nonwoven how to form a glass fiber mat?design considerations leo bos nonwoven tappi fiberglass...

HOW TO FORM A

GLASS FIBER MAT?DESIGN CONSIDERATIONS

LEO BOS

NONWOVEN

TAPPI FIBERGLASS COMMITTEE MEETING SEPTEMBER 2019

• Control the fiber formation

• Having the right fiber consistency and water

flow

• Finding the ideal fan pump configuration

• Keep the fibers well dispersed up to the former

• Laying fibers with the right fiber orientation

and well distributed on the wire

• Keep the web forming process stabile

when creating a fiber mat

CHALLENGES

/ ANDRITZ NONWOVEN / TAPPI FIBERGLASS COMMITTEE SEPTEMBER 2019 / © COPYRIGHT 20192

01 FORMATION

CHAPTER OVERVIEW


02 CONSISTENCY

03 DISPERSING

04

05 CONTACT

07

08

09

10

06

WETLAID FORMING OF A WEB WITH FIBERS

4 / ANDRITZ NONWOVEN / TAPPI FIBERGLASS COMMITTEE SEPTEMBER 2019 / © COPYRIGHT 2019

White water loop of a inclined wire former

What is good formation?



• Most fibers in water have a tendency

to agglomerate and build up flocs

• Small flocs are necessary to form a

sheet on the wire

• Larger flocs appears as clouds in the

formed web

How good the formation highly depends

on the product requirements

+

Quality Level should not fluctuate

Three design points are essential

1. Give the fibers enough room to move freely around in the water-fiber suspension

2. Bring enough turbulence in the water-fiber suspension. Keep the fibers moving.

3. Lay the fibers in the best fiber orientation and good distributed on the wire

Chemicals can be added to slow down the floc building

• Viscosity modifiers: more resistance from the fluid and slow down agglomeration to flocs

=> Consequence: More dispersing energy is needed

• Surfactants: Reduction of force by which the fibers agglomerate

=> Consequence: To be minimized due to associated foam formation!

Wet end design of a fiber glass mat wetlaid line has a significant impact on the forming process.

Applying best design can limit the dependency on white water viscosity and surfactant chemicals.



How can formation be influenced?

01 HOW TO INFLUENCE FORMATION

CHAPTER OVERVIEW


02 CONSISTENCY

03 DISPERSING

04

05 CONTACT

07

08

09

10

06

• Consistency = weight-% of solids in

the fiber slurry, AKA “solids”

• The longer the fiber, the lower the

consistency need to be

• The lower the consistency, the higher

the flow in the white water loop at a

constant line throughput

• The capacity of the former and fan

pump will be defined by: consistency,

line speed, base weight and forming

width

• The former & the fan pump should be

able to handle the large flow!

The required flow defines the former design and fan pump choice

GIVE THE FIBERS ROOM - CONSISTENCY


0,0000%

0,0500%

0,1000%

0,1500%

0,2000%

0,2500%

0 5 10 15 20 25 30 35

Consit

ency

Fiber length

Fiber 1, normal formation

Fiber 1, good formation

Fiber 2, normal formation

Fiber 2, good formation

Key figures for a centrifugal pump: Head

GIVE THE FIBERS ROOM - FAN PUMP


Static

head

Fan pump

• (Total) Head: The pressure difference between the

discharge and suction side of the pump

• It consists of:

• Static head (height difference between level on

suction side and discharge side)

• Vacuum in the white water return tank

• Friction head (friction losses, caused by the

flow of the fluid)

Friction head is based on assumptions because of the

operating range diversity of a line, chemicals usage and

associated complex calculations.

The range of real total head value of an inclined

wire former requires design slack

The Q-H curve (Q=Flow; H=Head)

GIVE THE FIBERS ROOM - PUMP CURVES


Underload

area

Overload area

Optimal

operation

window

Lines of constant

efficiency

Lines of constant

rpm

Flow (Q)

Design operating points

• NPSHa: Net Positive Suction Head available (at

the suction flange of the pump) is the Absolute

Pressure head minus the Vapor Pressure of

the liquid.

• NPSAa is the result of a process design. An

important influencers is the level above the

suction flange.

• NPSHr: NPSA required and is directly linked to

the pump design.

• Cavitation occurs if NPSHa < NPSHr. Under

low pressure conditions, the liquid turns in

vapor bubbles. The bubbles implode when the

pressure increases. Those implosions cause

damage to the suction side of the impeller.

Key figures for a centrifugal pump: NPSH



NPSHa

Fan pump

The NPSHr curve

GIVE THE FIBERS ROOM - PUMP CURVES


• The NPSHr curves are giving the NPSHr for each

constant RPM line

• Optimal operating points for NPSHr are in the most

horizontal part of the curve

Uncertainties in the head calculations can lead to NPSH problems

GIVE THE FIBERS ROOM - COMPARE 2 PUMPS


Pump 1

• Seems to be the right choice.

