Method for producing a separation product containing predominantly hydrocarbons with two carbon atoms
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Solution Overview
Problem
Conventional methods for separating hydrocarbons with two carbon atoms from cracked gases produced by steam cracking, especially when using mixed feedstocks, face difficulties due to low methane content, requiring larger separation equipment and increased compressor power, and often necessitate methane recycling or external methane supply.
Innovation Solution
A method and plant utilizing a modified cooling process and increased pressure in the rectification column, combined with a contraflow absorption column, to enhance the recovery of hydrocarbons with two carbon atoms, allowing for single-stage condensation and efficient separation of methane and hydrogen, reducing the need for larger equipment and external methane supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional separation methods are used for cracked gases with low methane content, then hydrocarbons with two carbon atoms can be separated, but larger separation equipment and increased compressor power are required
Solution Approach 1:
The patent applies parameter changes by operating the rectification column at increased pressure levels and using modified cooling temperatures. This changes the phase equilibrium parameters to enable effective separation even with low methane content (up to 30 mole percent), thereby avoiding the need for larger equipment sizes that would be required under conventional operating conditions.
Solution Approach 2:
The patent employs a composite separation approach combining rectification and absorption columns with specific operating conditions. The rectification column operates at increased pressure with specific cooling agents, while the absorption column uses tailored absorbents, creating a composite system that efficiently handles low-methane cracked gases without requiring oversized equipment.
2Quantity of substance
If conventional separation methods are used for cracked gases with low methane content, then hydrocarbons with two carbon atoms can be separated, but compressor power consumption increases
Solution Approach 1:
By operating the rectification column at increased pressure levels and using modified cooling temperatures, the patent reduces the compression work required. The pressure increase facilitates better phase separation, reducing the need for additional compression stages and lowering overall compressor power consumption compared to conventional methods.
Solution Approach 2:
The patent implements feedback control through the integration of the rectification and absorption columns, where the output of one column feeds into the other. This creates a closed-loop system that optimizes methane recovery and minimizes energy consumption by continuously adjusting operating parameters based on the composition of the cracked gas feed.
3Productivity
If mixed feedstocks are used in steam cracking, then production efficiency is improved, but the cracked gas contains comparatively little methane requiring recycling or external supply
Solution Approach 1:
The patent enables the separation system to be self-sufficient by eliminating the need for external methane supply or recycling loops. The rectification and absorption columns are designed to effectively concentrate and recover methane from low-methane cracked gases produced by mixed feedstock cracking, allowing the system to serve itself without additional methane input or complex recycling infrastructure.
Solution Approach 2:
By changing the operating parameters of the rectification column (increased pressure, modified cooling temperatures), the patent enables effective methane recovery even when the cracked gas contains comparatively little methane. This allows mixed feedstocks to be used for improved production efficiency without creating the problem of insufficient methane for conventional separation processes.
4Quantity of substance
If methane recycling is implemented to compensate for low methane content, then separation can proceed, but equipment size and compressor power increase
Solution Approach 1:
The patent extracts and concentrates methane from the low-methane cracked gas stream using the rectification and absorption columns operating under specific conditions. This extraction process eliminates the need for complex recycling systems, as the methane is directly recovered and concentrated in a single pass through the separation train, simplifying the overall device complexity.
Solution Approach 2:
By operating the separation columns at increased pressure and with modified cooling parameters, the patent achieves effective methane concentration without requiring recycling loops. The parameter changes enable single-pass separation, removing the need for complex methane recycling infrastructure and reducing device complexity.
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 enables efficient separation and recovery of hydrocarbons with two carbon atoms from cracked gases with reduced methane content, minimizing equipment size and compressor power consumption, and eliminating the need for external methane supply by optimizing the use of existing cooling agents.
Implementation Method 1
subjected, at least partially at a second pressure level above the first pressure level, to a low-temperature rectification
Implementation Method 2
The gaseous separation feedstock is cooled in a known manner to a temperature below the dew point
Implementation Method 3
at least one part of the first gaseous fraction is subjected to a contraflow absorption in the contraflow to an absorption liquid containing predominantly methane
Data Source
AI summary
The invention relates to a method (100) for the recovery of a separation product which contains predominantly hydrocarbons with two carbon atoms, with the use of a separation feedstock which contains predominantly methane, hydrogen and hydrocarbons with two carbon atoms, wherein the methane content of the separation feedstock is up to 20%, and the separation feedstock is provided in a gaseous state. It is provided that, at a first pressure level, the separation feedstock is partially condensed in a single step by cooling from a first temperature level to a second temperature level, thereby obtaining precisely one first liquid fraction and precisely one first gaseous fraction; at least one part of the first gaseous fraction is partially condensed in a single step through further cooling from the second temperature level to a third temperature level, thereby obtaining precisely one second liquid fraction and precisely one second gaseous fraction; at least one part of the second gaseous fraction at the second pressure level is subjected to a contraflow absorption in the contraflow to an absorption liquid containing predominantly methane, thereby obtaining precisely one third liquid fraction and precisely one third gaseous fraction; the first, the second and the third liquid fraction are at least partially combined and, at least partially, at a second pressure level above the first pressure level, subjected to a low-temperature rectification, thereby obtaining a sump liquid and an overhead gas; at least one part of the overhead gas at the second pressure level is partially condensed in a single step through further cooling from the second temperature level to the third temperature level, thereby obtaining a fourth liquid fraction and a fourth gaseous fraction; and the absorption liquid containing predominantly methane is formed through further cooling of at least a part of the fourth gaseous fraction to a fourth temperature level. A corresponding plant also forms the subject matter of the invention.