US3770257A - Level control for rotating furnaces - Google Patents

Level control for rotating furnaces Download PDF

Info

Publication number
US3770257A
US3770257A US00159259A US3770257DA US3770257A US 3770257 A US3770257 A US 3770257A US 00159259 A US00159259 A US 00159259A US 3770257D A US3770257D A US 3770257DA US 3770257 A US3770257 A US 3770257A
Authority
US
United States
Prior art keywords
furnace
particulate material
helical
flight
discharging end
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00159259A
Other languages
English (en)
Inventor
J Bell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Huntington Alloys Corp
Original Assignee
International Nickel Co Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by International Nickel Co Inc filed Critical International Nickel Co Inc
Application granted granted Critical
Publication of US3770257A publication Critical patent/US3770257A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
    • F27B7/20—Details, accessories or equipment specially adapted for rotary-drum furnaces
    • F27B7/42—Arrangement of controlling, monitoring, alarm or like devices
    • 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
    • F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
    • 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
    • F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
    • F27B7/20—Details, accessories or equipment specially adapted for rotary-drum furnaces
    • F27B7/2083—Arrangements for the melting of metals or the treatment of molten metals

Definitions

  • ABSTRACT A horizontally mounted rotary cylindrical furnace is provided with an internal helical flight for at least the preponderant part of one revolution but not more than two revolutions of the furnace so that two zones are formed within the rotary furnace.
  • the pitch of the flight can be controlled so that material fed to the first zone is conveyed to the second zone at a rate greater than the rateof feedto the first zone.
  • the height of the helical flight can be set so a deeper bed and greater retention time is obtained in the solids down stream of the flight.
  • a discharge mechanism which is a tapered helical rotor with its larger vanes being coextensive with and fixed to the furnace diameter and the smaller vanes being mounted in an coextensive with and fixed to a take-off conveyer tube.
  • the present invention pertains to furnaces, and more particularly to rotary furnaces and processes conducted therein.
  • the present invention is particularly applicable to rotary furnaces which are employed in the reduction, oxidation or other heat treatment of ores, ore concentrates, or other metallurgical intermediates and will be described with particular reference thereto although it will be appreciated .that the invention has broader applications such as in the use in cement kilns or in any other process apparatus in which a continuous process is dependent on distinct chemical or physical mechanisms that involve different treating times.
  • Rotary metallurgical furnaces have heretofore comprised a horizontally mounted and refractory-lined cylindrical steel shell, heat generating means to heat and to maintain the material being treated at treating temperatures, atmosphere control means and means for rotating the furnace.
  • heat generating means to heat and to maintain the material being treated at treating temperatures
  • atmosphere control means and means for rotating the furnace.
  • rotary furnaces In order to transport material from one end of the furnace to the other, rotary furnaces have most often been mounted at a slight inclination from the horizontal and in some instances, flights, both lateral and helical, and dams have been employed to control the rate of flow of material through the entire furnace.
  • Rotary furnaces have also been provided with means for feeding material to one end and with means for withdrawing the material from the other end. Charging raw material to rotary furnaces has not presented many problems but difficulties are often encountered in discharging processed material therefrom. Occasionally, the desired metallurgical treatment is conducted at other than atmospheric pressures and such pressures, whether subatmospheric or superatmospheric, must be maintained throughout the furnace during discharge which, if continuous, presents numerous problems.
  • Rotary furnaces as described hereinbefore, have been used, and are currently being used, to reduce ores, ore concentrates and other metallurgical intermediates.
  • iron oxides containing nickel are selectively reduced to reduce substantially all the nickel values to metallic nickel while reducing only controlled amounts of iron.
  • the selectively reduced ore is then treated, either hydrometallurgically or vapometallurgically, to recover the reduced nickel values.
  • the chemical reduction of metallurgical ores involves two distinct processes.
  • the ore must first be preheated to the reduction temperature, and thereafter the heated ore is reduced with an appropriate reductant.
  • Preheating involves well understood heat exchange principles and is a relatively fast process since the ore, which is not generally massive, presents large surfacevar eas at and through which heat exchange rapidly and readily occurs.
  • chemical reduction when effected in the solid state, is a relatively slow process since diffusional processes are involved.
  • the ore is preheated as fast as possible while ja longer period is allowed for chemical reduction, but this ideal has rarely been realized in actual practice.
  • the bed of ore in a preheating zone should be relatively shallow in order to increase the rate of heat exchange while the bed of ore in a reducing zone is maintained relatively dam.
  • the increase in depth of the bed is not so great as to significantly improve the efficiency of the preheating operation or to materially increase the time of residency'in the reducing zone.
  • flights in a preheating zone can increase the preheating'rate, problems associated with dusting are encountered and the flights, extending throughout the preheating zone, provide extensive surfaces and angles over which and inwhich massive accretions can rapidly form. At times, such massive accretions build up so rapidly that any advantage gained by improved preheating is lost by the time required to remove such accretions.
