Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/001—Injecting additional fuel or reducing agents
  • C21B5/002—Heated electrically (plasma)
• • 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 present invention relates to the conduct of a blast furnace, in particular of a steel blast furnace.
• the present invention aims to respond positively to such an expectation.
• Another object of the invention is to expand the usual ranges of pig iron produced in a blast furnace.
• the subject of the invention is a method for increasing or at least temporarily modifying the production of a blast furnace, in particular of a steel blast furnace, method according to which nozzles are introduced directly into the combustion zone , oxidized solid metalliferous materials, together with a supply of thermal energy to ensure the heating, reduction and melting of said metalliferous materials, said supply being produced by a gaseous current heated before its introduction into the apparatus by a supply of electrical energy, and, while continuing the usual loading of the blast furnace by the blast pipe, and simultaneously with the introduction, into the combustion zone of the nozzles or at a neighboring level, of said oxidized solid metalliferous materials and of said preheated gas stream, adds a compensating agent for over-oxygenation in a determined amount to compensate for the effect of over-oxygenation of the ven t due to the oxygen provided by said metalliferous materials, and simultaneously the flow rate of said wind from the cowpers is adjusted to maintain the operating characteristics of the blast furnace above said combustion zone of the nozzles, with respect to
• the metalliferous materials are transported in the device by the electrically overheated gas stream or by the wind coming from the cowpers, or by both, said materials being previously conditioned in particles of small particle size preferably in the form of fines or dust so that they can be easily transported pneumatically.
• the preheated gas stream is blown in through the existing blast furnace nozzles after being mixed with the wind from the cowpers.
• This variant is applicable both when this gas mixture is blown alone into the nozzles or containing in suspension the metalliferous material.
• the pneumatic transport of the particles can very well be replaced by a fluid transport, the particles then being packaged into pulp by suspension in a liquid medium which can perfectly be water.
• the means for overcoming the possible effect of over-oxygenation of the wind by the injected oxides consist of a supply of nitrogen gas in the nozzle area.
• the invention therefore consists in introducing, directly into the nozzle area of the apparatus, in addition to the usual wind coming from the cowpers, from the ore, a plasma gas providing the energy of electrical origin necessary for the transformation of this ore in cast iron, and nitrogen or any other fluid capable of compensating for the over-oxygenation of the wind induced by the ore.
• a plasma gas providing the energy of electrical origin necessary for the transformation of this ore in cast iron, and nitrogen or any other fluid capable of compensating for the over-oxygenation of the wind induced by the ore.
• the invention makes it possible, without substantially disturbing the usual operation of the blast furnace, to produce marginal ferrous or chromiferous pig iron (or both), depending on the nature of the ore injected and by consuming only energy for this purpose thermal of electrical origin brought from outside the appliance and the amount of carbon necessary for the carburetion of this cast iron.
• the blast furnace in question is planned, at maximum speed, to produce 6000 tonnes of pig iron per day, which leads to a "putting in the thousand" of coke put in the 450 kg blast furnace per tonne of pig iron produced, that is to say a daily consumption of 2700 tonnes.
• This blast furnace is equipped with twenty eight nozzles for blowing the wind.
• pig iron could be increased to more than 6500 tonnes per day by injecting iron ore in particulate form, with a particle size of less than 1 mm approximately, at a rate of 10% by weight of iron injected with respect to the through-cast iron, the latter representing the cast iron resulting from the ore placed in the mouth as agglomerate.
• a superheated wind is blown into the nozzles, using plasma torches, so that the energy provided by the plasma torches satisfies the thermal needs for reduction and fusion of the injected ore. to the nozzles.
• the total wind flow injected is 902 Nm 3 per ton of pig iron and its temperature rises to 1777 ° C.
• the consumption of coke per tonne of total pig iron produced becomes more than 35 kg lower than that of the traditional step of column 1.
• the "putting in the mile" of coke per tonne of pig iron going through remains equal to that of the blast furnace in conventional operation, which clearly shows that the charging of materials to the blast furnace is not modified by the injection of ore and that all the coke is used, as in conventional operation, for processing the through cast iron.
• the pipe according to the invention also makes it possible to maintain the internal functioning of the blast furnace (invariant flame temperature, same temperature, flow and composition characteristics for the blast gas). Everything finally happens as if the entire blast furnace "ignored” the changes made in the nozzle area by the implementation of the invention.
• the superheating of the wind blown into the nozzles is obtained by mixing a main flow of wind from the cowpers at 1200 ° C, completing a secondary flow of plasma wind, brought to a high temperature by means of plasma torches.
• the combination of these two gas streams has a flow rate equal to 799 Nm 3 per tonne of pig iron.
• the oxygen supplied by the injected ore is also taken into account.
• this oxygen is advantageously supplemented with an addition of nitrogen which, in this example, amounts to 103 Nm 3 per ton of pig iron.
