Patent Publication Number: US-2005139523-A1

Title: Apparatus and method for air classification and drying of particulate matter

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS AND PRIORITY CLAIM  
      This non-provisional patent application claims priority to, and the full benefit of, Provisional Application No. 60/528,413, filed Dec. 10, 2003, and entitled “Device and Method for Air Classification and Separation of Water”. 
    
    
     TECHNICAL FIELD  
      The present invention relates generally to apparatuses and methods for separation of heterogeneous mixtures, and more specifically to an apparatus for air classification and drying of particulate matter. In particular, the present invention relates to drying solid materials by separation of the aqueous fraction and solid fraction, and removal of the water fractional component by air classification, thereby leaving only dried solids.  
     BACKGROUND OF THE INVENTION  
      Moisture remaining on particulates can interfere with physical and/or chemical processes, most particularly by facilitating packing of the finer particles, leading to formation of clumps. Such clumps can then impede mechanical and chemical processes carried out downstream from the pulverization operation.  
      Source materials for a variety of applications may be of any size and often must be broken up for use and/or drying. Materials, such as rock, utilized in physical applications, such as roadbeds, usually need not be broken, but only require removal of water. Rock utilized in chemical processes, such as gypsum or cementitious rock, often requires pulverizing to form suitably-sized particles, and usually undergoes a further chemical process prior to use. Processing of grains, such as, for exemplary purposes only, barley and/or other brewers&#39; grains, also often requires the removal of moisture.  
      Accordingly, there are various apparatuses and associated methods for drying particulate matter. Most commonly, heat, with or without air, may be utilized. Heat applied to particulate matter will raise its temperature, along with that of the bound water, until the vaporization of the water takes place. Vaporized water then departs the surface of the particulate matter and may be removed in an air stream. Although some processes require heat for further processing, such as, for exemplary purposes only, calcining of gypsum or cementitious rock, occasionally, for other materials and/or processes, such as those involving grains, it is undesirable to heat the material due to potential ensuing chemical changes and concurrent product degradation. Further, for those materials that do not require heating for further utilization in a process or product, the addition of heat energy to drive off water unnecessarily increases the cost of the overall process and/or product produced thereby. Additionally, some materials may well be damaged by the addition of heat, and it can be wholly undesirable to degrade the materials in such a fashion. Moreover, in order to facilitate the drying process and to expose a larger surface area to dry and/or heated air, particulate matter is typically broken up into smaller particles. It would be advantageous to utilize only the process of breaking apart of particles, since that would be necessary whether heat is to be utilized or not.  
      In the course of breaking particulate materials, water that is occluded within the physical structure can be released, thus enabling removal by drying or other subsequent separation method. Moreover, water may often be adsorbed upon surfaces of solid materials and thus a desorption process is necessary to separate and remove the bound water.  
      Additionally, airflow of a suspension of particles, wherein the particles impinge upon metal bars, has been utilized as a method to break up solid materials. For example, flowing material through breaker bars, knives and/or other blades, either as a solid mass or within a fluid stream will serve to break particles allowing water removal. Because it is typically desired that water be removed, use of an aqueous stream as a carrier would circumvent the purpose of the drying process; thus, the most common fluid, or medium, for suspending particulates is a stream of air. However, such a method is generally suitable for breaking up particles in gross only. Thus, while it may serve to provide various fractions of solid particles having a range of moisture content, and may even release some free water quotient, such a method fails to provide fractions of solids and water vapor, as water particles may continue to adhere to the surface of the solid particles.  
      As such, cyclones have also been utilized in concert with breaker bars for separation of moisture from solid particles. Breaking apart the solid materials into solid particles via breaker bars takes place prior to introduction of the particles into the cyclone. Typically, a flow of solid particles enters the cyclone, wherein particles having higher mass relative to water are driven to the outside of the cyclone; thereby, classifying and separating layers of finer particulates based on differing specific gravities. The moisture, having been classified by the rotation of air within the cyclone, then exits the center of the cyclone stream due to its lower density. Disadvantageously however, it has not been possible heretofore to completely separate and remove the water fraction, while leaving dry particulate matter behind, as the use of breaker bars does not provide an adequate collision energy to effectively vaporize the moisture.  
