ES2880039T3 - Biomass heat generator for home use - Google Patents

Abstract

The biomass heat generator (1) for domestic use, comprising: a box-shaped main casing (2) having an elongated extension inside which a reaction chamber (3) and a combustion chamber (4 ) of the gases coming from said reaction chamber (3), said reaction chamber (3) being located below said combustion chamber (4); a box-shaped secondary casing (5) having an elongated extension and branching from said box-shaped main casing (2) into said reaction chamber (3), said box-shaped secondary casing (5) having an open end (5a) to introduce the biomass and define a pre-established angle (a) with respect to said box-shaped main casing (2) in such a way as to allow the biomass to descend by gravity; at least one first inlet (6) for the air in said reaction chamber (3); at least one second inlet (7a, 7b, 7c) for air in said combustion chamber (4); a first grid (8) housed inside the main box-shaped casing (2) below the reaction chamber (3), characterized in that it comprises: a second grid (9) housed inside said main box-shaped casing ( 2) between said combustion chamber (4) and said reaction chamber (3) in the branch of said box-shaped secondary casing (5) to concentrate the gases, said first grid (8) having a curvilinear shape with oriented concavity towards said reaction chamber (3) so as to receive biomass from said box-shaped secondary casing (5).

Description

DESCRIPTION

Biomass heat generator for home use

The present invention relates to a biomass heat generator for domestic use.

In the domestic sphere, stoves or boilers are known that take advantage of biomass combustion to generate heat.

As is known, biomass is an organic material that is obtained through a biological process and allows to obtain heat in a sustainable way, limiting CO2 emissions during combustion.

Regardless of the embodiment variants, the operating principle is based on the injection of stoichiometric air into the chimney. By increasing the air supply, the performance improves, but so do the emissions in terms of fumes and polluting particles that, in a certain percentage, are discharged into the atmosphere.

A more ecological and efficient heat generation technology is represented by pyrolysis and gasification. Pyrolysis is a thermochemical decomposition process of biomass in the absence of oxidizing elements and at high temperatures, generally above 400 ° C.

Unlike pyrolysis, gasification is a process of thermochemical conversion of a solid / liquid fuel into "synthesis gas", by means of an external agent (for example, air or oxygen or steam) in suitable quantities.

Pyrogasification is already used in some industrial sectors, for example, in waste combustion plants or cogeneration.

Patio heaters and stoves for cooking outdoors or in semi-enclosed environments that take advantage of pyrogasification are also known.

In the domestic field, some stoves are known that work through the use of single charge pyrogasification. In particular, the applicant has developed some hybrid solutions in which the reaction is substoichiometric combustion, that is, poor in oxidizing agent. In these solutions no visible smoke is emitted to the naked eye. Furthermore, due to the fact that temperatures of about 700 ° C and above are generated, complete combustion of all substances occurs, including PAHs (polycyclic aromatic hydrocarbons).

These solutions include the introduction of single-load biomass carried out from above into the combustion chamber, which is usually delimited by a cylindrical or parallelepiped container. The reaction is not easily controllable, that is, it is not very modulable depending on the heat generated and it can only be interrupted with a jet of water towards the interior, with an evident dispersion of smoke in the environment, or by covering the container above and below below. Furthermore, the introduction of cold fuel reduces the internal temperature, so that the additional fuel supply, once the reaction has been triggered, is not feasible if it is not very slow. The risk is, in fact, to interrupt the reaction.

Document WO 2014/064300 describes a biomass heat generator for domestic use according to the preamble of claim 1.

US 2007/234937 describes a biomass heat generator comprising two grids.

In this context, the technical task underlying the present invention is to provide a biomass heat generator for domestic use that eliminates the drawbacks of the prior art as described above. In particular, an object of the present invention is to propose a biomass heat generator for domestic use that has a higher efficiency and lower emissions with respect to known solutions.

Another object of the present invention is to propose a biomass heat generator for domestic use that allows a continuous supply of fuel in safety conditions.

Another object of the present invention is to propose a biomass heat generator for domestic use that is easily controllable, in particular to allow modulation of the intensity of the flame based on the desired amount of heat.

Another object of the present invention is to propose a biomass heat generator for domestic use, in which the interruption of combustion occurs in a short time and without the generation of unpleasant emissions.

Another object of the present invention is to propose a biomass heat generator for domestic use that generates less combustion residues with respect to known solutions.

Another object of the present invention is to make available a biomass heat generator for domestic use that is compact, structurally simple, easy to maintain, modular, capable of heating and / or cooking.

