GB1564294A

GB1564294A - Plate cooler for shaft furnace

Info

Publication number: GB1564294A
Application number: GB304778A
Authority: GB
Original assignee: VNI I PROEK I OCHISTKE TEKHNOL
Current assignee: VNI I PROEK I OCHISTKE TEKHNOL
Priority date: 1978-01-25
Filing date: 1978-01-25
Publication date: 1980-04-02

Description

(54) PLATE COOLER FOR SHAFT FURNACE (71) We, VSESOJUZNY NAUCHNO ISSLEDOVATELSKY I PROEKTNY INSTITUT PO OCHISTKE TEKHNO LOGICHESKIKH GAZOV, STOCHNYKH VOD I ISPOLZOVANUU VTORICH NYKH ENERGORESURSOV PRED PRIYATY CHERNOI METALLURGII VNIPI CHERMETENERGOOCHISTKA, of prospekt Lenina, 9, Kharkov, Union of Soviet Socialist Republics, a Corporation organised and existing under the laws of the Union of Soviet Socialist Republics, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to coolers for the walls of shaft furnaces such as blast furnaces.

Because of elevated temperatures created in the working space of a blast furnace, the shell thereof is subjected to severe heat.

Therefore, special arrangements are called for to ensure mechanical strength of such shells and protect them from heat loads.

The arrangements in question are plate coolers which are usually mounted on the furnace shell at the side of the furnace working space.

It is modern practice to intensify the blast-furnace process by raising the blast temperature, increasing the amount of oxygen contained in the blast, or else by building up pressure in the furnace space.

The above factors are detrimental to the operation of heat-protecting arrangements, placing more stringent requirements upon their ability to resist heat.

It is therefore desirable to improve the operating reliability of the coolers.

The invention provides a cooler in a shaft furnace, comprising a plate adapted to protect the furnace wall from the effect of heat flux to which it is exposed, the plate being formed of two layers, viz. a higher-heat-conducting layer facing the interior of the furnace and a lower-heatconducting layer facing the exterior, and plate-cooling means in the form of pipes each partly filled with a coolant and sealed at the ends, coolant-filled ends of the pipes being rigidly connected to the plate within the plate, coolant-free ends of the pipes being arranged above the coolant-filled ends and mounted in a cooling chamber through which a coolant is to pass, the chamber being arranged outside the furnace wall, the interface of the said two layers being parallel to the longitudinal central axes of the parts of the pipes within the plate, which parts lie between the two layers.

Such constructional arrangement of the cooler plate makes it possible to create in each plate-cooling pipe a circulating flow of a definite form.

Owing to the fact that the plate is made of two layers, with the highheat-conducting layer facing the furnace working space and the ow-heatconducting one being presented to the furnace wall, the interfacial plane of said layers running parallel to the longitudinal axes of the plate-cooling pipes, there occurs in each pipe a separation of the coolant flow into a vapour-liquid mixture flow and a water flow. The aforesaid separation takes place owing to non-uniform heating of the surfaces of the pipes around their periphery.

The part of a pipe which faces the furnace working space and is adjacent to the highheat-conducting layer is heated more than that in contact with the plate layer made of low-heat-conducting material. In the part of the pipe interior passage which is confined by the overheated walls thereof, there takes place vigorous vapour-forming process accompanied by an ascending flow of vapour-liquid mixture. In the other part of the pipe interior passage a flow of liquid passes down unhindered, i.e. natural or gravity circulation of coolant is formed within the pipe. Thus, favourable operating conditions are created for the plate-cooling pipes and for the cooler as a whole.

Such circulating conditions can be maintained in the pipes if there is not too high a rate of heat flow. Excessive rate of heat flow will tend to upset the aforedescribed conditions of the coolant circulation in the pipes; an upwardly moving flow of vapour-liquid mixture takes up the entire interior space of the pipe, blocking the downward passage of water towards the end of the pipe fixed in the plate, thereby disrupting normal conditions of cooling the plate.

This problem can be solved by providing each pipe with a partition extending short of the closed ends of the pipe and parallel with the longitudinal axis of the pipe, the partition defining two cavities, one of which is a heat-absorbing cavity facing the highheat-conducting layer, the partition being substantially coincident with the interface of the two plate layers.

