Method for processing organic waste by pyrolysis

Abstract

The invention relates to a process for pyrolyzing organic waste, in which ceramic toroidal elements (T) are used to heat the waste.

Description

[0001] This patent application relates to the field of treatment of organic waste by pyrolysis.

[0002] Organic waste means waste comprising organic matter with a moisture content typically between 15 and 25% by mass.

[0003] This organic waste, which can be in the form of solid, semi-pasty, pasty or liquid bodies, can be of various origins: organic fraction of household waste in the form of solid recovered fuels (SRF), sewage treatment plant sludge, low-humidity agricultural waste, composting rejects, low-humidity organic matter from the food industry (slurry, droppings, grease, slaughterhouse waste, animal meal, etc.), low-humidity organic matter that cannot be recovered from industries: tires, hospital waste, soil contaminated by organic matter, all organic waste whose burial is prohibited by law due to the fact that it contains organic molecules that cannot be incinerated because they are likely to cause atmospheric pollution.

[0004] There are various ways of treating this organic waste: Incineration, suitable for large volumes of organic waste, has a number of well-known disadvantages: long-distance transport, complex treatment of fumes, poor energy efficiency, atmospheric pollution; methanization, consisting of the anaerobic decomposition of organic waste, is mainly suitable for organic waste with a high humidity level, and pyrolysis, which consists of a chemical decomposition of organic waste in an environment practically devoid of oxygen, allows the transformation of organic waste into gas, oil, coal, ash and mineral matter.

[0005] The gas(es) resulting from the pyrolysis reaction can be used in particular to operate thermal engines, or hydrogen fuel cells, depending on the composition of these gases.

[0006] The oils resulting from the pyrolysis reaction can be stored and subsequently used to produce energy, for chemical recovery of the components of this oil, to produce a fuel such as diesel or gasoline, or to power a heat engine.

[0007] The coal produced by the pyrolysis reaction has a high calorific value and can be used advantageously to heat boilers or other industrial equipment.

[0008] The ash and mineral materials resulting from the pyrolysis reaction constitute ultimate waste that can be used as filling material, for example for road embankments, and / or be buried in a specialized center in classes 1 or 2 as defined by current legislation.

[0009] French patent application FR2945817 discloses a process for the pyrolysis of organic waste, using toroidal metal elements preheated to a high temperature and then conveyed inside a reactor in which they are intimately mixed with the organic waste to be pyrolyzed.

[0010] This intimate mixture makes it possible to raise the temperature of the organic waste to be treated very quickly and evenly, in temperature ranges typically between 400°C and 950°C.

[0011] When carrying out pilot installations in accordance with the teaching of FR2945817, a certain number of drawbacks were noted.

[0012] The toroidal elements have a high weight, typically around 8 kg / l, making their conveyance in the installation both complex and energy-intensive.

[0013] Archimedes' screws must be used to carry out this conveyance, which can easily get stuck when certain metallic elements are present in the organic waste: nails, staples, etc.

[0014] We have observed fairly frequent breakdowns, making installations according to FR2945817 not very compatible with the constraints of industrial use.

[0015] Furthermore, these installations are not well suited to situations where a significant quantity of hydrogen is to be recovered as a product of pyrolysis, while there is a growing demand on the market for bio-sourced hydrogen (as opposed to hydrogen from water electrolysis).

[0016] Thus, the present invention aims in particular to remedy these drawbacks.

[0017] This object, as well as other advantages, are achieved by a method, installations and toric elements in accordance with the appended claims.

[0018] Other characteristics and advantages of the invention will emerge from reading the description which follows, with reference to the appended figures: [ Fig. 1 ]: schematically represents a first embodiment of an installation making it possible to implement the method according to the invention; [ Fig. 2 ]: represents two views, respectively from above and in perspective, of a preferred embodiment of a toric element making it possible to implement the method according to the invention; [ Fig. 3 ]: schematically represents a second embodiment of an installation making it possible to implement the method according to the invention; [ Fig. 4 ]: schematically represents a third embodiment of an installation making it possible to implement the method according to the invention; [ Fig. 5 ]: schematically represents a fourth embodiment of an installation making it possible to implement the method according to the invention.

[0019] For clarity, identical or similar elements are identified by identical or similar reference signs throughout the figures.

