Patent Description:
The need to search for solutions suited to new values and lifestyles is increasingly felt at a point in history in which the transition from a linear economy logic (in which every process creates new waste) to a circular economy logic has become vitally important, and in which fossil fuels are becoming increasingly scarce and expensive. Self-generation is the most suitable answer in terms of sustainability, autonomy, and safety in electrical energy production.

Biomass-fueled cogeneration systems consisting of three basic parts, i.e. a pyrolytic gasifier, a burner, and a Stirling engine, are well known. The fuel syngas is produced starting from the biomass in the pyrolytic gasifier; the syngas produced is burned with a controlled supply of air in the burner; the Stirling engine, by virtue of the heat generated by the combustion of the syngas, sets the electric generator in oscillation, thus producing electrical energy.

Pyrolytic gasification is a thermal-chemical process by virtue of which a combustible gas (syngas), comprising a mixture of hydrogen, carbon monoxide, methane and, to a lesser extent, other compounds, can be extracted from organic material, such as biomass. Pyrolytic gasification occurs by maintaining the biomass at a particularly high temperature in a low-oxygen environment. The by-product of pyrolytic gasification is a solid residue, named char, which contains almost exclusively carbon.

The use of pyrolytic gasification, compared with direct combustion of the biomass, reduces carbon emissions into the atmosphere because, once the fuel syngas is extracted, only the char remains which contains the portion of carbon that will not be emitted into the atmosphere in the form of CO<NUM>, but is evacuated in solid form and collected. Furthermore, the use of pyrolytic gasification provides a fuel gas which is much more effective in the combustion in terms of maximum achievable temperature, emissions of particulate matter and heating of the heat exchangers.

Examples of cogenerators based on the application of the pyrolytic gasification and the Stirling engine are described in <CIT> and <CIT>. <CIT> discloses an apparatus for generating energy by gasification. <CIT> discloses a horizontal double-layer tube rotary superconducting waste pyrolysis gasifier.

However, to date, the need is increasingly felt to maximize the efficiency and the chemical and mechanical resistance of the pyrolytic gasifier, which is a particularly delicate element of the micro-cogenerator, inside which an environment that is difficult to manage and control is created.

The pyrolytic gasifier contains a reaction chamber inside which the biomass is gasified in the presence of a given amount of air, generating syngas. By its nature, the atmosphere inside said reaction chamber during its operation is strongly reducing, because, since it is rich in hydrogen, carbon monoxide and methane, it has a strong tendency to react with oxygen. In such an environment, the refractory materials do not show the same heat resistance they would have in a neutral or oxidizing environment, but rather their classification temperature undergoes a significant reduction. As a consequence, said materials rapidly tend to degrade chemically.

For these reasons, the need is strongly felt to increase the chemical resistance of the pyrolytic gasifier under such process conditions and at very high temperatures of approximately <NUM>-<NUM>, ensuring at the same time good mechanical strength, excellent resistance to thermal shock due to the thermal gradient generated longitudinally to the reactor itself, and maximizing gasification efficiency.

Therefore, the technical problem underlying the present invention is to provide a micro-cogenerator for domestic or small consumer use, in which the pyrolytic gasifier can ensure high performance characteristics and meet the requirements presented above.

The problem described above is solved by a micro-cogenerator as outlined in the accompanying claims, the definitions of which form an integral part of the present description.

The object of the present invention is a micro-cogenerator comprising:.

For ease of reference, the terms energy source and biomass will be used indiscriminately in the description below. Therefore, the term biomass should by no means be understood as limiting.

Advantageously, said energy source is gasified in the presence of a sub-stoichiometric amount of air.

According to an embodiment of the present invention, said polycrystalline alumina fiber-based material comprises at least <NUM>% by weight of polycrystalline alumina, preferably at least <NUM>% by weight, such as about <NUM>% by weight. Preferably, said polycrystalline alumina fiber-based material further comprises an amount of silica of at least <NUM>% by weight, preferably between <NUM>% and <NUM>% by weight, more preferably between <NUM>% and <NUM>% by weight, even more preferably between <NUM>% and <NUM>% by weight.