  • metallurgical rotary furnaces can be operated at subatmospheric or superatmospheric pressures for thermodynamic and kinetic reasons.
  • discharging treated materials can present numerous problems. Even when operated at ambient pressures discharging treated material from rotary furnaces can be troublesome if it is required to maintain a neutral or protective atmosphere over the treated material while leaving the atmosphere in the furnaceundisturbed.
  • the problems associated with discharging treated material were overcome by enclosing the entire discharge end of the furnace with a separate and distinct housing which acted as a pressure seal.
  • horizontally mounted rotating cylindrical furnaces can be improved by providing the furnace with a helical flight to establish two zones along the longitudinal axis of the furnace to control the rate of flow of material from one zone to the other.
  • the diameter of the helical flight can be arranged so that the bed depth down stream from the flight is increased-Such rotary furnaces can be further improved by providing the discharge end of the furnace with a discharge tube and a helical'rotor with the larger vanesof the rotor being coextensive with and fixed to the inside diameter of the furnace and the smaller vanes being coextensive with and fixed to the internal diameter of the discharge'tube.
  • a rotary furnace of the type described wherein the furnace has an internal helical flight for at least a pre ponderant part of one revolution but not more than about two revolutions of the furnace so that the furnace is separated into two zones along its longitudinal axis and so that the rate of passage of material through the two zones can be independently varied. In this fashion the depth of material in each section and the retention time in each section can be varied.
  • Another object of the present invention is to provide a cylindrical furnace in which the rate of flow of material through various zones therein can be controlled and which has an improved discharge mechanism.
  • FIG. 1 is a longitudinal cross-sectional view of a rotary furnace in accordance with the present invention
  • FIG. 2 is a cross-sectional view of the furnace taken along the lines 22 in FIG. 1;
  • FIG. 3 is a cross-sectional view showing an improved discharge mechanism of a rotary furnace in accordance with the present invention.
  • FIG. 1 shows an improved rotary furnace in accordance with the present invention.
  • the rotary furnace A includes a cylindrical shell 12, generally steel, which is suitably lined with refractory 13.
  • the charging end of the furnace A is generally represented at B and includes a flue 14 and a feeding device 15.
  • the discharging end of the furnace A is provided with burner 16 and a housing 17, which housing acts as a gas seal and a discharge hopper.
  • the cylindrical shell is provided with steel tires 18 which in conjunction with driving means 19 rotate the cylindrical furnace at preselected speeds.
  • the rotary furnace can be provided with air vents or side burners 20.
  • the cylindrical furnace is provided with a helical flight 21 which can be constructed of the same material as that of the refractory lining 13, or a suitable metallic material. Since, as described hereinafter, helical flight 21 has a pitch such that particulate material is conveyed from one zone to another at a rate greater than that provided by gravity and the inclination and rotation of the furnace, dam 22 can optionally be located immediately before flight 21 to provide more readily controllable depths in the first zone.
  • the helical flight is an important feature of the present invention.
  • the flight can be of any height as long as it is at least as high as the depth of the deepest bed.
  • the furnace is a metallurgical furnace in which an oxide is preheated in zone D and reduced in zone B
  • the ore in zone E is maintained at a greater depth than in the preheating zone D to provide a longer residence time in zone E and the height of the flight is at least equal to the depth of the ore in zone E.
  • Placement of the helical flight along the longitudinal axis of the cylindrical furnace is not mechanically critical. However, such' placement can be of great importance for particular chemical or metallurgical operations.
  • the furnace is employed to directly reduce metal oxides, as iron oxide or nickel oxide
  • the helical flight is placed at the position in the furnace where a shallow bed and the metal oxide will have been preheated to effect the reducing temperatures.
  • the pitch of the helical flight can be varied to suit individual requirements.
  • the inclination of the furnace will cause material to flow through the furnace, and the helical flight will have a pitch such that the flow of material will be greater than that caused by the inclination of the furnace, i.e., the leading edge of the helical flight cuts into the ore flowing along the furnace longitudinally under the impetus of gravity and the usual slight inclination of the furnace toward the discharge end.
  • the pitch of the helical flight can be such that preheated ore in zone D is transferred to the reducing zone E at a rate greater than the rate of feeding iron oxide to the preheating zone D whereby the preheating operation is made more efficient and the residence time of iron oxide in the reducing zone is increased.
  • drying or preheating will be conducted in the first zone or zones and chemical processes are effected thereafter. Since these chemical reactions will most frequently be diffusion controlled processes, it is desirable to have the bed of material shallow in the initial zones and deeper thereafter.
  • more than one helical flight can be employed in a single cylindrical furnace so that three or more distinct zones can be established.
  • zones of different depths can be formed so that surface area dependent operations can be conducted more efficiently in shallow beds while diffusion controlled (time dependent) operations are affected with deeper beds.
  • FIG. 3 depicts a preferred embodiment of the present invention. Only the discharge end of the cylindrical furnace is shown in FIG. 3 since the preferred embodiment relates to a discharging mechanism.
