CA1110072A - Process for producing solidified granular slag from molten blast furnace slag and apparatus therefor - Google Patents
Process for producing solidified granular slag from molten blast furnace slag and apparatus thereforInfo
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- CA1110072A CA1110072A CA308,483A CA308483A CA1110072A CA 1110072 A CA1110072 A CA 1110072A CA 308483 A CA308483 A CA 308483A CA 1110072 A CA1110072 A CA 1110072A
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- slag
- stream
- air
- solidified
- granular
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Abstract
ABSTRACT OF THE DISCLOSURE
A continuous stream of blast furnace molten slag flows down through a trough. The slag stream is dispersed by blowing a jet air stream against the back side of the stream in an upwardly inclined direction crossing the stream. The dispersed slag is carried by the air stream to granulate the slag. The amount of the jet air stream is not less than 500 m3 per ton of the slag stream; The width of the jet air stream is greater than the width of the slag stream against which the air stream is blown, and the blowing speed of the jet air stream is 50 - 140 m/s at a nozzle outlet.
A continuous stream of blast furnace molten slag flows down through a trough. The slag stream is dispersed by blowing a jet air stream against the back side of the stream in an upwardly inclined direction crossing the stream. The dispersed slag is carried by the air stream to granulate the slag. The amount of the jet air stream is not less than 500 m3 per ton of the slag stream; The width of the jet air stream is greater than the width of the slag stream against which the air stream is blown, and the blowing speed of the jet air stream is 50 - 140 m/s at a nozzle outlet.
Description
The present invention relates to a process and apparatus for producing granular solidified slag from molten blast furnace slag. More particularly the present invention relates to a process and apparatus for producing solidified granular slag having a high density and uniform quality, useful as a fine aggregate and road subbase.
The objects and features of the present invention will be clear from the following description referring to the attached drawings showing embodiments of the present invention.
Brief ExPlanation of the Drawinqs:
Fig. 1 and Fig. 2 show schematically conventional methods.
Fig. 3 is a schematic cross sectional view of the entire system of the apparatus for practising the method according to the present invention.
Fig. 4 is a graph showing production rate of the slag wool in correlation with changes in the air blowing speed at the nozzle.
Fig. 5 is a cross sectional view of one embodiment of the blowing nozzle and its positional arrangement.
Fig. 6 is a cross sectional view of a preferable structure of the blowing nozzle.
Fig. 7 is a perspective view of the blowing nozzle shown in Fig. 6.
Fig. B is a side view of one embodiment of the tunnel.
Fig. 9 is a cross sectional view of the apparatus according to the present invention showing particularly the arrangement of the collision plate in the tunnel.
Fig. 10 is a cross sectional view of a desirable shape of the semi-solidified slag formed by collision against the collision plate.
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Fig. 11 is a schematic virw showing the shape of the semi-solidified slag formed when the collision angle (~) with which the semi-solidified slag collide with the collision plate is out of the predetermined range.
Fig. 12 is a schematic view of one embodiment of the arrangement of the collision plate.
Fig. 13 (a) and 13 (b) are, respectively, lateral and longitudinal cross sectional view of duct.
Fig. 14 (a), 14 Ib) and Fig. 15 ta), 15 (b) are views similar Fig. 13 (a) and 13 (b), but undesirable structure of the transfert duct.
Fig. 16 (a) to 16 (b) are cross sectional views of other embodiments of the transfer duct.
Fig. 17 is a graph illustrating the effects of the lateral cross section of the transfer duct on the granular slag, in which the solid line P shows the results obtained by using a transfer duct having a rectangular cross section as shown in Fig. 13 (a) and 13 (b) with the ratio of the width to the length being 0.1, and the broken line Q shows the results obtained by using a transfer duct having a circular cross section as shown in Fig. 14 (a) and 14 (b).
Fig. 18 is a schematic view of one ernbodiment of the recovering device for recovering the granular slag.
Description of Prior Art:
For the production of granular slag from molten blast furnace slag, which is produced in large amount during in the blast furnace operation, by blowing a high-pressure gas, such as air and steam, to the molten blast furnace slag, it is conventionally known as shown in Fig. 1 to blow compressed air, inert gas, steam or high-pressure water to molten slag falling down from a trough 4 so as to finely divide the slag and cause the finely divided slag to be carried by the air and then fall , into a cooling tank 6, where the slag is solidified, and the solidified slag is recovered by means of a conveyor 7.
However, this conventional system requires a large floor area for the equipment and large size of equipment for recovering the granular slag. Further the granular high-tem-perature slag 1 is subjected to rapid cooling so that the quality of the product is thereby adversely influenced.
Thus, according to the conventional system, the molten blast furnace slag is blown off by high-pressure gas, and the blown slag is immediately subjected to rapid cooling by a rapid cooling agent, such as water, so that the molten slag is not always blown into a granular product. Rather the production rate fibrous slag wool is high, and even when a granular slag product is obtained, it is a swollen slag which is porous and has an angular surface, and thus inferior physical properties, particularly strength. Therefore, the product of the conventional system has been considerably limited in its application.
According to another conventional system as shown in Fig. 2, the molten blast furnace slag 1 is spouted into the air by means of a rotary drum 2 and is cooled in the air to obtain small granules of solidif ed slag, which are caused to fall onto a collection yard 3. In order to produce granular slag efficiently by this system, it is necessary to increase the diameter of the rotary drum 2 or increase the rotational speed thereof. However, this re~uires a larger area of the collection yard because the increased diameter or rotational speed expand the flying zone of the granular slag, so that the recovery efficiency is very low.
Also there is certain limitation in increasing the centrifugal force of the rotary drum 2 from a practical point of view. Therefore, according to this conventional system, 111q~72 the high-temperature slag is not completely solidified while it is flying through the air and it is very often that the 81ag granules fuse together even in the collection yard, so that efficient production of granular slag is not achieved.
SummarY of the Invention:
Therefore, one object of the present invention is to solve the above disadvantages of the conventional system and provide a process and apparatus which can produce granular blast furnace slag (hereinafter called simply "granular slag") having uniform quality, high density and excellent physical properties, particularly useful as structural aggregates and road subbase materials.
The above object of the present invention can be achieved by a process consisting of forming a continuous stream of blast furnace molten slag flowing down through a trough, dispersing the slag stream by blowing a jet air stream against the back side o~ the stream in an ùpwardly direction crossing the stream, thereby carring the dispersed slag together with the air stream to thus granulate the slag. The amount of the jet air stream is not more than 500 m3 per ton of the slag stream. The width of the jet air stream is greater than the width of the slag stream by an amount not less than 50 m/m from both sides of the slag stream against which the air stream is blown, and the blowing speed of the jet air stream is 50 - 140 m/s at a nozzle outlet. The above object of the present invention can be achieved by use of an apparatus comprising a vessel for receiving molten blast furnace slag, a trough for receiving the molten blast furnace slag from a slag hole of the vessel, a flat nozzle positioned below the trough for blowing an air stream in a strip form against the molten slag flowing down from the end of the trough in an upwardly inclined direction from the lower side of the slag stream, and a device for supplying the air to the nozzle.
A collision plate is arranged in an angular direction across the path of the granulated semi-solidified slag dispersed in and carried by the air, so as to cause the slag to collide on the plate.
A cylindrical cell has a hole for discharging the solidified slag falling down below the collision plate.
An air-transfer duct connected to the discharge hole transfer the solidified slag together with the air stream to a storage tank by means of suction force of an induction fan.
The storage tank has a receiving opening connected to the air-transfert duct and a device for discharging the solidified slag. ~he unduction fan is connected to an exhaust duct of the storage tank.
Detailed Description of the Invention:
The present invention will be described in detail referring to the embodiments shown in the attached drawings.
In Fig. 3 showing one embodiment of the apparatus for producing the granular slag according to the present invention, 11 is a ladle for storing the molten slag 12, below which a trough 13 is provided. Below the trough 13, a blowing nozzle 14 is provided. The slag stream 12 flowing down from the trough 13 is divided and granulated in a tunnel 15 into semi-solidified granular slag 12a having a circular or almost circular cross section by air blown from the nozzle 14 across the slag stream in a direction inclined upwardly direction from the lower side. The granules of semi-solidified slag 12a are cooled while they are flying or entrained in the air within the tunnel 15, and hecome granular slag 12 b and collide with a collision plate 16 prov~ded at the rear portion of the tunnel lS, and are sucked into a transfer duct 17 together with the transfer gas ~entioned hereinafter. In the tunnel 15 and the lllQ~72 transfer duct 17, the blowing air, the air sucked from opening 15a of the tunnel 15, or the transfer gas forcedly supplied to the tunnel 15 is sucked in the direction marked by an arrow (a) by induction fan 18 as a slag carrying gas. The granular slag 12b sucked into the transfer duct 17 together with the transfer gas is further cooled by the transfer gas in the transfer duct 1~ and introduced into a separator 19, such as a separator tank,where the slag granules are separated from the transfer gas, and the separated slag granules are recovered through a discharge gate 20 provided at the lower portion of the separator 19, while the separated transfer gas is exhausted through an induction pipe 21 the induction fan 1~.
