US3792816A - Gas distributors for fluidized beds - Google Patents

Gas distributors for fluidized beds Download PDF

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Publication number
US3792816A
US3792816A US00196578A US3792816DA US3792816A US 3792816 A US3792816 A US 3792816A US 00196578 A US00196578 A US 00196578A US 3792816D A US3792816D A US 3792816DA US 3792816 A US3792816 A US 3792816A
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Prior art keywords
pipe
gas
inner pipe
pipes
hole means
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Expired - Lifetime
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US00196578A
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English (en)
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B Evans
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Broken Hill Proprietary Company Pty Ltd
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Broken Hill Proprietary Company Pty Ltd
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    • 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
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
    • B01J8/1818—Feeding of the fluidising gas

Definitions

  • An object of this invention is to provide a gas distributor for fluidized bed apparatus which operates satisfactorily to fluidize particulate material, while a more specific object is to preventundesirable backflow of bed material which would tend to block the gas distributor.
  • gas includes air or other fluidizing gas, or vapour such as steam or LPG.
  • a gas distributor for fluidized bed apparatus which comprises a pair of pipes disposed one within the other, a space between at least a substantial part of the adjacent surfaces of said pipes, holes in the inner pipe for admitting gas from the inner pipe to said space, and holes in the outer pipe for discharging gas from said space to the fluidized bed.
  • the pipes may be of cylindrical, polygonal or other suitable shape in cross-section, and are preferably cylindrical.
  • Theinner pipe may be disposed concentrically or eccentrically within the outer pipe.
  • holes in this specification includes apertures of circular, polygonal or any other suitable shape.
  • the holes in the outer pipe are preferably arranged to face downwardly, i.e., are positioned in the lowermost onethird of the circumference of the outer pipe and are preferably above the lowermost portion of the said pipe by a circumferential distance not exceeding one-eighth of the circumference of the said pipe.
  • such holes are preferably positioned in the lowermost portion of the said pipe, and desirably are located in the lowermost one-third of its circumference.
  • the holes in-the inner and outer pipes are spaced in a substantially regular pattern along the length of the pipes so that the flow of gas from the holes in the inner pipe to the holes in the outer pipe is substantially uniform along the length of the pipes.
  • the pipes are concentric and there is a single row of regularly spaced holes in the lowermost portion of the inner pipe, and two rows of regularly spaced holes in the outer pipe, one row on one side of the outer pipe and the other row on the other side of the outer pipe, each row being above the lowermost portion of the outer pipe by a circumferential distance equivalent to about one-eighth of the circumference of the outer pipe, there being at each longitudinal position midway between the holes in the inner pipe either a pair of holes or a single hole alternately on one side and then the other of the outer pipe.
  • the invention is not confined to the foregoing arrangements since other workable possibilities exist.
  • backflow into the space between the pipes during non-fluidization periods can be tolerated providing the gas flow during the next fluidization period can sweep material out of the space to an extent sufficient to allow the desired gas discharge through the holes in the outer pipe.
  • the holes in the outer pipe can be arranged to face horizontally or even upwardly providing the gas flow from the holes in the lower portion of the inner pipe is strong enough to adequately clear the space between the pipes.
  • the holes in the inner pipe can be in positions higher than those preferred providing the amount of material that might accumulate inside the lower portion of the pipe does not interfere with satisfactory operation of the distribu- 1201.
  • a combination that should obviously be avoided is one having coincident holes in the uppermost portion of both pipes, which would enable a direct flow of particulate material into the inner pipe, and into the space, during non-fluidization periods.
  • an arrangement in which there are holes in the uppermost portion of the outer pipe is workable providing these holes are not coincident with holes in the inner pipe, and especially if the distance between the adjacent surfaces of the pipes at this location is sufficiently small in relation to the hole size that the backflow of material is arrested by the formation of small heaps supported by the inner pipe.
  • the end holes in the inner pipe are preferably located outwardly of the end holes in the outer pipe, i.e., there is one less longitudinal hole position in the outer pipe than there is in the inner pipe.
  • the inner and outer pipes may be spaced .apart and connected together by means of spacers secured to the inner pipe and arranged at circumferential and longitudinal intervals. Such spacers are not necessary if the pipes are relatively short.
  • the gas distributor preferably comprises a series of double pipes arranged horizontally in parallel relationship and spaced apart by a suitable distance.
  • the pipes forming the gas distributor extend across the area of the fluidizing chamber, e.g., across the lower area or base thereof, and are connected to a source of fluidizing gas under pressure.
  • any particulate material e.g., sand
  • any particulate material flows back into the space between the pipes it is blown back into the bed with the next fluidization cycle. Also any small particles in the gas supply are completely blown through the double pipe diffuser system.
