US3766663A - Preheater for lime kiln - Google Patents

Preheater for lime kiln Download PDF

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Publication number
US3766663A
US3766663A US00232579A US3766663DA US3766663A US 3766663 A US3766663 A US 3766663A US 00232579 A US00232579 A US 00232579A US 3766663D A US3766663D A US 3766663DA US 3766663 A US3766663 A US 3766663A
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United States
Prior art keywords
section
offtake
ports
holding
preheater
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Expired - Lifetime
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US00232579A
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English (en)
Inventor
M Parsons
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Detroit Lime Co
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Detroit Lime Co
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Publication date
Application filed by Detroit Lime Co filed Critical Detroit Lime Co
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Publication of US3766663A publication Critical patent/US3766663A/en
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    • 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
    • F27B7/2016—Arrangements of preheating devices for the charge
    • F27B7/2025—Arrangements of preheating devices for the charge consisting of a single string of cyclones

Definitions

  • a rotary kiln calcining device has relatively low thermal efficiency, particularly with highly endothermic processes such as the burning of lime. Rising fuel costs have increased the economic feasibility of preheating devices for commercial rotary kilns.
  • preheating devices are based'on convection heat transfer with the hot gases exhausting from the kiln being passed through voids in the feed material as in a vertical'shaft kiln. Because of the relatively small size of rotary kiln feeds and the large volume of combustion gases, impractically high pressure drops will be developed in the system unless the beds are relatively wide and shallow. The gases should have uniform motion across the entire bed to avoid overheating or fus- Because of the relatively higher heat transfer efficiency of preheaters, the calcining reaction tends to move from the rotary kiln into the preheater resulting in higher kiln exhaust gas temperatures.
  • the'invention comprises a'moving'bed of material so arranged that the kiln exhaust gases are introduced at a level in the preheater considerably above the feeder which discharges the stone to the rotary kiln. This creates a soaking or holding zone between the gas entry and discharge levels which may have a sufficient retention time to allow the high surface temperatures developed on each particle to'be diffused substantially into its entire volume.
  • the result is a preheated material of more uniform'temperature with a lower surface temperature but a greater stored heat content. When this'material is'fed to the rotary kiln it will not have the tendency to return heat to the gas stream but will absorb some heat, maintaining gas temperatures at a lower level.
  • the conically formed holding zone contributes to the uniform motion of the material and facilitates coupling the large preheater area to the single feeder.
  • the hot gases are introduced around the outer periphery of a circular cross-section and are removed from the center. Since flow resistance is higher for hot than for cooler gases,
  • this arrangement allows the development of stone bed void areas roughly proportional to the gas temperatures to give efiicient use of the bed area.
  • FIG. 1 is a cross-sectional view in elevation of the novel preheater taken along the line l1 of FIG. 2;
  • FIG. 2 is a plan crosssectional view taken along the line 2-2 of FIG. 1;
  • FIG. 3 is a fragmentary cross-sectional view taken along the line 33 of FIG. 2 and showing louver construction.
  • the preheater is generally indicated at 11 and in general comprises a vessel having an outer steel shell or framework generally indicated at 12 and an inner lining generally indicated at 13 of refractory material. Since the invention pertains to the configuration rather than the specific structural details of the preheater, the individual portions of the shell, framework and lining are not described in full detail. It will be understood however that appropriate supports, braces, refractory linings, poke and blow holes and other structural elements may be varied to suit requirements.
  • the stone beds 14 are formed in a cylindrically shaped section 15 of'this vessel.
  • An exhaustofftake 16 is concentrically mounted in section 15 and is of downwardly open, flared shape having an outer diameter of perhaps 60 to percent of the vessel diameter.
  • the offtake is shown as supported by a horizontal duct 17 extending through section 15 and leading to a blower intake (not shown).
  • the top of vessel section 15 is enclosed by an air lock feed device indicated schematically in dot-dash lines at 18 through which the stone is introduced, so that the kiln exhaust gases may be drawn by induced draft through the stonebeds without drawing in cool ambient air.
  • the air lock feed device may take any of various conventional forms,'such as a rotating gate having a plurality ofpockets formed by radial vanes.
  • the upper level 19 of material is maintained at a point above exhaustofftake 16 so that the material forms a symmetrical stone volume for exhaust of the gases.
  • the cylindrical preheater walls are increased to a larger diameter as indicated by the reference numeral 20.
  • the preheater has a horizontal ledge 21 which interconnects wall sections 15 and 20 and extends outwardly beyond section 20.
  • a wall 22 extends downwardly from the outer edge of ledge 21, thus creating an annular distribution duct 23 between vessel section 20 and wall 22. Exhaust gases 24 from the rotary kiln (not shown) are fed upwardly through a conduit 25 to this duct.
  • a plurality of ports 28 are provided in the upper edge of section immediately below ledge Zl, and hot gases will be drawn inwardly from duct 23 through these ports to the stone bed.
  • the flow of hot gases as they pass through the ports will be generally in an inward radial direction, and transverse to the downward movement of material.
  • the hot gases will thus be evenly distributed over the relatively large frustoconical area of the material which is symmetrical with respect to the offtake area.
  • the gases will flow upwardly through the voids in the material as they pass through section 15 to the offtake.
  • Duct 23 will allow dust entrained in the gases to settle, the dust being removable through drains 29.
