GASIFIER STOVE

Abstract

 A gasifier stove (1) comprising a containment structure (2) housing a storage tank (3) for biomass fuel (4), a gasification crucible (6) connected to a combustion chamber (15) and being fluidically connectable to a heat exchanger, wherein the gasification crucible (6) is hollow and extends axially, along a vertical axis (Y-Y), from a lower end (7) having a first opening (8), to an upper end (11), having a second opening (12). The gasification crucible (6) is connected to the tank (3) by means of an outlet pipe (14) which leads to the crucible (6) through a feed hole (114), positioned, along the vertical axis (Y-Y), between the lower end (7) and the upper end (11). Advantageously, the gasification crucible (6) has a variable cross-section along its axial extension, measured perpendicular to said vertical axis (Y-Y), and, at the lower end (7), the first opening (8) has an inlet cross-section smaller than a feed cross-section at the feed hole (114) of the pellets (4).

Description

FIELD OF APPLICATION

[0001] The present invention relates to a gasifier stove.

PRIOR ART

[0002] Heating appliances, such as in particular stoves or boilers, that may be fuelled with solid fuel, e.g., wood or pellets, are known and widely used for heating air and/or water in living environments.

[0003] Said appliances of a known type usually comprise a containment structure housing the following, respectively: a combustion chamber, an electric igniter, a storage tank for solid fuel, means for moving the fuel into the combustion chamber, a first pumping means, or fan, for moving the combustion air by blowing or suction and for the related evacuation of the flue gases, a heat exchanger, and a second pumping means, or fan, for forced heat exchange and conveyance of hot air into the home environment.

[0004] The combustion chamber usually houses a brazier in which the fuel is deposited by means of prearranged devices, usually of the auger type.

[0005] The combustion air is drawn from outside the containment structure by the action of first pumping means, such as a first bladed fan actuatable by an electrically powered motor and conveyed through an inlet pipe at the brazier; here, by appropriate ignition means, the combustion is ignited, which generates high-temperature flue gases.

[0006] The gases then pass through a heat exchanger, usually arranged downstream of the combustion chamber, to exchange heat with the containment structure of the appliance, which in turn dissipates the heat, by irradiation and/or natural convection, to the home environment of installation.

[0007] Possibly, second pumping means, such as a second fan actuatable by an electric motor, may be provided to distribute heat to the outside environment in a forced convective manner, improving the thermal yield of the appliance and allowing rooms other than the one of installation to be heated as well.

[0008] The flue gases are expelled from the appliance through a special exhaust duct by the action of said first pumping means.

[0009] Command and control means, such as an appropriately programmed circuit board, are generally provided to manage and coordinate the various electrical devices provided in the appliance to enable its proper operation.

[0010] In the case of pellet stoves for domestic use, a flame visible through a glass is generated, and the heat is released into the room due to the combination of irradiation and forced and natural convection implemented in the stove structure.

[0011] The pellet stoves of the prior art are able to support the power demands of devices by modulating from a maximum to minimum power, depending on the heat needs required.

[0012] A common way to reduce emissions, specifically for particulate matter, used for biomass in general, and thus pellets, wood chips, and wood, is to carry out a multistage combustion, in which first pyrolysis and gasification take place, and then complete oxidation occurs, and thus the visible flame, at a location far from the original biomass.

[0013] This contrivance, coupled with the use of glass to view the flame from outside the stove, while reducing particulate emissions on the one hand, also generates a flame of a more aesthetically pleasing shape and color, visibly more attractive than one anchored to the biomass.

[0014] An example of a known gasifier stove is illustrated in patent EP3356495, in which the amount of pellets in the brazier is manually loaded discontinuously, and allows a combustion regime of the gases generated at a predetermined power.

[0015] Lacking an automatic pellet feed system, the presence of pellets in the brazier relies on manual or gravity filling, with no possibility of changing the power regime provided by the appliance.