  • the cylindrical furnace includes a cylindrical steel shell 30 which is lined with a suitable refractory 31 the furnace is rotated about its longitudinal-axis by drive means (not shown in the drawing). Flow of material through the furnace is controlled by helical flights as described hereinbefore.
  • the furnace is provided with a fixed discharge tube 32 which can be a steel shell 33, suitably lined with refractory 34 to handle hot material.
  • the discharge tube is provided with a gas seal 35 so that the escape of furnace gases through the discharge end are minimized.
  • an advantageous feature of the present invention is that the diameter of the discharge tube is vconsiderably smaller than that of the cylindrical furnace so that any gas seals that are provided are more effective since it is well known that smaller fixtures are easier to seal than are larger ones.
  • the discharge mechanism is a conveyor screw 36 with helical flights 38 extending into the furnace being substantially equal to the internal diameter of the furnace while those helical flights 39 extending to the discharge tube are substantially coextensive with the internal diameter of the discharge tube.
  • the helical flights for the discharge mechanism can be made of suitable metals or refractories.
  • the screw 36 is fixedly mounted in the furnace so that it rotates with the furnace. Thus, flights 39 rotate in fixed discharge tube 32 as the furnace rotates.
  • the pitch of flights 39 is regulated so that the material is fed out faster than it arrives.
  • the rate of discharge can be effectively controlled by regulating the rotation of the conveyor screw.
  • the shaft upon which the helical screw is mounted can be hollow so that gases such as air and/or fuel can be introduced into the interior of the furnace so that the shaft can act as a burner for supplying heat to the cylindrical rotating furnace.
  • gases such as air and/or fuel
  • the rate of air and fuel can be varied to provide oxidizing and reducing conditions at that portion of the rotating furnace into which the shaft extends.
  • a rotary furnace including a cylindrical furnace having a charging end, a discharging end and a substantially uniform cross section and being rotatable about its longitudinal axis and mounted at a preselected inclination so that rotation of the furnace transports particulate material fed to the charging end to the discharging end
  • the improvement which comprises: at least one helical flight mounted on the furnace walls between said charging and discharging ends forming within said furnace two zones, said helical flight extending for at least the preponderant part of one revolution of said furnace but not more than two revolutions of said furnace, so that the rate of flow of particulate material through the zones can be controlled by controlling the speed of rotation of the rotary furnace and a conveyer tube fixedly mounted at the discharging end of the furnace, a conveyor screw having helical flights that are substantially coextensive with the internal diameter of the conveyor tube and the furnace-and fixed to the furnace wall so that particulate material is conveyed out of the furnace into the conveyor tube by the helical flights by rotation of the furnace
  • a rotary furnace including a cylindrical furnace having a charging end, a discharging end and a substantially uniform cross section and being rotatable about its longitudinal axis and mounted at a preselected inclination so that rotation of the furnace transports particulate material fed to the charging end to the discharging end
  • the improvement which conprises: an internal helical flight for a preponderant part of at least one revolution of the furnace mounted on a furnace wall between the ends of the furnace to provide the furnace with two separate zones along its longitudinal axis whereby the depth of particulate material in the respective zones can be controlled by regulating the speed of revolution of the furnace and a conveyor tube fixedly mounted at the discharging end of the furnace, a conveyer screw havinghelical flights that are substantially coextensive with the internal diameter of the conveyor tube and the furnace and fixed to the furnace wall so that particulate material is conveyed out of the furnace into the conveyor tube by the helical flights by rotation of the furnace.
  • a rotary furnace including a cylindrical furnace having a charging end, a discharging end and a substantially uniform cross section and being rotatable about its longitudinal axis and mounted at a preselected incliulate material fed to the charging end to the discharging end, the improvement which comprises: an internal helical flight for the preponderant part of at least one revolution but not more than two revolutions of the furnace mounted on the furnace wall and between the ends of the furnace to provide two zones along the longitudinal axis of the furnace whereby particulate material treated in the furnace can be controlled to have different depths within the two zones in the furnace and a conveyer tube fixedly mounted at the discharging end of the furnace, a conveyer screw having helical flights that are substantially coextensive with the internal diameter of the conveyor tube and the furnace and fixed to the furnace wall so that particulate material is conveyed out of the furnace into the conveyor tube by the helical flights by rotation of the furnace.
  • the furnace as described in claim 4 further including a dam proximately mounted to the helical flight so that the dam controls the depth of particulate material nearer the charging end and the helical flight feeds par-- ticulate material to the zone nearer the discharging end.
  • a hollow shaft onwhich the conveyor screw is mounted so that the hollow shaft can function as a burner.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Muffle Furnaces And Rotary Kilns (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Furnace Charging Or Discharging (AREA)
US00159259A 1970-07-08 1971-07-02 Level control for rotating furnaces Expired - Lifetime US3770257A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA087,693A CA946148A (en) 1970-07-08 1970-07-08 Level control for rotating furnaces

