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Title:
COMBUSTOR FOR BIOMASS TREATMENT
Document Type and Number:
WIPO Patent Application WO/2018/146544
Kind Code:
A1
Abstract:
The object of the present invention is a combustor (1) for the combustion heat treatment of a fuel, preferably biomass (C). Said combustor (1) comprises at least, from top to bottom: a feeding and loading chamber (10) of said biomass (C) which engages on a combustion chamber (11) substantially with equal section and develops upwards with a diverging section also serving as a discharge for the combustion fumes, said combustion chamber (11) of said biomass (C) and an injection chamber (12) of the combustion air necessary to said combustion, said combustion chamber (11) and said injection chamber (12) being separated by at least one divider element (15). Inside said combustor (1) there is identified a first flow, descending, of said biomass (C) and a second flow, ascending, of the fumes generated by its combustion, said flows being in countercurrent with each other.

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Inventors:
USCI ROSALINO (IT)
MARCANTONI MICHELE (IT)
Application Number:
IB2018/000103
Publication Date:
August 16, 2018
Filing Date:
February 09, 2018
Export Citation:
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Assignee:
TRE P ENG S R L (IT)
International Classes:
F23G5/04; F23G5/24; F23G7/00
Domestic Patent References:
WO2016023412A12016-02-18
Foreign References:
EP1462718A12004-09-29
US4616572A1986-10-14
US4346661A1982-08-31
EP1990576A12008-11-12
DE102013104598A12014-11-06
Attorney, Agent or Firm:
PREMRU, Rok (Mar.Bre S.r.l, 2 Via San Filippo, Fabriano, 60044, IT)
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Claims:
CLAIMS

Combustor (1) for the treatment of a shovelable or liquid-pastelike fuel, preferably biomass (C), comprising at least, from top to bottom:

- a feeding and loading chamber (10) of said biomass (C), which:

- engages on a combustion chamber (11) substantially with equal section,

- develops upwards with a diverging section, said chamber (10) also serving as a discharge of the fumes produced from the combustion of said biomass (C) and reducing their outflow rate from the upper surface of said biomass (C),

- said combustion chamber (11) of said biomass (C),

- an injection chamber (12) of the combustion air necessary to said combustion of said biomass (C), said chamber (12) comprising an injection system (4) of said combustion air

at least one divider element (15) being provided between said combustion chamber (11) and said injection chamber (12), capable of:

- providing rest and support for said biomass (C) fed from the top

- allowing the simultaneous passage of said combustion air from the bottom towards said biomass (C)

- the fall and the passage of combustion ash

inside said combustor (1) there being provided:

- a first flow, descending, of said biomass (C) that arranges and accumulates, stratifying vertically, in said combustor (1), and

- a second flow, ascending, of the fumes generated by the combustion of said biomass (C),

said flows in countercurrent to each other allowing at least:

- cooling of said combustion fumes,

- drying of said biomass (C)

characterised in that said combustor (1) comprises at least one "inner body" (2) in vertical position for at least the housing of one or more functional components (21; 24; 30.n) of said combustor (1),

and in that the aforesaid combustion chamber (11) of said combustor (1) is defined between the perimeter confining walls (110) of said combustor

(1) and the inner perimeter confining walls of said at least one inner body

(2) facing said biomass (C).

Combustor (1) according to the previous claim,

characterised in that said inner body (2) may comprise in one inner cavity (20) thereof at least:

- a series of vertically arranged temperature sensors (24), adapted to detect the temperatures inside the combustor 1, and/or

- one or more heat exchangers (30. n) for the selective cooling of at least said inner confining walls (200) of said at least one inner body (2) of the combustor (1).

Combustor (1) according to one or more of the previous claims,

characterised in that said inner body (2) may further internally comprise at least:

- a circuit (21) for starting the combustion of said biomass (C), and/or

- injection or drawing devices for fluids, such as combustion air, gases, fumes or other; and/or

- possible mechanical stirrers; and/or

- additional sensors, such as pressure, gas and fumes analysis sensors or the like.

Combustor (1) according to any previous claim,

characterised in that it comprises therein at least a first filter of said combustion fumes, said filter consisting of said biomass (C) accumulated and stratified therein and crossed by said combustion fumes.

Combustor (1) according to any previous claim,

characterised in that it further comprises a compartment (12; 13) for the interception and collection of the ash.

Combustor (1) according to any previous claim, characterised in that it comprises:

- control means (6, 8) of the level (F) of said biomass (C) inside said combustor (1) and adjusting means (52, 132) of the same,

- control (42) and adjusting (41) devices of the combustion air flow rate, adapted to ensure a diffusive combustion.

Combustor (1) according to the previous claim,

characterised in that

- said control means (6, 8) of the level (F) of said biomass (C) comprise:

- at least a level sensor (8) of the biomass (C), inside the combustor (1), and/or

- at least a meter (6) of the weight of said combustor (1), said meter. (6) being able to comprise at least a load cell whereon said combustor (1) rests,

- said adjusting means (52,132) of the level (F) of said biomass (C) comprise at least:

- a weighing and dosing system (52) of said biomass (C) adapted to adjust the inlet flow rate thereof, said weighing and dosing system (52) being located substantially at the mouth of an opening (103) for the inlet of the biomass (C) in said feeding and loading chamber (10) of said combustor (1), and/or

- a mill (132) for discharging the combustion ash, said mill (132) keeping said ash below the said injection chamber (12) of the combustion air.

- said control (42) and adjusting (41) devices of the combustion air flow rate comprising at least a blower (41) and with a mass flow rate meter (42) of said combustion air.

Combustor (1) according to any previous claim,

characterised in that

it comprises additional temperature sensors, adapted to detect the temperatures along the vertical of the same combustor (1), positioned on any other inner surface of said combustor (1) cooperating with said biomass (C),

and in that it comprises at least one flow rate meter (7) of the said combustion fumes.

9. Combustor (1) according to any previous claim,

characterised in that said combustion chamber (11), delimited by said at least perimeter (110, 120) and inner (200) confining walls of said combustor (1), may consist of a chamber (1 1) having as horizontal section a surface S of substantially constant area A along its entire height H.

10. Combustor (1) according to the previous claim,

characterised in that said perimeter (1 10, 120) and inner (200) confining walls have axial symmetry relative to a vertical axis a-a of said combustor (1) with their polygonal or circular horizontal section.

11. Combustor (1) according to claim 9 and/or 10,

characterised in that for said area A and said height H there being defined limit values Lmin, Lmax of the mutual distance L between said perimeter (1 10, 120) and inner (200) confining walls within which a correct combustion of said biomass (C) and the compliance with constructive and/or functional constraints is at least guaranteed.

