US3603569A - Kiln preheat and drying section - Google Patents

Kiln preheat and drying section Download PDF

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Publication number
US3603569A
US3603569A US888378A US3603569DA US3603569A US 3603569 A US3603569 A US 3603569A US 888378 A US888378 A US 888378A US 3603569D A US3603569D A US 3603569DA US 3603569 A US3603569 A US 3603569A
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United States
Prior art keywords
dust
kiln
fraction
inner shell
raw material
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
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US888378A
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English (en)
Inventor
Harry I Abboud
Oren C Furnish
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Kaiser Aluminum and Chemical Corp
Original Assignee
Kaiser Aluminum and Chemical Corp
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Filing date
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Application filed by Kaiser Aluminum and Chemical Corp filed Critical Kaiser Aluminum and Chemical Corp
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Publication of US3603569A publication Critical patent/US3603569A/en
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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
    • 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
    • F27B7/32—Arrangement of devices for charging
    • F27B7/3205—Charging
    • 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
    • F27B7/14—Rotary-drum furnaces, i.e. horizontal or slightly inclined with means for agitating or moving the charge
    • F27B7/16—Rotary-drum furnaces, i.e. horizontal or slightly inclined with means for agitating or moving the charge the means being fixed relatively to the drum, e.g. composite means
    • F27B7/161—Rotary-drum furnaces, i.e. horizontal or slightly inclined with means for agitating or moving the charge the means being fixed relatively to the drum, e.g. composite means the means comprising projections jutting out from the wall
    • F27B2007/165—Rotary-drum furnaces, i.e. horizontal or slightly inclined with means for agitating or moving the charge the means being fixed relatively to the drum, e.g. composite means the means comprising projections jutting out from the wall forming a helical lifting projection
    • 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
    • F27B2007/2008—Devices for reintroducing dust in the drum
    • 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
    • F27B7/32—Arrangement of devices for charging
    • F27B7/3205—Charging
    • F27B2007/3211—Charging at the open end of the drum
    • 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
    • F27B7/32—Arrangement of devices for charging
    • F27B7/3205—Charging
    • F27B2007/3211—Charging at the open end of the drum
    • F27B2007/3217—Charging at the open end of the drum axially, optionally at some distance in the kiln

