Pyrolysis tube support system

Abstract

A pyrolysis tube support system comprising: a pyrolysis tube 1 with feed and discharge ends, a fixed pinned support 5 proximate the discharge end and a sliding pinned support 6 proximate the feed end.

Description

Introduction and background to the invention Pyrolysis tubes operate at high temperatures and are exposed to large temperature differences 5 between the top and bottom. This results in the tube bending upwards due to differential thermal expansion, a condition known as hogging. Pyrolysis tubes are typically made from special alloys with high coefficients of thermal expansion. If the thermal expansion is constrained, it creates significant thermal stresses that accelerate fatigue and creep failure. This leads to a relatively short lifespan. 10 The arduous operating conditions and large differential movement due to thermal expansion also makes it difficult to achieve reliable seals between the moving pyrolysis tube and other components. Leakage can present a hazard and can reduce process efficiency. Replacing failed pyrolysis tubes is expensive due to the specialty alloys required. It is desirable to increase the lifespan of pyrolysis tubes. 15 This invention aims to prolong pyrolysis tube life by supporting the tube in a way that allows free thermal expansion and hogging without restraint. This eliminates thermal stresses. The supports are also arranged favourably for creating effective seals despite tube movements. Summary of the Invention (Also known as a ‘statement of invention’) In summary, the invention supports the pyrolysis tube in such a way that thermal induced 20 stresses are minimised, the pyrolysis tube can be effectively sealed, and that the pyrolysis tube can be effectively replaced. Definitions: Auger - a spiral shaped screw used to transfer material. Creep - a failure mode in which a material deforms or thins over time when subjected to a 25 continued stress. Fatigue - a failure mechanism that involves the cracking of materials and structural components due to cyclic stress. Hogging - is the upward bending deflection of a beam. For the purposes of this document hogging is the bending deflection of the tube due to different temperatures on the sides of the 30 tube. It is not limited to the vertical plan. Thermal expansion - is the tendency of matter to change in shape, volume, and area in response to a change in temperature. Stress corrosion cracking - is the growth of crack formation in a corrosive environment. 21 05 25 List of Figures The invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows a schematic diagram of the pyrolysis tube support system. 5 Figure 2 shows a sectional drawing of the pyrolysis tube heating chamber, support and sealing system. Figure 3 shows an isometric drawing of the pyrolysis tube hot end fixed pinned support. Figure 4 shows an isometric drawing of the cold end sliding support. Figure 5 shows a plan sectional view of the cold end sliding support. 10 Figure 6 shows a schematic diagram of a pyrolysis support system with a fixed pinned support at the cold end of the pyrolysis tube. Figure 7 shows a schematic diagram of a pyrolysis support system with a fixed pinned support at the hot end of the pyrolysis tube. Figure 8 shows a schematic diagram of a pyrolysis support system with a fixed pinned support 15 at the cold end and a sliding pinned support at the hot end of the pyrolysis tube. Detailed Description of the Invention In Figure 1, a pyrolysis tube (1) penetrates through a pyrolysis chamber (2) that provides heat to the pyrolysis tube. The material to be processed is fed into the pyrolysis tube through a feed 20 tube (3) that is fixed in position. The feeder tube (3) has a smaller outer diameter than the internal diameter of the pyrolysis tube (1) and extends a short distance into the pyrolysis tube. The pyrolysis tube discharges the material that has been pyrolysed into a separation box 4. The separation box separates the solids from the gases produced by the pyrolysis process. The pyrolysis tube (1), made from Inconel 625 (RTM), is resistant to heat and corrosion, 25 essential for durability in pyrolysis environments. The pyrolysis tube (1) is designed with dimensions to accommodate the operational requirements of the system. It features an outer diameter of approximately 500mm, a length of approximately 6000mm, and a wall thickness of approximately 20mm. These dimensions are optimized to balance structural integrity, thermal conductivity, and heat transfer efficiency 30 within the pyrolysis chamber. The pyrolysis system operates within specific temperature and pressure ranges to facilitate efficient conversion of feedstock materials. The pyrolysis tube (1) is subjected to temperatures ranging from 500 to 900C, with variations depending on the process parameters such as feedstock composition and flow rate. These operating temperatures are crucial for achieving 35 desired conversion efficiencies and extending the lifespan of the pyrolysis tube. Additionally, the system operates under a slight negative pressure which is carefully controlled to ensure safe operation of the facility. The pyrolysis tube (1) is held in position by the pyrolysis tube fixed pinned support (5) located at the hot discharge end of the pyrolysis chamber. The pinned support (5) prevents horizontal and vertical movement but allowing rotation about a horizontal axis of the pin. The pyrolysis tube (1) is supported by the pyrolysis sliding support (6) located at the cold feed 5 end of the pyrolysis chamber. The sliding support (6) is also a pinned support. The sliding support prevents vertical and lateral movement but allows axial movement and rotation about a