[0016] This solution does not solve the problem related to the need to be able to modulate the power regime of the stove, from a minimum power, if little heat is needed, to a maximum power, when more heat and a more spatially extended flame is desired.

[0017] A further disadvantage of the prior art is that the equilibrium between the pellets introduced and the primary air required for combustion is variable depending on the heating value of the fuel, and slower or faster gasification processes result, with alterations in the pellet level in the gasification crucible and the consequent need for instruments to check the aforesaid pellet level.

DISCLOSURE OF THE INVENTION

[0018] There is therefore a need to solve the drawbacks and limitations mentioned with reference to the prior art.

[0019] Thus, the main task that forms the subject matter of the present invention is to solve the highlighted technical problems by eliminating the drawbacks referred to in the cited prior art.

[0020] More specifically, the object of the present invention is to devise a gasifier stove that allows the generation of pollutants to be contained while at the same time precisely modulating the heat generation from a minimum value to a maximum value according to the user's requirements.

[0021] The task and objects mentioned, as well as others that will become clearer later on, are achieved by a gasifier stove according to claim 1.

DESCRIPTION OF THE DRAWINGS

[0022] Further features and advantages of this invention will become more apparent from the following detailed description of preferred, non-limiting embodiments thereof, in which:

Figures 1-2 represent perspective views from different angles, in partial cross-section, of a gasifier stove according to a possible embodiment of the present invention;

Figure 3 illustrates a front view, not sectioned, of the gasifier stove in Figure 1, from the side of the arrow III shown in Figure 1;

Figure 4 illustrates a side view, not sectioned, of the gasifier stove in Figure 2, from the side of the arrow IV shown in Figure 2;

Figure 5 represents a cross-sectional view of the gasifier stove in Figure 4, along the cross-sectional plane V-V indicated in Figure 4;

Figure 6 represents a cross-sectional view of the gasifier stove in Figure 3, along the cross-sectional plane VI-VI indicated in Figure 3;

Figure 7 represents the cross-sectional view of Figure 5, with some enlarged details highlighted;

Figure 8 represents the cross-sectional view of Figure 6, with some enlarged details highlighted.

[0023] Elements or parts of elements common to the embodiments described hereinafter will be indicated with the same numerical references.

DETAILED DESCRIPTION

[0024] In the following exemplary embodiments, individual features, given in relation to specific examples, may actually be interchanged with other different features, existing in other exemplary embodiments.

[0025] With reference to the previously mentioned figures, a gasifier stove comprising a containment structure 2, of the desired shape, in which there are housed a storage tank 3 for biomass fuel, such as pellets 4, for example, has been denoted by the number 1.

[0026] The tank 3 is connected at the bottom to an outlet pipe 14 for pellets 4, at a feed hole 114 through which the pellets 4 from the outlet pipe 14 enter the gasification brazier or crucible 6.

[0027] The tank 3 is also made airtight and thus does not allow air to enter from the outlet pipe 14 for pellets 4.

[0028] A gasification crucible 6 is provided, which is substantially tubular in shape, i.e., hollow. The geometry of the gasification crucible, with respect to a cross-sectional plane perpendicular to a vertical axis Y-Y, may be of any shape. For example, the geometry provided may be circular, elliptical, square, rectangular, trapezoidal, etc. It is also possible to provide for irregular and asymmetrical geometries. The gasification crucible 6 is connected to a combustion chamber 15 and is fluidically connectable to a heat exchanger (not illustrated).

[0029] The gasification crucible (6) is hollow and extends axially, along a vertical axis (Y-Y), from a lower end 7 having a first opening 8, to an upper end 11, having a second opening 12.

[0030] The first opening 8 is suitable to allow the passage of a first gasification air 9. Said first opening 8 typically has a grid configuration with a determined full-to-empty ratio. The full-to-empty ratio of the first opening 8 is such that it retains the pellets 4 intact and allows the passage of the air that a possible suction pumping means 22, such as a fan, provides for suctioning downstream of the combustion chamber 15. As an alternative to the suction fan, a pressurized pumping means may also be provided.

