Expansion/
Modernization

Ozone-based bleaching system used on hardwood fiberline fits both operationally and economically for company's Wisconsin-based Kraft Division

Consolidated Papers Shifts to ECF
with Wisconsin Rapids C-Free Line" Image

BY KIRK J. FINCHEM, Editor

The choice of Union Camp's C-Free technology was, according to the division's managers, driven primarily by the technology's operational and economic fit with the mill's existing process. And the improved environmental performance that C-Free makes possible was viewed as an important bonus.

Prior to the September conversion to ECF bleaching, the mill's 580 tpd hardwood fiberline used a DC-EOP-D bleaching sequence with 65% substitution of chlorine dioxide in the first bleaching stage and peroxide addition in the bleached high-density storage tank for a final brightness boost. While hydrogen peroxide is still added in the high-density storage tank -- albeit in smaller amounts -- elemental chlorine is no longer used for pulp bleaching at the mill.

Pulp & Paper has covered the development and implementation extensively, including startup of the original system at Union Camp's Franklin, Va., mill (P&P, Nov. 1992, p. 42) and an update on use of the process around the world (P&P, March 1997, p. 58).

THE BIG PICTURE. "In making the decision to install the C-Free technology, we considered our long-term commitments to our stakeholders -- customers, employees, the community, and our shareholders -- and saw C-Free bleaching as the next logical step on our 'journey' to be a minimum impact mill," says Ron Swanson, vice president, manufacturing. "In that context, it was a logical choice, one that is consistent with every facet of our operation.

"We are not interested in any 'causes' special interest groups may have on their agenda. The choice simply made operational and economic sense and was consistent with our long-term direction and Consolidated's philosophy of continuous improvement."

Swanson explains, "Consolidated Papers is a company committed to remaining a leader in several areas -- coated paper products, coating technology development, environmental performance, as well as customer service and financial performance. Our decisions are fairly easy to understand in light of these commitments. While we are not one of the world's largest chemical pulping 'players,' we do have very creative, dedicated and energetic employees."

The company's environmental policy dates back to 1967. "It's more that just words on a sheet of paper," says Swanson. "It's a philosophy that we live by, and I think it is unique in our industry. We do not look at regulatory compliance as the bottom line goal. We work for continuous environmental improvement, just as we do in product quality and financial performance."

MAKING THE DECISION. "Pulp quality is a key issue for us," Swanson continues. "We make the most demanding paper grades -- ultra lightweight coated groundwood and heavier weight coated free-sheet -- and the quality of our kraft pulp is critical to our paper quality."

The quality of the Kraft Div.'s pulp is important to Consolidated's operations throughout the area. Hardwood pulp is piped to the company's Wisconsin Rapids free-sheet mill (one-half mile away) and softwood pulp to its Biron Div. lightweight coated mill (four miles away by road). A portion of the mill's pulp is also shipped as "wet lap" to the Stevens Point area coated specialty and lightweight coated divisions. (For a related story on the Stevens Point Division's new No. 35 machine, see P&P, July 1997, p. 63)

According to Steve Enz, Kraft Div. manager, "Once we were convinced that the ozone-based technology could deliver the required product quality, making the decision became a question of determining which technology (ozone-based or a more traditional chlorine dioxide-based ECF system) was best suited to our mill."

The project team estimated that the capital expense of ozone would be higher. But, the team also estimated that C-Free offered a significant operating cost advantage. Further, they reasoned, in the event that there are environmental, pulp quality, or cost reasons to move toward bleach plant closure or to a totally chlorine free (TCF) mill, the ozone technology offered the most logical transition.

"Installing C-Free on the hardwood line also gave us an opportunity to gain ozone-based bleaching operating expertise and leverage it in the future," says Enz. "We have confidence in both the ozone-based technology that we use on our hardwood fiberline and the dioxide-based, ECF technology we use on our softwood fiberline. And we are comfortable with the environmental performance of both."

As for the continued use of ECF bleaching on the softwood fiberline, "As it happens, the D-EOP-D softwood line bleaches to a lower brightness. We were able to switch to full dioxide substitution with very little capital expense in 1994," says Enz. "On the other hand, the hardwood side bleaches to full market brightness."

The mill's Ahlstrom Kamyr continuous digesters typically produce hardwood pulp to a 10.5 K-number. The oxygen delignification stage reduces the lignin content further to a K-number of 6.5.

Enz says, "The change to eliminate elemental chlorine use was going to require an equipment change. Even with full substitution, we knew that we would have to modify our bleaching towers and make other process changes."

As for converting the softwood line in the future, Enz says, "We have not looked at it in any detail yet. But we are getting more comfortable with the technology, and we are gaining a lot of experience with ozone bleaching on the hardwood fiberline. We believe that ozone's performance on our softwood fiberline would be acceptable, too."

