proposed modifications in yankee hood

Proposed Modifications in Proposed Modifications in Yankee HoodYankee Hood

Concept:

D K Singhal

[email protected]

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 to � Still, 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.

Proposed Modifications in Yankee Hood, June 2015 2

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 surface the air; which is impinged on the surface of paper over yankee dryer.


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 of and availability of fuel, amount of investment required etc.


Typical Hood DesignTypical Hood Design

� Typical hood design has two sections, WE (wet end) and DE (dry end) and DE (dry end) and the air system is a cascading one.


Overview of Yankee DryingOverview of Yankee 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.


Typical Drying CurveTypical Drying Curve


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.


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%


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, moisture cascading 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.


Typical CalculationsTypical Calculations

Position Moisture Water Removed

Inlet to Wet End 65


Middle of Wet End 45 58%

Inlet to Dry End 25 27%

Out from Dry End 5 16%

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 and and hence increased drying rate and production.


Use of Pocket VentilationUse of Pocket Ventilation

� 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 yankeemachine.


Sketch of a Yankee MachineSketch of a Yankee Machine


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 have section 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.


Proposed PV Box PositionProposed PV Box Position


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 for reposition/redesign the felt circuits for the same.

� Such a position is shown on next slide.


Another PositionAnother Position


� Please do share your experiences, knowledge and comments about this.knowledge and comments about this.


Thank You.


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 & Paper Technical 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 a Yahoo 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 [email protected]

21Proposed Modifications in Yankee Hood, June 2015

proposed modifications in yankee hood

Technology

wet end hood

control of yankee hood

dry end

wet end section

wet end exhaust

middle of wet end

yankee hoodyankee hood

water removal