GB2060437A - Method of and apparatus for depositing refractory material on lining of an upright converter - Google Patents

Abstract

In a method of depositing a refractory material on a lining of an upright converter 1, a flame of oxygen and a flow of a mixture of fuel and a pulverized refractory material are directed onto the converter lining and are projected over its height as two flame jets 5 directed in opposite directions from the longitudinal axis of the converter. An apparatus for carrying out this method comprises a lance (2) together with a drive for its rotation mounted on a carriage mounted on guides and geared to a further drive for its longitudinal movement; the lance is formed with ducts for the separate supply of oxygen and a mixture of fuel and refractory material to respective nozzles positioned in rows along the lance wall in coaxially aligned pairs and built into the lance wall along the section thereof corresponding to 0.1 to 0.9 times converter height. <IMAGE>

Description

SPECIFICATION Method of and apparatus for depositing refractory material on a lining of an upright converter The present invention relates to a method of and apparatus for deposing a refractory material on a lining of an upright converter, and in particular to a method of hot patching a converter lining by flame spraying, The invention can be advantageously employed for the hot patching of a converter immediately after tapping off metal and slag therefrom, with the temperature of the converter being about 1 5000 C.

Commonly known in the art are methods of wet gunniting a converter lining which comprise depositing on the working surface of the lining a powdered refractory mass mixed with water. Such methods are time-consuming and require an excessive amount of refractory powder. Also, the refractory coating produced by such methods has a short surface life.

There is known a more advanced method of flame yunniting converter linings, according to which a flame together with a refractory powder and fuel are directed from a nozzle onto the lining surface. The mixture of these materials is fed in one flame jet projected perpendicularly or at an angle to the working surface of a converter lining.

In this gunniting method the refractory pulverized material is plastified under the effect of high temperature and thus closely adheres to the lining.

However, the method described above has several disadvantages. For instance, the operating period is time-consuming, since one flame jet is clearly insufficient to effect an efficient flame spraying operation. The consumption of the refractory powder is very high, since only 30 to 50 per cent of the total amount used adheres to the lining surface, the remainder being carried away with flue gases. Also, the refractory coating is of insufficient quality since the flame spraying process, when effected in one flame jet, fails to provide enough time for the particles of the pulverized refractory material to achieve a high temperature; hence the built-up deposit has a low resistance to slag.

Furthermore, it is impossible to ensure that the particles of refractory material uniformly adhere to the surface of the converter lining in all regions thereof. For example, particles of the pulverized refractory material adhere poorly to the upper wall of a horizontal converter, and still worse to the lower wall thereof, since on the latter there accumulates molten slag which obstructs the passage of the refractory material to the lining of the converter lower wall.

Federal Republic of Germany Patent No.

2 200 667, British Patent No. 1 313 986, French Patent No. 2 168 916, Canadian Patent No.

969 434 and United States Patent Nos.

3 883 078 and 3 911175 describe a method and apparatus for hot patching linings of horizontal converters. According to this method, converter linings are hot patched by flame spraying with the aid of a fuel oxygen torch which directs onto a converter lining a pulverized refractory material fed into its flame which is projected tangentially in relation to the lining surface.

Howeverm this method fails to meet an ever growing demand for a shorter operating period and a longer service life of converter linings. In addition, this method is inefficient, since the horizontal position of the converter permits better gunniting to be effected in the trunnion regions of the converter lining. Also considerable difficulties are encountered in the course of collecting and purifying the flue gases of the process. This calls for additional protective means and equipment.

Thus, this method is carried into effect by means of a device for flame spraying or gunniting converter linings which comprises a lance mounted on a manipulator mounted on a selfpropelled truck. To the rear of the manipulator is connected a conduit which encloses ducting for feeding to the lance nozzle a mixture of a pulverized refractory material with the fuel and oxygen which is required to initiate the flame spraying process.

Notwithstanding its numerous advantages, such a device is complicated and buiky in construction, and occupies considerable working floor space during its operation. In addition, the device is complicated in operation, since it requires the provision of a conduit enclosing flexible metal pipes for respectively supplying the pulverized refractory-fuel mixture, oxygen and water used as a cooling agent.

Attempts have been made to effect the flame spraying of an upright converter lining by moving the flame together with a flow of the pulverized refractory material in vertical and horizontal directions. However, the above-mentioned disadvantages and difficulties encountered in the prior-art have not been eliminated by this method.