In the production of the granular slag 12b, the type and ~.ind of the gas blown from the nozzle 14 and the blowing condition are important for obtaining a high ~uality of the slag granules.
Conventionally, steam has often been used for the blowing gas, because it is very easy to obtain high-pressure steam in large amount, and it has been common to use a high pressure not lower than 5 kg/cm2. However, such steam is expensive and presents problems in handling and safety.
Further, when steam under a high pressure is used, the molten slag is hardl~ formed into granular slag and the production rate of slag wool becomes high as mentioned hereinbefore, and thus steam is not desirable for the production of granular slag The present inventors have made various and extensive studies for utilizing air which is available at low cost and easy to handle, and have found that remarkable effect can be obtained by blowing air at a low velocity.
Thus, as the gas blown toward the slag stream 12' from the nozzle 14, air supplied from a blower 22 as shown in Fig. 3 is used, and the wind velocity at the nozzle 14 is controlled appropriately. Thereby a high quality of granular slag can be achieved.
Fig. 4 shows the results of producing the granular slag 12b by using the apparatus shown in Fig.3, and particularly shows the production rate of slag wool in correlation with changes in the air velocity. As clearly understood from Fig. 4, as the air velocity, or nozzle jet velocity is reduced, the production rate of slag wool is reduced. However, below a certain air velocity, the slag stream is not but rather falls dispersed and is not satisfactorily granulated, falling down as untreated slag on the lower portion of the tunnel 15, so that efficient production of granular slag is prevented. On the contrary, if the air velocity is increased, the problem of the non-treated slag is eliminated, but a large amount of slag wool is formed and a special means is required for remov-ing the slag wool from the granular slag 12b, so that the resistance of the transfer gas to the suction increases and a larger capacity of induction fan 18 is required.
A higher air velocity has less limitation in the production of granular slag 12b, but a very large capacity of the blower 22 is required for increasing the air velocity, and in an extreme case a compressor is required, so that it is difficult to maintain a required amount of air, and there are caused problems such that the noise of the air blowing is tremendous. There is no substantial difference in quality between the granular slag obtained by blowing the air at a high velocity and that obtained by blowing the air at a low velocity.
On the basis of the forgoing discoveries, the present 3~ inventors have made various studies for minimizing the formation of the slag wool, and have found that if the velocity of the air blown from the nozzle is within the range from 50 to 140 lllOQ72 m/sec. The formation of the slag wool can be maintained at 0.2~ or less so that no special means or device is required for removing the slag wool, and granular slag 12b of dense 8tructure can be efficiently obtained without the occurrence of non-treated slag. In this case, it has also been found that if the amount of air as measured at the nozzle 14 is maintened at at least 500 m3 per ton o~ the slag stream, increased energy is provided for the flying or entrained of the granular slag and a desirable distribution of the granular slag can be obtained. Meanwhile, in order to carry almost all of the granular slag after granulation over a sufficient distance (at least 4 m or longer), it is necessary to maintain the width of the air stream greater than the width of slag stream by at least 50 mm or longer on both side of the slag stream.
In addition, it is necessary to maintain the amount of air at 500 m3/T or larger.
The limitations of the air velocity, the amount of air and the width of the air stream in the present invention are set determined the above reasons.
It is natural that the remperature of the molten slag 12 flowing down from the trough 13 must be high enough for avoiding solidification of the molten slag in the ladle 11 and the trough 13.
However, when the temperature is too low, even if the solidification does not take place, the viscosity of the molten, slag 12 increases and the particle size of the granular slag 12b obtained by blowing low velocity is too large and a large amount of the molten slag remains untreated.
On the other hand, when the temperature of the molten slag 12 is too high, the production rate of the slag wool increases, Thus, it is satisfactory of the temperature of the molten slag 12 flowing down from the trough 13 is about 1400C, and if l~lQQ7Z
the temperature is low, it i~ necessary to control the temperature of the molten slag at 1300C or higher the ladle 11 or the trough 13 with a conventional burner.
The semi-solidified granular slag 12a granulated by the air blowing at low velocity from the nozzle 14 is cooled while flying or being carried through the tunnel 15 by the blown air and the air sucked in through the opening 15a of the tunnel 15.
The tunnel 15 in the embodiment shown in Fig. 3 is an open type having an opening 15a However, the tunnel 15 may be of a closed type into which the air or inert gas etc. is supplied as the transfer gas and in which the semi-solidified granular slag 12a is cooled and transferred by the transfer gas and the blown air while they are sucked by the induction fan.
The process in which the slag stream 12' is blown and the semi-solidified granulated slag 12a is cooled without fusing together again is very important for the quality of the granular slag 12b.
Thus, according to conventional methods, it is com-mon that the semi-solidified granular slag, immediately after granulation and still at high temperatures, is allowed into fall in a water tank or is cooled by a rapid cooling agent, such as water curtain. Therefore, the granular slag 12b absorbs water during the cooling and becomes very often a swollen slag having a porous structure.
One of the features of the present invention is that ~- the semi-solidified granular slag 12a immediately after granulation is caused to fly or be carried over a predetermined distance by the propelling force of the blown air and the sucking force of the transfer gas, and that the surface temperature of the semi-solidified granular slag 12a is lowered _ g _ ~1~7;~
during the cooling to a temperature not higher than the solidifying temperature.
In order to obtain better results by the present invention, it is necessary to control the dispersion direction of the molten slag stream flowing down the trough 13 and to extend the distance the granular slag is carried as far as possible.
In Fig. 5 showing the arrangement of the nozzle, the nozzle 14a is designed to be a complex type in which the tip openings 14al are stepwisely displaced with respect to the slag stream 12'. A detailed description of this nozzle will be made with reference to Fig. 6 and Fig. 7.
The nozzle 14a in Figs. 6 and 7 has a plurality of rectangular tip openings 14al, 14a2 and 14a3 arranged successively one above the other, with the ends thereof being stepwisely displaced by the lengths Ll and L2.
The air streams blown from the tip openings 14al, 14a2 and 14a3 are parallel to each other as shown by the arrows Xa, Xb and Xc.
When the nozzle described above is arranged below the trough tip 13a as shown in Fig. 6 and the air jet is blown toward the slag stream 12', the pressure of the air jet colliding against the stream 12' can be equalized and the flying direction of the slag, i.e. the direction is which the slag is carried forward is stabilized so that accurate and satisfactory granulation and dispersion of the slag can be effected, the degree of granulation is remarkably increased and the flying time of the semi-solidified granular slag 12a is elongated.
In Fig. 7, 14bl, 14b2 and 14b3 are respectively a guide plates for restricting the respective air jet stream.
With the width of the tip opening 14al of the complex nozzle 14a being wider than the slag stream 12' by at least S0 mm beyond each side of the slag stream, and with the nozzle arranged with its center line extending at an upwardly declining angle (B) from 10 to 45 to the horizontal, the flying distance is elongated, and the dispersion effect is remarkably enhanced.
According to the present inventors' experiences, better results can be obtained with a nozzle having a plurality of tip openings than a with a nozzle having only one tip openingc The structure and size of the tunnel 15 may be determined depending on the flying range of the granular slag 12a and the cooling capacity, etc.
As described above, the granular slag 12a dispersed within the tunnel 15 by the blown air is collected together with the transfer gas into the duct 17. In this connection, in order to collect efficiently the semi-solidified granular slag 12a dispersed in the tunnel 15, it is desirable that a collision plate 16 surface polished or water cooled is provided in the rear portion of the tunnel 15.
As described hereinbefore, the slag stream 12' falling down from the trough is formed into granular slag 12a when blown with the air, and the semi-solidified granular slag 12a is carried into and through the tunnel 15 by the force of the blown air. The semi-001idified granular slag 12a, immediately after the commencement of its beiny carried is cooled while it is being carried and is gradually solidified from its surface.
- ~ Therefore, when the carrying distance is determined by free flying, the cooling of the semi-solidified granular slag 12a proceeds to form a relatively thick surface shell around the granular slag, and the shape of the granular slag is hardly deteriorated. However, as mentioned hereinbefore, various problems, such as the requirement for a vacant space for the treatment, are encountered.
~1~q~72 The present inventors have made various studies on this point and have found that the above problems can be over-come by providing a collision plate 16 in the path of the carried semi-solidified granular slag 12a.
Thus, the semi-solidified granular slag 12a, as shown by the dotted lines in Fig. 9 is carried along path Y. In the present invention, the collision plate 16 is arranged at an appropriate position opposing the path Y.
Regarding the position of the collision plate 16, if the distance (d) from the nozzle 14a is too short, the temperature of the semi-solidified granular slag 12a is still high and the thickness of a solidified shell formed on the surface is very thin, so that when such a semi-solidified slag 12a collides with the collision plate 16, the thin solidified shell is broken and the granular slag i5 flattened, thus resulting in a deteriorated shape quality.