12. Combustor (1) according to any previous claim,

characterised in that it comprises a cooling system (3) of at least its aforesaid perimeter (110, 120) and inner (200) confining walls.

13. Combustor (1) according to the previous claim,

characterised in that said cooling system (3) may comprise at least:

- heat exchangers (31.n; 32.n) for the selective cooling of at least some parts of said perimeter confining walls (110, 120) of said combustion (1 1) and/or injection (12) chamber of said combustor (1), and/or - said at least one heat exchanger (30.n) of said one or more inner bodies (2) for the cooling of their inner confining walls (200). 14. Combustor (1) according to claim 12 and/or 13, characterised in that it further comprises heat exchangers (32.n) of the perimeter confining walls (130) of said compartment (12; 13) for the interception and collection of the ash.

15. Combustor (1) according to claim 13 and/or 14,

characterised in that said heat exchangers (30.n, 31.n, 32.n) are advantageously placed outside the combustor (1).

16. Combustor (1) according to any previous claim,

characterised in that the aforesaid divider element (15) between said reaction chamber (11) and said injection chamber (12) is a grid (15) compatible with solid and/or liquid-pastelike biomasses (C) and/or having suitable granulometry and consistency to be retained by the meshes of said grid (15).

17. Combustor (1) according to the previous claim,

characterised in that said grid (15) is a grid with one or more openings adapted to house said one or more inner bodies (2), respectively.

18. Combustor (1) according to any previous claim,

characterised in that said injection system (4) of the combustion air in said injection chamber (12) comprises at least:

- one or more nozzles, preferably mounted on at least one radial lance (40) inside said injection chamber (12)

- the aforesaid control (42) and adjusting (41) devices of the combustion air flow rate.

19. Combustor (1) according to any previous claim,

characterised in that said biomass (C) is poultry dejection, in particular "manure".

20. Method for the treatment of a fuel, preferably biomass (C), inside a combustor (1) according to one or more of claims 1 to 19,

characterised in that it keeps the level (F) of said biomass (C) in said combustor (1) to values such that the outflow rate of the combustion fumes from the surface of said biomass (C) is less than 0.5 m/s.

Description:
COMBUSTOR FOR BIOMASS TREATMENT

D E S C RI P T I O N

The present invention relates to a waste-to-energy and energy recovery system of rejection or waste material, preferably of organic origin.

More precisely, the object of the present invention is a waste-to-energy system for biomasses.

Even more precisely, the object of the present invention is a system for the waste-to-energy treatment and disposal of animal effluents, preferably poultry dejections, for example "manure" available from farms by direct combustion. As known, the term "biomass" refers to the biodegradable fraction of products, waste and residues of biological origin coming from agriculture, forestry and related processing industries, as well as the biodegradable part of industrial and urban waste.

According to a more general and less stringent meaning, "biomass" can be considered as all the waste-to-energy material of organic origin, both vegetable and animal, for example for the production of electrical, thermal energy and or of by-products.

At present, a plurality of plant engineering solutions exist for the waste-to- energy and recovery of said biomasses.

The most used processes are attributable to "thermochemical processes", based on the action of heat that allows the chemical reactions necessary for the transformation of biomass to obtain energy therefrom or to "biochemical conversion processes" due to the contribution of enzymes, fungi, bacteria or similar microorganisms that are formed in the biomass under particular conditions (e.g., in the absence of oxygen).

Among the thermochemical processes, "direct combustion" or "gasification" may be listed, while among the biochemical ones the well-known "anaerobic digestion" may be considered.

The choice of the most appropriate technology is normally made on the basis of the chemical-physical characteristics of the biomass to be treated, depending on the "size" of interest and/or the end uses of the producible energy (thermal and/or electrical).

For example, poultry dejections are preferably treated "thermochemically" not lending themselves to an anaerobic digestion.

It is known that laying hens, broilers, turkeys, ducks and geese, quails and similar animals, as a consequence of their well-known anatomical characteristics, expel their dejections simultaneously with the urine.

Such dejections are therefore particularly rich in nitrogen and nitrogen compounds that, in the case of biochemical treatment, would inhibit those microorganisms responsible, as seen, for their digestion and degradation.

For these reasons, in fact, the waste-to-energy treatment of the manure is normally conducted thermochemically, in particular in biomass combustion plants.

Among the very few types of plants installed to date, a very common one is represented in Fig. 1.

Said plant for the treatment and waste-to-energy of the manure provides at least three stages: a first stage SI of drying, grinding (or pelletizing) and loading of the biomass, a subsequent stage S2 in which its combustion and the possible energy recovery of at least part of the heat released is carried out and a final stage S3 of treatment and abatement of the pollutants carried by the combustion products.

More in detail, the stage SI comprises a hopper Γ in which the manure is loaded and a first screw (not shown) which pushes it, if already dried, directly inside a combustor 2' for its combustion, or, if still wet inside a dryer 10' placed immediately upstream of the same combustor 2' and communicating therewith. The drive motor of the screw is preferably equipped with and controlled by an inverter so as to be able to continuously adapt the flow rate of manure to be fed to the combustor 2' depending on its inner temperature.

Said combustor 2' is part of the subsequent combustion stage S2 and may consist of a "movable grid" combustor.

Said "movable grid" combustor 2, adaptable to different biomasses and to their different moisture contents, is characterised by a combustion chamber 20' with walls coated with refractory material resistant to the process temperatures, at the base whereof a grid is normally placed which has the function of supporting and moving the biomass from its entrance zone up to the waste exit and discharge zone.

For such function the grid, which is therefore internal to the combustion chamber 20', is equipped with movable elements or with a combination of fixed and movable elements.

At least one methane gas pilot burner manages the starting steps of the combustion inside said combustion chamber 20' while a discharge system 4' allows the expulsion of combustion ash, mainly containing metal oxides, phosphoric anhydride and heavy metals (especially copper).

Advantageously, the discharge 4' of the combustion ash is obtained on the bottom of said combustion chamber 20' and may provide the use of a second screw 40'.

"Movable grid" combustors 2 are characterised, during the combustion of the biomass, by the presence of open flames capable of exchanging heat by convection (but, sometimes, also radiative) with a heat exchanger 30' of an energy recovery system 3'.

Said energy recovery system 3' may preferably consist of a superheated water boiler and its heat exchanger 30' in a pipe bundle exchanger 30', normally inside the combustion chamber 20'.

The combustion fumes, by lapping said pipe bundle 30', are cooled and consequently superheat the water circulating therein.

