Regenerative parallel flow vertical shaft furnace

Abstract

vertical regenerative parallel-flow kiln comprising at least two vessels (1,2) interconnected by a gas transfer channel (3), each vessel comprising, in the in-service or out-of-service position, a loading inlet (5) for carbonate mineral rock at the top of the vessel, means for firing the rock, a discharge outlet (8) for the decarbonated calcined material produced at the bottom of the vessel, a cooling air inlet (7) at the bottom of the vessel for counter-cooling the calcined material produced, and a central collecting element (21) having, at its upper end, a collection opening (24) for the cooling air heated by the calcined material and, at its lower end, an extraction outlet (22), each vessel further comprising a protective cap-shaped element (25) which is fixed in the vessel in a position independent of the central collecting element (21),by covering and surrounding its upper end down to a level lower than the harvest opening (24), so as to leave, between this upper end and the cap (25), a free passage for the collection of heated cooling air through the harvest opening (24).

Description

[0001] The present invention relates to a regenerative vertical parallel flow straight furnace for calcining carbonate mineral rock.

[0002] The vertical parallel flow regenerative kiln, or regenerative lime kiln, also known as a "PFRK" (Parallel Flow Regenerative Kiln), has an energy efficiency of 85% to 90%; this is the highest in the lime sector, and indeed in all energy-intensive industries such as cement, steel, and glass. Approximately 60% of lime produced in Europe is manufactured in this type of kiln. This proportion is expected to increase in Europe and worldwide, in line with roadmaps for the energy and ecological transition.

[0003] The classic "PFRK" kiln is a vertical, double-chamber kiln where fuel is alternately injected into one chamber and then the other for approximately 10 to 15 minutes, with a pause of about 1 to 2 minutes between cycles to reverse the air and fuel circuits. This is the "reversal" period. The two chambers are connected by a connecting flue. When one chamber is in combustion (firing mode), the hot combustion gases pass through the connecting flue (gas transfer channel) and transfer some of their heat to the mineral rock being calcined, preheating it in the other chamber, which is in regeneration or preheating mode. The chambers of the PFRK kiln are either cylindrical or rectangular. In some cases, there are three chambers: two in preheating mode and one in firing mode.

[0004] For the purposes of this invention, carbonate mineral rock refers in particular to limestone, dolomitic rock, and / or magnesite, which calcine into quicklime, quickdolomite, and / or magnesia, respectively. The calcination equation for limestone to lime is as follows: CaCO3 (solid) + heat → CaO (solid) + CO2 (gas)

[0005] It is a reversible endothermic reaction and the lime recombines with CO2 at the first opportunity below 900°C, with an equilibrium and kinetics that are more or less rapid depending on the temperature and the ambient concentration of CO2.

[0006] During this process, the initial limestone or dolomitic rock releases a significant volume of CO2 as it is calcined into lime or dolomite. Furthermore, this calcination requires high temperatures, which commonly involve burning fuels, often fossil fuels, which in turn generates a substantial release of CO2. Overall, calcination processes have the drawback of actively contributing to the increase in the greenhouse effect.

[0007] This very common calcination process also has the drawback of requiring fuel combustion in the presence of air and the cooling of the calcined product by air. This results in the release at the top of the furnace of a gaseous effluent with a high level of diatomic nitrogen and a comparatively low level of CO2 (volume concentration of approximately 20% to 30% on a dry gas basis), which is costly to capture due to the high presence of dinitrogen from the air used.

[0008] Attempts have already been made to extract the cooling air, heated by contact with the decarbonated calcined material produced, from the kiln during firing. In the case of circular kilns, a central, tubular collector element is provided, rising vertically in the bottom of the kiln and featuring several collection openings at its top. This central collector element generally connects to an external draft element to allow, at a level below the connecting flue, the extraction of heated cooling air from the kiln (see WO2022 / 111817 and WO2022 / 229119).