      Considering the above available methods for separating particulate matter, each is disadvantageous when compared to the present invention, as such methods and devices remove only a small portion of the water that is adsorbed on the surface of solid particles.  
      Accordingly, there is a need for an apparatus and method for air classification and drying of particulate matter, which provides a low energy device and method for removal of water, without modifying the solid matter in an undesirable fashion.  
     BRIEF SUMMARY OF THE INVENTION  
      Briefly described, in a preferred embodiment, the present invention overcomes the above-mentioned disadvantages and meets the recognized need for such an invention by providing an apparatus and method for air classification and drying of particulate matter, by atomizing water, classifying the atomized water and separating the classified atomized water from the particulate matter, wherein the particulate matter is not significantly degraded, and wherein a minimal amount of energy input is required.  
      According to its major aspects and broadly stated, the present invention in its preferred embodiment is an apparatus and method for air classification and drying of particulate matter, comprising a high-flow rate impingement system, wherein moist particles are impinged upon a steel plate or wall at a sufficiently high speed to cause atomization of water adsorbed on the particulate. The atomized water is subsequently classified within a cyclone and, the atomized water, being lighter than the solid particulate material, is removed; thus, separating the water fraction from the particulate fraction.  
      More specifically, the present invention enables the suspension of particulate matter within an air flow, wherein impact of the particulate matter, normally upon a steel plate, or at an angle upon a steel wall, causes not only the breakup of particulate matter, but also encourages atomization of the water adsorbed thereon, thus creating a fraction of water vapor for removal via classification. In the preferred form, the classification subsequently occurs within a classification cyclone, wherein the particles, including the water vapor fraction, are circulated rapidly, leading to centrifugal forces acting thereupon. The water vapor, having lower mass, is less affected by the centrifugal forces than are the solid particles. Thus, while the particulate matter accelerates towards the outside of the cyclone, the water molecules decelerate and drift to the center outlet of the cyclone, and are subsequently targeted for removal.  
      Thus, the present invention, in a generally preferred form, is an apparatus and method for air classification and drying of particulate matter to facilitate separating water from solids, wherein a suspension of solid materials having an undesirably high moisture content is carried by a high velocity airstream, for example, at approximately between 44,000 and 100,000 feet per minute. The airstream parameters are particularly regulated for the material and density of the suspension and the desired atomization of water. The airstream containing moist particulate matter is then impacted against a steel plate to atomize the water, or alternately against the steel walls of a tube carrying high volume low pressure airflow to the cyclone. The level of atomization necessary for separation of water is essentially dependent upon the speed of the material as it impacts against the steel plate or wall. The solids and water then classify in a cyclone, wherein the water fraction, having lower mass, decelerates sooner and exits the center of the cyclone.  
      Accordingly, a feature and advantage of the present invention is its ability to remove water adsorbed on particulate matter.  
      Another feature and advantage of the present invention is that it is suitable for drying heat-intolerant materials.  
      Still another feature and advantage of the present invention is that it can advantageously remove tightly adsorbed water particles from solid matter, thereby drying the solid matter.  
      Yet another feature and advantage of the present invention is its ability to break apart solid materials.  
      Yet still another feature and advantage of the present invention is its suitability for drying a variety of different materials.  
      A further feature and advantage of the present invention is that it does not require additional heat relative to other drying processes.  
      Yet still a further feature and advantage of the present invention is its suitability for incorporation in many different manufacturing processes.  
