Pyrolysis System

Abstract

A mid-span support system for a pyrolysis tube 1 comprises a metal strap 9 adapted to extend within the pyrolysis chamber 2 and at least partially wrap around the pyrolysis tube, as well as an adjusta

Description

Title: Pyrolysis system 21 05 25 Description Introduction and background to the invention This invention relates to an improved support system for pyrolysis tubes used in high temperature 5 industrial processes. Pyrolysis tubes must withstand significant thermal stresses while resisting failure modes such as creep and corrosion. The disclosed support system aims to minimize static stresses on the pyrolysis tube by providing an external mid-span support to counteract the tube's self-weight. This approach enhances longevity and reliability compared to existing supports focused only on accommodating thermal expansion and hogging deflection. 10 Pyrolysis Tubes are crucial components in high-temperature environments, subject to significant temperature differentials and thermal stresses. Typically manufactured from specialized alloys with high coefficients of thermal expansion, these tubes are susceptible to creep and stress corrosion cracking, particularly in corrosive environments. The costly replacement of these tubes, owing to the specialized materials involved, underscores the necessity of extending their lifespan. 15 The present invention addresses this challenge by introducing a novel approach to supporting Pyrolysis Tubes. Unlike previous solutions primarily focused on accommodating thermal expansion, this invention aims to minimize static stresses induced by the tube's self-weight, auger, and material contents. By doing so, it mitigates stress corrosion cracking, creep, and other failure modes, thereby prolonging the life of Pyrolysis Tubes. 20 This invention supports the Pyrolysis Tube in a manner that minimizes bending moments while allowing unrestricted thermal expansion and hogging movement. By minimizing stresses experienced by the Pyrolysis Tube, it enhances the durability and reliability of pyrolysis systems, addressing a critical need in the field of waste processing and resource recovery. Summary of the Invention (Also known as a 'statement of invention') 25 In summary, the invention provides a Mid-Span Support system for Pyrolysis Tubes that effectively reduces static stresses resulting from the weight of the tube and its contents. By counteracting these downward forces with a Lifting Device external to the Pyrolysis Chamber, the Mid-Span Support mitigates bending moments on the tube, enhancing longevity and reliability compared to existing supports that primarily accommodate thermal expansion and hogging. 30 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 continued stress. 35 Fatigue - a failure mechanism that involves the cracking of materials and structural components due to cyclic stress. 21 05 25 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 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 5 change in temperature. Static Stress - A stress that results from a slowly applied load and which does not involve any acceleration forces. Stress corrosion cracking - is the growth of crack formation in a corrosive environment. List of Figures 10 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. Figure 2 shows an isometric drawing of the Mid-Span Support. Figure 3 shows a schematic diagram of the Mid-Span Support with a sprung Lifting Device. 15 Figure 4 shows a schematic diagram of the Mid-Span Support with a gravitational pulley system Lifting Device. Figure 5 shows a schematic diagram of the Mid-Span Support with a gravitational lever system Lifting Device. Figure 6 shows a schematic diagram of the Mid-Span Support with a fluidic Lifting Device. 20 Figure 7 shows a schematic diagram of the Mid-Span Support with a Spreader Beam and a single Lifting Device. Figure 8 shows a schematic diagram of the Mid-Span Support with two Lifting Devices but without a Spreader Beam. Figure 9 shows a schematic diagram of the Mid-Span Support not located mid-way between the main 25 supports. Figure 10 shows a schematic diagram of the more than one Mid-Span Supports. Figure 11 shows a sectional elevation of a Mid-Span Supporting system with a pneumatic Lifting Device without a Spreader Beam. Figure 12 shows a sectional drawing of the Supporting Strap in the lowered and raised position. 30 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 Tube (3) that is fixed in position. The feeder tube (3) has a smaller outer diameter than the internal diameter 35 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, essential for durability in pyrolysis environments. 5 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 within the Pyrolysis Chamber. The pyrolysis system operates within specific temperature and pressure ranges to facilitate efficient 10 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 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. 15 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 end of LO the Pyrolysis Chamber. The sliding support (6) is also a pinned support. The sliding support prevents 20 vertical and lateral movement but allows axial movement and rotation about a horizontal axis. LO 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 hogging, in the vertical plane. By permitting these movements without constraint, these supports effectively 1““ minimize thermal stresses on the Pyrolysis Tube, thereby prolonging its lifespan. The bent tube CXI 25 (hogged) position is illustrated by the dotted line (7). 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. The support configuration detailed in the prior art primarily addresses unrestricted thermal 30 expansion to reduce thermally induced stresses on the Pyrolysis Tube. However, the present invention introduces a novel Mid-Span Support system designed to specifically target static stresses resulting from the self-weight of the Pyrolysis Tube, auger, and material. This Mid-Span Support system comprises a Supporting Strap (9) and a Lifting Device (8) positioned outside the Pyrolysis Chamber (2). By effectively counteracting the downward forces exerted by the 35 tube and its contents, the Mid-Span Support mitigates static stresses, thereby enhancing the longevity and reliability of the pyrolysis system. Traditional supports in hot arduous environments are often made from refractory materials, which typically work in compression only and must support the tube from beneath. The rigid nature of these refractory supports means that they cannot provide support to the Pyrolysis Tube when the 40 Pyrolysis Tube lifts up off the support due to hogging movement. Other traditional supports are bottom supported with a support that can move vertically. These supports include a moving interface between the support and the stationary Pyrolysis Chamber. If the pyrochamber is heated with hot exhaust gases, these interfaces are prone to clogging with dust and deposits since they are located at the bottom of the chamber. The novelty of this invention lies in its ability to accommodate large axial, vertical, and lateral 5 movements (typically 50mm, 25mm, and 25mm, respectively). This flexibility allows for greater adaptability to dynamic conditions, minimizing stress concentrations and extending the Pyrolysis Tube's lifespan. Another novel aspect is the design of the support strap, which penetrates through the roof of the Pyrolysis Chamber. This design feature reduces the risk of fouling from particles and deposits within 10 the moving joint or seal between the Pyrolysis Chamber and the support. By mitigating fouling issues, the invention improves reliability and reduces the need for frequent maintenance, enhancing operational efficiency. Additionally, the Mid-Span Support is not essential for the operation of the Pyrolysis Tube. It can be considered as a "bonus" to extend the life of the Pyrolysis Tube. Failure of the Supporting Strap (9) 15 before a planned shut down only reduces the Pyrolysis Tube life rather than stops the process. This means that the Supporting Strap does not need to be over-engineered and can be designed for cost effectiveness. This is another novel aspect of the invention. By specifically targeting static stresses, the present invention offers a complementary solution to existing approaches, enhancing the overall durability and reliability of pyrolysis systems. 