ZA200105805B

ZA200105805B - Blow form for shaft furnaces, especially blast furnaces or hot-blast cupola furnaces.

Info

Publication number: ZA200105805B
Application number: ZA200105805A
Authority: ZA
Inventors: Kurt Peter Stricker; Rainer Altland; Juergen Witte
Original assignee: Mannesmann Roehren Werke Ag
Priority date: 1999-02-05
Filing date: 2001-07-13
Publication date: 2002-10-14
Also published as: AR022491A1; KR20020019890A; DE19963259A1; DE19963259C2; DE50003178D1

Description

®

BLAST TUYERE FOR SHAFT FURNACES, IN PARTICULAR

BLAST FURNACES OR HOT-BLAST CUPOLA FURNACES

Description

The invention relates to a blast tuyere for shaft furnaces, in particular blast furnaces or hot-blast cupola furnaces according to the preamble of claim 1.

Blast tuyeres of this type, which are water-cooled and mainly made from copper or from parts cast with a copper alloy, are commonly used for supply of hot air to ensure an effective operation of the shaft furnace. When used in connection with a blast furnace, the hot blasts may reach temperatures in the range between 700 up to more than 1300 degrees Celsius at pressures between 2.5 and 5.5 bar.

Hereby, not only the inner casing of the blast tuyere and in particular the front portion are exposed to severe stress but increasingly also the casing area through melting phases, such as e.g. pig iron, slag, partially reduced burden materials and zinc, and through abrasion with coke and/or wind, as the refractory lining of the shaft progressively wears-off and the front portion of the blast tuyere thus becomes exposed. In order to attain a sufficient service life under such severe strains, the blast tuyere must be intensely cooled by a circulating coolant, normally cooling water, to maintain acceptable temperatures. Moreover, surface wear of the blast tuyere as a consequence of corroding effect of the melting phases and abrasion should be minimized through suitable measures.

DE-OS 35 05 968 describes a blast tuyere for shaft furnaces. In this construction, a double-walled hollow body is mounted on a base and is comprised of an inner casing and an outer casing interconnected by a front portion. The hollow space formed between the inner and outer casings is subdivided into an antechamber and a connected main chamber by an intermediate wall in the area of the front portion. A feed line arranged in the base for coolant extends in the form of a pipe

( through the main chamber and the intermediate wall to the antechamber. The intermediate wall has several openings so that coolant can flow back from the antechamber to the main chamber and from there via the openings in the base into a ring chamber which is provided with a return flow connection. A drawback of this construction is the fact that the tuyere has only one cooling circuit and is exposed to sever stress, when the cooling system breaks down or leaks occur in the blast tuyere, accompanied necessarily by a throttling of the coolant amount, that the blast tuyere is destroyed in a short time with all consequences relating to disturbances and risks. A further drawback resides in the fact that the cooling water is not guided at various locations, experiencing turbulences which promote steam bubbles and thus greatly impair the heat dissipation in these locations. In a worst case scenario, this may lead to localized melting and eventually to a destruction of the blast tuyere.

A further development of the blast tuyere is known from U.S. 2,735,408. In this known embodiment, the hollow body is subdivided into an anterior chamber, disposed in the area of the front portion, and a main chamber which is connected to the anterior chamber, wherein the antechamber and the main chamber are completely hydraulically separated from one another and using separate coolant circuits with their own connections. The coolant circuit of the main chamber includes a tightly wound helical pipe which forms the outer casing, whereas the coolant circuit of the anterior chamber includes two straight pipes arranged in parallel relationship and terminating in a U-shaped ring channel of the front portion. In a first embodiment, the inner casing is formed as smooth conical pipe, with both straight pipes of the anterior chamber disposed between the inner and outer casings. In a second embodiment, the inner casing is also formed by a tightly wound helical pipe. The front portion is made as separate member and connected either via anchors with the rear connection piece or directly via a welding seam with the inner and outer casings. This known construction has the drawback that the configuration dictates that the cooling channels in the area of

® the main chamber area are very small and have adverse transverse shape (rectangular), and that the configuration dictates that the feed pipes to the antechamber have very small cross sections. In view of the cross sectional reduction and an increasing deviation from a round cross section, the volume stream of coolant decreases superproportionally in the antechamber as well as in the main chamber, resulting in a significant deterioration of the cooling effect. A further drawback is the fact that according to the description of the mentioned disclosure the cross section of the cooling channel of the anterior chamber should be of similarly small size as the one of the cooling channel of the main chamber. As a consequence, the cross sectional configuration dictates a rectangular cooling channel of the antechamber, resulting in very poor side proportions and thus in a poor cooling effect. It is also disadvantageous that the feed channel terminates in the cooling channel of the anterior chamber, because it leads to a high hydraulic resistance in this cooling circuit, resulting in a smaller volume flow of coolant and lower coolant speed in the anterior chamber and thus in a poor cooling effect. The overall construction is very complicated to manufacture and exhibits many critical sealing areas which remain partially unsolved. Also the problem of external attack on the main chamber of the tuyere : through dropping melting phases in the blast furnace remains unsolved.

