EP0044792B1 - Cooling plates for a blast-furnace cooling arrangement - Google Patents

Abstract

This invention relates to a cooling installation for a blast furnace using stave coolers in which circulates a cooling fluid, these staves being arranged in successive superimposed rings along the internal wall of the shell of the blast furnace and being traversed by internal fluid circulation tubes, the internal tubes of two staves adjacent in a vertical plane being interconnected so as to define a network of vertical fluid circulation lines, wherein this network is connected at each of its extremities to an external circulation and fluid cooling circuit defining a pressurized forced closed circuit in which the cooling fluid is maintained in the liquid phase.

Description

The present invention relates to an installation for cooling metallurgical units, the walls of which are subjected to high heat fluxes and more particularly to the cooling of blast furnaces using cooling plates.

Modern blast furnaces are more and more exploited at speeds and pressure levels such that it is important to control the heat flows and their transfer, especially in the areas of displays, belly, bottom of tank and mid tank. In particular, in the case of self-supporting units, it is essential that the shield does not reach the temperature levels or does not undergo temperature variations which could jeopardize its resistance to the forces to which it is subjected.

The heat flux emitted in the different zones of the blast furnace must be captured by a heterogeneous system formed of the refractory lining, the cooling element, i.e. the cooling plate, the shielding, such as the element cooler fulfills a double function of energetic cooling of the refractory and of screen as the flow passes to the shielding.

The cooling plates arranged against the internal face of the shielding between the latter and the refractory lining, fulfill this dual function. These plates consist of cast iron elements traversed in their mass by a network of tubes in which circulates a cooling fluid which, in the techniques known until now, consists of water subjected to vaporization in contact with the flow of heat that the cooling plate is intended to absorb.

However, this type of cooling has all the drawbacks inherent in a cooling system in which a fluid is vaporized, which relate to the high pressure, the uncontrolled formation of gas vaporization pockets at hot spots, the difficulty of controlling the flow rates circulation and the increased risk of leaks as well as the corrosive nature of the vapor.

Known in particular from US-A-2,275,515 is a blast furnace cooling installation in which a coolant recycled in a closed circuit is used, this fluid consisting of molten salts whose boiling point is very high and therefore not encountering vaporization problems. However, this technique is aimed at a cooling installation of the cooling box type, different from the cooling plate technique and therefore not using for the cooling of the shielding a set of tubes embedded in cast iron plates constituting a network of vertical coolant circulation lines.

Application DE-A-2 017 569 describes a cooling installation essentially aimed at cooling the blast furnace nozzles, comprising an external circuit for circulation of the cooling fluid which, according to one of the embodiments, allows the liquid phase to be maintained in the coolant.

This document does not however make any reference to cooling the shielding of a blast furnace by the technique of cooling plates which form a network of vertical circulation lines of the cooling fluid, embedded in the plates.

Patent FR-A-2 054 737 describes an installation for cooling the shielding of a blast furnace using a technique using cooling plates, but according to the principle of spray cooling.

The present invention aims to remedy these drawbacks by proposing to provide a cooling installation having greater reliability, lower cost and an operation making it possible to know and control the operation of the blast furnace by detecting thermal fluxes. emitted by the different zones of the latter.

The present invention thus relates to a cooling installation of a blast furnace using cooling plates in which a cooling fluid circulates, these plates being arranged in successive rings superimposed along the internal wall of the shielding of the blast furnace and being traversed by internal tubes for circulation of the coolant, the internal tubes of two adjacent plates in a vertical plane being interconnected so as to define a network of vertical fluid circulation lines, said network being connected at each of its ends to an external circuit for circulation and cooling of the fluid defining a closed, forced and pressurized circuit comprising a supply circular, a return circular, a battery of heat exchangers connected to the return circular by a return line and to the supply circular by a supply line, a battery of rec pumps including the coolant disposed on the supply line, and at least one expansion tank placed on the return line at the selected pressurization level, characterized in that the external circuit comprises at least one supply circular, said (said) supply circular (s) being connected to the various inlets of the circulation lines situated at different levels of rings of cooling plates corresponding to the various inlets, and at least one return circular, said (said) return circular (s) being connected to the various outlets of the circulation lines situated at different levels of rings of cooling plates corresponding to the various outlets thereby creating a variable density of the vertical circulation lines of the cooling fluid on the circumference of the blast furnace, said external circuit maintaining the coolant in the liquid phase.

The cooling fluid is in particular water which is normally maintained in the liquid state throughout the entire circuit. A special oil resistant to 300 ° C can also be used as the cooling fluid.