According to the present inventors' experiences, when the collision plate 16 is positioned at such a distance ~d) at which the temperature of the semi-solidified granular slag 12a is 1250 C or lower, the formation of the solidified shell is promoted and the thickness thereof is also appropriately increased, so that the above adverse phenomena will very rarely take place, and although some granular slag 12bl having flat portions 12b2 as shown in Fig. 10 will be made, granular slag 12b of good quality can be obtained. However, if the angle (~) at which the semi-solidified granular slag 12a collides with the collision plate 16 is outside a predetermined range, the semi-solidi~ied granular slag 12a is formed into elongated or flattened granules 12b3, even when the collision plate 16 is positioned at the distance (d) where the temperature o~ the semi-solidified slag 12a is 1250C or lower.
The present inventors have repeated various experiments ~C.
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and have found that as the collision angle (~) approaches 90 better granular slag 12b can be obtained, but if the angle falls outside the range of from 80 to 100, the occurrence of the elongated granula~ slag 12b is sharply increased. When the granular slag 12b including, flattened, elongated particles is used as filler in building materials, only lowered strength can be obtained, and e.g. the flowability of cement mortars will be deteriorated. Therefore, in such a case the molten slag stream 12 can not have practical utility. The collision plate 16 may be arranged opposing the path Y in such a way that the temperatures of the semi-solidified granular slag 12a is not higher than 1250C at the collision and that the semi-solidified granular slag 12a collides with the collision plat with a collision angle within the range of from 80 to 100, in view of the blowing directions of the air which is determined by the arrangement of the nozzle and the air pressure, the path Y
of the semi-solidified granular slag 12a, the amount and temperature of the molten slag stream 12 flowing down from the trough and the ambient temperature.
In order to increase portions of the semi-solidified granular slag 12a which collide with the collision plate at a collision angle near 90, a screen-like collision plate 16a, as shown in Fig.12, having an arc-shaped cross section with a radius equivalent to the above distance (d) from the tip of the nozzle 14a, or a screenlike collision plate including a similar arc-shaped portion is efficient.
On the other hand, when the positiGnal distance (d) of the collision plate 16 is increased, the range of the collision angle (~) of the semi-solidified granular slag 12a can be expanded, and the deterioration of the slag shape hardly takes place. ~owever, if the positional distance (d) is longer than the distance at which the temperature of the semi-solidified Q7~
granular slag 12a is looo& or lower, the flying range of the semi-solidified granular slag 12a is considerably expanded so that the collision plate 16 must have a very large siæe, thus causing problems in the supporting structure for the plate and in its manufacture, and lowering the recovery efficiency of the granular slag 12b.
For the above reasons, it is preferable that the collision plate 16 is positioned at a position at which the temperature of the semi-solidified granular slag 12a is in the range of from 1250 to looo& .
When the collision plate 16 is provided according to the present invention, the despersed semi-solidified granular slag 12a collides with the plate 16 at an earlier stage and drops down and is sucked together with the transfer gas so that it is possible to collect easily the semi-solidified granular slag 12a widely dispersed in the tunnel 15 into the duct 17 having a relatively small opening diameter and to transfer the granular slag quickly to the subsequent step, namely a separator 19. Therefore, the granular slag can be recovered efficiently, and the entire system can be made compact in size. Further, it is possible to produce the granular slag 12b even when the tunnel 15 is not completely closed and has many open parts.
In order to avoid as much as possible the difficulty that the semi-solidified granular slag 12a is not carried to the collision plate 16 but rather drops to the bottom of the tunnel lS where the particles fuse together again and/or can not be recovered, it is preferable to forcedly supply air, or inert gases, such as N2 gas as the transfer gas along the 3~ bottom and the side wall of the tunnel 15 as shown in Fig. 3, or to provide a vibration feeder 24 at the lvwer port~on of the tunnel 15~ as shown in Fig. 8, so as to transfer the Q7;~
dropping semi-solidified granular slag 12a to the inlet of the duct 17. In some cases, a hopper (not shown) may be efficiently provided at the lower portion of the tunnel 15 from which the granular slag is recovered.
In the present invention, it is preferable that the duct 17 is designed so as to prevent fusing together of the semi-solidified granular slag 12a'during the transfer operation and to perform the transfer operation efficiently.
Fig. 13~a) and 13~b) show configuration of a prefe-rable duct 70. As shown, the such duct has a rectangular crosssection with a longer horizontal side B and a shorter vertical side A. The semi-solidified granular slag 12a is transferred through the duct 70, floating on or mixed with the transfer gas, and is cooled by contact with the transfer gas, solidifying into the solidified granular slag 12b before it reaches the separator tank 19. Therefore, in the first half portion of the duct 70, all of the semi-solidified granular slag 12a, but as the slag advances into the last half portion the proportion of the solidified granular slag 12b increases~
Hereinafter, the semi-solidified granular slag 12a and the solidified granular slag 12b including the semi-solidified granular slag which are transferred through the duct 70 are referred to as mixed granular slag 12c. It is very important for preventing the contact among the particles of the semi-- solidified slag 12b and for enhancing the cooling effect that the semi-solidified slag 12b in the transfer duct 70 is transferred in a state equally dispersed over the entire cross section of the duct 70.
According to the present inventors' experiences, in the use of the conventional duct, such duct 17a having a circular cross section as shown in Figs. 14(a) and 14Ib~ and duct 17b having a square cross section as shown in Figs. 15(a) and 15~b), most of the mixed granular slag 12c is dispersed in the lower half portion of the duct 17a or 17b, and as shown in Fig, 14(b) and in Fig. 15(b). There is a remarkable difference in density between the upper portion and the lower portion of the mixed granular slag because the mixed granular slag is transferred separately from the major portion of the transfer gas, and in the lower portion having a larger density, particles of the mixed granular slag 12c are vigorously contact and collide with each other so that the cooling effect is remarkably hindered and the resultant granular slag fuses together considerably. The above phenomenon is particularly vigorous in cases where the mixed granular slag 12c is subjected to centrifugal force as in the curved portion of the duct 17a or 17b, and the fusing together of the particles of the mixed granular slag 12c is very often seen in the such curved portions. The present inventors have made various studies of the relation between the cross sectional shape of the transfer duct and the transfer of the mixed granular slag 12c, and have solved the problems as mentioned above by using the transfer duct 70 having an elongated cross section with a shorter vertical side A and a longer horizontal side B as shown in Fig. 13 (a). As there is a large difference in the specific gravity between the transfer gas and the mixed granular slag 12c, the mixed granular slag 12c tends to sink -- -~ down in the lower portion of the transfer duct 17a or 17b having a circular or square cross section, and in order to prevent such sink-down phenomenon, it is necessary to increase the suction of the transfer gas and to increase the velocity of the transfer gas in the duct 17a or 17b. However, the increase of any suction of the transfer gas requires an increased capacity of the suction blower 18 and a huge capital expense.
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In the present invention, the ration of the vertical side A to the horizontal side B, namely A/B is maintained at a small value so that the mixed granular slag 12c can be dispersed uniformly over the entire area of the duct 7C, even with a small amount of the transfer gas, thus increasing the effective cross sectional dimension for transferring the mixed granular slag in the duct 70, A smaller value of A/B can produce a better result. It has been found through experiences of the present inventors that when the ratio of A/B is not larger than 0.5 the mixed granular slag 12c is dispersed over the entire area, of the duct 70 as shown in Figs. 13(a) and Fig.
13(b) so that the desired results of the present invention can be fully obtained, and it has also been found that it is advantageous to maintain the ration of A/B to 1.0 or less when a larger amount of slag is treated. However, when the ratio of A/B is 0.02 or less, the resistance to the transfer in the duct 70 is remarkably increased and the load on the suction blower is sharply increased, and the length of the horizontal side B is too long for a practical operation.
Therefore, in the present invention, the ratio of A/B is limited to the range from 0.5 to 0.02. In the drawing, the duct 70 is shown to have a rectangular cross section for easier manufacturing but it should not be limited to the rectangular cross section and it may have any cross sectional shape as long as the ratio of A/B falls within the range of from 0.5 -~ - to 0.02. For example, a duct 70a having an elliptic cross section as shown in Fig. 16~a), duct 70b having a trapezoidal cross section as shown in Fig. 16(b) or a duct 70c having a triangular cross section as shown in Fig. 16(c) may be used.
In cases where the amount of slag to be treated is large and the ratio of A/B must be made small, so that some operational problems are mos~ likely to occur due to a too greately 111~72 elongated width of the duct 70, it is advantageous that the duct 70d is formed by a plurality of ducts 70dl each having a ratio of A/B within the range of from O.S to 0.02 and mounted in a multiple layers as shown in Fig. 16(d).
Fig. 17 shows results, particularly the particle size of the granular slag 12b and its portion obtained by embodiments of the present invention in which the solidified granular slag 12b is produced from a molten blast furnace slag using the granular slag production apparatus as shown in Fig. 3 with various cross sections of the duct 17. In Fig. 17, the solid line P represents the results obtained by experiments using the duct 70 having a rectangular cross section with the ratio of A/B being. 0.1 and the broken line Q represents results of experiments using the duct 17a having a circular cross section as shown in Fig. 14(a). In the experiments the ducts 70 and 17a had the same cross sectional area and the same velocity of the transfer gas was used. The amount of the molten blast furnace slag treated in these experiments were about 15 tons per hour, the velocity of the transfer gas was 40 m per second and the length of the ducts 70 and 17a was 20 m.
