FR3146691A1 - Device for pyrolysis of rubber granules - Google Patents

Abstract

Device for pyrolyzing rubber granules. The pyrolysis device (10) comprises a pyrolysis module (12) through which the rubber granules are intended to pass. The pyrolysis module (12) comprises: - at least one thermally conductive tubular element (20) extending vertically between an upper inlet (20a) for the rubber granules and a lower outlet (20b), - a heating enclosure in which each tubular element (20) extends, the heating enclosure comprising a plurality of gas circulation channels (24a, 24b, 24c), arranged parallel to each other and perpendicular to the tubular element (20). Figure for abstract: Figure 1

Description

Rubber Granules Pyrolysis Device

The present invention relates to a device for pyrolyzing rubber granules.

Such aggregates are produced in particular by crushing used tires.

The rubber industry generates significant amounts of production and use waste. The final shape and operating parameters of the products are obtained during the irreversible vulcanization process. For this reason, the recycling of rubber objects requires costly operations, requiring a lot of time and labor.

Generally, recycled materials have inferior physical and mechanical properties and are not competitive with original rubber raw materials. For this reason, rubber waste is a serious problem both economically and ecologically.

The scale of this problem can be estimated based on the production of the rubber industry, which is about 35 million tons per year. More than 150 years ago, attempts were made to recycle rubber waste. Today, after many years, the development of adequate technologies for its disposal remains an important problem in the rubber industry. From the point of view of environmental protection, recycling of tires is an important issue because they account for 60-70% of the rubber industry's production.

Used tires can be burned (e.g. in cement plants, pulp and paper mills, industrial boilers). They can also be mechanically crushed to obtain rubber, textile and scrap metal residues. Among them, rubber residues, depending on their particle size, will be called crumb or aggregates, with crumb having an average diameter of less than 2 mm, and aggregate having an average diameter of 2 to 10 mm. Rubber aggregates can be used in particular in sports surfaces, sound insulation, etc. Crumbs can be used in road surfaces, insulating concrete, etc. Rubber granulate has the advantage of having a high rubber content (depending on the specifications, for example 98%). It is very advantageous to use rubber granulate, as its selling price is low and it also has very few outlets on the market.

Tyre pyrolysis is one of the methods developed to treat used tyres. The pyrolysis products are on the one hand high temperature gases (above 600°C), which are generally burned to recover the available energy, and on the other hand a solid residue with a high carbon content, which is either landfilled or used as coal.

The term "pyrolysis" is used in its most classic meaning, namely the chemical decomposition of rubber granules by the action of heat in an oxygen-deficient atmosphere. In practice, the introduction of oxygen, air, or any gas containing oxygen is minimized during pyrolysis. However, pyrolysis is not necessarily carried out in an inert atmosphere (under nitrogen, argon for example). It is simply sufficient to limit or prevent the supply of air during pyrolysis, to limit the supply of oxygen.

The term “rubber granulate” generally refers to rubber fragments having a size of 2 mm to 10 mm, in particular 3 mm to 9 mm, preferably 4 mm to 8 mm and a rubber purity generally greater than 95%, preferably greater than 98%. In particular, the rubber granulate used in the invention is free of iron particles. In general, the rubber granulate comes from the grinding of tires, rubber conveyor belts or rubber parts.

Different pyrolysis processes have been described in the state of the art.

The invention aims in particular to propose a more efficient pyrolysis device.

For this purpose, the invention relates in particular to a device for pyrolyzing rubber granules, comprising a pyrolysis module through which the rubber granules are intended to pass, characterized in that the pyrolysis module comprises:

- at least one thermally conductive tubular element extending vertically between an upper inlet for the rubber granules and a lower outlet,

- a heating enclosure in which each tubular element extends, the heating enclosure comprising a plurality of gas circulation channels, arranged parallel to each other and perpendicular to the tubular element.

A pyrolysis device according to the invention may further comprise one or more of the following characteristics, taken alone or in any technically conceivable combination.

- The air circulation channels are connected in series, via deflectors, from a general gas inlet to a general gas outlet.

