EP3551733B1

EP3551733B1 - System for transforming an organic material into syngas

Info

Publication number: EP3551733B1
Application number: EP17825936.2A
Authority: EP
Inventors: Paolo BRANDA
Original assignee: Site SpA Con Socio Unico
Current assignee: Site SpA Con Socio Unico
Priority date: 2016-12-09
Filing date: 2017-12-07
Publication date: 2021-02-03
Anticipated expiration: 2037-12-07
Also published as: WO2018104907A1; IT201600124642A1; EP3551733A1

Description

TECHNICAL FIELD

The present invention relates to a system for transforming an organic material into syngas.
In particular, the present invention relates to a so-called open-air system, i.e. without an upper cover.

BACKGROUND ART

Systems are known for transforming organic material, for example vegetable biomass, into a syngas, i.e. a mixture of gas intended for oxidisation to obtain heat and/or mechanical energy. The syngas essentially comprises carbon monoxide, hydrogen, methane and carbon dioxide.
In further detail, systems are known comprising a reactor passed through by the air and organic material in a descending direction, i.e. from top to bottom, and inside which the chemical reactions take place that transform the organic material into syngas.
The reactor essentially comprises:

a hopper for supply of the organic material;
an outlet that can be passed through by the syngas and fluidly connected to the user;
a shell housing the hopper; and
a reactor housed inside the shell, supplied by the hopper with air and organic material, and inside which the organic material is transformed into syngas.

Proceeding from top to bottom, the reactor of the above-mentioned type of system comprises:

a first layer, in which the organic material is dried and set on fire, thus undergoing partial carbonization;
a second layer, in which the organic material undergoes a process of pyrolysis in the absence of combustion agent, i.e. in the absence of air; and
a third layer, in which the heat generated by the pyrolysis is used to completely dissociate the organic material and generate the syngas.

It is known in the sector that the syngas coming out of the reactor cannot be immediately used, since it contains compounds that are useless or even potentially harmful for the final user, such as chains of aliphatic hydrocarbons or solid condensate residues.
In order to re-associate the above-mentioned compounds, the syngas coming out of the reactor is cooled in a controlled manner in cooling systems, which are arranged downstream and externally to the system for transforming the organic material into syngas.
Said choice is due to the fact that the feeding speed of the syngas inside the systems of a known type is particularly high.
The provision of said cooling systems obviously represents an additional cost, in terms of both construction costs and running costs.
In order to reduce said additional cost, the application TO2013A000332 proposes the provision of cooling means upstream of the reactor outlet and integrated inside the system itself.
Said cooling means are housed, at least partly, in a tubular jacket surrounding the reactor shell.
More specifically, said cooling means comprise a plurality of ducts through which the syngas passes, respective cooling circuits of a heat transfer fluid and respective radiators for exchanging heat with syngas.
In the sector, the need is nevertheless felt to make the syngas available at the system outlet at a temperature even lower than the known solutions, so as to reduce the need to use materials able to withstand high temperatures and, therefore, limit the overall cost of the system.
In the sector, the need is furthermore felt to simplify as far as possible construction and operation of the system.
CN-U-202849349 and US-A-3988123 describe a system according to the preamble of claim 1.

DISCLOSURE OF INVENTION

The object of the present invention is the construction of a system for transforming organic material into syngas, which meets at least one of the needs specified above.
The above-mentioned object is achieved by the present invention, since it concerns a system for transforming an organic material into syngas, as defined in claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention a preferred embodiment is described below, purely by way of nonlimiting example and with reference to the attached figures, in which:

