Refractory Vessel for Electromagnetic Stirring of Molten Silicon
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Solution Overview
Problem
Vessels designed to hold high-temperature electrically conductive fluids face structural weakening due to induced eddy currents and torque from electromagnetic stirring, which compromises their ability to maintain structural integrity and effectively stir the fluid.
Innovation Solution
A high-strength vessel is created by reinforcing annular structural elements with refractory and embedded reinforcing members, separated by high-temperature electrical insulating material, and placed within a stator with phase-shifted alternating current coils to induce a cylindrical stir pattern in the fluid without overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a solid stainless steel vessel is used to hold molten silicon, then the vessel has sufficient structural strength to support the contained material, but eddy currents induced in the vessel will overheat and structural weaken the vessel
Solution Approach 1:
The vessel employs a composite structure combining stainless steel annular structural elements with refractory material and high-temperature electrical insulating material. This composite design allows the stainless steel to provide structural strength while the refractory and insulating materials prevent eddy current heating, resolving the contradiction between structural integrity and temperature control.
Solution Approach 2:
The vessel is divided into multiple annular structural elements separated by refractory material and electrical insulating material. This segmentation interrupts the continuous conductive path that would otherwise allow eddy currents to flow through the entire vessel structure, reducing heat generation while maintaining structural support through the distributed annular elements.
2Productivity
If electromagnetic stirring is applied to the molten silicon, then the fluid material is effectively stirred, but electromagnetic forces apply torque to the vessel instead of the fluid material
Solution Approach 1:
The refractory material and electrical insulating material serve as intermediaries between the electromagnetic field and the vessel structure. These materials allow the electromagnetic field to penetrate and stir the molten silicon while preventing the transmission of electromagnetic forces and torque to the vessel walls, enabling effective stirring without vessel interference.
3Temperature
If the vessel is made thinner to reduce eddy current heating, then less heat is generated, but the vessel loses structural strength to support the high-density molten material
Solution Approach 1:
The composite construction allows the use of thinner stainless steel annular elements since the refractory and electrical insulating materials bear part of the thermal and structural load. This distributed composite structure maintains structural strength while reducing the continuous conductive metal pathways that generate eddy current heat.
Solution Approach 2:
By segmenting the vessel into multiple thin annular structural elements separated by non-conductive refractory and insulating materials, the design reduces eddy current heating in each individual element while the collective arrangement of segmented elements maintains overall structural strength through the distributed support system.
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 provides a structurally robust vessel capable of withstanding high-density, high-temperature fluids while effectively stirring and heating them electromagnetically, preventing vessel deformation and ensuring efficient material handling.
Implementation Method 1
electromagnetic stirring in the holding vessel by coupling the material with an alternating magnetic flux field originating external to the vessel
Implementation Method 2
eddy currents induced in the solid stainless steel vessel would overheat
Implementation Method 3
A high-temperature electrical insulating material is disposed at least between the spaced-apart plurality of annular structural elements and forms the interior surface of the vessel
Implementation Method 4
windings associated with each stator are connected to an alternating current source to induce a horizontally oriented cylindrical stir pattern in the fluid material
Data Source
AI summary
Apparatus for, and method of, containing, transferring and electromagnetically stirring an electrically conductive fluid is provided. A vessel is formed from spaced-apart annular structural elements, or hoops, that are bound together by a high-temperature electrical insulating material, which also forms the interior surface of the vessel. Reinforcing members are embedded in the high-temperature electrical insulating material and passed through the hoops. The vessel is disposed within an electrical stator having multiple electrical poles. Each pole is wound with a separate coil. Current can be supplied to each coil winding, with a suitable phase shift between currents to all coil windings, to achieve an electromagnetically induced stirring and heating of the electrically conductive fluid. The vessel may be removably disposed in the electrical stator so that the vessel can be transported to and from the electrical stator for induced stirring.