It is an object of the invention to provide a blast tuyere of the afore-stated type, which realizes with acceptable manufacturing expenditure an extremely effective cooling action of the thermally highly stressed front portion while having a disproportionately long service life at low costs, as well as ensures a positive operating behavior of the shaft furnace equipped therewith, without substantially altering available coolant amounts and differential pressures. A further object resides in the provision of a beneficial geometric configuration of the blast tuyere for substantial protection against dripping melting phases in the shaft furnace and in the provision of the main (rear) chamber, which is normally not quite as much exposed to stress, with an extremely effective cooling action, without

® substantially altering available coolant amounts and differential pressures, as well as the directly relating operating costs for the coolant.

This object is attained on the basis of the preamble in conjunction with the characterizing features of claim 1. Advantageous configurations are part of sub-claims.

The essence of the invention is the formation of the outer casing by a single- piece base body which is symmetric with respect to the vertical axis, when viewed in cross section, and has a forward end which terminates in the front portion without shoulders. The inner casing is formed by a conical weld-in part which forms the inner wall of the helical cooling channel of the main chamber. A further important feature is the arrangement of channels in 12 o'clock position of the blast tuyere, that is relating to the longitudinal axis of the blast tuyere, outside the original cross section of the main chamber, for supply of coolant to the front portion. The proposed arrangement of the cooling channels of the antechamber takes into account the different stress of the blast tuyere, as viewed in circumferential direction. Evidently, the blast tuyere is under greater stress in 12 o'clock position than in the lateral zones. The intense cooling of this stressed zone significantly increases the service life of the blast tuyere. The coolant circuit of the main chamber may selectively be configured as two-threaded helical cooling channel or provided with one helical cooling channel and a straight cooling channel in 6 o'clock position of the blast tuyere. The straight cooling channel in parallel relationship to the longitudinal axis of the blast tuyere and provided without ribs is arranged in relation to the longitudinal axis of the blast tuyere outside the original cross section of the main chamber of the blast tuyere, with the connections for the supply flow and the return flow disposed adjacent to the connections of the antechamber in the area of the 12 o'clock position. The arrangement of the straight cooling channel in 6 o'clock position of the blast tuyere takes into account the different stress of the blast tuyere in circumferential

® direction. Apart from the 12 o'clock position, the blast tuyere is also under greater stress in the 6 o'clock position than in the lateral zones. The intense cooling also in this zone further increases the service life of the blast tuyere.

As already mentioned, the proposal provides to move the supply and return channels for the antechamber as well as the return channel of the main chamber away from the area of the original cross section of the main chamber of the blast tuyere, that is radially outside the main chamber, as relating to the longitudinal axis of the blast tuyere. This realizes that the cooling channel of the main chamber is free of cross sectional restrictions by means of supply and return channels. As a consequence, optimum conditions for enhancing flow dynamics are effected in the main chamber with greatest possible coolant speeds.

Moreover, all stated channels have over the length a substantially constant cross section and the required cross sectional changes in the connection zone as well as the directional changes of small radii are rounded and without irregularities.

These measures implement in the main chamber flow rates for the coolant which are higher by at least twofold as compared to conventional designs. This is accomplished through elimination of dead zones, swirling regions, throttle areas, backup regions as well as optimum design of the cross sectional configurations of the cooling channels (round, trapezoid) and the cross sectional size of the individual channel portions. The optimum design option of the supply and return channel for the antechamber results also in significantly higher flow rates in the antechamber, without changing the differential pressure. If further implementing a balanced ratio of pumping capacity and channel cross section to realize the intended high flow rates, bubble formation is substantially suppressed hereby. It is also desired to realize a flow rate of > 10 m/sec for the cooling of the highly stressed antechamber and > 6 m/sec for the main chamber, when lower differential pressure of for example, 2 bar is available. The proposed configuration of the blast tuyere is suitable for antechambers with only one ring channel as well as for longer antechambers with a helical channel.

As already mentioned above, the blast tuyere is, however, under stress not only purely thermally, but also additionally chemically and mechanically; in particular when the refractory lining of the shaft furnace is worn-off to a certain degree.

Hereby, it is proposed to configure the cross section of the blast tuyere in the area of the 12 o'clock position in a roof-shaped manner. This is advantageous because material falling or dripping on the blast tuyere can slide off or drain easier. This configuration should decrease in particular the undesired contacting of liquid zinc, pig iron or slag with the blast tuyere made of copper or copper alloy. As it is known, zinc reacts with copper so that the copper wall diminishes through chemical degradation.

