US 3846231 A
Description (OCR text may contain errors)
NOV. 5, 1974 w.. CRQSBY ETAL 3,845,231
APPARATUS FOR DETERMINATION 0F THE MAGNITUDE 0F TOTAL.- SPECIFIC ENERGY ABsoRBED BY A SAMPLE 0F PULP STOCK;-
FLAT BOXES l FOURDRINIER FP -WASHERS ROI. L@
COUCH LIQUOR DIGESTER Nov. 5, 1974 w. E, CROSBY ErAL 3,846,231
E ofI TOTAL ABsoRBED BY A SAMPLE 0F PULP STOCK APPARATUS FOR DETERMINATION OF THE MAGNITUD SPECIFIC ENERGY Filed July 25, 1972 4 Sheets-Sheet 2 SET POINT wooo FURNISH u "K" N2 x wooo FURNISH v llKll Y I I 2o 4 WILLIAMS sLowNEss- SEC.
ZOO-I O IR r.O 6 m n A .Q E M G l G A l T m m D m R W F D U P E C A R K A L C V E m w H 1 L S C P W w P A A R `C O 22.214.171.124 9876 5. 6655 3 2 2 2 2 2 nog. .0mm .0I .Z
O lm O r2 V E T A R E G G m m N I I A M F R U l E D U R C K A C V I D O F. T H U S C P W U x D. A O A R C O 5.0.50. 9876 5 6655 M ma E man. .0mm 0I .7:
ELAPSED TIME- SEC.
NOV. 5, 1974 w, E, CRQSBY E TAL 3,845,231
APPARATUS FOR DETERMINATION 0F THE MAGNITUDE oF TOTALv SPECIFIC ENERGY ABSORBED BY A SAMPLE OF PULP STOCK 4 Sheets-Sheet .3
Filed July 25, 1972 xOmo mI OF EDDO IODOO mmImSS 20mm Nov. 5, 1974 w. E. CROSBY ErAL APPARATUS FOR DETERMINATION OFTHE MAGNITUDE 0F TOTAL SPECIFIC ENERGY ABSORBED BY A SAMPLE OF PULP STOCK Filed July 25, 1972 4 Sheets-Sheet 4 STOP TIMER CGMPUTER AIR SUPPLY "nited States atent 3,846,231 APPARATUS FOR DETERMINATION F THE MAGNITUDE 0F TOTAL SPECIFIC ENERGY ABSORBED BY A SAMPLE GF PULP STOCK William E. Crosby, Hanahan, and Hong H. Lee, Charleston Heights, S.C., assignors to Westvaco Corporation, New York, N.Y.
Filed July 2S, 1972, Ser. No. 274,967 Int.. Cl. D21d 1/20 U.S. Cl. 162-263 3 Claims ABSTRACT 0F THE DISCLOSURE Pulp stock water retention properties may be measured with high reliability by separating fiber from the water vehicle of a fixed volume sample of stock that is pressure differentially drawn across a perforated partition disposed between a stock reservoir and a sample chamber. Freeness of the stock is proportional to the time interim required to fill the chamber between two level switches with water strained through the fiber mat accumulated on the partition. The level switches respectively start and -stop a chronometer. Continuous operation of the apparatus at a rapid cycle rate is achieved by chronometrically pacing the emission of electric starting pulses. By transmitting the freeness time interim to a coordinating computer prograined with a laboratory determined freeness to refining tensile and bursting characteristics of the finished paper. the sampled stock, the degree of total specific energy absorbed by the stock may also be determined.
BACKGROUND OF THE INVENTION Field of the Invention This invention relates to the measure of water retention and refining energy absorption properties of aqueous slurried wood pulp for the manufacture of paper and Pulp- Description of the Prior Art Refining engines, as characterized by the papermaking art are wood pulp preparation machines that induce fibrillation along the surface of the cellulose fiber. When bonded together, the intertwined fibrils increase the structural tenacity between adjacent fibers to improve the tensile and bursting characteristics of the finished paper. However, tear resistance of the finished paper is diminished by such fibrillation. Consequently to achieve an optimum balance between these contradictary effects of refining, the degree of fibrillation must be carefully controlled.
For any given paper, each of these characteristics, tensile, bursting and tear strength, may be related, by a determinable function, to the magnitude of refiner work imparted to the pulp stock (specific energy) from which the paper is formed.
