JP3226809B2 - Manufacturing method of hollow granule mold flux - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hollow granular mold flux used for continuous casting of steel.

[0002]

2. Description of the Related Art For example, mold flux added to a mold during continuous casting of steel plays various roles. In other words, to keep the surface of the molten steel to be cast warm, to prevent oxidation of the molten steel surface in the mold and to quickly dissolve the floating inclusions, to control the lubrication between the mold and the slab,
Tasks such as controlling the optimal heat removal from the slab are imposed.

[0003] These effects of mold flux (hereinafter simply referred to as "flux") have the effect of eliminating the surface defects of the slab and forming a beautiful casting surface, and in particular, the stability of the casting operation in the continuous casting operation. This is indispensable for securing and improving the yield of slab casting.

The flux is usually in the form of powder or granules (including hollow granules), and its components are generally CaO, S
It is made of iO ₂ as a main component, and in addition to Al ₂ O ₃ , a compound of an alkaline earth metal and an alkali metal (oxide, carbonate, fluoride, etc.). Further, a flux composition is formed by adding carbon in order to adjust the melting rate. In the case of a granular form, an organic or inorganic binder or the like is used to maintain a certain shape.

However, as a method for producing a hollow granular flux, a raw material flux containing the above composition is mixed with an appropriate amount of water to form an aqueous slurry, which is sprayed from a nozzle into a hot air drying tower (chamber). Then, it is dried by exposure to hot air to obtain a product flux having an appropriate particle size.

As a known technique of such a method for producing a flux, Japanese Patent Publication No. 3-79100 is disclosed. The gist of this technology is that an aqueous slurry containing a carbonaceous powder and a flux component for metal casting is made, and the aqueous slurry is spray-dried to evaporate water. Generated, and the carbonaceous powder is dispersed and contained throughout the solid portion in the particle, and the ratio of the carbonaceous powder on the surface of the particle in the solid portion is larger than the ratio of the carbonaceous powder in the entire particle. It is characterized by having.

Although the publication does not specifically mention a production apparatus, according to the above-described method for producing a flux for metal casting, spray drying involves dispersing an aqueous slurry as atomized particles from a sprayer by a supply pump. Then, the dispersion is put on the hot air supplied from the air heating and lowered in the drying chamber, and during the descent, the particles are heated with the hot air to instantaneously evaporate the moisture in the particles to form voids in the particles. In addition, it is described that the particles are dried to obtain spherical particles having a porous structure, and the particles thus obtained are introduced into a cyclone together with hot air, where the product and the hot air are separated to obtain a desired flux.

[0008]

Problems to be Solved by the Invention Japanese Patent Publication No. 3-791
The flux production technology in Japanese Patent Publication No. 00 is based on a method of supplying a raw material slurry of flux to a hot air drying chamber and supplying hot air for drying.
A so-called co-current system in which the air is discharged in the same direction from above the drying chamber is used.

In such a system, the size of the drying room needs to be increased due to the long time required to be exposed to the hot air, so that the equipment is expensive. Further, as seen from the attached drawings, the slurry is ejected from a single nozzle, and no countermeasures such as nozzle clogging of the slurry are mentioned.

In the hot air drying of the raw material slurry of the mold flux as described above, the operation of effectively drying the droplets generated from the raw material slurry in a limited drying region is continued for a long time, and the drying region is dried. It is desired to suppress the adhesion of droplets to the constituent wall surfaces of the tower.

The drying of the droplets produced from the raw material slurry is limited by the temperature of the atmosphere in the drying zone. In order to secure the distance for drying up to the maximum, the length of the drying area may be increased, but the equipment cost increases.

If the ambient temperature is increased to suppress this problem, the moisture in the droplets evaporates rapidly, explosion occurs during the drying and solidification process, and the desired spherical hollow granule mold flux cannot be obtained. .

The hot air drying of such a slurry has the above-mentioned problems, and the present invention has been made to solve such problems. The aim is to provide a method.

[0014]

The present invention adopts the following means in order to solve the above problems. (1) When the raw material slurry of the mold flux is spray-dried in a hot air drying tower and the hollow mold flux is discharged from the lower portion of the drying tower, hot air for drying at 400 to 550 ° C. is supplied downward from the top of the drying tower. From a plurality of lance nozzles for spraying the raw material slurry disposed below the drying zone in the drying tower, a solid-liquid ratio of 55 to 75% and a viscosity of 50 to 1000 mPa. A method for producing a hollow granular mold flux, comprising injecting a raw material slurry of S in an upwardly spread state, and performing initial drying of produced droplets of the raw material slurry by countercurrent contact with hot air for drying.

