US3789513A - Pneumatic dryers - Google Patents

Pneumatic dryers Download PDF

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Publication number
US3789513A
US3789513A US00326962A US3789513DA US3789513A US 3789513 A US3789513 A US 3789513A US 00326962 A US00326962 A US 00326962A US 3789513D A US3789513D A US 3789513DA US 3789513 A US3789513 A US 3789513A
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chamber
divided material
drying
column
drying gas
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US00326962A
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A Mark
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
    • F26B17/10—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by fluid currents, e.g. issuing from a nozzle, e.g. pneumatic, flash, vortex or entrainment dryers
    • F26B17/107—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by fluid currents, e.g. issuing from a nozzle, e.g. pneumatic, flash, vortex or entrainment dryers pneumatically inducing within the drying enclosure a curved flow path, e.g. circular, spiral, helical; Cyclone or Vortex dryers

Definitions

  • the present invention relates to the pneumatic drying of divided materials.
  • the material to be dried is conveyed by a stream of a hot and dry gas in which it is suspended, this gas absorbing the moisture from the particles of the material. Since for obvious reasons the initial temperature of the gas is limited and since at any given temperature the transfer of the internal moisture from the particles to the gas is only progressive, the socalled residence time during which the particles are retained in suspension in the gas should be long enough. Moreover since the velocity of the drying gas stream cannot be lowered below a safe minimum beyond which the bigger particles would not be entrained, the path followed by the gas and divided material should be relatively long, in order to obtain the residence time required, which leads to cumbersome and expensive apparatus.
  • the length of the said path may be reduced by injecting hot and dry gas substantially free from divided material into the drying conduit at an appropriate distance from the inlet end thereotI
  • the drying power of the gas is thus locally enhanced, and the drying operation is therefore more rapid.
  • a method for the pneumatic drying of a divided material in suspension in an ascending stream of drying gas within a substantially vertical chamber consists in injecting into the said chamber and at successive levels along the height of the latter, additional drying gas streams substantially free from divided material, each directed substantially tangentially to a circumference co-axial to the said chamber, the said streams being alternately in one and the other direction about the axis of the chamber.
  • the ascending stream of drying gas with divided material in suspension therein is preferably obtained by injecting drying gas substantially free from divided material into the chamber through a lower non-tangential inlet and gas with divided material in suspension therein through a tangential inlet above the said lower inlet but below the lowermost of said successive levels.
  • the invention further concerns a dryer for the carrying into practice of the said method, this dryer comprising a substantially vertical and substantially cylindrical drying chamber, a central tubular column with closed upper end axially disposed within the said drying chamber, the said column defining an annular space between its periphery and the wall of the said chamber, and the peripheral wall of the said column being provided at successive levels along the height thereof with substantially vertical slots opening substantially tangentiallyto the periphery of the said column, the successive slots being directed alternately in one and the other direction about the axis of the said chamber, means for producing in the said annular space an ascending flow of drying gas with the divided material to be treated in suspension therein, between a lower inlet and an upper outlet of the said space, means for injecting a stream of drying gas substantially free from divided material into the open lower end of the said column, and means for separating the dried material from the gas issuing from the said drying chamber.
  • the means for producing an ascending stream of drying gas with the divided material to be treated in suspension therein preferably comprise a lower nontangential inlet in the said chamber, the said inlet being adapted to receive drying gas substantially free from divided material, and a tangential inlet disposed above the said lower inlet but below the lowermost one of said slots, the said tangential inlet being adapted to receive drying gas with the divided material in suspension therein.
  • FIG. 1 is a view in elevation with parts in section, showing a pneumatic dryer according to the invention.
  • FIGS. 2 to 5 are cross-sections taken along lines Il- -II, III-III, IVIV and V-V of FIG. 1.
  • FIG. 6 is an enlarged fragmental cross-section illustrating a device for the adjustment of the operative cross-sectional area of the tangential slots.
  • FIG. 7 is a fragmental vertical section of a modification concerning the injection of drying air into the lower end of the central column.
  • FIG. 8 illustrates a modified embodiment of a dryer according to the invention.
  • the dryer comprises a vertical cylindrical drying chamber 1 having an upper and a lower frusto-conical ends, respectively 2 and 3.
  • the upper end 2 is connected by a lateral conduit 4 with the tangential inlet of a cyclone separator 5 of any conventional type, while the lower end 3 communicates axially with the outlet or high pressure side of a blower or fan 6 the inlet of which is connected with a conduit or flue 7, the latter receiving hot an dry gas from an appropriate generator.
  • the hot gas conduit or flue is also connected with the inlet of another blower or fan 8 whose outlet or high pressure side is in turn connected with a conduit 9 which opens tangentially into the upper portion of the lower end 3 of the drying chamber 1, as indicated at 9a in FIG. 2.
  • the inlet of blower 8 is provided with an appropriate device 10 through which the divided material to be dried may be introduced into the gas which flows into the blower.
  • This device may be of any conventional description. It may for instance be realized in the form of a hopper associated with an air lock, or of a propelling screw in which the wet material forms a substantially air-tight mass.
  • a central tubular column 11 is axially disposed within the drying chamber 1.
  • the closed conical upper end 11a of this column is connected with the upper end 2 of chamber 1 by means of arms such as 12, while its open lower end terminates within the lower end 3 of the said chamber, short of the frusto-conical wall thereof and at a level situated below the tangential outlet 9a of conduit 9.
  • Column 11 thus defines between its outer periphery and the inner periphery of chamber 1 an annular space which has been referenced A, while its lower end leaves an annular passage between its outer edge and the wall of the lower end 3, a fine grid or wire mesh 13 (see FIG. 2) being disposed in this passage.