There is known an advanced apparatus for gunniting converter linings, which comprises a lance mounted on guides and provided with a driving means for its rotation. Pulverized refractory material, oxygen, fuel and water for cooling the lance are fed to the lance along flexible ducts. The lance has concentrically mounted conduits and a multi-nozzle head. In operation the lance is introduced into a converter and removed therefrom by means of a suitable driving mechanism. During upward and downward movements of the lance, as well as during its rotation, a thin layer of gunnite is deposited either onto the entire surface of the converter lining or to the regions thereof subject to a higher degree of wear. However, this apparatus also does not operate altogether satisfactorily. In general, stringent requirements are imposed upon the duration and quality of the repair of converter linings.However, the prior art methods and apparatuses used for gunniting converter linings are unsatisfactory by reason of being timeconsuming and also by requiring an excessive consumption of refractory material due to unavoidable losses thereof in the course of operation accompanied by contamination of the workshop atmosphere with the gases liberated during the flame spraying process.

The present invention in one aspect provides a method of depositing a refractory material on a lining of an upright converter, comprising directing a flame of oxygen together with a flow of a mixture of fuel and a pulverized refractory material onto a converter lining over its height as two flame jets projected in opposite directions from the longitudinal axis of the converter, and displacing the said flame jets backward and in the longitudinal direction relative to the converter longitudinal axis.

Such a flame spraying method permits the duration of its operating period to be substantially reduced and the quality of the built-up deposit to be improved owing to the fact that all the converter regions are pre-heated prior to being flame sprayed or gunnited and are equally well exposed to the operating process. In addition, the flue gases of the process are passed to a chimney positioned over the converter and are then collected in a suitable gas collecting and refining system. The operating conditions are improved, since the upright position of the converter prevents cold air from penetrating into the converter in the course of operation, as is the case with a horizontally disposed converter subjected to gunniting.

Simultaneous flame spraying the two opposite walls of the converter with a refractory material is necessitated by the presence of two trunnion regions in the converter lining, which regions are exposed to the most intense wear and, therefore, require more intensive gunniting.

Thus, by effecting the flame spraying process with two oppositely directed flame jets, it becomes a possible for the two trunnion lining regions to be simultaneously gunnited and, as a result, the duration of the gunniting process to be substantially reduced.

To effect the operating process with more than two flame jets would be of no benefit On the contrary, this would bring about an increase in the speed of the outgoing gases, resulting in higher losses of particles of the refractory material entrained by the gas flows passing out of the converter. This, in turn, may lead to a higher consumption of the refractory material.

It would be disadvantageous to effect the flame spraying process with one flame jet, since this would nearly double duration of the operating process and would result in reacting forces.

The displacement of the flame jets in vertical and horizontal directions permits a layer of the refractory material to be uniformly deposited onto the entire surface of the converter lining.

Each of the flame jets directed onto the converter lining is preferably projected over a range of from 0.1 to 0.9 times the converter height.

Projecting the flame jets over the converter height permits the area under gunniting to be increased per unit time. This is possible due to the fact that particles of the refractory material rebounding from the lining surface at the point where each flame impinges on the converter lining are entrained by the flow of rotating gases and travel therewith from the converter bottom to its mouth. As this happens, the particles are passed to the upper flame jets to be directed therewith to the lining surface to which they finally adhere. As a result, the efficiency of the process is enhanced and its consumption of refractory material is reduced.

The invention in another aspect comprises apparatus for carrying out the method according to the first aspect of the invention, comprising a lance mounted together with a drive for rotation thereof on a carriage mounted on guides and geared to a further drive for longitudinal displacement thereof, the lance being formed with ducts for supplying oxygen under pressure and a mixture of fuel and refractory material to respective nozzles positioned in rows along the lance wall in coaxially aligned pairs, the said pairs of nozzles being built into the lance wall along the section thereof corresponding to 0.1 to 0.9 times the converter height.

The arrangement of the nozzles in rows along the opposite walls of the lance creates favourable conditions for simultaneously producing two oppositely directed flame jets wherein a fuel fed into oxygen burns to plastify the pulverized refractory material. Such a constructional arrangement is advantageous in that no reacting forces are formed at the end of the lance. In addition, the arrangement of the nozzles in two rows along the lance is easy to carry into effect.

