Patent ID: 12209054

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Some embodiments of the present invention will be described hereinafter, by making reference to the above-mentioned figures.

By way of preamble, the ceramic mixture therewith traditionally the porcelain stoneware is produced is usually constituted by the following components:one or more alkaline feldspars;usually they are sodium or potassium feldspars which can be found in Italy (Calabria or Sardinia) or in Turkey or in Pyrenees. Usually the feldspar enters the mixture with amounts not lower than 40-45%, and such raw material has the purpose of giving fusibility to the mixture itself, so that the melting temperature remains at values lower than 1200° C. The dosing of these ingredients, as well as their grinding level, allows to optimize the firing curve of the product and to give a structure without porosity thereto.one or more plastic clays;they are usually clays with high percentage of alumina (20-25%) with low amounts of iron oxide (light firing), or higher iron amounts (red-brown firing). They enter the mixture around 35%. They have the purpose of keeping together the not plastic ingredients so as to provide malleability and workability to the mixture before cooking. The most precious clays can be found in Germany and Ukraine and in lower percentage in Spain.Inerts or fillers;The inerts can be quartz or feldspathic sands, pre-cooked kaolins, chamotte. Usually they enter the ceramic mixture with % around 15-20% and usually the come from local quarries and then represent even the less expensive portion of the mixture.

With the objective which was indicated above, many solutions were tried to integrate recovery materials in the mixtures for producing porcelain stoneware, with the purpose of detecting the one which would meet at best all so far highlighted requirements.

To this purpose, crystals of automobiles, phials of medicines, glasses of bottles (all treated suitably), or ashes of power plants, that is the ashes which constitute the solid residue, which the thermoelectric power plants produce during the coal combustion phase, were then tested.

However, none of these materials allowed to obtain the wished results.

Then, the inventors thought to use the ashes produced by the incinerators of urban waste.

In fact, in the modern incinerators, these, after having been crushed and minced, are treated in specific self-combustion ovens by obtaining as main product electric energy and as by-product (waste product) combustion ashes up to now destined to special dumps.

With the present invention one has arrived to introduce into the mixture for producing porcelain stoneware such ashes coming from waste-to-energy plants (with partial replacement of other raw materials) without the technical features of the product being altered and consequently the use of this raw material (ashes) involves the evident advantage of lowering sensibly the cost of the mixture and solve then the problem of the cost of the mixture for producing high thicknesses.

By firstly referring toFIGS.1A to10they show some examples of porcelain stoneware products according to the present invention, in particular sanpietrini.

For example,FIG.1shows a sanpietrino1made of porcelain stoneware usable as element of a driveway.

The sanpietrino1has a tread surface2and a base surface3, and it is characterized in that it has an average thickness Sm, measured between the tread surface2and the base surface3, which on the average is greater than or equal to 4.5 cm.

An indication of the average thickness is provided, considering that the tread and base surfaces can be not perfectly regular (even intentionally to give a particular aspect to the sanpietrino).

As already explained, advantageously, an element for the construction of driveways according to the present invention, made of porcelain stoneware, could include in its composition a percentage Pc other than zero of recycled material coming from the treatment of waste.

In particular, the recycled material could advantageously come from processes for treating urban waste and substantially comprise the residual ashes from the combustion of such waste.

Preferably, the percentage Pc of recycled material, in particular ashes, is between 1% and 40% of the volume of the mixture used for the production of porcelain stoneware.

According to a preferred embodiment, such percentage Pc is between 10% and 30%, still more preferably between 15% and 25%.

From a geometrical point of view, according to a possible embodiment, an element according to the present invention has a tread surface2the sizes thereof are about 10×10 cm.

However, it is to be meant that even elements with different shape, such as for example special pieces for pavements, angles, and so on, can be implemented with the same chemical/physical feature.

For example, elements could be provided, the tread surface thereof (2) has the sizes of about 20×20 cm or 20×40 cm or 40×60 cm.

