A gas pipe exit with a device for disruption of bubbles from a gasiform fluid

Abstract

The present invention concerns a gas pipe having a downwardly directed gas pipe exit, which is adapted for exiting a gasiform fluid below a liquid surface in a vessel, such as an oil reactor vessel in a pyrolysis plant, said gas pipe exit is provided with a device for the disruption of bubbles from a gasiform fluid in the gas pipe with the downwardly directed gas pipe exit below a liquid surface, wherein the device comprises at least one external annular ring assembly externally mounted around the downwardly directed pipe exit, wherein said annular ring assembly has at least one annular gap. The invention further concerns a method of disrupting bubbles from a gasiform fluid in a gas pipe with a downwardly directed gas pipe exit below a liquid surface in a vessel, such as an oil reactor vessel in a pyrolysis plant.

Description

[0001] A GAS PIPE EXIT WITH A DEVICE FOR DISRUPTION OF BUBBLES FROM A GASIFORM FLUID

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a gas pipe having a downwardly directed gas pipe exit, which is adapted for exiting a gasiform fluid below a liquid surface in a vessel, such as an oil reactor vessel in a pyrolysis plant, said gas pipe exit is provided with a device for the disruption of bubbles from a gasiform fluid.

[0004] BACKGROUND OF THE INVENTION

[0005] It is a known phenomenon that small particles tend to attach to droplets, sometimes referred to as the small particles "piggyback ride" on droplets, referring to the phenomenon in which tiny particles, such as pollutants, aerosols attach themselves to larger liquid droplets suspended in the air and travel along with them. This phenomenon plays a significant role in various scientific fields, including, environmental studies, and disease transmission.

[0006] When a droplet is formed, it can capture smaller particles present in the surrounding air through a process known as droplet scavenging or droplet capture. The smaller particles can be solid or liquid and may include dust, pollutants, bacteria, viruses, or other microscopic substances. The attachment occurs due to various forces, including adhesion, electrostatic interactions, and diffusion.

[0007] The primary mechanism behind small particle "piggyback rides" on droplets is the relative motion between the droplets and the particles in the air. As the droplets move through the atmosphere, they encounter and collide with the smaller particles. If the forces between the droplet and the particle are strong enough, the particle can adhere to the droplet's surface. In theory the smaller the bubble, the greater the possibility of scavenging small airborne particles. In relation to a pyrolysis plant, a pipe from the pyrolysis reactor to the oil-reactor is filled with gas created in the pyrolysis reactor, and the exit of the pipe is submerged into the oil-reactor vessel below the liquid surface. At the exit of the pipe gas bubbles may form and any small particles suspended in the gas in the pipe may be caught in these bubbles and these bubbles may then transport the particles caught onto the surface of the oil reactor, which is undesirable as any such small particles should rather sink to the bottom of the reactor so that they can be transferred back into the pyrolysis reactor.

[0008] Hence, it is an object of the present invention to address the imperfections identified above in relation to gas bubbles and to provide a gas pipe exit that can reduce the amount of particles caught by the bubbles by controlling the formation of bubbles at the exit of the pipe.

[0009] SUMMARY OF THE INVENTION

[0010] This object is achieved in a first aspect of the invention by providing a gas pipe having a downwardly directed gas pipe exit, which is adapted for exiting a gasiform fluid below a liquid surface in a vessel, such as an oil reactor vessel in a pyrolysis plant, said gas pipe exit is provided with a device for the disruption of bubbles from a gasiform fluid in the gas pipe with the downwardly directed gas pipe exit below a liquid surface, wherein the device comprises at least one external annular ring assembly externally mounted around the downwardly directed pipe exit, wherein said annular ring assembly has at least one annular gap.

[0011] In a second of the invention, there is provided a method of disrupting bubbles from a gasiform fluid in a gas pipe with a downwardly directed gas pipe exit below a liquid surface in a vessel, such as an oil reactor vessel in a pyrolysis plant, whereby the method comprises the steps of

[0012] - providing a flow of a gasiform fluid in a gas pipe with a downwardly directed gas pipe exit, and

[0013] - releasing the gasiform fluid at the gas pipe exit below the liquid surface in the vessel thereby causing a phase-change of a majority of the gasiform fluid into liquid as well as a formation of gas bubbles, and - disrupting the formation of bubbles in the region of the gas pipe exit by providing an annular ring assembly around the pipe exit having a small substantially annular gap, whereby any bubbles are forced radially sideways and thereby passing the lower surface of the annular ring assembly.

[0014] By the invention, it is advantageously found that it is possible to break down any large bubbles containing many and typically very small black carbon particles into smaller bubbles and this bubble breaking device according to the invention may cause the capture of a large part of the air borne particles into the liquid itself so that they may fall to the bottom for removal from the liquid, e.g. by reintroduction to the pyrolysis reactor.

