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

Definitions

• the invention relates to a process for the direct reduction of iron oxide-containing materials to sponge iron in a rotary tube furnace, the feed being passed through the rotary tube furnace in countercurrent to the gas atmosphere, solid carbon-containing reducing agent with a high content of volatile constituents being charged into the loading end of the rotary tube furnace, and solid carbon-containing reducing agent high volatile content is blown through the discharge end of the rotary kiln and is distributed over part of the length of the kiln to the feed and oxygen-containing gases are introduced into the rotary kiln at several points through the jacket.
• the zone of the rotary kiln before the discharge end of the kiln is particularly sensitive to temperature fluctuations and carbon depletion in the material bed. This can lead to fluctuations in the degree of metallization, formation of deposits in the furnace and increased heat consumption.
• CA-PS 872 728 From CA-PS 872 728 it is known to blow coal with a grain size up to 6 mm into the discharge end with a blowing device and to feed the remaining coal into the loading end, but the grain size below 1 mm is also blown in from the discharge end.
• the invention has for its object to constantly maintain optimal operating conditions in the end zone of the rotary kiln.
• This object is achieved according to the invention by separating solid carbon-containing material with a high volatile content into a coarser and a finer fraction, mixing part of the coarser and finer fraction and blowing it into the discharge end of the rotary kiln with a blowing device, the mixture consists of 10 - 40% finer fraction and 90 - 60% coarser fraction, the amount of the mixture blown up to 50% of the total the solid carbon-containing material that is fed in, the blown-in mixture is distributed up to a maximum of 50% of the furnace length and the remaining solid carbon-containing material is charged into the loading end of the rotary kiln.
• the solid, carbon-containing reducing agent contains more than 20% of flammable, volatile components.
• a part with a lower volatile content can also be inserted in the loading end of the furnace.
• the oxygen-containing gases generally air
• the oxygen-containing gases are blown in through jacket pipes, the outlet openings of which lie in the longitudinal axis of the furnace, and / or through nozzle stones, the outlet openings of which lie approximately in the lining of the furnace.
• air is expediently introduced through the air tube of the central burner.
• the central burner is used to heat the furnace during commissioning and standstills, but can also be switched on briefly to increase the temperature.
• the coarser and the finer fraction can be generated by separating the entire solid reducing agent or a partial stream. The separation is advantageously carried out on vibrating screens. The amount of finer and coarser fraction that is not needed for blowing is charged into the feed end.
• the reducing agent which is not subjected to this separation, may also be charged into the loading end.
• the furnace length over which the reducing agent is blown is calculated from the end of the discharge.
• the proportion of finer fraction in the blown mixture is selected in the upper range if the content of volatile constituents in the reducing agent is relatively low, since then a larger one Amount of fine-grained reducing agent must be burned to cover the heat requirement.
• the proportion is selected in the lower range if the volatile content is relatively high, since more heat is then covered by the combustion of the volatile components expelled.
• the sieve cut for the separation of the reducing agent is selected depending on the reactivity of the coal, its volatile content and the required operating conditions in the furnace. With low throughputs of the rotary kiln, the percentage of the blown carbon-containing material in the total amount used is in the upper range.
• a preferred embodiment is that the separation of the solid carbonaceous material takes place with a screen cut of 3 to 5 mm.
• screen cut means that a certain screen size is used in this area. The screen cut in this area results in particularly good operating conditions in most cases.
• a preferred embodiment is that the mixture of the blown carbon-containing material consists of 15-30% finer fraction and 85 to 70% coarser fraction. In most cases, this mixing ratio results in particularly good operating conditions.
• a preferred embodiment is that the amount of the mixture of solid carbonaceous material blown in is 15-30% of the total carbonaceous material fed.
• One embodiment consists in that the upper grain size of the blown coarser fraction is limited and the coarse grain above it is separated off and charged into the loading end of the rotary kiln.
• the coarse grain can be separated before the separation into the finer and coarser fraction or after the separation from the coarser fraction.
• coarse coal particles are not blown in with the coarser fraction, as a result of which the excess carbon content of the discharge material is reduced and the operating conditions in the furnace can be made more uniform. This separation is carried out in particular when the reducing agent contains larger and changing proportions of coarse grain.
• a preferred embodiment is that the upper grain size of the blown coarser fraction is limited to 10 to 15 mm. This limitation gives very good operating conditions in the rotary kiln.
• a preferred embodiment consists in that after the separation, the finer fraction is passed into one container and the coarser fraction into another container, the corresponding amounts of finer and coarser fraction are drawn off from the containers, mixed and blown into the discharge end, the excess Drain the quantities of the finer and coarser fractions separately from the containers and into the entry end of the Rotary kiln can be charged.
• the term "container” means chutes, bunkers and the like. Dispensing devices are arranged at the lower end of the containers, which allow metered removal and control the desired amount of finer and coarser fractions from the respective containers. The excess amount of finer and coarser fraction flows out of the upper part of the container and is charged into the entry end of the furnace.
• the streams of the fractions are passed into bunkers and then metered out.
• the desired mixture of coarser and finer fractions for blowing in can be achieved with very little effort, regardless of fluctuations in the grain composition of the coal supplied.
• the rotary kiln had a diameter of 4.8 m and a length of 80 m. It was equipped with 8 jacket pipes and 3 systems of nozzle stones. Air was blown into the free furnace space through the casing pipes and nozzle stones and also into the feed through the nozzle stones. A coal blowing device and a central burner were arranged at the discharge end of the furnace.
• 1.2 t / h were in a grain size of 0 - 5 mm and 3.8 t / h in a grain size of 5 - 15 mm.
• the temperature of the furnace atmosphere in the last part of the rotary kiln could be kept constant at around 1090 ° C.
• the advantages of the invention are that very constant furnace conditions can be maintained in the end zone of the rotary kiln before the discharge end.
• a precisely metered and constant ratio of coarser to finer fraction can be set and maintained even with the usually constantly fluctuating fine fractions of the coal supplied.
• this keeps the temperature and, on the other hand, the carbon content in the feed largely constant and, if necessary, can be changed quickly and in a controlled manner.
• the ratio can be set and kept constant so that - in connection with the use of only one blowing device - by the rapid combustion of the fine-grained coal in flight a constant temperature and a rapid and constant consumption of the oxygen of the carrier air is achieved and thereby the combustion of the coarser coal is kept low during the flight. This also brings a constant amount of carbon into the loading bed.