[0009] It should be noted that this central collector element must be able to withstand the pressure of a material bed at least 12 m deep, regularly reaching a height of 20 m, and therefore must have a very robust structure. It must also resist potential force imbalances due to the uneven descent of this material bed, with the possibility of local blockages. The central collector element must therefore inevitably have minimum dimensions, which represents a major drawback, particularly for small kilns producing less than 400 tonnes per day, as is the case for most PFRK kilns in Europe. Indeed, the presence of a bulky central collector element impedes the downward flow of the calcined material produced.Furthermore, the lower part of the circular chambers of these small, common kilns, where the calcined material is cooled, is usually shaped like an inverted truncated cone, meaning that the upper base has a larger area than the lower base. In this configuration, the presence of a bulky central collector is quite detrimental given the narrowness of the lower part of the chamber.

[0010] Moreover, these central collecting elements known from the previous technique have the disadvantage of not allowing to effectively prevent the penetration of fines of the calcined material produced by their harvesting openings.

[0011] To address this particular problem, it was previously designed for the central collecting element to have a cap-shaped element at its top, thus protecting the collection opening from unwanted fines (see DE102023102447). Unfortunately, adding this element to the top of the central collecting element further increases the weight it must bear in the lower part of the vessel, necessitating an extremely robust and therefore even bulkier central collecting element. Such a structure is not suitable for an existing, small kiln where the lower part of the vessel tapers progressively towards the bottom.

[0012] The present invention aims to significantly reduce the drawbacks and structural risks presented by prior art central collector elements, while maintaining their functional design and thus the efficiency of extracting heated cooling air from the center of the circular oven chamber during firing. It is also desirable that these central collector elements be adaptable to existing, smaller ovens.

[0013] To solve these problems, the invention provides a vertical, parallel-flow regenerative furnace comprising at least two vessels interconnected by a gas transfer channel, each of said vessels having, in the operating or out-of-service position, at least one loading inlet for carbonate mineral rock, at the top of the tank, at a level higher than said gas transfer passage; means for heating said carbonate mineral rock as it descends from said tank; at least one loading inlet for producing a charge of decarbonated calcined material; at least one discharge outlet for the produced decarbonated calcined material, at the bottom of the tank; at least one gaseous effluent discharge conduit at the top of the tank, at a level lower than said gas transfer passage; at least one cooling air inlet at the bottom of this lower part of the tank for counter-cooling the produced decarbonated calcined material; and a central tubular collector element having, at its upper end,at least one collection opening through which cooling air heated by the decarbonated calcined material is collected inside the central tubular collecting element and, at its lower end, at least one extraction outlet allowing collection of this heated cooling air outside the furnace, in which each tank further comprises a protective, hat-shaped element which is fixed within the tank an independent position of the aforementioned central tubular collecting element, covering and surrounding the upper end of the latter down to a level lower than said at least one harvesting opening, so as to leave, between this upper end and the cap, a free passage for a collection of heated cooling air through said at least one harvesting opening.

[0014] In such a furnace, the load on the descending material bed is supported solely by the protective, cap-shaped element. This arrangement relieves the central tubular collector element, which can then be made lighter and therefore less bulky in the narrowest part of the lower chamber. Advantageously, it can be a simple cylindrical tube. When the furnace has chambers with an inverted cone-shaped lower section, the protective, cap-shaped element is located in the widest part of this lower section, thus minimizing any obstruction to the downward flow of material.

[0015] In addition to its mechanical function, the protective, hat-shaped element creates a vacuum beneath it. This vacuum allows heated cooling air to pass freely through the central collector element, exiting the furnace from the bottom and preventing it from mixing with the calcination gas stream exiting from the top. This design is therefore particularly robust, simple, and well-suited to small furnaces where the air outlet remains proportionally large.

