CA2254896A1 - Method and apparatus for controlling thickeners, clarifiers and settling tanks - Google Patents

Abstract

Computerized, "intelligent" systems and methods for monitoring, diagnosing, operating and controlling various parameters and processes of thickeners, clarifiers, and settling tanks are presented. The computer control system actuates at least one of a plurality of control devices based on input from one or more monitoring sensors so as to provide real-time, continuous, operational control. The response of the control system is based on the system's own process model, which in turn is based on sensor input and one or more advanced analysis techniques including, but not limited to, neural networks, genetic algorithms, fuzzy logic, expert systems, statistical analysis, signal processing, pattern recognition, categorical analysis, and combination thereof. Process and operating parameters of particular interest include rate and amount of chemical (flocculant) addition, power consumption, control of underflow/overflow rates and composition, and control of the drive mechanism. In a particularly preferred embodiment, the apparatus comprises a thickener or the like with at least one sensor for providing input consisting of a continous profile of the settling zone and the bed, which is analysed by a process model generated by a combination of statistical methods and neural networks. As a result of the analysis, at least one output may be generated to activate a control device that effects changes in operating variables as suggested by the process model and leads to optimization of the operation of the thickener. Preferably, the sensor(s) is a non-invasive sensor such as an ultrasonic (sonar) or millimeter-wave radar sensor.

Description

CA 022~4896 1998-11-13 WO 97/43027 PCT~US97/08027 METHOD AND APPARATUS FOR CONTROLLING THICKENERS, CLARIFIERS AND SETTLING TANKS

Background of the Invention:
1. Field of the Invention This invention relates generally to thickeners, clarifiers, settling tanks and like equipment which are generally used for the separation of particles from a liquid slurry or pulp. More particularly, this invention relates to methods and apparatus for autom~tic~lly monitoring, ope.~ting, and controlling thickeners, clarifiers, settling 10 tanks, and the like using "intelligent" computer control systems and remote sensing devices.

2. BriefDescription of the Prior Art Slurries or suspensions cor.,~.,ising liquids carrying suspended particles are typically subjected to a process called clarification to separate suspended particles from supernatant liquid. Typically, clarification is accomplich~d by continuously feeding an influent slurry or suspension feed stream into a settling tank, clarifier or thickener, where suspended particles are allowed to gravity settle and form a sludge or thickened mud on the bottom of the tank. The thi-~oned material (or thickener underflow) is removed and further processed or disposed of, while the clarified liquid supernatant (or thickener overflow) is either discharged, reused, or subjected to further clarification.
A thickener usually is a vertically positioned, cylindrical vessel of a size determined by the amount of slurry to be treated in a given unit of time. The central portion of the bottom of the thickener usually is conical and slopes d~w,,wc.l dly towards the underflow discharge port. Slurry which comprises finely divided solid particles and solution is fed into the upper part of the thickener. Solid particles settle towards the bottom and solution rises to the top. A conventional rake n~eçh~nism is provided and is rotated at a speed determined by the solids settling rate to produce a solids-liquid ratio desired in the underflow, from which optimum results are obtained in the following solids-liquid separation step.

CA 022~4896 1998-11-13 W 097/43027 PCTrUS97/08027 The sedim~nt~tion process is sometimes expedited by adding a flocc~ ting reagent to the influent before it enters the settling tank. The flocc~ ting reagent typically has a polymeric molecular structure which agglomerates with suspended particles in the influent to form aggregate clusters called flocs. Flocs have a greater density or effective diameter than the discrete suspended particles, and settle to the floor of the tank quickly.
There are generally four distinct zones of settling slurry within the thickener.At the top there is a zone of clear water. Beneath this is a zone consisting of aggregates or flocs of solid particles of uniform consistency. This zone is commonly referred to as the zone of flocclll~ted slurry. Beneath this zone is a transition zone and at the bottom a zone of pulp which is undergoing conll)ression and in which the flocs have settled to a point where they rest directly one upon another. The specific gravity of the underflow slurry closely appl o~ ates the specific gravity of the slurry in the compression zone. The pulp in the transition zone decreases in percentage solids from the bottom, where flocs enter, to the top, where the con~ist~ncy of the floccul~ted pulp is the same as that of the original slurry.
Automatic control and optimized operation of thickeners has been a contimling concern and objective of thickener operators and m~nllf~cturers Typically, such automatic control systems utilize a sensor which communicates process information to a controller whereby the process is in some way altered. A number of sensors have been proposed in the prior art. For example, several prior art references disclose the use of photodetectors, light sensors, and other optical components in conjunction with thickener control systems. In Japanese Patent No. 259902, a plurality of television cameras is arranged in a settling cell. These cameras detect the grain size distribution and compare the detected image to standard distribution conditions to control flocculant formation. The use of light sensors is disclosed in U.S. Patent Nos.
4,279,759 and 4,976,871. More particularly, these two references disclose the use of photosensors comprising a light source and a photo cell to measure the concentration of suspended solids, based on such measurements, the rate of flocculant introduction to the cell is controlled. Similarly, U.S. Patent No. 5,240,594 discloses a system for CA 022~4896 1998-11-13 W O 97/43027 rCT~US97108027 monitoring and/or controlling a liquid/solid separator using photodetectors which view the surface of the composition being separated and correlate the corresponding signals from the photodetectors to a dryness value.
U.S. Patent Nos 3,375,928, 3,551,330, and 4,348,278 all disclose the use of pres~ule sensors for monitoring the interface levels in a settling tank. In addition to monitoring the interf~ce, some ofthese patents also monitor density, as do U.S. Patent No. 4,273,658 (~658) and Australian Patent No. 75958. The '658 patent utilizes aradioactive based sensor for sensing density. The sensor is lowered on a cable to provide a profile along the depth of the thickener. Similarly, the Australian patent discloses a device which is lowered on a cable for measuring density. The deviceincludes two rigidly spaced, ultrasonic tran.cd-1cers, which transmit signal through a fixed path length, thereby dete. ,l,inil1g density.
U.S. Patent No. 4,040,954 utilizes a turbidity sensor probe to continuously monitor turbidity and compare such monitored turbidity to a desired value or set point.
The probe is raised or lowered to .~ the known set point. The supply of flocculant is controlled in response to change in turbidity and position of the probe.
U.S. Patent No. 4,226,714 discloses a thickener which m~int~inc steady state by controlling mass flow rates of influent to and underflow from the separator. This control system uses influent specific gravity and flow rate signals for such control.
U.S. Patent No. 4,867,886 discloses a non-contact sensor, based on sonic or laser p~ o~illlily technology for reporting the cake surface. In response to the sensor signal, flocculant flow rate is adjusted.
U.S. Patent No. 4,876,888 utilizes a simple level sensor comprising a float strung on a continuous line to monitor level and control the amount of flocculant introduction. In general, level sensing in the prior art is accomplished by a wide variety of devices incl~lcling the capacitive pl oxh.lily sensors disclosed in U.S. Patent Nos. 5,305,779 and 4,888,989.
U.S. Patent Nos. 5,013,442 and 5,094,752 disclose the use of an ~lk~linity profile of the influent which is measured at a plurality of dif~ points in the process.

