CA2026170A1 - Gas distributor and heater for spray drying - Google Patents
Gas distributor and heater for spray dryingInfo
- Publication number
- CA2026170A1 CA2026170A1 CA002026170A CA2026170A CA2026170A1 CA 2026170 A1 CA2026170 A1 CA 2026170A1 CA 002026170 A CA002026170 A CA 002026170A CA 2026170 A CA2026170 A CA 2026170A CA 2026170 A1 CA2026170 A1 CA 2026170A1
- Authority
- CA
- Canada
- Prior art keywords
- gas
- flow
- annular
- outlet
- guide duct
- 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.)
- Abandoned
Links
- 238000001694 spray drying Methods 0.000 title description 32
- 239000007789 gas Substances 0.000 claims abstract description 301
- 238000001035 drying Methods 0.000 claims abstract description 72
- 239000007921 spray Substances 0.000 claims abstract description 54
- 238000010438 heat treatment Methods 0.000 claims abstract description 42
- 238000002485 combustion reaction Methods 0.000 claims abstract description 20
- 239000007788 liquid Substances 0.000 claims abstract description 15
- 239000012527 feed solution Substances 0.000 claims description 14
- 239000002245 particle Substances 0.000 claims description 7
- 241000538562 Banjos Species 0.000 claims description 5
- 238000011144 upstream manufacturing Methods 0.000 claims description 3
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 239000000843 powder Substances 0.000 claims description 2
- 238000012545 processing Methods 0.000 abstract description 17
- 238000012546 transfer Methods 0.000 abstract description 2
- 239000003570 air Substances 0.000 description 22
- 239000000463 material Substances 0.000 description 20
- 229910052751 metal Inorganic materials 0.000 description 10
- 239000002184 metal Substances 0.000 description 10
- 238000000034 method Methods 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 230000008901 benefit Effects 0.000 description 5
- 238000005507 spraying Methods 0.000 description 5
- 239000002440 industrial waste Substances 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 239000011236 particulate material Substances 0.000 description 4
- 239000011819 refractory material Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 230000007704 transition Effects 0.000 description 4
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 239000012080 ambient air Substances 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 239000000295 fuel oil Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000013022 venting Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 239000005995 Aluminium silicate Substances 0.000 description 1
- 102100025840 Coiled-coil domain-containing protein 86 Human genes 0.000 description 1
- 101000932708 Homo sapiens Coiled-coil domain-containing protein 86 Proteins 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 235000012211 aluminium silicate Nutrition 0.000 description 1
- 238000000889 atomisation Methods 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- GPUADMRJQVPIAS-QCVDVZFFSA-M cerivastatin sodium Chemical compound [Na+].COCC1=C(C(C)C)N=C(C(C)C)C(\C=C\[C@@H](O)C[C@@H](O)CC([O-])=O)=C1C1=CC=C(F)C=C1 GPUADMRJQVPIAS-QCVDVZFFSA-M 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 229910052570 clay Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000002274 desiccant Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- XGFJCRNRWOXGQM-UHFFFAOYSA-N hot-2 Chemical compound CCSC1=CC(OC)=C(CCNO)C=C1OC XGFJCRNRWOXGQM-UHFFFAOYSA-N 0.000 description 1
- LELOWRISYMNNSU-UHFFFAOYSA-N hydrogen cyanide Chemical class N#C LELOWRISYMNNSU-UHFFFAOYSA-N 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910000358 iron sulfate Inorganic materials 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910001629 magnesium chloride Inorganic materials 0.000 description 1
- 239000008267 milk Substances 0.000 description 1
- 210000004080 milk Anatomy 0.000 description 1
- 235000013336 milk Nutrition 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000002674 ointment Substances 0.000 description 1
- HCTVWSOKIJULET-LQDWTQKMSA-M phenoxymethylpenicillin potassium Chemical compound [K+].N([C@H]1[C@H]2SC([C@@H](N2C1=O)C([O-])=O)(C)C)C(=O)COC1=CC=CC=C1 HCTVWSOKIJULET-LQDWTQKMSA-M 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/16—Evaporating by spraying
- B01D1/18—Evaporating by spraying to obtain dry solids
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B3/00—Drying solid materials or objects by processes involving the application of heat
- F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
- F26B3/10—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour carrying the materials or objects to be dried with it
- F26B3/12—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour carrying the materials or objects to be dried with it in the form of a spray, i.e. sprayed or dispersed emulsions or suspensions
Landscapes
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Microbiology (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Drying Of Solid Materials (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A gas distributor and heating device for a spray dryer which includes a feed liquid atomizer in a drying chamber, a gas distributor for supplying a uniform flow of gas, a guide duct for conveying the flow of gas from the gas distributor and to an outlet providing a flow of processing or drying gas to contact liquid droplets dispersed by the atomizer. A gas heater is located in the device between the gas distributor and the guide duct outlet to heat the gas just prior to its introduction into the spray chamber.
This provides a high temperature drying gas close to the atomizer and avoids problems encountered in attempting to transfer a gas that has been heated at a location remote from the spray chamber.
A guide duct in the form of an annular guide duct provides an annular flow of heated gas concentric with the atomizer. A gas burner extends circumferentially around the interior of the guide duct and is disposed to emit the gases of combustion in the direction of the outlet. The guide duct may also include a plate shielding a portion of the gas flow from direct contact with the burner and the gases of combustion to provide an insulating flow of gas between the annular duct and the combustion zone.
A gas distributor and heating device for a spray dryer which includes a feed liquid atomizer in a drying chamber, a gas distributor for supplying a uniform flow of gas, a guide duct for conveying the flow of gas from the gas distributor and to an outlet providing a flow of processing or drying gas to contact liquid droplets dispersed by the atomizer. A gas heater is located in the device between the gas distributor and the guide duct outlet to heat the gas just prior to its introduction into the spray chamber.
This provides a high temperature drying gas close to the atomizer and avoids problems encountered in attempting to transfer a gas that has been heated at a location remote from the spray chamber.
A guide duct in the form of an annular guide duct provides an annular flow of heated gas concentric with the atomizer. A gas burner extends circumferentially around the interior of the guide duct and is disposed to emit the gases of combustion in the direction of the outlet. The guide duct may also include a plate shielding a portion of the gas flow from direct contact with the burner and the gases of combustion to provide an insulating flow of gas between the annular duct and the combustion zone.
Description
~02~.~7V
TITL;53 GAS DISTRIBUTOR ~ND HEATER FOR SPRAY DRYING
The present invention is directed to an improved gas distributor and heating devicP for a spray drying apparatus for drying of a feed solution and, more specifically, to an improved air distributor and heating device for directing a concentric flow ' of drying gas to ~ff~K~-o~ a drying space in a drying chamber .~2, ~ having an atomizing device.
Backqround of the Invention Spray drying is the transformation of a feed material from a flu~d state into a dried particulate ~orm by ~praying the feed material into a hot drying medium. It is a one-step, continuous particle-processing operation involving drying. ~ackground information relative to the field in which this invention finds application is provided in Spray Drying Handbook, third edition, K. Masters (John Wiley and Sons, New York~.
The invention is applicable to spray drying, spray evaporation and spray reaction operations and processes which usually involv~
the introduction of a liquid ~eed material in the form o~ a 20 solution or a suspension to an atomizing device which sprays small particles of the liquid feed material into a drying chamber where the droplets are dried or reacted and the resulting desired particulate material is collected and removed in the form of a powder. A rotary atomizing wheel which provides a continuous spray Z5 of the liquid droplets is often used at the to~ of a tower-type drying chamber. In addition ~o the droplets of liquid feed material, a processing gas in the form o~ a temperature controlled gaseous medium is al50 introduced to the to~er-~ype drying chamber 1 7 ~
to evaporate the moistur~ ~rom the liquld droplets and thu~ provide the desired particulate material.
Drylng ~hamhers of this type utilizing a rotary atomizer wheel and heated air introduced at the top of a drying chamber have been widely used to dry consumable food products, such as milk, to produce chemical products such as kaolin clay, titanium dioxide and calcium carbonate, and for processing wast~ effluents. Such processes are critically dependent ~pon the particle size of the material being dried, the temperature of the drying medium and the timely effective contact of each particle with the drying medium.
Rotary atomizer wheels or spray nozzles are generally used ~or spraying the feed material into the hot gas medium.
Various types of heating devices have been utilized to provide the hot gaseous medium. Gas heaters of the direct and indirect type have been utilized as well as steam, fuel oil, heat transfer fluids and electricity. Selection of a heat source Eor a partiaular process depend~ upon the product beiny ~pray dried a~
well a the availability, suitablllty and cost o~ the energy required in order to heat the gaseous medium. Open oil an~ gas ~ired burners may b~ utilized where products can withstand the h~gh temperature generated by such heat sources as well as contact with the resulting products of combustion. Indirect heaters utilizing eleotrical heating elements, gas or fuel oil burners may also be utilized to provide a hot gaseous medium when it is necessary to protect the product being sprayed from contact with products of combustion.
The processing or drying gas medium is delivered from a source to a gas distributor or distribution means from which it is 2~2~:17(~
supplied to the interior o~ the spray dryir)g chamber. The ga~ ls typiaally heated while moving through the deli~ery system by means of a burner or other heat source located in the gas delivery system before the gas is delivered to the gas distributor. The heated gas ls then conveyed through insulated ducts to the gas distributor for introduction into the dryiny chamber and subsequent admixture with the feed spray.
A typical process and apparatus ~or provlding a hot drying ga~
around an atomizing device in a spray drying chamber i6 disclosed S~ '5~ Y'l 10 ~ 'in Patent Nos. ~,621,902 and 4,227,896. In those processes, the gaseous medium is heated by means o~ a device located in the ga~
delivery system remote ~rom the spray drying chamber. Patent No.
4,227,896 also discloses an e~ficient gas distributor having a sp~ral supply duct and a plurality o~ vanes which provide a gas flow of substantially constant velocity through a conical guide duct.
Patent No. 3,499,476 di~closes a proces~ ~or the production of par~iculate solids from a solution or suspen~ion by nozzle spraying the feed material through a 1ame zone provided by an annular burner at the top oP a spray towsr. In this process, the ga~eous products o~ ¢om~ustlon are in~roduced directly into the drying chamber with the liquid particles of feed material.
