Report on my Attendance at the Fall 2003 Meeting of
the Black Liquor Recovery Boiler Advisory
Committee, BLRBAC, Western Canada
BLRBAC is a “Trade Association” that exists for the
purpose of generating safety procedures and guidelines
that govern the operation of Black Liquor Recovery
Boilers.
This organization was formed in 1963 by several
groups of concerned professionals that had become
alarmed by the number of Black Liquor Recovery
Boiler explosions that had resulted in many injuries
and death to personnel operating these boilers. These
groups consisted of Insurance Companies, Boiler
Manufacturers, and Paper Company professionals
that were involved in operating, insuring, or manufacturing
Black Liquor Recovery Boilers.
The Fall 2003 Western Canada BLRBAC was held November
5—6 at the Crown Plaza Hotel Georgia, Vancouver,
with representatives of 19 of the 22 Western
Canada Kraft Mills from Manitoba, Alberta, and British
Columbia. This provided means of communication
from mills with common interest in various aspects
of operation.
The conference commenced on Tuesday evening of
the 4th with a “meet and greet”. Another social event
was on the evening of the 5th. The social events gave
an opportunity to speak to vendors, guests, and associates
in a casual non-structured atmosphere.
On Wednesday the 5th there was a closed session
business meeting for BLRBAC members and boilermakers
with the main focus on incident reports. Also
on the agenda were reports from Eastern BLRBAC,
Atlanta BLRBAC, PAPTAC, and other steering committees.
Incident Reports
1. ABB Recovery Boiler: rated at 3.4 MM lbs/day,
363,000 lbs/hr steam, 900 psi, 750 deg. F. There was a
1/2 inch transverse crack on the crown of a floor tube
adjacent to the side wall in the right rear corner of the
furnace. On September 9 at 01:25 it was reported by
the Recovery Boiler Fireman that there was a wave
motion in the smelt at the spouts. It later disappeared.
Then it was discovered that the smelt had
burned through the right side wind box and had
flowed to the basement burning wiring to the dissolving
tank agitator. Later, irregular combustion was
noticed in front of the windbox. There was a small
smelt pool with erratic waves occurring frequently.
The boiler was taken off liquor and put on gas and
inspected again, the erratic waves continued and the
boiler was ESP (Emergency Shutdown Procedure) on
September 10 at 03:20. The crack appeared to have
been caused by a chipping hammer that was used to
remove the char bed 2 years earlier. The recommendation:
Use high pressure water for char bed removal
and restrict the use of chipping hammers. Outage
was 56 hours.
2. ABB Recovery Boiler: rated at 4.0 MM lbs/day,
587,000 lbs/hr, 800 psi, and 750 deg. F. Rear economizer
tube 17, row 3, had a 1/16 inch hole at the butt
weld, 24 inches above the bottom header. At 19:00,
May 26, the Recovery Boiler Assistant, during his routine
walkdown, observed water in the ash hopper and
ESP was initiated. The weld had been done during a
regular shutdown. The back part was done by mirror,
was x-rayed, and accepted. Notes: The insurance
companies require that a walkdown with the soot blowers
off be completed at least once per shift. Note:
The low solids alarm is at 66% and firing stops at 64%
solids content.
3. B&W Recovery Boiler: rated at 2.8 MM/day,
350,000 lbs/hr, 750 psi. On September 17 the boiler
was off liquor for about 6 hours when steam and water
was noticed leaking from the casing. The boiler
Steam Lines 9
was shutdown, depressurized, and a visual inspection
made. Leaks were located in the last pass of super-heaters
on top of the bull nose. A 1/4 inch pin hole
washed out two adjacent tubes causing a 1/8 inch
pinhole in each. The initial cause was a cracked tube
at a weld termination. This location is not readily accessible
during inspections due to a baffle plate. In
future inspections the baffle plate will be removed for
inspection purposes. Noteworthy is that the mass
balance leak detection showed a leak was present 4
weeks before the incident but credibility was not
given to the instrument. The outage time was 83
hours.
4. B&W Recovery Boiler: rated at 3.78 MM/day,
563, 200 lbs/hr, 1,125 psi, and 815 deg. F. On October
22 the unit was coming off liquor with the bed burned
down when a Field Operator found a leak in the
economizer. An inspection during depressurizing
resulted in discovery of a second leak, located in the
screen tube. The bottom header handhole was leaking
into primary hopper. A stress crack in the handhole
was ground out and welded. The screen tube
had a 1 inch circumferential crack in the butt weld
just above the nose arch. The crack was ground out
and welded. A hydrostatic test found another screen
tube leaking at a membrane termination. It was repaired
and the second hydrostatic test discovered another
leak in the same tube. It too was repaired. Outage
time was 73 hours.
