Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B1/00—Shaft or like vertical or substantially vertical furnaces
  • F27B1/10—Details, accessories, or equipment peculiar to furnaces of these types
  • F27B1/16—Arrangements of tuyeres
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/02—Making special pig-iron, e.g. by applying additives, e.g. oxides of other metals
  • C21B5/023—Injection of the additives into the melting part

Definitions

• the invention relates to a method for optimizing the operation of a shaft furnace.
• Bowls have long been used for the production of pig iron and over the years have been modified and improved to increase their productivity.
• a certain number of factories are at the limit of the production capacity of their shaft furnaces, in particular because the limit of the load of the wind blowers is reached.
• the document DE 312 935 C describes the introduction of pre-reduced iron ore finely divided, by the nozzles into the crucible of the blast furnace.
• lime is either mixed in advance with the prereduced, or added to the nozzles.
• finely ground carbon can be added to the hot wind in the nozzles.
• the injection of pre-reduced iron ore by the nozzles with coal seems advantageous to provide part of the heat necessary for the fusion of the pre-reduced.
• the application of the measures described in document DE 312 935 C results in blockage of the nozzle cavities, and a lowering of the temperature of the molten metal in the crucible of the blast furnace.
• the object of the present invention is to provide a method for optimizing the operation of a shaft furnace.
• this objective is achieved by a process for optimizing the operation of a shaft furnace comprising nozzles comprising the following steps: a) manufacture of fine particles of pre-reduced iron; b) mixing the fine particles of pre-reduced iron with a solid carbonaceous reducing agent, the fine particles of pre-reduced iron preferably having a particle size less than 2 mm and the solid carbonaceous reducing agent preferably having a particle size less than 200 ⁇ m; c) injection of the mixture into the shaft furnace through the nozzles; d) fusion of the pre-reduced iron particles.
• One of the advantages of this process consists in the fact that the operating principle of the shaft furnace is not disturbed.
• the production of pig iron is rapidly increased, thanks to the nature of the mixture proposed by the present process.
• a mixture of pre-reduced iron particles and carbon reducer is injected into the shaft furnace where these particles are reduced and melted and the carbon reducer is consumed.
• the particle sizes chosen for the carbon reducer and the fine particles of pre-reduced iron allow the injection of a mixture which is well assimilated by the blast furnace. It is therefore essential not only to make a mixture of the prereduced and the carbonaceous reducer, but also to choose the particle sizes of the components of the mixture.
• the injection of such a mixture ensures stable operation of the nozzles and coke cavities opposite the nozzles.
• the additional thermal requirements associated with the injection can be covered by the energy released during the oxidation of the carbon reducer.
• an intimate mixture of fine particles of pre-reduced iron and of solid carbonaceous reducing agent is injected. This can be obtained by providing a transport distance of the mixture before its injection into the shaft furnace through the nozzles equal to at least 25 times, preferably 50 times, the diameter of the orifice ejection of the mixture at the nose of the nozzle.
• An intimate mixture facilitates the melting of the mixture in the crucible of the blast furnace.
• the placing of coke in the charge of the shaft furnace can be adapted. This is another aspect of the optimization of the shaft furnace since it can save the coke introduced by the mouth.
• the solid carbon reducer that is used is normally carbon.
• a mixture comprising 300 to 600 kg of carbon per tonne of fine particles of pre-reduced iron.
• Up to 6% additional pig iron obtained by melting the pre-reduced iron it is not necessary to change the operating parameters of the blast furnace.
• Preferably, between 6% and 20% additional pig iron, about 100 m 3 additional pure oxygen is introduced into the shaft furnace per tonne of pre-reduced iron particles.
• the proposed mixture makes it possible to significantly increase the quantity of cast iron produced in the shaft furnace by limiting the modification of operating parameters.
• the present process can be implemented on any production site with a shaft furnace such as a blast furnace. It is not necessary that the production site has a pre-reduction furnace, it is simply necessary to carry out the mixing before the introduction into the hot wind of the nozzles.
• the mixing and injection of the fine particles of pre-reduced iron and of the solid carbonaceous reducing agent are carried out hot.
• the additional thermal requirements associated with the injection are low and can be easily covered by the energy released during the oxidation of the carbonaceous reducing agent.
• Mixing and hot injection can advantageously be carried out when a pre-reduction oven, e.g. a multi-stage oven is located near the blast furnace.
• the quantity of oxygen introduced into the shaft furnace is adjusted. That is to say that the quantity of oxygen introduced into the furnace is adapted so as to have sufficient oxygen for the traditional operation of the blast furnace and the oxidation of the carbonaceous reducing agent added to the iron ore. pre-reduced.
• This adaptation which generally consists in increasing the quantity of oxygen introduced into the blast furnace, is a function of the quantity of carbonaceous reducing agent injected but also of its quality.