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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)
• Muffle Furnaces And Rotary Kilns (AREA)
• Manufacture Of Iron (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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Cited By (2)

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Citations (7)

Family Cites Families (1)

• 1986
  • 1986-06-21 DE DE19863620842 patent/DE3620842A1/de not_active Withdrawn
  • 1986-07-31 IN IN584/CAL/86A patent/IN164140B/en unknown
• 1987
  • 1987-06-05 ES ES87201059T patent/ES2021694B3/es not_active Expired - Lifetime
  • 1987-06-05 EP EP87201059A patent/EP0255154B1/fr not_active Expired - Lifetime
  • 1987-06-05 DE DE8787201059T patent/DE3769394D1/de not_active Expired - Lifetime
  • 1987-06-08 ID IDP43987A patent/ID929B/id unknown
  • 1987-06-16 US US07/062,731 patent/US4838934A/en not_active Expired - Fee Related
  • 1987-06-19 AU AU74522/87A patent/AU590862B2/en not_active Ceased
  • 1987-06-19 ZA ZA874437A patent/ZA874437B/xx unknown
  • 1987-06-19 TR TR435/87A patent/TR23022A/xx unknown
  • 1987-06-20 CN CN87104326A patent/CN1011893B/zh not_active Expired
• 1991
  • 1991-04-18 GR GR90400902T patent/GR3001794T3/el unknown

Patent Citations (7)

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