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Title:
DOUBLE CHAMBER PYROLYTIC BURNER
Document Type and Number:
WIPO Patent Application WO/2017/202853
Kind Code:
A1
Abstract:
The present invention relates to a double chamber pyrolytic burner for solid fuel comprising a combustion chamber, an outer jacket of diameter B, defining a toroidal interspace between the outer jacket and the combustion chamber, a cap which closes upwardly said interspace, a bottom and a ventilation apparatus coupled to the bottom, wherein the combustion chamber comprises a hollow cylinder of diameter D and height H, and a bottom coupled to the cylinder. The cylinder is provided with a first set of holes of diameter D1 arranged at a distance H1 from the upper edge and a second set of holes of diameter D2 arranged at a distance H2 from lower edge. The first set of holes and the second set of holes have a diameter respectively D1 and D2. The first and second sets of holes are arranged radially along the wall of the hollow cylinder according to an angle a between 12 and 36°. The bottom is provided with a central hole of diameter D3 and a set of at least three holes also of a diameter D3, equidistant from each other and arranged along a circumference of diameter between D and D/4. The pyrolytic burner also comprises a flow stabilizer ring arranged between the bottom of said burner and the bottom of the combustion chamber, provided with a central hole of diameter D4 and a shielding plate coupled to said flow stabilizer ring and arranged between the flow stabilizer ring and the bottom. The shielding plate is provided with a central body of diameter D5, and at least two brackets suitable for coupling to said flow stabilizer ring or to the bottom of the burner.

Inventors:
MURA, Ivan (Via Marconi 14, Bosa, I-08013, IT)
Application Number:
EP2017/062433
Publication Date:
November 30, 2017
Filing Date:
May 23, 2017
Export Citation:
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Assignee:
ENKI STOVE S.R.L. (Via G. Marradi 4, Livorno, I-57126, IT)
International Classes:
F23G5/027; A47J36/24; C10J3/02; F23B20/00; F23B90/04; F23B90/06; F23L1/00; F23L5/02; F23L9/06; F23L15/00; F24B1/20; F24B5/02; F24B7/04; F24C9/00
Domestic Patent References:
WO2016075646A12016-05-19
Foreign References:
US20100258104A12010-10-14
FR900525A1945-07-02
US20030200905A12003-10-30
US6615821B12003-09-09
EP2342500A12011-07-13
US8459193B22013-06-11
ITPI20140016U2014-07-22
Attorney, Agent or Firm:
ZANOLI, Enrico et al. (Via Melchiorre Gioia 64, Milano, I-20125, IT)
Download PDF:
Claims:
CLAIMS

1. Double chamber pyrolytic burner for solid fuel comprising a combustion chamber (10), an outer jacket (20) of diameter B, defining a toroidal interspace (60) between said outer jacket and said combustion chamber, a cap (30) which closes upwardly said interspace (60), a bottom (40) and a ventilation apparatus (50) coupled to said bottom (40), characterized in that said combustion chamber (10) comprises a hollow cylinder (110) of diameter D and height H in which D<B and D/3<H<107xD, and a bottom (120) coupled to said cylinder, said cylinder being provided with a first set of holes (130) of diameter Dl arranged at a distance HI from the upper edge, in which Hl>2xDl, and a second set of holes (140) of diameter D2 arranged at a distance H2 from the lower edge, wherein H2>2xD2, said first set of holes (130) having a diameter Dl such that D2<Dl<3xD2 and said second set of holes (140) having a diameter D2 such that D/50<D2<D/10, said first and second sets of holes (130, 140) being arranged radially along the wall of said hollow cylinder (110) according to an angle a such that 12° <a< 36°, said bottom (120) being provided with a central hole (151) of diameter D3 and a set of at least three holes (150) also of diameter D3, equidistant from each other and arranged along a circumference of diameter between D and D/4, said diameter D3 being greater than or equal to the diameter D2 of the holes of said second holes (140), and in that it comprises a flow stabilizer ring (200) arranged between the bottom (40) of said burner and the bottom (120) of said combustion chamber (10), provided with a central hole of diameter D4 such that D4>D/4, and a shielding plate (300) coupled to said flow stabilizer ring (200) and arranged between said flow stabilizer ring (200) and said bottom (40), said shielding plate (300) being provided with a central body (301 ) of diameter D5, and at least two brackets (302) suitable for coupling to said flow stabilizer ring (200) or to the bottom (40) of the burner, such that D5>D4.