Said superheated water is usually channelled and used as a working fluid in any generic energy conversion plant, for example in an "Organic Rankine cycle turbine" (hereinafter referred to as the "ORC unit") for the production of electrical and/or thermal energy, the latter usable, for example, for the preliminary drying of the same manure or for heating or cooling purposes.

Another type of combustor 2' often used in said plants for the treatment of biomass is that known as the "fluidized bed reactor".

Being it a technology known to the person skilled in the art, herein it is only noted that the lower part of this reactor is filled with sand (or other inert material) made fluid in a state of ebullience by an ascending air flow injected from the bottom of the same reactor.

When this fluid is brought to incandescence, the biomass is injected therein, which is dried, pulverized and thermally dissociated into its component molecules and finally oxidized.

Said biomass is injected within intense convective motions of combustion air and inert material, with which it is mixed and reacts.

When the combusted material is degraded to such an extent as to make the particle's weight insufficient to oppose to the ascending air flow, it is dragged upwards to a zone of the combustor 2' wherefrom the unburnt particles are forced to fall back into the fluid bed of incandescent inert material, until complete depletion.

With respect to the movable grid combustors previously seen, fumes and gases remain in the reactor for longer times, thereby ensuring more complete thermal degradation of the combustion by-products and of the pollutants.

In Figure 1, of the fume treatment end stage S3 there are shown, according to the direction of travel of the same:

- a "urea-ammonia conversion chamber" 5' - a dedusting system 6'

- a selective catalytic reduction system DE-NOx" 7'

- a two-stage scrubber 8' for their final "cleaning".

Since the aforesaid components are well known to the man skilled in the art, it is not necessary to dwell to much on their technical features and related operation. However, it is herein useful to note that in the "urea -ammonia conversion chamber" 5' urea is injected in solution which, upon being transformed into ammonia by processes and reactions known to the man skilled in the art, is used to favour and ease, in the subsequent selective catalytic reduction system DE- NOx" 7', the abatement and reduction of nitrogen oxides of the combustion fumes.

Given the considerable amounts of urea to be used, it can be advantageously produced in situ in a special dissolver (not shown) and then supplied directly in the conversion chamber 5' by known injection and dosing systems 50' comprising one or more pneumatic nozzles fed by a respective volumetric pump. Since the urea-ammonia conversion can be favoured by sufficiently high temperatures of the combustion fumes, their cooling can be slowed down by providing a preheating carried out for example in a preheater 31 ' downstream of said conversion chamber 5', of the water in inlet to the pipe bundle 30' of the energy recovery system 3' inside the combustor 2'.

According to a preferred constructive configuration, the selective catalytic reduction section DE-NOx" 7' for the removal of the nitrogen compounds from the combustion fumes consists of a series of prismatic modules of catalyst capable of favouring the transformation of the nitrogen oxides into molecular nitrogen and water.

By way of an example, a vanadium pentoxide and tungsten trioxide based catalyst is particularly active.

The actual quantity of catalyst to be used is normally determined by means of combustion tests within the reach of the man skilled in the art to be carried out in a laboratory, in special muffle furnaces, on samples of the same biomass or manure to be treated.

Between said urea-ammonia conversion chamber 5' and the selective catalytic reduction system DE-NOx" 7 a system for the dedusting 6' of the fumes produced by the combustion of the manure is normally positioned.

Said dedusting system 6' comprises at least two sections: a first section comprising a multicyclone 60' for the removal of the coarser particulate from the fumes and a second section downstream provided with at least one filter 6Γ, for example of the "sleeve" type, for the reduction of the concentration of dusts to the stack 9'.

Further, downstream of said dedusting system 6', a well-known two-stage scrubber 8' with acid phase + alkaline phase may be provided for the final "cleaning" of the combustion fumes which, despite the passage through the catalytic reduction system DE-NOx" 7' may still contain acid gases, mainly hydrochloric acid and sulphur dioxide, and ammonia residues.

In the scrubber 8', sulphur acid in the first stage and caustic soda in the second are dosed, while to reduce the formation of steam plumes, a Venturi "quencher" fed by fresh make-up water may be provided at the inlet thereof.

This description already shows the high structural and constructive complexity of a typical plant for the thermal treatment of biomasses of animal origin, in particular of poultry dejections.

This complexity generally depends on the composition and characteristics of the combustion fumes leaving the combustor 2' previously described, which are rich in powdery material in suspension and of highly polluting and toxic substances (among which the known chemical NOx resulting from the nitrogen compounds), thus requiring the articulated and severe purification and filtration treatment seen above.

Although the management of the plant is fully-automated, due to its complexity, adequate training must be provided to the operating personnel.

The system described above is further subject to high costs for routine maintenance (spare parts, assistance interventions by external companies, etc.) and disposal of solid residues and waste resulting from the treatment of the same manure, for example of combustion ash.

The same chemical-physical characteristics of the biomass used as a fuel may cause the plant, at least of its combustor 2' and the relative energy recovery system 3', to malfunction.

This depends substantially on the high concentrations of undesired substances detectable in the fumes resulting from its combustion which can cause incrustations, corrosion and fouling of at least components and devices inside the combustor 2', such as the refractory materials of its combustion chamber 20', the pipe bundle 30' of said energy recovery system 3' and/or the connecting pipes to the energy conversion unit ORC.

For example, the phosphoric anhydride produced during the start of the combustor 2' and the very first heating of the manure, which anticipates the actual combustion, sublimates forming incrustations on the "colder" outer surfaces of the pipe bundle 30', triggering corrosive phenomena.

This, besides being the cause of breakages or malfunctions, penalises the cooling of the combustion fumes and their energy recovery.

Said incrustations can also be removed only by providing automatic mechanical cleaning devices with a further worsening of the structural complexity of the plant and of its running and maintenance costs, in particular of the combustor 2'. Although present in small quantities in the combustion fumes of the manure, also chlorine can contribute to the aforesaid corrosive phenomena.

Furthermore, the effect of alkaline earth metals, in particular calcium, that during the combustion of the manure can act as low-melting for the refractory materials of the combustor 2' is not to be ignored.

Said refractories must therefore be suitably selected and/or previously protected with coatings having a high alumina content in order to be sufficiently resistant to this type of stress; this also affects the construction, running and maintenance costs of the combustor 2'.

Phosphorus and its compounds, as well as sulphur when present in the combustion fumes of the manure, are pollutants that can compromise the efficiency of the aforesaid catalyst DE-NOx" 7'.

It should be noted that all the above stated with reference to the treatment of the manure may be extended and generalised to any other type of animal biomass or not having the same or equivalent compositions and chemical-physical characteristics.