United Kingdom Patent Specification ~o. 1,191,032 discloses apparatus providiny a preliminary drying zone wherein feed material is sprayed through a nozzle surrounded by a burner and the gases of combustion intermingle with the liquid particles of feed material. A secondary drying agent is delivered around the spray nozzle and gas burner.
2~2~7~
Still another spray drylng apparatus ut~liz~ny an air heater provlded in a chamber located directly above a spray drying chamber ls disclosed ~n Patent No. 4,187,617. In that apparatus air i5 delivered by means of a fan through a transition duct to a distribution chamber located above the spray drying chamber. ~n air heater and a profile plata are provided in the distribution chamber together with a perforated diffuser. Cold air i~ delivered past the profile plate and heater to ensure that the air is uniformly heated and then received through the perforations in the diffuser and ducted to the spray drying chamber. The object of that apparatus is to ensure uniform heating of the air being introduced to the distribution chamber and both uniform temperature and ~low of the heated air into the spray drying chamber.
Gonventional systems of producing hot processing Dr drying gas using either direct or indirect heating means in the form of a furnace or combustion device and then ducting or delivering the hot gas from the heating area into the drying chamber by conventional air distributors are known in the art. Such conventional system~
are suited f or spray drying procesges reqlllriny dryiny ga~
temperatures which are not in exce~s of abou~ 550'C. ~lowever, such conventional systems ar~ seldom used in spray drying operations requiring drying gas temperatures near or in exaess of lOOO-C since conventional systems would re~uire the generation of substantial ; thermal energy remote from the point of use and extensive use of refractory materials in the delivery system hetween the heat source and a gas distributor adjacent the spray drying chamber.
One object of the present invention is to provide a gas heater and alr distributor for high temperature spray dryin~ systems which reguires mlnimum refractory lining of the heating chamber and hot 2~2~i7~
gas ductlng or c~veying surface~. This ob~ect is achieved by ~t~ of , providing the heat source directly ~4~ the point o~ use in the spray drying chamber thus permitting delivery of a cold gas by conventional conduits to a gas distributor adjacent a spray chamber ; and then heating the gas supplied from the gas distributor as it is conveyed to the spray chamber. The high tempsrature, hot drying gas is conveyed directly into the drying chamber which minimizes the refractory material required since the high temperature drying gas is exhausted directly from the area where the gas i~ heated into the drying chamber. ~ G~
The present invention is dis inctly different ~rom the apparatus disclosed in Patent No. 3,499,476 and United Kingdom Specification No. 1,191,032 since the heat source and the flame of the present invention do not directly contact the liquid particles of feed material in the drying chamber and the particulate material will not be adversely effected by the products of co~bustion.
The spray drying apparatus of the present invention i~ al~o ~ ' Cl G~
d~fferent ~rom the apparatus disclosed by Patent No. 4, l~7, 617?~
since the ga5 di~user ox distributor in that apparatus ie provided ~ J`
between the a~r heater and the spray nozzle. 'rhe apparatu~ of tha~ I
patent would also be limited to spray drying processes utilizing / `
drying gas heated to only a moderately hlgh gas temperature on the order of 550'C because of the diffuser and wire screens downstream of the air heater.
As will be more ~ully described here below, the apparatus of the present invention is particularly suit~d for use in high temperature spray drying of materlals such as iron oxi~e pi~ments, magnesium chloride, and titanium oxide, or industrial waste ef~luents such as an acid solution of iron sulfate and magnesium `` ~02Sl~
sulfate wherein drying gas or ho~ air having a temperature in the range of lO~O'C or more is required.
Thus, one objeck of this inventlon is to provide a gas distributor, gas heater and atomizer for a high temperature drying system.
A further object of this invention i5 to provide a spray drying apparatus having a drying yas delivery system wherein the maxlmum amount of gas distribution is accomplished before the gas is heated to the desired temperature, the gas is then heated and conveyed directly to the spraying chamber.
A still further object i5 to provide a ga~ heater for receiving gas fxom a cold gas distributor and haviny an outlet exiting in the Yicinity of the liquid droplet~ being discharged from an atomizer device~
15A further object is to provide a hot processing or drying gas with its maximum temperature attained adjacent an atomiæiny device.
A ~till further object is to provide a gas heater ~or high temperature drying systems comprising a circularly di~po~d cold ; air dlstributor circumscribing and venting pa~t a circum~erential array of ya~ burner~ located in a circular passageway exiting ln ~he vicinity o~ an atomizer device.
Su~mar~ of the Invention A gas distributor and heating deYiae for a spray dryer of the type including a feed liquid atomizer at the top of a drying ~ 25 chambsr which includes a gas distributor for supplying a flow of gas having a substantially uni~orm velocity, a guide duct for conveying the flow of gas ~rom the gas distributor and having an outlet providing a flow of gas concentric with the atomizer, and 7 ~
a ga~ heater located in the device between the gas di~tribu~or and the outlet.
The guide duct for conveying the flow of gas from the gas distributor is preferably provided in the form of an annular guide duct defined by two spaced surfaces and the outlet provid~s an annular ~low of heated gas concentrio with a llguid atomizer. Thr spaced surfaces may be two radially spaced cylindrical surfaces or conical surfaces and, in the case o~ an annular guide duct de~ined by two spaced conical ~urfaces, the outlet directs an annular flow L0 of heated gas converging toward ~ centerline of the guide duct.
0~?, ~'1 ~ b ;n a ~`~ th~ ~o The spaced conical surfaces may be convergen~ or div ~ to control the vQlocity of the gas at the outlet of the guide duct.
'~ Spaced surfaces comprising a cylindrical surface and a conical surface may also be utilized.
15In the pre~erred embodimentg, the gas heater is one or a plurality of gas burners provided internally of an annular guide duct and extending circumferentially around the interior o the yuide duct.
In the pre~erred embodiment, the gas burner i6 disposed to emit the gases o~ combustion in the directioll of the outlet of the annular guide duct and may further include a plate or pla en - shielding a portion of the gas flow conveyed from the gas distributor from direct contact with the burner and the gases of combustion and thereby providing an insulating flow of gas between at least one side of the annular duct and the temperature of the burner and the gases of combustion.
. In certa~n applications of the invention, it is also preferred that the gas burner ls disposed to emit a flame in the dir~ction o~ the outlet and the gas burner is located a greater distance from 202~ 7~
the outlet than a length of the flame emitted by the burner B0 as f V~
to ~nsure that the gases of combustlon forming ~he flame are completely burned internally of the annular ~uide duc~.
c~ In a preferred embodiment of the invention, the gas ; distributor is provided in the form of a horizontal spiral supply duct of constantly decreasing cross section and having a plurality of vanes for uniformly distributing an annular supply of pressurized gas from the supply duct to the guide duct for conveying the flow of gas.
LO In an alternate embodiment of the invention, the gas distributor is provided in the form of a banjo shaped chamber having a circular portion and an arm extending radially relative to the circular portion and providing a supply inlet. The circular portion includes an annular outlet for supplying an annular flow of gas to the guide duct and at least one continuous circular perforated plate spaced between an interior zurface of the circular portion and the annular outlet for distributing a uniform flow of gas from the supply inlet to the annular outlet.
In certain embodlments of the invention, a plurality o~ vanes are al50 provided lnternally o~ the guide duct to direat the flow of gas in a desired direction.
The ga~s distributor and heating device of the present invention may be utilized with atomizer wheels or ~pray nozzles.
When used with an atomizer wheel, it is preferred that the guide duct provide an annular flow of heated ~as concentric with the atomizer wheel. In applications using spray nozzl~s, it is preferred that a plurality of spray nozzles be arrayed at the top of a spray chamber and the guide duct provide a flow of heated gas ~ubstantially centered with the top of the spray chamber and ~` 2~12~;~70 concentric with the ~urrounding array of ~pray nozzles. ~he yas distrlbutor and heating devicP may also be used with spray nozzles sprayinq from below in a fountain configuration.
The present invention and the advantages provided thereby will be more fully understood with reference to the following detailed description of the preferred embodiment taking in con~unction wlth the accompanying drawings.
~rief Description of the Drawinqs Fig. 1 is an elevation view~ partly broken away, showing a spray drying plant utilizing one embodiment of the present invention:
Fig. 2 is an enlarged sectional view showing the structure of a gas distributor and heating device of Fig. l;
Fig. 3 iB a plan view showing the interior of the gas distributor of Fig. 2;
Fig. 4 is a view slmilar to Fig. 2 showiny an alternate gulde duct for heating and conveying gas supplied by a gas dlstributor as shown by Figs. l and 3;
Flg. 5 i5 a plan vlew similar ko Fiq. 3 ~howing an alternate gas distributor and heating device;
Fig. 6 is a sectional view taken along line VI-VI of Fig. 5;
Fig. 7 is a plan view similar to Fig. 5 and showing a modification of the structure shown by ~ig. S; and Fiy. 8 is a partial elevation view of an alternate embodiment of the spray drying apparatus of the presen~ invention.
2~17~
~es~ tion~ h~_Prefe~.r~L~nbod~h~nt With reference to the drawiny~ wherein like re~erence numerals designate the same or like parts throughout, there is shown in Fig.
1 a spray drying plant designated by the reference numeral 10 which is particularly adapted for high temperature drying of an industrial waste effluent such a~ an aoid ~olution derived a~ a wa~te product of a metal treating facility. The plant 10 is se~eral stories high and i~cludes a spray or drying chamber 12 and a penthouse 14 supported by means of a superstructure 11. The penthouse 14 provides an enclosure and work area for servicing a gas dlstributor 20 and rotary atomizing wheel 30 provided adjacent a roof or top closure 15 of the spray drying chamber 12. The spray drying chamber 12 has a cylindrical outer wall which is substantially closed at the top by the closure 15 and by a funnel or conical-shaped lower portion 18~ An opening 16 is provided in the top closure 15 and a valve 19 is provided at the bottom of the lower portion 18 to permit removal of the particulate materials dried in the spray chamber 12. The spray ahamber 12, opening 16 and the funnel-shaped lower portion 18 are ~ub~tantially 6yrnmetrioal about a vertiaal axi~.
A gas distributor 20, as best shown by Fig. 2, is mounted ln the penthouse 14 with a conical-shaped guide duct 40 dependlng to a position substantially aligned with the top closure 15 and centered in the opening 16. The rotary atomi~er wheel 39 is rotatably mounted in a housing 31 supported internally of the gas distributor ~0 to project into the top o the s~ray drying chamber 12.