figure 1 illustrates in schematic cross section a system for transforming organic material into syngas, produced according to the teachings of the present invention and with parts removed for clarity;
figure 2 is a section along the line II-II of Figure 1;
figure 3 is an exploded perspective view of some components of the system of Figures 1 to 2; and
figure 4 is a front view on a particularly enlarged scale of some components of Figures 1 to 3.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to the attached figures, the number 1 indicates a system for transforming an organic material into syngas.
In the case illustrated, the organic material is vegetable biomass. Alternatively, the organic material could be formed of agricultural products deriving from traditional intensive cultivation, appropriately shredded, or with residues of olive pressing and grape pomace, chaff and/or rice husks, wheat, maize and cereals in general.
The syngas is a mixture of gas intended for oxidisation to obtain heat and/or mechanical energy in a user (not illustrated), for example an internal combustion engine, positioned downstream of the system 1. The syngas essentially comprises nitrogen, carbon monoxide, hydrogen, methane and carbon dioxide.
The system 1 essentially comprises:

a supply hopper 2 for supplying the organic material;
an outlet 3 that can be passed through by the syngas and is fluidly connected to the user;
a shell 4 housing the hopper 2; and
a reactor 5 housed inside the shell 4, supplied by the hopper 2 with air and organic material, and inside which the organic material is transformed into syngas.

In particular, the hopper 2 comprises a chute and is driven by a motor 17 to facilitate descent of the organic material and distribute the latter uniformly within the reactor 5.
The shell 4 has a substantially tubular-shaped axis A and is delimited by a pair of cylindrical walls 12, 13 and arranged in a position radially internal and external respectively to the axis A.
Preferably, the shell 4 houses a laser sensor which detects the level of organic material reached inside the reactor 5, and allows or prevents loading of the organic material inside the hopper 2 on the basis of said level.
The casing 4 further comprises a frustoconical wall 14 made of ceramic material.
The reactor 5 is housed in a substantially coaxial manner inside the shell 4.
The reactor 5 has a tubular shape and extends along an axis A, vertical in the case illustrated.
The reactor 5 further comprises an outlet section 7 of the syngas of said reactor 5.
Section 7 is furthermore arranged at a lower height than the hopper 2 and higher than the wall 14.
More specifically, section 7 of the reactor 5, is arranged at a lower height than the hopper 2.
In this way, the organic material moves inside the reactor 5 from top to bottom, according to a procedure known in the sector as down-draft.
For said purpose, the system 1 comprises a fan (not illustrated), which maintains the reactor 5 in underpressure.
The reactor 5 comprises, proceeding from the hopper 2 towards the section 7:

a plurality, three in the case illustrated, of stages 8, 9, 10 overlapping one another, inside which respective reactions of transformation of the organic material into syngas occur, one after the other; and
a barrier 18 and a grid 19, which obstructs the section 7 of the reactor 5.

The stages 8, 9, 10 are arranged one after the other, from the hopper 2 towards the section 7.
In greater detail, stage 8 is a pre-heating stage, stage 9 is a pyrolysis stage and stage 10 is a stage of complete dissociation of the organic material.
In stage 8, the organic material undergoes a process of drying and subsequent combustion in the presence of a combustion agent, for example hot air. Said combustion brings the temperature of the organic material in the layer 8 to a value of approximately 600-700°C, favouring carbonization of the organic material, by means of breakdown of the volatile components present in the wood fibres.
In stage 9, the partially carbonized organic material undergoes a pyrolysis process.
In particular, the pyrolysis process is due to the high temperature and lack of combustion agent. In other words, the pyrolysis process takes place substantially without oxygen.
Following the pyrolysis process, the original chemical bonds of the organic material are disaggregated and a gaseous mixture is formed containing aromatic hydrocarbons.
Stage 9 further comprises a pair of grids 20 fixed to the wall 14 and provided to slow down the carbonic material in stage 9 and thus allow said carbonic material to remain in stage 9 for the necessary time.
In particular, the grids 20 are shaped like a double upturned cone with a plurality of calibrated holes (not illustrated).
The grids 20 are furthermore effective in preventing feed of the ashes, which are formed of the aromatic hydrocarbon components present in the gaseous mixture.
In the case illustrated, the grids 20 are made of ceramic material.
Stage 10 comprises:

a surface 11 maintained at a temperature of approximately 1300°C by the pyrolysis reaction that takes place in stage 9; and
a plurality of obligatory passages (not illustrated), which guide the gaseous mixture against the surface 11.