[0016] In a conventional manner, the oven according to the invention includes a system for reversing the operation of the tanks, arranged so that each tank operates, in production mode, alternately in cooking mode and in preheating mode, one tank being in cooking mode for a predetermined period of time while at least one other tank is in preheating mode, and vice versa, this reversing system controlling for this purpose the said positions in service and out of service.

[0017] During the reversing cycle, the reversing system synchronously controls all the necessary changes to switch from one mode to another, for example, by opening the carbonate mineral rock loading inlet to the tank when it is in cooking mode and closing it when it switches to preheating mode. The reversing system therefore controls not only numerous valves and gates, but also the operation of loading and unloading equipment, as well as various suction, pumping, and injection components.

[0018] Depending on the case, said at least one cooling air inlet is thus controlled in the operating position in all the oven tanks or only in the tank in cooking mode.

[0019] Production mode refers to the furnace operating in its normal operating condition, continuously producing calcined material. This mode does not include furnace start-up, shutdown, or maintenance phases in case of malfunction.

[0020] According to one embodiment of the invention, the central tubular collecting element has, at its upper end, a single opening oriented axially upwards. An upper portion of the protective element, shaped like a hat, is arranged above and at a distance from this single opening, flaring downwards to a lower cylindrical portion extending coaxially and at a distance from the aforementioned upper end of the central tubular collecting element. The downward flare of its upper portion facilitates the flow of the decarbonated calcined material away from the central tubular collecting element, thereby minimizing blockages of the harvesting opening. Advantageously, the protective element is conical in its upper portion and cylindrical in its lower portion.

[0021] According to an advantageous embodiment of the invention, several support spacers, preferably 3 or 4 spacers, arranged between the outer wall of the tank and the hat-shaped protective element support the latter above the central tubular collector element.

[0022] Preferably, the protective hat-shaped element is traversed by at least one cooling circuit supplied with cold cooling fluid, for example, cold air, from at least one inlet duct passing through at least one of the aforementioned support struts. Heated cooling fluid is discharged from this at least one cooling circuit through at least one outlet duct passing through at least one of the aforementioned support struts. There are no ducts connecting the central tubular collector element to the protective hat-shaped element, which is particularly advantageous for the passage of heated cooling air. Furthermore, the cooling fluid is supplied via the struts, which are themselves cooled. This is a simple and robust system to construct and operate, especially in a small furnace where the air outlet cross-section remains proportionally large.

[0023] According to one embodiment of the invention, the central tubular collector element is, in its lower part, fixed to the outer wall of the tank by several beams, preferably four beams, arranged horizontally. Advantageously, the protective, hat-shaped element is supported centrally above the upper end of the central tubular collector element by vertical uprights supported by said horizontal beams.

[0024] Preferably, in this case, the protective hat-shaped element is traversed by at least one other cooling circuit which is supplied with cold cooling fluid, for example cold air, from at least one supply duct running through at least one of the aforementioned beams and uprights, heated cooling fluid being discharged from said at least one other cooling circuit by at least one discharge duct running through at least one of the aforementioned uprights and beams.

[0025] Advantageously, the central tubular collector element carries at least one cooling fluid circuit, supplied with cold cooling fluid, for example, cold air, from outside the furnace. Heated cooling fluid is then discharged from this circuit outside the furnace. The central tubular collector element and the protective cap-shaped element are thus cooled by independent circuits. Each of these circuits can be short, increasing their efficiency compared to a single circuit that would have to cool both elements. In the latter case, the cooling of the cap-shaped element occurs unfavorably at the end of the circuit, even though it is the element subjected to the highest temperatures, on the order of 900 to 1000°C, or even up to 1200°C.According to one embodiment of the invention, each tank is further equipped with an annular collector that communicates with it via several doors located around the periphery of the tank and with an external extraction device for drawing heated cooling air from the furnace. In this way, the extraction efficiency is increased, as it occurs both in the center of the tank and around its periphery. The risk of fine particles from the decarbonated calcined material escaping into at least one collection opening of the central collector element, potentially causing blockage, is thus significantly reduced.

