Cascades, Kingsey Falls Paper Division, Gets Its Second Wind
By Pulp & Paper Canada
By Pulp & Paper Canada
ric Par, production manager at the Cascades Kingsey Falls paper mill in Kingsey Falls, QC, slowly unfolded the original plan of the machine. It is a plan, stained and yellowed by many years of service, to which Mr. Par still refers from time to…
ric Par, production manager at the Cascades Kingsey Falls paper mill in Kingsey Falls, QC, slowly unfolded the original plan of the machine. It is a plan, stained and yellowed by many years of service, to which Mr. Par still refers from time to time. This is because the only machine at the Kingsey Falls Paper mill dates back to 1919. It was purchased in New York State by the Lemaire brothers in 1972-73. This turned out to be a master stroke in Cascade’s 40-year success story. Not only was the machine very affordable at the time, but it still has a niche in the highly competitive pulp and paper market. Par folded up the plan again (before it had a chance to tear) and pointed out that, even though several machine parts have been replaced, the frame remains the same. The author was able to examine this little gem close up, along with Par and Paul Ct, regional sales manager of Johnson Canada, the supplier mandated to make major modifications to the drying section.
Productivity . . .
The machine, with 250 tonnes/day of capacity (85,000 tonnes/year) and an intermittent board machine cutting width of 3250 mm, is in very great demand: it makes chipboard-type recycled multi-layer board (9-ply) and core board in grammage ranges from 265 to 865 g/m2. All this within an eight-day production timeframe to satisfy the customers’ needs. It is obvious that flexibility is the key. This represents great progress, considering that this machine produced 80 tonnes/day in 1973.
Depending on the product grade, the machine can reach speeds ranging from 60 to 200 metres/minute. Even though the drying section was modernized in 1991 (replacement of 20 dryers), in 1996 (open hood and replacement of 20 more dryers) and in 1999 (closed hood), 70 of the 110 dryers are original components. The machine is fed by two pulp lines, with an overall capacity of 350 tonnes/day, one line for the padding and the other for the liner. This pulp, made with 100% recycled fibre, is composed of old cardboard and newsprint.
“Part of our supply comes from our converters. We’re constantly working to become the leader in reclamation of lower-quality raw materials,” Par pointed out. These materials are collected by the subsidiary Cascades Rcupration.
. . . and safety
It all began with a drying section study, commissioned from Johnson Canada in July 2002. This study focused on some very specific criteria: improve drying of cardboard and the variations of the humidity profile in the machine direction; improve the internal cohesive force on the machine (which the variations in recycled fibres make difficult); improve the drying section’s energy efficiency; and if, possible, increase the drying capacity, especially in production of grammages greater than 650 g/m2. In other words, the drying capacity was quite sufficient for cardboards from 265 to 650 g/m2, but above this range, the management would like to have surplus power.
“So we’re talking about necessary modifications that have an impact not only on the quality of the product, but on the essential aspect of workers’ safety,” said Par. “The way we see it, having to close thirty dryers manually isn’t the optimum situation. It’s temporary, and ultimately we want to eliminate this” he assured us. Par pointed out that this concern reflects a shift in corporate policy. “The will of management and its commitment to health and safety are very clear at all levels.”
Johnson Canada therefore conducted this one-week study during full production. The heat exchange and the temperature profile on each cylinder were verified and a performance constant was established, which served as a good target to identify bottlenecks in the drying section.
“For some sections, we noticed a difference in temperature between the steam and the cylinder. This led us to a drainage problem in predrying and in section 2,” Ct explains. “We checked the heat transfer and concluded that the tanks at the dry end were too small. With an inadequate tank condensate evacuation system operating with steam traps, this caused the dryers to flood. There was a considerable load on each drainage component,” he adds.
ric Par admitted that these strong temperature fluctuations had been known for some time. “The mechanics regularly take temperature readings at different points in the drying section, and that’s what put a bug in our ear. Sometimes, we had difficulty controlling the machine’s humidity profile adequately.”
Johnson used more precise themodynamic control gauges and confirmed the situation. “Even the operators heard a sloshing sound from the full dryers. This is typical of flooded dryers in a cascade system (with steam traps) like this one,” Cot added.
Before proceeding with the suggested changes, the Cascades Kingsey Falls Paper Division, assisted by its Engineering Department, proceeded with a second expert evaluation, which found that Johnson’s conclusions were fully justified.
The predrying section is composed of nine dryers, fed by the cascade line (with no addition of steam). The drying process is divided into three groups: Group 1 is composed of 61 dryers with 35-lb capacity, feeding the predryer; Group 2, composed of 18 dryers, cascades to the Group 1 dryers; Group 3 (top) is composed of 11 dryers and Group 3 (bottom) also includes 11 dryers, each with 150-lb capacity, which all cascade to Group 1.
“Under Phase 1 of the project, we removed three flash tanks (condensate and steam) and replaced them with three bigger tanks with greater capacity,” Ct explained. “The old tanks were rerouted to the Group 1 condensate collector. Now the condensate goes directly to a Group 1 tank.”
“This makes it easier to identify a section’s condensate discharge problems through adequate control: previously we had level readings, but no stable level control due to the traps,” Par contributed.
Vents were added to the dryer sections to ensure an adequate differential in case of a system bottleneck. And there are no more steam traps. They have all been replaced with control valves.
Following this first phase, the positive results were not slow in coming. “We monitored the dryer temperature internally by product grade, taking two series of measurements per week. Our humidity variances have already improved by 10%,” Par assured us. “For the highest grammages, there is an interesting gain in capacity. For low grammages, we can operate with 14-15 closed dryers, compared to 30 to 32 dryers previously. We can operate different sections of the drying section more tightly with low pressure differentials. It’s good to have this level of flexibility. We also have a better understanding of what’s happening in the drying section and have the diagnostic tools to manage it optimally.”
Phases 2 and 3
The second phase of the project will deal more fully with the health and safety aspect, while Cascades Kingsey Falls Paper Division will eliminate manual closing of the dryers on 100% of the network. During this second phase, management will also be able to integrate the energy, efficiency and product quality aspects.
“This involved installation of additional equipment to allow the drying section to operate at lower pressure for the lower grammages,” Ct explained. “Essentially, two thermocompression units will be added. This will allow a certain quantity of steam to recirculate, resulting in better energy efficiency.”
Parallel to the modifications to the drying section, Kingsey Falls Paper is working on increasingly converting the mill water to a closed system (currently 3.8 m3/tonne, with a target of 1 m3/tonne). It is currently necessary to use steam to reheat the white water tank for recirculation, but the system temperature will soon have increased enough to stop this practice and save steam.
Finally, the project’s third and last phase will involve dividing Dryer Group #1 with the goal of operating at 75 psi. “By increasing this dryer group’s capacity, we will be able to optimize the drying curve, improving the internal cohesive forces for production of our heavier grades,” Par added. At press time, C
ascades had not issued directives for the Phase 2 and 3 schedule.
Apart from its impact on the process and the mill’s employees, the project is a fine example of cooperation and partnership between a paper mill and a supplier. As Par pointed out, Cascades could have relied exclusively on the extensive experience of its internal Engineering Department to obtain these results. Instead, it opted to team up with a drying section specialist that offered all the tools to make precise diagnosis and propose the necessary modifications. By combining their know-how, this working group managed to obtain optimal solutions for the mill.