Definitions

  • An improved kiln preheat and drying section comprising an inner shell concentric and axially aligned with the kiln shell, and provided with a means to feed raw material to be processed into the inner shell and means to feed dust into the annular space defined by the inner shell and kiln shell; and a process for operating the improiled preheat and drying section.
  • Rotary kilns generally comprise a long cylindrical steel shell inclined toward the discharge end.
  • the shell is provided with circumferential tires at spaced intervals along the length thereof and suitably supported by rolls.
  • the shell is lined in whole or in part by refractory material such as brick and the like.
  • the raw material to be processed is fed into the relatively cold upper or feed end of the kiln; and, due to the rotating action of the kiln, slowly moves toward the relatively hot discharge end.
  • Fuel such as pulverized coal, natural gas and fuel oil is burned at the discharge end, and the hot gases are passed countercurrent to the raw material flow through the kiln, and then usually directed through one or more dust-col lecting means before being discharged into the atmosphere.
  • the dust removed from the hot gases can be recycled to the kiln or disposed of as waste, depending upon process economics. Due to waste disposal problems, most present-day processes recycle the dust to the kiln.
  • the present invention provides an improved design and operating process for the preheat and drying section of an inclined rotary kiln for the pyroprocessing of alumina, lime, cement clinker and the like.
  • the improved feed section design of the present invention comprises a concentric cylindrical shell (hereinafter referred to as the inner shell) specially disposed and axially aligned within the outer shell of the kiln.
  • a means is provided to feed the raw material to be processed into the inner shell.
  • the dust entrained in the exiting gases is removed by any suitable dust-collecting means and is fed by suitable means to the annular space between the inner and outer shells.
  • means are disposed within the annulus such as plows, spiral flights and the like to move the dust toward the discharge end of the kiln.
  • a suitable coarse fraction is one, 80 percent of which will have a mean particle diameter greater than microns. It is preferred to maintain this coarse fraction 90 percent 20 micron. In most operations the fine dust fraction will have a mean particle diameter less than 20 microns. 1n installations where there are primary and secondary dust-collecting means, it is advantag'eous to recycle dust from the primary dust collectors, which is relatively coarse, to the inner shell along with the raw material to be processed and the dust from the secondary and subsequent dust collectors, which is relatively fine, to the annular space between the two shells. It is most advantageous to mix the coarse dust fraction with the incoming raw material prior to feeding the raw material to the inner shell.
  • the feeding of the coarse dust fraction for example from the primary dust collector, into the inner shell with the raw material feed and the fine dust fraction from the secondary and subsequent dust collectors into the annular space.
  • the coarse dust fraction contains considerable heat and by introducing this dust with the raw material, considerable heat transfer can be effected.
  • By mixing the coarse dust fraction with the raw material before feeding to the inner shell a substantial increase in heat transfer can be obtained.
  • the premixing substantially reduces the scaling of lifters and heat exchange grates in the inner shell resulting in further substantial increases in heat transfer.
  • the material throughput can be increased up to 3 0 percent or more over the conventional designs with substantial increases in thermal efficiency-ie, large decreases in B.t..u./lb. of product.
  • the dimensions of the inner shell with respect to the outer shell depend on many factors such as the material being treated, material throughput, gas velocity and temperature and the like. The only requirement is that the annular space be of sufficient size to handle the dust returned. The diameter of the inner shell should not be reduced to such an extent that the gas velocity is substantially increased, resulting in substantially increased draft fan requirements.
  • the length of the inner shell with respect to the total length of the kiln will depend considerably upon the form of the raw material; i.e., whether it is a slurry, moist nodules or a dry particulate matter, and the type of processing desired; e.g., dehydration, decarbonation, or pyrochemical reactions between the components of the raw materials as in cement clinker manufacture.
  • heat exchange grates, lifters and dams may be provided on the inner surface of the inner shell.
  • FIG. 1 is a sectional elevation view of an inclined rotary kiln and the dust collectors associated therewith.
  • FIG. 2 is a detailed cross-sectional drawing of the preheat and drying zones of the kiln.
  • the kiln is generally shown at 10. It comprises a cylindrical shell 11 which is suitably supported by tires 12 and rolls 13. At the discharge end 14 of the kiln and encased by a hood 15 is a burner 16. A hood or dust chamber 17 covers the feed end 18 of the kiln. Screw conveyor 19 is provided for feeding the raw material into the feed end 18 of the kiln. A duct 20 connects the dust chamber 17 with the primary dust collector 21. Conduit 22 is provided at the discharge of dust collector 21 for returning the coarse dust fraction to the screw conveyor, or as shown in phantom, conduit 22a is provided for returning the dust to the inner shell 23 of the kiln.
  • Duct 24 is provided to connect the primary dust collector gas discharge outlet with the gas inlet of the secondary dust collector 25.
  • Conduit 26 is provided to connect the dust discharge outlet of the secondary dust collector with the doughnut-shaped feed chamber 27.
  • Conduit 26a is provided for the dust returned from dust collectors subsequent to the secondary dust collector. Attached to the gas discharge exit of the secondary dust collector 25 is conduit 28, which connects the secondary dust collector with the fan 29 and subsequent dust collector means (not shown).
  • the inner shell 23 is axially aligned with the kiln shell 11 and suitably supported and fixedly attached therein by supports (not shown). Some compensation usually must be given for the longitudinal expansion of inner shell with respect to the kiln shell which occurs during the operation of the kiln. This can be accomplished by fixably attaching the cooler end of the inner shell and slidably sup porting the hotter end of the inner shell. Also, the supports may all be slidably attached to the kiln shell, but slidable only in the longitudinal direction (i.e., axially with the kiln shell).
  • plows 31 are provided to move the raw material into the area of the inner shell containing heat exchange grates, lifters, dams and the like (not shown).
  • a doughnutshaped chamber 27 Integral with the feed end of the kiln is a doughnutshaped chamber 27 containing plows 32 for moving the dust returned therein into the annulus 35 through apertures 33.
  • a means 34 Within the annulus is provided a means 34, a spiral flight, for moving dust through the annular area toward the discharge end of the kiln upon the rotation thereof.
  • hot gases are provided by burner 15 which may burn fuels such as pulverized coal, natural gas, and fuel oil.
  • Primary and/or secondary air may be provided for combustion.
  • the gases are passed through the kiln by the action of a draft fan 29.
  • the raw material is introduced into the inner shell 23 by the feed means 19.
  • a screw conveyor is shown in the drawings, any suitable feed means may be used; for example, a conduit if the raw material is a slurry, and vibrating or belt conveyors and the like if the raw material is relatively dry.
  • the dust-laden gases pass from the kiln into the dust chamber 17 and then into the primary dust collector 21 through conduit 20.
  • the coarse fraction of dust is separated from the gases and is returned to the inner shell of the kiln by conduit 22 or conduit 22a.
  • the dust-laden gases from the primary dust collector 21 are passed to the secondary dust collectors through conduit 24 for further separation.
  • the fine dust fraction from the secondary dust collector is returned to the doughnut-shaped chamber 32 through conduit 26.
  • the gases from the secondary dust collectors pass through conduit 28 to the draft fan 29 and then to the stack or other dust collectors (not shown).
  • the plows 32 move the fine dust fraction into the annulus space 35 through apertures 33.
  • Spiral flight 34 moves the fine dust fraction through the annulus toward the discharge end of the kiln.
  • dust-feeding means associated with said dust-splitting means and disposed at the feed end of the kiln, said dustfeeding means arranged in a manner so as to feed the coarse dust fraction into said annular space and said fine dust fraction into said inner shell;
  • d. means disposed at the feed end of the kiln to feed raw material to said inner shell.
  • the inclined rotary kiln of claim 1 having means to mix the coarse dust fraction with the raw material before said raw material is fed to the inner shell.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Muffle Furnaces And Rotary Kilns (AREA)
  • Furnace Details (AREA)
US888378A 1969-12-29 1969-12-29 Kiln preheat and drying section Expired - Lifetime US3603569A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US88837869A 1969-12-29 1969-12-29

