Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/08—Making spongy iron or liquid steel, by direct processes in rotary furnaces
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/14—Multi-stage processes processes carried out in different vessels or furnaces
  • C21B13/146—Multi-step reduction without melting

Definitions

• the invention relates to a process for the direct reduction of materials containing iron oxide to sponge iron with pre-reduction in a fluidized bed and final reduction below the melting temperature in a rotary kiln.
• the invention has for its object to produce a largely metallized sponge iron made of fine-grained materials in the rotary kiln without build-ups or agglomerations disturb the operation of the rotary kiln.
• This object is achieved according to the invention in that fine-grained materials containing iron oxide in the fluidized bed are reduced to 50 to 80% metallization of the iron content and the pre-reduced fine-grained material in the turn tube furnace is reduced.
• the ratio of metallic iron to the total iron content in percent is referred to as metallization
• a fluidized bed both low-expanded fluidized beds with a defined bed surface can be used as well as more expanded fluidized beds which are operated above the floating speed of the individual particles, such as. B. circulating fluidized beds.
• the pre-reduced material is preferably charged hot into the rotary kiln. On the one hand, this saves heating energy and relieves the rotary kiln - which is a poor heat exchanger - of the heating work. In principle, the pre-reduced material can also be charged cold into the rotary kiln. Coals, gas, oil or combinations of these reducing agents can be used as reducing agents in the rotary kiln.
• the rotary kiln can be operated in countercurrent or cocurrent and can be equipped with jacket pipes, jacket burners and / or nozzle stones. If necessary, desulfurizing agents are added. Any excess solid carbon in the discharge can be separated off and returned to the rotary kiln.
• the material pre-reduced according to the invention can be finished-reduced without problems in the rotary kiln, although its particle size in the fluidized bed has not been significantly increased.
• Special measures, such as B. high peripheral speed of the rotary kiln or limitation of the lower grain size are not required.
• a preferred embodiment is that the pre-reduction takes place in the fluidized bed to 60 to 70% metallization. This metallization leads to particularly favorable conditions both in the fluidized bed and in the rotary tube oven.
• a preferred embodiment is that the final reduction in the rotary kiln is carried out using solid carbon-containing reducing agents.
• the use of solid reducing agents loosens the feed in the rotary kiln. On the one hand, this further reduces the risk of agglomeration and formation of deposits and, on the other hand, has a favorable influence on the reduction.
• a preferred embodiment consists in that at least the major part of the solid carbon-containing reducing agent for the final reduction is already charged in the fluidized bed and is hot-charged with the pre-reduced material in the rotary kiln.
• the coal is also preheated and charged into the rotary kiln and, on the other hand, difficult, baking coals can also be used, the direct use of which in the rotary kiln would lead to malfunctions.
• a preferred embodiment is that the upper grain size of the fine-grained iron oxide-containing material is about 2 mm. This achieves advantageous operating conditions for the fluidized bed.
• a preferred embodiment is that a solid, fine-grain desulfurizing agent is added to the rotary kiln.
• the grain size of the desulfurization agent is less than 3 mm.
• Common desulfurization agents such as. B. limestone or dolomite is used. This enables a low sulfur content in the sponge iron to be achieved.
• a preferred embodiment consists in that the material to be discharged from the rotary kiln is separated into sponge iron, excess fuel and desulfurizing agent after cooling. In this way, the sulfur-containing desulfurization can be removed from the process in a simple manner and the excess carbon is also separated.
• a hematitic iron ore with 67% Fe was used.
• the grain size distribution was:
• the iron ore was used together with a lignite coal in an amount corresponding to 0.5 kg C fix / kg Fe in an electrically heated rotary kiln.
• the oven was heated to 980 ° C over four hours and held at that temperature.
• Material samples were taken from the furnace at intervals of one hour with an N 2 -flushed sample spoon and it was found that, starting with a degree of reduction (calculated as 0 2 -degradation) of approximately 50%, corresponding to a degree of metallization of approximately 25%, the material sintered together. A further reduction was therefore not possible.
• Example 1 The ore / coal mixture used in Example 1 was also reduced in a fluidized bed at 980 ° C. to a degree of reduction of 50%, corresponding to a degree of metallization of 25%.
• the pre-reduced material was then placed in an electrically heated rotary kiln. At a temperature of 980 ° C, the sintering of the Determine the contents of the oven.
• Example 1 The ore / coal mixture used in Example 1 was treated as described in Example 2, but was now reduced to a degree of reduction of 75%, corresponding to a degree of metallization of 63%, and, as described in Example 2, was used in the rotary kiln.
• the metallization could be increased to 92% without the furnace contents sintering.
• the advantages of the invention are that fine-grained materials can be reduced to sponge iron easily and economically, only cheap primary energy being required in both stages, and in particular in the final reduction stage.
• the rotary kiln is relieved of heating work.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Manufacture Of Iron (AREA)
• Apparatus For Disinfection Or Sterilisation (AREA)
• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)

Applications Claiming Priority (2)

Publications (2)

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Citations (7)

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• 1982
  • 1982-03-20 DE DE19823210232 patent/DE3210232A1/de not_active Withdrawn
  • 1982-06-18 IN IN707/CAL/82A patent/IN158419B/en unknown
  • 1982-09-14 US US06/417,958 patent/US4443250A/en not_active Expired - Fee Related
• 1983
  • 1983-02-19 DE DE8383200255T patent/DE3360636D1/de not_active Expired
  • 1983-02-19 EP EP83200255A patent/EP0090438B1/fr not_active Expired
  • 1983-03-02 NZ NZ203437A patent/NZ203437A/en unknown
  • 1983-03-03 NO NO830733A patent/NO159864C/no unknown
  • 1983-03-18 AU AU12664/83A patent/AU556203B2/en not_active Ceased
  • 1983-03-18 CA CA000423928A patent/CA1204943A/fr not_active Expired
  • 1983-03-18 ZA ZA831901A patent/ZA831901B/xx unknown
  • 1983-03-18 PH PH28668A patent/PH20105A/en unknown

Patent Citations (7)

Non-Patent Citations (1)

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