The set of technical tasks and the specified objectives are substantially achieved by a biomass heat generator for domestic use, according to one or more of the appended claims.

Other characteristics and advantages of the present invention will become more apparent from the following indicative and therefore non-limiting description of a preferred but not exclusive embodiment of a biomass heat generator for domestic use as illustrated in the attached drawings, in those who:

- Figure 1 schematically illustrates a biomass heat generator for domestic use according to the present invention in a sectional view;

figure 2 illustrates a part (first grid) of the biomass heat generator of figure 1, according to a first embodiment;

Figures 3a, 3b, 3c illustrate three embodiments of the first grid of Figure 2;

Figures 4a and 4b illustrate a part (second grid) of the biomass heat generator of Figure 1, according to two further embodiments.

With reference to the figures, the reference number 1 refers to a biomass heat generator for domestic use.

The generator 1 comprises a box-shaped main casing 2 and a box-shaped secondary casing 5, both with elongated and branched extensions to each other.

In particular, the box-shaped main casing 2 encloses a reaction chamber 3 and a combustion chamber 4 for the gases coming from reaction chamber 3.

As can be seen in figure 1, the box-shaped main casing 2 extends substantially vertically, that is, in height, the reaction chamber 3 is located below the combustion chamber 4.

The box-shaped secondary housing 5 branches from the box-shaped main housing 2 into the reaction chamber 3 and has an open end 5a for introducing the biomass.

Branching from the box-shaped main casing 2, the box-shaped secondary casing 5 forms with it a pre-established angle, indicated by "a", in such a way as to allow the descent by gravity of the biomass introduced through of the open end 5a.

The preset angle is preferably an acute angle, more preferably between 25 ° and 45 °. The box-shaped main casing 2 and the box-shaped secondary casing 5 are preferably tubes having a rectangular or square or circular section.

In particular, a hole is made in the box-shaped main casing 2 in the reaction chamber 3 to allow coupling (eg by welding) of the box-shaped secondary casing 5.

In a variant embodiment, the box-shaped secondary casing 5 is a tube that tapers from its open end 5a towards the branch of the box-shaped main casing 2. Therefore, the diameter of the box-shaped secondary casing Box 5 is at a maximum at the open end 5a thereof and tapers as it moves towards the box-shaped main housing 2.

The box-shaped main shell 2 and the box-shaped sub shell 5 are made of metal or a metal alloy. For example, iron can be used, which has the advantage of being a catalyst. Alternatively, steel can be used.

Preferably, means (not illustrated) are provided to interrupt the fuel inlet from the box-shaped secondary casing 5 towards the box-shaped main casing 2. For example, it may be used an internal shutter, within the box-shaped secondary housing 5, which is moved to open or close using a manual lever outside the box-shaped secondary housing 5.

Preferably, the generator 1 further comprises a connection screen (not illustrated) between the box-shaped secondary housing 5 and the box-shaped main housing 2.

The connection screen is, in fact, a hood screen that allows to retain the heat emitted by the box-shaped main housing 2 in the reaction chamber 3, which facilitates:

i) formation of an internal hot zone that heats the fuel prior to its entry into the box-shaped main casing 2

ii) keep heat in reaction chamber 3

so that the fuel enters the reaction chamber 3 at an optimum temperature that accelerates the pyrolysis step. In other words, the zone within the connection screen constitutes a heat zone to aid drying in the box-shaped secondary shell 5.

Furthermore, an access hole for igniting combustion is provided in the box-shaped main casing 2. For example, the access hole (to which a hatch door is associated) is located above the reaction chamber 3. This This arrangement allows ignition from above that occurs immediately and without release of fumes.

Generator 1 further comprises:

- at least one first inlet 6 for the air inside the reaction chamber 3;

- at least one second inlet 7a, 7b, 7c for the air in the combustion chamber 4;

- a first grid 8 housed inside the box-shaped main casing 2 below the reaction chamber 3;

- a second grid 9 housed inside the box-shaped main casing 2 between the combustion chamber 4 and the reaction chamber 3 in the branch of the box-shaped secondary casing 5.

The first inlet 6 for air is obtained in the box-shaped main casing 2 under the first grid 8. In particular, the first inlet 6 is interposed between the first grid 8 and a drawer for collecting combustion residues. , indicated by the reference number 10. The drawer 10 closes the box-shaped main casing 2 which lies below, that is to say, it constitutes the bottom thereof.

