| |
|
When Georgia-Pacific's Woodland, Me., mill began considering how it would make the switch from using elemental chlorine in its bleach plant to 100% chlorine dioxide substitution, one of the issues was adding ClO2 capacity. While generator technology is fairly standard across the industry, G-P wanted the installation to be a fast-track project that would provide quick delivery of equipment and rapid assembly at the mill site.
The reality of construction projects in Maine, however, is that winter weather many times extends the completion of projects. Woodland managers began exploring other engineering and construction options that included an innovative modular approach offered by Jacobs Applied Technology (a subs. of Jacobs Engineering) that would mean building the generation system offsite in modules and then shipping the modules to the mill for assembly.
Choosing this first-of-its-kind approach has meant that G-P was able to shave about seven months off what would normally be an 18-month project schedule. And at a time when the paper industry is searching for ways to use capital dollars more effectively and implement projects more quickly, this project-which came with a total price tag of $22 million-offered an alternative to traditional engineering and construction approaches. In fact, G-P's mill in Palatka, Fla., which also is converting to 100% ECF bleaching, is considering this type of approach for its ClO2 generation system and was involved in the design of the Woodland project.
CONVERSION CATALYST. Georgia-Pacific has made a corporate commitment to convert all of its kraft mill bleach plants in North America to 100% elemental chlorine free (ECF) bleaching, which will help the company in complying with EPA's cluster rule requirements. In addition, the Woodland mill-which produces bleached hardwood kraft market pulp and uncoated fine papers-was under a state-legislated mandate that mills in Maine must be non-detect for dioxin in bleach plant effluent by August 1, 1998, and that mills be able to certify that they are non-detect, based on the state's measurements. Thus, the mill was under a time constraint to complete the project as quickly as possible.
Lee Bingham, v.p. of Georgia-Pacific's Maine Operations, says that the corporation has also put pressure on individual operations to investigate how to perform projects faster and consider the cost of capital. He says this modular approach made the most sense from both aspects.
"It's probably true of most pulp and paper companies that we have historically over-engineered and over-built projects," Bingham says. "This was another opportunity in a string of projects that this mill has undertaken in the past few years to significantly reduce capital costs. This project has been reduced somewhere on the order of at least 10% compared with other, conventionally-built projects.
 Georgia-Pacific's new chlorine dioxide generation system at the Woodland, Me., mill produces 42 tpd for use in manufacturing elemental chlorine free (ECF) kraft market pulp.
"So even though time drove us to make this decision, looking at the results right now and if time wasn't an issue, this modular approach would still be the preferred choice," Bingham adds.
With preliminary planning work done and proposals from the two major suppliers of ClO2 generation systems, Woodland's project team began investigating the engineering and construction aspects. Two companies offered a modular approach to the project, but the team chose Jacobs Applied Technology, which at that time was based in Orangeburg, S.C. The company is now based in Charleston, S.C.
"Even though time drove us to make this decision, looking at the results right now and if time wasn't an issue, this modular approach would still be the preferred choice,"
-Lee Bingham v.p., Georgia-Pacific's Main Operations
The mill chose Sterling Pulp Chemicals as its generator system supplier. Pre-engineering work for the project was completed in mid-1997, and the project was approved on July 28 of that year, allowing almost exactly one year for the generation plant to be built and started up. Excavation at the mill began on October 6, 1997.
 The individual modules of the ClO2 generation system were built in South Carolina and shipped horizontally to the Woodland, Me., mill. After unloading, the units were lifted to vertical for the first time and put in place by crane.
BUILT DOWN SOUTH. Mason Pottle, senior project engineer at Woodland, notes that the real time saver on the project was that the modules were built at Jacobs' facility in Orangeburg. "If we had 'stick built' (conventional construction) this project in Maine, with the severe winter we had, I can't say that we would have finished the project in time," Pottle says. "Or if we had finished it on time, the cost would have been significantly higher." For example, Pottle estimates that more than $180,000 was saved simply by not having to incur expenses for winter heating fuels if the structure had been built onsite.
The number of craft people onsite is another savings. For example, instead of about 200 to 300 people needed for a conventional construction project of this kind, the modular assembly only required about eight to 12 craft people.
The steps Jacobs takes to modularize a system such as the one at Woodland is to obtain equipment arrangements and sizes from the mill and the system supplier. Then, the footprint of the mill site (Woodland was 45-ft. x 38-ft.) is broken into sections, and the major equipment is fit into each section.
Included in Jacobs' work on the project is a three dimensional computer design of the entire generator that provides a virtual "walkthrough" to eliminate possible interferences and safety hazards. Pottle comments, "There is no better way to review a project. You can literally walk through the building and see any poor clearances or valves that operators can't reach. If you want to check the distance from the floor to a particular hand valve, you just click on it and it will tell you the distance. You can check leads and runs for instrumentation to ensure you have incorporated good engineering practices. It saves so much time and also saves rework."