Although the rotary atomizer wheel 30 is provided at the top of the spray dxying chambsr 12 ln Fig. 1, the atomiæer devic~ may -~- 2~2~7~
be one or mora 6pray noz.zle~ located at ~he top o~ th~ spray drylng chamber or elsewher~ in the spray drying chamber an~ spraying in the direction of the gas distributor 20.
A pressurixed source of cold gas usually in the form of ambient air is provided to the gas distributor by me~ns of a fan 2 and inlet or delivery duct 4 connected to the gas distributor 20. An outlet or exhaust port provided in the funnel shaped lower portion 12 at one side of the plant is connected by means of an exhaust duct or pipe 17 to a fines separator 6 which ~ay be in the form of a cyclon~ separator. The fine particles are retained in the separator 6 where they may be periodically withdrawn and the gas is exhausted through a conduit 7 to an exhaust fan 8 where the gas may be exhausted to atmosphere or recycled by duct work to the ~an 2. The fan 2 and inlet duct 4 comprise a delivery system for delivering cold processing gas to the gas distributor 20. The outlet duct 17, separator 6, exhaust duct 7 and exhaust fan 8 comprise means for withdrawing the processing gas from the spray chamber 12.
The gas distributor 20 is of the type disalo~ed in Patent No.
4,227,896 and includes an inlet 21 opening to a splral ~upply duct 22 which i~ internally opened to an annular transitlon zone 23.
The transition zone 23 includes two succeeding sets of stationary guide vanes 25 and 26. The vanes 25 are shaped to deflect the flow of gas from a purely tangential flow a~ indicated by the ~rrow6 adjacent the inlet 21 to a flow direction as shown hy the arrows ~7 in whlch the radial velocity component toward a center axis of the gas distributor 20 excseds the tangential velocity component and the vanes 26 o~ the other set project into a space between the vanes 25 and extend substantially parallel to the direction which ~ 2V2~ I V
the gas flow has been deflected by the adjacellt vane 25. The vanes 25 and 26 in the annular transltion zone change the direct~on of flow of the gas supplied to thP gas distributor 20 and direct the gas to a mouth 42 of an annular gulde duct 40 while the vanes 26 also minimize turbulance in the flow. As best shown by Flgs. 2 and 3, the internal dimensions or volume of the spiral duct 22 constantly decreases in the direction of gas flow from the inlet 21 around the annular transition zone so as to supply a substantially constant volume and velocity of gas moving from the spiral duct through the annular transition zone 23 to the mouth 42 of the annular guide duct 40.
The annular guide duct 40, as best shown by Fig. 2, is' comprised o~ a hollow conical shaped insulating member 41 whi~h may also provide support for the atomizer wheel drive housing 31. A
conical shaped plate 24 i5 radially spaced ~rom the insulating member 41 and the annular guide duct 40 is provided in the conically shaped radial space between the ~nsulating member 41 and the plake 2~.
A rlng ~haped or annular gas burner 50 is also provid~d internally o~ the annlllar guide duat 40 be-tween the insulating member 41 and plate 24. As shown by Fig. 2, the gas burner 50 is disposed to emit the gases of combustion or direct the flame in the direction o~ the outlet 44 of the annular guide duct 40.
In the pre~erred embodiment, an annular plate 46 or series of plate~ are provided around the interior of the annular guide duct 40 between the gas burner 50 and the outer metal plate 24 to deflect a portion of the gas supplied by the gas distributor around the burner 50 and serve as a heat shield between the burner and the outer plate 24. The plate 46 may be attached at 48 to the outer ~ 2~2~7~
~onical plate 2~ and shields ~ portion of the ga~ ~lowlny fr~m tha gas distributor from direct contact with the burner and the ~lame or gases of combustion emitted by the burner. The plate 46 thus provides an insulating flow of cold gas between the metal plate 24 providing one side of the annular guide duct 40 and the temperature o~ the burner and the gases of combustion.
The feature of cooling one or both of the walls of ths annular guide duct by means of an insulating flow of cold gas is an important feature particularly in extremely high temperature drying applications o~ the present invention. For example, in a process ~or spray drying industrial waste e~fluents, it may be desirable to convey gas heated to a temperature in the range of about 700-to 1200-C in order to dry the des~red material. The temperature of a flame issuing from a burner such as the burner 50 shown by Fig. 2 may be as high as 2,00UC. Such high temperatures ~ignif~cantly limit the choice o~ materials which may be utilized in a ~tructure adjacent such a high temperature flame. Although a number of ceramic and re~ractory materials are aapable o~
withs~nding ~uch high temperatures, some o~ the material~ are not capable of providiny long term service in such a high temperature en~ironment and such materials are both heavy and dl~Picult to work with and the most temperature resistent materials are relatively expensive. Thus, although ceramic and refractory materials may be used for flame and high temperature resistance, it is of course desirable to have other devices and arrangements whereby more conventional high temperature steel plates may be suitably ~ormed and used in such environments. This i~ signi~icant since most high temperature steel and other metal plate materials cannot withstand temperature~ greater than about 550~C, and there~ore sp~cial . , ~ .
~ 2 ~ 7 ~
arrangements or ~evice3 must be prov~d~d if one wishes to obtain the low cost and fabrication advantages offered by ~uch materlals.
The heat shield guide plates or deflector plates 46 which provide an insulating flow of cool gas between the burner 50 and the ou~er conical plate 24 of the annular duct 40 provide such an advantageous arrangement.
The temperature of the flame or gases of combu~tion emitted from the burner 50 with 20% surplus air is on the order of about 1700C. By appropriately spacing and positioning the guide plates 46 in the annular guide duct 40 to bypass 40% of the air supplied by the gas distributor 20 around he burner 50, the average gas temperature after mixing in the ~icinity of the outlet 44 will be on the order of 1~00C with the advantage that the insulating air flowing between the guide plate 4S and the outer conical plate 24 of the annular guide duct ~0 will have served to thermally insulate the outer conical plate 24 from the high temperature of the flame and also provide a cooling effect to the guide plate 46 AS the air flows past or through that plate. I~ 50~ of the a~r is bypa~sed around the burner 50 and ~lame, the gas temperature a~ter mixing will be on the order o~ abou~ lOOO'C and if 6~% o~ the alr is bypassed, the temperature of the gases after mixing will be about 715-C. Thus, substantial amounts of the air supplied by the gas distributor 20 may be bypassed around the burner S0 ~or cooling purposes and still proYide a gas mixture at the outlet 44 of the annular duct 40 that has a temperature in the range of between about 715-C and 1200-C.
The length of the flame or gases of combustion to be emitted from a burner such as the burner 50 shown in Fig. 2 can be calculated or det~rmied by experimentation. In the embodiment ~2~7~
shown in Fiy. 2, the burner 50 iB positioned in the annular outlet 40, a distance d from the outlet 44 of the annular guide duct 40 which is greater than tha flame length l. This in turn ensures that the droplets of feed solution being disperséd by the atomizer S wheel 30 will only be contacted by hot gas conveyed through the annular guide duct 40 and never have direct contact with the flame.
In other embodiments, the burner 50 may be positioned in the annular outlet 40, a distance d from the outlPt 44 which is only 1/2 to 2~3 the flame length to permit the flame tip; i.e., the lomaximum temperakure of the flame, to project out of the guide duct 40 without impinging on the spray issuing from the atomizing device.
In the preferred embodiment, a plurality of directional vanes 49 are also spaced circumferentially around the annular guide duct 1540. The directional vanes 49 may be fixed in place or adjustable to direct the flow of gas conveyed through the annular guide duct 40 in a desired direction. That is, after the gas has been uniformly dietributed and ~upplied to the mouth 42 o~ th~ annular guide duct ~o, it may b~ desirable to change the dlrect~on o~ g~s flow ~o as to nok only converge toward but rotake around the atomizer wheel 30. Directional vanes such the vanes 49 would be located in the flow of gas downstream from the vanes 25 or such other mPans as may be utilized for uniformly distributiny the gas delivered to the annular guide duct 40 and upstream of the gas 25burner 50 60 as not to interfere with the uniform di~tribution of the gas flow on the one hand and ko avoid exposure to the high temperature of the gas burner and flame on the other hand The operation of the high temperature, waste effluent spray drying plan~ ~hown by Figs. 1-3 will now be briefly described. A
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source of pressurized ambient air is provided by the compre~sor 2 and ~nlet 4 ts the gas dlstributor 20 where it is uniformly distributed around and supplied with a substantially uniEorm velocity to the mouth 42 of the annular guide duct 40. The annular guide duct 40 serves as means for conveylng the flow of gas from the gas distributor 20 to the outlet 44 in a flow that converges toward the atomizer wheel 30. The gas burner 50 i8 located internally of the annular guide duct 40 between the gas distributor 20 and the outlet 44 and heats the gas conveyed through the annular lo guide duct 40 to a predetermined temperature suitable for drying droplets of a feed solution dispersed by the atomizer wheel 30.
The industrial waste effluent in the form of a liquid feed solution is conveyed by conventional means to the atomizer wheel 30 where it i6 dispersed in the form of small droplets and is distributed by centrifugal force radially across the top of the spray chamber 12 thereby forming an atomiæation zone radially outward of the atomizer wheel 30. The high temperature gas conveyed by ths annular duct 40 converges toward the atomizer wheel 30 and evaporates the liquid content of the droplets permitting the solid~
to fall to the funnel shaped lower portlon 18 whera they m~y be removed. The drying gas is withdrawn through the outlet or exhaust conduit 17 and delivered to a separator 6 where fine particles retained in the drying ga~ may be recovered. The gas i5 then withdrawn from the separator 6 through the conduit 7 by exhaust fan 8 where the gas may be exhausted to atmosphere or returned partly as source gas to the fan 2. In the event that other gases may be released from the droplets of feed solution and mixed with the drying gas, it mav of course be desirable to provide a scrubber or other device to separate the additional gases released dur~ng the `` 2~J1~0 drying proces6 from the drying ya~ before the drylng ga8 exhausted to atmosphere or returned to ~he compressor.
