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
  • C21B5/003—Injection of pulverulent coal
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/006—Automatically controlling the process
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/06—Making pig-iron in the blast furnace using top gas in the blast furnace process
• • 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
  • C21B2100/26—Increasing the gas reduction potential of recycled exhaust gases by adding additional fuel in recirculation pipes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/25—Process efficiency

Definitions

• This invention relates to a process and apparatus for increasing the high temperature heat consumption in, critical ratios of injected coal to
• one of the reasons for employing oxygen is the value of the recovered top gas as a viable replacement for natural gas, which the steel industry con ⁇ sumes to the extent of some 600 billion scf, 17 billion 3 , annually in the nearby soaking pits, reheating furnaces, annealing furnaces and the like.
• My invention is a process for the production of molten ferrous metal in a blast furnace comprising charging the top with a ferrous ore,a flux ing agent and coke in an amount at least that for providing the desired carbon in the hot metal, and injecting oxygen of at least 65% purity and a solid carbonaceous fuel suspended in gas withdrawn from the stack, at level below that where reduction begins, through the tuyeres.
• the carbon dioxide-carbon reaction only begins at a level of about 2000°F, n00°C, slowly, increasing in rate with temperature. But at this level in the oxygen-blown furnace the reversible reaction, C0 2 + C -> 2 CO will be inhibited by the very high concentration of carbon monoxide as by this level the reduction is substantially complete. Thus there will be very little carbon dioxide generated to begin with and further, if much coal is injected the coke concentration will be vary low.
• the amount of carbon monoxide or mixture- thereof with nitrogen needed to hold the heat is temperature dependent, the volume obtained by dividing the high temperature heat by the product of the flame temperature and th mean heat capacity.
• a flame temperature 3300°F, 1800°C, ' about 31,880 scf, 1,080 m 3 /t, and at 4300°F, 2400°C, about 27,300 scf, 852 nrr/t, gas would be required.
• MM kc/t of hot metal and it's heating value would be about 100 Btu's/sc 3 890 kc/m . Indeed, were the oxygen for this less than 65% purity the top gas carbon monoxide concentration would be less than 20%, only about
• T.G. C0/C0 2 x scfC0 2 + 3.5 scfC0 2 C.Z. CO difference where the combustion zone carbon monoxide difference is that required to hold the heat THM,t less that provided by the carbon necessary.
• the combustion zone carbon monoxide difference is that required to hold the heat THM,t less that provided by the carbon necessary.
• 621 pounds, 311 kg/t, of carbon for 2.5 MM Btu's/THM, 0.7 MM kc/t would result in 19,633 scf, 614 m /t, carbon monoxide ergo at 4000°F, 2200°C, the difference would be 29,600 scf, 924 m 3 /t, minus 19,633 scf,
• the stack gas removed can be used alone for the recycle gas, mixed with the top gas to obtain the desired recycle composition or employed for making carbon monoxide based chemicals.
• stack gas removed and mixed with recovered top gas while top gas alone were recycled, the effect would be to increase the high temperature heat consumption of the process of my Serial Number 939,431, now US 4,198,228 noted earlier. This would represent a signifi ⁇ cant improvement as the top gas-stack gas recovered mixture would contain more carbon monoxide and its heating value increase.
• recycle gas can range in carbon dioxide concentration; indeed,-from essentially carbon monoxide alone to carb ⁇ n- dioxide alone and all the mixtures in between. Assuming essentially pure oxygen is injected to minimize nitrogen, in using coal its hydrogen and contained moisture which results in hydrogen will affect the carbon monoxide concentration in the stack, top gas and recycle stream. In lignite, bituminous coal and an-
• Slag is relatively valueless, composed of mono-calcium sili ⁇ cate and mono-calcium aluminate. It is thus my invention to increase the lime or lime containing compounds such as limestone, super-fluxed iron ore etc.; thus the basicity of the slag is greatly increased, but so too is its melting temperature. In conventional practice the basicity is expres-
• ⁇ :- ⁇ -A j temperature of the higher basicity slag can be adjusted by adjusting the amount of calcium alu inates present to some degree and as portland cement is composed of tricalciu silicate or mixtures of it with dicalciu sili ⁇ cate and calcium aluminates, especially tricalcium aluminate, it is ideal
• the slag can be.of calcium aluminates or titanates, or even mixtures if desired.
• calcium titanate or even monocalcium titanate slags are not produced in the conventional blast furnace process because of the viscosity and melting temperature consideration; but by my
• the alumina should be considered AlO j 5, and by my process the basicity should be about or over 2:1 or 2.
• the calcium carbide can be converted in situ to calcium cyanamide. Both are tapped at over 3000°F, 1650°Cby my process.
• the oxygen concentration entering the raceways should be less than about 36%.
• this problem can be overcome by injecting massive quantities of carbonaceous fuel such that the ratio If injected carbon to injected oxy ⁇ gen limits the gasification to mostly carbon monoxide. In this way the oxygen and carbon dioxide content of the resulting gas is low and there ⁇ fore has little influence on the carbon content while limiting the temper ature of the raceways.
• this has been- overlooked, but it is a critical factor in practical stable operation.
• the raceways temperature could be further lowered by injecting another 120 lbs, 55.5 kg, to consume the remaining 3,800 scf, 108 , carbon dioxide endothermically.
