range that does not generate free water. Since the slag do not contact with free water, the slag with a low CaO content can be obtained without producing strongly alkaline water, as in conventional methods. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for treating high-temperature slag generated in a steelmaking process or a hot metal preliminary treatment process.

  A large amount of high-temperature slag of 1200 ° C. to 1600 ° C. is generated from the steel making process and the hot metal pretreatment process. Normally, these slags are discharged to a slag yard with a large area and sprayed with a large amount of water to cool them. However, cooling efficiency is poor, so cooling takes a long time and occurs from the surface of the solidified slag. In order to prevent dust from being scattered, there is a problem that the dust collection cost increases. Moreover, when watering becomes non-uniform | heterogenous, CaO component remains in slag and there existed a possibility of becoming a hindrance when using slag as a roadbed material.

Moreover, the unreacted CaO component dispersed in the fine powder portion in the slag is dispersed as Ca (OH) _{2 in the} water, and further, the Ca (OH) ₂ adheres to the entire slag in contact with the water, When it becomes strongly alkaline and slag is used for roadbed materials or marine applications, it causes white turbidity, and thus neutralization is required. In addition, this strong alkaline water may corrode processing equipment such as centralized piping. Furthermore, it is necessary to neutralize the strong alkaline water generated in this way.

  In Patent Document 1, molten steelmaking slag is poured onto a shallow pan and subjected to primary cooling by sprinkling, then secondary cooling by sprinkling is performed in a waste cart, and further immersed in a water storage pit. A method for stabilizing steelmaking slag is disclosed. However, since this method immerses slag in water, there is a problem that the strong alkaline water described above is generated.

In Patent Document 2, steel slag is put into a slag container and slowly cooled, and the resulting slag large block containing a large amount of α′-Ca ₂ SiO ₄ is crushed into a slag small block, which is rapidly cooled. it is described that the transformation caused by to powdered slag and α'-Ca ₂ SiO ₄ in γ-Ca ₂ SiO ₄ Te. However, this method is effective only for stainless slag capable of precipitating γ-Ca ₂ SiO ₄ in a large amount, and cannot be applied to slag generated from a general steelmaking process. Moreover, as described in the examples of Patent Document 2, there is a problem that productivity is low because cooling time for 24 hours is required for slow cooling.
Japanese Patent Publication No. 5-42380 JP 2003-247786 A

  The present invention solves the above-mentioned conventional problems, does not cause the problem of dust generation as in the conventional water cooling method in the slag yard, and does not generate strong alkaline water in the treatment process, and is long in processing. It aims at providing the processing method of the high temperature slag which does not need time and can collect | recover slag efficiently as a valuable material.

  The present invention made in order to solve the above-mentioned problems is a method for treating high-temperature slag, in which high-temperature slag containing CaO is primarily cooled and secondarily cooled while moving inside the cooling device. Both the secondary cooling and the secondary cooling are water cooling within a range in which free water is not generated.

  In the present invention, as in claim 2, as a cooling device for performing secondary cooling, a rotary cooler provided with cooling air spraying means and cooling water supply means is used, and free water is not generated. Water cooling and air cooling can be used in combination. Further, as in claim 3, as a cooling device for performing secondary cooling, a vibration cooling conveyor provided with cooling air blowing means, cooling water supply means, and a diaphragm in the casing is used, and free water is not generated. Water cooling and air cooling can be used in combination.

  In addition, it is preferable to maintain the slag temperature at the outlet of the cooling device at 100 ° C. or higher as in claim 4, and in the slag after completing the primary cooling by installing a grizzly at the inlet of the cooling device as in claim 5. It is preferable to separate the bullion mass. Furthermore, it is preferable that the slag containing CaO is steelmaking slag or hot metal pretreatment slag as in claim 6, and the temperature of the slag after primary cooling is 800 to 1250 ° C as in claim 7. It is preferable that

  According to the present invention, when the hot slag containing CaO discharged from the furnace is cooled from the hot state, both primary cooling and secondary cooling are performed by water cooling in a range in which free water is not generated. Therefore, CaO in the slag is not eluted into the cooling water as in the conventional case, and strong alkaline water is not generated. For this reason, the whole slag does not become alkaline, and the apparatus is not corroded by strong alkaline water.

Moreover, when the high-temperature slag comes into contact with water molecules, the water gasification reaction of carbon and water in the slag proceeds, and a shift reaction in which CO generated by this reaction becomes CO ₂ also proceeds, and the generated CO ₂ changes CaO in the slag to CaCO ₃ . As a result, the CaO content in the cooled slag can be reduced.