Such an arrangement of the partitions in the plate-cooling pipes is required to enable mechanical separation of the ascending flow of vapour-liquid mixture formed in the part of the pipe adjacent to the high-heatconducting layer, and the downwardly passing flow of water formed of the condensed vapour. Thus, the upwardly moving flow will not impede the downward passage of water to the pipe end fixed in the plate. This allows for reliable cooling of the plate and affords protection to the furnace wall against the effects of heat.

For simplicity of manufacture, the partition preferably coincides with the longitudinal central axis of the pipe. Such an arrangement of the partition is the best possible, the partition being equal in width to the inner diameter of the pipe into which it is inserted.

The passageway of the pipe is thus divided by the partition into cavities equal in cross section, which, however, is undesirable from the point of view of hydraulic resistance to the ascending flow of vapour-liquid mixture in the cavity adjacent the high-heat-conducting layer of the plate.

When the heat load acting on the plate and pipes becomes excessive, a great amount of vapour is formed in the cavity adjacent the high-heat-conducting layer, the cavity being small enough in cross-section to enable the escape of vapour alone. This being the case, directed coolant circulation in the pipes is disrupted and the cooling of plate is deteriorated.

The above disadvantage may be eliminated by displacing the partition from the longitudinal central plane of the pipe towards the furnace wall by 0.1 to 0.3 of the pipe inside diameter.

Such mounting of the paritions in the plate-cooling pipes brings about an increase in the cross sectional area of the pipe cavity adjacent to the high-heat-conducting layer of the plate, i.e. hydraulic resistance to the ascending flow of vapour-liquid mixture is reduced. This, in turn, results in reliable circulation of coolant in the pipes.

Such an arrangement of the partitions makes for the removal of specific heat loads on the order of 30 x 106 Kcal/m2h through the cross sectional area5 of the pipe cavity adjacent to the high-heat-conducting layer without upsetting the coolant circulation in the pipe.

The high-heat-conducting layer of the two-layer plate is preferably manufactured from such material as heat-resistant iron and the low heat-conducting layer from heat-resistant concrete. Since specific weight of concrete is considerably less than that of cast iron, the cooler plate is reduced in weight.

With the purpose of enhancing heat resistance of the high-heat-conducting layer, the latter may be formed of individual blocks which are mounted on the pipes for free movement during thermal expansion along the axes of the pipes.

With the cooler constructed so that the plate thereof consists of two layers, namely a high-heat-conducting layer and a low-heat-conducting one, and the pipes provided with partitions, it becomes possible to considerably expand the operating range of heat loads which do not adversely effect the cooler plate being under effective cooling protection of the pipes, and thus to enhancing heat resistance of the cooler. It has been found feasible to make practical use of the pipes which are sealed at their ends and filled with a coolant, the ends of the pipes at one side being rigidly fixed in the plate and extending at the other side beyond the plate and through the furnace wall body into a cooling chamber to be fixed therein. This allows for removing severe heat fluxes which arise in individual coolers independently of moderate heat fluxes; it also precludes the penetration of large amounts of water into the furnace working space in case of any damage to a pipe; and makes it possible to reduce the weight of coolers adapted for use on metallurgical installations.

The invention will be described further, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-sectional view of a cooler; Figure 2 is a cross-section taken along line 11-11, with the low-heat-conducting layer omitted; Figure 3 is a cross-section taken along line rn-rn of Figure 2; and Figure 4 is a cross-section take along line TV--TV of Figure 2, with an alternative partition arrangement in the pipes.

The drawings illustrate a cooler for a blast furnace, comprising a two-layer plate 1 (see Figure 1), of which the layer 2 facing the furnace inner space is formed of individual cast-iron blocks 3 extending horizontally for a length greater than vertically, the other layer 4 thereof facing a furnace casing 5 and formed of heat-resistant concrete. The plate 1 also incorporates at least two pipes 6, which pipes are partially filled with a coolant (water) and sealed at the ends thereof with plugs 7, each pipe being provided with a partition 8 extending short of the plugs 7.

