VERTICAL FURNACES DESCRIPTION

Technical field of the invention

The present invention relates to an innovative limestone loading system in industrial processes, in particular in vertical furnaces (with one or more vats) for the production of lime.

Known art

As known, the correct conveying and distribution of limestone in pieces inside a vertical lime kiln, is a determining factor for a homogeneous cooking of the material and for an excellent quality of the finished product .

A plurality of systems (both static and dynamic) are currently known and normally used: some of them are mainly able to improve the distribution of limestone stones in order to cover in a homogeneous way the furnace section, and other systems are also able to avoid segregation of the material in pieces, namely to prevent separation and lack of homogeneity among large and small stones .

For example, in the static loading systems through which limestone is generally brought to a height by a vertical elevator, skip or conveyor belt, stones are directed by means of slides and valves in one or more vats of the furnace. Such systems, which are rather simple from the point of view of plant engineering, involve a rather important segregation of the pieces according to their dimension, especially in furnaces with a large section. In hybrid systems, the material is conveyed in one or more vats through the use of slides, valves and fixed or mobile distribution and conveying plates. In this way a good coverage of the vat surface is obtained, but the segregation of the pieces according to their dimension is not prevented.

Finally, in the movable and dynamic systems of known art, buckets, "skip" or rotary hoppers are used, which are filled during rotation. Such movement permits to mix the limestone in pieces, by trying to avoid segregation, before a vertical and direct discharge occurs in the vat. Such SYSTEMS are more complex from the construction point of view and do not permit a control of the conveying and distribution of pieces according to their dimension, along the vat section.

As already mentioned, the correct loading system of limestone inside a vertical furnace, is one of the most important aspects for the preparation of lime, especially when the pieces may be fine and/or very variable in size. Also cost, encumbrance and height of the plant must be considered, as also ease of installation, calibration and programming. Moreover, limestone and raw materials are critical from a chemical and mechanical point of view, so that the choice of a loading system which can reduce the stress of the stones during conveying them, and the consequent crumbling with fine material production, becomes very important and strategic.

There is therefore a need to obtain an efficient system, which allows to solve the technical problem mentioned above and is able to control the load and size of pieces of incoming raw material, especially in critical industrial environments, such as those of regenerative furnaces with two or more vats for limestone cooking .

Summary of the invention

Purpose of the present invention is to produce a system for loading limestone for vertical lime kilns which due to its rotation on the vertical axis of its loading hopper and the parametric control of an engine driven by the inverter, permits to accurately position the hopper and to unload the limestone in the vat of the furnaces, with different angles from cycle to cycle, by controlling the segregation of pieces at each loading step, thus being able to ensure a completely uniform distribution of the pieces inside the furnace volume, according to the independent claim of the annexed system.

A further purpose relates to the possibility either of moving, in regenerative furnaces with two or more vats, the hopper from a vat to another one of the furnace, or from a furnace to another one (in case of one or more batteries of vertical furnaces with single vat), through a rack-and-pinion translation system. In particular, for large and modern regenerative furnaces with vats, with a double material inlet for each vat, such system (including two limestone conveyor and distribution hoppers) permits loading the raw material needed for each cooking cycle, alternatively at 100% in the same vat or at 50% in both vats. Due to the engine driven by an inverter and the control with an absolute encoder, the hopper can be positioned with extreme precision on the vat to be loaded.

Advantageously, such configuration allows to have a single loading point of the hopper (through a "skip", a bucket elevator or a conveyor belt), so avoiding the installation of additional machinery and simplifying the loading configuration of the furnace.

A further advantage of the subject system of the present invention, due to the use of a double plate discharge valve, consists in being able to project the limestone in the desired direction (by opening both or partially individual plates) inside the vat, by properly and homogeneously covering the furnace section. Moreover, such type of valve allows a handling of the plates (in contrast to the most commonly used conical valves) by means of hydraulic cylinders installed externally to the valve itself, which simplifies installation, maintenance and allows more space within the hopper. In addition, the inside of the hopper and the valve is coated with high- strength rubber panels, which reduce the impact force of the incoming material, by reducing the formation of fines and noise.

Advantageously, the machine still in construction phase allows the use of electrical and hydraulic plants, in order to simplify the plant connection and commissioning .

Finally, the machine is parameterized and programmed directly during the construction phase, with the need to configure just simple basic operations at the time of installation in the plant.

According to a further aspect of the present invention, a method is described for the distribution of the limestone according to size, in lime kilns by means of the object system of the present invention, having the features set forth in the independent annexed method claim.

