CA2042874A1 - Counter-current air agglomerator - Google Patents
Counter-current air agglomeratorInfo
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- CA2042874A1 CA2042874A1 CA 2042874 CA2042874A CA2042874A1 CA 2042874 A1 CA2042874 A1 CA 2042874A1 CA 2042874 CA2042874 CA 2042874 CA 2042874 A CA2042874 A CA 2042874A CA 2042874 A1 CA2042874 A1 CA 2042874A1
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- chamber
- particulate matter
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- moist
- gas
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Abstract
ABSTRACT OF THE DISCLOSURE
Apparatus and agglomeration process for controlling the particle size distribution of moist fines from a vertical agglomerator wherein a countercurrent, gas-driven agglomerator is inserted between a vertical agglomerator and a fluid bed dryer so as to provide control over particle size distribution of the agglomerator.
700.68
Apparatus and agglomeration process for controlling the particle size distribution of moist fines from a vertical agglomerator wherein a countercurrent, gas-driven agglomerator is inserted between a vertical agglomerator and a fluid bed dryer so as to provide control over particle size distribution of the agglomerator.
700.68
Description
COU~TER-CURRENT AIR ~GGLC MERATO~
This invention relate6 to particle size enlargement by agglomeration of particulate m~ter into particles of S larger size. In particular, the invention concerns the agglomeration of wet or moist particles into larger size particles so that the particle size distribution of the materials is more uniform.
Backqround of the Invention Various conventi~nal processing techniques may be employed in order to form particulate matter and particle size enlargement. Such processes include spray drying, rotary and vertical agglomeration, pressure compaction, fusion, and agglomeration from liquid suspensions, all of which produce particulate materials having varying particle sizes with a wide particle size distribution.- 5ince the particle size distribution may vary widely, it is not uncommon to deal with products having particle ~izes ranging from 10 to 5,000 microns in diameter. Large particle ~ize distributions carry with it certain unsatisfactory characteristics of the product. For ~xample, the product having particle sizes of a narrower range will have decreased desegregation of the products; when mixed or ~lended with other materials, the product of uniform or near uniform particle size will mix ~ore evenly; and enlarged particle size product will reduce adver~e dust control.
In certain materials, the presence of powder will require ~ncreased agitation in order to wet the product and bring it into ~olut$o~. Also, du~ to the var~ety of ~izes there is an uneven wetting of the particles and hence the solution thereof is adversely effected. Oftentimes, large masses of material are wetted from the outside, forming a barrier of highly concentrated product, thereby preventing internal wetting and resulting in the ~ormation of large, 700.68 undispersed lumps of essentially sticky massed material.
Various methods are proposed for size enlargement of particu-late matter.
Although this problem ~ay be overco~e by ag~tating the mixture, in some instances agitation may require elabo-rate mixing equipment in order to achieve complete dissolu-tion of all the particles in a widely varying particle size composition. However, it is preferable to solve this problem by producing agglomerate powder which has more even particle size distribution. Agglomeration will produc~ a more even particle size product, which will facilitate more even dispersibility and solvation of the material, and bulk density control. These factors are related to the overall particle size distribution of the material. Other advantages of even particle size distribution include improved flowability, uniform handling and measuring, and in some ` instances bulk conveyance. Dust problems also are eliminated when very fine flocculent types of powders are no longer present.
Fluidization ic a process of holding particles in turbulent suspension by aeration with heated or cooled gases or air. At the correct velocity flow, the particles behave much like a boiling liquid. The fluidiæing action allows intimate contact between suspended particles and the ga~.
This fluidization proces~ is effective for such normal opera-tions as drying, heating, cooling, calcining, reacting or agglomerating. The fluidization proce~s ha~ no moving parts. T~e gas or air enables the product to ~low continuous-ly throug~ the fluid bed until it i6 discharged. Forming larqe part~cles from fine powdexs i~ often a problem ~or conventional processing eguip~ent~ By necessity, the powder~
must be made sticky so the material will agglomerate. Th~s often causes troublesome build-up o~ material on processing 3~
700.68 ~~~
equipment surfac2s and may result in cloqging. ~he design o~
the instant invention utilizes the benefi~s of fluid bed ~gitation, wherein the problcms as~ociated with other means for selective particle enlargemen~ are overcom~
Prior Ar~.
U.S. Pat. 3,700,461 (Dicken~ et al.) relates to a gas suspension agglomeration for agglomerating fine particles which are water wettabla/ wher~in the material to be agglo~er-ated is supplied to an entrance at the base of the chamber where it is to be wetted, and the material is suspended in a gaseous (air) medium in the chamber. This is essentially a co-current fluidization process.
U.S. Pat. 3,143,428 ~Reimers et al.) relates to separating the agqlomeration procedure into two different and successive steps. In the first step, a downwardly flowing curtain of the powde~ed material is subjected to bal~ced downwardly directed converging jets of steam, or in the alter-native to horizontal balanced opposing jets of steam.
Thereafter, the powdered mate~ial is subjected, in a separate agitation stage, to the action of downwardly directed or horizontally directed and opposed jets of either substantial-ly dry steam or air to act on the powder after it has been moistened and cause the moistened powder to move turbulently, so that there will be a sufficient number of collisions be-tween the particles in order that agglomerates ~hereof ~ill be built up. Although agglomeration is taking place in the turbulent zone, in ef~ect the solids and liquids are falling together directly onto a ~luid bed dryer. The residence time of the material~ to be agglomerated is very short in the ~agglomeration zone" and there appears to b~ litltle or no control over the particle ~ize distribution o~ ~he ulti~ate product.
700.68 ~3 U.S. Pat. 4,640,839 (~su), relates to agglomerating a water-solu~le material by pro~ecting the particulate mate-rial in a stream through a mvi~tening zone. Thl~ proce~s attempts to achieve an agglomerated product with a 6harp-edg~
granular texture. Thi~ process o~ the prior ~rt attempt~ to control product texture, or particle shape, color, and density, to resemble roast and ground coffee particles.
