INSTALLATION AND PROCESS OF PRECALCI NATION

The present application relates to an installation for pre-calcination of mineral materials intended to feed a cement kiln and using alternative fuels, in particular waste materials. The present patent application also relates to a process of pre-calcination of such mineral materials.

Cement is a hydraulic binder obtained by grinding and burning a mix of limestone and materials providing silicon, alumina and iron, for example clay to the burning process in order to produce clinker, said clinker is then ground with added calcium sulphate in the form of gypsum (calcium sulphate dihydrate, CaS04.2H20), hemi-hydrate (CaS04.1/2H20), anhydrite (anhydrous calcium sulphate, CaS04) or a mixture thereof.

The thermal treatment applied to the mixture of mineral materials, called the cement raw mix, covers all the stages of chemical transformations resulting in clinker. It pertains mainly to the heating, to the decarbonation of the limestone, which takes place at around 850°C and to the clinkering step, which takes place at around 1450°C. Decarbonation corresponds to the transformation reaction of the limestone into lime. Clinkering corresponds to the reaction resulting in the formation of the minerals of the clinker.

The pre-heating step and most of the decarbonation generally take place in a decarbonation tower, whilst the remaining decarbonation and the clinkering step take place in a cement kiln.

The decarbonation tower most often comprises a series of cyclones arranged vertically on several levels. The cement raw mix, which comes in the form of pulverulent mineral materials, is introduced into the top part of the tower and is put into suspension in each cyclone by hot gases coming from the cement kiln. The raw mix is heated in each cyclone by contact with the gases, then it is separated and falls by gravity into the cyclone on a lower level where it is again put into suspension. After this passage through the different cyclones, the mineral materials are introduced into the cement kiln.

The cement kiln generally corresponds to a steel cylinder comprising an interior refractory lining. The steel cylinder is inclined, by a few degrees, relative to the horizontal direction and turns around its axis. The lower end of the kiln is equipped with a burner, which can produce a flame which can reach approximately 10 metres in length. The raw mix is fed into the kiln at the higher end of the cylinder opposite the burner. The rotations and the inclination of the kiln entrain the mineral materials through the kiln.

It is desirable that the decarbonation rate of the mineral materials when the mineral materials enter the cement kiln be as high as possible in order to reduce the decarbonation phase in the cement kiln. The decarbonation reaction is indeed a very endothermic reaction, requiring efficient thermal exchanges between the hot gases and the pulverulent mineral materials. Because the cement kiln, is not designed to optimize these exchanges, if the decarbonation phase in the cement kiln is too high, it may be necessary to reduce the flow rate of the material through the kiln.

Nevertheless, only relatively low decarbonation rates are obtained by the passage of the mineral materials through the cyclones, generally from 30 to 40%. This is why the decarbonation tower generally further comprises a pre-calciner, located along the path of the mineral materials, said pre-calciner corresponds to an enclosure in which fuel is burnt. This makes it possible to increase the degree of decarbonation of the mineral materials, up to approximately 90 % at the input of the cement kiln. An example of a pre-calciner is described in the French patent application FR 2 691 790.

The pre-calciner can consume a substantial part of the fuel provided at the cement plant, for example up to 70%. Fuels used in a typical manner comprise petroleum coke, coal, petroleum or natural gas.

It would be desirable to use alternative fuels as fuel for the pre-calciner, for example, coming from waste materials. These waste materials are, for example, tyres, household waste, sludge, combustible solids or industrial waste. However, one disadvantage is that in current pre-calciners, the fuels have to be shredded and/or ground to be able to be used in significant quantities, for example more than 15 % of the fuel required for the pre-calciner. The cost for preparation of these fuels is therefore not compatible with their use in a cement plant.

Thus, a feature of an embodiment of the present invention is to resolve, at least partially, the disadvantages of the previously-described pre-calciners.

Another feature of an embodiment of the present invention is to make it possible to use waste materials as fuel in a pre-calciner, by limiting their prior treatment, in particular, prior grinding.

Another feature of an embodiment of the present invention is that the pre-calciner can be used in a cement-plant installation.