The area between the drawer 10 and the first grid 8 has the purpose of circulating the air coming from the first inlet 6. In figure 1, the first inlet 6 is made up of a duct that leads into the box-shaped main casing. 2. The first entrance 6 is preferably protected by a movable hatch door (not illustrated). In this area, when the combustion is in full swing, the temperatures remain very high due to the fact that there are hot charcoal that are consumed by contact with the air. The amount of air required is modest, so it is enough to open the door of the hatch of the first inlet 6 just a little to inject the necessary air, thus preventing too much heat from being dispersed to the outside.

The second inlet 7a, 7b, 7c for air is obtained in the box-shaped main housing 2 above the second grille 9.

In figure 1, the second air inlets within the combustion chamber 4 are three, indicated by 7a, 7b, 7c. They are obtained at different heights in the box-shaped main casing 2 and / or on opposite sides with respect to the combustion chamber 4.

The second inlets 7a, 7b, 7c for the air in the combustion chamber 4 have the function of efficiently burning the gas mixture coming from the reaction chamber 3, helping to maintain high temperatures.

The realization of the inlets at different levels (ie heights) in the box-shaped main casing 2 and on opposite sides thereof with respect to the combustion chamber 4 facilitates the mixing of air and gas. In particular, some of the inlets have a fixed intake rate to ensure a minimum necessary intake of air. One or more of the inlet ports have an adjustable inflow rate in order to modify the mixing parameters.

To ensure that the air injected into the combustion chamber 4 is already hot, closed pathways are made (by screening or shielding or ducts) that partially surround the box-shaped main casing 2, from which they receive heat and reach progressively higher temperatures. high until reaching the inlet (or inlets 7a, 7b, 7c) made in the box-shaped main casing 2. The heating of the air injected into the combustion chamber 4 (in the jargon known as "secondary air") is of fundamental importance to increase combustion efficiency.

In the most advantageous solution experienced so far, a conduit is included that starts from the area below the drawer 10 and extends upwards, being welded to the box-shaped main casing 2, up to one or more of the entrances 7a, 7b, 7c in the combustion chamber.

The first grid 8 has a curvilinear shape with a concavity facing the reaction chamber 3 in such a way that it collects the biomass from the secondary box-shaped casing 5.

In the embodiment of figure 2, the first grid 8 comprises a first frame 18 in which a plurality of first bars 28 are fixed, the plurality of first bars 28 are parallel and bent in such a way as to give the first one a curvilinear shape. grid 8.

In particular, the first frame 18 has a substantially rectangular shape.

As seen in Figures 3b-3c, the first bars 28 can be bent in such a way that they define a more or less accentuated curve and extend between two opposite sides of the first frame 18.

The distance between the adjacent bars 28 is preferably equal to or less than 4 mm. In fact, from 6 mm wood granules, the dimension of the charcoal after contraction due to the release of energy will be about 4.5 mm. With a distance between the bars 28 equal to or less than 4 mm, the charcoal is retained by the first grate 8 and, therefore, is subjected to the primary air (that is, coming from the first inlet 6) to be consumed. .

The first grid 8 is preferably fitted removably, i.e. not fixedly, within the box-shaped main casing 2 so that the first bars 28 are parallel to the direction of entry of the biomass from the secondary casing in the form cash 5.

The first frame 18 preferably engages flush with the box-shaped secondary casing 5 to allow a continuous descent of the fuel, that is, a descent without jamming.

The first grid 8 is preferably fitted inside the box-shaped main casing 2 so that the first bars 28 are parallel to the direction of entry of the biomass from the box-shaped secondary casing 5. In this way, it is produced a scraping effect on the first grid 8 that facilitates the fall of the ashes and minerals created by the combustion of charcoal.

The variant of the first grid 8 illustrated in figure 3a demonstrates that the first bars 28 do not extend between two opposite sides of the first frame 18 (as in figures 3b-3c). Rather, the first bars 18 extend from one side of the first frame 18 to meet a flat plate 38 that connects them to the opposite side of the first frame 18.

The second grid 9 comprises a second frame 19 on which a plurality of second bars 29 are fixed, said second bars 29 are reciprocally parallel and spaced and in a number that allows an amount of air passage comprised between 22% and 40%.

The second frame 19 preferably has a substantially rectangular shape. The second bars 29 extend between two opposite sides of the second frame 19. For example, as illustrated in Figure 4b, each bar is made up of a hollow tube having a square section. Alternatively, the tube can have a rectangular or circular section.

Instead, Figure 4a illustrates a variant in which each bar 29 is in the form of a folded sheet of metal with a V or U-shaped cross section.