[0020] We now refer to the figure 1 , on which a first embodiment of an installation is shown for implementing the method according to the invention, and typically for treating 1000 to 20,000 tonnes of organic waste per year.

[0021] This process uses toroidal elements which are heated to a high temperature, in order to allow the heating of organic waste for pyrolysis.

[0022] Contrary to the teaching of FR2945817, these toric elements are made essentially, or entirely, of ceramic, possibly coated with a metal or a metal alloy.

[0023] For example, a ceramic of the alumina or alumina alloy type may be suitable.

[0024] The density of such a ceramic is approximately half that of a refractory steel, and its calorific value (specific heat) is approximately 1.8 times higher than that of a refractory steel.

[0025] Thus, the mass required to provide the energy necessary for the pyrolysis reactions of organic waste will be significantly half that of ceramic toric elements compared to refractory steel toric elements.

[0026] Advantageously, it can be envisaged that these ceramic toroidal elements are covered with a catalytic coating, such as a high nickel alloy.

[0027] In practice, it has been observed that toroidal elements with a diameter of around 10 mm make it possible to optimize the heat transfer to the organic waste to be treated, and therefore the pyrolysis reaction, but depending on the desired pyrolysis reactions and the inputs, the toroids can be much larger, up to around 50 mm.

[0028] The toric T elements can have an elliptical, circular, rectangular, square axial section, or any other section easily produced on an industrial production scale.

[0029] Preferably, and to reduce manufacturing costs, toric elements T with a rectangular axial section will be chosen, so that these toric elements T can have a substantially cylindrical ring shape, that is to say a cylinder hollowed out in its center, as illustrated in the two views of the figure 2 .

[0030] As can be seen on the figure 1 , the toric elements are conveyed vertically from bottom to top using a vibrating elevator 1.

[0031] The travel time of the toroidal elements inside the vibrating elevator 1 is typically between 3 and 5 minutes, and the processing capacity of such a vibrating elevator is typically of the order of 8 tons per hour.

[0032] This vibrating elevator opens in its upper part inside a transfer pipe 3 allowing the toroidal elements to be brought inside a heating furnace 5, essentially in the form of a silo and comprising in its lower part a burner 7 allowing the temperature of the toroidal elements to be raised to a temperature typically between 400 and 950°C.

[0033] The toroidal elements are heated counter-currently inside the heating furnace 5, that is to say that the heating gases produced by the burner 7 circulate from bottom to top inside the heating furnace 5, while the toroidal elements circulate from top to bottom: this configuration makes it possible to heat the toroidal elements to a perfectly controlled temperature, and thus to precisely control the desired pyrolysis reaction.

[0034] When passing close to the flame of burner 7, the toroidal elements undergo high-temperature oxidation to regenerate the catalyst effect of the catalytic coating, if applicable.

[0035] The interior of the heating furnace 5 is free of any mechanical element likely to form roughness, making it possible to avoid any blockage of the toric elements, as well as pressure losses at the periphery.

[0036] This also prevents fouling of internal parts of the heating furnace, which are difficult to access during maintenance operations.

[0037] The burner 7 can be supplied with natural gas, or with syngas, that is to say a mixture of gases capable of releasing heat by combustion.

[0038] An exchanger 9 located in the upper part of the heating furnace 5 makes it possible to recover the heat from the combustion inside the furnace 5, in order to heat the combustion air of the burner to improve combustion, and / or to produce water vapor for different applications such as the cogeneration of electrical energy.

[0039] A vibrating conveyor 11 is connected to the lower part of the heating furnace 5, making it possible to convey at the desired flow rate the toroidal elements heated to a temperature between 400 and 950°C to a pyrolysis reactor 13 which is also substantially in the form of a silo, and the interior part of which is devoid of any mechanical element likely to form roughness.

[0040] A sealing airlock 15 allows the toroidal elements coming from the vibrating conveyor 11 to penetrate into the pyrolysis reactor 13 with practically no circulation of gas between the heating furnace 5 and the reactor 13: this avoids the supply of oxygen and the combustion of part of the syngas produced inside the pyrolysis reactor 13.

[0041] An organic waste inlet pipe 17, opening into the upper part of the pyrolysis reactor 13, makes it possible to bring the waste to be treated inside this reactor 13, so that it mixes intimately with the toroidal elements, so that the pyrolysis reaction can occur.

