GB2189260A

GB2189260A - Improved process for producing metallized pellets

Info

Publication number: GB2189260A
Application number: GB8707680A
Authority: GB
Inventors: Thomas Willard Hoffman
Original assignee: Midrex International BV Rotterdam Zurich Branch
Current assignee: Midrex International BV Rotterdam Zurich Branch
Priority date: 1986-04-17
Filing date: 1987-03-31
Publication date: 1987-10-21
Also published as: DE3712846C2; MY101724A; GB8707680D0; ATA88887A; JPH0575808B2; DE3712846A1; JPS62290811A; AT396253B

Description

GB 2 189 260 A 1

SPECIFICATION whereby the sulfurcontaining components of the

Improved process for producing metallized pellets spent reducing gas are lowered, thereby reducing the sulfur contamination of the gas reformer Background of the Invention catalyst. Reducing sulfur contamination of the gas

Direct reduction processes for producing 70 reformer catalyst improves the overall efficiency of metallized iron from iron oxide pellets, lump ores, or the direct reduction process.

similar materials which include iron oxide, are widely known and used in the steel industry. Objects of the Invention Suitable direct reduction processes forforming It isthe principal object of this invention to metallized iron are disclosed in U.S. Patent 75 provide an improved process for producing Numbers 3,128,174 and 3,881,916. In a direct metallized pellets in a shaft furnace direct reduction reduction process such as the Midrex Process, process wherein reducing gas is formed in a pellets of metal oxides are introduced at top of a stoichiometric reformer, including means for shaft furnace to establish gravitational flow utilizing spent reducing gas as reformer gas feed therethrough. Reducing gas consisting essentially 80 while reducing sulfur contamination of the reformer of carbon monoxide and hydrogen is heated to catalyst.

sufficient temperature to effect direct reduction, is It is also an object of this invention to providd introduced to the metal oxide burden in the furnace, apparatus for reducing sulfur contamination of passes through the burden in counter-flow relation catalyst in a stoichiometric reformer used in to the gravitationally descending burden, and reacts 85 conjunction with a direct reduction shaft furnace.

with the burden, forming metallized pellets and a reacted top gas consisting principally of carbon Brief description of the accompanying drawings dioxide and water along with some unreacted Figure 1 is a schematic diagram of a vertical shaft reductants, which are drawn off as sulfur-containing furnace and its associated equipment for producing spent top gas. 90 metallized iron in accordance with the preferred Additionally, U.S. Patent Number 3,748,120 embodiment of the invention.

discisoes a shaft furnace direct reduction process in Figure 2 is another schematic diagram illustating which spent reduction gas is catalytically reformed a second implementation of the invention.

from a mixture of gaseous hydrocarbon and spent reducing gas from the reduction process. In this 95 Description of the preferred embodiment process the spent reducing gas is cleaned and Referring now to Figure 1, a vertical shaft furnace cooled upon exiting the reduction furnace and prior 10 has a feed hopper 12 mounted thereon into to being introduced into a catalyst containing which iron oxide 14, such as iron oxide pellets, lump reformer. In the direct reduction process the ore, or similar material is fed. The force of gravity reducing gas passes through and reacts with the 100 causes the iron oxide to flow through a feed pipe 16 burden to produce sulfur containing gases which to form a packed bed burden 18 within the shaft contaminate the catalyst. Sulfur contamination of furnace 10. As is conventional, metallized iron, the catalyst lowers the overall efficiency of the preferably in the form of pellets or lumps, descends process. Processes for reducing the sulfur level in through the furnace, exiting through discharge pipe the recycled spent reducing gas by increasing the 105 20, and is removed by conveyor 22. Adding metallic iron content of the scrub water utilized by particulate iron oxide material to the hopper 12 the cooler-scrubber or by introducing a sulfur establishes a gravitational flowthrough the shaft reducing agent into the spent reducing gas are also furnace 10 comprising an input of iron oxide known. material 14 and an output of particulate metallized By contrast with prior art processes, which require 110 iron.

a specialized sulfur reducing agent, the present The furnace 10 is surrounded by a bustle and invention provides an improved method and tuyere system generally illustrated at 24. Reducing apparatus for reducing the sulfur contamination of gas is introduced into the furnace 10 through a gas the gas reformer catalyst by selectively introducing port 28 and a gas pipe 52. Reacted of spent reducing into the scrub water dust having an affinity for 115 gas is removed from the upper portion of the sulfur. The spent reducing gas interacts with the furnace 10 through a gas take off pipe 30. The take dust-laden scrub water, reducing the sulfur content off pipe 30, through which spent reducing gas of the recycled spent reducing gas, thereby reducing leaves the furnace is coupled to a cooler scrubber the sulfur contamination of the gas reformer 34. The cooler scrubber 34 is a conventional venturi catalyst. 120 scrubber surrounded by an annular or sectional packed bed cooler and employs a recirculating Brief Summary of the Invention scrub water system. The spent reducing gas flows