CA 022~4896 1998-11-13 WO 97/43027 ~CTrUS97/08027 When the sensed ~lk~linity at any given point is more than a predetermined amount above a base line alkalinity, a change is made.
U.S. Patent No. 5,183,562 controls the addition of flocculant using measu~en.el.ls made by a heat transfer detector and an electric conduction meter. U.S.
Patent No. 4,783,314 discloses the use of fluoresce,.l tracers in sepal ~lion equipment.
In general, all of the aforementioned thickener control techniques involve simple feedbac~ or feed forward control loops and utilize a narrow range of sensors and control devices which limit the overall ability of the operator to provide an accurate system control. Furthermore, it is not believed that any of the aforementioned prior art provides a comprehensive, computerized, "intelligent" control system for opel~ling, controlling, and monitoring various thickeners, clarifiers, settling tanks, and like equipment. The ability to provide, precise, real time control and monitoring of such equipment con~titute~ an on-going, critical industrial need.

Summary ofthe Invention:
The above-~ cl-.csed and other problems and deficiencies of the prior art are overcome or alleviated by the several methods and appal al~ls of the present invention for providing computerized, "intelligent" systems for optl~ling, controlling, monitoring and diagnosing various parameters and processes of thickeners, clarifiers, settling tanks, and like equipment. For purposes of this invention, any reference to "thickener" shall include all equipment of the type where solids are separated from liquids through settling in a tank, incln(iing the aforementioned clarifiers and settling tanks.
In accordance with the present invention, a computer control system achlates at least one of a plurality of control devices based in part on input from one or more monitoring sensors so as to provide real time continuous operational control.
It will be appreciated that it is difficult to sense and communicate certain parameters in real time within thickeners. Thus, in accordance with an importantfeature of the present invention, a variety of technologies incl~ltiing ultrasonic, absorption and reflection, laser heated cavity spectroscopy, X-ray fluorescence spectroscopy, neutron activation spectroscopy, pressure measurement, microwave or millimeter wave radar, reflectance or absorption, and other optical and acousticmethods may be utilized. In addition, several novel comm--nic~tions methods for c,~ g and receiving data and power to and from the interior of the thickener areS provided. Such comm~mications techniques may include hard-wired electrical systems, optical systems, RF systems, acoustic systems, video systems, and ultrasonic systems.
In a p,ert;lled embodiment, the sensor or sensors colll~,lises a non-intrusive (non-invasive) or nearly non-intrusive (nearly non-invasive) system for determining bed profile (preferably both vertically and horizontally). Such a non-intrusive (or invasive) sensor is dictin~lich~ble from intrusive sensors known in the prior art such as probes lowered into a bed. Such prior art intrusive sensors typically require struts and other structure within the tank which impede settling and rake movement. A non-intrusive sensor avoids these problems. A nearly non-intrusive sensor is installed slightly below the surface of the liquid in the thickener tank, but is not required to travel to any greater depth. Neither the non-intrusive nor the nearly non-intrusive type sensors require extraction of samples for extended analysis. As used hereinafter, the term "non-intrusive" sensor shall include both the non-intrusive and nearly non-intrusive sensors disc~-ssecl above.
~1 erel I ed, non-intrusive sensors include ultrasonic sensors, sonar sensors and millimetrr-wave radar based sensors. Such sensors may oscillate in an arcwise path or may move linearly along a radius of the tank to provide a bed profile of the entire tank or at least that portion of the tank which is of interest. Also, multiple, spaced sensors may be used to obtain a complete bed profile.
The response of the control system is preferably based on a series of expert rules, determined initially in advance and continually updated based upon the control system's own analysis of its performance. The control system preferably generates and continuo-.cly updates its own "process model," using the data inputs described above and one or more of several advanced analysis techniques, incl~ltling but not limited to neural networks, genetic algorithms, fuzzy logic, expert systems, signal processing, pattern recognition, categorical analysis, statistical analysis or a combination thereof.

CA 022~4896 1998-11-13 W 097/43027 PCTrUS97/08027 Preferably, the control system has the ability to independently select the best analysis technique ffir the current data set. Thus, the computer controller may actuate one or more control devices to control any number of process and operational control variables based not only on one or more of the sensor inputs but also on the currently sPlected process model.
The computer controller used in the system of the present invention is ple~l~bly a personal computer or woll~slalion, with a display device (CRT screen) and input/output device (keyboard or touch-sensitive screen). The microprocessor controller may be located at the thickener or at a remote location such as a central control room in a plant. Importantly, the controller may control one or a plurality of thickeners at a single or plurality of sites.
The above-described computerized control and monitoring system for this~ners provides a comprehensive scheme for monitoring and controlling a variety of input and output pal ~.l.e~ers as well as a plurality of operational parameters res ~lting in greater efficiency, opli~ dlion of operation, and increased safety.
The above-diccussed and other features and advantages ofthe present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.

Brief Description of the Drawin~s:
Referring now to the drawings whel ein like elements are numbered alike in the several FIGURES:
FIGURE 1 is a schematic, sectional view of a conventional thickener with which the monitoring and control system of the present invention is used;
FIGURE 2 is a sçh~m~tic of the monitoring and control system for a thickener in accordance with the present invention;
FIGURE 3 is a sch~m~tic of a preferred monitoring and control system employing a non-intrusive sensor system;
FIGIJRES 4 is a schematic of a monitoring and/or control system employing a non-intrusive sensor system for a tank cont~inin~e a multiphase material.

CA 022~4896 1998-11-13 WO 97/43027 ~CT/US97/08027 FIGURE S is a sçhe~tic of a top view of a typical sensor mounting and sc~nning axis employing a non-intrusive sensor;
FIGURE 6 is a schematic of a side view of a typical sensor mounting and sç~nning axis of a non-intrusive sensor;
FIGI 1RE 7 is a srh~.m~tic of a video display color coded for return signal strength of a sonar sensor signal in SC~nning mode; and FIGURE 8 is a sçhem~tic of a video display of return signal strength of a sonar sensor signal in fixed mode.

