US20060081513A1 - Sorting recycle materials with automatically adjustable separator using upstream feedback - Google Patents

Abstract

Methods and systems are provided for controlling an automatic separator apparatus of a Materials Recovery Facility. An input stream of recycled materials is provided, wherein the composition of the input stream is subject to variation during a time interval. At least one characteristic of the input waste material stream is measured. An initial value is selected for an adjustable parameter of the automatic separator apparatus based upon the measured characteristic of the input stream.

Description

• This is a Utility Patent Application filed by Garry R. Kenny, a citizen of the United States, residing in West Linn, Oreg. 97068, in an invention entitled “Sorting Recycled Materials With Automatically Adjustable Separator Using Upstream Feedback”
• This application claims benefit of U.S. Provisional Patent Application No. 60/600,206, filed Aug. 10, 2004, entitled “Materials Recovery Facility Process Optimization Via Unit Operation Feedback”, the details of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates generally to the field of sorting of recycled materials, and more particularly, but not by way of limitation, to methods and apparatus for optimizing the operation of an adjustable sorting apparatus or sorting system.
• 2. Description of Prior Art
• Materials Recovery Facilities (MRFs) have been receiving and processing recyclable materials for the past 25 years. The recyclable material normally consists of newspaper, plastic bottles, steel and aluminum cans, and sometimes glass bottles and fragments. The newspaper stream was typically kept separate from the containers. During the first five to ten years the processing typically involved conveying the recyclables under a magnet to remove the steel, then past an air stream to separate the plastic and aluminum cans from the glass bottles. The rest of the components were then sorting manually by hand.
• In the mid 1980s eddy current separators were introduced to automatically remove the aluminum from the plastic bottle and aluminum can stream. Then in the mid 1990s separation modules became available to separate the plastic bottles by resin type and by color. These separators did not, however, begin use in MRFs until around 1998. At about the same time the first system to automatically sort office paper was introduced by the assignee of the present invention (MSS, Inc.) in collaboration with Weyerhaeuser Company. An example of those systems is seen in U.S. Pat. No. 6,250,472 to Grubbs et al., assigned to assignee of the present invention and the details of which are incorporated herein by reference.
• Mechanical screens saw limited use in MRFs until the late 1990s when the first cardboard screens were introduced. These screens were used to remove oversize cardboard from the newspaper stream. With the introduction of so called “single stream” collection in the late 1990s, however, screen technology was improved to address sorting of containers (i.e. plastic and glass bottles and metal cans) from the mixed paper and cardboard stream.
• The first generation of screens involved either one or two flat bed screen “decks” which were inclined in the direction of motion of the material. The screens themselves were comprised of a number of discs attached to rotating shafts. In operation, the more 3 dimensional materials such as containers would tend to roll or bounce down the screen deck while more 2 dimensional materials such as newspaper and cardboard would go up and over the top of the screen. An example of inclined flat bed rotary disc screens is seen in U.S. Pat. No. 6,250,472 to Grubbs et al.
• This screen technology evolved to where the angle of the screen, as well as the rotor speed, was adjustable to compensate for differing material composition and moisture content. The latest generation screen patented by CP Manufacturing is in the shape of a wide bottom V, with the entire V bottom tilted from horizontal. This screen has additional adjustable settings with include not only the rotor speed and tilt angle of the V sides, but also the tilt angle of the entire V. In this screen the paper is propelled by the discs up and over each side of the V. The containers roll back from the sides of the V and migrate down the bottom of the V in the direction of the tilt. Examples of such V shape rotary disc separators are seen in U.S. Pat. No. 6,460,706 to Davis and U.S. Pat. No. 6,648,145 to Davis et al., the details of which are incorporated herein by reference.
• Unfortunately, however, very few MRF operators are capable of determining the optimum operating parameters for these new screens. Experience in MRFs also shows that even when the screens are properly set for a certain mixture of recyclables and moisture content, that setting is only good for a matter of a few minutes as the composition and moisture content changes.
• FIG. 1 schematically illustrates the flow of material through a typical prior art Materials Recovery Facility (MRF) generally designated by the numeral10. An inputwaste material stream12 enters the MRF10. As indicated atblock14 oversized and non-recyclable objects are removed by hand.
• As indicated at block16 a screening device may be used to separate large cardboard items which go to acardboard destination18. The bulk of the material which is made up typically of containers of various types and newspaper goes to amechanical screening device20 which separates the newspaper from the containers. Themechanical screening device20 may for example be an adjustable angle trough-shaped screen such as those shown for example in U.S. Pat. Nos. 6,648,145 and 6,460,706.
• Thescreening device20 separates the material stream into a first stream orpaper stream22 which includes some containers, and a second stream orcontainer stream24 which includes some paper.
• Typically thepaper stream22 is hand sorted as indicated atblock25 into acontainer destination26, apaper destination28, acontaminant destination30, and with ferrous and aluminum materials directed todestinations34 and44, respectively.
• The container stream24 fromseparator20 then passes through amagnetic separator32 which removes ferrous items into aferrous metal stream34. The container stream continues at36 to ahand sorting location38 where newspaper is removed at40 and returned to thenewspaper destination28, and the containers are hand sorted into plastic containers which go todestination42 and aluminum containers which go to destination44.
• The plastic containers atdestination42 are then again hand sorted as indicated byblock46 into PET (Polyethylene Terephalate) containers todestination48, colored HDPE (High Density Polyethylene) todestination50, and natural HDPE (High Density Polyethylene) todestination52.
• What is needed then is a way to optimize the screen parameter settings and to modify those settings in real time as the composition and moisture content of the feedstream changes continuously. Even when set optimally the screens are not 100% effective. Containers (particularly flat ones) are sometimes carried over with the paper fraction, and as well some paper is carried along with the containers.
• What is also needed is a way to optimize all of or a portion of a Materials Recovery Facility which includes one or more adjustable screens.
SUMMARY OF THE INVENTION
• In one embodiment the invention provides a method of separating an input waste material stream. The method includes measuring at least one characteristic of the input waste material stream correlating to a density of the input waste material stream. An initial value is selected for an adjustable parameter of an adjustable material separator based upon the at least one characteristic measured. The input waste material stream is separated with the adjustable material separator into a first output stream containing a majority of a first material and some of a second material, and a second output stream containing a majority of the second material and some of the first material.
• In another embodiment the present invention provides a method of sorting recycled materials, comprising:
• (a) providing an input stream of recycled materials, wherein a composition of the input stream is subject to variation during a time interval;
• (b) moving the input stream through a separator machine having a plurality of adjustable machine operating parameters;
