Reactor with rotor discs having varying radial distance between rotor hub and rotor housing

Abstract

Device in the form of a reactor arranged and operative for the recovery of hydrocarbon in gaseous form from a disintegrated solid hydrocarbon-based material, which reactor comprises a rotor driven in rotation inside a circular rotor housing shell comprising a set of rotor discs each of which has a number of rotor arms extending in radial directions from a rotor hub, wherein the radial distance between the rotor hub and the rotor housing shell is increasing in the direction towards an outlet for the recovered process gas from the reactor housing.

Description

[0001] Reactor

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to a device in the form of a reactor arranged and operative for the recovery of hydrocarbon in gaseous form from a disintegrated solid hydrocarbon-based material.

[0004] BACKGROUND AND PRIOR ART

[0005] The invention is based on a thermo-mechanical depolymerization technology. The inventive reactor enables the conversion of hydrocarbon-based waste material including, for example, mixed plastic waste and vehicle tires into process gas containing hydrocarbons for the production of hydrocarbon condensate and other commercial products. The hydrocarbon condensate can thereby be used as fuel or raw material in chemical plants and refineries that manufacture chemical end products.

[0006] A central part of the invention is a reaction chamber in which specially designed rotating rotor arms generate high kinetic energy and high temperature created through friction between the fed waste material, the reaction chamber itself and the rotating arms. This results in the breaking of chemical bonds in the waste material and the gasification of hydrocarbons.

[0007] The friction-driven process takes place in an airtight, oxygen-free atmosphere. The process is an environmentally friendly, continuous process that operates at atmospheric pressure under rapid and continuous heat generation. The rapid process contributes to the creation of a high-quality, usable hydrocarbon condensate. The process results in low emission levels and a significant reduction in carbon dioxide. The process is controlled by a combination of regulated energy input and the quantity of feedstock supplied. The control of the process control can be made programmable to allow optimization under varying production conditions.

[0008] Reactors for carrying out the above briefly described thermo-mechanical process have previously been described in the patent literature. As examples of known older embodiments, SE534399C2 and SE537075C2 can be mentioned. Both can be seen as representatives of the state of the art with regard to reactors for this type of thermomechanical processes. These reactors briefly have a rotor driven in rotation in a circular rotor housing comprising a set of rotor discs, which rotor discs are non- rotatably mounted one after the other on a rotor shaft extending concentrically in the rotor housing, whereby the rotor discs are mutually angularly offset in the direction of rotation. The individual rotor disc has a number of rotor arms which extend at a mutual distance in the direction of rotation, angularly evenly distributed from a rotor hub, in a radial direction towards the shell of the rotor housing. During the process, a rotating fluidized bed is formed, resulting in the breaking of chemical bonds and the conversion of essentially all hydrocarbons to process gas. Heavier materials in the rotating bed are thrown out by centrifugal force against the rotor housing shell and fed to a radial outlet at a downstream end of the reaction chamber. Gas and any lighter materials are forced out of the surrounding denser part of the bed and are directed inward into the reaction chamber, to be gradually discharged via an axial outlet at the downstream end of the reaction chamber.

[0009] To support the separation of process gas from the denser part of the rotating bed, it is advantageous if the gas pressure inside the denser part of the bed can be kept at a low level through the reaction chamber to the outlet, preferably at most at atmospheric pressure or in the order of 0.1 MPa. A proven way to influence the gas pressure in the reaction chamber is to install a venturi nozzle downstream of the outlet, which generates a negative pressure at the gas outlet. However, such a solution entails costs for installation and operation.

[0010] SUMMARY OF THE INVENTION

[0011] An object of the invention is to provide improvements to the known reactor, particularly with regard to the efficiency of gasifying the waste material and discharge of process gas from the reaction chamber.

[0012] Another object of the invention is to provide improvements to the known reactor with respect to assembly and maintenance of mechanical components in the reaction chamber.

