Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
  • C21B2100/20—Increasing the gas reduction potential of recycled exhaust gases
  • C21B2100/24—Increasing the gas reduction potential of recycled exhaust gases by shift reactions
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
  • C21B2100/20—Increasing the gas reduction potential of recycled exhaust gases
  • C21B2100/28—Increasing the gas reduction potential of recycled exhaust gases by separation
  • C21B2100/282—Increasing the gas reduction potential of recycled exhaust gases by separation of carbon dioxide
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
  • C21B2100/40—Gas purification of exhaust gases to be recirculated or used in other metallurgical processes
  • C21B2100/44—Removing particles, e.g. by scrubbing, dedusting

Definitions

• the present invention relates to a method of producing liquid crude iron and high-grade top gas with a molecular ratio of (CO+H2)/N2 > 2.8 in a blast furnace in which normal temperatures are maintained in the hearth and top zones, and which is fed by a charge of conventional composition, at the same time as additional fuel and preheated blast, obtained by mixing air, oxygen and water, are supplied to the raceways.
• the invention also relates to a way of making steel and ammonia by producing liquid crude iron and high-­grade top gas in the way mentioned above and processing the top gas to ammonia.
• THM/m2.24h tons of crude iron per m2 of hearth area and 24 hours.
• Raceways refers to the hot zone ranging from the tuyeres and usually penetrating 1,5-2 m towards the blast furnace centre.
• a great number of patents, magazine articles etc. discuss the way of optimizing the blast furnace operation, especially by minimizing the costs of fuel/THM.
• the steps suggested to obtain optimum working conditions include (1) increased blast temperature, (2) charge preparation, (3) gas injection into the stack, (4) pre-reducing the charge, (5) blast additives, (6) high top pressure, and so on.
• one or more of the steps (1), (2), (5) and (6) are usually applied.
• blast furnace optimization has implied steps that reduce the costs of fuel consumption/THM, especially by measures reducing the coke content of the charge, but also by replacing the coke with a cheaper fuel, for instance coal dust, injected into the raceways.
• the optimization has been very successful, and existing blast furnaces, operated in a conventional manner, usually have a fuel consumption less than 370 kgs of coke + 100 kgs of coal dust/THM.
• the specific crude iron production usually amounts to 55 - 65 THM/m2.24h.
• Such a blast furnace may be operated in a range of ⁇ 20% of the optimum production, but the prime cost of crude iron will then be higher on both sides of the optimum conditions.
• the furnace hearth diameter is 8.5 m and its optimum crude iron capacity, that is the capacity having the lowest costs of production/THM, amounts to an average of 130 THM/h at a degree of utilization of 96%.
• the optimum capacity corresponds to a specific crude iron capacity of 57 THM/m2.24h.
• Required charging of iron raw materials, slag formers, fuel and air blast are shown in Table No 1 that also shows analyses in percentage by weight of the charge components, additional fuel, slags and crude iron together with vol% in the air blast.
• the specific slag flow in the hearth area amounts to 8.5 tons of slag/m2.24h.
• the adiabatic flame temperature in the raceways is calculated to 2460°K, and the top gas has a temperature of 430°K.
• the hearth and top gas analyses in vol% etc will be seen in Table 2.
• the low fuel consumption/THM of a conventional optimized blast furnace results in a lean low energy top gas with high contents of CO2 as well as N2, as shown in Table 2. This means that the gas is unsuitable as a raw material for further chemical processing, and its principal application has become as fuel, for instance for preheating the air-blast.
• the quality improvement of the top gas is obtained by replacing the normal air blast with oxygen enriched air and recirculated top gas, in case (2) combined with fuel injection into the raceways.
• the first mentioned article is most interesting in relation to the present invention, since it deals with industrial ammonia production on basis of processed top gas from a blast furnace with modified operating conditions.
• the same article (1) also outlines operation without recirculation of top gas - instead 80 kgs of heavy-oil/THM was injected into the raceway and the production capacity of crude iron was increased by about 10%; the molecular ratio (CO+H2)/N2, however, was reduced to 0.67, and therefore the suitability of the top gas for further processing to synthesis gas for ammonia production was eliminated.