Therefore, this prior art process and the product produced thereby is accomplished by the addition of moisture to a relatively dry product entering the agglomerator. I is noted that the steam and compressed air pass together down-stream in a co-current movement parallel to the axis of the agglomerator and centrally located feed tube. Steam is dif-fused through the wall of the collar under very low pressure and passes downstream from the orifice at a subsonic velocity lS adjacent the stream of entering particles along and toward the axis of the stream.
, U.S. Pat. 4,197,086 (Taylor) relates to a method and apparatus for agglomerating solid, non-combustible waste material. In this device and method, solid particulate waste material is heat~d and fluidized in a bed of non-combustible granular material. The granular material is a slurry contain-ing the material to be agglomerated, which was introduced into the bed. The combustible material in ~he slurry is then partially oxidized by msan~ of heat generated by fu~l combined with material in the ~;lurry ~or dryirlg and agglomerating the material. The process of '086 involves a combustion in th~ fluid m~dia which cau~es the waste material to be agglomerated through partial oxidation, by means of the heat generated by the fuel combined with the waste material.
It i~ found in accordance with t~e present invention, that an improved agglomeration system and results in defining the particle size distribution therefrom for moist fines can be achieved . The instant invention adds a degree of process control that is absent ln the agglomeration processes of the prior art.
700.68 Summar~ of the Invention The pre~ent lnvention provide8 adYantag~ous improve-ments to agglomeratlon processes and apparatus whereby im-proved particle size distribution can be achieved.
It is found in accordance with the present invention that improved results can be and are obtainable by inserting a coun~ercurrent, air driven agglomerator between a vertical agglomerator and a fluid bed dryer. In the vertical agglomer-ator essentially dry solids and liquids are contacted and mixed together with the resulting falling particles moving downwardly into the next zone of the process. Under the present existing agglomeration technology the next zone is usually a fluid bed dryer.
Although a vertical agglomerator can be operated to effectively produce a product of a specific density or at a desired mean particle size, it offers little or no control over the particle size distribution of the agglomerate, Various factors determine the overall particle slze distribu-tion of the agglomerate. Such factors, but in no way excluding others, include residence time o the particles in the agglomerator, the initial particle size distribution of a pre-blend, and the consistency at which the ~aterial~ are fed into the system.
Therefore, the countercurrent agglomerator o~ the present invention comprises an inverted conical section sus-pension chamber, an air supply inlet port in th~ lower por-tion o~ the suspensio~ chamber and exhaust mean~ with baffles in the upper portion.
Althou~h the present invention i~ not limited by any theory of operation, it is believed that the rapidly u~ward flowing air or gas will suspend the moist fine particles entering the conical-shaped chamber from the vertical 700.68 -S-agglomerator. The partlcle~ with su~fil-ient den8ity will ~all through the chamber and exit through the bo'ctom.
Meanwhile, 'che ~uspended ~ine particles will randômly ~nove within the turbulent gas strea~ in the chamber. P.~ the popu-lation of ~he moi~;t f ine particles increa eR, the probability S of collision will increase. Hence, as the particle~ engage one another, fusion or agglomeration takes place until the resulting particle attains a density which no longer can be suspended in the turbulent gas stream and finally falls to be discharged out of the bottom of the conical chamber.
The present invention also provides an improved apparatus for treating fine moist particulate material to obtain larger desired particles. The apparatus according to this invention may incorporate means for rapidly projecting ~5 air or an inert gas upward into a section of an inverted coni~al chamber while moist material, including fine parti-cles, is fed into the section from a vertical agglomerator.
The apparatus may also include means ~or baffling the e~haust air or gas to prevent the powder feed Prom ~eing discharged in the exhaust air stream and to retain within the conical chamber the fine particles for further processing.
The apparatus of this invention operates on the general principle that a rapidly moving vertical ~rea~ of air or gas can suspand a solid particle by balancing the entrainment force with the grav~etric force. Particles leaving and falling from the vertical agglo~erator vill vary in size. ~he air or ga~ stream can be used to 6u~pend only a specif~c particle ~ize and density by adjusting the velocity of the gas or air stream. The velocity of the gas or air stream i8 dependent on ~he diameter of the ~ntraining chaFber in the invertsd conical section.
The foregoing and other objects, features and advan tages of the present invention will be more fully apparent from the detailed description of the preferred embodiments 700.68 -6-set forth below taken in conjunction with the accompallyinq drawings .
rie~ 12çsçriP~iQn o~ ~he D~nsL~
FIGo 1 iL~ a fichematic diagr~n of app~ratu3 a ::cording ~o one embodiment of the present invention.
FIG. 2 is a schematic sectional view on an enlarged scale of the apparatus illustrated in FIG. 1.
FIG. 3 is a cross sectional view taken on 3~3 on the inverse air agglomerator apparatus of this invention.
Detailed DescriPtion of the_Tnvention The apparatus illustrated in FIG. 1 includes an inlet chute for moist solids coming from the vertical agglomerator. The moist solids enter the upper portion of the i~verted conical section agglomerating chamber of ~he present invention. An air inlet means or orifice, such as a ; sparger ring, for introducing air ox a gas is mounted in ~he bottom of the conical section. The inlet means cooperated with the outer wall of the conical ~ect~on So define an annular gap which is open to discharge solids exiting the conical agglomerating chamber thereabove.