2. Pyrolytic burner according to claim 1, characterized in that D<H<7xD.

3. Pyrolytic burner according to claim 1, characterized in that 2xD<H<3xD.

4. Pyrolytic burner according to claim 1, characterized in that Hl>3xDl e H2>3xD2.

5. Pyrolytic burner according to claim 1, characterized in that 1.5xD2<Dl<2.5xD2 and D/30<D2</20

6. Pyrolytic burner according to claim 1, characterized in that 18°<a<30°.

7. Pyrolytic burner according to claim 1, characterized in that the number of said holes (150) provided in said bottom (120), besides said central hole (151), is comprised between 5 and 20, said holes being equidistant from each other and arranged along a circumference of diameter between D/2 and D/3.

8. Pyrolytic burner according to claim 1 , characterized in that D4>1.5xD.

9. Pyrolytic burner according to one or more of the preceding claims, characterized in that said hollow cylinder (110) of said combustion chamber (10) has a thickness between 0.5mm to 20mm.

10. Pyrolytic burner according to one or more of the preceding claims, characterized in that B=1.5xD.

11. Pyrolytic burner according to one or more of the preceding claims, characterized in that it is made of a material selected from the group consisting of: iron based alloys and titanium.

12. Pyrolytic burner according to one or more of the preceding claims, characterized in that said ventilation apparatus (50) coupled to said bottom (40) is a forced ventilation apparatus.

Description:
DOUBLE CHAMBER PYROLYTIC BURNER

DESCRIPTION

The present invention relates to a double chamber pyrolytic burner, in particular to a double chamber pyrolytic burner for solid fuel.

Pyrolysis, or cracking, is a thermochemical decomposition of organic material, obtained by applying heat and in the total absence of an oxidizing agent, normally oxygen. In normal combustion, heating a biomass in the presence of oxygen gives rise to combustion, through oxidation, which generates heat and produces oxidized gaseous compounds visible in the form of smoke. Vice versa, by heating the biomass in the total absence of oxygen, the material is subjected to cleavage of the original chemical bonds, with the formation of simpler molecules. The heat supplied in the pyrolysis process is therefore used to cleave the chemical bonds, implementing what is defined thermally induced homo lysis.

There are numerous examples of pyrolytic burners, commonly defined pyrolytic stoves, in which pyrolysis of biomasses takes place in order to produce syngas and thereby obtain optimal combustion that generates low impact residues that can be re-used as fertilizers.

The residues of pyrolytic combustion, commonly defined "biochar", are formed of 90% carbon, and play an important role as improvers for agricultural use capable of improving the water retention capacity of the soil, of reducing the acidity of the soil, of increasing the mass and microbial respiration of the soil and of reducing the use of fertilizers.

Common pyrolytic burners are formed of a combustion chamber and of an outer jacket, provided with a bottom, separated from the combustion chamber and which defines an interspace between the two. The combustion chamber is provided with a set of holes that allow passage of an air flow into the same burner that, by heating up, triggers the pyrolytic process giving rise to the gas that is conveyed partially into the upper area of the burner and partially into the biomass, so as to obtain combustion thereof and the consequent formation of more syngas.

However, these apparatus are somewhat inefficient, as they do not allow correct pyrolytic combustion, thereby reducing the production of syngas and the general efficiency of the burner.

Moreover, these apparatus do not use up all the fuel inside the combustion chamber through the pyrolytic process, and consequently release a large amount of smoke during extinguishing of the burner.