  • a soaking or holding chamber 30 is formed on the preheater extending below section 20. This portion of the preheater is formed conically at a relatively steep angle, leading downwardly to a single centrally located discharge port 31 of relatively small area.
  • a feeding device indicated schematically in dot-dash lines at 32 is attached to outlet 31 and dispatches the material through a conventional feed pipe or chute indicated in dot-dash lines at 33 to the rotary kiln (not shown).
  • a baffle 34 is mounted inwardly of conical section 30, this baffle having a conical shape along the major portion of its length which is complementary to section 30 and a reverse conical shape 35 in its upper portion.
  • the baffle which is supported by a plurality of radially extending beams 36, will thus insure movement of the material over the entire cross-section of preheater section 30 to outlet 31. Little gas flow will take place in this zone because of the high resistance of the deep beds and the relatively small cross-sectional area, and the section will thus constitute a holding zone in which heat will be absorbed by the interiors of the particles.
  • the stone which has just exited gas-stone section 20 has a surface temperature equal to the gas temperature.
  • the thermal diffusion might almost equalize the temperature over the outer threeeighths inch (or seven-eighths of the total lump volume) in 7 to 11 minutes.
  • hot gases 24 will flow upwardly through conduit 25 and around duct 23, entering chamber 27 through ports 28 and passing through the voids in material 14. These gases will flow upwardly through cylindrical section 15 of the preheater to exhaust offtake 16. As the material moves downwardly through this zone, it will spread out against vessel section 20, this section, like section 15, being an active heating area in which the hot gases flow through the material voids. Because the heating area is relatively close to feed device 18 through which the particles enter at ambient temperatures, there will be large temperature differentials between the hot gases and the surfaces of the particles. This will result in immediately high rates of heat absorption, contributing to higher production for a given amount of fuel, or less fuel per unit of productivity.
  • the heated material As the heated material continues to descend, it will enter holding section 30 where it will gradually be narrowed down to a relatively small cross-sectional area so as to be discharged at central opening 31. During the time the material is in the holding zone, the heat absorbed by the outer portions of the particles will soak into their interiors to create a more uniform temperature throughout.
  • a refractory lined vessel having an upper material intake section, an exhaust offtake concentrically mounted in said section, means for feeding material into said section, a gas intake section below said material intake section, a plurality of circumferentially arranged ports around said gas intake section, means feeding hot gases to said ports, whereby the gases will flow radially inwardly through said material, a material holding section extending downwardly from said gas intake section, said material holding section being entirely below said ports and being sufficiently deep to permit heat to be absorbed by the interiors of the particles of material, and a material discharge port at the bottom of said material holding section.
  • said gas feeding means comprising an annular distribution duct around said ports, the ports being located adjacent the top of said enlarged section.
  • a refractory lined vessel having a cylindrical section, a circular exhaust offtake concentrically mounted in said section, means for feeding material into the top of said vessel so that the level of material is maintained above said offtake, a section of larger diameter than said cylindrical vessel section below the offtake and so shaped that the angle of repose of descending material will form an outwardly and downwardly inclined frustoconical surface around its periphcry, a plurality of circumferentially arranged ports adjacent the top of said enlarged section, means feeding hot gases to an annular distribution duct around said ports, a conical material holding section extending downwardly from said enlarged section, said material holding section being entirely below said ports and being sufficiently deep to permit heat to be absorbed by the interiors of the particles of material, and a single centrally located material discharge port of relatively small area at the bottom of said holding section.
  • said offtake comprising a downwardly open frustoconical member connected to a horizontal duct passing through said cylindrical vessel section.
  • a refractory lined vessel having a cylindrical section, a circular exhaust offtake concentrically mounted in said section, means for feeding material into the top of said vessel so that the level of material is maintained above said offtake, a section of larger diameter than said cylindrical vessel section below the offtake and so shaped that the angle of repose of descending material will form an inclined frustoconical surface around its periphery, a plurality of circumferentially arranged ports adjacent the top of said enlarged section, means feeding hot gases to an annular distribution duct around said ports, said annular distribution duct being so formed as to allow settling of dust entrained in said gases, drains for said dust in the bottom of said duct, a conical material holding section extending downwardly from said enlarged section, and a single centrally located material discharge port of relatively small area at the bottom of said holding section.
  • a refractory lined vessel having an upper material intake section, an exhaust offtake in said section, means for feeding material into said section, a gas intake section, means feeding hot gases to said gas intake section, a material holding section extending downwardly from said gas intake section, and a material discharge port at the bottom of said material holding section, said gas intake section being located a substantial distance above said discharge port whereby the hot gases will flow across stone having a relatively low surface temperature, said material holding section being entirely below said gas intake section and of sufficient dimensions to allow time for substantial inward diffusion of the surface heat on particles descending therethrough.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Furnace Details (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)
  • Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
  • Muffle Furnaces And Rotary Kilns (AREA)
US00232579A 1972-03-07 1972-03-07 Preheater for lime kiln Expired - Lifetime US3766663A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US23257972A 1972-03-07 1972-03-07

