Pellet quality is usually expressed as the Pellet Durability
Index(PDI) and measured by using a tumbling can device, in which the
pellet sample to be tested is first sieved to remove fines, then tumbled
in the tumbling can devise for a defined period of time. Then after
tumbling, we compare the fines produced during tumbling with actual
weight.
Factors
that affect PDI are:1.
Formulation:
In today’s dynamic world, Nutritionists face the challenge of
formulating feeds using available raw materials at the lowest possible
cost while meeting the feed specifications, while the production
managers face the challenge of producing the good quality pellets from
these ingredients at the optimum mill setting. Pellet quality is
proportionally dependent on several factors, with diet/feed formulation
being the most important.
Raw
materials affect pellet quality depending on their “binding properties”
and its proportion in the formulation. From our experience, we know that
starch gelatinization is the most important factor for achieving the
desired pellet quality.
Dietary
inclusion of oil has a positive effect on animal growth but an adverse
effect on pellet quality.
Oil also
reduces the friction generated between the die and the feed particles,
which subsequently reduces the compression pressure required to produce
good pellets and also decreases the starch gelatinization rate.
Inclusion of natural pelleting aids can help overcome these bottlenecks
and improve pellet quality, increase pellet throughput and lower the
power consumption.
High starch-containing
raw materials like wheat generally contribute to good quality pellets.
Formulation governs approx.40 % in pellet quality &
PDI.
2. Grinding
Size:
Better grinding helps in better absorption of steam due to the
increased surface area which leads to better conditioning and a good
level of gelatinization of starch. Good gelatinization increases
pelleting properties and PDI index. Grinding governs approx. 20 % in
pellet quality.
3.
Conditioning:
Minimum 1.5 to 2.0 % moisture should be added in the conditioning
process. Also, temperature above 80 helps to achieve good gelatinization
level which leads to better binding properties and good
PDI.
Proper steam of good quality is
required for better performance of machines and production of quality
feed. Steam parameters required
are:
1. Dry Saturated Steam
Minimum 8.5-9 kg/cm2 at the boiler.
2. 2-2.5 Kg/Cm2
after PRV
3. Good & reputed make boiler,
Water softener.
4. Proper Steam traps, insulation of
steam line and supporting
valves.
Conditioning
governs approx. 20 % in Pellet Quality &
PDI.
4. Die
configuration:
Selecting a die as per formulation is very important. As Broiler
contain fewer fibers and more oil %age (soft formulation), which
provides better pelleting properties, less frictional load on pellet
die. Hence, we can use a compression ratio of 1:12, 1:13 & even
more.
Using high compression ratio
for layer feed may lead to poor die life, die chocking, non-uniform PDI,
more power consumption in layer feed, low output, more wear &
tear.
And using low compression
dies in soft broiler formulation may lead to poor PDI (Pellet
Durability Index – Pellet Strength). Considering all the above factors
using a separate die for both layer & broiler feed is a better
and
cost-effective solution. Die selections govern approx. 10-15 % in pellet
quality & output.
The above information is based on data collected
from our existing customers & internet sources and is only for
your reference. As expertise in feed mill engineering only, Lark
Engineering will not be responsible for any type of loss occur due to
above-stated information.