GB2073387A - Flat cooling plates or boxes for blast furnace walls - Google Patents

Abstract

A flat circular cooling plate 100 is mounted between the furnace wall 101 and the refractory lining. A supply duct 103 extends through the wall 101 and supports the plate. The cooling liquid is supplied to a port 107 at the periphery and deflected by plate 108 to enter the enclosure 102 tangentially. Some of the outflow goes by way of port 109 and duct 110 to central chamber 111. Other liquid spirals inwards and passes directly into chamber 111 where spiral vanes 112 encourage the circulation. Outflow from chamber 111 is by a port opposite the vanes 112 and through a duct 104 coaxial with inflow duct 103. Similar structures can be used as cooling boxes with the plane of the box extending into the refractory perpendicular to the furnace wall. The direction of flow can be reversed with liquid entering at centre and leaving at periphery. <IMAGE>

Description

SPECIFICATION Heat exchanger for cooling blast furnace walls The present invention relates to a heat exchanger suitable for use in cooling the wall of a blast furnace and comprising a chamber for the circulation of cooling liquid which is substantially in the form of a body of revolution defined by a peripheral wall and two end walls spaced at a distance less than the radius of the peripheral wall.

Fiat heat exchangers of this kind can be arranged in the most exposed parts of the blast furnace between the metal casing and the refractory lining to prevent overheating of the metal casing. The end walls of the chamber in this case lie parallel to the casing and lining surfaces and such heat exchangers are called "cooling plates". Alternatively the heat exchanger can extend into the refractory to provide mechanical support and cooling. In this case the end walls of the chamber and perpendicular to the casing and lining surfaces and heat exchangers used in this way are known as "flat cooling boxes".

In accordance with the present invention there is provided a heat exchanger comprising a chamber for the circulation of cooling liquid, the chamber being substantially in the form of a body of revolution defined by a peripheral wall and two end walls spaced at a distance less than the radius of the peripheral wall, a flow conduit communicating with the chamber adjacent the peripheral wall and arranged for flow between the conduit and the chamber in a direction tangential to the chamber, a port at the centre of the chamber in a wall extending perpendicular to the axis of the chamber, and deflection means arranged within the chamber opposite the said port to give a tangential component to the flow of liquid through the port, whereby a spiral circulation of cooling liquid will occur between the centre of the chamber and the peripheral wall thereof.

The central port may communicate with a radially-extending duct and preferably this duct is within the chamber and has lateral walls spaced from the end walls of the chamber, a central port is formed in each lateral wall of the duct and corresponding deflection means are arranged between the end walls of the chamber and the lateral walls of the duct.

Such a construction is particularly suitable for a flat cooling box. For a cooling plate the heat exchanger preferably has supply and discharge ducts disposed about a common axis and extending from the centre of one end wall of the chamber to pass through an opening in a furnace wall and support the heat exchanger on that wall. In a preferred embodiment the discharge duct communicates with the chamber through the central port and the supply duct coaxially surrounds the discharge duct and communicates with the said flow conduit, the latter extending radially from the supply duct adjacent one end wall of the chamber.

In one form of embodiment to be described the heat exchanger has means for tangential injection of the liquid opening tangentially into the chamber at the periphery or in the vicinity of the periphery thereof and means for tangential discharge of liquid situated in the centre of the chamber, and the tangential discharge means comprise at least one assembly of deflecting means situated in the centre of the chamber and a duct opening into a face of the chamber opposite said deflecting means.

Because of the presence of the deflecting means, recovery of the cooling liquid is facilitated in its spiral rotating movement and its delivery at the port of the discharge duct. This recovery is affected more rapidly, which further improves the flow of the liquid and allows more efficient cooling of the walls of the chamber or enclosure to be achieved.

The discharge duct may extend radially from the centre of the enclosure towards the periphery of the enclosure.

So as not to increase the thickness of the heat exchange device, it is advantageous for the radial discharge duct to be inside the enclosure, for it to extend substantially at the same distance from the two lateral walls of the enclosure and for it to be provided with two assemblies of deflecting means situated on each side of said duct. Preferably, the radial discharge duct is then shaped outwardly so as to offer minimum resistance to the liquid rotating in the enclosure.

Advantageously, the radial discharge duct opens into a transit chamber, outside the enclosure and comprising a water outlet orifice.

