TREATMENT AND ABATEMENT OF SUCH POLLUTANT SUBSTANCES

The invention relates to a device for the treatment of liquid, gaseous and/or solid pollutant substances of various kind, contained into the exhaust smokes, which is so structured as to resolve pollutant complex molecules into not pollutant elementary molecules and substances before the smokes be discharged in the environment, in such a way that to reduce considerably the environment impact.

The invention also relates to a process for the treatment and abatement of such pollutant substances, for obtaining the above mentioned effect.

As it is known, the emission of pollutant substances, produced by various sources, provides for a change of environmental conditions, and first of all of the air quality, which in the long run cause or may cause harmful effects to the health. Generally, the atmospheric pollution is because of combustion processes of substances of various kind, above all during the operation of civil or industrial thermic plants, and the traffic of vehicles powered by explosion engines. Many studies and searches have been effected for treatment of the combustion smokes, in order to reduce or possibly eliminate the emission of pollutant substances in the atmosphere, and this at the present time is obtained with various processes and systems.

The solutions which are currently employed in a wide extent for abatement of the pollutant substances of the combustion smokes are the following.

- Pre-depuration: the main systems employed are the deposition chambers or cyclones and multi- cyclones, in which the treatment of the contained air is obtained by the partial abatement of the pollutant substances contained into the exhaust smokes by means of the gravity force or the inertia force of the particles of the substances contained into the same smokes.

The drawbacks deriving from the use of these systems for abatement of smokes consist in that : - they serve for removing the powdered substances or the rough materials only, therefore the efficiency of such abatement systems depends on the type of pollutant substance being treated ;

- the operation of these systems require necessarily the presence of other depuration systems connected to the abatement system employed from time to time ;

- textile filtration : abatement system which is realized by letting the air flow to pass through some filters constituted by textile fiber of various kind ;

The drawbacks deriving from the use of these systems for abatement of smokes consist in that :

- they aren't suitable for each type of powdered substances (no adhesive powders or liquids) ;

- they may be used for the treatment of smokes with low temperatures only (about max. 140° C), and which cannot be used on to powders, gases and combustible steams.

- Electrostatic precipitation : process which utilizes a high voltage electric field for loading the solid or liquid particles of the pollutant substances being deposited by electrostatic attraction on to the electrode, from which they are then removed ;

The drawbacks deriving from the use of these systems for abatement of smokes consist in that :

- to require necessarily periodical checking for the maintenance for possible mechanical or electrical problems ;

- not suitable for being utilized for powders of the pollutant substances with low resistivity ;

- to require low operation temperatures (max. 270°C) ;

- to be much expensive.

- Wet abatement : this kind of process, also called washing process, foresees the removal of the pollutant substances into a gaseous flow by means of the action of a liquid, normally the water.

The drawbacks deriving from the use of these systems for abatement of smokes consist in that :

- the particulate must have low concentrations ;

- a production of muds and waste liquids is determined, which can be disposed of with difficulty.

There are also existing further systems and processes specialized for abatement of more pollutant factors, consisting in :

- Plasma torches : they consist of systems for abatement of smokes which utilize the very high temperature (up to over 6000° C) reached by some materials, usually gas like argon and air, when they found themselves at the plasma state, for reducing the residual particles of smokes at the elementary state ;

The drawbacks deriving from the use of these systems for abatement of smokes consist in that :

- to be little used owing to the very high costs of the plants and the operation thereof ;

- they provide for the production of NO x and a strong volatility of the pollutant elements into the smokes ;

- to be able to be used for the plants having reduced overall dimensions only ;

- to require a continuous maintenance, which cannot be sustained owing to the quick consumption of the electrodes (after about 400 hours of continuous work).

- Catalytic ceramic post-heaters : these systems for abatement of smokes use the thermal oxidation at high temperature for transforming the component parts of the pollutant substances, by exploiting the presence of a catalyst.

The drawbacks deriving from the use of these systems for abatement of smokes consist in :

- the high cost of the catalyst ;

- the impossibility to work at high temperatures ;

- not optimal efficiencies, relative to the physical and mechanical wearing of the catalyst ;

- they are not suitable for abatement of all the types of pollutant composed substances.

- Catalytic conversion : such a process consists to the fact to promote, by means of a proper sponge of catalytic material, the conversion of the unburnt hydrocarbons, the nitrogen oxides, and the carbon monoxide into the carbon dioxides, water and nitrogen ; such an abatement system is utilized into the catalytic mufflers for reducing as much as possible the quantity of the above mentioned substances into the exhaust gases.

The drawbacks deriving from these systems for abatement of smokes consist in that :

- they are rather ineffective during the first minutes of operation of the car (the system operates correctly when a temperature between 300 ° C and 900 ° C is reached) ;

- they are scarcely effective during the acceleration and deceleration steps (the air/fuel ratio is variable too fast) ;

- the catalyst may deteriorate itself in the course of time because of the presence in the exhaust gases of small quantities of sulphur and lead ;

- the 80-90% of the pollutant substances are at the utmost eliminated.

- Condensation: in this process for abatement of smokes the steams of the pollutant substances are removed by changing their physical state from gaseous to liquid, with a pressure increase and/or a temperature reduction.

The drawbacks deriving from these systems for abatement of smokes consist in that :

- to be limited to processes of organic nature ;

- the most part of the applications requires additional abatement systems ;

- the more stressed parts of these systems may be subjected to erosion or incrustation ;

- they are needed periodical normal maintenance and cleaning operations.

- Biological filtration : this process for abatement of smokes exploits the biological oxidation, in that the polluted air is lets to pass through a means into which some micro-organisms are present, which are suitable for decomposing the pollutant substances, by utilizing these latter as nourishing source for such micro-organisms.

The drawbacks deriving from the use of these systems for abatement of smokes consist in that : - to require specific and accurate designs for being utilized in an optimal way ; - a complex management of the biological filters ;

- the possibility to utilize such systems solely with air flows with low concentration of pollutant substances ;

- they aren't suitable for being utilized with smoke flows into which toxic substances for the micro-organisms are present ;

- to require a frequent monitoring for keeping a satisfying efficiency.