Still, according to an additional embodiment, an element can be provided, the tread surface thereof2has sizes of approximately 4.5×4.5 cm.

Generally, all elements produced according to the present invention, have a base surface3, the extension thereof, with respect to that of the tread surface2, can be in a variable ratio between 0.1 and 1.3, proportion corresponding to sizes which indicatively can vary between 1×1 cm to 13×13 cm.

According to the preferred embodiments, an element of the invention has a substantially truncated-pyramid shape, the tread surface2of which represents a large base thereof. Then, excepting some special pieces, in this case the base surface3will always have a lower extension than that of the tread surface2.

However, it will have to be meant that the base surface3could also have an extension equal to zero, or almost zero, this involving a substantially pyramidal shape.

At last, as already reminded, the shapes attributed to such elements, have not to be considered necessarily regular in the strictly mathematical sense. Actually, deviations from the regular geometrical shapes can be also wished and inserted intentionally to provide the pieces a more ‘artisan’ and less ‘standard aspect.

As already stated, the average thickness Sm of such elements is greater than or equal to 4.5 cm. However, preferred embodiments thereof provide an average thickness Sm greater than or equal to 6 cm.

By referring to the flow chart ofFIGS.2A to2C, this illustrates the main phases of a process according to the present invention.

In particular, the ashes coming from the incinerators before being used have to remain in the storage for at least 20-30 days, with the purpose of lowering the PH thereof through carbonation reactions.

At this point, the ashes can be in case treated to be reduced in sizes, deferrized and-metallized.

Although there are apparatuses for treatments of this type on the ashes, for the implementation of this phase, the inventors also devised and developed a process and an innovative apparatus, innovative on itself, providing effectively more performing results than known art and which, generally, could also be used in other fields, outside the present invention.

Consequently, a plant was devised for implementing this deferrization process.FIGS.3A to3Erelate to the de-metallization plant according to the present invention. With reference to such figures, the plant elements are identified by numbers shown in the following legend:

21Mill opening power unit20Conveyor belt mm 650 × 12,00019Conveyor belt mm 650 × 8,50018Conveyor belt mm 500 × 550017Separator EMC 150016Vibrating table 1400 × 75015Magnetic drum TM-N30.14014Magnetic drum TM-N30.14013Vibrating table 1400 × 150012Conveyor belt mm 650 × 900011Conveyor belt mm 650 × 17,30010Tertiary mill BSI type PFC 1059Mill vibrating feeder8Conveyor belt mm 600 × 90007Vibrating screen 2 Planes mm 1200 × 30006Bandaboard belt 650 × 81705Deferrizing belt4Conveyor belt mm 800 × 45003Extracting belt 800 × 62602Grid control hydraulic power unit1Loading hopper with light grid 80 mm

According to such process, the ashes are subjected to two deferrization phases.

A primary deferrization phase provides that the material is extracted from an inlet hopper and re-launched on a belt5wherein a powerful deferrizer having permanent magnets separating the coarser ferrous portions is mounted.

By way of example, for this phase a belt magnetic separator5can be used having the following features:Plate with permanent magnets made of Neodymium (sizes 900×700 h 180 mm);Drums with diameter 300 mm with keyed and interchangeable through shaft with diameter 50 mm;Interaxis drums 1,500 mm;Rubber mat class 400, three cloths 4+2 with strips h=30 mm pitch 400;Installed power 2.2 Kw The so roughly deferrized material is transported, through a belt system, to a vibrating screen7which separates the fine fraction 0÷8 mm from the coarse fraction 8÷80 mm.

By way of example, the vibrating screen7can preferably have the following features:Screening planes: twoSizes of the screening planes 1,200×3,000 mm.Screening surface of each plane: 3.60 mqPower motorization: 5.5 kw

At this point, the coarse fraction is transferred to an impact mill10wherein it is subjected to a grinding phase and it is subjected to a granulometric reduction (with a reduction ratio of about ⅙-⅛). The more one pushes on crushing, the more effective the separation level is if the objective is not that of re-using the inert as MPS (Secondary Raw Material), a granulometric reduction as high as possible is preferred.