[0013] A further object of the invention is to provide improvements to the known reactor with respect to the reduction of self-oscillation in a rotating cantilevered rotor shaft.

[0014] One or more of these objects are met in a reactor which comprises a rotor driven in rotation in a circular rotor housing, comprising a set of rotor discs which are non- rotatably mounted one after the other on a rotor shaft which extends concentrically in the rotor housing, wherein the rotor discs are mutually angularly offset in the direction of rotation. The individual rotor disc has a number of rotor arms which extend at a mutual distance in the direction of rotation, angularly evenly distributed from a rotor hub, in a radial direction towards the rotor housing shell, so that between the rotor arms circular sector-shaped cavities are defined which, in conjunction with the circular sector-shaped cavities of the other rotor discs in the rotor, provide a spiral-shaped channel extending in the longitudinal direction of the rotor, wherein the cross-sectional or flow area of the channel is related to the radial distance between the rotor hubs and the shell of the rotor housing.

[0015] According to one aspect of the present invention, the radial distance between the rotor hubs and the rotor housing shell, and thereby the cross-sectional or flow area of the channel, is increasing in the direction of the process flow through the rotor housing and thus also in the direction towards an outlet for the recovered process gas from the rotor housing.

[0016] In other words, according to the present invention, a cavity is provided through the rotor in the longitudinal direction of the rotor, the flow area of which increases in the direction towards the downstream end of the rotor and thus also in the direction towards the process gas outlet. This ensures a gas pressure in the reactor housing that is favorable to the process without the need for additional devices or investments.

[0017] An embodiment according to the invention comprises that the rotor hubs have a diameter that decreases in the downstream direction of the rotor, in that each subsequent rotor hub in said direction has a smaller diameter than the preceding rotor hub. An advantage of this embodiment is that all rotor hubs can be designed with a uniform hole diameter for mounting on a rotor shaft that has the same shaft diameter along the length of the rotor.

[0018] According to an alternative embodiment of the invention, the radial distance between the rotor hubs and the rotor housing shell increases incrementally in the downstream direction of the rotor. This embodiment has the advantage that groups of rotor discs may be designed with hubs of uniform diameter, which reduces the need to stock replacement parts of multiple designs and dimensions. Also in this alternative, all rotor hubs can advantageously be designed with uniform bore diameter for mounting on a rotor shaft having the same shaft diameter along the length of the rotor.

[0019] According to another alternative embodiment, the rotor shaft extends in a cantilevered manner into the rotor housing with a freely rotating shaft end and has a shaft diameter which stepwise decreases in the direction of the shaft end in the length of the rotor. An advantage of this embodiment is that the rotor hubs within one and the same group of rotor discs may be designed with the same radial dimensions from the center hole to the periphery of the hub, which is of importance for the dimensioning and strength of the hub.

[0020] Another advantage of this embodiment is that the rotating mass decreases in the direction towards the free end of the rotor shaft, which may have a beneficial effect on the natural frequency or self-oscillation of the cantilevered rotor shaft.

[0021] The rotor housing has an end located upstream in the direction of movement of the process material and an end located downstream, whereby an inlet for disintegrated solid material / process material is arranged with a radial feed direction in the upstream end of the rotor housing, an outlet for remaining solid particles / residual material is arranged with a radial feed direction at the downstream end of the rotor housing, and the process gas outlet is arranged with an axial feed direction from the downstream end of the rotor housing.

[0022] According to one embodiment, the spiral-shaped channel has an end located upstream and an end located downstream in the direction of movement of the process material, wherein the direction of rotation of the rotor is such that the upstream end of the channel with the comparatively smaller flow area rotates ahead of the downstream end with the relatively larger flow area. This embodiment provides the advantage that the rotor discs, through their rotation, drive the movement of the process gas in the channel in the direction towards the process gas outlet.

