JP2013082582A - Twin roll cooling apparatus for treating molten slag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a both outer sides delivery-type twin roll cooling apparatus for treating molten slag that can advantageously treat large steel slag with a large-production scale.SOLUTION: A flow path of cooling water of the twin roll cooling apparatus forms a two-line spiral with different grooves 5A and 5B of core 4 coated with a jacket 6, and is served as flow paths 7A and 7B for cooling water with a double spiral structure wherein the mutually adjacent spiral grooves of different systems have the same direction of a cooling water flow as each other.

Description

  The present invention relates to a twin roll cooling device for treating molten slag.

  As a process for continuously processing the molten slag, as shown in FIG. 2, a pair of cooling rolls 3, 3 horizontally arranged opposite to each other through the roll gap 12 are rotated downward from the roll gap 12 ( There is known a twin-roll cooling technique in which molten slag 10 is injected onto the roll gap 12 while being inwardly rotated) and cooled and solidified to be sent downward from the roll gap 12 (for example, Patent Documents 1 to 3). This is tentatively referred to as an inner delivery type. In addition, 1 is a slag pan, 2 is a slag bowl, 11 is a solidified slag (the same is true hereafter).

  On the other hand, as shown in FIG. 3, the pair of cooling rolls 3, 3 that are horizontally opposed to each other and arranged opposite to each other are rotated upward (rotated outward) from the mutual contact portion 13. There is known a twin-roll cooling technique in which molten slag is poured upward and cooled and solidified, and sent from the upper pole side of the cooling roll pair to both outer sides opposite to the opposing surfaces (Non-Patent Document 1). This is tentatively referred to as a double-side delivery type. This both-outside delivery type can take a longer slag residence time on the cooling roll than the inside delivery type, and is more suitable for cooling and solidifying a slag having a low thermal conductivity.

JP 60-264349 A JP 2003-137617 A JP 2008-308398 A

Akashi, Ichikawa, Suzuki: “New slag cooling technology by twin roll indirect water cooling”, JFE Technical Report No. 19 (February 2008) p. 61-64

The inventors have processed the double-roll cooling device of the both-outside delivery type with a steelmaking slag having a large production scale (60 t / h), high slag basicity, and various target thicknesses of solidified slag (product). It was found that there are the following problems.
(B) In order to process steelmaking slag with a large production scale, it is necessary to scale up the cooling roll diameter from the conventional 1.0 m or less to 1.2 m or more.
(B) From the viewpoint of securing the durability of the cooling roll and reducing the manufacturing cost for the scale up, the inner structure of the roll as shown in FIGS. 4 (a) and 4 (b) A twin roll cooling device having a jacket water cooling structure in which a single spiral groove 5 provided in a cylinder (4) is covered with a copper alloy jacket (outer cylinder) 6 to form a cooling water flow path 7 is tentatively proposed. In this provisional candidate device, the copper alloy as the jacket material is chromium-zirconium copper (mass%, 0.5 to 1.5% Cr—0.08 to 0.30% Zr—remainder Cu and unavoidable impurities. Hereinafter, it is also referred to as CCMB). SUS304 etc. are suitable for the stainless steel as the core material. A water supply pipe (not shown) to the cooling water flow path 7 and a rotation mechanism (not shown) of the cooling roll 3 are disposed on the inner surface side of the inner cylinder 4.
(C) However, it has been found that the jacket water cooling structure has the following problems. That is, in the single helical structure cooling water flow path of the temporary candidate device, the groove wall upper end portion of the groove 5 and the jacket 6 are in close contact with each other as shown in FIG. 4 (b), but FEM (finite element method) is used. According to the water flow calculation and heat transfer calculation, the copper alloy jacket 6 thermally expands in the circumferential direction when the high-temperature molten slag contacts the cooling roll 3 during operation, and the amount of thermal expansion is in contact with this. Since it exceeds that of stainless steel, which is the material of the core 4, a gap is inevitably formed between the jacket 6 and the upper end of the groove wall that defines the groove 5 of the core 4, as shown in FIG. 14 is formed, and a short-circuit flow 9 is generated from the gap 14 to the adjacent downstream flow path. The short-circuit flow 9 is a flow velocity of the spiral flow that flows through the central portion of the flow path that is the main flow 8 that contributes most to the cooling capacity. It has been found that there is a problem that causes a decrease in the cooling capacity of the twin-roll cooling device. It was.
(D) In the conventional apparatus configuration as shown in FIG. 3, the thickness of the solidified slag (product) can be adjusted by adjusting the number of rotations of the cooling roll. That is, as the number of rotations of the cooling roll is increased, the thickness of the product becomes thinner. However, according to a model experiment, it was found that as the target thickness was increased, an unsolidified free surface remained in the solidified slag delivered to both outer sides of the twin rolls, resulting in a large variation in product thickness.