Specific energy consumption is a work per unit of stock mass relationship and is usually determined in kilowatthours per ton of stock or some equivalent thereof such as BTU per ton of stock. Specific energy may be the calculated product of such measurable parameters as stock flow rate, stock consistency and refiner motor currrent supply or stock fiow stream temperature differential across the refiner engine.
Also related by a determinable function to the reiner work on the pulp stock are the water holding properties of the stock. These properties describe the ease with which water passes through papermaking fibers while they are being forced into a wet mat on the fourdrinier screen of a paper machine. A free pulp drains readily whereas a slow pulp drains its Water slowly. Consequently, for the ICC given pulp stock, a measure of such water retention properties may provide a direct indication of tensile, bursting and tear characteristics of a paper to be produced from the pulp stocks.
Numerous tests have been devised to quantify pulp stock properties of water retention. Typical among such tests are the Canadian Standard =Freeness Test wherein 1- liter sample of standard consistency stock is allowed to flow freely into a funnel. Flow from the funnel is restricted by yan orifice of select size. A side outlet is selectively positioned in the funnel Wall. 'I'hat portion of the l-liter sample not accommodated by the flow rate of the orifice is drawn off for volumetric measurement as a quantity of the pulp freeness. A low volume represents a free stock whereas a high volume represents a slow stock.
Another type of Water retention property test is that for drainage factor. This quantity may be determined by forming sheets on a British standard sheet machine under standard conditions and taking the drainage time and Weight of the test sheets. The drainage factor is the slop of the line produced when drainage time is plotted against weight of stock added to the sheet machine. Units for drainage factor are in seconds per gram.
A third test for pulp water retention, the Bolton- Emerson test, is a variation of the drainage factor test wherein the weight of the test sheet is standardized for a test series. In the Bolton-Emerson test, a standardized volume of pulp slurry having a standardized consistency is passed through a screen of such mesh as to allow the passage of water but not fiber. The test sample is subjected to standardized pressure differential conditions across the screen. These conditions leave only the time factor as a variable in the test, the weight of plup, quantity of water and pressure drive being standardized. Accordingly, to obtain a quantitative measure of freeness or slownessf one need only measure, in seconds, the time interval required to separate the fiber from the water. A low time interval indicates a free stock whereas a high time interval is indicative of a slow stock.
Lacking in all the above described water retention property tests is consideration for the vibratory dynamics actually present on the fourdrinier wire. Since the drainage performance of a pulp on the fourdrinier wire is generally characterized, in the art, as drainage rate any test for pulp Water retention properties independent of the fourdrinier shall be characterized for purposes of this disclosure, as a test for static drainage rate.
If, in a particular mill, producing a particular pulp, the raw stock, direct from the digesters or defiberizing engines, had consistent water retention properties, it would be a relatively simple mater to merely control, in a direct manner, the magnitude of refining energy applied to the stock in order to consistently achieve the desired retention property at the paper machine headbox.
However, many uncontrollable factors infiuence the raw stock retention property such as the moisture content and species characteristics of the raw wood furnish to the digester. Accordingly, the degree of digestion and defiberization necessary to yield a constant raw stock retention property is continuously changing for practicably indeterminate reasons.
Consequently, it is of limited value to the papermaker to know exactly how much refining energy he will or has applied to the raw stock since he doesnt know exactly how much energy is necessary for the run of stock, then flowing, to yield the desired retention property as an end result.
If the papermaker knew, precisely, the retention properties of the presently flowing raw stock, at the time the power setting of the refiners must be determined, he could do so with confidence. However, the known and accepted tests for such properties are, definitively, of a batch or incremental nature, usually performed under the exact conditions of a laboratory. Such test procedures are much too slow and cumberson to provide the papermaker with refiner control information at the time it is needed.
In lieu of a timely water retention property test of the stock, papermakers have relied on the indicated vacuum drawn from the flat box or couch roll of the paper machine fourdrinier section as a continuous measure of these properties. U.S. Pat. No. 2,699,095, Re. 24,185 and 3,654,075 are examples of automatic refiner control systems that are monitored by vacuum measurements taken at the fourdrinier section.