Eastern Canada BLRBAC
There were two incidents reported.
New Brunswick requires a 4 minute confined
space rescue to be in place.
One mill has the Shift Supervisor looking after the
fibre line.
Precipitator dampers must be locked in a secure
closed position, both inlet and outlet, for confined
space entry in Ontario.
Atlanta BLRBAC
Smelt explosion in a recovery boiler from a water
wash, 32 hours after being off liquor.
Methods of heat measurement of the bed was discussed.
Insurance company asking for alternate ESP in the
event the ESP push-buttons do not work.
The trend for incidents has been decreasing over
the years but now there is a sudden rise, perhaps
related to the longer run times between majors.
PAPTAC
There were 3 near misses with oil strainer gasket
blowouts.
Boiler oil gun gaskets blew out and caused a fire
that was extinguished quickly. One reported using
superheated steam for atomization.
One mill had a tube leak caused by circulation restricted
by a welding can lid stuck in the tube.
Suggested is a count of all items taken into the
drum during maintenance to ensure everything
comes back out.
Burning 2—5 % sludge with BFB boilers in Ontario.
One recovery boiler had a bottom rebuilt.
Round Table Discussion
Out of 4 incidents, leak detection detected 2 and
confirmed 1.
Loss of cooling water to spouts. Operator put
cooling water back on. This could have been a
very serious situation that has caused explosions
in other mills. The boiler was later shutdown and
the spouts replaced.
Steam plant Superintendents are coming under
increasing pressure to extend maintenance shut-downs
to 18—24 months.
There are 7 mills or pulp companies in France that
are running for two years without a shutdown for
maintenance or inspections. They have formed
their own insurance company, similar to an insurance
co-operative.
One company is having initial success with fireside
additives. Normally they had to shutdown
after 3 months of operation. They are able to go as
long as 6 months. The load on the precipitator is
down and smoke density dropped from 120 ppm
to 60 ppm
Boiler Manufacturers’ Short Presentations
Presentation on electric port rodders improve performance
and reliability. They are being used by
2 companies.
Gas igniters are like the ones being used by us
here in BC on our Power Boilers.
New materials for BL spray nozzles.
Chromize tubes/composite tubes.
Chromize dry spouts. About 70% left after 1 year
compared to 35% on wet spouts.
It is possible to operate up to 3 years with skilled
refractory applicators. Comparative costs are
$14K to $7K each.
Scrubber performance and upgrades.
Air improvements at Thunder Bay from two levels
to three improved the running time from 2—14
months with one company.
Day 2—Technical Session
Combustion Analysis Around Primary Air Ports.
Presenter: Keith Rivers of Aker Kvaerne
Large Recovery Boiler in China is designed for 13 MM
lbs/day with capability of 15 MM lbs/day. Five levels
of air input with unique steam membrane panels,
one stack, with the dissolving tank flume going back
into the RB. Intelligent soot blowers that operate in
the areas that are needed — no pre-program sequence.
Recovery Boiler Air System
Presenter: Ralf Holm of Andritz
Covered vertical air systems.
Environmental Improvements
Presenter: Randy Reeves of Alstrom
A lot of money has been invested in Electro Static Precipitator
improvements with marginal returns over
the years. In many mills improvement is required to
precips due to their “bottle-necking” the system. The
dust pH needs to be tracked. Precip performance
tests can be done, inspection recommended before
cleaning so that appearance can be checked, corona
quenching, mechanical deficiencies, alignment of
plates, and tramp air were typical topics. Randy also
spoke about particulate size resistively, adhesive
characteristic differences between front end and back
end. New Epic control has shown improvements.
Multipeak electrode in the first bank makes significant
difference. Different types of rappers may need
upgrading.
Use of Automated Pulse Spray Gas Metal Arc Welding
(PSGMAW)
Presenter: John Grimes of GE Welding Specialty Services
The GE Company can specify welding electrodes with
specific alloys that will best match the boiler. The machines
can do 18—20 square feet per shift or 1—1.5
square feet per hour. Unlike with metal spray, the
area does not have to be evacuated when using PSG
MAW for restoration of boiler waterwall tubes. The
weld can be done from 80th thickness and restored to
170th thickness. Maybe it is an alternative answer to
a bottom replacement..
Two Wall Primary Air Systems
Presenter: Colin MacCallum of BIAS
The same amount of air is used but a larger up-flow
of gas gives improved retention time, higher bed temperature,
reduced emissions, can cut back excess air
requirements, cleaner precipitators, and improved
reduction efficiency. This system is being used in
Western Mills with success.
David Goodwin
First published in January/February 2004 Steamlines.
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