horizontal axis. The pyrolysis tube fixed pinned support (5) and the sliding pinned support (6) allow the pyrolysis tube to expand axially towards the cold feed end while enabling unrestricted bending, or 10 hogging, in the vertical plane. By permitting these movements without constraint, these supports effectively minimize thermal stresses on the pyrolysis tube, thereby prolonging its lifespan. The bent tube (hogged) position is illustrated by the dotted line (7). The fixed pinned support (5) has a small clearance gap between the pin and socket typically as a loose running fit C11 / h11. Although this allows a minimal amount of play both horizontally and 15 vertically, it also allows a small amount of rotation about the vertical axis of the pin support. This allows the pyrolysis tube to also bend (hog) freely without restraint on the horizontal plane, or any combination of the horizontal and vertical planes. The fixed pinned support (5) also has a 5mm clearance between the clamping ring (13) and the shoulder of the pin (14) to allow for radial expansion of the pyrolysis tube. LO 20 Additionally, the pinned supports (5 &6) provide a reaction torque onto the tube to prevent the CM pyrolysis tube from turning caused by friction with the internal waste and auger. LO The clearance gap between the feed tube (3) and the pyrolysis tube (1) is sufficient to maintain clearance under all potential expansion and hogging movements. This clearance gap is typically ___ 5-10mm. 1— CXI 25 The pyrolysis tube fixed pin support (5) and sliding support (6) ensures that the pyrolysis tube is not constrained due to thermal expansion and ensures that large thermally induced stresses are eliminated from the pyrolysis tube. Where the pyrolysis tube penetrates the separation box (4) a separation box seal (8) must be provided to prevent the release of pyrogas out of the process, or the leakage of air into the 30 process. Due to the nature of the pyrolysis process, the temperature at this location is high (circa 600C). High temperature seals with large, multi-axis movements are difficult to achieve. However, since the fixed pin support (5) is close to the separation box seal (8), axial and lateral movement is minimised making it easier to achieve a good seal in this high temperature environment. This seal is designed with robust materials and construction to accommodate the 35 large multi-axis movements of the pyrolysis tube while maintaining a reliable barrier. In certain pyrolyser configurations utilizing exhaust gases for heating, it is imperative to establish effective seals where the pyrolysis tube (1) enters the pyrolysis chamber (2). These seals situated where the pyrolysis tube penetrates the pyrolysis chamber prevent air ingress or exhaust gas leakage. By strategically locating the hot pyrolysis chamber seal (9) in proximity to 40 the pyrolysis tube fixed pinned support (5), the system minimizes axial and lateral movements, facilitating the seal's effectiveness in high-temperature environments. Additionally, the large axial tube movements due to thermal expansion occur at the cold feed end so that the cold end pyrolysis chamber seal (10) can use conventional expansion compensators in a low temperature environment. Where the feed tube (3) penetrates the pyrolysis tube (1) a pyrolysis tube seal (11) needs to be provided to prevent the release of pyrogas out of the process, or the leakage of air into the 5 process through the clearance gap between the two tubes. This seal will be operating at low temperatures and the large movements due to thermal expansion can easily be accommodated with conventional sealing devices such as expansion compensators. In summary, by locating the pyrolysis tube fixed pinned support (5) at the hot end of the pyrolysis tube, all the hot seals (8 &9) experience small movements whereas the cooler seals 10 (10 &11) accommodate large thermal expansion movements. It is easier to achieve seals with large movements if they operate at lower temperatures. Figure 2 shows the design where the pyrolysis chamber (2), separation box (4) are in section and the pyrolysis tube (1), pyrolysis tube pinned support (5), sliding support (6) and pyrolysis tube seals (8, 9,10 &11) are shown as side elevation. 15 Figure 3 shows the pyrolysis tube fixed pinned support system (5). In this embodiment, a clamping ring (13) is clamped to the pyrolysis tube (1). The clamping ring has female sockets that engage with the male support pins (14). The support pins (14) are bolted to a rigid mounting arm (15). The clamping ring (13) is clamped to the pyrolysis tube so that it can be removed when the pyrolysis tube needs to be replaced. It is advantageous if there are no permanent LO 20 protrusions beyond the outer surface of the pyrolysis tube so that the pyrolysis tube can be CM withdrawn through the pyrolysis chamber when it needs to be replaced. LO In this implementation, the support pins are arranged horizontally since the hogging movement due to differential tube temperatures are most likely to occur in the vertical plane. 