• (c) providing stored historical data representative of a set of historical values of the operating parameters corresponding to improved quality of separation for given values of a characteristic of said input stream;
• (d) sensing a present value of said characteristic of said input stream; and
• (e) adjusting said plurality of adjustable machine operating parameters, via a computerized control system, in response to said sensed present value of said characteristic of said input stream so that said adjustable machine operating parameters approach said historical values of the adjustable machine operating parameters corresponding to improved quality of separation for said sensed present value of said characteristic of said input stream.
• In another embodiment the invention provides an automated separator apparatus for separating an input material stream into first and second output streams, including a plurality of spaced rotating discs defining a screen having a length, a first actuator for adjusting an angle of inclination of said length, a second actuator for adjusting a rotational speed of said rotating discs, a sensing unit for sensing at least one characteristic of said input material stream, and a control system responsive to said sensing unit and operably connected to said actuators, so that said screen automatically adjusts to changes in the sensed characteristic of said input material stream.
• Accordingly, it is an object of the present invention to provide methods of adjusting the operation of an adjustable separator, using upstream feedback.
• Another object of the present invention to provide improved methods of adjusting the operation of an adjustable separator based upon the density of an incoming material stream.
• And another object of the present invention is to provide methods of automated control of adjustable separators.
• Still another object of the present invention is the provision of methods and systems for continuously monitoring and adjusting the operation of a material separator to improve the efficiency of operation of the separator.
• Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the following disclosure when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a flow chart of a typical prior art Materials Recovery Facility.
• FIG. 2 is a schematic flow chart of the Materials Recovery Facility of the present invention utilizing automated sorting devices, and utilizing sensors and counting technology for automating the control of the sorting devices.
• FIG. 3 is a schematic vertical elevation view of a trough shape rotary disc screening apparatus.
• FIG. 4 is a plan view of the apparatus ofFIG. 3.
• FIG. 5 is a view similar toFIG. 3 illustrating the mechanism for adjusting the V angle of the separator ofFIGS. 3 and 4.
• FIG. 6 is a schematic side elevation view of the apparatus ofFIGS. 3-5 showing the manner of adjustment of the inclination along the length of the trough.
• FIG. 7 is a schematic side elevation view of an alternative separator system including two inclined flat bed rotary disc screening devices.
• FIG. 8 is a schematic illustration of the computerized control system.
• FIG. 9 is a graphical representation of separating efficiency versus throughput or feed rate for a mechanical or automated separator.
• FIG. 10 is a graphical representation of the operating cost of mechanical equipment as a function of time of operation.
• FIG. 11 is a first graphical representation of manual labor costs versus time of operation where labor is available on an hourly basis.
• FIG. 12 is a graphical representation of manual labor costs versus time of operation when labor is only available in larger increments due to shift work requirements.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• The Overall MRF System
• Referring now toFIG. 2, the Materials Recovery Facility (MRF) of the present invention is shown and generally designated by the numeral200.FIG. 2 schematically illustrates the major components of and the material flow through theMaterials Recovery Facility200.
• An inputwaste material stream202 enters theMRF200. As indicated atblock204, oversized and non-recyclable objects are removed by hand.
• A weight andprofile sensor206 and amoisture sensor208 are provided to monitor the weight, the height profile and the moisture content of theinput material stream202.
• As indicated at block210 a largearticle screening device210 may be used to separate large cardboard items which go to acardboard destination212.
• The bulk of the material which is typically made up of containers of various types and newspaper goes to amechanical screening device214 which may, for example, be an adjustable angle trough shape screening device such as that further described below with regard toFIGS. 3-6. Alternatively the screening device may include inclined flat bed screens like those described below with regard toFIG. 7 or other suitable screening devices.
• Thescreening device214 separates the material stream into a first stream orpaper stream216 which includes some containers, and a second stream orcontainer stream218 which includes some paper.
• As further described below, the weight andprofile sensors206 andmoisture sensor208 will be used to provide, among other things, an initial estimation of the composition of theincoming material stream202 for the initial setting of operating parameters on theadjustable screening device214.
• Thepaper stream216 is carried to afirst sorting module220, which may for example be a FiberSort™ module, available from Advanced Sorting Technologies of Nashville, Tenn. Thefirst sorting module220 separates thepaper stream216 into anewspaper stream222, asecondary container stream224 and acontaminant stream226. Thecontaminant stream226 fromfirst separator220 may include cardboard, six pack carriers, pizza boxes, frozen food boxes and the like.
• Thefirst sorting module220 has associated therewith afirst sensing device228 which counts the number of items of various types flowing into thenewspaper stream222, thesecondary container stream224 and thecontaminant stream226. As is further disclosed below, this counting is preferably done on the basis of area so that what is actually counted is the area occupied by the various streams on a conveyor as they pass through thefirst sorting module220. As further described below, the data collected from thefirst sensing device228 and other sensing devices to be described below, is utilized with an automated control system (seeFIG. 8) to adjust various operating parameters of the automated equipment and to adjust flow rates for various portions of the MRF in order to optimize the operation of the MRF as desired or necessary.
• Thecontainer stream218 exiting theseparator apparatus214 passes through amagnetic separator230 which removes ferrous items into aferrous metal stream232. Thecontainer stream218 then flows to asecond sorting module234. Thesecond sorting module234 may also be a FiberSort™ module from Advanced Sorting Technologies, similar to thefirst sorting module220 described above. Thesecond sorting module234 separates thecontainer stream218 into aplastic container stream236, analuminum container stream238 and asecondary newspaper stream240.
• Thesecond sorting module234 has asecond sensing device242 associated therewith which counts the plastic containers, aluminum containers and newspaper sorted by thesecond sorting module234. Again, this counting is preferably done on the basis of the area of the conveyor belt or other conveyor mechanism passing throughsorting module234 which is occupied by the various materials.
• Thesupplemental newspaper stream240 is returned to and joined with themain newspaper stream222 exitingfirst sorting module220. Similarly, thesecondary container stream224 existingfirst sorting module220 is returned to thecontainer stream218 upstream ofmagnetic separator230.
• Theplastic container stream236 passes to athird sorting module244. Thethird sorting module244 may for example be an Aladdin™ or Sapphire™ sorting module, each available from MSS, Inc., which provide sorting of different types of plastic containers. Sortingmodule244 sorts theplastic container stream236 into a PET (Polyethylene Terephalate)container stream246, a colored HDPE (High Density Polyethylene)stream248, and a natural HDPE (High Density Polyethylene)stream250.
• Third sorting module244 has athird sensing device252 associated therewith for sensing and counting the number of containers in thePET stream246, thecolored HDPE stream248, and thenatural HDPE stream250.