The patent application US8459193 describes a device for gasification and pyrolysis of combustible materials comprising an inner chamber suitable to contain the fuel, and an outer chamber coaxial to the inner chamber, so as to produce an interspace between the two chambers suitable for passage of the gas produced. The device is provided with an aperture in the lower part of the inner chamber suitable for passage of the gases produced by the fuel into the interspace arranged between the two chambers. The device is also provided with a set of passages for the air arranged at the base of the same device and with a top plate suitable to convey the outflowing gas, allow correct combustion thereof.

However, this device has the limitation of not providing for complete conversion the solid fuel, which, as described above, can release a large amount of smoke both during use and mainly during extinguishing of the device.

The Italian utility model patent application PI2014U000016 describes a pyro lytic burner provided with an inner chamber, an outer chamber and a forced ventilation apparatus, i.e. a fan, arranged at the base of the burner so as to convey a large amount of air into the interspace present between the inner chamber and the outer chamber, and simultaneously into the same inner chamber where combustion of the solid takes place. The inner chamber is provided with a set of holes arranged in the top portion and in the base thereof, which allow passage of the gases and of air in order to generate the pyrolytic process and ensure total combustion of the solid present in the inner chamber.

However, this device has a series of drawbacks that limit its use and performance. In particular, the introduction of a forced air current at the base of the burner generates a series of turbulences close to the holes arranged at the base of the inner chamber, which limit and prevent correct outflow of the gas produced by pyrolysis, reducing the performance of the same burner. Moreover, as the fan is generally made of plastic material and is connected directly to the base of the burner, it suffers from the heat generated by combustion of the solid in the inner chamber, which can compromise its integrity and consequently reduce the performance of the burner.

The main aim of the present invention is therefore to provide a double chamber pyrolytic burner for solid fuel that allows the aforesaid drawbacks to be overcome.

Within this aim, one of the objects of the present invention is that of producing a double chamber pyrolytic burner for solid fuel that allows correct conversion of the solid used, so as to obtain a large amount of syngas and therefore combustion without gaseous residues that are harmful and disturbing for humans.

Another object of the present invention is that of producing a double chamber pyrolytic burner for solid fuel that optimizes the air flow circulating inside the same burner, limiting turbulences and in this way allowing an optimal reaction with a high production of syngas to be achieved.

Another object of the present invention is that of providing a double chamber pyro lytic burner for solid fuel that allows total conversion of the solid used, in this way preventing smoke from being generated during extinguishing of the burner.

Yet another object of the present invention is that of producing a double chamber pyro lytic burner for solid fuel that preserves the integrity of all its parts, in particular that preserves the integrity of the ventilation apparatus required to ensure correct inflow of air into the same burner.

These and other objects of the present invention are achieved by means of a pyro lytic burner according to claim 1 and to the related dependent claims appended to the present description. In a general definition thereof, the double chamber burner according to the present invention comprises a combustion chamber of diameter defined D and an outer jacket of diameter B that defines a toroidal interspace between said outer jacket and said combustion chamber.

The burner also comprises a cap which closes upwardly said interspace, a bottom and a ventilation apparatus coupled to said bottom.

The combustion chamber comprises a hollow cylinder of diameter D and of height H in which D<B and D/3<H<10xD, and a bottom coupled to said cylinder. The cylinder is provided with a first set of holes of diameter Dl arranged at a distance HI from the upper edge, in which Hl>2xDl, and of a second set of holes of diameter D2 arranged at a distance H2 from the lower edge, in which H2>2xD2.

The first set of holes has a diameter Dl such that D2<Dl<3xD2 and the second set of holes has a diameter D2 such that D/50<D2</10, said first and second set of holes being arranged radially along the wall of said hollow cylinder according to an angle a such that 12°<a<36°. Said bottom is provided with a central hole of diameter D3 and with a set of at least three holes also of diameter D3, equidistant from each other and arranged along a circumference of diameter between D and D/4, the diameter D3 being greater than or equal to the diameter D2 of said second holes.

