WO2007036974A1

WO2007036974A1 - Method and device for lowering the polluting components of exhaust smokes in a combustion heat generator

Info

Publication number: WO2007036974A1
Application number: PCT/IT2006/000691
Authority: WO
Inventors: Valerio Abate; Alberto Conti; Michaela Bianchi
Original assignee: Nonox Ltd
Priority date: 2005-09-28
Filing date: 2006-09-28
Publication date: 2007-04-05
Also published as: ITPD20050281A1

Abstract

A device for lowering the polluting components of the smokes produced by combustion heat generators comprising a vertical development duct (23) arranged as a by-pass of a portion of the exhaust duct, a vortex filter (26) , mounted on the by-pass duct for intercepting the smokes for purifying them from polluting solid particles; an electric resistor (40) mounted on said by-pass duct and arranged downstream of the filter; a grid (41) consisting of multiple layers of metal meshes mounted on the by-pass duct for intercepting the smokes and arranged downstream of the electric resistor; a catalyst (42) mounted on the by-pass duct for intercepting the smokes and arranged downstream of the grid; suction means (43) , for circulating the smokes into the by-pass duct or in the exhaust duct . The electric resistor can be actuated for preheating the catalyst and for burning the particles laid on the grid or the particles of unburnt products initially present in the smokes.

Description

"Method and device for lowering the polluting components of exhaust smokes in a combustion heat generator"

Field of application [0001] The present invention relates to a method and device for lowering the polluting components of exhaust smokes in a combustion heat generator.

[0002] The subject method and device are intended to be used for reducing and/or lowering the polluting components of the smokes produced by combustion heat generators comprising at least one combustion chamber and at least one exhaust duct intended for guiding such smokes from the interior outwards of the combustion chamber . State of the art

[0003] One of the major problems in modern cities with a high concentration of inhabitants is air pollution. [0004] Air pollution is due to substances that mix up with the air itself and to substances that modify the components naturally present in the air. These substances are commonly called pollutants. Therefore, there are two types of pollutants: direct and indirect pollutants. [0005] Typically, indirect pollutants are divided into gaseous pollutants and solid pollutants. [0006] Direct pollutants are substances that modify the oxygen into the air, bringing it from its natural state, that is consisting of two atoms of oxygen bound to one another, to a modified form with three atoms of oxygen, i.e. in the form of ozone. [0007] In order to reduce pollution and the damages correlated thereto, it has been deemed suitable and necessary to identify the sources of pollutants and intervene thereon. The sources of pollution are all the sources that emit pollutants of gaseous type and pollutants of solid type to the air, in particular the main sources of pollutants are cars, houses, industrial plants .

[0008] The solutions introduced for reducing the pollutants in the air and their negative effects differ according to the sources of pollutants, the type of pollutant to be reduced and the historical period when the sources have been introduced.

[0009] At first, the aim was to limit the pollution of some types of pollutants in the industrial plants, for example see US patent 5,879,645, which discloses a catalyst and a relative method for reducing the nitrogen oxides in the smokes of industrial plants. Where smokes means exhaust gases mainly produced by the combustion. [0010] A similar solution was therefore used for means of transport like motor vehicles, three-wheelers, etc. [0011] In fact, in patent US 5,879,645 catalyst and a relative method are applicable in the same way in the case of smokes produced by cars. The introduction of catalytic converters has allowed considerable reduction of the emission of pollutants.

[0012] However, it can be noted that such solutions for reducing the pollution of industrial plants and cars are not sufficient for reducing pollutants especially in large towns . [0013] As mentioned hereinabove, it is especially important also to reduce the pollutants produced by the houses. The increase of the living density considerably contributes to the introduction of pollutants in the air mainly thanks to the hot water production and heating systems in homes and offices.

