Company’s 220,000-tpy greenfield mill in Lawton, Okla., produces lightweight board that is setting new standards for gypsum wallboard

Republic’s Gypsum Liner Machine Is First to Utilize Two Gap Formers

The fiber preparation area includes pulping, coarse and fine screening, forward and reverse cleaning, fractionation and refining. A distributed control system monitors and controls material flow to the paper machine, thereby minimizing process variation.

The strong level of housing starts drove gypsum wallboard and gypsum liner shipments to record levels in 1999. Thus, it seems that the timing of Republic Paperboard’s startup of its greenfield gypsum linerboard mill in April of this year was right on the mark. The mill, located in Lawton, Okla., effectively doubled the company’s recycled paperboard capacity and introduced a new level of quality not only to its own plants but also to the industry at large.

The centerpiece of the $170 million project is a 161-in.-trim paperboard machine that has capacity to produce 220,000 tpy of gypsum liner. The machine produces multi-ply paperboard in basis weights ranging from 30 lb. to 50-lb./1000 ft² and has a maximum design speed of 2500 fpm. Voith Sulzer Papertechnology supplied the major components for the project, including the recycling plant, stock preparation equipment, complete paper machine, and roll handling system.

The project took eighteen months to complete from the purchase of the paper machine to startup. Groundbreaking was in May 1998, with the first reel off the machine on November 27, 1999. A key highlight of the construction project was that there were no lost time accidents (including sub-contractors) during the 1.3 million hours of labor required.

During Pulp & Paper’s visit to the mill in southwestern Oklahoma several key executives and project managers were interviewed for this story. They included Janey L. Rife, vp and treasurer; Jim Nelson, director of engineering; Todd. T. Brown, vp-paperboard operations; Roger Smith, mill manager; and Lon D. Lewis, vp-paperboard sales and recycling.

FIBER SUPPLY/PROCESSING. The Lawton mill is 100% recycled fiber based. Fiber for the machine is provided by a variety of sources, including the company’s own reclaimed paper recycling centers in Kansas City, Mo., Denver, Colo., and Topeka, Kansas.

To secure supply for the new machine without disrupting the market, the mill began sourcing fiber eight months before the mill came online. The bulk of the fiber used at the mill consists of old corrugated containers (OCC) and old newspaper (ONP) grades. The white fiber for the top stock system is provided by a variety of higher quality grades.

There are two separate fiber processing lines supplied by Voith Sulzer (Figure 1). The filler stock system supplies fiber for the backside or grey back liner used on the wallboard, consisting of ONP and OCC grades. The top stock system produces stock for the cream side liner, using the higher quality recycled grades. The capacity of the filler line allows it to supply the whole mill when running gray-backed grades, since the pulper can process 700 tpd. The top filler line is smaller, with a 150-tpd capacity, accounting for about 25% of the overall mill throughput. A guillotine roll splitter was added recently to allow the mill to process broke rolls and roll stock that may be purchased for the top filler system.

Each of the two lines feeds bales of wastepaper to their respective pulper via a conveyor. Following each pulper is a high density cleaner system followed by further cleaning and screening. The top system has screening and forward cleaning equipment. The filler system has a four-stage system. The filler stock system has additional stock preparation equipment since it processes lower quality wastepaper grades, compared with the white grades handled in the top stock system. Following the high density cleaners and barrier screens, filler stock is processed by forward cleaners, fine screening, and lightweight cleaning stages. Each stock line is thickened using an Andritz thickener prior to high density storage.

In addition, a rejects system removes further contaminants, mainly lightweights, using a variety of equipment including Voith Sulzer Turboseparator, Contaminex and Combisorter stock prep equipment.

The filler stock from high density storage is also refined differently than the top stock. Filler stock is sent through a Multifractor fractionator (screen) to separate out long fiber and short fiber fractions. These are then refined separately by TwinFlo double disk refiners. The top system includes deflakers as well. Stock for the machine is processed by approach flow primary and secondary pressure screens before the paper machine. These feeds are combined to produce a multiply sheet, performed via the use of multiply headboxes on each of the machine’s two formers.

FIGURE 1: Recycled fiber is processed in two lines at Republic’s Lawton mill, with the filler line using added cleaning (four stages) and fractionation.