[0023] In one embodiment, the rotor arms of the individual rotor disc are arranged with a mutual angular distance of 60° in the plane of the rotor disc. Each rotor disc thus defines six (6) circular sector-shaped cavities which are limited by two rotor arms and by the outer periphery of the rotor hub. According to one embodiment, the rotor discs in the rotor may be mutually angularly offset by 20° in the direction of rotation. In this way, the individual cavities of the successively mounted rotor discs are accumulated to form a spiral-shaped channel with a depth in the radial direction which is limited by the outer periphery of the rotor hubs. It is understood that in this embodiment, eighteen (18) rotor discs arranged in succession create a channel which turns one revolution or 360° around the rotor axis for the transport of process gas.

[0024] Further advantages and details of the invention will become apparent from the following description of exemplary embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0025] Embodiments of the invention are explained in more detail below with reference to the accompanying drawings, of which:

[0026] Fig. 1 shows an axial cross-section through a reactor in which an embodiment of the invention is applied,

[0027] Fig. 2 shows on a larger scale a reaction chamber included in the reactor with a partially broken away rotor housing shell, and

[0028] Fig. 3 is a plan view of a rotor disc included in the rotor.

[0029] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] Fig. 1 shows a reactor 1 resting on a reactor foundation 2. A reaction chamber 3 is supported at the right end of the reactor foundation. In the reaction chamber 3, a rotor 4 is supported by a rotor shaft 5 which extends cantilevered into the reaction chamber. By cantilevered here is meant that the rotor shaft lacks a support or bearing point for its free downstream end in the reaction chamber. Outside the reaction chamber, the rotor shaft 5 is mounted in support bearings 6, 7 which are supported by the reactor foundation. A motor 8 drives the rotor shaft and rotor to rotate via a gearbox 9.

[0031] The reaction chamber 3, see also Fig. 2, comprises a rotor housing defined by a circular-cylindrical rotor housing shell 10, an upstream end wall 11 fixed to the reactor foundation 2 and a downstream end wall 12 connected to the rotor housing shell 10. The terms upstream and downstream refer to the flow direction F of the process material through the reaction chamber 3. Raw material for the process is introduced radially into the reaction chamber via an opening in the upstream end of the rotor housing shell, constituting a process material inlet 13. Remaining solid particles are discharged radially via an opening in the downstream end of the rotor housing shell, constituting a residual material outlet 14. The process material inlet 13 and the residual material outlet 14 may advantageously have the same diameter, which is considered to extend the residence time of the process material in the reaction chamber. Process gas recovered in the process is removed through the downstream end wall 12 via a process gas outlet 15.

[0032] In this context, it should be mentioned that the residual material outlet 14 of the exemplary embodiment is arranged close to the end wall 12 and the process gas outlet 15. This measure is intended to reduce the amount of coal powder and other residual material at the process gas outlet 15. The rotor 4, see also Fig. 3, is composed of a set of rotor discs 16 which are non- rotatably mounted on the rotor shaft 5. Each rotor disc comprises a number of rotor arms 17 which extend in radial directions, evenly spaced in angular distribution from a rotor hub 18. At the end of each rotor arm 17 an anvil or a hammer 19 is arranged. The rotor arms in the exemplary embodiment are six in number and extend from the rotor hub with an intermediate angle a of 60°.

[0033] The rotor discs 16 are arranged closely together on the rotor shaft 5 and may be non- rotatably mounted on the rotor shaft by means of keys and keyways 20. The rotor discs are arranged in groups of three, wherein the three rotor discs are angularly offset relative to each other in the rotational direction R by an angle of 20°. In Fig. 3, the front or first rotor disc in a group of three is shown in its entirety with a solid line, the second or intermediate rotor disc is partially shown with a dashed line, and the third rotor disc is partially shown with a dashed-dotted line.