[0026] The aforementioned heating methods for the carbonate mineral rock during its descent involve injecting a fuel and an oxidizer into the heating chamber. These components, through combustion, allow the rock to reach its calcination temperature. In a conventional furnace, the fuel is typically a fluid, such as natural gas, or a solid, such as coal or lignite powder, and the oxidizer can be air. A mixture of CO2 and oxygen can also be used as an oxidizer, which is highly advantageous.

[0027] As a means of cooking the carbonate mineral rock during its descent, one can also consider injection elements into the tank to cook a gas or gas mixture heated, outside the tank, to a calcination temperature for the rock. Electrical devices, for example, using plasma torches, could be considered for this purpose.

[0028] As can be seen, the furnace according to the invention requires only a few structural modifications to the lower part of the furnace chambers. Existing and / or new furnaces can therefore be easily adapted to implement a calcination process during which the cooling air introduced from the chambers can be extracted particularly efficiently, without causing extreme deterioration in the flow and discharge of the calcined material produced.

[0029] Other details and features of the oven according to the invention are indicated in the attached claims.

[0030] Other features of the invention will also become apparent from the description given below, by way of non-limiting reference and with reference to the attached drawings.

[0031] There figure 1 schematically represents a PFRK oven according to the invention.

[0032] THE figures 2 et 3 represent partially broken views of the lower inverted truncated cone-shaped part of a PFRK furnace tank according to the invention.

[0033] There figure 4 represents a partially broken view of the lower inverted truncated cone-shaped portion of a tank of another PFRK furnace according to the invention.

[0034] In the figures, identical or analogous elements bear the same references. Conventionally, the tank illustrated on the left in the figure 1 is in cooking mode and the tank shown on the right is in preheating mode. To avoid cluttering the drawings with standard elements, such as loading or unloading equipment, they are either not shown or are represented very schematically.

[0035] As can be seen at the figure 1 The illustrated PFRK furnace is a straight, double-walled furnace (1, 2) where fuel is alternately injected into one wall (1) and then into another (2) for approximately 12 minutes, with a pause between cycles of 30 seconds to 2 minutes to reverse the circuits. This is the "reversal" period. Both walls have a circular cross-section and are equipped with peripheral channels (13, 13') interconnected by a connecting flue (3). The walls are divided vertically into three zones: the preheating zone (A) where the carbonate rock is preheated before calcination, the calcination zone (B) where the carbonate rock is baked, and the cooling zone (C) where the calcined material is cooled. In this last zone, the circular cross-section of the wall has a section shaped like an inverted truncated cone (38).

[0036] In the illustrated example, when a tank is in firing mode, here tank 1, a fuel supply device in the form of lances 4 injects a fuel 9, which in this case is natural gas, into the tank. The carbonate rock, loaded at the top of the tank through an open inlet 5, gradually descends into it. An oxidizer is introduced at the top of the tank through a supply opening 6, which allows combustion of the fuel at the outlet of the lances 4 and decarbonation of the carbonate rock into calcined material 10. The gas stream 11 formed by combustion and decarbonation descends in co-current with the calcined material and, via the peripheral channel 13, passes into the connecting flue 3. Cooling air is introduced, through a supply duct 7, at the bottom of the tank, counter-current with the calcined material, to cool it. The calcined material is discharged through outlet 8 into unloading equipment 26.

[0037] When a tank is in preheating mode, in this case tank 2, the fuel supply system is closed and the nozzles 4 are therefore out of service. The same applies to the inlet 5 for the carbonate rock and the opening 6 for the oxidizer supply. However, the supply duct 7 for the cooling air and the outlet 8 for the calcined material remain open. The gas stream 11, coming from the connecting flue 3, enters tank 2 via the peripheral channel 13'. This gas stream 11 travels to the top of the tank where it is discharged from the furnace via a discharge duct 14 and transferred to a chimney 15, advantageously passing through a draft fan and a filtration unit (not shown). In the tank in firing mode 1, this discharge duct 14 is closed.