Anther arrangement, to which recourse is had either in combination with one or other of the preceding ones consists in the tangential discharge means comprising a duct opening tangentially into the enclosure, at the periphery thereof, the port of said duct being diametrically opposite the port of the tangential injection means.

In another embodiment according to the invention, it is envisaged that, with the tangential injction means opening into the central part of the enclosure and with the tangential discharge means situated at the periphery of the enclosure, the tangential injection means comprise at least one liquid supply duct opening into at least one face of the enclosure and substantially in the center of said face and at least one assembiy of deflecting means situated opposite the port of said duct, so as to impart a tangential force component the liquid emerging into the enclosure.

The flat cooling boxes used up to now have a general flattened substantially parallelepipedic shape whose rear part is provided with means for fixing to the plating and whose front part (or nose) is formed by a flat face which is fitted with a small radius to the lateral faces.

So as to cause the cooling liquid to flow in the nose, there is provided inside the enclosure thus formed at least one separating wall forcing the liquid to follow the outer wall of the box.

However, in the 90 bends, the speed of the streams of liquid-which are situated outermost (i.e. in contact with the wall of the boxWis greatly reduced; the result is that this band zone is poorly cooled whereas the nose is precisely the part of the box which is the most exposed to the heat.

Furthermore, this reduction in the speed of the liquid may be such that recirculation, or dead water zone, is created in the bend promoting decantation of solid particles which slow down the heat exchange. The wall of the enclosure heats up, which further increases scaling, which slows down even further the heat exchanges.

This cumulative phenomenon spreads by degrees and the box finishes by being destroyed under the action of thermo-mechanical abrasion, for poorly cooled copper (from wich these boxes are generally made) loses all its mechanical characteristics and is very easily worn, not only by the charges but also by hot gases, dust charges, etc.

As far as the streams of liquid which are situated innermost in the bend (in contact with the internal separating wall) are concerned their speed is greatly increased, which may lead to.very high speeds of the liquid if the flow has been increased to improve cooling of the plate.

The effects of this high flow rate of the liquid are even more harmful than in the preceding case for, in this region where the liquid undergoes a 180 change of path, there occurs cavitetion causing a pressure drop and rapid wear of the separating wall.

Furthermore, the increase in the speed of the cooling liquid can only be obtained practically by reducing the section of the ducts, which leads to a reduction of the volume of liquid and so of the thermal flywheel.

Finally, those boxes are difficult to construct and so costly.

Implementation of the arrangements in accordance with the invention for constructing a flat cooling box allows an enclosure to be obtained which comprises no bend having a small radius of curvature and in which the streams of liquid follow paths whose radii are sufficiently great to avoid creation of the above-mentioned dead zones; furthermore, there exists no part likely to cause a cavitation phenomenon. Deposits of solid particles are then avoided and no region of the box is subjected to particular destructive wear.

Moreover, it will be noted that the whole of the cooling liquid mass is set in rotation inside the enclosure and that the whole of this mass participates at all times in cooling the walls.

The result is a considerably increased cooling efficiency with respect to what was obtained up to now.

Finally, the manufacture of flat boxes thus constructed is very simple and so less expensive than that of known flat boxes.

In a preferred embodiment, there is provided, for supply and discharge of the cooling liquid, connection means disposed side by side and connnected to the enclosure by ducts which extend between two planes containing the two substantially parallel faces of the enclosure.

Finally, a complementary arrangement, more particularly advantageous in the case where the heat exchange device is intended to be used as a cooling box, consists in providing a second enclosure covering at least the front part of the first enclosure, no communication for the cooling liquid existing between the first and second enclosures.

The addition of this second enclosure increases considerably the efficiency of the heat exchange device of the invention for a bulk which is in general scarcely greater.

Moreover, by causing the cooling liquid to flow in opposite directions in the two enclosures, better distributed and more even cooling is obtained over the whole of the periphery of the device since there corresponds, to one region of an enclosure through which flows heated liquid, a region of the other enclosure through which still cold liquid flows.

The arrangements of the invention find a second application in the so-called "vaporization" cooling boxes in which there is formed vapor bubbles on contact with hot walls.

This type of box is arranged so that the vapor bubbles are collected, by gravity, in the discharge duct for the cooling liquid.

