WO2014097236A1

WO2014097236A1 - Pyro-gasification reactor

Info

Publication number: WO2014097236A1
Application number: PCT/IB2013/061182
Authority: WO
Inventors: Salvatore MARASA'
Original assignee: Marasa Salvatore
Priority date: 2012-12-21
Filing date: 2013-12-20
Publication date: 2014-06-26
Also published as: ITTO20121122A1

Abstract

A pyro-gasification reactor (3) of the downdraft type, which is adapted to be applied to a pyro-gasification plant (2). The reactor (3) comprises: • at least one first inlet (32), through which a predetermined amount of biomass is introduced; • a storage tank (31), into which the biomass to be pyrolyzed and gasified is introduced; · at least one second inlet (34), through which a fluidizing agent is introduced into the reactor (3) by means of a fluidizing agent introducing plant (A); • a core (4), in which the pyrolysis and gasification processes take place and which is arranged under said storage tank (31). Said core (4) comprises at least one first reaction chamber (41) and at least one first grate (43), which is adapted to support the biomass during the pyro-gasification process. The reactor comprises a cooling structure (5), which is adapted to surround the core (4), thus enclosing it, creating a hollow space (51). The cooling structure (5) is fluidly connected to said fluidizing agent introducing plant (A), so as to allow a fluid to flow through said hollow space (51). The second inlet (34) to introduce the fluidizing agent is arranged in correspondence to said core (4), thus allowing the fluidizing agent contained in said hollow space (51) to be at least introduced into said first reaction chamber (41).

Description

TITLE: PYRO-GASIFICATION REACTOR

The present invention is relative to a pyro- gasification reactor of the downdraft type, which is comprised in a pyro-gasification plant and is adapted to produce synthesis gases or syngases starting from a biomass, for example a biomass of organic origin.

A pyrolysis process is known, which, following a heating process that substantially takes place in absence of oxygen, through a molecular dissociation process affecting the substances introduced, which are preferably organic, permits the creation of a solid phase, which substantially consists of coal, and of a gaseous phase, which mainly comprises, in variable proportions, hydrocarbons.

The ratio between solid and gaseous phase is a function of the parameters of the reaction, for example the process actuation time and the temperature at which the reaction takes place.

This process substantially takes place at temperatures ranging from 400°C to 700°C.

The hydrocarbons comprised in the gaseous phase have a very complex molecular structure, with a reduced heating value .

Furthermore, a gasification process is known, which consists in an incomplete oxidation of a solid fuel, with the presence of a gasifying agent suited to give up oxygen, at a temperature ranging from 800°C to 1300°C and in a oxygen-poor environment .

Several pyro-gasification plants of the downdraft type are known, adapted to produce synthesis gases. In these plants, the biomass introduced from above flows downwards and is subject to the following reactions: drying, pyrolysis, and carbonization of the biomass introduced. The production waste, which substantially consists of ashes, is gathered in the lower part of the plant and then properly removed .

These plants are affected by several technical problems, among which there are:

• the formation of tar and, hence, the scarce quality of gas produced;

• the long times and the high costs needed to start up and turn off the plant;

• the high plant manufacturing costs due to the large use of refractory material, which is needed to reach the above-mentioned temperature without the risk of a possible melting of the material making up the gasification reactor .

The use of refractory material, besides the high costs of the material itself, determines a series of problems, such as for example thermal inertia, maintenance problems, and plant mass problems. As a matter of fact, refractory materials intrinsically have a high thermal inertia and, thus, heat up and cool down very slowly. This means that, in case maintenance works have to be performed, operators have to wait many hours after having turned off the plat before actually being able to operate on the plant, because the temperature of the material itself has to reach a temperature that allows operators to safely carry out maintenance works.

In the solutions of the prior art, a grate is provided in the lower part of the reactor, under the core, so as to support the coal or char obtained from the pyrolysis process. The coal is expelled when it reaches a size that allows it to move past the meshes of the grate itself, since the coal has reached a size that is smaller than the openings of the grate itself.

