System comprising a rotatable hollow chamber and a heating system and method of heating a rotatable hollow chamber

Abstract

According to an example aspect of the present invention, there is provided a system (1) comprising a rotatable hollow chamber (2) having a front end (3) and a back end (4), a feeding system (5) configured to feed material into the hollow chamber (2) via at least one feed outlet (7), a gas outlet (8) for collecting a product comprising a gas (9) from at least partially pyrolyzed material, wherein the system (1) is configured to allow flowing of the gas (9) from at least partially pyrolyzed material within the rotatable hollow chamber (2) substantially in a direction from the front end (3) to the back end (4), and a heating system (10) comprising a muffle (6) enclosing at least a part of the rotatable hollow chamber (2) thereby providing a cavity (23) between at least a part of an outer surface (14) of the rotatable hollow chamber (2) and a wall (20) of the muffle (6), wherein a heating gas inlet (11) for guiding a heating gas (15) into the cavity (13) is located in the proximity of the back end (4) of the rotatable hollow chamber (2) and a heating gas outlet (12) for guiding the heating gas (15) out of the cavity (13) is located in the proximity of the front end (3) of the rotatable hollow chamber (2), wherein the heating system (10) further comprises at least one first cooling gas inlet (16) between the heating gas inlet (11) and the heating gas outlet (12) for guiding a cooling gas (17) into the cavity (13) in order to mix the cooling gas (17) with the heating gas (15) present in the cavity (13), and wherein the heating gas inlet (11) comprises a vent (19) capable of adjusting, limiting or blocking a heating gas flow into the cavity (13).

Description

SYSTEM COMPRISING A ROTATABLE HOLLOW CHAMBER AND AHEATING SYSTEM AND METHOD OF HEATING A ROTATABLE HOLLOWCHAMBERFIELD

[0001] The present invention relates to a system comprising a rotatable hollow chamber and a heating system. Particularly, the present invention relates to rotary kiln reactors.

[0002] Further, the present invention relates to a method of heating a rotatable hollow chamber.BACKGROUND

[0003] Rotary kiln reactors are known for a variety of applications, for example for treating polymer waste material. Polymers are used in a wide variety of products. The polymers are typically acquired through petroleum resources, which are considered nonrenewable. In this connection, the need for a sustainable supply of raw material has arisen. In addition, accumulation of polymer waste has been recognized as an environmental problem. As a consequence, polymer waste is often collected and sorted for recycling or thermal decomposition purposes. Environmental problems can be reduced by subsequent polymer waste material treatment and re-use of at least a part of the material as a raw material for new products.

[0004] For example, polymer waste material can be treated by pyrolysis, i.e. by thermal decomposition of the polymer waste material at elevated temperatures in an inert atmosphere, in order to obtain a product comprising a gas from at least partially pyrolyzed polymer waste. Such treatment may, for example, take place in a reactor, such as a rotary kiln reactor, into which the polymer waste is fed.

[0005] In existing rotary kiln reactors, a heating system comprising a muffle is typically provided. High temperature flue gas is introduced into the muffle at multiplelocations along a length of the muffle, thus heating distinctive reactor zones individually to a specific temperature by a crossflow for thermal decomposition of the material fed into the reactor. In other words, a plurality of cross-flow heating zones is provided, wherein each cross-flow heating zone has at least one dedicated heating gas inlet and at least one dedicated heating gas outlet.

