Process and plant for producing an olefin
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Solution Overview
Problem
The separation of process gases from oxidative dehydrogenation (ODH) processes, such as ODH-E, faces challenges due to low methane content, leading to product and reactant losses, and excessive enrichment of carbon monoxide and oxygen, which can result in explosions and safety hazards.
Innovation Solution
A two-stage low-temperature rectification process is employed, using a liquid reflux rich in hydrocarbons to recover olefins and reduce oxygen content, thereby minimizing product losses and ensuring safety by diluting hazardous regions in separation units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single-stage low temperature separation is used to remove methane and lower boiling components, then separation of process gas components is achieved, but product and reactant losses occur due to low methane content, and carbon monoxide and oxygen become excessively enriched creating safety hazards
Solution Approach 1:
The single-stage separation process is divided into two sequential rectification stages. The first stage performs initial separation at a first temperature level, and the second stage performs further separation at a second temperature level. This segmentation allows progressive removal of components without excessive enrichment of hazardous gases in any single stage, thereby reducing product losses while maintaining safety.
Solution Approach 2:
The invention introduces a temporal dimension to the separation process by implementing sequential stages at different temperature levels rather than a single simultaneous separation. This dimensional approach enables controlled progressive separation, where the first stage operates at one temperature and the second stage operates at another, preventing the excessive enrichment that occurs in single-stage processes.
2Quantity of substance
If a single-stage low temperature separation is used, then separation is achieved, but carbon monoxide and oxygen undergo enrichment beyond desirable concentrations leading to explosion risks
Solution Approach 1:
The separation process is segmented into two stages operating at different temperature levels. The first stage separates components at a first temperature, and the second stage separates remaining components at a second temperature. This segmentation prevents the excessive concentration of carbon monoxide and oxygen in a single stage, thereby eliminating explosion risks while achieving complete separation.
Solution Approach 2:
The first rectification stage performs preliminary separation of the process gas before the second stage. By removing a portion of components in the first stage at a first temperature level, the feed to the second stage is pre-conditioned, preventing excessive enrichment of hazardous gases in the final separation stage.
3Adaptability or versatility
If known separating processes from steamcrackers are employed for ODH process gas, then separation capability is provided, but product and reactant losses occur due to low methane content in the process gas
Solution Approach 1:
The invention changes the operating parameters of the rectification process by implementing two stages at different temperature levels rather than using a single stage optimized for steamcracker gases. The first stage operates at a first temperature level and the second stage at a second temperature level, adapting the separation process to the specific composition of ODH process gas with low methane content, thereby preventing product losses.
4Reliability
If two-stage rectification with liquid reflux is implemented, then product recovery and safety are improved, but additional apparatus complexity is introduced
Solution Approach 1:
The separation system is segmented into two rectification stages, each with its own temperature control and liquid reflux system. While this increases the number of components, each stage is relatively simple and can be operated independently, allowing the complexity to be managed through modular design while achieving superior safety and product 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 effectively recovers valuable olefins, reduces product losses, and maintains safe oxygen levels, enhancing the efficiency and safety of the separation process while minimizing additional apparatus costs and complexity.
Implementation Method 1
the first gas fraction is at least partly subjected to a second low temperature rectification using a liquid reflux containing predominantly or exclusively the hydrocarbon having N−1 carbon atoms in which the first gas fraction undergoes depletion in the olefin having N carbon atoms
Implementation Method 2
a first low temperature separation in which the separation input is cooled stepwise over a plurality of temperature levels and condensates are separated from the separation input
Data Source
AI summary
A process for producing an olefin having N carbon atoms is proposed in which using a dehydrogenation a process gas is formed which contains at least the olefin having N carbon atoms, a paraffin having N carbon atoms and a hydrocarbon having N−1 carbon atoms and in which using at least a portion of the process gas a separation input is formed which is subjected to a low temperature separation in which the separation input is cooled stepwise over a plurality of temperature levels and condensates are separated from the separation input, wherein the condensates are at least partly subjected to a first low temperature rectification to obtain a first gas fraction and a first liquid fraction, wherein the first gas fraction contains at least the olefin having N carbon atoms in a lower proportion than in the condensates and the hydrocarbon having N−1 in a higher proportion than in the condensates. It is provided that the first gas fraction is at least partly subjected to a second low temperature rectification using a liquid reflux containing predominantly or exclusively the hydrocarbon having N−1 carbon atoms in which the first gas fraction undergoes depletion in the olefin having N carbon atoms. A corresponding plant (100) likewise forms part of the subject matter of the invention.