[0031] The gasification crucible 6, as seen, is connected to the tank 3 by means of the outlet pipe 14 which leads to the crucible 6 through a feed hole 114, positioned, along the vertical axis Y-Y, between the lower end 7 and the upper end 11.

[0032] Advantageously, said gasification crucible 6 has a variable cross-section along its axial extension, measured perpendicular to said vertical axis Y-Y. In particular, at the lower end 7, the first opening 8 has an inlet cross-section smaller than a feed cross-section at the feed hole 114 of the pellets 4.

[0033] Preferably, the inlet cross-section of the first opening 8 coincides with the minimum cross-section of the gasification crucible 6.

[0034] Advantageously, the cross-section of the gasification crucible 6 varies in a manner monotonically increasing from the inlet cross-section of the first opening 8 up to the feed cross-section at the feed hole 114. It should be pointed out that the concept of a monotonically increasing progression should be understood in a broad sense, so as to include progressions of the cross-section of the gasification crucible 6 that also provide for constant segments. In fact, a constant segment, which is not decreasing, satisfies the general definition of an overall monotonically increasing progression. Such monotonically increasing progression of the gasification crucible cross-section 6 allows the pellets to be kept below the level of the feed hole 114 of the outlet pipe 14, facilitating the achievement of an equilibrium between the gasification front and the rising level of the pellets. In other words, there is equilibrium between the rate of rise of the pellets (which gradually slows down due to the monotonically increasing progression of the cross-section of the gasification crucible 6) and the increase in the gasification surface area (resulting in an increase in the rate of consumption of the pellets). In this way, an equilibrium may be found between the rate of increase of the level of the pellets and the rate of consumption of said pellets.

[0035] According to one embodiment, the feed cross-section at the feed hole 114 coincides with the maximum cross-section of the gasification crucible 6, wherein said feed cross-section, at the feed hole 114, is constant. It should be noted that the height of the feed hole 114 is limited with respect to the overall height of the gasification crucible 6.

[0036] According to a possible embodiment, the gasification crucible 6, in the segment between the inlet cross-section and the feed cross-section, has a truncated conical geometry; for example, said truncated conical geometry is axial-symmetric with respect to an axis of symmetry parallel to said vertical axis Y-Y. The truncated conical geometry may also be non-axial-symmetric, comprising, for example, a truncated pyramid with a base that is rectangular, square, elliptical, trapezoidal, etc.

[0037] Preferably, the second opening 12 of the upper end 11 has an outlet cross-section smaller than or equal to said feed cross-section at the feed hole 114.

[0038] Preferably, but not exclusively, the area of the inlet cross-section of the first opening 8 of said gasification crucible 6 is between 1.000 and 10.000 mm².

[0039] Preferably, but not exclusively, the area of the feed cross-section at the feed hole 114 is between 2.000 and 20.000 mm².

[0040] According to one embodiment, between the gasification crucible 6 and the combustion chamber 15 an expansion chamber 13 is interposed having an inlet 113 coinciding with the upper end 11 of the crucible and an outlet 115 at which the expansion chamber 13 fluidically connects to the combustion chamber 15. Therefore, the expansion chamber 13 fluidically connects the gasification crucible 6 and the combustion chamber 15.

[0041] Preferably, the cross-section at the second opening 12 is less than or equal to the cross-section at the outlet 115 of the expansion chamber 13.

[0042] According to an embodiment, the expansion chamber 13 has a larger cross-section at an intermediate portion between the inlet 113 and the outlet 115, said cross-section being larger than the feed cross-section at the feed hole 114 of the gasification crucible 6.

[0043] The air inlets of the gasification crucible 6 all come from a portion of pipe called a plenum, meaning a portion of piping for the containment in a "still" state of higher or lower air flow rate and the main function of which is as a distributor or general manifold.

