Aquafeed producers are losing about $4 to $10 per ton of product produced in terms of lost production, higher energy consumption and lowered product quality. These losses can be recovered by substituting a more effective moisture (MC) sensing and control technology for currently used traditional MC sensing and control.

1. I N C O R P O R AT I N G
f i s h far m ing t e c h no l og y
January | February 2013
Profitable aquafeed moisture control
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The International magazine for the aquaculture feed industry

3. FEATURE
Profitable aquafeed
moisture control
by John Robinson, President, Drying Technology Inc, USA
A
quafeed producers are losing such that the mean MC can be maximized aquafeed inside the harsh environment of a
about $4 to $10 per ton of without exceeding the upper specification dryer while it is being dried with a belt dryer.
product produced in terms of limit (USL). Fortunately, a solution for poor As illustrated by Figure 2, patented Delta T
lost production, higher energy MC sensing and control was supplied by technology invented a new type MC sensor that
consumption and lowered product quality. the derivation of a MC sensing and control can be installed ‘inside-the-dryer’ which reduces
These losses can be recovered by substitut- model from first principles. The Delta T the dead time (time to detect a disturbance
ing a more effective moisture (MC) sensing model: entering with the feed) by at least 30 percent.
and control technology for currently used Since dead time is directly proportional to the
traditional MC sensing and control. MC = K1(ΔT)p – K2/Sq product standard deviation, use of this ‘inside-
the-dryer’ sensor reduces the standard deviation
relates the product MC exiting a dryer at least 30 percent below that achieved by use
to the temperature drop (ΔT) of hot air of currently used MC sensing methods. It should
after contact with the wet product and the be noted that use of raw Delta T data will not
production rate or evaporative load (S). The work—it must be processed by the model
model solved the two main problems with before use. Figure 3 illustrates the advantage of
MC sensing and control by producing. Firstly, reducing dead time for aquafeed drying.
a rugged, reliable ‘inside-the-dryer’ moisture Three possible locations are shown for install-
sensor; and secondly, a new and powerful ing the MC sensor. Dead time for each installation
control algorithm that precisely adjusts the set point is the time it takes for the individual MC
Figure 1: Typical MC point for evaporative load changes. method to detect a change in evaporative load
distribution curve entering with the feed. The lowest dead time
produced by poor MC A new type of MC sensor is 14 minutes for the Delta T sensor inside the
sensing and control Figure 2 describes how the Delta T MC dryer; the next lowest dead time is 20 minutes for
sensor continuously measures the MC of a MC meter located at the dryer exit; the longest
The control problem
Two main problems prevent traditional
MC sensing and control technology from
being effective. Firstly, the lack of timely
and accurate MC data upon which to base
control action (poor MC sensing). Secondly,
the inability to correctly adjust for evaporative
load changes entering with the feed.
Figure 1 shows a typical normal MC dis-
tribution curve produced by traditional MC
sensing and control technology. The curve
is relatively wide as a result of the effect of Figure 2: Delta T ‘inside-the-dryer’ MC sensor
high MC standard deviation. It is obvious
that the wider the MC variation the lower
the target mean MC must be to prevent
production of wet product. Consequently,
use of currently available control technol-
ogy forces manufacturers to over dry their
products which causes significant costs in
terms of lower production, higher energy
usage, and poorer quality. Figure 1 illustrates
the effect of poor MC sensing and control
on MC variation.
The control solution
Losses caused by poor MC sensing
and control may be recovered if the MC
Figure 3: Delta T reduces dead time on belt dryer
variation (standard deviation) is reduced
14 | InternatIonal AquAFeed | January-February 2013

4. 99
99
99
99

5. FEATURE
Extruder OEE for the Production of Fish Feed
at:
it us
se vis IA
Plea
V. AS
V.I.d H104 D032
Stan
AMANDUS KAHL GmbH & Co. KG, Dieselstrasse 5-9, D-21465 Reinbek / Hamburg,
Phone: +49 40 727 71 0, Fax: +49 40 727 71 100, info@amandus-kahl-group.de www.akahl.de
January-February 2013 | InternatIonal AquAFeed | 15

7. FEATURE
Delta T
BREAKTHROUGH
Current
MC
in Aquafeed Technology
Many leading aquafeed manufacturers in the industry
count on Extru-Tech to engineer the perfect aquafeed Figure 4: Delta T MC control allows mean MC
production solution. to be maximized without exceeding USL
industry leading equipment and engineered production
advantages will give you the upper hand over the
competition. could you use a cost effective improvement Figure 5:
in performance and finished product quality? Outside
view of
contact one of the Aquafeed consultants at Extru-Tech Delta T MC
today at 785-284-2153. system
demAnd
GEnUin E
ExTRU-TEcH
Oem PAR dead time is 30 min- MC in spite of frequent changes in evapora-
TS
utes for MC samples tive load entering the dryer with the feed.
taken downstream of Proprietary methods are used in adapting the
the dryer and ana- model to the dryer and product.
lyzed by a laboratory
instrument. Application of Delta T to
For the above aquafeed manufacture
conditions, the Delta The above-mentioned reduction in standard
T accomplishes dead deviation enables the target MC to be increased
time reductions of by 0.5 percent to as much as 1.25 percent with-
30 percent and 53 out fear of producing wet product which might
percent below that mold in transit or storage. Figure 4 shows sche-
for the moisture matically how reducing the standard deviation
meter method and enables the mean MC to be increased by shifting
the laboratory MC the Delta T curve rightward until the upper + 3
sample method standard deviation points (USL) of both curves
respectively. The coincide. The difference in mean MCs represents
Take this opportunity to visit www.extru-techinc.com/at standard deviation the economic gain from using Delta T technology.
to see the next level in aquafeed technology. reductions would
also be reduced 30 Results and conclusions
percent and 53 per- From 10 to 25 lbs of additional water can be
cent respectively. safely sold with the product per ton of product
produced without exceeding the upper specifica-
A new MC tion limit using this new technology. The return to
control the aquafeed manufacturer is $4 to $10 per ton
® algorithm of product for a wholesale product price of $800
As a result of per ton. In addition, energy savings of approxi-
its theoretical basis, mately four to seven percent possible. The Delta
Corporate offiCe the Delta T technol- T has been successfully applied in the US for MC
P.O. Box 8 • 100 Airport Road ogy provides a new sensing and control of many products, including
Sabetha, KS 66534, USA
Phone: 785-284-2153
control algorithm aquafeed using a Beltomatic conveyor dryer.
Fax: 785-284-3143 that enables precise
extru-techinc@extru-techinc.com calculation of the set
www.extru-techinc.com More InforMatIon:
point necessary to
Website: www.moisturecontrols.com
maintain the target
16 | InternatIonal AquAFeed | January-February 2013
ET-233A.indd 1 12/27/12 10:51 AM

8. C L E A N C O N T R O L
Swivel Valve Cooler MkII
No hollow spaces | No cross contamination
Excellent cleaning access | Filtered air inlet
Temperature control | Moisture control | Cleaning in Place
cool and dry
clean and lean
Geelen Counterflow info@geelencounterflow.com
Holland / USA / Argentina / China www.geelencounterflow.com
T +31-475-592315

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