Other appropriate devices, ~uch as adjustabl~ pres-sure regulating valve to regulate the air or ga~ velocity, also may be provided for monitoring and controlling the flow rate, pressure and, if steaDI i~ use~l as the ~lui~ zing gas, to monitor and control the temperature of steam ~:uppliea to the ~nlet ~eans. The inlet means incorporates a porou~ ring 7, collar or series of tubes ~o as to def~ne an inlet for fluidizing gaseous material. Although any suitable gaseous medium may be employed as the fluidizing ga~, it has b~en found that air is particularly effective, convenient and inexpensive to enter the chamber and form a fluidized bed therein. A~r is forced through the inlet means ~n the lower 700.68 ~7~
openiny of the chamber 3 and hence through the ~ha~ber to the exhausts 4 in the upper portion 15 of the chamber 3.
T~e wall ~tructure defines an annular channel 8 sur-rounding the gas inlet ring 7. The annular channel 8 i~
mounted above a dryer means and aligned above a conveyor leading into the dryer means. The dryer chamber may be the chamber of a dryer known in the trade as a fluid bed dryer.
Such a dryer includes appropriate conventional equipment connected thereto for maintaining heated air or gas circulatiny therethrough, and at a velocity to fluidize the particles falling thereon.
Dust produced in the fluidized bed dryer is removed from the fluid bed dryer area through a separate exhaust only if fluidizing air or gas from the sparger ring 7 is in the chamber 3. A conveying system 11 removes the dry particles from the dryer 10 ready for packaginq or further proceSsing~
For example, the material is usually sifted and separated into select, oversize and fine productO The fine product can be reintroduced into the air conveying syste~ of the inverted conical chamber, while the oversize material i8 passed through necessary crushing rollers and again retuxned to the sifting device.
In the presently preferred cons~ruction, the agglo~-eration chamber 3 ~ncludes a circumferential wall 18 disposed in substantially vertical position. The wall of the chamber may be made of any ~uitable non-reactive mat2rlal usabl~ in t~e handling of the product to be treated in the cha~ber.
The chamber 3 is an inverted conical con~iguration with the greater cross-sectional area at th2 upper portion 15 of th~
chamber rather than at the lower port$on 14 th~r~o~. Main-taining a larger cross-sectional ~rea at th~ upper portion 15 of the chamber 3 rather than at the lower portion 14 de-creases the velocity of the gases in the upper port~on of the chamber. The velocity decreases because o~ the comparatively 700.6B -8-larger cross-sectional area at the upper portion 15 of th~
chamber 3. It also permits the suspension of the particulate fine matter m~intained wi~hin ~he chamber to for~
a ~'fluidized state~ o solid materlal.
"Fluidized skate~ is a term o~ art that re~ers to a s~spension of solids that oc~-urs when an upward flowing stream of gas or air passes through a mass of particulate matter to create a swift, turbulent motion. The turbulence causes the moist particles from the vertical agglomerator 2 to move in a turbulent flow and thereby creates a condition such that a large number of collisions between moist particles will occur, which in turn causes agglomeration in accordance with the theory presently believed to be descriptive of the process. The inverted con~cal shape of chamber 3 employed in the present apparatus has been found to be preferred for this action.
.
- In the vicinity of the upper portion of the inverted conical chamber on the wall thereof there are exhau6t ports 4- The exhaust ports 4 provide means for the fluidizing gases to escape from the chamber. In order to prevent fine particulates from leaving the chamber, baffle means are provided to cooperate with the exhaust port~. As shown in the Figures, the solids inlet chutes from the vertical agglomerator 2 enter the inverse air agglomerator cha~ber 3 in the vicinity and between ~Ae ba~fle mean~ 5. Such confinement as afforded by the baffle means keeps the f~ne particles and th~ entering solid~ ~rom e~it~ng the agglomeration chamber 3.
In operating the representative apparatus desoribed herein, fine particulate matter i8 ~ntroduced into ths ~n-verted conical chamber from the vertical a~glomerator throug~
the solids inlet chute. By adjusting the rate of flow of the fluidizing gas entering fro~ the lower opening, the fine 700.~8 _9_ particles can be selectively re~ained and suspended in a fluidized zone, while the larger particles from the vertical agglomerator are permitted to fall through the chamber 3 2nd exit therefrom at the botto~ op~ning 8 of the conical section. ~he a~ount o~ gas flowing through the chamber can be regulated by appropriate adjusting mean~. By maintaining the movement of the gaseous medium through the cha~,ber 3, a turbulent fluidizing flow within the chamber is established.
The turbulent flow within the chamber 3 causes the suspended moist particulate matter ~o strike against each other and to agglomerate into particles of larger size and mass. The gaseous medium passes through chamber 3 and exits through exhaust ports 4 at the upper portion 15 of the conical section. When the particles have agglomerated into suffi-cient size by continued accretion, the enlarged particles lS will overcome the buoyant force of the fluidizing gaseous medium. The agglomerated particles will then be discharged thro~gh the opening in the bottom of the conical section 8 and further directed to drying, cooling, screening and other processes .
In a vertical agglomerator 2, solids and liquid are united to produce wetted or moist product and can be operated to produce a specific density or targeted at a given ~ean particle size. However, in a v~rtical agglomerator 2, little control can be asssrted over the particle size ~i~tribution of the agglomerate produced therein.
In the in~erse agglomerator chamber 3 the ran~e of particle size distribution and the density o~ the pr~duct can be controlled separately. Therefore~ by i~creasing the residence time of a specific percentage o~ the wet ~ateri~l exiting the vertical agglomerato~ 3, time will ~e available to allow the wet material to collide with other fine particles 25 and agglomerate into larger particle~ 24. There is little or no effect on the density of the final product.
700.68 -10-The following examples illustrate the practice of t~e process in the apparatus described, but it will be und~r-stood tha~ the invention i8 no~ limited to the spQCl~ic mate-rials or apparatus describ~d therein.
EXAMPLES
Developme~t of the particle equation~ and design operation of the agglomerator of the instant invention will depend upon the followinq information.
