FROM DOMESTIC HEATING PLANTS

DESCRIPTION

Field of the invention

The present invention refers to a device and a related method for the abatement of the noxious emissions into atmosphere from the domestic heating plants, such as pellet stoves, fuel oil stoves and wood-burning stoves, or gas boilers, as well as of the emissions from wood-burning ovens for domestic and commercial use, and of the emissions from industrial plants and from large ships, and it finds therefore application in the field of such plants.

State of the art

The whole world is currently experiencing a period of profound environmental crisis mainly due to the needs that modern life imposes on us, to the increased consumption and consequent industrial production, to the thoughtless use of heating means and to the increase of vehicular traffic. Also under the pressure of public opinion and of the associations newly formed in recent years for the protection of environment, there is now a plethora of initiatives from international organizations to local governments aimed at limiting the damages caused by pollution and especially at reducing their causes for the future. Unfortunately, these initiatives usually result in mild remedies such as alternating use of motor vehicles, having purely palliative and apparent effects, while cities continue to be plagued by serious air pollution problems with more than harmful consequences on people's health.

Domestic heating means as well as heating plants for tertiary and trade sectors represent a significant source of pollution, comparable to the transport sector or the industrial production as far as harmful emissions are concerned. If up to now, at least in the transport sector, national and European Community regulations have been imposed establishing limits to atmospheric emissions through the Euro classification of vehicles, for the domestic emissions no significant environmental measures have been adopted. This may be due to the lack of information on this type of emissions, to the difficulty to register the number of stoves and boilers on a certain territory; it is also not known the actual impact on environment of emissions of pollutants such as those from domestic fuel oil boilers or from wood stoves, therefore up to now specific, effective measures have not been adopted. In addition to this, there are economic reasons but also psychological reasons that guide the choice of a heating system rather than another: it is in fact proved that the emissions of particulate into the atmosphere from a fireplace or from a pellet stove or a wood stove are much greater than those emitted by a gas or natural gas boiler, even higher than emissions from fuel oil heating plants, but in general in recent years wood or pellet heating plants have found enthusiastic supporters, and this kind of heating plants has experienced a certain expansion. In addition, the wood or pellet heating is considered a cheap type of heating and the choice of a heating plant instead of another is just driven by economic reasons, so that often these heating systems are without filters or special rooms of combustion, which are available in order to generate lower quantities of particulate but they are discarded as more expensive. The result is that a fireplace or a pellet stove emit into the atmosphere much higher particulate emissions than it is usually perceived; it has been estimated, for instance, that a single pellet stove emits in the atmosphere a quantity of particulate comparable to that produced by 350 natural gas boilers.

Particulate matter or PM is among all pollutants in emissions from plants, the one considered to have a greater negative effect on air quality, particularly in the cities where it is also produced by car exhausts. This term particulate matters usually indicates the substances, liquid and solid, suspended in the air and made of metals, silica, carbon particles, etc. having a diameter varying between a few nanometres up to 500 micrometres and beyond. Particularly dangerous to people's health is the particulate fraction known as PM10, consisting of particles of diameter less than 10 micrometres that, because of such small size, once inhaled by people, may arrive in the deep airways depending on their size, and even reach the alveolar walls of the lungs, with more or less harmful effects on the respiratory and cardiovascular systems, up to determine the onset of tumours and other serious diseases.

In addition to the particulate emissions, the combustion of biomasses, and in particular of wood, produces organic compounds and nitrogen oxides in large amounts, thus irritating and harmful emissions for the health, and also contributes to the increase in the amount of C0 ₂ in the atmosphere, today no longer balanced by the forests. This gaseous emission is the greenhouse gas that is most responsible for global warming and for depletion of the ozone layer surrounding the earth, so it is a dangerous environmental pollutant to all effects.

Even the exhaust gases from large ships are considered a major source of air pollution in the commercial and tourist harbours; since they contain nearly 10% sulphur, these exhaust gases also contribute to acid rain, which damages crops and buildings.

CH 676436 discloses a process for the treatment of the gas exiting from domestic and industrial plants.

For the above said reasons it is strongly felt the issue of the polluting emissions from the domestic or commercial plants, and in particular the issue of the emissions of particulate materials and of C0 ₂ . To date however it is still unsolved the technical problem of providing a device efficient in reducing such emissions, without having secondary drawbacks or conferring restrictions to the plants.

Summary of the invention

Scope of the present invention is to provide a device for the abatement of noxious emissions from the outlet of the domestic heating plants and of the commercial wood-burning ovens, useful in particular for the reduction of particulate and of carbon dioxide in the emissions, having a high efficacy of abatement thus contributing to the reduction of the air pollution caused by this kind of plants.