10 Desc.iy~ion ofthe Preferred Embodiment:
This invention relates to methods and apparatus for automatically controlling, ope, ~Lillg, and monitoring thickeners using "intelligent" computer controlled systems and remote sensing devices. By "intetligçnt" is meant the use of computer control methods inclndine but not limited to neural networks, genetic algorithms, fuzzy logic, expert systems, st~ti.cti~l analysis, signal processing, pattern recognition, categorical analysis, or a combination thereof to analyze input in terms of one or more self-generated, continuously updated, internal models, and to make changes in opG~lh~g variables as s~lg~ested by the models. It is to be understood that the term thickener is used in its most general sense, being inclusive of traditional separation cells, clarifiers, and thickeners wherein solids and liquids are separated by a settling process. It is further to be understood that a thickener in the context of the present invention my refer to a single tank or column or to a bank of tanks or columns.
Referring to FIGllRE 1, a simplified example of a thickener contemplated by the present invention is shown. In FIGURE 1, a conventional thickener or settling tank is shown at 10. Conventionally, it is a cylindrical vessel of a height and tli~met~r determined by the nature of the slurry and the desired slurry underfiow output per unit of time. It may or may not be covered, or shown in FIGURE 2.
The thickener is provided with an inlet conduit 12 which is connected to a source of slurry to be treated. The conduit 12 extends into the top of the thickener.

CA 022~4896 1998-11-13 W O 97/43027 PCT~US97/08027 An overflow launder 14 surrounds the top ofthe thickener in which the overflow is collected and passed to further tre~tm~nt.
The thickener bottom has a conical central portion 16 which slopes downwar(i from a generally sloping lower wall or floor 18 towards a discharge outlet 20 at the center thereof. A rake 22 is positioned near the bottom and is rotated to move solids radially inward toward outlet 20.
The feed of slurry to the thickener, the overflow of clear liquid from launder 14 and the discharge of thickener underflow from outlet 20 are continuous. The rates of feed and discharge are usually adjusted to achieve a high solids concentration underflow slurry while m~int~inin~ the solids concentration ofthe overflow below a predetermined limit.
The profiles of the zones of settling slurry within the thickener will depend upon the nature of the slurry and the rates of feed and discharge, as well as the addition of chemical flocculants. The profile in dashed lines in the drawing areillustrative of what may be typical boundaries between zones of a slurry. The rate of feed of the slurry to the thickener and the rate of discharge therefrom are adjusted to m~int~in the specific gravity of the slurry at one of the levels indicated by the profile lines in the drawing. The numeral 24 designates the upper zone of clear liquid and numeral 26 deci~n~tes the zone of flocc~ ted slurry of uniro~ ll- consistency. Numerals 28 and 30 identify a transition zone and a con,plession zone, respectively. Beneath conll)res~ion zone 30 at the periphery ofthe thi~çner is a dead-bed 32.
A conduit 34 is connected to the outlet port 20 which conduit extends to a variable speed pump 36. This pump 36 is of a conventional type, such as a centrifugal pump, for pumping mixtures of solids and }iquids. A conduit 38 extends from pump36 to an optional solids-liquid separation appa-~ s, not shown.
In accordance with the present invention, thickeners of the type discussed above are provided with one or more sensors for the sensing of one or more p&-~l-lelers related to the processes and operation ofthe thickeners. In addition, a computerized control system which may be located at the thickener, near the thickener, or at a remote location from the thickener is provided for interaction with the sensor or CA 022~4896 1998-11-13 sensors in the thickener. This computer control system inrludes a control computer and one or more control devices which are ~ctu~ted in response to a col",lland signal from the control computer. Importantly, the response of the control system will pre~lably be based both on sensor input and on a series of expert rules, determined initially in advance and continually updated based upon the control system's ownanalysis of its performance. The controller will generate and continuously update its own "process model," using the data inputs described and one or all of several advanced analysis techniques, inclu(lin~ neural networks, genetic algorithms, fuzzy logic, expert systems, statistical analysis, or a coll.bh-alion of these. The control system will have the ability to independently select the best analysis technique for the current data set. The computer control system will actuate one or a plurality of control devices based on input from one or more monitoring sensors so as to provide real time, continuous, operational control. In addition, the control system may include a monitoring system for data logging, preventative m~inten~nce, or failure and wear prediction. The control system may additionally include diagnostics relating to the condition of the equipment.
Referring now to FIGURE 2, a schematic is shown depicting examples of the monitoring sensors, control devices, and components and features of the control system of this invention. FIGURE 2 more particularly shows a thickener 40 having20 associated therewith one or more process sensors 42 and/or one or more equipment sensors 44, and preferably in~ludes sensors 46 for providing a real time, continuous bed profile. In addition, the thickener is associated with one or more operational control devices 48. The sensors 42, 44, and 46 comm..nic~te through an applop"ate c~ ;c.~tions system, i.e., an analog and/or digital data acquisition interface 50 with the central control computer 52 The control devices 48 communicate through an approp,iate communications system, i.e., an analog and/or digital control outputinterface 54 with the central controller 52. As previously mentioned, the control computer 52 may be located on the thickener, near the thickener, or at a remote location such as a control room. Computer 52 has associated therewith a display 56 for displaying data and other parameters, a keyboard 58 or other means for inputting CA 022~4896 1998-11-13 W O 97/43027 PCT~US97/08027 control signals, data, and the like, a memory or recorder 60, and a modem 62 forinputting and outputting data to the computer 52 from remote locations.
Still referring to FIGURE 2, the microprocessor controller 52 receives a varietyof inputs which have been categorized generally in terms of (1) h~fo~ alion stored in memory when the thickener is m~n-~f~ct~red; (2) information pro~.~nll.led at the site where the th;r~ner is to be used; (3) process pa~.llelers sensed by the process sensors 42; and (4) eq~1irment (operational) parameters sensed by the equipment sensors 44.
The outputs from the control computer may be generally categorized as (1) data stored in memory 60 associated with the computer 52; (2) operational control of the thicl~n~r; and (3) real time info--na~ion provided to the operator at the monitor 56 ~s.sociqted with the computer 52. The various inputs and outputs are su,llmaliGed in the following Table.

W 097143027 PCT~US97/08027 --.. Z
O J
~ --Z ~ o ~_ a ~ z Z ~ Z a O ~ ~ ~ ~ ~ z ~ ~

t- ~L > ~ C ~ Z g~ 6 1Y
6 P~ ~ ~ _ ~ ~ ~ ~ Z r ~ ~ ~~ ~ ~
OC O " LL~ O ~ ~ ~ p~ O

~' p o Z
C~ ~ 6 é' ~ Y~

- ~ ~ ~

4~ o u~ o CA 022~4896 1998-11-13 W O 97t43027 PCTAUS97/08027 Il~,lllalion Stored in Memory Examples of information originally stored in memory include i,lro"nalion relating to the operation and maintenance of the thickener and operator trainingh~,.,lalion, all of which will be readily available to an operator on display screen 56 associated with ".icroprocessor controller 52.

Inro""alion Pro~rammed at Site F.x~mrle, of ;.~ol ",a~ion programmed at the site where the thickener is to be used include the operating ranges, equip~nent parameters, and desired feed parameters, along with other site-specific data such as relative humidity and other environm~ont~l factors. Input into the control computer also includes various process models and process controls, and guidelines. These models and goals may be either stored inmemory or programmed at the site as approp, iale.