Further preferred and/or particularly advantageous embodiments of the invention are described according to the characteristics set forth in the attached dependent claims .

Brief description of the drawings

The invention will now be described with reference to the accompanying drawings, which illustrate some nonlimiting embodiments thereof, in which:

Figure 1 is a side view of the system according to the present invention, Figure 2 is a horizontal section of the system of Fig.l ,

- Figure 3 is a cross-section of the system of Fig.l ,

Figure 4 is an axonometric view of the system of Fig.l,

Figures 5A, 5B and 5C show a schematic representation of the system in a working phase,

Figure 6 shows a schematic representation of the system, in a two-vat regenerative lime kiln,

Figures 7A and 7B show a schematic representation of the system according to Fig.6, with double material inlet on each vat.

Detailed description

The invention relates to a limestone loading system for vertical lime kilns, as shown in the attached Figures .

The system 100, as shown in the various views of Figures 1-4, comprises:

a hopper 1 for receiving the material, internally coated with impact-resistant rubber/polyurethane panels 2,

- a support structure 3, provided with wheels for linear displacement on a rail 4, on which the hopper 1 is fixed by means of a wheel 5 that allows its rotation on the vertical axis,

- two motor-geared reducers 6, 7 completed with parking brake and encoder, which allow the rotation of the hopper 1 on vertical axis, and movement on a rail with rack 26. The first motor-geared reducer 6 allows to carry out the rotation of the hopper 1, by means of a pinion which meshes with the wheel 5; the second motor-geared reducer 7 allows the linear movement by means of a pair of pinions 8, which geared to a rack 26,

- a pair of tubular catenaries 9 for the passage of electric cables and hydraulic piping, protected by a system of rotating carter 10,

- a valve 11 provided with a pair of plates 11', 11'', being flanged with the hopper 1; the plates 11', 11' 'in the closed position of the valve are arranged so that their distal ends, with respect to the valve 11 are in contact by ensuring sealing. In the opening phase, one or both plates 11', 11'' can rotate about a fulcrum coincident with their proximal end. The opening of the plates 11', 11'' is controlled by a pair of oleo-dynamic cylinders 12,

- a pair of dust-sealing bellows 13, controlled by short stroke hydraulic cylinders 14,

- a metal guide 15 to bring electric cables and hydraulic pipes to an external linear catenary,

- a pair of inclination meters 16 for the control of opening angle a of the pair of discs 11', 11'' of the valve 11, and

- a pair of limit switches to verify the "zero" position of the hopper 1. Advantageously, the inside of the double-plate valve 11a is also coated with rubber panels and/or impact-resistant polyurethane 2.

According to prior art, the operation of the system 100 in a lime kiln, for example with a single vat 20, as schematically shown in Figures 5A, 5B and 5C, is made according to following main steps :

a. raising the limestone in pieces according to size, atop of the lime kiln, by means of a bucket of a lifting system 22 or conveyor belt or bucket elevator,

b. loading the material, through a conveying slide 23, into the hopper 1,

c. directing at least one plate 11, 11' of the valve 11 and discharging the material from the hopper 1 into the vat 20 of the lime kiln.

In this way, obviously the limestone inside the vat 1 will be arranged randomly and in any case non-homogeneously .

The present invention provides for a control of the angular position of the hopper 1, in order to overcome the present drawback.

In fact, in the subsequent loading cycle of the furnace 20, the limestone will be introduced into the hopper 1, still with the same segregation and lack of homogeneity due to the different trajectory that the various pieces of limestone take in the conveying device (the larger particles will tend to reach further with respect to the smaller ones) .

According to the invention, however, before the introduction of the material inside the furnace, the hopper 1 will be placed at an angle b between 0° and 180° (as shown in Figure 5B) , in order to vary the orientation of the segregation of the material to be loaded. The rotation of the hopper 1 is controlled according to manual or automatic modes (in the latter case according to predetermined logics).

Furthermore, by opening the valve 11 with double plate 11', 11'', the limestone can be introduced into the vat 20. The segregation, at this point, will balance the previous limestone loading, so homogenizing the material distribution along the height of the vat 20.

The use of the valve 11 with double plate 11', 11'' has the advantage of allowing the alternative opening of the one or the other plate 11’, 11'', so that the material can be introduced with a different trajectory within the furnace, so making its distribution more uniform, as shown in Figure 5C.In particular, each plate 11', 11' 'can rotate at an angle a between 0° and 120°.