From what it has been specified, it is to point out that the currently used systems for abatement of smokes involve a series of functional drawbacks, consisting in that :

- to require high costs for the operation and the maintenance or the renewal of the plants, which do not allow a spreading on a large extent thereof ;

- to require high costs for some of the plant component parts ;

- not to be suitable for the abatement of all the types of pollutant substances ;

J to be suitable to operate with limited utilization temperatures only ;

- to produce, in some cases, other pollutant substances.

The object of the present invention is to realize an innovative device for abatement of liquid, gaseous and/or solid pollutant substances contained into the exhaust smokes, which may be spread on a large extent, with limited expenses, and which allows to obtain a considerable energetic saving and allows the sure abatement of a high percentage of the pollutant

substances of smokes, on the complete spectrum of the same pollutant substances.

The object of the invention is also to make available a process for the treatment of abatement of such pollutant substances, for obtaining the above described purposes.

The invention will be better understood by the following description, given by way of a not limiting example only, of the constructive and functional characteristics of the device

referred to, and of the steps of the above described process for the treatment of abatement, with particular reference to the attached drawings, in which : Figure 1 shows a schematic perspective front view of the device for abatement of smokes in accordance to the present invention, and the different component parts thereof ;

Figure 2 shows a perspective front view of one of the component parts of the device of the Figure 1 , separated from the other component parts of the same device ;

Figure 3 shows a perspective view from below of the component part of the Figure 2 ;

Figure 4 shows a perspective view from below of a portion of the component part of the Fig. 3 ; Figure 5 shows a longitudinally cutaway view of the component part of the Fig. 2, with its internal component parts ;

Figure 6 shows a schematic front view of the back part of another component part of the device for abatement of smokes of the Fig. 1 ;

Figure 7 shows a perspective front view of the component part of the Fig. 6 ;

Figure 8 shows a perspective front view cutaway in a longitudinal direction of the component part of the Fig. 6 ;

Figures 9a and 9b show schematically the interaction among dipoles of molecules of

materials, respectively in absence of an external electromagnetic field, and in presence of an external electromagnetic field, generated by microwaves, for obtaining the heating of materials for xhe effect of the microwaves in accordance to a first physical principle ;

Figures 10a and 10b show schematically an atom of material respectively in absence of an external electromagnetic field, and in presence of an external electromagnetic field, like that generated by the microwaves, for obtaining the heating of the material referred to for the effect of the microwaves, according to a second physical principle ;

Figure 1 1 shows the diagram temperature/heating time in presence of the microwaves of some of the materials which may be used in the device according to the invention ;

Figure 12 shows a longitudinally cutaway and enlarged view of the component part of the Fig. 5, with its internal component parts, with the path of a microwave passing through said internal component parts, and the physical effects which are determined along the entire path of such a microwave.

The invention relates to a device for abatement of liquid, gaseous and/o solid pollutant substances of various kind, which are contained into the exhaust smokes deriving from the combustion processes of pollutant substances, produced by various sources, and in particular but not exclusively in the case of use of civil or industrial thermic plants, and the traffic of vehicles powered by explosion engines. This abatement device will be described in detail in the following Figures, together with the process for the treatment and abatement of the pollutant substances, and to the different steps of this process. Such a device being adapted for resolving the most part of the pollutant complex molecules into elementary and not pollutant molecules and substances before the smokes be discharged into the environment, in a way that they may be discharged in the environment without determining the pollution thereof.

The physical process with which the resolving of the pollutant substances into single not pollutant component substances are obtained is the thermal dissociation, in which the breaking of a complex molecule into more simple molecules, or of a compound into other compounds or quite into its constituting parts is obtained by heating at high temperatures (usually greater than 160C ° C) of the exhaust smokes containing the pollutant substances of various kind.

Such a dissociation, which occurs by absorbing heat, is represented like a homogeneous or heterogeneous chemical reaction, the balance of which is changed in the sense to active the decomposition when the temperature increases. The temperature to which such a process occurs depends on the compound or the molecule referred to, but usually it is too high.

Examples of forming and consequently decomposition of some molecules of pollutant gases : - NOx : nitrogen oxides, where "x is utilized for identifying in a generic way all the nitrogen oxides, therefore it indicates the different number which can be present of atoms of nitrogen and oxygen bonded to each other. The nitrogen oxides which have been checked during a combustion are mainly the nitrogen monoxide (NO) and the nitrogen dioxide (N02).

During the combustion, the nitrogen N2 and the oxygen 02 react to each other at high temperature, by forming the nitrogen monoxide which, in turn, by oxidizing itself forms the nitrogen dioxide in accordance to the following relations :

N2 + 02 → 2N0

2ΝΌ+ 02*-»"2N02

At the high temperatures, usually over 1600 °C, the molecules of nitrogen (N2) and oxygen (02) dissociate themselves into their atomic states. In order to achieve a good decomposition, therefore, the temperatures and the times must be checked, in a manner that an excessive production of NO during the heating and an excessive production of N02 during the cooling be avoided.

In fact, the quantities of NO depend on :

- combustion temperature : the higher the combustion temperature and the greater the production of NO ;

- persistence time at such temperatures of the combustion gases : the greater the persistence time the higher the production of NO ;

- quantity of free oxygen contained in the flame : the more limited the excess of the combustion air, the lower the production of NO with respect to the production of CO.

On the contrary, the production of N02 increases with the temperature decrease, therefore during cooling of smokes. Such a production is proportional to the concentration of 02 and to the square of the concentration of NO. The slower the cooling, the greater the production of N02. Since the solutions employed for the abatement of the pollutant substances have been already considered, it is therefore now proposed a schema summarizing the solutions currently used specifically for reducing the emissions of NOx, and which are distinguished in : 1. PRIMARY TECHNICS (used for reducing the NOx during the combustion)

- Flame cooling : the water or steam are injected into the combustion chamber, which use the thermic energy for evaporating or overheating, with the result to lower the flame temperature and consequently to reduce the production of NOx.