[0038] The furnace includes a reversing system 12, shown schematically, which synchronously controls the operation of the tanks during the tank reversal period, either directly or remotely. It controls the activation or deactivation of all furnace components so that, during production, each tank operates alternately in baking and preheating modes.

[0039] In some cases, there are three tanks, two for preheating and one for combustion.

[0040] In the oven illustrated on the figure 1 A separation device 17 is provided on the exhaust duct 14, capable of drawing off a portion of the flue gas discharged from the furnace and introducing it into a recirculation circuit 18. In this circuit, the drawn-off portion of the flue gas is advantageously treated in a treatment unit 19, where it can, for example, be filtered, cooled, and / or dried. Oxygen is supplied to the recirculation circuit 18 via the supply duct 20. This circuit 18 then carries the combustion mixture, formed from the recirculated fraction of the flue gas and O2 concentrated at the top of each of the tanks, to the supply opening 6. In some cases, it is also possible to supply this combustion mixture to the flue 3 or to the peripheral channels 13, 13', as shown in the figure. figure 1 .

[0041] The operation of the PFRK furnace of the figure 1 The following is the configuration. The separation unit 17 is in continuous operation, as are the treatment unit 19 and the oxygen supply 20. As previously mentioned, the reversing system 12 closes the exhaust duct 14 at the top of the tank during cooking mode. Conversely, it opens the supply opening 6 at the top of the tank to allow the introduction of the combustion mixture, whereas this opening is closed at the top of the tank during preheating mode.

[0042] The oven illustrated on the figure 1 According to the invention, the system comprises, at the bottom of each tank, a central tubular collector element 21 having, at its lower end, at least one extraction outlet 22 and, at its upper end located below the flue 3, a collection opening 24 oriented axially upwards. Through this opening, the cooling air heated by contact with the decarbonated calcined material is collected inside the central tubular collector element 21, so as to allow its extraction from the furnace. In the illustrated example, this hot air extracted from the furnace is transferred, by means of a draft fan 23, to a heat exchanger 16 mounted on the recirculation circuit 18, so as to preheat the portion of the gaseous effluent exiting the furnace that is collected, preferably before its mixing with concentrated oxygen.

[0043] Each tank further comprises a protective hat-shaped element 25 which, fixed in the tank in a position independent of the central tubular collecting element 21, covers the upper end of the latter by surrounding it down to a level lower than the harvesting opening 24. In the illustrated example, an upper part of the protective hat-shaped element 25 is arranged above and at a distance from the harvesting opening 24, flaring downwards in a conical manner to a lower cylindrical part which extends coaxially and at a distance from the upper end of the central tubular collecting element 21. This arrangement thus leaves, between the upper end of the collecting element 21 and the hat 25, a free passage for collecting the heated cooling air through the opening 24 of the central tubular collecting element.

[0044] As it is depicted on the figures 1 à 3 The protective, hat-shaped element 25 is centrally supported in the tank by several support struts 27, here four struts. As is particularly evident from the figure 2 The lower, inverted truncated cone-shaped section 38 is, in this example, formed of two successive truncated cone-shaped tiers separated by a shoulder on the outer wall 28 to which these struts are fixed. This allows for the creation, together with the cap 25, of a very robust structure capable of supporting the load of the carbonate rock and calcined material during its descent. As is particularly evident from the figure 3 , the central tubular collector element 21 can thus be designed in the form of a lighter structure which does not become cumbersome for the descent of the calcined material which takes place between the spacers 27. In the illustrated example, the central collector element 21 is fixed in the tank by four beams 34 arranged horizontally in a cross at the bottom of the tank.