The burner according to the invention further comprises a flow stabilizer ring arranged between the bottom of said burner and the bottom of said combustion chamber, provided with a central hole of diameter D4 such that D4>D/4. The burner according to the invention also comprises a shielding plate coupled to said flow stabilizer ring and arranged between said flow stabilizer ring and said bottom. The shielding plate is provided with a central body of diameter D5 and with at least two brackets suitable for coupling to said flow stabilizer ring or to the bottom of the burner, such that D5>D4. Further features and advantages of the double chamber burner according to the present invention are illustrated with reference to the description given below and to the accompanying figures, provided purely for explanatory and non-limiting purposes, wherein:

- Fig. 1 schematically represents an isometric sectional view of a burner according to the invention;

- Fig. 2 schematically represents an isometric sectional view of the burner of Fig. 1, with indication of the air and gas flows inside the burner;

- Fig. 3 is an isometric schematic sectional view of the burner of Fig. 1, with indication of the operation of the shielding plate;

- Fig. 4A is a top view of the shielding plate of a burner according to the invention;

- Fig. 4B is a lateral view of the shielding plate of a burner according to the invention;

- Fig. 5A is a top view of the stabilizer ring of a burner according to the invention;

- Fig. 5B is a lateral view of the shielding ring of a burner according to the invention;

- Figs. 6 A, 6B and 6C schematically represent the combustion chamber of a burner according to the invention;

- Fig. 7 schematically represents a sectional view of a double chamber burner according to the prior art.

With reference to the aforesaid figures, the present invention relates, in a first embodiment, to a double chamber burner for solid fuel 1 comprising a combustion chamber 10 and an outer jacket 20, coaxial to the combustion chamber, which defines a toroidal interspace 60 between the jacket and the combustion chamber. The outer jacket is provided with a bottom 40 that contributes to defining the volume of the interspace 60. The bottom 40 is coupled to a ventilation apparatus 50, preferably a forced ventilation apparatus such as a fan, that through a hole made in the bottom 40 allows passage of air through the bottom and therefore into the interspace 60. Upwardly the interspace is closed by a cap 30 that prevents both direct outflow of the air current generated by the ventilation apparatus and outflow of the gases generated during pyrolysis that takes place in the combustion chamber, as will be illustrated below. The combustion chamber 10 comprises a cylinder 110 of diameter D and of height H in which D<B and D/3<H<7xD and a bottom 120. The volume of the combustion chamber, which depends on the proportion between height and diameter, determines the capacity of the burner and therefore the duration of combustion and of production of heat thereof. The combustion chamber is suitable to contain the solid fuel that, through pyrolysis, produces the syngas that is used both to produce heat and to maintain the fuel active as will be described below.

In a preferred embodiment of the burner, the height H of the combustion chamber follows the relation D<H<7xD.

In a more preferred embodiment of the burner, the height H of the combustion chamber follows the relation 2xD<H<3xD, even more preferably the height H is 2.5 times the diameter D of the combustion chamber.

Examples of solid fuel that can be used in the burner according to the present invention are: wood chips, wood pellets, dried agricultural waste and dried food waste.

The diameter B of the outer jacket 20 is between 1.5xD and 2xD so as to obtain a volume of the toroidal interspace 60 adequate for the flow of air and of gases generated by the solid fuel and that allows correct operation of the burner. In a preferred embodiment, the diameter B of the outer jacket is between 1.5xD and 1.7xD, even more preferably is equal to 1.5xD.

The hollow cylinder 110 of the combustion chamber 10 is provided with a first set of holes

130 of diameter Dl arranged at a distance HI from the upper edge of the cylinder, and with a second set of holes 140 of diameter D2 arranged at a distance H2 from the lower edge of the cylinder 110.

Therefore, the two sets of holes place the inside of the combustion chamber 10 in communication with the toroidal interspace 60, and in particular the second set of holes 140 allows the gases produced by pyrolysis of the solid fuel, passing through the toroidal interspace 60, to flow out of the first holes 130 arranged in the upper edge of the cylinder, where their combustion takes place generating the characteristic toroidal flame typical of the pyrolytic burners.

The diameter Dl of said first holes 130 follows the relation such that D2<Dl<3xD2, while the diameter D2 of said second holes 140 follows the relation D/50<D2<D/10.

