External Ignition Source for Smelting Vessel Hot Zone Formation
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Solution Overview
Problem
Molten bath-based smelting processes face challenges in starting or restarting due to the formation of a crusty slag layer, which prevents spontaneous ignition of coal and cold oxygen, potentially leading to un-combusted coal and oxygen mixtures and risk of coal dust explosions in downstream equipment.
Innovation Solution
A method involving the insertion of an external ignition source to create a hot zone in the smelting vessel, followed by the supply of cold oxygen and carbonaceous material, and eventually metalliferous material, to establish a stable ignition and heat generation, even when thermal conditions are too cold for spontaneous ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cold oxygen-containing gas and carbonaceous material are supplied directly into the main chamber, then the smelting process can be started, but spontaneous ignition cannot occur and coal dust explosion risk arises
Solution Approach 1:
The patent applies preliminary action by first inserting an external ignition source into the main chamber to create a hot zone before supplying cold oxygen-containing gas and carbonaceous material. This preliminary heating action ensures that when the combustible materials are introduced, they will ignite reliably rather than creating a dangerous un-combusted mixture.
Solution Approach 2:
The patent applies preliminary action by first establishing a hot zone through an external ignition source before introducing cold oxygen and carbonaceous material. This preparatory step ensures reliable ignition and prevents the formation of explosive un-combusted mixtures, thereby resolving the contradiction between fast start-up and ignition reliability.
2Reliability
If an external ignition source is inserted to create a hot zone, then reliable ignition is achieved, but the process complexity increases
Solution Approach 1:
The patent uses an external ignition source as an intermediary element to bridge the gap between cold oxygen/carbonaceous material supply and spontaneous ignition. This intermediary hot zone facilitates reliable combustion without requiring complex modifications to the core smelting system, as the ignition source can be removed once combustion is established.
3Loss of energy
If a crusty slag layer forms on the molten bath, then heat loss is reduced, but spontaneous ignition of supplied materials is prevented
Solution Approach 1:
The patent applies preliminary action by inserting an external ignition source to create a hot zone before supplying cold oxygen and carbonaceous material. This preliminary heating overcomes the insulating effect of the crusty slag layer, ensuring reliable ignition despite the reduced heat transfer from the molten bath.
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
Ensures safe and reliable ignition and heat generation in the smelting vessel, preventing coal dust explosions and enabling the resumption of the smelting process by forming a stable hot zone independent of initial conditions, thus maintaining process efficiency.
Implementation Method 1
inserting an external ignition source into the main chamber of the smelting vessel to form a hot zone in the main chamber
Implementation Method 2
gas evolution in the molten bath, with the gas evolution being at least partly the result of devolatilisation of carbonaceous material in the molten bath
Implementation Method 3
Hot reaction gases (typically CO, CO2, H2, and H2O) produced in the molten bath is partially combusted by oxygen-containing gas (typically technical-grade oxygen) in an upper part of the main chamber. Heat generated by the post-combustion is transferred to molten droplets in the upper section
Implementation Method 4
Oxygen-containing gas (typically technical-grade oxygen) is injected into the smelt cyclone via tuyeres that are arranged in such a way as to generate a cyclonic swirl pattern in a horizontal plane
Implementation Method 5
This injection of oxygen-containing gas leads to further combustion of smelting vessel gases, resulting in very hot (cyclonic) flames
Implementation Method 6
The reduction is due to both thermal decomposition of hematite and the reducing action of CO/H2 in the reaction gases from the main chamber
Implementation Method 7
the reducing action of CO/H2 in the reaction gases from the main chamber
Implementation Method 8
Hot reaction gases (typically CO, CO2, H2, and H2O) produced in the molten bath is partially combusted by oxygen-containing gas (typically technical-grade oxygen) in an upper part of the main chamber. Heat generated by the post-combustion is transferred to molten droplets in the upper section that fall back into the molten bath to maintain the temperature of the bath
Data Source
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AI summary
A method of starting a molten-bath based melting process includes establishing a sufficiently large and stable "hot zone" for ignition of oxygen and coal in a main chamber of a smelting vessel by independent means, i.e. independently of and before supplying cold oxygen and coal into the main chamber.