[0044] In general, the plenums are sized so that the velocity of the air inside them is decidedly less (lower) than the velocity of the air in the inlet channel and in the outlet channel of the portion under consideration.

[0045] The first opening 8, through which the first gasification air 9 passes at least partially, is connected to a first plenum 10a fed by an inlet pipe in turn fed by a general air supply pipe 30.

[0046] There is also provided, externally to said gasification crucible 6 and in the vicinity of said upper end 11, a second plenum 10b, advantageously circumscribing externally said gasification crucible 6, having a series of second openings 112, for the passage of a second combustion air 28, and thus coinciding with the passage from the cross-section of the gasification crucible 6 and the expansion chamber 13.

[0047] There is also provided, externally to the combustion chamber 15, and in the vicinity of the outlet 115 of the expansion chamber 13, a third plenum 10c, advantageously circumscribing said cross-section having a 360° opening with an inlet 116, for the third combustion air 38, and thus coinciding with the passage from the expansion cross-section to the combustion chamber 15.

[0048] The combustion chamber 15 and all the passages and all the openings above it are responsible for allowing the proper mixture of the syngas and the combustion air, and for completing the formation of the visible flame.

[0049] There is also, coinciding with the combustion chamber 15, a glass 19 that allows the flame to be viewed from outside and allows for heat transmission by irradiation from inside the stove to the surrounding home environment.

[0050] The combustion chamber 15 has an additional inlet 23, for a fourth combustion air 24, formed on one of its walls 25 and connected to a fourth plenum 10d, connected to the air supply pipe 30.

[0051] An igniter 29 is also provided, communicating with the inside of the gasification crucible 6.

[0052] The combustion circuit is thus composed of distinct chambers defined by the gasification crucible 6, which extends from the lower end 7 forming the inlet of the first gasification air 9, which passes through the first opening 8 to the inlet cross-section of the second combustion air 28, which passes through the second openings 112, and from the combustion chamber 15, which extends above the expansion chamber 13, which comprises the inlet 116 for the third combustion air 38 and the feed inlet 23 for the fourth combustion air 24.

[0053] Subsequently, the combustion chamber 15 connects with the rest of the containment structure 2 to convey the gases resulting from combustion to a heat exchanger and then to the flue gas exhaust system through flue pipes of a known type.

[0054] That which defines the beginning and the end of the components is the location of the air inlet points, with the exception of the fourth air 24.

[0055] The pump-ready fan may operate by blowing, if mounted at the combustion air intake (positive pressure combustion system), or in suction, if mounted at the outlet of the stove, before the flue pipe (negative pressure combustion system).

[0056] Operating in suction, the air enters from one or more pipes that are connected to the various plenums 10a,10b,10c,10d; each plenum fulfils the function of distributing air over all the provided passage openings.

[0057] Ideally, but not necessarily, each plenum allows for distribution over the entire perimeter of the area involved in the air intake.

[0058] Ideally, but not necessarily, two or more plenums may be merged into a single, larger plenum, leaving the air outlet points unchanged.

[0059] The operation of a gasifier stove according to the present invention will now be described.

[0060] The operation of the gasifier stove is as follows: the pellets 4, contained in the sealed tank 3, are transported through the pellet outlet pipe 14 into the gasification crucible 6 using, for example, a worm, or a propeller, or a motorized screw with suitable motorized means.

[0061] The pellets 4 fall into the gasification crucible 6 and are retained by the first opening 8: the full-to-empty ratio of the first opening 8 is such that it keeps the pellets intact, and allows the passage of air that any pumping means, such as a fan, provides for blowing or suctioning from the gasification crucible 6.

[0062] Once the gasification crucible 6 is partially full, the igniter 29, for example, being of the glow plug type, provides for heating of the crucible until a first combustion process is initiated.