Said first set of holes 130 is arranged at a distance HI from the upper edge according to the relation Hl>2xDl, preferably Hl>3xDl, even more preferably at a distance HI equal to

3.5xDl

The second set of holes 140 is arranged at a distance H2 from the lower edge according to the relation H2>2xD2, preferably H2>3xD2, even more preferably at a distance H2 equal to 3.5xD2

In this way, high efficiency of the combustion chamber is obtained in relation to passage of the gases produced by pyrolysis through the holes 140 and their subsequent outflow into the upper edge of the burner through the holes 130, without having to necessarily oversize the fan 50.

In a preferred embodiment, the diameter Dl is D2<Dl<2xD2, even more preferably Dl is 1.6xD2 In a preferred embodiment, the diameter D2 is D/20<D2<D/10, even more preferably Dl is D\20.

The first and the second set of holes 130 and 140 are arranged radially along the wall of the hollow cylinder 110 of the combustion chamber 10 according to an angle a between 12 and 36°, preferably according to an angle between 18° and 30° providing in this way a sufficient number of holes suitable for passage of the gases produced, ensuring high operating efficiency of the burner.

The bottom 120 of the combustion chamber 10 is also provided with a set of holes, and in particular is provided with a central hole 151 of diameter D3 and with a set of at least three holes 150 as well as the central hole, also of diameter D3, arranged along a predetermined circumference. These holes 150 and 151 provided in the bottom 120 of the combustion chamber 10 allow passage of the air coming from the ventilation apparatus 50 through the bottom 40 of the same burner, which ensures correct combustion of the solid fuel in order to obtain pyrolysis thereof and the consequent production of syngas.

Preferably, the number of holes 150 provided in the bottom 120 is between 5 and 20, and their diameter D3, and also the diameter D3 of the central hole 151, is greater than or equal to the diameter of the holes D2 of said second set of holes 140 arranged at the base of the hollow cylinder 110.

The holes 151 are arranged in the bottom 120 along a circumference of diameter between De d/4, preferably on a circumference between De D/3, even more preferably are arranged along a circumference equal to D/2.

Operation according to the present invention, with reference to Fig. 2, can be described as follows.

A predetermined amount of a solid fuel is fed into the combustion chamber 10 so as to reach the predetermined level of variable filling based on the volume of the same combustion chamber.

The primary solid fuel is ignited by means of an auxiliary starting fuel, such as paraffin, ethanol or flammable hydrocarbons in this way generating an amount of heat that allows heating of the combustion chamber 10, taking the primary fuel to the predetermined optimal temperature so that the pyrolytic process is triggered.

The air thrust by the ventilation apparatus 50, traveling along the toroidal interspace 60 is heated and, passing through the upper part of the combustion chamber 10 through the first set of holes 130, creates a "stack effect" inside the toroidal interspace 60.

Combustion of the primary fuel generates a flammable gas, also called syngas, in the combustion chamber 110. A part of syngas is drawn by the combustion chamber 110 and through the second set of holes 140 exploiting the "Venturi effect" generated by the second holes 140, is thrust toward the toroidal interspace 60.

The air flow present in the toroidal interspace 60 generated by the ventilation apparatus 50 guides the gases into the upper part of the toroidal interspace, until they flow out from the first set of holes 130 where combustion thereof takes place producing the particular toroidal flame. In this way the process can repeat until the gas produced by the primary fuel has been used up or until all the primary solid fuel has been used up.

By regulating the ventilation, it is possible to vary the reaction temperature and consequently to obtain different process results.

By feeding 1 CFM (Cubic Feet per Meter) of air every 48cm 3 of volume of the combustion chamber into the apparatus, it is possible to obtain a minimum sustainable capacity, optimizing the

production of charcoal, or of biochar, with respect to the production of gas (slow pyrolysis). By feeding 1.7 CFM of air every 48cm 3 of volume, the apparatus will instead be taken to a situation of maximum sustainable capacity, maximizing the production of gas with respect to the biochar (fast pyrolysis).

All the ventilation intervals between these two values are considered acceptable for correct operation of the device.

