Radiative Recuperator Preheating Combustion Reactants
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Solution Overview
Problem
Existing methods for preheating combustion reactants in furnaces using waste heat from flue gas face safety concerns and economic limitations, particularly when dealing with oxygen and natural gas, due to the high reactivity of oxygen and the need for separate heat exchangers, which can increase capital costs and limit thermal energy recovery.
Innovation Solution
A furnace design incorporating a duct with high thermal conductivity materials and insulating walls surrounding metallic pipes, allowing for radiative and convective heat exchange without direct contact between flue gas and preheated reactants, thereby reducing safety risks and enhancing energy recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a single metallic pipe is used for direct heat exchange between flue gas and combustion reactants, then heat transfer efficiency is improved, but safety reliability deteriorates due to corrosion and potential leakage
Solution Approach 1:
The heat exchange system is divided into multiple independent components: an outer duct for flue gas, an intermediate non-reactive gas space, and inner metallic pipes for combustion reactants. This segmentation prevents direct contact between corrosive flue gas and reactive combustion gases, eliminating leakage risks while maintaining heat transfer through radiative and convective mechanisms across the gas space.
Solution Approach 2:
A non-reactive gas space filled with inert gas (nitrogen or carbon dioxide) is introduced as an intermediary medium between the flue gas duct and the combustion reactant pipes. This intermediary layer acts as a protective barrier that prevents direct chemical interaction and corrosion, while still allowing thermal energy transfer through radiation and convection, thus maintaining safety without compromising heat exchange functionality.
2Reliability
If separate heat exchangers are used for preheating air and oxygen/natural gas, then safety reliability is improved, but device complexity and capital cost increase
Solution Approach 1:
The patent combines multiple heat exchange functions into a single integrated Recuperator structure. The outer duct contains flue gas while inner metallic pipes convey both combustion air and oxygen/natural gas, all within one unified housing. This merging reduces the number of separate heat exchanger units, simplifies installation, lowers capital costs, and maintains safety through the protective non-reactive gas space that prevents contamination between different gas streams.
Solution Approach 2:
The Recuperator is designed as a multi-functional device that can simultaneously preheat multiple different combustion reactants (air, oxygen, natural gas) within a single unit. The universal design accommodates various gas types through separate metallic pipes, all protected by the same non-reactive gas space, thereby eliminating the need for multiple specialized heat exchangers and reducing overall system complexity.
3Reliability
If separate heat exchangers are used for preheating air and oxygen/natural gas, then safety reliability is improved, but thermal energy recovery is limited by preheated air temperature
Solution Approach 1:
The non-reactive gas space serves as a thermal intermediary that enables direct radiative and convective heat transfer from the hot flue gas duct to the metallic pipes containing oxygen or natural gas. This intermediary arrangement allows these highly reactive gases to be preheated to much higher temperatures than conventional air preheating (limited to ~650°C), thereby maximizing thermal energy recovery from the flue gas without the temperature constraints that apply to air preheating systems.
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
This design effectively preheats combustion reactants while minimizing safety hazards and improving economic viability by allowing for increased thermal energy recovery and reduced capital costs, enabling more efficient fuel usage and longer duct lifespan.
Implementation Method 1
Heat is exchanged between the duct and the one or more metallic pipes by radiative heat exchange
Implementation Method 2
at least portions of the duct are comprised of a material having a thermal conductivity of greater than 1 W/(m·K)
Implementation Method 3
a non-reactive gas space being defined between an outer surface of the duct and an inner surface of the insulating wall
Implementation Method 4
one or more insulating walls extending parallel to the duct axis and adjacently to an outer surface of the duct
Data Source
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AI summary
A radiative recuperator preheats oxidant and/or fuel for combustion at one or more burners of a furnace. The recuperator includes a duct, at least portions of which comprise a material having a thermal conductivity of greater than 1 W/(m•K), preferably greater than 3 W/(m•K), that receives hot flue gas produced by the burner(s). The duct radiatively transfers heat to oxidant or fuel (for preheating) flowing through one or more metallic pipes disposed in between the duct and an insulating wall.