For example, said polycrystalline alumina fiber-based material is produced by the company Unifrax under the trade name High Temperature Saffil® Rigiform™. Preferably, said material is produced by the company Unifrax under the trade name Saffil® <NUM> HD.

According to an embodiment of the present invention, said pyrolytic gasifier comprises an outer coating with respect to said reaction chamber, said outer coating having an annular shape.

Preferably, said outer coating is made of microporous insulating material, preferably comprising silica. Preferably, said microporous insulating material comprises powder or reinforcing filaments of pyrogenic silica, to which opacifiers and/or inorganic oxides may be added. For example, said microporous insulating material is produced by the company Promat under the trade name Promalight®, or by the company Bifire under the trade name Microbifire®, or by the company Unifrax under the trade name Excelfrax®.

According to a preferred embodiment, the aforesaid outer coating having an annular shape consists of a plurality of superimposed rings made of said microporous insulating material.

According to an embodiment of the present invention, the pyrolytic gasifier comprises a layer of said polycrystalline alumina fiber-based material having varying thickness interposed between said reaction chamber and said outer coating. Preferably, said reaction chamber and said layer of polycrystalline alumina fiber-based material form a monolithic structure.

According to a preferred embodiment, said truncated-cone reaction chamber has an upper surface and a lower surface, wherein the diameter of the upper surface is smaller than the diameter of the lower surface, said diameters being such as to give the inner surface of the truncated-cone reaction chamber a draft angle comprised between <NUM>° and <NUM>°, preferably comprised between <NUM>° and <NUM>°, preferably of about <NUM>°.

In an embodiment of the present invention, the pyrolytic gasifier comprises:.

Preferably, said hopper comprises an upper frame (or edge) adapted to support the aforesaid outer coating, preferably through an appropriate support plate.

Preferably, said hopper comprises a lip, which projects below said frame and defines a support base for the reaction chamber through which the hopper receives the syngas produced.

Preferably, the reaction chamber comprises an electric heater adapted to heat the reaction chamber to the gasification temperature, and a thermocouple adapted to monitor the temperature in the upper part of the reaction chamber. Preferably, the reaction front is comprised between said heater and said thermocouple. The aforesaid heater integrates a special sensor inside it, e.g., a thermocouple.

In a preferred embodiment, the energy source under reaction is supported by the biochar produced during the gasification of said energy source, and the micro-cogenerator does not comprise any support grid for said energy source.

The micro-cogenerator object of the present invention comprises an exhaust system adapted to receive exhaust fumes exiting the hot exchanger of the Stirling engine. Said exhaust system comprises an exchanger for the recovery of heat from said exhaust fumes, a lambda probe and a thermocouple which measures the temperature of said exhaust fumes. Said lambda probe regulates the air-to-syngas ratio at the burner inlet; more in particular, it provides a signal based on which said air-to-syngas ratio is adjusted.

According to this embodiment, the micro-cogenerator object of the present invention further comprises an extraction fan connected to said exchanger for the recovery of heat from the exhaust fumes, such as to extract the exhaust fumes thus creating a vacuum inside the burner and the pyrolytic gasifier and, in turn, to adjust the inflow of the syngas from the pyrolytic gasifier to the burner and the inflows of air into both the pyrolytic gasifier and the burner.

The combustion air inflow to the burner is advantageously adjusted by means of an electronically-driven motorized valve. Advantageously, such a valve is driven based on the signal provided by the lambda probe, i.e., based on the information provided by the lambda probe about the amount of air present in the exhaust fumes. The need to carefully control the amount of air is related to the fact that performance and emissions (CO, NOx) are strongly affected by the fuel/combustion air ratio; an optimal ratio of combustion air to syngas can be maintained by virtue of the signal provided by the lambda probe. The position of the valve which regulates the combustion air supply is preferably calculated by a PID (Proportional Integrative Derivative) control, which takes as input the value read by the lambda probe and outputs the position of the air adjustment valve.