Although the operation of the spray drying plant as shown in Fig. 1 has been described in terms of prov~ding a source of cold gas or air to the gas distributor 20, it should o~ course be understood that the drying gas provided to the gas di~tributor 20 ; may be warm or preheated and then the burner 50 serves to increase the temperature of the warm or preheated source gas to the desired ; temperature.
Figure 4 illustrates an alternate annular guide duct 52 which may be utilized in place of the annular guide duct 40 shown by Figs. 1-3. In Figure 4, a gas distributor 20 similar to that shown by Fig. 3 distribu~es a uniform flow of gas to an annular guide duct 52 provided by two radially spaced cylindrical surfaces in the form of the interfacing surfaces of metal plates 53 and 54.
uniform and constant velocity flow of gas is supplied by the gas distributor 22 by means of the vanes 25 and 26 to a mouth 51 of the annular guide duct 52~ Directional vanes 49 are provided in th~
annular guide duct 52 upstream of a pair o~ annular burners 55 and 5G. In this embodiment, a pair of annular sh~eld or guide plates 57 and 58 are provided internally of the annular guide duct 52 to shield the metal plates 53 and 54 from the high temperature of the burner~ 55 and 56 and the flames i~suing therefrom. The guide plate 57 is provided between the buxner 55 and a surface of the metal plate 53 and the guide plate 58 is provided between the burner 56 and a surface of the metal plate 54 to provide an insulating ~low of cold air between the deflector plates 57 and 58 and the metal plates 53 and 54, re~pectively, and thereby insulate the metal plates 53 and 54 fror the high temperature oL the burner~
~ 17 :
2 ~ 2 ~
55 and 56 and the flame~ i~euing thererom.
The annular guide duct 52 of Fig. 4 would operate in the waste effluent spray drying plant shown by Fig. 1 in much the same manner a~ the annular guide duct 40 shown by Fig~ 2. The major difference i5 that the annular guide duct 52 of Fig. 4 would convey a flow of gas in the form of an annular column o~ air into the atomization zone concentric with the atomizer wheel 30 rather than providing a flow of drying gas converging toward the atomizer wheel 30.
Figs. 5 and 6 illustrate an alternate gas distributor and heating device which could be utllized in the high temperature spraying plant of Fig. 1 in place of the gas distributor 20 and annular guide duct 40. In Figs. 5 an~ 6 there is shown a banjo shaped gas distributor 60 having a generally circular portion 61 and a radially e~tending arm 62 providing a processing gas inlet lS 63 similar to the inlet 21 of the gas distributor 20~ A plurality of vanes 64 are provlded at the inlet 63 to distribut~ th~
processing gas around the interior of the circlllar port~on 61. A
pair of circular perforated plates 65 and 66 are provided : lnternally and concentric with the circular portion of the gas distributor 60 to diPfuse and provide a gas ~low of substantially uniform velocity in the direction of a mouth 67 of an annular guide ~ duct 68. A plurality of vanes 6uch as the vanes 25, 26 of Fig. 2 : may also be utilized instead of the perforated plates 65 and 66 to distribute the drying gas.
2S A plurality of gas burners ~9 are provided internally of the ~as dispersing perforated plates 65 and 66 in a circumferential array surrounding the mouth 67 of the annular guide duot 68. The perforated plates 65 and 66 serYe to supply a gas flow of substantially uniform velocity toward the mouth 67 of the annular ---` 2~2~70 guide duct 68. The circum~erentlal array of ga~ burners 6~ serve to uniformly heat the gas flow of substantially uniform velociky vented through the circularly di~posed perforated air ~ietribution plates 65 and 66. A~ ~hown by Fig. 6, the high temperature flow of gas heated by the burners 69 1B conveyed between ~paced conical surfaces provided internally of an annular guide duct 68 formed o a refractory material. The annular guide duct 68 conveys the flow of gas from the gas distribut~r 60 to an outlet 71 where the flow o~ heated gas is directed in a flow of gas converging toward t~e atomizing wheel 30.
A gas distributor 70 is shown in Fig. 7 which is a modification of the gas distributor 60. In Fig. 7 a plurality o~
gas burners 72 are arrayed in a different circular pattern between the perforated plates 65, 6~ and the mouth 67 of the annular guide duct 68. In both embodiments, that is, the continuous circumferential array provided by the hexagonal arrangemellt o~ the burners 69 in Fig. 5 and the burners 72 which are ~paced but stlll provide a ci.rcum~erential array o~ heating meanG~ the ~low of gas havlng a ~ubstantially equal velocity venting through the perfora~ed plates 65 and 66 is uniformly heated before it arrives at the mouth 67 of the annular guide duct 68 which conveys the gas to the outlet 71 concentric with the atomizer wheel 30.
~ig. 8 illustrates a spray chamber 80 which is distinctly different from the spray chamber 12 shown by Fig. 1. In Fig. 8 the spray chamber 80 is comprised of a cylindrical wall 81 closed by a top member 82 which converges toward the central axis of the spray chamber and ha~ an opening B3 provided ~herein. The ga~
distributor is a cylindrical chamber 84 located adjacent to and above the top member 82 and includes perforated plate3 85 and ~6 ~2~ 17~
for 6upplying a ~low of ga~ havlng a substantially uni~orm velocity. A plurality of burners 88 are provided intQrnally of a tubular or cylindrical refractory member 89 conveying the flow of gas from the gas distributor 84 to the spray chamber 80. A
plurality of spray nozzles 90 are equally spaced around the top member ~2. The spray nozzle~ 90 are distinctly dif~erent from the atomizer wheels utilized in the other embodiments and a relatively large numbar of spray nozzles 90 p~rhaps as many as 20 to 40 spray nozzles are equally distributed around the top member 82 and the droplets of -Eeed solution material are sprayed internally toward ; a vertical axis of the spray chamber 80. The processing or dryinggas flow supplied by the distributor 84 and heated by the gas burners 88 is directed downwardly in a column having a substantially circular cross section concentric with the plurality of ~pray nozzles 90 arrayed around the top member 82.
The present invention thus provides an improved ga6 ; distributor and heating device which not only ~acilitates the use of hiyh t~mperature proce~ing or drying gase~; that is, drylng ga~
havlng a tomperakure on the o~dQr oP 715-C to 1200'C which wa~
7,0 hereto~ore not economically feasible5 but also provides a novel arrangement and struature ~or heating processing or drying gas while conveying the same directly into a spray drying chamber which provides distinct advantages over prior art systems wherein the processing or drying gas was h~ated at a location remote from the spray drying chamber in the system delivering the processing or drying gas to a gas distributor. That is, the present invention not only ~acilltates the use of a drying gas having a temperature ~ubstantially greater than that heretofore considered ~conomically feasible, but it also provides a novel arrangement wherein ~`~s" ~
~2~.7~
processing or drying gas may be heated after the gas hae passed through a distributor for providing an annular flow of gas having a substantially uniform velocity as that gas is being conveyed directly to a spray chamber. The apparatus of the present invention thus offers significant advantages over the prior art practice ~f heating the processing or drying gas in a delivery system before the gas is provided to a gas distributor and may be ~P ~ ~ost ~ffc~t;~
' also utilized to provide more ~h~i~ 6pray drying at conventional temperature ranges.
Although specific embodiments of the invention and several modifications of a gas distributor and an annular guide duct have been disclosed, ths present invention is not to be construed as limited to the particular embodiments and forms disclosed herein, since the foregoing description is to be regarded as illustrative rather than restrictive and it should be understood that modifications and variati~ns in details of construction may be made ~` without depar~ing from the spirit and scope of the ~nvention as defined by the claims appended hereto.
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TITL;53 GAS DISTRIBUTOR ~ND HEATER FOR SPRAY DRYING
The present invention is directed to an improved gas distributor and heating devicP for a spray drying apparatus for drying of a feed solution and, more specifically, to an improved air distributor and heating device for directing a concentric flow ' of drying gas to ~ff~K~-o~ a drying space in a drying chamber .~2, ~ having an atomizing device.
Backqround of the Invention Spray drying is the transformation of a feed material from a flu~d state into a dried particulate ~orm by ~praying the feed material into a hot drying medium. It is a one-step, continuous particle-processing operation involving drying. ~ackground information relative to the field in which this invention finds application is provided in Spray Drying Handbook, third edition, K. Masters (John Wiley and Sons, New York~.
The invention is applicable to spray drying, spray evaporation and spray reaction operations and processes which usually involv~
the introduction of a liquid ~eed material in the form o~ a 20 solution or a suspension to an atomizing device which sprays small particles of the liquid feed material into a drying chamber where the droplets are dried or reacted and the resulting desired particulate material is collected and removed in the form of a powder. A rotary atomizing wheel which provides a continuous spray Z5 of the liquid droplets is often used at the to~ of a tower-type drying chamber. In addition ~o the droplets of liquid feed material, a processing gas in the form o~ a temperature controlled gaseous medium is al50 introduced to the to~er-~ype drying chamber 1 7 ~
to evaporate the moistur~ ~rom the liquld droplets and thu~ provide the desired particulate material.
Drylng ~hamhers of this type utilizing a rotary atomizer wheel and heated air introduced at the top of a drying chamber have been widely used to dry consumable food products, such as milk, to produce chemical products such as kaolin clay, titanium dioxide and calcium carbonate, and for processing wast~ effluents. Such processes are critically dependent ~pon the particle size of the material being dried, the temperature of the drying medium and the timely effective contact of each particle with the drying medium.
Rotary atomizer wheels or spray nozzles are generally used ~or spraying the feed material into the hot gas medium.
Various types of heating devices have been utilized to provide the hot gaseous medium. Gas heaters of the direct and indirect type have been utilized as well as steam, fuel oil, heat transfer fluids and electricity. Selection of a heat source Eor a partiaular process depend~ upon the product beiny ~pray dried a~
well a the availability, suitablllty and cost o~ the energy required in order to heat the gaseous medium. Open oil an~ gas ~ired burners may b~ utilized where products can withstand the h~gh temperature generated by such heat sources as well as contact with the resulting products of combustion. Indirect heaters utilizing eleotrical heating elements, gas or fuel oil burners may also be utilized to provide a hot gaseous medium when it is necessary to protect the product being sprayed from contact with products of combustion.