- Combustion at steps : a combustion is obtained (the temperature of which is lower than the flame adiabatic temperature) by letting some steam generating tubes to pass in the interior of the combustion chamber, which tubes absorb some heat from the reaction

(heat extraction step), by lowering the temperature (1027 ⁰ C).

After such a step, a reheating is realized in which, by adding the remaining part of

combustible, another combustion is started for reaching again the stoichiometric

conditions.

2. SECONDARY TECHNICS (used for reducing the NOx before the smokes are coming out from the plant) : they consist mainly in the injection into the flow of burnt gases of ammonia, urea or other compounds suitable for reacting with the NOx, for promoting the reducing effects.

- Selective not catalytic reduction : process based upon the selective reduction, by the ammonia or the urea, of the nitrogen oxides in absence of catalysts and therefore it

occurs at high temperatures (from 850 ° C to 1 100 ⁰ C).

- Selective catalytic reduction : process based upon the selective reduction, by the ammonia or the urea, of the nitrogen oxides in presence of a catalyst. The reduction of the NOx occurs on to the surface of the catalyst at a temperature comprised from 320 °C and 400 ° C.

- S02 : the generation of SO 2 is strictly correlated to the content of sulphur in the combustible being used. The production of SO 2 is formed by the combustion of the sulphur with air in accordance to the following process :

S + 02— ^► S02 It decomposes itself, over the 2000° C, in S and S03, SO and O :

S02—► SO + O

2S02— S03 + SO

3S02— 2S03 + S

By referring to the Fig. 1 , it is now described synthetically the device for abatement of the liquid, gaseous and/or solid pollutant substances of various kind contained into the exhaust smokes, and the different component parts of the same device. Such a device is constituted substantially by the following main component parts :

- heating module 5, through which the exhaust smokes containing the pollutant substances to be abated are let to pass, and in the interior of which there are installed the component elements which will oe described, so shaped as for producing internal temperatures of the module 5 which are typically from about 1200 ° C up to about 2200 ⁰ C, and which determine the heating of smokes at these temperatures, in order to dissociate at the most wide extent and in the manner and with the physical phenomena which will be described the molecules of the different compounds constituting such pollutant substances , in order to let coming out from the module the smokes containing a high percentage of single not pollutant component substances, which could so be discharged afterwards in the environment ;

- module 6 for partial recovering of the exhaust smokes, connected to the heating module 5 and adapted to recover partially the purified smokes that are coming out from such a heating module 5, in the manner and for the functions that will be described;

- flue 7 enclosing the heating module 5 and the module 6 for partially recovering of smokes, and shaped as it will be described, which is connected with its inlet to the combustion chamber 8 of the pollutant products through a conduit 9 and is provided for conveying and discharging in the outer environment the smokes coming out from the heating 5 and the module 6 for partial recovering of the smokes. All the component parts of the device illustrated in the Fig. 1 will be ) described in detail later on, after the description of the arrangement of the heating module 5 and the module 6 for partial recovering of smokes.

Turning now to the Figs. 1 -4, in which the structural configuration of the heating module 5 is shown, it is noted that it is substantially constituted by a lengthened container 10 comprising an outer envelope Π preferably of cylindrical shape, but which may be shaped also with otker geometrical shapes, which is made of a not magnetic metallic material, withstanding the high temperatures and impermeable to the microwaves and delimiting an inner chamber, multi-modal or with dimensions greater than the electromagnetic wave spreading inside thereof (not indicated in the Figures), which chamber is suitable for containing the component parts which will be described. As metallic material it may be utilized advantageously but not exclusively the stainless steel AiSI 304. The metallic outer envelope 1 i is closed at its lower end portion by a flat closing disc 12 preferably of circular shape, which is also made of mechanically withstanding metallic material and impermeable to the microwaves, which may be of the same type of material of the outer envelope i i, said disc 12 being joined seaiingly with a short vertical cylindrical sleeve 13 directed downward, also of metallic material having the same characteristics of the preceding metallic materials, which is bored axially and internally for its entire length for communicating with said inner chamber.

The vertical sleeve 13 is welded at its lower end portion with a flat joining flange 14, in the example shaped of circular form and made of mechanically withstanding metallic material, suitable for withstanding the high temperatures for the contact with the gases deriving from the combustion and stable at the high temperatures, in turn, the joining flange 14 is provided with a central through hole Ί 5 coinciding with the hole (not indicated) of the sleeve 13 and is screwed on and fixed to a correspondent component part of the flue 7, as it will be described. The metallic outer envelope 11 ;s closed at its opposite end portion, from which the smokes are coming out ana passing, which smokes are directed toward the module 6 for partial recovery of smokes (in this case, the upper end portion), in the same way of the lower end portion namely with a flat closing disc 16 preferably of circular shape, which is joined sealingly with a short vertical cylindrical sleeve 17 directed upward, which sleeve is welded at its upper end portion with a flat joining flange 18, in the example of circular shape, which is secured sealingly with the inlet end portion of the module 6 for partial recovering of smokes as it will be described. Also in this case, the upper closing disc 16 and the vertical sleeve 17 are made of the same material and shaped in the same manner of the correspondent elements of the lower end portion of the outer envelope 11.

By referring now to the Fig. 5, in which it is shown the inner chamber 19 (multi-modal or having dimensions greater than the electromagnetic wave spreading therein) of the outer envelope 11 of the heating module 5, it is noted that the same is delimited by a lengthened internal cylindrical container 20 made of mechanically withstanding metallic material and impermeable to t e microwaves, which may be constituted for example by stainless steel AISI 304 or other suitable material with these characteristics, such an internal container being shaped with a vertical peripheral wall 21 having the same length and smaller diameter with respect to the outer envelope 11, which peripheral wall is joined at its end portions by a lower disc 22 and an upper disc 23, and these elements are housed in a way that between the outer envelope 11 and the internal container 20 a free space be defined, into which an insulating material 24 be inserted, which covers all the internal peripheral surface of the outer envelope 11 and all the external peripheral surface of the lengthened container 20. Such an insulating material 24 may be constituted for example of mineral wool or other suitable thermic insulating material withstanding the high temperatures.