Thus, an embodiment of the present invention provides an installation for pre-calcination of pulverulent mineral materials, intended for the production of cement, said installation comprising a pre-calciner, said pre-calciner comprising:

- an enclosure,

- supply ducts of the mineral materials into the enclosure,

- supply ducts of hot gases into the enclosure,

- at least one exhaust duct of the hot gases from the enclosure,

- a first chamber communicating with the enclosure,

- supply ducts of waste materials into the first chamber,

- at least one second chamber communicating with the enclosure,

- at least one first mobile pushing part arranged to push the waste material out of the first chamber, the second chamber being intended to receive the waste material pushed out of the first chamber, and

- at least one second mobile pushing part arranged to push the waste material out of the second chamber.

According to an embodiment of the present invention, each pushing part is mobile in a translation movement relative to the enclosure.

According to an embodiment of the present invention, at least part of the waste material is not ground.

According to an embodiment of the present invention, the waste materials are selected from the group comprising tyres, household waste, sludge, combustible fuels or industrial waste.

According to an embodiment of the present invention, the installation comprises at least one first actuator connected to the first pushing part and arranged to move the first pushing part in the first chamber between two end positions and the installation comprises at least one second actuator connected to the second pushing part and adapted to move the second pushing part in the second chamber between two end positions.

According to an embodiment of the present invention, the installation further comprises, a mixing chamber communicating with the enclosure and intended to be fed with fume coming from a burning kiln, and a separation cyclone of the material connected to the reaction chamber by a duct.

According to an embodiment of the present invention, the installation comprises a first feeding duct of hot gases discharged into the enclosure and a second feeding duct of hot gases discharged into the connecting duct, connecting the mixing chamber to the cyclone.

According to an embodiment of the present invention, the distance between the base of the second chamber and the base of the first chamber varies from 200 mm to 1200 mm.

An embodiment of the present invention provides a process for operating the installation of pre-calcination defined herein above, comprising the following steps:

supply the waste materials in the first chamber;

keep the waste materials in the first chamber for a first duration;

- evacuate the waste materials out of the first chamber into the second chamber via said first mobile pushing part adapted to push the waste materials out of the first chamber;

- keep the waste materials in the second chamber for a second duration; and - evacuate the waste materials out of the second chamber via said second mobile pushing part adapted to push the waste materials out of the second chamber.

According to an embodiment of the present invention, a process for gasification of the waste materials is carried out in the first and second chambers.

According to an embodiment of the present invention, the residence time of the waste materials in the pre-calciner varies from 5 minutes to 90 minutes.

These characteristics and advantages, as well as others, will be described in detail in the following description of particular non-restrictive embodiments of the present invention relative to the enclosed figures, among which:

Figure 1 partially represents, in a diagram form, an example of a cement plant comprising an in-line pre-calciner;

Figure 2 partially represents, in a diagram form, an example of a cement plant comprising a parallel pre-calciner;

Figure 3 represents in more detail an embodiment of the pre-calciner in Figure 1 ; Figure 4 represents in more detail an embodiment of the pre-calciner in Figure 2;

Figures 5 and 6 are cut sections in diagram form of the pre-calciner of Figures 3 and 4, respectively,

Figures 7 and 8 are cut sections of the pre-calciner of Figures 3 and 4, respectively, comparable to the cut section of Figure 6, with two operating steps of the pre-calciner; and

Figures 9 and 10 represent two other embodiments of the pre-calciner of Figures 1 or 2.

For purposes of clarity, the same elements have been designated by the same references in the different figures and, furthermore, the various figures are not traced on scale. Furthermore, in the next parts of the description, unless otherwise specified, the terms "substantially", "approximately" and "by the order of" mean " more or less 10 % ". Additionally, the adjectives "lower" and "upper" are used in the next part relative to a reference direction, for example the vertical direction. Furthermore, only the elements useful for comprehension of the present description have been represented and are described. In particular, the detailed structures of the elements of a cement plant are well known to the person skilled in the art and are not described in detail in the following description.