Meanwhile, it has been found from other experiments that most of the granular slag 12b produced by the production apparatus mentioned above is susceptible to fusing together after granulation when the particle size is 5 mm or larger, and the shape and qual~ty of the granular slag 12b are severely degraded. As will be understood from Fig. 17, in the case of the duct 17a of a circular cross section, the granular slag 12b having a diameter not smaller than 5 mm reaches 40~ or higher and the granules having a particle size of 5 mm or larger fuse together into larger granules, maintaining almost no initial shape of the granular slag 12b. However, in the l~OQ72 case of the duct 70 according to the present invention, the granular slag 12b having a diameter of 5 mm or larger is only 12% and most of the granules having a diameter of 5 mm or larger retain the initial shape. Thus, the excellent effects of the duct according to the present invention has been confirmed.
As described above, when the transfer duct 70 having a broad width is used, it is possible to efficiently utilize the transfer gas sucked into the duct, and even when the velocity of the transfer gas is small, the mixed granular slag 12c is dispersed widely and uniformly in the duct 70. Thus the density of the mixed granular slag 12c being transferred is relatively low and uniform throughout the duct so that there is no danger of being together of the mixed granular slag in the duct 70, and the mixed granular slag is cooled efficiently.
As compared with the conventional duct 17a or 17b, the transfer duct 70 having the same cross sectional area according to the present invention has technical advantage in that the amount of the air to be sucked can be reduced, that the length of the duct can be reduced, that the danger of fusing together of the granular slag 12b recovered in the separator tank is remarkably lessened that the fine granular slag 12b of good quality can easily be obtained, and that the mixed granular slag is transferred in a completely entrained condition in the duct 70 so that the mixed granular slag does not adhere to the inside wall of the duct 70. Thus quite efficient transfer of the mixed granular slag can be performed and the granular slag 12b can be efficiently recovered at a predetermined position~
The transfer gas used in the present invention is often used as a generic term to include the air blown from the nozzle, the air sucked from the opening 15a and other openings of the tunnel 15, and the transfer gas supplied into the tunnel l~lOQ7Z
15 or along the bottom surface and side surface of the tunnel 15.
In the enbodiment shown in Fig. 3, the air of ordinary temperature is blown through the nozzle blowing, and only this blown air of ordinary temperature and the air of ordinary temperature sucked through the opening 15a and other openings of the tunnel are used as the transfer gas. In this case, h~wever, the surface temperature of the granular slag 12a, when it solides with the end portion, namely the collision plate 16 and drops down, is lowered to about 1100 C and at this point the granular slag 12a is almost complete.
In this embodiment, the length of the tunnel is 13 m, the length of the duct 17 is 10 m andthe temperature of the granular slag 12a at the time of discharge from the separator 19 is about 750 to 800C.
The feasibility of handling the granular slag 12b discharged from the separator lg is very good, and the granular slag 12b is taken out through a heat exchanger 25 (Fig. 18) connected to the discharge gate 20a of the separator 19 so that industrial recovery of heat can be achieved, thus assuring a great industrial utility.
When the surface temperature of the granular slag 12a at the end portion of the tunnel 15 is about 1100C or lower, water is sprayed on the granular slag in the transfer duct 17, so as to increase the cooling effect. Even in this case, there is no influence on the quality of the granular slag 12b and the ~ length of the duct 17 can be shortened. Thus such water spraying is effective, particularly when a large amount of slag is treated.
Tables 1 to 3 show physical properties of the granular slag 12b produced according to the present invention.
In Table 1 one example of the particle size distribution of the r~
lllQQ7~
granular slag 12b according to the present invention is compared with the particle size distribution of natural sand (sea sand of Muroki Iland of Kagawa-Ken, Japan) and the standard particle size specified by Japan Civil Engineering Association. The granular slag 12b alone is outside the rougher side of the standard of the association. However, it is understood that the particle size distribution in'accordance with the standard can be almost achieved when the granular slag is mixed with fine natural sand or conventionally known water-broken slag in a mixing ratio of 1 : 1. Also it has been revealed that granular slag which fall down on the lower portion of the wind tunnel 15 and slightly fused together can satisfy the above standard of particle size distribution when it is slightly crushed.
- 20a -- l~lOQ7Z
r~ .E 1 ~ .~
Nr.,-ninal Total~Amount passing the Sieve (%) Si~e of Si~ve __ _ _ _ _ _ ~ . .
Granular Sea Synthetic Sand Standa~d Slag Sand = l(Granular Slag) of Parti-: 1 (Sea Sand) cle Size by C.E.A.
_, _ _ ,.. __. _ .__ .. _.. __ . _ _. , .. _ _,_ ___ __ _ ,_ ., ,.. _ __.. _._ 1~ 100 100 100 100 99.4 g9.9 99.7 90 - ]00
The objects and features of the present invention will be clear from the following description referring to the attached drawings showing embodiments of the present invention.
Brief ExPlanation of the Drawinqs:
Fig. 1 and Fig. 2 show schematically conventional methods.
Fig. 3 is a schematic cross sectional view of the entire system of the apparatus for practising the method according to the present invention.
Fig. 4 is a graph showing production rate of the slag wool in correlation with changes in the air blowing speed at the nozzle.
Fig. 5 is a cross sectional view of one embodiment of the blowing nozzle and its positional arrangement.
Fig. 6 is a cross sectional view of a preferable structure of the blowing nozzle.
Fig. 7 is a perspective view of the blowing nozzle shown in Fig. 6.
Fig. B is a side view of one embodiment of the tunnel.
Fig. 9 is a cross sectional view of the apparatus according to the present invention showing particularly the arrangement of the collision plate in the tunnel.
Fig. 10 is a cross sectional view of a desirable shape of the semi-solidified slag formed by collision against the collision plate.
111~7~
Fig. 11 is a schematic virw showing the shape of the semi-solidified slag formed when the collision angle (~) with which the semi-solidified slag collide with the collision plate is out of the predetermined range.
Fig. 12 is a schematic view of one embodiment of the arrangement of the collision plate.
Fig. 13 (a) and 13 (b) are, respectively, lateral and longitudinal cross sectional view of duct.
Fig. 14 (a), 14 Ib) and Fig. 15 ta), 15 (b) are views similar Fig. 13 (a) and 13 (b), but undesirable structure of the transfert duct.
Fig. 16 (a) to 16 (b) are cross sectional views of other embodiments of the transfer duct.
Fig. 17 is a graph illustrating the effects of the lateral cross section of the transfer duct on the granular slag, in which the solid line P shows the results obtained by using a transfer duct having a rectangular cross section as shown in Fig. 13 (a) and 13 (b) with the ratio of the width to the length being 0.1, and the broken line Q shows the results obtained by using a transfer duct having a circular cross section as shown in Fig. 14 (a) and 14 (b).
Fig. 18 is a schematic view of one ernbodiment of the recovering device for recovering the granular slag.
Description of Prior Art:
For the production of granular slag from molten blast furnace slag, which is produced in large amount during in the blast furnace operation, by blowing a high-pressure gas, such as air and steam, to the molten blast furnace slag, it is conventionally known as shown in Fig. 1 to blow compressed air, inert gas, steam or high-pressure water to molten slag falling down from a trough 4 so as to finely divide the slag and cause the finely divided slag to be carried by the air and then fall , into a cooling tank 6, where the slag is solidified, and the solidified slag is recovered by means of a conveyor 7.
However, this conventional system requires a large floor area for the equipment and large size of equipment for recovering the granular slag. Further the granular high-tem-perature slag 1 is subjected to rapid cooling so that the quality of the product is thereby adversely influenced.
Thus, according to the conventional system, the molten blast furnace slag is blown off by high-pressure gas, and the blown slag is immediately subjected to rapid cooling by a rapid cooling agent, such as water, so that the molten slag is not always blown into a granular product. Rather the production rate fibrous slag wool is high, and even when a granular slag product is obtained, it is a swollen slag which is porous and has an angular surface, and thus inferior physical properties, particularly strength. Therefore, the product of the conventional system has been considerably limited in its application.
According to another conventional system as shown in Fig. 2, the molten blast furnace slag 1 is spouted into the air by means of a rotary drum 2 and is cooled in the air to obtain small granules of solidif ed slag, which are caused to fall onto a collection yard 3. In order to produce granular slag efficiently by this system, it is necessary to increase the diameter of the rotary drum 2 or increase the rotational speed thereof. However, this re~uires a larger area of the collection yard because the increased diameter or rotational speed expand the flying zone of the granular slag, so that the recovery efficiency is very low.
Also there is certain limitation in increasing the centrifugal force of the rotary drum 2 from a practical point of view. Therefore, according to this conventional system, 111q~72 the high-temperature slag is not completely solidified while it is flying through the air and it is very often that the 81ag granules fuse together even in the collection yard, so that efficient production of granular slag is not achieved.
