SE546534C2 - Radial clearance reactor and process for extracting or recovering hydrocarbon products from hydrocarbon-containing materials - Google Patents

Abstract

Reactor (1) for extracting or recovering hydrocarbon products from hydrocarbon-containing material by disintegrating and gasifying the material in a reactor housing (2) comprising a radial clearance (D) formed between the periphery of a rotor and the inside of the reactor housing, amounting to at least 3 cm and at most 6 cm.

Description

Reactor with radial clearance and method for extracting or recovering hydrocarbon products from hydrocarbon-containing material TECHNICAL FIELD OF THE INVENTION The invention relates to a reactor and a method for extracting or recovering hydrocarbon products from hydrocarbon-containing material, comprising a cylindrical reactor housing extending axially between a rear, first end wall and a front, second end wall, a rotor rotatably arranged in the reactor housing which is driven for rotation by means of a motor and a rotor shaft coaxially aligned with the reactor housing and extending into the reactor housing through the rear end wall, to which reactor housing process material is fed radially or axially via an inlet to the reactor housing, gasified hydrocarbon products are discharged axially via a reactor gas outlet opening centrally in the front end wall, and the remaining solid process material is discharged via a residual material outlet opening peripherally in the reactor housing, BACKGROUND AND PRIOR ART Devices and methods for this purpose are previously described in the patent literature, see for example patents SE 537 075 G2, SE 536 795 G2, SE 534 399 G2 and PGT publication no.

WO 2014/098746 A1. In this context, US 6,165,349 A should also be mentioned.

Since the process is essentially known from description in previous patents, only a summary of the working principle of a reactor arranged for agitating or grinding hydrocarbon-containing material while developing heat therein and for gasifying hydrocarbon products contained in the material shall be given here.

Process material, which may be in the form of plastic or rubber waste, other hydrocarbon-based waste products or hydrocarbon-contaminated soil or sand, is fed to a reactor housing for grinding, comminution, agitation and by means of a rotor rotating in the reactor housing. The material is disintegrated by the kinetic energy developed by the rotor, whereby longer hydrocarbon chains and larger hydrocarbon molecules in the process material are broken by the agitation of the rotor and by the frictional heat generated between the particles in the comminuted and swirling material. Inorganic material such as sand, glass powder or metal can be fed into the reactor housing to increase friction and raise the temperature. Hydrocarbon compounds, water and other organic matter present are gasified, whereby gas and solid fractions are separated by the centrifugal force generated by the rotor so that gas can be discharged from a central part of the reactor housing while the remaining solid material can be discharged from a peripheral part of the reactor housing.

SUMMARY OF THE INVENTION A problem in this context is that unwanted hard objects in the process material not only risk damaging the rotor and reactor housing, but can also disrupt the formation of the fluidized state of the process material which is a condition for stratification and separation between solid material, liquid and gas in the reactor housing. It is an object of the invention to provide a solution to this problem.

This object is achieved by the invention providing a reactor for the extraction or recovery of hydrocarbon products from hydrocarbon-containing material, comprising a cylindrical reactor housing extending axially between a first/rear end wall and a second/front end wall, a rotor rotatably arranged in the reactor housing which is driven for rotation by means of a motor and a rotor shaft coaxially aligned with the reactor housing and extending into the reactor housing through the first/rear end wall, to which reactor housing process material is fed radially or axially via an inlet to the reactor housing, gasified hydrocarbon products are discharged axially via a reactor gas outlet opening centrally in the second/front end wall, and the remaining solid process material is discharged via a residual material outlet opening peripherally in the reactor housing, whereby a radial clearance of 2 - 8 cm, preferably at least 3 cm and at most 6 cm, is formed between the periphery of the rotor and the inside of the reactor housing.

This creates a peripheral zone where harder and non-degradable objects can be discharged and from where they cannot affect and disrupt the fluidized bed-like flow conditions that are to produce a radial stratification and separation of gas from solid particles in the reactor housing.

The rotor comprises rotor arms extending radially from the rotor axis with hammers hingedly mounted at the outer ends of the rotor arms which, during rotation of the rotor, can swing between a position folded against the rotor arm and a position substantially radially outwards from the rotor arm, the length of the rotor arms being dimensioned so that in the folded position of the hammer a radial distance of 3 - 6 cm remains between the hammer and the inside of the reactor housing.

