Cracked Gas Demethanization Reflux Without Cryogenic Pumps
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Solution Overview
Problem
Current processes for treating cracked gas from hydrocarbon pyrolysis installations are energy-intensive and complex, requiring multiple distillation columns and cryogenic pumps to achieve high ethylene recovery and purity, which can be costly and difficult to maintain.
Innovation Solution
A simplified process that eliminates cryogenic pumps by using a gravity flow reflux system and integrated heat exchangers within distillation columns, achieving efficient ethylene recovery through sequential cooling and condensation stages, and utilizing a JOULE-THOMPSON cycle for temperature control, thereby reducing energy consumption and equipment complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple distillation columns and cryogenic pumps are used to achieve high ethylene recovery and purity, then ethylene recovery rate is improved, but device complexity and energy consumption increase
Solution Approach 1:
The patent combines the functions of multiple distillation columns and cryogenic pumps into a single integrated distillation column with internal heat exchangers. The heat exchangers are positioned within the column to provide both cooling and heating functions, eliminating the need for separate cryogenic pumps and reducing the number of external heat exchange units required.
Solution Approach 2:
The internal heat exchangers serve multiple functions simultaneously: they cool the rising vapor to condense overhead components, provide reflux liquid back to the column, and are heated by the same unit to create a self-sustaining thermal cycle. This multi-functionality reduces the need for separate dedicated equipment for each function.
2Manufacturing precision
If multiple distillation columns and cryogenic pumps are used to achieve high ethylene recovery and purity, then ethylene purity is improved, but energy consumption increases
Solution Approach 1:
The internal heat exchangers operate continuously with vapor constantly flowing through them, providing uninterrupted cooling and condensation. The heated exchanger surfaces continuously generate reflux liquid that flows back into the column, maintaining a continuous thermal cycle that improves energy efficiency while sustaining high purity separation.
Solution Approach 2:
The heat exchangers are self-heated by the process vapor itself, eliminating the need for external heating utilities. The cold vapor passing through the exchangers absorbs heat from the warmer exchanger surfaces, automatically generating the temperature differential needed for condensation and reflux without additional energy input.
3Productivity
If cryogenic pumps are used to maintain reflux flow, then ethylene recovery is improved, but ease of operation and maintenance difficulty increase
Solution Approach 1:
The patent replaces the mechanical cryogenic pump system with a gravity-driven reflux system. The internal heat exchangers produce condensed liquid that flows back into the column under gravity, eliminating the need for mechanical pumping equipment and associated maintenance requirements for seals, bearings, and motor controls in cryogenic conditions.
Solution Approach 2:
The invention extracts and eliminates the cryogenic pump component from the system entirely. By using internal heat exchangers positioned within the distillation column, the system generates its own reflux liquid internally, removing the need for external pumping equipment that would require complex installation and maintenance.
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 allows for the recovery of over 99.5% of ethylene with reduced energy consumption and simplified installation structure, minimizing costs and maintenance while maintaining high ethylene purity and recovery rates.
Implementation Method 1
utilizing a JOULE-THOMPSON cycle for temperature control
Implementation Method 2
the cracked gas is successively cooled in increasingly cold heat exchange regions
Implementation Method 3
The cracked gas is partially condensed in each heat exchange region
Implementation Method 4
using a gravity flow reflux system
Data Source
AI summary
Process for treating a stream of cracked gas coming from a hydrocarbon pyrolysis plant, and associated plant. This process comprises the separation of an upstream partially condensed cracked gas stream in an intermediate separator (44B) so as to recover an intermediate liquid (136) and an intermediate cracked gas stream (138) and the injection of the intermediate liquid (140) into an intermediate demethanization column (68). The process includes sampling a portion of the intermediate liquid (136) and expanding at least a first fraction (194) obtained from the sampled portion (190). The process comprises bringing the expanded first fraction into heat exchange relationship with the overhead intermediate stream (146) from the column (68) in order for the overhead intermediate stream (146) to be at least partially condensed. The process includes the separation of the partially condensed overhead intermediate stream in a reflux first separator (76) so as to form a liquid stream (148) fed into the intermediate column (68) and a gaseous fuel stream (150).