Profitable aquafeed moisture control
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Transcript of Profitable aquafeed moisture control
January | February 2013
Profitable aquafeed moisture control
The International magazine for the aquaculture feed industry
International Aquafeed is published six times a year by Perendale Publishers Ltd of the United Kingdom.All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies, the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis of information published. ©Copyright 2013 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058
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64 | InternatIonal AquAFeed | January-February 2013
Aquafeed producers are losingabout $4 to $10 per ton ofproduct produced in terms oflost production, higher energy
consumption and lowered product quality.Theselossescanberecoveredbysubstitut-ingamoreeffectivemoisture(MC)sensingand control technology for currently usedtraditionalMCsensingandcontrol.
The control problem Two main problems prevent traditional
MC sensing and control technology frombeing effective. Firstly, the lack of timelyand accurate MC data upon which to basecontrol action (poor MC sensing). Secondly,theinabilitytocorrectlyadjustforevaporativeloadchangesenteringwiththefeed.
Figure1showsatypicalnormalMCdis-tributioncurveproducedbytraditionalMCsensing and control technology. The curveisrelativelywideasaresultoftheeffectofhigh MC standard deviation. It is obviousthat thewider theMCvariation the lowerthe target mean MC must be to preventproduction of wet product. Consequently,use of currently available control technol-ogy forcesmanufacturers tooverdry theirproducts which causes significant costs interms of lower production, higher energyusage,andpoorerquality.Figure1illustratestheeffectofpoorMCsensingandcontrolonMCvariation.
The control solutionLosses caused by poor MC sensing
and control may be recovered if the MCvariation (standard deviation) is reduced
such that themeanMCcanbemaximizedwithout exceeding the upper specificationlimit(USL).Fortunately,asolutionforpoorMC sensing and control was supplied bythederivationofaMCsensingandcontrolmodel from first principles. The Delta Tmodel:
MC=K1(ΔT)p–K2/Sq
relates the product MC exiting a dryerto the temperature drop (ΔT) of hot airafter contact with the wet product and theproductionrateorevaporative load(S).Themodel solved the two main problems withMCsensingandcontrolbyproducing.Firstly,a rugged, reliable ‘inside-the-dryer’ moisturesensor; and secondly, a new and powerfulcontrolalgorithmthatpreciselyadjuststhesetpointforevaporativeloadchanges.
A new type of MC sensorFigure 2 describes how the Delta T MC
sensor continuously measures the MC of
aquafeed inside the harsh environment of adryerwhileitisbeingdriedwithabeltdryer.
As illustratedbyFigure2,patentedDeltaTtechnologyinventedanewtypeMCsensorthatcanbeinstalled‘inside-the-dryer’whichreducesthe dead time (time to detect a disturbanceenteringwiththe feed)byat least30percent.Sincedead time isdirectlyproportional to theproduct standard deviation, use of this ‘inside-the-dryer’sensorreducesthestandarddeviationatleast30percentbelowthatachievedbyuseofcurrentlyusedMCsensingmethods.ItshouldbenotedthatuseofrawDeltaTdatawillnotwork—it must be processed by the modelbeforeuse.Figure3illustratestheadvantageofreducingdeadtimeforaquafeeddrying.
Threepossiblelocationsareshownforinstall-ingtheMCsensor.Deadtimeforeachinstallationpoint is the time it takes for the individualMCmethodtodetectachange inevaporative loadentering with the feed. The lowest dead timeis14minutes for theDeltaTsensor insidethedryer;thenextlowestdeadtimeis20minutesforaMCmeterlocatedatthedryerexit;thelongest
Profitable aquafeed moisture control
by John Robinson, President, Drying Technology Inc, USA
Figure 1: Typical MC distribution curve produced by poor MC sensing and control
Figure 2: Delta T ‘inside-the-dryer’ MC sensor
Figure 3: Delta T reduces dead time on belt dryer
14 | InternatIonal AquAFeed | January-February 2013
FEATURE
January-February 2013 | InternatIonal AquAFeed | 15
99999999
14 | InternatIonal AquAFeed | January-February 2013 January-February 2013 | InternatIonal AquAFeed | 15
FEATURE
Extruder OEE for the Production of Fish FeedExtruder OEE for the Production of Fish Feed
AMANDUS KAHL GmbH & Co. KG, Dieselstrasse 5-9, D-21465 Reinbek / Hamburg, Phone: +49 40 727 71 0, Fax: +49 40 727 71 100, [email protected] www.akahl.de
Please visit us at:
V.I.V. ASIA
Stand H104 D032
Volume 16 / Issue 1 / January-February 2013 / © Copyright Perendale Publishers Ltd 2012 / All rights reserved
dead time is 30min-utes for MC samplestakendownstreamofthe dryer and ana-lyzed by a laboratoryinstrument.
For the aboveconditions,theDeltaTaccomplishesdeadtime reductions of30 percent and 53percent below thatfor the moisturemeter method andthe laboratory MCsample methodrespectively. Thestandard deviationreductions wouldalso be reduced 30percentand53per-centrespectively.
A new MC control algorithm
As a result ofits theoretical basis,theDeltaTtechnol-ogy provides a newcontrol algorithmthat enables precisecalculationofthesetpoint necessary tomaintain the target
MC in spiteof frequentchanges inevapora-tive load entering the dryer with the feed.Proprietarymethodsareusedinadaptingthemodeltothedryerandproduct.
Application of Delta T to aquafeed manufacture
Theabove-mentioned reduction in standarddeviationenablesthetargetMCtobeincreasedby0.5percenttoasmuchas1.25percentwith-out fearofproducingwetproductwhichmightmoldintransitorstorage.Figure4showssche-matically how reducing the standard deviationenablesthemeanMCtobeincreasedbyshiftingtheDeltaTcurverightwarduntiltheupper+3standard deviation points (USL)of both curvescoincide.ThedifferenceinmeanMCsrepresentstheeconomicgainfromusingDeltaTtechnology.
Results and conclusionsFrom10to25lbsofadditionalwatercanbe
safelysoldwiththeproductpertonofproductproducedwithoutexceedingtheupperspecifica-tionlimitusingthisnewtechnology.Thereturntotheaquafeedmanufactureris$4to$10pertonofproductforawholesaleproductpriceof$800per ton. In addition, energy savings of approxi-matelyfourtosevenpercentpossible.TheDeltaThasbeensuccessfullyappliedintheUSforMCsensingandcontrolofmanyproducts, includingaquafeedusingaBeltomaticconveyordryer.
More InforMatIon:Website: www.moisturecontrols.com
Figure 4: Delta T MC control allows mean MC to be maximized without exceeding USL
Figure 5: Outside view of Delta T MC system
Current
Delta T
MC
16 | InternatIonal AquAFeed | January-February 2013
FEATURE
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ET-233A.indd 1 12/27/12 10:51 AM
16 | InternatIonal AquAFeed | January-February 2013
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Volume 16 I s sue 1 2 013 - J anuary | f ebruary
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