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 iron ore pellets on a traveling grate under oxidizing conditions by means of hot gases passed through them, 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 burning of - iron ore pellets at temperatures of around 1200 to 1350 ° C takes place on straight or round traveling grates, which are provided with gas hoods, and which are also referred to as pellet burning machines.
• 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. in pre-drying and post-drying zones, heating zone, combustion zone, main combustion zone, post-combustion 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 less than with 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 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. For this purpose, solid, carbonaceous material in fine-grained form was incorporated into the pellets.
• the invention has for its object to keep the energy consumption as low as possible with increased throughput of the pellet burning machine and good pellet quality.
• the C fix content of the solid, carbon-containing material incorporated in the pellets is 1.3 to 1.8% by weight, based on the dry feed mixture in the case of haematite ores or in relation to the haematite content in mixtures of ores, the green pellets are charged to the moving grate at a temperature of 30 to 50 ° C or preheated on the moving grate to this temperature by pressure drying, the warm pellets are passed through suction drying and then in the suction with a negative pressure of 20 to 40 mbar with hot Gases from 1250 to 1350 ° C are hard burned.
• the pellets can consist of pure hematitic ores or a mixture of hematitic and magnetitic ores.
• the solid, carbonaceous material can consist of coals with a low content of volatile components - such as coke or anthracite - or of coals with a high content of volatile components - such as bituminous coals or lignites.
• volatile components - such as coke or anthracite -
• C fix content is set in the upper range.
• the C fix content is set in the lower range.
• the carbonaceous material is introduced into the mixture in the grain size required for pelleting. The cheapest C fix content for the respective operating case can be determined empirically.
• the ground material is heated to such an extent that the required feed temperature of the green pellets of 30 to 50 ° C can be reached if greater heat dissipation is prevented and possibly a warmer pelleting liquid is used.
• the required feed temperature can generally only be achieved in very warm areas, it possibly being necessary to work with warmed up turbid liquid.
• the green pellets on the traveling grate are preheated to this temperature in an upstream pressure dryer. The pressure is dried by warm gases that are pushed through the bed from below. The temperature of 30 to 50 ° C from the center to the surface of the bed must be reached. The temperature is higher in the lower part of the bed. About 10 to 15% of the moisture content is expelled during preheating.
• a preferred embodiment is that the suction drying is carried out with hot gases of 300 to 400 ° C and a vacuum of 20 to 40 mbar.
• the warm pellets are dried by suction by drawing the hot gases through the bed from top to bottom. Suction drying is carried out until the upper layer of the bed is dry. This is the case after about 2 to 3 minutes. With this operation, particularly good E are rgeb- nisse achieved.
• DAB derrost arrival on the W a grate-lining layer is charged 5-7 cm height of fired pellets.
• the throughput of the traveling grate is increased by reducing the layer of rust covering, which otherwise has thicknesses of approximately 9 to 11 cm.
• the pelleted carbon content enables the layer height to be reduced.
• a preferred embodiment consists in that the basicity of the pellets is set to 0.6 to 1.2, preferably 0.7 to 0.9.
• a preferred embodiment is that the preheating of the green pellets is carried out by pressure drying on the traveling grate with gases of 200 to 300 ° C, preferably 250 to 300 ° C, and a pressure of 20 to 50 mbar.
• the hematite concentrate had the following analysis (in% by weight, based on dry ore):
• 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 2% by weight of Cu (OH) 2 and 2% by weight of CaCO 3 , whereby the basicity was 0.7.
• the amount of C fix pelleted is given in the table.
• the moisture content of the green pellets was between 8.8 and 9.3% by weight.
• the advantages of the invention are that the throughput of the pellet burning machine can be increased considerably, producing pellets of good quality, reducing the total heat consumption and also reducing the electrical fan energy required. In addition, a significant proportion of the thermal energy required can be brought in by low-quality and cheap fuels.

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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)

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Citations (13)

• 1985
  • 1985-06-01 DE DE19853519666 patent/DE3519666A1/de not_active Withdrawn
• 1986
  • 1986-04-25 EP EP86200715A patent/EP0204355B1/fr not_active Expired
  • 1986-04-25 DE DE8686200715T patent/DE3661025D1/de not_active Expired

Patent Citations (13)

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