Parallel Distillation Columns for Heavy Hydrocarbon Energy Conservation
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Solution Overview
Problem
Aromatics complexes, particularly those producing xylene isomers, are substantial consumers of energy in distillation operations, leading to high processing costs and carbon emissions, with a need for energy conservation in separating xylenes from heavy aromatics.
Innovation Solution
A distillation process utilizing two or more xylene columns operating at different pressures to separate C8-aromatics from C9-and-heavier aromatics, with heat exchange between columns to optimize energy efficiency, including condensing overhead streams to provide heat for reboilers and steam generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional distillation operations are used to separate xylenes from heavy aromatics, then product separation is achieved, but energy consumption increases
Solution Approach 1:
The distillation system is segmented into multiple columns operating at different pressures. The first column operates at elevated pressure to separate C8-aromatics from C9-and-heavier aromatics, while the second column operates at low pressure for similar separation. This segmentation allows each column to be optimized for its specific separation task, reducing overall energy consumption compared to a single conventional distillation column.
Solution Approach 2:
The invention changes the pressure parameter across different distillation columns to optimize energy efficiency. By operating the first column at elevated pressure and the second column at low pressure, the system achieves better separation efficiency and reduces energy consumption. The pressure parameter is adjusted to match the boiling point differences of the components being separated.
2Loss of energy
If multiple distillation columns operate at different pressures, then energy efficiency improves, but system complexity increases
Solution Approach 1:
The invention merges the separation function across multiple columns while integrating heat exchange systems. The overhead stream from the first column is condensed by exchanging heat with the reboiler of the second column, and steam is generated from this heat exchange. This merging of functions reduces the need for separate heating and cooling systems, offsetting the increased complexity from having multiple columns.
Solution Approach 2:
The heat exchange system acts as an intermediary between the first and second columns. By using the overhead stream from the first column as a heat source for the reboiler of the second column, the system efficiently transfers energy between columns without requiring external heating or cooling systems, simplifying the overall process.
3Loss of energy
If heat exchange between columns is implemented, then energy conservation is achieved, but process complexity increases
Solution Approach 1:
The heat exchange system maintains continuous useful action by using the overhead stream from the first column to continuously heat the reboiler of the second column. This continuous heat transfer maximizes energy recovery and minimizes energy loss, as the thermal energy from the overhead stream is continuously utilized rather than being wasted.
Solution Approach 2:
The system utilizes phase transitions in the heat exchange process. The overhead stream from the first column condenses by exchanging heat with the reboiler of the second column, and steam is generated from this heat exchange. The phase transition from vapor to liquid in the overhead stream and from liquid to vapor in the reboiler enables efficient heat transfer and energy recovery.
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 energy consumption and processing costs while minimizing carbon emissions by effectively separating C8-aromatics from heavy aromatics, maintaining product yield, and avoiding equipment fouling.
Implementation Method 1
distilling the at least one lower-boiling feed stream in at least one first xylene column at an elevated pressure to separate a first C8-aromatics streams from a first C9-and-heavier aromatics stream, distilling the at least one higher-boiling feed stream in at least one second xylene column at a low pressure column to separate a second C8-aromatics stream from a second C9-and-heavier aromatics stream
Implementation Method 2
condensing an overhead stream from the at least one first column by exchanging heat with one or both of a reboiler of the second column and a steam generator
Implementation Method 3
condensing an overhead stream from the at least one first column by exchanging heat with one or both of a reboiler of the second column and a steam generator
Data Source
AI summary
An aromatics complex producing one or more xylene isomers offers a large number of opportunities to conserve energy by heat exchange within the complex. One previously unrecognized opportunity is through providing two parallel distillation columns operating at different pressures to separate C8 aromatics from C9+ aromatics. The parallel columns offer additional opportunities to conserve energy within the complex through heat exchange in associated xylene recovery facilities.