(2) Three to ten lance nozzles arranged at substantially equal intervals in the circumferential direction in an annular region having a radius of 1/3 to 2/3 from the side wall surface of the drying region in the drying tower. The method for producing a hollow granular mold flux according to (1), wherein the raw material slurry is injected.

(3) The intersection angle between the axis of the injection direction of the lance nozzle and the central axis of the drying zone is 5 to 35 °, and the spread angle of the droplets of the raw material slurry injected from the lance nozzle is 40 to 8
The method for producing a hollow granular mold flux according to (1) or (2), wherein the raw material slurry is injected in an inclined upward spread state set at 0 °.

(4) The method for producing a hollow granular mold flux according to any one of (1) to (3), wherein the injection pressure of the raw material slurry from the lance nozzle is set to 8 to 13 kg / cm ^2. .

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In view of the problems of the prior art, the present inventors exposed a flux raw material slurry during flux production to hot air in any form to achieve a target particle size in an ideal form. As a result of various studies on whether a hollow granular flux can be efficiently obtained, the present invention has been completed.

That is, the contact between the raw material slurry (hereinafter simply referred to as slurry) and the hot air can be made into a compact hot air drying tower by employing a countercurrent method. In order to obtain the desired spherical hollow granule mold flux, initial drying is performed by injecting a slurry into a drying zone of a predetermined temperature atmosphere provided by hot air flowing downward and causing generated droplets to fly upward. Is achieved, and drying to a desired low water content can be achieved in the process of inverting and free falling. That is, the particles can be dried effectively by reciprocating the droplets within the limited drying region.

In order to efficiently dry the droplets in a limited volume drying area in consideration of economy, for example, the slurry is sprayed from a single lance nozzle and the droplets are sprayed at a desired spread angle. May be distributed.

However, the flux slurry of the present invention is a fluid in which solid particles are suspended in water and a predetermined amount of a binder is blended. Although the solid particles are finely pulverized to a predetermined particle size, for example, 0.3 mm or less, nozzle clogging often occurs due to the inevitable inevitable mixing of uncontrollable coarse particles. There is an inherent problem of doing so.

Since the lance nozzle that has clogged the nozzle is constantly exposed to the high-temperature atmosphere in the drying area, the slurry staying in the lance nozzle is dried and solidified and cannot be repaired. Therefore, immediately after the nozzle clogging occurs, the operation must be stopped and the nozzle must be replaced, which significantly reduces productivity.

In order to achieve continuous operation on the premise that the slurry is clogged with nozzles, a plurality of lance nozzles are used, and each lance nozzle is arranged at a predetermined position in the drying area at a predetermined interval, and the slurry is directed upward. By spraying in the spread state, the generated droplets are evenly distributed in the drying zone, and drying is achieved in the process of reciprocating in the drying zone.

In the spray drying of the slurry, if nozzle clogging occurs in a specific lance nozzle, supply of the slurry only to the lance nozzle is stopped, and if the lance nozzle is replaced, product quality is not hindered. Continuous operation can be achieved without equipment failure. That is, drying can be uniformly performed in the drying tower by using a multi-type slurry injection nozzle.

Further, as described above, the slurry applied to the present invention is a fluid in which solid particles are suspended in water. Therefore, in the process of passing through the supply pipe, the slurry in which the solid particles are substantially evenly distributed is used. However, since the tip portion of the lance nozzle has a so-called squeezing structure for dispersing as droplets at a predetermined spread angle, that is, a so-called squeezing structure, it is regarded as a sparse and dense solid-liquid fluid microscopically, It is inevitable that the pulsating spray becomes minute.

This pulsating spray phenomenon may cause nozzle clogging in some cases when coarse particles inevitably intervening in the fluid pass through the nozzle tip, but if such a state is not reached, significant pulsation occurs. As a result, the generation of droplets of the slurry is partially hindered, and the unsprayed slurry is dripped from the nozzle tip portion.

The formation of the dripping is not limited to the fact that it must be dropped and mixed in the hollow granule product being discharged at the lower part of the drying tower, and the sorting operation must be performed. The direction fluctuates, and depending on the situation, before the initial drying of the droplets has progressed sufficiently, it adheres to the wall of the tower that constitutes the limited drying area, and then is dried, solidified, and deposited in that state. Then, there arises a problem that it cannot withstand its own weight, falls off partly and is mixed in the hollow granular product as described above.