EFFLUENT REDUCTION A BENEFIT. According to Enz, short-term effluent reduction was not a dominant consideration in the decision process, and since the mill is recovery furnace limited, the mill is presently not recycling its ozone-stage filtrate. That remains an option for the future.

"That is certainly something we shall explore," says Enz. "We are pursuing a minimum impact mill operation, and effluent is certainly one of those pieces."

James Weinbauer, director of environmental affairs at the company, explains, "Since our wastewater treatment facility currently operates at approximately 18% of our allowable limits, there is no immediate need to close up the bleach plant filtrate system. Closing the bleach plant will be costly and must be carefully considered before proceeding. But, we have the prerequisite technologies in place that will allow us to make that decision in the future."

But, of course, with the installation of the Sunds Defibrator wash press before the ozone stage, bleach plant effluent volume was reduced. "The wash press discharges at about 30% consistency and the acid press at about 40%," Enz notes. "Clearly, that is much better than the typical performance of a vacuum filter. The press has also reduced our associated chemical losses. The pulp is very clean as it enters the ozone stage."

According to Weinbauer, "The environmental benefits that we saw from our change to ECF bleaching on the softwood fiberline was tremendous. With the change to millwide ECF bleaching, we have eliminated detectable chlorinated organics -- including dioxin -- from our wastewaters, pulps, wastewater treatment biosolids and our treated effluents. Our AOX generation (from the bleach plant) has been reduced by 70%, and we expect our performance to improve as we continue to optimize the ozone stage."

Weinbauer explains that typical retention times in the mill's primary clarifier are about four hours, while retention time through the secondary treatment system is typically more than 48 hours. "The system handles the combined effluent of our Kraft Div., our coated free-sheet mill in Wisconsin Rapids, and our lightweight coated mill in Biron."

"We have also seen tremendous reductions -- more than 80% relative to 1988 emissions -- in chloroform air emissions, and we have reduced chlorine emissions by more than 90%. ECF has resulted in significant improvements in environmental performance," adds Weinbauer.

THE MARKETING PERSPECTIVE. "We are in business to meet our customer's needs -- both today and in the future," Swanson says. "This includes both the tangible and less tangible needs. Our view of product performance also includes meeting environmental and social needs."

He explains, "We are not interested in 'flavor of the month' marketing approaches. We cannot and will not market products as 'environmentally preferable' if the data do not support the claim.

"We have a very stable, long-term customer base. Some of our relationships date back 50 or 60 years. Our customers were aware of and supported our improvements plan, which included the conversion to C-Free bleaching. In fact, our customers provided a lot of input. We talked to them about the economic and social trends they and their customers expect during the next five to 10 years."

CONVERSION A 'NON-EVENT.' According to Enz, "For our papermakers, the change to C-Free was a 'nonevent.' The pulp properties are very similar. Viscosity is probably a little lower, but we do not think the difference is meaningful."

Swanson agrees, "As we expected, our customers have been with us all along. The reaction has been very favorable."

The addition of a second chlorine dioxide bleaching tower has yielded both chemical and steam savings. According to Enz, "We picked up some process efficiencies by going to a two-stage dioxide approach rather than a single stage, so we have seen a bit of improvement in pure chemical application despite the fact that we are doing a bit more work back there."

The chemical savings have allowed the mill to operate well within the capacity of its 40 tpd R-8 chlorine dioxide generator, even with the switch to ECF bleaching on the softwood fiberline.

TRAINING. "The Consolidated Papers' project team did an excellent job of developing the project, coordinating training among several suppliers and implementing the project," said Swanson. "Our engineering people exhibited excellent leadership."

Enz also credits Union Camp's openness as an important part of the success of the project. "We had operators, supervisors, and process engineers, as well as technical support personnel, travel to Union Camp's Franklin mill to see its C-Free process in operation."

The mill's project team worked with Union Camp, Sunds Defibrator, Ozonia and the project's other equipment suppliers to develop both operating and maintenance training programs which included field tours, equipment and line identification, and classroom and process simulator training.

Union Camp's openness was also important during the technology evaluation phase of the project -- which included Consolidated operating, research, engineering and environmental personnel -- leading up to the choice of C-Free. "With a new technology like this, there is a strong fear factor," says Enz. "Being able to tour facilities (the Franklin mill and the pilot plant at Union Camp's Eastover, S.C., mill) that were using C-Free eased our concerns."

Weinbauer agrees, "Early in the project, we had the opportunity to visit Union Camp's mill at Franklin and also the pilot plant at Eastover. We did a lot of work up front to evaluate the technology before we made our decisions."

Swanson adds, "We were impressed with the good, solid data that their research lab and pilot plant had developed. Our research and development, engineering, and operating people evaluated the process thoroughly. In addition, the time we spent at Franklin -- interacting with operating people and using the process models that had been developed -- gave us additional confidence."