[0014] The pollutant reduction is therefore subject to the introduction of suitable devices for lowering the pollutants themselves at source. In order to obtain concrete result it is necessary to provide the highest possible number of cars and houses with devices for reducing the pollutants. At present, the most developed countries have enforced laws that force the automotive companies to introduce on the market only cars fitted with devices for reducing the pollutants emitted with the smokes of the cars themselves. The average life of a car has brought the fleet of cars not fitted with such devices to be almost completely replaced within few years. Things with houses are different since the average life of a house does not let one presume that by adopting laws similar to those of the cars, it would be possible to provide all the houses with devices for reducing the pollutants within a short time. The solutions aimed at the houses must therefore be easy to install in existing houses, must not economically considerably affect the owners of the houses themselves so as not to discourage the installation and they must have life times comparable to the maintenance scale times of a house. The average life expected for replacing obsolete components is an especially important parameter. In fact, this time is considerable in the case of building works and solutions that do not require the complete replacement or the distortion of the works therefore are very interesting. [0015] In any country, moreover, there exist laws relating to the plant safety especially relating to the risk of fire or -explosion. In an industrial plant, a catalytic system requiring a thermal operating condition at high temperature, for low cost reasons is heated using gas, gas oil or other available fuels. In a living household system the changes required for this type of application are often incompatible for the type of rooms or require the modification of the rooms for meeting fire-prevention or explosion-prevention safety regulations if gas is used. [0016] Systems are known that improve the air quality in indoor spaces, drawing the air from the exterior, mechanically and chemically modifying the properties thereof and introducing it into the household systems or in the driver compartment of the vehicles. [0017] Devices are also known for lowering the polluting components of smokes of the type described in the following patents .

[0018] Document DE 19824204 describes a device for reducing the pollutants in the combustion smokes of a heat generator. It is provided with means for adjusting the pressure of the smokes passing in the device duct and with a catalyst for separating the gaseous pollutants. The catalyst is brought to the operating temperatures through special heating means. The catalyst pressure drop is compensated by a fan. [0019] Document DE 19627028 describes a device for reducing the pollutants in the combustion smokes of a heat generator provided with a ceramic filter for separating the polluting particles and with a catalyst for separating the gaseous ones. [0020] Also in this case, the catalyst is brought to the operating temperatures through special heating means. [0021] Both devices for lowering the polluting components described in the two German patents mentioned above exhibit the disadvantage of common to many other known solutions of being directly located on the smoke exhaust duct. This causes the disadvantage of a forced inefficiency of the heat generator if the device maintenance is required.

[0022] Such known devices, moreover, does not suitably treat the particles, in particular of unburnt products that are released by the heat generator during the repeated ^' ignitions .

[0023] As a consequence, the catalysts of known devices are not sufficiently protected from the particles that could build up and burn thereon, in particular in the transitory steps of start up of the combustion heat generator .

Summary of the invention

[0024] The problem at the basis of the present invention therefore is to provide a method and device for reducing and/or lowering the polluting components of the smokes produced, by combustion heat generators which should be easy to install in pre-existing systems, which should not be considerably expensive so as not to discourage the installation and which should be easy to configure and/or customise . [0025] Another object of the present invention is to provide a method and device the maintenance of which should not cause inefficiency of the heat generator it is connected to. Brief description of the drawings

[0026] The technical features of the invention, according to the above objects, are clearly found in the contents of the claims below and the advantages of the same will appear more clearly from the following detailed description, made with reference to the annexed drawings, which show a purely exemplifying and non-limiting embodiment thereof, wherein:

[0027] - figure 1 shows a heating system of a house with arranged a device according to the invention; [0028] - figure 2 shows a perspective view of the device according to the invention resting on the ground;

[0029] - figure 3 shows a cutaway view of the device according to the invention;

[0030] - figure 4 shows a section view of the bottom portion of the device of figure 2;

[0031] - figure 5 shows an exploded view of the bottom portion of the device of figure 2;

[0032] - figure 6 shows a section view of the top portion of the device of figure 2; [0033] - figure 7 shows an exploded view of the catalyst unit of the top portion of the device of figure 2 ; [0034] - figure 8 shows a detail of the device relating to a catalyst safety grid;

[0035] - photographs 9 and 10 show an electronic microscope-enlarged view of the particles separated by the filtering device and by the grid, respectively. [0036] - figures 11a, Hg show the operating steps of the subject device of the present invention. Detailed description of a preferred embodiment [0037] Figure 1 shows a schematic example of a heating system of a house according to the invention comprising a combustion heat generator 1 of known type, typically arranged into the house itself, connected to an apparatus 6 for supplying a fuel 7 and to an exhaust duct 2 (or flue) intended for conveying the smokes of heat generator 1 outside the house itself through device 12 subject of the present invention.

[0038] Heat generator 1 comprises a combustion chamber 5 intended for burning fuel 7 for generating heat . Fuel 7 is fed into the combustion chamber 5 by apparatus 6 in an in se known type.