The major disadvantage of the vaporization boxes used at present is that the heat is removed essentially by convection. In the case of harsh heat aggression in a given zone of the box, this heat flow may be all the less efficiently removed since in general no pump is provided in the circuit and since the flow of the cooling liquid takes place naturally by'a thermosiphon phenomenon. The result is a calefaction phenomenon in the zone considered, causing in the ducts formation of a vapor plug which interrupts, and may even sometimes reverse, the natural flow of the cooling liquid. Uncooled, the box is rapidly destroyed.

On the contrary, in a cooling box constructed in accordance with the invention, the vapor bubbles are subjected to the action of the centrifugal force due to the rotation of the liquid mass. Thus, because of the existence of the gravitational field, the vapor bubbles are torn from the wall as fast as they are created and are carried towards the center of the box.

For a cooling box formed in accordance with the preceding arrangements, it is provided for the radial duct, extending from the central zone of the box to the rear thereof, to be situated in the upper part of the box (in the mounted position thereof), and preferably outside the enclosure, so as to form a chamber for recovering the water-vapor emulsion which is then discharged.

The arrangements of the invention find a third application in cooling plates.

The cooling plates used at present are in the form of rectangular metal plates through which pass a plurality of ducts intended for circulation of the cooling liquid. The ducts are independent of each other and each has an inlet port and an outlet port provided respectively with securing means for connection to outside hydraulic circuits. Furthermore, these plates comprise securing means for the fixing thereof to the plating of the blast furnace.

Typically, a known cooling plate comprises at least twelve securing points, either for fixing them or for connecting them to outside circuits.

The very high temperatures to which the plates are exposed cause expansions which are incompatible with such a high number of rigid points and the plates are subjected to mechanical stresses such that they are rapidly made unusable.

Furthermore, the cooling liquid flow rate in these known plates is too low and the thermal fly-wheel thus created is too small to provide efficient cooling of the plating.

On the contrary, by its very design, the cooling device of the invention, because of the relatively high volume of liquid set in rotation, has a high thermal fly-wheel which allows much better cooling than that obtained up to present.

As for the problem of mechanical stresses, it is resolved in the cooling device of the invention by the fact that: -the two pipes for supplying and discharging the cooling liquid extend approximately perpendicularly to that one of the walls of the device which, in the mounted position in the blast furnace, is in contact with the plating of said blast furnace, from the central region of said wall, -the two ducts are concentric, at least in the vicinity of said wall, -and the means for fixing the plate to the plating of the furnace comprise that one of said ducts which is outside the other and an orifice, pierced in the plating, adapted to receive said outer duct, securing means being used for securing this outer duct to the edge of the orifice or to the zone of the plating surrounding the orifice.

Thus, with these arrangements, the cooling plate is only secured to the plating in a single zone, which removes any problem of mechanical stresses due to expansion during operation.

Moreover, still because of the simple structure of the cooling devices in accordance with the invention, cooling plates thus formed are simple to manufacture, so less expensive, than the plates known at present.

A variation of the plate which has just been described consists in providing it with an axial cavity open at both ends, the enclosure surrounding the cavity and the supply and discharge ducts surrounding at least partially the cavity, the transverse dimensions of the cavity being sufficient for it to be possible to introduce therein an elongate, and cylindrical cooling device.

It may thus be seen that a combined cooling device, associating a cooling plate and a cooling box, which ensures a particularly favorable result since, for a bulk which is that of the cooling plate, deep cooling is effected within the refractory material, on the one hand, and a thermal screen is formed protecting the plating, on the other.

Embodiments of the invention will now be described by way of example. In this description, reference is made to the accompanying drawings in which: Figure 1 represents schematically one embodiment of a heat exchange device constructed in accordance with the invention; Figure 2 is a sectional view along line ll-ll of Fig. 1; Figure 3 represents schematically another embodiment of a heat exchange device in accordance with the invention; Figure 4 shows schematically yet another embodiment of a heat exchange device in accordance with the invention; Figure 5 shows schematically yet another embodiment of a heat exchange device in accordance with the invention; Figure 6 is a side sectional view of a cooling plate constructed in accordance with the invention; Figure 7 is a sectional view along line VII-VII of the cooling plate of Fig. 6;; Figure 8 shows a further variation of the cooling plate of Figs. 6 and 7, and Figures 9 and 10 show respectively two possible arrangements of cooling plates and boxes in accordance with the invention.