Projecting the flame jets over the converter height permits the flame spraying area to be increased per unit time. This is possible due to the fact that the particles of the refractory material rebounding from the lining surface at the point where each flame impinges on the converter lining are entrained by the flow of rotating gases and travel therewith upwardly from the converter bottom to its mouth. As this happens, the particles are passed to the upper flame jets to be directed therewith to the lining surfaces to which they finally adhere. As a result, the effectiveness of the refractory material is enhanced and its consumption is reduced.

The lance together with a drive for its rotation are carried by a carriage, permitting the apparatus to be of compact size and reliable in operation. It should be observed that the carrying devices of similar type, used for introducing a lance into a converter, have been found suitable and easy in operation, being simple in construction and incorporating conventional drives and structural members.

The provision of guides makes it possible for the lance to be introduced into the converter in a desired direction, namely along the vertical longitudinal axis of the converter. The provision of the drive for rotating the lance about its longitudinal axis permits the flame jets to be displaced in the horizontal direction and the gunnite to be used deposited onto the entire surface of the converter lining for half a turn of the lance. Also, the drive permits reversible rotation of the lance. This drive for reversible rotation of the lance is secured on the carriage so as to be reliably geared to the lance, which is also mounted on the carriage.The drive intended for longitudinal movement of the carriage along the guides permits the flame together with the flow of the mixture of fuel and pulverized refractory material to be longitudinally displaced so as to enable an effective flame spraying process to be carried out.

It is preferred to use a hoist as the drive means for longitudinal displacement of the carriage and to mount the hoist on a platform which carries one or more further hoists for moving oxygen lances of the converter.

The use of a hoist as the driving means for longitudinal displacement of the carriage together with the lance ensures reliable operation of the apparatus according to the invention. In addition to being reliable and easy to service and maintain, this type of hoist can be easily interposed between further hoists mounted on the platform for displacing the converter lances.

The apparatus according to the invention is preferably provided with a means for centering the lance relative to the converter longitudinal axis, the centering means including a casing fixed on the lance and formed at the lower end thereof with a tapered portion, and arm levers articulated on a chimney of the converter and interacting with the casing.

Such a centering means is simple in construction, and also makes it possible to support the lance during its strictly vertical movement along the converter longitudinal axis. Furthermore, the arm levers serve as an additional support for the lance when displaced in the transverse direction and thus preclude transverse vibration thereof, and also prevent extra dynamic loads from acting on the carriage and guides.

The invention will be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal sectional view of a converter in which is carried out a flame spraying method according to the invention; Figure 2 is a cross-section of the converter shown in Figure 1; Figure 3 is a lateral view of an apparatus used for carrying out the method according to the invention for flame spraying of converter linings; Figure 4 is a plane view of the apparatus shown in Figure 3; Figure 5 is an enlarged lateral view of the lance and nozzles thereof of the apparatus shown in Figure 3; Figure 6 is an enlarged schematic crosssectional view of the nozzle region of the lance; Figure 7 is a partial view of carriage together with a drive for rotation of the lance;; Figure 8 shows a device for centering the lance relative to the vertical axis of the converter; Figure 9 is a side view of a flame spraying apparatus together with an oxygen lance; and Figure 10 is a plan view of the apparatus shown in Figure 9.

A flame spraying operation is initiated immediately after tapping off both the metal and the slag from a converter 1, with the temperature of the working surface of the converter lining being about 1 5000 C, and the converter arranged in the upright position. Then, flames 5 consisting of oxygen in which powdered fuel is burnt to plastify a pulverized refractory material is introduced into the converter 1 along a lance 2 through nozzles 3 and is directed onto the lining 4 of the converter 1. On being heated to a plastified temperature, particles of the refractory material are carried by the flame 5 to the opposite walls of the converter lining 4 and adhere thereto, thereby forming a layer of coating.The flames 5 are directed onto the opposite walls of the converter lining 4 in two jets projected in opposite directions relative to the longitudinal axis of the converter.

Each of the flame jets 5 is projected against the converter lining surface over a range of from 0.1 to 0.9 times the converter height. Particles of the refractory material rebounding from the surface of the converter lining 4 are entrained by the flow of rotating gases and travel therewith from the converter bottom to its mouth. In this way, the particles of the refractory material pass into the upper flame jets to be thereby driven back to the lining surface of the converter. At the bottom part of the converter, the deposition of the refractory material is effected under the action of circulating flows, whereas at the mouth thereof, where the extent of lining wear is insignificant, the deposit build-up of the lining surface takes place due to the particles of the refractory material carried by the flow of gas from the converter.Therefore, there is no need to supply the refractory material to the converter mouth.