[0039] Typically, the exhaust duct or flue 2 ends with a stack 3 optionally provided with a device 4 for facilitating the smoke output and dilution to the atmosphere . [0040] Device 12 is provided with a support structure 20 provided with legs 21 for the support on the ground, as in the case of the example of figures 2-4 or simply with a cylindrical jacket 22, as in the case of the example of figure 1.

[0041] The fuel used for supplying the heat generator may be fuel oil, wood, wood chips, and in this case a module for separating the solid particles 26 will be necessarily provided, or gas oil or gas and in this case the above module may be omitted.

[0042] As known, "wood chips" is chopped wood, that is, chopped wood obtained through special machines . Lower quality wood is used to produce the chips, such as the residues of wood, agricultural or urban trimming, brushwoods and stem tops, or sawmill by-products. Chopped wood in fact can advantageously be used for energy purposes, since its handiness allows automatic supply of the boilers, even though it must be noted that in this latter case, the chip size must be even and small (3-5 cm) .

[0043] The above structure 20 of device 12 supports a vertical development duct 23 having the function of bypass of ^"a portion of the exhaust duct 2. Such by-pass duct 23 at the top is connected to the exhaust duct 2 and at the bottom, through a branch section 90, to a union 30 in turn connected at opposite sides to the smoke exhaust 81 of heat generator 1 and to the exhaust duct 2. Duct 23 therefore is connected to the exhaust duct 2 through two sections, of which a first safety one 24 for the passage of the smokes coming from the combustion chamber 5, and a second one 25 for ejecting the smokes for their release to the atmosphere.

[0044] The union exhibits a profile with a seat facing the heat generator for favouring the smoke flow conveyance into the by-pass duct 23.

[0045] On the by-pass duct 23 upstream of the thermo- catalytic system described hereinafter, there is arranged a module for separating the solid particles, in particular of mechanical type. Such module 26, in the case of fuels susceptible of producing considerable combustion residues, like for example in case fuel oil or wood chips are used, advantageously is of the cyclone type (or vortex type) , as it allows high reduction of the solid particles suspended in the smokes by a separation action due to the centrifugal force.

[0046] By way of an indication, this module 26 allows lowering the particles of the fuel oil and of wood chips from a quantity respectively in the order of 50 mg / Nm3 and 100 mg / Nm3 up to about a quantity in the order of 5 mg / Nm3 [milligrams per normal cubic metre] . [0047] Surprisingly, it has been noted that the use of such module treating the hot exhaust smokes of the burner allows withholding the particles of sizes comprised within the range between 2- 15 micron (see photographs 9) , when in the current known applications the same module was provided for withholding only larger particles. [0048] In conditions of smoke outward flow up to 250 ⁰C, the system separates considerable amounts (~40%) of particles of diameter equal to 2.5 mm and almost all (>95%) the 10 mm particles.

[0049] As can be understood from figures 3 and 4 , the smokes coming from the combustion chamber 5 through union 30 not shown, go up through the central duct 27 and then go down ^"into the single cyclones 28 of conical shape, forcedly taking a rotational motion. Thanks to the action of the centrifugal force, such motion causes a separation of the solid particles that as a consequence fall into the underlying containment means 29 (for example consisting of a removable box for emptying the heaps) , leaving the smoke purified and free to go up through the central channel up to exit from the top outlets 31. The discharge and subsequent treatment thereof follow the procedures and rules currently in use for cleaning and treating, the waste resulting from the cleaning of smoke ducts . [0050] To optimise the filter efficiency, outlets 31 are advantageously open only in a number corresponding to the power of heat generator 1. With reference to the example shown in the annexed figures it may be considered that each cyclone 28 on an average treats 90 cubic metres per hour of smokes and that the 12 cyclones envisaged will all be open for meeting the requirements of a 350 kW heat generator . [0051] The adjustment of pressure meters for determining the ratio between the two pressure drops in the two measurement sections is preferably carried out at the factory.

[0052] Moreover, preferably for production cost reasons, cyclones 28, with the exception of outlets 31, are integrated in a single cylindrical body obtained in a single piece by casting.

[0053] If heat generator 1 is intended to be supplied with gas oil or gas, or with products with few residues of suspended particles after the combustion, it is possible to envisage a simpler and less expensive mechanical filter for example consisting of grid 41 only, which shall be described hereinafter.