The lambda probe provides an electrical signal (in mV) through which it is possible to have a measurement of the "lambda value (λ)" properly so called, i.e., the ratio between the actual AFR (air-fuel-ratio) and the stoichiometric AFR (air-fuel-ratio); in other words, the "lambda value (λ)" properly so called is to be understood as the ratio of air to fuel relative to the stoichiometric ratio of the fuel used. The electrical signal provided by the lambda probe is an indirect measurement of said lambda value (λ); the higher the value of the electrical signal, the lower the lambda value (λ).

Preferably, the pyrolytic gasifier comprises a first butterfly valve at the input interface of the energy source into the reaction chamber such as to allow the inflow of the energy source into the chamber and the hermetic closure thereof during the shutdown phase.

Preferably, the pyrolytic gasifier further comprises a second butterfly valve at the output interface of the biochar from the unloading auger such as to allow the evacuation of the biochar from the reaction chamber, if necessary.

Preferably, said first and second butterfly valves comprise a cylindrical valve body, a plate-like shutter, and an insert having the shape of an arc of circumference. When the butterfly valve is in the fully open position, the shutter takes a position parallel to the longitudinal axis X-X of the cylindrical valve body, and the insert adheres to a portion of the edge of the shutter, thus filling the gap between the valve body and the shutter along the longitudinal axis X-X of the cylindrical valve body. This prevents the deposition of the energy source or, respectively, of the biochar on the edge of the shutter. Therefore, said insert fulfills the function of protecting the seal of the plate-like shutter when the valve is in the fully open position.

The pyrolytic gasifier according to the present invention, thanks to the peculiar characteristics mentioned above, both with regard to its structure and the materials with which it is made, can ensure high performance characteristics and remarkable durability, by virtue of a surprising chemical and mechanical resistance in a strongly reducing environment which reaches temperatures of approximately <NUM>-<NUM>. Furthermore, the pyrolytic gasifier according to the present invention has compact dimensions, provides high thermal insulation and high resistance to thermal shock, and allows a good flow of the biomass inside it.

Further features and advantages of the invention will be apparent from the description of some embodiments, given here by way of a non-limiting example.

With reference to <FIG>, a micro-cogenerator according to an embodiment of the present invention is globally indicated with reference numeral <NUM>.

Said micro-cogenerator <NUM> comprises a pyrolytic gasifier <NUM>, a burner <NUM> and a Stirling engine <NUM>.

The pyrolytic gasifier <NUM> is shown in more detail in <FIG>, while the burner <NUM> and the Stirling engine <NUM> are more visible in <FIG>.

The reactor <NUM> defines a reaction chamber <NUM> and comprises an electric heater <NUM> and a thermocouple <NUM>. The electric heater <NUM> brings the biomass contained in the reaction chamber <NUM> to the gasification temperature of, e.g., <NUM>, while the thermocouple <NUM> monitors the temperature in the upper part of the reaction chamber <NUM> during the gasification process. The heater <NUM> and the thermocouple <NUM>, respectively, represent the lower limit and the upper limit of the zone within which the biomass reaction front <NUM> must be maintained.

A connecting element <NUM>, named "buffer", is interposed between the loading auger <NUM> of the biomass <NUM> and the inlet <NUM> of the reactor <NUM>. A sensor <NUM> detects the filling level of the buffer <NUM>, and the loading auger <NUM> of the biomass <NUM> is started whenever said sensor <NUM> detects that the filling level of the buffer <NUM> is below a predetermined threshold value.

The biomass <NUM> under reaction is supported by the biochar <NUM> generated during the pyrolytic gasification process seamlessly inside the reaction chamber <NUM>. Advantageously, the pyrolytic gasifier <NUM> according to the present invention has no support grid for the biomass under reaction which separates it from the spent biochar <NUM>. Preferably, the unloading auger <NUM> and the hopper <NUM> are constantly kept full of biochar <NUM>.