The processing or drying gas medium is delivered from a source to a gas distributor or distribution means from which it is 2~2~:17(~
supplied to the interior o~ the spray dryir)g chamber. The ga~ ls typiaally heated while moving through the deli~ery system by means of a burner or other heat source located in the gas delivery system before the gas is delivered to the gas distributor. The heated gas ls then conveyed through insulated ducts to the gas distributor for introduction into the dryiny chamber and subsequent admixture with the feed spray.
A typical process and apparatus ~or provlding a hot drying ga~
around an atomizing device in a spray drying chamber i6 disclosed S~ '5~ Y'l 10 ~ 'in Patent Nos. ~,621,902 and 4,227,896. In those processes, the gaseous medium is heated by means o~ a device located in the ga~
delivery system remote ~rom the spray drying chamber. Patent No.
4,227,896 also discloses an e~ficient gas distributor having a sp~ral supply duct and a plurality o~ vanes which provide a gas flow of substantially constant velocity through a conical guide duct.
Patent No. 3,499,476 di~closes a proces~ ~or the production of par~iculate solids from a solution or suspen~ion by nozzle spraying the feed material through a 1ame zone provided by an annular burner at the top oP a spray towsr. In this process, the ga~eous products o~ ¢om~ustlon are in~roduced directly into the drying chamber with the liquid particles of feed material.
United Kingdom Patent Specification ~o. 1,191,032 discloses apparatus providiny a preliminary drying zone wherein feed material is sprayed through a nozzle surrounded by a burner and the gases of combustion intermingle with the liquid particles of feed material. A secondary drying agent is delivered around the spray nozzle and gas burner.
2~2~7~
Still another spray drylng apparatus ut~liz~ny an air heater provlded in a chamber located directly above a spray drying chamber ls disclosed ~n Patent No. 4,187,617. In that apparatus air i5 delivered by means of a fan through a transition duct to a distribution chamber located above the spray drying chamber. ~n air heater and a profile plata are provided in the distribution chamber together with a perforated diffuser. Cold air i~ delivered past the profile plate and heater to ensure that the air is uniformly heated and then received through the perforations in the diffuser and ducted to the spray drying chamber. The object of that apparatus is to ensure uniform heating of the air being introduced to the distribution chamber and both uniform temperature and ~low of the heated air into the spray drying chamber.
Gonventional systems of producing hot processing Dr drying gas using either direct or indirect heating means in the form of a furnace or combustion device and then ducting or delivering the hot gas from the heating area into the drying chamber by conventional air distributors are known in the art. Such conventional system~
are suited f or spray drying procesges reqlllriny dryiny ga~
temperatures which are not in exce~s of abou~ 550'C. ~lowever, such conventional systems ar~ seldom used in spray drying operations requiring drying gas temperatures near or in exaess of lOOO-C since conventional systems would re~uire the generation of substantial ; thermal energy remote from the point of use and extensive use of refractory materials in the delivery system hetween the heat source and a gas distributor adjacent the spray drying chamber.
One object of the present invention is to provide a gas heater and alr distributor for high temperature spray dryin~ systems which reguires mlnimum refractory lining of the heating chamber and hot 2~2~i7~
gas ductlng or c~veying surface~. This ob~ect is achieved by ~t~ of , providing the heat source directly ~4~ the point o~ use in the spray drying chamber thus permitting delivery of a cold gas by conventional conduits to a gas distributor adjacent a spray chamber ; and then heating the gas supplied from the gas distributor as it is conveyed to the spray chamber. The high tempsrature, hot drying gas is conveyed directly into the drying chamber which minimizes the refractory material required since the high temperature drying gas is exhausted directly from the area where the gas i~ heated into the drying chamber. ~ G~
The present invention is dis inctly different ~rom the apparatus disclosed in Patent No. 3,499,476 and United Kingdom Specification No. 1,191,032 since the heat source and the flame of the present invention do not directly contact the liquid particles of feed material in the drying chamber and the particulate material will not be adversely effected by the products of co~bustion.
The spray drying apparatus of the present invention i~ al~o ~ ' Cl G~
d~fferent ~rom the apparatus disclosed by Patent No. 4, l~7, 617?~
since the ga5 di~user ox distributor in that apparatus ie provided ~ J`
between the a~r heater and the spray nozzle. 'rhe apparatu~ of tha~ I
patent would also be limited to spray drying processes utilizing / `
drying gas heated to only a moderately hlgh gas temperature on the order of 550'C because of the diffuser and wire screens downstream of the air heater.
As will be more ~ully described here below, the apparatus of the present invention is particularly suit~d for use in high temperature spray drying of materlals such as iron oxi~e pi~ments, magnesium chloride, and titanium oxide, or industrial waste ef~luents such as an acid solution of iron sulfate and magnesium `` ~02Sl~
sulfate wherein drying gas or ho~ air having a temperature in the range of lO~O'C or more is required.
Thus, one objeck of this inventlon is to provide a gas distributor, gas heater and atomizer for a high temperature drying system.
A further object of this invention i5 to provide a spray drying apparatus having a drying yas delivery system wherein the maxlmum amount of gas distribution is accomplished before the gas is heated to the desired temperature, the gas is then heated and conveyed directly to the spraying chamber.
A still further object i5 to provide a ga~ heater for receiving gas fxom a cold gas distributor and haviny an outlet exiting in the Yicinity of the liquid droplet~ being discharged from an atomizer device~
15A further object is to provide a hot processing or drying gas with its maximum temperature attained adjacent an atomiæiny device.
A ~till further object is to provide a gas heater ~or high temperature drying systems comprising a circularly di~po~d cold ; air dlstributor circumscribing and venting pa~t a circum~erential array of ya~ burner~ located in a circular passageway exiting ln ~he vicinity o~ an atomizer device.
Su~mar~ of the Invention A gas distributor and heating deYiae for a spray dryer of the type including a feed liquid atomizer at the top of a drying ~ 25 chambsr which includes a gas distributor for supplying a flow of gas having a substantially uni~orm velocity, a guide duct for conveying the flow of gas ~rom the gas distributor and having an outlet providing a flow of gas concentric with the atomizer, and 7 ~
a ga~ heater located in the device between the gas di~tribu~or and the outlet.
The guide duct for conveying the flow of gas from the gas distributor is preferably provided in the form of an annular guide duct defined by two spaced surfaces and the outlet provid~s an annular ~low of heated gas concentrio with a llguid atomizer. Thr spaced surfaces may be two radially spaced cylindrical surfaces or conical surfaces and, in the case o~ an annular guide duct de~ined by two spaced conical ~urfaces, the outlet directs an annular flow L0 of heated gas converging toward ~ centerline of the guide duct.
0~?, ~'1 ~ b ;n a ~`~ th~ ~o The spaced conical surfaces may be convergen~ or div ~ to control the vQlocity of the gas at the outlet of the guide duct.
'~ Spaced surfaces comprising a cylindrical surface and a conical surface may also be utilized.
15In the pre~erred embodimentg, the gas heater is one or a plurality of gas burners provided internally of an annular guide duct and extending circumferentially around the interior o the yuide duct.
In the pre~erred embodiment, the gas burner i6 disposed to emit the gases o~ combustion in the directioll of the outlet of the annular guide duct and may further include a plate or pla en - shielding a portion of the gas flow conveyed from the gas distributor from direct contact with the burner and the gases of combustion and thereby providing an insulating flow of gas between at least one side of the annular duct and the temperature of the burner and the gases of combustion.
. In certa~n applications of the invention, it is also preferred that the gas burner ls disposed to emit a flame in the dir~ction o~ the outlet and the gas burner is located a greater distance from 202~ 7~
the outlet than a length of the flame emitted by the burner B0 as f V~
to ~nsure that the gases of combustlon forming ~he flame are completely burned internally of the annular ~uide duc~.
c~ In a preferred embodiment of the invention, the gas ; distributor is provided in the form of a horizontal spiral supply duct of constantly decreasing cross section and having a plurality of vanes for uniformly distributing an annular supply of pressurized gas from the supply duct to the guide duct for conveying the flow of gas.
LO In an alternate embodiment of the invention, the gas distributor is provided in the form of a banjo shaped chamber having a circular portion and an arm extending radially relative to the circular portion and providing a supply inlet. The circular portion includes an annular outlet for supplying an annular flow of gas to the guide duct and at least one continuous circular perforated plate spaced between an interior zurface of the circular portion and the annular outlet for distributing a uniform flow of gas from the supply inlet to the annular outlet.
In certain embodlments of the invention, a plurality o~ vanes are al50 provided lnternally o~ the guide duct to direat the flow of gas in a desired direction.
The ga~s distributor and heating device of the present invention may be utilized with atomizer wheels or ~pray nozzles.
When used with an atomizer wheel, it is preferred that the guide duct provide an annular flow of heated ~as concentric with the atomizer wheel. In applications using spray nozzl~s, it is preferred that a plurality of spray nozzles be arrayed at the top of a spray chamber and the guide duct provide a flow of heated gas ~ubstantially centered with the top of the spray chamber and ~` 2~12~;~70 concentric with the ~urrounding array of ~pray nozzles. ~he yas distrlbutor and heating devicP may also be used with spray nozzles sprayinq from below in a fountain configuration.
The present invention and the advantages provided thereby will be more fully understood with reference to the following detailed description of the preferred embodiment taking in con~unction wlth the accompanying drawings.
~rief Description of the Drawinqs Fig. 1 is an elevation view~ partly broken away, showing a spray drying plant utilizing one embodiment of the present invention:
Fig. 2 is an enlarged sectional view showing the structure of a gas distributor and heating device of Fig. l;
Fig. 3 iB a plan view showing the interior of the gas distributor of Fig. 2;
Fig. 4 is a view slmilar to Fig. 2 showiny an alternate gulde duct for heating and conveying gas supplied by a gas dlstributor as shown by Figs. l and 3;
Flg. 5 i5 a plan vlew similar ko Fiq. 3 ~howing an alternate gas distributor and heating device;
Fig. 6 is a sectional view taken along line VI-VI of Fig. 5;
Fig. 7 is a plan view similar to Fig. 5 and showing a modification of the structure shown by ~ig. S; and Fiy. 8 is a partial elevation view of an alternate embodiment of the spray drying apparatus of the presen~ invention.
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~es~ tion~ h~_Prefe~.r~L~nbod~h~nt With reference to the drawiny~ wherein like re~erence numerals designate the same or like parts throughout, there is shown in Fig.