  Although secondary cooling may be performed by gas cooling so as not to generate free water, cooling capability is increased by performing water cooling as in the present invention, and the slag temperature on the outlet side of the cooling device is stabilized. . In addition, since the particle size of CaO added to hot metal or molten steel as a desulfurizing agent or dephosphorizing agent in the steelmaking process is usually around 75 μm, the particle size of unreacted CaO remaining in the slag is This is less than this. For this reason, when the cooled slag is classified into coarse particles and fine particles, unreacted CaO gathers on the fine particle side, and the unreacted CaO content in the coarse particles is further reduced. For this reason, by classifying, it can isolate | separate into slag with a low unreacted CaO content rate, and a slag with a comparatively high unreacted CaO content rate, and each effective utilization becomes easy.

Preferred embodiments of the present invention are shown below.
FIG. 1 is an explanatory diagram of an embodiment of the present invention, in which high-temperature slag containing CaO is caused to flow down from a slag pan 1 to a pit 2 to perform primary cooling first. The high-temperature slag to be treated in the present invention is steelmaking slag discharged from the furnace or pan or hot metal pretreatment slag. Desulfurization slag, etc. are included.

  In these steelmaking slag or hot metal pretreatment slag, a part of fine CaO powder (around 75 μm as described above) blown into the hot metal is contained as unreacted free CaO. In addition, although the temperature of the slag discharged | emitted from a furnace or a pan changes with kinds of slag, generally it is 1400-1600 degreeC in steelmaking slag, and is 1200-1400 degreeC in hot metal pretreatment slag.

  The structure of the pit 2 for performing the primary cooling is not particularly limited, but here, a structure in which a slab having a thickness of 0.25 m is laid on the crushed stone layer is adopted. In addition, primary cooling can also be performed using a cooling box. The hot slag is leveled on the pit 2 to a uniform thickness, and large lumps and bullion are removed. Further, cooling water is sprayed from the watering nozzle 3 within a range in which free water is not generated. At this time, it is necessary for the sprayed cooling water to instantly evaporate and take the heat of vaporization from the slag, so that it does not remain in the state of free water. If free water is generated, there will be a problem of alkali elution from the entire slag. Is not preferable. By this primary cooling, the slag temperature is lowered to about 800 to 1250 ° C.

  Next, slag is taken out from the pit 2 with an appropriate device such as a power shovel, and secondary cooling is performed in the cooling device 10. A hopper 11 is installed in the front stage of the cooling device 10, and a grid 12 for sieving called a grizzly is provided in an inclined state on the surface thereof. The bulk metal in the slag after the primary cooling is separated by the sieving grid 12, and only the small-diameter slag that has passed through the grizzly is put into the cooling device 10 by the vibration feeder 13.

  Although various types of cooling devices 10 for secondary cooling can be used, a rotary cooler is used in this embodiment. In this case, the casing 14 is rotated around an axis that is slightly inclined with respect to a horizontal plane, and cooling air blowing means 15 is provided inside the casing 14. The cooling air blowing means 15 is installed so as to penetrate the center of the casing 14, and is a cooler having a structure in which cooling air is jetted from the cooling air blowing means 15 to cool the internal slag. A cooling water supply means 19 is also arranged on the outer periphery of the casing 14 to perform external cooling. The slag that has reached 800 to 1250 ° C. by the primary cooling is introduced from the hopper 11 at the upper end of the casing 14 and gradually moves in the direction of the outlet 16 as the casing 14 rotates.

  As the cooling device 10 for secondary cooling, in addition to such a rotary type cooling device, as shown in FIG. 2, vibration cooling provided with cooling air blowing means 15 and a diaphragm 21 inside the casing 14. A conveyor can also be used. The slag moves in the direction of the outlet 16 while flowing by the cooling air blown from below the diaphragm 21. The cooling device 10 is used in any case in order to advance the water gasification reaction or shift reaction by effectively utilizing the retained heat of the slag. Further, by using the cooling device 10, it is possible to prevent a risk that CO generated by the water gasification reaction is released into the surrounding atmosphere.

  As described above, in the present invention, the cooling device 10 is used to perform secondary cooling of the slag, but not only the primary cooling but also the secondary cooling is characterized by water cooling in a range that does not generate free water. . For this purpose, a cooling water supply means 17 is disposed inside the cooling device 10 and sprays water on the slag that moves inside the cooling device 10. However, the amount of water sprayed is the amount that vaporizes at the moment when the hot slag and water spray come into contact with each other and does not generate free water. At this time, a large amount of heat of vaporization is taken from the slag, and the slag is cooled to 300 ° C. or lower, preferably 250 ° C. or lower. In addition, in order to prevent generation | occurrence | production of free water reliably, it is necessary to maintain the slag temperature in the exit of the cooling device 10 at 100 degreeC or more.

  Thus, in the present invention, since the slag and free water do not come into contact in the primary cooling and secondary cooling steps, alkaline water is not generated as in the prior art. Therefore, the entire slag does not become alkaline, and the apparatus can be prevented from being corroded by strong alkaline water. Moreover, free CaO in the slag can be reduced by advancing the water gasification reaction and the shift reaction.

