At Interstate Paper in Riceboro, GA, a linerboard machine press section rebuild demonstrates how owner commitment can make the difference in competitive position
November 2007
By Monica Shaw
For Interstate Paper LLC (IPC) in Riceboro, GA, removing process bottlenecks throughout the mill remains a major objective. Fueled by the commitment of its parent company, the privately-held Interstate Resources Inc (IRI), IPC has a history of continuously improving processes and equipment at the linerboard mill, such as the installation of a new topwire former and soft calender in 2002 (see Pulp & Paper, September 2002).
More recently, IPC completed a multi-million dollar rebuild of its linerboard machine's press section. In addition to a shoe press, the rebuild included dryer, drives and lubrication upgrades, as well as installation of new stock preparation refiners (see sidebar below, "Refiners maintain quality and support speed increases"). However, the paper machine has not been the mill's sole focus, as a variety of other improvements throughout the mill confirm (see sidebar below, "Improving more mill processes").
"There is no doubt we've benefited from our owners," says the vice president and general manager Gene Millard of the 1968-era Riceboro mill. "A lot of larger companies might not have invested in us, but our owners did and we've been successful."
Since the rebuild project was completed in November 2005, the paper machine has met or exceeded quality and performance guarantees, as well as improving on other properties.
"By upgrading the refiners, drives and press, we're now able to make more linerboard due to faster speeds with more secondary fiber, while still maintaining quality," Millard describes.
Press redesign, dryer changes
In late 2004, IPC chose Metso Paper to provide the equipment, engineering, training, controls and startup services for the new press section. The decision, says Millard, was based on price and on the press design. The equipment was ordered in January 2005 and set for a nine month delivery.
The IPC press reconfiguration consists of a suction pickup, relocating the old second press rolls to the new first press (800 pli), a suction transfer roll between the two presses and adding a new double felted SymBelt shoe press (6,600 pli).
Next, a blow box was installed to carry the sheet from the second press to a new baby dryer and into the first dryer section. The first dryer section was split in half to accommodate a new unirun arrangement (first 6 dryers).
Also for the dryer section, IPC contracted with GL&V as part of the rebuild project to replace all dryer felt rolls and stretchers. "We needed them to keep higher tension on the felts at the faster speeds," says Millard.
Other paper machine upgrades
To maximize benefits from the new press section, additional equipment was necessary. Stock preparation required new refiners (see sidebar below), and the existing drives and lubrication systems were inadequate for a higher performing paper machine.
IPC chose Siemens Energy & Automation to design and install a fully integrated Sinamics paper machine drives system that would allow the rebuilt paper machine to run 3,000 fpm. The AC drives would replace the mill's existing steam turbine line shaft drive system. The order included power distribution, transformers, drives, electrical housing, motors and control automation. The scope of work included demolition of existing equipment; civil and structural engineering work for the electrical housing; installation of motors, gearboxes and control stations; and complete cabling and startup services.
Although the new press section would come with its own lubrication system, the rest of the paper machine would be under lubricated for the faster speeds. To address the issue, IPC ordered a new Safematic lubrication system for the dryer and felt roll bearings.
Executing a retrofit
IPC's paper machine rebuild project ran for 27 days from November 6 to December 2, 2005. Millard wishes the shutdown could have been held to 22 days, but concedes that the project progressed pretty well given the challenges.
"With a retrofit like ours, you never know what you will run into – everything from piping to US vs metric issues," explains Millard. "Plus, the nine months from order to delivery of the press was very tight, and we may have missed things during pre-erection of the press, which resulted in a lot of field work to correct problems."
IPC chose LaFramboise, a general contractor, to install the press section. Siemens, GL&V and Safematic were responsible for installing their own equipment. During the project, there were 250-300 contractors working on the paper machine, in addition to IPC mechanics performing annual outage tasks.
"At times, they were crawling over each other on the machine's back side, but safety performance was still excellent," Millard says.
IPC has DCS control throughout the mill, except for the powerhouse. For the rebuild, Metso supplied controls packages, such as those for interlocks, which were capable of interfacing with the mill's DCS as well as drive control programs supplied by Siemens. Most controls were tied directly into the DCS, but Metso also provided some standalone PLC packages. Metso provided software support during and after the startup to fine-tune the control systems.