[0045] Given the high temperature of the calcined material during descent, it is advantageous to cool the hat-shaped cover element 25 by a cooling circuit 29 shown schematically, in which a cooling fluid, for example air, circulates (see in particular the figure 2 ). In the illustrated example, this circuit is supplied with cold cooling fluid along arrow F1 from an inlet conduit 30 running through each of the support spacers 27. The cooling fluid heated during its passage through the circuit 29 is discharged from it along arrow F2 through an outlet conduit 31 running through each support spacer 27. The protective hat-shaped element, which is in contact with materials having a very high temperature, is thus cooled by a short, particularly efficient cooling circuit.

[0046] Advantageously, the spacers have a double-pitched roof-shaped cover 32 at the top to facilitate the descent of the calcined material.

[0047] As is particularly evident from the figure 3 The cooling air, heated by contact with the calcined material during its descent, is collected in the passage between the cap 25 and the tubular collector element 21, following the path F3. This air is at a very high temperature, and it is therefore preferable to provide a refrigeration circuit 33, which runs along this tubular wall as schematically represented, to protect the tubular wall of the collector element 21. This circuit 33 is supplied with refrigerant, for example, cold air, from outside the tank, and the heated fluid is then discharged.

[0048] As seen above, the arrangement, according to the invention, between the hat-shaped protective element 25 and the central collecting element 21, makes it possible to collect the cooling air which is heated by contact with the calcined material and which rises to the center of the tank. As illustrated in particular on the figure 3 , the tank can also be provided, at a level below the connecting flue 3 and the peripheral channels 13 and 13', with a collector ring 35 which communicates outside with a drawing element, for example the draft fan 23, and opens into the tank through several peripheral doors 36 so as to allow extraction from the furnace of the heated cooling air which is rising at the periphery of the tank.

[0049] It is possible to imagine that the protective, hat-shaped element 25 is, in another way, supported in the tank independently of the tubular collector element 21. For example, as shown in the figure 4 , the hat-shaped protective element 25 is centrally supported above the upper end of the tubular central collector element 21 by vertical uprights 37 supported by the horizontal beams 34.

[0050] In this case, the protective hat-shaped element is traversed by at least one cooling circuit 29 which is supplied with cold fluid, for example cold air, from at least one supply duct running, along arrow F4, through a beam 34 and a vertical post 37. The heated cooling fluid is evacuated from the cooling circuit through at least one discharge duct running through a vertical post 37 and a beam 34, along arrow F5.

[0051] It must be understood that the oven according to the invention is in no way limited to the examples described above and that many modifications can be made to it without going out of the scope of the following claims.

[0052] For example, it can be stipulated that the inlet opening 6 for the oxidizer can be used, in a shared manner, for the exhaust gas, depending on whether the tank is operating in cooking or preheating mode. In cooking mode, opening 6 is connected to the recirculation duct 18, and in preheating mode to the exhaust duct 14.

[0053] We can also consider the presence of a CO2 buffer tank in parallel with the furnace, to allow CO2 recycling during the reversal period when the furnace is stopped for a short time to reverse the operation of the tanks, to allow a supply to the downstream of the installation (concentration unit, CO2 purification for example) without suffering from the cessation of gas flow from the furnace, and to compensate for the various small daily stops of the furnace for fault, small breakdowns, by ensuring a supply to the downstream during these short stops.

Claims

1. Regenerative parallel flow vertical straight furnace, comprising at least two tanks (1, 2) interconnected by a gas transfer path (3), each of said tanks comprising, in the in-service or out-of-service position, - at least one loading inlet (5) for a carbonated mineral rock, at the top of the tank, - at a level above said gas transfer path (3), means for cooking said carbonated mineral rock during descent from said at least one loading inlet (5), intended to produce a charge of decarbonated calcined material, - at least one discharge outlet (8) for the decarbonated calcined material produced, at the bottom of the tank, - at least one gaseous effluent discharge conduit (14) at the top of the tank, and - at a level below said gas transfer path (3), at least one cooling air introduction inlet (7) at the bottom of the tank for counter-current cooling of the decarbonated calcined material produced,and a central tubular collector element (21) having, at its upper end, at least one collection opening (24) through which cooling air heated by the decarbonated calcined material is collected inside the central tubular collector element and, at its lower end, at least one extraction outlet (22) allowing collection outside the furnace of this collected heated cooling air, characterized in that each tank further comprises a hat-shaped protective element (25) which is fixed in the tank in a position independent of the aforementioned tubular central collector element (21), covering and surrounding the upper end thereof up to a level below said at least one collection opening (24), so as to leave, between this upper end and the hat (25), a free passage for collection of the heated cooling air through said at least one collection opening (24).