An exemplified embodiment of the blast tuyere according to the invention will now be described in more detail with reference to the drawing, in which:

FIG. 1 is a longitudinal section in the direction A-A in FIG. 2 through a blast tuyere according to the invention;

FIG. 2 is a side view in the direction X of FIG. 1;

FIG. 3 is a section in the direction B-B in FIG. 1.

The blast tuyere according to the invention includes a base body 1 forming the outer casing 2 and a weld-in part 4 forming the inner casing 3. The hollow body forming between the outer casing 2 and the inner casing 3 has a forward end _ closed by a thermally highly stressed front portion 5. At the entry side, the base body has a double-cone inlet portion 6 for insertion of the nozzle tip of a blast connection, not shown here. The refractor lining 7 for placement upon the inner casing 3 is indicated in the upper part of the inner casing 3. The area of the end

® ~ face of the front portion 5 is provided with a cladding 8 to protect the front portion against mechanical damage and wear. As it is known, the hollow body is circulated by coolant and subdivided in an antechamber 9 and a main chamber 10. Both chambers 9, 10 are completely separated hydraulically from 5 one another and connected to separate cooling circuits.

According to the position of the section in A-A in FIG. 2, FIG. 1 shows the supply channel 11 for the antechamber 9 in the upper part of the blast tuyere. On the entry side, the supply channel 11 is provided with a connection 12 in the form of a threaded section for threaded engagement of a feed pipe, not shown. The supply channel 11 then terminates in the antechamber 9 which is formed by a ring channel 22 extending transversely to the supply channel. Instead of the ring channel, it is also possible to provide the arrangement of a helical channel having several turns. :

FIG. 2 shows that the return channel 13 for the antechamber 9 is arranged in the area of the 12 o'clock position of the blast tuyere in parallel relationship to the supply channel 11. It has also an end face provided with a connection 14 in the form of a threaded section for threaded engagement of a drain pipe, not shown here. The position of both channels 11, 13 can be seen especially well in the illustration of FIG. 3.

In order to conduct the coolant also in the main chamber 10 in an efficient fluidic manner, the main chamber has a helical cooling channel 15. The inside wall of this cooling channel 15 is realized by the inner casing 4. Supply and drainage of the coolant in the main chamber 10 is implemented in the area of the 11 o'clock and 1 o'clock positions, respectively, adjacent to the connections 12, 14 for the antechamber S. As viewed in clockwise direction, the coolant is guided behind the supply connection 18, arranged in the 1 o'clock area, through a semi-circular channel 20 (shown in FIG. 2 by broken lines) in the double-cone inlet portion 6

( . downwards into the 6 o'clock position to enter there the helical cooling channel 15. After streaming through the helical cooling channel 15, the coolant enters directly in front of the antechamber 9 into a return channel 16, also arranged in 6 o'clock position and located beneath the helical cooling channel 15 for returning the coolant to the double-cone inlet portion 6. In the double-cone inlet portion 6, the coolant is again conducted into a semi-circular channel 21 (shown in FIG. 2 by broken lines) upwardly to the 11 o'clock position up to the drain connection 17. At their end faces, both cooling channels 15, 16 for the main chamber 10 are also provided with a threaded section 17, 18 for threaded engagement of the supply pipe and drain pipe, respectively. The supply and return connections 12, 14, 17, 18 for the antechamber as well as for the main chamber are exchangeable, without changing anything with respect to the desired effect of an intense cooling action.

According to the invention, the cooling channels 11, 13 for the antechamber 9 and the ring channel 22, respectively, have a substantially same cross section, but are smaller than the cross sections F1, F2 of the cooling channels 15, 16 of the main chamber 10. Thus, the following applies:

F4=F5<F1=F2

The cross sectional transitions as well as the directional changes of small radii of the channels are substantially rounded so as to prevent swirling zones or dead zones.

The further experienced additional chemical and mechanical stresses of the blast tuyere are greatly influenced by the geometric configuration. The hollow body is conically tapered in the direction of the shaft furnace, whereby half a cone angle in the range of 12-14° has proven beneficial. Effective in a same way is, according to the invention, also the roof-like configuration 19 in the area of the

12 o'clock position of the blast tuyere.

Material of the shaft furnace, falling or dropping onto the blast tuyere, can thus easily slide off or drain sideways in the direction of the center of the shaft furnace.