Process and EquiPment Parameters A further important feature of the present invention is the large number of process and equipment sensors 42, 44, and 46 which sense a variety of aspects relating to the thickener, its operations, and its feed, underfiow, and overflow streams.Particularly important are sensors relating to rate of chemical addition and the bed profile. Other process parameters which may be sensed include, but are not limited to the volume or mass flow rates into the feed, underflow and/or, overflow streams; the density of the feed, underflow and/or overfiow streams; the chemical or mineralogical composition of the feed, underflow and/or overflow streams; the particle size, concent~tion, and distribution of solids in the feed, underflow and/or overflow streams; or digiti7ed video images of the surface or other key parts of the process, analyzed to determine the key characteristics of the subject being imaged.
Equipment parameters which may be sensed include but are not limited to rake speed, rake torque, rake power consumption, or rake lift above the floor of the thickener.

CA 022~4896 1998-11-13 W O 97/43027 PCT~US97/08~27 Since the mode of operation of a sensor may vary in terrns of the emitted frequency, signal ~LIel~glll, and threshold return (noise cutoff) from one in~t~ tion to the next, prefel ~bly, each sensor is progl d-llmed to initi~li7e itself by sweeping a range of freq~1enc;es7 signal strengths and threshold returns to find an effective value for each of these parameters.
It will be app~ec;aled that it is often difficult to sense and commlmicate certain pal~,llelers in real time within thickeners. Thus, a variety of technologies in~ ding laser based system which determine liquid/solid and like interfaces within a liquid body, laser-heated cavity spectroscopy, laser-in~ ced breakdown (LIB) spectroscopy, laser-in~lced mass spectroscopy, ultrasonic, sonar, pressure measurement, X-ray fluorescence spectroscopy, neutron activation spectroscopy, microwave or millimeter-wave radar reflect~nce or absorption, and other optical and acoustic methods may be utilized in the present invention. A suitable microwave sensor for sensing moisture and other constihl~ntc in the solid and liquid phase influent and effluent streams may be measured using the instrllment~tion described in U.S. Patent 5,455,516, all ofthe contents of which are incol ~,or~ted herein by reference. An example of a suitable appalalLls for sensing using LIB spectroscopy is disclosed in U.S. Patent 5,379,103, all of the contents of which are incorporated herein by reference. A pl efelled embodiment employing a non-intrusive sensor system such as an ultrasonic, sonar,laser or millim~ter-wave radar sensor is described in detail hereinafter with reference to FIGURES 3 -8.
Suitable techniques for communicating among the sensors, microprocessor, and other co"lponenls include hard-wired electrical systems, optical systems, RF systems, acoustic systems, video systems, and ultrasonic systems.
Data Stored in Memory Referring more particularly to the data stored in memory, it will be appreciatedthat the computerized monitoring and control system of this invention may utilize the aforementioned sensors to monitor various parameters with respect to time and thereby provide a detailed historical record ofthe thickener operation 66. This record CA 022~4896 1998-11-13 may be used by the microprocessor to model thickener operation, adjust models for thickener operation, or generally learn how the thickener behaves in response toç~l~ng~c in various inputs. At any time, such opw ~ling data may be retrieved from a position local to the thickener or remotely. The data may be displayed in real time while the thickener is operating using monitor 56, or as a historical record of some prior ope.a~ g sequence. This record may also be used to provide a data log, provide trending and preventative m~inten~nce inrolllldlion, predict failure and predict m~c~ine wear 68. Pre-formatted reports may present the retrieved data to show information such as operating hours, alarms generated, number of starts, number of trips, electrical power used, mq-cimllm and minim~lm values for measured variables, total feed processed, and the like. Using the operating data, the thickener m~mlf~cturer may recollllllend measures to avoid down time and to op~illli~e run time. Also, ~ nAnce procedures may be suggested based on the operating log of elapsed run time, and unusual opel ~ling conditions. The operating data log thus helps to trouble shoot various operating conditions of the thickener. This çnh~nces the thickener m~nllfact~lrer's ability to solve the customer's operational problems and to keep equipment on line. Optionally, these data 66,68 may then be used to provide alarms or emergency notification 70 when certain critical levels are reached.