[0034] Between the rotor arms 17 a circular sector-shaped cavity 21 is formed. In the rotor disc of the exemplary embodiment, six separate cavities 21 are defined between two consecutive rotor arms 17 and the rotor housing shell 10. The cavities 21 of all the rotor discs 17 are accumulated in the rotor 4 to a channel CH (see Fig. 2) which extends in a spiral shape through the rotor from its upstream end to its downstream end. Due to the circular division that the angular displacement of the rotor discs by 20° in the direction of rotation entails in the exemplary embodiment, said channel will turn one revolution or 360° around the rotor axis through eighteen (18) consecutively arranged rotor discs. It is understood that in the rotor of the exemplary embodiment, there are six (6) channels extending parallel through the rotor.

[0035] The size of the cavities 21, and the associated cross-sectional or flow area of the channel, depend on several factors such as the radial length I of the rotor arms and their width w in the direction of rotation R.

[0036] Some of these factors are, of course, limited by strength and manufacturing considerations. Given a specific angle, however, the radius r of the circular segment is the factor that has the greatest influence on the area of the circular segment / cavity 21 in the present application. The area of a circular segment may be calculated according to the formula 0.5 0 (the angle in radians) multiplied by the radius squared. As an example in this context, it can be mentioned that an increase in the radius r from 250 mm to 300 mm increases the area of the cavity 21 from about 328 cm2to about 473 cm2at the same angle a of 60 degrees (about 1.05 rad). In order to promote the movement of the process gas through the channels CH, the rotor 4 is composed of rotor discs having rotor hubs 18 with a gradually decreasing diameter D and, as a result, gradually increasing rotor arm lengths I in the direction towards the downstream end of the rotor. By this measure, the surface area of the cavities 21 and thus the flow area of the channels in the flow direction increases. One effect of the measure is that an unfavorable and increased process gas pressure can be avoided at the gas outlet 15 in the downstream end of the reaction chamber.

[0037] According to the exemplary embodiment shown in the drawings, see Fig. 1 , this increase in the flow area of the channel occurs incrementally or stepwise. More specifically, the rotor 4 of the exemplary embodiment is composed of a number of rotor discs 16 mounted on a rotor shaft 5 with a shaft diameter S that stepwise decreases in the direction towards the downstream end of the rotor shaft. The diameter S of the rotor shaft decreases in three steps Si, S2 and S3, and the rotor discs 16 are arranged in three groups, which differ from each other in that the rotor hubs 18 included have, in the direction towards the downstream end of the rotor, a groupwise decreasing diameter D and, in the same direction, a groupwise decreasing central hole O (see Fig. 3). This solution has several advantages: first, only three variants of rotor discs 16 need to be manufactured and stocked, second, the rotor hubs 18 can be designed with the same radial distance (DS) between the central hole and the periphery, which ensures strength, and third, the assembly of the rotor discs on the rotor shaft is simplified by the fact that through-keyways 20 may be used for all rotor discs in each step of the rotor shaft.

[0038] The stepwise reduction of the rotor shaft diameter S and the rotor hub diameter O in the exemplary embodiment results in a reduction of the total mass of the rotor in the direction of the free downstream end of the rotor and rotor shaft. The reduction may, where applicable, be on the order of 5-20%, and is considered to have a beneficial effect on the vibration that may occur in cantilever beam systems, which the rotor shaft 5 is likely to be classified as.

[0039] ALTERNATIVE EMBODIMENTS WITHIN THE SCOPE OF THE INVENTION

[0040] The invention has been described above in a preferred embodiment, which provides additional advantages beyond the technical effect primarily sought and achieved by the invention, namely to make the separation and discharge of process gas from the fluidized bed more efficient. However, the principle of solution may be realized in alternative embodiments, which at least partially provide the desired technical effect. Thus, an alternative embodiment may comprise the rotor hubs 18 having a decreasing diameter D in the direction towards the downstream end of the rotor, such that each subsequent rotor hub in said direction has a smaller diameter than the preceding rotor hub. This embodiment may include a rotor shaft of uniform diameter S.

[0041] Another alternative embodiment may comprise a group of consecutive rotor hubs 18 in the direction toward the downstream end of the rotor, having a uniform diameter D that is smaller than the diameter of a group of preceding rotor hubs with a uniform diameter. This embodiment may include a rotor shaft of uniform diameter S as well as a rotor shaft with a stepwise decreasing diameter S in the direction toward the downstream end of the rotor.

