Process for separating hydrogen from an olefin hydrocarbon effluent vapor stream
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Solution Overview
Problem
Existing processes for separating hydrogen from olefin hydrocarbon vapor streams in dehydrogenation units are inefficient and lack comprehensive steps to effectively isolate hydrogen, leading to suboptimal purification and energy recovery.
Innovation Solution
A multi-step process involving cooling, separation, isentropic expansion, and compression of vapor streams, followed by flashing and rectification to achieve high-purity hydrogen gas, utilizing a heat exchanger and expanders/compressors to optimize energy utilization and separation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple separation process is used, then the process complexity is reduced, but the hydrogen separation efficiency and purity are insufficient
Solution Approach 1:
The separation process is divided into multiple sequential stages: initial cooling and separation, isentropic expansion, compression, and rectification. Each stage performs a specific function to progressively purify hydrogen, transforming a single complex separation into multiple manageable steps that collectively achieve high efficiency without requiring an overly complex single-step process
Solution Approach 2:
The patent introduces intermediate processing steps including isentropic expansion and compression between separation stages. These intermediary processes modify the physical state of the vapor stream, enabling more effective separation in subsequent stages while maintaining overall process efficiency
2Manufacturing precision
If extensive cooling and separation steps are implemented, then hydrogen purity is improved, but energy consumption increases
Solution Approach 1:
The patent converts the energy that would normally be lost during cooling and separation into useful work through isentropic expansion. The expansion process recovers energy from the pressure drop, and the subsequent compression reheats the stream, reducing the cooling load required in later stages and overall reducing energy consumption while maintaining high purification efficiency
3Loss of energy
If isentropic expansion and compression are used, then energy recovery is improved, but the device complexity increases
Solution Approach 1:
The patent combines the expander and compressor into an integrated system where the expander drives the compressor through a shared shaft. This merging of functions allows energy recovery from expansion to directly power the compression process, improving energy efficiency while avoiding the need for separate independent systems that would increase complexity
4Productivity
If multiple separators and rectifiers are used, then separation efficiency is improved, but the process time and equipment size increase
Solution Approach 1:
The patent designs the process as a continuous flow system where vapor streams move sequentially through cooling, separation, expansion, compression, and rectification without interruption. This continuous operation eliminates idle time between stages and allows multiple separation functions to occur in parallel along the flow path, maintaining high separation efficiency without proportionally increasing process time
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 process enhances hydrogen separation efficiency, achieves high-purity hydrogen gas, and improves energy recovery by maintaining consistent mass and composition flow through the expander/compressor sets, leading to improved thermodynamic stability and reduced off-design flow distributions.
Implementation Method 1
cooling a compressed effluent vapor stream in a heat exchanger
Implementation Method 2
isentropically expanding, in a high-pressure expander, the second vapor stream, wherein the pressure and temperature of the second vapor stream are lowered
Implementation Method 3
compressing, in a high-pressure compressor, the second vapor stream
Implementation Method 4
lowering the pressure of the first liquid stream in a control valve
Implementation Method 5
flashing the partially vaporized first liquid stream in a liquid product drum to provide a hydrogen-rich gas
Implementation Method 6
combining the hydrogen-rich gas and the second liquid stream in the rectifier, further purifying the hydrogen-rich gas
Implementation Method 7
isentropically expanding, in a low-pressure expander, the split stream, wherein the pressure and temperature of the split stream are lowered
Implementation Method 8
compressing, in a low-pressure compressor, the split stream
Data Source
AI summary
One or more specific embodiments disclosed herein includes a method for separating hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream, employing a integrated heat exchanger, multiple gas-liquid separators, external refrigeration systems, and a rectifier attached to a liquid product drum.