[0006] In view of the foregoing, it would be beneficial to provide a system capable of obtaining a product comprising a gas from at least partially pyrolyzed material and comprising a heating system, by means of which no distinctive reactor zones are heated individually to a specific temperature.SUMMARY OF THE INVENTION

[0007] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0008] According to a first aspect of the present invention, there is provided a system comprising a rotatable hollow chamber having a front end and a back end, a feeding system configured to feed material into the hollow chamber via at least one feed outlet, a gas outlet for collecting a product comprising a gas from at least partially pyrolyzed material, wherein the system is configured to allow flowing of the gas from at least partially pyrolyzed material within the rotatable hollow chamber substantially in a direction from the front end to the back end, a heating system comprising a muffle enclosing at least a part of the rotatable hollow chamber thereby providing a cavity between at least a part of an outer surface of the rotatable hollow chamber and a wall of the muffle, wherein a heating gas inlet for guiding a heating gas into the cavity is located in the proximity of the back end of the rotatable hollow chamber and a heating gas outlet for guiding the heating gas out of the cavity is located in the proximity of the front end of the rotatable hollow chamber, wherein the heating system further comprises at least one first cooling gas inlet between the heating gas inlet and the heating gas outlet for guiding a cooling gas into the cavity in order to mix the cooling gas with the heating gas present in the cavity, and wherein the heating gas inlet comprises a vent capable of adjusting, limiting or blocking a heating gas flow into the cavity.

[0009] Various embodiments of the first aspect may comprise at least one feature from the following bulleted list:• the heating system is capable of heating the outer surface of the rotatable hollow chamber by heating gas present in the cavity• the system is configured to guide a heating gas flow of the heating gas via the cavity outside of the rotatable hollow chamber substantially in opposite direction to a gas flow of the gas from at least partially pyrolyzed material within the rotatable hollow chamber• the heating gas is different than the gas from at least partially pyrolyzed material• the muffle comprises at least one protrusion protruding from the wall of the muffle into the cavity and / or protruding from the outer surface of the rotatable hollow chamber into the cavity• the at least one protrusion is arranged downstream of the heating gas inlet and downstream of the at least one first cooling gas inlet• the muffle is made of steel or a refractory material or a combination of both• the heating system comprises a second cooling gas inlet connected to the heating gas inlet

[0010] According to a second aspect of the present invention, there is provided a method of heating a rotatable hollow chamber, the method comprising providing a rotatable hollow chamber having a front end and a back end, feeding material into the hollow chamber via at least one feed outlet of a feeding system, collecting, by a gas outlet, a product comprising a gas from at least partially pyrolyzed material, wherein flowing of the gas from at least partially pyrolyzed material within the rotatable hollow chamber is allowed in a direction from the front end to the back end, providing a muffle enclosing at least a part of the rotatable hollow chamber thereby providing a cavity between at least a part of an outer surface of the rotatable hollow chamber and a wall of the muffle, guiding a heating gas via a heating gas inlet into the cavity, wherein the heating gas inlet is located in the proximity of the back end of the rotatable hollow chamber, and guiding the heating gas via a heating gas outlet out of the cavity, wherein the heating gas outlet is located in the proximity of the front end of the rotatable hollow chamber, guiding a cooling gas via at least one first cooling gas inlet into the cavity and mixing the cooling gas with the heating gas, wherein the at least one cooling gas inlet is arranged between the heating gas inlet andthe heating gas outlet, and adjusting, blocking or limiting a heating gas flow into the cavity utilizing a vent.

[0011] Various embodiments of the second aspect may comprise at least one feature from the following bulleted list:• the method comprising heating the outer surface of the rotatable hollow chamber by heating gas present in the cavity• the method comprising guiding a heating gas flow of the heating gas outside of the rotatable hollow chamber substantially in opposite direction to a gas flow of the gas from at least partially pyrolyzed material• the method comprising increasing turbulence in the heating gas flow utilizing at least one protrusion protruding from the wall of the muffle and / or protruding from the outer surface into the cavity• the method comprising mixing of the cooling gas and the heating gas within the cavity• the cooling gas is air, recycled heating gas or recycled flue gas having a lower temperature than the heating gas, CO2, nitrogen or steam