  • This central column 11 comprises, starting from its lower end, a first cylindrical section 11b which is formed in its portion situated above the outlet 9a of conduit 9 with a slot opening substantially tangentially to the outer periphery of the column.
  • the peripheral wall of the said upper portion is not perfectly cylindrical, but more or less spiral-shaped.
  • slot 110 opens in the reverse direction with respect to the outlet of conduit 9 (counterclockwise for outlet 9a and clockwise for slot 11c).
  • This cylindrical section 1 1b is followed by a frusto-conical section 1 1d of upwardly decreasing diameter which connects with a second cylindrical section 1 1e of lesser length or height than section 1 1b and of course of smaller diameter.
  • This section He is also formed with a tangentially directed slot 11f (see FIG. 4) but which extends along the'full height of the said section. This slot is directed in the reverse direction with respect to slot 11c, i. e., counterclockwise.
  • Section lle is followed by a second frusto-conical section 11g also of upwardly decreasing diameter, which is in turn followed by a third cylindrical section 11h closed by the upper end 11a above referred to, this third cylindrical section, of smaller diameter than section 1 12, but of greater length or height, also having in its lower portion a tangentially directed slot lli which opens clockwise, i. e., in the reverse direction with respect to slot 11f.
  • the three slots 11c, 11f and 111' have substantially the same width and the same length.
  • Butterfly valves 14 and 15 are provided to act on the flow of hot gas respectively drawn by blowers 6 and 8 from the hot gas flue 7.
  • Another rotary valve 16 is disposed in the lower end ofcolumn 11.
  • an adjustable inlet of cool outer air may be provided, as for instance for reducing the temperature of the gas injected by blower 6 into the lower end of column 11.
  • the successive reductions in the diameter of column 11 are provided for taking into account the fact that the axial flow rate therein (i. e., the quantity of fluid flowing per unit of area through a transverse plane) de creases from its lower end to its upper end while conversely it increases in the annular space A.
  • column 11 instead of being formed of successive cylindrical and frusto-conical sections, column 11 could be regularly frusto-conical along its full height. It should besides be remarked that while this decrease in the diameter of column 11 is convenient in many cases, it could be dispensed with in order to simplify the construction without any major inconvenience.
  • the drying chamber could be somewhat frusto-conical with an upwardly increasing diameter in order to take into account the progressive increase of the flow rate in the annular space A.
  • slots such as 1 1c are adjusted in width by means of an angle iron 19 which is secured against the inner edge of the spiral-shaped cross-section of section 11b by means of rivets or bolts 20.
  • FIG. 7 illustrates another modification in which the annular passage provided between the lower end of column 11 and the frusto-conical wall of bottom 3 is adjustable by means of a sleeve 21 which may be fixed onto the periphery of the column at the height desired.
  • the grid or wire mesh 13 is preferably suppressed, the velocity of the gas through the annular passage being sufficient to prevent the bigger particles from falling therethrough.
  • Still a further modification would consist in injecting into the upper end of column 11 a gas at a temperature different from the temperature of the gas issuing from blower 6. This may be of advantage in the case of materials which, when partially dried, are damaged by temperatures which they support in the wet state.
  • FIG. 8 illustrates an embodiment which is convenient in the case of materials which may support very high temperatures, at least in the wet state.
  • the drying gas at an elevated temperature would have to flow through both blowers 6 and 8 and the latter should then be so constructed as to withstand such temperatures in normal operation, which would lead to a relatively expensive dryer.
  • This is obviated in FIG. 8 by providing a single exhaust fan 22 having its inlet side connected by a conduit 23 with the outlet 17 of the cyclone separator 5.
  • the conduit 9 for the gas and divided material is directly connected with the hot gas flue 7, the material inlet device 10 opening into the said conduit.
  • the bottom 3 of the drying chamber is connected with flue 7 by means of a laterally opening conduit 24 the butterfly valves 14 and 15 being respectively mounted in conduits 24 and 9, as shown. It is obvious that the operation of the dryer remains the same as in the case of the embodiment of FIG. 1, but the single fan 22 only receives relatively cool gas and has not therefore to be constructed for high temperatures.
  • the step of obtaining said ascending stream of drying gas with divided material in suspension therein by injecting nontangentially into said chamber drying gas substantially free from divided material at a lower level situated below said successive levels, and by injecting tangentially into said chamber drying gas with divided material in suspension therein at a level situated between said lower level and said successive levels.
  • a pneumatic dryer for divided material comprismg:
  • a drying chamber having a substantially vertical axis and a given height, said chamber including a lateral wall and being formed with an upper outlet;
  • said column being disposed axially within said drying chamber with said peripheral wall defining an annular space with the lateral wall of said drying chamber, and said column having its peripheral wall formed with a succession of substantially vertical slots opening substantially tangentially to said peripheral wall at successive levels along the height of said chamber, the openings of said successive slots being alternately directed in one and the other direction about the axis of said chamber;
  • said means to produce in said annular space an ascending stream of drying gas with divided material in suspension therein comprising means to tangentially inject a stream of drying gas with divided material in suspension therein into said annular space below said successive slots.
  • a grid disposed in said annular passage to retain biggers particles of said divided material.
  • said column being formed of an alternate succession of cylindrical portions including said slots and of plain frusto-conical connecting portions.
  • said drying chamber having a substantially axial lower inlet situated below the open lower end of said column;
  • said means to injects drying gas substantially free from divided material into the open lower end of said column comprising a first blower having its high pressure side connected with said lower inlet of said drying chamber;
  • said means to tangentially inject into said annular space drying gas with divided material in suspension therein including a second blower independent from said first blower.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Drying Of Solid Materials (AREA)
US00326962A 1972-02-04 1973-01-26 Pneumatic dryers Expired - Lifetime US3789513A (en)

