5736/MF/1916 032 - P111/10
MAY 1995
______
NEW PATENTS ON IRON CARBIDE
CONTENTS :
PRODUCTION OF IRON CARBIDE
1 -Magnetic Separation of Iron Carbide
2 -Loading and Unloading System for a Pressurized Reactor with No Moving Parts.
3 -Process for the Production of Iron Carbide with Feedstocks of Various Sizes in a Fluid Bed Reactor.
4 -Fluidization Sensor.
5 -Thermomagnetic Analyser.
6 -Battery of Fluid Bed Reactors.
UTILIZATION OF IRON CARBIDE
7 -Steel Fountain.
8 -Hot Carbide Injection System for Electric Arc Furnaces.
9 -Hot Carbide Charging System for Basic Oxygen Furnaces.
1 - MAGNETIC SEPARATION OF IRON CARBIDE
A process for the production of iron carbide of good purity in a fluid bed reactor including the following steps :
The reactor elaborates a product which is a mix of iron carbide, metallic iron, iron oxides and gangue.
The reactor output material is maintained at a temperature comprised between 230°C and 570°C . A first magnetic screening separates the metallic iron and the oxides from the carbide and the gangue.
The magnetic fraction is cooled below 180°C and is further beneficiated to separate the pure iron carbide from the gangue.
The process allows the production of iron carbide in a circulating fluid bed reactor with a feedstock of fine ore particles.
2 -LOADING AND UNLOADING SYSTEM FOR A PRESSURIZED REACTOR WITH NO MOVING PARTS
System to feed continously a reactor working under a pressurized atmosphere comprising a column of feed material. The loading height of material is sufficient to counter-balance the reactor overpressure. The gas leak through the feed is utilized to purge the material from the air gases. The cross section of the column varies along the height following approximately a hyperbolic function.
Similar system for the reactor discharge, where the material in the column is fluidized.
3 -PROCESS FOR THE PRODUCTION OF IRON CARBIDE WITH FEEDSTOCKS OF VARIOUS SIZES IN A FLUID BED REACTOR
The process includes the following steps:
Classification of the iron ore into classes having narrow-cut size distributions.
Processing of the different classes one after another in a fluid bed reactor. The reactor discharge port is designed in order to allow a control of the bed depth. Large particles are treated with a high gas velocity and a deep bed, whereas fine ores are treated at a much lower gas velocity in a shallow bed. This process makes it possible to work with iron ores containing many fines and to maintain the fluid bed stability.
4 -FLUIDIZATION SENSOR
Device for the control of the local condition of a fluidized bed, particularly a bubbling bed.
The system comprises one or several insulated electrodes which are located slightly above the average bed surface level. Bubbles erupting below an electrode are detected by a change of the electrode insulation resistance, because iron carbide as well as magnetite or metallic iron are electrically conductive.
The design of the electrode supports includes a flushing of the insulators with clean gas in order to avoid a permanent grounding of the detector by the dust.
The impedance of the electronic sensing system is sufficiently low to accommodate the build-up of electrostatic charges.
5 - THERMOMAGNETIC ANALYSER
The analyser utilizes the variation of the magnetic properties of the different iron chemical species with the temperature to determine their presence and quantities.
The powder to analyse is introduced in a refractory tube in an inert atmosphere. The powder temperature can be varied and is monitored. The tube is submitted to a magnetising field and the magnetic flux is measured.
The changes of the magnetic permeability of the powder with the temperature are translated in terms of relative quantities of Fe3C, Fe, Fe3O4, non magnetic substances.
The FeO is not magnetic but can be determined after a holding period below 570°C.
The system can be constructed as a device installed on the reactor itself to make in-situ analyses.
6 - BATTERY OF FLUID BED REACTORS.
The system is composed of several fluidized bed reactors. Each reactor is operated in batch. The ore is introduced at the beginning of the cycle. After sufficient carbide transformation, the product is tapped and a new cycle can be initiated.
This design allows :
A very large overall bed surface. The pressure drop of the fluidizing gas is then reduced in a large extent.
The possibility to utilize different gas velocities in different chambers in order to process in parallel the various size classes after classification.
Less particle attrition and less mechanical erosion thanks to the low gas velocity.
The possibility to recirculate the gas from one chamber into a second one to perform a prereduction of the ore before going to the scrubber.
The possibility to work close to the atmospheric pressure and to have a light structure.
The simplification of the construction, the chambers being composed of repetitive small weight components.
The different reactors can be arranged in the same housing with a thermal insulation common to all chambers. The process heaters can be immerged in the bed in order to take advantage of the high heat transfer rates.
The process is particularly useful for the processing of ores containing a large proportion of fines.
7 - STEEL FOUNTAIN
The process performs a continuous production of liquid steel from a feed of cold iron carbide.
The carbide is first preheated with the flue gases. During the preheating, the carbide is dissociated by an oxidizing gas and a flow of combustible gas is generated.
The iron resulting from the carbide dissociation is introduced in a vessel in the form of a free falling curtain and melted by the heat radiated by the axial flamme which burns the combustible gas with oxygen. A swirling movement of the metallic particles can be provided in order to assist the collection of the liquid droplets onto the wall.
The liquid metal is tapped continuously at the bottom.
The combustion of the gas is completed by air along the ore preheating section.
A control of the final carbon content can be obtained through the amount of decarburizing gas used in the carbide preheating zone.
8 -HOT CARBIDE INJECTION SYSTEM FOR ELECTRIC ARC FURNACES.
The EAF off-gas is burned in a post-combustion chamber. The lateral wall of this chamber is composed of an assembly of vertical heat-resisting tubes, or is formed by an annular space enclosed between two concentric cylinders.
The carbide is allowed to fall freely inside the tubes or the annular space. The corresponding atmosphere is inert and does not react with the carbide.
The hot carbide is collected at the base of the chamber and is continuously injected into the EAF by a pneumatic transportation system.
9 -STEELMAKING PROCESS WITH HOT CARBIDE CHARGING IN BASIC OXYGEN FURNACES.
A part of the converter off-gas is burned in a post-combustion chamber. The lateral wall of this chamber is composed of an assembly of vertical heat-resisting tubes, or is formed by an annular space enclosed between two concentric cylinders.
The carbide is allowed to fall freely inside the tubes or the annular space. The corresponding atmosphere is inert and does not react with the carbide.
The hot carbide is collected at the base of the chamber and is stored in a thermally insulated hopper.
At the beginning of the next charge, the hot carbide is introduced into the converter before the start of the blow.