Referring first of all to Figs. 1 and 2 concerning a first embodiment, cooling box 60 comprises a cylindrical enclosure 61 having a flattened shape, i.e. its height is small in relation to its radius.

A duct 62 for supplying cooling liquid opens tangentially into enclosure 61.

For discharging the liquid there is provided, on the one hand, an outlet port 63a, substantially diametrically opposite the port of supply pipe 62 and, on the other hand, a channel 63 extending radially approximately from the centre to the periphery of enclosure 61; channel 63 is situated at the same distance from flat walls 64 of the enclosure and it is flattened and shaped, as can be seen at 65 in Fig. 2, so as to only disturb the liquid flow to a lesser degree.

The holes 66, pierced respectively in the lateral faces thereof and centered at the centre of the enclosure, allow the cooling liquid to pass from the enclosure into channel 63.

To facilitate this passage, there is furthermore provided, on each side of channels 63 (i.e. between each face 67 of the channel and each wall 64 of the enclosure), a deflecting device 68 formed from blades wound in the direction of the center of holes 66.

Channel 63 extends towards the rear of cooling plate 60, i.e. opposite the zone (or nose) 69 intended to be directed towards the region of the blast furnace to be cooled when the box is installed in its operating position.

Channel 63 opens into a discharge chamber 70, contiguous with enclosure 61 and situated therebehind.

A duct 71 for discharging the cooling liquid opens into chamber 70, preferably opposite the port through which channel 63 opens into chamber 70 or opposite port 63a.

The cooling liquid (in general water), supplied by duct 62 (arrow 72) arrives in enclosure 61 in which, considering the form thereof, there is created a spiral movement (arrow 73). A part of the liquid of the external stream, which is in fact the most heated in contact with the wall of nose 69, passes directly through port 63a (arrow 73a) to be discharged. The rest of the mass of water, once in the vicinity of the central region of the enclosure, is recovered by the deflecting devices 68 (arrow 74) and penetrates into channel 63 from where it passes into chamber 70 (arrow 75) then leaves through duct 71 (arrow 76).

It will be noted that the whole of cooling box 60 is comprised between two parallel planes containing the faces 74 of the enclosure. The result is that box 60 may be easily introduced through the plating of the blast furnace into its housing provided in the refractory material. Conversely, it may be easily removed therefrom, for example with a view to its replacement.

Fig. 3 (in which the elements identical to those in Figs. 1 and 2 are designated by the same reference number) shows a so-calledY vaporization" cooling box 77 whose construction corresponds in a general way of that of box 60 of Figs. 1 and 2, with the exception of channel 63 which is transferred to the outside of the enclosure.

More precisely, there is associated with one of the walls of the enclosure (in the present case the one 78 which is disposed at the top in the mounted position of the box on the plating of the blast furnace, such as shown in Fig. 3), an elongate shell 79 defining with wall 78 an outer channel 80.

A supply duct 62 opens tangentially into enclosure 61, for example in accordance with the configuration of Fig. 1 or in accordance with any other configuration, whereas a discharge duct 71 leaves from channel 80. Just as in the preceding embodiment, vanes 68 are provided for causing the liquid to pass through a hole 66 communicating enclosure 61 with channel 80.

Another hole 81 is provided for connecting discharge chamber 70 with channel 80.

During operation, the vapor bubbles which form particularly in contact with the wall of nose 69, the most exposed to the heat, are torn away as fast as they are created and carried by the rotating liquid mass into enclosure 61.

Considering the gravitational field which reigns within the liquid mass, the vapor bubbles are brought to the center of enclosure 61 where they pass into channel 80. Since the liquid is in continuous circulation within the enclosure, there cannot be formed, along the internal face of the walls, particularly in the nose, a vapor veil preventing heat exchanges neither a vapor plug stopping circulation of the water.

The cooling box 83 shown in Fig. 4 is designed, contrary to the preceding ones, with a central inlet and a tangential discharge.

A supply duct 84 opens into the center of an enclosure 85 cylindrical in revolution, the liquid penetrating perpendicularly to the circular face 86 of the enclosure.