Control of Operations Controller 52 preferably communicates through standard commllnication cards used on personal computers or wolk~lalions As such, Ethernet, RS-232, and modem capabilities exist for the operator's use. The present invention thererol e allows a given plant to collect thickener operating data through a plant-wide Ethernet or othernetwork. Additionally, the present invention may communicate with other process devices not supplied by the m~nuf~cturer. In this way the operator uses the control and monitoring system of this invention to gather information on a larger portion of the process.
Using a connected plant network, the operator may monitor the thickener's real time pelrolll'allce and historical log. Suitable software for this activity inçludes CA 022~4896 1998-11-13 operator screens for data display, and message displays for operating ~esiet~nce, and may also include an on-line operation and m~inten~nce manual. The operator may also control and opli,l.~ze the pe~ "~ance of the thickener through the plant network. The operating pala"~elers as described below may also become part of an overall Supervisory Control and Data Acquisition (SCADA) system or Distributed Control System (DCS). As is well known, in a SCADA system, or DCS, microprocessor devices convert plant measurement and status inputs into computer data for logging and tran.emieeion to higher level processors. Supervisory controllers make strategic decisions for the operation of a process unit or plant and send out set points to dedis~ted controllers which will make the changes to actuators and Illtim~tely the process as a whole. The SCADA network therefore connects to many controllers andfield devices to gather i~ .alion and make global decisions.
Continuing to refer to FIGURE 2, a further important feature of this invention is that in response to the one or more parameters sensed by the sensors 42, 44, the operation of the thickener and thereby its ultim~te efficiency can be adjusted, changed, and preferably opl;~ized using one or more advanced computerized control methods.
Such advanced computerized control methods include but are not limited to neuralnelwurk~ genetic algorithms, fuzzy logic, expert systems, statistical analysis, signal proceseing~ pattern recognition, categorical analysis, or a co"ll)il-aliûn thereof.
Thus, in a pl e~ll ed embodiment, this invention comprises at least one of thesecontrol methode and other methods more advanced than conventional, stabilizing control methods, for example, the simple feedbac~ or feed forward control loops of the prior art. The response of the system is based on a series of expert rules, determined initially in advance and continually updated based upon the control system's ownanalysis of its pCI~Ol ll.ance. The control system will generate and continuously update its own "process model" using the sensor inputs described and the above-mentioned analysis techniques. The control system may have the ability to independently select the best analysis technique for the current data set.
While controller 52 may operate using any one or more of a plurality of advanced computerized control methods, it is also contemplated that these methods CA 022~4896 l998-ll-l3 W O 97/43027 PCTrUS97/08027 may be co,llbined with one or more of the prior art methods, inr.~ lin~ feed forward or feedb~rl~ control loops. Feed forward is where process and m~r.hine measwellle"ls (or c~lcul~te.l, inferred, modeled variables normally considered ahead of the machine in the process) are used in the controller 52 to effectively control the operation of the 5 thicl~ener. Feed forward sçh~mes inhel enlly acknowledge that the conclition.~ and state of the feed material to the thickener change over time and that by sensing or calc..l~ting these changes before they enter the thickener, control schemes can be more effective than otherwise might be possible. Feedbaçk is where measurements and calculated values that indicate process pelrollllance and m~.h;ne state are used by 10 controller 52 and the control scheme contained therein to stabilize the performance and to oplimize pelrollllance as feed conditions changes and m~r.hine performance çh~nges in rt;relence to set points and optimization objectives.
Process and m~chine models are embedded in controller 52, as are methods to evaluate the models to determine the present and future optimum operating conditions l S for the m~chine. Optimum conditions are specified by flexible, objective functions that are entered into the controller 42 by the operators or plant control system that is dealing with plant-wide control and oplillli alion. The models contained therein are adaptive in that their form or m~th~m~tic~l repres~..lalion, as well as the pal~lllclers associated with any given model, can change as required. These models include, but 20 are not limited to first principles and phenomenological models as well as all classes of empirical models that include neural network r epresen~alions and other state space approaches. Oplilnizalion is accomplished by colllbh~ing the contained knowledge of the process and machine through these mode}s with expert system rules about the same. These rules embody operational facts and heuristic knowledge about the 25 thirL ~n~r and the process streams being processed. The rule system can embody both crisp and fuzzy rel)resenlalions and combine all feed fOIv~ald, feedb~c~, and model replesenlalions ofthe m~r.hine and process to ~ stable, safe, and also optimal operation inr~ ling the machine and the process. Determination of the optimum operating states includes ev~lu~ting the model representation ofthe m~rhine and 30 process. This is done by conll)illàlion of the expert system rules and models in CA 022~4896 1998-11-13 W 097/43027 PCT~US97/08027 conjunr,tion with the objective functions. Genetic algorithms and other op~ .Al;on metho~c are used to evaluate the models to determine the best possible operatingconditions at any point in time. These methods are combined in such a way that the combined control approach changes and learns over time and adapts to improve pe~ru~ll.ance with regard to the m~chine and the process pelr~l-"ance.
A detailed description of a suitable system employing an internal process model as described herein for use in connection with the present invention is disclosed in U.S.
Application Serial No. 60/037,355 filed February 21, 1997, aesigned to the accignee hereof, all of the contents of which are incorporated herein by reference.
As dicc~ssed above, the adaptive control system ofthis invention uses one or a combination of internal and/or external machine and/or process variables to characterize or control the pe.~...,ance of the thickener, in terms of the desired process outputs. Preferably, the control system continually updates its knowledge of the process, so that its control performance improves over time.
One ofthe important calculated values inr.l~lded in this process is the economicpc.ru,..,ance ofthe thickener. Economic performance incl~1des base m~çhine operating costs, inrhl-~in~ power usage and chemical additive usage, and the normalized pe rol-,.ance cost dealing with throughput rates and the quality of the productsproduced both in absolute terms and terms normalized for feed conditions.
Still le~llh-g to FIGURE 2, in response to the one or more pa.~l"e~ers sensed by the sensors 42 and 44, the advanced control system of the microprocessor may actuate one or more process and/or equipment control devices 48 to control operations. The operational outputs from the central controller 52 may be processed though a control output interface 54. In some cases, the control devices will beact~l~ted if certain sensed parameters are outside the normal or preselected thiç~ener ope,~ling range. This operating range may be programmed into the control system either prior to or during operation. Examples of operational parameters which may be ~djllsted include but are not limited to volume or mass flow rates into the feed, underflow and/or overflow ~ an,s, the particle size, concenll alion~ and distribution of solids in the feed, underflow and/or overflow streams; the rate of addition of CA 022~4896 1998-11-13 flocc~ ntc and other chemical additives; speed of rotation of the rake, rake power consumption; rake configuration, lift of the rake above the floor of the thickener, underflow density, overflow rheology and withdrawal rates of underflow and overflow streams. The foregoing operational controls and c~al~ples of actual control devices which will provide such operational control will be described in more detail below.

Readout at Monitor Referring still to FIGVRE 2, other outputs include the real time status of various parameters at the thickener to the operator. Thus, the operator may use the computerized control and monitoring system of the present invention to diagnose the present condition of the equipment, order spare parts (a modem/fax 66 may be inf luded for spare parts ordering), or obtain a read-out as part of a SCADA system or DCS as described above.
A particularly pleÇe,led embodiment ofthe present invention employs an im~ginp system colnplis;ilg ultrasonic, sonar or millimet.or wave sensors or the like 46 producing a continuous profile bed which is converted to data usable by the process models of the present invention. Continuously measuring and profiling the bed greatly rnh~nees process control since the operator can then opth~ e the bed gradient in real time by adjusting the flocculant dosage and/or the underflow or overfiow withdrawal rates. The data from the ultrasonic, sonar or other im~ging system may be interpreted by a video sensor system. Such a system, dçcigned for use in mineral processing operations is described in "The Development of a Color Sensor System to Measure Mineral Compositions" by J.M. Oestreich et al., Minerals F.ngine~ring, Vol. 8, Nos. 1-2, pp. 31-39, 1995, herein incorporated by re~rence. The color sensor system described therein CO-.lpl ;ses a color video camera, a light source, a video-capture board, a computer, and a computer program that compares measured color vector angles to a previously stored calibration curve. Several cameras may be connected to a single color sensor computer or a single camera may cimlllt~neously observe several locations using a network of fiber-optic cables.