- The plurality of air circulation channels comprises an upper channel located above all other channels, a lower channel located below all other channels, and at least one intermediate channel located vertically between the upper channel and the lower channel, such that: the inlet of the upper channel forms said general hot air inlet, and it is connected to a hot gas blowing device, and the outlet of the upper channel is connected to the inlet of the intermediate channel just below, the inlet of the lower channel is connected to the outlet of the intermediate channel just above, and the outlet of the lower channel forms the general air outlet, and each intermediate channel has its inlet connected to the outlet of the channel, upper or intermediate, just above, and its outlet connected to the inlet of the channel, intermediate or lower, just below.

- The pyrolysis device comprises a plurality of tubular elements, arranged parallel to each other, each tubular element passing through each gas circulation channel.

- Each gas flow channel includes gas flow centering baffles between each pair of adjacent tubular elements.

- Each tubular element comprises at least one heat diffusion grid, comprising at least one ring held by spokes, each ring and spoke being thermally conductive.

- The pyrolysis device comprises a supply module of the pyrolysis module, comprising a hopper for introducing aggregates, at least partially filled with water, and comprising at its base a vertical tube opening onto a first screw conveyor, the first screw conveyor comprising a first helical endless screw and an enclosure at least partially filled with water, into which the vertical tube opens, and into which the first endless screw partly extends, the first screw conveyor opening onto a second conveyor comprising a second endless screw opening into feed members of each tubular element.

- Each feeder is equipped with a valve comprising a sealed shutter, movable between an open position allowing the insertion of aggregates and a closed position, the operation of the second worm screw being controlled by the position of the shutter, so that the second worm screw is actuated when the shutter is in the open position, and stopped when the shutter is in the closed position.

- The pyrolysis device comprises a collection hopper arranged at the outlet of each tubular element, and opening onto a cooling device.

Various aspects and advantages of the invention will be highlighted in the description which follows, given solely as a non-limiting example and made with reference to the appended figures, among which:

There is a perspective view of a pyrolysis device according to an exemplary embodiment of the invention.

There is a profile and transparency view of a pyrolysis module equipping the pyrolysis device of the .

There is a schematic longitudinal sectional view of a gas circulation channel of the pyrolysis module of the .

There is a cross-sectional view of a tubular element of the pyrolysis module of the .

There is a perspective view of a cooling device of the pyrolysis device of the , cut in the height direction.

It was represented, on the , a device 10 for pyrolyzing rubber granules.

The pyrolysis device 10 comprises a pyrolysis module 12, a module 14 for supplying the pyrolysis module with aggregates, a cooling module 16, and a hopper 18 connecting the pyrolysis module 12 to the cooling module 16.

The pyrolysis module 12, shown more particularly on the , comprises at least one thermally conductive tubular element 20 extending vertically between an upper inlet 20a for the rubber granules and a lower outlet 20b. Preferably, the pyrolysis module 12 comprises a plurality of tubular elements 22, for example at least five tubular elements 22

The tubular elements 20 are arranged parallel to each other, for example vertically to allow the aggregates to fall inside the tubular elements 20.

The pyrolysis module 12 also comprises a heating enclosure 22 in which each tubular element 20 extends.

The heating enclosure 22 comprising a plurality of gas circulation channels 24, arranged parallel to each other and perpendicular to the tubular elements 20. Advantageously, the gas is hot air.

Each gas circulation channel 24 comprises a gas inlet 26a and a gas outlet 26b, each arranged at a respective end of the corresponding circulation channel 24.

In the example described, the heating enclosure 22 comprises six circulation channels 24.

Advantageously, the circulation channels 24 are connected in series, via deflectors 28, from a general gas inlet 30 to a general gas outlet 32. The deflectors 28 are therefore shaped to rotate the gas flow 180°, in order to guide the gas flow coming from a circulation channel 24 to the circulation channel 24 immediately below.

The general gas inlet 30 is connected to a gas blowing device 34, shown schematically in the .

The general gas outlet 32 is connected to a gas recovery device 36, shown schematically in the .

The blowing device 34 is also capable of heating the gas to a temperature sufficient for the pyrolysis of the aggregates, for example between 600 and 800°C. The hot gas then winds from channel to channel, from top to bottom, before being extracted by the recovery device 36, generally at a temperature between 450 and 550°C.