Suppliers conducted training during the shutdown period, as well as follow up training for operators after the startup. "You never know until your hands are on the steering wheel, so the operators knew better what questions to ask after the startup," Millard explains.
The first paper was on the reel by December 2, 2005, and Millard reports that within the first month, the mill was producing 805 tpd of linerboard compared with the previous 770 tpd. "We then quickly hit the 850-tpd range," he notes.
"Smooth" learning curve
By November 2006, production on the rebuilt machine had risen to around 880 tpd and now exceeds 900 tpd. Speeds have increased between 150 fpm and 200 fpm for every grade, as Table 1 shows. Press solids rose from 40% to 44%, even at the higher speeds.
Also, paper machine availability had increased from 87.5% in January to 94% range by the end of 2006. "It's been a relatively smooth learning curve," Millard notes.
Most issues that adversely affected the yearly average machine availability occurred between January and July 2006. Early on, operators had to learn how to maintain the baby dryer doctor and how to operate the draw between dryer section 1A (new unirun dryers) and section 1B. In the March through June timeframe, the new refiners were coming up to speed. Also, the mill had to work out "bugs" associated with the new equipment, including installation of heavier duty housings on the new dryer section stretch rolls to prevent bearing failures.
As for the shoe press, its first two sleeves only lasted six weeks each due to delamination. IPC replaced this sleeve with a model from Albany International, which lasted six months.
"We removed the sleeve at that point, and analysis showed that it could have lasted another two months. Since then, sleeve life has been three to six months." Millard says.
Millard says that runnability is much better than before the rebuild.
"We used to average 2-3 breaks per day and now we average one break every two days," Millard reports. "In November 2006, the paper machine went 24 days without a break while going through the entire linerboard grade structure almost twice. You always have break issues, but we're much more stable than we used to be."
Sheet results pay off
While the main focus of IPC's rebuild was speeding up the paper machine, sheet parameters have improved on its five major linerboard grades, as Table 1 shows. The paper machine has also met Metso performance guarantees for the four stipulated grades (all in Table 1 except 52-lb).
IPC controls to Mullen on its kraft linerboard grades and STFI on its high compression grades. Millard notes that other sheet parameters are now much better, without really trying. These include smoothness (especially Emveco smoothness), porosity, scuff and Z directional tensile.
Significantly, Metso guaranteed performance with up to 25% secondary fiber in the sheet; it is presently around 20%. This is critical should the mill decide to increase speeds on the machine again.
From a customer standpoint, do these sheet improvements pay off?
"Yes, they certainly do," says Millard. "Having high quality sheet properties is one important piece of the puzzle which can earn you the position of Preferred Supplier with valuable customers.
"Along with quality, we are also proud of our customer and sales service. For example, we average over 96% on-time delivery. We work hard to become partners with our customers and provide for their needs in all areas."
|
|
35# HS |
42# KLB |
52# HS |
55# HS |
69# KLB |
|
Pre |
Post |
Pre |
Post |
Pre |
Post |
Pre |
Post |
Pre |
Post |
| Speed |
2,334 |
2,572 |
2,254 |
2,482 |
1,724 |
1,941 |
1,608 |
1,839 |
1,335 |
1,616 |
| Mullen |
98 |
96 |
106 |
105 |
124 |
124 |
130 |
126 |
147 |
144 |
| Porosity |
23 |
44 |
22 |
35 |
27 |
41 |
29 |
40 |
26 |
33 |
| ZDT* |
62 |
77 |
51 |
64 |
51 |
60 |
52 |
59 |
40 |
42 |
| Caliper |
10.0 |
9.1 |
11.6 |
10.8 |
14.0 |
13.1 |
14.8 |
14.0 |
18.6 |
17.8 |
| Smoothness |
370 |
353 |
372 |
362 |
379 |
369 |
384 |
373 |
386 |
385 |
| Emveco |
179 |
158 |
170 |
157 |
160 |
140 |
159 |
148 |
175 |
167 |
| STFI |
20.1 |
20.4 |
20.8 |
20.5 |
29.7 |
29.5 |
31.3 |
31.1 |
32.6 |
33.2 |
| Scuff |
55 |
68 |
44 |
55 |
50 |
65 |
55 |
63 |
41 |
53 |
| Slide Angle |
24 |
24 |
24 |
24 |
26 |
24 |
26 |
25 |
25 |
25 |
| * z-directional tensile |
Future considerations
Even though the new drive is designed for 3,000 fpm, IPC's paper machine has topped out at speeds of 2,700 fpm due to dryer limitations. For the future, IPC is considering the addition of dryer cans and/or felting the bottom dryer cans.