Figure 1 represents an example of a cement plant installation 10. The mineral materials, provided in a pulverulent state, successively pass through a pre-heater 12, a pre-calciner 14, a cement kiln 16, and a cooler 18. The pre-heater 12 and the pre-calciner 14 form the pre-calcination tower 20. The pre-calciner 14 can be integrated in the pre-heater 12.

Pulverulent mineral materials 22, corresponding to a cement raw mix, are fed into the pre-heater 12. The pre-heater 12 can comprise a series of cyclones positioned vertically on several levels. The mineral materials are in the form of a powder, generally at least 90 % by mass is composed of particles having a size less than 100 μηη. They comprise, in particular, limestone and materials carrying silicon, alumina and iron, for example clay. Hot fumes 24 coming from the burning kiln 16, through a junction box 26, rise through the pre-heater 12 and pre-heat these mineral materials. The fumes 27 are released outside of the installation 10 after being filtered.

The heated mineral materials 28 exiting the pre-heater 12 are calcined in the pre-calciner 14 by the combustion of fuel with pre-heated air coming from the cooler 18 through a duct 30. The pre-heated and pre-calcined materials 34 are fed into the kiln 16 through a junction box 26 to finish the burning by a supply of energy coming from the combustion of fuel 36 with pre-heated air 38 coming from the cooler 18. The burnt product 40 exiting the kiln 16 corresponds to clinker; it is cooled in the cooler 18. The cooled clinker 42 is evacuated from the cooler 18. The arrow 44 in Figure 1 illustrates the excess hot air exiting the cooler 18 and intended for other uses.

Figure 2 represents another example of a cement plant installation 45. The cement plant installation comprises the same elements as the cement plant installation 10 represented in Figure 1 the difference being that the pre-calciner 14 is positioned parallel to the pre-heater 12. The pulverulent mineral materials successively pass through the pre-heater 12, the pre-calciner 14, the pre-heater again 12, the cement kiln 16, and the cooler 18. In particular, the pre-calcined mineral materials 32 coming from the pre-calciner 14 are re-introduced into the pre-heater 12.

Figures 3 and 4 represent two examples in more detail, still remaining in diagram form, of part of the decarbonation tower 20 comprising an embodiment of the pre-calciner 14, respectively for the cement plant installation 10 represented in Figure 1 and for the cement plant installation 45 represented in Figure 2.

Figures 5 and 6 are cut sections in diagram form of the pre-calciner 14 of Figure 3 and 4, respectively, according to lines V-V and VI-VI.

The pre-calciner 14 comprises an enclosure 50 connected, at its lower part, by a duct 52, to a mixing chamber 54. The mixing chamber 54 is connected by means of a valve 56 to the junction box 26 from which fumes 24 penetrate the lower part of the

mixing chamber 54. The upper part of the mixing chamber 54 communicates with a post-combustion duct 57, for example in the form of a gooseneck, discharged into a cyclone 58, wherefrom the pre-calcined mineral materials 34 can be recovered.

The enclosure 50 can be axially symmetrical relative to a D axis. The inside wall can comprise an upper portion 60 prolonged by a lower portion 62 forming successive levels around the D axis drawing closer to the D axis from top to bottom. According to a variant of the present invention, the successive levels are on one sole side of the enclosure 50, and are therefore not positioned around the D axis. The inside wall of the enclosure 50 can be made of refractory bricks.

One part of the hot air recovered from the cooler 18, designated by the arrow 64, and carried by the duct 30, is used as entrained air in the pre-calciner 14. The duct 30 further divides into several ducts, in particular one or more ducts 65 arriving in the lower part of the enclosure 50, for example at the level of the duct 52, as represented in Figure 4. The duct 30 further divides into ducts 66 arriving in the upper part of the enclosure 50. Another duct 68 can arrive in the upper part of the mixing chamber 54, as represented in Figure 3, or in the connecting duct 57 of the mixing chamber 54 with the cyclone 58, as represented in Figure 4. By way of a variant, it is possible that the duct 68 can be absent. Valves, not represented in the figures, can be provided for adjustments of the flow rates of the hot gases circulating in the ducts 65, 66 and 68.