The operation of the inverse conical agglomerator is based on the principle that a vertical stream of gas (air) can suspend a solid particle by balancing the entrainment force with the gravimetric force. Inasmuch as the size o~
the particles falling from a vertical agglomerator vary, an air stream can be used to suspend only a speci~ic particle size. Furthermore, it was found the range of particles that can be suspended within a single cha~ber having a certain diameter is a particular to the velocity of the air stream.
The size of particle suspended by an air stream with a ~iven superficial velocity can be predicted by the formula:
U = (ps - pa) (g)(d)2/18(~3 wherein U : superficial air velocity ps : density o~ solid pl : den~ity of air g : acceleration due to grsvity : viscosity of air ~ : particle diameter The superf icial velocity of an air ~trea~ i8 governed by the cross-section diameter of the entrainment chamber (the con-tainer the air passes through) and the volumetric air through-put according to the following for~ula:
U = (Va/3.1416(r)2 wherein U : superficial air velocity Va : volumetric air ~low rate r : chamber radius 700.68 With these two equations, a chamber was designed to suspend a range of particles until their collision and adhesion formed larger particl~s. Onae the particle~ became l~rge enough, the particle~ fell through the entraining a~r stream and exited the coni~al section.
A conical section chamber was designed according to the equations such that the lower portion radius was 5 inches and the upper portion radius wa~ 12 inches. The height re-quired to establish a steady flow profile was determined to l~ be 6 times the radius of th~ upper section, or, in this instance, 72 inches.
The unit was placed between a vertical agglomerator and a fluid bed dryer in a detargent pilot plant. The pro-cess in the vertical agglomerator produced detergent at the rate of 300 lb/hr. With the inverse agglo~erator conical section operating, the air flow rate ~rom the blower was adjusted to suspend and selectively agglomerate the following particle sizes:
Entrainment yeloci~y Particle Ran~ç
650 ft/min 710 pm 470 ft/min 350 ~m 170 ft/min 210 ~m 100 ft/min 150 ym For example, in order to suspend and bind the parti~les ofless than 350 microns from the vert~cal agglomerator, the air ~low czlpacity must be 1476 cu rt/min (1 a~n, 25C) to pro-duce an average air stream o~ 470 ft/~in in the inverse ag-glomerator conical section.
In another test of the inverse conical agglomerator a prototype unit was placed in-line between a vertical agglom-erator and the fluid bed dryer. Air was used as the ~luidiz-ing medium. ~ir entered the unit through a 2 inch nozzle 700. 68 -12-located in the center of the lower opening of the chamber.
The test consisted of running the proce~s at three settings:
(1~ full capaci~y (5~20 cu ft/hr~, ~2~ half capacity (2610 ~U
t~hr) and ~3) with the air to chamber off.
Samples were collected at the base of the inverse conical chamber and at the exit of the fluid bed for the three tests. These were analyzed for density and particle size distribution. The percentage o~ fines not bound to larger particles was estimated by visually determining the percentage of colored tracer particles that were unbound in the ~inal product.
The following is a summary of the results obtained during these tests:
(a) The agglomerates exiting the chamber exhibited a 50 percent decrease in the -60 mesh particles, whilP
density was only decreased by 0.5 percent;
(b) the overall particle size distribution was narrowed by 20 percent (average variance fro~ the mean) when operating the inverse conical agglomerator chamber; and (c) through the use of colored tracer particle~, it was æhown that 80 percent o~ the f~nes are bound in the vertical agglomerator, and virtually all of the - 60 mesh particle~ were bound upon ex~ting the inverse conical agglomerator chan ber .
While several embodi~nents o~ the pre~ent invention ~ave been described a~d exemplified, it will be obviou~ and clear to those ækilled in the art to which th~ invention pertains that changes and modifications can be made within the scope of the present invention. Therefore, it is the purpose of the amended claim to cover all æuch changes and 700.68 -13 modif ications as withln the true and full ~pirlt and scope of the invention.
700 . 68 -14--
This invention relate6 to particle size enlargement by agglomeration of particulate m~ter into particles of S larger size. In particular, the invention concerns the agglomeration of wet or moist particles into larger size particles so that the particle size distribution of the materials is more uniform.
Backqround of the Invention Various conventi~nal processing techniques may be employed in order to form particulate matter and particle size enlargement. Such processes include spray drying, rotary and vertical agglomeration, pressure compaction, fusion, and agglomeration from liquid suspensions, all of which produce particulate materials having varying particle sizes with a wide particle size distribution.- 5ince the particle size distribution may vary widely, it is not uncommon to deal with products having particle ~izes ranging from 10 to 5,000 microns in diameter. Large particle ~ize distributions carry with it certain unsatisfactory characteristics of the product. For ~xample, the product having particle sizes of a narrower range will have decreased desegregation of the products; when mixed or ~lended with other materials, the product of uniform or near uniform particle size will mix ~ore evenly; and enlarged particle size product will reduce adver~e dust control.
In certain materials, the presence of powder will require ~ncreased agitation in order to wet the product and bring it into ~olut$o~. Also, du~ to the var~ety of ~izes there is an uneven wetting of the particles and hence the solution thereof is adversely effected. Oftentimes, large masses of material are wetted from the outside, forming a barrier of highly concentrated product, thereby preventing internal wetting and resulting in the ~ormation of large, 700.68 undispersed lumps of essentially sticky massed material.
Various methods are proposed for size enlargement of particu-late matter.
Although this problem ~ay be overco~e by ag~tating the mixture, in some instances agitation may require elabo-rate mixing equipment in order to achieve complete dissolu-tion of all the particles in a widely varying particle size composition. However, it is preferable to solve this problem by producing agglomerate powder which has more even particle size distribution. Agglomeration will produc~ a more even particle size product, which will facilitate more even dispersibility and solvation of the material, and bulk density control. These factors are related to the overall particle size distribution of the material. Other advantages of even particle size distribution include improved flowability, uniform handling and measuring, and in some ` instances bulk conveyance. Dust problems also are eliminated when very fine flocculent types of powders are no longer present.