Due to the high temperature of the surface 11, the volatile components of the gaseous mixture that had not been blocked by the grids 20 are completely dissociated. Said volatile components are formed, in particular, of carbon micro-dust, which could damage and/or compromise the operation of the motors supplied with the syngas.
In particular, said carbon dust, in the area of the surface 11, reacts with the water vapour giving rise to carbon oxide and hydrogen.
The barrier 18 is formed, in the case illustrated, by alumina spheres.
In particular, the alumina spheres store heat and dissociate the last particles of carbon still present in the syngas.
The system 1 further comprises:

a storage tank 22 for storing the unburnt waste and ashes removed from the syngas; and
a transfer system 21, which is supplied, by gravity, with the unburnt waste and ashes falling from the section 7 of the reactor 5 and transfers said waste and ashes to the tank 22, by means of a system of augers not illustrated.

Advantageously, the system 1 comprises cooling means 30 which comprise a tube heat exchanger 80 formed of a plurality of tubes 81 (Figures 2 to 4) passed through by the syngas and embedded in a bath 82 of a heat transfer liquid, which in the case illustrated is water.
The tube heat exchanger 80 is in a position immediately below the section 7 and receives the syngas from said section 7.
In further detail, tube heat exchanger 80 extends parallel to the axis A between:

a third height, lower than the second height; and
a fourth height, lower than the third height.

In further detail, the tube heat exchanger 80 comprises a pair of plates 83, 84, upper and lower, lying on respective planes parallel to each other and orthogonal to the axis A.
The tubes 81 have respective axes B parallel to each other and parallel to the axis A and extending between the plates 83, 84.
The tubes 81 are welded, at respective upper ends 86 and lower ends s to the plates 83, 84.
The plates 83, 84 have respective pluralities of holes arranged in the area of the open sections of the tubes 81.
In particular, the tubes 81 are arranged inside the tube heat exchanger 80 so as to form, in section orthogonal to the axis A, a plurality of circumferences concentric to the axis A (Figure 2).
The tubes 81 are kept in position by respective baffles 88 interposed between pairs of tubes 81 (Figure 3).
The tube heat exchanger 80 furthermore comprises:

a shell 90, which extends between the plates 83, 84 and delimits a volume for the bath 82; and
a circuit 91 for exchange of the heat transfer liquid heated with fresh heat transfer liquid (Figure 4).

The circuit 91 comprises, in particular:

a plurality of openings 92 defined by the shell 90 and adapted to allow inlet and outlet of the heat transfer liquid;
a heat exchanger (not illustrated) to cool the heat transfer liquid flowing out of the bath 82; and
a hydraulic pump (not illustrated) to send the cooled heat transfer liquid back into the bath 82.