Furthermore, the opening angle a of the pair of plates 11', 11'' is controlled by means of suitable inclination meters 16 and, therefore, the plates 11', 11'' can be opened according to a desired angle for generating different trajectory jets of limestone pieces, according to their size.

The system 100 is also advantageously used in a lime kiln with two vats 20, 20', provided with a linear translation system, as schematically shown in Figure 6.

Similarly to what has been described with respect to the furnace 20, the material is introduced through a conveying slide 23 into the hopper 1, by means of a limestone lifting system.

Advantageously, sealing bellows 13d can be installed, positioned both at the upper inlet and at the lower inlet of the hopper 1, in order to prevent the dust from escaping. The bellows 13, controlled by oleo-dynamic cylinders or a pneumatic system, are placed in an extended configuration in order to seal the counterparts installed on the furnace vat 20, 20', for example a valve 29 which is necessary for keeping the furnace under pressure, to prevent the powder escaping from the hopper 1 and from the underlying double-plate valve 11, during loading and unloading phases of limestone. The same bellows 13, however, are retracted once the loading phase is ended, to prevent them from rubbing and interfere with the rotational and translational movement of the hopper 1 itself .

In the case of a furnace with two vats 20, 20', the hopper 1, provided as said with the first motor-geared reducer 6 in order to rotate around its axis, and with a rack-and-pinion system 26 installed on the support structure of the furnace, so as to cooperate with the pair of pinions 8 of the system 100, is positioned on a first vat 20 of the lime kiln. When the hopper 1 is aligned with the first vat 20 and possibly has been rotated on itself according to a desired angle, the sealing bellowsl3 are extended on the upper side against dedicated sealing plates (such plates are installed on the surrounding structure, being part of the furnace and are not closely linked to the conveying system) and, on the lower side, against the valve necessary for pressure sealing of the furnace 29. At this point, the sealing valve of the furnace 29 can be opened. When the sealing valve 29 is completely open, the valve 11 with double plate 11', 11' ' is also open to load the limestone in pieces inside the vat 20 of the furnace.

Also in this double vat configuration, the valve 11 with double plates 11', 11'' can be opened with various angles, in order to allow a loading of limestone distributed into the vat.

In the next cycle, the hopper 1 due to the rack-and- pinion handling system 26, can load a second vat 20' of the regenerative lime kiln, according to the methods already described for the first vat 20.

According to an alternative configuration, the present system 100, as shown in Figures 7A and 7Ba is used as a lime kiln with two vats 20, 20' , equipped with a double inlet 27, 28 of the limestone in each vat. Similarly to what described for the single inlet of the double vat furnace, through a lifting system of the material limestone is introduced through a conveying slide 23 and through the diverter valve 11 with double plate 11', 11''. The limestone required for an operating cycle of a regenerative lime kiln with double vat is divided and conveyed to a first hopper 1 and subsequently to a second hopper 1 ' .

According to the present invention and as seen from the drawings of Figures 7A and 7B, the two hoppers 1 and 1' move on one or both vats 20, 20' following two modes: the hoppers 1 and 1' move simultaneously, by means of a rack-and-pinion transmission, onto the same vat 20, so loading the quantity of limestone necessary for a cooking cycle of the furnace, in the same vat, distributed according to the procedure shown in Figures 5A, 5B, 5C; otherwise the hopper 1 moves either towards the vat 20 (or the vat 20' following the sequence of the operating cycle of the lime kiln with double vat) , by loading half amount of limestone required for a cooking cycle of the furnace, in accordance with the procedure described in Figures 5A, 5B, 5C, and the hopper 1' moves simultaneously towards the opposite vat, by loading half the amount of limestone required for a cooking cycle of the furnace, according to the procedure described in Figures 5A, 5B, 5C.

Advantageously, through the use of motors completed with encoder and controlled by inverter, all movements are precise and constantly monitored.

In addition, due to the complete configuration of the driver, the torque control and the speed of the movement are managed in a dynamic and flexible way.

In addition to the embodiment of the invention described above, it must be understood that many further variants exist. It must also be understood that such embodiments are only exemplary and limit neither the object of the invention nor its applications, nor its possible configurations. On the contrary, although the above description makes it possible for a technician to implement the present invention according to at least one of its exemplary configurations, it must be understood that numerous variants are conceivable of the described components, without for this reason abandoning the object of the invention, as defined in the attached claims, literally interpreted and/or according to their legal equivalents .