Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
  • C22B1/24—Binding; Briquetting ; Granulating
  • C22B1/2413—Binding; Briquetting ; Granulating enduration of pellets

Definitions

• the invention relates to a process for the hard burning of hematite and / or heat-consuming additives containing iron ore pellets on a traveling grate under oxidizing conditions by means of hot gases passed through, the pellets containing solid, carbon-containing material incorporated, which provides part of the amount of heat required for hard burning.
• pellet burning machines The hard firing of iron ore pellets at temperatures of about 1 200 to 1 350 ° C takes place on straight or round traveling grates, which are provided with gas hoods, and which are also called pellet burning machines. These pellet burners have - seen in the direction of travel - different treatment zones, namely drying zone, burning zone and cooling zone. These zones can be divided, e.g. B. in pre-drying and post-drying zones, heating zone, pre-firing zone, main firing zone, post-firing zone and first and second cooling zones.
• the iron content of the finished pellets is largely in the highest oxidation state, ie as Fe 2 0 3 .
• the amount of heat to be introduced by means of the hot gases is lower than in the case of hematitic pellets, since the oxidation of Fe 3 0 4 to Fe 2 0 3 is exothermic.
• the specific throughput of a pellet burning machine depends to a large extent on the level of the magnetite content of the ore to be processed and increases with increasing magnetite content. Therefore, many attempts have been made to increase the throughput in the processing of hematites.
• the invention is based, with good throughput of the pellet burning machine and good pellet quality, to reduce the energy consumption even further.
• the object is achieved according to the invention in that the C fix content of the solid, carbon-containing material incorporated in the pellets is dimensioned stoichiometrically in such a way that it is both the amount which would be necessary to reduce any hematite present to magnetite and that Amount required to decompose the heat-consuming additives that are present, in each case by up to 50%, and that the hot gases in the combustion zone of the traveling grate are passed through the pellet bed with a vacuum of 5 to 20 mbar.
• the pellets can consist of pure hematitic ores or a mixture of hematitic and magnetitic ores.
• the solid, carbonaceous material can consist of highly reactive coals or weakly reactive coals. The coals can contain low or high levels of volatile components.
• the C fix content introduced by the coals is up to about 50% higher than the stoichiometric amount.
• the stoichiometric amount is based on the hematite content of the dry ore or dry or
• C fix is only added when such heat-consuming additives are added, and the amount is calculated accordingly.
• the carbonaceous material is introduced into the mixture in the grain size required for pelleting.
• the negative pressure with which the hot gases are passed through the pellet bed in the firing zone is compared to the values of around 30 to 40 mbar (millibars) that are otherwise customary in pellet burning. considerably reduced to 5 to 20 mbar.
• firing the thermal treatment of the pellets is meant at temperatures above about 1250 0 C.
• the specific amount of gas (amount of gas in Nm 3 / kg of the feed in the combustion zone) is also reduced accordingly.
• the expression “firing zone includes both the heating zone in which the dried pellets are heated to the desired firing temperature and the actual firing zone in which the pellets are kept at the desired firing temperature.
• the combination of reduced vacuum in the firing zone and increased C fix content in the pellets can maintain the mechanical strength of the pellets, increase the reducibility of the pellets, maintain the performance of the pellet burning machine, and the consumption of electrical energy and hot Gases are lowered.
• the C fix content of the pellets can be slightly higher than with coals with a higher proportion of volatile flammable components.
• the cheapest C fix content and negative pressure for each operating case can be determined empirically.
• a preferred embodiment is that the hot gases in the suction drying zone are passed through pellet bed with a negative pressure of 5 to 20 mbar. Drying is generally carried out in two stages. In the first stage, pressure drying takes place, whereby hot gases are forced upwards through the pellet bed. In the second stage, drying takes place by suction, with hot gases being sucked through the bed from top to bottom. The advantages are further increased by reducing the negative pressure and the specific amount of gas in the suction drying
• a preferred embodiment is that the hot gases in the burning zone of the traveling grate are passed through the pellet bed with a negative pressure of 10 to 15 mbar. With this negative pressure and the corresponding specific amount of gas, particularly favorable results are achieved.
• a preferred embodiment is that 1.7 to 2.0% by weight of C fiX , based on dry ore, are pelleted into hematitic pellets.
• the addition of C fix is related to the hematite content of the ore or mixture. If heat-consuming additives are added to the ore, their amount can be added to the hematite content. This addition of C fix gives very good results.
• a preferred feature is that in hematite pellets 1.8 to 1.9 wt .-% C fix, based on dry ore, are einpelletiert. Here too, any admixed, heat-consuming additives can be added. This addition gives particularly good results.
• the hematite concentrate had the following analysis (in% by weight, based on dry ore):
• the magnetite concentrate had the following analysis (in% by weight, based on dry ore):
• the charcoal had the following analysis (in% by weight, based on dry coal):
• the anthracite had the following analysis (in% by weight, based on dry coal):
• the coke had the following analysis (in% by weight, based on dry coal):
• the pellet firing was carried out on a 26.5 cm diameter pan.
• the pellets were produced with the addition of 10% by weight of dolomite and 0.5% by weight of bentonite.
• the humidity of the green pellets was between 9.0 and 9.3%.
• the advantages of the invention are that the heat consumption and energy consumption of the pellet burning machine is reduced, the burned pellets have good mechanical strength and reducibility and the investment costs for the plant are reduced with the same throughput.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Geochemistry & Mineralogy (AREA)
• Geology (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1984
  • 1984-05-18 DE DE19843418468 patent/DE3418468A1/de not_active Withdrawn
  • 1984-07-25 IN IN529/CAL/84A patent/IN161245B/en unknown
• 1985
  • 1985-04-30 JP JP60093529A patent/JPS60245732A/ja active Pending
  • 1985-05-07 EP EP85200718A patent/EP0161721B1/de not_active Expired
  • 1985-05-07 DE DE8585200718T patent/DE3562492D1/de not_active Expired
  • 1985-05-15 ZA ZA853695A patent/ZA853695B/xx unknown
  • 1985-05-16 BR BR8502306A patent/BR8502306A/pt not_active IP Right Cessation
  • 1985-05-17 CA CA000481829A patent/CA1258376A/en not_active Expired
  • 1985-05-17 AU AU42687/85A patent/AU571695B2/en not_active Ceased
  • 1985-06-08 CN CN85104327.5A patent/CN1003943B/zh not_active Expired

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