The reactor <NUM> of the pyrolytic gasifier <NUM> is shown in greater detail in <FIG>.

As mentioned above, the reactor <NUM> comprises a reaction chamber <NUM> in which the biomass <NUM> is gasified in the presence of a given amount of air (sub-stoichiometric). The reactor <NUM> further comprises an outer coating <NUM> to said reaction chamber <NUM>. Said reaction chamber <NUM> is truncated-cone in shape and is advantageously made of a polycrystalline alumina fiber-based material, preferably formed under vacuum, comprising at least <NUM>% by weight of polycrystalline alumina and having a density preferably between <NUM> and <NUM>/m<NUM>. For example, said polycrystalline alumina fiber-based material is produced by the company Unifrax under the trade name High Temperature Saffil® Rigiform™, e.g. Saffil® <NUM> HD.

The reaction chamber <NUM> has an upper surface <NUM> and a lower surface <NUM>, wherein the diameter of the upper surface <NUM> is slightly smaller than the diameter of the lower surface <NUM> in order to give an adequate draft angle, e.g., about <NUM>°, to the inner surface of the reaction chamber <NUM>. For example, the diameter of the upper surface <NUM> is comprised between <NUM> and <NUM> and the diameter of the lower surface <NUM> is comprised between <NUM> and <NUM>. Said geometry of the reaction chamber <NUM> facilitates the downward flow of the biomass <NUM>.

Said outer coating <NUM> has an annular shape and is advantageously made of a microporous insulating material comprising silica. For example, said microporous insulating material is produced by the company Promat under the trade name Promalight®, or by the company Bifire under the trade name Microbifire®, or by the company Unifrax under the trade name Excelfrax®.

Said outer coating <NUM> consists of a plurality of overlapping rings <NUM> made of said microporous insulating material, which guarantee the thermal insulation of the reactor <NUM>.

In the example in <FIG>, the reactor <NUM> further comprises a layer <NUM> of said polycrystalline alumina fiber-based material having varying thickness interposed between the reaction chamber <NUM> and the outer coating <NUM>. Preferably, the reaction chamber <NUM> and the layer <NUM> of the polycrystalline alumina fiber-based material form a monolithic structure. According to a specific example, said monolithic structure is sealed on top with the structure by means of a rubber gasket <NUM>; on the bottom, instead, given the high working temperature, it is sealed by means of a polycrystalline alumina fiber-based gasket <NUM>.

The hopper <NUM> shown in <FIG> and <FIG> comprises an upper frame (or edge) <NUM> adapted to support the outer coating <NUM> through an appropriate support plate <NUM>, preferably annular. In the example of <FIG>, an insulating plate <NUM>, which is also preferably annular, made, e.g., with biosoluble refractory fibers, is placed above said support plate <NUM>; said plate <NUM> ensures the thermal break with the support plate <NUM> and thus with the hopper <NUM>, as well as an airtight seal. Both the hopper <NUM> and the support plate <NUM> are advantageously made of stainless steel.

Said hopper <NUM> further comprises a lip <NUM>, which projects below said frame <NUM> and defines a support base for the reaction chamber <NUM> through which the hopper <NUM> itself receives the produced syngas <NUM>. Said geometry allows creating an annular volume in the upper part of the hopper <NUM> through which the syngas <NUM> is sucked into the duct <NUM>.

The syngas feeding duct <NUM> has a gasket at the interface with the support plate <NUM> consisting of polycrystalline alumina fiber-based rings <NUM>.

The hopper <NUM> is advantageously insulated from the unloading auger <NUM> by means of an element <NUM> made of said microporous insulating material.

A first valve <NUM> separating the biomass <NUM> (shown in <FIG> and <FIG>) is placed at the inlet interface of the biomass <NUM> in the reactor <NUM>, in particular above the buffer <NUM>. A second valve <NUM> separating the biochar <NUM> (shown in <FIG>) is positioned at the outlet interface of the biochar <NUM> from the unloading auger <NUM>.