An improved method and apparatus for downward through the venturi and upwardly decreasing the sulfur content of the recycled spent through the packed bed through which scrub water reducing gas in a direct reduction process is 125 is descending, providing intimate contact of the disclosed. Dust, including components having an spent reducing gas with the scrub water.

affinity for sulfur, is recovered from the process and Waste (used) scrub water flows from the cooler introduced in controlled quantities into the scrub scrubber 34 and is divided into first and second water to increase the interaction between the dust- parts. The first part is coupled by a pipe 35 to a laden scrub water and the spent reducing gas 130pump 36 and recirculated to the cooler-scrubber 34 2 GB 2 189 260 A 2 as a portion of the scrub water. The second portion conventional metallic ion source 68 and added to of the waste scrub water flows from the cooler- the scrub water at a controlled rate by a suitable scrubber 34 to a clarifier 60 which removes flow control device 70. The remaining portions of particulate materials to produce clean hot water. this system are essentially identical to those Particulate material rmeoved from the waste water 70 discussed in Figure 1 and will thus will not be is discharged as solid waste by the clarifier 60, and described in detail.

removed using any convenient means. The clean The catalyst 46 includes active ions such as nickel water directed to and cooled by a cooling tower 63. oxide which are believed to provide "active sites- in The hot water, after being cleaned and cooled by the course surfaces of the catalyst carrier.

clarifier 60 and cooling tower 63, is pumped by way 76 Catalyzation is thought to take place at or near the of a suitable pipe 64 and combined with the active sites (see Roberton, AFP Catalyst of Gas discharge of the recirculating pump 36 to form the Reaction by Metal, Logas, (1970).

scrub waterto the cooler-scrubber 34. Sulfur compounds mask or reduce the activity of Cleaned and cooled spent reducing gas from the these active sites. An excess of sulfur adhering to cooler scrubber 34 is coupled through pipe 40 to the 80 the sites in the catalyst carrier will reduce catalyst input of a stoichiometric reformer 38. A plurality of effectiveness by reducing the area or number of indirect heat exchanger catalyst-containing tubes 46 active sites. Thus, the presence of sulfur can poison are positioned in the reformer 38 and are heated by the catalyst. The disclosed process and apparatus burners 42 using any convenient fuel. Hot reducing removes sulfur from the spent reduction gas gas flows from the catalyst tubes 46 of the reformer 85 thereby reducing the sulfur contamination of the 38 to the bustle and tuyere system 24 through the active sites of the catalyst 46. Reducing the sulfur pipe 52, as previously discussed. contamination of the catalyst 46 improves the It has been demonstrated that the system efficiency of the process.

illustrated in Figure 1 substantially lowers the sulfur ---Pellets"as used through this specification and content of the spent reducing gas, the result being 90 claims means: pellets, lumps, nodules, pieces, less sulfur contamination of the catalyst 46. It is granules, agglomerated particulates, and the like, believed that the waste water emerging from the which are small enough to flow through a direct cooler scrubber 34 includes process dust having an reduction furnace and to have sufficient surface area affinity for sulfur. Recirculating a portion of this to react with reducing gas passing therethrough, yet waste water as scrub waterthrough pipe 35 and 95 large enough to support the weight of the burden.

pump 36 increases the concentration of process Finely divided material, which would plug the dust particles in the scrub water. Increasing the interstices between the pellets, blocking the gas concentration of process dust in the scrub water passageway around them, are not included in the increases the interaction between the scrub water definition of pellets.

and the spent reducing gas. As the spent reducing 100 "Metailized", as used throughout this gas interacts with the process dust laden scrub specification, does not mean coated with metal, but water, sulfur-containing solids are formed which means nearly completely reduced to the metallic precipitate out and are removed as solid waste by state, i.e., always in excess of 60% metal, and the clarifier 60. The interaction between the process usually in excess of 80% metal in the material. Such dust and the sulfur containing portions of the spent 105 metallized iron in many forms, including pellets and reducing gas is believed to be due to metallic ions lump, is well suited as feed material to steelmaking contained in the process dust. Other interactions furnaces such as an electric arc furnace.

between the spent reducing gas and the process Although the invention has been disclosed and dust laden scrub water (not fully understood atthis described with respectto a process for the direct time) are also probable. 110 reduction of iron oxide to form metallized iron, other Some water loss is experienced through the metal oxide ores such as nickel or cobalt oxide, for discharge of the particulates and solid wastes from example, can be reduced to the metallized state the clarifier 60 and from other sources. This loss is using the disclosed process and apparatus. All such compensated for by adding a suitable amount of alternative uses of the disclosed process and - - feed waterto the pipe 64 using a conventional.115 apparatus are within the scope of the invention.