The coal that moves past the grate reaches an ash-pit, where it will be removed. The coal reaching the ash-pit has not completely exhausted its thermal and filtering functions for the production of the synthesis gas yet. This implies a non-optimal use of the biomass introduced.

Hence, the prior art cannot ensure that the biomass is entirely exploited during the pyro-gasification process. Therefore, only the ash, which is a physiological waste of the pyro-gasification process, should reach the ash-pit, thus preventing the coal from reaching the latter.

The object of the present invention is to solve the above-mentioned technical problems by providing a reactor for pyro-gasification plants, which comprises a cooling system, which allows constructors not to use refractory material and permits the complete reaction of the biomass, and a special grate system to optimize the exploitation of the biomass .

An aspect of the present invention is relative to a reactor having the features set forth in appended claim 1.

A further aspect of the present invention is relative to a pyro-gasification plant having the features set forth in appended claim 10.

Further accessory features are set forth in the appended dependent claims.

The features and advantages of the reactor according to the present invention will be best understood upon perusal of the following description of a preferred non- limiting embodiment of the reactor and of the plant with reference to the accompanying drawings, which respectively show what follows:

· figure 1 shows, in an overall prospective view, the pyro-gasification plant comprising a reactor according to the present invention;

• figures 2A, 2B, and 2C show the reactor according to the present invention; in particular, figure 2A shows a prospective view of the reactor, and figures 2B and 2C show two lateral views of the reactor;

• figures 3A, 3B, and 3C show the core of the reactor according to the present invention; in particular, figure 3A shows, in an overall view, the reactor comprising the cooling structure, figure 3B shows a lateral section of figure 3A, and figure 3C shows, in a prospective view, the core with the cooling structure removed;

• figures 4A and 4B show a preferred embodiment of the grates comprised in the core according to the present invention; in particular, figure 4A shows, in a view from the top, section B-B of the reactor of figure 2C, whereas figure 4B shows, in a view from the top, section C-C of the reactor of figure 2C.

With reference to the figures mentioned above, pyro- gasification reactor 3 is of the downdraft type.

For the purposes of the present invention, the term "reactor of the downdraft type" means a co-current gasifier, in which the gasification flow follows the flow of fuel, such as biomass, downwards, along a vertical axis " Z " . The reactor according to the present invention is adapted to be applied to a pyro-gasification plant 2. An embodiment of pyro-gasifier 2 is shown by way of example in figure 1.

Reactor 3 according to the present invention comprises: at least one first inlet 32, through which a predetermined amount of biomass is introduced; a storage tank 31, into which the biomass to be pyro-gasified is introduced; and at least one second inlet 34, through which a fluidizing agent, such as for example air and/or oxygen and/or other gas mixtures, is introduced into reactor 3 by means of a fluidizing agent introducing plant "A", which is shown by way of example in figures 2A, 2B, and 2C.

Said fluidizing agent introducing plant "A" is adapted to introduce into pyro-gasification plant 2 a fluidizing fluid or agent, such as for example air and/or oxygen and/or other gas mixtures.

Reactor comprises a core 4, in which the pyrolysis and gasification processes take place and which is arranged under said storage tank 31 relative to said vertical axis "Z". The fuel or pyrolyzed biomass reaches said core 4. In said storage tank 31, during the downward movement of the biomass itself, the drying of the biomass and its pyrolysis take place.

Said core 4 comprises at least one first reaction chamber 41, where the gasification process takes place, and at least one first grate 43.

Said first grate 43 is adapted to support the biomass, which falls from storage tank 31, during the pyro- gasification process; in particular, it is adapted to support the coal obtained from the previous pyrolysis step. Figures 3A-3C show, in different views, a preferred embodiment of reactor 3 according to the present invention.

Reactor 3 according to the present invention comprises a cooling structure 5, is adapted to surround core 4, thus enclosing it, creating a hollow space 51. Said cooling structure 5 is fluidly connected to said fluidizing agent introducing plant "A", so as to allow a fluid to flow through said hollow space 51, for example air and/or oxygen and/or a gas mixture.