The separation valve <NUM> of the biomass <NUM> is opened at the process start-up and allows the inflow of biomass <NUM> and air into the reactor <NUM>. The air supply, although limited, is necessary to support the gasification process by providing heat through the combustion of a small portion of the biomass <NUM> and the produced syngas <NUM>.

The separation valve <NUM> of the biochar <NUM> is opened whenever it is necessary to expel the biochar <NUM>, thus operating discontinuously.

Said separation valves <NUM>, <NUM> are butterfly valves and are shown in more detail in <FIG>. The valve <NUM>, <NUM> shown in <FIG> is in the fully closed position, while the valve <NUM>, <NUM> shown in <FIG> is in the fully open position.

The valve <NUM>, <NUM> according to the embodiment of <FIG> comprises an actuator <NUM>, a cylindrical valve body <NUM>, a plate-like shutter <NUM> and an insert <NUM> shaped as an arc of circumference.

When said valve <NUM>, <NUM> is in the fully open position (<FIG>), the plate-like shutter <NUM> assumes a position parallel to the longitudinal axis X-X of the cylindrical valve body <NUM> and the insert <NUM> adheres to a portion <NUM> of the edge of the shutter <NUM> which would otherwise come into contact with the biomass <NUM> or with the biochar <NUM>. In this manner, the gap between the valve body <NUM> and the shutter <NUM> is filled along the longitudinal axis X-X of the valve body <NUM>, preventing the biomass <NUM> and the biochar <NUM> from settling on the edge of the shutter <NUM>, clogging the valve <NUM>, <NUM> and preventing the proper closing of the valve itself.

In light of the aforesaid description, it is apparent that the gasifier <NUM> is of the "downdraft" (i.e., the biomass <NUM> flows downward and the syngas <NUM> produced transits in the same direction) "open core" (i.e., with air supply from above along with the biomass) type.

As mentioned above, <FIG> illustrate the assembly consisting of the burner <NUM> and the Stirling engine <NUM>.

Furthermore, the pre-mixing flanges <NUM> allow partial cooling of the fuel syngas <NUM> by means of the combustion air <NUM>.

The Stirling engine <NUM> comprises a high-temperature heat exchanger <NUM> (so-called "hot exchanger") shown in <FIG>, <FIG>, a low-temperature heat exchanger (so-called "cold exchanger"), a regenerator and an electric generator <NUM>. The cold exchanger and the regenerator are not visible in the figures. The hot exchanger <NUM> of the Stirling engine is inserted inside the combustion chamber <NUM>.

Downstream of the hot exchanger <NUM> of the Stirling engine, a tubular element <NUM> is placed, also indicated as a cooling ring, inside which a cooling fluid flows, so that heat transfer downstream of said hot exchanger <NUM> is prevented. In other words, the cooling ring <NUM> performs the thermal break function between the burner <NUM> and the Stirling engine <NUM>, preventing unwanted heat from entering the part of the Stirling engine <NUM> under the hot exchanger <NUM> and safeguarding the underlying components from excessive heating.

The combustion chamber <NUM> of the burner <NUM> consists of a cylinder which integrates connections for the feeding duct <NUM> of the fuel syngas <NUM> coming from the gasifier <NUM> and for the feeding duct <NUM> of the combustion air <NUM>. Furthermore, the combustion chamber <NUM> integrates the attachment flange <NUM> to the Stirling engine <NUM> and the attachment flange <NUM> to the exhaust system <NUM>.

A bell <NUM> and an element <NUM> made of porous ceramic material (porous ceramic means <NUM>) are placed inside the combustion chamber <NUM> of the burner <NUM>.