This characteristic allows a global control of the water flow and therefore a leakage detection by differential measurement. In addition, lower water pressures and temperatures can be maintained, which makes it possible to use an apparatus whose technical characteristics are lower and therefore the cost of the installation is lower. Knowledge of the exact flow rates of liquids as well as the measurement of temperatures at different points also makes it possible to know the quantities of heat evacuated in determined zones of the blast furnace, consequently the measurement of the flows emitted in these different zones. Since the water is kept in the liquid state, the formation of local gas pockets preventing the correct evacuation of calories is completely avoided and the risks of deterioration by overheating are limited. Finally, it is possible to treat the water in order to give it the quality of boiler water with corrosion inhibitors and therefore to avoid both the problems of racking and corrosion.

Furthermore, it should be noted that in vaporization systems, it is practically impossible to detect the places where this vaporization takes place and therefore to properly regulate the liquid and gaseous flow rates in the various zones of the installation.

• - la Fig. 1 est une vue schématique générale de l'installation de refroidissement adaptée à. un haut-fourneau;
• - la Fig. 2 est également une vue schématique de cette même installation mettant en évidence les différents niveaux d'alimentation et de prélèvement du fluide de refroidissement;
• - la Fig. 3 est une vue dévéloppée partielle du réseau de lignes de circulation du fluide de refroidissement sur un partie de la circonférence totale du haut-fourneau.

Other characteristics and advantages of the present invention will appear during the description which follows, given with reference to the appended drawings in which:

• - Fig. 1 is a general schematic view of the cooling installation adapted to. a blast furnace;
• - Fig. 2 is also a schematic view of this same installation showing the different levels of supply and withdrawal of the coolant;
• - Fig. 3 is a partial developed view of the network of cooling fluid circulation lines over part of the total circumference of the blast furnace.

The installation shown in FIG. 1 comprises a blast furnace 1 against the inner wall of which are placed cooling plates of which only the internal pipes have been shown connected to each other by the general reference 2. The cooling plates in fact comprise internal tubes which open out to the upper and lower parts of the latter and are connected to the adjacent upper plate and to the immediately lower adjacent plate in a vertical plane, to define a circulation line consisting of all the internal tubes connected to each other defined by the general reference 2.

A circular supply pipe 3 surrounding the blast furnace at its lower part comprises a set of individual supply pipes 4 which are respectively connected to the inputs 5 of the circulation lines 2. A circular return pipe 6 surrounding the blast furnace at a higher level also comprises a set of individual return lines 7 connected to the outputs 8 of the circulation lines. This set of vertical circulation lines constitutes a network placed along the shield of the blast furnace which is respectively connected at its bottom part to the feed circular 3 and at the top part to the return circular 6.

This network of circulation lines is connected at each of its ends by means of the feed circulars 3 and return 6 to an external circuit on which it is closed.

This circuit comprises at least one heat exchanger 9 which is connected to the return circular 6 by a return pipe 10. One (or more) expansion tank 11 connected by the return pipe 10, downstream to the exchanger 9 and upstream of the return circular 6, is placed at a level such that the desired pressurization is effectively carried out in the zones of intense thermal flux.

A battery of recycling pumps 12a, 12b, and 12c returns the coolant from the exchanger 9 to the supply circular 3 by a supply line 13. This battery of pumps comprises two electric pumps 12a and 12b and a 12c diesel backup pump. A line 14 makes it possible to bypass the exchanger 9. A line 15 for supplying additional coolant fluid opens into the supply line 13 at a point located between the battery of the recycling pumps 12a, 12b and 12c and the feed circular 3.

The expansion tank has a level regulator 32 which controls a valve 33 for the intake of the auxiliary coolant, placed at the inlet of the pipe 15. The tank 11 also includes a degassing cyclone 34 (deaeration) eventual.

A counter 35 is placed on the pipe 15 downstream of the valve 33 to detect a possible leak on the circuit and functions as a primary alert.

In this installation, the cooling fluid is kept in the liquid state, although provision is made, thanks to the flask 11, for the possibility of accidental boiling. The flow rates in the various circulation lines 2 are regulated by means of valves not shown, positioned to obtain identical flow rates in each of the lines. Sufficient flow is provided by the battery of recycling pumps.

As shown in Fig. 2, a line 36 allows the battery of recycling pumps 12a, 12b and 12c to be bypassed and therefore authorizes autosiphon operation as a backup. Line 36 also includes a valve 37.

The heat exchanger can be an air cooler as shown or a liquid / liquid heat exchanger and several branches can be arranged in parallel to form a battery.

In the schematic view of FIG. 1, there has been shown, for the sake of simplification, only a supply circular and a return circular for a refrigerant circulation line. Likewise, all references to the majority of stop and control valves and their control mechanisms which are well known have been deleted.