[0063] Once the first ignition phase has passed, the amount of air entering the crucible 6 is reduced to switch from standard combustion to the chemical phenomenon of pyrolysis, particularly in the inner, woody part in the absence of air (endothermic reaction with the liberation of gases, liquid compounds, and combustible solids), and the phenomenon of gasification (exothermic partial oxidation reaction) is also triggered where there is a minimum amount of air.

[0064] Once the reaction is triggered, the pumping means, such as a fan, provides for the amount of air to be blown or suctioned out of the crucible 6, always in such an amount as to maintain the situation of heating the woody mass in oxygen deficiency, which does not allow the reaction to proceed to complete combustion, and thus what are generated are a syngas and a possible weak flame that consumes a small part thereof.

[0065] The gasification phenomenon, being exothermic, allows the entire pyro-gasification process within the crucible 6 to be self-sustaining.

[0066] This gasification phenomenon is a function of the mass of pellets 4 contained in the crucible 6, the amount of primary air entering from the lower inlet 8, the thermal stratification of the pellets 4, and the extent of surface area of fresh pellets 4, i.e., that part where the new pellets 4 fall within the crucible continuously and at a cadence, or pellet 4 flow rate, proportional to the power intended to be developed.

[0067] If the power of the gasifier stove 1 requires an inlet for pellets 4 that tends to make said granules accumulate more and more, regardless of the appropriate primary air, the consumption of the pellets 4 does not counteract their growth, the result being that the crucible 6 will inevitably be filled up to the feed hole 114 of the pellets 4, resulting in a clogging in the supply system for the pellets 4.

[0068] However, the variable-area shape of the gasification crucible 6 causes the fresh cross-section of the pellets 4 to become gradually larger as the pellets 4 increase. The gasification capacity is proportional to this area, and thus the gasification process also accelerates, always reaching equilibrium with the velocity of growth of the pellets 4. Therefore, the aforementioned monotonically increasing progression of the cross-section of the gasification crucible 6 allows the pellets to be maintained below the level of the feed hole 114 of the outlet pipe 14, as the equilibrium between the gasification front and the increase of the pellet level is achieved, and thus the equilibrium between the rate of increase of the pellet level and the rate of pellet consumption.

[0069] In this way, the shape of the crucible allows for there to always be a level of pellets 4 in which the accumulation rate of the pellets 4 and the consumption rate of the pellets 4 for gasification find an equilibrium between the crucible inlet section 8 and the feed cross-section at the inlet or feed holes 114 of the pellets 4.

[0070] Said equilibrium makes it unnecessary to resort to means of detecting the level of the pellets 4, resulting in savings on sensor technology.

[0071] The equilibrium between feed of pellets 4 and consumption of pellets 4 is achievable even at flow rates of pellets 4, and thus powers, other than the maximum. Simply, a lower input of pellets 4 for the same gasification air 9 will reach equilibrium with the gasification velocity of a lower area than the equilibrium level attainable at the maximum power, shifting the equilibrium level to a lower height of the crucible of variable cross-section. Similarly, with the same load of pellets 4 and solely by varying the gasification air 9, it is possible for the consumption of the pellets 4 to be accelerated or decelerated, resulting in a shift in the equilibrium level within the gasification crucible 6.

[0072] The gas generated inside the gasification crucible 6 that is not involved in combustion rises upward until it encounters the second combustion air 28 coming from the second plenum 10b through the second openings 112.

[0073] It is at that time and position that the mixing of syngas and oxygen sufficient to develop the actual flame is triggered. In addition, the third combustion air 38, corresponding to the plenum 10C, contributes to the combustion of the syngas at the inlet of the combustion chamber 15.

[0074] The combustion chamber 15 also has an additional inlet 23 for the sole purpose of providing the excess air necessary to ensure the complete combustion of each fuel gas molecule.

[0075] The air needed for the gasification and combustion processes flows into the stove through one or more suitable pumping means, or fans, such as a first suction means 22 operating in suction or a second pumping means operating by blowing.