Advantageously, the recovery device 36 is connected to the blowing device 34, in order to supply it with gas. Thus, the gas recovered at the outlet is sent to a reheating generator assembly supplied by the combustion gases of a burner operating preferentially with pyrolysis gas. The reheated gases are returned to the head of the module.

The plurality of airflow channels include an upper channel 24a located above all other airflow channels 24, a lower channel 24b located below all other airflow channels 24, and at least one intermediate channel 24c located vertically between the upper channel 24a and the lower channel 24b.

The inlet of the upper channel 24a corresponds to said general gas inlet 30, and it is, and the outlet of the upper channel 24a is connected to the inlet of the intermediate channel 24c just below, via one of the deflectors 28.

The inlet of the lower channel 24b is connected to the outlet of the intermediate channel 24c just above via one of the deflectors 28, and the outlet of the lower channel 24c corresponds to the general air outlet 32.

Each intermediate channel 24c has its input connected to the output of the channel, upper 24a or intermediate 24c, just above, and its output connected to the input of the channel, intermediate 34c or lower 24b, just below.

Each tubular element 20 passes through each circulation channel 24. Thus, each tubular element 20 passes through the hot gas as many times as there are circulation channels.

When rubber granules pass through one of the tubular elements 20, they are subjected to a high temperature provided by the gas flow, and thus undergo a pyrolytic transformation into, on the one hand, carbonisate (carbon black), and on the other hand a mixture of pyrolysis vapors.

As shown in the , each circulation channel 24 comprises deflectors 38 for centering the air flow between each pair of adjacent tubular elements 20. These centering deflectors 38 are intended to recenter the gas flow after it has bypassed a tubular element 20, in order to direct this gas flow onto the following tubular element 20. This ensures that each tubular element 20 is optimally located on the path of the gas flow.

Advantageously, each tubular element 20 comprises a stack of heat diffusion grids 39, as shown in the . Each grid 39 comprises at least one ring held by spokes, and more particularly, a central ring 39a, an intermediate ring 39b, central spokes 39c connecting the rings 39a, 39b together, and external spokes 39d connecting the intermediate ring 39b to a wall 41 of the tubular element 20. All the spokes 39c, 39d extend radially relative to a central axis of the tubular element 20.

Rings 39a, 39b and spokes 39c, 39d are thermally conductive to facilitate the diffusion of heat from the outside to the center.

For example, a tubular element 20 having a height of between 3500 and 4500 mm preferably comprises between 15 and 25 diffusion grids 39.

Reservations are provided in each grid 39 so as to allow the passage of a level probe 43 indicating the level of aggregates in the tubular element 20, as well as multipoint probes 45 for continuous measurement of the temperature over the entire height of the tubular element 20, for example between 3 and 5 multipoint probes 45. These multipoint probes measure the temperature of the reaction bed between each diffusion grid 39.

Each tubular element 20 is furthermore connected to means for extracting the pyrolysis gas. In particular, each tubular element comprises a tube 20c for extracting the pyrolysis gases.

The pyrolysis gases released by the decomposition of the aggregates rise to the top of the tubular element from where they exit through the inclined pipe 20c. Each extraction pipe 20c is connected to a general collector 55 which sends the gases from all the tubular elements 20 to two condensers in series.

It should be noted that, since the pyrolysis gases rise, there is necessarily less pyrolysis gas in the lower part of each tubular element 20. Heat convection therefore benefits less from the presence of hot pyrolysis gas in this lower part.

Advantageously, each tubular element 20 comprises, in this lower part, injectors 57 of liquid, in particular water. The liquid water, by evaporating, will increase the flow rate of the pyrolysis gases in the lower part of the tubular element. The volume flow rate of the gases (pyrolysis gas + water vapor) in each tubular element 20 thus remains approximately constant over the entire height of the tubular element.

Each tubular element 20 is equipped at the outlet with a gas-tight shutter 56. The function of each shutter 56 is to allow the mechanical extraction of the carbonized material, while preventing the continuous infiltration of pyrolysis gases from the tubular element 20 towards the collection hopper 18.