This is to say that the waste-to-energy plant described above is suitable, except minimum component and constructive adaptations within reach of the man skilled in the art, for the treatment of any biomass in a solid/pastelike state (also called "shovelable") with a high content at least of Nitrogen and/or Phosphorus and/or Sulphur and/or Chlorine and/or heavy metals and/or their compounds. The main object of the present invention is to obviate the drawbacks outlined above, by providing a combustor of a biomass treatment and waste-to-energy plant capable of minimising the polluting emissions and the dispersion of powdery material into the atmosphere.

A further object of at least some variants of the present invention is to provide a combustor of a plant for biomass treatment and waste-to-energy capable of processing any type of biomass as is, i.e. without the need for preliminary drying and/or grinding treatments.

A further object at least of some variants of the present invention, is to provide a combustor of a plant for biomass treatment and waste-to-energy free from corrosive, fouling and/or incrustation phenomena on their components and/or internal construction elements.

A further object at least of some variants of the present invention is to provide a combustor of a biomass treatment and waste-to-energy plant, characterised by a high thermal conversion efficiency, also suitable for small power plants, extremely compact and with low running and maintenance costs.

These and other objects, which shall appear clear hereinafter, are achieved with the combustor disclosed in the following description and in the annexed claims, which constitute an integral part of the same description. Further features of the present invention shall be better highlighted by the following description of a preferred embodiment, in accordance with the patent claims and illustrated, purely by way of a non-limiting example, in the annexed drawing tables, in which:

- Fig. 1 shows a common and known plant for biomass treatment and waste-to- energy;

- Fig. 2 shows a combustor according to the invention installable in a biomass treatment and waste-to-energy plant;

- Fig. 3a and 3b show, respectively, the distribution of the temperatures inside the combustor of the invention according to two different operating configurations;

- Figs. 4a to 4f show, schematically, different geometric configurations of at least one component part of the combustor of the invention

Unless otherwise specified, in this report any possible absolute spatial reference such as the terms vertical/horizontal or lower/upper, previous/next, upstream/downstream refers to the position in which the elements are arranged in operating conditions.

With the purpose of highlighting some features instead of others, not necessarily what described in the annexed drawings is to scale.

With reference to Fig. 2, number 1 indicates the combustor for the thermal treatment and waste-to-energy of biomasses C according to the invention.

More specifically, of said combustor 1 , there are shown a first summit zone 10, called "feeding or loading chamber" wherein the biomass C to be treated, dosed, is continuously introduced, a second intermediate zone 1 1 called "reaction" or "combustion" "zone or chamber" wherein the combustion reactions of the biomass C take place and a third bottom zone 12 substantially consisting of the part of the combustor 1 dedicated to the injection of combustion air and therefore said "injection zone or chamber 12".

The presence of a chamber 12 dedicated to the injection of combustion air avoids the need for known more complex and expensive systems, for example for a progressive injection and on multiple levels along the vertical development of a combustor.

The injection chamber 12 can also act as a compartment for the interception and collection of ash resulting from the aforesaid combustion or, as preferred, be advantageously communicating with an underlying and separate compartment 13 for the storage and discharge of the same.

Said injection chamber 12 being exposed at least by proximity and structural continuity both to the combustion zone 11 and to the relative ash, is capable of producing pre-heating of the inlet combustion air.

With such a structural configuration of the combustor 1 of the invention it will be readily apparent that the biomass C, which behaves as a charge or fuel, is arranged and accumulates, vertically stratified inside the combustor 1, flowing slowly by gravity from the loading chamber 10 to the reaction or combustion chamber 11, from top to bottom.

The fresh and wet layers of the biomass C will therefore be located near the dome 100 of the loading zone 10, the hottest and driest ones for the reasons which will be illustrated below, at the underlying combustion chamber 11.

The combustion air (or simply the "comburent"), preferably with a considerable excess compared to the stoichiometric amount theoretically necessary for the complete combustion, is injected into the combustor 1 from the bottom so as to create a uniform vertical air flow that reacts starting from the lower and deeper layers of the same biomass C, triggering its combustion in the manners that will be detailed shortly.

The excess of comburent determines and influences the field and the distribution of the temperatures inside the combustor 1 and, consequently, the flow rate, the composition and the temperature of the reaction products.

The level or "head" of the biomass C, i.e. the quantity loaded in the combustor 1, instead, determines the counterpressure that said comburent must overcome in order to go up therein and ensure the continuity of the combustion.

Said hot reaction products (hereinafter referred to as "combustion fumes" or simply "fumes") will consequently have an ascending flow from bottom to top and therefore opposed to that of the charge of the biomass C.

Said fumes, passing through the biomass C in countercurrent, are therefore directed towards the aforesaid feeding summit zone 10 of the combustor 1 wherefrom they can be expelled directly into the atmosphere or, as preferred, sent through a conduit 101 towards the purification and depuration stages downstream which can also be completely similar to those of the prior art.

Said feeding chamber 10 acts, for the reasons just mentioned, also as a fume discharge chamber. Their composition (in particular their organic content), temperature and flow rate will depend, as partly anticipated, at least on the chemical-biological characteristics of the biomass C, on the level of its head inside the combustor 1 and/or on the geometry and pattern of the profile of its feeding chamber 10.

As a result of the heat exchange establishing between said two countercurrent flows, the hot fumes that go up the combustor 1 and the biomass C which is compacted from the top to the bottom of the combustor 1, there is a:

- cooling of said fumes and/or reaction products,

and a simultaneous

- pre-heating of the loaded biomass C with a consequent and progressive drying thereof; from its summit stratifications to the deeper ones.

Under such conditions, the combustion which is triggered and carried out in the combustor 1 is a completely "diffusive" combustion, that is, as is known, achievable when fuel (the biomass) and comburent (air) mix with each other only in the combustion chamber 1 1 and characterised by the total absence of flames.

The combustor 1 of the invention differs, therefore, both from the "movable grid" ones of the prior art, which, as seen, have "open" flames and exchange heat by convection and/or radiance and from the "fluidised bed" ones in which the biomass is introduced and/or injected within intense convective motions of combustion air and inert material, with it is mixed and reacts. In the combustor 1 of the invention, instead, the biomass C in combustion can be considered as substantially stationary; in fact, as partly anticipated, said biomass C falls, altogether, very slowly downwards while the combustion fumes "leak" through it without convective motions.

Part of the combustion heat transferred by the biomass C is transmitted by conduction to at least some areas of the perimeter 1 10, 120 and possibly "inner" 200 (as will be clearer later) walls of the combustor 1 for the confinement of the same biomass C, wherefrom such heat can be at least partially recovered, removed and used for other purposes, for example for the production of electrical and/or thermal energy. Such aspects of the invention and the relative heat exchangers or energy recovery devices shall be referred to hereafter.

