This document proposes modifications to yankee hood designs to increase paper production. It suggests splitting the existing two-section hood into a three-section hood to reduce moisture levels in the last section, allowing for faster drying. Another proposal is to add pocket ventilation boxes near the wet end and between touch rolls to help remove vapor. These modifications could reduce the moisture removed in the final hood section from 27% to 16%, resulting in drier air and higher production rates.

1. Proposed Modifications inProposed Modifications in
Yankee HoodYankee Hood
Concept:
D K Singhal
deveshksinghal@gmail.com

2. Yankee HoodYankee Hood
A lot of work has been done on design,
optimization and control of yankee hood
already.
Still, there are few other possibilities toStill, there are few other possibilities to
increase production from yankee hoods.
The purpose of this presentation is to
present first hand information about
some of these possibilities.
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3. Type of Heating MediumType of Heating Medium
Yankee hoods can be of direct fire type,
or may use alternate source of thermal
energy like thermic fluid or steam to heat
the air; which is impinged on the surfacethe air; which is impinged on the surface
of paper over yankee dryer.
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4. Type of Heating MediumType of Heating Medium
Generally, it is the mills decision to decide
upon the type of heating medium
considering the expected production, cost
and availability of fuel, amount ofand availability of fuel, amount of
investment required etc.
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5. Typical Hood DesignTypical Hood Design
Typical hood
design has two
sections,WE (wet
end) and DE (dryend) and DE (dry
end) and the air
system is a
cascading one.
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6. Overview ofYankee DryingOverview ofYankee Drying
It has been found by many researchers
that the paper moisture profile along the
machine direction –or along yankee-
reduces (almost) in a linear trend.reduces (almost) in a linear trend.
A typical graph of the same is shown on
the next slide.
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7. Typical Drying CurveTypical Drying Curve
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8. Moisture RemovalMoisture Removal
From the curve shown on the previous
slide, one can understand a major part of
water vapor is removed from the wet end
side of the hood.side of the hood.
If we calculate, on the basis of linear trend
of paper moisture profile, we may
calculate that more than 75% of the water
removal is being done in the wet end
section of the hood.
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9. Typical CalculationsTypical Calculations
Position Moisture Water Removed
Inlet to Wet End 65Inlet to Wet End 65
Wet End to Dry End 35 73%
After Dry End 5 27%
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10. Using a Three Segment HoodUsing a Three Segment Hood
High moisture removal from wet end hood
gives a clue to split a part of the wet end
exhaust in two parts.This way, in place of
two, hood will contain three sections with
cascading arrangement.Thus, moisturecascading arrangement.Thus, moisture
removal will be much lesser in last section
thus meaning less humidity in hood and
hence better production rates.A typical
moisture removal pattern will look as shown
on next slide.
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11. Typical CalculationsTypical Calculations
Position Moisture Water
Removed
Inlet to Wet End 65
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Middle of Wet End 45 58%
Inlet to Dry End 25 27%
Out from Dry End 5 16%

12. Reduced Air DrynessReduced Air Dryness
As one can see less water vapor being
removed from paper in the third section
(16% against 27%), which means drier air
and hence increased drying rate andand hence increased drying rate and
production.
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13. Use of PocketVentilationUse of PocketVentilation
On most MF machines, PV has been used
since long. However, the application of PV
is limited in MG (Yankee) paper machines
maybe because of space constraints.maybe because of space constraints.
Next slide contains a sketch of a yankee
machine.
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14. Sketch of aYankee MachineSketch of aYankee Machine
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15. Location of PV BoxLocation of PV Box
In the next slide, a typical position of blow
box (PV Box) has been shown.
Normally, the vapor generation in this
section is so high that several mills havesection is so high that several mills have
mounted exhaust fans to spread away
water vapors generated in this area.
Position of proposed PV box is given in
the next slide.
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16. Proposed PV Box PositionProposed PV Box Position
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17. Other PositionsOther Positions
If space permits, another PV box can be
positioned between the two touch rolls.
In some cases, it may be required to
reposition/redesign the felt circuits forreposition/redesign the felt circuits for
the same.
Such a position is shown on next slide.
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18. Another PositionAnother Position
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19. Please do share your experiences,
knowledge and comments about this.knowledge and comments about this.
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20. ThankYou.
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21. About the Author:
Born in 1968, D K Singhal is B.E., M.E. (Pulp & Paper, 1993) from Deptt. of Paper
Technology, University of Roorkee (now IIT, Roorkee). He is a Certified Energy
Auditor and Chartered Engineer also.
With nearly 7 dozen publications, he has emphasized on development of low cost
technologies and management practices for quality and profitability improvement.
With publications on slideshare.net, energymanagertraining.com and
paperonweb.com, he has been constantly contributing to IPPTA (Indian Pulp &
PaperTechnical Association). He is also serving IPPTA as a member of Editorial
Board.Board.
An initiative by D K Singhal, a cyber campaign initiated against unjustified targeting
of paper industry by “Idea” mobile, in their “Sirjee” advertisement campaign, after
which this advertisement was taken off air.
He also moderated aYahoo group,“PaperTechnology” with nearly 360 members
from India and abroad to discuss problems related to pulp & paper making for five
years.
He can be contacted at deveshksinghal@gmail.com
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