SummarY of the Invention:
Therefore, one object of the present invention is to solve the above disadvantages of the conventional system and provide a process and apparatus which can produce granular blast furnace slag (hereinafter called simply "granular slag") having uniform quality, high density and excellent physical properties, particularly useful as structural aggregates and road subbase materials.
The above object of the present invention can be achieved by a process consisting of forming a continuous stream of blast furnace molten slag flowing down through a trough, dispersing the slag stream by blowing a jet air stream against the back side o~ the stream in an ùpwardly direction crossing the stream, thereby carring the dispersed slag together with the air stream to thus granulate the slag. The amount of the jet air stream is not more than 500 m3 per ton of the slag stream. The width of the jet air stream is greater than the width of the slag stream by an amount not less than 50 m/m from both sides of the slag stream against which the air stream is blown, and the blowing speed of the jet air stream is 50 - 140 m/s at a nozzle outlet. The above object of the present invention can be achieved by use of an apparatus comprising a vessel for receiving molten blast furnace slag, a trough for receiving the molten blast furnace slag from a slag hole of the vessel, a flat nozzle positioned below the trough for blowing an air stream in a strip form against the molten slag flowing down from the end of the trough in an upwardly inclined direction from the lower side of the slag stream, and a device for supplying the air to the nozzle.
A collision plate is arranged in an angular direction across the path of the granulated semi-solidified slag dispersed in and carried by the air, so as to cause the slag to collide on the plate.
A cylindrical cell has a hole for discharging the solidified slag falling down below the collision plate.
An air-transfer duct connected to the discharge hole transfer the solidified slag together with the air stream to a storage tank by means of suction force of an induction fan.
The storage tank has a receiving opening connected to the air-transfert duct and a device for discharging the solidified slag. ~he unduction fan is connected to an exhaust duct of the storage tank.
Detailed Description of the Invention:
The present invention will be described in detail referring to the embodiments shown in the attached drawings.
In Fig. 3 showing one embodiment of the apparatus for producing the granular slag according to the present invention, 11 is a ladle for storing the molten slag 12, below which a trough 13 is provided. Below the trough 13, a blowing nozzle 14 is provided. The slag stream 12 flowing down from the trough 13 is divided and granulated in a tunnel 15 into semi-solidified granular slag 12a having a circular or almost circular cross section by air blown from the nozzle 14 across the slag stream in a direction inclined upwardly direction from the lower side. The granules of semi-solidified slag 12a are cooled while they are flying or entrained in the air within the tunnel 15, and hecome granular slag 12 b and collide with a collision plate 16 prov~ded at the rear portion of the tunnel lS, and are sucked into a transfer duct 17 together with the transfer gas ~entioned hereinafter. In the tunnel 15 and the lllQ~72 transfer duct 17, the blowing air, the air sucked from opening 15a of the tunnel 15, or the transfer gas forcedly supplied to the tunnel 15 is sucked in the direction marked by an arrow (a) by induction fan 18 as a slag carrying gas. The granular slag 12b sucked into the transfer duct 17 together with the transfer gas is further cooled by the transfer gas in the transfer duct 1~ and introduced into a separator 19, such as a separator tank,where the slag granules are separated from the transfer gas, and the separated slag granules are recovered through a discharge gate 20 provided at the lower portion of the separator 19, while the separated transfer gas is exhausted through an induction pipe 21 the induction fan 1~.
In the production of the granular slag 12b, the type and ~.ind of the gas blown from the nozzle 14 and the blowing condition are important for obtaining a high ~uality of the slag granules.
Conventionally, steam has often been used for the blowing gas, because it is very easy to obtain high-pressure steam in large amount, and it has been common to use a high pressure not lower than 5 kg/cm2. However, such steam is expensive and presents problems in handling and safety.
Further, when steam under a high pressure is used, the molten slag is hardl~ formed into granular slag and the production rate of slag wool becomes high as mentioned hereinbefore, and thus steam is not desirable for the production of granular slag The present inventors have made various and extensive studies for utilizing air which is available at low cost and easy to handle, and have found that remarkable effect can be obtained by blowing air at a low velocity.
Thus, as the gas blown toward the slag stream 12' from the nozzle 14, air supplied from a blower 22 as shown in Fig. 3 is used, and the wind velocity at the nozzle 14 is controlled appropriately. Thereby a high quality of granular slag can be achieved.
Fig. 4 shows the results of producing the granular slag 12b by using the apparatus shown in Fig.3, and particularly shows the production rate of slag wool in correlation with changes in the air velocity. As clearly understood from Fig. 4, as the air velocity, or nozzle jet velocity is reduced, the production rate of slag wool is reduced. However, below a certain air velocity, the slag stream is not but rather falls dispersed and is not satisfactorily granulated, falling down as untreated slag on the lower portion of the tunnel 15, so that efficient production of granular slag is prevented. On the contrary, if the air velocity is increased, the problem of the non-treated slag is eliminated, but a large amount of slag wool is formed and a special means is required for remov-ing the slag wool from the granular slag 12b, so that the resistance of the transfer gas to the suction increases and a larger capacity of induction fan 18 is required.
A higher air velocity has less limitation in the production of granular slag 12b, but a very large capacity of the blower 22 is required for increasing the air velocity, and in an extreme case a compressor is required, so that it is difficult to maintain a required amount of air, and there are caused problems such that the noise of the air blowing is tremendous. There is no substantial difference in quality between the granular slag obtained by blowing the air at a high velocity and that obtained by blowing the air at a low velocity.
On the basis of the forgoing discoveries, the present 3~ inventors have made various studies for minimizing the formation of the slag wool, and have found that if the velocity of the air blown from the nozzle is within the range from 50 to 140 lllOQ72 m/sec. The formation of the slag wool can be maintained at 0.2~ or less so that no special means or device is required for removing the slag wool, and granular slag 12b of dense 8tructure can be efficiently obtained without the occurrence of non-treated slag. In this case, it has also been found that if the amount of air as measured at the nozzle 14 is maintened at at least 500 m3 per ton o~ the slag stream, increased energy is provided for the flying or entrained of the granular slag and a desirable distribution of the granular slag can be obtained. Meanwhile, in order to carry almost all of the granular slag after granulation over a sufficient distance (at least 4 m or longer), it is necessary to maintain the width of the air stream greater than the width of slag stream by at least 50 mm or longer on both side of the slag stream.
In addition, it is necessary to maintain the amount of air at 500 m3/T or larger.
The limitations of the air velocity, the amount of air and the width of the air stream in the present invention are set determined the above reasons.
It is natural that the remperature of the molten slag 12 flowing down from the trough 13 must be high enough for avoiding solidification of the molten slag in the ladle 11 and the trough 13.
However, when the temperature is too low, even if the solidification does not take place, the viscosity of the molten, slag 12 increases and the particle size of the granular slag 12b obtained by blowing low velocity is too large and a large amount of the molten slag remains untreated.
On the other hand, when the temperature of the molten slag 12 is too high, the production rate of the slag wool increases, Thus, it is satisfactory of the temperature of the molten slag 12 flowing down from the trough 13 is about 1400C, and if l~lQQ7Z
the temperature is low, it i~ necessary to control the temperature of the molten slag at 1300C or higher the ladle 11 or the trough 13 with a conventional burner.
The semi-solidified granular slag 12a granulated by the air blowing at low velocity from the nozzle 14 is cooled while flying or being carried through the tunnel 15 by the blown air and the air sucked in through the opening 15a of the tunnel 15.
The tunnel 15 in the embodiment shown in Fig. 3 is an open type having an opening 15a However, the tunnel 15 may be of a closed type into which the air or inert gas etc. is supplied as the transfer gas and in which the semi-solidified granular slag 12a is cooled and transferred by the transfer gas and the blown air while they are sucked by the induction fan.
The process in which the slag stream 12' is blown and the semi-solidified granulated slag 12a is cooled without fusing together again is very important for the quality of the granular slag 12b.
Thus, according to conventional methods, it is com-mon that the semi-solidified granular slag, immediately after granulation and still at high temperatures, is allowed into fall in a water tank or is cooled by a rapid cooling agent, such as water curtain. Therefore, the granular slag 12b absorbs water during the cooling and becomes very often a swollen slag having a porous structure.
One of the features of the present invention is that ~- the semi-solidified granular slag 12a immediately after granulation is caused to fly or be carried over a predetermined distance by the propelling force of the blown air and the sucking force of the transfer gas, and that the surface temperature of the semi-solidified granular slag 12a is lowered _ g _ ~1~7;~
during the cooling to a temperature not higher than the solidifying temperature.
In order to obtain better results by the present invention, it is necessary to control the dispersion direction of the molten slag stream flowing down the trough 13 and to extend the distance the granular slag is carried as far as possible.
In Fig. 5 showing the arrangement of the nozzle, the nozzle 14a is designed to be a complex type in which the tip openings 14al are stepwisely displaced with respect to the slag stream 12'. A detailed description of this nozzle will be made with reference to Fig. 6 and Fig. 7.
The nozzle 14a in Figs. 6 and 7 has a plurality of rectangular tip openings 14al, 14a2 and 14a3 arranged successively one above the other, with the ends thereof being stepwisely displaced by the lengths Ll and L2.