In the central zone of the lengthened internal container 20 there are housed and secured one or more lengthened vertical rectilinear tubes 25, through the inner cavity of which the smokes containing the pollutant substances are let to circulate, and such tubes are made of the

32 material and for performing the function which will be described later on.

In the example referred to, there are provided three lengthened tubes 25 which, as visible from the Fig. 4, are at physical contact with the outer surface of their walls 26, for allowing a thermic transmission among all the tubes. In the space comprised among the vertical tubes 25 and the outer surfaces of the walls 26 of all the tubes 25 it is inserted an internal insulating material 27 for the entire height of the same tubes, which material fully covers all the outer surfaces of the walls 26 of the same tubes, and the surfaces of the lower and upper end portions of such an internal insulating material 27 are covered by a respective plug 28 and 29 o the same insulating material, which is secured on to the same surfaces, and is bored for permitting the passage of smokes in the interior and is joined sealingly at the lower side with the underlying sleeve 13 and at the upper side with the overlying sleeve 17, and said vertical tubes 25 are extended from the plug 28 to ihe plug 29.

Such an internal insulating material 27 is a not-organic material or of any other type, suitable to withstand temperatures comprised between - 50° C and 3000 ⁰ C, with characteristics of radio-transparency to the frequencies comprised between 0,2 GHz and 5 GHz, therefore to the microwaves frequencies, to have a high mechanical strength, a capacity to be machined and to withstand the contact with the smokes deri ing from the combustion reaction and submitted to processes of thermal, physical and chemical type as well as to pyrolysis phenomena, in the interior of the hollow tubes 25.

An example of insulating material which may be utilized is constituted by a product made with polycrystalline fibers having a high content of alumina, which is mixed with the not- organic binders and withstands i6G0 ⁰ C. For measuring the temperature of the internal chamber 19 of the heating module 5 there are provided preferably two optical pyrometers (not indicated), fixed in the interior of such a chamber 19 in two positions offset to each other in the vertical direction and entering the chamber through correspondent through holes 30, provided in positions coincident to each other through the outer envelope 11, the vertical peripheral wall 21, and the insulating materials 24 and 27, of which the relative optical part is visible from outside, and which are electrically connected to a control central station (not shown) connected to the electric circuit of the present device, in order to detect steadily the internal temperature of the heating module 5.

Such a heating module 5 is also provided with a plurality of through openings 31 provided through the outer envelope 11 and the vertical peripheral wall 21, in positions coinciding to each other, which through openings are aligned and adequately spaced away from each other in the vertical direction, and in the Figures such through openings 31 are for example in the number of 4, but of course they may be made also with different numbers thereof.

As visible from the Fig. 2, such through openings 31 are communicating with at least a relative microwave generator 32 (magnetron), through correspondent waveguides 33 connected sealingly between the microwave generator 32 and the through openings 31, in such a way that the microwaves generated by the generator 32 be distributed, directed and let to interfere with the material constituting the vertical tubes 25, for obtaining the effects which will be described hereinafter. The microwaves generated by the generator 32 may be transmitted to the vertical tubes 25 even in different manners with respect to what just specified, thus without departing from the protection sphere of the present invention.

The microwave generator 32 is of per se known type and is disposed externally the outer envelope 11 and enclosed by an outer casing (not indicated), together with all the component parts of the present device for abatement of the pollutant substances.

Such a microwave generator may be regulated in such a way as to generate microwaves with a power comprised preferably between 200 W and 20000 W.

There may be provided also more microwave generating sources, in a number multiple of one, each one having the same above described output. Now, there are described the causes for obtaining the heating of the material for effect of the microwaves, and this in order to explain how the pollutant smokes circulating through the present device are abated in large extent in presence of the microwaves. A first cause is produced by the interaction among the dipoles contained into a material, wherein, as it is known, the dipoles are pairs of particles with opposed electric charge, that is positive and negative, contained in ^~ o a material, in this case, the produced thermic effect is a consequence of the interaction dipole-dipole among the molecules of the material in presence of an electromagnetic field, like the one generated by the microwaves. With particular reference to Fig. 9, it is shown how this theimic effect produced by the interaction among dipoles is revealed. In particular, in the Fig. 9a there are schematically shown various dipoles 34 contained into a material. Such dipoles 34 are oriented at random, no orientation direction is privileged, in absence of one alternate electric filed, such as for example the one produced by the microwaves acting on to the material referred to.

On the contrary, in the F ig. 9b, it is noted that the presence of an alternate electric field, such as for example the one produced by the microwaves, acting on to the same material, the dipoles 34 change orientation at each alternance of the alternate electric field. If the electric field is of the high frequency type (for example, of 2,45 GHz), in presence of microwaves, such an alternate electric field 35 induces an agitation and an inteimoiecular friction (and therefore among the various dipoles 34), with consequent production of heating and therefore the emission of infrared rays. A second cause of production of heating is produced by the physical phenomenon of the dielectric relaxation, in the Fig. 10 it is schematically noted the internal nucleus 36 of an atom of a material (having positive charge) and the electrons rotating around the nucleus 36 (having negative charge), which are schematically represented as a "cloud" of electrons rotating around an orbit 37. In such a case, in aosence of an alternate electric field, thus in the balanced condition, the electronic "cloud" is distributed along the orbit 37 equally around the nucleus 36. In presence of an alternate electric field, such as for example the one produced by the microwaves interacting with the same material, the electronic "cloud" rotating around the orbit 37 is deformed and is moved (see Fig. 10b), for example as it is illustrated in this Figure, with the consequent origin of a polarization that will reach the maximum deformation when the perturbation produced by the alternate electric field will reach the maximum level. By reducing the intensity of such a perturbation, such an electronic "cloud" will tend to reach again its balanced condition, as above described, and under this circumstance the return to the balanced condition of the same electronic "cloud" involves the releasing of heat and therefore the generation of infrared radiations.

