Steam Cracking Heat Balance Using Expanded High-Pressure Steam
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Solution Overview
Problem
Existing steam cracking plants face challenges in integrating electrified components, such as electrically driven compressors and pumps, which disrupt the balanced heat and steam production, leading to inefficiencies and increased carbon dioxide emissions.
Innovation Solution
A method and system for steam cracking that includes fired furnaces with electrically driven rotating equipment, utilizing moderately superheated high-pressure steam for process heat, and adiabatically expanding it to meet specific temperature levels for efficient heat distribution and reduced emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If steam turbines are used to drive rotating equipment in conventional steam cracking plants, then mechanical energy is recovered from steam, but exergy losses increase and carbon dioxide emissions rise
Solution Approach 1:
The invention extracts steam turbines from the system entirely, replacing them with electric motors. This removes the source of exergy losses associated with steam turbine operation and eliminates the need to burn additional fuel for steam generation, thereby reducing carbon dioxide emissions while maintaining all necessary rotating equipment functionality.
Solution Approach 2:
The invention substitutes the mechanical steam turbine system with an electrical motor system. Instead of using steam expansion through turbines to drive compressors and pumps, electric motors directly provide the necessary mechanical drive, eliminating the intermediate steam generation and turbine conversion steps that cause exergy losses.
2Object-generated harmful factors
If electrified components are integrated into steam cracking plants, then carbon dioxide emissions are reduced, but the balanced heat and steam production is disrupted
Solution Approach 1:
The invention changes the operational parameters of the steam system by eliminating steam turbine consumption. This creates a surplus of steam that must be managed, leading to optimized steam generation levels and redistributed heat utilization across the process, thereby maintaining balance while reducing emissions.
Solution Approach 2:
The invention makes the steam system multi-functional by using steam not only for process heating but also for driving electrically coupled equipment through optimized heat exchange. The excess steam from electrification is utilized in multiple process areas, maintaining system balance while achieving emission reductions.
3Power
If steam is highly superheated for steam turbine operation, then sufficient temperature for turbine drive is achieved, but exergy losses increase when steam is used for process heat
Solution Approach 1:
The invention extracts the steam superheating function from the turbine drive context and applies it directly to process heat needs. By eliminating steam turbines, the system no longer requires high-temperature superheated steam for mechanical work, allowing steam to be generated at lower temperatures that are more appropriate for process heating applications, thereby reducing exergy losses.
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 reduces greenhouse gas emissions by 20-100% and optimizes energy efficiency by flexibly managing thermal energy for process heat needs, avoiding the need for steam turbines and minimizing exergy losses.
Implementation Method 1
The superheated high pressure steam at the first pressure level is at least in part adiabatically and isenthalpically expanded to a second pressure level below the first pressure level such that its temperature level is lowered to a second temperature level
Implementation Method 2
The thermal energy required for initiating and maintaining the endothermic cracking reactions in steam cracking is provided by the combustion of fuel gas in a refractory furnace
Implementation Method 3
The convection zone is usually positioned above the radiant zone and composed of various tube bundles traversing the flue gas duct from the radiant zone. Its main function is to recover as much energy as possible from the hot flue gas leaving the radiant zone
Implementation Method 4
The quench zone is positioned downstream of the radiant zone along the main process gas route. It is composed of one or more heat exchanger units, having the main functions of quickly cooling the process gas below a maximum temperature level to stop the cracking reactions
Data Source
AI summary
A method of steam cracking includes using a steam cracking arrangement that has a fired cracking furnace, a quench cooling train, and rotating equipment at least partly driven by electric energy. A process gas stream is passed through the furnace and the cooling train. A steam generation arrangement, operated in thermal association with the cracking arrangement, results in superheated high pressure steam at a first pressure level of 30 and 175 bar absolute pressure and at a first temperature level. No steam at a higher temperature level than the first is generated. The superheated high pressure steam is partially adiabatically and isenthalpically expanded to a second lower pressure level. The first temperature level is selected such that each intermediate temperature level reached at intermediate pressure levels of more than 20 bar during the adiabatic and isenthalpic expansion process is between 5 and 120 K above the dew point of steam.