The aforesaid confining walls 1 10, 120, 200 shall be therefore referred to as "cooled" and substantially correspond to at least those circumscribing and defining at least the combustion 11 and/or injection 12 chamber of the combustor 1, i.e. those in contact with the hottest stratifications of the biomass C.

At the same time, with the pre-heating of the biomasses C by the same fumes, the preliminary drying and/or grinding treatments typical of the plants of the prior art and normally located upstream of the combustor 1 are no longer required.

As a consequence, in the combustor 1 of the invention both dry and extremely wet biomasses can be indifferently loaded, with a degree of humidity at least up to the order of 60%.

This leads to a greater versatility and breadth of use of the combustor 1 of the invention as well as a reduction of its complexity and of the construction, installation and maintenance costs of the entire treatment plant.

According to the invention and as clearly shown in Fig. 2, combustion chamber 11 and injection chamber 12 are separated by means of a divider element 15 capable of:

- providing rest and support for the biomass C to be treated and, at the same time,

- allowing the passage and the crossing, from the bottom, of the comburent necessary for the combustion of the biomass C and for its diffusion according to a uniform vertical flow,

- allowing the fall and the passage of ash to the underlying collection and storage zone 12 and/or 13.

The technical-structural features of said divider element 15 can therefore influence and determine the types of biomasses C that can be treated inside the combustor 1. Technically, according to the design choice made for said divider element 15, many types of solid or liquid biomass C can be loaded and burnt in the combustor 1 of the invention.

Without any limiting intent and according to a preferred embodiment of the invention, said divider element 15 is a mesh grid mainly compatible with solid or liquid-pastelike biomasses C or, more generally, having suitable granulometry and consistency to be retained by the meshes of said grid 15.

Said types of biomasses C may be those known, in jargon, with the term "shovelable", among which there may be included, as a non-exhaustive example, straws, grains, pomace, shells, vegetable and/or fruit and vegetables waste, organic fraction of MSW {Municipal Solid Waste), woodchip, manure, animal manure and dejections, and the like.

Preferably, hereinafter, reference will be made to the treatment and waste-to- energy of animal dejections, in particular poultry dejections, otherwise known as "manure" for the treatment whereof the invention is particularly useful.

From a purely geometric point of view, the aforesaid combustion chamber 1 1 of the combustor 1 is delimited and defined by the aforesaid perimeter confining walls 110.

Preferably, said combustion chamber 11 has perimeter confining walls 110 axially symmetrical with respect to a vertical axis a-a with their polygonal or circular horizontal section of diameter D.

According to a preferred embodiment variant of the invention and for the reasons which will be explained shortly, inside said combustor 1 one or more hollow bodies 2, also with a polygonal or circular horizontal section, with confining walls 200 (hereinafter referred to as "inner confining walls 200" or more simply "inner walls 200") may be provided. In such case, said combustion chamber 1 1 is defined between the aforesaid perimeter confining walls 110 of the combustor 1 and said inner confining walls 200 of said one or more hollow bodies 2 (see, for example, the constructive variants of Fig. 4).

In general, said combustion chamber 1 1 consists of a chamber 11 having as horizontal section a surface S of substantially constant area A along its entire height H.

For said substantially constant area A, two "limit values" relating to the mutual distance between the "cooled" walls 110, 200 may be defined; in particular a distance Lmin and a distance Lmax are defined, where:

- Lmin is the minimum distance between cooled walls 110, 200 below which the combustion of the biomass C in said combustion chamber 11 would be incomplete with the consequent production of unburnt

- Lmax is the maximum distance between cooled walls 1 10, 200 beyond which said combustion reactions would become unstable and such as to cause excessive heat losses through the fumes that go up the same combustor 1. By way of a non-limiting example, reference should be made to Fig. 4 annexed to the present description in which the possible horizontal sections, polygonal or circular, of said at least combustion chamber 1 1 of the combustor 1 and the said distances L, Lmin, Lmax between its cooled walls 1 10, 200 are shown.

Of course, the values of Lmin and Lmax depend on the height H and the type of biomass C. Also the height H of the combustion chamber 11 is limited by at least constructive and/or functional upper and lower constraints.

More in detail, in fact, the maximum height Hmax can be chosen according to purely economic reasons and in order to optimise the effectiveness of the heat exchange between said biomass C and combustion fumes in countercurrent, while the minimum height Hmin of the reaction zone 1 1 may depend on the need to make the exothermic combustion reactions occur between the biomass C and the combustion air injected from below; by way of an example, Hmin may depend on the possible descent rate of the biomass inside the combustor 1 , depending, in turn, on the combustion rate of the same and therefore, for each type of biomass, on its humidity.

Although in the enclosed figures the combustion chamber 1 1 is always shown with a constant section, nothing prevents the possibility of providing for it variable sections as long as suitable for guaranteeing the correct combustion according to what already illustrated.

It is instead clearly shown how the section 10 for feeding the biomass C and for the evacuation of the fumes overlying the combustion chamber 1 1 (whereon it engages substantially with equal section) develops upwards with a diverging section in order to lower as much as possible the outflow rate of the fumes from the upper surface of the same biomass.

The "natural" resistance offered by the biomass C to the countercurrent rising of the fumes allows retaining polluting substances, such as powders and particulates, in the combustor 1 , by implementing an actual first filtration stage. In other words, the biomass C itself acts as a filter, inside the combustor 1 , of the combustion fumes, retaining at least some of its harmful and polluting substances; in particular, particulate emissions with a PM {Particulate Matter) < 50 are avoided.

The low outflow rates of the fumes from the surface of the charge of the biomass C, generally less than 0.5 m/s, allow an ascending laminar flow to be achieved, which further limits the transport of the powdery material in the same fumes. This improves the quality of the fumes evacuated by combustor 1 with the possibility of providing, downstream, a less stringent and severe purification and depuration of the same and therefore an undoubted constructive simplification of the entire biomass C treatment plant.

The lower portion of the injection chamber 12 can assume a converging profile from top to bottom in order to direct and convey the combustion ash towards the bottom or the underlying storage and discharge compartment 13.

Having described the combustor 1 of the invention in a general form thereof, it is now possible to proceed to describe an embodiment thereof which is among the preferred ones.

As shown in the annexed Figs., the combustor 1 may be of the annular type internally comprising said at least one "inner body" 2, in vertical position and hollow, the walls 200 whereof towards the biomass C are those already mentioned as possible inner confining walls 200.