[0076] The air path extends from a generic inlet to the confines of the stove, passes inside the general air supply pipe 30 of the various plenums flowing into the first plenum 10a, second plenum 10b, third plenum 10c, and fourth plenum 10d, is distributed through the first opening 8, the second openings 112, the third opening 116 and the additional inlet 23, and ends up in the fluid volume between the gasification crucible 6 and the combustion chamber 15; then, in the form of flue gas, the whole flows into a prepared exchanger (not illustrated) and then into an exhaust gas expulsion duct.

[0077] The partialization of air at the various inlets by a possible single pumping means, in suction or in blowing, is ensured by appropriate geometries of air passages placed downstream of the various plenums.

[0078] As may be appreciated from that which has been described, the present invention overcomes the drawbacks of the prior art.

[0079] It was thus found that the invention has achieved its intended task and the objects by having obtained a gasifier stove that allows the pyrolytic and gasifying phenomena to be activated in one zone of the stove and then the complete oxidation of the syngas to be achieved in another zone, with appropriate air inlets, self-adapting to the various pellet/gasifying air supply velocities, and thus to the various powers.

[0080] The flame inside the combustion chamber is soft, i.e., without the sinewy, glaring flames typical of all pellet stoves, and thus has a conspicuously much larger volumetric development for the benefit of pleasing aesthetics, visible from the outside through the related glass.

[0081] A further advantage is the fact that, while common, prior-art pellet stoves at varying burned power turn out to have a very small flame that at minimum power is almost completely inside the brazier, becoming in some moments invisible through the glass, the flame referred to in the present solution develops inside the combustion chamber, in front of the glass, even at the corresponding minimum power and in a much more conspicuous manner than in prior-art stoves.

[0082] An additional advantage of the present invention is that staged combustion, passing through distinct locations in which gasification and syngas combustion take place, emits less particulate matter and NOx than combustion with a flame anchored to the actual woody mass.

[0083] Another advantage of the present invention is the possibility of increasing or decreasing the presence of air inside the stove by one or more pumping means, operating by suction or blowing, which, suitably fractionated on the various inlets to the various plenums, distributes that air to the various inlets.

[0084] The presence of the means of conveying the pellets from the tank to the gasification crucible also allows the input of the woody mass or pellets to be increased or decreased.

[0085] The two actions, coordinated through electronic controls, enable the stove of the present invention to operate at different power regimes.

[0086] An additional advantage of the present invention is that it provides a self-adaptive geometry of the properties of various fuels (pellets that are energetically rich to a greater or lesser extent, varying grain size, combustion conditions at different ambient temperature regimes) and has a self-adaptive equilibrium between the rate at which pellets are introduced and the rate at which they gasify and are consumed, without ever having to check the level of pellets introduced.

[0087] Naturally, the materials used, as well as the dimensions constituting the individual components of the invention, may be more relevant depending on the specific requirements.

[0088] The features indicated as advantageous, appropriate, or similar may also be eliminated or replaced by equivalent ones.

[0089] Those skilled in the art, in order to satisfy contingent and specific needs, may make numerous modifications and variations to the solutions described above, said modifications and variations all being contained within the scope of the invention as defined in the following claims.

Claims

1. A gasifier stove (1) comprising a containment structure (2) housing a storage tank (3) for biomass fuel (4), a gasification crucible (6) connected to a combustion chamber (15) and being fluidically connectable to a heat exchanger,

the gasification crucible (6) being hollow and extending axially, along a vertical axis (Y-Y), from a lower end (7) having a first opening (8), to an upper end (11), having a second opening (12),

the gasification crucible (6) being connected to the tank (3) by means of an outlet pipe (14) which leads to the crucible (6) through a feed hole (114), positioned, along the vertical axis (Y-Y), between the lower end (7) and the upper end (11),

characterized in that

said gasification crucible (6) has a variable cross-section along its axial extension, measured perpendicular to said vertical axis (Y-Y), and in particular, at the lower end (7), the first opening (8) has an inlet cross-section smaller than a feed cross-section at the feed hole (114) of the pellets (4),

wherein the cross-section of the gasification crucible (6), measured perpendicularly along its vertical axis (Y-Y), varies in a manner monotonically increasing from the inlet cross-section up to the feed cross-section at the feed hole (114).