  The slag cooled to 300 ° C. or less by the secondary cooling is discharged to the conveyor 20. As described above, most of CaO remaining in the slag is approximately 75 μm or less, and since it is dispersed as fine particles in the slag cooled without generating free water, the discharged slag is sieved. For example, unreacted CaO is concentrated on the fine grain side and hardly contained on the coarse grain side. For this reason, it is also possible to obtain coarse grains having a low CaO content and fine grains having a high CaO content.

  Note that dust is generated inside the cooling device 10 due to slag cooling and mechanical stirring, so the air inside the cyclone dust collector 18 is collected and exhausted to the outside. ing.

  Since the slag treated by the method of the present invention has a low CaO content, the slag can be used as a marine material such as a fishing reef, for example, as it is or just by being slightly carbonated. Conventionally, when slag was used as a roadbed material, aging treatment was required. However, since the coarse slag obtained by the present invention has a low free CaO content, it is possible to reduce aging or shorten the aging period. It becomes possible to plan.

  As described above, according to the method for treating high-temperature slag of the present invention, the high-temperature slag is primarily cooled, and then the secondary cooling is performed while moving the inside of the cooling device. A huge dust collector is not required. Further, since cooling is performed without bringing the slag into contact with free water, strong alkaline water is not generated in the treatment process, and the apparatus does not corrode. Moreover, since a forced cooling method using water cooling is adopted, it does not require a long time for processing.

  The hot metal pretreatment slag generated at the time of dephosphorization / desulfurization treatment of hot metal by blowing CaO powder was transferred to the pit of the slab floor, and it was mixed to a uniform thickness. Water was sprinkled and primary cooling was performed to 1000 ° C. The slab layer has a thickness of 0.25 m and an area of about 6 m × 5 m. The cooling water evaporates instantly and no free water is generated.

The primary cooled slag was put into a hopper, the bulk metal ingot was separated and removed by grizzly, and then supplied to a rotary cooler having a diameter of about 2 m and a length of about 8 m to perform secondary cooling. The slag temperature at the inlet of the rotary cooler is 850 ° C. The cooling air of 142 m ³ / h was blown onto this slag to cool it internally. In addition, the outer peripheral surface of the rotary cooler is cooled with 30 T / h of cooling water, and 1 T / h of cooling water is sprinkled from the internal cooling water supply means into the slag, and the slag is cooled in a range that does not generate free water. It was. The average residence time of the slag in the rotary cooler is 20 minutes.

  As a result, the slag cooled to about 220 ° C. was discharged from the outlet of the rotary cooler, and the temperature drop of the slag while passing through the inside of the rotary cooler was 630 ° C. The slag is pulverized while being conveyed inside the rotary cooler to form pulverized slag. In addition, although the content rate of CaO contained in the original slag is 6 to 9%, it decreased to 2.5 to 4% at the outlet of the rotary cooler. This slag can satisfy the characteristic of an expansion ratio of 1.5% or less required for roadbed materials in JIS-5015 without performing post-treatment.

  On the other hand, when the internal cooling of the rotary cooler is gas cooling, the temperature drop of the slag while passing through the rotary cooler stays at 450 ° C, and free water is not generated, but the cooling capacity is clearly reduced. Met.

It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Slag pan 2 Pit 3 Sprinkling nozzle 10 Cooling device 11 Hopper 12 Screening grid 13 Vibrating feeder 14 Casing 15 Cooling air spraying means 16 Outlet 17 Cooling water supply means 18 Cyclone dust collector 19 Cooling water supply means 20 Conveyor 21 Diaphragm

Claims (7)

  A high-temperature slag treatment method in which high-temperature slag containing CaO is primarily cooled and then secondary-cooled while moving inside the cooling device, in which both primary and secondary cooling do not generate free water A method for treating high-temperature slag, which is characterized by water cooling in the furnace.   As a cooling device that performs secondary cooling, it uses a rotary cooler with cooling air spraying means and cooling water supply means inside, and uses both water cooling and air cooling in a range that does not generate free water The processing method of the high temperature slag of Claim 1 to do.   As a cooling device for performing secondary cooling, a vibration cooling conveyor provided with cooling air spraying means, cooling water supply means, and a diaphragm in the casing is used to perform water cooling and air cooling within a range in which free water is not generated. It uses together, The processing method of the high temperature slag of Claim 1 characterized by the above-mentioned.   The method for treating high-temperature slag according to claim 1, wherein the slag temperature at the outlet of the cooling device is maintained at 100 ° C. or higher.   The processing method of the high temperature slag of Claim 1 which installs a grizzly at the inlet of a cooling device, and isolate | separates the metal bullion in the slag which finished primary cooling.   The method for treating high-temperature slag according to claim 1, wherein the slag containing CaO is steelmaking slag or hot metal pretreatment slag.   The temperature of the slag which finished primary cooling is 800-1250 degreeC, The processing method of the high temperature slag of Claim 1 characterized by the above-mentioned.

Images