Vacuum dewatering of paper
SPCI Convention
September 2013
Lars Nilsson
Environmental and Energy Systems
Karlstad University
Content of presentation
- Typical industrial data
Energy consumption of vacuum systems
- Overview of past research
Influence of vacuum dwell time and vacuum level
- Current research at Karlstad University
Air flow measurements
Steady flow modelling (one phase)
Unsteady flow modelling (two phases)
- Typical industrial data yet again
- Research in the pipeline
Lars Nilsson
Typical industrial data
Data from Lahtinen & Karvinen (2010)
Lars Nilsson Typical industrial data Environmental and Energy Systems Overview of past research
Paper grade
No of PM
Energy consumption
Lowest
Highest
Fine paper
27
37 kWh/ton
132 kWh/ton
Liner board
18
32 kWh/ton
115 kWh/ton
Typical industrial data
Considerable spread among industrial data:
•
Vacuum pumps and flow control systems
differing in efficiency?
•
Vacuum needed for other things than dewatering
the paper material alone?
•
Paper producers aiming at different dry content
after vacuum dewatering?
Lars Nilsson Typical industrial data Environmental and Energy Systems Overview of past research
Current research
Typical industrial data yet again Research in the pipeline
Overview of past research
Räisänen et al., Paperi ja
Puu 78: 461-467
Data from 1996
Increased vacuum level
leads to an increased
achievable dry content
Lars Nilsson Typical industrial data
Overview of past research
Lars Nilsson Typical industrial data
Environmental and Energy Systems Overview of past research Current research
Typical industrial data yet again Research in the pipeline
Neun, Tappi Journal
77(9): 133-138
Data from 1994
Shorter sampling
times
Overview of past research
Granevald et al.,
NPPRJ 19(4): 428-433
Data from 2004
Forming fabric will
influence dewatering
Lars Nilsson Typical industrial data
Overview of past research
Lars Nilsson Typical industrial data
Environmental and Energy Systems Overview of past research Current research
Typical industrial data yet again Research in the pipeline
Pujara et al., Drying
Technology 26(3):
341-348
Data from 2008
Dry content will reach
an almost constant
value
Overview of past research
Åslund et al., NPPRJ 23(4): 403-408
Data from 2008
Investigated dewatering of different kinds of pulp
Lars Nilsson Typical industrial data
Overview of past research
Lars Nilsson Typical industrial data
Environmental and Energy Systems Overview of past research Current research
Typical industrial data yet again Research in the pipeline
Nilsson, Drying
Technology
(accepted)
Overview of past research - summary
•
The dry content increases with the vacuum dwell time.
•
The dewatering rate is high initially and decreases until
it is close to zero.
•
The dry content will reach an almost constant level
which increases with the vacuum level.
•
Choice and preparation of pulp will influence the
achievable dry content.
•
Choice of forming fabric will influence the dewatering
rate and the achievable dry content.
Lars Nilsson Typical industrial data
Current research at Karlstad University:
Air flow measurements
Lars Nilsson Typical industrial data Environmental and Energy Systems Overview of past research
Current research
Typical industrial data yet again Research in the pipeline
Current research at Karlstad University:
Steady flow modelling (one phase)
Lars Nilsson Typical industrial data Environmental and Energy Systems Overview of past research
Current research at Karlstad University
Lars Nilsson Typical industrial data Environmental and Energy Systems Overview of past research
Current research
Typical industrial data yet again Research in the pipeline
- Steady flow modelling (one phase)
Air flow rate is the model result
- Unsteady flow modelling (two phases)
Dry content and flow rates rates of water and air
as a function of time are model results
Current research at Karlstad University:
Unsteady flow modelling (two phases)
How?
•
Fiber diameter is measured
•
Amount of ”free” water is estimated
•
Structure is built up in CFD software
•
Movement of the boundary between
water and air is traced by the
program
Lars Nilsson Typical industrial data Environmental and Energy Systems Overview of past research
Current research at Karlstad University:
Unsteady flow modelling (two phases)
Rezk et al., Chemical Engineering Science 101: 543-553
Data from 2013
Model predictions
A rapid initial dewatering of
large pores is followed by a
reduced dewatering rate as
water from smaller pores is
removed.
Air flow increases and a
steady flow rate will be
reached.
Lars Nilsson Typical industrial data Environmental and Energy Systems Overview of past research
Current research
Typical industrial data yet again Research in the pipeline
Typical industrial data yet again
Lars Nilsson Typical industrial data Environmental and Energy Systems Overview of past research
Nilsson, Drying Technology (accepted)
Industrial data
Research in the pipeline
•
Improvement of current CFD model - 3D fiber
network, network compression and forming fabric
influence
Lars Nilsson Typical industrial data Environmental and Energy Systems Overview of past research
Current research
Typical industrial data yet again Research in the pipeline
Research in the pipeline
•
A better description of the amount of water that
can be removed by application of vacuum
•
Rewetting in laboratory equipment and in paper
machines
Lars Nilsson Typical industrial data Environmental and Energy Systems Overview of past research
Thank you!
Lars Nilsson Typical industrial data Environmental and Energy Systems Overview of past research
Current research
Typical industrial data yet again Research in the pipeline