  Further, in the conventional double-roll cooling device for melting slag treatment of both outer side delivery types, there is an unsolved problem that when the cooling roll diameter is scaled up, the cooling capacity of the jacket water cooling structure is lowered. Further, when the target thickness is increased, there is a problem that the variation in product thickness increases.

The inventors have made extensive studies to solve the above problems, and as a result, by devising a jacket water cooling structure, the flow rate of the short-circuit flow is reduced even if the gap occurs, and thus the flow rate of the main flow is reduced. Based on this finding, the present invention has been achieved.
That is, according to the present invention, a pair of cooling rolls arranged opposite to each other in horizontal contact with each other is rotated outwardly, and molten slag is injected onto the mutual contact portions to cool and solidify and are sent to both outer sides of the cooling roll pair. The cooling roll has a cooling water flow path with a jacket water cooling structure in which a groove formed on the outer surface side of a core that is an inner cylinder made of stainless steel is covered with a jacket that is an outer cylinder made of copper alloy. A twin-roll cooling device for slag treatment, wherein the cooling water flow path is formed by two spirals in which the grooves are different from each other and the direction of the cooling water flow is the same between adjacent spiral grooves in different systems. It is a twin-roll cooling device for molten slag treatment characterized by having a cooling water flow path having a structure.

  In the present invention, it is preferable that each of the pair of cooling rolls is provided with a shape control roll that presses and spreads the slag passing through the roll surface against the roll surface.

  According to the present invention, the cooling water flow path of the cooling roll has a double spiral structure in which the grooves form two different spirals and the direction of the cooling water flow is the same between the adjacent different spiral grooves. Since the water flow path is used, the short-circuit flow that escapes from the gap inevitably formed by the difference in thermal expansion between the jacket and the core in the jacket water cooling structure to the adjacent downstream flow path is weakened, and the cooling capacity is increased. A decrease in the flow velocity of the spiral flow, which is the main flow of cooling water, is reduced, and a decrease in the cooling capacity of the twin roll cooling device can be effectively prevented. In addition, by adopting a configuration in which a shape control roll is provided, the product thickness accuracy can be improved even when the target thickness is larger.

FIG. 2 is a schematic diagram showing a jacket water cooling structure (a) and (b) and the function and effect (c) showing an embodiment of the present invention. It is the schematic which shows an inner delivery type twin roll cooling technique. It is the schematic which shows the double roll cooling technique of both outer side delivery type | molds. It is a schematic diagram which shows the jacket water cooling structure (a) and (b) of a temporary candidate apparatus (comparison apparatus), and its problem (c). It is the schematic which shows embodiment which attached the shape control roll which concerns on this invention. FIG. 2 is a plan development view of a groove formed on the outer surface of the inner cylinder in FIG. 1.

  The twin roll cooling device according to the present invention (hereinafter also referred to as the present device), for example, as shown in FIG. 3, rotates a pair of cooling rolls 3 and 3 that are horizontally opposed to each other while facing each other. The point where the molten slag 10 is injected onto the mutual contact portion 13 and cooled and solidified, and sent to both outer sides of the pair of cooling rolls, and the cooling water flow path 7 of the cooling roll 3 is, for example, as shown in FIG. In terms of the jacket water cooling structure in which the groove 5 formed on the outer surface side of the core (inner cylinder) 4 made of stainless steel is covered with a jacket (outer cylinder) 6 made of copper alloy, This is the same as the comparison device). Also, the CCMB is suitable as the copper alloy as the jacket material, and the SUS304 as the stainless steel as the core material, which is similar to the comparative device.