1” In this embodiment, the support pins and sockets have sufficient clearance to accommodate CXI 25 differential thermal expansion of the pin and socket diameter, thermal expansion of the pyrolysis tube diameter along the axis of the pins, and hogging movement of the pyrolysis tube should it occur perpendicular to the axis of the support pins. The support pin (14) can be adjusted in vertical and horizontal alignment by releasing the fixing bolts. In this embodiment, a jacking screw (16) can be used to adjust and set the vertical 30 position. Another feature of the pyrolysis tube fixed pinned support system (5) comprising items (13,14, 15 &16), is that it is designed for simple assembly, alignment, and disassembly. Furthermore, the pyrolysis tube fixed pin support system (5) is designed to minimise intrusion into the space between the pyrolysis chamber 2 and the separation box 4 to provide better access to the hot 35 seals (8 &9). These features assist with the ease and speed of the pyrolysis tube replacement activity. Figure 4 shows the pyrolysis tube sliding support system (6). The guide rail (18) is shown sectioned so that the bearing lug (17) can be seen. In this embodiment, bearing lugs (17) are fixed to the pyrolysis tube 1. These bearing lugs are retained within a recessed guide rail (18). 40 The bearing lug slides axially upon the bottom surface of the guide rail. The sliding support (6) is additionally shown in plan sectional view in Figure 5. The axial movement of pyrolysis tube (1) due to thermal expansion is illustrated with arrows (19). The tolerances of the sliding support is important to provide full freedom of movement of the pyrolysis tube due to thermal expansion whilst still providing constraints for the sealing system and feed system. Vertical and lateral tolerance must allow for differential thermal expansion between the bearing lug and the guild rail since it is possible for the pyrolysis tube and bearing 5 lug to become significantly hotter than the supporting system. The gap between the pyrolysis tube (1) and pyrolysis chamber (2) is indicated by the dotted line region (20) and is sealed by the pyrolysis chamber seal (10). The gap between the pyrolysis tube (1) and the feed tube (3) is indicated by the dotted line region (21) and is sealed by the pyrolysis tube seal (11). Since these seals experience large axial movements but are located at the cold 10 feed end of the pyrolysis tube, conventional metallic expansion compensators or fabric expansion compensators are suitable for this application. Another aspect of the sliding support system (6) is that it is easy and simple to engage and disengage the bearing lug within the guide rail. Another feature of the sliding support system (6) is that it has a low profile so that it can be contained within a conventional expansion 15 compensator. These features assist with the ease and speed of the pyrolysis tube replacement activity. In some existing pyrolysis facilities, the pyrolysis tube (1) is fixed to the feed tube (3) with a rigid flanged connection (22). This is illustrated in Figure 6. The pyrolysis tube is allowed to expand axially towards the separation box (4). The expanded tube is illustrated with a dotted line (7). In 20 this design solution, the largest axial movements occur at the hot end of the pyrolysis tube and the hot seals (8 &9) must accommodate high temperatures and high axial movements. Another problem with this design solution is that it assumes that the pyrolysis tube has uniform temperatures across the transverse plane and that there is no hogging deflection of the pyrolysis tube. Temperature gradients across the transverse plane will occur when material is 25 transferred through the pyrolysis tube. For example, the top of the pyrolysis tube is likely to be hotter than the bottom and the pyrolysis tube will hog. Either the hot seals (8 &9) will have to accommodate large transvers movement due to the hogging deflection or the seals will constrain the hogging deflection and impart high loads and stresses onto the pyrolysis tube. In other existing pyrolysis facilities, the pyrolysis tube (1) is fixed to the separation box (4) with a 30 rigid flanged connection (23). This is illustrated in Figure 7. The pyrolysis tube is allowed to expand axially towards the feed tube (3). The expanded tube is illustrated with a dotted line (7). In this design solution, there is only one high temperature pyrolysis chamber seal (9) that must accommodate a small axial movement and the large axial movement is accommodated by the cold seals (10 &11). However, a problem with this design solution is that it assumes that the 35 pyrolysis tube has uniform temperatures across the transverse plane and that there is no hogging deflection of the pyrolysis tube. When hogging occurs, either the cold seals (10 &11) will have to accommodate large transvers movement due to the hogging deflection or the seals will constrain the hogging deflection and impart high loads and stresses onto the pyrolysis tube. Another design approach is to fix the pyrolysis tube at the cold feed end with a fixed pinned 40 support 25 and support the pyrolysis tube at the hot end with a sliding pinned support (24). This is illustrated in Figure 8. This solution the pyrolysis tube is allowed to expand axially toward the separation box and the pinned supports allow the pyrolysis tube to hog without generating large transverse deflections or large stresses. Although this embodiment is better able to accommodate hogging deflection than the embodiments given in figures 6 &7, this 45 embodiment still requires the hot seals (8 &9) to accommodate large axial movements. Furthermore, the sliding pinned support (24) must also operate at the high temperature end of the pyrolysis tube. The pyrolysis tube support system depicted in Figure 1 presents clear advantages over existing designs showcased in Figures 6, 7, &8. Notably, by eliminating constraints on hogging 5 deflection resulting from differential thermal expansion, the system enhances the longevity of the pyrolysis tube. Furthermore, by reducing the demands on sealing systems and strategically locating the sliding pinned support at the cold end of the pyrolysis tube, this innovative design minimizes stresses on critical components while optimizing operational efficiency. 10 21 05 25 05 09 25