CA 022~4896 1998-11-13 W 097/43027 PCTrUS97/08027 This piere,l ed embodiment of the present invention may further comprise an advanced control system employing both pattern analysis by neural networks, as well as st~ti.ctics and color vector analysis. For example, gray level deprndçnr.e matrix methods are used to extract statistical features form digiti7ed images of froths. These st~tietir~l realules constitute a comr~ct set ofthe essrnti~l data contained in the original image, which can then be related to the met~ rgical par~tlers of the flotation process by means of neural nets. Either supervised neural nets, such as learning vector q~nti7~tion systems, unsupervised nets, such as self-olgalfi~ed ".apph-gs, or a self-o~ r~;~.;ng neural net which can map high-dimensional inputvectors to lower-dimensional maps in a topological order-preserving manner are used.
Topological maps have the advantage that they can be used to track the pe~Çu~l"ance of flotation processes on a continuous basis, as opposed to the discrete classification by other classification paradigms. For e~a~nple, the thickener process could be monitored by means of a characteristic profile on a two-dimensional feature map,which would enable the early detection of deviation from optimal conditions by intelligent automation systems through compa~ison ofthe actual profile ofthe system with an ideal or optimal profile.
In addition to color, both viscosity and mobility of the bed slurry may be recorded and analyzed by visual means. Thus, in a further embodiment of this invention, a series of modules may be used to monitor di~re~enl features with a high degree of accuracy. Thus, a machine vision system based on the inte,~re~a~ion ofvisual features of bed slurry structure has a modular structure, in which one module will riis~in~ich bctween the bed levels based on differences in morphology, a next module will base the dictinr~tion on slurry mobility, another will extract cl)~ollla~ic information, another average particle size, and so on.
Referring now to FIGUR~ 3, a ~lc;relled embodiment of the present invention is shown wherein the intelligent control system includes one or more non-intrusive sensors for dete"";niJ-g bed profile and other parameters. In FIGIJRE 3, a thickener is shown at 80. Thickener 80 inr,llldes a feed input 82 and a flocculant input 84. A rake is shown at 86 associated with a rake driving system 88. Feed is pumped from a feed CA 022~4896 1998-11-13 W 097/43027 PCTnUS97108027 source by feed pump 90 through feed control valve 92 and then into feed input 82.
Similarly, flocculant is pumped from flocculant tank 94 via flocculant pump 96 and into flocculant inlet 84. As is well known, underflow is emitted from the bottom of tank 80 using an underflow pump 98 through an underflow control valve 100.
In acco-dance with an important feature of this plt;r~lled embodiment~ a nearly non-intrusive sensor 102 is associated with thickener 80. As mentioned, by nearly non-intrusive, is meant that this sensor is not required to be lowered into the bed (as many conventional prior art probes) nor is the sensor required to be positioned onto struts or other structure within the tank. Tn~tefl~, the sensor may be mounted above or just beneath the liquid surface in a manner which does not impede the movement of rake 86 or the settling of materials within the bed. In the embodiment shown in FIGURE 3, the non-intrusive sensor 102 is positioned on walkway 104. Plere,~bly,sensor 102 will obtain a bed profile over the entire bed (or at least that portion of the bed which is of interest), both holi~onlally and vertically. In order to obtain such a complete profile, the sensor 102 is preferably mounted in a manner such that it may oscillate, describing an arcwise motion or move linearly along a radius of the tank.
Also, a plurality of sensors 102 may be mounted in strategic positions along the bed so as to obtain the desired partial or complete bed profile. For c,~a~?lc, with respect to thickeners, one area of particular interest is around the central feed well 108, where the buildup of solids occurs. In order to monitor this build up of solids, a first sensor is positioned above the area adjflcent to the feed well, and a second sensor is positioned midway to the periphery. Alternatively, a single sensor may be mounted on a carriage that moves it to the area of interest. In any case, sensor(s) 102 is mounted such that it is able to provide information for at least a plane of investigation through a sludge bed 2~ or other area of interest. Prior interface analyzer sensors, for example, have been restricted to analysis along a single line of investigation. At most, such sensors can only provide information legardh-g di~rent density or other measurements along that one line. Even where a computer program is provided that allows monitoring of profiles from multiple sensors, such a readout from multiple sensors could still not CA 022s4896 1998-11-13 W O 97/43027 PCT~US97/08027 present a filll two-dimensional depiction of the relevant plane of investigation. Tnste~d, only multiple discrete lines of investigation are provided.
As shown by the dashed lines in FIGURE 3, sensor 102 communic.~tes with control system 106 which consists of a suitable computer or microprocessor control device. In turn, control system 106 has the ability to commun:~~te or control rake 86, feed pump 90, feed control valve 92, flocculant pump 96, under~cow pump 98, and underflow control valve 100.
Non-intrusive sensor 102 pre~elably comprises an acoustic (ultrasonic or sonar) sensor or a millimet~r wave radar sensor. An example of a suitable ultrasonic sensor is ~ r.losed in U.S. Patent 5,148,700 (all ofthe COI-telllS of which are incorporated herein by reference). A suitable commercially available acoustic sensor is sold by Entech Design, Inc. of Denton, Texas under the trademark MAPS~. Preferably, the sensor is op~.aled at a multiplicity of frequencies and signal strengths. Ordinarily, sensors operate to "see" the line of predetermined density in the plane of investigation. In other words, the ultrasonic signal is not returned by densities lighter than thepredetermined density that lie above that line, and the signals do not penetrate to the greater densities that lie below the predetermined sludge density. However, by Gl~gil~g the frequency and strength of the signal, the predetermined density to be investi&~ted is also çh~n~ed.
Suitable millimeter wave radar teçllniques used in conjunction with the present invention are described in chapter 15 of Principles and Applications of ~illimetçr Wave Radar, edited by N.C. Currie and C.E. Brown, Artecn House, Norwood, MA
1987. The ultrasonic technology referenced above can be logically çYtçn~ed to millimeter wave devices. It will be noted that while the ultrasonic and millimeter wave radar sensors are characterized as being "non-intrusive", the ultrasonic and sonar sensor does enter, to a limited extent, the top of the liquid above the bed, since contact is needed between the bed and the sensor in order for such sensors to propclly function. The millimeter wave sensor will operate in a true, non-intrusive manner, being mounted above the liquid surface. Such limited penetration of the bed is shown sçh~m~tic~lly in FIGURE 3 by sensor 102.

CA 022~4896 1998-11-13 W O 97/43027 PCTrUS97/08027 The output of sensor 102 provides i~lrol~,alion regarding the concentration of solid particles in the thickener bath, as a function of ~ict~nce from the sensor head at a given time. This h~.."dlion is used to calculate a profile ofthe thickener, providing a digital picture of the solids concentration from top to bottom. The c~lcul~ted profile 5 also indicates the relative height of the sludge bed (the settled solids on the bottom of the thickener). This profile may be numerically integrated to provide an accurate es~ e of solids holdup in the thickener.
Sensors 102 may be configured to measure Doppler shi~c from the particles sensed in the settling zone, thus allowing the calculation of settling velocity. In 10 addition, the sensor 102 may be configured to measure the spectral reflectance from the surface of the sludge bed, allowing a calculation of solids concentration in the sludge bed. Other c~lc~ tions may be made from the raw sensor data.
The plt:Ç~"ed control system shown in FIGURE 3 utilizes a single sensor to dele..,line one or more of the following: solids settling velocity, solids settling profile, sludge bed level, solids holdup, and sludge bed solids content. These measurements, along with other measurell-enl~ which may be made as needed can be used to control one or more of the following: feed rate, flocculant addition rate, and underflow rate.
Control of feed and underflow rates may be made by r.h~ngin~ pump speed, controlvalve opening, or both. Other control variables include, but are not limited to, volume and mass flow rates of feed, overflow, and underflow; clarity or turbidity of feed, overflow and underflow; rake torque, and rake lift height.
Thus, while sensor 102, by itself, may be used to provide accurate measurell,enls of sludge (or other material inventory), and control over the inventory by a:ljustmçnt of feed and sludge withdrawal rates, preferably, sensor 102 is used in con-billalion with a feed mass meter 1 10 to effect further control of inventory and flocculant addition. Other parameters of particular interest in co~llbination with sensor 102 is measurement and control of rake speed, rake lift, and rake toro~ue.
Control decisions will be made by the '/intelligent" control system (described above) to opLh~i,e the performance of the thickener as desired.