The rotor comprises rotor arms arranged spirally one after the other along the rotor axis resulting in a surrounding and substantially tubular agitated layer of non-fluidized finely ground particulate material between the rotor and the inside of the reactor housing. A substantially cylindrical mass of finely divided particles is thus formed inside the reactor housing which protects the reactor housing/reactor chamber against wear as well as increases the efficiency of the process.

In another aspect of the invention, the object is achieved by a method for recovering or recycling hydrocarbon products from hydrocarbon-containing material using a reactor of the above-mentioned type, which method comprises generating and maintaining an agitated layer of non-fluidized finely ground material surrounding the reactor rotor with a radial extension of at least 3 cm and at most 6 cm, between the rotor and the inside of the reactor housing. More specifically, in one embodiment of the method, a rotor with a helical structure is provided by rotor arms distributed helically one after the other along a rotor axis. The rotor is driven in rotation in order to generate and maintain a particle layer surrounding the rotor of substantially homogeneous radial depth by means of the rotor arm tips distributed evenly over the periphery of the rotor in this way.

It should be clarified here that fluidized material in a fluidized bed in this context refers to a volume in which solid particles move essentially friction-free in a flowing gas or liquid. In the surrounding outer layer of the reactor housing, on the contrary, a non-fluidized state prevails in which particles of solid material are worn against each other and heat is generated by friction between solid material particles.

It should further be clarified that even though the rotor rotates mainly within the surrounding layer, a desired mixing and agitation occurs at depth through shear forces and turbulence generated by the tangential velocity Vi of the rotor arm tips (see Fig. 2) at the interface to the surrounding layer.

Among the advantages and technical effects provided by the generation and maintenance of a surrounding agitated layer of non-fluidized finely ground material between the rotor and the inside of the reactor housing can be counted the recovery of energy supplied to the process mechanically via the rotor. This energy is converted into heat which is largely generated by friction between the finely divided particles in the surrounding layer, and contributes to the thermal decomposition of molecular chains and larger molecules in the hydrocarbon-containing process material. More specifically, the particles consist mainly of carbon which remains from hydrocarbon formations during the depolymerization of hydrocarbon chains in plastic, rubber, oil and other hydrocarbon-containing material. In the surrounding layer, the particles are worn against each other and ground so that they are finely divided down to a size of a few thousandths of a millimeter (approximately 1 - 50 μm), which results in a very large accumulated heat transfer surface and associated high efficiency.

The specified interval of 3 to 6 cm has been determined through studies and measurements of pressure, force and flow conditions in the reactor. These studies include computer simulation in the form of CFD analysis (Computational Fluid Dynamics). With knowledge of the conditions prevailing in the reactor housing during simulated operation of the reactor, it has been found, taking into account radially distinguishable pressure zones and volume fractions of carbon particles, as well as shear forces generated by the rotor arms, that the specified interval is a particularly favorable combination of static pressure, particle size and impact/agitation from the rotor for the reactor of the invention.

It has been found that at a layer thickness of more than about 6 cm, the risk of insufficient agitation in the outermost part of the layer at the reactor housing wall increases, since the static pressure in the particle layer is typically significantly higher next to the reactor housing wall than at the interface at the periphery of the rotor. At a layer thickness of less than about 3 cm, on the other hand, the potential energy recovery that can be achieved through the surrounding layer is not utilized. On both sides of the specified interval, efficiency is thus lost.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention are described in more detail below with reference to the attached schematic drawings, of which Fig. 1 shows a longitudinal cross-section through a reactor, Fig. 2 shows a broken-away cross-section through a reactor housing with a rotor, Fig. 3 shows an embodiment of a rotor in perspective, and Fig. 4 is a diagram showing the size distribution of solid particles in a peripheral area of the reactor housing surrounding the rotor. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS A reactor 1 comprises a rotor 3 rotatably arranged in a cylindrical reactor housing 2. The rotor 3 is driven in rotation by a motor 4 via a rotor shaft 5. The rotor 4 can be driven electrically, with diesel, or gasoline, or with another energy source. The speed of the motor can be reduced by a gear 6 in a gear housing 7 to a rotor speed suitable for the reactor. A suitable rotor speed can typically be in the order of 400 to 600 revolutions per minute. The rotor shaft 5 is supported radially and axially in a reactor frame 10 by means of two bearing sets 8 and 9, respectively. From its support in the reactor frame, the rotor shaft 5 extends cantilevered into the reactor housing 2 via a centrally located feedthrough in a first/rear end wall 11 of the reactor housing. The rotor shaft and the rotor 3 are thus coaxially aligned with the reactor housing. The rotor shaft's insertion through the end wall 11 is sealed against the environment by means of a seal box 12 with seals in contact with the rotor shaft 5. The seal box 12 can be of the active type to which a fluid, e.g. nitrogen gas or other inert medium, is fed at a pressure higher than the pressure prevailing in the reactor housing during operation, in order to counteract leakage of gasified hydrocarbon products out of the reactor housing along the rotor shaft.