[0054] Moreover, into the by-pass duct 23 there are arranged in a sequence a heating electric resistor 40, a smoke intercepting grid 41, a catalyst 42 and suction means 43.

[0055] The latter preferably consist of a centrifugal fan with electric motor powered by an inverter and have the function of: restoring load losses generated by the upstream" systems for the introduction in the flue in conditions of transparency as compared to the original system; checking the smoke withdrawal at the generator outlet so as to keep flow rate and pressure at optimum levels; favouring the controlled passage in condition of natural ventilation.

[0056] If fan 43 remains switched off or does not work, smokes do not pass into the by-pass duct 23 where there are located filter 26, catalyst 42 and grid 41, which act as a plug and cause a slight loss of pressure, but they would cross the union to directly reach the exhaust duct 2 through the second section 24.

[0057] On the other hand, when the fan is actuated the smoke circulation is forced inside duct 23 to subject the flow to the treatment of filter 26, catalyst 42 and grid 41.

[0058] The electric resistor 40 is preferably actuated only in the early operating steps of device 12 or at each start and re-start step of the combustion heat generator. It carries out the dual function of burning the particles laid on grid 41 during the previous operating cycle of the heat generator and of preheating catalyst 42 before the arrival of the smokes.

[0059] To this end, resistor 40 preferably has a module that becomes incandescent for burning the particles on grid 41 by heat radiation and two conduction modules for heating the catalyst .

[0060] The module operating by incandescence intervenes for supporting the other two elements, where required during the fluxing step. [0061] Moreover, it is possible to envisage that the incandescence module intervenes at the end of the operating cycle of the heat generator rising the temperature of the multilayer grid filter by heat radiation above the combustion threshold of the collected particles favouring the decomposition thereof and the subsequent treatment by the already warmed catalyst. [0062] As can be seen in figure 10, the overlapping of metal grids of thin meshes also stops the residual small sized carbon particles that have passed through the cyclone and that have a size comprised between 0.5 and 3 micron .

[0063] Upstream and downstream of the branching section 90 there are arranged two measurement sections A and B with associated relative flow meters indicated with reference numerals 91 and 92. Advantageously, each flow meter is obtained with an annular partition 93, of which one arranged concentric on union 30 and one on duct 23, and with two pressure meters arranged one 94 upstream and the other 95 downstream of partition 93 as indicated in figure 4.

[0064] Each partition determines a pressure drop detectable by the two meters 94 and 95, proportional to the smoke rate.

[0065] Advantageously, it is possible to force the flow rate passing on union 30 in output from the heat generator or through the first measurement section A to be equal to the flow rate passing on by-pass duct 23 for the second measurement section B. This causes the pressure drop detectable in the second section B to be proportional to that detectable in the first section A according to a proportionality constant adjustable during the device setup (for example closing section 81 and measuring pressure drops in the two measurement sections) . Therefore, it will be possible to control the inverter of the centrifugal fan by a control unit to keep such ratio of pressure drops and ensure in this way that the flow rate passing through the first measurement section is the same passing through the second measurement section. [0066] The first measurement section, like the first one, is designed in accordance with the standards envisaged for flow rate measurement systems.

[0067] AS mentioned hereinbefore, the calibration is carried out at the factory and has an accuracy of 3-6 % more than enough for the requirements of the present invention, also in the case where the heat generator is provided with a last generation burner with variable combustion ratio.

[0068] As said, the flow rate is obtained by measuring the pressure upstream and downstream of the partition or diaphragm 93, also calibrated at the factory. The minimum section of diaphragm 93 is equal to or slightly larger than the original section of the duct and the flow rates and flow conditions therefore are compatible with the safety and calculation conditions of the stack before the machine installation.

[0069] The first measurement section A has the feature of being visible and reachable from the outside and the two pressure outlets, as well as the point of introduction of the thermocouple that measures the temperature, are visible on the machine in the top inlet portion of the duct upstream and downstream.

[0070] The second measurement section B is inside the device and is arranged before the inlet in the smoke treatment zone . [0071] The second measurement section is visible and reachable only in extraordinary or two-year maintenance. [0072] The above adjustment controlled by inverter U is based on the correlation of the pressure differences in the two sections and is especially accurate. [0073] Of course, without departing from the scope of protection of the present patent application, the flow meters described above, which in any case represent the preferred embodiment, may be replaced with other devices of known type, for example Pitot pipes, mechanical pressure switches or flow switches.