1 a spray drying plant designated by the reference numeral 10 which is particularly adapted for high temperature drying of an industrial waste effluent such a~ an aoid ~olution derived a~ a wa~te product of a metal treating facility. The plant 10 is se~eral stories high and i~cludes a spray or drying chamber 12 and a penthouse 14 supported by means of a superstructure 11. The penthouse 14 provides an enclosure and work area for servicing a gas dlstributor 20 and rotary atomizing wheel 30 provided adjacent a roof or top closure 15 of the spray drying chamber 12. The spray drying chamber 12 has a cylindrical outer wall which is substantially closed at the top by the closure 15 and by a funnel or conical-shaped lower portion 18~ An opening 16 is provided in the top closure 15 and a valve 19 is provided at the bottom of the lower portion 18 to permit removal of the particulate materials dried in the spray chamber 12. The spray ahamber 12, opening 16 and the funnel-shaped lower portion 18 are ~ub~tantially 6yrnmetrioal about a vertiaal axi~.
A gas distributor 20, as best shown by Fig. 2, is mounted ln the penthouse 14 with a conical-shaped guide duct 40 dependlng to a position substantially aligned with the top closure 15 and centered in the opening 16. The rotary atomi~er wheel 39 is rotatably mounted in a housing 31 supported internally of the gas distributor ~0 to project into the top o the s~ray drying chamber 12.
Although the rotary atomizer wheel 30 is provided at the top of the spray dxying chambsr 12 ln Fig. 1, the atomiæer devic~ may -~- 2~2~7~
be one or mora 6pray noz.zle~ located at ~he top o~ th~ spray drylng chamber or elsewher~ in the spray drying chamber an~ spraying in the direction of the gas distributor 20.
A pressurixed source of cold gas usually in the form of ambient air is provided to the gas distributor by me~ns of a fan 2 and inlet or delivery duct 4 connected to the gas distributor 20. An outlet or exhaust port provided in the funnel shaped lower portion 12 at one side of the plant is connected by means of an exhaust duct or pipe 17 to a fines separator 6 which ~ay be in the form of a cyclon~ separator. The fine particles are retained in the separator 6 where they may be periodically withdrawn and the gas is exhausted through a conduit 7 to an exhaust fan 8 where the gas may be exhausted to atmosphere or recycled by duct work to the ~an 2. The fan 2 and inlet duct 4 comprise a delivery system for delivering cold processing gas to the gas distributor 20. The outlet duct 17, separator 6, exhaust duct 7 and exhaust fan 8 comprise means for withdrawing the processing gas from the spray chamber 12.
The gas distributor 20 is of the type disalo~ed in Patent No.
4,227,896 and includes an inlet 21 opening to a splral ~upply duct 22 which i~ internally opened to an annular transitlon zone 23.
The transition zone 23 includes two succeeding sets of stationary guide vanes 25 and 26. The vanes 25 are shaped to deflect the flow of gas from a purely tangential flow a~ indicated by the ~rrow6 adjacent the inlet 21 to a flow direction as shown hy the arrows ~7 in whlch the radial velocity component toward a center axis of the gas distributor 20 excseds the tangential velocity component and the vanes 26 o~ the other set project into a space between the vanes 25 and extend substantially parallel to the direction which ~ 2V2~ I V
the gas flow has been deflected by the adjacellt vane 25. The vanes 25 and 26 in the annular transltion zone change the direct~on of flow of the gas supplied to thP gas distributor 20 and direct the gas to a mouth 42 of an annular gulde duct 40 while the vanes 26 also minimize turbulance in the flow. As best shown by Flgs. 2 and 3, the internal dimensions or volume of the spiral duct 22 constantly decreases in the direction of gas flow from the inlet 21 around the annular transition zone so as to supply a substantially constant volume and velocity of gas moving from the spiral duct through the annular transition zone 23 to the mouth 42 of the annular guide duct 40.
The annular guide duct 40, as best shown by Fig. 2, is' comprised o~ a hollow conical shaped insulating member 41 whi~h may also provide support for the atomizer wheel drive housing 31. A
conical shaped plate 24 i5 radially spaced ~rom the insulating member 41 and the annular guide duct 40 is provided in the conically shaped radial space between the ~nsulating member 41 and the plake 2~.
A rlng ~haped or annular gas burner 50 is also provid~d internally o~ the annlllar guide duat 40 be-tween the insulating member 41 and plate 24. As shown by Fig. 2, the gas burner 50 is disposed to emit the gases of combustion or direct the flame in the direction o~ the outlet 44 of the annular guide duct 40.
In the pre~erred embodiment, an annular plate 46 or series of plate~ are provided around the interior of the annular guide duct 40 between the gas burner 50 and the outer metal plate 24 to deflect a portion of the gas supplied by the gas distributor around the burner 50 and serve as a heat shield between the burner and the outer plate 24. The plate 46 may be attached at 48 to the outer ~ 2~2~7~
~onical plate 2~ and shields ~ portion of the ga~ ~lowlny fr~m tha gas distributor from direct contact with the burner and the ~lame or gases of combustion emitted by the burner. The plate 46 thus provides an insulating flow of cold gas between the metal plate 24 providing one side of the annular guide duct 40 and the temperature o~ the burner and the gases of combustion.
The feature of cooling one or both of the walls of ths annular guide duct by means of an insulating flow of cold gas is an important feature particularly in extremely high temperature drying applications o~ the present invention. For example, in a process ~or spray drying industrial waste e~fluents, it may be desirable to convey gas heated to a temperature in the range of about 700-to 1200-C in order to dry the des~red material. The temperature of a flame issuing from a burner such as the burner 50 shown by Fig. 2 may be as high as 2,00UC. Such high temperatures ~ignif~cantly limit the choice o~ materials which may be utilized in a ~tructure adjacent such a high temperature flame. Although a number of ceramic and re~ractory materials are aapable o~
withs~nding ~uch high temperatures, some o~ the material~ are not capable of providiny long term service in such a high temperature en~ironment and such materials are both heavy and dl~Picult to work with and the most temperature resistent materials are relatively expensive. Thus, although ceramic and refractory materials may be used for flame and high temperature resistance, it is of course desirable to have other devices and arrangements whereby more conventional high temperature steel plates may be suitably ~ormed and used in such environments. This i~ signi~icant since most high temperature steel and other metal plate materials cannot withstand temperature~ greater than about 550~C, and there~ore sp~cial . , ~ .
~ 2 ~ 7 ~
arrangements or ~evice3 must be prov~d~d if one wishes to obtain the low cost and fabrication advantages offered by ~uch materlals.
The heat shield guide plates or deflector plates 46 which provide an insulating flow of cool gas between the burner 50 and the ou~er conical plate 24 of the annular duct 40 provide such an advantageous arrangement.
The temperature of the flame or gases of combu~tion emitted from the burner 50 with 20% surplus air is on the order of about 1700C. By appropriately spacing and positioning the guide plates 46 in the annular guide duct 40 to bypass 40% of the air supplied by the gas distributor 20 around he burner 50, the average gas temperature after mixing in the ~icinity of the outlet 44 will be on the order of 1~00C with the advantage that the insulating air flowing between the guide plate 4S and the outer conical plate 24 of the annular guide duct ~0 will have served to thermally insulate the outer conical plate 24 from the high temperature of the flame and also provide a cooling effect to the guide plate 46 AS the air flows past or through that plate. I~ 50~ of the a~r is bypa~sed around the burner 50 and ~lame, the gas temperature a~ter mixing will be on the order o~ abou~ lOOO'C and if 6~% o~ the alr is bypassed, the temperature of the gases after mixing will be about 715-C. Thus, substantial amounts of the air supplied by the gas distributor 20 may be bypassed around the burner S0 ~or cooling purposes and still proYide a gas mixture at the outlet 44 of the annular duct 40 that has a temperature in the range of between about 715-C and 1200-C.
The length of the flame or gases of combustion to be emitted from a burner such as the burner 50 shown in Fig. 2 can be calculated or det~rmied by experimentation. In the embodiment ~2~7~
shown in Fiy. 2, the burner 50 iB positioned in the annular outlet 40, a distance d from the outlet 44 of the annular guide duct 40 which is greater than tha flame length l. This in turn ensures that the droplets of feed solution being disperséd by the atomizer S wheel 30 will only be contacted by hot gas conveyed through the annular guide duct 40 and never have direct contact with the flame.
In other embodiments, the burner 50 may be positioned in the annular outlet 40, a distance d from the outlPt 44 which is only 1/2 to 2~3 the flame length to permit the flame tip; i.e., the lomaximum temperakure of the flame, to project out of the guide duct 40 without impinging on the spray issuing from the atomizing device.
In the preferred embodiment, a plurality of directional vanes 49 are also spaced circumferentially around the annular guide duct 1540. The directional vanes 49 may be fixed in place or adjustable to direct the flow of gas conveyed through the annular guide duct 40 in a desired direction. That is, after the gas has been uniformly dietributed and ~upplied to the mouth 42 o~ th~ annular guide duct ~o, it may b~ desirable to change the dlrect~on o~ g~s flow ~o as to nok only converge toward but rotake around the atomizer wheel 30. Directional vanes such the vanes 49 would be located in the flow of gas downstream from the vanes 25 or such other mPans as may be utilized for uniformly distributiny the gas delivered to the annular guide duct 40 and upstream of the gas 25burner 50 60 as not to interfere with the uniform di~tribution of the gas flow on the one hand and ko avoid exposure to the high temperature of the gas burner and flame on the other hand The operation of the high temperature, waste effluent spray drying plan~ ~hown by Figs. 1-3 will now be briefly described. A
. ~5 / ~ ~
---`` 2 0 ~
source of pressurized ambient air is provided by the compre~sor 2 and ~nlet 4 ts the gas dlstributor 20 where it is uniformly distributed around and supplied with a substantially uniEorm velocity to the mouth 42 of the annular guide duct 40. The annular guide duct 40 serves as means for conveylng the flow of gas from the gas distributor 20 to the outlet 44 in a flow that converges toward the atomizer wheel 30. The gas burner 50 i8 located internally of the annular guide duct 40 between the gas distributor 20 and the outlet 44 and heats the gas conveyed through the annular lo guide duct 40 to a predetermined temperature suitable for drying droplets of a feed solution dispersed by the atomizer wheel 30.