Said bell <NUM> is open at the bottom and houses the hot exchanger <NUM> of the Stirling engine inside. In particular, said hot exchanger <NUM> is inserted from the open bottom of the bell <NUM>. Said bell <NUM> is such to convey the hot combustion gases <NUM> into the hot exchanger <NUM>, where they undergo heat exchange providing heat and generating exhaust fumes <NUM> (or combustion fumes <NUM>). In other words, said bell <NUM> constrains the hot combustion gases <NUM> to flow through the entire hot exchanger <NUM> with minimal heat dissipation to the outside, thus optimizing the heat exchange with the Stirling engine <NUM>.

Said bell <NUM> comprises steel walls internally lined with a refractory insulating material, preferably a material based on polycrystalline alumina fiber. For example, said material comprises at least <NUM>% by weight of polycrystalline alumina, preferably at least <NUM>% by weight, more preferably at least <NUM>% by weight, such as about <NUM>% by weight. Preferably, said material further comprises at least <NUM>% by weight of silica, preferably between <NUM>% and <NUM>% by weight of silica, more preferably between <NUM>% and <NUM>% by weight of silica, even more preferably between <NUM>% and <NUM>% by weight of silica. For example, said polycrystalline alumina fiber-based material is produced by the company Schupp under the trade name ITM-Fibermax®, preferably Blanket <NUM>-<NUM>.

The aforementioned nozzle or duct <NUM> may be replaced by a hole made in said refractory insulating material, such as to convey the fuel syngas <NUM> and the combustion air <NUM> inside the combustion chamber <NUM>.

There is a gap <NUM> between said bell <NUM> and said combustion chamber <NUM> which is traveled upward by the exhaust fumes <NUM> exiting the hot exchanger <NUM>, as evident from <FIG>.

The porous ceramic means <NUM> is housed in the upper part of the bell <NUM> above the hot exchanger <NUM> and is supported at least partially by the refractory insulating material of the bell <NUM>. Said porous ceramic means <NUM> is an optimized combustion volume in which the syngas <NUM> is combusted in the presence of combustion air <NUM> generating hot combustion gases <NUM> (<FIG>). Furthermore, the porous means <NUM> allows a homogeneous temperature distribution, ensuring optimal heat exchange with the Stirling engine <NUM> and low polluting emissions.

According to an embodiment, the porous material with which said means <NUM> is made comprises silicon carbide, alumina and silica and is, for example, produced by the company Lanik under the trade name Vukopor® S.

According to another embodiment, said porous ceramic material comprises alumina, silica, zirconia and magnesium oxide. Preferably, said porous ceramic material is produced by the company Lanik under the trade name Vukopor® HT.

In the example of <FIG>, the bell <NUM> comprises an additional element <NUM> made of refractory insulating material, e.g., based on polycrystalline alumina fiber, immediately below the porous ceramic means <NUM>, such as to prevent unwanted entry of heat through the top of the Stirling engine below. Said element <NUM> mimics the shape of the upper dome of the hot exchanger <NUM> of the Stirling engine, visible in <FIG>, <FIG>.

The exhaust system <NUM> mentioned above receives the combustion fumes <NUM> exiting the hot exchanger <NUM> of the Stirling engine <NUM>, once the latter have traveled upward through the gap <NUM> present between the combustion chamber <NUM> and the bell <NUM>.

Said exhaust system <NUM> comprises an exhaust <NUM> from which combustion fumes <NUM> escape, a heat exchanger <NUM> connected to said exhaust <NUM> for recovering heat from the exhaust fumes <NUM> (<FIG>), a lambda probe <NUM> which provides a signal based on which the air-syngas ratio at the inlet of burner <NUM> is adjusted (<FIG>, <FIG>), and a thermocouple <NUM> which measures the temperature of the combustion fumes <NUM> (<FIG>, <FIG>).

An extraction fan <NUM> (shown in <FIG> and <FIG>) of the combustion fumes <NUM> is connected to said heat exchanger <NUM>, by virtue of which the combustible syngas <NUM> from the gasifier <NUM> and the combustion air <NUM> are sucked inside the combustion chamber <NUM>. Said extraction fan <NUM> has variable speed.

