Hydrogen Separation from Olefin Effluent via Isentropic Expansion
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Solution Overview
Problem
Current processes for separating hydrogen from olefin hydrocarbon rich compressed effluent vapor streams in dehydrogenation units are inefficient and lack comprehensive steps to achieve high purity and recovery rates.
Innovation Solution
A multi-step process involving cooling, separation, isentropic expansion, compression, and rectification to isolate hydrogen, including the use of heat exchangers, separators, expanders, and compressors, with optional booster compressors and refrigeration systems to optimize hydrogen recovery and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If current separation processes are used, then hydrogen separation is achieved, but purity and recovery rates are insufficient
Solution Approach 1:
The separation process is divided into multiple stages: initial cooling and separation, isentropic expansion, recompression, and rectification. Each stage targets specific components at different concentration levels, progressively achieving high purity through sequential refinement rather than attempting single-stage separation.
Solution Approach 2:
The effluent stream undergoes preliminary cooling and separation before the main separation process, removing bulk amounts of olefin and paraffin components. This preliminary action reduces the load on subsequent separation stages and improves overall process efficiency.
2Quantity of substance
If simple separation methods are used, then process complexity is low, but hydrogen recovery rate is insufficient
Solution Approach 1:
The process utilizes changes in temperature and pressure parameters to achieve separation. Isentropic expansion dramatically lowers temperature to condense heavier components, while compression raises pressure for phase separation. These parameter changes enable high recovery rates through physical property differences rather than complex chemical processes.
Solution Approach 2:
The isentropic expansion process self-generates the cold temperature required for separation without external refrigeration. The expansion of compressed gas naturally produces the low temperatures needed to condense olefin and paraffin components, making the system self-sufficient for cooling.
3Use of energy by moving object
If isentropic expansion is used, then thermodynamic efficiency improves, but process complexity increases
Solution Approach 1:
The isentropic expansion device serves multiple functions: it cools the effluent stream, separates components through condensation, and generates the cold temperature required for subsequent rectification. This multi-functionality reduces the need for separate refrigeration and separation equipment.
Solution Approach 2:
The expanded cold stream acts as an intermediary cooling medium. It provides the low temperature required for separation and rectification processes without requiring external refrigeration systems, mediating between the compression energy input and the separation requirement.
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 process effectively separates hydrogen from olefin hydrocarbons, achieving high purity and recovery rates, improving thermodynamic efficiency and stability in dehydrogenation unit operations.
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
isentropically expanding, in a low-pressure expander, the split stream, wherein the pressure and temperature of the split stream are lowered
Implementation Method 5
compressing, in a low-pressure compressor, the split stream
Implementation Method 6
lowering the pressure of the first liquid stream in a control valve
Implementation Method 7
vaporizing the combined feed in the heat exchanger
Implementation Method 8
combining the hydrogen-rich gas and the second liquid stream in the rectifier, further purifying the hydrogen-rich gas
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.