• This additional supply of oxygen is achievable, either by increasing the oxygen concentration of the hot wind, or by increasing the flow of hot wind, or even by injecting pure oxygen directly into the nozzles, hot or cold.
• the solid carbon reducer that is used is normally carbon.
• the coal is advantageously brought to a temperature at which it is released from its volatile fraction.
• step a) it may be useful to inject an oxygen-containing gas in order to burn the volatile matter contained in the coal.
• the heat released during the combustion of the volatile materials of the coal can be used in step a) for the manufacture of fine particles of pre-reduced iron or else to heat the mixture of particles of pre-reduced iron and of coal.
• the wind / oxygen control leads to a reduction in coke consumption for “through” cast iron, a reduction in the wind flow rate, and a CO enrichment of the gas from the shaft furnace.
• slag-forming agents are also added during step a) or step b). These slag-forming agents are chosen, preferably from the group consisting of lime, limestone and magnesia as well as their mixtures.
• a sufficient quantity of carbon will be used during step b) to completely reduce and melt the pre-reduced iron particles in the shaft furnace.
• an excess of coal is used during step b) which is sufficient to cover the coal requirements of the shaft furnace. This avoids having to inject carbon separately through the nozzles.
• Fig. 1 Schematic diagram of the coupling of a pre-reduction oven and a shaft oven.
• a shaft furnace such as a blast furnace is supplied from the top, the top, with agglomerated ore and coke. Hot air, and in some cases coal, is blown into the bottom of the blast furnace. The blown air burns part of the carbonaceous fuel to generate the heat necessary for the chemical reactions and for the fusion of iron in the bottom of the blast furnace, while the rest of the carbonaceous fuel as well as part of the gases reduce the iron oxides.
• the crucible are the molten iron and the slag.
• Cowpers are refractory brick regenerators placed in a circular metal enclosure covered with a dome. Before introducing air into the cowpers, the refractories are brought to temperature by burning blast furnace gases and a rich gas (natural gas for example).
• the well-operated blast furnace operates at the limits of its productivity. It uses the maximum hot wind flow for its blowers, and, to minimize coke consumption, this wind is heated to the maximum temperature achievable in cowpers: between 1200 and 1300 ° C. This has in return an expensive maintenance of the cowpers, whose refractories and the metal carcass are at the limits of the stresses authorized by the state of the art. In the long term, refractories are destroyed by high temperature thermal cycles and the metal carcass is attacked by cracking corrosion. Finally, a rich gas must be used in addition to blast furnace gas to reach the necessary flame temperature.
• a mixture of fine particles of pre-reduced iron and coal is injected through the nozzles.
• the fine particles of pre-reduced iron have a particle size of less than 2 mm, preferably less than 1 mm if it is desired to inject large quantities.
• the solid carbonaceous reducing agent, carbon is preferably so-called “pulverized” carbon with a particle size less than 200 ⁇ m and a median diameter less than 100 ⁇ m.
• the mixture is therefore advantageously prepared upstream of the nozzle and brought by a pipe into the nose of the nozzle, where it is introduced into the hot wind through an injection orifice.
• a first embodiment of the present method proposes the mixing and the injection of the cold mixture. That is to say, the blast furnace is not coupled with a pre-reduction reactor.
• a blast furnace As part of the injection of the cold mixture, a blast furnace is used by way of example, the operating characteristics of which are as follows:
• the pre-reduced iron ore injected has the characteristics of a commercial-grade pre-reduced iron ore, that is to say 5 to 8% gangue, metallization from 90 to 95%, and 0 to 2% carbon.
• a range of injection of a pre-reduced iron ore / coal mixture allowing the blast furnace to absorb this injection with a minimum of modification of the basic parameters is as follows:
• a mixture of hot pre-reduced iron ore and coal is injected into the crucible of the blast furnace, as soon as it leaves the pre-reduction furnace, through the nozzles of the blast furnace.
• a pre-reduction reactor such as a stage oven
• US-2, 089,782 in which the iron ore is prereduced by a solid carbonaceous reducer. It is a multiple hearth oven, the hearths being annular and spaced vertically. Loading and unloading decks are arranged alternately. The former have an open central circular part; the seconds have a series of orifices spaced along the periphery of the sole.
• the oven is also provided, in its central part, with a vertical rotation shaft to which are attached rakes extending over the entire radius of the hearths.
• the iron ore is introduced through the upper part of the furnace and falls on the first loading floor. Rakes, driven by the rotation shaft vertical, spread the iron ore and bring it back to the central opening through which it falls on the lower unloading floor.
• the rakes then direct the iron ore to the peripheral orifices, through which it falls on the bottom loading floor. These steps are repeated until the iron ore reaches the lowest stage.
• the iron ore is then removed and we speak of pre-reduced iron ore.
• the reducing material, carbon can be introduced at the level of the first loading floor, but also at a lower level.
• the reduction gases are burned in the upper part of the oven by injecting air or oxygen.