[0012] Considerable advantages are obtained by certain embodiments of the invention. In particular, a system capable of obtaining a product comprising a gas from at least partially pyrolyzed material and comprising a heating system, by means of which no distinctive reactor zones are heated individually to a specific temperature, is provided. In other words, no cross-flow heat transfer in the heating system results from countercurrent flow of the heating gas within the cavity. The heating gas is introduced into the cavity of the muffle in the proximity of the back end of the rotatable hollow chamber, and consequently the highest temperature difference from heating gas to kiln internal process flow is in the back end of the reactor. Additionally, the energy efficiency of the system can be improved due to increased heating gas total flowrate, which results in increased turbulence and heat transfer efficiency for similar muffle cavity geometry. Further, energy efficiency improvement is obtained from the countercurrent flow arrangement, as more heat can be recovered from the heating gas than in a cross-flow arrangement, since the heating gas outlet temperature can be lower while reaching the same kiln internal temperatures.

[0013] According to certain embodiments of the present invention, high temperature flue gas is introduced into the muffle only in the proximity of the back end of the rotatable hollow chamber and a temperature control or fine tuning of the temperature is based on introducing a cooling gas into the cavity via at least one first cooling gas inlet.

[0014] The heating system according to the invention is further less complex than existing heating systems, as less equipment, instruments, ducting, etc. is required for introducing a heating gas such as hot flue gas into the kiln muffle compared to implementations in which a heating gas is introduced into several muffle zones.

[0015] Arrangements for introducing a cooling gas such as air or lower temperature flue gas have further lower complexity and costs compared to hardware designed for higher operating temperatures.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIGURE 1 illustrates a schematic view of an example of a rotary kiln reactor,

[0017] FIGURE 2 illustrates a schematic view of a system in accordance with at least some embodiments of the present invention,

[0018] FIGURE 3 illustrates a schematic view of another system in accordance with at least some embodiments of the present invention,

[0019] FIGURE 4 illustrates a schematic view of a further system in accordance with at least some embodiments of the present invention, and

[0020] FIGURE 5 illustrates a schematic view of a heating gas inlet of a system in accordance with at least some embodiments of the present invention.EMBODIMENTS

[0021] In FIGURE 1 a schematic view of an example of a rotary kiln reactor is illustrated. The reactor comprises a hollow chamber 2 into which material 23, for example polymer waste, can be fed by a stationary feeding system 5 via a feed outlet 7. The material 23 fed into the hollow chamber 2 via the at least one feed outlet 7 falls on a heatedinner surface 21 of the rotatable hollow chamber 2 due to gravity. The rotation of the hollow chamber 2 around an axis of rotation A causes the material 23 to distribute over at least a part of the inner surface 21 of the hollow chamber 2. The high temperature wall of the hollow chamber 2 heated by a heating system 10 heats the material to pyrolysis reaction temperature leading to thermal decomposition of the material 23 within the hollow chamber 2, thus converting the material 23 into a gas 9 from at least partially pyrolyzed material and a residue. The reactor further comprises a gas outlet 8 for collecting a product comprising a gas 9 from at least partially pyrolyzed material. The reactor is configured to allow flowing of the gas 9 from at least partially pyrolyzed material within the rotatable hollow chamber 2 substantially in a direction from the front end 3 to the back end 4 - as indicated by arrows 24 - of the hollow chamber 2 prior to guiding the gas 9 via the gas outlet 8 out of the reactor.

[0022] In FIGURE 2 a schematic view of a system 1 in accordance with at least some embodiments of the present invention is illustrated. The system 1 represents a rotary kiln reactor comprising a rotatable hollow chamber 2 having a front end 3 and a back end 4. The rotatable hollow chamber 2 is typically in the form of an elongated hollow cylinder. The term ’’elongated” means that a length of the hollow cylinder is substantially greater than a diameter of the hollow cylinder. For example, the length of the hollow cylinder may be 18 m and the diameter of the hollow cylinder may be 2 m. Typically, a length to diameter ratio is in the range between 3-20. The hollow chamber 2 is typically made of a metal or metal alloy. The entire hollow chamber 2 is configured to be rotated around an axis of rotation A. The axis of rotation A is typically orientated horizontally or substantially horizontally. The term ’’axis orientated horizontally” means an axis that is orientated perpendicular to a gravity vector or perpendicular to the normal on the surface of the Earth. Similarly, the term ’’axis orientated substantially horizontally” means an axis that is tilted a few degrees, for example less than 10 degrees, from the axis that is orientated perpendicular to a gravity vector or perpendicular to the normal on the surface of the Earth. The rotational speed of the entire hollow chamber 2 may be, for example, in the range between 0.1 and 5 revolutions per minute (rpm), for example in the range between 1 and 2 rpm.