Deflecting means 87, formed for example like those 68 of Fig. 1 to 4, impart to the liquid a tangential component so that it is set in rotation and describes a spiral path from the inside to the outside of the enclosure (arrow 88).

A discharge duct 89 extends tangentially and recovers the heated liquid, Fig. 5 shows yet another embodiment of a cooling box in accordance with the invention.

Box 90 of Fig. 5 is designed from plate 60 of Figs. 1 and 2 all the elements of which it employs (the same reference numbers have been kept in Fig. 5).

There is however added a second enclosure 91 which is simply formed by a tubular duct bent in a semi-circle so as to assume the rounded shape of nose 69 of plate 60 of Fig.

1. Tubular duct 91 is connected to the outside hydraulic network by means of supply 92 and discharge 93 ducts.

It will be noted that, in enclosure 61 and in duct 91, the flow directions for the liquid are opposite (respectively arrows 94 and 95).

The result is that in the vicinity of discharge duct 93,where the liquid already heated by its travel through duct 91 is less efficient, beneficial cooling is provided by the cold liquid arriving through duct 62 and emerging into enclosure 61. And conversely in the region of ducts 71 and 92. It is thus possible to obtain better distribution of the cooling of the refractory and, in a general way, improved efficiency.

It will be noted that in Fig. 5 cooling box 91 has been shown in an operational position, i.e., as has already been explained moreover above, the plate extends practically perpendicularly to the plating 96 of the blast furnace to which it is fixed in an appropriate way by means of an intermediate shoe 97 and it penetrates into the refractory 98, its nose 99 being turned towards the hot regions of the blast furnace, Figs. 6 and 7 show a cooling plate 100, for inserting (as has already been indicated above) between the plating 101 of a blast furnace and the refractory wall (not shown).

Cooling plate 100 has an enclosure 102 cylindrical in revolution, a supply duct 103 for the cooling liquid and a discharge duct 104 for this liquid.

The two ducts 103 and 104 extend, at least in a zone adjacent the cooling plate, substantially perpendicularly to that one 105 of the walls of the enclosure which is turned towards plating 101. Furthermore, the two ducts 102 and 104 are coaxial, duct 104 being inside duct 103, which surrounds it.

By way of example, the arrangement for the cooling plate may be the following.

Supply duct 103 communicates with a channel 106, provided on the outer face of said wall 105 of the enclosure, which opens into enclosure 102 at the periphery thereof through a port 107. A deflecting wall 108 is provided in front of port 107 to deflect the liquid flow so that it gushes tangentially into the enclosure.

Diametrically opposite port 107 is an outlet port 109 by means of which enclosure 102 communicates with a channel 110 (also situated outside wall 105 for example) ending in a central chamber 111 of the enclosure. This central chamber communicates with the rest of the enclosure through apertures 11 2. In chamber 111 are also disposed deflecting vanes 11 2 situated opposite the port through which discharge duct 104 opens into said chamber 111.

For fixing cooling plate 100 in the blast furnace, a hole 11 3 with a diameter corresponding substantially to the outer diameter of supply duct 103 is bored in plating 101; duct 103 introduced into hole 11 3 is welded to the plating. Cooling plate 100 is thus securely fixed to the plating solely by its central region, represented by duct 103 serving as a fixing sleeve.

Whatever the deformations which the cooling plate may undergo through the action of the heat, it will be able to freely expand without it being the seat of destructive stresses as was the case with the prior cooling plates presenting a plurality of fixing zones.

Of course, it will be understood that the arrangements which have just been described and combining the supply and discharge means for the cooling liquid with the fixing means are not dependent on the particular configuration of the enclosure shown in Figs.

6 and 7, and which has only been given by way of example, and that they may just as readily be associated with other enclosure configurations, such as those previously described.

Fig. 9 shows an arrangement combining cooling plates 100, such as those which have just been described, disposed in a staggered arrangement and cooling boxes 1 00a disposed in the free sectors between the plates.

Thus deep cooling of the refractory, provided by the boxes, may be combined with surface cooling, intended to protect the plating, created by the plates.

Fig. 8 shows a cooling plate 11 4 which is a variation of the cooling plate 100 of Figs. 6 and 7.

Plate 114 comprises an axial annular chamber 11 5 surrounding an axial cylindrical cavity 11 6 open at both its ends.