By way of example, the impact mill can be a hammer mill10with the following features:Casing made of properly stiffened sheetInner armour plate made of chromium alloyHammers made of reversible chromium alloySide plates made of steelComplete motorization (motor, belts, pulley and protection carter)Coated discharge caissonSupply ventVibrating feeder complete with suspensionsHydraulic plant for the machine openingComplete with sustaining structureSide ramps complete with hand railsAccess ladder

Downwards of the mill10the crushed material is joined again with the previously separated fine fraction to be subsequently treated in a secondary deferrization phase.

In this secondary deferrization phase, preferably through a vibrating feeder13, the material is fed on a pair of high-efficiency magnetic drums14,15which perform further separation of the ferrous fraction.

By way of example, the vibrating feeder13can have the following features:Plate sizes 1,400×1,500 mm.Two electromechanical vibrators with adjustable massesSuspensions with elastic springsVibrating casing coated with anti-wear materialInstalled power 2×1.5 kw
Still by way of example, the magnetic drums14,15can have the following features:Diameter 300 mm.Drum length 1.400 mm.Constructed with permanent magnets made of Neodymium having high magnetic powerRotating structure made of Stainless steel AISI 304 with cross strips on the surface for iron detachmentRotating support and fixed support for fasteningMotor and reducer

Then, downwards of the magnetic drums the material is supplied, preferably by means of a vibrating feeder16(similar to the first vibrating feeder13), to a separator EMC17which separates, through a system with induced currents, the aluminium portions existing in the material.

By way of example, the induction separator17can have the following features:

Magnetic rotor: diameter 350 mm.—useful width 1.500 mm.—dynamic balancing level G 0.4 (maximum precision level)—keyed and replaceable through shaft—special magnets made of Neodymium, locked mechanically and sealed from the external environment, for a maximum safety and to prevent iron powder from entering and the consequent damage thereof—supplementary protection of the magnetic rotor implemented with cylinder made of stainless steel—outer cylinder made of fiberglass for belt rolling—CONCENTRIC technology—Belt traction roller: steel with biconical turning for the belt self-centring—keyed and replaceable through shaftConveyor belt: PVC material with two antistatic cloths with “Bandebord” for the containment of the materials to be treatedMotorization: for traction of magnetic rotor—for traction of conveyor beltSwitchboard: equipped with two inverters for adjusting the speed of the belt and of the magnetic rotor—emergency system which in case of black-out allows to remove the material present on the belt.

The ashes coming from the pre-treatment phase, preferably, according to the present invention have a composition similar to the one indicated in the following Table 1.

TABLE 1Ideal composition of the ashesNa2OMgOAl2O3SiO2P2O5SO3Cl2OK2OCaOTiO2Fe2O3CuOZnO%2.842.7517.0836.081.230.851.121.0630.211.744.030.450.56

Preferably, the percentage Pc of ashes to be used according to the invention, is between 1% and 40% of the volume of the mixture used for the production of porcelain stoneware.

According to a preferred embodiment, such percentage Pc is between 10% and 30%, still more preferably between 15% and 25%.

Although it is to be meant that the other raw materials (apart from the ashes) which can be used to implement the porcelain stoneware according to the present invention could be evidently selected among those normally and typically used for such purpose, according to a preferred embodiment, raw materials having specific physical/chemical features can be used.

These materials were selected, also among those which can be found on the market, according to the following Table 2:

TABLE 2Raw materialsPercentage inRaw materialthe mixture1Kaolin BG (Industrial Minerals):12-15%2MF/TV (Svimisa)12-15%3Sigillo Clay (Saxa Gres)25-45%4Sasifo Sand (Sibelco)10-16%5Sigillo (Plasticizer clay)6-12%

The producer of the commercial product is shown in brackets, however it is clear that raw materials with similar features could be used. The features of the raw materials shown in Table 1 are illustrated hereinafter.