The air streams blown from the tip openings 14al, 14a2 and 14a3 are parallel to each other as shown by the arrows Xa, Xb and Xc.
When the nozzle described above is arranged below the trough tip 13a as shown in Fig. 6 and the air jet is blown toward the slag stream 12', the pressure of the air jet colliding against the stream 12' can be equalized and the flying direction of the slag, i.e. the direction is which the slag is carried forward is stabilized so that accurate and satisfactory granulation and dispersion of the slag can be effected, the degree of granulation is remarkably increased and the flying time of the semi-solidified granular slag 12a is elongated.
In Fig. 7, 14bl, 14b2 and 14b3 are respectively a guide plates for restricting the respective air jet stream.
With the width of the tip opening 14al of the complex nozzle 14a being wider than the slag stream 12' by at least S0 mm beyond each side of the slag stream, and with the nozzle arranged with its center line extending at an upwardly declining angle (B) from 10 to 45 to the horizontal, the flying distance is elongated, and the dispersion effect is remarkably enhanced.
According to the present inventors' experiences, better results can be obtained with a nozzle having a plurality of tip openings than a with a nozzle having only one tip openingc The structure and size of the tunnel 15 may be determined depending on the flying range of the granular slag 12a and the cooling capacity, etc.
As described above, the granular slag 12a dispersed within the tunnel 15 by the blown air is collected together with the transfer gas into the duct 17. In this connection, in order to collect efficiently the semi-solidified granular slag 12a dispersed in the tunnel 15, it is desirable that a collision plate 16 surface polished or water cooled is provided in the rear portion of the tunnel 15.
As described hereinbefore, the slag stream 12' falling down from the trough is formed into granular slag 12a when blown with the air, and the semi-solidified granular slag 12a is carried into and through the tunnel 15 by the force of the blown air. The semi-001idified granular slag 12a, immediately after the commencement of its beiny carried is cooled while it is being carried and is gradually solidified from its surface.
- ~ Therefore, when the carrying distance is determined by free flying, the cooling of the semi-solidified granular slag 12a proceeds to form a relatively thick surface shell around the granular slag, and the shape of the granular slag is hardly deteriorated. However, as mentioned hereinbefore, various problems, such as the requirement for a vacant space for the treatment, are encountered.
~1~q~72 The present inventors have made various studies on this point and have found that the above problems can be over-come by providing a collision plate 16 in the path of the carried semi-solidified granular slag 12a.
Thus, the semi-solidified granular slag 12a, as shown by the dotted lines in Fig. 9 is carried along path Y. In the present invention, the collision plate 16 is arranged at an appropriate position opposing the path Y.
Regarding the position of the collision plate 16, if the distance (d) from the nozzle 14a is too short, the temperature of the semi-solidified granular slag 12a is still high and the thickness of a solidified shell formed on the surface is very thin, so that when such a semi-solidified slag 12a collides with the collision plate 16, the thin solidified shell is broken and the granular slag i5 flattened, thus resulting in a deteriorated shape quality.
According to the present inventors' experiences, when the collision plate 16 is positioned at such a distance ~d) at which the temperature of the semi-solidified granular slag 12a is 1250 C or lower, the formation of the solidified shell is promoted and the thickness thereof is also appropriately increased, so that the above adverse phenomena will very rarely take place, and although some granular slag 12bl having flat portions 12b2 as shown in Fig. 10 will be made, granular slag 12b of good quality can be obtained. However, if the angle (~) at which the semi-solidified granular slag 12a collides with the collision plate 16 is outside a predetermined range, the semi-solidi~ied granular slag 12a is formed into elongated or flattened granules 12b3, even when the collision plate 16 is positioned at the distance (d) where the temperature o~ the semi-solidified slag 12a is 1250C or lower.
The present inventors have repeated various experiments ~C.
7~:
and have found that as the collision angle (~) approaches 90 better granular slag 12b can be obtained, but if the angle falls outside the range of from 80 to 100, the occurrence of the elongated granula~ slag 12b is sharply increased. When the granular slag 12b including, flattened, elongated particles is used as filler in building materials, only lowered strength can be obtained, and e.g. the flowability of cement mortars will be deteriorated. Therefore, in such a case the molten slag stream 12 can not have practical utility. The collision plate 16 may be arranged opposing the path Y in such a way that the temperatures of the semi-solidified granular slag 12a is not higher than 1250C at the collision and that the semi-solidified granular slag 12a collides with the collision plat with a collision angle within the range of from 80 to 100, in view of the blowing directions of the air which is determined by the arrangement of the nozzle and the air pressure, the path Y
of the semi-solidified granular slag 12a, the amount and temperature of the molten slag stream 12 flowing down from the trough and the ambient temperature.
In order to increase portions of the semi-solidified granular slag 12a which collide with the collision plate at a collision angle near 90, a screen-like collision plate 16a, as shown in Fig.12, having an arc-shaped cross section with a radius equivalent to the above distance (d) from the tip of the nozzle 14a, or a screenlike collision plate including a similar arc-shaped portion is efficient.
On the other hand, when the positiGnal distance (d) of the collision plate 16 is increased, the range of the collision angle (~) of the semi-solidified granular slag 12a can be expanded, and the deterioration of the slag shape hardly takes place. ~owever, if the positional distance (d) is longer than the distance at which the temperature of the semi-solidified Q7~
granular slag 12a is looo& or lower, the flying range of the semi-solidified granular slag 12a is considerably expanded so that the collision plate 16 must have a very large siæe, thus causing problems in the supporting structure for the plate and in its manufacture, and lowering the recovery efficiency of the granular slag 12b.
For the above reasons, it is preferable that the collision plate 16 is positioned at a position at which the temperature of the semi-solidified granular slag 12a is in the range of from 1250 to looo& .
When the collision plate 16 is provided according to the present invention, the despersed semi-solidified granular slag 12a collides with the plate 16 at an earlier stage and drops down and is sucked together with the transfer gas so that it is possible to collect easily the semi-solidified granular slag 12a widely dispersed in the tunnel 15 into the duct 17 having a relatively small opening diameter and to transfer the granular slag quickly to the subsequent step, namely a separator 19. Therefore, the granular slag can be recovered efficiently, and the entire system can be made compact in size. Further, it is possible to produce the granular slag 12b even when the tunnel 15 is not completely closed and has many open parts.
In order to avoid as much as possible the difficulty that the semi-solidified granular slag 12a is not carried to the collision plate 16 but rather drops to the bottom of the tunnel lS where the particles fuse together again and/or can not be recovered, it is preferable to forcedly supply air, or inert gases, such as N2 gas as the transfer gas along the 3~ bottom and the side wall of the tunnel 15 as shown in Fig. 3, or to provide a vibration feeder 24 at the lvwer port~on of the tunnel 15~ as shown in Fig. 8, so as to transfer the Q7;~
dropping semi-solidified granular slag 12a to the inlet of the duct 17. In some cases, a hopper (not shown) may be efficiently provided at the lower portion of the tunnel 15 from which the granular slag is recovered.
In the present invention, it is preferable that the duct 17 is designed so as to prevent fusing together of the semi-solidified granular slag 12a'during the transfer operation and to perform the transfer operation efficiently.
Fig. 13~a) and 13~b) show configuration of a prefe-rable duct 70. As shown, the such duct has a rectangular crosssection with a longer horizontal side B and a shorter vertical side A. The semi-solidified granular slag 12a is transferred through the duct 70, floating on or mixed with the transfer gas, and is cooled by contact with the transfer gas, solidifying into the solidified granular slag 12b before it reaches the separator tank 19. Therefore, in the first half portion of the duct 70, all of the semi-solidified granular slag 12a, but as the slag advances into the last half portion the proportion of the solidified granular slag 12b increases~
Hereinafter, the semi-solidified granular slag 12a and the solidified granular slag 12b including the semi-solidified granular slag which are transferred through the duct 70 are referred to as mixed granular slag 12c. It is very important for preventing the contact among the particles of the semi-- solidified slag 12b and for enhancing the cooling effect that the semi-solidified slag 12b in the transfer duct 70 is transferred in a state equally dispersed over the entire cross section of the duct 70.
According to the present inventors' experiences, in the use of the conventional duct, such duct 17a having a circular cross section as shown in Figs. 14(a) and 14Ib~ and duct 17b having a square cross section as shown in Figs. 15(a) and 15~b), most of the mixed granular slag 12c is dispersed in the lower half portion of the duct 17a or 17b, and as shown in Fig, 14(b) and in Fig. 15(b). There is a remarkable difference in density between the upper portion and the lower portion of the mixed granular slag because the mixed granular slag is transferred separately from the major portion of the transfer gas, and in the lower portion having a larger density, particles of the mixed granular slag 12c are vigorously contact and collide with each other so that the cooling effect is remarkably hindered and the resultant granular slag fuses together considerably. The above phenomenon is particularly vigorous in cases where the mixed granular slag 12c is subjected to centrifugal force as in the curved portion of the duct 17a or 17b, and the fusing together of the particles of the mixed granular slag 12c is very often seen in the such curved portions. The present inventors have made various studies of the relation between the cross sectional shape of the transfer duct and the transfer of the mixed granular slag 12c, and have solved the problems as mentioned above by using the transfer duct 70 having an elongated cross section with a shorter vertical side A and a longer horizontal side B as shown in Fig. 13 (a). As there is a large difference in the specific gravity between the transfer gas and the mixed granular slag 12c, the mixed granular slag 12c tends to sink -- -~ down in the lower portion of the transfer duct 17a or 17b having a circular or square cross section, and in order to prevent such sink-down phenomenon, it is necessary to increase the suction of the transfer gas and to increase the velocity of the transfer gas in the duct 17a or 17b. However, the increase of any suction of the transfer gas requires an increased capacity of the suction blower 18 and a huge capital expense.