If said at least inner body 2 is alone it is preferably "central"; if more bodies 2 are provided, preferably, they can be arranged axially symmetrical with respect to the axis a-a of the combustor 1.

The divider element 15 between the combustion chamber 11 and the underlying injection chamber 12 is preferably a grid 15 with one or more openings where one or more bodies 2, correctly positioned, are housed.

The biomass C introduced through the feeding chamber 10 in said combustor 1 is therefore intended to occupy, stratifying, the internal volume substantially identified, as anticipated, between its perimeter 102, 1 10 and inner confining 200 walls of the at least one body 2.

As a result of such constructive choice, the volume inside each of said one or more inner bodies 2 is in no way occupied or in contact with the biomass C to be treated and can define as many cavities 20 adapted to house easily disassemblable and maintainable components and/or functional groups of the combustor, such as, for example:

- vertically arranged sensors, directly or indirectly in contact with the loaded biomass (by way of a non-limiting example, temperature sensors 24, gas and combustion products analysis, pressure sensors, etc.); and/or

- one or more heat exchangers 30.n for the removal of heat from said biomass in a controlled and selective manner on multiple levels along the height H of the combustor 1, that shall be referred to in more detail; and/or

- at least the circuit 21 for starting the combustion process of the biomass (Fig. 2), in turn, comprising at least the inlet conduit 22 of methane gas or LPG, connected in a known manner to the gas supply network, and an igniter (not shown); and/or

- fluid injection or drawing devices (non explicitly shown in the annexed figures), such as combustion air, gases, fumes or other; and/or

- possible mechanical stirrers allowing a more homogeneous and levelled distribution of the biomass loaded to the combustor 1.

Said one or more inner bodies 2, therefore, contribute by means of the components that they include and/or integrate (for example, as will be seen, at least the temperature sensors 24 and the exchangers 30.n) to a precise monitoring and control of the combustion of the biomass that continues to develop vertically carrying out a stratified and diffusive reaction.

The development and the longitudinal dimensions of the one or more inner bodies 2 are also chosen to allow the housing and the correct operation of the aforesaid functional components and/or groups as well as to allow the injection of the mains gas for the start of the combustion preferably at the combustion air inlet sections in the injection chamber 12 of the combustor 1. Once the diffusive combustion (flameless) has been triggered, the supply of said mains gas is stopped simultaneously by the automated closure of suitable valve units and known control means and within reach of the man skilled in the art.

In Fig. 2, the references 23 identify a plurality of gas injectors for the triggering of the combustion of the biomass C.

As anticipated above, according to a possible embodiment of the invention, a series of vertically arranged temperature sensors 24 that allow a complete measurement of the temperatures inside the combustor 1, from its feeding 10 to the injection 12 and/or ash discharge chamber can be installed along an external generating line of said at least one inner body 2.

Said sensors 24 allow detection of the temperatures along the vertical of the combustor 1 and, therefore, of the temperatures of all the layers of the biomass loaded and in combustion, with which they can also be in direct contact. Nothing prevents additional temperature sensors from being placed in other positions suitable for temperature detection and measurement, for example on any inner surface of the combustor 1 and/or in contact with the biomass C.

This allows a better measurement of the temperatures inside the combustor 1 and of the biomass loaded therein; in particular, it would allow control of the distribution and of the temperature gradient of the biomass both vertically and transversely (for example, radially in the case of combustor 1 with a circular section).

Inside the cavity 20 of the at least one internal body 2 of the combustor 1 , as anticipated, one or more exchangers 30.n for the recovery and removal of that heat that the biomass C, subjected to combustion, transfers by conduction to the inner confining walls 200 of the central body 2 of the combustor 1, with which it is in contact, may be further housed.

The heat absorbed by said at least one first heat exchanger 30.n can therefore be "disposed of in any generic energy conversion and recovery plant or stage, for example in a "Organic Rankine cycle turbine" (called "ORC unit") for the production of electrical and/or thermal energy, similarly to what anticipated with reference to the prior art.

More precisely, according to an embodiment of the invention, the combustor 1 comprises an efficient cooling system 3 of its outer and inner confining walls 110, 120, 200, comprising at least:

- said one or more exchangers 30.n inside said one or more inner bodies 2 and capable of cooling the walls 200 thereof and/or

- a plurality of additional heat exchangers 31.n for the cooling of said outer perimeter walls 1 10, 120 of at least the combustion 11 and/or injection 12 chamber of the combustor 1 whereon they rest, and also connected to an energy conversion and recovery plant.

Preferably, said exchangers 30.n and 31.n can be connected to the same energy conversion and recovery plant ORC, each capable of partially feeding it.

Preferably, said exchangers 30.n and/or 31.n can act on more levels, selectively and locally cooling the surfaces of the walls 110, 120, 200 whereon they rest; by controlling and adjusting their heat removal capacity, it will therefore be possible to control the local temperature of the wall and therefore of the biomass inside the combustor 1.

Said adjustment can be implemented by means of a combustor 1 control unit capable of servo-adjusting the individual flow rates of the heat transfer fluid to the exchangers 30.n, 31.n according to the operation of the same combustor 1 and/or of the conversion and recovery plant.

Therefore, according to the invention, heat can be removed selectively and suitably from each layer of the burning biomass in order to control the same combustion reaction.

Thanks to said selective removal of heat from the outer and inner perimeter walls, 110, 120, 200 of the combustor 1, it is possible to obtain different vertical distributions of temperature with different levels of biomass loaded and different values of the combustion air flow rates fed: it is therefore always possible to obtain different specific volumetric flow rates of the combustion fumes (and output rates of the same always lower, as seen, at 0.5 m/s) for fixed level of the biomass, by managing the outlet temperatures of the fumes (see Figs. 3a, 3b). According to the invention, limiting the outlet speed of the fumes does not therefore imply limiting directly the mass flow rate of the same or the thermal power of the same combustor 1.

Additional heat exchangers 32.n may be advantageously provided also at the ash storage compartment 13.

Without loss of generality, said exchangers 30.n, 31.n, 32.n may consist of exchangers of the coil, pipe-bundle type, or of the jacket type, or similar functionally equivalent devices, the heat transfer fluid whereof may be diathermic oil, water, or other equivalent fluids.

Advantageously, said exchangers 30.n, 31.n, 32.n can be placed outside the combustor 1, located in the cavity 20 of the central body 20, i.e. outside its confining walls 200 and/or outside the perimeter confining walls 110, 120 of the same combustor 1.

Unlike the prior art, therefore, none of these exchangers 30.n, 31.n and 32.n is neither in direct and close contact with the biomass C to be treated nor exposed to the combustion fumes and to the ash.