However, in the comparative apparatus, the cooling water flow path 7 has a single spiral structure as shown in FIGS. 4 (a) and 4 (b), whereas in the apparatus of the present invention, the cooling water flow path has the double helical structure. In this respect, the device of the present invention is different from the comparison device.
1 (a) and 1 (b) are schematic views showing an embodiment of the apparatus of the present invention, and FIG. 6 is a plan development view of a groove formed on the outer surface of the inner cylinder of FIG. 1 (a). In FIGS. 1 (a), (b) and 6, 5A and 5B are grooves (spiral grooves) forming spirals of two different systems (for example, system A and system B). 5A and 5B are alternately arranged in the roll axis direction, and as shown in FIG. 6, each spiral groove 5A and 5B is provided with cooling water inlets 15A and 15B on one end side in the roll axis direction. Cooling water outlets 16A and 16B are provided on the other end side in the axial direction so that the direction of the cooling water flow is the same between the adjacent spiral grooves 5A and 5B of different systems.

In FIG. 1, the cooling water flow paths 7A and 7B having a jacket water cooling structure in which the grooves 5A and 5B are covered with a jacket 6 form two adjacent spirals, and the grooves 5A and 5B are adjacent to each other. The cooling water flow paths 7A and 7B have a double spiral structure in which the direction of the cooling water flow is the same between the spiral grooves 5A and 5B of different systems.
FIG. 1 (c) is a schematic view showing the function and effect of the device of the present invention. During operation, a gap 14 is inevitably formed between the jacket 6 and the upper end portion of the groove wall that defines the groove 5 of the core 4, as in FIG. A short-circuit flow 9X that flows from the first to the adjacent downstream flow path is generated. However, the cooling water flow path 7 of the comparison device has a single spiral structure, and in the adjacent portion of the cooling water flow path of the same system, the downstream side is longer than the upstream side by a distance of one turn of the spiral from the cooling water inlet. The flow path resistance from the cooling water inlet to the adjacent location is large by the amount. On the other hand, the cooling water flow paths 7A and 7B of the apparatus of the present invention have a double spiral structure, and the downstream side and the upstream side of the adjacent portions of the cooling water flow paths 7A and 7B of different systems are from the cooling water inlet. Since the distances along the spiral are substantially equal, the flow path resistance from the cooling water inlet to the adjacent location is also substantially equal.

  Therefore, the flow velocity difference of the main flow between adjacent cooling water flow paths at the same roll axial direction position is smaller in the device of the present invention than that of the comparison device, and therefore the flow velocity of the short circuit flow 9X in the device of the present invention is It becomes smaller than the flow velocity of the short-circuit flow 9 in the comparison device, and the flow velocity decrease of the main flows 8A and 8B is reduced.

  Next, FIG. 5 is a schematic view showing an embodiment provided with a shape control roll according to the present invention. In the figure, reference numeral 20 denotes a shape control roll, and the same or corresponding members as those in FIG. As shown in the figure, the shape control roll 20 is provided with a solidified slag 11 (or a solidified slag including an unsolidified portion on the surface side) passing through the respective roll surfaces of the pair of cooling rolls 3 and 3. Press to the surface and spread. Thereby, even if it is a case where the target thickness is thicker and an unsolidified free surface remains in the solidified slag 11, variation in product thickness can be suppressed to a small value.

  In order to make the roll gap between the shape control roll 20 and the cooling roll 3 variable, it is preferable to support the shape control roll 20 with an air cylinder or the like so that the position in the height direction is variable. The roll material of the shape control roll 20 is SS400, and the roll diameter is preferably about 1/3 to 1/4 as a ratio to the roll diameter of the cooling roll 3. The shape control roll 20 is preferably rotated in synchronism with the cooling roll 3 and the peripheral speed. Further, the shape control roll 20 may have the same internal structure as the cooling roll 3.

  In the apparatus of the present invention shown in FIG. In Example 1 of the present invention having the given conditions shown in the column 2 and the comparison apparatus shown in FIG. For Comparative Example 1 with the given conditions shown in the first column, using FLUENT (fluid analysis software), two points separated from the midpoint in the roll axis direction of the cooling roll 3 by 1/4 of the full width of the roll on each side. The main flow and short circuit flow velocities in the central region of the roll width at both ends were calculated. In addition, the gap amount was set to a value obtained in advance by calculation of the amount of thermal expansion.

Table 1 shows the calculation results of the flow rates of the main flow and the short-circuit flow. These flow velocities were calculated at a plurality of positions in the roll width central region. Table 1 shows the average values of the calculated data.
According to Table 1, the first embodiment of the present invention has a smaller short-circuit flow velocity than the first comparative example, and the main flow velocity is about 30% higher than that of the comparative example, and a gap is generated between the jacket and the core during operation. However, it turns out that the cooling capacity fall of a twin roll cooling device can be prevented effectively.