• The sensor systems used in each of the sorting modules described above such as the Aladdin™, Sapphire™ or FiberSort™ sorting modules available from MSS, Inc., divide the area on the conveyor belt into an array of pixels. Each pixel is scanned by the sensor to determine various measurable characteristics of the material located in that pixel. The data representative of each scanned pixel is then compared to a set of data maps and either matches one of the known data maps or is determined to be an unknown material, or is determined not to be an object at all. For example, the maps may be representative of metal, plastic, paper or other material. Thus each pixel, and accordingly each increment of area on the conveyor belt passing below the sensor, is identified as either being: (1) metal, (2) plastic, (3) paper, or (4) other. Periodically thecontrol system300 described below with regard toFIG. 8 will query the sensor units and the units will send the count total for the number of pixels falling in each category to themicroprocessor304, and then reset the counts to zero. Alternatively, the unit could calculate a moving average of each count type over some period (such as one minute) and then report those values directly to themicroprocessor304 when asked. Themicroprocessor304 will use the four count totals or averages to calculate the percentage of each material in the feedstream and the total feed rate, if desired. This pixel count is representative of the area that each of the identified material types occupies on the conveyor. This information will then be used to optimize the feed system.
• The V Shape Rotary Disc Screen
• One preferred separator apparatus for use as theseparator apparatus214 ofFIG. 1 is the adjustable V shape trough type rotary disc screen available from CP Manufacturing previously noted. Such an adjustable screening device is schematically illustrated inFIGS. 3-6 and referred to by the numeral214A. The V troughstyle separator apparatus214A is preferably constructed in accordance with the teachings of U.S. Pat. No. 6,648,145 to Davis et al., the details of which are incorporated herein by reference.
• Theseparator apparatus214A is in the form of a trough-shapeddisc screen112 equipped with a pair ofseparator air manifolds114 and116. Referring toFIGS. 3 and 4, therecycling apparatus214A includes aframe118 that rotatably supports a plurality of laterally extendingshafts119 that spin about laterally extending axes such as120. Theshafts119 of the trough-shapeddisc screen112 are longitudinally spaced and are located at progressive heights to provide a generally V-shaped configuration as best seen inFIG. 3. The shaft that rotates about the axis120 (FIG. 4) and the additional shafts to the left ofaxis120 are rotated by amotor122 through adrive linkage124 in a counter-clockwise direction inFIG. 3. The shafts to the right of the axis120 (FIG. 4) are rotated by another motor126 (FIG. 3) via adrive linkage128 to rotate thediscs129 on these shafts in a clockwise direction inFIG. 3. Thedrive linkages124 and128 preferably each include a plurality of sprockets (not illustrated) which are mounted to the ends of theshafts119 and a plurality of separate chains (not illustrated) entrained about these sprockets. Sprockets (not illustrated) are also mounted on separate gear reduction assemblies (not illustrated) driven by each of themotors122 and126. Theshafts119 could be driven directly or indirectly with gears, belts, chain drives, transmissions, electric motors, hydraulic motors, internal combustion engines, and various combinations of these drive means.
• Theinput stream12 of mixed recyclable materials is carried by a conveyor130 (FIG. 3) and deposited onto alowermost region131 of the trough-shapeddisc screen112. While thediscs129 are referred to as “discs” they preferably have an irregular outer contour or shape so that when all of theshafts119 of therecycling apparatus214A are rotated, mixed recyclable materials deposited thereon will be agitated and moved along in various conveying directions. In accordance with well known techniques, the spacing of thediscs129 and the resulting dimensions of the openings therebetween determines the size of the materials that will fall downwardly between thediscs129.
• The shafts of thelowermost region131 are preferably slightly downwardly angled from the horizontal, at an angle, for example, of about five degrees. The spacing of thediscs129 along the various shafts of the trough-shapeddisc screen112 and the angle of vertical inclination of the two verticallyinclined regions112A and112B of thedisc screen112, along with the rotational speed of these discs, is adjustable as further described below.
• Optimum classification by therecycling apparatus110 is enhanced by theair manifolds114 and116 which are connected tosquirrel cage blowers132 and134 (FIG. 4). Themanifolds114 and116 may be formed of segments of plastic or metal pipe with holes bored therein at intervals to form nozzles that eject streams of air toward thediscs129 to press newspaper against the discs and aid in thediscs129 conveying the same upwardly. Preferably the streams of air are inclined to help advance the newspaper upwardly. Each of theair manifolds114 and116 includes a plurality of laterally extending and longitudinally spaced conduits each having a plurality of laterally spaced nozzles. The conduits are coupled to a longitudinally extending header, the headers being connected to respective ones of theblowers132 and134. These conduits are positioned sufficiently close to the first and second verticallyinclined regions112A and112B so that containers that are partially conveyed upwardly along the first and second verticallyinclined regions112A and112B can tumble over the first andsecond air manifolds114 and116. Other sources of pressurized air besides thesquirrel cage blowers132 and134 may be utilized, such as fans, pumps, pressurized tanks, and so forth.
• The lateral spacing between thediscs129 of thelowermost region131 is less than the lateral spacing between thediscs129 of the verticallyinclined regions112A and112B. Broken glass falls downwardly between thediscs129 of thelowermost region131 of the trough-shapeddisc screen112. Mixed recyclable materials fall through thediscs129 located along the intermediate portions of the verticallyinclined regions112A and112B. Newspaper is conveyed upwardly over the output ends at the upper terminal ends of the verticallyinclined regions112A and112B to thenewspaper stream222. Large articles such as plastic milk bottles and soda pop containers tumble down the verticallyinclined regions112A and112B of the V-shapeddisc screen112 and eventually fall off of the side of therecycling apparatus214A to thecontainer stream224. Preferably the axes of theshafts119 of theinclined region112A all extend in a first common plane and the axes of the shafts of theinclined region112B all extend in a second common plane.
• Thus a stream of mixed recyclable materials is conveyed onto one side of the V-shapeddisc screen112 by theconveyor130 at the end marked “INFEED” inFIG. 4 and large articles are conveyed out of the other side of the V-shapeddisc screen112 at the side marked “CONTAINERS OUT” inFIG. 4.
• FIG. 5 is a view similar toFIG. 3 but illustrating the structure and manner of adjustment of the V angle of theseparator apparatus214A ofFIG. 3. Theinclined portions112A and112B are pivotally mounted to abase frame portion136 viapivot assemblies138 and140. Thepivot assemblies138 and140 comprise selected ones of theshafts119 that support thediscs129. Lifting devices in the form ofhydraulic cylinders142 and144 are provided for independently varying the angle ofinclination146 of theinclined sections112A and112B to adjust and optimize the separation of mixed recyclable materials. The liftingdevices142 and144 can be any other conventional lifting devices such as motorized jack screws, pneumatic lifters, and equivalent mechanical mechanisms used in heavy machinery to lift and move large frame members.
• The articulating V shapedisc screen apparatus214A ofFIG. 5 also incorporatesinternal air ducting148 and150 which feedsair manifolds152 to provideair jets154 blowing onto the face of theinclined screen portions112A and112B to aid in holding newspaper against the inclined portions.
• As schematically illustrated in the side elevation view ofFIG. 6, thebase frame136 of theseparator apparatus214A is also inclined along itslength156, which is generally parallel to theaxis120 ofFIG. 4. An angle ofinclination158 along thelength156 is adjustable by a lifting means160 which pivots theframe136 about apivot point162. The lifting means160 may be a hydraulic cylinder or any of the other suitable lifting means described above with regard to lifting means142 and144.