To obviate the fact that the pyrolytic gasifier and the Stirling engine, by their nature, have rather slow start-up and control reaction times, the micro-cogenerator <NUM> can advantageously be coupled to electrical energy storage systems (batteries) and thermal energy accumulation systems (puffers). The remaining capacity is measured for both accumulations so that micro-cogenerator <NUM> will only turn on if a minimum operating time necessary for heat regulation of all syngas ducts is guaranteed. In particular, a temperature probe is used for the puffer, and a voltage probe is used for the batteries. For the batteries, there is the possibility of both voltage reading and SoC ("state of charge") reading from the Bus and input of a digital request signal.

The micro-generator <NUM> is equipped with an electronic control, which manages the operation of the machine through the installed sensors and actuators and is independently powered by on-board batteries so that it can be safely shut down even in case the external electrical connection is interrupted. To be able to start up, the micro-generator <NUM> checks for the presence of the external power grid (both "on-grid" and "off-grid" via inverter).

The process of cogeneration of electrical energy and heat within the micro-cogenerator <NUM> starting from the biomass <NUM> is described below with reference to the figures.

The pyrolytic gasification process is started by means of the electric heater <NUM>, which brings the biomass <NUM> to the gasification temperature, e.g., about <NUM>. During the start-up phase of the process, the separation valve <NUM> of the biomass <NUM> is opened. During the start-up phase of the process, the extraction fan <NUM> is activated with a speed proportional to the temperature of the electric heater <NUM>.

The biomass <NUM> is fed into the reactor <NUM> of the pyrolytic gasifier <NUM>, through the inlet <NUM>, by means of the loading auger <NUM>. When the filling level of the buffer <NUM> is under a given threshold, the biomass loading auger <NUM> is started; when the filling level of the buffer <NUM> is above said threshold, the biomass loading auger <NUM> is stopped and the feeding of the biomass <NUM> to the reactor is interrupted.

Once the gasification has been started and the biochar <NUM> has accumulated in the reactor <NUM>, the reaction front advances from the bottom to the top where biomass <NUM> not yet gasified is located.

The reaction chamber <NUM> is maintained at a suitable gasification temperature at which the biomass reacts generating syngas and biochar, preferably comprised between <NUM> and <NUM> in order to maximize the syngas production.

The thermocouple <NUM> keeps the temperature of the upper part of the reaction chamber <NUM> monitored; when the integral over time of the temperature measured by thermocouple <NUM> exceeds a given threshold value of said integral, the separation valve <NUM> of the biochar <NUM> is opened, the unloading auger <NUM> is started and part of the biochar <NUM> is extracted. In this manner, the reacting biomass <NUM> is made to flow downward and along with it the reaction front as well, which remains confined to the reaction zone delimited between the thermocouple <NUM> and the electric heater <NUM>.

The gasifier <NUM>, once fully operational, works with a slow and intermittent flow of biomass <NUM> such as to maintain the reaction front within the aforementioned reaction zone.

The produced fuel syngas <NUM>, before flowing out of the gasifier <NUM> through the duct <NUM>, crosses a layer of biochar <NUM>, which is still warm and ensures a good abatement of dust and tar.

During the step of shutting down the process, a small amount of biochar <NUM> is extracted to ensure that the biomass <NUM> is in a sufficiently low and safe zone of the reaction chamber, and the biomass separation valve <NUM> is closed to prevent air from entering the reactor <NUM> and fumes from escaping.

By operating the extraction fan <NUM>, the system consisting of the gasifier <NUM> and the burner <NUM> is depressurized and the inflows of fuel syngas <NUM> from the gasifier <NUM> to the burner <NUM> and of air to both the gasifier <NUM> and the burner <NUM> are adjusted.

By operating the extraction fan <NUM>, the combustion fumes <NUM> are extracted which travel upward through the gap <NUM> between the combustion chamber <NUM> and the bell <NUM>, creating a vacuum inside the burner <NUM>. In turn, the fuel syngas <NUM> exiting the gasifier <NUM> and the combustion air <NUM> are sucked into the combustion chamber <NUM> of the burner, respectively, through the supply ducts <NUM> and <NUM>. In turn, air is sucked into the gasifier <NUM>.

