Energy-saving paper making

Making paper takes up an expansive amount of steam and power. While most paper mills use separate heat and power—an on-site boiler for steam and power from the grid or from a power plant—Interstate Resources Inc., Arlington, Virginia, decided to take an alternative route toward combined heat and power (CHP) for its paper mill located in Reading, Pennsylvania. It built Evergreen Community Power LLC (ECP) to provide fuel and heat for its 100 percent recycled corrugated medium paper mill, United Corrstack (UCI).

Chady Zablit has been general manager of the power facility since it became operational in 2010. He began his career with Interstate Resources and in 1995 and managed the design and construction of ECP in 2006.

“Interstate’s mission spins around sustainability,” he says. “Its core beliefs are that industries can and should care for the environment. Simply put, Evergreen Community Power is one attempt for U.S. manufacturing companies to be less reliant on foreign oil, reduce our carbon footprint and have a diversified national energy source.”

CREATING THE ALTERNATIVE

UCI has the ability to produce 200,000 tons of corrugated medium each year. Each ton of paper requires about 6 million British thermal units (mmBtu) of energy.

ECP combusts two primary types of fuel in its boilers: alternative fuel (AF) and clean fuel (CF). AF is the result of a negative picking process where contaminants in the feedstock that increase ash, chlorine and sulfur are removed. The feedstock is shredded and screened before being delivered to ECP. AF is composed of 85 percent wood with the remainder being paper, some plastic and inerts, such as sand and gravel.

CF is the result of a positive picking process where clean and untreated wood is picked, shredded and finely screened out before being delivered to ECP. The plant also receives tire-derived fuel, shredded rail road ties, utility poles, paper mill rejects and sludge in limited quantities.

Since it opened, ECP has combusted more than 1.4 million tons of these fuels. Zablit says when the plant began operations, it had one local feedstock supplier that had all the permits to process the materials but no experience to produce it to the quality required. Over the years ECP geographically broadened its fuel supply mix with feedstock coming to the plant from several different states within a 200-mile radius, including Maryland, Pennsylvania, New Jersey, New York and Connecticut.

“ECP constantly conducts search activities to identify potential feedstock suppliers through information available from the states and permits issued to processors and transfer stations,” Zablit says. Another way the plant discovers feedstock suppliers is through word of mouth among haulers, suppliers and contractors, he adds.

Once a new source is identified and deemed qualified, ECP builds a contractual relationship with the partner.

Since the feedstock is already brought to ECP as a processed material ready to be used as boiler fuel, the company coordinates with a supplier if it doesn’t have the proper equipment to process the feedstock, such as permit changes, adding a shredder or sorting line or introducing a new type of permitted feedstock, explains Zablit.

As the plant progressed, feedstock quality from suppliers started to improve as well. Contaminants such as ash, chlorine and sulfur dropped sharply within ECP’s requirements, which was a result of “a combined effort of ECP’s team and our suppliers, who we value as stakeholders in our business,” says Zablit.

The feedstock’s quality also depends on the weather and several different markets. In the winter, obtaining feedstock is difficult because of the snow and freezing temperatures, and the spring causes a wood shortage due to mulch production.

The health of the housing market has its impact on the generation of feedstock materials from construction and demolition (C&D) debris, and industrial power plants using the same type of feedstock can cause unwanted competition.

HOW IT WORKS

The plant uses a circulated fluidized bed boiler to heat up the waste used as feedstock. This particular type of boiler, Zablit says, exceeds 99 percent combustion efficiency and is primarily used to fire solid feedstocks such as wood and coal. The temperature of the furnace is between 1,500 and 1,600 degrees Fahrenheit.

The ECP boiler is rated at 300,000 pounds per hour of steam flow generation with 1,500 pounds per square inch gage pressure and a temperature of 840 degrees Fahrenheit.

The steam created from the boiler is fed to a 33-megawatt rated turbine equipped with three extractions at different pressure levels. These different pressure levels were implemented to support the steam demand of the plant and the paper mill, according to Zablit.

A water-cooled condenser is located at the exhaust of the turbine to cool down the balance of the steam exiting the turbine which becomes water and is fed back into the boiler to complete the steam-water cycle. The cold water is supplied from a cooling tower, which minimizes water needed from outside sources, Zablit says.

The turbine then drives an electric generator that provides electricity to the plant, the mill and to a grid belonging to PJM Interconnection LLC, a Valley Forge, Pennsylvania-based regional transmission organization (RTO) that, according to its website, coordinates movement of wholesale electricity in the District of Columbia and 13 states, including Pennsylvania.

About 70 percent of what is produced at ECP is used for the plant and the mill, Zablit says. The rest is sold to the PJM grid for use in the surrounding area.

Zablit says ECP is currently evaluating the feasibility of adding a grinding operation to the plant, which would allow the company to source clean but oversized wood materials for feedstock.

THE DOWNS IN REVENUE

While ECP is saving about 100,000 metric tons of carbon dioxide equivalent per year, competition is tough.

“Without Interstate Resource’s commitment to the mission and the raison d’être of ECP, I am afraid the plant would have been curtailed a long time ago,” Zablit says. “ECP is in a competitive market where others enjoy a much lower cost to operate and compete.”

ECP has been working to get the ash generated from the combustion process to become integrated into beneficial use with certain applications, but a lack of interest and regulatory barriers add to the challenges.

“It’s very challenging to operate ECP profitably with the lack of incentives to support this renewable form of generating energy,” Zablit says. “Sales to the PJM grid comes with significant losses, and natural gas, which is the other alternative to generate energy for the paper mill, is also cheap.”

ECP has been running on less than 75 percent of its capacity due to the lack of cost-effective feedstock and a decrease in grid pricing.

“I believe that the public notion of ECP should be positive after converting so many million tons of what would have ended in landfills into a useful form of energy while meeting one of the most stringent air emission permits that regulators produced,” Zablit says. “Such a notion is needed to help establish some incentives and help ECP stay in business.”

The author is assistant editor of Renewable Energy from Waste and can be reached at hcrisan@gie.net.