Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/08—Making spongy iron or liquid steel, by direct processes in rotary furnaces
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/28—Moving reactors, e.g. rotary drums
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B25/00—Phosphorus; Compounds thereof
  • C01B25/16—Oxyacids of phosphorus; Salts thereof
  • C01B25/26—Phosphates
  • C01B25/30—Alkali metal phosphates
  • C01B25/305—Preparation from phosphorus-containing compounds by alkaline treatment
  • C01B25/306—Preparation from phosphorus-containing compounds by alkaline treatment from phosphates
• • 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
  • C22B5/00—General methods of reducing to metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
  • B01J2208/00008—Controlling the process
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00051—Controlling the temperature
  • B01J2219/00157—Controlling the temperature by means of a burner
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00051—Controlling the temperature
  • B01J2219/00159—Controlling the temperature controlling multiple zones along the direction of flow, e.g. pre-heating and after-cooling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00164—Controlling or regulating processes controlling the flow
  • B01J2219/00166—Controlling or regulating processes controlling the flow controlling the residence time inside the reactor vessel

Definitions

• This invention relates to the carrying out of reactions which require heat to be input in order to maintain the reaction. It more particularly refers to reactions in which metal ore is reduced from its combined form to its metallic form. k
• Rotary kilns are used to a great etxent in carrying outmetal ore reduction processes as well as other similar reactions.
• particulate solids to be treated are fed to the rotary kiln together with the treating gas or other material which is used for treating purposes.
• the treating gas or other material which is used for treating purposes.
• little or no attention has been paid to the form, shape or size of the ore or other material being treated.
• solid particle ores are charged to the kiln in whatever size and size distribution they are available.
• the kiln operates at a lower efiiciency than is desired. It has been discovered that this is largely due to a combination of facts.
• the large particle size ore tends to move about the kiln at a relatively fast rate and thus to have a relatively low residence time.
• the larger particles often require the greatest or longest treatment in the kiln; but because of their physical size are subjected to the shortest relative treating times.
• the throughput velocities in processes of the type described have generally been set to accommodate the shortest residence time materials in order to provide for suflicient'time to permit adequate treatment of these short residence time materials. It is apparent, that in this situation, the longer residence time materials, that is the smaller particles, are subjected to too long treatment times. In addition, since the treatment is keyed to the short residence times of the larger particles, the throughput of any given kiln is reduced as compared to what it would be for any given particle size material except the largest. I i
• Processes of this general type are used for magnetizing roasting of iron ore, for direct reduction of ironand/or nickel ore to form sponge iron or sponge nickel respectively, for the solubilization of phosphates with the aid of sodium carbonate slag or relatively. pure sodium carbonate, or for the treatment of zinc containing residues among other processes.
• Some of these processes have special problems peculiar to them which have not-been particularly met and solved by the prior art treating process as generally described above.
• the kiln charge passes through a state in which the constituent particles tend to agglomerate even when such particles are below the melting temperature of either the ore being treated or the softening temperature of the treating material where such is a solid.
• the surplus coal or other solid treating agent is not readily recoverable from the product and therefore remains a part thereof to the economic loss of the process.
• This excess coal could possibly be disposed of during the process by burning; in which case there is not only the economic loss occasioned by the cost of the excess coal but also the utility cost necessary to furnish the additional air or oxygen necessary for combustion of the excess coal.
• Unpelletized, fine particle size ore is generally charged directly as such to a reducing kiln only in those cases where a subsequent operation is to be carried out, such as melting in an electric furnace, and where the reduction required of the charged ore, need be carried only to about 70 percent of completion.
• this invention resides, in one of its aspects, in a process for treating particulate solids having a distribution of particle sizes, wherein said particles being charged are separated, as by screening, for example, into three (3) grades; below about 60 microns; between about 60 microns and about 5 millimeters; and above about 5 millimeters. :The fraction between about 60 microns and about 5 millimeters is fed through the lower end (discharge end) of otherwise conventionally operating kiln. The varying particle size charge stock is propelled into the kiln in such a' manner that the particles travel a distance Within the'kiln substantially proportional to their size. That is, the large size particles tend to travel within the kiln a distance which is proportional to their size and relatively greater than the distance travelled within the kiln of the smaller particle sized ore.
• the charged particles distribute themselves over at least about 4 meters of kiln length since it has been found that for the particle size range set forth, this distance is sufficient to provide for a quantitative distribution of particles according to their size assuming that all of the particles have about the same density.