      These and other features and advantages of the present invention will become more apparent to one skilled in the art from the following description and claims when read in light of the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Having thus described the invention in general terms, the present invention will be better understood by reading the Detailed Description of the Preferred and Selected Alternate Embodiments with reference to the accompanying drawing figures, which are not necessarily drawn to scale, and in which like reference numerals denote similar structures and refer to like elements throughout, and in which:  
       FIG. 1  is a cross-sectional side view of an apparatus for air classification and drying of particulate matter according to a preferred embodiment of the present invention;  
       FIG. 2  is a detailed cross-sectional side view of the first stage of an apparatus for air classification and drying of particulate matter according to the preferred embodiment of the present invention shown in  FIG. 1 ;  
       FIG. 3  is a detailed cross-sectional side view of the second stage cyclone separator component of an apparatus for air classification and drying of particulate matter according to the preferred embodiment of the present invention shown in  FIG. 1 ;  
       FIG. 4  is a detailed cross-sectional side view of the third stage of an apparatus for air classification and drying of particulate matter according to the preferred embodiment of the present invention shown in  FIG. 1 ; and,  
       FIG. 5  is a detailed cross-sectional side view of the second stage cyclone separator component shown in  FIG. 3  of an apparatus for air classification and drying of particulate matter, according to an alternate embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED AND SELECTED ALTERNATE EMBODIMENTS  
      In describing the preferred and selected alternate embodiments of the present invention, as illustrated in  FIGS. 1-5 , specific terminology is employed for the sake of clarity. The invention, however, is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish similar functions.  
      Referring now to  FIGS. 1-4 , apparatus  10  for air classification and drying of particulate matter is preferably a multi-stage separator, preferably having a source of high flow rate air, namely, high pressure blower  12 , wherein high pressure blower  12  generates air stream  34 , and wherein air stream  34  is preferably introduced from high pressure blower  12  via tube  14  to feeder  16 . It will be recognized by those skilled in the art that any means for providing a source of high flow rate air could be substituted for high pressure blower  12 , such as, for exemplary purposes only, stored air and/or a compressor.  
      Raw material solid matter SM is preferably introduced to feeder hopper  18  and further conducted via feeder control gates  20  and metering section  22  into air stream  34 , preferably downstream from blower  12 . Although the term “solid” is utilized to describe the particulate materials undergoing treatment within apparatus  10 , the term is utilized herein in a non-limiting fashion to describe a non-aqueous particle; that is, particles treated via apparatus  10  could be semi-solid or otherwise porous, but may include water adsorbed thereon or absorbed therein. As solid matter SM is introduced, a slurry or suspension  36 , of particles and air is formed preferably in air stream  34 . The concentration, or level, of suspension  36 , that is, the ratio of cubic feet of air to pounds of wet material, is important for flow and stability of suspension  36  as is more fully described hereinbelow, wherein the heavier the particle, the higher the rate of flow required to keep it in suspension within air stream  34 . Suspension  36  is preferably accelerated to a target velocity, typically approximately between 70,000 and 100,000 feet per minute, by the forced air of air stream  34 , wherein the speed of suspension  36  is preferably selected to accommodate the type of material and the density of suspension  36  thereof. A range of between 44,000 feet per minute and 100,000 feet per minute has been found to be suitable for most materials. For example, a more dense material may require a greater velocity and/or a denser quantity of air.  
      Solid matter SM preferably travels via tube  39 , wherein bend  38  is defined in tube  39 , enabling continuation as vertical tube  40 . Preferably, solid matter SM enters atomizing cyclone  24  at a high velocity, preferably via tip outlet  42 , wherein suspension  36  is thereby preferably driven approximately normally against steel plate  44  at a high velocity, preferably at approximately between 70,000 and 100,000 feet per minute. Although a high velocity such as between 70,000 and 100,000 feet per minute is preferred, other higher or lower velocities could be utilized. As solid matter SM impacts against steel plate  44 , solid matter SM is preferably broken apart into particulates P, and water previously adsorbed to solid matter SM is preferably atomized by the force of the impact to form atomized water vapor WV. Although it is preferred that plate  44  is steel, other appropriate materials could be utilized, such as other metals, glass or plastics.  
      Referring now more particularly to  FIG. 3 , steel plate  44  is a flat plate located at top  23  of inner cylinder  26  of atomizing cyclone  24 , proximate tip outlet  42 , wherein flat plate  44  provides a hard surface for impact of particulates exiting tip outlet  42 .  