The functions of the second grid 9 are:

i) concentrating the gases that are formed within the reaction chamber 3 in such a way that it has a more condensed and rapid flow of combustible gases;

ii) prevent the secondary air from coming into contact with the fuel, especially during the ignition stage, since the flow of exhaust gases drives the secondary air away;

iii) creating a turbulence in the expelled gases that as soon as they leave, they slow down and mix with the secondary air;

iv) due to high temperatures, the material of the second grid 9 (which is metal or an alloy) becomes very hot, and especially in the central part of it it helps the decomposition of pollutants

v) guiding the fuel inlet from the box-shaped secondary casing 5 to the box-shaped main casing 2.

Above the combustion chamber 4, the path of the gases branches and then recombines thanks to an annular structure 11 (in technical jargon called "smoke circuit"), which has the following objectives: i) absorb the heat emitted by combustion and irradiating it to the outside towards the environment, through an exhaust pipe 12 to which a valve 13 is associated;

ii) creating a zone for mixing the gases sent to the outlet, which when colliding with the walls of the two branches 11 a, 11 b of the annular structure 11, slows down and therefore facilitates the deposition of the particles. The annular structure 11 illustrated here is suitable for heating the surroundings and can vary in shape and dimensions. The annular structure 11 is preferably mounted on the box-shaped main casing 2 and can be disassembled and replaced by other structures suitable for different uses (for example, a cooktop, a boiler for heating liquids, etc.).

The valve 13 of the exhaust pipe 12 regulates the speed of the general reactions of the generator 1, thus also allowing the regulation of the heat emitted.

The operation of the biomass heat generator for domestic use proposed here is briefly described below.

The biomass, after being introduced through the box-shaped secondary casing 5, enters the reaction chamber 3 and is deposited on the first grid 8. A lighter liquid is sprayed through the access hole made in the box-shaped main casing 2 on the second grate 9, which as it filters through the openings thereof, reaches the underlying biomass. The flame can be lit using a long nozzle lighter.

In this step it is advisable to fully open the valve 13 of the exhaust pipe 12 to achieve the maximum air flow and therefore accelerate the ignition. As the pyrolysis occurs almost instantaneously, the emission of fumes is practically imperceptible.

The flames are distributed over the entire surface area of the biomass and spread to the underlying zone so that the entire volume of biomass present undergoes pyrolysis.

This step lasts approximately 13-20 minutes (depending on the amount of biomass injected into reaction chamber 3) and is of fundamental importance since it allows reaching the optimal thermal conditions for the next step.

No smoke is emitted as it is a pyrolytic step. In reaction chamber 3, the fuel undergoes a dimensional reduction due to energy production and is transformed into charcoal. The volume thus released is charged with new fuel that falls continuously by the force of gravity from the box-shaped secondary casing 5. The new fuel, therefore injected, is heated so much by the effect of the bed from underlying embers as by the upward gas flow, and begins to pyrolyze. Before the pyrolysis of all the fuel below, the pyrolysis of the fuel continuously injected through the box-shaped secondary casing 5 is already started.

When the biomass parts below have completed pyrolysis, gasification of the residual charcoal begins, which, in contact with the primary air, dissolves and generates gases and releases heat. The gas thus generated rises through the embers, mixes with the pyrolysis generated by the fuel and reaches the combustion chamber 4. In practice, the charcoal layer is in the middle, between two contemporary reactions different, pyrolysis from above and gasification from below. These reactions are thermally held together to keep the overall reaction high.

The descending biomass is already very hot and quickly reacts; in addition, the gasification of the coal absorbs and burns the oxygen coming from the primary air and removes it from the pyrolytic reaction that takes place above. As it continues to be consumed, the charcoal reduces in volume with downward shifts, leaving space at the top for the entrance of new fuel already hot (and therefore only a little humid, if there is one), since it heats up before entering the reaction chamber 3.

During this step, the opening of the valve 13 of the exhaust pipe 12 can be adjusted to obtain the required heat within a minimum and a maximum.

The continuous flow of charcoal downwards causes a kind of "scraping" of the first grate 8, so that inorganic particles and ashes fall into the drawer 10 below.

The reactions continue in the same sequence as long as there is fuel at the inlet of the box-shaped secondary shell 5.

To terminate the operation of the generator it is sufficient to interrupt the fuel supply, for example by covering the free end 5a of the box-shaped secondary housing 5 with a lid. Alternatively, it is possible to include a flow regulating valve within the box-shaped secondary housing 5. Residual fuel from below the cap or valve continues to flow into reaction chamber 3. As long as fuel is present to pyrolyze, the two reactions continue; When the fuel runs out, there is only gasification of the remaining charcoal.