Annular chamber 11 5 is subdivided into two semicylindrical half chambers 11 7 and 11 8 in which emerge respectively the supply 11 9 and discharge 1 20 ducts for the cooling liquid.

For the rest, the cooling plate may be arranged in a substantially identical way to plate 100 of Figs. 6 and 7 or be constructed in accordance with one or other of the preceding examples.

Plate 114 as a whole is formed so that the axial cayity 11 6 has a sufficient transverse dimension for a cooling box 121 of elongated cylindrical type.

It is thus possible to form cooling plate + box assemblies which provide, in the same zone of the blast furnace, cooling of the refractory wall (deep cooling) and cooling between the plating and the refractory wall (surface cooling or thermal screen effect).

Fig. 10 shows the combination of such cooling assemblies (plate 11 4 + box 121) disposed in a staggered arrangement with cooling boxes 1 22 alone of elongated cylindrical type disposed in the sectors left free (arrangement at the corners of a hexagon circumscribed on plates 114).

It is thus possible to create veritable thermal barriers, whose action extends not only in depth in the refractory but on the surface and which, through the arrangement of the cooling boxes, provides good anchorage for the refractory.

Claims (14)

1. A heat exchanger comprising a chamber for the circulation of cooling liquid, the chamber being substantially in the form of a body of revolution defined by a peripheral wall and two end walls spaced at a distance less than the radius of the peripheral wall, a flow conduit communicating with the chamber adjacent the peripheral wall and arranged for flow between the conduit and the chamber in a direction tangential to the chamber, a port at the centre of the chamber in a wall extending perpendicular to the axis of the chamber, and deflection means arranged within the chamber opposite the said port to give a tangential component to the flow of liquid through the port, whereby a spiral circulation of cooling liquid will occur between the centre of the chamber and the peripheral wall thereof.

2. A heat exchanger as claimed in claim 1 in which the central port communicates with a radially-extending duct.

3. A heat exchanger as claimed in claim 2 in which the radially-extending duct is within the chamber and has lateral walls spaced from the end walls of the chamber, a central port is formed in each lateral wall of the duct and corresponding deflection means are arranged between the end walls of the chamber and the lateral walls of the duct.

4. A heat exchanger as claimed in claim 3 in which the duct is profiled to offer minimum resis'tance to the circulating liquid within the chamber.

5. A heat exchanger as claimed in claim 2, 3 or 4 in which the radially-extending duct opens into a discharge chamber outside the cooling chamber, the discharge chamber having an outlet port.

6. A heat exchanger as claimed in any of the preceding claims in which the flow conduit communicating with the periphery of the chamber includes an end portion extending peripherally within the chamber.

7. A heat exchanger as claimed in claim 6 in which the end portion communicates with the rest of the flow conduit by way of an aperture in an end wall of the chamber.

8. A heat exchanger as claimed in any of the preceding claims having supply and discharge ducts disposed about a common axis and extending from the centre of one end wall of the chamber, to pass through an opening in a furnace wall and support the heat exchanger on that wall.

9. A heat exchanger as claimed in claim 8 in which the discharge duct communicates with the chamber through the central port and the supply duct coaxially surrounds the discharge duct,and communicates with the said flow conduit, the latter extending radially from the supply duct adjacent one end wall of the chamber.

1 0. A heat exchanger as claimed in any of the preceding claims having an axial cavity extending therethrough and open at both ends to receive an elongate cylindrical cooling device.

11. A heat exchanger as claimed in any of claims 1 to 5 in which ducts for the supply and discharge of liquid circulating in the chamber lie between the planes containing the end walls of the chamber to facilitate mounting of the heat exchanger as a cooling box extending perpendicular to a blast furnace wall.

1 2. A heat exchanger as claimed in claim 11 in which a flow passage for cooling liquid is arranged around the part of the periphery of the chamber remote from the supply and discharge ducts, there being no communication between the flow passage and the chamber.

1 3. A heat exchanger as claimed in any of the preceding claims designed for the circulation of liquid within the chamber from the periphery to the centre and having a peripheral discharge opening at a position substantially diametrically opposite the point where the flow conduit enters the chamber.

14. A heat exchanger substantially as described with reference to Figs. 1 and 2, Figs.

3, 4 or 5, Figs. 6 and 7 of Fig. 8 of the accompanying drawings.