Although fourdrinier section vacuum is related to the final water retention properties of the stock, it is also related, unfortunately, to numerous other mechanical characteristics of the paper machine and web that are independent of water retention or drainage rate as it is called in connection with the fourdrinier. Disturbances or changes in the couch roll vacuum, therefore, may or may not be related to a change in the stock drainage rate. For example, an undetected mechanical change in the headbox slice lip opening of unobvious magnitude could cause a shift in the couch roll vacuum. If the vacuum shift is assumed to be drainage rate related, correction of the vacuum indication may be obtained by an appropriate alteration of the refiner energy application. This action, however, will establish a new balance between the adjusted drainage rate and the quantity of stock deposited by the new slice opening on the fourdrinier screen. Hence, the finished paper will be over or under refined for the desired mechanical characteristics and, moreover, will have an undesired basic weight.
Accordingly, couch roll or fiat box vacuum offers an unreliable alternative to direct Water retention property monitoring for refiner control.
Even if it were possible to reliably isolate fourdrinier section vacuum measurements due to stock drainage rate from those due to other sources, as is attempted by the teaching of U.S. Pat. No. 3,654,075, for example, there would yet remain the wasted effort problem attendent with a feed-back control system. Whether practiced manually or automatically, any control system which monitors one or more quality characteristics of a product subsequent to the operational station responsible for the characteristics inherently tolerates the production of a small amount of error for the benefit of the larger amount. Of course, small and large are relative quantities and in years past, when a typical paper machine lwould produce approximately 2 tons of paper per hour, there would only be approximately l ton of refined pulp fiber in storage between the refiner and the fourdrinier wire. In other Words, from the time the inferior quality condition was detected to the time it could be corrected, only 1 ton of inferior quality product need be produced.
By contemporary standards, a typical paper machine is supplied with 30 tons of pulp fiber per hour from as many as parallel flow refiners to produce as much paper product per hour. At this production rate, 5 tons of refined pulp fiber may be in storage between the refiners and the fourdrinier wire. If this storage stock is of inferior quality, the production of 6 tons of inferior and possibly unmarketable paper product must be produced before correction of the condition may be effected by the prior art feed-back control systems.
Although some effort has been given of late to continuous, on-line, measurement of pulp stock Water retention properties as represented by U.S. Pat. No. 3,655,980 and the Aug. 21, 1961, publication in the Paper Trade Journal of an article entitled Continuous Freeness Measurement and Control, such teachings have not been Wide'y adopted by the industry. Furthermore, no teaching is found to suggest that the specific energy input of stock refiners may be directly controlled by such prior art stock water retention measurement systems. More particularly, not teaching is found to suggest that pulp refiners may lbe directly controlled most advantageously by sampling the stock water retention property before refining for feedforward control of the refiner energy input.
It is, therefore, an object of the present invention to teach the construction of a simple, on-line, rapidly cycling static drainage rate measuring device having reliability of performance characteristics comparable to laboratory determinations.
Another object of the present invention is to teach an automatic refiner control strategy pursuant to direct, static drainage rate measurement.
A further object of the present invention is to teach a feed-forward automatic refiner control strategy.
SUMMARY OF THE INVENTION These and other objects of the invention may be achieved by electrically pacing and measuring the pneumatic control cycle of a Bolton-Emerson type of water retention property test meter disposed for continuously sampling raw pulp supply stock to refiners. Simultaneous with a water retention test, tests are also taken of stock temperature, consistency and pH. If test conditions are within predetermined limits, a signal proportional to measured water retention may be accepted as a reliable measure of static drainage rate. Said static drainge rate signal is processed, either manually or by computerized logic, to determine, from a laboratory and operationally developed history of the stock type, the magnitude of refiner work needed of the approaching stock to achieve a desired final static drainage rate. Signals proportional to the needed refiner work are then entered as set-point control signals to an automatic refiner control system such as is disclosed in U.S. Pat. No. 3,568,939.
DESCRIPTION OF THE DRAWINGS FIG. l is a flow diagram of the papermaking process between the digester vessel and the fourdrinier section of the paper machine.
FIG. 2 is a graphic plot of refiner applied specific energy as a function of static drainage rate for two pulp stocks distinct in furnish, as to Wood species, and degree of coking, as to Kappa number.
FIG. 3 is a composite plot against elapsed time of a typical change in the static drainage rate of raw stock to illustrate the consequent effect on couch roll vacuum and applied refining energy pursuant to a feed-back corrective control system.