There is even room for future

flow increase.

Pump 1 Pump 2

Design point

with “safety”

in head

Real

operating

point

Design point

with “safety”

in head and

future flow

Real

operating

point future

flow

NPSHr < NPSHa but

already on inclining

part of curve

NPSHr > NPSHa

Pump runs in

cavitation!

Design point

with “safety”

in head

Design point

with “safety”

in head and

future flow

Real

operating

point

Real

operating

point future

flow

NPSHr <

NPSHa

NPSHr <

NPSHa

• But if in reality the head is

significant lower, the pump is

already running close to overload

area and there is no room for

future flow increase.

Pump 2

• Is running in underload at the

original design point, but can be

used.

• If the real head is lower, the pump

is running in the preferred

operating window, the future flow

will be the optimum

Low pulse - double suction – split case pumps



Take away:

For a reliable and long-term fan pump

choice ensure Design Slack: pump shall

be able to handle theoretical and future

head and flow:

Is the position of the pump low enough

to ensure NPSHa > NPSHr?

Too small pumps and shallow basement

are suspicious!


CHAPTER OVERVIEW


02

03 DISPERSING

04

05 CONTACT

07

08

09

10

06

Mixing fibers in white water: Flocs but no clumps…

DISPERSING – KEEP THE FIBERS MOVING


Mixing glass fibers in white water is:

• Depending of the fiber length and diameter

• Depending of the fiber finish

• Depending of the white water chemicals

• Depending of the residence time in the mix and store chests

Testing of glass fiber dispersing in specialized technology centers is highly recommended

before choosing the type of mixers and stock prep configuration!

• For most glass fibers, dosing fibers in one step to the final thick stock consistency is not the

optimal solution

• Beside suboptimal dispersing, there is no possibility to adjust fiber dosing fluctuations/errors

Dilution water in steps



0,00%

0,10%

0,20%

0,30%

0,40%

0,50%

0,60%

0 50 100 150 200 250 300

Consis

tency

Time

Consitency mix tank in

Consitency mix tank out

Consitency machine tank out

• Mixing on higher consistency. This is very often more efficient.

• Extra dilution step can reduce consequences of fiber feed dosing errors.

Controlled second dilution step



0,00%

0,20%

0,40%

0,60%

0,80%

1,00%

1,20%

1,40%

0 50 100 150 200 250 300

Consis

tency

Time

Consitency mix tank in

Consitency mix tank out

Consitency machine tank out

Double diffusor



Pre diffusor

Decoupling of functions

• Pre diffusor for changing flow in header from cross machine direction in machine direction

• Main diffusor optimized for optimal turbulence: Defloccing

Main diffusor


20 / ANDRITZ NONWOVEN / TAPPI FIBERGLASS COMMITTEE SEPTEMBER 2019 / © COPYRIGHT 2019

1 2 3 4 5 6 7 8 9 10 11

Speed

Pos

Fluid speeds double diffusor

Double diffusor => More DISPERSING ENERGY

1 2 3 4 5 6 7 8

Sp

ee

d

Pos

Fluid speeds single diffusor

Two peaks

One peak

1. MF IN

2. MF OUT

3. HDF IN

4. HDF OUT

5. DUS IN

6. DUS OUT0

20

40

60

80

100

double

diffusor

single

diffusor

Dip

sers

ing e

nerg

y

(%)


CHAPTER OVERVIEW


02

03

04 FIBER ORIENTATION

05 CONTACT

07

08

09

10

06

Guiding of the slurry flow to the wire

FORMING THE WEB – GOOD FIBER LAYING


Control factors for forming process

FORMING THE WEB – GOOD FIBER LAYING


Wire speed

Gap 1

Speed of the slurry

Gap 2 HB Pressure Flow

Flow control valves

Flow transmitters

To fan pump

Vacuum

Overflow

Even dewatering in Machine Direction and Cross Machine Direction

FORMING THE WEB– GOOD FIBER LAYING


A combination between the materials , the process and the machine

FORMING THE WEB– GOOD FIBER LAYING


An optimized machine and process

design:

• Reduce the dependency of excipients

as viscosity modifier and dispersants

• Reduce operating costs

• Improve formation Quality


CHAPTER OVERVIEW


02

03

04

05 CONTACT

07

08

09

10

06

Our team is at your disposal

WE LOOK FORWARD


Leo Bos

Business Development Manager Wetlaid

ANDRITZ Küsters GmbH

Eduard-Küsters-Strasse 1

47805 Krefeld, Germany

p: +49 2151 34 1436

m: +31 6 5472 5045

[email protected]

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