Management of offgas duct accretions in a smelting process
AssigneeNucor Corporation
InventorsRodney James Dry, Mark Hayton, Christopher Manning
Life of this patent
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Abstract
The present disclosure is directed to an improved direct smelting process for improving the efficiency of energy/heat recovery from hot smelter offgas for the purpose of steam raising and power generation. In examples, the formation of alkali sulfate accretions in the temperature range 500-1000° C. are removed by introducing a mechanical sweep-cleaning system to an offgas duct of the smelter. The sweep-cleaning system comprises at least one central rotating shaft with chains, with each chain optionally having an accretion-removal member at its distal end. When rotated, the chains lift and the accretion-removal member sweeps the walls of the duct to remove the accretions.
Claims23
A sweep-cleaning system for a smelt reduction vessel offgas hood, the sweep-cleaning system comprising:
- at least one centrally rotating vertical shaft configured for positioning within a downflow duct of the offgas hood;
- a plurality of chains proximally coupled to each of the at least one centrally rotating vertical shaft and extending distally therefrom;
- an accretion-removal member coupled to a distal end of the plurality of chains;
- and
- at least one drive motor configured to rotate the centrally rotating vertical shaft at a rotational speed, causing the plurality of chains to rise vertically proportional to the rotation speed within the at least one downflow duct.
An offgas system hood configured for operably coupling with a smelt reduction vessel (SRV), the offgas system comprising
- at least one downflow duct having a interior surface;
- at least one centrally rotating shaft positioned within the at least one downflow duct;
- and
- at least one chain connected along each of the at least one centrally rotating shaft and distally extend therefrom, wherein rotation of the centrally rotating shaft causes the chain to rise vertically proportional to a rotation speed within the at least one downflow duct.
A method of management of offgas accretions in a smelting reducing vessel coupled to a hood, the method comprising:
- providing at least one downflow duct operably coupled to the hood, the at least one downflow duct comprising:
- an interior surface;
- at least one centrally rotating shaft positioned within the at least one downflow duct;
- and
- at least one chain proximally connected along each of the at least one centrally rotating shaft and distally extend therefrom;
- an accretion-removal member connected to a distal end of the at least one chain;
- rotating the at least one centrally rotating shaft at a rotation speed and causing the chain to rise vertically proportional to the rotation speed within the at least one downflow duct;
- and
- removing at least some offgas accretions from the downflow duct.
A direct smelting process comprising:
- a smelt reduction vessel (SRV) configured for containing a bath of molten metal and slag;
- an offgas system comprising at least one downflow duct, the at least one downflow ducts are each equipped with a centrally rotating shaft and a series of connected chains extending distally therefrom configured to rotate within an interior surface of the downflow ducts;
- injecting carbonaceous material and final smelting of metalliferous ore into the SRV producing carbon-containing hot metal, molten slag, and CO-containing offgas,
- injecting oxygen-containing gas into a topspace above the molten slag;
- at least partially combusting the CO-containing offgas;
- removing at least some accretions from the walls of the at least one downflow duct with the series of connected chains connected to a rotating shaft positioned in the downflow duct;
- and
- providing enhancement of wall heat transfer and SRV process heat.
Dependencies are inferred from the claim text.