The tube heat exchanger 80 is arranged in a position immediately below the grid 19 and the barrier 18.
In the case illustrated, the plates 83, 84 and the tubes 81 are made of stainless steel.
Due to the cooling action of the tube heat exchanger 80, the syngas is cooled to a temperature of approximately 20°C.
In use, the carbonic material is placed in the hopper 2 and from here reaches the reactor 5 together with a combustion agent, typically air.
Inside the reactor 5, the carbonic material undergoes combustion in the presence of the combustion agent at a temperature of approximately 600-700°C in stage 8; and undergoes a pyrolysis process in stage 9 substantially in the absence of air.
In particular, the grids 20 prevent feeding of the ashes formed by the aromatic hydrocarbons present in the gaseous mixture.
In stage 10, the syngas is guided against the surface 11 at high temperature. In this way, the carbon dust not eliminated by the grids 20 is completely dissociated.
The barrier 18 is effective in removing the last particles of carbon still present in the syngas.
The unburnt waste and the ashes removed from the syngas reach, by gravity, the system 21 and are then stored in the tank 22.
The syngas then passes through the section 7 and flows into the tubes 81 of the tube heat exchanger 80, which are in contact with the bath 82 of heat transfer liquid.
Due to the cooling action of the bath 82, the temperature of the syngas drops inside the tube heat exchanger 80 to a value of approximately 40 degrees centigrade.
The syngas cooled in a controlled manner and filtered reaches the outlet 3 of the system 1 and can be made available to the users.
From an examination of the system 1 produced according to the present invention, the advantages it offers are evident.
In particular, the cooling means 30 comprise a tube heat exchanger 80 immersed in the bath 82 and the syngas is cooled by surface contact of the syngas with the cold heat transfer liquid in the bath 82.
It is therefore possible to cool the syngas by simply installing the tube heat exchanger 80 in the system 1 and without the presence of an additional external jacket to house the cooling means.
This makes the system 1 particularly inexpensive to produce and run compared to the solutions of a known type.
In addition, the Applicant has observed that use of the cooling means 30 comprising the tube heat exchanger 80 allows reduction of the overall lateral dimensions of the system 1 compared to the solutions of a known type described in the introductory part of the present description.
The use of the tube heat exchanger 80 also allows a higher portion of materials not requiring great resistance to high temperatures to be used in production of the system 1 compared to the solutions of known types, with further evident savings.
The cooling action of the tube heat exchanger 80 allows reduction of the temperature of the syngas flowing out of the system 1 to values around 40 degrees centigrade with corresponding elimination of the harmful presence of chains of aliphatic hydrocarbons or solid condensate residues.
The barrier 18 is formed, in the case illustrated, of alumina balls and is interposed between tube heat exchanger 80 and outlet 3.
In particular, the alumina balls store heat and dissociate the last carbon particles still present in the syngas.
In other words, the alumina balls, due to their low thermal conductivity, allow an accumulation of heat which favours dissociation of the last particles of carbon still present in the syngas.
This allows further elimination of the harmful presence of chains of aliphatic hydrocarbons or solid condensate residues.
Lastly, it is clear that modifications and variations can be made to the system 1 previously described and illustrated without departing from the protective scope of the present invention.

Claims

A system (1) for transforming a.n organic material into syngas, comprising:
- an inlet (2) that can be supplied, in use, with said organic material and/or with a combustion agent;

- an outlet. (3) that can be passed through, in use, by said syngas produced by said system (1) and can be fluidly connected with a user;

- an open reactor (5), interposed between said inlet (2) and said outlet .(3) that can be supplied, in use, at a first height with said organic material and adapted, in use, to supply at a second height, lower than said first height, said syngas; and

- cooling means (30) positioned upstream of said outlet (3) and downstream of said reactor (5) according to a direction of feed, in use, of said syngas inside said system (1) and adapted to cool, in use, said syngas inside said system (1);
said cooling means (30) comprising a tube heat exchanger (80) formed by a plurality of tubes (81) through which said syngas can pass, in use, and housed inside a bath (82) filled, in use, with a heat transfer liquid;
characterised in that it comprises a barrier (18) made of ceramic balls and a grid (19), which is interposed between said barrier (18) and said tube heat exchanger (80) ;
said tube heat exchanger (80) being arranged between said barrier (18) and said outlet (3).
the system according to claim 1, characterised in that said tube heat exchanger (80) extends between a third height and a fourth height;
said fourth height being arranged, in use, below said third height.
The system according to claim 2, characterised in that it comprises a down-draft direction of extension arranged vertically in use, and in that said tubes: (81) have respective axes (B) parallel to said direction of extension.
The system according to any one of the preceding claims, characterised in that the sections orthogonal to the respective axes (B) of said tubes (81) are arranged according to a plurality of concentric circumferences.
The system according to any one of the preceding claims, characterised i:n that said tube heat exchanger (80) comprises two perforated plates (83, 84) opposite each other;
said tubes (81) being welded to said two plates (83, 84).
The system according to claim 5, characterised in that said tube heat exchanger (80) comprises baffles (88) interposed between said tubes (81) and provided to maintain said tubes (81) at given distances from one another.
The system according to any one of the preceding claims, characterised in that it comprises recirculation means (91) adapted to create a forced circulation of said heat transfer liquid inside said bath (82).
The system according to any one of the preceding claims, characterised in that said inlet (2) is open at the top.