[0074] In this way, the device does not affect the operation of the heat generator since the latter is not affected by the presence of the device. [0075] The fan thus adjusted moreover avoids bringing cold air sucked through the exhaust duct 2 inside the device or dispersing smokes not purified through the device through the exhaust duct 2.

[0076] The ^• need of passing all the rate of smokes exiting from the heat generator in the by-pass duct 23 implies the advantageous introduction of a correction due to the temperature difference that can be found in the two measurement sections, which can introduce errors due to the different volumes occupied by the smokes (and thus different flows) as the temperature varies. [0077] The proportionality constant in the pressure ratio mentioned above must keep into account a correction factor related to such temperature difference. [0078] In order to detects such possible temperature difference of the smokes in the two measurement sections, there are two thermocouples, of which a first one 96 in union 30 and one 97 in the by-pass duct 23 susceptible of reading the temperature of the smoke flow and allowing the calculation of the correction factor with which the fan motor inverter is to be managed. [0079] The temperature data may also be used for generating alarms or actuating the call procedure for the remote control or the extraordinary maintenance operations of the heat generator; the option can be actuated by installing a modem on the device. [0080] More clearly, the operation of the subject device of the present invention shall be described hereinafter. [0081] At first, the heat generator envisages a fluxing step for about 10-30 seconds without flame wherein there is a forced circulation of air into the smoke pipes intended for allowing the discharge of any unburnt products which otherwise could produce small explosions during the fire ignition.

[0082] The beginning of the fluxing is perceived by the device through the pressure meters of the first measurement section or through an electrical connection with the same means of the heat generator responsible for the fluxing.

[0083] At this point, the control unit actuates the electric resistor 40 and in few seconds, by heat radiation it brings the surface of grid 41 to a temperature comprised between 400 and 700⁰C so that all the carbon particles that have collected thereon during the previous operating cycle of the heat generator are burnt . [0084] At the same time, resistor 40 brings the catalyst 42 to temperature to allow the maximum efficacy thereof at the first arrival of the smokes. The same catalyst 42 is capable of treating the emissions generated by the particles burning on grid 41. [0085] During this fluxing period, the fan is switched off and as a consequence, the fluxing rate does not pass through the by-pass duct and is directly conveyed to the exhaust duct 2 without any particular problems since it essentially consists of air, as will be better understood hereinafter .

[0086] It is possible to envisage a reduced speed actuation of the fan for favouring the heating of the catalyst. [0087] At the end of the fluxing step, the heat generator ignites the flame that is again detected by the device through the pressure meters or through an electrical connection with the same means of the heat generator responsible for the fuel delivery.

[0088] It should be noted that the pressure wave produced by the flame and detected by the pressure meter runs much faster than the smokes that must cover the metres of the smoke pipes inside the heat generator required for the heat exchange and that are usually slowed down by the turbolators arranged in the same smoke pipes for increasing the thermal conductivity thereof . [0089] Consequently, with the catalyst and the grid already brought to temperature by the electric resistor, the control unit actuates fan 43 forcing, through the regulation of the inverter, all the smoke flow emitted by the heat generator to pass through the by-pass duct and be subject to the device treatment.

[0090] The above regulation of the inverter is made possible by the flow rate check carried out by the flow meters described above. [0091] In the practice, the power required to the fan is minimal and equal to the losses of pressure present in the by-pass duct and due to the presence of filter 26, of grid 41 and of catalyst 42. In this way, the device does not change the operating conditions of heat generator 1, which is not affected by the operation of device 12. [0092] When the smokes reach union 30 the fan already is at operating conditions and the smokes are all conveyed in the by-pass duct 23.

[0093] In particular, in this way the unburnt particles emitted by the heat generator during the early start up and forming steps of the flame are burnt on the incandescent grid.

[0094] After that, the heating means are switched off. [0095] At the end of the operating cycle of the heat generator, generally controlled by a thermostat, the flame into the combustion chamber is put out. The fan is still kept operating for the few seconds required for filtering with device 12 all the smokes left in the smoke pipes when the flame is put out. In this way, in the following fluxing step, substantially only air is made to circulate.