[0042] Depending on the nature of the organic waste and its viscosity, circulation within the pipe 17 may be carried out purely by fluid circulation, or may require an endless screw or the like.

[0043] The syngas resulting from the pyrolysis of organic waste inside the pyrolysis reactor 13 is discharged through an outlet pipe 19 for the purpose of treating this gaseous mixture, or for its use, such as for example to operate a heat engine and / or to supply the burner of the heating furnace.

[0044] A gasifying agent inlet pipe can also be provided approximately halfway up the reactor: this pipe allows water vapour to be introduced into the reactor, depending on the nature of the organic waste and / or the products that are to be recovered at the end of the pyrolysis reaction.

[0045] Once the toroidal elements have arrived in the lower part of the pyrolysis reactor 13, and have transferred their heat to the organic waste so as to allow the pyrolysis reaction, they are evacuated by a vibrating screen 21 towards the base of the vibrating elevator 1, a second sealing airlock 23 similar to the first airlock 15 making it possible to prevent air from penetrating inside the vibrating elevator 1.

[0046] The coal, ash and mineral matter which separates from the toroidal elements under the effect of the vibration of the vibrating screen 21, are recovered and inside an ash pan 25.

[0047] An Archimedes screw 27, always in charge in order to prevent air from entering the ash pan 25, allows the cooled coal and ash to be evacuated to a mobile container for recovery or landfill.

[0048] As will be understood in light of the above, the installation is designed so as to avoid as much as possible the arrival of air in the various conduits, and inside the heating furnace 5 and the pyrolysis reactor 13, so that the pyrolysis reaction can take place in an optimal manner.

[0049] The various means of conveying the toric elements do not include any moving mechanical elements, and in particular no Archimedean screws: the movement of these toric elements is carried out exclusively by gravity and / or by vibration, this movement being facilitated by the relatively low weight of the ceramic toric elements.

[0050] This avoids all the problems of jamming of moving mechanical elements, observed in an installation compliant with FR2945817.

[0051] In addition, the various vibrating elements (elevator 1, conveyor 11, screen 21) allow the toroidal elements to be freed from soot and other impurities, helping to maintain their capacity to quickly transfer heat to the organic waste to be treated, as well as the action of the catalytic coating in the pyrolysis reaction, if applicable.

[0052] We now refer to the variant embodiment of the figure 3 , suitable when you want to obtain a larger quantity of hydrogen.

[0053] This installation differs from the previous one in that it comprises, in addition to the elements previously described, a gasification / reforming reactor 29 located downstream of the pyrolysis reactor 13, and upstream of the vibrating screen 21.

[0054] The gasification / reforming reactor 29 also takes the form of a silo without any mechanical elements inside which could form roughness.

[0055] A connecting pipe 31 connects the lower part of the pyrolysis reactor 29 to the lower part of the gasification / reforming reactor 13.

[0056] This connecting pipe 31 makes it possible to bring the syngas resulting from the pyrolysis reaction inside the pyrolysis reactor 13, towards the inside of the gasification / reforming reactor 29.

[0057] This pipe 31 is coated with heating means, for example electrical, to avoid the risk of condensation of the syngas circulating inside.

[0058] Sealed airlocks 33, 35 are arranged respectively at the lower outlet of the pyrolysis reactor 13, and at the upper inlet of the gasification / reforming reactor 29.

[0059] A heating conveyor 37 heated by coal and / or syngas from the pyrolysis reaction inside the pyrolysis reactor 29, is interposed between the sealed airlocks 33 and 35.

[0060] This 37 heated conveyor allows: to raise by several hundred degrees the temperature of the toroidal elements T which leave the pyrolysis reactor 13, prior to their entry into the gasification / reforming reactor 29, and to raise to a very high temperature - typically in a range between 900 and 950°C - water vapor which is introduced substantially halfway up the gasification / reforming reactor via a water vapor inlet pipe 39.

[0061] A gas outlet pipe 19 is also arranged approximately halfway up this reactor 29.

[0062] In this variant of the installation according to the invention, the toroidal elements T are brought by the burner 7 to a temperature typically between 500 and 700°C, so as to carry out the pyrolysis of the organic waste inside the pyrolysis reactor 13.

