Direct Contact Condenser for Dehydrogenation Offgas Compression
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Solution Overview
Problem
The existing technologies for processing offgas from dehydrogenation reactor systems, such as those producing styrene, face challenges in efficiently removing organic compounds and water vapor, which increase the duty on compressors and can lead to polymerization issues due to high temperatures and long residence times.
Innovation Solution
The implementation of a direct contact condenser upstream of the offgas compressor to remove steam and organic compounds, utilizing chilled water or a mixture of chilled water and ethylbenzene as the cooling medium, effectively condensing these components before they enter the compressor, thereby reducing the compressor's duty and preventing polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If offgas is compressed directly after dehydrogenation reaction, then the vacuum required for dehydrogenation is maintained, but the compressor duty increases due to high volume of water vapor and organics
Solution Approach 1:
The patent extracts and removes water vapor and organic compounds from the offgas stream before compression through condensation and separation processes. This reduces the volume of gas requiring compression while maintaining the vacuum necessary for dehydrogenation, thereby reducing compressor duty without compromising reaction conditions
2Use of energy by moving object
If offgas is cooled and condensed to remove water vapor and organics, then compressor duty is reduced, but styrene polymerization occurs due to high temperature and long residence time
Solution Approach 1:
The patent applies preliminary action by quickly cooling the offgas immediately after the dehydrogenation reactor to condense and remove styrene and other condensables before they can polymerize. This rapid initial cooling prevents the harmful polymerization reaction while still allowing subsequent compression at reduced duty
Solution Approach 2:
The patent rushes through the high-temperature zone by minimizing residence time at elevated temperatures through rapid cooling and sequential condensation stages. This allows the offgas to quickly pass through the temperature range where polymerization occurs, removing condensables before they can undergo harmful chemical reactions
3Object-generated harmful factors
If scrubbing with organic condensate is used to remove polymerizable components, then polymerization is prevented, but additional equipment and process complexity are required
Solution Approach 1:
The patent uses self-service by employing the process's own condensate stream to scrub and remove polymerizable components from the offgas. The condensate generated during normal operation is recirculated through the offgas stream, eliminating the need for external scrubbing agents or additional complex equipment while effectively preventing polymerization
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 solution decreases the compressor's duty, allows for operation at lower pressures, reduces capital costs, and prevents styrene polymerization by preferentially condensing styrene monomer, thus maintaining equipment efficiency and economic feasibility.
Implementation Method 1
A direct contact condenser located between the reactor and the offgas compressor that is capable of contacting the offgas stream with a quench stream prior to the offgas stream exiting the condenser and entering the offgas compressor
Implementation Method 2
The quench stream cools the offgas stream and enables the condensation of organic compounds and steam contained within the offgas stream
Data Source
Figure 1
AI summary
Methods and systems for the dehydrogenation of hydrocarbons include a direct contact condenser to remove compounds from an offgas process stream. The reduction of compounds can decrease duty on the offgas compressor by removing steam and aromatics from the offgas. The dehydrogenation reaction system can be applicable for reactions such as the dehydrogenation of ethylbenzene to produce styrene, the dehydrogenation of isoamiline to produce isoprene, or the dehydrogenation of n-pentene to produce piperylene.