The temperature interval reached inside the combustion chamber when operating at full capacity varies from 400°C to 1300°C. This means that the materials that can be used for its construction must be able to withstand these high temperatures with a discrete margin.

Preferably, the pyrolytic burner according to the present invention is made of a material selected from the group consisting of: iron based alloys, such as steel or cast iron, or titanium. In order to allow correct heating of the air flow circulating in the interspace 60, the thickness of the hollow cylinder 110 forming the combustion chamber 10 is between 1 and 20 mm, preferably between 2 and 5, even more preferably 3mm.

The ventilation apparatus 50 is preferably a forced ventilation apparatus capable of varying the inflow of air into the burner in a predetermined manner in order to regulate the implementation of pyrolysis as described above. The ventilation apparatus can be a radial or axial apparatus based on construction requirements.

The ventilation apparatus is coupled to the bottom 40 of the burner and allows passage of the air through a hole made in the same bottom. The hole of the bottom 40 is suitably sized based on the dimension of the ventilation apparatus used, in particular based on the dimension of the air outlet of the ventilator.

The burner according to the present invention also comprises a flow stabilizer ring 200 arranged between the bottom 40 of the burner and the bottom 120 of the combustion chamber 10 provided with a central hole of diameter D4. As illustrated in Figs. 5 A and 5B, said stabilizer ring is a circular ring formed of the same material as the burner, and with outer diameter coincident with the inner diameter of the outer jacket 20, and inner diameter, i.e. diameter of the central hole, between the diameter D of the hollow cylinder 110 of the combustion chamber 10 and the diameter of arrangement of the holes 150 provided in the bottom 120 of the combustion chamber 10.

The stabilizer ring has the function of reuniting, channelling and directing the air flow in an optimal manner, triggering extraction of the gases from the set of second holes 140 and inflow of the primary air into the set of holes 150 and 151 provided in the bottom 120 of the combustion chamber 10. The stabilizer ring is connected to the rest of the components coaxially thereto, at a minimum distance from the bottom 120 of the combustion chamber between 10mm and 30mm, preferably between 15 and 20, even more preferably at a distance of 15mm.

The burner is also provided with a shielding plate 300 coupled to the flow stabilizer ring 200 and arranged between said stabilizer ring 200 and the bottom 40 of the burner.

As illustrated in Figs. 4A and 4B, the shielding plate is provided with a central body 301 of diameter D5 and with at least two brackets 302 suitable for coupling of the same plate to the stabilizer ring 200 or to the bottom 40 of the burner.

The shielding plate is made of the same material as the burner, and the diameter D5 of the central body 301 is greater than or equal to the diameter D4 of the central hole provided in the flow stabilizer ring 200 and greater than or equal to the diameter of the hole made in the bottom 40 of the burner suitable for passage of the air flows.

The shielding plate 300, as illustrated in Fig. 3, has the function of shielding and protecting the portion of the ventilation apparatus 50 facing the combustion chamber as, due to the high temperatures, the same combustion chamber emits infrared radiation that could damage the ventilation apparatus.

A further function of the shielding plate 300 is division of the turbulent air flow generated by the forced ventilation apparatus 50 that allows initial stabilization and channelling thereof toward the toroidal interspace 60.

The shielding plate is connected to the rest of the components coaxially thereto, at a minimum distance from the flow stabilizer ring 200 between 10 and 30, preferably between 15 and 20, even more preferably at a distance of 15mm and at a minimum distance from the bottom 40 of the burner between 10 and 30, preferably between 15 and 20, even more preferably at a distance of 15mm.

The pyrolytic burner according to the invention is characterized by its ease of use and high efficiency.

The pyrolytic burner according to the invention can therefore be used, reliably, to heat small environments or as source of heat for barbecues or camp stoves.

With the pyrolytic burner according to the present invention it is possible to obtain efficient pyrolysis that allows heat to be produced without the production of gases that are toxic and harmful to humans.

The pyrolytic burner according to the present invention also allows protection of ventilation apparatus used in the burner, so as not to compromise the integrity and maintain efficient operation.

The pyrolytic burner according to the invention is easy to produce on an industrial scale.