make-up water source 72. From the foregoing, it is obvious that an improved direct reduction process and apparatus which Alternative Embodiments lowers the sulfur contamination of the reformer Figure 2 illustrates an alternate embodiment of catalyst has been invented.

the invention. This embodiment is esentially 120

Claims

identical with the embodiment previously discussed CLAIMS with reference

to Figure 1, except for the method 1. An improvement in a process for producing used to control the process dust content or the scrub metallized pellets by direct reduction of metal oxide, water and the inclusion of an option for adding the method including the steps of passing a metallic ions to the scrub water at a controlled rate. 125 reducing gas thorugh a furnace having a reducing In this embodiment, a process dust recovery zone and containing metal oxide material such that system 74 recovers process dust using any said reducing gas reacts with said metal oxide convenient means. This process dust is then material to produce metallized pellets and a spent combined with water and added to the scrub water. reducing gas which contains sulfur, removing said Additional metallic ions may be supplied by a 130 spent reducing gas containing sulfur from said 3 GB
2 189 260 A
3 furnace, introducing said spent reducing gas and thereby reducing the sulfur content of said spent scrub water into a cooler-scrubber to cool and scrub reducing gas; and said spent reducing gas to produce cooled spent e) means for recycling said spent reducing gas reducing gas, introducing waste scrub water from 55 through a gas reformer to produce said reducing the cooler-scrubber into a clarifier to produce scrub gas.

water, reforming said spent reducing gas into an 7. Apparatus in accordance with claim 6, further effective reducing gas, and introducing said including means for collecting process dust, means reducing gas into said reducing zone, the for combining a selected portion of said process improvement comprising the additional step of 60 dust with water to produce a mixture of water and selective introduction of process dust into said process dust, and means for combining said scrub waterto produce dust laden scrub water, mixture of process dust and water with cooled and whereby said dust laden scrub water interacts with clarified waste water f rom said cooler scrubber to sulfur containing components of said spent produce said scrub water.

reducing gas, thereby reducing the sulfur content of 65 8. Apparatus in accordance with claim 6 or 7, said reducing gas. including means for supplying a source of metallic 2. A process in accordance with claim 1, including ions and means for injecting said metallic ions into the additional steps of dividing said waste scrub said scrub water at a predetermined rate whereby water into first and second portions, and combining said metallic ions react with reduced sulfur in said the second portion with the output of said clarifier to 70 spent reducing gas to form solids containing sulfur.

control the process dust content of said scrub water. 9. Apparatus in accordance with claim 6 wherein 3. A process in accordance with claim 1 or 2, said means for controlling the process dust content further comprising the step of introducing selected of said scrub water includes means for dividing the metallic ions into said scrub water. used scrub water into first and second parts and
4. A process in accordance with claim 3, wherein 75 means for recirculating said second part as a portion said metallic ions are selected from the group of said scrub water to increase the process dust consisting of: ions of iron, zinc, and calcium. content of said scrub water.
5. A process in accordance with claim 1, 2,3 or 4, 10. Apparatus in accordance with claim 9 further in which said oxide is iron oxide. including a source of metallic ions and means for
6. Apparatus for the direct reduction of metal 80 injecting said metallic ions into said scrub water at a oxide pellets to form metallized pellets in which predetermined rate whereby reducing sulfur in said metal oxide is introduced into a furnace and flows scrub water reacts with said metallic ions to produce downwardly under the force of gravity as a hot solids containing sulfur.

reducing gas from a gas reformer flows upward 11. Apparatus in accordance with any of claims 6 through and interacts with said metal oxide thereby 85 to 10, wherein said metal oxide is iron oxide.

producing metallized pellets and spent reducing gas 12. A process for producing metallized pellets by and recycling said spent reducing gas through a direct reduction of metal oxide, substantially as cooler-scrubber to the gas reformerto produce said hereinbefore described with referencesto Figure 1 reducing gas, comprising in combination: of the accompanying drawings.

a) a furnace continuously charged with metal 90 13. A process for producing metallized pellets by oxide to form a burden which moves downwardly direct reduction of metal oxide, substantially as under the force of gravity; hereinbefore described with reference to Figure 2 of b) means for introducing a reducing gas into said the accompanying drawings.

furnace such that reducing gas flows upwardly 14. Apparatus forthe direct reduction of metal interacting with said burden to produce spent 95 oxide pellets, substantially as hereinbefore reducing gas and metallized pellets; described with reference to Figure 1 of the c) cooler-scrubber means accepting as input said accompanying drawings.

spent reducing gas and scrub water for cooling and 15. Apparatus for the'direct reduction of metal scrubbing said spent reducing gas; oxide pellets, substantially as hereinbefore cl) means for controlling the process dust content 100 described with reference to Figure 2 of the of said scrub water such that said spent reducing accompanying drawings.

gas interacts with said dust laden scrub water Printed for Her Majesty's Stationery Office by Courier Press, Leamington Spa, 10187. Demand No. 8991685. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.