• Inclined Flat Bed Screens
• Referring now toFIG. 7, analternative separator apparatus214B includes a pair of inclinedflat bed screens164 and166. Theflat bed screens164 and166 may, for example, be constructed in accordance with the teachings of U.S. Pat. No. 6,250,472 to Grubbs et al. with reference toFIGS. 8 and 9 thereof, the details of which are incorporated herein by reference. The inclinedflat bed screens164 and166 may also be constructed in accordance with the teachings of U.S. Pat. No. 6,460,706 to Davis, with reference toFIGS. 1-3 thereof, the details of which are incorporated herein by reference.
• Each of the flat bed screens such asscreen164 includes a plurality of shafts such as168 seen in end view inFIG. 7, having discs such as170 rotatable with theshaft168. Theshafts168 are mounted upon aframe172 which is pivotable about apivot point174 due to liftingmechanism176 to adjust an angle ofinclination178. Theshafts168 anddisc170 are rotated by amotor180 which drives the shafts throughchain182 or other suitable linkage.
• Anair manifold184 has air provided fromair supply186 so thatjets188 are directed onto the face of theflat bed screen164.
• Thesecond flatbed screen166 is similarly constructed.
• Controls Based Upon Monitoring Characteristics of Input Stream
• One approach to determining the composition of thefeedstream12 is to measure the weight and depth profile of the material on the conveyor that feeds the screen withsensor206. The density of the feed material can then be computed from the weight and depth profile and an estimate made of the composition of the material entering thescreens210 and214. An approximate correlation between the density of the feedstream and its composition can be determined by taking samples of the feedstream over time and analyzing their composition as compared to the measured density.
• This approach can provide a first approximation to optimizing the screen operating parameters in real time. Detailed observation of the operation of the screen and experimentation with the operating parameters with feed material of differing densities would be used to develop a table of optimum operating parameters for the different feed material densities. Then as the feed material density changes the operating parameters of the screen would be automatically changed via variable frequency drives for the shaft motors and hydraulic or actuator controls for the screen angle.
• The above method while approximate would still provide an improvement over current operating practices wherein the screen parameters are only occasionally adjusted manually using only the operator's estimate of the feed material composition.
• Using the information from the weight andprofile sensors206 on the infeed belt an approximate correlation can be made between the density of the infeed and the optimum screen parameter settings. This information can also be used to determine the approximate optimum screen parameters and shorten the time for the optimization program to find the actual optimum settings.
• The moisture content of the feedstream strongly effects the operation of the screens. The moisture is primarily contained in the paper, and alters the infrared signature of the paper depending upon the amount of moisture in the paper; the amount of moisture can be measured in this way. Also devices are available for measuring the moisture content of the air in proximity to the paper. By adding amoisture sensor208 to the system, a further data point is available for “presetting” the screen parameters based on the “setup” data collection process.
• Adjustment Based Upon Measuring The Effectiveness of the Separation
• Another more accurate approach to the above problem is also possible now. In the past few years automated sorting devices such as sortingmodules220,234 and244 have become available for MRFs. This equipment uses near infrared spectrometer technology to identify and separate plastic bottles by resin type and to distinguish fiber (paper) objects from plastic. Other equipment is available which uses eddy current technology to identify metal type (e.g. ferrous versus nonferrous such as aluminum).
• By incorporating additional software into these systems, the sorting modules can also be used to count the number of plastic, metal and paper objects that pass through them as indicated at228,242 and252 inFIG. 2. What is proposed then is a system wherein data are taken from at least two sorting modules and used to optimize the screen operating parameters.
• Onesorting module220 would receive thepaper output stream216 from thescreen214 while theother sorting module234 would receive thecontainer output stream218 from thescreen214. Thefirst sorting module220 would reclaim the containers lost to the paper stream while at the same time counting the number of containers and paper objects viasensor228. Thesecond sorting module234 would reclaim the paper lost to thecontainer stream218 while also counting, viasensor242, the number of paper objects reclaimed and the number of containers passing through thesensor242.
• This information can then be used to optimize the screen parameters with the following as an example. Other approaches to implementing the software algorithm can also be implemented. It should also be understood that it is relatively straightforward to determine the practical operating range of the screen parameters by visual observation of the operation of thescreen214. For example the angle between thesides112A and112B on the V screen typically ranges from about 35 to 50 degrees, thetilt angle158 of the V typically ranges from about 5 to 12 degrees, and the rotor motor variable frequency drive frequency typically ranges from about 40 to 70 Hertz.
• Data from sortingmodules220 and234 would be recorded for some period of time (fromsay 1 minute to 5 or 10 minutes). Then the number of paper and plastic objects counted by each module would be averaged over that period of time. Then either the screen angle or rotor speed or tilt angle would be changed by a few percent (say 5 percent of the total range of change available). Then the data from the two sorting modules would be averaged over a same period of time and the results compared with the previous result.
• If the comparison shows an improvement (reduced total paper in the containers and containers in the paper) then the parameter would be changed by a few percent further in the same direction (increased or decreased). This process would be continued until a decrease in screen performance was found.
• If the parameter change produces a decrease in screen performance then the change would be reversed and a few percent change made in the parameter in the opposite direction. If no change in performance is measured after the parameter change, then the selected parameter would be sequentially changed in addition incremental percents until a change is measured.
• The actual software process would be equivalent to making a series of operation measurements for different settings of the selected parameter, plotting the operational efficiency again the parameter setting and then finding the maximum of the operation efficiency.
• When the optimum setting has been determined for the selected parameter, the next parameter (e.g. rotor speed) would be changed as above while operating measurements are made. After all the operating parameter maximums are determined, the process is started over again. A body of operational data will then be collected such that each of the operating parameters maximums are found with different values of the other parameter settings. That is, it may be thatparameter 1 could have a different maximum operating setting whenparameter 2 is set differently than when the maximum forparameter 1 was determined for thefirst parameter 2 setting.
• The data collected above can then be stored in 3 dimensional look up tables (tilt angle axis, rotor speed, and V angle) or as concentrations of optimum points in a 3 dimensional graph for each range of feed material composition. The composition data would be derived from the outputs of the sensor modules.