[0015] As the exit pipe is equipped with the externally mounted annular ring around the pipe exit so that a thin annular gap is provided, this assembly ensures that the large bubbles are trapped and are being broken up into smaller bubbles that can be released through smaller gap.

[0016] In relation to a pyrolysis plant, the purpose of this "catching" of bubbles is in principle to facilitate the capture and scavenging of small airborne black carbon particles in the process. The particles are unwanted in the downstream process, and it is a desire to force as many of these particles to be transported out of the process together with the majority of the black carbon though the intended black carbon exit in the bottom of the oil reactor.

[0017] By the invention it is realised that the pipe exit may be provided with the device for breaking bubbles, or the device may be retrofitted to an existing pipe exit structure.

[0018] It is further found advantageous that the at least one ring has a lowermost surface, which is provided with at least one annular indentation, such as an inverted V-shaped groove. The bubbles will move along the lowermost surface of the ring, so by providing an uneven surface, for instance with an indentation the bubbles will be disturbed and may break into smaller bubbles. In a preferred embodiment, the external annular ring comprises a first annular ring and a second annular ring with a ring-shaped gap between said first and second rings. The ring-shaped gap may be in addition to the afore mentioned annular gap of the annular ring assembly or the ring-shaped gap between the rings is provided in addition thereto.

[0019] In an embodiment of the invention, the rings are radially wider than the gap between the rings, preferably the width is at least double as much as the gap.

[0020] In order to provide further disturbance of the bubbles travelling radially outwards from the pipe exit, each of the first annular ring and the second annular ring are preferably provided with at least one annular indentation, such as an inverted V- shaped groove.

[0021] In the preferred embodiment, the downwardly directed gas exit is vertically oriented. This ensures an efficient bubble breaking and liquification of the gas when being filled into the vessel, such as an oil reactor vessel in a pyrolysis plant.

[0022] In the present disclosure, the terms breaking of bubbles or disruption of bubbles are used synonymously and refers to any action of reducing the size of the bubbles of gasiform fluids, dispersing the bubbles in the liquid or completely removing the bubbles from the liquid.

[0023] DETAILED DESCRIPTION

[0024] In the following, the invention is described in more detail with reference to the embodiments shown in the accompanying drawings, in which:

[0025] Fig. 1 is a schematic view of an embodiment of a pyrolysis plant for recycling of plastics making use of the present invention;

[0026] Fig. 2 is a schematic view of a first embodiment of the invention;

[0027] Fig. 3 is a schematic detailed view of the gas exit with the bubble disruption device of fig. 2; Figures 4 and 5 are perspective end views of a pipe exit with a bubble breaking device fitted; and

[0028] Fig. 6 is a schematic view of a second embodiment of the invention.

[0029] In fig. 1, a schematic diagram of a pyrolysis plant for recycling of plastics making use of the present invention is shown.

[0030] In this pyrolysis plant, a residual polymer product (also referred to as waste plastic) is fed to a densifier 101 wherein the product is compressed, preferably at a ratio of 2-3.5, by screw conveyors 111. A vapour outlet 121 is provided to release water vapour released from the residual polymer products being compressed. By removing the water vapour, vapour explosions in the system may be avoided as well as it is avoided that the pyrolysis oil produced is being oxidized. The compressed residual polymer product is forwarded through a degas feeder 101a, where a pH regulating additive, preferably Calcium Oxide (CaO), is added through an inlet 132 at the entry region in the degas feeder 101a. The Calcium Oxide is then mixed with the residual polymer product quickly in the degas feeder 101a. During the travel through the degas feeder the residual polymer product is heated in a heatable pipe 131. In a first section 102a the product is heated to 180-220°C and in a second section 102b, 102c further heated to approx. 200-280°C. The residual polymer product is then fed into the degasser 102. In the degasser 102 the residual polymer product is moved substantially horizontally by a screw conveyor 112 through three heating zones 102a, 102b and 102c. In the degasser 102, the zones heat the media, i.e. the residual polymer product, up to max. 240°C in the first zone 102a and heat the media up to max. 260°C in the second zone 102b and up to max. 280°C in the third zone 102c. A gas outlet 122b is provided above at least the zones 102b and 102c as shown in the fig. 1. Inside the degasser 102 the pressure is within the range of 0.1 to 1 bar, such as 0.2-0.45 bar.

[0031] The residual polymer product, also referred to as the media or plastic pulp is then transferred to the pyrolysis reactor 103 through a pipe conveyor 150 containing a transport screw conveyor. The degasser, which is horizontally oriented, and the pyrolysis reactor, which is tilted upwards, are connected so there is a fluid communication between the outlet 122a at the bottom of the degasser 102 and the inlet 123a at the lowermost region of the tilted pyrolysis reactor 103. As indicated in fig. 1 the liquid level 191 is about the same as in the degasser 102.