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FR7204761A FR2171667A5 (fi) 1972-02-04 1972-02-04

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CA (1) CA965602A (fi)
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GB (1) GB1391033A (fi)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3938259A (en) * 1973-12-22 1976-02-17 Richter Gedeon Vegyeszeti Gyar Rt Process for continuous drying of chemical products by milling-fluidisation
US4399633A (en) * 1981-04-09 1983-08-23 Interox Chemicals Limited Production of alkali metal or alkaline earth metal peroxides
US4525934A (en) * 1980-12-12 1985-07-02 Werner & Pfleiderer Method and apparatus for drying moisture-laden powder-like products, particularly of starches and flours
EP0153704A2 (en) * 1984-02-24 1985-09-04 Aktieselskabet De Danske Sukkerfabrikker Process and apparatus for removal of liquid from a solid particulate material
US4594793A (en) * 1984-08-16 1986-06-17 The United States Of America As Represented By The United States Department Of Energy Drying of pulverized material with heated condensible vapor
US20010046460A1 (en) * 2000-01-06 2001-11-29 Zhurin Viacheslav V. System for thermal and catalytic cracking of crude oil
US6393721B1 (en) * 1998-04-23 2002-05-28 Articare As Drying apparatus
US20110150744A1 (en) * 2009-12-22 2011-06-23 Flsmidth A/S Method for Drying Potash
RU2476792C1 (ru) * 2011-07-26 2013-02-27 Артем Александрович Селиверстов Пневматическая сушилка
WO2014155214A1 (en) 2013-03-28 2014-10-02 Basf Se Production of pyripyropenes from dry biomass
US8951308B2 (en) 2011-03-17 2015-02-10 Solazyme, Inc. Pyrolysis oil and other combustible compositions from microbial biomass
US20180017325A1 (en) * 2015-01-14 2018-01-18 Schenck Process UK Limited Apparatus for drying conveyed material

