Drying is an energy intensive
operation, accounting for 35% of the steam energy requirements of
an integrated paper mill. Drying capacity is a function of the number
of steam drums in the line. As lines have been made to run faster,
often additional steam drums are required.
Infrared dryers can be
placed along the line to compliment existing steam drum dryers. This
can give a boost to drying capacity and allow the speed increase of
dryer-limited lines, without the high cost of lengthening the line
with steam drums.
The IR energy penetrates
the paper and dries from the inside out. There is no contact
so on some types of paper, product quality is improved. When
used with cross-directional moisture scanning (CD), the burners can
be staged to get correct/ even drying across the web. Bands can be
as narrow as 3".
Burners are made of metal
or ceramic materials that heat up and cool down very quickly, allowing
the tight CD control, and improving safety. They cool below ignition
temperature as quick as 1 second after shutdown. They heat up to operating
temperature in about 10 seconds.
The IR wave-length is more
acceptable to paper than that of electric, so it is more efficient
in addition to being a lower cost fuel. Gas burners are considered
30 -60% efficient when measuring the paper temperature before and
after the burner. If used in conjunction with gas fired convection
drying, efficiencies increase to 65 -80% by keeping the air above
the surface of the paper moving. Production increases of 10 -20% are
common.
Locating
IR Heaters
The diagram shows potential
locations of IR Heaters to accomplish required results and require
the minimum amount of retro-fit work:
Also see Why
Gas IR
IR
Drum Heater
ABB has developed a unique
in-drum radiant heater system that increases drying capacity by increasing
the surface temperature of a drying drum/can over what is possible
with a steam system. The gas fired drum is a direct replacement for
an existing steam drum and provides drying via direct contact with
the hot surface of the drum.
For More Information see
ABB AndritzAG
More
Information
Paper
Manufacturing
Paper
Drying
Paper
Glossary
Manufacturers
Marsden
Solaronics
Krieger
- Voith
ABB
- (bought by Andritz)