A further scope of the invention is to provide a device of the above said type that may be easily installed in the flue of any kinds of plants without impairing their efficiency or causing other drawbacks in the operations of the plant itself.

Still a further scope of the invention is to provide a device of the aforesaid type that is able to accumulate the noxious emissions in the inside and can be easily regenerated maintaining over time a high efficiency of emissions abatement.

Still a further scope of the present invention is to provide an efficacious method for the abatement of the noxious emissions from the domestic heating plants and from the wood-burning ovens for commercial use, comprising treating the gases coming from the plants before their emission in the atmosphere.

Still a further scope of the present invention is to provide a device and a method efficacious for the abatement of the noxious emissions from industrial plants and from large ships, comprising treating their exhaust gas before entry into the atmosphere.

These scopes are achieved by the device and the method according to the present invention, whose essential characteristics are respectively defined in the independent claims here attached.

Further important features are included in the dependent claims.

Brief description of the drawings

The features and advantages of the device of the invention will be evident from the following exemplary, non-limiting description of embodiments thereof, with reference to the attached drawings wherein:

- figure 1 shows a front view, partially exploded, of the present device in a first embodiment thereof;

- figure 2 is a front view of the inner structure (part a) and of the element external container (part b) of the device of figure 1 ;

- figure 3 is a front view of the present device in a second embodiment thereof;

- figure 4 shows a view in longitudinal section of an element of the inner structure in the device of figure 1 or of figure 3, indicated in the following as "micro- perforated element".

Detailed description of the invention

With reference to the attached figures, a device of the invention for treating the exhaust emissions from domestic heating plants and from commercial ovens comprises a tubular container 1 having substantially cylindrical form, provided with at least two holes, one in the central part of the device for the inlet, through a special inlet duct E, of exhaust gases to be treated and one in the upper part for the outlet of the exhaust gases treated, through a special outlet duct U.

With particular reference to the Figures 1 and 2 the modular structure of the container 1 is shown in a preferred embodiment thereof (see in particular the Figure 2, part b), formed by three separated portions 1 1 , 12 and 13; in general, the container 1 consists of at least two separated portions, joined to each other by supporting flanges better described in the following, so as to facilitate the maintenance of the device and possible operations of repair that the inner structure may require. A first embodiment of the present device, particularly suitable for the treatment of emissions coming from stoves and boilers, is illustrated in Figure 2a, wherein from the duct E the exhaust gas to be treated is directed inside an array of perforated elements 3, having for instance a substantially parallelepiped form and positioned in a radial pattern on a plane perpendicular to the longitudinal axis of the container 1 , and placed in a lower portion thereof, for instance at the portion 1 1 of the container with reference to the Figure 2b. The micro-perforated elements 3 are positioned on an inner cylindrical surface 4 through which they are in fluid communication with the inside of the device wherein the emissions to be treated arrive. Through the elements 3 and their micro- perforated surface the exhaust gas then comes out in the interspace formed between the portion 1 1 of external container and the inner cylindrical surface 4. In this portion 1 1 of container an absorbing solution is contained in such amount as to maintain the array of perforated elements 3 completely immersed in this solution, with the gas that escapes by bubbling inside the solution; therefore, in the present description, the array of elements 3 is sometimes referred to as "bubbler". Advantageously, the level of absorbing solution exceeds for instance the height of the array of elements 3 of 5-10 cm, so that their complete immersion in the solution is ensured.

In the present invention by "absorbing solution" any liquid substance or solution is meant, which is suitable for the abatement of the noxious substances present in the exhaust gases, in particular of the particulate matters and of the carbon dioxide; preferably by "absorbing solution" a concentrated aqueous solution of ethylene glycol is meant, and more preferably an ethylene glycol aqueous solution 50%. These aqueous solutions of ethylene glycol have been widely used also in the automotive industry, in particular as an anti-freezing liquid additive in combustion engines, in fuels and in the tanks for liquids to wash car glasses. As a matter of fact, ethylene glycol generates a cryoscopic lowering and an ebullioscopic raising of water, that respectively make this solution solidify at -38°C and boil at +108°C, therefore the solution remains liquid in a very wide range of temperatures, to also include temperatures in the most extreme weather conditions, from which derives the use as anti-freezing additive or as cooling liquid for radiators in combustion engines. The aqueous solution of ethylene glycol according to the invention can moreover comprise further agents useful for the abatement of the noxious substances in exhaust gases, for instance one or more oxidising agents.