Fluidization ic a process of holding particles in turbulent suspension by aeration with heated or cooled gases or air. At the correct velocity flow, the particles behave much like a boiling liquid. The fluidiæing action allows intimate contact between suspended particles and the ga~.
This fluidization proces~ is effective for such normal opera-tions as drying, heating, cooling, calcining, reacting or agglomerating. The fluidization proce~s ha~ no moving parts. T~e gas or air enables the product to ~low continuous-ly throug~ the fluid bed until it i6 discharged. Forming larqe part~cles from fine powdexs i~ often a problem ~or conventional processing eguip~ent~ By necessity, the powder~
must be made sticky so the material will agglomerate. Th~s often causes troublesome build-up o~ material on processing 3~
700.68 ~~~
equipment surfac2s and may result in cloqging. ~he design o~
the instant invention utilizes the benefi~s of fluid bed ~gitation, wherein the problcms as~ociated with other means for selective particle enlargemen~ are overcom~
Prior Ar~.
U.S. Pat. 3,700,461 (Dicken~ et al.) relates to a gas suspension agglomeration for agglomerating fine particles which are water wettabla/ wher~in the material to be agglo~er-ated is supplied to an entrance at the base of the chamber where it is to be wetted, and the material is suspended in a gaseous (air) medium in the chamber. This is essentially a co-current fluidization process.
U.S. Pat. 3,143,428 ~Reimers et al.) relates to separating the agqlomeration procedure into two different and successive steps. In the first step, a downwardly flowing curtain of the powde~ed material is subjected to bal~ced downwardly directed converging jets of steam, or in the alter-native to horizontal balanced opposing jets of steam.
Thereafter, the powdered mate~ial is subjected, in a separate agitation stage, to the action of downwardly directed or horizontally directed and opposed jets of either substantial-ly dry steam or air to act on the powder after it has been moistened and cause the moistened powder to move turbulently, so that there will be a sufficient number of collisions be-tween the particles in order that agglomerates ~hereof ~ill be built up. Although agglomeration is taking place in the turbulent zone, in ef~ect the solids and liquids are falling together directly onto a ~luid bed dryer. The residence time of the material~ to be agglomerated is very short in the ~agglomeration zone" and there appears to b~ litltle or no control over the particle ~ize distribution o~ ~he ulti~ate product.
700.68 ~3 U.S. Pat. 4,640,839 (~su), relates to agglomerating a water-solu~le material by pro~ecting the particulate mate-rial in a stream through a mvi~tening zone. Thl~ proce~s attempts to achieve an agglomerated product with a 6harp-edg~
granular texture. Thi~ process o~ the prior ~rt attempt~ to control product texture, or particle shape, color, and density, to resemble roast and ground coffee particles.
Therefore, this prior art process and the product produced thereby is accomplished by the addition of moisture to a relatively dry product entering the agglomerator. I is noted that the steam and compressed air pass together down-stream in a co-current movement parallel to the axis of the agglomerator and centrally located feed tube. Steam is dif-fused through the wall of the collar under very low pressure and passes downstream from the orifice at a subsonic velocity lS adjacent the stream of entering particles along and toward the axis of the stream.
, U.S. Pat. 4,197,086 (Taylor) relates to a method and apparatus for agglomerating solid, non-combustible waste material. In this device and method, solid particulate waste material is heat~d and fluidized in a bed of non-combustible granular material. The granular material is a slurry contain-ing the material to be agglomerated, which was introduced into the bed. The combustible material in ~he slurry is then partially oxidized by msan~ of heat generated by fu~l combined with material in the ~;lurry ~or dryirlg and agglomerating the material. The process of '086 involves a combustion in th~ fluid m~dia which cau~es the waste material to be agglomerated through partial oxidation, by means of the heat generated by the fuel combined with the waste material.
It i~ found in accordance with t~e present invention, that an improved agglomeration system and results in defining the particle size distribution therefrom for moist fines can be achieved . The instant invention adds a degree of process control that is absent ln the agglomeration processes of the prior art.
700.68 Summar~ of the Invention The pre~ent lnvention provide8 adYantag~ous improve-ments to agglomeratlon processes and apparatus whereby im-proved particle size distribution can be achieved.
It is found in accordance with the present invention that improved results can be and are obtainable by inserting a coun~ercurrent, air driven agglomerator between a vertical agglomerator and a fluid bed dryer. In the vertical agglomer-ator essentially dry solids and liquids are contacted and mixed together with the resulting falling particles moving downwardly into the next zone of the process. Under the present existing agglomeration technology the next zone is usually a fluid bed dryer.
Although a vertical agglomerator can be operated to effectively produce a product of a specific density or at a desired mean particle size, it offers little or no control over the particle size distribution of the agglomerate, Various factors determine the overall particle slze distribu-tion of the agglomerate. Such factors, but in no way excluding others, include residence time o the particles in the agglomerator, the initial particle size distribution of a pre-blend, and the consistency at which the ~aterial~ are fed into the system.
Therefore, the countercurrent agglomerator o~ the present invention comprises an inverted conical section sus-pension chamber, an air supply inlet port in th~ lower por-tion o~ the suspensio~ chamber and exhaust mean~ with baffles in the upper portion.
Althou~h the present invention i~ not limited by any theory of operation, it is believed that the rapidly u~ward flowing air or gas will suspend the moist fine particles entering the conical-shaped chamber from the vertical 700.68 -S-agglomerator. The partlcle~ with su~fil-ient den8ity will ~all through the chamber and exit through the bo'ctom.