FIG. 4 is a composite plot against elapsed time of a typical change in the static drainage rate of raw stock to illustrate the consequent effect on couch roll vacuum and applied refining energy pursuant to the feed-forward refiner control system of the present invention.
FIG. 5 is a stock tiow piping schematic of the overall refiner control system of the present invention having superimposed thereon an integrated control logic flow schematic representative of the invention.
FIG. 6 is an integrated electrical-pneumatic circuitry diagram for the static drainage rate sampling device of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS For orientation, reference is first made to FIG. l showing the primary operational stations of a typical pulp mill. The present invention is .most suitably exploited to control pulp stock refining engines operative between the pulp washers and the paper machine headbox.
Referring next to FIG. 5, details are shown relative to the raw stock chest 1; the refiners R1, R2, R3; the lmachine chest 4; and, the interconnecting stock Iflow piping 2 and 3, also seen in FIG. l.
To the raw stock chest 1, raw pulp stock is delivered from one or `more pulp Washers for blending. Subsequently, the greater bulk of blended raw stock is pumped through conduit 2 for distribution to one or more refiners as represented by R1, R2, R3. A sample portion of blended raw stock is taken from the chest 1 through conduit 2a in parallel ow with the trunk line 2 as a continuously flowing source reservoir for the static drainage rate meter 20. Instruments 21 and 22 in the test sample shunt 2a are a pH meter and a thermometer, respectively. Instruments 23 and F21, provide electrical signals proportional to stock consistency and ow rate, respectively.
Before entering the refiners R1, R2, and R3, respectively driven by motors M1, M2, and M3, the stock flow rate respective to each refiner is measured by flow meters F1, F2, and F3. The stock flow stream temperature to each refiner is taken by thermometers 11, 12, and 13.
Refined stock emerges from the refiners into pipeline 3 to be measured of heat content again by thermometers 11a, 12a, 13a and thence carried to the machine chest 4 for further blending and storage before delivery to the paper machine head box.
Refined stock ow shunt 3a provides a sampling reservoir for a second static drainage rate meter 30 and attendant instrumentation including fiow meter F311, pH meter 31, thermometer 32 and consistency gauge 33. Although data from the static drainage rate meter 30 is not necessary to the feed-forward feature of this invention, such accessory data may be used advantageously for calibration and control trim purposes in a manner to be described subsequently.
Alternatively, data from the static drainage rate meter 30 may be used exclusively or primarily for a most efcient feed-back control system, if desired.
Elements AT1, AT2, and AT3 represent logic circuitry for receiving and comparing signals from respective pairs of thermometer 11-11a, 12-12a, and 13-13a. Responsive to the comparison, computers AT1, AT2, and AT3 transmit original signals proportional to respective stock temperature differentials.
Computer 2R receives the temperature differential signals from computers AT1, AT2, and AT3 for mathematical combination and processing with signals proportional to the respective stock ow rates from meters F1, F2, and F3. All of these signals are combined by computer 2R pursuant to the relation:
The calculated product of this relation is proportional to the specific energy (ES) applied by the several refiners to the stock, units being corrected to BTU per ton of stock. If units are desired in terms of kilowatt-hours per ton of stock, the temperature differential signals from computers AT1, AT2, and AT3 may be corrected by the appropriate mathematical equality for heat and power. Alternatively, current and voltage signals may be transmitted from the motors M1, M2, and M3 in lieu of the stock temperature measurements for direct calculation of specific energy in units of kilowatt-hours per stock ton. This calculation would take the form:
Signal 41 is an original emission from computer 2R proportional to the momentary specific energy application of all refiners R1, R2, and R3, collectively.
Receiving signal 41 is refiner correction computer 2c for comparison to a set-point or reference signal 40. Computer 210 is the source of signal 40 and generates it in response to data received from the static system and processed as a function of laboratory and other applied data. In essence, signal 40 represents the magnitude of collective refiner applied specific energy that is needed to work the stock to the desired final water retention property. Accordingly, computer 2c compares the magnitude of specific energy that the refiners are momentarily delivering, as represented by signal 41, to the magnitude of energy necessary for the desired drainage rate, as represented by signal 40, and derives and emits a signal 44 proportional to the necessary change, if any, to the refiner engine effort needed to match the objective.