• The above can be considered to be the data collection phase of the optimization system. It is anticipated that for each new installation of a screen as part of an overall sorting system (or a retrofit) that the data collection phase would be implemented for sufficient time to cover the feed material collected from all the different locations. It is well known that recyclables from different neighborhoods are often of differing composition of paper versus containers, glass versus aluminum, etc.
• These graphs or lookup tables would then be used to determine the best starting point setting for the screen parameters for day to day implementation of the optimization program. The actual running of the program would proceed as above with continual varying of the operating parameters while continually measuring the paper contamination in the plastic and the plastic contamination in the paper.
• A further goal of the program is to refine the starting parameters based on the measured composition of the feedstream. The closer the initial setting of the screen parameters are to optimum the less time it will take to reach optimization for that particular composition. Thus, the more data available on the composition the more refined the starting parameters can be.
• Newly available eddy current sorting modules for aluminum cans utilize an array of eddy current detectors spanning a sorting belt. As aluminum or steel cans cross the array their presence is detected and with appropriate timing an air jet array ejects the aluminum can away from other cans, paper or plastic containers. The array can additionally be used to count the number of aluminum (and separately steel cans) which pass through the module. This newly available eddy current separator can thus be used to provide additional composition data for the optimization program.
• Recently the eddy current array has been added to the near infrared plastic sensor array to allow reclamation of aluminum cans from the screen's paper stream in addition to the reclamation of plastic bottles. This allows counting of all the aluminum cans in the feedstream (those in the container stream as well as those lost to the paper stream). Further the plastic bottle stream typically needs to be separated into the three standard types, PET (drink bottles), colored HDPE (detergent bottles) and natural HDPE (milk bottles).
• This separation is accomplished with thethird separator module244. Thus, further information on the composition of the feedstream is now available as these modules can also count the number of each type of plastic bottle (as well as the color).
• Two components of the recyclable stream that at this time cannot be directly measured are the glass bottles and the steel cans. If we, however, combine the data from the three separation modules such that the number and therefore the approximate weight of the paper, aluminum, and plastic in the feedstream is known, then the majority of the remaining weight is glass and ferrous metal. Since the ferrous metal is typically baled and sold on a daily basis, the approximate weight of the glass can then be calculated.
• The Automated Control System
• The control system ofFIG. 8 is generally designated by the numeral300. Thecontrol system300 includes a microprocessor basedcontroller302 which includesmicroprocessor304,memory306, asoftware portion308, and an input-output device310.
• Thesystem300 also includes the various sensors and actuators previously described and schematically illustrated inFIG. 8, along with various communication lines (or wireless systems) connecting the sensors to thecontroller302, and the various actuators for the mechanical separators along with control devices for those actuators which are capable of converting an electronic control signal fromcontroller302 into a physical action of the actuator.
• The sensors includeweight sensor206A andprofile sensor206B which comprise the weight andprofile sensor206 ofFIG. 2. Also included is themoisture sensor208 ofFIG. 2, and thecounting devices228,242 and252 associated with the first, second and third sorting modules, respectively.
• The actuators include the first andsecond lifting mechanisms142 and144 for controlling the V angle of theV shape separator214A. Also included is thelifting mechanism160 for controlling the bed tilt angle of theseparator214A. Also included are themotors122 and126 which control the rotor speeds for theseparator214A. Also included are theblowers132 and134 for controlling the air pressure directed to the air jets blowing on the faces of theseparator apparatus214A.
• Themicroprocessor304, in response to input signals from the various sensors, and in accordance with the programming contained insoftware308, and instructions received from an operator via input-output device310, sends various control signals viacontrol signal lines312,314,316 and318.
• Control signals overline312 go to controldevices320 and322 associated with liftingmechanisms142 and144, respectively.
• A control signal communicated overcontrol line314 to controldevice324 controls the flow of hydraulic fluid to liftingmechanism160.
• Control signals are carried overcontrol line316 to controldevices326 and328 to control the speed ofmotors122 and126.
• Control signals overcontrol line328 are carried to controldevices330 and331 for controlling the speed ofblowers132 and134 which provides pressurized air to the air jets.
• As will be appreciated by those skilled in the art many other types of sensors could be used to sense various parameters of the input stream and of the various product streams, and various actuators can be utilized to control the various operating parameters of the separating devices.
• Methods Of Sorting Recycled Materials With Automatically Adjustable Separator Using Downstream Feedback
• One method of operation of theMaterials Recycling Facility200 can be described as a method of sorting recycled materials which begins with providing theinput stream202 of recycled materials, wherein a composition of theinput stream202 is subject to variation during a time interval. This is very common for any typical materials recycling facility where the makeup of the recycled materials and other input parameters such as moisture content can vary rapidly throughout the day.
• Thatinput stream202 is moved through a separator machine such asseparator apparatus214A ofFIGS. 3-6 or214B ofFIG. 7, which separating machine has a plurality of adjustable machine operating parameters.
• For the Vshape separator device214A ofFIGS. 3-6, the adjustable parameters include the angle of the V between thesides112A and112B, thetilt angle158 of the frame parallel to itscentral axis120, the speed of the rotors as determined by the speed ofmotors122 and126, and the flow of air to the air jets fromair manifolds114 and116.
• For the inclined flat bed separators such asseparator214B ofFIG. 7, the adjustable parameters includetilt angle178, the rotor speed as determined by the speed ofmotor180, and the air flow toair jets188 directed against the face of the separator screen.
• Typically a feedback control loop for any type of control system will simply monitor a downstream parameter and compare that to some preset target and then adjust the upstream adjustment in order to achieve the predetermined target. Such a feedback system could be utilized in some cases with the present invention, but the preferred control system instead takes each of the adjustable machine operator parameters in turn and via thecontrol system302 adjusts a first one of those adjustable machine operating parameters while monitoring with the computerized control system a quality of separation achieved by the separator machine, so as to select a value of the first parameter that improves the effect of the first parameter on the monitored quality of separation.
• After the first adjustable parameter has been optimized, thecontroller302 will begin adjusting a second one of the adjustable machine operating parameters while monitoring the quality of separation achieved by the separator machine, so as to select a value of the second parameter that improves the effect of the second parameter on the monitored quality of separation. This can be continued until the second adjustable machine operating parameter has been optimized. This is continued with each of the adjustable machine operating parameters for the separator machine in question, and then the process is repeated, returning to the first of the adjustable machine operating parameters and adjusting it to see if further optimization can be achieved.