Kaolin BG

XRF Chemical analysis:%SiO279.5Al2O314.0Fe2O31.40TiO20.15CaO0.05MgO0.10K2O0.25Na2O0.10P.F.4.60S0.08Average grainsize distribution:ClassWeightmm%+20.0620.0-10.01810.0-1.0691.0-0.13−0.14Moisture9%Average mineralogical analysis:%Quartz63Kaolin32feldspars3Other2
MF/TV

[%]CHEMICAL ANALYSISSiO278.5±1.5Al2O311.5±1.0Fe2O30.6maxCaO0.3MgO0.4Na2O2.2-2.5K2O4.2-4.5TiO20.06MnO2TrL.O.I.1.5-1.8CarbonabsentSulphurabsentFIRED PROPERTIESFiring shrinkage[%]10.5-11.5AbsorptionH2O[%]<0.13Colorimetric coordinatesL *65a *3b *81Cooking Cycle[min.]50Temperature[° C.]12302Oven thermal work[° C.]1130MINERALOGY ANALYSIS [%]QUARTZ40ORTHOCLASE35ALBITE12CLAY15OTHER PROPERTIESSupplying humidity (max)[%]10Granulometry[mm]<3.5Resistance to bending (drying)[kg/cm2]20.0Test piece forming pressure[kg/cm2]350Post pressing expansion[%]0.3
SIGILLO CLAY

Oxides%SiO273.60B2O3Al2O313.15Fe2O33.30PbOCaO2.70BaOMgO1.25ZnOK2O2.70Na2O2.30Li2OMnO20.10TiO20.75P2O5TrCalc. Loss2.25Total99.85
SASIFO SAND

SiO2[%]Al2O3[%]Fe2O3[%]K2O [%]Na2O [%]TiO2[%]CaO [%]MgO [%]89.555.880.3652.1301.7090.0850.1900.082

All raw materials belonging to the formulation are dosed in the prefixed portion and carried, for example through a sequence of weighing caissons working continuously, to a grinding compartment. Herein they are finely ground, with granulometry preferably lower than 120 microns.

To this purpose, for example, the “hard” raw materials (for example ashes, Sasifo sand, MF/TV) enter continuously the mill containing ground bodies such as pebbles and/or high-density alumina spheres, from the bottom thereof they come out finely ground, with granulometry preferably lower than 150 microns, preferably lower than 120 μm.

The other “soft” raw materials (for example clays) which do not require energy action, are finely dispersed, for example in a bowl mill.

At this point the two channels of raw materials join again, by forming one single mixture of components, still according to a controlled dosage.

Such mixture is then homogenized, thereafter through a wetting action during the rotation phase they are “granulated” that is brought to a humidity rate between 4% and 8%, preferably around 6%, and made basically spherical or granular to provide a correct evenness, this for example by wetting in bentonite dispersed in water.

At this point the mixture is ready to proceed to the subsequent steps.

The mixture is stored in silos, wherein it can rest and mature. The accumulation in silos further allows to implement a “lung”, that is a reserve of material always available for the subsequent process stages.

After such storage, the process provides a phase for forming the product which can follow two different ways: pressing and extrusion.

The pressing, for example performed with presses SACMI PH 690, consists in carrying the mixture powders within a mould made of hardened steel wherein they are subjected to a pressing with a load comprised between 100 Kg/cmq and 400 Kg/cmq, preferably between 130 Kg/cmq and 250 Kg/cmq, providing the shape to the piece.

For example, for a typical sanpietrino, each piece will have sizes of about 11×11 cm for its tread surface, 8×8 cm for its base surface, and a thickness of about 7 cm. Upon preparing the piece, the shrinkage the product is subjected to during cooking is taken into consideration and therefore that the end product will have sizes of about 10×10 cm for the tread surface, circa 7×7 cm for the base surface and about 6 cm for the average thickness.