      Within inner cylinder  26 , air preferably flows in a cyclonic fashion. Air from fan  96  passes through tube  98 , branch  100 , tubes  102   a  and  102   b , branches  104   a  and  104   b , tubes  106   a ,  106   b ,  106   c  and  106   d  and outlets  108   a ,  108   b ,  108   c  and  108   d . Outlets  108   a ,  108   b ,  108   c  and  108   d  are preferably arranged in pairs  108   a  and  108   b , and  108   c  and  108   d , respectively, on opposing sides of inner cylinder  26 , penetrating inner cylinder wall  110 , such that outlets  108   a ,  108   b ,  108   c  and  108   d  preferably face nearly tangentially to the periphery of inner cylinder  26 . Air flowing through outlets  108   a ,  108   b ,  108   c  and  108   d  thus forms a cyclone of air within inner cylinder  26 . Other arrangements or means of generating a cyclonic flow of air having an appropriate velocity could alternately be utilized.  
      Atomizing cyclone  24  preferably has outer cylindrical section  28 , inner cylinder  26 , conical section  30 , top cover  31 , damper  32 , fan  50  with blades  52  (preferably driven by fan motor  54  via drive  56 ), and outlet  58  to tube  60  preferably leading to cyclone separator  62 . Preferably, air is introduced via damper  32  to flow upward between outer cylindrical section  28  and inner cylinder  26 , preferably under influence of fan  50 , wherein the flowing air preferably carries particulates P and atomized water vapor WV therewithin.  
      Air from fan  96  preferably fills lower and upper chambers  46  and  48 , respectively, of atomizing cyclone  24 . Air from fan  96 , pulled by fan  50 , preferably travels in a circular fashion, preferably creating a cyclonic updraft within cylindrical section  28  and conical section  30  of atomizing cyclone  24  carrying particulates P and water vapor WV therewithin.  
      Rotation of fan  50  is preferably designed such that its airflow  53  is exerted in the same direction as the incoming suspension  36 , pulling air toward the top of outer cylindrical section  28 . Thus, following passage downward out of inner cylinder  26  of atomizing cyclone  24 , air is preferably pulled upward by airflow  53  towards fan  50 . Upon reaching top cover  31 , airflow  53  with suspended particulates P and water vapor WV passes via outlet  58  into tube  60  and then to cyclone  62  as airflow  63 .  
      Airflow  63  preferably enters cyclone  62  via inlet  64 , wherein a preferred near tangential orientation of inlet  64  relative to cyclone  62  enables the production of a cyclonic airflow therein. Due to the action of centrifugal force within cyclone  62 , and the fact that atomized water vapor WV preferably has a lower specific gravity than particulate matter P from which it was separated, and the higher density particulate matter P preferably drifts to outer wall  65  of cylindrical section  66  of cyclone  62 , gradually falling downward through conical section  68 , wherein particulate matter P preferably exits cyclone  20  through outlet gate  70  as substantially dry material DM. Water vapor WV, having a lower density than particulate matter PM, is less affected by centrifugal forces and, therefore, drifts to center  71  of cyclone  62 . Subsequently, water vapor WV preferably exits cyclone  62  via center pickup  72  through top  74  into tube  76  to baghouse  78 .  
      Water vapor WV entering baghouse  78  preferably condenses therein, wherein water then falls to conical section  82  and is drawn out via air lock  84 , or, alternately, water vapor WV passes through top  88  of baghouse  78  via outlet  90  through tube  92 , exiting through expelling fan  94 . Expelling fan  94  preferably draws air from baghouse  78  and exhausts to the atmosphere.  
      Preferably, if any residual fine particulates remain mixed within water vapor WV, same are trapped within bag section  80  of collector  86  of baghouse  78  and contained therein. Periodically, bag section  80  of collector  86  is emptied, wherein accumulated fine particulates are removed for disposal or recycling.  
      It is envisioned in an alternate embodiment that a high speed mixer or beater cyclone may be utilized to ensure an adequate level of suspension through air stream  34 .  