Said fluidizing agent, which, for example, is at room temperature and is introduced by means of said fluidizing agent introducing plant "A", is forced to flow through said hollow space 51. This fluidizing agent, preferably at room temperature, cools down, thanks to its continuous flow, outer walls 40 of core 4, thus transferring heat by convection and preventing outer walls 40 themselves from reaching dangerous temperatures, such as for example the melting temperature. Said hollow space 51 is clearly shown in figure 3B.

Said second inlet 34 for the introduction of a fluidizing agent is arranged in correspondence to said core 4, thus allowing the fluidizing agent contained in said hollow space 51, such as for example air, to be at least introduced into said first reaction chamber 41.

The position of said second inlet allows the oxidizing element contained in the fluidizing agent, in this case air, to be distributed where it is mostly needed. The introduction of the fluidizing agent into core 4 permits the molecular dissociation reaction of the gases flowing through said core, which is typical of the gasification process, thus allowing this process to take place in a complete manner, thanks to the high temperature of core 4 itself. Figures 4A-4B show core 4 with cooling structure 5. Figures 4C, on the other hand, shows core 4 without cooling structure 5.

Said core 4 and said cooling structure 5 are preferably completely made of a non-refractory metal material, such as steel. The present solution, therefore, allows the manufacturing costs of reactor 3 and, hence, of plant 2 to be reduced, since no refractory materials have to be used to control the temperature of core 4. Reactor 3 according to the present invention, anyway, allows optimal temperatures of core 4 to be reached, so as to pyrolyze and gasify the biomass and obtain a high-quality synthesis gas.

In the preferred embodiment, said second inlet 34 for the introduction of the fluidizing agent, for example air, is an opening, preferably a slot-shaped one, which substantially follows the entire outer perimeter of said first chamber 41.

Said second inlet 34 allows the oxidizing element to be introduced in a substantially uniform manner into all the sections of core 4. This solution causes the introduction of the oxidizing element into the first reaction chamber 41 to become uniform, so as to have a uniform introduction and not a punctual introduction like the one provided by the solutions of the prior art.

In the preferred embodiment, said second inlet 34 for the introduction of the fluidizing agent is substantially arranged in correspondence to the central portion of said first chamber 41, as shown by way of example in figures 3B and 3C. This arrangement of core 4 and of the second second inlet 34 allows the introduction of the oxidizing element into the core - and in particular into the first reaction chamber 41 - to be optimized, so as to optimize the reaction inside core 4.

In the preferred embodiment, core 4 comprises at least one second reaction chamber 42. Said reaction chamber 42 is arranged under said first reaction chamber 41, relative to said vertical axis "Z".

The first and the second reaction chambers (41, 42) are divided by the first grate 43. The second reaction chamber 42 is delimited on the lower side by a second grate

44, as shown by way of example in figure 3B.

Said second grate 44 is adapted to cause the coal or char resulting from the pyrolysis process to stop for a larger amount of time inside core 4.

Said second reaction chamber 42 comprises a plurality of first openings 422, adapted to allow the fluidizing agent contained in said hollow space 51, for example air, to be introduced into said second reaction chamber 42.

Preferably, said first openings 422 are preferably holes, for example circular holes, which are uniformly distributed on outer walls 40 in correspondence to said second reaction chamber 42.

The second grate 44, together with said first openings, cause the coal or char to be hit again by the fluidizing agent, for example air, so as to complete its thermal functions, thus completing the reaction and becoming ash. As a matter of fact, the oxygen contained in the fluidizing agent, when coming into contact with the activated coal or ember, allows the temperature to remain high, thus allowing the pyrolysis gases to perform a complete molecular dissociation, so as to obtain a synthesis gas without long carbon molecules called tar.

In the preferred embodiment, the first grate and the second grate (43, 44) have a density of second openings 45 that is substantially equivalent, preferably identical.

