Foaming Slag Former via Aggregation and Carbonation
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Solution Overview
Problem
The existing methods for preparing foaming slag formers for electric arc furnaces face challenges such as high raw material costs, environmental hazards from solid slag disposal, poor flowability, and inefficient recycling of fine metal inclusions, along with safety concerns due to water absorption and potential explosions during introduction into the furnace.
Innovation Solution
The process involves aggregating solid slag particles into coarser grains and carbonating them to produce a foaming slag former with increased flowability and reduced raw material consumption, using industrial flue gases for carbonation, and incorporating additives like sand and carbonaceous materials to enhance gas permeability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If natural carbonates (limestone, dolomite, magnesite) are used as slag formers and carbon dioxide sources, then foaming capability is improved, but raw material cost increases
Solution Approach 1:
The patent replaces expensive natural carbonates with a cheaper alternative: solid slag itself. The slag is carbonated to form calcium carbonate on its surface, creating a self-contained foaming agent. This disposable approach uses the waste material (slag) as the source of carbon dioxide for foaming, eliminating the need for costly imported carbonates while maintaining effective foaming capability.
Solution Approach 2:
The slag serves dual purposes: it is both the base material for the foaming slag former and the source of carbon dioxide for foaming. By carbonating the slag surface to form calcium carbonate, the system makes the slag self-sufficient for its own foaming requirements, eliminating dependency on external carbonate additives and reducing raw material costs.
2Loss of substance
If fine solid slag particles are recycled by reintroduction into the electric arc furnace, then metal inclusion recovery is attempted, but yield is low due to blow-out by strong updraft
Solution Approach 1:
The patent segments the fine slag particles by aggregating them into larger granules through carbonation. The calcium carbonate formed on the slag particle surfaces acts as a binding agent, clustering fine particles into coarser granules (0.5-5 mm) that are heavy enough to resist being blown out by the furnace updraft, while still allowing metal inclusions to be effectively recovered.
Solution Approach 2:
The patent creates a composite structure where fine slag particles are bound together by calcium carbonate formations. This composite granular material combines the fine particles (which contain metal inclusions) into a matrix that provides sufficient weight and structural integrity to prevent blow-out, while maintaining the ability to recover metal inclusions through the granular structure.
3Reliability
If dicalcium silicate-containing ladle slag is introduced to improve foaming behavior, then CO nucleation sites increase, but flowability deteriorates due to powdery form and clogging of chutes and trough lances
Solution Approach 1:
The patent aggregates the powdery fine particles into larger granules through the carbonation process. By forming calcium carbonate on and between the particles, they clump together into coarser granules that flow freely through chutes and lances, eliminating the clogging problem while preserving the nucleation sites within the granular structure for effective foaming.
Solution Approach 2:
The patent changes the physical state and size parameters of the slag material. Through carbonation, the fine powdery particles are transformed into coarser granules with different flow characteristics. This parameter change (from fine powder to coarse granules) improves flowability and handling while maintaining the internal structure necessary for foaming performance.
4Productivity
If solid slag is disposed of as waste material, then production capacity is maintained, but environmental hazard increases due to leaching of heavy metals and halogens
Solution Approach 1:
The patent converts the harmful waste slag into a beneficial product. By carbonating the slag to form calcium carbonate on its surface, the process creates a protective layer that stabilizes heavy metals and halogens, preventing their leaching. The waste material becomes a useful foaming slag former with reduced environmental hazard, turning a liability into an asset.
Solution Approach 2:
The patent changes the chemical composition and surface properties of the slag through carbonation. The formation of calcium carbonate on the slag surface alters its chemical parameters, creating a more stable and less hazardous material. This parameter change reduces the leaching potential of heavy metals and halogens while maintaining the slag's utility as a foaming agent.
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
This approach results in a safer, more effective foaming slag former with improved handling and thermal insulation, reduced environmental impact, and efficient recycling of metal inclusions, while minimizing the use of costly raw materials and hazardous waste disposal.
Implementation Method 1
carbonating them to produce said slag former
Implementation Method 2
aggregating solid slag particles to form a granular material formed by coarser grains
Implementation Method 3
carbonating them to produce said slag former, using industrial flue gases for carbonation
Implementation Method 4
these natural carbonates are normally obtained from limestone, dolomitic limestone, dolomite and magnesite, raw materials of increasing cost... produce carbon monoxide bubbles in the slag
Implementation Method 5
the slag also acts as a thermal blanket, reducing heat losses
Implementation Method 6
the introduction of dicalcium silicate particles which form suspended second-phase particles in the molten slag acting as CO nucleation sites
Data Source
Figure 1
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AI summary
The present invention relates to a process for preparing a foaming slag former 40 for electric arc furnaces 1, with at least 20 wt. % of solid slag particles, to the product of this process, and to its use in electric arc furnaces 1. The process of the invention comprises the steps of aggregating solid slag particles into a coarser granular material 33 and carbonating them to produce said slag former 40. In a preferred embodiment, said solid slag particles are aggregated before said carbonation, so that the carbonates form a solid matrix binding the particles together.