: '~
- lllQ~7Z
In the present invention, the ration of the vertical side A to the horizontal side B, namely A/B is maintained at a small value so that the mixed granular slag 12c can be dispersed uniformly over the entire area of the duct 7C, even with a small amount of the transfer gas, thus increasing the effective cross sectional dimension for transferring the mixed granular slag in the duct 70, A smaller value of A/B can produce a better result. It has been found through experiences of the present inventors that when the ratio of A/B is not larger than 0.5 the mixed granular slag 12c is dispersed over the entire area, of the duct 70 as shown in Figs. 13(a) and Fig.
13(b) so that the desired results of the present invention can be fully obtained, and it has also been found that it is advantageous to maintain the ration of A/B to 1.0 or less when a larger amount of slag is treated. However, when the ratio of A/B is 0.02 or less, the resistance to the transfer in the duct 70 is remarkably increased and the load on the suction blower is sharply increased, and the length of the horizontal side B is too long for a practical operation.
Therefore, in the present invention, the ratio of A/B is limited to the range from 0.5 to 0.02. In the drawing, the duct 70 is shown to have a rectangular cross section for easier manufacturing but it should not be limited to the rectangular cross section and it may have any cross sectional shape as long as the ratio of A/B falls within the range of from 0.5 -~ - to 0.02. For example, a duct 70a having an elliptic cross section as shown in Fig. 16~a), duct 70b having a trapezoidal cross section as shown in Fig. 16(b) or a duct 70c having a triangular cross section as shown in Fig. 16(c) may be used.
In cases where the amount of slag to be treated is large and the ratio of A/B must be made small, so that some operational problems are mos~ likely to occur due to a too greately 111~72 elongated width of the duct 70, it is advantageous that the duct 70d is formed by a plurality of ducts 70dl each having a ratio of A/B within the range of from O.S to 0.02 and mounted in a multiple layers as shown in Fig. 16(d).
Fig. 17 shows results, particularly the particle size of the granular slag 12b and its portion obtained by embodiments of the present invention in which the solidified granular slag 12b is produced from a molten blast furnace slag using the granular slag production apparatus as shown in Fig. 3 with various cross sections of the duct 17. In Fig. 17, the solid line P represents the results obtained by experiments using the duct 70 having a rectangular cross section with the ratio of A/B being. 0.1 and the broken line Q represents results of experiments using the duct 17a having a circular cross section as shown in Fig. 14(a). In the experiments the ducts 70 and 17a had the same cross sectional area and the same velocity of the transfer gas was used. The amount of the molten blast furnace slag treated in these experiments were about 15 tons per hour, the velocity of the transfer gas was 40 m per second and the length of the ducts 70 and 17a was 20 m.
Meanwhile, it has been found from other experiments that most of the granular slag 12b produced by the production apparatus mentioned above is susceptible to fusing together after granulation when the particle size is 5 mm or larger, and the shape and qual~ty of the granular slag 12b are severely degraded. As will be understood from Fig. 17, in the case of the duct 17a of a circular cross section, the granular slag 12b having a diameter not smaller than 5 mm reaches 40~ or higher and the granules having a particle size of 5 mm or larger fuse together into larger granules, maintaining almost no initial shape of the granular slag 12b. However, in the l~OQ72 case of the duct 70 according to the present invention, the granular slag 12b having a diameter of 5 mm or larger is only 12% and most of the granules having a diameter of 5 mm or larger retain the initial shape. Thus, the excellent effects of the duct according to the present invention has been confirmed.
As described above, when the transfer duct 70 having a broad width is used, it is possible to efficiently utilize the transfer gas sucked into the duct, and even when the velocity of the transfer gas is small, the mixed granular slag 12c is dispersed widely and uniformly in the duct 70. Thus the density of the mixed granular slag 12c being transferred is relatively low and uniform throughout the duct so that there is no danger of being together of the mixed granular slag in the duct 70, and the mixed granular slag is cooled efficiently.
As compared with the conventional duct 17a or 17b, the transfer duct 70 having the same cross sectional area according to the present invention has technical advantage in that the amount of the air to be sucked can be reduced, that the length of the duct can be reduced, that the danger of fusing together of the granular slag 12b recovered in the separator tank is remarkably lessened that the fine granular slag 12b of good quality can easily be obtained, and that the mixed granular slag is transferred in a completely entrained condition in the duct 70 so that the mixed granular slag does not adhere to the inside wall of the duct 70. Thus quite efficient transfer of the mixed granular slag can be performed and the granular slag 12b can be efficiently recovered at a predetermined position~
The transfer gas used in the present invention is often used as a generic term to include the air blown from the nozzle, the air sucked from the opening 15a and other openings of the tunnel 15, and the transfer gas supplied into the tunnel l~lOQ7Z
15 or along the bottom surface and side surface of the tunnel 15.
In the enbodiment shown in Fig. 3, the air of ordinary temperature is blown through the nozzle blowing, and only this blown air of ordinary temperature and the air of ordinary temperature sucked through the opening 15a and other openings of the tunnel are used as the transfer gas. In this case, h~wever, the surface temperature of the granular slag 12a, when it solides with the end portion, namely the collision plate 16 and drops down, is lowered to about 1100 C and at this point the granular slag 12a is almost complete.
In this embodiment, the length of the tunnel is 13 m, the length of the duct 17 is 10 m andthe temperature of the granular slag 12a at the time of discharge from the separator 19 is about 750 to 800C.
The feasibility of handling the granular slag 12b discharged from the separator lg is very good, and the granular slag 12b is taken out through a heat exchanger 25 (Fig. 18) connected to the discharge gate 20a of the separator 19 so that industrial recovery of heat can be achieved, thus assuring a great industrial utility.
When the surface temperature of the granular slag 12a at the end portion of the tunnel 15 is about 1100C or lower, water is sprayed on the granular slag in the transfer duct 17, so as to increase the cooling effect. Even in this case, there is no influence on the quality of the granular slag 12b and the ~ length of the duct 17 can be shortened. Thus such water spraying is effective, particularly when a large amount of slag is treated.
Tables 1 to 3 show physical properties of the granular slag 12b produced according to the present invention.
In Table 1 one example of the particle size distribution of the r~
lllQQ7~
granular slag 12b according to the present invention is compared with the particle size distribution of natural sand (sea sand of Muroki Iland of Kagawa-Ken, Japan) and the standard particle size specified by Japan Civil Engineering Association. The granular slag 12b alone is outside the rougher side of the standard of the association. However, it is understood that the particle size distribution in'accordance with the standard can be almost achieved when the granular slag is mixed with fine natural sand or conventionally known water-broken slag in a mixing ratio of 1 : 1. Also it has been revealed that granular slag which fall down on the lower portion of the wind tunnel 15 and slightly fused together can satisfy the above standard of particle size distribution when it is slightly crushed.
- 20a -- l~lOQ7Z
r~ .E 1 ~ .~
Nr.,-ninal Total~Amount passing the Sieve (%) Si~e of Si~ve __ _ _ _ _ _ ~ . .
Granular Sea Synthetic Sand Standa~d Slag Sand = l(Granular Slag) of Parti-: 1 (Sea Sand) cle Size by C.E.A.
_, _ _ ,.. __. _ .__ .. _.. __ . _ _. , .. _ _,_ ___ __ _ ,_ ., ,.. _ __.. _._ 1~ 100 100 100 100 99.4 g9.9 99.7 90 - ]00
2.5 62.6 96.9 79.8 80 ~ 0 1.2 18.7 83.6 51.2 50 - 90 0.6 2.1 53.6 27.9 25 - ~5 0.3 0.4 16.4 8.4 10 - 35 _ . .. _ 0.2 0.5 _ ~ ~ . 2 - L0 111~072 ':i`.~BLE 2 r;r~ ~lular ,Sea starldard Water Hard Water ,B . Granu- Granulated Standard lated Slag ~~ ~ _ _ _ Valu ~ Slag Unit Wei~ht 1.5 - 1.85 g/cm3 1.76 1.51 ~(None) O.J3 - 1.0 1.35 JIS A]104 Specific 2.50 - 2.80 Gravity (Not less (Dry Stlrface) than 2.5) g/cm3 2.83 2.54 2.50- 2.3 2.56 JIS AllO9 Water 1 - 2 A~sorptOjon 1.2 2.01 ~ ot more - 2.3 ~nount which Not more ~loa~s on than 0.5 a Specific 0-5 Gravity of 1.~5 (%) . --. .. ... . . . . _ _ . ..... . . . . _ _ _ .. _ .. _ _ _ _ nl,~nt of ~aterial 3 - 5 Finer thân 0.2 0.1(Not Inore - 6.04 S~,~nda.rd than 3 ) ~Siove 0.88 (%) St:a~ility (%) Not more ~J~S Al722 1.. 11 - ~han 10 - 10.88 ( " ~
. . _ . . . _ . . . _ _, . . . _ . . _ .