In fact, as shown in Fig. 2, the cooling fluid which, in the following description will be considered without limitation as being water, is introduced at different levels in the same vertical plane along different rows of the cooling plates which are schematically illustrated by rectangles numbered from 0 to 11. The installation in a practical way in fact comprises two circular feeders 3a and 3b from which are fed different inputs 5a, 5b, 5c, 5d ... of the internal tubes of the plates cooling defining separate parallel circulation lines. The installation likewise comprises two return circulars 6a and 6b which take the cooling fluid from different levels of cooling plates. These supply circulars 3a, 3b and return 6a, 6b are connected to the external cooling circuit, respectively as regards the supply circulars by lines 13a and 13b opening into the supply line 13 and in that relates to return circulars, via lines 10a and 10b opening into the return line 10.

Individual supply lines 4a, 4b, 4c, 4d etc. cooling plates opening out at the inputs 5a, 5b, 5c and 5d of the internal tubes of the latter, are connected to plates of different levels, rows 0, 1, 2 and 3, since the number of internal tubes varies over the circumference of the blast furnace according to the different zones of the latter. It has been indicated previously that the heat fluxes emitted in a blast furnace vary according to the zones of the blast furnace and it is obvious that the greater the heat flux, the more it is necessary that the density of internal cooling tubes on a given circumference is important. Thus, we therefore vary according to the level of the blast furnace, the number of circulation lines that we have. It is then necessary to introduce inputs 4a, 4b, etc. and to take at the outlets 8a, 8b, 8c, 8d the cooling fluid according to different levels in order to respect the density of circulation lines which it is desired to assign.

Thus, the greater the heat flux emitted in a blast furnace, the more the cooling plates have a dense network of internal tubes, and the more plates are available having the same number of internal tubes, but narrower, because the spacing of these tubes is weaker.

These previously stated characteristics are illustrated in FIG. 3 on which there is shown a developed view of cooling plates placed on the internal surface of the blast furnace on four nozzles. In this view, the respective inputs 5 and outputs 8 of the cooling tubes have been represented by black, white circles, hatched or crossed with a horizontal line, to materialize the points corresponding to the same circulation line. This developed view corresponds exactly to the number of rows of rings of cooling plates illustrated in FIG. 2 with partial sections between rows 3 and 5, since rows 3 to 5 inclusive have identical plates and likewise, between rows 7 and 8, and 9 and 11 respectively.

A first row 0 of cooling plates is arranged surrounding the nozzles 16. From the supply circular 3a, start sixteen individual supply tubes which are connected to the respective inlets of the sixteen circulation lines for the four lower cooling plates. These sixteen circulation lines run in a roughly vertical plane towards the upper part of the blast furnace.

In the schematic view of FIG. 3, for the sake of clarity of the figure, for row 0, only five circulation lines 17, 18, 19, 20 and 21 are shown, which are supplied by individual supply lines (not shown) coming from of circular 3a, respectively at entries 17a, 18a, 19a, 20a and 21a.

The circulation lines 17, 18, 19 and 20 open respectively at the outlets 17b, 18b, 19b and 20b, at the level of the row plates 5 and the cooling fluid is evacuated via the individual return pipes 17c, 18c, 19c and 20c to the return circular 6b. These lines 17c, 18c, 19c and 20c of FIG. 3 correspond to the reference 7d shown diagrammatically by a single individual pipe in FIG. 2. We therefore see that at row 5 four lines are extracted as represented by the corresponding value -4 on the line extracted from row 5 and ending in the return circular 6b.

It will be noted that the circulation line 21 connecting the inlet 21 to the outlet 21 crosses all the rows of the plates on the same vertical to exit at row 11.

At the entries of the internal tubes of the cooling plates respectively of rows 1, 2 and 3, there are also introduced, from circular 3b, eight additional rows for row 1, four other additional rows for row 2 and, finally, four additional rows for row 3 as indicated by the numbers +8, +4 and +4.

It has been indicated by way of illustration in FIG. 3 a circulation line 22 which is supplied at the level of row 3 of cooling plates by an inlet 22a from the circular 3b by an individual supply pipe (not shown) and from which the coolant is withdrawn at the outlet 22b at row 11 to be evacuated by circular 6a.

At the level of the plates of rows 3, 4 and 5, we then have 16 + 8 + 4 + 4 = 32 lines of circulation tion for four nozzles, these levels corresponding to the maximum density of the circulation lines where the center distance of the internal water circulation tubes is the lowest. Note also that at this corresponding level the smallest dimensions of the cooling plates which have four internal tubes per plate.