Richard Zieminski, Jacobs' project manager, points out that this type of modular project isn't like purchasing a modular home, where the entire package comes pre-designed and pre-built. "We took all the specifications that G-P and Sterling had-P&IDs, drawings, etc.-then we basically cut the pie up and manufactured the facility using all the standard commercial techniques that are available in a manufacturing environment. This is not a skid-mounted system.
"We were able to fit an equipment arrangement that is identical to a typical Sterling Pulp Chemicals field-constructed plant but do it in 12 units constructed offsite," Zieminski says. "That includes all the steel framing, getting it painted, inserting the equipment, putting in the piping system, installing the electrical supplies and instrumentation control systems, and providing for all the interconnects between the modules."
Another factor that must be considered in building each section is how the modules will be shipped. According to Zieminski, in the case of the Woodland project, all the modules were to be trucked from South Carolina because sending the modules by barge to Maine proved to be cost-prohibitive for this particular project.
"Each section couldn't exceed the heights that are required by highway bridges, etc., so we were limited to a design of 13-ft. wide x 13-ft. high x 75-ft. tall," he says, adding that the modules weighed between 30,000 and 74,440 lb. each. The 12 modules needed for the Woodland project were constructed horizontally at the South Carolina facility, and the units were not brought upright until they were lifted into position by crane at the Woodland mill.
Transportation of the modules was a tremendous logistics feat coordinated by Jacobs' Zieminski and handled by Turner Trucking of Greensboro, N.C. Shipping the modules over road required permits and pre-approved routes through 11 states-South Carolina, North Carolina, Virginia, West Virginia, Maryland, Pennsylvania, New York, Connecticut, Massachusetts, New Hampshire, and Maine. Permits could not be obtained until the unit actually reached each individual states' border. In some states, such as Connecticut, the modules were only allowed passage on Tuesday, Wednesday, or Thursday.
The modules were shipped four at a time, caravan style, and each modular unit had its own escort. Because a lifting and setting plan was in place to ensure efficient assembly at the mill site, the modules had to be shipped in a specific sequence. The first four units left South Carolina on March 16, 1997, and the last two units (the largest of the 12) arrived at the mill on April 7.
ASSEMBLED UP NORTH. In addition to the modular generator, the $22 million ECF conversion project included two chlorine dioxide storage tanks, sulfuric acid unloading and storage equipment, sodium chlorate unloading equipment (including a new unloading mix tank), upgrade of existing methanol unloading and storage facilities, and an upgraded chilled water system. The mill's existing elemental chlorine and chlorine dioxide generation systems are being demolished.
As individual units arrived at the mill, construction crews were scheduled to place the units into position based on the lifting and setting plan and using two large cranes. Ten of the 12 units took less than one hour to place. The last unit was lifted into place on April 10.
Prior to arrival of the modules, steel was erected for a new electrical room and the chiller building. All electrical pre-work was ready to energize the modules once the final unit was placed. On April 15, the ECF building was lighted.
 Where modules met, the piping was designed to meet, as well. The pipes were designed to within a 1/8-in. tolerance so that gaskets (attached to the end of the left hand pipe) could be used to attach the pipes.
Pottle and Zieminski both comment that by using the computer-aided 3-D design tools, the tolerances once the modules were set in place were very close. "Everything was manufactured in our facility to within a 1/8-in. tolerance from one module to the next," Zieminski says. "So when we actually brought it into the field, the flanges were within 1/8-in. to slide a gasket in and bolt it down. It makes for much cleaner assembly." However, Zieminski comments that changes in the field could be made fairly easily when the customer felt such changes were necessary.
PROCESS CHANGES. The mill generally sells about two-thirds of the 465,000-tpy of bleached kraft hardwood pulp that it makes. The other one-third is used internally to make the mill's fine paper grades. Twenty-five percent of the market pulp is sold to European customers who have demanded ECF pulp.
Prior to this conversion project, the Woodland mill had used an older, three-reactor ClO2 generation system that operated at atmospheric pressure and produced a maximum of 28 tpd. However, the system was water chiller limited. Utilizing that capacity along with elemental chlorine (25% substitution rate), the mill typically ran a bleaching sequence of CD-EOP-D-E-D in warmer months. During winter months, the mill was able to make ECF pulp at 100% substitution for the European market due to the colder river water temperatures (35 to 40 F) allowing more ClO2 to be absorbed into the water.
The new process uses a single generator-operating under pressure and producing 42 tpd-that will change the bleaching sequence to D-EOP-D-E-D. Ken Nusche, Woodland's operations capital coordinator, comments that there is some chemistry change in the way the two systems operate. The old system used peroxide in generating ClO2 whereas the new system will use methanol.
The old and new systems are definitely different in the way they are operated and controlled, prompting the mill to purchase a Honeywell Hi-Spec (Pointe Claire, Que.) simulator for training the 14 hourly operators who run the plant. The controls for the plant tie in directly to the pulp mill's existing Honeywell-Measurex distributed control system.
|