The shutter 56 comprises a rotary alveolar extractor for the carbonisate and a gas-tight bell valve flap. The operation of the shutter 56 is sequential. The bell valve is first opened before extracting carbonisate using the alveolar extractor and, at the end of the filling cycle, the closing is carried out in the reverse direction so as to never accumulate carbonisate in the bell valve.

It should be noted that the rubber granules are introduced into the pyrolysis module 12 by means of the feed module 14.

The feed module 14 comprises a hopper 40 for introducing aggregates, into which the aggregates are poured, for example continuously by means of a circuit scale.

The introduction hopper 40 is at least partially filled with water, and comprises at its base a vertical tube 42 opening onto a first screw conveyor 44. The first screw conveyor 44 comprises a first helical endless screw 46, for example inclined at an angle of between 45 and 55° relative to the vertical tube 42.

The first screw conveyor 44 also comprises an enclosure 48 filled with water, into which the vertical tube 42 opens, and into which the first endless screw 46 partly extends.

The foot of the first worm screw 46 is thus submerged in water, which has the effect of forming a hydraulic seal with a siphon effect, intended to prevent pyrolysis gases coming from the pyrolysis module 12 from escaping through this inlet.

The water level in the auger 46 will always be higher than the level of the siphon to avoid breaking the hydraulic seal. The water level will preferably be more than 500 mm above the siphon in the auger and the level in the hopper will be 300 to 800 mm higher than the level in the inclined auger.

The aggregates flow from the hopper 40 to the auger 46 through the enclosure 48. A safety system controls the water level which is adjusted by adding water via a solenoid valve TOR.

It should be noted that, in some cases, the aggregates may be greasy, which makes them hydrophobic and may cause them to float, which would prevent them from being evacuated by the first auger. In order to overcome this drawback, a surfactant is advantageously added to the water in the hopper 40 in order to modify the surface tension of the aggregates and allow them to sink in the water.

The wet aggregate is transported to at least one second conveyor comprising a second auger 50. Alternatively, the pyrolysis device 10 could comprise several second conveyors, in the case where it comprises several pyrolysis modules.

Advantageously, the operation of the second worm screw 50 is controlled by that of the first worm screw 46, so that they are actuated together and stopped together.

The feed module 14 also comprises, for each tubular element 20, a feed member 52, extending between the second endless screw 50 and the corresponding tubular element 20.

Each feed member 52 comprises an inlet fed by the second worm screw 50 and an outlet feeding one of the tubular elements 20 arranged below this feed member 52, opposite it.

The inlet of the feed member 52 is equipped with a valve 54, for example of the “bell valve” type, that is to say whose shutter is bell-shaped.

Valve 54 has a sealed shutter, movable between an open position allowing the insertion of aggregates and a closed position.

The operation of the second worm screw 50 is controlled by the position of the shutter, such that the second worm screw 50 is actuated when the shutter is in the open position, and stopped when the shutter is in the closed position.

Thus, when the valve 54 is open, the first 46 and second 50 augers are actuated to convey aggregates in order to introduce them into the corresponding tubular element 20 until it is filled to a predefined level. When the predefined level is reached, the augers stop, the time to evacuate the aggregate into the valve 54 which can then be closed.

The valves 54 are thus activated one after the other in a sequential manner, to fill the tubular elements 20 one after the other. It will be noted that the second worm screw 50 therefore only feeds one feed member 52 at a time.

The aggregates are thus stacked in the tubular elements 20, where they undergo pyrolysis.

The carbonized material produced by pyrolysis is extracted from each tubular element 20 by the shutter 56, and flows into the collection hopper 18, which directs the carbonized material towards the cooling device 16.

This harvesting hopper 18 is completely sealed thanks to the shutters 56 of each tubular element, as well as an outlet shutter 58 supplying the cooling device 16.

The hot carbonisate (generally between 450 and 550 °C) is extracted by the shutter 56 of each tubular pyrolysis element 20 to be stored in small quantities in the hot carbonisate collection hopper 18. At the outlet of the collection hopper 16, the outlet shutter 58, preferably of the same type as the shutters 56, allows the controlled flow rate introduction into the cooling device 16.

The cooling device 16, shown in more detail in the , has an upper inlet opening 16a into which the outlet shutter 58 of the harvesting hopper 18 opens, and a lower outlet opening 16b.