Claims

PCT/DEOO/00216 : CLAIMS

1. Blast tuyere for shaft furnaces, in particular blast furnaces or hot-blast cupola furnaces, comprising a conical double-walled hollow body with an inner casing and an outer casing as well as a front portion interconnecting the inner and outer casings, with hot air conducted to the shaft furnace through the inner casing, and with a hollow space formed between the inner and outer casings for passage of a coolant stream during operation, wherein the hollow space is subdivided into an antechamber in the area of the front portion and a connected main chamber, which are completely separated hydraulically from one another and both including a separate coolant circuit with own connections, wherein the coolant circuit for the anterior chamber includes two channels, which are arranged in parallel relationship to the longitudinal axis of the blast tuyere in the area of the 12 o'clock position of the blast tuyere and have a substantially constant cross section, for formation of the supply flow and the return flow, and which terminate in the front portion in a ring channel, which is arranged transversely to the channels, and wherein the coolant circuit of the main chamber is provided with a helical cooling channel, which has a substantially constant cross section as viewed over the length, characterized in that the outer casing is formed by a single-piece base body which is symmetric with respect to the vertical axis, when viewed in cross section, and has a forward end which terminates in the front portion without shoulders, and that the inner casing is formed by a conical weld-in part, wherein the channels for supply of coolant to and drainage of coolant from the front portion are arranged in the area of the 12 o'clock position of the blast tuyere and relating to the longitudinal axis of the blast tuyere, outside the original cross section of the main chamber of the blast tuyere, and wherein the weld-in part forms the inner wall of the helical cooling channel of the main chamber. 10 AMENDED SHEET

PCT/DEOO/00216

2. Blast tuyere according to claim 1, characterized in that the helical cooling channel of the main chamber has a two-threaded configuration to define a helical cooling channel for supply, and the other helical cooling channel for the return, and both helical cooling channels are interconnected by a 180° bend.

3. Blast tuyere according to claim 1, characterized in that the coolant circuit of the main chamber includes a straight cooling channel in 6 o'clock position of the blast tuyere, with the straight cooling channel, which extends in parallel relation to the longitudinal axis of the blast tuyere and is formed without ribs, being arranged, in relation to the longitudinal axis of the blast tuyere, outside the original cross section of the main chamber of the blast tuyere, wherein the connections for the supply flow and the return flow are arranged in neighboring relationship to the connections of the antechamber in the area of the 12 o'clock position.

4. Blast tuyere according to one of the claims 1-3, characterized in that the cross sectional configuration of the channel of the antechamber, which extends in the longitudinal axis, is circular, and the cross sectional configuration of the helical channel of the main chamber is substantially trapezoidal with rounded corners.

5. Blast tuyere according to one of the claims 1-4, characterized in that the cross sectional modifications for all channels of the antechamber and the main chamber in the connection zone as well as the required cross sectional modifications in the connection zone as well as the directional changes of small radii are rounded and without irregularities. 11 AMENDED SHEET

PCT/DEOO/00216

6. Blast tuyere according to claim 3, characterized in that there are arranged in the double-cone inlet portion two semi-circular channels connected to the connections and guided downwards up to the area of the 6 o'clock position and completely separated hydraulically from one another in the area of the 12 o'clock position as well as 6 o'clock position and establish the connection to the helical cooling channel of the main chamber, wherein the straight cooling channel connects directly at the partition wall to the anterior chamber to the forward end of the helical cooling channel and is located underneath the helical cooling channel in the area of the 6 o'clock position and ends again in the double-cone inlet portion.

7. Blast tuyere according to one of the claims 1-6, characterized in that the cross sections of the supplying and draining channel of the antechamber as well as the cross section of the ring channel in the anterior chamber are substantially of same size, but smaller than the cross sections of the cooling channels of the main chamber.

8. Blast tuyere according to one of the claims 1 and 3-7, characterized in that the straight cooling channel of the main chamber has a cross section which substantially corresponds to the cross section of the helical cooling channel of the main chamber.

9. Blast tuyere according to the claims 7 and 8, characterized in that the cross sections of the cooling channels of the antechamber are smaller by up to 35% than the cross sections of the cooling channels of the main chamber. 12 AMENDED SHEET

PCT/DEOO/O0216

10. Blast tuyere according to the claims 7-9, characterized in that the flow rate in the cooling channels of the main chamber is at least 60% of the flow rate in the cooling channels of the antechamber, at substantially same pumping capacity for the coolant supply of the antechamber and main chamber.

11. Blast tuyere according to claim 10, characterized in that the rate of the coolant in the cooling channels of the antechamber is at least 10 m/sec and the rate of the coolant in the cooling channels of the main chamber is at least 6 m/sec, when a coolant differential pressure at the blast tuyere is 2 bar.

12. Blast tuyere according to one of the claims 1-11, characterized in that the blast tuyere has a cross section in the form of a roof in the 12 o'clock position, with the cooling channels of the antechamber being arranged in this roof-like region and in the bulbed area of the cooling channel of the main chamber.

13. A blast tuyere according to claim 1, substantially as herein described and illustrated.

14. A new blast tuyere, substantially as herein described. 13 AMENDED SHEET