2. The gasifier stove (1) according to claim 1, wherein the cross-section of the gasification crucible (6), referred to a cross-sectional plane perpendicular to said vertical axis (Y-Y), has a circular, elliptical, square, rectangular, or trapezoidal geometry.

3. The gasifier stove (1) according to claim 1, wherein the cross-section of the gasification crucible (6), referred to a cross-sectional plane perpendicular to said vertical axis (Y-Y), has an irregular and/or asymmetrical geometry.

4. The gasifier stove (1) according to claim 1, 2 or 3, wherein the inlet cross-section coincides with the minimum cross-section with respect to the other cross-sections of the gasification crucible (6) measured perpendicularly along its vertical axis (Y-Y).

5. The gasifier stove (1) according to any one of claims 1 to 4, wherein the feed cross-section at the feed hole (114) coincides with the maximum cross-section of the gasification crucible (6) and wherein said feed cross-section, at the feed hole (114), is constant.

6. The gasifier stove (1) according to any one of claims 1 to 5, wherein the gasification crucible (6), in the segment between the inlet cross-section and the feed cross-section at the feed hole (114), has a truncated conical geometry, axial-symmetric or otherwise with respect to an axis of symmetry parallel to said vertical axis (Y-Y).

7. The gasifier stove (1) according to any one of claims 1 to 6, wherein the second opening (12) of the upper end (11) has an outlet cross-section smaller than or equal to said feed cross-section, at the feed hole (114) .

8. The gasifier stove (1) according to any one of claims 1 to 7, wherein between the gasification crucible (6) and the combustion chamber (15) an expansion chamber (13) is interposed having an inlet (113) coinciding with the upper end (11) of the crucible and an outlet (115) at which the expansion chamber (13) fluidically connects to the combustion chamber (15).

9. The gasifier stove (1) according to claim 8, wherein the cross-section at the second opening (12) is less than or equal to the cross-section at the outlet (115) of the expansion chamber (13).

10. The gasifier stove (1) according to claim 8 or 9, wherein the expansion chamber (13) has a larger cross-section at an intermediate portion between the inlet (113) and the outlet (115), said cross-section being larger than the feed cross-section at the feed hole (114) of the gasification crucible (6).

11. The gasifier stove (1) according to any one of the preceding claims, wherein the area of the inlet cross-section of the first opening (8) of said gasification crucible (6) is between 1.000 and 10.000 mm².

12. The gasifier stove (1) according to any one of the preceding claims, wherein the area of the feed cross-section at the feed hole (114) of said gasification crucible (6) is between 2.000 and 20.000 mm².

13. The gasifier stove (1) according to any one of the preceding claims, wherein the first opening (8) is suitable to allow the passage of a first gasification air (9), coming from a first plenum (10a), wherein said gasification crucible (6) has, at its upper end (11), a series of second openings (112) suitable to allow the passage of a second combustion air (28), and, at the passage of gases towards said overlying combustion chamber (15), extending above the expansion chamber (13), has a third opening (116) for a third combustion air (38), and lastly in the combustion chamber (15) there is an additional inlet (23) for a fourth combustion air (24) .

14. The gasifier stove (1) according to any one of the preceding claims, wherein the outlet pipe (14) of said biomass fuel (4) comprises a worm, or a propeller, or a motorized screw with motorized means suitable for transferring pellets into the gasification crucible (6).

15. The gasifier stove (1) according to any one of the preceding claims, wherein said gasifier stove (4) comprises one or more pumping means suitable to increase or decrease the passage of air inside said stove, said pumping means and said outlet pipe (14) allowing said gasifier stove to operate at different power regimes.

Drawing