One duct, 65 and two ducts 66 are represented in Figures 3 and 4 and two ducts

66 are represented in Figures 5. Nonetheless, a greater number of ducts 65 and 66 can be provided. According to an embodiment of the present invention, the ducts 66 enter the enclosure 50 substantially tangent relative to the inside wall of the enclosure 50 in order to impose a turbulent movement to the gases entering the enclosure 50, as illustrated in Figure 5 by the arrows 68. The ducts 66 communicating with the upper part of the enclosure 50 can carry, for example 80 % of the hot air recovered from the cooler 18. The duct 65 communicating with the lower part of the enclosure 50 can carry, for example 20 % of the hot air recovered from the cooler 18.

Ducts 70 supply part of the pulverulent mineral materials to the enclosure 50. These mineral materials can come from another cyclone, not represented in the figures, of the decarbonation tower 20. By way of example, the ducts 70 arrive in the ducts 66 substantially at the level of their junction to the enclosure 50. The ends of the ducts 70 are represented by dotted lines in Figure 5. Disturbance devices can be placed in the ducts 66 and/or ducts 70 to facilitate obtaining a turbulent flow.

The enclosure 50 extends from its upper part via a duct 71 communicating with the post-combustion duct 57 and serves to evacuate the gases from the enclosure 50 into the mixing chamber 54.

Waste material reaction chambers are placed on several levels on the lower wall 62 of the enclosure 50. The number of levels can vary from 2 to 20, preferably from 2 to 10. In the present embodiment of the present invention, represented in Figures 3 to 6, the reaction chambers are positioned on two levels. Reference 72 designates the closest reaction chamber to the summit of the enclosure 50 and reference 74 designates the reaction chamber closest to the duct 52. Each reaction chamber 72, 74 corresponds to a substantially horizontal portion of the inside wall 62. Each reaction chamber 72, 74 is open on to the internal space of the enclosure 50 at the top and on the side oriented towards the D axis.

Ducts 78 are provided for the supply of waste materials into the upper reaction chambers 72. The waste materials can be tyres, household waste, sludge, combustible solids or industrial waste. The waste materials may, at least partially, not be ground or only coarsely ground. The average size of each element of waste material introduced in the enclosure 50 can be comprised in a sphere, the radius of which can vary from 20 to 500 mm. The maximum size of the waste elements of the material introduced in the enclosure 50 can vary from 10 to 1500 mm. By way of example, each duct 78 opens on to the enclosure 50 in a vertical plane of the upper chamber 72, preferably along the outside border of the upper chamber 72. The waste materials can fall by gravity into the upper chamber 72. The waste materials 80 are represented in diagram form in Figures 3 and 4 in the reaction chambers 72, 74. Shutters or rotating lock ducts, not represented in the figures, can be provided to close the chambers 78 in a leak-proof manner when waste materials are absent.

Waste-displacement devices 82 are associated to each reaction chamber 72, 74. In the present embodiment of the invention, four waste-displacement devices 82 are associated to each reaction chamber 72, 74. Each device 82 can comprise actuators

84, two actuators 84 per waste-displacement device 82 being represented in Figure 6, adapted to move a pushing part 86 in the associated reaction chambers 72, 74. The pushing part 86 may have the shape of a block or of a blade and may optionally be traversed by circulation ducts of a cooling liquid. The pushing part 86 can be made of a refractory material. Each actuator 84 can correspond to a hydraulic jack, a pneumatic jack or an actuator with an electric motor. The pushing part 86 can be moved in each reaction chamber 72, 74 between first and second end positions, for example according to a translation movement. In the first end position, the pushing part 86 is the farthest from the D axis and therefore penetrates as little as possible into the reaction chamber 72, 74. In the present embodiment of the invention, in the first end position, each pushing part 86 does not substantially penetrate into the enclosure 50. In the second end position, the pushing part 86 is closest to the D axis and therefore

penetrates as much as possible into the reaction chamber 72, 74.