In addition, according to the heat transfer analysis calculation result corresponding to the operating state, Example 1 of the present invention has a maximum jacket outer surface temperature of 246 ° C., which is lower than 330 ° C. corresponding to the allowable upper limit of CCMB. There is no problem of proof stress reduction, and the jacket inner surface temperature is a maximum of 155 ° C., which is below the saturation temperature of 165 ° C. under the cooling water supply pressure (6 kgf / cm ² ). Nor. In addition, the suitable range of a cooling water supply pressure is 6-10 kgf / cm < ² >.

Using the twin-roll cooling device of Example 1 of the present invention, the roll rotation speed of the cooling roll was variously changed as shown in Table 2, and the converter slag of CaO / SiO ₂ = 3.8 (injection temperature to the mutual contact portion of the cooling roll: An experiment to cool and solidify (1500 ° C. to 1600 ° C.) was conducted, and this was regarded as Example 2 of the present invention. On the other hand, using a twin roll cooling device with a shape control roll obtained by attaching the shape control roll 20 in the form of FIG. 5 to the twin roll cooling device of Example 1 of the present invention, a roll gap between the shape control roll and the cooling roll is set. Experiments for cooling and solidifying the same slag as in Example 2 of the present invention were carried out as shown in Table 2 together with the number of roll rotations, and Example 3 was obtained. The material of the shape control roll was SS400, the roll diameter was Φ400 mm, and the roll width was the same as that of the cooling roll 3.

  As a result, in both inventive examples 2 and 3, the molten slag spreads in a plate shape with a width of about 1,000 to 1,300 mm on the surface of the cooling roll, and after falling away from the cooling roll 3, it falls onto the conveyor and is conveyed by the conveyor. It was done. Although the slag is solidified on the cooling roll 3 on the contact surface side with the cooling roll, the free surface side may be unsolidified and may flow in a molten state and reach the conveyor. However, the slag was almost completely solidified when it dropped from the end of the conveyor, and it was broken during transportation on the conveyor or when it dropped from the end of the conveyor to form a plate-like piece having a size of about 20 to 80 mm.

Thirty pieces of the plate-like pieces were collected at the end of the conveyor for each roll rotation speed level, and the thickness (referred to as product slag thickness) was measured. Table 2 shows the average value and the variation range of the measurement data.
From Table 2, the product slag thickness becomes thicker as the cooling roll speed is lowered in Example 2 of the present invention. Therefore, the product slag thickness can be controlled by the roll speed, but if the control is made thicker, the variation range will be sharp. It became bigger. On the other hand, in Example 3 of the present invention, by changing the roll gap together with the roll rotation speed, it was possible to keep the variation range small even when it was desired to control the product slag thickness to be thick.

1 Slag pan 2 Slag bowl 3 Cooling roll 4 Stainless steel core (inner cylinder)
5 Groove (A means A line, B means B line)
6 Copper alloy jacket (outer cylinder)
7 Cooling water flow path (A is A system, B is B system)
8 Main flow (spiral flow in the center of the channel; A means A system, B means B system)
9 Short-circuit current (related to the comparison device)
9X Short-circuit current (according to the device of the present invention)
10 molten slag 11 solidified slag 12 roll gap 13 mutual contact portion 14 gap (gap between jacket and core)
15 Cooling water inlet (A is A system, B is B system)
16 Cooling water outlet (A is A system, B is B system)
20 Shape control roll

Claims (2)

  A pair of cooling rolls arranged opposite to each other in horizontal contact with each other is rotated outwardly, and molten slag is injected onto the mutual contact portion and cooled and solidified, and sent to both outer sides of the cooling roll pair. The roll is a twin roll cooling for molten slag treatment having a cooling water flow path with a jacket water cooling structure in which a groove formed on the outer surface side of a core which is an inner cylinder made of stainless steel is covered with a jacket which is an outer cylinder made of copper alloy. A cooling water flow path having a double helix structure in which the cooling water flow path is formed in two different spirals of the groove and the direction of the cooling water flow is the same between adjacent spiral grooves of different systems. A twin-roll cooling device for molten slag treatment characterized by the above.   2. The molten slag according to claim 1, wherein each of the pair of cooling rolls is provided with a shape control roll that presses and spreads the slag passing through the respective roll surfaces against the roll surface. Twin roll cooling device for processing.

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