The structure of the present gas bubbler with reference to a particular embodiment thereof is illustrated in greater details in the Figure 4 that illustrates the structure of the single element 3. From the duct E the gaseous emissions to be treated go into the elements 3, from which they come out through holes on their surface. According to a preferred embodiment of the present device, the elements 3 have the holes positioned on their only surface facing the interspace between the surface 4 and the portion 11 of container; as a matter of fact, in this way, the gas comes out from the gas bubbler maximising the residence time of the gas bubbles in contact with the absorbing solution. This can be appreciated in particular from the Figure 4, wherein the numeral 31 indicates the perforated surface of the element 3. Still with reference to the Figure 4, a particular embodiment is illustrated wherein the element has such an inner structure that the gas entering the duct E, directly or by means of a collection container, through an inlet hole 33 is directed towards the perforated surface 31 through a curved duct 32.

According to a preferred embodiment of the invention, the holes in elements 3 of the gas bubbler have moreover such dimensions that the gas flow exiting from them towards the solution is finely divided creating micro-bubbles, and typically these holes have a diameter comprised between 0,7 and 5,0 mm, and preferably equal to about 3,5 mm. This preferred feature of the present device allows maximising the efficiency in the treatment of the gas in the absorbing solution all other conditions being the same, thanks to a wider contact surface between the gas bubbles and the solution itself; and moreover allows an easier ascent of the gas bubbles inside the container facilitating their escape.

The microbubbles of treated gas inside the absorbing solution therefore go upwards inside the container 1 towards a second array of perforated elements 5, for instance of substantially parallelepiped form and positioned in a radial pattern on a plane perpendicular to the longitudinal axis of the container 1 , and placed in an upper portion thereof, for instance of the portion 13 with reference to the Figure 2, above the absorbing solution. The gas can go upwards inside the container thanks to the holes on the supporting flanges for the portions of the container 1 ; with reference to the Figure 2a the holes are visible on the flange 6, which joins the portions 1 1 and 12 of the container 1 , and on the flange 7, which joins the portions 12 and 13 of the same container. The gas coming from the holes on the flange 7 may enter through their micro-perforated surface inside the elements 5, in fluid communication with the inside of the cylindrical surface 8 on which they lean, and by them be directed towards the outlet duct U.

The second array of micro-perforated elements 5 is in fact in communication with the outlet duct U of the treated exhaust gases, directly or through a collecting element, which puts in communication the elements 5 with the outlet duct U. As it is for the above-mentioned gas bubbler and the elements 3, also for the array of perforated elements 5 an embodiment is preferred wherein the holes have the size reported above for the elements 3 and/or they are positioned only on the surface of the element 5 that faces the interspace between the surface 8 and the portion 13 of the container.

According to a particular embodiment of the invention the present device may further comprise, in a portion of the container 1 intermediate between the two arrays of micro-perforated elements 3 and 5, a module for producing electric energy from the power of the exhaust gases flow exiting the device, for instance by means of hydroelectric turbines connected to an inverter.

Advantageously, the above said module for producing energy is a removable module, which can be installed or uninstalled with relative ease depending on the needs in the use of the present device.

With particular reference to the Figure 3 here attached a second embodiment of the present device is described, particularly suitable for the treatment of the emissions coming from commercial ovens and fireplaces, wherein from an inlet duct E on the bottom of the device the emissions to be treated are forced to pass through an absorbing solution as described above, contained in a tubular portion of surface 4 on which are positioned in a radial pattern micro-perforated elements 3, having a configuration and position as described above for the device of Figure 2a. The treated gas at the outlet of the micro-perforated elements 3 go upwards inside the container 1 and, through the holes in a flange 7, get to the micro-perforated elements 5 positioned in a radial pattern on a tubular surface 8 by entering through their micro-perforated surface inside the tubular 8 and from here the gas escapes from the outlet duct U. The internal structure of the present device illustrated in Figure 3 is also placed inside a container 1 , preferably of modular structure, as that illustrated in the Figure 2b and described above.

The gas exiting from the duct U can be guided directly to the outside for emission into the air or, preferably, it is directed into a dedicated tank outside of the container 1 containing a suitable filter for capturing possible unburned particles escaped from the capture in the gas bubbler, for instance an activated carbon filter. Advantageously, this tank can be opened for replacing this filter upon reaching saturation.