• In this manner, there is a continuous ongoing process of sequential adjustment of each adjustable machine operating parameter while observing the effect of that adjustment on the quality of separation, so that in effect a continuous adjustment of the separator machine is provided throughout its period of operation thus accommodating changes in the input stream very quickly.
• When utilizing counting devices such ascounters228,242 and252 as the means of sensing the effect on the downstream product, very precise measures of the effect of the change in one of the machine operating parameters can be achieved.
• More particularly, this method of adjustment can be described as a method of sorting an inputwaste material stream202 including a mixture of first and second material such as paper and containers. That inputwaste material stream202 passes through theadjustable separator214 and is separated into afirst output stream216 which in this case is a paper stream containing the majority of the paper and some contaminant containers, and asecond output stream218, which in this case is thecontainer stream218, containing the majority of the containers and some contaminant paper.
• Thecounting devices228,242 and252 can very accurately count the amount of contaminant containers in thesupplemental container stream224 which is extracted from thepaper stream216, and the amount of contaminating paper in thesupplemental paper stream240 which is extracted from thecontainer stream218.
• Then, when one of the adjustable machine operating parameters ofseparator214 is adjusted, the amount of contaminant containers insupplemental container stream224 and the amount of contaminant paper insupplemental paper stream240 are observed, and a signal is generated indicative of whether the combined amount of contaminant material has decreased. If the total amount of contaminant material contained instreams224 and240 has decreased, then that first adjustable parameter is further adjusted in the same direction which is the direction indicated as being favorable to decreasing the combined amount of contaminant material. If, however, the first adjustment resulted in an increase in the total amount of contaminant material instreams224 and240, then the next adjustment of the first adjustable parameter would be in the opposite direction. The first adjustable parameter ofseparator machine214 is continuously adjusted in this manner until there is no further improvement or reduction in the total amount of contaminants.
• Thefirst counter228 may also be referred to as afirst detector228 for detecting an amount of container contaminants in thepaper stream216. Thesecond counter242 may be referred to as a second detector for detecting an amount of paper contaminants in thecontainer stream218.
• It will be appreciated that thecontroller302 may be readily programmed to either equally weight the contaminants in each of the paper stream and container stream, or to favor a reduction in contaminants in one stream at the expense of an increase in contaminants in the other stream.
• As previously noted, the sortingmodules220,234 and244 may be selected from a number of available models which can be obtained from MSS, Inc., the assignee of the present invention, including for example the FiberSort™ model, the Aladdin™ model and the Sapphire™ model. These separators can use various types of sensor systems, but in general these systems utilize sensors which are capable of sensing the identification of each item in the product stream via reflection of light from the item. Light energy of a selected type is projected onto the conveyor belt and optical sensors detect reflected light thus enabling the sensor to identify the type of material at each location on a conveyor belt flowing past the sensor.
• Typical examples of such optical sensing technology are found for example in the following U.S. patents and applications which are assigned to the assignee of the present invention or its subsidiary AST, Inc., and the details of which are incorporated herein by reference: U.S. Pat. Nos. 6,570,653; 6,778,276; 6,369,882; U.S. patent application Ser. No. 09/516,257, entitled “Multi-Grade Object Sorting System and Method”, filed Feb. 29, 2000; U.S. patent application Ser. No. 10/921,000, filed Aug. 18, 2004 for “Sorting System Using Narrow-Band Electromagnetic Radiation”; U.S. Pat. Nos. 5,318,172; 5,460,271; 5,917,585; 5,966,217; 6,137,074; 6,144,004; 6,504,124; and 6,497,324.
• The chosen sensor technology, as previously noted, is preferably utilized to measure the presence of the various material types on an area basis.
• Methods of Sorting Recycled Materials with Automatically Adjustable Separators Using Upstream Feedback
• In another aspect of the present invention a method is provided for separating the inputwaste material stream202. In this method, at least one characteristic of the input waste material stream correlating to a density of the waste material stream is measured. Preferably both weight and a height profile of the input waste material stream are measured. The weight can be measured bysensor206A through any suitable device for weighing the incoming material on a portion of an incoming conveyor belt. Theprofile sensing device206B can be a light beam or the like across the conveyor at various height intervals so as to determine the height of the incoming stream of waste material. Since the width of the stream on a conveyor belt is relatively constant, by knowing the weight and height the density of the incoming waste material stream can be approximated.
• Based upon that sensed density, an initial value is selected for one or more of the adjustable parameters ofseparator device214. This initial value is preferably determined based upon comparison of the sensed density to a historical database ofcontroller302 which correlates to the particular input stream.
• Thus by sensing characteristics of the incoming material stream and comparing the same to a historical database, an initial setting for one or more of the various adjustable parameters of theseparator machine214 can be selected so as to quickly place theseparator machine214 in a condition relatively close to its optimum operating condition.
• Then, theseparator machine214 can be run through the process of individually adjusting each of its adjustable parameters and monitoring the downstream effect of that adjustment on the outgoing product streams to further optimize the individual machine.
• The initial setting of the separator machine can also be based upon measurements of moisture content in the incoming stream as sensed bymoisture sensor208.
• The historical database is built by taking a plurality of samples of a sample waste material stream and determining both the density and composition of each sample, to compile the database of density versus composition. Thus the initial estimation of the composition of the input waste material stream is based upon the measured incoming density, as compared to the historical database.
• Thecontroller302 can collect this data over a period of time and correlate the content of the various product streams to the measured parameters such as density and moisture content of the input stream, and to the optimum settings for the various adjustable parameters of theseparator machine214 so as to further build the historical database and provide a basis for rapid selection of the optimum settings for the adjustable operating parameters of the separator device.
• Methods of Optimization of the Overall Materials Recovery Facility
• MRFs are designed to handle a “typical” composition of recyclables such that each sorting step is optimally loaded but not overloaded. In overloaded operation, whether it be automated, mechanical or a manual sorting process, removal efficiency suffers as does product purity. Also MRFs typically must process all the material that is delivered each day.
• Therefore, as the composition of the feedstream changes it is likely that either one or more of the separation unit operations is being overloaded or that the system is being run at less than its optimum capacity, or that it is not being run at its optimum shift length.
• What is needed is a system that optimizes the system operation in terms of the three above considerations. The addition of sensor modules to the MRF can provide real time feedback as to the number of objects going through the various unit operations of the system. Comparing the known capacity of each unit operation with the actual throughput of that operation allows the efficiency of that operation to be determined.