This ensures, on the one hand, an optimal and long-lasting operation of said exchangers 30.n., 31.n and 32.n not subject to wear, incrustations or corrosion by the effect of the more or less aggressive substances and compounds released by the combustion and carried by its reaction products; on the other hand, the ease of cleaning of the confining walls 102, 110, 120, 200 and the smooth sliding by gravity of the biomass C and/or the ash. As a consequence, the number and frequency of the operating stops of the combustor 1 for routine or extraordinary maintenance and the related running costs will be reduced.

The (primary and excess) combustion air supply system 4 of the combustor 1 is also shown, servo-regulated by the aforesaid control unit and capable of acquiring the flow rate and pressure signal.

Said air supply system 4 of the injection zone or chamber 12 may consist of a pressurised system comprising one or more injection nozzles preferably mounted on at least one radial lance 40.

Unlike the exchangers 30.n, 31.n, 32.n, said at least one lance 40 is inside the injection zone 12 of the combustor 1 and therefore potentially exposed to the combustion fumes and ash. In order to reduce the risk of clogging and incrustations of the nozzles, it can be protected by special covering pipes (not shown).

According to a preferred embodiment of the combustor 1 , said at least one lance 40 may consist of a plurality of lances 40, preferably of three lances arranged radially at 120° from one another, which produce a flow distributed and aligned to the vertical of the combustor 1, below the aforesaid separation element or grid between the combustion chamber 11 and injection chamber 12

This configuration ensures greater homogeneity of supply of combustion air to the combustion zone 11. The combustion air supply system 4 comprises at least a blower 41 sized and servo-driven to precisely guarantee the right combustion air flow rate as the quantity of biomass C within the combustor 1 varies and to pressurise, as anticipated, at least said injection zone or chamber 12.

Said blower 41, for example, is equipped with a variable speed motor controlled by inverter with revolution speed feedback and can cooperate with a mass flow meter 42 of the comburent to supply it to the combustor 1 with the excess of air necessary for the desired diffusive combustion process.

Before discussing the operation and dynamics of the diffusive combustion inside the combustor 1, it is useful to describe other components cooperating with and/or integrated to the same combustor 1.

First of all, reference will be made to the loading system 5 of the biomass C inside the combustor 1, positioned externally and at its summit zone and cooperating with a section or opening 103 for introducing said biomass C.

Of said loading system 5 there are shown:

- a hopper 50 possibly equipped with sensors for the measurement and identification of the characteristics of the biomass C in inlet, and

- a ducted system for the handling and lifting 51 of the same biomass C, hereinafter also referred to as "feeding system 51 ".

Said feeding system 51, according to a preferred embodiment, may consist of a first loading screw 51 servo-regulated by the control unit of the combustor 1 to control flow rate and level of fresh biomass C to be fed.

Finally, reference numeral 52 indicates a possible weighing and dosing system 52 of the biomass C, comprising for example a load cell, placed substantially at the mouth of the inlet opening 103 to the combustor 1. The latter may preferably be provided with at least one bulkhead 150 which can be sealed against undesired leaks of the combustion fumes and/or possible reflux of the fed biomass C and then opened only during the loading of the biomass C.

Fig. 2 clearly shows a second screw 131 located at compartment 13 for the collection and storage of combustion ash and said "unloading screw 131 " being intended for their disposal.

Still with reference to the combustor 1 of Fig. 2, reference numeral 132 further indicates a mill (or any other functionally equivalent device) to facilitate the passage and expulsion of combustion ash from the injection zone 12 to the underlying one of collection and storage 13, when present and separate from the first, and to check its level.

Preferably, said mill 132 can be a mechanical-volumetric doser which pneumatically insulates the injection chamber 12 from the ash collection and storage compartment 13 and, rotating in a controlled manner about its own axis (preferably perpendicular to the axis "a-a"), reduces the granulometry of the ash passing from said injection chamber 12 to said compartment 13.

It is also noted an appropriate meter 6 of the weight of the combustor 1 and therefore, indirectly, of the quantity of biomass C present from time to time therein.

Without any limiting intent, said weight meter 6 may consist of a load cell whereon the combustor 1 rests, in particular with its bottom zone.

Finally, a measurer 7 of the real-time flow rate of said fumes can be provided on the combustion fumes discharge conduit 101 with the simultaneous possibility of detecting their pressure, temperature and humidity, while at least one sensor 8, for example mechanical, for the detection of the inner level of the biomass C, may be provided to the dome 100 of the combustor 1.

Once the combustor 1 of the invention has been defined in all its main components, at this point it is possible to proceed to describe, as anticipated, the dynamics of the diffusive combustion that is carried out therein and that can be schematised from the point of view of the temperatures involved, with the two different configurations shown in Fig. 3a and 3b.

The two macro-parameters for adjusting the combustion process are: the flow rate of combustion air introduced into the injection zone 12 below the biomass C, which serves as fuel, and the level of the biomass C itself inside the combustor 1 , per fixed percentage of humidity of the biomass in inlet. With the same combustion air inflow, in fact, the distribution of the temperatures inside the combustor 1, and therefore the combustion steps, depend on the stratification of the reaction products or fumes that flow in countercurrent through the loaded biomass C.

The greater the head of the biomass C inside the combustor 1 (i.e. the height of the inner biomass column) the greater and the longer the heat exchange with the combustion fumes in countercurrent and therefore their consequent cooling. Conversely, low levels of "fresh" biomass C in the combustor 1 will correspond to higher fume discharge temperatures.

Such results are visually shown in Fig. 3a and 3b; in particular, experimental tests have shown that when the head of the biomass C is at its maximum level F, represented by the arrow Fl, the combustion fumes can be cooled up to temperatures in the order of 50-60 °C while in presence of a minimum head F2, their discharge temperatures would be around 150-170 °C.

Low temperatures of the combustion fumes can lead to the production of organic and/or organic -nitrogenous substances in gas and vapour phase.

Instead, it is not necessary to dwell on the definition of the other temperatures inside the combustor 1 ; it is herein noted that the maximum temperatures, in the order of 1000-1200 °C, are reached in the proximity of the separation grid 15 between the combustion chamber 11 and the underlying injection chamber 12 of the comburent while they decrease as we move away from it approaching both the bottom of the combustor 1 (where temperatures will be in the order of 600- 800 °C) and its summit zones, characterised by at least one section, called "converting", with temperatures of about 800-1000 °C and by a "distillation" one with temperatures ranging between 200 °C and 400 °C.

As already widely said, the analysis and knowledge of such temperatures, achievable by means of at least the temperature sensors 24 described above, allow the optimal control of the operating speed of the heat exchangers 30.n, 31.n, 32 .n for the selective cooling of at least some parts of the walls 110, 120 of the combustor 1 and of the confining ones 200 of the one or more inner bodies 2.

