Nov. 1, 2005
Located in McKinley County in the middle of the New Mexico desert, some 20 miles from the nearest town of Grants, Durango-McKinley Paper was founded to produce recycled linerboard for customers in the Los Angeles region.
Due to its unique location, the mill enjoys a number of benefits, according to general mill manager Isaac Rosas. These include access to the turbine blow heat, in the form of steam generated by the nearby Tri-State power plant, as well as excellent logistics connections. Interstate 40 runs past the site, as well as one of the four main rail lines linking the Western U.S. with the eastern states. Legendary Route 66 also runs close by.
â€?Although we are located in an opportune location logistics-wise, and we've got access to the energy we need, the site doesn't have the water to sustain a standard mill process, nor do we have waterways to discharge water into either,â€? Rosas says. â€?All the water we use has to be treated and reused."
Durango-McKinley Paper was started up as a greenfield project by Australian-based Amcor in 1994. A depressed economy saw the project get off to a slow start, however, and the mill was taken over by Mexican-based Corporacion Durango in 1997. Operations were streamlined, and capacity increased from 130,000 tpy to 220,000 tpy.
Major Environmental Recognition
Some of the mill's initial problems were the result of its unique process, according to technical manager John Shaw. It took time before the locally recruited personnel were able to gain the experience necessary to manage the mill effectively. In addition, two major capital process improvements were done at the facility to assist in improving the productivity of the mill.
"Our operations are closely regulated by tough county, state, and federal environmental limits, and we are allowed to have only a very small impact on the surrounding environment," Shaw says.
"Mill areas, even most of the storage areas, are enclosed, and 'practically' speaking Durango-McKinley Paper doesn't have a significant environmental footprint. We've been able to steadily reduce our waste streams, cut our energy and raw material use as well. And we're committed to improving our environmental performance even further."
The mill's achievements in the environmental area received national recognition earlier this year when the plant received a national Environmental Performance Award from the Environmental Protection Agency (EPA), one of only four plants in the country to receive such an award in 2005. "We have improved the fiber yield by 20% over recent years, and improved the efficiency of our energy use by 11%. This has cut our electricity bill and reduced the amount of dry solids sent for landfill. We've also succeeded in cutting our water consumption by several million gallons a year," continues Rosas. "We've achieved this through a variety of measures - self-managed team concept, training, better maintenance and creating partnerships with our suppliers."
A Closed Water Cycle
Despite having a closed water cycle, Durango-McKinley requires approximately 325 gal of fresh water for each gross ton of board it produces, as water evaporates from the mill's various processes, particularly during the paperboard drying process. The water bound in the product leaving the mill is not an issue, in terms of overall water usage, however, because it is compensated for by the water contained in the recycled board used as the plant's raw material.
"The make-up water required by Durango-McKinley Paper is purchased from the power plant, which takes it from artesian bores. The plant needs approximately 225,000 gal/day of fresh water. This compares to the 1.5 million gal/day of water that a similar-sized recycled paperboard plant would use," says Rosas.
Using a closed cycle means that process water must be treated to ensure that impurities and chemicals do not accumulate in the system and create operational problems.
"Water is fed to the water reclamation plant as separate streams from our various processes. These are then treated in line with how much effluent they contain and how clean the water needs to be for reuse. In practice, we run five different treatment stages,â€? Rosas adds.
Pretreatment removes the dirt, fiber, and other solids contained in the raw material, which is recovered and used for soil improvement, for example.
Smaller impurities are removed using dissolved air flotation and biological treatment. Organic material with a high molecular weight and dissolved solids are removed using microfiltration, while dissolved inorganic material is removed using reverse osmosis. The resulting salt residue is crystallized.
After going through all five stages, the water is very pure, clean enough to drink, in fact. Not all the water the mill uses, though, has to be this clean.
A Light, Strong End-Product
To make its linerboard, Durango-McKinley uses 100% recycled board and old corrugated containers (OCC), which it sources from suppliers in New Mexico and neighboring states, as well as through its own procurement centers located in Albuquerque, N.M., Phoenix, Ariz., and El Paso, Tex.