CA 022~4896 1998-11-13 W O 97/43027 PCTrUS97/08027 Still other examples of suitable non-invasive sensors for use in the present invention are those known laser based sensors which detect and monitor the interfaces between, for example, liquid and solids or liquids of varying density. Such known laser detection systems are used to penetrate a liquid (i.e., water) layer and detect interfaces with solids and other dense objects and layers. Examples of such laser systems are disclosed in U.S. Patents 4,862,267;4,964,721;4,967,270;5,013,917; and 5,450,125;
as well as in the following publications: "Laser Remote Sensing" by Raymond M.
Measures, published by John Wiley & Sons, Inc. (1984); M.F. Penny, B. Billard, R.
Abbott "LADS - The Australian Laser Airborne Depth Sounder," International Journal of Remote Sensing, (10) 1463(1989); and J. Lillycrop, J. Banic, "Advancements in the U.S. Army Corps. of F.n~ineçrs Hydrographic Survey Capabilities: The SHOALS
System," Marine Geodesy (15) 177(1989), all ofthe contents ofthe foregoing patents and publications being incorporated herein by I Grel ence.
In a plGrGllGd embodiment ofthe present invention incorporating a laser based system of the afol emenlioned type, a red laser beam is split. Half the beam is then frequency-doubled, beconling green. When the dual beam is directed at, for example, a thickener tank, the red beam reflects from the surface of the water, providing a rererGnce point, while the green beam penetrates the water and reflects from theinterface of the settled solids with the water. Thus, the level of the settled solids may be c~lc~ ted using an instrument that does not require contact with the water, that is, using a non-lnvasive sensor.
While non-invasive monitoring, diagnosing, opel~ling and controlling of various pal ~IlGLers and processes of thickeners, clarifiers, and settling tanks is a prerel I ed embodiment of the present invention, simple monitoring operations using ultrasonic and sonar sensors is also within the scope of the present invention. Such monitoring operations are not required to be coupled to any computerized controloperations. Thus, as shown in FIGURE 3, an ultrasonic sensor 112 pivots about a single axis to give a single planar view of, for example, the sludge bed 130, and then projects this view throughout the thickener 120 to give a three-dimensional rGprese"l~lion. Such projection of a three-dimensional leplesentation from a two-CA 022~4896 1998-11-13 dimensional view is possible where the feed meçl-~ni~m.~ result in generally uniform distribution ofthe influent across the thickener, and the withdrawal me~ i$1~ result in a generally uniform withdrawal from the sludge bed. The operation of a rake arm 86 would f~cilit~te the uniform distribution of materials throughout the tank. Suchmonitoring should compensate for the movement of a rake arm or other equipment into the plane of investig~tion of the sensor. Monitoring of this type may be used alone, or in cGl..bh-alion with the other sensors and intelligent computer control systems described above.
It will be app~ eciated by those skilled in the art that the use of a non-intrusive sensor for providing a bed profile for thickeners, clarifiers and settling tanks will also be extremely useful for monitoring or controlling other processing tanks such asreaction vessels, which hold multiphase materials having either single or multiple components. Examples of such other types of proce~ine tanks wherein the p, e[~" ed embodiment of this invention will be ~".li el..ely useful include chemical reaction vessels such as those used in r~nenlalion, spray dryers, flash crystallizers and other reactor vessels. Thus, it will be appreciated that this invention also inrludes the use of the non-intrusive sensors and associated control systems shown in FIGURE 3 for use with any other type of processi~ tank holding multiphase materials such as the a~relllt;,llioned reactors and like vessels. The use of such non-invasive sensors and associated control systems for other types of processing tanks is shown sch~ tically in FIGURE 4 with like elements bearing the same identifying numerals with the addition of a prime. Thus, in FIGURE 4, the processing tank for holding a multiphase material which may contain a single or multiple component is shown at 106 and isassociated with the same non-intrusive sensor control system as that depicted inFIGURE 3 whereby bed profiles can be accurately determined and subsequent control of the processing tank can then be executed.
Referring now to FIGURES 5-8, a se~liment~tion process, in which solids are separated from liquids by settling, e.g., a thickener, may be controlled using the output of a sonar sensor 210. For sedimentation control, sonar sensor 210 is dç~igned to operate in either stationary or scAn~ g mode. Sensor 210 is mounted just below the CA 022~4896 1998-11-13 W O 97/43027 PCT~US97/08027 surface of the liquid in the process vessel 80, to achieve adequate acoustic coupling.
The sonar signal is directed into the process liquid. The return signals, or echoes, arising from reflections along the signal path are detected, with their signal strengths and transit times being recorded. Given the speed of sound in the process liquid, the transit time allows ç~lc~ tion of the ~ t~nce traveled by a given return signal. The return signal strength is proportional to the solids concenl, ~lion at the point from which the reflection occurred. Thus sonar sensor 210, with approp,iately configured signal processing can calculate the solids concentration profile along its signal path.
Sensor 210 can operate in sc~nning mode, in which its sensing head, or tr~n.cd~lcer, rotates about an axis allowing its path to scan along a radius ofthe process vessel, as shown in FIGURES 5- 6. In this mode, sensor 210 will provide information regarding the level of solids being held at the bottom of the vessel 80. By integrating the sc~nned solids level over the entire radius of the vessel 80, the total contained solids, or solids holdup, can be estim~ted at a given time. The scanned profile will also provide indication of certain common process irregularities, including the buildup of solids on or in front of the rake 86 of thickener 80 or a clarifier. These irregularities are commonly described as islands or doughmltc. A typical video display of the sonar sensor signal is shown in FIGURE 7. Such displays are typically color or otherwise coded such that the signal strength is displayed visually.
When detailed inforrnation regarding the sedim.ont~tion process is required sensor 210 may operate in a fixed or stationary mode, with its tr~n~ducer directed along a single path. This path will normally be vertical, but may be otherwise. In the fixed position, a det~iled profile of the return signal may be recorded and processed.
In general, that profile will resemble the one shown in FIGIJRE 8. The profile in FIGURE 8 shows the change in return signal strength in response to four primary variables from which key process control parameters can be calculated. Peak 1 lepresenls the sudden change in solids concentration at the beginnin~e ofthe settling zone, where the solids begin to thicken. Peak 2 repl esenls the sudden change in solids concentration at the bep;l---ing of the sludge bed, where the settled solids reside and are comr~cted before leaving the process vessel. Area 3 represents the gradual change in CA 022~4896 1998-11-13 WO 97/43027 PCTrUS97/08027 solids conce"~ ion between the beginning ofthe settling zone and the beginnin~ of the sludge bed, this rate of change being indicative of the settling rate in the settling zone, and area 4 rep, ese"ls the change in solids concentration from the be~inning to some ~lict~nce within the sludge bed, in~icating the degree of compaction taking place 5 within the sludge bed. The peak labeled five is due to near field reflection.
The process pa~"ele~, as derived from the sonar signal, will allow control of pa~ a,.,cters such as the rate of flocculant addition and of the rate at which the settled solids are removed from the tank.
This sensor 210, with its two operating modes, may be part of an expert or 10 intellig~nt control system 106, in which the sensor's operation is controlled by a computer program, which program is designed to opli",ize the process, and to operate the sensor as required to control the process in an optimal manner. The operational mode ofthe sensor 210 (sc~nning or fixed) will be selected either m~nl-~lly, or automatically. For automatic mode selection, the sensor system will include a microprocessor or similar control device, so that the sensor can communicate with a process control computer or system through a standard communications interface.
Thus the sensor system will be capable of responding to various co....~.AI--ls from a process control computer or system, which comm~n-l~ will control its sc~nning action.
More than one sensor may be used on a given process vessel, depending on the vessel size and the speed and ~ttenll~tion of the sonar signal within the process media.
Multiple sensors may also be used to provide more detailed h~o,l"alion about theprocess, for optimized control.
The sensor system may also be provided with multiple tr~n.~ducers, so that it can operate at varying sonar frequencies. The sonar frequency of the sensor (sc~nnitlg or fixed) will be selected either m~m~lly or automatically. For automatic signal~llen~h selection, the sensor system will include a microprocessor or similar control device 106, so that the sensor can communicate with a process control computer or system through a standard communications interface. Thus the sensor system will be capable of responding to various comm~n-l~ from a process control computer or system, which co,.. l~l-ds will control its sonar frequency.