The final charcoal combustion can only last 15-20 minutes. During this step, the maximum CO emission of the entire procedure is produced, which is however very modest, practically insignificant. Before starting a new process, it is convenient to eliminate the residues that have remained in the first grid 8. From the description provided, the characteristics of the biomass heat generator for domestic use according to the present invention, as well as the advantages, are clear.

In particular, the proposed generator is based on two contemporaneous reactions that mutually support each other to maintain a high thermal level. This leads to the emission of high temperature gas that triggers the cracking of the tars (tar residues, aromatic hydrocarbons).

The gas produced by gasification rises through the charcoal overlay that functions as a filter. A high temperature reaction environment, as is known, leads to lower carbon production, but with higher thermal power, and also leads to higher production of high thermal quality synthesis gas, given the calorific value of tar, which It is in ready-to-burn condition.

Heating and drying of the biomass is obtained prior to its entry into the reaction chamber, back into the box-shaped secondary shell.

The heat generation process takes place continuously and does not depend on load blocks.

The generator is compact and therefore suitable for use in domestic or similar environments.

The operation with natural air is also very advantageous, since it makes the generator usable also in geographical areas outside the national electricity grid, or where the connection has been lost due to external causes (ie earthquakes).

In addition, the generator is easy to assemble and disassemble even by non-expert personnel, that is, non-technical personnel. The modular structure allows easy transport and maintenance.

The regulation of the heat is also within the reach of non-technical personnel, since it is enough to open / close the valve of the exhaust pipe.

Pollutant gas emissions are negligible, and even under the worst operating conditions (peak emissions), they are always much lower than known solutions.

Claims (10)

1. The biomass heat generator (1) for domestic use, comprising: a box-shaped main casing (2) having an elongated extension inside which a reaction chamber (3) and a combustion chamber (4) for the gases coming from said reaction chamber (3) are located, being located said reaction chamber (3) below said combustion chamber (4); a box-shaped secondary housing (5) having an elongated extension and branching from said box-shaped main housing (2) into said reaction chamber (3), said box-shaped secondary housing (5) having an open end (5a) to introduce the biomass and define a preset angle (a) with respect to said main box-shaped casing (2) in such a way as to allow the biomass to descend by gravity; at least one first inlet (6) for air in said reaction chamber (3); at least one second inlet (7a, 7b, 7c) for the air in said combustion chamber (4); a first grid (8) housed within the box-shaped main casing (2) below the reaction chamber (3), characterized in that it comprises: a second grid (9) housed within said box-shaped main casing (2) between said combustion chamber (4) and said reaction chamber (3) in the branch of said box-shaped secondary casing (5) to concentrating the gases, said first grid (8) having a curvilinear shape with a concavity oriented towards said reaction chamber (3) so as to receive the biomass from said secondary box-shaped casing (5). 2. The biomass heat generator (1) according to claim 1, wherein said preset angle (a) is between 25 ° and 45 °. The biomass heat generator (1) according to any of the preceding claims, wherein said first grid (8) comprises a first frame (18) on which (18) are fixed a plurality of first bars ( 28), bent in such a way as to give the first grid (8) a curvilinear shape and parallel to each other. The biomass heat generator (1) according to claim 3, wherein said first bars (28) are parallel to the direction of entry of the biomass from said secondary box-shaped casing (5). The biomass heat generator (1) according to any of the preceding claims, wherein said second grid (9) comprises a second frame (19) on which a plurality of second bars (29) are fixed, said second bars (29) being parallel to each other and being spaced and in a number that allows the passage of air comprised between 22% and 40%. The biomass heat generator (1) according to any of the preceding claims, wherein at least one first inlet (6) for air is obtained in the box-shaped main casing (2) below the first grid (8). The biomass heat generator (1) according to any of the preceding claims, wherein at least one second inlet (7a, 7b, 7c) for air is obtained in the box-shaped main casing (2 ) above the second grid (9). The biomass heat generator (1) according to claim 7, comprising a plurality of second inlets (7a, 7b, 7c) for the air in said combustion chamber (4), said second inlets (7a) being obtained , 7b, 7c) at different heights in the box-shaped main casing (2) and / or on opposite sides with respect to said combustion chamber (4). The biomass heat generator (1) according to any of the preceding claims, wherein said box-shaped main casing (2) and said box-shaped secondary casing (5) are rectangular section tubes, square or circular. The biomass heat generator (1) according to claim 9, wherein said box-shaped secondary shell (5) is a tube tapering from its open end (5a) towards the branch of said shell box-shaped main (2).