At the outlets of the internal tubes for cooling the rank 5 plates, four circulation lines are taken by individual return lines which are connected to the return circular 6b. Similarly, at the outlet level of the internal tubes for cooling the row 6 plates, four circulation lines are taken which are connected to the return circular 6b. Finally, at the outlet level of the internal tubes of the cooling plates of rows 8 and 11, four and twenty circulation lines are taken respectively which are connected to the return circular 6a. If we refer to Fig. 2, it can be seen that the illustrated cooling installation comprises, in addition to a main network of substantially vertical fluid circulation lines, an annex network of circulation lines intended to cool localized parts 23 of these plates called "curbs". In these copings 23, other internal circulation tubes are placed which are arranged in a horizontal plane. These tubes are added to those of the main network and are also connected as in the case of the main network to their counterparts located above in a vertical plane.

Thus, a supply circular 3c is connected to the supply line 13 by a line 13c. The annex supply circular 3c supplies the inputs 24 of the internal horizontal cooling tubes at the level of the plate 5. These horizontal internal tubes of the cooling plate 5 are connected to those of the cooling plate of row 6 by a pipe 25 and the outlets 26 of the internal horizontal cooling tubes of the row 6 plate are connected to an intermediate circular 27 of the annex network which performs an even distribution of the cooling fluid. This cooling fluid is sent into the horizontal internal tubes of the row 7 cooling plates, then the outlets 28 of these horizontal tubes of the row 7 plates are connected to the inlets 29 of the horizontal tubes of the row 8 plates, the outlets 30 of which are linked to an annex return circular 6c. This return circular 6c is connected to the return pipe 10 by means of a pipe 10c.

Each individual circulation line of the main and annex network can be isolated in the event of failure of one of these lines, for example for leaks. The flow in each of these lines as well as the temperature rises of the fluids can be measured individually along the different levels in a vertical plane.

The battery of exchangers may include, as shown in FIG. 2, two exchangers 9a and 9b, and an additional pump 31 connected to the return circuit of the battery of the exchangers 9a and 9b.

All the internal tubes of the cooling plates have the same diameter and the speed of the cooling liquid is maintained at a value between 1.2 and 2.0 m / s, in order to obtain an appropriate cooling by eliminating any risk of caking .

Claims (5)

1. An installation for cooling a blast-furnace by means of cooling plates in which circulates a cooling fluid, these plates being disposed in superimposed successive ring arrangements along the inner wall of the shell of the blast-furnace and being traversed by internal cooling fluid circulating tubes, the internal tubes of two adjacent plates in a vertical plane being interconnected in such a manner as to define a system (2) of vertical fluid circulation lines, said system being connected at each of its ends to an external circulating and cooling circuit for the fluid defining a closed, forced and pressurized circuit including a circular supply conduit (3), a circular return conduit (6), a battery of thermal exchangers (9) connected to the return conduit (6) through a return conduit (10) and to the circular supply conduit (3) through a supply conduit (13), a battery of pumps (12,12b, 12c) for recycling the cooling fluid disposed in the supply conduit (13), and at least an expansion vessel (11) placed in the return conduit (10) at the chosen pressurization level, characterised in that the external circuit comprises at least one circular supply conduit (3), said circular supply conduit(s) being connected to the various inlets (5) of the circulation lines located at different levels of cooling plate ring arrangements corresponding to the various inlets (5), and at least one circular return conduit (6), said circular return conduit(s) being connected to the various outlets (8) of the circulation lines located at different levels of cooling plate ring arrangements corresponding to the various outlets (8) thereby creating a variable density of the vertical cooling fluid circulation lines on the circumference of the blast-furnace, said external circuit maintaining the cooling fluid in a liquid phase.

. 2. An installation according to claim 1, characterised in that it further comprises an accessory system of cooling fluid circulation lines constituted by a series of internal cooling tubes disposed inside the cooling plates in a horizontal plane for the purpose of cooling localized parts (23) of the plates, the horizontal tubes of two adjacent plates in a vertical plane being interconnected and, in respect of a part thereof, connected to an equal distribution intermediate circular conduit (27), the inlets (24) and outlets (30) of the accessory circulation lines being connected to an accessory circular supply conduit (3c) and to an accessory circular return conduit (6c) which are respectively branch-connected to the supply conduit (30) and the return conduit (10).

3. An installation according to claim 1, characterised in that it comprises two circular supply conduits (3a) and (3b) and two circular return conduits (6a) and (6b) connected to the cooling plates in different rows.

4. An installation according to any one of the preceding claims, characterised in that the internal cooling tubes have a constant diameter.

5. An installation according to any one of the preceding claims, characterised in that the cooling fluid is water or a special oil resisting 300°C.

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