The coolant-filled end of the pipe 6 is mounted in the plate 1, the coolant-free end of the pipe 6 being mounted within a cooling chamber 9 arranged exteriorly of the furnace casing 5 and connected to the furnace cooling circuit (not shown) for passage of a coolant.

The partition 8 divides the interior of the pipe 6 into two cavities, of which a heat-absorbing cavity 10 is adjacent to the high heat-conducting layer 2, the other cavity 11 being adjacent to the low heat-conducting layer 4 formed of heat-resistant concrete. Provided on the surface of each block 3 facing the furnace casing 5 are recesses 12 (Figure 3) adapted to receive the pipes 6; the surfaces of the blocks facing the furnace working space are formed with ribs 13 (Figure 1). The pipes 6 are interconnected by means of bars 14 (Figure 2). The interconnected pipes 6 are accommodated in the recesses 12. By means of pins 15, cast-in in the interspaces between the recesses 12, the blocks 3 are fixed on the pipes 6 with the aid of plates, such as plate springs 16, which are secured against the pipes 6 by screw nuts 17.To enable mounting the plate 1 on the furnace casing 5 the pipes 6 have welded lugs 18 (Figure 3) fitted with threaded holes 19 adapted to receive studs 20. The cooler is secured on the furnace casing 5 by means of the studs 20 and screw nuts 21. All the coolers are mounted on the furnace casing 5 so that a gap 22 is provided for a heat-insulating material to be placed therein, the size of the gap being determined by the height of the lug 18. To facilitate heat transfer from the blocks 3 to the pipes 6, the recesses 12 accommodate a layer 23 of heat-conducting material.

The number of the blocks 3 which make up the metal layer 2 of the plate 1 is determined by the cooler height and width parameters so that the height-width ratio of each block 3 is within the range of 2 to 4.

The number of the pipes 6 provided in the cooler is determined by the width of the plate 1, as well as by the heat load acting on the cooler used in a given metallurgical installation.

The diameter of the pipe 6 is selected in accordance with the required rigidity of the cooler construction and the heat loads acting thereupon.

The provision of the partition 8 in the pipe 6, as well as its arrangement therein, is governed by the heat loads acting on the cooler and, consequently, by the heat loads transferred through the cross-section of the pipe 6. The cast-iron blocks 3 of each cooler are heated with the heat of the furnace working space, transferring the absorbed heat through the heat-conducting layer 23 to the walls of the cooling pipes 6. The transferred heat causes boiling of water in the heat-absorbing cavities 10 of the pipes 6, with the resultant ascending flow of vapourwater mixture being formed in each of the said cavities. The heat flowing to the pipes 6 from the side of the concrete-made layer 4 is considerably less in amount, owing to the lower heat conductivity of heat-resistant concrete compared with that of metal.

Therefore, the hydraulic resistance, created in the cavity 11 of the pipe 6, to the downwardly passing flow of condensate formed in the coolant-free end of the pipe 6 cooled by the coolant flowing through the chamber 9, is very small. Thus, a directed circulation of the vapour-water mixture and the water originates in the interior of the pipe 6, i.e. in the cavity 10 of the pipe 6 a flow of vapour-water mixture rises to the fluid-free end of the pipe 6 wherein vapour is separated from water to be thereby condensed, the water draining down through the cavity 11 to the lower end of the pipe 6. In this manner reliable' cooling is provided for the walls of the pipes 6 and blocks 3, and the cooler thus fulfils its function aimed at affording protection to the walls of furnaces from overheating and destruction.

When subjected to heating the blocks 3 tend to increase in dimensions, freely elongating in the direction parallel to the axes of the pipes 6, with the fixture elements 15, 16, and 17 permitting such elongation.

As a result, the displacement of the blocks 3 cause no mechanical strains in the pipes 6.

With higher heat fluxes, which fluxes are removed through the cavity 10 of the pipe 6, it is advisable to install the partition 24, as shown in Figure 4, in the plane off-set from the longitudinal central plane of the pipe towards the layer 4 by 0.1 to 0.3 of the pipe inside diameter d, which increases the crosssectional area of the cavity 10 and, consequently, decreases hydraulic resistance to the ascending flow of vapourwater mixture in the cavity 10.

