Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/14—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment
  • F27B9/20—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment the charge moving in a substantially straight path tunnel furnace
  • F27B9/201—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment the charge moving in a substantially straight path tunnel furnace walking beam furnace
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/30—Details, accessories, or equipment peculiar to furnaces of these types
  • F27B9/36—Arrangements of heating devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/30—Details, accessories, or equipment peculiar to furnaces of these types
  • F27B9/39—Arrangements of devices for discharging
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/30—Details, accessories, or equipment peculiar to furnaces of these types
  • F27B9/40—Arrangements of controlling or monitoring devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
  • F27D17/004—Systems for reclaiming waste heat

Definitions

• the invention relates to continuous steel reheating furnaces.
• Steel reheating furnaces are used to heat steel semi-finished products such as slabs, billets, blooms, beam-blanks and ingots to a suitable temperature in order to prepare these products for rolling, forging or extrusion operations, or more generally to any other hot forming operation.
• the flames heat several steel products at a time, over the whole width of the oven during the progression of these, so that it is practically impossible to have different instructions from one product to another, thus prohibiting any flexibility in the use of the reheating furnace.
• the axial length of the roof noses or lower recesses corresponds to a length that is lost for heating, which de facto decreases the heating power that can be implemented for a given length.
• the structure of such ovens is relative- It is expensive, especially for long furnaces, with the further risk of certain fragility of certain parts of the furnace, particularly in the area adjacent to vaulting noses, which fragility may induce a risk of breakage.
• vault burners which are also arranged in transverse rows by being integrated into the vault of the oven.
• the advantage over the front burner arrangement is that the zone directly below the vault is heated, so that the iron and steel products are heated by radiation without any direct impact of the flames on the products. This makes it possible to improve the homogeneity of the heating, and to obtain an operation all the more satisfactory that the reheating furnace is heavily filled with iron products to be heated.
• the vault burners have several drawbacks, the first of which is the emission of NOx pollutants resulting from the very hot flames emitted by the vault burners.
• vault burners Since the vault burners emit a substantially rotating flame around the burner axis, flame velocities generally remain low, so that some NOx confinement can not be avoided in the upper zone of the reheat furnace.
• use of vault burners is generally done with a common supply of all the burners of the same row or the same group of adjacent rows, so that it is excluded to decouple the arch burners . This lack of flexibility is particularly unfavorable when products of cross-section significantly less than the width of the furnace are introduced into the reheating furnace.
• small steel products are generally arranged at the level of the plan vertical median of the reheating furnace, so that the lateral zones adjacent to the side walls of the furnace constitute spaces without products to heat, and consequently create in these spaces areas of overheating that can be dangerous, especially if the temperature at these lateral zones reaches temperatures close to 1600 ° C., because there is then a risk of irreversible vitrification of the refractory material constituting the enclosure of the furnace.
• the arch burners of the same row induce a thermal field which is essentially distributed in a vertical plane, so that it is excluded to be able to simultaneously heat several steel products.
• FIGS. 1 and 2 illustrate a furnace F with tubular longitudinal members, of traditional design, which makes it possible to implement a heating of the iron and steel products. circulating in said furnace relating to both the upper and lower faces of each of the products conveyed.
• the furnace F comprises a heat-insulated enclosure 10 whose upper and lower walls are denoted 11 and 12, and the left and right walls, with reference to the direction of progression of the iron products marked P in the tunnel (direction indicated by the arrow 100). are noted 13 and 14.
• Figure 1 which is a section along II of Figure 2, illustrates various equipment associated with the conveyance of steel products in the tunnel, as well as other external equipment associated with the evacuation of fumes and control of the process, while the Figure 2, which is a section along II-II of Figure 1, makes it possible to better distinguish the arrangement of side burners, here provided both at the upper level and lower by reference to the conveying level of steel products P.
• the enclosure 10 includes an upstream charging zone 15 and a downstream transfer zone 16, which are equipped with doors not shown here.
• a charging system 17 causes the products P to be heated in the charging zone 15, and a dewatering system 18 discharges the heated products P at the dewatering zone 16.
