Bitumen-Coated Calcium Oxide Desulfurization Agent
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Solution Overview
Problem
Existing desulfurization agents for molten metals, particularly pig iron, face inefficiencies due to the formation of inhibiting phases that restrict the diffusion of sulfur, leading to high iron losses and the need for excessive additives, and are hindered by poor handling and pneumatic conveying properties.
Innovation Solution
A desulfurization agent comprising calcium oxide, optionally combined with alkaline or earth metals, and bitumen or paraffinic oil, which enhances reactivity and flowability, allowing for effective sulfur removal with reduced iron loss and improved handling characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If calcium oxide is used as a desulfurization agent, then the cost is reduced, but the desulfurization efficiency is limited due to silicate layer formation
Solution Approach 1:
Bitumen serves as an intermediary substance that coats the calcium oxide grains, preventing the formation of silicate layers during desulfurization. This mediator allows sulfur to diffuse to the calcium oxide surface without being blocked by inhibiting phases, thereby maintaining high desulfurization efficiency while using cost-effective calcium oxide
Solution Approach 2:
The invention changes the surface properties of calcium oxide by coating it with bitumen, which alters the chemical environment at the grain surface. This parameter change prevents silicate formation and maintains the reactivity of calcium oxide toward sulfur, significantly improving desulfurization efficiency
2Productivity
If calcium carbide and magnesium carbide are used for desulfurization, then good desulfurization is achieved, but iron loss increases due to slag containing considerable iron
Solution Approach 1:
The invention uses calcium oxide as a substitute for expensive calcium carbide and magnesium carbide. By coating calcium oxide with bitumen, it achieves desulfurization performance comparable to carbide-based agents while producing less iron-containing slag, thus reducing iron loss
3Productivity
If aluminum powder is added to calcium oxide, then calcium aluminates are formed which facilitate sulfur diffusion, but aluminum powder segregation and cost increase occur
Solution Approach 1:
Bitumen acts as an intermediary coating that prevents the segregation of aluminum powder from calcium oxide. The bitumen layer binds the components together, maintaining mixture homogeneity during pneumatic conveying while still allowing calcium aluminates to form and facilitate sulfur diffusion
4Productivity
If polymers are added to desulfurization agents, then reactivity is enhanced, but pneumatic conveying fails due to demixing and lance clogging
Solution Approach 1:
The invention changes the physical state and properties of the coating material from polymer to bitumen. Bitumen has appropriate viscosity and flow characteristics that prevent demixing during pneumatic conveying and do not cause lance clogging, while still providing the beneficial effect of preventing silicate layer formation and enhancing reactivity
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 agent achieves low sulfur content in molten metals, maintaining flowability and preventing iron loss, with a significant reduction in the amount of desulfurization agent required, thereby lowering costs and improving metallurgical efficiency.
Implementation Method 1
bitumen in a quantity of 1 to 30% by weight or a mineral oil and/or paraffinic oil, in a quantity of 1 to 25% by weight
Implementation Method 2
Mixtures based on calcium oxide, magnesium carbide and calcium carbide have established themselves as desulfurization agents since they result per se in good desulfurization of the pig iron
Implementation Method 3
A desulfurizing agent is, for example, known from DE 17 58 250 which is composed of a mixture of 40 to 90% by weight technical grade calcium carbide and calcium carbonate
Data Source
AI summary
The invention relates an agent for treating molten metals, in particular for dephosphorizing pig iron melts, containing at least calcium oxide, optionally at least one other element in the elementary and/or bound state, selected from the group including alkali metals, alkaline earth metals or earth metals and bitumes in an amount between 1-30 wt.-% or a mineral oil and/or paraffin oil, in an amount between 1-25 wt. %. The agent is suitable, in particular, for treating pig iron melts, according to a mono-, co- or multi-injection method, but also for stirring, for example, according to the KR stirring method.