De Laval Nozzle Supersonic Expansion for C2-C4 Hydrocarbon Separation
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Solution Overview
Problem
Current methods for separating and recovering hydrocarbons, particularly C2 to C4 hydrocarbons, from gas streams under supersonic conditions are inefficient, as they struggle to effectively condense and separate these gases due to limitations in temperature and pressure changes within de Laval nozzles.
Innovation Solution
The method involves passing a gas stream through a de Laval nozzle, where the gas is expanded to supersonic speeds, causing a reduction in temperature and pressure, allowing for the condensation of hydrocarbons. Swirling devices are used to direct condensed droplets towards the nozzle walls for collection, and multiple nozzle stages can be employed for enhanced separation and recycling of hydrocarbons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gas stream is expanded to supersonic speeds through a de Laval nozzle, then the temperature and pressure reduction enables hydrocarbon condensation, but the collection efficiency of condensed droplets remains insufficient
Solution Approach 1:
The de Laval nozzle is divided into distinct functional zones: a convergent section for subsonic acceleration, a throat for sonic transition, and a divergent section for supersonic expansion. This segmentation allows each zone to optimize its function, with the divergent section specifically designed to maximize temperature and pressure reduction for hydrocarbon condensation while the convergent section maintains flow control.
Solution Approach 2:
A swirl device is introduced as an intermediary element within the nozzle to generate rotational flow. This swirl creates centrifugal forces that act as a mediator between the supersonic flow and the nozzle walls, enhancing the transport of condensed hydrocarbon droplets toward the collection region without disrupting the overall supersonic expansion process.
2Productivity
If multiple nozzle stages are employed for enhanced separation, then the hydrocarbon recovery improves, but the device complexity increases
Solution Approach 1:
The de Laval nozzle design integrates multiple functions into a single device: it provides supersonic acceleration, temperature and pressure reduction, hydrocarbon condensation, and droplet collection. The inclusion of the swirl device adds rotational flow generation and enhanced droplet transport capabilities without requiring separate dedicated components, thereby achieving multi-functionality that improves recovery efficiency while controlling complexity.
Solution Approach 2:
The swirl device is nested within the divergent section of the de Laval nozzle, with the swirl generator positioned upstream and the collection region downstream. This nested configuration allows the rotational flow to be generated within the expanding supersonic flow field, enabling enhanced separation functionality while maintaining a compact, integrated structure that avoids the complexity of multiple separate nozzle stages.
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 enables the efficient separation and recovery of hydrocarbons by leveraging the temperature and pressure changes within de Laval nozzles, improving the collection efficiency of hydrocarbons and allowing for their recycling back into chemical processes.
Implementation Method 1
The gas flow through a de Laval nozzle is normally isentropic. As the nozzle cross-sectional area increases, the gas expands, and the gas velocity becomes supersonic. Under conditions of supersonic flow at constant, or nearly constant, entropy, the gas temperature decreases and the gas pressure decreases.
Implementation Method 2
By inducing swirl in the gas flow, the condensed phase may be driven by centrifugal force to the wall of the nozzle, and recovered through an opening at the nozzle wall or in a flow pipe leading away from the nozzle.
Data Source
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AI summary
Selective recovery of C2 to C4 hydrocarbons is achieved through the use of a converging-diverging nozzle, or de Laval nozzle. The vapor stream comprising C2 to C4 hydrocarbons is fed into an inlet of a de Laval nozzle having a throat. The vapor stream may have an initial temperature of between 0 C and 100 C, and an initial pressure of between 200 psig and 500 psig. In the de Laval nozzle, the vapor stream expands after passing through the throat of the de Laval nozzle, producing a vapor stream having reduced temperature and pressure. Then, C2 to C4 hydrocarbons condense from the reduced-temperature vapor stream as liquid droplets, which may be recovered. Fractionation of C2 to C4 hydrocarbons by means of a de Laval nozzle is possible; the technique allows selective recovery of a stream enriched in propene from a mixture of propane and propene.