When the pushing part 86 advances into the associated reaction chambers 72, 74, it pushes at least part of the waste materials present in the reaction chambers 72, 74 out of the reaction chamber.

The upper and lower chambers 72, 74 are substantially positioned at different levels. Thus, when the waste materials are expelled from the upper chamber 72, they fall into the lower chamber 74. When the waste materials are expelled from the lower chamber 74, they fall into the duct 52.

By way of example, for each reaction chamber:

- two waste-displacement devices 82 are placed symmetrically relative to the

D axis and the corresponding pushing parts 86 are moved in direction D1 and

- two waste-displacement devices 82 are placed symmetrically relative to the D axis and the corresponding pushing parts 86 are moved in direction D2 perpendicular to direction D1 .

Directions D1 and D2 can be horizontal. In Figure 6, the four pushing parts 86 associated to the lower reaction chamber 74 are represented in the first end position.

According to an embodiment of the present invention, during a production phase of cement, each pushing part 86 can make a back and forth movement between the first end position and a third intermediary position, between the first end position and the second end position. The third intermediary position corresponds, for example from 25 % to 75 %, for example, approximately 50 %, of the total path of the pushing part 86 in the combustion chamber. This means that the pushing part 86 therefore does not penetrate to a maximum in the associated combustion chamber 72, 74. One advantage of this embodiment of the present invention is to reduce the interfaces between the fixed and mobile parts during a production phase of cement. Another advantage is to permanently keep waste material on the fixed and mobile parts. When the cement plant is stopped, the pushing parts 86 can be conveyed to the second end position so that the totality of the waste material is evacuated from the pre-calciner.

A burner, not represented in the figures, can optionally be present in the enclosure 50 or in the duct 52. Preferably, there is not a burner in the enclosure 50 or in the duct 52. The decarbonation tower 20 can further comprise a standard pre-calciner equipped with a burner.

The decarbonation tower 20 operates in the following manner. Pulverulent mineral particles are introduced in the enclosure 50 via the ducts 70. The mineral materials can come from another cyclone of the decarbonation tower 20, and may already be heated and partially decarbonated.

The particles of mineral materials are entrained by the gases present in the enclosure 50, in particular, gases 64 coming from the cooler 18 and supplied by the ducts 65, 66. After passing through the pre-calciner 14, the particles of mineral materials are entrained through the duct 71 , then through the post-combustion duct 57. The particles of mineral materials are entrained by the fumes 24 coming from the kiln 16, into the cyclone 58, where they are separated and fall by gravity to the input of the kiln 16. The duration of the passage of the particles of mineral materials in the enclosure 50 can vary from 0.1 seconds to 10 seconds, in particular by the order of 2 seconds.

A gasification process of the waste materials 80 present in the reaction chambers

72, 74 is predominant in the enclosure 50. This is a process according to which the waste materials 80 are converted into carbon monoxide, hydrogen, carbon dioxide and other volatile hydrocarbons. This process is used at temperatures higher than 700°C, without substantial combustion with a controlled quantity of dioxygen. The supply of dioxygen can be provided by the gases 64 coming from the cooler 18. A gasification process is predominant when there is not a mix between the dioxygen and the waste materials. By way of example, the average temperature in the enclosure 50 can vary from 700°C to 1000°C. Combustion reactions can nevertheless be present simultaneously with the gasification process. The hot gases from the gasification process of the waste materials 80 mix with the hot gases 64 from the cooler 18 and induce the combustion and decarbonation of the particles of mineral materials.

The waste materials are introduced in the upper chamber 72 via the ducts 78. When the gasification of the waste materials in the upper chamber 72 has progressed sufficiently, the upper pushing parts 86 are moved in the upper chamber 72 in order to entrain the fall of the waste material from the upper chamber 72 to the lower chamber

74. The gasification process of the waste material then continues in the lower chamber 74 whilst new waste material is placed in the upper chamber 72. When the gasification process in the lower chamber 74 has progressed sufficiently, the lower pushing parts 86 are moved in the lower chamber 74 to entrain the fall of the waste material from the lower chamber 74 into the duct 52.