• the ratio should be over 1.5:1, ideally about 1.7:1.
• the raceway temperature should be below the boiling temperature of iron, preferrably about or be- low 5000°F, 2760°C, and ideally about or below 4600°F, 2540°C.
• the raceway temperature can be made much lower by injecting a coal-inert gas or liquid, but that is undesirable as noted earlier.
• the sulfur re moved by the slag will end up as the alkaline earth sulfide thereof, but it can be removed if desired; for example by blowing very hot steam through portland cement while molten, ergo liberating hydrogen sulfide, whist any free lime formed will immediately combine with dicalcium sili- cate to form tricalcium silicate.
• sulfur has been the very anathem .of the conventional blast furnace process, it can be easily managed by m process- The accepted specifications for sulfur in blast furnace hot metals are easily met; these are listed with a maximum of about 0.06% in The Making, Shaping and Treating of Steel, Eighth Edition, U.S. Steel Corp., Pittsburgh, PA 1964, page 386, Table 14-11.
• the oxygen is supplied by a pipe or mul tiplicity of pipes extending into the tuyere, wherein the diameter of th pipe or resulting effective diameter of the pipes is smaller by at least one-forth, ideally about half and the depth adjustable such that under the conditions of velocities and pressures for each of the streams mixin and initial partial combustion is begun within the tuyere but the flame front only minimally impinges on the inner tuyere surface if at alt.
• the oxygen pipe(s) may be tipped with nozzles or other devices to improve mixing with the suspension .and inhibit backfiring.
• the temperature of the slag and metal by my process may be quite high as a result of high raceway temperatures.
• recycle stack gas containing practically no carbon dioxide can be injected at any desired temperature and quantities to adjust the slag and hot metal temperatures as desired.
• whatever gas is injected or results therefrom must be considered in the heat balance.
• a hot(molten)metal of carbon content of from about 0.0% to about 4% can easily be realized.
• a hot mixture of carbon monoxide-dioxide, the latter to the extent needed to adjust the carbon level can be injected, or a mixture of relatively cold carbon monox de-oxygen, the latter as needed to effect the desired carbon removal, that would control the temperature of the hot metal by the exo ⁇ thermic reaction.
• suspension of oxidizing materials may be added to effect car ⁇ bon adjustment and provide other benefits such as alloying.
• a carbon monoxide suspension of the oxides of nickel, manganese, chromium, vana-. ' ... dium and others may be injected to adjust the carbon content while produ ⁇ cing the desired alloy.
• other compounds of may alloying metals may be employed including the carbonates, sulfides, silicates, aluminates and others.
• the process can be operated over a wide range of temperatures and pressures, a flame temperature of from about 3300°F, 1800°C, to about 4400°F, 2450°C, whist the pressure may range from about atmospheric to 50 atmospheres, although ideally from about 2 to 6 atmospheres absolute.
• the amount of scrap added to the BOP furnace is . about that which ⁇ an be accomodated by the added heat available, about or over 20%, preferrably about or over 25%, and ideally over 30%.
• the conventional blast furnace complex has evolved historically, wher as the complex ideal for my process should encompass a blast furnace pro ⁇ per having the usual top gas handling facilities.and additionally at leas one stack gas take-off pipe at a level at or below where reduction is sub stantially completed with means for withdrawing the stack gas without a ⁇ substantial pressure drop within the furnace and means for cooling the withdrawn gas by heat * transfer to the desired temperature.
• a recycle com ⁇ pressor is required that can handle either or both top gas and stack gas with ductwork to convey the gas recycled to the pulverizer which can be o roller ring, attrition, ball or other types mills.
• the mill can be fe by known means with a solid carbonaceous fuel larger in particle size than will be produced by the mill, ideally the mill will provide uel of minus 325 mesh, 44 microns, preferrably minus 100 mesh, 149 microns, but it can be larger, whist the feed to the mill is ideally about one-eighth inch, 3 mm, coal.
• the recycle gas in part passes through the mill assisting in classifying the particles and leaves carrying suspended carbonaceous fines which ' are ducted to the tuyeres by known means, even via the in-place bustle pipe.
• Another recycle gas stream or separate gas stream is handled by ductwork to the lower tuyeres, wherein such ductwork is in ⁇ corporated a hopper for adding powders, for example of metal oxides- such as nickel, iron, manganese and others.
• the carbonaceous suspension is fed to the upper tuyeres as noted, whereas pipes carry the oxygen into the tuyeres as detailed earlier.
• the in-place top gas boilers are optionally converted to firing by pulverized coal, which steam of course drives the blowers which are incorporated into the oxygen facility to obviate in part purchased compressor capacity.
• the cryogenic oxygen facility provides gas ⁇ eous oxygen at the desired pressure to the pipes into the tuyeres, which pipes are adjustable in terms of depth within the tuyere and optionally also adjustable in nozzle size.
• the blast furnace proper has heretofore always been lined with silica, aluminosilica and alumina refractories; more recently there has been a trend to carbon linings for the hearth and bosh. Indeed, it is desirable

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• 1981
  • 1981-03-11 EP EP81900906A patent/EP0047314A1/de not_active Withdrawn
  • 1981-03-11 WO PCT/US1981/000326 patent/WO1981002584A1/en unknown

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