[0023] The system 1 further comprises a feeding system 5 configured to feed material 23 into the hollow chamber 2 via at least one feed outlet 7. The feeding system 5 may, for example, comprise a lance having a single feed outlet 7. The lance is typicallystationary, i.e. the lance is not configured to rotate and the rotatable hollow chamber 2 is configured to rotate around the lance. The lance may be, for example, in the form of a hollow cylinder. A center axis of the lance is typically arranged or orientated coaxially with the axis of rotation A. The lance is typically made of metal or a metal alloy. The lance may, for example, extend into the hollow chamber 2. The system 1 may be, for example, configured to feed polymer waste into the hollow chamber 2 via the feed outlet 7. If the feeding system is an extrusion-type feeding system, the material 23 is (predominantly) premolten so that the feed is converted into a flowable form allowing travelling through the lance. Alternatively, the material is not pre-molten before feeding it into the reactor.

[0024] The material 23 fed into the hollow chamber 2 via the at least one feed outlet 7 falls on a heated inner surface 21 of the rotatable hollow chamber 2 due to gravity. The rotation of the hollow chamber 2 causes the material 23 to distribute over at least a part of the inner surface 21 of the hollow chamber 2. Distribution of the material 23 over at least a part of the inner surface 21 of the hollow chamber 2 may be improved by tilting the rotatable hollow chamber 2 a few degrees, for example 1 degrees to 5 degrees from the horizontal axis. In such a configuration, the rotatable hollow chamber 2 is arranged substantially horizontally. Additionally, the rotational speed of the hollow chamber 2 affects distribution of the material.

[0025] The high temperature wall of the hollow chamber 2 heats the material 23 to a pyrolysis reaction temperature leading to thermal decomposition of the material 23 within the hollow chamber 2, thus converting the material 23 into a gas 9 from at least partially pyrolyzed material and a residue. The residue may comprise inorganics or inorganic contaminants, for instance.

[0026] The system 1 yet further comprises a gas outlet 8 for collecting a product comprising a gas 9 from at least partially pyrolyzed material. The system 1 is configured to allow flowing of the gas 9 from at least partially pyrolyzed material within the rotatable hollow chamber 2 in a direction from the front end 3 to the back end 4 of the hollow chamber 2 as indicated by arrow 24.

[0027] Furthermore, the heating system 10 of the system 1 according to the present invention comprises a muffle 6. The muffle 6 has a cavity 13 between at least a part of an outer surface 14 of the rotatable hollow chamber 2 and a wall 20 of the muffle 6. Typically, a cylindrical opening is provided in the muffle 6 so that the rotatable hollowchamber 2 can rotate within the stationary muffle 6. The muffle 6 is typically in the form of a hollow cylinder. The muffle 6 comprises a heating gas inlet 11 for guiding a heating gas 15 into the cavity 13. The heating gas inlet 11 is located in the proximity of the back end 4 of the rotatable hollow chamber 2. Additionally, the muffle 6 comprises a heating gas outlet 12 for guiding the heating gas 15 out of the cavity 13. The heating gas outlet 12 is located in the proximity of the front end 3 of the rotatable hollow chamber 2. Typically, only a single heating gas inlet 11 and a single heating gas outlet 12 are provided. The heating system 10 is capable of heating the outer surface 14 of the rotatable hollow chamber 2 by heating gas 15 present in the cavity 13.

