Direct Contact Condenser for Dehydrogenation Offgas Cooling
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Solution Overview
Problem
The dehydrogenation offgas stream from styrene production contains organic compounds and steam that increase the duty of the offgas compressor, leading to inefficiencies and potential polymerization of styrene at high temperatures, necessitating an economic solution for removal.
Innovation Solution
A direct contact condenser is installed upstream of the offgas compressor to remove steam and organic compounds by contacting the offgas stream with a cooling medium, such as chilled water or a combination of water and ethylbenzene, allowing for condensation and reduction of compressor duty.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the offgas compressor operates at sub-atmospheric pressure to enable dehydrogenation reaction, then the reaction can proceed effectively, but the compressor duty increases due to increased suction volume of water and organic vapors
Solution Approach 1:
A direct contact condenser is installed upstream of the offgas compressor to pre-cool and condense water and organic compounds from the offgas stream before compression. This preliminary removal of condensable vapors reduces the suction volume and mass flow through the compressor, thereby reducing compressor duty while maintaining the sub-atmospheric pressure operation needed for effective dehydrogenation reaction
2Reliability
If the offgas stream is cooled to condense styrene, then polymerization is prevented, but additional cooling equipment and complexity are required
Solution Approach 1:
The direct contact condenser combines multiple functions into a single unit: it cools the offgas stream to prevent styrene polymerization, condenses water and organic compounds to reduce compressor duty, and provides a simple spray-based cooling mechanism. This merged approach achieves polymerization prevention without requiring complex multi-stage cooling equipment
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
The direct contact condenser effectively reduces the content of organic compounds and steam in the offgas stream, lowering the compressor duty, preventing styrene polymerization, and maintaining economic feasibility by reducing capital and operational costs.
Implementation Method 1
contacting the offgas with a cooling medium, such as chilled water or a combination of water and ethylbenzene, allowing for condensation and reduction of compressor duty
Implementation Method 2
direct contact condenser is installed upstream of the offgas compressor to remove steam and organic compounds by contacting the offgas stream with a cooling medium
Data Source
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.