• the high temperatures prevailing inside the oven are reached with additional energy such as natural gas.
• the rakes by their permanent brewing, allow an intimate mixture of iron ore and coal. The angles and the speed of the rakes are calculated to avoid crushing and agglomeration of the ore.
• any reactor capable of producing pre-reduced iron from iron ore can be used within the scope of the present.
• FIG. 1 the operation of the method according to the present invention is presented using a block diagram.
• iron ore is introduced in the form of fines.
• the arrow 12 illustrates the gradual reduction of the iron ore which descends the stages of the stage furnace 10.
• the arrow 13 symbolizes the ascending reduction gases.
• Fine particle sizes of iron ore and coal allow good heat exchange and promote chemical reactions.
• the reduction carbon can be inserted on the upper hearth, or in a lower part of the tiered oven 10.
• bonding agents and slag forming agents chosen from the group are also injected into the tiered oven. lime, limestone and magnesia as well as their mixture.
• the iron ore is at a temperature of around 1000 ° C.
• the mixture of smelting coal and pre-reduced iron ore can be done either in the last zone of the stage furnace 10, or in a separate enclosure. In both cases, the mixture causes a rise in temperature of the coal, the volatile materials of which pass into the gas phase; the temperature of the mixture is approximately 500 ° C.
• the next step is to transfer the degassed mixture to a blast furnace 14, which can be done pneumatically. Then, the mixture is injected through the nozzles into the crucible of the blast furnace 14. The latter is in turn supplied in the traditional manner with agglomerated ore and coke.
• the path of the agglomerated ore through the blast furnace is represented by the arrow 16, the arrow 18 symbolizes the path of the blast furnace gases which escape through the blast pipe. Cowpers, generators of hot wind, are designated by the reference 20.
• iron will be recovered from the melting of the agglomerated ore as well as from the iron from the melting of fines.
• the desired production surplus is 25 t / h, for a total production of 275 t / h of pig iron.
• 29 t / h of DRI fines mixed with 12 t / h of lean smelting coal are injected through the nozzles.
• the temperature of the mixture deposited in the nozzles is between
• the quantity of oxygen introduced into the furnace is therefore adapted so as to have sufficient oxygen for the traditional operation of the blast furnace and the oxidation of the carbon reducer added to the pre-reduced iron ore.
• the adaptation of the quantity of oxygen consists of a 2.7% increase in the oxygen concentration of the hot wind.
• Another alternative would be to increase the flow of hot wind, or to inject oxygen, hot or cold, directly through the nozzles.
• a rate of 2.7% additional oxygen corresponds to the injection of 12 t / h of lean coal. This rate obviously varies according to the quantity and the quality of this carbonaceous reducer.
• the wind / oxygen control leads to a reduction in the consumption of coke for "through" cast iron, a reduction in the wind flow rate, and a CO enrichment of the gas from the oven to the shaft. It will be noted that the lowering of the wind temperature and the simultaneous increase in the calorific value of the furnace gas make it possible to achieve a substantial savings on the cost of heating the wind, and on the maintenance of cowpers, an economy which is added to that made on coke. In addition, the reduction in wind flow gives a potential for increased productivity compared to the blower limit.
• the present process therefore makes it possible to increase the overall production of the blast furnace.
• the deck oven is particularly advantageous in this process, because of its counter-current operation, because it allows better energy exploitation of volatile materials from coal.
• a certain additional quantity of coal is injected by the nozzles.
• This additional coal can be injected independently, but can also be mixed at the same time as the smelting coal with pre-reduced iron ore.
• part of the fusion carbon and / or the additional carbon can be injected at the same time as the reduction carbon in the stage oven, which does not in any way harm the reduction reactions.
• the mixture which is injected here has a very interesting health characteristic: it is “self-deepening. In fact, it contains the reducing agent, the fuel and the "flux" necessary for its fusion in the crucible of the blast furnace.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Metallurgy (AREA)
• Manufacturing & Machinery (AREA)
• General Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Organic Chemistry (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Manufacture Of Iron (AREA)
• Processing Of Solid Wastes (AREA)
• Furnace Charging Or Discharging (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (2)

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ID=19731792

Family Applications (1)

Country Status (7)

Citations (4)

Family Cites Families (4)

• 1998
  • 1998-12-23 LU LU90333A patent/LU90333B1/fr active
• 1999
  • 1999-04-30 TW TW088107016A patent/TW473546B/zh active
  • 1999-12-23 EP EP99964668A patent/EP1154825B1/de not_active Expired - Lifetime
  • 1999-12-23 AU AU30432/00A patent/AU3043200A/en not_active Abandoned
  • 1999-12-23 DE DE69912003T patent/DE69912003T2/de not_active Expired - Lifetime
  • 1999-12-23 AT AT99964668T patent/ATE251487T1/de active
  • 1999-12-23 WO PCT/EP1999/010348 patent/WO2000038496A2/fr active IP Right Grant

Patent Citations (4)

Non-Patent Citations (1)

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