Publications (1)

Publication Number Publication Date
US3603569A true US3603569A (en) 1971-09-07

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Family Applications (1)

Application Number Title Priority Date Filing Date
US888378A Expired - Lifetime US3603569A (en) 1969-12-29 1969-12-29 Kiln preheat and drying section

Country Status (3)

Country Link
US (1) US3603569A (enrdf_load_stackoverflow)
FR (1) FR2074380A5 (enrdf_load_stackoverflow)
GB (1) GB1266299A (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3799735A (en) * 1972-01-05 1974-03-26 Smidth & Co As F L Conveyor flights for rotary kiln
US4952147A (en) * 1986-10-01 1990-08-28 Champion International Corporation Lime sludge kiln
WO1991000251A1 (en) * 1989-07-03 1991-01-10 A. Ahlstrom Corporation Feeding system for a lime reburning kiln
US5213496A (en) * 1989-07-03 1993-05-25 A. Ahlstrom Corporation Feeding system for a lime reburning kiln
US5989018A (en) * 1996-07-05 1999-11-23 Ahlstrom Machinery Oy Lime sludge feed arrangement
US20100086476A1 (en) * 2005-11-21 2010-04-08 Andritz Oy Method and apparatus for treating lime mud
US20230347270A1 (en) * 2022-04-29 2023-11-02 Hamilton Sundstrand Corporation Mid-pressure water collector (mpwc) with helical flow channel and radial scuppers

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NZ182202A (en) * 1975-10-15 1979-03-28 Smidth & Co As F L Kiln plant with inclined rotary kiln:device for lowering temperature at upper kiln end

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2039645A (en) * 1932-10-04 1936-05-05 Chemical Construction Corp Treatment of sulphur bearing ores

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2039645A (en) * 1932-10-04 1936-05-05 Chemical Construction Corp Treatment of sulphur bearing ores

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3799735A (en) * 1972-01-05 1974-03-26 Smidth & Co As F L Conveyor flights for rotary kiln
US4952147A (en) * 1986-10-01 1990-08-28 Champion International Corporation Lime sludge kiln
WO1991000251A1 (en) * 1989-07-03 1991-01-10 A. Ahlstrom Corporation Feeding system for a lime reburning kiln
US5213496A (en) * 1989-07-03 1993-05-25 A. Ahlstrom Corporation Feeding system for a lime reburning kiln
US5989018A (en) * 1996-07-05 1999-11-23 Ahlstrom Machinery Oy Lime sludge feed arrangement
US20100086476A1 (en) * 2005-11-21 2010-04-08 Andritz Oy Method and apparatus for treating lime mud
US8703079B2 (en) * 2005-11-21 2014-04-22 Andritz Oy Method for treating lime mud
US20230347270A1 (en) * 2022-04-29 2023-11-02 Hamilton Sundstrand Corporation Mid-pressure water collector (mpwc) with helical flow channel and radial scuppers
US12036498B2 (en) * 2022-04-29 2024-07-16 Hamilton Sundstrand Corporation Mid-pressure water collector (MPWC) with helical flow channel and radial scuppers

Also Published As

Publication number Publication date
FR2074380A5 (enrdf_load_stackoverflow) 1971-10-01
GB1266299A (enrdf_load_stackoverflow) 1972-03-08

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