• the reheating furnace is equipped with conveying means marked 20 which make it possible to advance the steel products P inside the tunnel from upstream to downstream of said tunnel, said steel products being subjected to the action of the lateral burners. to undergo the desired progressive heating within their mass.
• the iron products P are supported by movable spars 21 and fixed spars 22 arranged alternately in the longitudinal direction of the furnace.
• the movable spars 21 have pins 23 which pass through the bottom wall 12 of the furnace and are fixed on a sole 25 resting on a frame 26.
• the fixed spars 22 have bowling pins 24 which are anchored in the lower wall 12 of the oven enclosure.
• the frame 26 is equipped with a plurality of rollers 27, 28, respectively interposed between the frame 26 and the sole 25, and between the frame 26 and supports 29 with an inclined plane 29.1
• the upper rollers 27 are driven by means not shown here.
• the frame 26 is pushed by means of cylinders not shown here at its upstream end (as shown by the arrow)
• the lower rollers 28 roll on the inclined planes 29.1 of the supports 29, which induces an uplift of the sole 25 and movable spars 21, and consequently an uprising of the steel products P which then rest only on said movable spars 21 being released from the fixed spars 22.
• rollers 27 are then driven and can then make a shift of a step in the longitudinal direction of the furnace of the movable assembly and raised and steel products supported by it, after which the rollers 27 are stopped and the frame is unlocked, so that the rollers 28 back down on the inclined planes 29.1 supports 29, for a new axial position of all iron and steel products.
• Such a step-by-step conveying process according to a square or rectangular cycle, is well known in the field of steel furnaces.
• an upstream chimney has been illustrated 31 for the evacuation of fumes, and whose output is connected to a network 32 for evacuation of the fumes from combustion, these fumes being here discharged to energy recovery means, with for example a heat exchanger 33 transmitting the energy of the fumes, then discharged through a chimney 34, to the combustion air supplied by a fan 35 through the heat exchanger 33.
• the process control is provided from a control center 38 which is connected in particular by a line 37 to different thermo-couples 36 integrated in the vault of the furnace enclosure, which serve to monitor the temperature at different abscissae of the furnace in order to comply with a heating curve which is predetermined in functions relevant steel products.
• the side burners equipping the furnace F allow to heat both the upper face and the lower face of the steel products P passing through the flames of said burners.
• For a better identification of the different side burners equipping the oven use a two-letter notation followed by a number, the first letter being G for a burner associated with the left side wall or D for a burner associated with the right side wall , and the second letter being S for a side burner associated with the upper level or I for a side burner associated with the lower level, the corresponding number for its index 1, 2, ... k, ... n of the row of burners substantially disposed in a common vertical plane, from upstream to downstream of the furnace.
• FIGS 3 and 4 there is illustrated an oven F 'with refractory longitudinal members whose design, also traditional, has many common features with that of the tubular string oven that has just been described.
• the main difference with respect to the previous furnace F is in the means of support and travel of the steel products P which progress inside the tunnel.
• the oven F 'with refractory longitudinal members of FIGS. 3 and 4 does not heat the refractory products P circulating inside the furnace except in the upper zone of those here, only the upper surface of the products is heated up.
• Figure 4 which is a section along IV-IV of Figure 3, said Figure 3 being a section III-III of Figure 4, there are two lateral burners GS2 and DS2 respectively associated with the left side wall 13 and the right side wall 14 of the furnace chamber.
• FIG. 5 is a longitudinal section of the furnace by a horizontal plane
• this disadvantage is illustrated by the arrows which symbolize the preferred paths of the fumes in the axis of the furnace. It goes without saying that the view of FIG. 5 is applicable to a tubular frame furnace equipped with upper and lower side burners, as well as to a refractory beam furnace equipped only with upper side burners.
• FIG. 5 thus makes it possible to clearly understand that the fumes are grouped substantially in the median vertical plane of the furnace, which results from the arrangement substantially face to face of the homologous burners of the same row, moving in one direction which is opposed to the direction 100 of progression of steel products P in the furnace.