[0028] In other words, the system 1 is configured to introduce a heating gas 15 into the cavity 13 and to guide a heating gas flow of the heating gas 15 through the cavity 13. The heating gas 15 introduced into the cavity 13 may be hot flue gas, for instance. The temperature of the heating gas 15 introduced into the cavity 13 may be, for example, 750 °C or higher at the heating gas inlet 11. The heating gas 15 is typically not identical with the gas 9 obtained via the gas outlet 8. In other words, the gas 9 is normally not utilized for heating of the wall of the hollow chamber 2. The gas 9 is typically not introduced into the cavity 13. The heating gas flow is guided outside of the rotatable hollow chamber 2 substantially in opposite direction to a gas flow of the gas 9 from at least partially pyrolyzed material flowing within the rotatable hollow chamber 2. Subsequently, the heating gas 15 is guided out of the cavity 13 in the proximity of the front end 3 of the hollow chamber 2 via the heating gas outlet 12.

[0029] In FIGURE 3 a schematic view of another system 1 in accordance with at least some embodiments of the present invention is illustrated. The system 1 comprises the elements described above in connection with FIGURE 2. Optionally, the heating system 10 comprises at least one first cooling gas inlet 16, for example three first cooling gas inlets 16, between the heating gas inlet 11 and the heating gas outlet 12. Any number of first cooling gas inlets 16 may be provided. The at least one first cooling gas inlet 16 is provided for guiding a cooling gas 17 into the cavity 13 in order to mix the cooling gas 17 with the heating gas 15 present in the cavity 13. In other words, the heating system 10 comprises at least one first cooling gas inlet 16 downstream of the heating gas inlet 11. The at least one first cooling gas inlet 16 may optionally further comprise a vent for controlling the amount of cooling gas to be introduced into the cavity 13. The cooling gas 17 may be air, recycled heating gas or recycled flue gas having a lower temperature than the heatinggas 15, for instance. High temperature heating gas 15 is introduced into the cavity 13 of the muffle 6 via the heating gas inlet 11 only in the proximity of back end 4 of the hollow chamber 2 and temperature control or fine tuning of the temperature within different sections of the cavity 13 is based on introducing the cooling gas 17 at at least one different location, preferably at several locations. In other words, mixing the cooling gas 17 with the heating gas 15 causes lowering of the temperature of the heating gas 15 in a section of cavity 13 downstream of a respective first cooling gas inlet 16.

[0030] In FIGURE 4 a schematic view of a further system 1 in accordance with at least some embodiments of the present invention is illustrated. The system 1 comprises the elements described above in connection with FIGURES 2 and 3. Additionally, the muffle 6 comprises at least one protrusion 22 protruding from the wall 20 of the muffle 6 into the cavity 13 between the heating gas inlet 11 and the heating gas outlet 12, i.e. the at least one protrusion 22 is stationary. The at least one protrusion 22 may be, for example, made of thermal insulation material. Thus, the outer surface 14 of the rotatable hollow chamber 2 can remain smooth. As a consequence, cleaning of the outer surface 14 of the rotatable hollow chamber 2 can take place easily. Additionally, providing at least one sensor, such as a temperature sensor, on the outer surface 14 of the rotatable hollow chamber 2 for measuring a surface temperature and / or measuring a characteristic with a contactless sensor can take place easily. A thermocouple or thermoelectrical thermometer may be, for example, coupled to the outer surface 14 of the rotatable hollow chamber 2. Instead or in addition, a pyrometer or radiation thermometer may be provided for remote measurement of the temperature of the outer surface 14 of the rotatable hollow chamber 2. For each cooling gas inlet 16 a protrusion 22 may be provided, for instance. A protrusion 22 may be, for example, in the form of a ring or ring-like structure. Each protrusion reduces the crosssection of a passage or channel between the protrusion 22 and the outer surface of the rotatable hollow chamber 2 through which the heating gas 15 is able to flow. As a consequence, turbulence in the heating gas flow is increased. Cross-sections of protrusions 22 may be different in different sections of the cavity 13. In this document, the term “choke point” means a point or place where turbulence is caused to the heating gas flow. Each protrusion 22 forms a choke point for improving mixing of heating gas 15 with cooling gas 17.

