Composite Ceramic Reaction Tube With Integrated Electric Heating
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Solution Overview
Problem
Current reaction tubes used in the chemical industry for endothermic processes, such as steam cracking, face limitations due to the maximum outer tube wall temperature being restricted to 1100°C, leading to inefficiencies in heat transfer and energy consumption, and the use of metallic materials which are not suitable for higher temperatures and pressures due to brittleness and thermal conductivity issues.
Innovation Solution
A multi-layer composite pipe design featuring a non-openly porous monolithic oxide ceramic inner layer and an oxidic fiber composite ceramic outer layer with integrated electrically conductive systems, providing enhanced heat transfer, temperature resistance, and pressure resistance, while allowing for segmented heating and temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If metallic reactor materials are used, then ease of manufacture and pressure resistance are improved, but maximum tube wall temperature is limited to 1050-1100°C
Solution Approach 1:
The patent employs a composite structure consisting of an inner layer made of monolithic oxide ceramic (providing high temperature resistance up to 1800°C) and an outer layer made of fiber-reinforced oxide ceramic (providing mechanical strength and fracture toughness). This composite design enables the reactor tube to withstand temperatures exceeding 1100°C while maintaining structural integrity and pressure resistance, overcoming the limitations of both pure metallic and pure ceramic materials.
2Temperature
If monolithic oxide ceramic is used, then temperature resistance is improved, but brittleness and reliability are worsened
Solution Approach 1:
The patent combines monolithic oxide ceramic (inner layer) with fiber-reinforced oxide ceramic (outer layer). The fiber reinforcement in the outer layer significantly enhances fracture toughness and prevents catastrophic failure, while the monolithic inner layer provides the primary high-temperature barrier. This composite approach achieves both high temperature resistance and improved reliability.
Solution Approach 2:
The patent applies different ceramic material properties to different regions of the tube wall. The inner layer uses dense monolithic ceramic optimized for thermal barrier properties, while the outer layer uses porous fiber-reinforced ceramic optimized for mechanical strength and damage tolerance. This localized material differentiation optimizes both temperature resistance and fracture resistance.
3Use of energy by moving object
If external combustion heating is used, then energy input is improved, but heat transfer efficiency and energy consumption are worsened
Solution Approach 1:
The patent replaces the conventional external combustion heating system with an internal electric heating system. Electrical heating elements are integrated within the reactor tube structure, allowing direct heating of the reaction zone. This substitution eliminates the need for external combustion, reduces heat transfer losses through the tube wall, and improves overall energy efficiency by heating the process fluid directly.
4Productivity
If higher outer tube wall temperature is used, then heat transfer for cracking reactions is improved, but coke deposits and energy consumption increase
Solution Approach 1:
By replacing external combustion heating with internal electric heating, the system achieves higher cracking reaction efficiency through direct heating of the reaction zone without requiring elevated outer wall temperatures. This eliminates the thermal insulation effect of coke deposits on the outer wall and reduces energy consumption associated with maintaining high outer wall temperatures for heat transfer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The multi-layer composite pipe achieves a heat transfer coefficient greater than 500 W/m²K, supports temperatures up to 1300°C, and maintains pressure resistance up to 20 bar, reducing energy consumption and enabling efficient and localized heating, while preventing coking and ensuring reliable operation.
Implementation Method 1
The function of the tube walls is to transfer heat from an external heat source into the reaction volume
Implementation Method 2
an electrically conductive system is integrated
Data Source
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AI summary
The present invention relates to a gas-tight, multilayer composite pipe with a thermal transmittance coefficient of > 500 W/m²/K comprising at least two layers, the structure of which, across the cross-section of the wall of the composite pipe, has as an inner layer a non-porous monolithic oxide ceramic, which is enclosed by an outer layer of oxide fiber composite ceramic, wherein this outer layer has an open porosity ε of 5% < ε < 50%, preferably 10% < ε < 30%, wherein an electrically conductive system is integrated in the outer annular space of the multilayer composite pipe, the boundaries of which are defined on the one hand by the outer surface of the inner layer, which is formed from the non-porous monolithic oxide ceramic, and on the other hand by the outer surface of the outer layer, which is formed from an oxide fiber composite ceramic, and the use of the multilayer composite pipe as a reaction tube for endothermic reactions.Jet nozzles or rotary nozzles.