• All typical MRFs weigh the incoming recyclables, and many receive all their material before noon. Knowing the amount of material needing to be processed and the capacity of the system allows the approximate processing time to be calculated. A relatively straightforward program can then be implemented which takes the data in real time from the unit operations and knowing the dollar value of each component and the approximate feedrate versus efficiency curves for each unit operation can calculate the optimum processing rate. Conversely if the operating time is fixed, the program can calculate the loss in revenue due to lower product purity or the number of manual sorters that would need to be added to the system to maintain optimum purity.
• The ultimate optimization of the Materials Recovery Facility includes an overall assessment of each of the separator devices while taking into consideration other factors such as the economic value of various ones of the output material streams, the cost of operating the various machinery, the cost of manual labor which may be necessary to supplement the automated machinery in certain situations, and various time constraints such as the number of hours the Materials Recovery Facility can be operated each day, and of course taking into account the total volume of material which must be recycled and separated during the operating day for the facility.
• Optimizing the profitability of the Materials Recovery Facility depends upon operating the mechanical equipment at the best capacity versus efficiency while minimizing the cost of manual operations, all the while producing the highest possible saleable material quality.
• In general, the lower the feed rate to mechanical and automated sorting equipment the higher the quality of the saleable output material (i.e. glass, ferrous material, aluminum, plastic, cardboard, and paper). It is possible to measure the general sorting parameters of both mechanical and automated sorters with regard to sorting efficiency versus throughput. The specific operating parameters will depend upon other factors such as moisture content and percentage composition, but these are second order effects as compared to throughput. Data representative of the feed rate versus separating efficiency relationship for an automatic separator apparatus will typically take the form of a curve generally like that ofFIG. 9.
• In general, but with less connection, the higher quality saleable output materials will command a higher selling price. However, due to market conditions it is often the case that higher quality does not bring a higher selling price. Further, prices for saleable materials such as glass, paper, aluminum, cardboard and steel are readily available on a day-to-day basis.
• The operating costs of mechanical and automated sorting equipment are largely proportional to the length of time the equipment is operated, rather than on the total amount of material processed. The amount of material processed does contribute to wear on the equipment, but the dominant cost factors are electrical usage and wear due to running, whether material is being processed or not. Disc screens are somewhat of an exception to this as material flow over the screen causes significant wear to the discs which must be periodically replaced. Cost for electrical power and spare parts costs are also readily available on a day-to-day basis and may be entered into the system. Data representative of the operating costs of mechanical equipment will typically take the form of a curve like that set forth inFIG. 10.
• Materials Recovery Facility operating costs due to manual labor are proportional to the length of time the Materials Recovery Facility is in operation regardless of the amount of material being processed. Manual sorters cannot be sent home and then called back in a matter of a few hours. It is also well known from experience how much material a human sorter can on average process per hour. Again, labor costs are also well known on a day-to-day basis and can be input into the system. Data representative of the cost of manual labor will typically take the form of a curve like that of FIGS.11 or12.FIG. 11 is representative of manual labor costs which are directly variable according to the time of labor required.FIG. 12 is representative of the situation in which labor can only be obtained in increments such as the length of a minimum shift for a worker of four hours, eight hours or the like.
• The present invention utilizes a computer program in thesoftware portion308 into which daily material prices can be entered along with current manual sorting hourly costs, the amount of material that needs to be processed that day, and in which the program can compute the optimum processing time and/or personnel for the day's material to generate the maximum possible net revenue. The program has operating characteristics available, such as in lookup tables or in graph form, for feed rate versus separation quality, manual sorting capacity, wear characteristics of the various mechanical components and the like, as well as the material pricing data noted above.
• One such method of optimization can be described as a method of controlling a Materials Recovery Facility. An automatic separator apparatus is used for separating the input material stream into at least afirst output stream216 and asecond output stream218 containing predominantly first and second materials, in this case paper and containers, respectively. Data representative of a feed rate versus separating efficiency relationship for theautomatic separator apparatus214 is provided to theautomatic control system300. It will be appreciated that the faster theseparator device214 is operated, the less efficient it will typically be and the more contaminants will be contained in each of thestreams216 and218. On the other hand, if theseparator214 is operated too slowly it may not be possible to process all of the material that may be processed within the allotted time. Theautomatic control system300 can calculate an optimum processing rate to maximize the profitability of the separation process. The control system can then adjust the feed rate of the input material stream to the automatic separator apparatus so that said feed rate approximates the optimum processing rate.
• The control system can provide such a calculated optimum processing rate for theseparator214 and for the various sortingmodules220,234 and244, each of which will have a feed rate versus separating efficiency relationship.
• The control system will further take into account costs that are representative of a cost of operating the Materials Recovery Facility. That cost data can include data representative of a cost of manual labor for supplemental manual sorting to sort contaminants from one or more of the various output streams. That cost data can further include consideration of an increased cost of manual labor for supplemental manual sorting needed as a result of increased feed rate to one or more of the separators.
• Thesoftware portion308 ofcontroller302 includes a data input software portion for receiving data representative of such an economic value of a product of at least one of the product streams. The data input software portion can also receive inputs of current costs of operation of various portions of the Materials Recovery Facility along with the current cost of manual labor for supplemental manual separation.
• It will be appreciated that the historical database can also include data representative of the amount of supplemental manual labor that may be necessary, for example when one or more portions of the Materials Recovery Facility are operated at such a high feed rate that totally efficient separation cannot be achieved and thus manual supplementation may be required. The data input software portion of the automatic control system is also adapted to receive input of total throughput requirement for the facility for a given time interval and a constraint for processing the total throughput requirement through the facility.
• Thus it is seen that the apparatus and methods of the present invention readily achieve the ends and advantages mentioned as well as those inherent therein. While certain preferred embodiments of the invention have been illustrated and described for purposes of the present disclosure, numerous changes in the arrangement and construction of parts and steps may be made by those skilled in the art, which changes are encompassed within the scope and spirit of the present invention as defined by the appended claims.