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US3766663A true US3766663A (en) 1973-10-23

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US (1) US3766663A (forum.php)
JP (1) JPS519715B2 (forum.php)
AU (1) AU467775B2 (forum.php)
CA (1) CA984145A (forum.php)
DE (1) DE2310853B2 (forum.php)
ES (1) ES412199A1 (forum.php)
GB (1) GB1394654A (forum.php)
IT (1) IT983447B (forum.php)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4702019A (en) * 1985-07-17 1987-10-27 Ishikawajima-Harima Jukogyo Kabushiki Kaisha Apparatus for cooling high-temperature particles
RU2241182C1 (ru) * 2003-05-07 2004-11-27 Открытое акционерное общество "Новолипецкий металлургический комбинат" Подогреватель кускового сырья

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5336380B2 (forum.php) * 1974-07-31 1978-10-02
JPS5395004A (en) * 1977-01-31 1978-08-19 Teac Corp Cassette type reelldrive magnetic tape runner reel
JPS54143873U (forum.php) * 1978-03-31 1979-10-05
DE3534166A1 (de) * 1985-09-25 1987-04-16 Braun Ag Messerblock fuer trockenrasierapparate

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1778281A (en) * 1928-01-19 1930-10-14 Sobek Emanuel Discharge funnel for kilns
US2653809A (en) * 1949-07-23 1953-09-29 Azbe Corp Kiln
US2739800A (en) * 1952-06-13 1956-03-27 Erie Mining Co Controls for pelletizing furnace

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1778281A (en) * 1928-01-19 1930-10-14 Sobek Emanuel Discharge funnel for kilns
US2653809A (en) * 1949-07-23 1953-09-29 Azbe Corp Kiln
US2739800A (en) * 1952-06-13 1956-03-27 Erie Mining Co Controls for pelletizing furnace

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4702019A (en) * 1985-07-17 1987-10-27 Ishikawajima-Harima Jukogyo Kabushiki Kaisha Apparatus for cooling high-temperature particles
RU2241182C1 (ru) * 2003-05-07 2004-11-27 Открытое акционерное общество "Новолипецкий металлургический комбинат" Подогреватель кускового сырья

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Publication number Publication date
GB1394654A (en) 1975-05-21
DE2310853A1 (de) 1973-09-13
DE2310853B2 (de) 1976-08-19
IT983447B (it) 1974-10-31
ES412199A1 (es) 1976-01-01
AU467775B2 (en) 1975-12-11
JPS519715B2 (forum.php) 1976-03-29
AU5273073A (en) 1974-08-29
JPS49200A (forum.php) 1974-01-05
CA984145A (en) 1976-02-24

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