Meanwhile, 'che ~uspended ~ine particles will randômly ~nove within the turbulent gas strea~ in the chamber. P.~ the popu-lation of ~he moi~;t f ine particles increa eR, the probability S of collision will increase. Hence, as the particle~ engage one another, fusion or agglomeration takes place until the resulting particle attains a density which no longer can be suspended in the turbulent gas stream and finally falls to be discharged out of the bottom of the conical chamber.
The present invention also provides an improved apparatus for treating fine moist particulate material to obtain larger desired particles. The apparatus according to this invention may incorporate means for rapidly projecting ~5 air or an inert gas upward into a section of an inverted coni~al chamber while moist material, including fine parti-cles, is fed into the section from a vertical agglomerator.
The apparatus may also include means ~or baffling the e~haust air or gas to prevent the powder feed Prom ~eing discharged in the exhaust air stream and to retain within the conical chamber the fine particles for further processing.
The apparatus of this invention operates on the general principle that a rapidly moving vertical ~rea~ of air or gas can suspand a solid particle by balancing the entrainment force with the grav~etric force. Particles leaving and falling from the vertical agglo~erator vill vary in size. ~he air or ga~ stream can be used to 6u~pend only a specif~c particle ~ize and density by adjusting the velocity of the gas or air stream. The velocity of the gas or air stream i8 dependent on ~he diameter of the ~ntraining chaFber in the invertsd conical section.
The foregoing and other objects, features and advan tages of the present invention will be more fully apparent from the detailed description of the preferred embodiments 700.68 -6-set forth below taken in conjunction with the accompallyinq drawings .
rie~ 12çsçriP~iQn o~ ~he D~nsL~
FIGo 1 iL~ a fichematic diagr~n of app~ratu3 a ::cording ~o one embodiment of the present invention.
FIG. 2 is a schematic sectional view on an enlarged scale of the apparatus illustrated in FIG. 1.
FIG. 3 is a cross sectional view taken on 3~3 on the inverse air agglomerator apparatus of this invention.
Detailed DescriPtion of the_Tnvention The apparatus illustrated in FIG. 1 includes an inlet chute for moist solids coming from the vertical agglomerator. The moist solids enter the upper portion of the i~verted conical section agglomerating chamber of ~he present invention. An air inlet means or orifice, such as a ; sparger ring, for introducing air ox a gas is mounted in ~he bottom of the conical section. The inlet means cooperated with the outer wall of the conical ~ect~on So define an annular gap which is open to discharge solids exiting the conical agglomerating chamber thereabove.
Other appropriate devices, ~uch as adjustabl~ pres-sure regulating valve to regulate the air or ga~ velocity, also may be provided for monitoring and controlling the flow rate, pressure and, if steaDI i~ use~l as the ~lui~ zing gas, to monitor and control the temperature of steam ~:uppliea to the ~nlet ~eans. The inlet means incorporates a porou~ ring 7, collar or series of tubes ~o as to def~ne an inlet for fluidizing gaseous material. Although any suitable gaseous medium may be employed as the fluidizing ga~, it has b~en found that air is particularly effective, convenient and inexpensive to enter the chamber and form a fluidized bed therein. A~r is forced through the inlet means ~n the lower 700.68 ~7~
openiny of the chamber 3 and hence through the ~ha~ber to the exhausts 4 in the upper portion 15 of the chamber 3.
T~e wall ~tructure defines an annular channel 8 sur-rounding the gas inlet ring 7. The annular channel 8 i~
mounted above a dryer means and aligned above a conveyor leading into the dryer means. The dryer chamber may be the chamber of a dryer known in the trade as a fluid bed dryer.
Such a dryer includes appropriate conventional equipment connected thereto for maintaining heated air or gas circulatiny therethrough, and at a velocity to fluidize the particles falling thereon.
Dust produced in the fluidized bed dryer is removed from the fluid bed dryer area through a separate exhaust only if fluidizing air or gas from the sparger ring 7 is in the chamber 3. A conveying system 11 removes the dry particles from the dryer 10 ready for packaginq or further proceSsing~
For example, the material is usually sifted and separated into select, oversize and fine productO The fine product can be reintroduced into the air conveying syste~ of the inverted conical chamber, while the oversize material i8 passed through necessary crushing rollers and again retuxned to the sifting device.
In the presently preferred cons~ruction, the agglo~-eration chamber 3 ~ncludes a circumferential wall 18 disposed in substantially vertical position. The wall of the chamber may be made of any ~uitable non-reactive mat2rlal usabl~ in t~e handling of the product to be treated in the cha~ber.
The chamber 3 is an inverted conical con~iguration with the greater cross-sectional area at th2 upper portion 15 of th~
chamber rather than at the lower port$on 14 th~r~o~. Main-taining a larger cross-sectional ~rea at th~ upper portion 15 of the chamber 3 rather than at the lower portion 14 de-creases the velocity of the gases in the upper port~on of the chamber. The velocity decreases because o~ the comparatively 700.6B -8-larger cross-sectional area at the upper portion 15 of th~
chamber 3. It also permits the suspension of the particulate fine matter m~intained wi~hin ~he chamber to for~
a ~'fluidized state~ o solid materlal.
"Fluidized skate~ is a term o~ art that re~ers to a s~spension of solids that oc~-urs when an upward flowing stream of gas or air passes through a mass of particulate matter to create a swift, turbulent motion. The turbulence causes the moist particles from the vertical agglomerator 2 to move in a turbulent flow and thereby creates a condition such that a large number of collisions between moist particles will occur, which in turn causes agglomeration in accordance with the theory presently believed to be descriptive of the process. The inverted con~cal shape of chamber 3 employed in the present apparatus has been found to be preferred for this action.
.