Publications (1)

Publication Number Publication Date
US3770257A true US3770257A (en) 1973-11-06

Family

ID=4087152

Family Applications (1)

Application Number Title Priority Date Filing Date
US00159259A Expired - Lifetime US3770257A (en) 1970-07-08 1971-07-02 Level control for rotating furnaces

Country Status (9)

Country Link
US (1) US3770257A (enrdf_load_html_response)
JP (1) JPS5327203B1 (enrdf_load_html_response)
CA (1) CA946148A (enrdf_load_html_response)
DE (1) DE2133918A1 (enrdf_load_html_response)
DO (1) DOP1971001824A (enrdf_load_html_response)
FR (1) FR2100442A5 (enrdf_load_html_response)
GB (1) GB1322427A (enrdf_load_html_response)
NO (1) NO129587B (enrdf_load_html_response)
ZA (1) ZA714231B (enrdf_load_html_response)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995001208A1 (en) * 1993-06-29 1995-01-12 Aluminum Company Of America Waste management facility
CN116354388A (zh) * 2023-03-15 2023-06-30 安徽赛尔新能源科技有限公司 一种锂离子电池负极材料钛酸锂的制备装置及其制备方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2393009C1 (ru) * 2009-05-12 2010-06-27 Открытое акционерное общество "Конструкторское бюро специального машиностроения" Реактор синтеза металлоорганических соединений