• the ore to be treated in the kiln has a fraction having a particle size larger than about 5 millimeters, such fraction is preferably separated and fed to the kiln through or near the upper end (charge end) thereof.
• the fines of the ore to be treated that is that fraction of the ore having a particle size less than microns, are suitable pelletized by known techniques to agglomerate them into larger particles.
• Pellets having a particle size above 5 millimeters are preferably fed to the kiln from the upper end.
• Pellets having a particle size less than 5 millimeters are preferably charged to the kiln by propelling from the lower end of the kiln.
• the process according to the invention When the process according to the invention is applied to the direct reduction of iron ore to metallic iron it is suitable to maintainthe contents of the kiln at a temperature above 800 C., preferably 9001000 C. at leastin the range in which the relatively fine-grained iron ore which is blown in falls into the charge.
• the process according to'the invention may be generally carried out with a co-current or counter-current flow. Where a counter-current flow isused, the finer. particles being blown in at the discharge end, theusual advantages of a counter-current flow operation are obtained together with the further advantage that the distribution of the various particle size classes over the length of the kiln is particularly well in accordance with the residence time required for each of these classes. 7 e
• the carrier gas for the solids to be blown in includes suitably at least part of the combustion air which is introduced through the central burner.
• the injected solids When a more uniform distribution of the injected solids over a particularly large part of the length of the kiln bed is desired, it may be suitable to blow the solids through a plurality of pneumatic conduits which protrude into the interior of thekiln. These conduits are then suitably arranged at dilferent inclinations relative to the kiln axis and/or are operated at different gas velocities and/or difierent gas pressures. For the same purpose it may be desirable to .supply the injecting carrier gas under a pulsating pressure.
• One practical method of accomplishing this preheating is to provide a heat exchange system using the kiln exhaust gases as the heating medium. These exhaust gases may be blown over or through the ore to be kiln-treated. It is preferred to preheat the ore to a temperature up to the kiln reaction temperature, since by this procedure the required residence time in the kiln is shortened. It is within the scope of this invention to utilize the preheat gases, or at least a portion thereof, as the conveyor gases by means of which the ore to be treated is blown into the kiln.
• these preheat gases are used as the pneumatic conveyor for the charging of ore, it is required that these gases not contain substantial amount of material which is detrimental to the kiln operation. It is of course preferred that the pneumatic conveying gases contain nothing which is detrimental to the kiln operation.
• insufficient heat sources are economically available to preheat the feed ore to a temperature up to the kiln operating temperature, it may be practical to preheat the ore to a somewhat lower temperature, e.g. about 300 to 900 C. rather than the preferred 900 to 1100 C. It also may be practical to supplement heat exchange type heating, where such is insufliciently economically available, with direct fired type of preheating. This can oftenbe accomplished by providing appropriate conditions to afterburn exhaust gases normally used for preheating by heat exchange alone. If this supplemental direct fired heating is employed, it is often necessary to add oxidizing agent, suitably air or oxygen, to these exhaust gases in order to support combustion thereof. This after-burning can be accomplished during or prior to heating of the feed ore as desired.
• heat exchange preheating gases either with or without after-burning
• the preheating gases are used to heat the feed ore in the form of passing these gases through the particles of ore to be kiln-treated
• the fine fraction and the fraction with a particle size between about'60 microns and about millimeters of the ore to be processed in the kiln is preferably at least partially fed to the kiln through feeders suitably spatially located within the kiln.
• Shell burner or air inlet tubes have been found to be eminently well suited to use for this purpose. These devices are conventionally known in the art. Such shell burners and/or air inlet tubes are described in, for example, U.S.- Pats. "2,829,842 and 3,029,141.
• Thisprocess can also be used to advantage in processing sulfur containing ores, particularly iron and/or nickel ore.
• sulfur containing ores particularly iron and/or nickel ore.
• Conventional materials known for this purpose are lime and dolomite among others.
• the sulfur combining admixture adheres quite tenaciously to the solid reducing agent, e.g. coal etc., used. It has been found to be difficult, if not impossible, to remove the deposited sulfur combining material from the particulate reducing agent, particularly when the product discharged from the kiln, is subjected to wet classification.
• a further aspect of this invention is to adjust the relative particle sizes of the sulfur combining agent and the reducing agent such that the sulfur combining agent is present in smaller particle sizes than is the reducing agent.
• This practice severely reduces the tendency of the sulfur combining agent to deposit on and coat the surplus reducing agent.
• the kiln product may then be separated by dry methods, e.g. conventional screening, thereby further reducing the tendency of the sulfur combining material to tenaciously adhere to the surplus reducing agent discharged from the kiln.
• the relatively large particles of recovered coal to be recycled may be fed through the top of the kiln or at any other point convenient and/or according to this invention.