The present device may further comprise a system for the regeneration of the absorbing solution that has accumulated particulate matter coming from the treatment of the exhaust emissions. This system includes for instance a tank 9, visible in the Figures 1 , 2 and 3, for taking the absorbing solution to be regenerated from the bottom of the container 1 , containing a special filter suitable for the depuration of the solution from the accumulated particulate and means for cooling the solution. Advantageously, also this filter can be easily replaced from the outside upon reaching saturation. The so regenerated and cooled solution can be brought back inside the container 1 by means of a recycling pump and a special pipeline. In this system one or more valves can be provided at the aim of assisting and controlling the access at the filter of the solution to be regenerated and the entry into the container 1 of the regenerated solution. According to a preferred embodiment of the present device, this tank with filter is made of a transparent material so that a direct and immediate visual control of the exhaustion of the filter is allowed.

According to a preferred embodiment of the present device, the device can further comprise an additional tank provided in the inside with a special filter for collecting the condensate in order to collect the absorbing solution dragged by the gas bubbles going upwards towards the outlet. When present, this additional tank is preferably placed at an intermediate portion of the container 1 , above the maximum level of absorbing solution, and it is provided by pipes 10 for transferring the liquid condensate back inside the container 1 so that it may be used once again for the treatment of emissions.

On the container 1 , in a position more easily reachable from the outside, an opening with a sealing plug may be provided for the refilling of the absorbing solution when this proves necessary.

The present device 1 further comprises, in the intermediate area between the gas bubbler and the array of perforated elements 5 for the outlet of the gas once treated, one or more walls for the separation of the space, and in particular for the separation of the portions 1 1 and 12 of the container, so that the gas emissions can go up inside the container 1 only through the holes in the flanges and so that the absorbing solution is prevented from going upwards.

Thanks to the special internal structure of the device of the invention, and in particular to the separation walls described above, the gas bubbles are subjected to a treatment by passing through the absorbing solution in the lower part of the container, then they go upwards through the cells formed by the separation walls up to the outlet in the upper part of the container; this occurs with a particular ease for the gas bubbles to go upwards, carried and directed to the outlet, and without risk for the absorbing solution to spill outside, thanks to the stabilization given also to it by the presence of the separation walls.

The device of the invention can be produced with different shapes and size from those illustrated in the attached figures, depending on the flue on which the device is to be installed. The present device can be furthermore installed also in industrial plants and may be useful in the shipbuilding industry for installation on the exhaust systems of large ships, and it is an efficient system for abatement of the noxious emissions also in these cases, with important benefits for the environment and the people's health.

According to a preferred embodiment of the present device, it further comprises sensor means suitable for detecting the level and/or the saturation degree of the absorbing solution inside the gas bubbler and for signalling these data to an electronic control unit connected to a fault signalling system thereof visible from the outside of the device. Thanks to these sensor means, a user may be informed in real time when the solution and/or the external filter require a maintenance service. Further sensor means can be included in the present device for the detection of the saturation degree of the filter in the collecting tank of the outlet gases and/or of the filter for the regeneration of the absorbing solution. Also in this case the detected data may be signalled, by means of a dedicated electronic system, on a display outside of the container.

The present device may moreover comprise sensor means for measuring the temperature inside the container, by means of a probe installed that is able to detect the temperature inside the container.

In experiments it was observed that the device of this invention has a high efficiency in the abatement of harmful substances, and in particular of the particulate matters, without requiring for example increased temperature but working under normal pressure and temperature conditions. The present device does not have therefore any influence on the operation of the boiler or of the stove to which it is connected, or a negative effect on their consumption. Apart from the abatement of the particulate matters, the present absorbing solution is also capable of capturing up to 50% of the C0 ₂ emitted by the discharges of stoves, boilers and commercial ovens. As described in more detail below, it was experimentally observed a significant reduction of particulates in the emissions for the same vehicle on which the opacity of the exhaust is measured before and after the installation of the device of the invention.

The present device is also useful for reducing noxious substances in emissions from stoves and boilers that use any fuels, including wood, pellet, gas, fuel oil.

A first main advantage of the present device and of the method of the invention is represented by the fact that the absorbing solution used can be an aqueous solution and in general the solutes of possible use, in particular ethylene glycol, are non- polluting products, completely innocuous for the environment. The present device, therefore, not only allows efficiently reducing the emission of pollutants in the atmosphere, but it does not introduce other pollutants in the environment.

Still a further advantage of the present device and method is represented by the fact that the absorbing solution can be continuously regenerated inside the plant where the device is installed, in a simple and environmentally friendly way, also giving the possibility to collect the residues of particulate accumulated in an external filter, which may be easily replaced once exhausted. The present invention has been described up to here with reference to preferred embodiments. It should be understood that there may be other embodiments deriving from the same inventive core, as defined by the scope of protection of the claims given hereinafter.