  • the pressure drop of the gas in flowing through the holes in the inner pipe is large compared with the pressure drop along the length of the inner pipe, and the pressure drop of the gas in flowing through the holes in the outer pipe is large compared with the pressure drop of the gas in flowing through the space between the pipes.
  • the fluidizing gas velocities in the inner pipe should be such as to achieve horizontal transport of suspended solids (e.g., sand) that may have back-filled into the pipes.
  • the gas distributor of this invention has the following advantages: I
  • the distributor can be made from pipe of any suitable cross-sectional configuration and from any suitable material depending on the service conditions, particularly temperature.
  • TI-Ie distributor operates satisfactorily up to high temperatures without buckling or warping. Buckling severely limits the operating conditions for existing perforated plate distributors.
  • the distributors are easier to manufacture and install than existing perforated plate or bubble cap type distributors. They can be installed at various levels in a fluidized bed for injecting different fluids; e.g., a lower row of double pipe distributors could supply air or oxygen and an upper row could supply gas for fluidized bed combustion. Alternatively, gases could be injected at various levels for chemical reactions to take place.
  • FIG. 1 is a view in sectional elevation, partly broken away, of a fluidized bed apparatus incorporating a gas distributor according to this invention
  • FIG. 2 is a view in sectional plan taken on the line .,2 -2 of FIG. 1.
  • FIG. 3 is a view in enlarged sectional elevation taken on the line 33 of FIG. 2,
  • FIG. 4 is a view in sectional elevation taken on the line 4-4 of FIG. 3, and
  • FIG. 5 is a viewin sectional elevation, similar to FIG. 4, showing a modified arrangement in which the inner pipe is disposed eccentrically within the-outer pipe.
  • the reference numeral indicates a fluidizing chamber or vessel having vertical side walls 11 and a bottom wall or floor 12.
  • the walls 11 and 12 comprise a refractory lining 11a, 12a and an outer metal casing 11b, 12b.
  • a series of double pipes 14 are arranged in parallel relationship in the lower part of the fluidized bed chamber 10, the said double pipes 14 being horizontal.
  • the double pipes 14, which constitute the distribtuor for the fluidizing gas, may be located at any desired level in the fluidizing chamber 10 and if desired a plurality of gas distributors each comprising a series of double pipes 14 may be arranged at different levels in the fluidizing chamber 10.
  • Each double pipe which is shown in greater detail in FIGS. 3 and 4, is arranged so that one end projects through an aperture in the wall 11 of the chamber 10, and the inner pipe of each double pipe 14 is connected externally of the chamber 10 to a source of fluidizing gas, such as air, under pressure.
  • a source of fluidizing gas such as air
  • each double pipe 14 comprises an inner pipe 15 and an outer pipe 16, the inner pipe 15 being concentrically disposed within the outer pipe 16 in the form of the invention shown in FIGS. 1 to 4.
  • the pipes are held in their relative positions by spacers 17 which are conveniently located at I20 apart and at intervals along the pipes 15, 16 and which are normally secured to the inner pipe 15.
  • each double pipe 14 projects through an aperture 19 in the side wall 11 of the chamber 10 and the outer pipe 16 fits through a sleeve 20 having an outer flange 21 which engages the outer face of the casing 11b.
  • the outer end 22 of the outer pipe 16 is externally threaded and an internally threaded bush 23 is screwed onto the end 22 of the outer pipe 16.
  • An inner flange 24 on the bush 23 is secured to the flange 21 of the sleeve 20 by studs 25.
  • a plug 26 is fitted over and welded to the projecting outer end of the inner pipe 15 and is screwed into the outer end of the bush 23, A flange 27 on the plug 26 abuts against the outer endof the bush 23.
  • the inner ends of the pipes 15 and 16 within the chamber 10 are closed by plates 28b and 280 respectively.
  • the outer ends of the inner pipes 15 are connected to a source (not shown) of fluidizing gas under pressure.
  • Each inner pipe 15 is provided with a series of gas apertures 30 which are directed downwardly and are conveniently located along the lowermost edge of the pipe 15 at spaced intervals therealong.
  • Each outer pipe 16 is provided with a series of gas Outlet apertures 31, 32 which may be at any point on the periphery of the pipe 16 and are preferably arranged in pairs located at points spaced by about oneeighth of the circumference of the pipe 16 above the lowermost edge of said pipe, as shown in FIG. 4.
  • the apertures 31, 32 in the pipe 16 are offset or staggered both circumferentially and longitudinally relative to the apertures 30 in the pipe 15.
  • the apertures 30, 31, 32 may be of any suitable configuration and are preferably circular.
  • fluidizing gas under pressure is supplied to the outer ends of the innerpipes 15 and is caused to flow through the apertures 30 in each inner pipe into the annular space 33 between each inner pipe 15 and its outer pipe 16.
  • the fluidizing gas then flows through said annular space 33 to the apertures 31, 32 in the outer pipe 16 and then outwardly through the apertures 31, 32 into the fluidization chamber 10 where it is distributed into and maintains the fluidized 'bed (not shown).
  • the inner pipe 15 is arranged eccentrically within the outer pipe 16 and the said pipes 15, 16 are in contact at their uppermost points, the maximum distance between the said pipes being at their lowermost points.
  • the apertures 30 in the pipe 15 and the apertures 31, 32 in the pipe 16 are located similarly to the corresponding apertures in the double pipe arrangement shown in FIG. 4.
  • the flow of gas through the apertures 31, 32 along the pipes 16 should be substantially equal, and this may be achieved by ensuring that the pressure drops across the gas distributor are maintained as previously specified.
  • any backflow of the particulate fluidizing medium such as sand
  • any of such medium which may back-flow into the outer pipes 16, when the flow of gas is interrupted, is effectively removed therefrom when the gas supply is re-applied.
