West Linn Paper mill uncovers new ways to save energy

Tags: energy management

In March 2006, West Linn Paper Company received a Save Energy Now assessment from the U.S. Department of Energy (DOE) at the company’s coated paper mill in West Linn, Ore. While the mill was already taking measures to improve the efficiency of its steam system, DOE energy expert Bill Moir of Steam Engineering Inc. conducted an assessment to help the plant identify ad­ditional opportunities with significant savings potential. Employees learned how to analyze the mill’s energy consumption using DOE’s suite of steam system software tools.

The assessment provided seven recommendations, including specific actions the plant could take immedi­ately to implement the energy savings opportunities that had been considered previously but not yet completed, such as:

  • Connecting two separate headers and installing a blowdown heat recovery system.

  • Adjusting the boiler combustion controls to lower the excess flue gas oxygen content.

  • Performing a steam trap survey, repairing broken traps and adding more insulation to the 200 psig header.

As a result of these efforts, the mill achieved annual natu­ral gas savings of approximately 58,200 MMBtu.

With annual cost savings of $379,000 and total imple­mentation costs of $176,000, the mill’s simple payback was under six months.

Company and Plant Background
Founded in 1889 in West Linn, Ore., the West Linn Paper Company is the oldest active paper mill and the largest manufacturer of coated free-sheet paper in the western United States. The mill’s 250 employees produce close to 700 tons daily of coated paper under the Sonoma, Capistrano and Nature Web brand names. The company’s paper products are sold throughout North America and are used for high-end advertising materials, magazines, catalogs and book publishing.

The mill’s steam system is served by three boilers, including two dual fuel (natural gas and No. 6 fuel oil) units and one natural gas-fired boiler. Steam is very important for the mill’s production as it is used to dry paper and to power two back pressure tur­bines that drive the line shafts on two papermaking machines. At the time of the assessment, the steam system generated approximately 166,000 pounds per hour at 200 psig.

While the mill does not have a formal energy man­agement policy, energy efficiency is a strong priority. In the late 1990s, the mill’s steam load averaged nearly 200,000 pounds per hour. At a DOE-sponsored work­shop several years earlier, mill personnel obtained 3E Plus, DOE’s insulation assessment tool that en­abled them to analyze their insulation levels. The mill began adding insulation to various parts of the steam distribution network and taking steps to improve efficiency, including performing regular steam trap surveys and maintenance. Plant personnel first began to realize the value of energy efficiency when they fixed the steam traps for the first time and the steam load was reduced by nearly 12,000 pounds. Since the mill began improving its steam system efficiency, energy use has declined from 7,500 to 5,200 pounds per ton of paper and production has increased by 40 percent.

Assessment Overview
The Save Energy Now assessment conducted at the West Linn mill was sponsored by the DOE Industrial Technologies Program (ITP), which provides energy experts to help industrial facilities evaluate and improve system efficiency. As a qualified special­ist in the use of DOE’s steam system assessment tool (SSAT) software, the energy expert formed an assessment team with mill employees and installed the SSAT on their computers. This enabled them to learn the software and review the data together to determine how they could make the mill’s steam system more efficient. They also used SSAT to model the mill’s steam system.

Assessment Recommendations
After modeling the mill’s steam system and evaluating the data, the assessment team identified seven energy sav­ings opportunities and evaluated each one for technical and economic feasibility. They also compared the expected energy savings and associated payback periods in order to decide which were near-, medium- or long-term op­portunities.

Near-term opportunities

  • Tune boiler controls: The mill had upgraded the boiler controls prior to the assessment. However, the team found that the average flue gas oxygen levels were above 4 percent. By adjusting the oxygen trim controls to lower the oxygen levels, the assessment showed that boiler efficiency would improve. Annual energy and cost savings were estimated at $118,000 and more than 15,500 MMBtu.

  • Improve insulation; survey and repair steam traps: Some areas of the 200 psig header were under insulated and the steam traps were due for the six-month survey. Mill employees already familiar with DOE’s 3E Plus software used the tool to estimate heat losses after the assessment, as well as energy savings from adding insulation and repairing malfunctioning steam traps.

Medium-term opportunities

  • Extend 40 psig header to machine No. 3: At the time of the assessment, the 40 psig steam header in the boiler room was unconnected to the 40 psig steam header that served paper machine No. 3. In addition, the boiler room 40 psig steam header vented approxi­mately 2,000 pounds of steam per hour. The assessment showed that if these headers were connected, the steam currently being vented could supply the paper machine. This would lower the mill’s total steam load and yield natural gas savings of more than 23,000 MMBtu and cost savings of $175,000 annually.