The filtering capacity of pollutants and particulate carried by the combustion fumes also depends on the level F of the head of the biomass C loaded inside the combustor 1; in fact, the greater said head, the greater the resistance that the biomass C offers to the flow in countercurrent of said fumes and therefore the quantity of substances and particulates that can be retained by it.

The level F of the head of the biomass C can be retro-activated on the basis of the data and measurements provided by suitable control means 6, 8 cooperating with the control unit of the combustor 1, in particular from the aforesaid:

- at least one level sensor 8, and/or

- meter 6 of the weight of the combustor 1,

while its consequent adjustment and/or restoration can be carried out by acting through devices or regulation means comprising at least:

- the weighing and dosing system 52 of biomass C of the loading system 5 upstream of the combustor 1, so as to regulate the inlet flow, and/or

- the mill 132 for discharging the combustion ash that keeps, as seen, the ash below the injection chamber 12 of the combustion air,

all taking into account the profile of the temperatures inside the combustor 1 and/or the flow rate, temperature and humidity of the combustion fumes and, obviously, the combustion air flow rate, by means of the aforesaid temperature sensors 24, the fumes meter 7 and the combustion air mass flow rate meter 42, respectively.

In practice, known a priori the characteristics of the biomass to be treated (especially its humidity at inlet), the control and adjustment unit of the combustor 1 back-drives:

- the combustion air flow, and/or

- the "fresh" biomass flow in inlet, and/or

- the flow rate of the refrigerant fluid of the heat exchangers 30.n, 31.n, 32.n, and therefore their selective heat removal capacity

based on: - values and distribution of the temperatures inside the combustor 1, in particular its combustion chamber 11, known by means of the aforesaid temperature sensors 24, and/or

- flow rate and temperature of the fumes (and possibly their humidity) known at least from the said fumes meter 7, and/or

- weight of the loaded biomass C, detected by the said at least one meter 6, and/or

- level F of the charge of the biomass C inside the combustor 1, particularly with reference to its loading zone 10.

It is clear that several variants of the invention described above are possible for the man skilled in the art, without departing from the novelty scopes of the inventive idea, as well as it is clear that in the practical embodiment of the invention the various components described above may be replaced with technically equivalent ones.

For example, nothing prevents the possibility of providing within the combustor 1 means suitable for guaranteeing a homogeneous distribution of the biomass C, i.e. adapted to limit the formation of localised deposits and build-ups normally concentrated in the proximity of the inlet opening 103 of the same biomass C; said means may consist of homogenising and levelling arms or spatulas and/or vibrating devices or the like.

It is clear that with the combustor 1 of the present invention it is possible to obviate the drawbacks of the prior art; in particular, the filtering action achievable as a result of the passage of the combustion fumes in countercurrent inside the biomass C of the combustor 1 and the possibility of adjusting the outflow rate from the same biomass C and the temperature by varying the head of the same biomass C and by appropriately profiling the fume discharge chamber 10 allow minimising and reducing polluting and toxic emissions as well as the dispersion of powdery material and particulates.

This, as seen, allows equipping the biomass waste-to-energy plant C with systems for the treatment and purification of fumes and combustion products, downstream of the combustor 1, of simple manufacture and therefore cheaper, simpler to manage and that require less maintenance.

Furthermore, the absence of mechanical components inside the combustor 1, e.g. the various exchangers 30.n, 31.n, 32.n no longer directly exposed to the biomass or to the diffusive flames or to the combustion fumes and ash, reduces the related problems of corrosion, incrustations and fouling.

Furthermore, inside at least the combustion chamber 11 of the combustor 1 of the invention there are no moving mechanical parts as instead in the case of the "movable grid combustors" of the prior art.

The removal of heat from the combustion fumes and products does not take place by convection and/or radiance as in the case of the prior art, but, as illustrated, exclusively by conduction.

This also contributes to a considerable reduction in the routine and extraordinary maintenance of the combustor 1 and its accessory components as well as a high thermal conversion efficiency.

The flow in countercurrent between hot combustion fumes and biomass C and the consequent effective heat exchange that is carried out allows introducing wet biomass (with degrees of humidity, as seen, at least up to 60%) into the combustor 1 of the invention, eliminating in fact those complex and expensive preliminary drying treatments of the biomass, external to the same combustor 1. In conclusion, the combustor 1 of the invention carries out in a single suitably shaped chamber at least three basic functions of a waste-to-energy process of biomasses: drying, combustion, preliminary filtering of the fumes.

Its particular shape also ensures such functions in a natural way and therefore automated controls of fuel and comburent dosages are only preferred and not necessary to a basic version.

Furthermore, the presence of one or more inner bodies 2 to the combustor 1 of the invention which carry functional groups and components, in particular one or more heat exchangers 30.n and/or temperature sensors 24, allow precise monitoring and control of the combustion of the biomass (for example, of the manure) that develops vertically according to a stratified and diffusive reaction. Said one or more inner bodies 2 further allow setting up, inside the combustor 1 , components usually placed outside, without these being in direct contact with the biomass; this preserves its effective operation and avoids all those problems and malfunctions deriving from their close interaction with the biomass.

Lastly, the maintainability of said components is greatly simplified; by way of an example, it should be noted that the replacement or repair of the one or more exchangers 30.n may be carried out without necessarily proceeding to the preventive emptying of the combustor 1 from the biomass contained therein and/or the turning off of the same combustor 1.

Similar considerations are obviously valid also with reference to the other exchangers 31.n, 32. n described above, all arranged preferably outside the combustor 1.

Finally, it should be noted that with the same combustor 1 and type of biomass C to be treated, said combustible biomass C in the time unit is lesser the greater its humidity because it must be sufficiently dried before reaching the combustion chamber 1 1.

The fact remains that, when fully operational, the quantity of biomass C introduced into the combustor 1 is equal to the quantity expelled in the form of combustion fumes and ash; therefore, the level F of the biomass C that ensures the desired outflow rate defined above, whatever it is meant to be, can remain constant and independent of the biomass flow rate per time unit.

One way to control the amount of biomass C to be introduced into the combustor 1 of the invention can therefore be to check that the temperature in the combustion chamber 1 1 is that suitable for the combustion that is desired, for example by using the plurality of sensors 24 described above.

If the detected temperatures are excessively low, indicating a very wet biomass C, the flow rate of the biomass C introduced is slowed down so that it dries sufficiently, in the manners seen above.

Therefore, this has an effect on the level F of biomass C in the combustor 1.