[0096] For example, it is possible to envisage that with a 300 kW heat generator it is sufficient to arrange a resistor having a power of 6 kW intended for remaining on in the initial operating step of the equipment (that is, upon each re-start of the heat generator) for an interval equal to 10 - 120 seconds according to the type of heat generator from the beginning of the fluxing step. The consumptions of resistor 40, which advantageously is only intended for producing heat for a short interval of time and partly by irradiation, are virtually negligible. [0097] Moreover, thanks to the presence of resistor 40 it is possible to consider that grid 41 in the practice advantageously is of the self-cleaning type. [0098] In accordance with the embodiment of figure 8, grid 41 consists of multiple overlapped layers 41' of metal meshes 44, which exhibit increasing size in the direction of resistor 4.

[0099] The object of the present invention is also a method for reducing or lowering the polluting components of smokes produced by combustion heat generators.

[00100] For simplicity of description, reference shall be made to the same nomenclature already used with reference to device 12. [00101] The method therefore envisages a treatment step of the smokes that are made to circulate by fan 43 in the vertical development by-pass duct 23.

[00102] The smoke treatment envisages the filtering, in particular by centrifugal action, for purifying them from polluting solid particles, as well as a passage through the catalyst for lowering the polluting gases.

[00103] In accordance with the idea at the basis of the present invention, the method envisages that in a start up step of device 12 subsequent to the ignition of the fluxing of heat generator 1, with fan 43 initially switched off, the preheating of catalyst 42 and the heating of grid 41 mounted into the by-pass duct 23 takes place through electric resistor 40 for burning particles collected thereon during the previous operating step of the heat generator. [00104] After that, the burner ignition takes place, which causes the actuation control of fan 43 through the pressure wave produced by the trigger of the combustion and detected by the pressure meter. [00105] The combustion smokes are immediately conveyed to the by-pass duct 23.

[00106] A flow rate check operation is envisaged through pressure measurement in two measurement sections and consequent adjustment of the inverter in order to convey all the combustion smokes through device 12 without sucking air from the exhaust duct 2 and without modifying the operation of the heat generator. [00107] The resistor heating step is transitory and ends a little after the start up of the suction means in order to allow the preheating of the catalyst and the pyrolysis on the grid of the particles collected during the previous combustion step, as well as the combustion of unburnt products present in the first smokes produced by the ignition of the heat generator. [00108] In a different way or in addition it is possible to envisage a grid heating step through the resistor after switching off the heat generator in order to burn the carbon particles collected during the combustion.

[00109] Preferably, after switching off the burner, the fan continues to operate for a few seconds more to suck in the remaining gases from the smoke pipes . [00110] Figures lla-Hg schematically show the smoke pattern in the different portions of the device by arrows. More in detail : [00111] - figure Ha shows the inlet of smokes with particles from the heat generator to the device; [00112] - figure 11 b shows that at the device inlet, at a first measurement section A, pressure, temperature and flow rate are measured and the values are transferred to the control unit;

[00113] - figure lie shows that the flow rate is deviated into the by-pass duct 23 by the effect of the fan;

[00114] - figure 11 d shows that the smoke flow passes into the second measurement section where pressure, temperature and flow rate are measured and the values are transferred to the control unit that regulates the exhaust fan so as to ensure that all the flow rate is deviated in the by-pass duct 23 by the fan, allowing perfect transparency of the device to the effects of the heat generator, of the ducts and of the flue; the same figure shows that the flow passes through the vortex filter for separating the roughest and most numerous particles; [00115] - figure lie shows the conveyance of the smoke flow in a preheating zone where if the flow has not reached suitable temperatures it is heated; [00116] - figure Hf shows the crossing of a series of grids by the smoke flow designed for withholding the micro-powders on the surface, and of a thermo-chemical action catalyst that lowers the gaseous pollutants and decomposes very fine particles left in the smokes; [00117] . - figure Hg shows that the fan extracts the smokes thus treated and conveys them towards the flue . [00118] The invention thus conceived achieves therefore the intended purposes.

[00119] Of course, in the practical embodiment thereof, it may take shapes and configurations differing from that illustrated above without departing from the present scope of protection.

[00120] Moreover, all the parts may be replaced by technically equivalent ones and the sizes, shapes and materials used may be whatever according to the requirements .