• the last burners GSn, GIn, and DSn, DIn are disturbed by the burners which are directly upstream, especially at the angles of the zone 34. These disturbances induce a heating heterogeneity con- a major disadvantage that is difficult to overcome.
• JP 09-145 260 A thus discloses a modular furnace wall structure, with quilted ceramic fiber elements which are hooked to the top wall of the furnace.
• the document is limited to a purely structural teaching, and does not address the question of the location of the partition in the oven, nor a possible function related to the operation of the burners.
• Document AT 387 652 B describes an oven equipped with a vertical partition, with an upper wall and a lower wall between which the steel products circulate, with a passage interval corresponding to one third of the cross section of the furnace.
• This partitioning is arranged in the upstream zone of the furnace (the first third or the first quarter of the length), to constitute a pre-conditioning airlock.
• the aim is to avoid the propagation of radiation to the input of the products, and to increase the temperature of the furnace due to the retention of the combustion gases, and consequently reduce the number of burners and therefore the energy consumption.
• JP 04 187 989 A JP 2002/310 562 A, JP 07 103 659 A, US 4,741,695 A, US 3,512,628 A, EP 0 018 677 Al and FR 2 520 100A.
• the object of the invention is to design an improved reheating zone reheating furnace, improving the homogeneity of the heating of the steel products in the downstream zone of said oven.
• the object of the invention is also to design a reheating furnace whose layout of the diversion zone makes it possible to better manage the thermal shutdowns and resumptions of production.
• a steel reheating furnace comprising an enclosure equipped with burners intended to heat the iron products circulating from one end to the other of the furnace, said enclosure comprising a downstream zone, by reference to the direction of progression of iron and steel products in the tunnel, which is associated with the diversion of iron and steel products and closed by a diverting gate, characterized in that the downstream diversion zone is delimited, on the upstream side, by at least one geometric obstacle defining an airlock, said at least one geometric obstacle being arranged to achieve separation of the flows and heat transfer, so that the steel products present in said deblacking chamber are thermally homogenized.
• said at least one geometric obstacle is sized to both prevent smoke from the burners that are upstream from disturbing the airlock and create a differential pressure.
• the at least one geometrical obstacle comprises an upper wall. and a substantially vertical bottom wall, between which the steel products pass to enter the airlock, with a chosen range in relation to the desired pressure differential.
• the bottom wall is arranged in the form of refractory brick walls disposed between the tubular stringers.
• the at least one geometric obstacle comprises an upper wall in which pass the steel products to enter the airlock, with a chosen interval in relation to the desired pressure differential.
• the top wall is fluidly cooled.
• the upper wall is constituted by a hollow frame in which circulates a cooling fluid, and whose central space is occupied by fibrous panels.
• the airlock is equipped with low heat demand burners for homogenizing the temperature in steel products that are present in said airlock.
• the burners of the airlock that are closest to the door muffler remain lit continuously to ensure the sealing of the airlock during the openings of said door, and maintain a slight overpressure inside said airlock of rusting.
• the airlock is equipped with arch burners preferably controlled in proportional mode, and side burners preferentially driven pulse mode.
• Figure 1 is a longitudinal section of a tubular stringers heating furnace of traditional type
• Figure 2 is a cross section along the line II-II of Figure 1 of the kiln tubular stringers;
• FIG. 3 is a longitudinal section of a traditional refractory beam furnace, and the Figure 4 is a cross section along the line IV-IV of Figure 3 of the furnace refractory beams;
• FIG. 5 is a top view in longitudinal section illustrating the preferred paths of the fumes with a conventional reheating furnace designed according to Figures 1 and 2 or 3 and 4;
• FIG. 6 comprises two sections similar to that of FIG. 5, illustrating the arrangement, in accordance with the invention, of a diversion lock in the downstream zone of the furnace, with the indication of the preferential paths of the fumes for said zone. downstream, and also for the upstream recovery zone in which there is provided a control side burners with an alternating left / right;
• FIG. 7 is a longitudinal sectional view of a tubular beam furnace arranged in accordance with the invention, with a diversion lock consisting here of an upper wall and a lower wall, and with, in addition, burners. vault and side burners; and
• FIG. 8 is a cross section along the line VIII-VIII of Figure 7, on a larger scale, to better distinguish the arrangement of the walls defining the lock gate on the upstream side of said lock.