UNIQUE WET END. In addition to the distinction of being one of a few greenfield paper mills installed in the U.S. in recent years, the facility boasts state of the art forming technology. The wet end of the machine is equipped with two Voith Sulzer formers, comprised of a DuoFormer Base former followed by a DuoFormer Top former. These are both essentially roll gap formers, with the first former having a dilution control headbox for CD basis weight profile control. Republic’s 161-in.-trim paperboard machine is believed to be the first in the world to be equipped with two gap formers.

The first roll former sheet is transferred to an extended bottom wire that carries the sheet to the next former. The second former’s sheet is transferred onto this wire carrying the first sheet to form the board. Unlike many multiply paperboard machines, no starch is needed to adhere the two sheets together at the Lawton mill due to the excellent formation provided by the machine. Multiply forming is traditionally done with multi-fourdriniers or with cylinder machines.

The company initially considered a number of forming options for the machine. A multi-fourdrinier wet end configuration was seriously looked at and trials of this setup were actually done. However, to obtain the formation desired, it was felt that a top wire was important. “The roll type gap former that was chosen provided better formation at equal or higher consistencies than other designs, as well as reducing the number of wires and providing better space utilization,” notes Nelson.

The top wire dewatering aspect is key in making the cream grade, which is the higher quality side of the wallboard that is finished (painted). Key attributes of the cream side are strength and appearance. Gypsum board is a specialty paperboard grade, with sheet chemistry and physical properties--such as MD/CD tensile ratio, tensile strength, porosity, sizing, etc. specified for each grade and/or customer. Thus, formation was a key aspect that drove the decision.

The sheet is vacuum transferred from the forming section to the first press. The press section has two Nipcoflex shoe presses to dewater the sheet. The dryer section of the machine has 67 dryer cans. A two-roll steel roll calender stack smooths the sheet and helps provide a uniform caliper. Following the calender is a short section of dryer cans that can be used to lower sheet temperature if desired to influence sheet properties important to the wallboard mill.

This forming and pressing design, in conjunction with the fiber system, allows the mill to produce a sheet that is 10% to 30% lighter than traditional gypsum liner and with an improved surface. One important overall trend in the gypsum liner business, as in other board markets, is that average basis weights are falling over time. The average weight is now headed towards 40 lb./1,000 ft². The Lawton machine is designed to run these lower weights.

The machine is a “three-wide” unit, i.e., it can produce a parent reel consisting of three standard 48-in. or 51-in.-wide rolls of gypsum. During wallboard manufacturing, this sheet is trimmed down to the industry standard 48-in.-wide, which when two sheets are joined produces a standard eight foot wall. The company’s Duke wallboard plant can run up to 54-in.-wide wallboard, which is used to produce a 9-ft. ceiling by butting them together. The machine can also accommodate the wider grade as well.

A wider machine, i.e., a four wide unit, was considered, but this would have had a lower operating speed at which a hydraulic headbox couldn’t have been used. It was determined that a hydraulic headbox was required for high quality sheet formation.

The Republic machine is probably the first new machine designed and built in North America that is dedicated to gypsum board production. The majority of other gypsum liner machines were rebuilt to make the grade. This fact provides the mill with an edge, particularly at the lighter weights, according to mill personnel.

The machine control system and scanners were provide by ABB and Voith Sulzer Automation and are integrated with a Bailey Controls DCS (Bailey is now owned by ABB). Fluor Daniel Inc. provided overall project management, engineering, procurement, and construction services. Marathon Engineers provided design and engineering services for the project. A separate Voith Sulzer system controls the dilution control headbox. The machine drive was supplied by General Electric. Key pumps were provided by Ahlstrom Pumps.

The piping layout and design work performed by Marathon were excellent, notes Nelson. He comments that Marathon provided a “tight layout and good space allocation.” The site was designed to accommodate a second machine with minimal disruption to the existing production line.

While the whole production line has performed very well, startup of the mill was not without incident. The most notable was a December 1998 fire in the temporary building that housed the construction office. However, while the building and contents were lost, the fire did not delay construction.

Mill staff has been very pleased with the performance of the new production line. Within three weeks of startup, they made product that ran through the company’s Duke wallboard mill. Overall, product quality has been very good. The machine produces a very smooth, lightweight sheet, with a bulk that compares with heavier weight sheets. Caliper is similar to paperboard made on traditional cylinder board machines, although that sheet is 10% heavier than the Lawton sheet.