As shown in figures 4A and 4B, the two grates (43, 44) are substantially identical. Said second openings 45 substantially have the shape of an oblong slot. As shown in figures 4A and 4B, each grate is divided into four quadrants, each quadrant comprising said second openings 45 aligned along a predetermined direction. Each quadrant has an alignment direction of the second openings 45 that is substantially rotated by 90° relative to the following and the previous quadrant. Furthermore, the second openings 45 arranged in non-consecutive quadrants are mirror-like doubles of one another.

The density of the second openings 45 in said first and second grates are a function of the dimensions of the reactor itself and, in particular, of storage tank 31, besides being a function of the particle size of the biomass introduced.

Said hollow space 51 of cooling structure 5, in the embodiment shown, comprises a first compartment 52 and a second compartment 53.

Substantially, said first compartment 52 surrounds the first reaction chamber 41, enclosing it; whereas said second compartment 53 surrounds said second reaction chamber 42, enclosing it.

Said first and second compartments (52, 53) are preferably divided by a perforated plate, adapted to allow a fluid flow, for example air, to flow between the two compartments (52, 53) .

In general, a pyro-gasification plant 2, which is shown by way of example in figure 1, comprises an outer casing 21, a lid 22, and an ash-pit 24.

Outer casing 21 preferably has a substantially cylindrical shape.

Reactor 3 according to the present invention is arranged inside outer casing 21.

Said lid is adapted to seal the upper portion of storage tank 31.

Said ash-pit 24 is adapted to collect the waste ashes of the biomass pyro-gasification process. Ash-pit 24 substantially has the shape of a truncated cone, thus acting as a funnel towards a discharge opening 25, which is arranged in correspondence to the smaller base and through which said ashes are automatically and/or manually removed.

As shown in figure 1, a synthesis gas drawing point 211 is provided, preferably in correspondence to outer casing 21. The gas drawn out by means of said gas drawing point 211 is sent to one or more gas purification and/or cooling plants, which are not shown. Said gas drawing point 211 is, for example, a flanged duct, which is arranged in a tangential manner relative to outer casing 21.

Said first inlet 32, which is comprised in reactor 3, is for example a tubular element, adapted to lead the biomass coming from a biomass introducing plant - not shown - towards reactor 3.

Said fluidizing agent introducing plant "A" comprises at least one duct 26. Said duct 26, at one end, is fluidly connected to colling structure 5 and, at the opposite end, comes out of reactor 3.

If necessary, said plant "A" comprises at least one fluidizing agent introducing device, which is not shown and is adapted to introduce a fluid into plant "A". Said fluidizing agent introducing device is connected to said duct 26.

In the preferred embodiment, said duct 26 substantially comprises two arms, which are adapted to introduce the fluidizing agent into hollow space 51 substantially in two spots that are at a distance of 180° from one another.

Pyro-gasification plant 2 according to the present invention comprises at least one heating device 24 of the known type, which is adapted to trigger the pyro- gasification process by causing reactor 3 to reach the right temperature. Said heating device 24 is, by way of example, an incandescent resistor.

Reactor 3 according to the present invention guarantees a passive protection of the parts subject to high temperatures, such as core 4, by implementing cooling structure 5 described above.

The presence of said second slot-shaped inlet 34, whose transverse extension is such as to leave a small crack in correspondence to core 4 and, in particular, in correspondence to the first reaction chamber 41, permits a substantially ideal distribution of the oxidizing element inside core 4.

The use of a cooling structure 5 without refractory materials allows the manufacturing costs to be significantly reduced. Furthermore, the use of materials such as steel, unlike refractory materials, permits the elimination of the problem concerning the thermal inertia of the plant, thus allowing reactor 3 itself to be rapidly turned on and/or off. The amount of time needed to turn the reactor on and off is equal to 1/10 of the time required by the solutions of the prior art using refractory materials. The reduction of the times needed to turn off the reactor allows operators to work on the reactor itself, for example for the maintenance of the latter, only a few hours after the plant has been actually turned off. The lack of refractory materials, besides implying a reduction of manufacturing costs, also leads to a reduction of maintenance costs during the life of the plant.

