Types of drum drying and related information

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2. DRYING
Removal of moisture to a
desired m.c in equilibrium
with normal atmospheric air.
Why drying??
• Increased shelf life (inhibiting bacterial
activity and enzyme activity)
• Reduction of bulk
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3. GENERAL DRYING BEHAVIOUR
m.c of milk(X) = mw TS(total solid mass fraction) = ms
mw + ms mw + ms
mass of amount of
water dry matter
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4. During concentration…..
𝑚 𝑤0
− 𝑚 𝑤
𝑚 𝑤0
= 1 −
𝑥 1 − 𝑥0
𝑥0 1 − 𝑥
𝑚 𝑤0
− 𝑚 𝑤 =
𝑥0
1−𝑥0
−
𝑥
1−𝑥
𝑚s
Subscript 0 – representing
the initial conditions
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5. PROBLEM
Skim milk of Xo = 0.91 is
evaporated to X=0.55.
Find out the % water
evaporated based on
the original water
content.
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6. Other
included
topics
• EMC (for milk 2.4% w.b
@ T=80c and R.H 50%)
• mechanism of drying
solids (constant and
falling rate period)
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7. Indirect
Also called -
>roller drying
->film drying
• Less space
• More economical than
spray dryers (small
volumes*)
• Steam consumption : water
evaporation :: 1.2-1.6:1
(120kg steam
to evaporate
100kg water)
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9. Construction
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doctor
Liquid enters
at 700 C
Heat
transferred to
the liquid by
convention
Vaporized
moisture
removed
through a
vapour hood
Milk is
generally
precondenssed
(<300C)
Doctor blade –
150-300
L : 360cm
D: 60-120cm
Rpm: 6-24
(contact with
drum < 3sec)

10. FACTORS
• Temperature difference (inside
drum temp as well)
• Time of contact
• Rotation speed
• Pressure inside vessel
• feed type and feeding
mechanism
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11. CLASSIFICATION
No. of drums
pressure surrounding
the product
feeding
arrangements
Material of
construction
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12. No. of drums
No. of drums
• Single drum
• Double drum
• Twin drum*
Pressure surrounding
Pressure
surrounding
Atmospheric vaccum*
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14. • Nip feed(simplest)
• Splash feed
• dip feed
• Roller feed
FEEDING
ARRANGEMENT
MATERIAL
CONSTRUCTION
• Alloy steel
• Stainless steel
• Nichrome steel
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16. Product may have a scorched
flavour
Solubility is much lower because of
protein denaturation (98% to (85%)
Power consumed little high as
indirect contact exists
control
temp
control
contact
time
use
polycab
wires
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17. Precautions
Smooth
drum
Sharp
knives
every
100h of
operation
Preconcent
rate 25%-
30%
Preheating
< 700 C
Not for
acidic
milk
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18. REFERENCES
Drum Drying Juming Tang Hao Feng Washington State University, Pullman,
Washington, U.S.A. Guo-Qi Shen Shanxi Agriculture University, Shanxi, People’s
Republic of China
DAIRY PLANT ENGINEERING AND MANAGEMENT, Tufail Ahmad
web REFERENCES
http://sites.bsyse.wsu.edu/tang/main/publications/pdfdocs/book-
drumdry-tang03.pdf
https://www.youtube.com/watch?v=JGb77K_K55M
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