20 The Lifting Device (8) is not necessarily a spring. Other devices such as fluid powered devices using pneumatic or hydraulic cylinders, or gravity powered devices such as counter balanced levered LO device or pulley device could be employed for this purpose. The Lifting Device (8) provides a lifting force to counteract the downward force due to the weight of 1““ the Pyrolysis Tube and the weight of the waste and auger contained within the tube. The Lifting CXI 25 Device is designed so that the amount of upward force can be changed by for example changing the lever arm or counterweight, changing the hydraulic or pneumatic pressure, or by changing the spring pre-load or spring rate. In some circumstances, it may be advantageous to reduce the load applied by the Lifting Device to reduce the load on the Supporting Strap (9). This is because the Supporting Strap is exposed to high operating temperatures and may suffer from creep if the stress is above the 30 creep rupture strength of the material. The Lifting Device (8) is designed to accommodate changes in the vertical axis due to: hogging of the Pyrolysis Tube, thermal expansion of the Supporting Strap and long-term creep of the Supporting Strap. Figure 2 shows an isometric view of the Pyrolysis Tube support system showing the Mid-Span Support in context with the pinned supports. The sides of the Pyrolysis Chamber (2) have been 35 hidden for clarity. In Figure 2, the Supporting Strap (9) wraps around the Pyrolysis Tube (1) and exerts an upward force onto the Pyrolysis Tube. If the Pyrolysis Chamber (2) is heated using exhaust gases, then seals (10) are required to prevent or minimise the egress of exhaust gases or ingress of air where the Supporting Strap penetrates the roof of the Pyrolysis Chamber. A Spreader Beam (11) connects both ends of the Supporting Strap (9) to a Lifting Device (12). The Lifting Device (12) is 40 connected to a Static Supporting Structure (13). In this implementation the Lifting Device is shown as a counterbalanced, levered device. The adjustable Lifting Device is a key feature of the invention, allowing the upward force on the MidSpan Support to be tuned for optimal static stress reduction. The amount of lifting force can be varied by methods including adjusting a counterweight, altering a lever arm, changing pneumatic or hydraulic pressures, or modifying a spring preload. This adjustability ensures bending stresses are minimized as the load in the Pyrolysis Tube changes during operation or over its lifetime 5 There are several different configurations for the Mid-Span Support system. These are detailed in figures 3, 4, 5, 6, 7 &8. In Figure 3, the Supporting Strap (9) is attached to a sprung Lifting Device (14). The Lifting Device (14) is connected to a Static Supporting Structure (13). In Figure 4, the Supporting Strap (9) is attached to a gravitational Lifting Device (15) comprising a 10 counterweighted pulley system. The Lifting Device (15) is connected to a Static Supporting Structure (13). In Figure 5, the Supporting Strap (9) is attached to a gravitational Lifting Device (16) comprising a counterweighted lever system. The Lifting Device (16) is connected to a Static Supporting Structure (13). 15 In Figure 6, the Supporting Strap (9) is attached to a fluidic Lifting Device (17) comprising a pneumatic or hydraulic cylinder system. The Lifting Device (15) is connected to a Static Supporting Structure (13). LO In Figure 7, the Supporting Strap (9) is connected to a Spreader Beam (11) so that a single Lifting £\J Device (18) is required to provide the uplift force. LO 20 In Figure 8, the Supporting Straps (9) are connected to two Lifting Device (19). A Spreader Beam is not required. __ Although the optimal location of the Mid-Span Support for minimising bending moment stresses is to locate it halfway between the fixed pinned support (5) and sliding pinned support (6), the Mid-Span Support can be located anywhere between the main supports. This is illustrated in Figure 9. 25 Furthermore, the static stresses on the Pyrolysis Tube can be further reduced by using more than one Mid-Span Support. This is illustrated in Figure 10 where three supports are shown by way of example. In cases where the support is not located centrally, or there is more than one support location, then it is not correct to call the support "Mid-Span Support", however for the purposes of this patent the 30 term "Mid-Span Support" will be used irrespective of its exact location. The Mid-Span Support strap (9) is fabricated from RA602-CA (RTM) or Inconel Alloy 617 (RTM) selected for high creep resistance and service temperature. The size and thickness of the strap are calculated to keep stresses below the alloy's creep rupture strength limit at maximum operating temperatures, preventing time-dependent deformation. 35 The Mid-Span Support system must accommodate axial, lateral and vertical movement of the Pyrolysis Tube. Figure 11 shows how this is achieved using flexible linkages (20) between the support strap (9), the Lifting Device (17) and the fixed static support (13). Figure 11 shows a pneumatic cylinder Lifting Device (17) by way of example. The shape of Supporting Strap (9) is such that the strap can be lowered so that it creates a clearance 40 gap between the Pyrolysis Tube (1) and the Supporting Strap (9). This clearance gap is to allow the Pyrolysis Tube (1) to be removed by pulling it out of the Pyrolysis Chamber (2) axially without having to remove the Mid-Span Supporting Strap (9). The clearance gap between the strap and the Pyrolysis Tube is approximately 25-50mm. The clearance gap needs to be sufficiently large to accommodate any distortion or misalignment of the Pyrolysis Tube so that the strap does not snag on the tube 5 when the Pyrolysis Tube is being removed. This is illustrated in Figure 12 which shows the Supporting Strap in the raised and in the lowered position. In this implementation, the clearance gap is achieved using a spacer (22) to set out the vertical legs of the strap away from the outer diameter of the Pyrolysis Tube. An alternative implementation is for the Supporting Strap legs to diverge away from the Pyrolysis Tube so that when the strap is lowered a clearance gap will be provided. 10 The invention's reliance on a single Supporting Strap as the only equipment exposed to the arduous environment distinguishes it from existing solutions. This simplifies the design, reduces complexity, and lowers manufacturing costs. Additionally, the strap can be designed to fail before the Pyrolysis Tube requires replacement, ensuring ease of replacement and minimizing downtime. In summary, the disclosed mid-span support system uniquely targets the static stresses experienced 15 by pyrolysis tubes, providing an adjustable counterforce to minimize bending moments. By mitigating the effects of the tube's own weight, the invention prolongs service life and enhances reliability. The simple yet effective support strap design, combined with flexibility to accommodate dynamic movements, distinguishes this invention over current solutions. With reduced maintenance needs and ease of replacing sacrificial components, this invention offers significant advantages for 20 supporting pyrolysis tubes in challenging high temperature environments. 21 05 25