Once the presence of fuel syngas <NUM> is detected inside the burner <NUM>, the latter is ignited and an increasing amount of combustion air <NUM> is supplied by acting on the air valve <NUM> located on the duct <NUM>.

The fuel syngas <NUM> and the combustion air <NUM> are sucked inside the combustion chamber <NUM> passing through the pre-mixing flanges <NUM>, then the nozzle or duct <NUM>, until they arrive inside the porous ceramic means <NUM>, which defines the volume in which the combustion takes place with the generation of the hot combustion gases <NUM>.

The hot combustion gases <NUM> are subjected to heat exchange within the hot exchanger <NUM> of the Stirling engine <NUM>, from which heat is recovered that puts the electric generator <NUM> in oscillation, thus obtaining the aforementioned combustion fumes <NUM> resulting from said heat exchange.

The combustion fumes <NUM> are extracted through the extraction fan <NUM>. Said combustion fumes <NUM> travel upward through the gap <NUM> present between the combustion chamber <NUM> and the bell <NUM>, pass through the exhaust <NUM> on which the lambda probe <NUM> and the thermocouple <NUM> are placed, then they are fed to the heat exchanger <NUM> for recovery of the heat contained therein. The lambda probe <NUM> provides a signal based on which the air-syngas ratio is adjusted accurately by virtue of the valve <NUM> located on the inlet duct <NUM> of the combustion air <NUM>, adjusting the pressure drop and thus the inflow.

Claim 1:
A micro-cogenerator (<NUM>) comprising:
a pyrolytic gasifier (<NUM>) adapted to produce syngas (<NUM>) and biochar (<NUM>) from a renewable and sustainable energy source (<NUM>), preferably woody biomass,
a burner (<NUM>) adapted to receive the syngas (<NUM>) produced by said pyrolytic gasifier (<NUM>) and to generate hot combustion gases (<NUM>),
a Stirling engine (<NUM>) comprising a heat exchanger (<NUM>) fed with said hot combustion gases (<NUM>), said Stirling engine (<NUM>) being adapted to generate electric energy,
wherein said pyrolytic gasifier (<NUM>) comprises a reaction chamber (<NUM>) inside which said energy source (<NUM>) is gasified in the presence of air, thus generating syngas (<NUM>) and biochar (<NUM>),
characterized in that said reaction chamber (<NUM>) has truncated-cone shape and is made of a polycrystalline alumina fiber-based material comprising at least <NUM>% by weight of polycrystalline alumina and, optionally, at least <NUM>% by weight of silica, said material having a density preferably between <NUM> and <NUM>/m<NUM>,
said micro-cogenerator comprising an exhaust system (<NUM>) adapted to receive exhaust fumes (<NUM>) leaving the heat exchanger (<NUM>) of the Stirling engine (<NUM>),
wherein said exhaust system (<NUM>) comprises an exchanger (<NUM>) for the recovery of heat from said exhaust fumes (<NUM>), a lambda probe (<NUM>) which provides a signal based on which the ratio of air (<NUM>) to syngas (<NUM>) at the burner (<NUM>) inlet is adjusted, and a thermocouple (<NUM>) which measures the temperature of said exhaust fumes (<NUM>),
said micro-cogenerator further comprising an extraction fan (<NUM>) connected to said exchanger (<NUM>) for the recovery of heat from the exhaust fumes (<NUM>), said extraction fan (<NUM>) is configured to extract the exhaust fumes (<NUM>) thus creating a vacuum inside the burner (<NUM>) and the pyrolytic gasifier (<NUM>) and, in turn, to adjust the inflow of the syngas (<NUM>) from the pyrolytic gasifier (<NUM>) to the burner (<NUM>) and the inflows of air into both the pyrolytic gasifier (<NUM>) and the burner (<NUM>).