  • Blowdown heat recovery: Before the assess­ment, the mill expected to install a blowdown heat recovery system with a flash tank and a plate-and-frame water-to-water heat exchanger. The team used the SSAT to analyze the effect this recovery system would have on the steam system’s energy consump­tion and determined that it would save approximately 18,000 MMBtu and $133,000 per year in energy costs. This estimate was consistent with the mill’s previous expectation.

  • Remove steam-heated feed water heater: This water heater was installed to condense the 40 psig exhaust steam from the boiler room turbine drives. When the boiler room 40 psig header is extended to the 40 psig header on paper machine No. 3, this water heater should be removed. Instead, a feed water economizer will be needed on boiler No. 2 to allow the mill to shut off the feed water heater. This could lower the mill’s steam load by 8,600 pounds per hour, yield­ing annual energy savings of approximately 97,000 MMBtu and $721,000.

Long-term opportunities

  • Use alternate fuel: At the time of the assessment, the mill depended primarily on natural gas that it fired in two boilers. The mill’s use of No. 6 fuel oil was limited by air permit restrictions. The assess­ment modeled a fuel mix of 60 percent natural gas and 40 percent No. 6 fuel oil and concluded that this combi­nation would be less expensive and more efficient than the current use of natural gas. The new fuel mix would increase average boiler efficiency yield­ing annual fuel savings of approximately 17,000 MMBtu and cost savings of $129,000. However, West Linn staff realized that greater use of No. 6 oil would produce adverse environmental impacts. In addition, sustained use of No. 6 oil would be capital-intensive because soot blowers would need to be designed and installed.

  • Install a feed water economizer on boiler No. 2: The assessment found boiler No. 2 had no heat traps and operated with a high flue gas temperature. An economizer installed to boost the temperature of the deaerated feed water before entering the boiler would reduce the flue gas tem­perature for the boiler. The efficiency of the system would be improved by enabling the boiler to use more heat, thereby reducing the amount of fuel it required. Estimated energy and cost savings were 27,000 MMBtu and $223,000 per year.

If all the above recommendations were implemented, the total annual energy cost savings was estimated at approximately $1.5 million.

Results
Encouraged by the findings in the assessment, mill personnel implemented several of the recommenda­tions by taking the following actions:

  • Extended the 40 psig boiler room steam header to the 40 psig steam header going to paper machine No. 3 and installed the blowdown heat recovery system.

  • Commissioned a technician to retune the boil­ers and reset the new combustion controls. This reduced the excess oxygen levels from 4.28 percent to between 2.5 percent and 3 percent.

  • Surveyed all the steam traps in the mill and repaired 30.

  • Used DOE’s 3E-Plus software to estimate steam losses from lack of insulation on portions of the 200 psig header, and then added the insulation needed to minimize heat losses. The calculated energy savings from the additional insulation was approximately 1,200 MMBtu per year with annual cost savings of nearly $8,000.

As a result of all these projects, the mill’s steam load now averages 164,000 pounds per hour. Although natural gas costs declined since the assessment, the mill achieved annual cost savings of $379,000 and energy savings of 58,200 MMBtu — approximately 3 percent of the plant’s energy use before the assessment. With total implementation costs of $176,000, the mill achieved a simple payback of about six months.
Due to the lower natural gas costs since the time of the assessment and the increased emissions that greater use of No. 6 oil would cause, substituting No. 6 oil for natural gas was found to be unfavorable. The two remaining long-term recommendations from the assessment were under serious consideration at the time of publication. A proposal and fund­ing request has been made to install a feed water economizer on boiler No. 2. If approved, the mill will be able to remove the feed water heater fairly easily, saving an additional estimated 27,000 MMBtu and $223,000 per year.

Lessons Learned
A strong commitment to energy efficiency can lead to significant energy savings. At the West Linn paper mill, the absence of a formal energy management program did not prevent mill employees from taking meaningful steps to improve the efficiency of the steam system. This included installing new controls, adding insulation and repairing steam traps. While the Save Energy Now assessment found more oppor­tunities for energy savings in the mill’s steam system using the SSAT, it also reinforced efforts already in progress to improve energy efficiency and helped justify the implementation of those projects.

In addition to the SSAT, other DOE software tools can be used to analyze industrial systems and pro­cesses and generate energy efficiency opportunities, including: AIRMaster+, the Fan System Assessment Tool (FSAT), MotorMaster+, the Process Heating Assessment and Survey Tool (PHAST), the Pumping System Assessment Tool (PSAT) and 3E Plus.

Save Energy Now
Save Energy Now is a national campaign started in 2005 in response to a rapid rise in energy prices. This cam­paign helps U.S. industry reduce energy use and supports national goals for energy security. Through Save Energy Now, DOE’s Industrial Technologies Program (ITP) helps industrial plants operate more efficiently and profitably by identifying ways to reduce energy use in key industrial process systems. Visit www.eere.energy.gov/industry/saveenergynow for more information.