      Referring now more specifically to  FIG. 5 , illustrated therein is an alternate embodiment of atomizing cyclone  24 , wherein the alternate embodiment of  FIG. 5  is substantially equivalent in form and function to that of the preferred embodiment detailed and illustrated in  FIGS. 1-4  except as hereinafter specifically referenced. Specifically, the embodiment of  FIG. 5  comprises drying separator  1000 , wherein drying separator  1000  comprises top section  1010 , middle section  1020  and bottom section  1030 . Middle section  1020  comprises upper portion  1040 , center portion  1050  and lower portion  1050 , wherein upper portion  1040  and lower portion  1050  are conical in shape.  
      Tube  14  from compressor or blower  12  (best shown in  FIGS. 1 and 2 ) comprises high pressure air at a flow rate of 1,000 feet per minute, wherein air flows through constriction  1210 , exiting tube  14  at tip  1230  into chamber  1240 . Solid material SM comprising a slurry is pumped via slurry line  1220  from feeder  16  (best shown in  FIGS. 1 and 2 ), wherein feeder  16  comprises a slurry pump (not shown). Solid material SM enters chamber  1240  proximate tip  1230 , wherein high velocity air exiting tip  1230  carries solid material SM through nozzle  1250 , causing solid material SM to become carried, along with water vapor WV, as entrained solids ES, and wherein entrained solids ES comprises heavy particulates HP and finer particulate matter P.  
      Nozzle  1250  is disposed within centrifugal air feed  1400 , wherein nozzle  1250  is positioned within approximately 1 to 3 inches from, and at an angle of approximately 45 degrees to, wall  1410  of centrifugal air feed  1400 . Air at a flow rate of 3000 feet per minute at 4 psi passes through centrifugal air feed  1400  from a high volume air source, such as fan  96 , thereby causing a cyclonic effect within bottom section  1030  and middle section  1020  of drying separator  1000 . At chamber  1240 , wherein air flow meets solid material SM, air flow is 1000 cubic feet/minute at 90 psi and airspeed is between approximately 70,000 to 100,000 feet/minute.  
      In addition to centrifugal air feed  1400  as depicted in  FIG. 5 , drying separator  1000  could comprise a second centrifugal air feeder disposed opposite to centrifugal air feeder  1400 , wherein a second flow rate of air at 0.3000 feet per minute at 4 psi could facilitate a high cyclonic effect within drying separator  1000 .  
      Conical baffle  1070  is disposed within middle section  1020 , wherein conical baffle  1070  can be selectively raised or lowered via adjusting means  1130 , and wherein adjusting means  1130  comprises threaded rod  1132  in rigid communication with conical baffle  1070  and adjusting nut  1134 . Threaded section  1136  of threaded rod  1132  is retained within block  1138 , wherein block  1138  has threads  1139  disposed therewithin, and wherein threads  1039  are adapted to receive threaded rod  1132 , thereby permitting adjustment by rotation of adjusting nut  1134 . Conical baffle  1070  is selectively adjusted to narrow or widen gap  1072 , and gap  1072  is preferably 3.5 inches when drying separator  1000  is utilized for drying of brewer&#39;s grains. The flow rate of air, water vapor WV, heavy particulates HP and particulate material P within gap  1072  is selected to be 1600 feet/minute at 4 psi for brewer&#39;s grains having a moisture content between 70% and 80%.  
      Funnel  1080  comprises straight shaft  1090  and funnel opening  1100 , wherein straight shaft  1090  is disposed partially within upper section  1010 , extending out of, and above, upper section  1010 , and wherein funnel opening  1100  is disposed within upper portion  1040  of middle section  1020 . Funnel  1080  is retained within upper section  1010  via positioning means  1120 , wherein positioning means  1120  comprises retaining frame  1122 , retaining rod  1123  and retaining nut  1124 . End  1126  of retaining rod  1123  is disposed proximate indicia  1128 , wherein the location of retaining rod  1123  proximate indicia  1128  indicates the position of funnel  1080 .  
      Sides  1110  of funnel opening  1100  extend outwardly within upper portion  1040  of middle section  1020 , and can be selectively positioned closer to, or farther from, top  1074  of conical baffle  1070  via positioning means  1120 , thereby forming space  1112 . For brewer&#39;s grains, space  1112  is preferably 4 inches.  
