Flashback Member Positioning for Silica Mixing
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Solution Overview
Problem
Conventional systems for producing pyrogenically generated silica particles face inefficiencies due to gel formation in the delivery system, leading to increased back pressure and equipment downtime, primarily caused by the polymerization of impurities in the precursor and oxygen mixture before reaching the burner.
Innovation Solution
A mixing apparatus with a flashback member positioned at a specific distance from the oxidizing gas delivery chamber, configured to minimize recirculation and extension length, reduces gel formation by ensuring sufficient mixing before the streams exit the burner, utilizing a mixer housing with a precursor and oxidizing gas delivery chamber and a flashback member that can include a tapered surface to prevent recirculation zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the precursor and oxidizing gas are mixed in a conventional delivery system, then the mixing occurs, but gel formation results in increased back pressure and equipment downtime
Solution Approach 1:
The patent applies preliminary action by positioning the flashback member at a specific calculated distance from the oxidizing gas delivery chamber output, and by ensuring sufficient mixing length is provided before the streams exit the burner. This preliminary configuration prevents gel formation by controlling the mixing conditions in advance, eliminating the need for periodic cleaning and maintaining continuous operation.
Solution Approach 2:
The flashback member acts as an intermediary element that mediates the interaction between the precursor and oxidizing gas streams. By positioning it at a specific distance and providing sufficient extension length, it controls the mixing process to prevent harmful gel formation while maintaining effective precursor-gas mixing for silica particle production.
2Device complexity
If the flashback member is positioned closer to reduce extension length, then device complexity is reduced, but recirculation zones increase causing gel formation
Solution Approach 1:
The patent applies parameter changes by establishing a specific quantitative relationship for the distance of the flashback member from the oxidizing gas delivery chamber output, defined by the formula Lminimum (cm) = 0.453U (Re)−0.5567, where U is the flow rate and Re is the Reynolds number. This parameter optimization balances extension length and recirculation zone formation, preventing gel formation while maintaining reasonable device complexity.
3Object-generated harmful factors
If the flashback member is positioned farther to reduce recirculation, then gel formation is reduced, but device complexity and space requirements increase
Solution Approach 1:
The patent optimizes the extension length parameter by establishing the minimum distance formula Lminimum (cm) = 0.453U (Re)−0.5567. This parameter change provides the precise distance needed to reduce recirculation zones and gel formation while minimizing the extension length to avoid excessive device complexity and space requirements.
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 solution effectively reduces or eliminates gel formation, maintaining system efficiency by preventing polymerization reactions, thereby minimizing equipment downtime and ensuring consistent production of silica particles for fused silica and optical fiber preforms.
Implementation Method 1
the mixture undergoes oxidation reaction at high temperature in the presence of a flame to form silica particles
Implementation Method 2
the mixture undergoes oxidation reaction at high temperature in the presence of a flame
Implementation Method 3
The precursor typically is a liquid that is vaporized in a vaporizer and flows in a stream through a delivery tube
Data Source
AI summary
An apparatus for mixing a vaporized precursor with a gas for producing silica particles is provided. The apparatus includes a mixer housing, a precursor delivery chamber having an output in communication with the mixer housing for delivering a vaporized precursor in the mixer housing, and an oxidizing gas delivery chamber having an output in communication with the mixer housing for delivering an oxidizing gas to be mixed with the vaporized precursor. The apparatus further includes a flashback member disposed within the mixer housing and between the output of the precursor delivery chamber and the output of the oxidizing gas delivery chamber. The flashback member is located at a minimum distance from the output of the oxidizing gas delivery chamber defined by Lminimum (cm)=0.453U (Re)−0.5567, wherein U is the flow rate in cm/sec of precursor and Re is the flow Reynolds number. The flashback member may include a tapered surface on at least one side to reduce recirculation of vaporized gas.