Dividing Wall Fractionation Integrated With an Ethane Steam Cracker
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Solution Overview
Problem
The existing naphtha cracking process for producing ethylene and propylene is energy-intensive and inefficient, with low yields and high energy consumption due to the need for refrigeration to separate light ends such as hydrogen and methane from ethane and propane, which are essential feeds for ethane and propane crackers.
Innovation Solution
A process utilizing a dividing wall fractionation column (DWC) to separate ethane and propane streams efficiently, integrating a common refrigeration system with an ethane steam cracker to optimize the separation and reduce energy consumption by sharing cooling resources, thereby enhancing ethylene and propylene production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If naphtha is directly fed to a naphtha cracker to produce olefins, then the process is simple, but ethylene plus propylene yields are low (less than 60% and typically less than 50% by weight)
Solution Approach 1:
The process is divided into two distinct sections: a naphtha-to-ethane-and-propane (NEP) reactor section that converts naphtha to ethane and propane, and a downstream ethane steam cracker section that converts ethane to ethylene. This segmentation allows each section to be optimized for its specific function, achieving higher overall olefin yields compared to direct naphtha cracking.
2Productivity
If the NEP unit is used to produce ethane and propane from naphtha, then higher olefin quantities are achieved, but light ends (hydrogen, methane) require refrigeration for separation which is energy intensive
Solution Approach 1:
The patent integrates the NEP unit with an existing ethane steam cracker, combining two previously separate processes into one unified system. The ethane produced in the NEP unit is directly fed to the cracker, and the light ends separation infrastructure of the cracker is utilized, reducing overall energy consumption compared to standalone systems.
Solution Approach 2:
The ethane steam cracker is designed to handle multiple feed sources (both ethane from the NEP unit and external ethane feeds) and performs multiple functions including cracking, light ends separation, and product recovery. This multi-functionality reduces the need for dedicated separation infrastructure and lowers energy requirements.
3Manufacturing precision
If a dividing wall fractionation column is used to separate ethane, hydrogen, and propane streams, then separation efficiency is improved, but device complexity increases
Solution Approach 1:
Instead of using multiple separate vertical columns for separation, the patent employs a dividing wall fractionation column that creates additional separation zones within a single column structure. The dividing wall introduces a new spatial dimension for separation, allowing simultaneous separation of multiple components (hydrogen/methane overhead, ethane side-cut, propane bottoms) in one column, thereby improving separation efficiency while limiting complexity increase.
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 process achieves a 15% reduction in energy usage and capital expenses while increasing ethylene and propylene yields by optimizing the separation of hydrogen, methane, ethane, and propane streams, making the process more efficient and flexible.
Implementation Method 1
A process utilizing a dividing wall fractionation column (DWC) to separate ethane, hydrogen, and propane streams
Implementation Method 2
The DWC top product comprising of hydrogen, methane and residual ethane is fed directly to the aforementioned compression train of the ESC where the components are separated along with similar components from the ESC cracking heater effluent
Implementation Method 3
The ethane stream is passed to an ethane steam cracker to produce cracking heater effluent comprising ethylene, unreacted ethane, hydrogen, methane, and other components. The cracking heater effluent is passed through a series of steps of the ethane steam cracker, compressed in a compression train
Data Source
AI summary
A process of producing ethylene and propylene from naphtha, the process comprising: producing light paraffins—ethane, hydrogen/methane/residual ethane and propane rich streams—in a dividing wall fractionation column from a stream of hydrogen, methane, propane, and residual C4+ produced in the reactor section of a naphtha-to-ethane-and-propane processing unit by reacting naphtha with hydrogen, a naphtha reactor effluent stream produced by a naphtha reactor of the naphtha-to-ethane-and-propane processing unit is cooled to produce a feed stream. The feed stream is passed to a dividing wall fractionation column. An ethane stream from the dividing wall fractionation column is passed to an ethane steam cracker to produce a cracking heater effluent stream. The cracking heater effluent stream is passed to a coldbox of the ethane steam cracker after multiple steps such as quenching, compression, cooling, caustic scrubbing, drying. One or more fluids for cooling the naphtha (NEP) reactor effluent stream and for cooling the coldbox of the ethane steam cracker are provided by a common refrigeration system.