      Funnel  1080  comprises opening  1114 , wherein water vapor WV and particulate matter P exiting from drying separator  1000  passes through opening  1114  exiting through top  1115 , and wherein water vapor WV and particulate matter P can be selectively collected or dispersed. Upper section  1010  further comprises outlet  1300 , wherein outlet  1300  is in communication with upper section  1010  and functions to permit recovery of heavy particulates HP as more fully discussed below.  
      For example particulate matter P, heavy particulates HP and water vapor WV formed from the impact of solid material SM against wall  1410  are carried via air from fan  96  into middle section  1020  of drying separator  1000  via gap  1072 , passing around conical baffle  1070 , thereby creating a cyclonic updraft within drying separator  1000 . Heavy particulates HP, being denser than water vapor WV and particulate matter P, are carried outboard of funnel  1100  through channel  1116  into outlet  1300 , passing therethrough and exiting opening  1310 , wherein heavy particulates HP can subsequently be collected. By varying the height of conical baffle  1070  and the position of funnel  1080 , the dwell time within drying separator  1000  can be selected according to the drying needs of the material under process.  
      Further, the shape and capacity of drying separator  1000  is selected such that a dwell time of approximately 45 seconds will result for brewer&#39;s grains having a beginning moisture content of 70 to 80% at a flow rate of 2 cubic feet per min of solid material SM (as a slurry). The longer the dwell time, the drier the heavy particulates HP, wherein volume, percent moisture, and amount of moisture to be removed, will require the selection of dwell time via varying flow rate of air and solid material SM. The selected air to material ratio depends upon material density and quantity of liquid to be removed, and is selected to be approximately 4000 to 7000 cubic feet air to 2 cubic feet material.  
      Water vapor WV and particulate matter PM migrates, carried by the air stream circulating within drying separator  1000 , to the center of drying separator  1000  and, subsequently, water vapor WV and particulate matter PM are carried into funnel  1080 , exiting therefrom and continuing to cyclone  62  (best shown in  FIGS. 1 and 4 ), wherein separation of water vapor WV and particulate matter PM is implemented as described hereinabove. Particulate matter P preferably exits cyclone  20  through outlet gate  70  as substantially dry material DM. Water vapor WV, having a lower density than particulate matter PM, is less affected by centrifugal forces and. Therefore, drifts to center  71  of cyclone  62 , wherein water vapor WV preferably exits cyclone  62  via center pickup  72  through top  74  into tube  76  to baghouse  78 . Within baghouse  78 , water vapor WV condenses and any residual particulate matter PM is collected.  
      In an alternate embodiment of the present invention, it is envisioned that tip  1230  and chamber  1240  could be replaced with a convergent/divergent nozzle, wherein the air flow passes through said convergent/divergent nozzle and solid material SM enters in the fully converged portion thereof.  
      It is envisioned in another alternate embodiment that a different device than atomization by steel plate  44  for classification/separation of atomized water could be utilized, such as, for exemplary purposes only, atomization via screen material, wherein particulates of small size would pass through correspondingly-dimensioned holes in a screen and out of the atomizing cylone, while larger particles would impact on the wires of the screen and be atomized.  
      It is contemplated in still another alternate embodiment that fewer or more cyclones could be utilized, wherein treatment could be sequentially decreased or increased.  
      It is contemplated in yet another alternate embodiment that the present invention could be utilized to separate dry particulate matter P of differing densities, wherein in lieu of water vapor WV collection, tube  76  would transfer the less dense dry particulate matter P for collection.  
      It is envisioned in a further alternate embodiment that apparatus  10  could be utilized for removal of any solvent from material to be dried.  
      The foregoing description and drawings comprise illustrative embodiments of the present invention. Having thus described exemplary embodiments of the present invention, it should be noted by those skilled in the art that the within disclosures are exemplary only, and that various other alternatives, adaptations, and modifications may be made within the scope of the present invention. Merely listing the steps of the method in a certain order does not constitute any limitation on the order of the steps of the method. Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Accordingly, the present invention is not limited to the specific embodiments illustrated herein, but is limited only by the following claims.