Although the aforedescribed system is perfectly adaptable to the control of a single refiner, such systems are more commonly utilized to control a multiplicity of refiners, in which case, it becomes necessary to allocate the energy correction signal 44 among the several refiners since some may be larger or more efficient than others and can take a disproportionate share of the needed change. Such allocation is the function of computer A which keeps an accounting of the present loading and capacity of each refiner. Operatively then, allocation computer A assigns that portion of the total needed correction, represented by signal 44, to each refiner R1, R2, R3 according to its individual need or capacity.
Signals 44a, 44b, and 44e, then, are individually assigned portions of signal 44 and dictate the refiner disc or plug setting via respective refiner controller C1, C2, and C3.
Heretofore has been described a prior art refiner control system such as that more completely described in U.S. Pat. 3,568,939 except for the briefly described contribution of the static drainage rate responsiveness of setpoint signal 40. It should be understood, however, that most of numerous other single and multiple refiner control systems are responsive to an externally provided reference signal to which the refiner control system can relate for control orientation. Consequently, the present invention may be adapted to any of such refiner control systems.
Regressing now, to focus on the static drainage rate measurement system in stock flow shunt 2a, it is seen from FIG. 6 that test meter 20 is merely a blind spur from shunt 2a having a sample barrel 29 separated from the shunt conduit 2a by a screen 28 of appropriate mesh as to permit the passage of Water but prohibit the passage of pulp fibers.
Entering at the top of barrel 29 is a pneumatic conduit 14 having controlled communication with an air supply line 15.
Internally of barrel 29 are lower and upper liquid level switches 24 and 25, more liquid level switches may be used if desired, the respective contact levels being separated by a precisely determined distance D to specify the desired test volume.
Pacing the entire operation of the static drainage rate test is a timing device K, set to transmit a single starting impulse to the initiating winding I1 for the purpose of closing starting switch S1. Timer K emits such a starting impulse at regular, periodic intervals determined by the desired cycle rate of the drainage test, cach seconds for example. The starting impulse is of selected magnitude and duration as is sufiicient to close the contacts of switch S1 long enough to establish sufiicient electromagnetic force in winding H1 to hold the switch S1 closed. Thereafter, the starting impulse stops.
When winding I1 is energized by the starting impulse from K, switch S1 closes to energize holding winding H1 and open solenoid valve 26. Communication of pneumatic conduit 14 is thereby established with the air supply subject to pressure controls 16. Pressure controller 16 holds the Ipressure in conduit 14 and, consequently, in barrel 29 at a constant, predetermined level that is slightly less than the pressure prevailing in shunt 2a so as to allow a fixed, pressure differential drive of the stock into barrel 29.
As the stock rises into barrel 29, the water vehicle thereof passes through screen 28 but not the fiber constituent. A fiber mat is established on the shunt side of screen 28 which inhibits continued transfer of water to a rate proportional to the water retention properties of the fibers. When sufiicient water has passed the screen 28 to reach the lower reference level 24, the fibrous mat on screen 28 has grown with suicient accumulation to provide a reliable water retention test. This event closes the contacts of lower level switch 24 to energize starting pulse circuit P1.
Starting circuit P1 is of a prior art type that, in response to an energized input, emits a single signal pulse of select magnitude and duration. Thereafter, the pulse energy stops and will not flow again until the input energy stops and starts again. Therefore, so long as switch 24 is closed, starting circuit P1 will not emit a second pulse.
The single pulse from startingV circuit P1 starts the running of a prior art elapsed time measuring device E. As the water continues to rise in barrel 29, the timer E accumulates data proportional to the elapsed interim.
When the water level has risen the prescribed distance D in the barrel 29, upper level switch 25 closes to energize a second single pulse transmitting circuit P2 and stop the running of elapsed timer E. Also energized by the P2 pulse are time delays L1, L2, and switch S1 reset relay O1.
When reset relay O1 is energized, the holding circuit of switch S1 is immediately opened to allow the mechanical bias of the moving contact point of S1 to open the solenoid valve 26 holding circuit thereby closing the valve 26 and disrupting fluid communication between line 14 and the pressure controller 16. There being no energized bias on the switch S1, the contacts thereof remain in the open position awaiting the next pulse from timer K.
In response to the stop pulse from circuit P2, time delays L1 and L2 merely retard the signal for respective, predetermined time periods before passing it on.
