Metallurgical Injection Lance Thermal Expansion Management
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Solution Overview
Problem
Lances used for injecting fluids into metallurgical vessels suffer from crack formation due to thermal gradients and differing coefficients of thermal expansion between metal inner tubes and refractory sheaths, leading to shear stresses and reduced service life.
Innovation Solution
A lance design featuring a hollow metal inner tube surrounded by a refractory sheath with an annular gap and annular guides that allow for movement between the inner tube and sheath, reducing shear stresses through thermal expansion, and an anchoring point to secure the lance during use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the inner tube is rigidly anchored to the refractory sheath, then the structural stability is improved, but crack formation increases due to thermal expansion differences
Solution Approach 1:
The patent transitions from a static rigid anchoring system to a dynamic one where the inner tube can move axially within the refractory sheath. The anchoring points at the ends of the inner tube provide stability, while the tube is free to expand and contract axially in response to thermal gradients, preventing crack formation in the refractory material.
Solution Approach 2:
The anchoring system is segmented into discrete points at the ends of the inner tube rather than continuous anchoring along the length. This segmentation allows the middle portion of the inner tube to move freely axially, accommodating thermal expansion while maintaining structural integrity through the end anchoring points.
2Reliability
If the inner tube is allowed to move freely within the refractory sheath, then crack formation is reduced, but structural stability deteriorates
Solution Approach 1:
The system implements controlled dynamics by anchoring the inner tube at its ends while allowing free movement in the middle section. This dynamic configuration enables the tube to accommodate thermal expansion axially without compromising overall structural stability, as the end anchoring points maintain positional integrity.
Solution Approach 2:
Different sections of the inner tube have different degrees of freedom: the end portions are anchored to provide structural stability, while the middle section is free to move axially to accommodate thermal expansion. This local differentiation of constraints optimizes both stability and crack prevention.
3Strength
If anchoring elements are distributed along the inner tube length, then structural support is improved, but shear stresses increase due to thermal expansion constraints
Solution Approach 1:
The anchoring elements are segmented and positioned only at the ends of the inner tube rather than distributed along the entire length. This segmentation provides structural support where needed while eliminating the shear stresses that would result from constraining thermal expansion at multiple intermediate points.
Solution Approach 2:
The anchoring function is extracted from being continuously distributed along the inner tube and concentrated only at the end portions. This removal of intermediate anchoring elements eliminates the source of shear stresses while maintaining sufficient structural support through the end anchoring points.
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 design significantly reduces crack formation and extends the service life of the lance by allowing relative movement between the inner tube and refractory sheath, maintaining refractory material integrity and protecting the inner tube from thermal damage.
Implementation Method 1
The coefficient of thermal expansion of steel can be about two orders of magnitude higher than the thermal expansion coefficient of refractory materials usually used for manufacturing such lances. The difference in coefficients of thermal expansion and the variation of strong temperature gradients generate substantial differences in thermal expansions between the steel inner tube and the refractory sheath material.
Data Source
Figure 1(a)~2
Figure 3
Figure 4(a)~4(b)
AI summary
The present invention concerns a lance for top injection of a fluid in metallurgical vessels that is less prone to cracking and comprising: (a) an inner tube (1), (b) a refractory sheath (2) surrounding the inner tube (1), (c) an anchoring point (4) rigidly coupled to said inner tube (1) and at least partially embedded in the refractory sheath (2), (d) an annular gap (1g) separating the inner tube from the refractory sheath; (e) at least one annular guide (5) surrounding the inner tube (1) and comprising: an annular portion (5A) circumscribing the inner tube (1), and at least two anchor protrusions (5P) rigidly extending transversally from the annular portion and at least partially embedded in the refractory sheath (2), wherein a guide gap (5g) is formed between the annular portion and an outer surface of the inner tube. According to the invention said at least two anchor protrusions (5P) are distributed over the external surface of the annular portion, separated from one another by an angle comprised between 90° and 270°.