- In the vicinity of the upper portion of the inverted conical chamber on the wall thereof there are exhau6t ports 4- The exhaust ports 4 provide means for the fluidizing gases to escape from the chamber. In order to prevent fine particulates from leaving the chamber, baffle means are provided to cooperate with the exhaust port~. As shown in the Figures, the solids inlet chutes from the vertical agglomerator 2 enter the inverse air agglomerator cha~ber 3 in the vicinity and between ~Ae ba~fle mean~ 5. Such confinement as afforded by the baffle means keeps the f~ne particles and th~ entering solid~ ~rom e~it~ng the agglomeration chamber 3.
In operating the representative apparatus desoribed herein, fine particulate matter i8 ~ntroduced into ths ~n-verted conical chamber from the vertical a~glomerator throug~
the solids inlet chute. By adjusting the rate of flow of the fluidizing gas entering fro~ the lower opening, the fine 700.~8 _9_ particles can be selectively re~ained and suspended in a fluidized zone, while the larger particles from the vertical agglomerator are permitted to fall through the chamber 3 2nd exit therefrom at the botto~ op~ning 8 of the conical section. ~he a~ount o~ gas flowing through the chamber can be regulated by appropriate adjusting mean~. By maintaining the movement of the gaseous medium through the cha~,ber 3, a turbulent fluidizing flow within the chamber is established.
The turbulent flow within the chamber 3 causes the suspended moist particulate matter ~o strike against each other and to agglomerate into particles of larger size and mass. The gaseous medium passes through chamber 3 and exits through exhaust ports 4 at the upper portion 15 of the conical section. When the particles have agglomerated into suffi-cient size by continued accretion, the enlarged particles lS will overcome the buoyant force of the fluidizing gaseous medium. The agglomerated particles will then be discharged thro~gh the opening in the bottom of the conical section 8 and further directed to drying, cooling, screening and other processes .
In a vertical agglomerator 2, solids and liquid are united to produce wetted or moist product and can be operated to produce a specific density or targeted at a given ~ean particle size. However, in a v~rtical agglomerator 2, little control can be asssrted over the particle size ~i~tribution of the agglomerate produced therein.
In the in~erse agglomerator chamber 3 the ran~e of particle size distribution and the density o~ the pr~duct can be controlled separately. Therefore~ by i~creasing the residence time of a specific percentage o~ the wet ~ateri~l exiting the vertical agglomerato~ 3, time will ~e available to allow the wet material to collide with other fine particles 25 and agglomerate into larger particle~ 24. There is little or no effect on the density of the final product.
700.68 -10-The following examples illustrate the practice of t~e process in the apparatus described, but it will be und~r-stood tha~ the invention i8 no~ limited to the spQCl~ic mate-rials or apparatus describ~d therein.
EXAMPLES
Developme~t of the particle equation~ and design operation of the agglomerator of the instant invention will depend upon the followinq information.
The operation of the inverse conical agglomerator is based on the principle that a vertical stream of gas (air) can suspend a solid particle by balancing the entrainment force with the gravimetric force. Inasmuch as the size o~
the particles falling from a vertical agglomerator vary, an air stream can be used to suspend only a speci~ic particle size. Furthermore, it was found the range of particles that can be suspended within a single cha~ber having a certain diameter is a particular to the velocity of the air stream.
The size of particle suspended by an air stream with a ~iven superficial velocity can be predicted by the formula:
U = (ps - pa) (g)(d)2/18(~3 wherein U : superficial air velocity ps : density o~ solid pl : den~ity of air g : acceleration due to grsvity : viscosity of air ~ : particle diameter The superf icial velocity of an air ~trea~ i8 governed by the cross-section diameter of the entrainment chamber (the con-tainer the air passes through) and the volumetric air through-put according to the following for~ula:
U = (Va/3.1416(r)2 wherein U : superficial air velocity Va : volumetric air ~low rate r : chamber radius 700.68 With these two equations, a chamber was designed to suspend a range of particles until their collision and adhesion formed larger particl~s. Onae the particle~ became l~rge enough, the particle~ fell through the entraining a~r stream and exited the coni~al section.
A conical section chamber was designed according to the equations such that the lower portion radius was 5 inches and the upper portion radius wa~ 12 inches. The height re-quired to establish a steady flow profile was determined to l~ be 6 times the radius of th~ upper section, or, in this instance, 72 inches.
The unit was placed between a vertical agglomerator and a fluid bed dryer in a detargent pilot plant. The pro-cess in the vertical agglomerator produced detergent at the rate of 300 lb/hr. With the inverse agglo~erator conical section operating, the air flow rate ~rom the blower was adjusted to suspend and selectively agglomerate the following particle sizes:
Entrainment yeloci~y Particle Ran~ç
650 ft/min 710 pm 470 ft/min 350 ~m 170 ft/min 210 ~m 100 ft/min 150 ym For example, in order to suspend and bind the parti~les ofless than 350 microns from the vert~cal agglomerator, the air ~low czlpacity must be 1476 cu rt/min (1 a~n, 25C) to pro-duce an average air stream o~ 470 ft/~in in the inverse ag-glomerator conical section.
In another test of the inverse conical agglomerator a prototype unit was placed in-line between a vertical agglom-erator and the fluid bed dryer. Air was used as the ~luidiz-ing medium. ~ir entered the unit through a 2 inch nozzle 700. 68 -12-located in the center of the lower opening of the chamber.
The test consisted of running the proce~s at three settings:
(1~ full capaci~y (5~20 cu ft/hr~, ~2~ half capacity (2610 ~U
t~hr) and ~3) with the air to chamber off.
Samples were collected at the base of the inverse conical chamber and at the exit of the fluid bed for the three tests. These were analyzed for density and particle size distribution. The percentage o~ fines not bound to larger particles was estimated by visually determining the percentage of colored tracer particles that were unbound in the ~inal product.