  • Gas distributors for fluidizing a given bed using a given gas may be designed by the following procedure, which makes use of known technology:
  • the required fluidizing gas flow rate in m /h per 1m of bed is determined experimentally or by calculation;
  • the inside diameter of the inner pipe in mm is de termined from the formula 11.8 X flow rate, which assures a gas velocity of 30 m/s, this velocity being sufficient to entrain and thus discharge particulate material such as sand from the inner pipe;
  • an available pipe size having as near as possible the calculated inside diameter is selected, the material of the pipe and wall thickness being selected having regard to service conditions; e. an outer pipe is selected with an inside diameter that gives sufficient clearance for easy assembly and disassembly, even if the pipes should have warped as a result of high temperature service.
  • an outer pipe is selected with an inside diameter that gives sufficient clearance for easy assembly and disassembly, even if the pipes should have warped as a result of high temperature service.
  • a suitable pitch for the holes is selected and whether a pair of holes or only one hole is to be used in the outer pipe at each longitudinal position is decided; from (b) and (f), the gas flow rate per hole is determined;
  • the pressure drop across the holes in the outer pipe is determined using equation 34, page 87, Fluidization Engineering, published by John Wiley (Sons, 1969.
  • the pressure drop across the holes in the inner pipe is usually selected to be about threequarters of the pressure drop across the holes in the outer pipe;
  • the hole sizes in the pipes is calculated using equations 34 to 37, pages 87 to 89 of the above reference, or equation 98, page 129, North American Combustion Handbook, first edit-ion.
  • the calculated holes sizes in the inner and outer pipes may be so nearly equal that in practice the same size holes are used in both pipes.
  • the holes in the inner pipe were regularly spaced along the length of the lowermost portion of the said pipe.
  • the holes in the outer pipe were located longitudinally midway between the holes in the inner pipe and circumferentially one-eighth part of the circumference above the lowermost portion of the outer pipe, there being one hole at each longitudinal position, the said holes being placed alternately on one side and then on the other side of the lowermost portion of the outer pipe.
  • the holes in both pipes were of the same diameter.
  • EXAMPLE 1 Dimensions of fluidization chamber 1m X 0.6m X 2m high Fluid bed Sand, 0.7m deep, bulk density 1400 kg/m", i.e. 600 kg of sand in bed. Temperature 850C Fluidizing gas Air, supplied through six stainless steel distributors at base of bed at a rate of 340 mlh Fuel gas burnt in the 14 m"'/h of LPG supplied through fluidized bed one stainless steel distributor located above the air distributors Air distributors Inner pipe 28 mm ID X 32 mm 0 with 36 holes, 4 mm dia at 25 mm pitch Outer pipe 38 mm ID X 42 mm 0D, with 35 holes, 4 mm dia at 25 mm pitch EXAMPLE 2 Fluid bed 3m X 1m 1m deep, having an incipient fluidization velocity of m/h per lm of bed Temperature Ambient Fluidizing gas Air supplied through 24 mild steel distributors at base of bed parallel to the 1m side of chamber at a rate four-times the incipient fluidization
  • Gas distributor means for use in a fluidizing vessel to fluidize particles contained in said vessel to permit operation with, if desired, intermittent fluidization, with substantial elimination of natural backflow of fluidized particles, said means comprising a pair of horizontal pipes disposed within one another and having a space between the inner pipe and the outer pipe, means for admitting fluidizing gas to the inner pipe, hole means in the inner pipe for admitting fluidizing gas from the inner pipe to the said space, hole means in the outer pipe for discharging fluidizing gas from the said space, the hole means in the outer pipe being located in the lowermost one-third ofthe circumference of said pipe and being staggered in a circumferential and/or longitudinal direction relative to the hole means in the inner pipe.
  • Gas distributor means according to claim 1 wherein the hole means in the pipes are spaced in a substantially regular pattern along the length of the pipes, and are arranged symmetrically along the length of the pipes.
  • Gas distributor means according to claim 1 wherein the pressure drop of the gas in flowing through the hole means in the inner pipe is large compared with the pressure drop along the length ofthe inner pipe, and the pressure drop of the gas in flowing through the hole means in the outer pipe is large compared with the pressure drop of the gas in flowing through the space between the pipes, so that the flow of gas through the hole means in the outer pipe is substantially uniform along its length.
  • a fluidized bed apparatus comprising a fluidizing vessel and means for distributing a fluidizing gas in said fluidizing vessel, the improvement comprising using, as said means for distributing said gas, a plurality of pairs of horizontal pipes disposed within one another and having a space between the inner pipe and the outer pipe, means for admitting fluidizing gas to the inner pipe, first hole means in the inner pipe for admitting fluidizing gas from the inner pipe to said space, second hole means in the outer pipe for discharging fluidizing gas from said space to the fluidized bed, said second hole means being located in the lowermost one third of the circumference of said outer pipe and being staggered in a circumferential and/or longitudinal direction relative to said first hole means, whereby said fluidized bed may be operated, with, if desired, intermittant fluidization, with substantial elimination of natural backflow of fluidized particles.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
  • Fluidized-Bed Combustion And Resonant Combustion (AREA)
  • Separation Of Gases By Adsorption (AREA)
  • Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
US00196578A 1970-11-10 1971-11-08 Gas distributors for fluidized beds Expired - Lifetime US3792816A (en)