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2449257A1 (fr) * 1979-02-14 1980-09-12 Mark Andre Perfectionnements aux sechoirs pneumatiques pour produits divises
FR2517565B1 (fr) * 1981-12-03 1986-07-11 Neu Ets Procede et appareil de traitement de particules solides a l'aide d'un fluide
IT1151577B (it) * 1982-06-03 1986-12-24 Italiana Essiccatoi Procedimento e relativa apparecchiatura per essiccare materiali polverulenti in genere
EP1204836B1 (en) * 1999-08-17 2005-01-05 Unilever N.V. Apparatus for removing a fluid component from particulized solid materials

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2316207A (en) * 1941-04-08 1943-04-13 Atlantic Res Associates Inc Method and apparatus for rapidly drying casein curd and like substances
US2363281A (en) * 1941-04-04 1944-11-21 Gerald D Arnold Apparatus and method for treating pneumatically borne material
FR1280968A (fr) * 1961-02-07 1962-01-08 Dispositif d'accouplement en série de plusieurs fours du type cyclone
US3049343A (en) * 1959-08-25 1962-08-14 Polysius G M B H Fa Apparatus for heating cement powder or similar fine-granular materials
US3319349A (en) * 1964-07-06 1967-05-16 Polysius Gmbh Heat exchange apparatus for carrying out chemical and physical reactions
US3740865A (en) * 1970-02-20 1973-06-26 P Laguilharre Drying installation

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2363281A (en) * 1941-04-04 1944-11-21 Gerald D Arnold Apparatus and method for treating pneumatically borne material
US2316207A (en) * 1941-04-08 1943-04-13 Atlantic Res Associates Inc Method and apparatus for rapidly drying casein curd and like substances
US3049343A (en) * 1959-08-25 1962-08-14 Polysius G M B H Fa Apparatus for heating cement powder or similar fine-granular materials
FR1280968A (fr) * 1961-02-07 1962-01-08 Dispositif d'accouplement en série de plusieurs fours du type cyclone
US3319349A (en) * 1964-07-06 1967-05-16 Polysius Gmbh Heat exchange apparatus for carrying out chemical and physical reactions
US3740865A (en) * 1970-02-20 1973-06-26 P Laguilharre Drying installation

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3938259A (en) * 1973-12-22 1976-02-17 Richter Gedeon Vegyeszeti Gyar Rt Process for continuous drying of chemical products by milling-fluidisation
US4525934A (en) * 1980-12-12 1985-07-02 Werner & Pfleiderer Method and apparatus for drying moisture-laden powder-like products, particularly of starches and flours
US4399633A (en) * 1981-04-09 1983-08-23 Interox Chemicals Limited Production of alkali metal or alkaline earth metal peroxides
AU581644B2 (en) * 1984-02-24 1989-03-02 Nino Holding A/S Process and apparatus for removal of liquid from a solid particulate material
EP0153704A3 (en) * 1984-02-24 1986-08-06 Aktieselskabet De Danske Sukkerfabrikker Process and apparatus for removal of liquid from a solid particulate material
EP0153704A2 (en) * 1984-02-24 1985-09-04 Aktieselskabet De Danske Sukkerfabrikker Process and apparatus for removal of liquid from a solid particulate material
US4594793A (en) * 1984-08-16 1986-06-17 The United States Of America As Represented By The United States Department Of Energy Drying of pulverized material with heated condensible vapor
US6393721B1 (en) * 1998-04-23 2002-05-28 Articare As Drying apparatus
US20010046460A1 (en) * 2000-01-06 2001-11-29 Zhurin Viacheslav V. System for thermal and catalytic cracking of crude oil
US6936230B2 (en) * 2000-01-06 2005-08-30 Viacheslav V. Zhurin System for thermal and catalytic cracking of crude oil
US20110150744A1 (en) * 2009-12-22 2011-06-23 Flsmidth A/S Method for Drying Potash
US8951308B2 (en) 2011-03-17 2015-02-10 Solazyme, Inc. Pyrolysis oil and other combustible compositions from microbial biomass
RU2476792C1 (ru) * 2011-07-26 2013-02-27 Артем Александрович Селиверстов Пневматическая сушилка
WO2014155214A1 (en) 2013-03-28 2014-10-02 Basf Se Production of pyripyropenes from dry biomass
US20180017325A1 (en) * 2015-01-14 2018-01-18 Schenck Process UK Limited Apparatus for drying conveyed material

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Publication number Publication date
GB1391033A (en) 1975-04-16
CA965602A (en) 1975-04-08
FR2171667A5 (fi) 1973-09-21

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