18-04-2012, 03:44 PM
Energy Savings through Optimized Doctoring at the Dryer Section
[attachment=20309]
Would you be interested in cutting your energy
costs while also gaining such additional benefits as
improved drying capacity, better runnability, lower
doctoring costs and less waste? What’s more, all this is
available without major capital outlays, long payback times
or extended shutdowns. Optimized doctoring processes
can improve dryer section performance and reduce energy
consumption, which are important considerations for any
production line or end product.
ROLE OF DOCTORING IN PAPERMAKING
Almost all rolls and cylinders need doctoring. The primary
functions of doctors are simple: shed the sheet at sheet
breaks or sheet threading and remove excess water and
contaminants from the doctored roll surface. The keys to an
optimal doctoring process are state-of-the-art blade materials,
modern roll covers and optimal doctoring parameters. Metso
has taken big steps forward in recent years both in terms of
materials technology and innovations dealing with roll covers
and doctor blade composition.
IMPORTANT FACTORS RELATED TO ENERGY SAVINGS
The total number of doctoring positions differs between
machine concepts. Modern paper machines typically employ
50 to 120 doctors. Pressing a doctor blade against a roll surface
generates friction (braking effect). In other words, there
are 50 to 120 mechanical brakes on a paper machine that
are trying to drag down the speed generated by electric
motors. Some 50 - 90% of these mechanical brakes are
located at the dryer section.
RESULTS THROUGH OPTIMIZED DOCTORING
The following real-life case examples show that energy
efficiency can be enhanced also with modest investments.
Improved doctoring processes help mills improve cylinder
drying capacity and runnability, achieve better paper quality
and higher production efficiency, reduce power consumption,
and cut both doctoring and operating costs. Optimal doctoring
can also have favorable safety and environmental effects.
CASE EXAMPLE 1
Significant Savings in Energy Costs. The targets were
clear. The mill wanted to reduce dryer section energy consumption
and improve doctoring results. A 30% difference
in dryer section electric motor energy consumption was
reported on the basis of onsite testing comparing section
operation with doctors engaged to operation with doctors
released (which could also be mathematically proven with
typical dryer section parameters, blade materials and operating
speeds).
[attachment=20309]
Would you be interested in cutting your energy
costs while also gaining such additional benefits as
improved drying capacity, better runnability, lower
doctoring costs and less waste? What’s more, all this is
available without major capital outlays, long payback times
or extended shutdowns. Optimized doctoring processes
can improve dryer section performance and reduce energy
consumption, which are important considerations for any
production line or end product.
ROLE OF DOCTORING IN PAPERMAKING
Almost all rolls and cylinders need doctoring. The primary
functions of doctors are simple: shed the sheet at sheet
breaks or sheet threading and remove excess water and
contaminants from the doctored roll surface. The keys to an
optimal doctoring process are state-of-the-art blade materials,
modern roll covers and optimal doctoring parameters. Metso
has taken big steps forward in recent years both in terms of
materials technology and innovations dealing with roll covers
and doctor blade composition.
IMPORTANT FACTORS RELATED TO ENERGY SAVINGS
The total number of doctoring positions differs between
machine concepts. Modern paper machines typically employ
50 to 120 doctors. Pressing a doctor blade against a roll surface
generates friction (braking effect). In other words, there
are 50 to 120 mechanical brakes on a paper machine that
are trying to drag down the speed generated by electric
motors. Some 50 - 90% of these mechanical brakes are
located at the dryer section.
RESULTS THROUGH OPTIMIZED DOCTORING
The following real-life case examples show that energy
efficiency can be enhanced also with modest investments.
Improved doctoring processes help mills improve cylinder
drying capacity and runnability, achieve better paper quality
and higher production efficiency, reduce power consumption,
and cut both doctoring and operating costs. Optimal doctoring
can also have favorable safety and environmental effects.
CASE EXAMPLE 1
Significant Savings in Energy Costs. The targets were
clear. The mill wanted to reduce dryer section energy consumption
and improve doctoring results. A 30% difference
in dryer section electric motor energy consumption was
reported on the basis of onsite testing comparing section
operation with doctors engaged to operation with doctors
released (which could also be mathematically proven with
typical dryer section parameters, blade materials and operating
speeds).