[0042] It is, of course, also conceivable that the diameter S of the rotor shaft may decrease incrementally in more or fewer than three steps for the assembly of a corresponding number of groups of rotor discs with adapted rotor hubs.

Claims

CLAIMS1. Device in the form of a reactor (1) arranged and operative for the recovery of hydrocarbon in gaseous form from a disintegrated solid hydrocarbon-based material, which reactor comprises:- a rotor (4) driven in rotation in a circular rotor housing (3) comprising a set of rotor discs (16), which rotor discs are non-rotatably mounted one after the other on a rotor shaft (5) which extends concentrically in the rotor housing (3), wherein the rotor discs (16) are angularly offset from each other in the direction of rotation (R),- wherein the individual rotor disc (16) has a number of rotor arms (17) which extend at a mutual distance in the direction of rotation (R) and are angularly evenly distributed from a rotor hub (18), in a radial direction towards a rotor housing shell (10),- so that between the rotor arms (17) circular sector-shaped cavities (21) are defined which, in conjunction with the circular sector-shaped cavities of the other rotor discs (16) in the rotor (4), provide a spiral-shaped channel (CH) extending in the longitudinal direction of the rotor, wherein the cross-sectional area of the channel is in relation to the radial distance (r) between the rotor hubs (18) and the rotor housing shell (10), characterized in that the radial distance (r) between the rotor hubs (18) and the rotor housing shell (10), and thus the cross-sectional area of the channel (CH), is increasing in the direction towards an outlet (15) for the recovered process gas from the rotor housing (3).

2. Device according to claim 1, wherein the rotor hubs (18) have a diameter (D) that decreases in the downstream direction (F) of the rotor (4), in that each subsequent rotor hub (18) in said direction has a smaller diameter than the preceding rotor hub (18).

3. Device according to claim 1, wherein the radial distance (r) between the rotor hubs (18) and the rotor housing shell (10) is increased incrementally in the downstream direction (F) of the rotor (4).

4. The device according to claim 3, wherein a group in the downstream direction (F) of the rotor (4) subsequent rotor hubs (18) have a uniform diameter (D) which is smaller than the diameter of a group of preceding rotor hubs (18) of uniform diameter.

5. Device according to any one of the preceding claims, wherein the rotor shaft (5) extends in a cantilevered manner into the rotor housing (3) with a freely rotating shaft end, and has a diameter (Si , S2, S3) which decreases stepwise in the direction towards the shaft end.

6. Device according to any one of the preceding claims, wherein the rotor housing (3) has an end located upstream and an end located downstream in the direction of movement (F) of the process flow, whereby an inlet (13) for process material is arranged with a radial feed direction in the upstream end of the rotor housing, an outlet (14) for residual material is arranged with a radial feed direction in the downstream end of the rotor housing, and a process gas outlet (15) is arranged with an axial feed direction from the downstream end of the rotor housing.

7. Device according to claim 6, wherein the process material inlet (13) and the residual material outlet (14) have the same opening diameter to the rotor housing.

8. Device according to claim 6 or 7, wherein the residual material outlet (14) opens into a feed screw arranged tangentially to the rotor housing (10).

9. Device according to claim 6, 7 or 8, wherein the spiral-shaped channel (CH) has an end located upstream and an end located downstream in the direction of movement (F) of the process material, and wherein the direction of rotation (R) of the rotor is such that the upstream end of the channel with the comparatively smaller cross-sectional area rotates ahead of the downstream end with the relatively larger cross-sectional area.

10. Device according to any one of the preceding claims, wherein the rotor arms (17) of the individual rotor disc (16) have a mutual angular distance (a) of 60° in the plane of the rotor disc.

11. Device according to claim 10, wherein the rotor discs (16) are angularly offset (P) from each other by 20° in the direction of rotation.

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