As described above, the lance nozzle having the dripping in such a state must be immediately replaced and repaired. However, the generation of the dripping unavoidably occurs. The fluctuation of the flight direction of the droplets ejected from the nozzle can be suppressed by adjusting the arrangement of each lance nozzle in the drying area, the injection direction and spread angle of the nozzle, and the injection pressure of the raw material slurry individually or in combination. Is possible.

In the present invention, a method for producing a flux having excellent product properties is developed by selecting appropriate production conditions for solving the above-mentioned problems and obtaining a product having a preferred flux particle size of 300 to 600 μm. It was a success.

Hereinafter, the features of the present invention and details thereof will be described with reference to FIG. The hot air 2 from the hot air generator is sent under pressure from the top of a hot air drying tower (hereinafter simply referred to as a drying tower) 5 for countercurrently drying the slurry 4. Near the lower part of the drying tower 5, a nozzle 9 is provided at the tip to blow the slurry 4.
A lance 10 having a nozzle penetrates the side wall 8 from the outside of the drying tower, and a nozzle is installed at a predetermined position in the drying tower at a specific angle upward and toward the center.

The slurry 4 is maintained at a predetermined slurry header pressure by an annular pipe 11 surrounding the periphery of the side wall of the drying tower 5, and the slurry 4 is uniformly supplied to each lance 10. Further, since the disposition position of the nozzle 9 is point-symmetrical in the drying tower 5, the slurry is sprayed substantially uniformly in the tower, and the contact with the hot air (usually 400 to 550 ° C.) is performed without unevenness.

Further, a dried hollow granular flux having a predetermined size is stored in the lower part of the drying tower by countercurrent heat exchange with hot air, and is substantially continuously provided by a rotary valve provided at a discharge port. Is cut out. Further, a hot air exhaust portion (hollow body) 13 having been subjected to heat exchange with the slurry 4 is provided in an upper portion of a lower portion of the drying tower, and is connected to an exhaust duct 18 to suck and discharge the exhaust gas to the outside of the drying tower 5. it can.

At this time, since the fine flux is also sucked together with the exhaust air and discharged outside the room, a product containing no fine powder is obtained as the hollow granular flux. In addition,
In the figure, reference numeral 14 denotes an observation window for constantly monitoring the state of the slurry 4 jetted from the nozzle 9, and reference numeral 20 denotes an entrance for checking the inside of the drying tower.

From the viewpoint of drying the slurry in the production of the flux, the conditions include the size of the drying tower, the amount and temperature of the supplied hot air, and the properties of the slurry from the viewpoint of the product of the produced flux. That is, the composition of the slurry, the solid concentration, the supply speed, the pressure, the flow rate per nozzle, and the like can be considered.

The characteristics of the flux that can be produced naturally change depending on these opposing conditions. Therefore, although it cannot be said unconditionally, the above-mentioned conditions of the slurry supplied into the drying tower and the nozzle setting conditions (pump spray pressure, etc.) are adjusted in consideration of the above two conditions, so that the flux having a predetermined particle size can be obtained. Manufacturing becomes possible.

Next, an example of the state of slurry injection from the nozzle disposed in the drying tower according to the present invention will be described with reference to FIGS.
It will be explained by. FIG. 2 is a schematic side view of the state of slurry injection in the drying tower, showing a case where four nozzles are arranged. FIG. 3 is a schematic plan view seen from AA in FIG.

In the drawing, the nozzles 9 are arranged point-symmetrically with respect to the central axis 16 of the drying zone of the drying tower 5 and at equal intervals. The injection direction axis 17 of the lance nozzle has an intersection angle α with the central axis 16 of the drying zone of the drying tower 5 and α = 5.
It is installed by inclining toward the central direction of 35 °. The spread angle of the spray droplets of the slurry sprayed from the nozzle is β, and the slurry is sprayed upward in the range of β = 40 to 80 °.

Although the nozzle inclination angle α is related to the nozzle setting position, if the value is small (close to 0), the amount of slurry adhering to the side wall of the drying tower is undesirably large.
Conversely, when the value is increased, the spray height of the slurry becomes too low, and the contact time with the hot air is reduced, so that a flux product in an undried state is generated. Therefore, as an allowable range, the angle is set to 5 to 35 ° in the present invention.

The angle of spread β of the slurry droplets ejected from the nozzle has an angle suitable for obtaining a product having an appropriate particle size as a flux. Particle size 300-6
In the case of 00μ, the angle is optimally 40 to 80 °, and when the angle is larger than this, the obtained product particle size becomes too large. Conversely, if the angle is too small, the product particle size will be small and fine powder will be generated, and the product will be conveyed to the outside of the tower at the same time as the exhaust gas, and the productivity will decrease. In addition, the amount of slurry directed toward the side wall of the drying tower increases, and the slurry adheres to the side wall.