[0031] Of course, at least one protrusion may also be provided on the outer surface 14 of the hollow chamber 2, thus extending into the cavity 13 and creating turbulence inthe heating gas flow. By way of illustration, a protrusion can be either a structure protruding from the wall 20 of the muffle 6 into the cavity 13 or a structure protruding from the outer surface 14 of the rotatable cylinder, herein referred to as the rotatable hollow chamber 2, into the cavity 13.

[0032] In FIGURE 5 a schematic view of a heating gas inlet 11 of a system 1 in accordance with at least some embodiments of the present invention is illustrated. The heating gas inlet 11 comprises a vent 19 capable of adjusting, limiting or blocking a heating gas flow into the cavity 13. As a consequence, an amount of the heating gas 15 can be adjusted or fine-tuned in the proximity of the back end 4 of the hollow chamber 2, where the heating gas 15 is introduced into the cavity 13. A temperature of the heating gas 15 may be adjusted earlier in the process, for instance. Fine-tuning of a wall temperature of the rotatable hollow chamber 2 in different sections or zones of the rotatable hollow chamber can be further improved by guiding a cooling gas 17 into the cavity 13 as described and shown in connection with FIGURE 3.

[0033] Optionally, a second cooling gas inlet 18 may be connected to the heating gas inlet 11 in order to mix a cooling gas 17 with a heating gas 15 prior to guiding the mixture into the cavity 13 of the muffle 6. The second cooling gas inlet 18 may optionally comprise a vent capable of adjusting, limiting or blocking a cooling gas flow. As a consequence, the temperature of the heating gas 15 can be adjusted or fine-tuned in the proximity of the back end 4 of the hollow chamber 2, where the heating gas 15 is introduced into the cavity 13.

[0034] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0035] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0036] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and examples of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0037] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0038] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0039] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.INDUSTRIAL APPLICABILITY

[0040] At least some embodiments of the present invention find industrial application in heating of rotary kiln reactors.REFERENCE SIGNS LIST system rotatable hollow chamber front end back end feeding system muffle feed outlet gas outlet gas from at least partially pyrolyzed material heating system heating gas inlet heating gas outlet cavity outer surface of rotatable hollow chamber heating gas first cooling gas inlet cooling gas second cooling gas inlet vent wall of muffle inner wall protrusion23 material24 direction of gas flow of gas from at least partially pyrolized material26 direction of gas flow of the heating gasA axis of rotation

Claims

CLAIMS:

1. A system (1) comprising:- a rotatable hollow chamber (2) having a front end (3) and a back end (4),- a feeding system (5) configured to feed material into the hollow chamber (2) via at least one feed outlet (7),- a gas outlet (8) for collecting a product comprising a gas (9) from at least partially pyro lyzed material, wherein the system (1) is configured to allow flowing of the gas (9) from at least partially pyrolyzed material within the rotatable hollow chamber (2) in a direction from the front end (3) to the back end (4),- a heating system (10) comprising: o a muffle (6) enclosing at least a part of the rotatable hollow chamber (2) thereby providing a cavity (13) between at least a part of an outer surface (14) of the rotatable hollow chamber (2) and a wall (20) of the muffle (6), o wherein a heating gas inlet (11) for guiding a heating gas (15) into the cavity (13) is located in the proximity of the back end (4) of the rotatable hollow chamber (2) and a heating gas outlet (12) for guiding the heating gas (15) out of the cavity (13) is located in the proximity of the front end (3) of the rotatable hollow chamber (2), characterized in that o the heating system (10) further comprises at least one first cooling gas inlet (16) between the heating gas inlet (11) and the heating gas outlet (12) for guiding a cooling gas (17) into the cavity (13) in order to mix the cooling gas (17) with the heating gas (15) present in the cavity (13), and o the heating gas inlet (11) comprises a vent (19) capable of adjusting, limiting or blocking a heating gas flow into the cavity (13).