The division of core 4 into two reaction chambers (41, 42) comprising a second grate 44 and the use of a cooling structure 5, which is adapted to allow the fluidizing agent to be also introduced into the second reaction chamber 42, allows the biomass introduced into the pyro-gasification plant to be entirely exploited. As a matter of fact, the biomass is exploited both in terms of thermal function, in order to increase the temperature of the core, and in terms of synthesis gas filtering function, thus obtaining, as a waste, only ash.

NUMERICAL REFERENCES

Pyro-gasification plant 2

Outer casing 21

Gas drawing point 211 Lid 22

Ash-pit 23

Heating device 24

Discharge opening 25

Duct 26 Reactor 3

Storage tank 31

First inlet 32

Second inlet 34

Core 4 Outer walls 40

First reaction chamber 41

Second reaction chamber 42

First openings 422

First grate 43 Second grate 44

Second openings 45

Cooling structure 5

Hollow space 51

First compartment 52 Second compartment 53

Fluidizing agent introducing plant A

Vertical axis Z

Claims

CLAIMS :

1. A pyro-gasification reactor (3) of the downdraft type, for being applied to pyro-gasification plant (2);

said reactor (3) comprises:

· at least one first inlet (32), through which a predetermined amount of biomass is introduced;

a storage tank (31), into which the biomass to be pyrolyzed and gasified is introduced;

at least one second inlet (34), through which a fluidizing agent is introduced into the reactor (3) by means of a fluidizing agent introducing plant (A) ;

a core (4), in which the pyrolysis and gasification processes take place, which is arranged under said storage tank (31) ;

said core (4) comprises at least one first reaction chamber (41) and at least one first grate (43), for supporting the biomass during the pyro-gasification process;

said reactor is characterized in that:

it comprises a cooling structure (5), for surrounding the core (4), thus enclosing it, creating a hollow space (51);

said cooling structure (5) is fluidly connected to said fluidizing agent introducing plant (A) , so as to allow a fluid to flow through said hollow space (51);

said second inlet (34) for introducing the fluidizing agent is arranged in correspondence to said core (4), thus allowing the fluidizing agent, contained in said hollow space (51), to be at least introduced into said first reaction chamber (41) .

2. Reactor according to claim 1, wherein said core (4) and said cooling structure (5) are entirely made of steel.

3. Reactor according to any of the previous claims, wherein said core (4) comprises at least one second reaction chamber (42), which is arranged under said first reaction chamber (41); said first and second reaction chambers (41, 42) are divided by said first grate (43) and said second reaction chamber (42) is delimited, on the lower side, by a second grate (44) .

4. Reactor according to claim 2, wherein said second reaction chamber (42) comprises a plurality of first openings (422), for allowing the fluidizing agent, contained in said hollow space (51), to be introduced into said second chamber (42) .

5. Reactor according to claim 1 or 2, wherein said second inlet (34) is an opening, which substantially follows the entire external perimeter of said first reaction chamber (41).

6. Reactor according to claim 5, wherein said second inlet (34) is substantially arranged in correspondence to the central portion of said first reaction chamber (41) .

7. Reactor according to claim 1 or 2, wherein said cooling structure (5) comprises a first compartment (52) and a second compartment (53), which are divided by a perforated plate, for allowing the flow of a fluid between the two compartments (52, 53) .

8. Reactor according to claim 7, wherein said first compartment (52) substantially encloses said first chamber (41) of the core (4) and said second compartment (53) substantially encloses said second chamber (42) of the same core (4) .

9. Reactor according to claim 3, wherein said first and second grates (43, 44) have a density of second openings (45) that is substantially equal.

10. A pyro-gasification plant (2) comprising an outer casing (21), a lid (22), an ash-pit (24); said plat (2) is characterized in that it comprises a reactor (3) according to claim 1.