Further, in the contact heat exchange between the drying gas of hot air and the slurry, it is necessary to uniformly disperse the slurry in the drying tower 5 from the viewpoint of drying efficiency and preventing drying unevenness of the product. In 5, in order to eject a large amount of slurry in a uniform spray pattern, the number of nozzles also depends on the size of the drying tower, but generally requires 3 to 10 nozzles,
Make up the match nozzle type. The set position of the nozzle tip is 1/3 to 2 in radius from the inner peripheral surface of the drying tower 5.
Within a range of / 3, they are arranged at regular intervals at a fixed distance.

In order to uniformly dry the slurry, the number of nozzles set is such that if a single nozzle generates deposits or the like at the nozzle tip, the spraying range of the slurry is unbalanced and a dead space that does not contribute to drying is generated. The number is preferably three or more. If the number is increased, the slurries sprayed from the adjacent nozzles interfere with each other, so that it is not necessary to set the number more than ten.

When the nozzle tip set position in the drying tower is L, it depends on the angle of inclination of the nozzle, but L is 2/3 in the radius (D / 2) direction from the side wall of the body of the drying tower. When the distance exceeds the distance, the distance between the nozzle and the facing nozzle is too short, and interference of the spray slurry occurs. If L is less than 1/3, there is hot air that does not contribute to drying at the center of the drying tower, and a part of the spray slurry may face the drying tower side wall surface and adhere to the side wall surface without drying. Therefore, the position may be set within the range of 1/3 to 2/3 in the radial direction of the drying tower.

Next, regarding the slurry, the quality of the flux production is also affected by the change in the characteristic value of the slurry. The present inventors have learned from the experience in the actual operation that if the solid content concentration of the slurry and the viscosity of the slurry are not set to a specific ratio, the required appropriate particle size (300 to 6) is required.
(Μm) cannot be obtained.

Therefore, in the present invention, the viscosity range of the slurry by the binder required for maintaining the shape of the flux product is empirically determined, and the amount of water added to the raw material is adjusted to adjust the solid content of the slurry to a certain range. By defining and drying, a product having a uniform viscosity could be obtained.

The range is 50 to 10 as slurry viscosity.
00 mPa. S, 55 to 75% as slurry solid concentration
Is to be kept within the range. This limit value is derived from the synergistic effect of the two, the powdering rate of the product is small,
The viscosity was determined from the value at which the size of the particle size became appropriate, and the solid content of the slurry was regulated within the viscosity range. If the value of the slurry solids concentration exceeds 75%, the product particle size tends to be coarse, whereas if it is less than 55%, the flux strength is weakened and the powder is pulverized during drying, and the content of fine powder increases.

Further, the spray pressure sprayed from the slurry jetting lance nozzle also affects the operation characteristics during drying and the characteristics of the produced flux. When the spray pressure is less than 8.0 kg / cm ² , the flux product is not Slurry dripping occurs due to insufficient spraying, and production efficiency is reduced. On the other hand, when the spray pressure exceeds 13.0 kg / cm ² , the flying distance of the slurry increases, and the amount of undried slurry adhering to the upper wall surface and the side wall surface of the drying tower increases. Therefore, it is necessary to regulate the conditions of the slurry within the above range.

As described above, by setting various conditions, the slurry ejected from the nozzle exchanges heat with the hot air descending from above while rising in the hot air to a certain height by the spray pressure from the nozzle. Dry and evaporate the water to form a hollow granular flux product.

In spouting the slurry 4 into the drying tower 5, according to the experience of the present inventors, if the single nozzle 9 is clogged, the operation of the entire apparatus must be stopped. Further, when a deposit is formed on a part of the tip of the nozzle 9, the ejection of the slurry from the part is hindered, so that the slurry 4 is not uniformly distributed in the drying tower 5 and a dead zone is formed. The drying hot air is wasted, and the jet of the slurry 4 from the nozzle 9 becomes abnormal due to the adhered matter, and the undried slurry (hollow products) on the inner wall of the drying tower 5 is required.
An undesired situation arises in that the adhesion of the particles increases.