• the overall gas flow injected into the nozzles therefore includes the wind flow (the flow rate of which is 799 Nm 3 per ton of pig iron) and the addition of nitrogen.
• the overall gas flow has a flow rate of 902 Nm 3 per ton of pig iron and its temperature rises to 1,777 ° C.
• the gas produced by the direct reduction of the iron ore injected is added, in the combustion zone of the nozzles, the gas produced by the direct reduction of the iron ore injected.
• the invention is perfectly suited to a possible replacement of all or part of the nitrogen, as a means of compensating for the excess oxygenation of the wind on the market of the blast furnace, by an auxiliary fuel according to a practice already known per se for a very long time (see for example French patent no. 1340 858).
• the quantities of nitrogen to be injected need not necessarily be adjusted solely as a function of the quantities of oxides injected, but that they must also take account, if necessary, of the operating parameters during operation. normal of the device.
• normal operation or "reference operation”
• the subsequent supply of nitrogen, during of the implementation of the invention will therefore be reduced as much compared to the figures in the table since the oxygen supplied by the ore will then replace, at least in part, pure oxygen which, previously, was added in excess to the wind.
• the useful energy given by the plasma torches is reduced in this case to 161 kWh per ton of pig iron.
• the addition of nitrogen is also reduced to 51 Nm 3 per tonne of pig iron, more than half of the previous case.
• the plasma torches are regulated to deliver a useful energy of 296 kWh per ton of pig iron, leading to global gas insufflation at a flow rate of 832 Nm 3 per ton of pig iron, and at a temperature of 1840 ° C.
• the coke cost per mile is, of course, lower than the steps described above. On the other hand, the daily consumption of coke remains the same. In addition, the characteristics of the top gas and the flame temperature do not vary.
• the invention applies generally to the injection of any oxidized metalliferous material, not only ore, but also iron scale (mill scale) or blast furnace dust, steelworks dust or fines from the return of agglomeration chains, etc.
• the invention is not limited to the quantities of ore injected, given in the previous examples.
• the limit may possibly be imposed by the power of the torches available, since the electrical energy to be supplied increases of course with the quantity of ore injected.
• the power of the torches currently available on the market is of the order of 4 to 8 MW, but that it should be able to reach 10 to 12 MW in the relatively near future.
• the invention may thus preferably be implemented by concentrating the injection of the ore and the electrical power on some of the nozzles instead of distributing them over all the nozzles fitted to the blast furnace.
• a plasma torch of 3.3 MW power with an electrical efficiency of 0.85
• the hot wind from the cowpers being distributed over the twenty and one remaining nozzle.
• a theoretical upper limit of the quantity of injectable ore can therefore be reached when all the wind's oxygen is supplied by the ore and all the wind is therefore replaced by nitrogen.
• an interesting variant may consist in injecting, no longer iron ore, but chromium ore, or a mixture of the two, which makes it possible to obtain at the outlet of the blast furnace directly chromium pig iron, for the further development of stainless steels, in particular.
• We understand the attractiveness of this application compared to the known practice which consists in carrying out this type of production by a mixture, excluding reactors, of a conventional cast iron from a blast furnace with ferrochrome possibly melted in an electric furnace.
• the blast furnace according to the invention then operates as a single reactor with two superimposed stages, each specialized in a different production, exchanging materials and heat without disturbing each other: the stage below, namely the nozzle zone, producing marginal chromiferous pig iron from the injected ore and the upper part producing, in the conventional manner from the charge placed in the top, the main through ferrous pig iron.
• the two liquid phases collect in the crucible of the furnace to form the desired chromium cast iron.
• the proportion of ore injected into the nozzles is therefore adjusted relative to the through-flow of pig iron, which is kept constant.
• the effect of the over-oxygenation induced by the wind by the injected oxides on the consumption of coke may, in accordance with a variant of the invention, be counteracted by the practice, already known per se, which consists of injecting into the vent to the nozzles an auxiliary fuel, such as a liquid or gaseous hydrocarbon, natural gas, coke oven gas or coal.
• an auxiliary fuel such as a liquid or gaseous hydrocarbon, natural gas, coke oven gas or coal.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Iron (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Blast Furnaces (AREA)
• Manufacturing Of Steel Electrode Plates (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

Family

ID=9309996

Family Applications (1)

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• 1984
  • 1984-11-21 FR FR8418075A patent/FR2573437B1/fr not_active Expired
• 1985
  • 1985-11-07 DE DE8585440065T patent/DE3579672D1/de not_active Expired - Lifetime
  • 1985-11-07 AT AT85440065T patent/ATE56473T1/de not_active IP Right Cessation
  • 1985-11-07 EP EP85440065A patent/EP0182730B1/fr not_active Expired - Lifetime
  • 1985-11-13 ZA ZA858727A patent/ZA858727B/xx unknown
  • 1985-11-20 SU SU853976890A patent/SU1500165A3/ru active
  • 1985-11-20 CA CA000495796A patent/CA1256703A/fr not_active Expired
  • 1985-11-20 BR BR8505820A patent/BR8505820A/pt not_active IP Right Cessation
  • 1985-11-20 JP JP60260991A patent/JPS61199006A/ja active Pending
  • 1985-11-21 US US06/800,465 patent/US4707183A/en not_active Expired - Fee Related

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