"The quality of our raw material has remained acceptable, and we monitor it continually to ensure that it stays acceptable. Before the mill was built, a significant amount of the OCC in the area was dumped at the local landfills along with other trash," says Shaw.
The mill's raw material and product storage areas are relatively small, as the production cycle in the packaging industry is fast.
Durango-McKinley Paper produces a range of different grades, using a combination of additives and process parameters to regulate end-product strength and functionality for the box plant and its customers. The mill has been optimized to produce high-performance linerboard.
Durango-McKinley Paper produces 23- to 40-lb corrugated medium board, 23- to 35-lb high-performance board, and 26- to 42-lb regular board.
"Thirty-five-pound high-performance board is used in many applications to replace 42-lb regular board, and commands a higher price as a result," continues Shaw.
Durango-McKinley Paper's lightweight, high-performance liner offers improved yields for packaging producers.
Another Durango-McKinley Paper strength is the mill's flexibility and ability to deliver rapidly, sometimes as early as the next day after receiving an order. The majority of the mill's customers are independent packaging producers and large packaging companies based in the Los Angeles, Calif., region.
"A large proportion of our products are converted into packaging the day after we deliver them, because manufacturers don't normally keep large inventories of lightweight liner on hand," adds Shaw.
A Challenging Process
In principle, the mill's production process, although based on a closed water cycle, does not differ from a normal system. In practice, however, the mill must run its process much more carefully, as its paper machine and water treatment plant are so interdependent on each other. Changes in process conditions in the paper machine immediately affect the treatment plant, and vice versa.
The mill aims to use as little additives as possible, as their residues have to be removed from the process water over at the water reclamation plant. This could not be done effectively unless the mill ran the process at a neutral pH, which it does.
Kemira has been responsible for McKinley's biocide program for the last five years, and Rosas has been very satisfied with this accomplishment. "We've not had problems with slimeholes or odor; those kind of things can put you out of business pretty quickly,â€? he says.
The biocide program has also proved very cost-effective. Durango-McKinley Paper initially selected Kemira as biocide supplier based on a combination of price, service, and the performance of its product, remembers Rosas.
"Normally in a closed mill like ours you have to wage a constant fight against slime holes, but we've run for years, most years actually, without a single customer complaint in this area. We can only remember two customer complaints since 1997," he says. "Because of the success with the biocide program, we are now looking to extend the business relationship with Kemira to other applications areas, such as sizing and dry strength."
Shaw is especially happy with the progress Kemira has made in improving the environmental and safety qualities of the active ingredients in its biocides and the fact that they do not leave residues in the plant's processes. The biocides in use are "water based" products. "Biocides need to meet our environmental norms and guarantee the quality of our product equally well," Shaw explains.
It is also important that a mill's biocides do not negatively affect the microbiological organisms used in the water reclamation plant. A badly chosen chemical, or too high a dosage, could kill these microbiological organisms. In a closed-cycle mill, that could shut down production altogether.
There is little margin for error here at a mill like Durango-McKinley Paper.
"The water cycles through our processes so quickly that the wrong biocide dosage would make itself felt in our treatment plant in a matter of minutes. Dosing too little biocide, on the other hand, may create quality and runnability problems, although they take a little longer to manifest themselves,â€? adds Shaw.
Both situations, resulting from too much or too little biocide dosage, are equally ineffective from a business point of view, according to Rosas and Shaw. Variations in raw material input mean that biocide dosage has to be regulated as often as every few hours, they say.
"Every new bale of OCC brings a fresh batch of microbiological organisms to deal with. The level of microbiological organisms that comes in with food packaging, for example, is of a completely different type to that which is found for example in shoe boxes or electronics packaging," says Shaw.
"To deal with the variation that enters the process, we use pulsed biocide dosage. In addition, based on observation and laboratory testing we will â€˜shockâ€™ the system in some areas to maintain control of the biological activity within the entire process."
This type of program management offers better results, lower overall dosage, and ensures that the mill can remove unwanted microbiological organisms while minimizing the impact to the water reclamation plant.
"We want our biocides to do their job quickly, and not have unwanted microbiological organisms swimming about our system. You can see how effective the biocide program is just by looking at the shower water around the paper machine,â€? Shaw concludes.
Jussi-Pekka Aukia is a writer based in Finland.