In order to avoid such a situation, in the present invention, a match type nozzle is provided, and even if one of the several nozzles causes the above-described phenomenon, the drying is performed. The operation is stopped by sequentially monitoring the situation from the viewing window 14 that looks into the tower, responding quickly and stopping the supply of the slurry 4 to the nozzle, and replacing the nozzle 9 with a new nozzle together with the lance 10. You don't have to.

[0050]

An embodiment of the present invention will be described below.
The apparatus used in the production of this example was the same as that shown in FIG. 1, and the raw material of the slurry produced a hollow granular flux for continuous casting having a general composition. The drying tower has a diameter of 7.1 m, a height of 7.0 m, a hot air temperature from a hot air generator of about 450 ° C., and a hot air volume of 180 Nm ^3.
/ Min.

On the other hand, eight lance nozzles for ejecting the slurry were arranged in the drying tower, and the set position of the nozzle tip was 1700 mm in the radial direction from the side wall of the drying tower. The nozzle had a slurry spread angle of 60 ° and an inclination angle with respect to the axis of the drying tower of 20 °. The slurry has a viscosity of 150 mP
a. In S, the slurry solid concentration was set to 72%, the slurry injection pressure was adjusted to 11.5 kg / cm ² , and the flow rate per nozzle was adjusted to 480 liter / hr to perform the slurry injection.

The production of the flux generally proceeded favorably, and about 13 hours of operation yielded 36 tons of a hollow granule flux having a target particle diameter of 400 to 500 μm, and the yield was about 97 hours.
%Met.

[0053]

According to the present invention, since the heat exchange between the hot dry air and the slurry is carried out in a countercurrent manner and specific drying conditions and slurry conditions are employed, the scale of the drying tower does not need to be increased, and the equipment cost can be reduced. Useful, and the multi-nozzle method allows easy production of hollow granule flux with an appropriate particle size without impeding operation even if nozzle clogging occurs during operation, and productivity Is not reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a drying tower used in an embodiment of the present invention.

FIG. 2 is a schematic side view showing an example of a distribution state of a slurry injected from a nozzle in a drying tower of the present invention.

FIG. 3 is a schematic plan view showing an example of a distribution state of a slurry injected from a nozzle in a drying tower of the present invention.

[Explanation of symbols]

 2 Hot air (air) 4 Aqueous raw material slurry 5 Hot air drying tower 8 Side wall 9 Nozzle 10 Lance 11 Annular tube 13 Hot air exhaust unit 14 Lookout window 15 Slurry distribution area 16 Central axis of drying area 17 Nozzle injection direction 18 Exhaust duct 19 Shut-off valve 20 Inspection mouth

Continuation of the front page (56) References JP-A-6-23257 (JP, A) JP-A-3-52637 (JP, A) JP-A-48-23941 (JP, A) JP-A-6-126403 (JP, A) JP-A-52-123330 (JP, A) JP-A-9-57407 (JP, A) JP-A-60-87960 (JP, A) JP-A-4-63129 (JP, A) 57-111301 (JP, U) JP 3-79100 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) B22D 11/108 B22D 11/07 C21C 7/076 B01J 2 / 04

Claims (4)

(57) [Claims] 1. A hot air for drying at 400 to 550 ° C. is supplied downward from the top of the drying tower when the raw material slurry of the mold flux is spray-dried in a hot air drying tower and the hollow mold flux is discharged from the lower part of the drying tower. At the same time, a plurality of lance nozzles for spraying the raw material slurry, which are disposed below the drying zone in the drying tower, have a solid-liquid ratio of 55 to 75.
%, Viscosity 50 to 1000 mPa. A method for producing a hollow granular mold flux, comprising injecting a raw material slurry of S in an upwardly spread state, and performing initial drying of produced droplets of the raw material slurry by countercurrent contact with hot air for drying. 2. The method according to claim 1, wherein a radius of 1 / radius from a side wall surface of the drying zone in the drying tower.
2. The hollow granule mold flux according to claim 1, wherein the raw material slurry is injected from 3 to 10 lance nozzles arranged at substantially equal intervals in a circumferential direction into an annular area in a range of 3 to 2/3. Manufacturing method. 3. An inclined upward spread in which the crossing angle between the axis of the injection direction of the lance nozzle and the central axis of the drying zone is set at 5 to 35 °, and the spread angle of the droplets of the raw material slurry injected from the lance nozzle is set at 40 to 80 °. The method for producing a hollow granular mold flux according to claim 1 or 2, wherein the raw material slurry is injected in a state. 4. The method for producing a hollow granular mold flux according to claim 1, wherein the injection pressure of the raw material slurry from the lance nozzle is set to 8 to 13 kg / cm ² .