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AU315270 1970-11-10

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US3792816A true US3792816A (en) 1974-02-19

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US (1) US3792816A (en:Method)
JP (1) JPS523336B1 (en:Method)
BE (1) BE775088A (en:Method)
CA (1) CA962434A (en:Method)
CS (1) CS166789B2 (en:Method)
FR (1) FR2113737A5 (en:Method)
GB (1) GB1341617A (en:Method)
ZA (1) ZA717286B (en:Method)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4606896A (en) * 1984-02-07 1986-08-19 Charbonnages De France Apparatus for supplying a controlled flow of gas to a fluidized grid
US6247631B1 (en) * 1999-01-18 2001-06-19 Hakko Corporation Electric soldering iron
US20140061338A1 (en) * 2010-10-14 2014-03-06 Samsung Display Co., Ltd. Gas injection device and solar cell manufacturing method using the same

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1596452A (en) * 1924-11-13 1926-08-17 Ironton Stove & Mfg Co Gas burner
US1729149A (en) * 1923-07-23 1929-09-24 Gen Electric Gas burner
US3347473A (en) * 1965-06-07 1967-10-17 Gen Motors Corp Fluid manifold
US3531053A (en) * 1969-10-09 1970-09-29 Westvaco Corp Steam distribution system
US3599877A (en) * 1969-07-02 1971-08-17 Burroughs Corp Nozzle arrangement for forming fluid wave

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1729149A (en) * 1923-07-23 1929-09-24 Gen Electric Gas burner
US1596452A (en) * 1924-11-13 1926-08-17 Ironton Stove & Mfg Co Gas burner
US3347473A (en) * 1965-06-07 1967-10-17 Gen Motors Corp Fluid manifold
US3599877A (en) * 1969-07-02 1971-08-17 Burroughs Corp Nozzle arrangement for forming fluid wave
US3531053A (en) * 1969-10-09 1970-09-29 Westvaco Corp Steam distribution system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4606896A (en) * 1984-02-07 1986-08-19 Charbonnages De France Apparatus for supplying a controlled flow of gas to a fluidized grid
US6247631B1 (en) * 1999-01-18 2001-06-19 Hakko Corporation Electric soldering iron
US20140061338A1 (en) * 2010-10-14 2014-03-06 Samsung Display Co., Ltd. Gas injection device and solar cell manufacturing method using the same

Also Published As

Publication number Publication date
ZA717286B (en) 1972-08-30
GB1341617A (en) 1973-12-25
JPS523336B1 (en:Method) 1977-01-27
FR2113737A5 (en:Method) 1972-06-23
BE775088A (fr) 1972-03-01
DE2155898A1 (de) 1972-05-18
CA962434A (en) 1975-02-11
CS166789B2 (en:Method) 1976-03-29
DE2155898B2 (de) 1977-06-08

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