The reactor housing 2 comprises a cylindrical casing 13 which extends axially between the first/rear end wall 11 and a second/front end wall 14. The reactor housing is supported in the reactor by the first/rear end wall 11 being fixedly connected to the reactor frame 10, for example by means of a bolted connection. The rotor 3 comprises a number of rotor arms 16 which are mounted in a rotationally fixed manner on the rotor shaft and extend radially therefrom. At their outer ends, the rotor arms support a hingedly arranged rotor arm tip or hammer 17. The rotor arms 16 may be distributed around the rotor shaft in groups of, for example, three, following one another in a number of mutually offset turns so that the rotor has a helical structure, see Fig. 3. This construction results in the rotor arm tips or hammers 17 being distributed evenly over the periphery of the rotor in both the axial direction and the circumferential direction.

For reasons already explained above, the casing 13 of the reactor housing 2 and the rotor 3 are dimensioned with respect to their radii so that a free space/an annular volume and a surrounding gap D are formed between them which has a radial depth of at least about 3 cm and at most about 6 cm from the inside of the reactor housing casing. This results in the formation of an essentially cylindrical layer L of solid particles on the outside of the rotor during operation of the reactor, see Fig. 2. The high tangential velocity Vi of the rotor, which can be in the order of 30 - 40 m/s, causes a strong agitation and stirring in the inner boundary surface of the layer L. In this area, an effective mechanical breakdown and grinding/comminution of solid material down to a minimum particle size of the order of a few thousandths of a millimeter is achieved. How the particle size is distributed in the layer L is illustrated by the diagram in Fig. 4 which indicates a concentrated presence of the finest particles within the range of about 30 mm to about 60 mm.

During operation, process material can be fed into the reactor housing via a radially opening inlet through the cylindrical casing of the reactor housing (not shown), or as in the exemplary embodiment via an axially opening process material inlet 18 incorporated in the front end wall 14. After processing in the reactor housing, the remaining process material, i.e. non-gasified material, is removed via a peripherally opening residual material outlet in the reactor housing, and is transported from there further through a tangentially connecting transport pipe. Hydrocarbons gasified in the process are removed in the axial direction via a centrally located, axially opening reactor gas outlet 20 in the front end wall 14. This solution is facilitated by the fact that the rotor shaft 5 extends self-supportingly into the reactor housing without the need for support from the front end wall 14. The solution also means that the rotor 3 can be extended rearward and utilize the entire length of the reactor housing up to the rear end wall 11, since the partition wall inside the reactor housing, as in previous solutions according to prior art required to separate a gas outlet located there from the process in the reactor housing, can now be avoided. This solution thus provides a larger effective process volume in the reactor housing or chamber and the load on the shaft 5 and the bearings 8, 9 becomes more favorable as the load is centered closer to the suspension in the bearings 8. A gas/particle separator device 21 is connected to the front end wall which is arranged to separate solid particles accompanying the gas from the reactor housing and directly return these to the reactor housing in the opposite direction to the axially flowing out gas.