~-a~se 2.3 - 3.1 ~alt:i.cle ~.17 2.~9( " ) 3.0 - 3.3 3.34 (~M--Value) .. _ _ . . . ... . . . . _ .. . ., . .,. . . _ . .. _, ...... _ ....
.,~ Ul ~
~ o~ ~ a ~ ~
:~ u~ ~ ''1 ~I N
_, ~ _~ i ~ ~ U ~ ~ O
~ ~ ~ ~ ~ ~D ~L> O~
h ~I S~ a) t1~ ~ ~ ~1 7J ~I) O ~ :~
~ a~ ~ r-l 0~,1 U cO a~ ~
,_1 r~l ,_ ~_i ~ r-l t 5) O S) ~--1 (~ C) C~
C~ ~ O
O
~ ~ u~u~ ~ c~
[~ ~ 0 h ~
47 'r-l a) V^ O O O
O 7-~ 7 ~.q ~ ~ c,)'~
7~ 7J
O ~ O O O
~ ~;-- U-~ U.) Ll^) V V~ u~ u~ n G~--`u~ , ~ Il~
7J ~ I~ I~ I'_ . ~_ ~; r~J
a ~ ~7 ~ ~1 -~
5~ ~ ~ r~.
~ ~ r~ r~ r~
r~
_ _~ ____ __ ~_~_ (17Z
, .
Table 2 shows physical properties of the granular slag 12a, sea sand, water granulated slag and hardwater granulated slag, and standard values (basic standard values) of the physical properties.
Table 3 shows results of mortar tests conducted for determining how much aggregate, namely the granular slag 12b and sea sand, can be used with a constant ratio of water to cement. In these tests flowability was used as the control value for measuring the workability. When granular slag 12b according to the present invention is used, the flowability increases 50 that is possible to increase the amount of aggregate, namely the granular slag 12b, per unit amount of cement, thus reducing cement consumption.
As described above, according to the present invention, it is possible to efficiently produce slag having a dense structure and a smooth surface in the form of spherical or nearly spherical granules having a uniform particle size, and the granular slag produced according to the present invention has very excellent physical properties, is very useful as aggregates in cement constructions and as road subbase. Thus the present invention has expanded the application of blast furnace slag and has a very significant industrial advantage.
. . _ . . . _ . . . _ _, . . . _ . . _ .
~-a~se 2.3 - 3.1 ~alt:i.cle ~.17 2.~9( " ) 3.0 - 3.3 3.34 (~M--Value) .. _ _ . . . ... . . . . _ .. . ., . .,. . . _ . .. _, ...... _ ....
.,~ Ul ~
~ o~ ~ a ~ ~
:~ u~ ~ ''1 ~I N
_, ~ _~ i ~ ~ U ~ ~ O
~ ~ ~ ~ ~ ~D ~L> O~
h ~I S~ a) t1~ ~ ~ ~1 7J ~I) O ~ :~
~ a~ ~ r-l 0~,1 U cO a~ ~
,_1 r~l ,_ ~_i ~ r-l t 5) O S) ~--1 (~ C) C~
C~ ~ O
O
~ ~ u~u~ ~ c~
[~ ~ 0 h ~
47 'r-l a) V^ O O O
O 7-~ 7 ~.q ~ ~ c,)'~
7~ 7J
O ~ O O O
~ ~;-- U-~ U.) Ll^) V V~ u~ u~ n G~--`u~ , ~ Il~
7J ~ I~ I~ I'_ . ~_ ~; r~J
a ~ ~7 ~ ~1 -~
5~ ~ ~ r~.
~ ~ r~ r~ r~
r~
_ _~ ____ __ ~_~_ (17Z
, .
Table 2 shows physical properties of the granular slag 12a, sea sand, water granulated slag and hardwater granulated slag, and standard values (basic standard values) of the physical properties.
Table 3 shows results of mortar tests conducted for determining how much aggregate, namely the granular slag 12b and sea sand, can be used with a constant ratio of water to cement. In these tests flowability was used as the control value for measuring the workability. When granular slag 12b according to the present invention is used, the flowability increases 50 that is possible to increase the amount of aggregate, namely the granular slag 12b, per unit amount of cement, thus reducing cement consumption.
As described above, according to the present invention, it is possible to efficiently produce slag having a dense structure and a smooth surface in the form of spherical or nearly spherical granules having a uniform particle size, and the granular slag produced according to the present invention has very excellent physical properties, is very useful as aggregates in cement constructions and as road subbase. Thus the present invention has expanded the application of blast furnace slag and has a very significant industrial advantage.
Claims (5)
1. A process comprising forming a continuous stream of blast furnace molten slag flowing down through a trough, dispersing the slag stream by blowing a jet air stream to the back side of the stream in a direction slantly upwardly crossing the stream, flying the dispersed slag together with the air stream to granulate the slag, the amount of the jet air stream being not less than 500 m3 per ton of the slag stream, the width of the jet air stream being greater than the width of the slag stream by an amount not less than 50 mm from both sides of the slag stream against which the air stream is blown, and the blowing speed of the jet air stream being 50 - 140 m/s at a nozzle outlet,
2. An apparatus comprising a vessel for receiving molten blast furnace slag, a trough for receiving the molten blast furnace slag from a slag hole of the vessel, a flat nozzle positioned below the trough for blowing an air stream in a strip form against the molten slag slowing down from the end of the trough in an upwardly inclined direction from the lower side of the slag stream, and a device for supplying the air to the nozzle; a collision plate arranged in an angular direction across the path of the granulated semi-solidified slag dispersed in and carried by the air so as to cause the slag to collide on the plate; a cylindrical cell having a hole for discharging the solidified slag falling down below the collision plate; an air-transfer duct connected to the discharge hole to transfer the solidified slag together with the air stream to a storage tank by means of suction force of an induction fan, said storage tank having a receiving opening connected to the air-transfer duct and a device for discharging the solidified slag, and said induction fan being connected to an exhaust duct of the storage tank.
3. An apparatus according to Claim 2, in which the nozzle has a plurality of tip openings stepwisely arranged said tip openings each having a rectangular cross section with a longer width and a shorter height and being directed in the same direction for blowing but ending at a different position in the blowing direction.
4. An apparatus according to Claim 2, in which the collision plate is arranged with an angle of 80 to 100° and in such a position as to maintain the semi-solidified slag at a temperature lower or equal to 1250°C.
5. An apparatus according to Claim 2, in which the air transfer duct has a rectangular cross section with a ratio of a longitudinal side A to a lateral side B being in a range from 0.02 to 0.05.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA308,483A CA1110072A (en) | 1978-07-31 | 1978-07-31 | Process for producing solidified granular slag from molten blast furnace slag and apparatus therefor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA308,483A CA1110072A (en) | 1978-07-31 | 1978-07-31 | Process for producing solidified granular slag from molten blast furnace slag and apparatus therefor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1110072A true CA1110072A (en) | 1981-10-06 |
Family
ID=4112030
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA308,483A Expired CA1110072A (en) | 1978-07-31 | 1978-07-31 | Process for producing solidified granular slag from molten blast furnace slag and apparatus therefor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1110072A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015184533A1 (en) * | 2014-06-03 | 2015-12-10 | Hatch Ltd. | Process and apparatus for dry granulation of slag with reduced formation of slag wool |
| WO2015184532A1 (en) * | 2014-06-03 | 2015-12-10 | Hatch Ltd. | Granulated slag products and processes for their production |
| CN111377589A (en) * | 2018-12-31 | 2020-07-07 | 潍坊奥华环保新材料科技有限公司 | A process for automatic gas injection feeding for producing rock wool electric melting furnace |
-
1978
- 1978-07-31 CA CA308,483A patent/CA1110072A/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015184533A1 (en) * | 2014-06-03 | 2015-12-10 | Hatch Ltd. | Process and apparatus for dry granulation of slag with reduced formation of slag wool |
| WO2015184532A1 (en) * | 2014-06-03 | 2015-12-10 | Hatch Ltd. | Granulated slag products and processes for their production |
| US10167423B2 (en) | 2014-06-03 | 2019-01-01 | Hatch Ltd. | Granulated slag products and processes for their production |
| CN111377589A (en) * | 2018-12-31 | 2020-07-07 | 潍坊奥华环保新材料科技有限公司 | A process for automatic gas injection feeding for producing rock wool electric melting furnace |
| CN111377589B (en) * | 2018-12-31 | 2022-05-06 | 潍坊奥华环保新材料科技有限公司 | Automatic gas injection charging process for producing rock wool electric melting furnace |
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