To initiate the spraying process, the lance 2 is introduced into the interior of the converter 1 along its longitudinal axis. In the course of operation the lance 2 is rotated relative to its longitudinal axis, and is then raised and withdrawn from the converter at the end of the operating process.

Thus, resulting from the supply of the refractory material to the lining 4 of the converter 1 there are obtained a higher operating rate of the flame spraying process, an improved quality of the builtup deposit, and a lower consumption of the refractory material used.

The apparatus for effecting the flame spraying or gunniting of the upright converter comprises a lance 2 (Figures 3, 4) formed with nozzles 3 (Figures 1, 2) for directing onto the converter lining 4 flames 5 of oxygen and a mixture of a pulverized refractory material and fuel.

The lance 2 is fixed on a carriage 6 mounted on guides 7, the carriage carrying a reversible drive 8 geared to the lance for rotating the latter. The drive used for longitudinal displacement of the carriage 6 together with the lance 2 is essentially a hoist 9 formed with flexible connections 10 (Figure 4). This apparatus is compact enough to be easily mounted on a platform 11 between hoists 12 (Figures 9, 10) intended for moving oxygen lances 13 of the converter. As a result, the flame spraying process can be effected in the interval between the metal tapping-off operation and a new charging operation.Arranged in coaxially aligned pairs on the opposite walls of the lance 2 are nozzles 14 and 15 (Figure 5, 6). The nozzles 14 communicate with a duct 1 6 for supplying a gunnite (pulverized refractory-fuel mixture), and the nozzles 1 5 communicate with a duct 1 7 for feeding oxygen. There are also provided ducts 18 and 19 which serve to supply the lance 2 with water for cooling thereof. The reversible drive 8 mounted on the carriage 6 consists of an electric motor 20, a reduction gear 21 and a gear drive 22 (Figure 7).

There is provided a suitable device 23 (Figure 8) for centering the lance 2 relative to the vertical axis of the converter 1, which device comprises a casing 24 rigidly fixed on the lance 2 and having a lower tapered portion 25, as well as arm levers 26 pivotally mounted at 27 on a chimney (not shown) of the converter.

The apparatus described above is operated as follows.

After tapping off both the metal and the slag from the converter 1 and on returning the latter to its initial upright position, the lance 2 is positioned so as to be coaxially aligned with the axis of the converter. The drive of the hoist 9, connected through the flexible connections 10 with the carriage 6, is then operated to bring down the lance 2 into the converter 1. As this happens, the carriage 6 is moved downwardly along the guides 7, and the lance 2 is introduced through an opening in the chimney (not shown) into the converter to reach its predetermined position.

During the downward movement of the lance 2 its lower free end is centered by means of the device 23 while the levers 26 mounted on the chimney of the converter interact with the casing 24 secured on the lance 2.

The lance 2 is introduced into the converter 1, the lining temperature of which is about 1 5000 C.

Therefore, the walls of the lance 2 are cooled with the water circulating through the ducts 18 and 19.

On introducing the lance 2 into the interior of the converter, the supply of the pulverized refractoryfuel mixture, fed along the duct 1 6 to the nozzles 14, and the oxygen supply, fed along the duct 17 to the nozzles 15, are simultaneously operated.

The fuel mixes with the oxygen, and ignites and burns forming a high-temperature flame whereby particles of the pulverized refractory are heated to a plastifying temperature and adhere to the surface of the lining 4. The flames 5 issuing from two rows of the nozzles 14 and 15, arranged in pairs as shown in Figures 5 and 6, form two oppositely directed flame jets, as shown in Figures 1 and 2. The drive 8 is operated to rotate the lance 2 about its longitudinal axis through an angle of about 180 deg. The converter lining is thus coated with a layer of a slag-resistant deposit.Particles of the pulverized refractory rebounding from the lining surface at the point where each flame jet impinges on the converter lining are entrained by the flow of rotating gases at the converter bottom, and, if they do not adhere there, are carried by the gas flow upwardly to the converter mouth, as shown in Figures 1 and 2, and, on again establishing contact with the working surface of the lining adhere thereto.

While thus travelling, the particles of the pulverized refractory pass into and out of the flames to be thereby heated to a plastifying temperature and directed onto the working surface of the converter lining. Therefore, the probability of the adherence of the particles of the refractory material to the lining surface increases.