The gas/particle separator device 21 consists of a cylindrical tube 22 open to the reactor gas outlet 20. An outlet 23 for gas flowing through the tube is provided at an opposite end facing the reactor housing and at the front end. The outlet 23 of the tube opens out substantially radially into the wall of the tube and can be in flow communication with a downstream aftertreatment device (not shown) via a transport line 24. A feed screw 25 is arranged in the tube 22 and can be driven for rotation by a motor, such as an electric motor 26. A drive shaft 27 extends from the motor 26 through a sealed bearing housing 28 connected to the front end of the tube 22. As indicated above, the aftertreatment device can be in the form of a condensation unit, distillation unit or combustion unit, for example. The feed screw 25 has a helically twisted blade and is driven by the motor 26 for refeeding to the reactor housing of solid material particles entering the tube 22. The feed screw 25 is driven at high speed, preferably in the order of 2500 - 3500 rpm, in order to achieve a radial stratification and separation of solid particles and gas through centrifugal action before the gas reaches the outlet 23 in the wall of the tube. The transport of the gas through the tube 22 is promoted by the relative negative pressure prevailing in the transport line. A free end 29 of the feed screw 25 extends past the open end of the tube to reach a distance into the reactor housing, such as 10 - 40 mm, via the reactor gas outlet 20. The embodiment is made possible by the rotor shaft 5 extending cantilevered into the reactor housing, effectively supported by the reactor frame 10 and mounted by the two bearing sets 8 and placed outside the reactor housing. In this preferred embodiment, the feed screw can throw the returned solid particles radially outwards in front of the rotor (seen in a direction from rotor 3 to motor 4).

This means that the particles are returned to the process a short distance outside the rotor axis and are prevented from returning directly with the gas stream out of the reactor housing.

From a free end 30 of the rotor shaft 5 protruding from the gear housing 7, a pair of longitudinally parallel channels 31 and 32 extend, inside the rotor shaft, which are interconnected by a transition 33 in a front region of the rotor shaft. The channels 31 and 32 extend in the longitudinal direction up to or slightly beyond the part of the rotor shaft surrounded by the seal box 12. It also follows from this that the cooling channels extend for cooling the rotor shaft in the part thereof which is mounted and supported in the reactor frame. At the opposite end, the channels 31 and 32 are in flow connection with a cooling medium which can circulate through the channels for cooling the rotor shaft. The channels 31 and 32 serve as supply and return flow channels for coolant from/to a coolant reservoir, and are individually in flow connection with a coolant supply 34 and a coolant drain arranged in a swivel rotatably supported on the rotor shaft. The cooling contributes to a lower temperature in the rotor shaft at the seal box 12 and at the bearings 8, 9, which increases the service life of these components and provides better economy and operational reliability compared to prior art.

The invention is of course not limited to the embodiments described above but can be varied within the scope of the following patent claims.

Claims (2)

A reactor (1) for the extraction or recovery of hydrocarbon products from hydrocarbon-containing material, comprising a cylindrical reactor housing (2) extending axially between a rear, first end wall (11) and a front, second end wall (14), a rotor (3) rotatably arranged in the reactor housing which is driven for rotation by means of a motor (4) and a rotor shaft (5) coaxially aligned with the reactor housing and extending into the reactor housing through the rear end wall (11), to which reactor housing process material is fed radially or axially (18) via an inlet to the reactor housing, gasified hydrocarbon products are discharged axially via a reactor gas outlet (20) opening centrally in the front end wall, and the remaining solid process material is discharged via a residual material outlet (19) opening peripherally in the reactor housing, wherein the rotor (3) has radially extending from the rotor shaft (5) and spirally one after the other along the rotor shaft distributed rotor arms (16) with hammers (17) hingedly mounted at the outer ends of the rotor arms which, during rotation of the rotor, can swing between a position folded against the rotor arm and a position substantially radially outwards from the rotor arm, characterised in that the length of the rotor arms is dimensioned such that in the folded position of the hammer (17) a radial distance (D) of 2 - 8 cm, preferably 3 - 6 cm, is formed between the hammer (17) and the inside of the reactor housing (2), resulting in a layer (L) of non-fluidised finely divided material surrounding the rotor and agitated by shear forces and turbulence between the rotor and the inside of the reactor housing, which layer (L) contains šseš particles in a size of approximately 1. 1-50 µm. Method for recovering or recycling hydrocarbon products from hydrocarbon-containing material using a reactor (1) according to any one of claims 1 - 3, characterized by - generating and maintaining an agitated layer (L) surrounding the reactor rotor of non-fluidized finely divided material containing š~§eè particles a size of approximately 1-50 µm, with a radial extent (D) of at least 2. 2 - 8 cm, preferably at least 3 cm and at most 6 cm between the rotor (3) and the inside of the reactor housing (2). Method according to claim 2, comprising providing a rotor (3) with a helical structure by means of rotor arms (16) distributed helically one after the other along a rotor axis (5), and driving the rotor in rotation in order to generate and maintain a particle layer (L) surrounding the rotor of substantially homogeneous radial depth (D) by means of the rotor arm tips (17) distributed evenly over the periphery of the rotor.