The industrial waste effluent in the form of a liquid feed solution is conveyed by conventional means to the atomizer wheel 30 where it i6 dispersed in the form of small droplets and is distributed by centrifugal force radially across the top of the spray chamber 12 thereby forming an atomiæation zone radially outward of the atomizer wheel 30. The high temperature gas conveyed by ths annular duct 40 converges toward the atomizer wheel 30 and evaporates the liquid content of the droplets permitting the solid~
to fall to the funnel shaped lower portlon 18 whera they m~y be removed. The drying gas is withdrawn through the outlet or exhaust conduit 17 and delivered to a separator 6 where fine particles retained in the drying ga~ may be recovered. The gas i5 then withdrawn from the separator 6 through the conduit 7 by exhaust fan 8 where the gas may be exhausted to atmosphere or returned partly as source gas to the fan 2. In the event that other gases may be released from the droplets of feed solution and mixed with the drying gas, it mav of course be desirable to provide a scrubber or other device to separate the additional gases released dur~ng the `` 2~J1~0 drying proces6 from the drying ya~ before the drylng ga8 exhausted to atmosphere or returned to ~he compressor.
Although the operation of the spray drying plant as shown in Fig. 1 has been described in terms of prov~ding a source of cold gas or air to the gas distributor 20, it should o~ course be understood that the drying gas provided to the gas di~tributor 20 ; may be warm or preheated and then the burner 50 serves to increase the temperature of the warm or preheated source gas to the desired ; temperature.
Figure 4 illustrates an alternate annular guide duct 52 which may be utilized in place of the annular guide duct 40 shown by Figs. 1-3. In Figure 4, a gas distributor 20 similar to that shown by Fig. 3 distribu~es a uniform flow of gas to an annular guide duct 52 provided by two radially spaced cylindrical surfaces in the form of the interfacing surfaces of metal plates 53 and 54.
uniform and constant velocity flow of gas is supplied by the gas distributor 22 by means of the vanes 25 and 26 to a mouth 51 of the annular guide duct 52~ Directional vanes 49 are provided in th~
annular guide duct 52 upstream of a pair o~ annular burners 55 and 5G. In this embodiment, a pair of annular sh~eld or guide plates 57 and 58 are provided internally of the annular guide duct 52 to shield the metal plates 53 and 54 from the high temperature of the burner~ 55 and 56 and the flames i~suing therefrom. The guide plate 57 is provided between the buxner 55 and a surface of the metal plate 53 and the guide plate 58 is provided between the burner 56 and a surface of the metal plate 54 to provide an insulating ~low of cold air between the deflector plates 57 and 58 and the metal plates 53 and 54, re~pectively, and thereby insulate the metal plates 53 and 54 fror the high temperature oL the burner~
~ 17 :
2 ~ 2 ~
55 and 56 and the flame~ i~euing thererom.
The annular guide duct 52 of Fig. 4 would operate in the waste effluent spray drying plant shown by Fig. 1 in much the same manner a~ the annular guide duct 40 shown by Fig~ 2. The major difference i5 that the annular guide duct 52 of Fig. 4 would convey a flow of gas in the form of an annular column o~ air into the atomization zone concentric with the atomizer wheel 30 rather than providing a flow of drying gas converging toward the atomizer wheel 30.
Figs. 5 and 6 illustrate an alternate gas distributor and heating device which could be utllized in the high temperature spraying plant of Fig. 1 in place of the gas distributor 20 and annular guide duct 40. In Figs. 5 an~ 6 there is shown a banjo shaped gas distributor 60 having a generally circular portion 61 and a radially e~tending arm 62 providing a processing gas inlet lS 63 similar to the inlet 21 of the gas distributor 20~ A plurality of vanes 64 are provlded at the inlet 63 to distribut~ th~
processing gas around the interior of the circlllar port~on 61. A
pair of circular perforated plates 65 and 66 are provided : lnternally and concentric with the circular portion of the gas distributor 60 to diPfuse and provide a gas ~low of substantially uniform velocity in the direction of a mouth 67 of an annular guide ~ duct 68. A plurality of vanes 6uch as the vanes 25, 26 of Fig. 2 : may also be utilized instead of the perforated plates 65 and 66 to distribute the drying gas.
2S A plurality of gas burners ~9 are provided internally of the ~as dispersing perforated plates 65 and 66 in a circumferential array surrounding the mouth 67 of the annular guide duot 68. The perforated plates 65 and 66 serYe to supply a gas flow of substantially uniform velocity toward the mouth 67 of the annular ---` 2~2~70 guide duct 68. The circum~erentlal array of ga~ burners 6~ serve to uniformly heat the gas flow of substantially uniform velociky vented through the circularly di~posed perforated air ~ietribution plates 65 and 66. A~ ~hown by Fig. 6, the high temperature flow of gas heated by the burners 69 1B conveyed between ~paced conical surfaces provided internally of an annular guide duct 68 formed o a refractory material. The annular guide duct 68 conveys the flow of gas from the gas distribut~r 60 to an outlet 71 where the flow o~ heated gas is directed in a flow of gas converging toward t~e atomizing wheel 30.
A gas distributor 70 is shown in Fig. 7 which is a modification of the gas distributor 60. In Fig. 7 a plurality o~
gas burners 72 are arrayed in a different circular pattern between the perforated plates 65, 6~ and the mouth 67 of the annular guide duct 68. In both embodiments, that is, the continuous circumferential array provided by the hexagonal arrangemellt o~ the burners 69 in Fig. 5 and the burners 72 which are ~paced but stlll provide a ci.rcum~erential array o~ heating meanG~ the ~low of gas havlng a ~ubstantially equal velocity venting through the perfora~ed plates 65 and 66 is uniformly heated before it arrives at the mouth 67 of the annular guide duct 68 which conveys the gas to the outlet 71 concentric with the atomizer wheel 30.
~ig. 8 illustrates a spray chamber 80 which is distinctly different from the spray chamber 12 shown by Fig. 1. In Fig. 8 the spray chamber 80 is comprised of a cylindrical wall 81 closed by a top member 82 which converges toward the central axis of the spray chamber and ha~ an opening B3 provided ~herein. The ga~
distributor is a cylindrical chamber 84 located adjacent to and above the top member 82 and includes perforated plate3 85 and ~6 ~2~ 17~
for 6upplying a ~low of ga~ havlng a substantially uni~orm velocity. A plurality of burners 88 are provided intQrnally of a tubular or cylindrical refractory member 89 conveying the flow of gas from the gas distributor 84 to the spray chamber 80. A
plurality of spray nozzles 90 are equally spaced around the top member ~2. The spray nozzle~ 90 are distinctly dif~erent from the atomizer wheels utilized in the other embodiments and a relatively large numbar of spray nozzles 90 p~rhaps as many as 20 to 40 spray nozzles are equally distributed around the top member 82 and the droplets of -Eeed solution material are sprayed internally toward ; a vertical axis of the spray chamber 80. The processing or dryinggas flow supplied by the distributor 84 and heated by the gas burners 88 is directed downwardly in a column having a substantially circular cross section concentric with the plurality of ~pray nozzles 90 arrayed around the top member 82.
The present invention thus provides an improved ga6 ; distributor and heating device which not only ~acilitates the use of hiyh t~mperature proce~ing or drying gase~; that is, drylng ga~
havlng a tomperakure on the o~dQr oP 715-C to 1200'C which wa~
7,0 hereto~ore not economically feasible5 but also provides a novel arrangement and struature ~or heating processing or drying gas while conveying the same directly into a spray drying chamber which provides distinct advantages over prior art systems wherein the processing or drying gas was h~ated at a location remote from the spray drying chamber in the system delivering the processing or drying gas to a gas distributor. That is, the present invention not only ~acilltates the use of a drying gas having a temperature ~ubstantially greater than that heretofore considered ~conomically feasible, but it also provides a novel arrangement wherein ~`~s" ~
~2~.7~
processing or drying gas may be heated after the gas hae passed through a distributor for providing an annular flow of gas having a substantially uniform velocity as that gas is being conveyed directly to a spray chamber. The apparatus of the present invention thus offers significant advantages over the prior art practice ~f heating the processing or drying gas in a delivery system before the gas is provided to a gas distributor and may be ~P ~ ~ost ~ffc~t;~
' also utilized to provide more ~h~i~ 6pray drying at conventional temperature ranges.
Although specific embodiments of the invention and several modifications of a gas distributor and an annular guide duct have been disclosed, ths present invention is not to be construed as limited to the particular embodiments and forms disclosed herein, since the foregoing description is to be regarded as illustrative rather than restrictive and it should be understood that modifications and variati~ns in details of construction may be made ~` without depar~ing from the spirit and scope of the ~nvention as defined by the claims appended hereto.
. ~
;'.
::
:, ''' , ~ .
,. ~
Claims (22)
1. A gas distributor and heating device for a spray dryer of the type including feed liquid atomizing means in a drying chamber comprising:
gas distribution means for supplying a flow of gas having a substantially uniform velocity, means for conveying said flow of gas from said gas distribution means and having an outlet providing a flow of said gas concentric with said atomizing means, and heating means located in said device between said gas distribution means and said outlet.
gas distribution means for supplying a flow of gas having a substantially uniform velocity, means for conveying said flow of gas from said gas distribution means and having an outlet providing a flow of said gas concentric with said atomizing means, and heating means located in said device between said gas distribution means and said outlet.
2. The gas distributor and heating device defined by claim 1, wherein said means for conveying said flow of gas from said gas distribution means is comprised of an annular guide duct defined by spaced concentric cylindrical surfaces and said outlet provides an annular flow of heated gas concentric with a liquid atomizing means.
3. The gas distributor and heating device defined by claim 1. wherein said means for conveying said flow of gas from said gas distribution means is comprised of an annular guide duct defined by two spaced conical surfaces and said outlet directs an annular flow of heated gas converging toward a centerline of said guide duct.
4. The gas distributor and heating device defined by claim 2 or claim 3, wherein said heating means is located in and extends circumferentially around said annular guide duct.
5. The gas distributor and heating device defined by claim 2 or claim 3, wherein said heating means is comprised of at least one gas burner provided internally of said annular guide duct and extending circumferentially around the interior of said guide duct.