2. The system (1) according to claim 1, wherein the heating system (10) is capable of heating the outer surface (14) of the rotatable hollow chamber (2) by heating gas (15) present in the cavity (13).

3. The system (1) according to claim 2 or 3, wherein the system (1) is configured to guide a heating gas flow of the heating gas (15) via the cavity (13) outside of the rotatable hollowchamber (2) substantially in opposite direction to a gas flow of the gas (9) from at least partially pyro lyzed material within the rotatable hollow chamber (2).

4. The system (1) according to any one of claims 1 - 3, wherein the heating gas (15) is different than the gas (9) from at least partially pyrolyzed material.

5. The system (1) according to any one of claims 1 - 4, wherein the muffle (6) comprises at least one protrusion (22) protruding from the wall (20) of the muffle (6) into the cavity (13) and / or protruding from the outer surface (14) of the rotatable hollow chamber (2) into the cavity (13).

6. The system (1) according to claim 5, wherein the at least one protrusion (22) is arranged downstream of the heating gas inlet (11) and downstream of the at least one first cooling gas inlet (16).

7. The system (1) according to any one of claims 1-6, wherein the muffle (6) is made of steel or a refractory material or a combination of both.

8. The system (1) according to any one of claims 1-7, wherein the heating system (10) comprises a second cooling gas inlet (18) connected to the heating gas inlet (11).

9. A method of heating a rotatable hollow chamber (2), the method comprising:- providing a rotatable hollow chamber (2) having a front end (3) and a back end (4),- feeding material into the hollow chamber (6) via at least one feed outlet (7) of a feeding system (5),- collecting, by a gas outlet (8), a product comprising a gas (9) from at least partially pyrolyzed material, wherein flowing of the gas (9) from at least partially pyrolyzed material within the rotatable hollow chamber (2) is allowed in a direction from the front end (3) to the back end (4),- providing a muffle (6) enclosing at least a part of the outer surface (14) of the rotatable hollow chamber (2) thereby providing a cavity (13) between at least a part of an outer surface (14) of the rotatable hollow chamber (2) and a wall (20) of the muffle (6),- guiding a heating gas (15) via a heating gas inlet (11) into the cavity (13), wherein the heating gas inlet (11) is located in the proximity of the back end (4) of the rotatable hollow chamber (2), and- guiding the heating gas (15) via a heating gas outlet (12) out of the cavity (13), wherein the heating gas outlet (12) is located in the proximity of the front end (3) of the rotatable hollow chamber (2), characterized by- guiding a cooling gas (17) via at least one first cooling gas inlet (16) into the cavity (13) and mixing the cooling gas (17) with the heating gas (15), wherein the at least one cooling gas inlet (16) is arranged between the heating gas inlet (11) and the heating gas outlet (12), and- adjusting, blocking or limiting the heating gas flow into the cavity (13) utilizing a vent (19).

10. The method according to claim 9, the method comprising heating the outer surface (14) of the rotatable hollow chamber (2) by heating gas (15) present in the cavity (13).

11. The method according to claim 9 or 10, the method comprising guiding a heating gas flow of the heating gas (15) outside of the rotatable hollow chamber (2) substantially in opposite direction to a gas flow of the gas (9) from at least partially pyrolyzed material.

12. The method according to any one of claims 9 - 11, the method comprising increasing turbulence in the heating gas flow utilizing at least one protrusion (22) protruding from the wall (20) of the muffle (6) and / or from the outer surface (14) into the cavity (13).

Images