Temple-Inland uses a single multi-fueled boiler to supply
650 psig steam to a board mill. Fuels are predominantly bark
and sawdust with two gas burners for times when bark or dust
is wet or curtailed. Load swings are significant with an average
load of 100 Kpph, and average swings in flow of 50 Kpph every
12 minutes. Swings have been noted up to 70 Kpph as frequent
as six minutes apart for an hour or more. Normal load changes
are 50 Kpph over 12 minutes. A steam accumulator is used to
help moderate steam swings to multiple digesters.
Emerson Process Management's preconfigured Boiler Control Package for
the DeltaV digital automation system was
adapted for use with this boiler system. Additions include:
a more advanced steam header pressure control strategy with
fuel allocation and feedforward, simultaneous multiple fuel
firing, and furnace pressure control with three transmitters
for redundancy.
The boiler strategy was designed by Emerson and the balance of
control system was engineered and installed by Scallon Controls
of Beaumont, TX. Most notable was that the boiler was converted
from older AC2 single loop controllers to the DeltaV system without a
shutdown (yes, it was converted with the boiler running).
Controls also include soot blowing, all motors and conveyors,
feedwater, deaerator, and makeup water. Next fall, the burner
management system will be converted from an older PLC to the DeltaV system.
Startup was completed early May 1998, and has been running
well. Notable improvements were: boiler trips for low drum
level due to load swings have been almost eliminated, header
pressure variation has been reduced from 50 to typically less
than 15 psi, manual intervention has been noticeably reduced,
and furnace pressure is controlling much better. Bark fuel
burning efficiency has improved as measured by the much-reduced
quantity of char in the ash pit.
The system includes two DeltaV controllers and two workstations and
redundant DeltaV controllers.
back to top
|