The signal from time delay L1 initiates a reset circuit W in timer E to transmit the accumulated time signal stored therein and clear the storage circuit for the next starting pulse from circuit P1. The transmitted signal is proportional to the measured static drainage rate of the tested stock and enters computer 220 as such.
Also energized by the delayed L1 signal is initiating winding I2 for the switch S2. When closed, switch S2 conducts energy to a holding relay H2 to keep the switch S2 closed and to the actuating winding of solenoid valve 27. When open, valve 27 places pneumatic conduit 14 into controlled fluid communication with the air supply source again but at a pressure greater than the pressure of shunt line 2a. This pressure differential drives the test charge of water standing in barrel 29 down through the screen 28 and back into the flow stream of shunt 2a, cleaning the accumulated fiberous mat against screen 28 in the process.
Adequate time for the foregoing barrel purge is allowed by time relay L2 before transmission of the stop pulse from circuit P2 on to the reset relay O2 to open the holding circuit H2 of solenoid valve 27 holding switch S1. Valve 27 closes to interrupt communication between line 14 and the air supply, thereby stopping the purge of barrel 29.
Due to the falling liquid level in barrel 29, switches 24 and 25 have opened thereby resetting the start and stop pulse circuits P1 and P2 in preparation of the next level switch closure due to rising iluid.
At this point, all circuits are quiet and open except for the continuing advancement of pace timer K. When the prescribed period has elapsed, the timer K issues another starting pulse to initiating winding I1 to start the cycle over again for another static drainage rate signal to cornputef 220.
If correct static drainage rate was consistently equivalent to the raw measure signal, it would be suicient to by-pass computer E20 for direct receipt of the timer E signal by computer 210. However, clue to stock Variations of pulp consistency, temperature and pH, a static drainage rate measure thereof may not be exactly equal to a true measure. For this reason, signals proportional to these parameters are also transmitted by instruments 23, 22, and 21, respectively, to computer E20.
These auxiliary signals from 21, 22 and 23 may be handled in either of two ways. Each may be received by a respective limit circuit whereby if one or more of the auxiliary signals exceds a predetermined value range, such as to render the signal from meter 20 unreliable, transmission of the static drainage rate signal to computer E10 is interrupted. In this respect, computer 220 performs a discriminatoin function in that it discriminates between valid and invalid static drainage signals.
Alternatively, computer 220 may be programmed with laboratory determined process data whereby a static drainage rate signal corrected to standardized conditions may be derived by computer 220 from the auxiliary signals notwithstanding the excursion of any one or more auxiliary signals from the standard value range.
Computer 21o constitutes the interface between the automatic refiner control system and the automatic static drainage rate determination system. Pursuant to this function, a data storage element of 210 is programmed with data such as that represented by the graphs of FIG. 2. Static drainage rate signals from computer 220 are compatible with the scale of one graph axis, the Williams Slowness Scale along the abscissa in this example, and needed refining energy signals 40 to computer 2c are compatible with the other axis of the plot.
210 must also be progremmed with data concerning the desired end result. Such is the set-point input of FIG. 5 and may take the form of either a target specific energy value or a target static drainage rate value. 4Unlike the program data that is definitive of the specific energy consumption to static drainage rate function for the wood furnish and cook type, the set point is an operator entered variable needed by the computer to establish a presently desired end point on the characteristic curve. A typical event to dictate the operators change of the set-point input would be the desire for a grade change in the iinished paper.
A representative operation of computer 210 may be thusly: Relative to FIG. 2, wood to furnish V is to be cooked to a K number of Y. Accordingly, data that is definitive of the typical specific energy relation to static drainage rate for that furnish and cook is made available to the active control circuit.
The grade characteristics of the finished paper that is desired suggests the linal static drainage rate which, in this example, constitutes a set-point value proportional to a Williams Slowness of 60 seconds. A corresponding total speciiic energy input of 160 kw.-hr./ton will need to be applied to the stock. Accordingly, the operator enters a set-point value of 60 seconds into the manual entry station of computer 210 control console. Responsively, the computer reviews the programmed data stored within the active control circuit and determines that 160 kw.hr./ton is the refining energy target. This determination is physically represented by an electric signal internal of computer 210 which is characteristic of the determined energy target.