• US-A 4.529.440 also describes an operating cycle for blast furnaces in which the air blast is replaced with air enriched to > 65 vol% O2 together with recirculated top gas containing carbonaceous material. Flow conditions are not stated.
• the top gas is said to contain a vol% of about 50 vol% CO, and gas discharged from the stack in the upper part of the hearth area is stated to contain about 75 vol% CO.
• the claims refer to a method of increasing the gas production without increasing the top gas temperature, by removing heat from the stack, for instance by discharging hot gas from the stack, increasing the slag production and the crude iron temperature, that is, by increasing the thermal losses on purpose.
• US-A 4.013.454 outlines a way of operation of a blast furnace in which the air blast is replaced by carbon dioxide and oxygen, or oxygen enriched air in case ammonia is the end-product of the top gas processing. Also in this case it is a kind of recirculation, since the carbon dioxide will be extracted from the top gas or from the same after water-gas shifting.
• US-A 2.593.957 describes a method of nitrogen-free operation of a blast furnace.
• the blast contains solely oxygen and water vapour.
• the specific crude iron production obtained with this method could have been high as compared with the normal specific production in 1948, but, with the knowledge of the present invention, it can, ex poste, be supposed that a specific crude iron production could not have been reached that would be considered high today.
• a very high specific production of liquid crude iron and high grade top gas with a molecular ratio of (CO+H2)N2 > 2.8 is possible in a blast furnace together with an energy consumption/THM even lower than that which is obtained in a conventional optimized blast furnace of identical dimensions.
• the energy consumption/Nm3 of the synthesis gas obtained from the top gas produced according to the invention is also surprisingly considerably lower than that required by industrial methods of production of such synthesis gas existing today. This is made possible fundamentally by the fact, that the charge flow, the additional fuel flow and the blast flow are controlled so that the specific crude iron production is > 75 THM/m2.24h.
• the oxygen content in the blast is controlled within the interval 40-60 vol%, the vapour content within the interval 15-30 vol% and the ratio O2/H2O is maintained > 2.0.
• the produced top gas is not utilized for recirculation but entirely or almost entirely it can be processed into synthesis gas especially suitable for ammonia production.
• the content of water vapour should preferably exceed 18 vol%. It can for example be 18-22 vol% and then, a specific production > 82 THM/m2.24h can be obtained.
• the high molecular ratio (CO+H2)/N2 of the top gas according to Example No 1 enables optimal economical exploitation of the exhaust gas from the oxygen fining of the crude iron by intermixing the exhaust gas with the top gas.
• the gas mixture obtained in this way may be further processed to a composition suitable for ammonia synthesis as will be described below in connection with Example No. 1.
• crude iron is obtained which, when fined in an LD converter, gives an exhaust gas which, when mixed with the top gas, results in a gas having the analysis shown in Table No 4 (dry gas).
• Example No 1 If utilization of exhaust LD-gas is of no current interest, the operating conditions are changed, as compared to Example No 1, in so far as the charge flow is controlled to be 51% higher than by conventional optimized operation, and the blast composition of air, oxygen and water vapour is changed to the proportions of 40.6/ 40.2/ 19.2, corresponding to 49 vol% oxygen.
• the blast flow will be controlled to 575 Nm3/THM, and the oil supply to the raceways to 74 kgs/THM in addition to the 100 kgs of coal dust/THM of the conventional operation.
• the total economy for a blast furnace operated according to the invention combined for instance with an LD-plant and a plant for ammonia synthesis, will be far superior to the economy of two separate plants based upon the same raw materials and producing steel and ammonia respectively, for instance a blast furnace + an LD-converter and a Texaco-gasifier + an NH3-synthesis unit.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Iron (AREA)
• Air Supply (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=20366530

Family Applications (1)

Country Status (4)

Cited By (3)

Families Citing this family (2)

Family Cites Families (9)

• 1986
  • 1986-12-05 SE SE8605226A patent/SE8605226L/ not_active Application Discontinuation
• 1987
  • 1987-12-02 WO PCT/SE1987/000571 patent/WO1988004329A1/fr not_active Ceased
  • 1987-12-03 EP EP87850378A patent/EP0271464A3/fr not_active Withdrawn
• 1988
  • 1988-07-28 DK DK421688A patent/DK421688D0/da not_active Application Discontinuation

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