The fall of the waste material from the upper chamber 72 into the lower chamber 74 makes it possible to advantageously stir the waste material during the gasification process, making it possible to increase the quantity of gasified waste material. By way of example, the height of the fall of the waste material between the base of the upper chamber 72 and the lower chamber 74 can vary from 200 mm to 1200 mm, in particular by the order of 600 mm. Furthermore, the evacuation of the waste material is carried out by a pushing part moved in a translation movement by an actuator, which is to say, by a system with a simple structure and a robust operating procedure, which is compatible with the strict operating specifications present in the pre-calciner 14.

Figures 7 and 8 illustrate a sequence of the action of the pushing parts 86 of the lower chamber 74 during a production phase of cement. In Figure 7, the pushing parts 86 represented at the top and bottom of the figure are in the first end position and the pushing parts 86 represented on the right and left of the figure are in the third intermediary position. In Figure 8, the pushing parts 86 represented on the left and right of the figure are in the first end position and the pushing parts 86 represented on the top and bottom of the figure are in the third intermediary position. The pushing parts 86 can be moved according to successive cycles, each cycle comprising the successive passage of the pushing parts 86 by the configurations represented in Figures 7, 6, 8, 6 and again in Figure 7. The pushing parts 86 associated with the upper chamber 72 can be moved in a comparable manner.

When the cement plant is stopped, an operating cycle, as described above, can be carried out to evacuate the totality of the waste material present in the pre-calciner, the difference being that the pushing parts move to the second end position.

The precalciner 14 comprises a regulation system of the production of energy, which is provided by gasification of the waste materials. This can be carried out by controlling the action sequence of the pushing parts 86 of the upper chamber 72 and the lower chamber 74, by controlling the input flow rate of the waste material in the pre-calciner and the flow rate in the ducts 65 and 66. The temperature in the enclosure 50 can be measured for this regulation as well as a representative measurement taken of the energy provided by gasification of the waste material.

By way of example, the residence time of the waste materials in the enclosure 50, from the moment they are introduced in the upper chamber 72 by the ducts 78 until they are evacuated into the duct 52, can vary from 5 minutes to 90 minutes, in particular within the order of one hour. The dimensions of the pre-calciner 14 are adapted to the desired flow rate of the cement kiln 16. The feed flow rate of the waste material in the enclosure 50 depends on the dimensions of the precalciner 14 and on the flow rate of the cement kiln 16. By way of example, the reception surface of waste material from the upper 72 and lower 74 chambers can vary from 20 m2 to 100 m2, in particular by the order of 60 m2. The maximum path of each pushing part 86 can be from 10 cm to 1 .50 m.

According to a variant of the present invention, the combustion reactions of the waste material can be predominant in the enclosure 50. In this case, supply ducts of pressurized air can be provided in the reaction chambers 72, 74.

Figure 9 represents another embodiment of the present invention of a pre-

calciner 100 comprising all the elements of the precalciner 14 represented in Figures 3 and 4, the difference being that the upper wall 92 of each pushing part 86 also plays the role of a combustion chamber. In the embodiment of the present invention in Figure 9, the precalciner 100 therefore comprises combustion chambers on four levels.

The waste material is supplied by the ducts 78 on the upper walls 92 of the upper pushing parts 86 which form the first reaction chamber 94. When the upper pushing parts 86 are far from the D axis, part of the waste material present on the upper walls 92 of the upper pushing parts 86, falls onto the parts of the wall 62 in front of the upper pushing parts 86, which form the second reaction chamber 96. When the upper pushing parts 86 are close to the D axis, they push part of the waste material out of the second reaction chamber 96. This waste material falls onto the upper walls 92 of the lower pushing parts 86, which form the third reaction chamber 98. When the lower pushing parts 86 are far from the D axis, part of the waste material present on the upper walls 92 of the lower pushing parts 86, falls onto the parts of the wall 62 in front of the lower pushing parts 86, which form the fourth reaction chamber 98. When the lower pushing parts 86 are close to the D axis, they push part of the waste material out of the fourth reaction chamber 52 into the duct 52.