Due to the fact that the stock may have been previously worked, to some degree, by deiiberizing engines at an earlier ow station for example, signal 42 from the drainage rate computer E20 informs computer 210 that the stock in transit has a raw static drainage rate of 10 seconds. From the internally stored data relative to the active stock curve, computer 210 determines that the static drainage rate signal 42 corresponds to a total applied specific energy value of 70 kw.hr./ ton. As in the case of the target energy determination, this determination is also physically represented by an electric signal internal of computer 210 which is characteristic of the determined value of total specic energy absorbed by a stock sample.
From the foregoing determinations, computer E10 further determines that the magnitude of additional refining energy needed by the stock in transit to reach the desired total is kw.hr./ton (160 kW.hr./ton desired minus 70 kw.hr./ ton received).
A signal proportional to the needed addition of 90 kw.hr./ton constitutes the substance of signal 40 from computer 210 and becomes the set-point signal for the automatic refiner control computer 2c.
To continue the example, assume that specific energy averaging computer ER is emitting a signal 41 to the effect that the average specific energy currently being applied to the stock ow is 85 kw.hr./ton. Upon receipt of signal 40 representing a need of 90 kw.hr./ton, computer 2c compares this need value to the presently applied average value of 85 kw.-hr./ ton and determines that an additional kw.hr./ton should be applied by the refiners. Such is the substantive value of signal 44.
Allocation computer A receives the 5 kw.hr./ton increase dictate of signal 44 and determines how the 5 kW.- hr./ton increase shall be apportioned among the several refiners.
If desired, the static drainage rate testing system in shunt 3a may be used as a feed back alternative to the feed forward system in shunt 2a described above. -In this case, however, an initial assumption must be made relative to the static drainage rate of raw stock received at the refiner. Nevertheless, such a system may be more efficient than other, prior art, feed back systems, since the post refiner static drainage rate is sampled directly, no opportunity being given for the introduction of irrelevant parameters. Moreover, the post refiner stock sample is taken from the refiner discharge manifold 3 or machine chest 4 before the accumulation of large quantities of nonconforming stock.
As to the applied logic of computer 210 in the feed back example, it may generally be characterized as the reverse of the feed forward system with an initial condition raw stock static drainage rate assumed and entered by the operator at the console manual entry station. The desired finished stock static drainage rate is also entered as in the case of the feed forward system. Actual or measured finished stock static drainage values are fed back to computer 210 for comparison to the assumed, initial condition, values with the assumed raw stock rate being corrected as the consequence of an increase or decrease in the refining energy demand signal 40 as is found necessary for the conformity of the actual or measured post refiner static drainage rate to the desired or set-point value.
As a third and preferred alternative, static drainage rate signals 4.2 and 43 from both test systems are offered to computer 210 simultaneously. Such data provides a reservoir of actual line information to correct the laboratory derived data forming the substance of the static drainage rate to refining energy function curves of FIG. 2. As operational time accumulates, the internally stored program data is corrected and honed to accuracy by the actual line measurements thereby increasing the corrective action response time of the refiner to a transient excursion of the raw stock static drainage value.
The significance of rapid response time and of the invention, generally, may be appreciated by a comparison of FIGS. 3 and 4. Therein, the couch vacuum is given as the reference value of performance rather than finished stock static drainage rate since the former parameter is more familiar to those of ordinary skill in the art. In both cases of FIGS. 3 and 4, couch vacuum disturbances are attributed exclusively to water retention property changes in the stock.
The control relation between the measured couch vacuum and refining engine response of FIG. 3 is a simple feed back system comprising an alert and skilled papermachine tender taking note of an initial departure of the couch vacuum from an established norm. Responsively, the machine tender informs a skilled rener operator of the changes which, in the personal judgement of the machine tender, are needed.
In contrast, FIG. 4 represents a system under group reliner control referenced by a feed forward static drainage rate set-point as described herein but without feed back correction of the internal program parameters. The reduced degree of couch vacuum departure from norm,
10 as shown from a comparison of FIGS. 3 and 4, is typical of system performance from the present invention. Not only is the degree of couch vacuum distrubance reduced by the present invention but, as a comparison of the FIGS. 3 and 4 time scales will substantiate, the invention eliminates the disturbance result more quickly.