The cooling device 16 also comprises tubes 60, preferably horizontal, in which a refrigerant fluid, for example cold water, circulates. The tubes 60 are for example arranged in columns, the tubes 60 of each column being connected together in series, so that the refrigerant fluid circulates in the tubes by winding in a boustrophedon from the top to the bottom. The refrigerant fluid is collected at the bottom to be conveyed to a cooling device, to then reinject the cooled refrigerant fluid at the top of the column.

The carbonized material flows in a moving bed on the tubes 60, vertically from top to bottom, to be taken up at the outlet of the cooler by a vibrating extractor corridor 62 which allows the product to be retained in the cooling device 16.

The vibrating extractor corridor 62 is set in motion to control the level in the collection hopper 18 and extract cold carbonisate towards a buffer hopper 64 located above a device for placing in barrels or, preferably, in containers. The cooling device 16 is kept full during the continuous operation of the pyrolysis device 10.

Claims (9)

Device (10) for pyrolyzing rubber granules, comprising a pyrolysis module (12) through which the rubber granules are intended to pass, characterized in that the pyrolysis module (12) comprises:
- at least one thermally conductive tubular element (20) extending vertically between an upper inlet (20a) for the rubber granules and a lower outlet (20b),
- a heating enclosure in which each tubular element (20) extends, the heating enclosure comprising a plurality of gas circulation channels (24a, 24b, 24c), arranged parallel to each other and perpendicular to the tubular element (20). Pyrolysis device (10) according to claim 1, wherein the gas circulation channels (24a, 24b, 24c) are connected in series, via deflectors (28), from a general gas inlet (30) to a general gas outlet (32). A pyrolysis device (10) according to claim 2, wherein the plurality of gas circulation channels comprises an upper channel (24a) located above all other channels, a lower channel (24b) located below all other channels, and at least one intermediate channel (24c) located vertically between the upper channel (24a) and the lower channel (24b), such that:
- the inlet of the upper channel (24a) forms said general gas inlet (30), and it is connected to a hot gas blowing device (34), and the outlet of the upper channel (24a) is connected to the inlet of the intermediate channel (24c) just below,
- the inlet of the lower channel (24b) is connected to the outlet of the intermediate channel (24c) just above, and the outlet of the lower channel (24b) forms the general gas outlet (32),
- each intermediate channel (24c) has its input connected to the output of the channel, upper or intermediate, just above, and its output connected to the input of the channel, intermediate or lower, just below. Pyrolysis device (10) according to any one of the preceding claims, comprising a plurality of tubular elements (20), arranged parallel to each other, each tubular element (20) passing through each gas circulation channel (24a, 24b, 24c). Pyrolysis device (10) according to claim 4, in which each gas circulation channel (24a, 24b, 24c) comprises deflectors (38) for centering the gas flow between each pair of adjacent tubular elements (20). Pyrolysis device (10) according to any one of the preceding claims, in which each tubular element (20) comprises at least one heat diffusion grid (39), comprising at least one ring held by spokes, each ring and spoke being thermally conductive. Pyrolysis device (10) according to any one of the preceding claims, comprising a module (14) for feeding the pyrolysis module (12), comprising a hopper (40) for introducing aggregates, at least partially filled with water, and comprising at its base a vertical tube (42) opening onto a first screw conveyor (44), the first screw conveyor (44) comprising a first helical endless screw (46) and an enclosure (48) at least partially filled with water, into which the vertical tube (42) opens, and into which the first endless screw (46) partly extends, the first screw conveyor (44) opening onto a second conveyor comprising a second endless screw (50) opening into feed members (52) of each tubular element (20). Pyrolysis device (10) according to claim 7, in which each feed member (52) is equipped with a valve (54) comprising a sealed shutter, movable between an open position allowing the insertion of aggregates and a closed position, the operation of the second worm screw (50) being controlled by the position of the shutter, so that the second worm screw (50) is actuated when the shutter is in the open position, and stopped when the shutter is in the closed position. Pyrolysis device (10) according to any one of the preceding claims, comprising a collection hopper (18), arranged at the outlet of each tubular element (20), and opening onto a cooling device (16).