Oxy-fuel Cracking Furnaces Using Recycled CO2
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Solution Overview
Problem
Conventional ethylene and propylene production through steam cracking generates significant greenhouse gases and pollutants, such as CO2 and NOx, posing environmental concerns due to high energy consumption and emissions.
Innovation Solution
Implementing a process that recycles CO2 as a working fluid in ethylene and propylene cracker units, utilizing oxy-fuel combustion and molecular sieve packed beds to minimize heat loss and emissions, and integrating heat exchange to generate power and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional steam cracking is used to produce ethylene and propylene, then high temperatures and steam-hydrocarbon ratio are required to achieve cracking reactions, but this generates large amounts of CO2 and other greenhouse gases
Solution Approach 1:
The patent changes the combustion parameters by using oxy-fuel combustion with pure oxygen instead of air, and by recycling CO2 back to the combustion chamber. This transforms the harmful CO2 emission into a reusable working fluid, fundamentally changing the parameter of oxidizer composition and CO2 concentration in the system.
Solution Approach 2:
The patent converts the harmful CO2 emission from the cracking process into a beneficial working fluid for oxy-fuel combustion. The CO2 that would normally be discarded is instead recycled to the combustion chamber where it serves as both a heat transfer medium and a component of the oxy-fuel mixture, turning the harmful emission into a useful resource.
2Power
If air is used as the oxidizer in combustion, then combustion can proceed, but NOx emissions are generated
Solution Approach 1:
The patent creates an inert combustion environment by using pure oxygen instead of air as the oxidizer. This eliminates nitrogen from the combustion atmosphere, thereby preventing the formation of NOx compounds while still allowing combustion to proceed effectively.
3Object-generated harmful factors
If CO2 is recycled as working fluid in oxy-fuel combustion, then CO2 emissions are reduced, but the system complexity increases
Solution Approach 1:
The recycled CO2 serves multiple functions within the system: it acts as a heat transfer medium in the combustion chamber, participates in the oxy-fuel combustion reaction, and can be reused as the working fluid in the cracking process. This multi-functionality reduces the need for additional separate systems.
Solution Approach 2:
The system is designed to be self-sufficient by recycling its own CO2 emissions back into the combustion process. The CO2 produced during cracking is captured and returned to the combustion chamber, creating a self-regulating cycle that reduces external CO2 emissions without requiring external intervention.
4Productivity
If high temperatures are used in cracking to achieve high conversion, then ethylene and propylene yield increases, but energy consumption increases
Solution Approach 1:
The patent implements continuous heat recovery by capturing the heat from the effluent stream and using it to preheat the feed stream and generate steam. This continuous heat exchange process ensures that thermal energy is continuously recovered and reused, reducing the net energy input required for cracking while maintaining high conversion temperatures.
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 significantly reduces CO2 emissions, minimizes heat loss, and lowers the carbon footprint of ethylene and propylene production, while also eliminating NOx emissions by using pure oxygen as an oxidizer, making the process more energy-efficient and environmentally friendly.
Implementation Method 1
CO2 is circulated through the combustion chamber and/or furnace to absorb heat from the combustion process and transfer it to the hydrocarbon feedstock
Implementation Method 2
molecular sieve packed beds to minimize heat loss and emissions
Implementation Method 3
oxy-fuel combustion
Implementation Method 4
using pure oxygen as an oxidizer
Implementation Method 5
integrating heat exchange to generate power and reduce energy consumption
Data Source
AI summary
Disclosed is an ethylene and/or propylene cracker unit that uses recycled carbon dioxide as a working fluid. A boiler may also use recycled carbon dioxide as a working fluid. In either instance, instead of releasing high-purity CO2 into the atmosphere, the bulk of the CO2 is utilized as the working fluid and the produced CO2 is captured and sent to the pipeline for utilization or storage. These systems will minimize heat loss and achieve essentially zero CO2 emission to the air.