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1353716A (en) * 1916-10-05 1920-09-21 Charles S Bradley Production of iron and steel
US2653809A (en) * 1949-07-23 1953-09-29 Azbe Corp Kiln
DE956514C (de) * 1952-02-26 1957-01-17 Gutehoffnungshuette Sterkrade Verfahren zum Behandeln von Metallschmelzen, insbesondere Roheisen
US3113859A (en) * 1961-02-09 1963-12-10 R N Corp Methods for ore reduction and processing of other chemically reactive aggregates

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1353716A (en) * 1916-10-05 1920-09-21 Charles S Bradley Production of iron and steel
US2653809A (en) * 1949-07-23 1953-09-29 Azbe Corp Kiln
DE956514C (de) * 1952-02-26 1957-01-17 Gutehoffnungshuette Sterkrade Verfahren zum Behandeln von Metallschmelzen, insbesondere Roheisen
US3113859A (en) * 1961-02-09 1963-12-10 R N Corp Methods for ore reduction and processing of other chemically reactive aggregates

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995001208A1 (en) * 1993-06-29 1995-01-12 Aluminum Company Of America Waste management facility
CN1098717C (zh) * 1993-06-29 2003-01-15 美国铝公司 处理电解熔融铝得到的废电解槽系列物的方法和废物管理设施
CN116354388A (zh) * 2023-03-15 2023-06-30 安徽赛尔新能源科技有限公司 一种锂离子电池负极材料钛酸锂的制备装置及其制备方法

Also Published As

Publication number Publication date
CA946148A (en) 1974-04-30
ZA714231B (en) 1972-04-26
DE2133918A1 (de) 1972-02-03
NO129587B (enrdf_load_html_response) 1974-04-29
GB1322427A (en) 1973-07-04
JPS5327203B1 (enrdf_load_html_response) 1978-08-07
DOP1971001824A (es) 1976-05-11
FR2100442A5 (enrdf_load_html_response) 1972-03-17

Similar Documents

Publication Publication Date Title
US4983214A (en) Method and apparatus for direct reduction of metal oxides
US3789126A (en) Electric furnace for heating and melting scrap iron and steel
US2861353A (en) Apparatus for cooling granular materials
US2348673A (en) Rotary kiln for extraction of mercury from its ores
US3770257A (en) Level control for rotating furnaces
KR102460319B1 (ko) 함철부산물 처리 장치
JP2010012409A (ja) 加熱処理装置および加熱処理方法
US3900696A (en) Charging an electric furnace
CN111172405B (zh) 一种微波转底炉氯化提金装置及方法
US2282584A (en) Method of operating rotary kilns
US3228670A (en) Methods and apparatus for ore reduction and processing of other chemically reactive aggregates
WO2025077072A1 (zh) 一种直接还原制备铁合金的冶炼装置及方法
US2039833A (en) Method and apparatus for roasting and heat treating ores and minerals
US3423080A (en) Electric arc furnace
CN112301221B (zh) 回转式还原电炉及还原冶炼方法
US3689251A (en) Reduction of solid iron ore to hot metallic iron in a rotary kiln-flash heater-rotary reactor complex
US962006A (en) Apparatus and process for preparing pulverous iron ores and the like for smelting in blast-furnaces and use in open-hearth furnaces.
US3599947A (en) Apparatus for direct iron and steel making
US2657990A (en) Feeding furnaces
US2993779A (en) Process of reducing metal oxides
CN207537511U (zh) 银精矿的处理系统
US2699388A (en) Method and apparatus for making metallic iron
KR20010024881A (ko) 산화철 환원방법 및 그 장치
KR20190084604A (ko) 스크류형의 직접환원철법 냉각장치
US3063826A (en) Method of reducing iron ores