The more the temperature to which a material is submitted is high, the greater is the ray of the orbit 37 of the electronic "cloud" and, consequently, it is simpler to deform the same orbit. An additional cause of production of the heating is determined by the Joule effect, in which into a semi-conductor material exposed to an electric field there are induced displacements of electric charges, with consequent releasing of heat for the Joule effect.

Now, if the device according to the present invention is considered, the microwaves generated by the magnetron 32 are directed against the surface of the lengthened tubes 25, housed into the heating module 5 and crossed by the smokes containing the pollutant substances and constituted by the so-called acceptor material, and the energy flow of such microwaves arriving on to the surface of such lengthened tubes 25 in tne time unit and on to the surface unit of this acceptor material is reflected in part (reflecting capacity) in to the direction opposite to the one where the microwaves are arriving, in part it is absorbed by the acceptor material of said lengthened tubes 25 (absorbing capacity), and in part passes through the wall of the same acceptor material (semi- transparent capacity).

The absorbing capacity of the acceptor material of the lengthened tubes 25 depends on the physical characteristics of the incident radiation (and therefore of the microwaves) and the nature of the same acceptor material.

In the Fig. 11 it is illustrated a diagram temperature/time of heating in presence of the

microwaves of some materials that may be used as acceptor materials, that is materials that keep and absorb the microwaves energy, for realizing the lengthened tubes 25 for smokes circulation of the present device. As acceptor material there have been selected the silicon carbide (SiC) and the zirconia, that is zirconium oxide (Zr02), that have revealed to be good acceptor materials, and the characteristics of these materials are compared with the ones of a refractory material, like alumina (A1203 ). The diagram has been obtained with the following conditions: frequency f of the microwaves = 2,45 GHz , density mass of the materials p : Zr02 = 2520 Kg/m ³ , A1203 = 1 88 Kg/m ³ : SiC = 965 Kg m ³ , thickness of the materials d : Zr02 = 7,5 mm., A1203 = 12,5 mm., SiC = 10 mm..

From the diagram it is noted that the silicon carbide shows a rapid increase of the heating temperature in a short time and, when it reaches a determined temperature (about 1000° C), it maintains itself almost at the same temperature for a long heating time, whereas on the contrary the zirconia ard the alumina don't show a rapid starting increase of the temperature and, anyway, after a certain heating time, the zirconia shows a rapid increase of the temperature, that exceeds the one of the silicon carbide at. the high temperatures, however such heating time is longer than that of the silicon carbide. On the contrary, the alumina shows only a reduced increase of the temperature during the heating time, since this material has a low absorption of the microwaves, being it a refractory material. From the comparison of the measured values, it has been observed how the silicon carbide must be considered the more suitable material for being used as acceptor material, for the greater capacity to absorb the microwaves and, therefore, for the quicker increase of its temperature. Consequently, the lengthened tubes 25 of the present device are preferably made of this latter kind of material, but this doesn't exclude that also the zirconia might be used for the same aim. Such a silicon carbide, which is a ceramic material that behaves almost like a diamond, has also the following advantageous characteristics: Low density, high hardness, high modulus of elasticity, high thermal conductivity, low linear expansion coefficient, maximum operating temperature in to inert gas of 1800° C, excellent withstand to thermal shocks, resistance to corrosion and wear also to high temperatures, toxicologically safe, good sliding properties, extreme resistance to acids and bases.