[0063] The syngas produced by this pyrolysis reaction, including in particular carbon monoxide, carbon dioxide and carbon, are sent via the connecting pipe 31 inside the gasification / reforming reactor 29.

[0064] The water vapor, introduced at very high temperature (900 - 950°C) inside the gasification / reforming reactor via line 39, makes it possible to carry out the following reforming reactions on the syngas coming from the connecting line 31, leading in particular to the production of hydrogen: CO + CO 2 -> 2CO C + H 2 O -> CO + H 2 CO + H 2 O -> CO 2 + H 2

[0065] The gas mixture resulting from these reforming reactions is discharged via the gas outlet pipe 19, for treatment and / or recovery, and in particular for the separation of hydrogen from other gases, by a membrane process or the like.

[0066] Typically, an installation that complies with the figure 3 allows 275 Nm 3< of hydrogen to be obtained for a flow rate of 500 kg / h of dry biomass, i.e. an efficiency of around 46% compared to the internal calorific value of the biomass.

[0067] We now refer to the variant embodiment of the figure 4 , suitable when we want to promote the production of incondensable syngas and achieve maximum conversion of coal (coke).

[0068] This installation is different from that of the figure 1 in that it comprises, in addition to the elements previously described, a gasification / reforming reactor 29 located downstream of the heating furnace 5 of the toroidal elements T and upstream of a pyrolysis reactor 13.

[0069] A vibrating conveyor 40 is used to convey the toroidal elements T from the heating furnace 5 to a sealing airlock 15, then inside the gasification / reforming reactor 29.

[0070] An air inlet pipe 41 makes it possible to bring air in metered volume into the gasification / reforming reactor 29.

[0071] A syngas outlet pipe 19 allows the syngas - essentially carbon monoxide and oxygen - from the gasification / reforming reaction inside the reactor 29 to be recovered, for treatment or recovery.

[0072] This reaction takes place at a temperature between 900 and 950°C, and the toroidal elements T exit through the lower part of the gasification / reforming reactor 29 at a temperature of around 600°C.

[0073] They then enter the interior of the pyrolysis reactor 13 via a vibrating conveyor and a sealed airlock 43, to carry out the pyrolysis at approximately 500°C of mineral material introduced via a mineral material inlet pipe.

[0074] The syngas generated by this pyrolysis reaction is returned via a connecting pipe 45 from the pyrolysis reactor 13 to the gasification / reforming reactor 29.

[0075] The coal, ash and mineral matter are separated from the toroidal elements at the outlet of the pyrolysis reactor 13 by a vibrating screen 21.

[0076] The toroidal elements then join the vibrating elevator 1, and the coal, ash and mineral matter recovered inside an ash pan 25 are returned to the interior of the gasification / reforming reactor by an Archimedes screw 47.

[0077] We now refer to the variant embodiment of the figure 5 , suitable when the pyrolysis of plastic materials is required, the aim being to produce oil that can be used as fuel or for other applications.

[0078] In this particular case, pyrolysis must be carried out at low temperature, typically below 500°C, in a very precise and constant manner.

[0079] To achieve this result, the toroidal elements T must lose approximately 100°C between their entry and their exit from the pyrolysis reactor, i.e. go from a temperature of approximately 500°C to a temperature of approximately 400°C.

[0080] In order to maintain a significant processing capacity, corresponding to the 8 tonnes per hour of toroidal elements T that the vibrating elevator 1 is capable of conveying, three pyrolysis reactors 13a, 13b, 13c are placed in series one behind the other, a heating conveyor 37a, 37b, 37c making it possible to convey the toroidal elements T inside each pyrolysis reactor while raising their temperature by approximately 100°C, so that they arrive heated to approximately 500°C inside each reactor.

[0081] In this embodiment of the invention, it is not necessary to provide airlocks, because as there is no combustion, there is no risk of syngas combustion.

[0082] The syngas condensable into oil is recovered from each pyrolysis reactor 13a, 13b, 13c by respective outlet pipes 49a, 49b, 49c which convey it to a condenser 51 to be transformed into oil.

[0083] The coals are recovered as in the previous embodiments by means of a vibrating screen 21 and an ash pan 25.