[0032] The pyrolysis reactor 103 preferably comprises two screw conveyors 113, preferably arranged in parallel hence only one is shown in fig. 1. The screw conveyors 113 are conveying the residual polymer product and mixing the product whilst lifting upwards and out of the liquid level towards a black carbon outlet 123b at the top of the reactor 103. The pyrolysis liquid in the reactor 103 is heated by a heater, such as an electrical heater, for heating the residual polymer product to a temperature of up to max. 500 °C to generate pyrolysis vapour. The heating can be arranged in heating zones. The pressure inside the pyrolysis reactor 103 is similar to the pressure of the degasser, i.e. 0.1 to 1 bar, such as 0.2-0.45 bar.

[0033] The pyrolysis vapour is released from the reactor 103 via a reactor vapour outlet 123c. The reactor vapour outlet 123c is away from the dry portion of the reactor to avoid dripping of any condensed vapour onto the dried black carbon. Towards the end of the reactor screw conveyors 113 substantially all of the residual polymer product will have been decomposed and a solid fraction comprising black carbon residue will leave the process in the end of the reactor 103. The black carbon is transported out of the reactor 103 via the black carbon outlet 123b placed in the reactor to receive the black carbon. At the outlet 123b a black carbon screw conveyor 133 may be arranged in extension of the black carbon outlet 123b for transferring the black carbon to a container. Advantageously, also a gas lock valve (not shown) may be provided to ensure that no gases escape through the black carbon outlet 123b.

[0034] The pyrolysis vapour released from the reactor 103 via a reactor vapour outlet 123c is fed into the oil reactor 104. The oil reactor 104 functions as a vapourliquid separator. The reactor vapour outlet pipe 123c is positioned in the oil reactor 104 such that the pipe exit 123d is below the liquid level 104d in the oil reactor 104. The oil reactor 104 may be heated in three zones 104a, 104b and 104c as indicated in fig. 1. In each zone the pyrolysis vapour product is heated to max. 450 °C. The pyrolysis vapour is released into the oil reactor 104 below the liquid level as shown in the fig. 1. If the product liquefies in the oil reactor 104 and fall to the bottom thereon, this heavy oil and any solid particles is returned to the pyrolysis reactor 103 via the pipe 124c for further decomposition in the pyrolysis reactor 103.

[0035] In the top of the oil reactor 104 two outlets 124a, 124b are provided for transferring vapour components to the two reflux condensers 105a, 105b. All the pyrolysis vapour enters at the bottom of each of the reflux condensers 105 and exits at the top of the reflux condensers 105a, 105b with a temperature of max. 260°C. From the top of the reflux condensers 105a, 105b, the pyrolysis vapour is led to the raw pyrolysis oil (RPO) condensers 106a and 106b, where the vapour is condensed to heavy products (Raw Pyrolysis Oil or RPO) with an outlet temperature of approx. 150-180°C. Furthermore, pyrolysis vapours are transferred to the Nafta Pyrolysis Oil condenser 107, in which the vapours are condensed and chilled and exits as a light product at a temperature of 10-35°C.

[0036] With reference to fig. 2, a first embodiment of the invention is shown where the bubble breaking device is implemented in the oil reactor 104 of the abovedescribed pyrolysis plant. As mentioned above, the reactor vapour outlet pipe 123c is positioned in the oil reactor 104 such that the pipe exit 123d is below the liquid level 104d in the oil reactor 104.

[0037] In figures 2 and 3 there is shown a schematic cross-sectional view of the oil reactor 104 where the gas pipe 123c is supplying gasiform fluids, such as vapourised oil, to the oil reactor 104. The gas pipe 123c has a downwardly directed gas pipe exit 12, which is positioned for exiting the gasiform fluid below a liquid surface 104d of the reactor vessel 104 in the pyrolysis plant. The gas is supplied into the oil reactor 104 or vessel as the gasiform fluid at the gas pipe exit below the liquid surface in the oil reactor 104 thereby causing a phase-change of a majority of the gasiform fluid into liquid as well as a formation of gas bubbles 14. The gas pipe exit 12 is provided with a device 10 for the disruption of the bubbles 14 from a gasiform fluid. Thus, the device 10 is provided for the disruption of bubbles 14 from a gasiform fluid in a gas pipe 123c with the downwardly directed gas pipe exit 12, which is below a liquid surface 104d. In the embodiment schematically shown in figures 2 and 3, the device 10 comprises a first annular ring 11 and a second annular ring 11' with a ring-shaped gap 13 between said first and second rings 11, 11'. With reference to the cylindrical gas pipe 123c, the rings 11, 11' are radially wider than the gap 13 between the rings 11, 11', for instance the width of the rings 11, 11' is at least double as much as the gap 13. As shown in the figures, each of the first annular ring 11 and the second annular ring 11' are provided with an uneven lower surface, in particular an annular indentation 15 in the form of an inverted V- shaped groove as shown in the figures. However, it is realised by the invention that other suitable irregular surface shapes may be provided.