Now, referring to Fig. 12, it is shown a longitudinally cutaway and enlarged vie w of a part of the inner chamber 19 of the heating module 5, delimited by the peripheral upright wall 21, with the internal component parts thereof comprising the internal insulating material 27, and two lengthened tubes 25 with the peripheral wall 26, of which the walls 26 of two tubes are into contact to each other, and wherein the internal cavity crossed by the smokes of each tube is marked with 38. In this view, it is also shown the internal path of a microwave generated by the magnetron 32 and passing in sequence through the internal insulating material 27, the peripheral wall 26 of the first tube 25, the internal cavity 38 of the first tube 25, the two peripheral walls 26 into contact to each other of the first and the second tube 25, the internal cavity 38 of the second tube 25, and the internal insulating material 27, which microwave is then reflected by the metallic material of the subsequent peripheral upright wall 26, along a path 39 tcward the upright wall 21. This graph serves to explain the physical effects that are determined along the microwave path, and that involves a consistent abatement of the pollutant substances of the smokes circulating through the lengthened tubes 25. As visible from the left to the right side, the microwave passes at first directly through the internal insulating material 27 along a first path 40, then it comes into contact with the external surface of the peripheral wall 26 of the first tube 25, and in this position a first part of the microwave is reflected by such a wall 26 toward the insulating material 27. A second part of this microwave passes through the peripheral wall 26 of the first lengthened tube 25, along a path marked 41, and is absorbed by the acceptor material (in the example referred to, the silicon carbide) of the above tube by generating an infrared radiation 42 (therefore a heating) into the internal insulating material 27, that is inhibited by the same material, by restricting the heat on the external wall 26, and an infrared radiation 43 (therefore a heating) that is irradiated into the internal cavity 38 of the same tube. Under this circumstance, the hot smokes circulating through the internal cavity 38 of this tube and directed toward the exhaust, in the ascending direction A, are further heated by such an infrared radiation, by increasing their temperature. A third part of this microwave is transmitted by the acceptor material of the first lengthened tube 25, because of its semi-transparent capacity, and comes out from the internal surface of the peripheral wall 26 of the tube 25, by passing directly through the internal cavity 38 of said tube, along a second path 44, by arriving into contact with the internal surface of the other portion of peripheral wall 26 of the same tube, and in this position a first part of the microwave is reflected by such a wall 26 toward the previous wall, and from this latter is reflected again toward the internal surface of the other portion of peripheral wall 26, thereby determining multiple reflections of the microwave between these two internal walls. In turn, a second part of the microwave is, like previously, absorbed by the acceptor material of this tube, by generating an infrared radiation (therefore a heating) that is irradiated in part through this portion of peripheral wall 26 and in part (marked with 45) into the internal cavity of the same tube. Aiso in this case, therefore, the circulating hot smokes are further heated by this additional infrared radiation, by increasing further on their temperature, while the microwave energy still decreases. By prosecuting to describe the path of the microwave referred to, it is noted that it passes through both the peripheral wall 26 of this first tube and through the peripheral wall 26 of the second tube, which walls are into close contact to each other, and the path of the microwave through the two peripheral walls into contact to each other is marked with 46. Consequently, the passage of the microwave through the second tube determines the same above described effects that are determined into the first mbe 25, namely an infrared radiation irradiatea in part through the peripheral wall 26 of the second tube 25, and in part (marked with 47) through the internal cavity 38 of the second tube 25, thereafter the microwave passes directly through the internal cavity 38 of said second tube, along a third path 48, and a first part of the microwave is reflected by the other portion of wall 26 of the second tube toward the previous peripheral wall 26, with consequent multiple reflections of such a part of microwave between the internal walls of the second tube. So, also in this case a second part of the microwave is absorbed by the acceptor material of the tube, along the path 49, by generating an infrared radiation (marked with 50) that is irradiated into the internal cavity 38 of said second tube. As a consequence, an additional heating of hot smokes is still determined into the second tube 25 by the so generated infrared radiation. By prosecuting its progress on to the path 49 through the other portion of wall 26 of the second tube 25, as explained, the microwave is absorbed by the acceptor material by generating also an infrared radiation marked with 51 (therefore a heating), that is irradiated toward the subsequent insulating material 27, where such an infrared radiation is inhibited by the same material, by restricting the heat on the external wall 26. Finally, a third part of microwave is transmitted and prosecutes along the path 52, defined by the thickness of the insulating material 27, and is directed against the metallic material of the peripheral upright wall 21 of the internal container 20, where the microwave is reflected toward the portion of wall 26 of the second tube, along an additional path 53, by passing through the insulating material 27. When the microwave comes into contact with the portion of wall 26 of the second tube, it is absorbed again by the acceptor material of the same wall, by generating also here an infrared radiation, that is irradiated in part (marked with 54) toward the insulating material 27, where such an infrared radiation is inhibited by the same material, by restricting the heat on the external wall 26. Finally, the microwave still passes through said portion of wall 26, along the path 55, being partially absorbed by it, by generating also here an infrared radiation, that is irradiated in part (marked with 56) through the internal cavity 38 of the second tube 25, thereby producing an additional heating of the smokes circulating through the internal cavity. In this manner, by passing as described through all the cited component parts of the imer chamber 19, the microwave energy gradually decreases and determines, at the one hand a considerable increase of temperature of the smokes circulating through both tubes 25 and at the other hand it determines, because of the repeated reflections of the same microwave through the internal cavities 38 of the relative tubes and its contact with the high temperatures, with the different unhomogeneities and densities of the gases contained into the circulating smokes, some energy the peaks of the microwaves (so-called hot spots) that aren't distributed in an orderly and homogenous manner into these internal cavities, but are surprisingly distributed randomly and in variable and different positions into the same internal cavities. As a consequence, by dimensioning opportunely both the characteristics (power, intensity, frequency, etc.) of the microwaves, that are directed into the internal cavity 19, and the size and the quality of the acceptor material of the tubes, it is possible that the so generated and randomly distributed hot spots into the above internal cavities might attain very high temperatures, also in the range comprised oetween about 1200° C and about 2600° C, that are sufficient to provide for heating the circulating smokes at these very high temperatures, and to dissociate the molecuies of the different compounds constituting the pollutant substances of the smokes, in order to let coming out from the present heating module 5 the smokes containing a high percentage of single not- pollutant component substances, that may therefore be discharged subsequently in the environment by reducing considerably the pollution thereof.

In the above description of the path of a microwave through the internal canity 19 of the heating moduie 5, reference has been made to one microwave only, but such a description of course refers also to all the microwaves generated by the magnetron 32 passing through the above described two lengthened tubes 25, as in fact it occurs in the practice. Furthermore, the microwaves generated by one or more magnetron 32 arranged as visible in the Figures, are directed also through any other lengthened tube secured into the inner chamber 19, in the present example in the third provided tube and visible in ±e Fig. 4, which pass through the relative tubes along analogous paths, for obtaining the abatement of the smokes circulating through the correspondent tubes with the same above described effects.

There are now described some examples of smokes that may be produced with some types of combustibles with excess of air, as it normally nappens in the practice, which smokes may contain, in addition to the same excess of air, some pollutant substances to be abated with the device and the process of the present invention.

- Methane (gaseous fuel) :

Into the smoke there are present H20 (in the form of steam or atomized), C02, 02, N2, nitrogen oxides (NOx, where 'x' is used for identify in a generic way all the nitrogen oxides, therefore it indicates the different number that may be present of atoms of nitrogen bound in various manner to atoms of oxygen) and particulates.

- Combustible oil or diesel (liquid fuels):

Into the smoke there are present H20 (in the form of steam or atomized), C02, O2, N2, nitrogen oxides (NOx), sulphur oxides (Sox, such initials identify the family of sulphur oxides, SO, S2O2, SO2 ; they depend on the contents of sulphur into the fuel) and particulates.

- Biomasses (solid fuel):

Into the smoke there are present H2O (in the form of steam or atomized), CO2, CO, 02, N2, nitrogen oxides (NOx), sulphur oxides (Sox) and particulates.