[0084] The various components of the installations described above (vibrating elevators, vibrating screens, vibrating conveyors, airlocks, etc.) are marketed, for example, by the company SINEX located in SAINT YRIEIX SUR CHARENTE (16710).

[0085] Naturally, the invention is described in the foregoing by way of example. It is understood that those skilled in the art are able to carry out different variant embodiments of the invention without departing from the scope of the invention.

Claims

1. Method for pyrolysing organic waste, wherein ceramic toric elements (T) are used to heat the waste, by intimately mixing these toric elements (T) with the organic waste, and said toric elements (T) are conveyed exclusively by gravity and / or vibration.

2. Method according to claim 1, wherein said toric elements (T) are heated up to a temperature between 400°C and 950°C and then mixed with organic waste in a pyrolysis reactor (13), and the syngas coming out of this reactor is recovered.

3. Method according to claim 2, wherein the syngas and the toric elements (T) derived from the pyrolysis reactor (13), as well as steam at very high temperature, are sent into a gasification / reforming reactor (29), and the resulting gas mixture is recovered.

4. Method according to claim 1, wherein said toric elements (T) are heated to a temperature between 900°C and 950°C and then mixed with air in a gasification / reforming reactor (29), the syngas exiting this reactor (29) is recovered, the toric elements (T) originating from this reactor (29) are sent into a pyrolysis reactor (13) where they are mixed at a temperature of the order of 500°C with mineral material, and the resulting gaseous mixture is returned to said gasification / reforming reactor (29).

5. Method according to claim 1, wherein said toric elements (T) are heated up to a temperature of about 500°C, and mixed with plastics in a plurality of pyrolysis reactors (13a, 13b, 13c) arranged in series, by raising the temperature of the toric elements (T) by about 100°C at the outlet of each pyrolysis reactor (13a, 13b, 13c), and the condensable syngas derived from each pyrolysis reactor (13a, 13b, 13c) is recovered and directed towards a condenser (51) for conversion thereof into oil.

6. Method according to any one of the preceding claims, wherein the carbons, ashes and mineral matter are separated from the toric elements (T) upon completion of the pyrolysis and / or gasification / reforming reactions.

7. Method according to claim 2, wherein a facility is used comprising in this order a vibrating elevator (1), a heating furnace (5), a vibrating conveyor (11), a first sealing airlock (15), a pyrolysis reactor (13), a vibrating screen (21), an ashpit (25) for recovering the carbons, ashes and mineral matter, and a second sealing airlock (23).

8. Method according to claim 2, wherein a facility is used comprising in this order a vibrating elevator (1), a heating furnace (5), a first sealing airlock (15), a pyrolysis reactor (13), a second sealing airlock (33), a heating conveyor (37), a third sealing airlock (35), a gasification / reforming reactor (29), a vibrating screen (21), an ashpit (25) for recovering the carbons, ashes and mineral matter, and a fourth sealing airlock (23).

9. Method according to claim 4, wherein a facility is used comprising in this order a vibrating elevator (1), a heating furnace (5), a vibrating conveyor (40), a first sealing airlock (15), a gasification / reforming reactor (29), a second sealing airlock (43), a pyrolysis reactor (13), a vibrating screen (21), an ashpit (25) for recovering the carbons, ashes and mineral matter, and a third sealing airlock (23).

10. Method according to claim 5, wherein a facility is used comprising in this order a vibrating elevator (1), a first heating conveyor (37a), a first pyrolysis reactor (13a), a second heating conveyor (37b), a second pyrolysis reactor (13b), a third heating conveyor (37c), a third pyrolysis reactor (13c), a vibrating screen (21), and an ashpit (25) for recovering the carbons, ashes and mineral matter.

11. Method according to any one of the preceding claims, wherein toric elements (T) formed essentially, or entirely, from ceramic are used, and the ceramic is alumina or an alumina alloy.

12. Method according to any one of the preceding claims, wherein toric elements (T) formed essentially, or entirely, from ceramic are used and wherein the ceramic is covered with a metallic and / or catalytic coating such as a high nickel content alloy, or other catalytic coating required by the pyrolysis reaction depending on the input.

13. Method according to any one of the preceding claims, wherein toric elements (T) having a substantially cylindrical ring shape are used.

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