The foregoing numerical examples are merely representative of several mathematical manipulations that may be performed with the various accumulated data, measured, derived and assumed, to achieve the desired end result of assuring that the refiners, collectively, will apply sufiicient work to the particular stock in transit so the average water retention properties of the machine chest 4 blend will remain at the desired level. To summarize, however, it will be appreciated that basic to the invention are at least one measured value of the stock static drainage rate; at least one assumed value of the desired stock static drainage rate; and, at least one derived value representative of a differential in average specific energy applied to the stock. Further, laboratory or experience derived data is necessary to relate the static drainage rate values to specific energy values or vice versa. From such data, the differential energy exerted by the refiners may be related in a quantitative manner, to the total or absolute energy absorption level for the stock that is desired. From this relation, a quantitative value representative of change from a present refiner energy exertion level to a future energy exertion level may be derived. This change value offers a quantitative reference for refiner adjustment.
The mechanics of such mathematical manipulations, whether performed manually or by electronic data process equipment, are well known to those of skill in the art. Accordingly, it is of no significance that the set-point value for the target or objective refining level is: entered as a slowness value or a total specific energy of refining value; combined iirst with the value represented by either of signals 41, 42, or 43; or, entered by the console of computer 2c or 210.
It will also be apparent to those skilled in the art that other changes may be made in the preferred embodiments described herein without departing from the spirit of my invention as set forth in the appended claims. Therefore, having now disclosed our invention, what we claim as new and unobvious and desire to secure by Letters Patent is:
1. An apparatus for the determination of the magnitude of refining energy absorbed by a sample of pulp stock, said apparatus comprising:
(A) stock sample chamber means separated from a stock reservoir by a perforated partition means adapted to pass the Water vehicle of said stock but substantially obstruct passage of the stock fiber;
(B) chamber pressure control means for regulation of pressure within said chamber relative to the pressure of said stock reservoir to selectively admit and expel said water vehicle;
(C) at least two liquid level sensing means positionally separated within said chamber to delineate a prescribed volume therebetween;
(D) chronometer measuring means started by Water vehicle actuation of one said sensing means and stopped by water vehicle actuation of the other said sensing means, said chronometer means emitting a first signal representative of an elapsed time interim between said starting and stopping; and
(E) signal processing means having data storage means disposed therewith, said data storage means being disposed and provided with data to relate such elapsed time interims to the magnitude of total specific energy absorbed by a stock sample representative of said stock sample, said signal processing means receiving and relating said first signal to said storage means data and deriving said corresponding total specific energy as a signal.
1 1 1 2 2. Apparatus as described by claim 1 wherein said rst y 3,687,802. 9/ 1972 Rummel et al. 162-254 X signal is intercepted by discriminator means, said dis- 3,538,749 10/1970 Danforth 73-63 criminator means permitting said rst signal to pass to 2,734,378 2/ 1956 Meyers 162-263 X said signal processing means if other measured stock 3,186,215 6/ 1965 Danforth 162-198 X parameters are within prescribed limits. 5 3,654,075 4/ 1972 Keyes et al. 162-254 3. Apparatus as described by claim 2 wherein said other measured stock parameters are provided by means for ROBERT L LINDSAY, JR Pflmaly Examiner measuring stock temperature, acidity, consistency and M S ALVO Assistant Examiner rate of fiow.
References Cited 10 U.S'. Cl. X.R.
UNITED STATES PATENTS 73-63; 162-198, 253, 254; 241-33 3,144,763 8/1964 Mayo 73-63 Umrsn STATES PATENT oFFICE CERTlFlCAE @F ClEC'liN Patent No. 3,846,231 Dated li\lo vernl:1er 5, 1974 Inventor(s) William E. Crosby and Hong l-l'. Lee
It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column l, line 28, delete entire line starting with "tensile and insert energy functional relationship for a stock representative of; line 49, following "Consequently" insert u. Column 2, line 7, following "wherein" insert a;'line 34, correct the spelling of pulp;
line 37, following "ness". delete and insert line 45, following "rate" should be Column 3, line 32, correct the spelling of basis. Column 8', line 2, vcorrect the spelling of -exceeds;
line 24, correct the spelling of "programmed". Column` l2, line 9, the following was deleted .Attorney, Agent, or Firm W. Allen Marcontell and Richard L. Schmalz-n sigma and seated this 28:11 say of January 1975.
McCOY M. GIBSON-JR. C. SHALL DANN Attestng Officer Coissioner of Patents FORM 30'1050 (10'59) uscoMM-Dc eos76-pss U.S. GDVERNMEN PRINTING OFFICE t 1969 0*"366-3S