Fundamentally, the biomass produces particulates because the physical characteristics of a piece of wood or of a single pellet are such as to make tie combustion more difficult than the one cf the other traditional fuels (liquids like diesel or gaseous like methane gas). By simplifying a process that is rather complex, a difficult combustion determines the presence of a high number of unburnt carbon particles, to which there are added all the volatile components being released during the various combustion steps and that, by co»densing around solid micro particles, increase further the particulates mass.

Even the liquid and gaseous fuels may produce, therefore, particulates or CO, this will depend by the type of fuel, by the technology and the mode of managing the plant.

Temperatures of the smokes:

The temperature of the smokes depends on the plant capacities. Approximately, for a medium sized plant, the temperatures of the smokes for the various fuels are:

- methane gas: 100°C-150°C :

- combustible oil: 200°C-250°C :

- diesel: 160°C-220°C ;

- wood/pellet fuel: 250°C-300°C .

By referring to the Fig. 1 again, it is noted that the flue 7 is shaped large and long for housing the heating module 5 and the module 6 for partial recovering of smokes connected to each other, arranged in vertical position and secured opportunely into the inner chamber 57 of the flue 7. Such a flue 7 is shaped with a closed and inclined circular lower wall, having inclinations 58 and 59 which are symmetrical to each other, the lower part of which is joined to the conduit 9 of the combustion chamber 8, and the upper part of which is joined to the cylindrical outer wall 60 of the flue 7. The upper part of the flue 7 is also shaped with an inclined circular upper wall, having inclinations 61 and 62 symmetrical to each other and opposite to those of the lower wall, and in the upper wall it is provided the upper opening 63 of the flue 7, from which the smokes purified at a large extent from the pollutant substances into the heating module 5 are coming out, which smokes pass also through the module 6 for partial recovering of the same smokes, and circulate upward in the direction A. Such smokes are produced, as already described, into the combustion chamber 8 and, by passing through the conduit 9, are conveyed in the interior of the heating module 5 through an inclined opened circular wall, having inclinations 64 and 65 symmetrical to each other, which wall is joined on its upper part to a portion of conduit 66 of cylindrical shape, the upper part of which is shaped for being screwed on and secured to the correspondent joining flange 14 of the inlet of the heating module 5.

The heating module 5 has a natural draught, therefore in this case it is obtained a self-regulating system. If the module 5 doesn't operate, the smokes pass without being treated both in the interior and outside the same module. If the module 5 is operating, a natural draught will take place, that will let to pass only the smokes that can be treated, without producing obstructions in the flue 7.

Finally, as visible in the Fig. 1, and in detail in the Figs. 6, 7 and 8, the module 6 for partial recovering of the smokes is substantially constituted by a short cylindrical conduit 67, to the free end portion of which it is fixed a tight flat circular flange 68, shaped for being screwed on and secured to the correspondent flat joining flange 18 of the heating module 5, in a manner to join the two above described modules 5 and 6, and to allow the passage of the smokes coming out from the heating module 5 toward the internal cavity of the such cylindrical conduit 67. In turn, the other end portion of the conduit 67 is joined to a correspondent end portion of an internally hollow short frusto-conical portion 69, which is enlarged gradually in the longitudinal direction of the module 6, up to its other end portion with the maximum width, that is joined with one end portion of a lengthened cylindrical conduit 70, enclosing a correspondent lengthened central body 7 ^" . secured to its interior, which is shaped preferably with a cylindrical shape and is provided with a set of horizontal through tubes 72 separated to each other and provided through the central body 71 and in the longitudinal direction of the same, suitable for the passage of the smokes, such tube being extended for the entire length of the lengthened conduit 70 and the central b ody 71, up to the opened end portion 73 of this latter, which is situated in an approached position and correspondent to the one of the through opening 63 of the flue 7, for discharging the smokes. The smokes arriving from the heating module 5, into which they are depurated with large extent from the pollutant substances, are iet to circulate through such internal tubes 72, of which an end portion is communicating with the internal cavities of the cylindrical conduit 67 and the frusto-CDnical portion 69, in a way that the smokes circulating through such internal tubes 72 are then discharged in part through said upper through opening 63 and in part are recovered as it will be described. Along the cylindrical conduit 67 there are provided two through holes 1 ^L approached to each other, for inserting and fixing some per se known sensors (not indicated), which are calibrated for detecting the parameters relating to the circulating smokes, and in particular the flow rate, the temperature and the composition of smokes entering the module 6 for partial recovering smokes, after having passed through the heating module 5. As flow rate sensor it may be utilized for example a measuring instrument for the differential pressure. As sensor for temperature and composition of smokes it may be utilized for example a per se known smoke analyzer of professional type. In this way, the detection of these parameters allows aiso to know the composition of the substances contained into the smokes regarding their single pollutant component parts, after the abatement of the smokes into the heating module 5. All the above described sensors are electrically connected to the control central station, together with the electric and electronic components of the magnetron 32 and the other electric components pertaining to the other component parts of the present device.

Furthermore, the module 6 for partial recovering of the smokes is provided with at least a short outlet pipe union 75, joined with its one end portion to a correspondent through hole (not indicated) provided in to the lengthened conduit 70, in a manner to communicate with the inner chamber (not incicatcd) of the same lengthened conduit, said outlet pipe union 75 being also joined with its other end portion to an end portion of a lengthened conduit 76 for recovering the smokes, the other end portion of which is joined to the suction inlet 77 of a suction device like a fan 78, in turn joined with its delivering outlet 79 to the combustion chamber 8, through a short conduit 80. In the interior of the recovering conduit 76 of the smokes it is also inserted, near the fan 78, at least a sensor 8 i for measuring the oxygen level present into the smokes circulating into the smokes recovering conduit 76 in the direction B, which sensor is connected with its electric component part 82 to the control central station of the present device.