Practically all regions of the converter lining are subjected to the flame spraying operation. The converter mouth and cylindrical portions are hot patched by flame spraying during the period of tapping analysis; the converter lining is hot patched during short idling periods of the converter.

The use of the method and apparatus described above for the flame spraying of a converter lining permits the efficiency of the flame spraying process to be increased by up to 90 per cent. It has been observed that the effectiveness of the flame spraying process increases with the spreading length of the flame jet. The length of plane-parallel flame jets is limited by the converter region to be flame sprayed, which region ranges from 0.1 to 0.9 times the converter height. This factor governs the arrangement of the flame producing nozzles on the lance.

The presence in the converter of two most rapidly wearing trunnion regions determines the number and direction of plane-parallel flame jets of oxygen and the pulverized refractory-fuel mixture; that is more than two flame jets will result in smaller cross-sectional areas of the circulating zones and, consequently, in higher axial speed of the gas flows rotating together with particles of the pulverzied refractory material and hence a higher rate of consumption of the refractory material. A decrease in the number of flame jets will double the time period of the flame spraying process, and will result in the appearance of reacting forces at the end of the flame spraying lance. This, in turn, will lead to the necessity of strengthening the apparatus construction, thereby making it more complicated in design.

The apparatus of the invention is superior to previously known apparatus of similar type in that it permits the flame spraying process to be substantially enhanced by introducing the flame spraying lance from the top and projecting the flame jets in opposite directions. Moreover, any moment of inertia with respect to the lance mass or to reacting forces is substantially absent.

Consequently, the apparatus is more simple in construction and is readily adaptable to automatic performance.

Owing to its small dimensions, the apparatus is easily interposed between oxygen lances 13 on a platform 11, as shown in Figures 9 and 10, in order to be used in combination therewith for charging metal into a converter and blowing oxygen therethrough.

The method and apparatus of the invention are especially advantageous in that, with the upright position of the converter, the flue gases escaping through the converter chimney during the flame spraying process may be collected in a gas purification system. Thus, it is unnecessary to erect a complex and cumbersome gas-collecting and gas purification system.

The method and apparatus of the invention have been tested to show the following positive results: - an increase in lining service life by 3 to 4 times has led to a decrease in converter downtime due to cold repair also by 3 to 4 times; - the time period for the flame spraying process has been reduced to 4 min. due to the employment of more effective apparatus and by combining the operation of bringing the apparatus back to its initial position with that of tapping off metal and feeding new batches of metal charge; - the costs required for the manufacture of various equipment incorporated in the apparatus has been halved due to the simplicity of its construction as well as due to its adaptability for use in the process units provided in a converter shop.

Claims (7)

1. A method of depositing a refractory material on a lining of an upright converter, comprising directing a flame of oxygen together with a flow of a mixture of fuel and a pulverized refractory material onto a converter lining over its height as two flame jets projected in opposite directions from the longitudinal axis of the converter, and displacing the said flame jets backward and in the longitudinal direction relative to the converter longitudinal axis.

2. A method as claimed in Claim 1, wherein the said flame jets are projected over a range of from 0.1 to 0.9 times the converter height.

3. A method of depositing a refractory material on a converter lining, substantially as herein described with reference to the accompanying drawings.

4. Apparatus for carrying out the method as claimed in Claim 1, comprising a lance mounted together with a drive for rotation thereof on a carriage mounted on guides and geared to a further drive for longitudinal displacement thereof, the lance being formed with ducts for supplying oxygen under pressure and a mixture of fuel and refractory material to respective nozzles positioned in rows along the lance wall in coaxially aligned pairs, the said pairs of nozzles being built into the lance wall along the section thereof corresponding to 0.1 to 0.9 times the converter height.

5. Apparatus as claimed in Claim 4, wherein the said drive for longitudinal displacement of the said carriage comprises a hoist secured on a platform carrying at least one further hoist for moving oxygen lances of the converter.

6. An apparatus as claimed in Claim 4 or 5, further comprising means for centering the lance relative to the longitudinal axis of the converter, the said centering means including a casing fixed on the lance and formed at the lower end thereof with a tapered portion, and arm levers articulated on a chimney of the converter and interacting with the said casing.

7. Apparatus according to Claim 4, substantially as herein described with reference to, and as shown in, the accompanying drawings.