6. The gas distributor and heating device defined by claim 5, wherein said at least one gas burner is disposed to emit the gases of combustion in the direction of the outlet of said annular guide duct and further including means internally of said annular guide duct shielding a portion of the gas flow conveyed from said gas distribution means from direct contact with the burner and the gases of combustion and thereby providing an insulating flow of gas between at least one side of said annular duct and the temperature of the burner and the gases of combustion.
7. The gas distributor and heating device defined by claim 5, wherein said at least one gas burner is disposed to emit a flame in the direction of the outlet and the gas burner is located a greater distance from said outlet than a length of said flame so as to insure that the gases of combustion are completely burned internally of said annular guide duct.
8. The gas distributor and heating device defined by claim 5, wherein said at least one gas burner is disposed to emit a flame in the direction of the outlet and the gas burner is located a distance from said outlet which is less than a length of said flame to locate a maximum temperature of the flame upstream of atomizing means.
9. The gas distributor and heating device defined by claim 1, wherein said gas distribution means is comprised of a horizontal spiral supply duct of constantly decreasing gross section and having a plurality of vanes for uniformly distributing an annular supply of pressurized gas from said supply duct to said means for conveying said flow of gas.
10. The gas distributor and heating device defined by claim 1, wherein said gas distribution means is comprised of a banjo shaped chamber having a circular portion and an arm extending radially relative to said circular portion and providing a supply inlet, said circular portion includes an annular outlet for supplying said annular flow of gas to said conveying means and at least one continuous circular perforated plate or set of distributor vanes spaced between an interior surface of said circular portion and said annular outlet for distributing a uniform flow of gas from said supply inlet to said annular outlet.
11. The gas distributor and heating device defined by claim 9 or 10, wherein said heating means comprise a plurality of gas burners arranged in a circular pattern for uniformly heating the uniform flow of gas supplied by said gas distributing means.
12. The gas distributor and heating device defined by claim 1, wherein a plurality of vanes are provided internally of said means for conveying said flow of gas from said gas distribution means to direct the flow of said gas in a desired direction.
13. A spray dryer for drying of a feed solution comprising:
a drying chamber having a vertical axis and a drying space concentric with said vertical axis, at least one atomizing means which forms and introduces dispersed droplets of feed solution in said drying space, gas distribution means for supplying a flow of gas having a substantially uniform velocity, means for conveying said flow of gas from said gas distribution means and having an outlet providing a flow of said gas concentric with said atomizing means, heating means located between said gas distribution means and said outlet for heating the flow of gas supplied by said gas distribution means, a gas delivery system for providing a continuous flow of gas to said gas distribution means, means for removing powder particles from said chamber, and means for withdrawing gas from said chamber.
a drying chamber having a vertical axis and a drying space concentric with said vertical axis, at least one atomizing means which forms and introduces dispersed droplets of feed solution in said drying space, gas distribution means for supplying a flow of gas having a substantially uniform velocity, means for conveying said flow of gas from said gas distribution means and having an outlet providing a flow of said gas concentric with said atomizing means, heating means located between said gas distribution means and said outlet for heating the flow of gas supplied by said gas distribution means, a gas delivery system for providing a continuous flow of gas to said gas distribution means, means for removing powder particles from said chamber, and means for withdrawing gas from said chamber.
14. The spray dryer defined by claim 13, wherein said drying chamber is comprised of a cylindrical wall closed by a top member, an opening in said top member, said atomizing means is comprised of a rotary atomizer wheel projecting through said opening to disperse droplets of feed solution to an atomizing zone in said drying chamber, and said means for conveying said flow of gas from said gas distribution means is comprised of an annular guide duct defined by a pair of spaced surfaces and said outlet directs an annular flow of heated gas toward said atomizing zone.
15. The spray dryer defined by claim 13, wherein said drying chamber is comprised of a cylindrical wall closed by a top member, an opening in said top member, said atomizing means is a rotary atomizer wheel projecting through said opening and introducing said dispersed droplets of feed solution to said drying space, and said means for conveying said flow of gas from said gas distribution means is an annular guide duct defined by two spaced conical surfaces and said outlet directs an annular flow of heated gas converging toward said dispersed droplets of feed solution introduced to said drying space.
16. The spray dryer defined by claim 13, wherein said drying chamber is closed by a top member having a central opening, said atomizing means is a rotary atomizer wheel projecting through said opening and introducing said dispersed droplets of feed solution to said drying space, said outlet directs an annular flow of heated gas converging toward said dispersed droplets of feed solution introduced to said drying space, and said gas distribution means is comprised of a banjo shaped chamber having a circular portion concentric with the vertical axis of said drying chamber and an arm extending radially relative to said circular portion and providing a supply inlet to said circular portion and said circular portion includes an annular outlet and at least one circular gas diffuser between an interior surface of said banjo portion and said outlet for distributing a uniform flow of gas from said supply inlet to said annular outlet.
17. The spray dryer defined by claim 16, wherein said heating means comprises a plurality of gas burners arrayed in a circular pattern adjacent said circular gas diffuser.
18. The spray dryer defined by claim 16, wherein said circular gas diffuser is comprised of at least one perforated plate.
19. The spray dryer defined by claim 13, wherein said drying chamber is closed by a top member having a central opening, said atomizing means is a rotary atomizer means projecting through said opening and introducing said dispersed droplets of feed solution to said drying space, said means for conveying said flow of gas is an annular guide duct defined by two spaced conical surfaces, said heating means is a gas burner provided between said two spaced conical surfaces and extending circumferentially around said guide duct, and said outlet directs an annular flow of heated gas converging toward said dispersed droplets of feed solution.
20. The spray dryer defined by claim 19, and further including means deflecting a portion of said gas supplied by said gas distribution means to bypass said gas burner and gases of combustion to provide a flow of gas insulating at least one of said conical surfaces from the temperature of said gas burner and said gases of combustion.
21. The spray dryer defined by claim 13, wherein said drying chamber is comprised of a cylindrical wall closed by a top member which converges toward said vertical axis, said gas distribution means is located adjacent said top member, said means for conveying said flow of gas is a conduit directing a flow of heated gas through an opening in said top member, and said atomizing means is comprised of a plurality of spray nozzles equally spaced around and supported by said top member between said opening and said cylindrical wall.
22. The spray dryer defined by claim 13, wherein said means for conveying said flow of gas from said gas distribution means includes a plurality of vanes for directing the flow of said gas in said means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US41274189A | 1989-09-26 | 1989-09-26 | |
| US412,741 | 1989-09-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2026170A1 true CA2026170A1 (en) | 1991-03-27 |
Family
ID=23634283
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002026170A Abandoned CA2026170A1 (en) | 1989-09-26 | 1990-09-25 | Gas distributor and heater for spray drying |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0493491A1 (en) |
| JP (1) | JPH05504090A (en) |
| AU (1) | AU636405B2 (en) |
| CA (1) | CA2026170A1 (en) |
| FI (1) | FI921295A0 (en) |
| WO (1) | WO1991004776A1 (en) |
| ZA (1) | ZA907568B (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5264078A (en) * | 1991-07-05 | 1993-11-23 | Aptus Inc. | Apparatus and method for spray drying solids-laden high temperature gases |
| DE19900247A1 (en) * | 1999-01-07 | 2000-07-13 | Henkel Kgaa | Spray tower for spray drying detergent ingredients or the like |
| CN100496685C (en) * | 2004-12-29 | 2009-06-10 | 中国科学院过程工程研究所 | Magnetic driven rotation gas distribution device in gas-fluid multi-phase system |
| EP3152503B1 (en) | 2014-06-04 | 2020-02-19 | GEA Process Engineering A/S | An air disperser for spray-drying, and a method for manufacturing an air disperser comprising metal forming |
| CN106461326B (en) | 2014-06-04 | 2020-02-04 | Gea工艺工程有限公司 | Air disperser of a spray drying apparatus comprising a guide vane frame and method for installing the air disperser in a spray drying apparatus |
| JP6422820B2 (en) * | 2015-05-21 | 2018-11-14 | アイエス ジャパン株式会社 | Air disperser, spray dryer drying chamber and spray cooler cooling chamber |
| EP3589398A1 (en) | 2017-03-01 | 2020-01-08 | Basf Se | Device and method for producing powdered polymers |
| WO2019075524A1 (en) * | 2017-10-20 | 2019-04-25 | The University Of Sydney | Spray dryer |
| CN112334727A (en) | 2018-06-28 | 2021-02-05 | 基伊埃工程技术股份有限公司 | Dryer and method for drying a liquid feed into a powder |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1782054A (en) * | 1927-09-01 | 1930-11-18 | Ind Spray Drying Corp | Method and apparatus for processing materials by means of gases |
| BE507042A (en) * | 1950-11-10 | |||
| NL124102C (en) * | 1959-05-02 | |||
| FR1557996A (en) * | 1968-03-22 | 1969-02-21 | ||
| DE2148051C3 (en) * | 1971-09-25 | 1975-06-12 | Krauss-Maffei Ag, 8000 Muenchen | System for heat and / or mass transfer between substances and gases, in particular atomization dryers |
| DK141671B (en) * | 1978-08-17 | 1980-05-19 | Niro Atomizer As | Gas distribution device for supplying a treatment gas to an atomization chamber. |
| US4187617A (en) * | 1978-12-18 | 1980-02-12 | Becker James J Jr | Spray dryer |
-
1990
- 1990-09-21 WO PCT/DK1990/000240 patent/WO1991004776A1/en not_active Application Discontinuation
- 1990-09-21 EP EP90914683A patent/EP0493491A1/en not_active Withdrawn
- 1990-09-21 ZA ZA907568A patent/ZA907568B/en unknown
- 1990-09-21 JP JP2513550A patent/JPH05504090A/en active Pending
- 1990-09-21 AU AU65021/90A patent/AU636405B2/en not_active Expired - Fee Related
- 1990-09-25 CA CA002026170A patent/CA2026170A1/en not_active Abandoned
-
1992
- 1992-03-25 FI FI921295A patent/FI921295A0/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05504090A (en) | 1993-07-01 |
| EP0493491A1 (en) | 1992-07-08 |
| FI921295A7 (en) | 1992-03-25 |
| WO1991004776A1 (en) | 1991-04-18 |
| FI921295A0 (en) | 1992-03-25 |
| ZA907568B (en) | 1992-05-27 |
| AU636405B2 (en) | 1993-04-29 |
| AU6502190A (en) | 1991-04-28 |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Discontinued |