Claims

1. A device for reducing or lowering the polluting components of the smokes produced by combustion heat generators provided with a combustion chamber and an exhaust duct for guiding such smokes from the interior outwards of said combustion chamber, characterised in that it comprises:

- a support structure;

- a vertical development duct arranged as a by-pass of a portion of the exhaust duct, supported by said support structure, connected to the smoke exhaust of the heat generator and to the exhaust duct through a union provided with two sections, of which a first safety one for the passage of the smokes coming from the combustion chamber, and a second one for ejecting the smokes treated in the device;

- a filter, in particular of the vortex type, mounted on said by-pass duct for intercepting said smokes for purifying them from solid polluting particles; - a heating electric resistor mounted on said by-pass duct and arranged downstream of said filter;

- at least one grid mounted on said by-pass duct for .intercepting said smokes and arranged downstream of said heating electric resistor; - at least one catalyst mounted on said by-pass duct for intercepting said smokes and arranged downstream of said grid;

- suction means, susceptible of selectively determining in ignition or in switch off the circulation respectively of said smokes in said by-pass duct or in the exhaust duct portion comprised between said first and second connecting section to said by-pass duct; said heating electric resistor being at least temporarily actuable for preheating said catalyst and for burning particles laid on said grid or particles of unburnt products initially present in the smokes.

2. A device according to claim 1, characterised in that there are provided removable containment means, in particular box type, for collecting said polluting solid particles.

3. A device according to claim 1, characterised in that said heating electric resistor faces said grid and in that it is provided with at least one heat radiation module susceptible of heating said grid at a temperature comprised between 400 and 700⁰C.

4. A device according to claim 1, characterised in that said grid consists of multiple layers of overlapped metal meshes.

5. A device according to claim 4, characterised in that the metal meshes of said overlapped layers are of decreasing size in the direction of said catalyst and of increasing size in the direction of said resistor.

6. A device according to claim 1, characterised in that it comprises a control unit susceptible of regulating said suction means conveying the smoke flow coming out of said heat generator through said by-pass duct by means of the flow measurements obtained from two measurement sections provided in said union and in said by-pass duct .

7. A device according to claim 6, characterised in that each measurement section is provided with an annular partition concentric relative to the union or to the bypass duct and with two pressure meters arranged upstream and downstream of said partition for measuring the pressure drop through said partition.

8. A device according to claim 1, characterised in that said union exhibits a profile with a seat facing said heat generator for favouring the smoke flow conveyance into the by-pass duct.

9. A method for reducing or lowering the polluting components of the smokes produced by combustion heat generators provided with a combustion chamber and an exhaust duct for guiding such smokes from the interior outwards of said combustion chamber, characterised in that it comprises : - a step of treating the smokes conveyable by suction means into a vertical development duct arranged as a bypass of a portion of the exhaust duct, and connected to the smoke exhaust of heat generator and to the exhaust duct through a union with two sections, of which a first safety one for the passage of the smokes coming from the combustion chamber, and a second one for ejecting the smokes treated in the device;

- said step of treating the smokes envisaging: . at least one filtering, in particular by centrifugal action, intended for purifying the smokes from polluting solid particles;

. at least one passage in a catalyst for lowering the polluting gases in the smokes; said method further comprising a step of heating at least one grid mounted on said by-pass duct for intercepting said smokes by an electric resistor, for burning the particles laid on said grid during the previous operating cycle of the heat generator.

10. A method according to claim 9, characterised in that said heating step takes place when the burner is started with said suction means off and is susceptible of preheating said catalyst .

11. A method according to claim 9, characterised in that said heating step starts with the fluxing step of said heat generator.

12. A method according to claim 9, characterised in that said heating step starts after switching off the burner of said heat generator for burning the carbon particles collected on said grid during the previous combustion step .

13. A method according to claim 9, characterised in that said heating step stops after the start of said suction means for burning the unburnt particles produced upon the start up of the heat generator .

14. A method according to claim 9, characterised in that said suction means are actuated following the start of the combustion in the heat generator.

15. A method according to claim 9, characterised in that said heating step is transitory, ends after the start of said suction means and has a duration comprised within the interval of 10 - 120 seconds.

16. A method according to claim 9, characterised in that said suction means are started in consequence of the step of igniting the heat generator and in time for conveying into the by-pass duct the first exhaust smokes produced by the heat generator following its ignition, so that the unburnt particles of the smokes burn on said grid heated by said resistor.