2. Oven according to claim 1, characterized in that , at its upper end, the tubular central collector element (21) has a single collection opening (24) oriented axially upwards and in that an upper part of the hat-shaped protective element (25) is arranged above and at a distance from this single opening, flaring downwards to a cylindrical lower part which extends coaxially and at a distance from the above-mentioned upper end of the tubular central collector element (21).

3. Oven according to either of claims 1 and 2, characterized in that each tank comprises an outer wall (28) from which several support struts (27), preferably 3 or 4 struts, centrally support the hat-shaped protective element (25) above the tubular central collector element (21).

4. Oven according to claim 3, characterized in thatthe hat-shaped protective element (25) is traversed by at least one cooling circuit (29) which is supplied with cold cooling fluid from at least one inlet duct (30) traversing at least one aforementioned support spacer (27), a heated cooling fluid being discharged from said at least one cooling circuit (29) by at least one outlet duct (31) traversing at least one aforementioned support spacer (27).

5. Oven according to any one of claims 1 to 4, characterized in that each tank comprises an outer wall (28) and in that the central tubular collector element (21) is, in a lower part, fixed to this wall by several beams (34), preferably four beams, arranged horizontally.

6. Oven according to one of claims 1 and 2, characterized in that each tank comprises an outer wall (28), in thatthe central tubular collector element (21) is, in a lower part, fixed to this wall by several beams (34), preferably four beams, arranged horizontally and in that the hat-shaped protective element (25) is centrally supported above the upper end of the tubular central collector element (21) by vertical uprights (37) supported by said horizontal beams (34).

7. Oven according to claim 6, characterized in that the hat-shaped protective element (25) is traversed by at least one cooling circuit (29) which is supplied with cold cooling fluid from at least one supply duct running through at least one aforementioned beam (34) and one aforementioned upright (37), a heated cooling fluid being discharged from said at least one cooling circuit (29) by at least one discharge duct running through at least one aforementioned upright (37) and one aforementioned beam (34).

8. Oven according to any one of claims 1 to 7, characterized in that the tubular central collector element (21) is traversed by at least one refrigeration circuit (33) which is supplied with cold refrigeration fluid from outside the furnace, a heated refrigeration fluid being discharged from this circuit to the outside of the furnace.

9. Oven according to any one of claims 1 to 8, characterized in that each tank is further provided with an annular collector (35) which communicates with it via several doors (36) located on the periphery of the tank and with an external extraction device for extracting heated cooling air from the furnace.

10. Oven according to any one of claims 1 to 9, characterized in that the central tubular collector element (21) has the shape of a cylindrical tube.

11. Oven according to any one of claims 1 to 10, characterized in thatthat at the level below said above-mentioned gas transfer path (3), each tank has a lower part (38) in the shape of an inverted truncated cone.

12. Oven according to any one of claims 1 to 11, characterized in that said means for cooking the carbonated mineral rock during descent are injection elements (4, 6) into the tank in cooking mode of a fuel and an oxidant which by combustion make it possible to reach a calcination temperature of said rock.

13. Oven according to any one of claims 1 to 11, characterized in that said means for cooking the carbonate mineral rock during descent are elements for injecting into the tank in cooking mode a gas or gas mixture brought, outside this tank, to a calcination temperature of said rock.

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