In general, industry wallboard quality historically has not varied that much from producer to producer. However, with this machine the company believes they will produce a sheet of paperboard, and in turn wallboard, that will become the preferred grade of contractors and builders.

For customers, the sheet coming off the new machine will provide a savings to wallboard plants due to lower freight costs on inbound paper and improved drying time due to better sheet porosity and openness. Mill staff equated this to the case in standard linerboard production because of the Rule 41 changes. By saving weight, the company can sell its product at a lower cost, because the customer gets more lineal footage per roll. Gypsum is sold on a square footage basis. The improved bulk is due to the use of shoe pressing and the sheet profile provided by the new wet. In addition, the stock preparation for the machine was designed to put fiber in the sheet where it is best used.

Gypsum-grade paperboard rolls are stretch wrapped, barcoded and labeled with the state of art equipment to meet customer's requirements and expectations.

MILL SERVICES. A primary clarifier followed by secondary sequencing batch reactors processes effluent from the mill. Treated effluent is discharged to the municipal treatment facility. All power for the mill is purchased and is supplied by a 128-kilovolt sub-station. Steam is generated via a natural gas-fired boiler. Other services, such as water and sewer are provided by the city. The mill is located on a 69-acre site that could accommodate expansion.

In terms of siting the mill, the company initially looked for sites that might be able to provide power and steam, such as locating adjacent to a power plant. However, they found that most if not all of these used all of the steam. The Lawton mill site was selected from a variety of sites in several states including northern Texas, Oklahoma, Arkansas, Kansas, and Colorado. The sites were evaluated based on criteria including minimum city size of 100,000 people, shipping and logistics, wastepaper supply, etc. This initial list was narrowed to three sites and Lawton was chosen.

Output from the new Lawton mill is primarily geared to supply premium quality gypsum paperboard to external customers, with about 50% sold to James Hardie Gypsum, a major independent wallboard suppler. Another 25% will be used to supply the Duke wallboard operation.

STAFFING/TRAINING. Staff for the new mill was hand selected for the most part from the local area. Mill manager Roger Smith notes that fourteen experienced paper mill operators were hired which formed the nucleus for the rest of the teams to be built. They were selected from more than forty interviews. A focus in selecting the experienced staff was to have high-speed fourdrinier experience.

This essential staff had experience in 26 startups and 11 major rebuild projects. These 14 voted on all the subsequent hires, using a numerical grading system based on a series of tests and interviews. All other employees, with the exception of five intra-company transfers with gypsum experience, were hired from the local area.

The local community and the state of Oklahoma provided great support for training employees as well as being very supportive of the location of the mill in Lawton. State vocational training centers, including one in Lawton, were used to train employees in how to operate the new mill.

The mill operates on a team basis, and staffing is small due to the level of automation. The mill has about 125 employees, including 21 maintenance workers employed through Rust Constructors. Mill staff works on a rotating shift, working 14 days out of 28. Each shift has about 21 staff, including personnel for in-bound wastepaper, paper machine, dry end lab, wet end lab, outbound shipping, and wastewater treatment. The mill runs two shifts per day on a 12-hour schedule. It is the only Republic mill on this schedule.

Each production shift constitutes its own team, as well as a maintenance team. Each meets every day before starting work in a “Focus 5” meeting to discuss quality, production, cost, and safety issues. The slogan “safety a first among equals” attests to its importance, and the mill safety record has been exemplary. Employees are encouraged to learn other skills, and learning another job also brings higher pay. In the last three months of 1999, the Republic team took over to start making paper. Employees worked 12-hour shifts every day from October 4 until Christmas and only two people called in sick during the entire period, illustrating the quality and dedication of the staff, Smith says. At 9:03 p.m. on November 27, the plant produced its first roll of paper.

The new machine is dedicated to, and named after, Stephen Gagnon, an executive vice president of the company that recently passed away in 1998, having been diagnosed with leukemia.

Key lead team staff members include: Donnie Parks, production superintendent; John C. Keeler, mill support manager and production superintendent for stock preparation; Dena Riede, human resource manager; Chuck Gollihar, national sales manager; Matt Winters, fiber procurement manager; Richard Thiemann, controller; and Wayne Schwartz, quality assurance manager.