Figure 10 represents another embodiment of the present invention of a precalciner 110 in which the reaction chambers 1 12, 114 are positioned in a staircase manner and oriented in the same direction, one being the extension of the other. In this embodiment of the present invention, the waste materials are introduced on one single side of the enclosure 50 and advance in a linear manner.

Particular embodiments of the present invention have been described. Various variants and modifications will appear to the person skilled in the art. In particular, even though the pre-calciner 14 has been described as being connected to the mixing chamber 54, which is itself connected to the cyclone 58 by an elbow duct 57, the precalciner 14 can be directly connected to the cyclone 58 or directly to the input of the kiln 16. Furthermore, even though in the previously-described embodiments of the present invention, a lower chamber is associated to each upper chamber, it is clear that the dimensions of a lower chamber can be sufficiently significant to receive the waste materials of two or more upper chambers.

CLAIMS

1 . An installation for pre-calcination (20) of pulverulent mineral materials (22), intended for the production of cement (42), comprising a pre-calciner (14), said pre-calciner comprising:

- an enclosure (50),

- supply ducts (70) of the mineral materials into the enclosure,

- supply ducts (65, 66) of hot gases into the enclosure,

- at least one exhaust duct (71 ) of the hot gases from the enclosure,

- one first chamber (72) communicating with the enclosure, supply ducts (78) of waste materials (80) into the first chamber,

- at least one second chamber (74) communicating with the enclosure,

- at least one first mobile pushing part (86) arranged to push the waste material out of the first chamber, the second chamber being intended to receive the waste material pushed out of the first chamber, and

- at least one second mobile pushing part (86) arranged to push the waste material out of the second chamber.

2. The installation for pre-calcination (20) according to claim 1 , wherein the enclosure (50) comprises the first chamber (72), and at least said second chamber (74)

3. The installation for pre-calcination (20) according to claim 1 or claim 2, wherein each pushing part (86) is mobile in a translation movement relative to the enclosure (50).

4. The installation for pre-calcination according to any one of claims 1 to 3, wherein at least one part of the waste material (80) is not ground.

5. The installation for pre-calcination (20) according to any one of claims 1 to 4, wherein the waste materials (80) are selected from the group comprising tyres, household waste, sludge, combustible fuels or industrial waste.

6. The installation for pre-calcination (20) according to any one of claims 1 to 5, comprising at least one first actuator (84) connected to the first pushing part and arranged to move the first pushing part in the first chamber (72) between two end positions and comprising at least one second actuator (84) connected to the second pushing part and arranged to move the second part in the second chamber (72) between two end positions.

7. The installation for pre-calcination (20) according to any one of claims 1 to 6, further comprising, a mixing chamber (54) communicating with the enclosure (50) and fed with fume (24) coming from a burning kiln (16) and a separation cyclone (58) of the material connected to the reaction chamber by a duct (57).

8. The installation for pre-calcination (20) according to claim 7, comprising a first feeding duct (66) of hot gases discharged into the enclosure (50) and a second feeding duct (68) of hot gases discharged into the connecting duct (57), connecting the mixing chamber (54) to the cyclone (58).

9. The installation for pre-calcination (20) according to any one of claims 1 to 8, in which the distance between the base of the second chamber (74) and the base of the first chamber varies from 200 mm to 1200 mm.

10. A process for operating the installation of pre-calcination (20) according to any one of claims 1 to 9, comprising the following steps:

- supply the waste materials (80) in the first chamber (72);

keep the waste materials in the first chamber for a first duration; evacuate the waste materials out of the first chamber into the second chamber (74) via said first mobile pushing part (86) adapted to push the waste material out of the first chamber (74);

- keep the waste materials in the second chamber for a second duration; and evacuate the waste materials out of the second chamber via said second mobile pushing part (86) adapted to push the waste materials out of the second chamber (74).

11. The process according to claim 10, wherein the process of gasification of the waste material (80) is carried out in the first and second chambers (72, 74).

12. The process according to claim 10 or claim 11 , wherein the residence time of the waste material in the pre-calciner (14) varies from 5 minutes to 90 minutes.