• FIG. 6 makes it possible to understand the result obtained by the arrangement of an airlock according to the invention, in particular by remedying the disturbance of the last row of lateral burners by the side burners directly upstream of them with a deflection of the flames shown in Figure 5 previously described.
• a geometric obstacle here realized in the form of a wall 50 which can be single or double depending on the type of furnace, the wall being only higher for a furnace with refractory spars, or being higher and lower for a kiln with tubular beams.
• This wall 50 single or doubled, creates an airlock 51 diverting which promotes the flow of fumes for the last row downstream side burners GSn, GIn, DSn, DIn, avoiding the disturbance caused by the side burners that are directly in upstream.
• FIG. 6 also illustrates another particular mode, with an alternating piloting of the burners of the first upstream row of side burners, with on the left the burners GS1 and GI1, or the only burner GS1 according to the type of furnace, and on the right the DSl and DIl burners, or the only DSl burner according to the type of oven.
• the ignition is only for the burner (s) on the left and in (b) the ignition is only for the right burner (s).
• a dead zone 31 is formed at the time of the left ignition, but that this zone is immediately swept and brewed during the alternation illustrated in b), where a dead zone 32 is created.
• the right / left alternation thus makes it possible to continuously alternate the generation of vortices in the zone 31 or the zone 32, which zones are therefore never cooled to excess because of this continuous stirring.
• it avoids the formation of a preferential zone set on the median vertical plane (zone 33 for the traditional control shown in Figure 5), so that it avoids localized overheating of the central part of the steel products circulating in the oven.
• FIG. 7 schematically illustrates an oven F with tubular longitudinal members of the type illustrated in FIG. in FIGS. 1 and 2, without its conveying means, but with more lateral burners (two lower burners such as GI1, GI2 by keel step instead of one, and as many upper burners as GS1, GS2), and with his diversion door 16.1.
• the downstream zone 34 of delamination is delimited, on the upstream side, by at least one geometrical obstacle 50 defining a deadlock, said at least one geometrical obstacle being arranged to achieve a separation of the flows and the heat transfers, so that the steel products P present in said sluice is thermally homogenized.
• the geometric obstacles that materialize this physical separation can be realized in several ways, for example in the form of low walls, vaulted noses, partitions cooled or not, etc.
• Furnace F of Figure 7 is tubular stringers, and is equipped with upper and lower side burners by reference to the circulation level of the iron products in the furnace.
• said at least one geometric obstacle 50 com ⁇ carries an upper wall 52 and a lower wall 53 essentially vertical, between which the iron products P pass to enter the airlock 51.
• said at least one geometrical obstacle 50 would comprise only an upper wall 52 (variant not illustrated here), with the same function and with a view to the same result, the furnace walls which are below the circulation level of the steel products in the furnace are indeed free of lower side burners because of the presence of fixed soles and mobile soles.
• FIG. 8 illustrates a particular embodiment for an oven F with tubular longitudinal members 22 with its pins 24.
• the lower wall 53 is arranged in the form of refractory brick walls 53.1 disposed between the central tubular stringers 22, in particular between the pins of said stringers, and between the tubular side rails 22 and the side walls 13, 14 of the enclosure 10.
• F. spaces 56, 57, 58 are provided to allow the flow of fumes from the airlock, with a dimension that is related to the desired pressure differential.
• the upper wall 52 under which the steel products P pass to enter the diversion lock 51 defines a passage slot 54 of height (d), with a chosen interval in relation to the desired pressure differential, as the side slots 55 which are adjacent to the side walls 13, 14 of the oven.
• the upper wall 52 is cooled fluidically.
• such wall constituted by a hollow frame 60, of rectangular shape, formed of sections 62, 61, 62 in which circulates a cooling fluid (as shown schematically by the arrows 101, 102), and whose central space is occupied by fibrous panels 63, for example made of ceramic fibers, here nested in pairs by complementary shapes in 63.1.
