Low Shear Gas Mixer Ignition Risk Reduction
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Solution Overview
Problem
Current gas mixers used in ethylene oxide production face a risk of ignition when mixing hydrocarbon and oxygen streams due to particle impacts, leading to potential damage and production interruptions.
Innovation Solution
A low-shear mixing design with long, parallel oxygen injection pipes and an impact labyrinth that fosters particle ignition and burning upstream of the mixing zone, minimizing particle impacts and energy within the mixing plume, combined with the use of corrosion-resistant materials and optional particle filtration systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gas mixer design with internal tubes or fingers is used, then mixing function is achieved, but particle impacts with metallic surfaces generate sparks causing ignition
Solution Approach 1:
The harmful metallic internal tubes or fingers are removed from the mixer design. Instead, a simple outer shell with inlet manifolds and a central outlet is used, eliminating the metallic surfaces that generate sparks when particles impact them.
Solution Approach 2:
The design accepts that particles will impact somewhere, but redirects them to impact only on the outer shell surface away from the mixing zone, or allows them to pass through unimpeded. The harmful spark-generating impacts are converted into harmless impacts on non-critical surfaces.
2Reliability
If mixing zone is positioned where internal tubes end, then gas mixing occurs, but this is the highly flammable zone where ignition damage occurs
Solution Approach 1:
The internal mixing structures (tubes or fingers) are removed entirely. Mixing occurs passively through the interaction of gas streams in the absence of solid surfaces, eliminating the source of ignition within the mixing zone.
Solution Approach 2:
The design uses the gas streams themselves as the mixing medium without introducing solid intermediaries. The hydrocarbon-containing gas and oxygen-containing gas mix through their mutual flow interaction, avoiding any solid surfaces in the mixing zone.
3Reliability
If corrosion-resistant materials are used, then particle generation is minimized, but device complexity and cost increase
Solution Approach 1:
The design accepts that some particle generation may occur in the inlet manifolds but eliminates the critical issue by removing internal mixing surfaces where particles would cause ignition. The focus shifts from preventing all particle generation to preventing particle impacts in the dangerous mixing zone.
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
Significantly reduces the likelihood of ignition events by minimizing particle generation and ensuring particles are cooled or burned before reaching the mixing zone, enhancing safety and operational reliability in ethylene oxide production.
Implementation Method 1
The impact labyrinth in the oxygen-containing gas stream includes structures forming a tortuous path through which the oxygen-containing gas stream must pass to reach the mixing point. The impact labyrinth fosters ignition of particles entrained in the oxygen-containing gas stream.
Implementation Method 2
The low-shear design, due to coaxial flow at the mixing point, also minimizes the relative velocity of oxygen with respect to hydrocarbon-containing gas within the mixing plume and hence the likelihood of breaking up larger particles entrained within the hydrocarbon-containing gas stream.
Data Source
Figure 1~1A
Figure 2~3
Figure 4~5
AI summary
A gas mixer (10) for mixing a first gas stream with a second gas stream includes an impact labyrinth (24) in the first gas stream having structures (25), e.g., corrugated walls, forming a tortuous path through which the first gas stream must pass en route to a mixing point (20) in the gas mixer. The labyrinth fosters ignition of particles entrained in the first gas stream. Elongate, straight pipes (30) receive the first gas stream from the impact labyrinth (24) and carrying the first gas stream to the mixing point (20) the pipes (30) are positioned with a vessel (12) carrying the second gas stream. The pipes (30) have openings which are sbustantially aligned with the flow direction of the second gas stream at the mixing point (20) thereby introducing the first gas stream into the second gas stream in a low shear manner.