Claims

ims1. A pyrolysis system comprising:a pyrolysis chamber;a pyrolysis tube within the pyrolysis chamber; anda pyrolysis tube support assembly comprising:- a mid-span support comprising a metal strap adapted to extend within the pyrolysis chamber and at least partially wrap around the pyrolysis tube; and- a lifting device positioned exterior to the pyrolysis chamber and operatively connected to the mid-span support to provide a variable adjustable upward force thereto.

2. The pyrolysis system of claim 1, wherein the lifting device is selected from the group consisting of: a sprung lifting device, a gravitational lifting device, a fluidic lifting device, and combinations thereof.21 05 253. The pyrolysis system of claim 2, wherein the gravitational lifting device comprises a counterweight and pulley system.

4. The pyrolysis system of claim 2, wherein the fluidic lifting device comprises a pneumatic or hydraulic cylinder system.

5. The pyrolysis system of claim 1, further comprising a spreader beam operatively connecting the lifting device to two ends of the metal strap.

6. The pyrolysis system of claim 1, wherein the metal strap is adapted to penetrate through a roof of the pyrolysis chamber.

7. The support assembly of claim 1, wherein a lifting force applied by the lifting device is adjustable by varying a lever arm, pressure, counterweight, spring rate or spring preload.

8. The support assembly of claim 1 .wherein the metal strap is designed to fail before the pyrolysis tube needs replacing.

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