• a cooling fluid as shown schematically by the arrows 101, 102
• fibrous panels 63 for example made of ceramic fibers, here nested in pairs by complementary shapes in 63.1.
• Such an embodiment is preferable to a brick wall which would be much heavier and could fracture and fall due to thermal shocks cashed.
• the pressure differential thus created promotes a smooth and undisturbed flow of fumes present in the airlock 51 upstream, in particular fumes generated by the burners that equip said airlock.
• the airlock 51 is in fact advantageously equipped with burners, which burners are then low heat demand (it is indeed only compensate for thermal losses), used to homogenize the temperature in steel products that are present in said airlock. push.
• n Two rows of such burners, indexed (n) and (n + 1), are provided here.
• row n there are, for the upper zone, vault burners Vn (for example three to eight burners depending on the width of the oven), and possibly also lateral burners GSn, DSn (denoted in dotted lines), and, for the lower zone, side burners GIn, DIn.
• the vault burners are interesting here because they favor the homogenization of the temperature of the steel products present in the airlock 51. As a constant low constant flow, these arch burners will preferably be controlled in proportional mode. The presence of side burners is interesting for the lower zone (when it exists, which is not the case of furnace F 'with refractory spars). For these lateral burners, proportional control will be avoided, since the small flames generated may be insufficient to heat the middle part of the steel products, and therefore impulse mode control will be preferred, that is to say in all or nothing.
• the burners of the airlock 51 which are closest to the diverting door 16.1 (here those of the row n + 1) will remain lit continuously to ensure the sealing of the diversion lock 51 during openings. the door 16.1, and maintain a slight overpressure inside said airlock that promotes the smooth flow of fumes upstream.
• the arrangement of said airlock that has just been described makes it possible to more effectively manage stops and resumptions of production.
• the temperature of the airlock is maintained at the target temperature of the products. This maintenance is preferably provided by the burners of the upper zone.
• the zones that are upstream of the airlock can in turn be de-indexed in temperature, that is to say that the set temperature is strongly lowered. This makes it possible to limit calamine production, and also to reduce energy consumption and polluting emissions.
• the products located in the airlock are ready for the conversion.
• the following products, located during shutdown in the de-indexed zones in temperature will have sufficient heating time, and the installed powers of the burners will be dimensioned sufficiently to ensure the reheating at the target brewing temperature without slowing down production.
• the air / gas ratio of all or part of the airlock burners may be different from the average air / gas ratio of the rest of the furnace, in order to take into account the possible parasitic air intake during the opening of the door which could nevertheless intervene despite the slight overpressure of the airlock.
• An air / gas ratio lower than the stoichiometric air / gas ratio makes it possible to burn the possible parasitic air inlets which could disturb the oxygen level in the furnace, which oxygen level therefore remains always low.
• the airlock improves the uniformity of heating products. Better heating quality helps divert products to a lower average temperature, which decreases the energy consumption of the furnace and requires less energy for rolling.
• the airlock also makes it possible to increase the productivity of the oven by minimizing production recovery time after stopping.
• the losses to the fire are reduced by the deindexing of the zones of the furnace which are upstream of the airlock and, as the sealing of the furnace is improved, one can better control the rate of oxygen in the furnace, which decreases NOx emissions and loss on ignition. It has thus been possible to design a steel reheating furnace which makes it possible to obtain an excellent homogeneity of the heating in the downstream zone of the furnace, and also to better manage the thermal shutdowns and resumptions of production.

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• General Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Tunnel Furnaces (AREA)

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• 2006
  • 2006-06-01 FR FR0604884A patent/FR2901868B1/fr not_active Expired - Fee Related
• 2007
  • 2007-05-31 EP EP07788816A patent/EP2027424A1/fr not_active Withdrawn
  • 2007-05-31 RU RU2008152063/02A patent/RU2388980C1/ru not_active IP Right Cessation
  • 2007-05-31 WO PCT/FR2007/000901 patent/WO2007138195A1/fr active Application Filing
  • 2007-05-31 CN CN200780019708XA patent/CN101454632B/zh not_active Expired - Fee Related

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