The following is a summary of the results obtained during these tests:
(a) The agglomerates exiting the chamber exhibited a 50 percent decrease in the -60 mesh particles, whilP
density was only decreased by 0.5 percent;
(b) the overall particle size distribution was narrowed by 20 percent (average variance fro~ the mean) when operating the inverse conical agglomerator chamber; and (c) through the use of colored tracer particle~, it was æhown that 80 percent o~ the f~nes are bound in the vertical agglomerator, and virtually all of the - 60 mesh particle~ were bound upon ex~ting the inverse conical agglomerator chan ber .
While several embodi~nents o~ the pre~ent invention ~ave been described a~d exemplified, it will be obviou~ and clear to those ækilled in the art to which th~ invention pertains that changes and modifications can be made within the scope of the present invention. Therefore, it is the purpose of the amended claim to cover all æuch changes and 700.68 -13 modif ications as withln the true and full ~pirlt and scope of the invention.
700 . 68 -14--
Claims (7)
1. The process of producing sized agglomerated material from moist fine particulate matter which comprises the steps of (a) introducing moist fine particulate matter con-sisting of individual particles, into the top of an inverted conical chamber in the form of free falling particles;
(b) suspending said particulate matter in an upward countercurrent gas flow;
(c) subjecting said moist particulate matter to violent random movement within the gas flow; said gas flow at a sufficient velocity to impart turbulence to said moist particulate matter so as to cause them to form enlarged agglomerated particles while supported by said gas flow;
(d) allowing the moist enlarged agglomerated particles to fall downwards out of the inverted conical chamber into a means for drying said moist agglomerated particles.
(b) suspending said particulate matter in an upward countercurrent gas flow;
(c) subjecting said moist particulate matter to violent random movement within the gas flow; said gas flow at a sufficient velocity to impart turbulence to said moist particulate matter so as to cause them to form enlarged agglomerated particles while supported by said gas flow;
(d) allowing the moist enlarged agglomerated particles to fall downwards out of the inverted conical chamber into a means for drying said moist agglomerated particles.
2. The process of Claim 1 wherein the gas for said gas flow is air.
3. The process of controlling the particle size distribution of agglomerated material formed from moist fine particulate matter comprising the steps:
(a) introducing said moist fine particulate matter into an inverted conical chamber in the form of free falling particles;
(b) suspending said fine particulate matter in a countercurrent flow of gas at a selected velocity to yield a predetermined particle size distribution;
700.68 -15-(c) agglomerating the suspended particulate matter into particles of sufficient particle size to overcome the suspending action of the counter flow of gas; and (d) removing the agglomerated particle from the chamber.
(a) introducing said moist fine particulate matter into an inverted conical chamber in the form of free falling particles;
(b) suspending said fine particulate matter in a countercurrent flow of gas at a selected velocity to yield a predetermined particle size distribution;
700.68 -15-(c) agglomerating the suspended particulate matter into particles of sufficient particle size to overcome the suspending action of the counter flow of gas; and (d) removing the agglomerated particle from the chamber.
4. The process of Claim 3 wherein said moist fine particulate matter is introduced into said conical chamber from a vertical agglomerator having a wide initial particle size distribution.
5. Apparatus for producing sized agglomerated material from moist fine particulate matter comprising an agglomerating chamber which is substantially a vertical inverted conical form having top and bottom openings wherein the bottom opening is of a smaller cross-sectional area than the top opening;
means for substantially continuously supplying said moist fine particulate matter downwardly through the top opening into said agglomerating chamber;
means for upwardly introducing in a countercurrent manner fluidizing gas into said chamber in proximity with said bottom opening, said fluidizing gas having sufficient velocity to suspend and impart sufficient turbulence to said moist fine particulate matter within the agglomerating chamber to as to cause said particles to agglomerate together, said agglomerated particles thereafter overcoming the suspending velocity of the fluidizing gas and falling out of said chamber through the bottom opening thereof for further processing;
exhaust means near the top opening for exit of the fluidizing gas;
and means for drying the agglomerated particles;
falling out of said agglomerating chamber.
700. 68 -16-
means for substantially continuously supplying said moist fine particulate matter downwardly through the top opening into said agglomerating chamber;
means for upwardly introducing in a countercurrent manner fluidizing gas into said chamber in proximity with said bottom opening, said fluidizing gas having sufficient velocity to suspend and impart sufficient turbulence to said moist fine particulate matter within the agglomerating chamber to as to cause said particles to agglomerate together, said agglomerated particles thereafter overcoming the suspending velocity of the fluidizing gas and falling out of said chamber through the bottom opening thereof for further processing;
exhaust means near the top opening for exit of the fluidizing gas;
and means for drying the agglomerated particles;
falling out of said agglomerating chamber.
700. 68 -16-
6. The apparatus according to Claim 5 wherein said exhaust means is a baffled exhaust means whereby agglomerated moist fine particles are prevented from leaving said agglomerating chamber with the exiting fluidizing gas.
7. The apparatus according to Claim 5 wherein said top opening cooperates with the outlet of a vertical agglomerator to provide moist fine particulate matter to said conical agglomerating chamber.
700.68 -17-
700.68 -17-
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2042874 CA2042874A1 (en) | 1991-05-17 | 1991-05-17 | Counter-current air agglomerator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2042874 CA2042874A1 (en) | 1991-05-17 | 1991-05-17 | Counter-current air agglomerator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2042874A1 true CA2042874A1 (en) | 1992-11-18 |
Family
ID=4147620
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2042874 Abandoned CA2042874A1 (en) | 1991-05-17 | 1991-05-17 | Counter-current air agglomerator |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2042874A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110048317A1 (en) * | 2009-08-31 | 2011-03-03 | Heat And Control, Inc. | Portable, compact, food seasoning replenishment system |
-
1991
- 1991-05-17 CA CA 2042874 patent/CA2042874A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110048317A1 (en) * | 2009-08-31 | 2011-03-03 | Heat And Control, Inc. | Portable, compact, food seasoning replenishment system |
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