Near the suction inlet 77 of the fan 78, it is provided at least a shutter 83 or a similar device, which is installed in the interior of the smokes recirculating conduit 76 and the actuating electric part thereof not indicated) is also connected to sdd control central station of the present devics, said shutter being installed in a manner to intercept and let to pass always the flow of the recovered smokes circulating through the smokes recovering conduit 76, and being controlled ty the central control station in a manner to be actua:ed from a opened position to a closed position thereof, and vice-versa, in the manner and for the functions that will be described. In a position correspondent to that one of the shutter 83, a short conduit 84 is also provided and joined with s one end portion to the smokes recovering conduit 76 and its other end portion 85 is free and communicating with the external environment, such a conduit 84 being adapted to be closed or opened by the shutter 83, for preventing or allowing the passage of the external air through the same conduit. Then, with this arrangement for recovering the smokes, the smokes passing through the internal tubes 72 of the module 6, are always partially discharged directly outside, by passing through said upper through opening 63 and are also partially recovered and let tD circulate through the smokes recovering conduit 76, thanks to the suction pressure produced by actuating the fan 78 with the control of the above control central station.

Then, in the first case the abated smokes being discharged in the environment pass through ths short distance existing between the two end portions of the internal tubes 72 and the discharging opening 63 and are quickly cooled down with the contact with the lower temperature of the external environment, thereby preventing that the abated substances contained into the discharged smokes might chemically re-combined again to each other, and forming again the abated pollutant substances. In the second case, the smokes circulating through the internal tubes 72 of the module 6 are at first deviated through the outlet pipe union 75, by passing through the inner chamber of the lengthened conduit 70, and then are conveyed through the smokes recovering conduit 76. The so recovered smokes contain a greater quantity of oxygen with respect to that one present before the treatment in the heating module 5, owing to the oxygen molecules being released during the molecular dissociations of the pollutant substances of smokes, which are resolved at a large extent in the heating module 5, therefore this condition is obtained withou: providing any dilution of the smokes. The so produced oxygen is recovered, together with the smokes, by means of suction and let to circulate through the smokes recovering conduit 76, and added to the one present in the combustion chamber 8 daring the combustion of the products therein, by adjusting the oxygen level for improving in this way the combustion in this chamber, in the manner that will be described, and by determining also a further abatement of the smokes in the subsequent heating module 5. The oxygen level contained in the so recovered smokes and let to circulate in the smokes recovering conduit 76 is measured by the sensor 81 and controlled by the control central station of the present device. Such a control central station, in particular, is provided for actuating or not actuating tne shutter 83 in an opened or closed position thereof, and therefore for allowing or preventing the passage of the air through the conduit 84, depending on the oxygen level measured by the sensor 81 and contained in the recovered smokes. Such a control central station, also, is set in advance in a manner that when the so detected oxygen level be comprised within determined limits, and such as to ensure a better combustion in the combustion chamber 8, it actuates the shutter 83 into a closed position tnereof, thereby preventing the passage of the air through the conduit 84. Furtnermore, such a control central station is also set in advance in a manner that when the so detected oxygen level is of quantities smaller than the ones needed to ensure a better combustion into the combustion chamber 8, it actuates the shutter 83 in the opened position thereof, with a consequent suction by the fan 78 also of the external air and passage of this air through the conduit 84 and mixing it with the smokes coming from the conduit 76, therefore containing also oxygen, in the combustion chamber 8. When the oxygen level is returned within the established limits, the control central station actuates the shutter 83 in the closed position thereof.

It is now described shortly the process for treatment and abatement of liquid, gaseous and/or solid pollutant substances of various kind contained into the exhaust smokes, that is effected into the above described abatement device, wherein the device is constituted by the above component parts, for performing the above described functions.

This process is effected by using particularly the heating module 5 of the device according to the invention, formed by the above described component parts, in a manner to treat and to abate in the most possible wide extent the pollutant substances contained into the exhaust smokes deriving from the combustion processes of pollutant substances, produced by various sources, and in particular but not exclusively in the case of use of civil or industrial thermal plants, and of traffic of vehicles powered by explosion engines. According to the present invention, the combustion of the pollutant substances to be abated is carried out into the combustion chamber 8, from which the smokes containing the pollutant substances that are developed are, as already described, let to pass at first through said heating module 5, and then through the module 6 for partial recovering of the present device, and under this condition the abated smokes at high percentages are then discharged in the outside environment.

The present process comprises the following steps:

- generation of microwaves by means of a magnetron 32, applied to said heating module 5, when the hot smokes containing the pollutant substances produced by the combustion are circulating in the internal cavities of one or more of said lengthened tubes 25 made of acceptor material that are internally fixed to the heating module, and are directed toward the outlet end portion of the same module;

- transmission of the microwaves generated by the magnetron 32 through the through holes 31 of the lengthened container 10 made of metallic material impermeable to microwaves, which contains said lengthened tubes 25 enclosed by said insulating material 27, said microwaves by passing in sequence at first through said insulating material 27 and then through all the peripheral walls 26 and the internal cavities 38 of the lengthened tubes 25, the acceptor material of which generates infrared radiations that are irradiated into the internal cavity of the same tube, by determining a further heating of the circulating hot smokes, and a simultaneous multiple reflection of the microwaves into the internal cavities delimited between the penpheral walls 26 of each tube 25;

- generation, because of the multiple reflections of the microwaves between the peripheral wall of each tube and the contact of the microwaves with high temperatures, and the different unhomogeneities and densities of the gases contained into the circulating smokes, some energy peaks of the microwaves (so-called hot spots) that are surprisingly distributed randomly and :n to variable and different positions into the internal cavities of all tubes, in such a way that, by dimensioning opportunely both the characteristics (power, intensity, frequency, etc.) of the microwaves passing through said inner chamber 19, and the size and the quality of the acceptor material of the lengthened tubes 25, the so generated hot spots distributed randomly might attain very high temperatures, also in the range comprised between about 1200° C and about 2600° C, for heating the smokes at these very high temperatures, thereby dissociating the molecules of the different compounds constituting the pollutant substances of the smokes, with consequent discharge in to the atmosphere of smokes with a high percentage of single not pollutant component substances.