CA 022~4896 1998-11-13 W O 97/43027 rcTrusg7/o8027 The sensor system may also be configured to operate at varying levels of sonar signal sl~ glh (amplitude). Again, the sonar signal strength of the sensor (sc~nning or fixed) will be sPIected either m~n-l~lly or automatically. For automatic signal ~llen~
selection, the sensor system will include a microprocessor or similar control device 106, so that the sensor can comrnunicate with a process control computer or system through a standard comm~-ni~tions interface. Thus the sensor system will be capable of responding to various comm~ntli from a process control computer or system, which co.. a~-ds will control its sc~nning action.
The ability to select sonar frequency and signal ~l,englh will make it possible to oplillli e the sensor's operation as the process media change, allowing for the ,,,zx;.,,..,,, signal penetration through the liquid phase and into the settled solids.
While prefe~ed embodiment.c have been shown and described, various modific~tiQns and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the presentinvention has been described by way of illustrations and not limitation.

Claims (22)

What is claimed is:
1. CLAIM 1. A processing tank for holding or processing a multiphase material comprising:
   at least one non-invasive sensor for continual sensing in real time of least oneparameter associated with the tank;
   a control computer associated with the tank and communicating with said sensor; and a control device for controlling said thickener, said control device communicating with said control computer, wherein said control computer actuatessaid control device in response to input from said sensor.
2. CLAIM 2. The processing tank of claim 1, wherein said sensor is selected from the group comprising sensors to sense solids settling velocity, solids concentration in bed, solids settling profile, sludge bed level and solids hold-up.
3. CLAIM 3. The processing tank of claim 1, wherein said sensor is selected from the group comprising ultrasonic sensors, sonar sensors, laser sensors and millimeter wave radar sensors.
4. CLAIM 4. The processing tank of claim 1, wherein said control computer includes a process model which is at least partially self-generated and continually updated and adapted.
5. CLAIM 5 The processing tank of claim 4, wherein said process model is updated using at least one of the advanced analysis techniques selected from the group consisting of neural networks, genetic algorithms, fuzzy logic, expert systems, statistical analysis, signal processing, pattern recognition, and categorical analysis.
6. CLAIM 6 The processing tank of claim 1 wherein:
   
   said control device controls at least one of flocculant addition, rake speed, rake power consumption, torque on rake, rake lift height, feed rate, chemical addition rate, underflow rate, underflow density, underflow rheology and rake configuration.
7. CLAIM 7. The processing tank of claim 1 wherein:
   said tank comprises a thickener.
8. CLAIM 8. The processing tank of claim 1 wherein:
   said sensor is initialized by sweeping at least one of a range of frequencies, signal strengths and threshold returns.
9. CLAIM 9 A method for controlling a processing tank for holding or processing a multiphase material, comprising:
   continual sensing in real time of at least one parameter associated with the processing tank using at least one non-invasive sensor system;
   controlling the processing tank based, at least in part, on information from said non-invasive sensor system.
10. CLAIM 10. The method of claim 9, wherein said sensor is selected from the group comprising sensors to sense solids settling velocity, solids concentration in bed, solids settling profile, sludge bed level and solids hold-up.
11. CLAIM 11. The method of claim 9, wherein said sensor is selected from the group comprising ultrasonic sensors, sonar sensors, laser sensors and millimeter wave radar sensors.
12. CLAIM 12. The method of claim 9 wherein the controlling step includes control ofat least one of chemical addition, rake speed, rake power consumption, torque on rake, rake lift height, feed rate, chemical addition rate, underflow rate, underflow density, underflow rheology and rake configuration.
13. CLAIM 13. An apparatus for controlling a thickener comprising:
    a computerized control system which continually monitors parameters associated with the thickener process and executes control instructions in response to said monitored parameters based on an internal process model which is at least partially self-generated and continually updated and adapted.
14. CLAIM 14. The apparatus of claim 13 wherein said process model is updated by means of at least one analysis method selected from the group comprising neural networks, genetic algorithms, fuzzy logic, expert systems, statistical analysis, signal processing pattern recognition, categorical analysis, or a combination thereof.
15. CLAIM 15. The apparatus of claim 14 wherein said process model is further generated and updated by at least one of feed forward or feedback loops.
16. CLAIM 16. A monitoring system for a processing tank for holding or processing a multiphase material, comprising:
    a sensor which senses in two dimensions a planar view of said multiphase material, said sensor projecting said sensed view into a three dimensional representation of said multiphase material.
17. CLAIM 17. The monitoring system of claim 16, wherein said sensor is an ultrasound or sonar sensor.
18. CLAIM 18. The monitoring system of claim 16, wherein the sensor pivots about an axis in order to generate said planar view.
19. CLAIM 19. The monitoring system of claim 16, wherein said sensor senses a planarview of a sludge bed, said sensor projecting said sensed view into a three dimensional representation of said sludge bed.
20. CLAIM 20. The monitoring system of claim 16, wherein said processing tank comprises a thickener.
21. CLAIM 21. The monitoring system of claim 16 wherein:
    said sensor is operable in a movable scanning mode where said sensor is directed along a plurality of paths and said sensor is operable in a stationary mode where said sensor is directed along a single path.
22. CLAIM 22. The monitoring system of claim 21 wherein:
    said sensor is rotatable about at least one axis to allow said sensor to scan along a radius of the tank when operating in said scanning mode.