Steam Cracking Heat Recovery for High Air Preheat Efficiency
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Solution Overview
Problem
Existing steam cracking processes face challenges in achieving high air preheating temperatures and efficient heat recovery, leading to suboptimal energy utilization and increased carbon dioxide emissions, particularly in scenarios with electrified components.
Innovation Solution
A method and system that prioritizes flue gas heat for air preheating and cracked gas heat for preheating process gas and feed, using multistream heat exchangers to achieve high air preheating temperatures exceeding 400°C, optimizing heat exchange between compatible media to reduce fuel gas usage and enhance energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If flue gas heat is used for air preheating in conventional proportions, then air preheating temperature is limited, but heat recovery efficiency and energy utilization are suboptimal
Solution Approach 1:
The patent segments the heat recovery process into distinct functional units: a flue gas heat recovery unit dedicated to air preheating, and a cracked gas heat recovery unit for process gas preheating. This segmentation allows each unit to operate at optimal temperature levels and heat exchange efficiency, enabling air preheating temperatures exceeding 400°C while maintaining overall energy efficiency.
Solution Approach 2:
The patent introduces multistream heat exchangers as intermediary devices that facilitate efficient heat transfer between flue gas and air, and between cracked gas and process gas. These heat exchangers act as mediators that maximize heat recovery while enabling the system to achieve high air preheating temperatures without compromising energy utilization efficiency.
2Use of energy by moving object
If high air preheating temperatures are achieved, then fuel gas consumption is reduced, but heat exchange efficiency between incompatible media becomes challenging
Solution Approach 1:
The patent employs multistream heat exchangers as intermediary devices that facilitate efficient heat transfer between flue gas and air, and between cracked gas and process gas. These heat exchangers act as mediators that maximize heat recovery while enabling the system to achieve high air preheating temperatures without compromising energy utilization efficiency.
Solution Approach 2:
The patent optimizes heat exchange parameters by matching compatible media: flue gas heat is applied to air preheating, and cracked gas heat is applied to process gas preheating. This parameter matching approach maximizes heat transfer efficiency and enables high air preheating temperatures with reduced fuel gas consumption.
3Loss of energy
If conventional heat recovery proportions are maintained (35-50% in radiant zone), then system simplicity is preserved, but energy utilization and CO2 emissions are suboptimal
Solution Approach 1:
The patent segments the heat recovery process into distinct functional units: a flue gas heat recovery unit dedicated to air preheating, and a cracked gas heat recovery unit for process gas preheating. This segmentation allows each unit to operate at optimal temperature levels and heat exchange efficiency, enabling air preheating temperatures exceeding 400°C while maintaining overall energy efficiency.
Solution Approach 2:
The patent fundamentally changes the heat recovery parameter distribution: the flue gas heat recovery unit is configured to use a first proportion of more than 35% (preferably 60-80%) of recovered heat for air preheating, while the cracked gas heat recovery unit uses a second proportion of more than 35% for process gas preheating. This parameter optimization achieves superior energy utilization and reduced CO2 emissions.
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 approach achieves high radiant zone efficiency with reduced fuel gas consumption, lowering carbon dioxide emissions and energy demand, while maintaining safety and flexibility in steam cracking operations.
Implementation Method 1
the flue gas heat recovery section comprises heat exchange structures which are provided in an amount and a configuration such as to use, at least during a part of the steam cracking operation, a first proportion of more than 35% of a total amount of heat recovered within the one or more heat exchangers of the flue gas heat recovery section from the flue gas for preheating the oxidizer gas
Implementation Method 2
the cracked gas heat recovery section is configured such as to use, at least during the same part of the steam cracking operation, a second proportion of more than 35% of a total amount of heat recovered within the one or more heat exchangers of the cracked gas heat recovery section for preheating the process gas and/or the hydrocarbon feed
Implementation Method 3
using multistream heat exchangers to achieve high air preheating temperatures exceeding 400°C, optimizing heat exchange between compatible media
Data Source
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AI summary
A method of steam cracking using a steam cracking system including one or more fired radiant sections is provided herein, wherein, during a steam cracking operation, a fuel is combusted with oxidizer gas to heat the one or more fired radiant sections, forming a flue gas, a process gas is formed using a hydrocarbon feed and process steam, and the process gas is passed through one or more coils in the one or more fired radiant sections, forming a cracked gas, wherein at least a part of the flue gas is cooled in a flue gas heat recovery section, wherein at least a part of the cracked gas is cooled in a cracked gas heat recovery section, wherein the flue gas heat recovery section and the cracked gas heat recovery section each comprise one or more multistream heat exchangers. The flue gas heat recovery section comprises heat exchange structures which are provided in an amount and a configuration such as to use, at least during a part of the steam cracking operation, a first proportion of more than 35% of a total amount of heat recovered within the one or more multistream heat exchangers of the flue gas heat recovery section from the flue gas for preheating at least a part of the oxidizer gas, and wherein the cracked gas heat recovery section is configured such as to use, at least during the same part of the steam cracking operation, a second proportion of more than 35% of a total amount of heat recovered within the one or more multistream heat exchangers of the cracked gas heat recovery section for preheating at least a part of the process gas and/or the hydrocarbon feed and/or the process steam. A corresponding system is also part of the present invention.