Claims (25)

1. A method of separating an input waste material stream, the method comprising:

(a) measuring at least one characteristic of said input waste material stream correlating to a density of said input waste material stream;

(b) selecting an initial value for an adjustable parameter of an adjustable material separator based upon the at least one characteristic measured in step (a); and

(c) separating said input waste material stream, with said adjustable material separator, into a first output stream containing a majority of a first material and some of a second material, and a second output stream containing a majority of the second material and some of the first material.

2. The method ofclaim 1, further comprising:

estimating a composition of the input waste material stream in terms of relative portions of said first and second materials, based upon the at least one characteristic measured in step (a); and

wherein step (b) includes selecting said initial value for said adjustable parameter based upon said estimated composition.

3. The method ofclaim 2, further comprising:

prior to step (a), taking a plurality of samples of a sample waste material stream, determining both the density and composition of each sample, and compiling a historical database of density versus composition; and

wherein said estimating step is based upon said historical database.

4. The method ofclaim 1, further comprising:

prior to step (a), taking a plurality of samples of a sample waste material stream, determining both the density and composition of each sample, and compiling a historical database of density versus composition; and

wherein said selecting step is based upon said historical database.

5. The method ofclaim 1, wherein step (a) comprises:

(a)(1) weighing a portion of said input material stream; and

(a)(2) sensing a height of said portion of said input material stream.

6. The method ofclaim 1, wherein said adjustable material separator is an inclined screen, and wherein:

in step (b), said adjustable parameter is an angle of inclination of said inclined screen.

7. The method ofclaim 1, wherein:

in step (b), said adjustable parameter is a flow of air against a face of the screen.

8. The method ofclaim 1, wherein said inclined screen includes a V-shape trough having an adjustable V-angle, and wherein:

in step (b), said adjustable parameter is said V-angle.

9. The method ofclaim 1, wherein said adjustable material separator is a screen having spaced rotating discs, and wherein:

in step (b), said adjustable parameter is a rotational speed of said discs.

10. The method ofclaim 1, wherein in step (b) said adjustable material separator is a flat bed inclined screen.

11. The method ofclaim 1, further comprising, after said selecting of said initial value:

monitoring an amount of contaminant second material in said first output stream and an amount of contaminant first material in said second output stream;

then adjusting said adjustable parameter from said initial value;

then again monitoring the amount of contaminant second material in said first output stream and the amount of contaminant first material in said second output stream;

then further adjusting said adjustable parameter in a direction indicated as being favorable to decreasing a combined amount of contaminant material in said first and second output streams.

12. A method of sorting recycled materials, comprising:

(a) providing an input stream of recycled materials, wherein a composition of the input stream is subject to variation during a time interval;

(b) moving the input stream through a separator machine having a plurality of adjustable machine operating parameters;

(c) providing stored historical data representative of a set of historical values of the operating parameters corresponding to improved quality of separation for given values of a characteristic of said input stream;

(d) sensing a present value of said characteristic of said input stream; and

(e) adjusting said plurality of adjustable machine operating parameters, via a computerized control system, in response to said sensed present value of said characteristic of said input stream so that said adjustable machine operating parameters approach said historical values of the adjustable machine operating parameters corresponding to improved quality of separation for said sensed present value of said characteristic of said input stream.

13. The method ofclaim 12, wherein the characteristic of the input stream is density.

14. The method ofclaim 13, wherein the density of the input stream is estimated by measuring a height of a portion of said input stream and a weight of said portion of said input stream.

15. The method ofclaim 12, wherein the characteristic of the input stream is moisture content.

16. The method ofclaim 12, wherein:

in step (a) the input stream is comprised primarily of paper and containers, the paper being primarily newspaper; and

in step (b) the separator machine separates the input stream into a paper stream made up primarily of paper, and a container stream made up primarily of containers.

17. An automated separator apparatus for separating an input material stream into first and second output streams, comprising:

a plurality of spaced rotating discs defining a screen having a length;

a first actuator for adjusting an angle of inclination of said length;

a second actuator for adjusting a rotational speed of said rotating discs;

a sensing unit for sensing at least one characteristic of said input material stream; and

a control system responsive to said sensing unit and operably connected to said actuators, so that said screen automatically adjusts to changes in the sensed characteristic of said input material stream.

18. The apparatus ofclaim 17, wherein said at least one sensed characteristic includes density.

19. The apparatus ofclaim 18, wherein said at least one sensed characteristic includes moisture content.

20. The apparatus ofclaim 17, wherein said at least one sensed characteristic includes moisture content.

21. The apparatus ofclaim 17, wherein said at least one sensed characteristic includes weight and a profile height.

22. The apparatus ofclaim 17, further comprising:

a first separator for further separating the first output stream;

a first optical sensor for identifying and measuring individual items of the first output stream and thereby determining a composition of the first output stream;

a second separator for further separating the second output stream; and

a second optical sensor for identifying and measuring individual items of the second output stream and thereby determining a composition of the second output stream.

23. The apparatus ofclaim 17, wherein:

said plurality of spaced rotating discs define said screen in a trough shape having inclined sidewalls; and

said apparatus further comprises a third actuator for adjusting an angle of lateral inclination of said side walls.

24. The apparatus ofclaim 17, wherein:

said screen is a flat bed screen.

25. The apparatus ofclaim 17, further comprising:

a third actuator for adjusting a flow of air against a face of the screen.

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