Therefore, the cooler construction described above makes it possible to improve operational reliability of the cooling system utilized on metallurgical installations by enhancing the heat resistance of cooler plates; provides for autonomous operation of each cooling pipe, which permits removal of vigorous heat fluxes forming in various places within the furnace; increases the working life of metallurgical furnaces between major repairs; brings down a minimum emergency situations due to destruction of the furnace walls; prevents penetration of water to the furnace working space; reduces the cooler weight by 1.5 times compared with conventional plate coolers.

WHAT WE CLAIM IS: 1. A cooler in a shaft furnace, comprising a plate adapted to protect the furnace wall from the effect of heat flux to which it is exposed, the plate being formed of two layers, viz. a higher-heat-conducting layer facing the interior of the furnace and a lower-heat-conducting layer facing the exterior, and plate-cooling means in the form of pipes each partly filled with a coolant and sealed at the ends, coolant-filled ends of the pipes being rigidly connected to the plate within the plate, coolant-free ends of the pipes being arranged above the coolant-fffled ends and mounted in a cooling chamber through which a coolant is to pass, the chamber being arranged outside the furnace wall, the interface of the said two layers being parallel to the longitudinal central axes of the parts of the pipes within the plate, which parts lie between the two layers.

2. A cooler as claimed in claim 1, wherein each pipe is provided with a longitudinal partition extending short of the pipe ends and being parallel with the longitudinal central axis of the pipe, the partition thus defining two cavities, one being a heat absorbing cavity adjacent to the higherheat-conducting layer, the partition being substantially coincident with the interfade of the said two layers.

3. A cooler as claimed in claim 2, wherein the partition coincides with the longitudinal central axis of the pipe.

4. A cooler as claimed in claim 2, wherein the partition is offset from the longitudinal central axis of the pipe towards the furnace exterior by 0.1 to 0.3 of the inside diameter of the pipe.

5. A cooler as claimed in any of claims 1 to 4, wherein the higher-heat-conducting layer of the plate is made up of separate blocks each extending horizontally for a length larger than its vertical dimension and having on the external surface thereof recesses adapted to accommodate the pipes and having placed therein a layer of heat conducting material, and mounted in the interspaces between the recesses are elements for fixing each block to the pipes, the pipes having members welded thereto to be thereby fixed to the wall.

6. A cooler as claimed in any of claims 1 to 5, wherein the higher-heat-conducting layer is of iron and the lower-heatconducting layer is of concrete.

7. A cooler in a shaft furnace, substantially as described herein with reference to, and as shown in, the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. it is advisable to install the partition 24, as shown in Figure 4, in the plane off-set from the longitudinal central plane of the pipe towards the layer 4 by 0.1 to 0.3 of the pipe inside diameter d, which increases the crosssectional area of the cavity 10 and, consequently, decreases hydraulic resistance to the ascending flow of vapourwater mixture in the cavity 10. Therefore, the cooler construction described above makes it possible to improve operational reliability of the cooling system utilized on metallurgical installations by enhancing the heat resistance of cooler plates; provides for autonomous operation of each cooling pipe, which permits removal of vigorous heat fluxes forming in various places within the furnace; increases the working life of metallurgical furnaces between major repairs; brings down a minimum emergency situations due to destruction of the furnace walls; prevents penetration of water to the furnace working space; reduces the cooler weight by 1.5 times compared with conventional plate coolers. WHAT WE CLAIM IS:

1. A cooler in a shaft furnace, comprising a plate adapted to protect the furnace wall from the effect of heat flux to which it is exposed, the plate being formed of two layers, viz. a higher-heat-conducting layer facing the interior of the furnace and a lower-heat-conducting layer facing the exterior, and plate-cooling means in the form of pipes each partly filled with a coolant and sealed at the ends, coolant-filled ends of the pipes being rigidly connected to the plate within the plate, coolant-free ends of the pipes being arranged above the coolant-fffled ends and mounted in a cooling chamber through which a coolant is to pass, the chamber being arranged outside the furnace wall, the interface of the said two layers being parallel to the longitudinal central axes of the parts of the pipes within the plate, which parts lie between the two layers.