[0038] In the figures 2 and 3, the annular rings are shown having the same cross- sectional shape. However, it is realised by the invention that this is not necessary and the annular rings may have different sizes and cross-sectional shapes. Likewise the number of substantially concentric annular rings may differ and the gaps (if there are more than one gap) between the rings and the grooves in the rings may vary in size. Furthermore, it is realised that the annular ring configuration must not be in the same plane.

[0039] By the double ring and annular gap, the bubbles 14 are then only able to leave the exit pipe 12 by breaking into smaller bubbles 14' at escape through the gap 13 or leave on the perimeter of the outermost ring 11'. Due to the groove 15, the bubbles 14 are being disturbed as they travel radially away from the gas pipe exit and the bubbles 14 are there also being disrupted and broken into small bubbles 14'.

[0040] The lowermost surfaces of the rings 11, 11' with the indentations 15 are also shown in figures 4 and 5, where the gas pipe 123c with the bubble breaking device 10 is shown in two perspective views. In this variant of the embodiment, it can be seen that in addition to the V-shaped annular groove 15 a number of discrete indentations 13' may be provided in the annular edge regions of the rings 11, 11' as well as some assembly elements 13" may be provided in order to mount the rings 11, 11' of the device 10 in the predetermined positions. With reference to fig. 6, in a most simple, second embodiment, the device 10 comprises only one external annular ring 11 externally mounted around the downward-facing pipe exit 12 with a small annular gap 13 between the gas pipe exit 12 and the ring 11. The lowermost surface of the ring 11 is also in this embodiment preferably provided with an uneven surface, such as an uneven surface with one or more inverted V-shaped grooves 15. The uneven surface pattern could also be other patterns either irregular or regular as long as the unevenness contributes to the disruption of larger bubbles passing along the surface.

[0041] Above, the invention is described with reference to some currently preferred embodiments. However, by the invention it is realised that other embodiments and variants may be provided without departing from the scope of the invention as defined in the accompanying claims. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

CLAIMS1. A gas pipe having a downwardly directed gas pipe exit, which is adapted for exiting a gasiform fluid below a liquid surface in a vessel, such as an oil reactor vessel in a pyrolysis plant, said gas pipe exit is provided with a device for the disruption of bubbles from a gasiform fluid in the gas pipe with the downwardly directed gas pipe exit below a liquid surface, wherein the device comprises at least one external annular ring assembly externally mounted around the downwardly directed pipe exit, wherein said annular ring assembly has at least one annular gap.

2. A gas pipe according to claim 1, wherein the at least one ring has a lowermost surface, which is provided with at least one annular indentation, such as an inverted V-shaped groove.

3. A gas pipe according to claim 1 or 2, wherein the external annular ring comprises a first annular ring and a second annular ring with a second ringshaped gap between said first and second annular rings.

4. A gas pipe according to claim 3, wherein the first and second annular rings are radially wider than the gap between the first and second annular rings, preferably the width is at least double as much as the gap.

5. A gas pipe according to claim 3 or 4, wherein each of the first annular ring and the second annular ring are provided with uneven surface patterns, such as irregular and / or regular patterns.

6. A gas pipe according to claim 5, wherein each of the first annular ring and the second annular ring are provided with at least one annular indentation, such as an inverted V-shaped groove.

7. A gas pipe according to any of the preceding claims, wherein the at least one external annular ring assembly is externally mounted concentrically around the downward-facing pipe exit, such that the at least one annular gap is radially uniform.

8. A gas pipe according to any of the preceding claims, wherein the downwardly directed gas exit is vertically oriented.

9. A method of disrupting bubbles from a gasiform fluid in a gas pipe with a downwardly directed gas pipe exit below a liquid surface in a vessel, such as an oil reactor vessel in a pyrolysis plant, whereby the method comprises the steps of- providing a flow of a gasiform fluid in a gas pipe with a downwardly directed gas pipe exit, and- releasing the gasiform fluid at the gas pipe exit below the liquid surface in the vessel thereby causing a phase-change of a majority of the gasiform fluid into liquid as well as a formation of gas bubbles, and- disrupting the formation of bubbles in the region of the gas pipe exit by providing an annular ring assembly around the pipe exit having a small substantially annular gap, whereby any bubbles are forced radially sideways and thereby passing the lower surface of the annular ring assembly.

10. A method according to claim 9, whereby the downwardly directed gas exit is according to any one of claims 1 to 8.

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