Some types of product provide geometrical features and complex shapes, which do not make them suitable to a treatment by pressing.

For example, still by making reference to the sanpietrino, some specific pieces (pavement stone, tiles in 20×20, 20×40, 40×60 format, small cubes 4.5×4.5×4.5) could be required for the construction of particular areas of the paving.

For these pieces, it is preferable to add to the mixture powders taken from the storage silos, previously turbo-dissolved specific clays, which make the mixture more elastic so as to be able to drawing it, that is forcing it through a screw die or extruder wherein the suitable shape and size is provided to the product.

For example, plasticizing clays, such as the same SIGILLO, or even other clays (for example English ball Clay) can be added by 5-12%.

The main extrusion parameters, according to the present invention, are a depression between 65 and 71 mm Hg, and a pressure between 18 and 21 kg/cmq.

In fact, in order to extrude, plasticity or malleability of the mixture (20% of humidity) has to be increased, thereafter a suitable depression is created to remove air and the mixture is forced, by using a screw, through a slit therewith the material assumes the wished shape.

Once come out of the press and/or the extruder, the pieces are positioned on wagons manufactured with materials suitable to withstand the oven's high temperatures.

Within the present invention, it was seen that with ovens having single-layered rollers, traditionally used for the treatment of porcelain stoneware, it would not be possible to cook the pieces sufficiently.

Therefore, according to the present invention, the cooking process takes place preferably in tunnel-like ovens, of the type used for sanitary articles and products for building (bricks and brick tiles).

Then the pieces are conditioned with humidity lower than 1%, preferably lower than 0.7%, still more preferably around 0.5%, thereafter they enter a tunnel-like oven wherein within 6/12 hours they are brought to about 1150° C. and subsequently brought back to low temperature, the whole according to a predefined firing curve.

Generally, a firing curve according to the present invention, is so as to allow to heat the pieces, from an inlet temperature Ti at the oven inlet between 50° C. and 100° C., until a maximum temperature Tm between 1,100° C. and 1,300° C. in a heating time Th between 6 and 10 hours.

Therefore, a cooking time Tc at this maximum pressure Tm between 40 min and 90 minutes is provided.

Subsequently, the pieces are subjected to a controlled cooling to as to bring them back to an outlet temperature Tu from the oven comprised between 100° C. and 200° C. in a cooling time TI comprised between 6 hours and 8 hours.

In all phases of course a punctual control of temperatures is provided, so that the resulting firing curve has no tracts with particularly steep course, and which keeps its course substantially monotonous (increasing, constant, decreasing) in the three main phases (heating, cooking, cooling).

FIG.4shows a preferred example of firing curve according to the present invention, wherein, as it can be seen from the graph, the parameters are the following:

Heating Phase

Ti: ≈70° C.;Tm: ≈1,200° C.;Tr: ≈9 h;
Cooking Phase:Tc: ˜1 h;
Cooling Phase;Tu: ˜120° C.;Ti: ˜7 h.

InFIG.4, the curves of temperature HT are shown at each one of the thermocouples present in the oven. It is evidently to be meant that these curves HT substantially and ideally should be all coincident therebetween.

The curve at the bottom LT is the reading of temperatures below the oven plane, wherein there are materials sensible to high temperatures and then it is required that in these areas the temperature does not increase too much to avoid damages.

At the outlet of the oven a selection phase can be provided to remove in case defective pieces.

At last, the pieces can be packaged before being sent to the warehouse of finished products.

The present invention has been so far described with reference to preferred embodiments thereof. It is to be meant that each one of the technical solutions implemented in the embodiments described herein by way of example, could advantageously be combined differently therebetween, to create other embodiments, belonging to the same inventive core and however all within the protective scope of the herebelow reported claims.