Claims

1. A pyrolysis tube support system comprising:a. a pyrolysis tube with a feed end and a discharge end,b. a fixed pinned support at the discharge end that prevents a movement of the discharge end perpendicularly to an axis of the pyrolysis tube and a movement of the discharge end parallelly to the axis of the pyrolysis tube while allowing a rotation of the discharge end about an axis of the fixed pinned support perpendicular to the axis of the pyrolysis tube, andc. a sliding pinned support at the feed end that prevents movement of the feed end perpendicularly to the axis of the pyrolysis tube while allowing a movement of the feed end parallelly to the axis of the pyrolysis tube and a rotation of the feed end about the sliding pin support.

2. The pyrolysis tube support system accordingto claim 1, wherein the fixed pinned support comprises female sockets that engage with male support pins, wherein the male support pins are mounted on either a rigid mounting structure or a clamping ring engaged with the pyrolysis tube.

3. The pyrolysis tube support system according to claim 1 or claim 2 wherein the sliding pinned support comprises bearing lugs retained in a guide rail.

4. The pyrolysis tube support system accordingto claim 3, wherein the bearing lugs are fixed to the pyrolysis tube.

5. The pyrolysis tube support system according to claim 3 or claim 4, wherein the bearing lugs slide upon a bottom surface of the guide rail.

6. The pyrolysis tube support system accordingto claim 1 further comprising seals between the pyrolysis tube and adjacent components.

7. The pyrolysis tube support system accordingto claim 1, wherein the fixed pinned support further comprises: a. a clamping ring clamped to the pyrolysis tube; b. female sockets within the clamping ring engaging with male support pins; c. the male support pins bolted to a rigid mounting arm.

8. The pyrolysis tube support system according to claim 7, wherein the male support pins and female sockets have a clearance gap.

9. The pyrolysis tube support system according to claim 1, wherein alignment of the fixed pinned support is adjustable by: a. releasing fixing bolts securing the fixed pinned support, b. using a jacking screw to adjust a position of the fixed pinned support, and c. tightening fixing bolts securingthe fixed pinned support.

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