Another consideration is to extend the fourdrinier by 33 ft for improved quality, as well as the possibility of creating a 3-ply linerboard sheet rather than the 2-ply one currently produced.
"We're still looking at what advantages might be gained by going to a 3-ply sheet in the future," says Millard, " but right now we're concentrating on running well in a fairly good market."
|
|
|
One important aspect of attaining the production and quality goals associated with the press section rebuild at Interstate Paper LLC (IPC) was an upgrade of the base sheet stock preparation refiners. Four 42-in Beloit Jones 3000 Series refiners were replaced by four 46-in GL&V 6000 Series refiners.
"Prior to the rebuild, we were already bumping against refiner limitations," explains vice president and general manager Gene Millard. "We could hit the quality targets, but our speed was limited because the refiners were maxed out."
To house the new refiner equipment, IPC constructed a new two-story building connecting to the main paper machine building. The building allows for the old refiners to be removed, providing space for a future fourdrinier extension. It also allowed the mill to maintain production during construction of the building and installation of the new refiners, gearboxes and motors. In addition, the building houses a lab for testing stock parameters.
The mill contracted with GL&V for engineering and startup assistance. From February through March 2006, after qualification of the press section, the new refiners were brought on line. They have since supported a 12% increase in paper machine speed while going from 10% to 20% secondary fiber consumption.
"The refiners have been critical in maintaining quality while increasing secondary fiber use," says Millard. "This was necessary because of liquor recovery cycle limitations that bottleneck our production of virgin fiber."
On the paper machine's 42-lb grade, speed has averaged between 2,550 fpm to 2,600 fpm. Some adjustments were made to plate patterns to achieve the required STFI on the 35-lb grade, but Millard says the refiners are close to achieving all targets.
"We have now excess capacity in the refiners and can use more refining and get faster speeds at the same time," Millard describes. "Combined with the press rebuild, we are now exceeding our production goal of 900 tpd."
Although not part of the rebuild package, IPC completely replaced its pulp washing line during the November 2005 shutdown with equipment from GL&V. The line went from struggling to process 700 tpd of virgin kraft fiber to a capacity of 900 tpd.
|
|
|
|
Though not part of the press rebuild project, Interstate Paper LLC's (IPC's) purchase and conversion of a coal boiler to a bubbling fluidized bed (BFB) boiler offers another example of Interstate Resources Inc's commitment to the Riceboro, GA, mill.
In 2003, Interstate converted a shutdown coal boiler purchased in Statesboro, GA. The purchase included the entire powerhouse, minus the steam turbine generator. Babcock & Wilcox redesigned the boiler to burn bark and tire derived fuel (TDF) to displace the fossil fuels burned in the old power boiler.
The refurbished boiler is "relatively small, producing around 200,000 lb steam/hour," says Gene Millard, vice president and general manager at IPC. Still, the BFB boiler and the recovery boiler are the Riceboro mill's primary boilers. The old power boiler is only used in emergencies, as a backup NCG burner or when maintenance is performed on one of the primary boilers.
"For the most part, we've kept fossil fuels out of the BFB boiler, and that's been very helpful for us as energy costs have risen," says Millard. "We are really blessed with owners who take a long-range view."
Several million dollars more will be spent on the refurbished boiler's fuel feed system, air system and ash handling system to allow use of more diverse fuels, including hardwood and tub grindings. "Pine bark has become more scarce as others have begun to use it for fuel," Millard remarks.
IPC's recovery boiler also underwent significant work recently. Although it did not require major capital, the boiler's entire floor was replaced in a maintenance effort.
|
Monica Shaw is a freelance writer located in Atlanta, GA.
Pulp & Paper magazine is FREE to qualified subscribers. Click here to find out more.