• the fine particle size reducing materials on the other hand, which still have a tendency to pick up coatings of the sulfur combining .materials can be fed in the vicinity of the kiln product discharge as set forth above.
• reducing agents generally referred to herein above, it is also within the spirit and scope of this invention to use substantially any carbonaceous solid fuel such as in addition to coke and anthracite coal, lignite, peat, brown coal', bituminous coal or other similar products.
• These reducing agents may be used singly or in admixture with each other or with other reducing agents.
• These materials may be utilized in the rough form as delivered or they may be ground to the size preferred by the operator as desired. It is also possible to pelletize these solid carbonaceous materials either alone or in admixture as desired.
• EXAMPLES The following examples were carried out in a rotary kiln of 7.8 meter length and an interior diameter of 0.5 meter.
• the rotary kiln was equipped with shell burners and a central burner through which gas and/or air was delivered into the kiln to control the temperature over the kiln length.
• the central burner was designed in such a manner that it was not only possible to deliver gas or air but also to feed pneumatically coal and fine grained ore or a mixture of said materials.
• the central burner was mounted by a sealing device at the discharge end of the kiln in such a manner that it was possible to vary the inclination of the burner with respect to the kiln axis.
• Example 1 Magnetising roasting of iron ores A low grade iron ore containing 37% Fe total was roasted with lignite-coal as reducing agent i.e. the ore was reduced from hematite to magnetite. This material was ground and concentrated by magnetic separation.
• the ore was ground before feeding into the kiln.
• the grain size distribution was as follows:
• Grain size, mm. Grain size distribution, percent The ground ore was separated in two fractions by screening the fraction with a grain size +3 millimeters was fed to the kiln in the conventional manner from the upper end (charge ends). The fraction with a grain size -3 millimeters was mixed with coal and pneumatically charged through the lower end (discharge end) of the kiln. The carrier medium was air which was preheated by the waste gas of the kiln.
• the above values being based on dry material.
• the net calorific value was 5790 kcaL/kg.
• the grain size was 2 millimeters.
• the feeding rate was:
• the temperature in the reduction zone was regulated at 800 C. by introducing gas through the central burner.
• the reduced ore was water quenched, ground and concentrated by known multiple wet magnetic separation.
• the concentrate contained 68% Fe total.
• the yield of Fe was 90%.
• Example 2 Prereduction of iron ores ⁇ mixture For producing pig iron in an electric furnace fine grained ores were prereduced with high volatile coal in a rotary kiln and hot charged to the electric furnace.
• the grain size distribution was:
• the net calorific value was 6710 kcaL/kg.
• the ore was separated in 2 fractions by screening.
• the pneumatically charged mixture consisted of Kg./h. Ore 45 Coal 60
• the temperature in the reduction zone was 1050- 1100", C.
• the temperature was regulated on a constant value by feeding air through the shell burners causing combustion of the volatile matter in the kiln gases.
• the reduction product was reduced to an amount of 49%. It contained:
• the material was hot charged into an electric furnace.
• the grain size distribution'of the ore was:
• Grain size mm. Grain size distribution, percent The ore contained ca. 66% Fe total in the form of hematite,
• the reducing agent was a high volatile pit coal with the following composition:
• the net calorific value was 6540 kcaL/kg.
• the cakingcapacity (Damm method) was about 7.5.
• the swellingindex was in the range from 2-2.5.
• the coal was used in a grain size -5 mm.
• the ore was separated by air separation in a fraction +0.09 mm. was pelletized with hot heavy oil on a pelletizing disk. The pellets had a diameter of 1 to 3 mm. and were pneumatically charged into the kiln together with the fraction +0.09 mm.
• the feeding rate was:
• the reduction product was cooled to a temperature below C. in a volating cooling cylinder which was cooled indirectly.
• the cooled material was separated in a magnetic and a non-magnetic fraction by magnetic separation.
• magnetic fraction was reduced greater than 95% and contained 90.5% Fe total and 87% Fe metallic.
• the ore was separated into a fraction +2 mm. and a fraction 2 mm.
• the fraction 2 mm. was mixed with 7.5% lignite-coal (from the same composition as that of Example 1) and during sprinkling with heavy oil agglomerated.
• the fraction +2 mm. was charged to the upper end of the rotary kiln.
• the mixture of agglomerated ore and coal was pneumatically fed through the lower end.
• the reduction temperature was about 1020 C. and was regulated by additional combustion of oil and burning the volatile constituents of coal and oil.
• the nickel content was metallized to an amount above 80% and the iron content to about 25%.
• the content of remaining fixed carbon was about 0.3%.
• the prereduced ore was hot charged into the smelting furnace.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Inorganic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Mechanical Engineering (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Muffle Furnaces And Rotary Kilns (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=7311544

Family Applications (1)

Country Status (6)

Cited By (2)

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• 1965
  • 1965-06-23 DE DE19651542305 patent/DE1542305A1/de active Pending
• 1966
  • 1966-06-06 NO NO163317A patent/NO117745B/no unknown
  • 1966-06-21 BE BE682904D patent/BE682904A/xx unknown
  • 1966-06-22 NL NL6608641A patent/NL6608641A/xx unknown
  • 1966-06-23 GB GB28248/66A patent/GB1098157A/en not_active Expired
• 1970
  • 1970-01-12 US US1952A patent/US3667933A/en not_active Expired - Lifetime

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