Operating a ‘green’ facility is nothing new to Potomac Supply Corp. in Kinsale, Va. Over the past 33 years, the company has won awards for clean air, conservation, protecting the Chesapeake Bay, and environmental stewardship. Most recently Potomac Supply won the 2007 Governor’s Environmental Excellence Award for its new biomass-fueled dry kiln project. This reflects a new push by Potomac to better utilize residual wood biomass while reducing its use of non-renewable energy.
In 2006, Potomac constructed and implemented a new 24 million BTU Unitemp biomass fueled dry kiln for its recently upgraded sawmill and high-speed planer mill. The company also retrofitted a propane fueled Unitemp kiln to run on wood biomass in the hopes of replacing an estimated 1.2 million gallons of propane per year.
Potomac’s sawing, planer, chipping and milling operations produce up to 200,000 tons of wood biomass per year – a mixture of dry wood shavings, chips, and sawdust. Wood bio-mass is a completely renewable byproduct.
All the logs processed at Potomac’s facility are harvested from managed forests within a 100-mile radius. Harvests are conducted in accordance with state government standards for optimum reforestation as well as the company’s best management practices for sustainable management.
Biomass is green in more ways than one. Potomac has reduced its propane usage to about 15% of its previous levels, which represents a very large savings. It also trimmed freight and fuel costs to ship wood waste by $182,500. The payback for the project should be less than 30 months.
William (Bill) Carden Jr., Potomac’s Chief Executive Officer, said, “I believe a big part of our future is in energy. We only use about 40% of the biomass that we generate from dry planer shavings, and are looking for new ways to use that material.”
Potomac has a number of potential energy projects on the drawing board and has considered everything from wood pellets to electricity generation. Bill said, “The forest products industry has been giving away its waste as a byproduct for years. We have had a disposal mentality as an industry, and we need to convert to a value-added perspective.”
Redesigning Drying Operations
The heart of the new kiln operation is a wood-waste dry wood fuel burner developed by McConnell Industries Inc. of Birmingham, Ala. Clifford T. McConnell is a pioneer in the area of biomass combustion. He installed his first dry wood-fuel burner in 1974 during the Arab oil embargo. After studying the market, Potomac selected the McConnell Energy System for its efficiency and controls.
The McConnell Energy System utilizes the latest technology in control instrumentation and digital displays, which allows for monitoring the lumber drying process in multiple zones throughout the kilns. It has rapid response to control signals. This allows for the use of a short flame with a completely clean burn. Finally, the system incorporates a cyclonic suspension type, dual-chambered combustor in which dry fuel is converted to heat energy with a conversion efficiency equal to that of fossil fuel burners. The moisture content of the wood fuel processed is less than 15%, and it is finely processed into particles about 1/8-inch in diameter.
Rich Gouldin, Potomac’s Chief Operating Officer, said, “The new process is more efficient and accurate at drying lumber. It allows for greater capacity and increased production with more controlled drying.”
Potomac uses a closed loop air system in the fuel processing system to reduce emissions. This limits the amount of particulates that are released into the atmosphere. The new system’s emission increase is miniscule. Potomac continues to operate well under state and hazardous air pollutant regulations while increasing kiln capacity by as much as 66%.
Potomac has three biomass collection points within the plant operations. Material is taken to the fuel staging area using Peerless bins for storage and walking floor trailers for transport. Potomac currently stores 4-5 days of processed fuel on site in the Harvestore silos.
The fuel processing system is what distinguishes Potomac from other facilities.
Cliff Mullin, Potomac’s Vice President over rough lumber drying and receiving/shipping, said, “We are not tied to any plant operation here to produce energy. As long as we have the Peerless bins, we can process material any time, day or night. Other mills are generally tied to the planer mill. When the planer mill is running, you have to make fuel. We decided not to do that because we want to make fuel when we are ready to do it, not just because another part of the facility is running.”
Once unloaded, biomass is processed through a hammermill to ensure consistency for the bio-fuel. The system is equipped with a Flamex spark detection system. Cliff said, “When you have dry fuel, you always have the chance for a fire. That is why we included the spark detection in our system.”
Magnets are placed near the hammermill to pick up any stray metal in the biomass. If the system detects a spark, it automatically shuts down and sprays water on the problem areas. This material is then kicked out to a waste bin to keep it from entering the silos.
Koger Air supplied the air handling system for the new fuel system and kilns – blower, cyclones, duct work and air handling system. Potomac requested that McConnell work with Koger because the company had done a good job in the past. Cliff said, “The McConnell installation crew was able to pick up the Koger parts and put them together without any problem. When we did have one little unforeseen problem, Koger quickly supplied the parts to remedy the design issue.”
Potomac believes in developing long relationships with quality suppliers that will back up their products. That was a key driver behind the company’s decision to hire National Barn to construct the pole building used to house the fuel station. Don’t be fooled by the name, National Barn offers a lot more than just barns. It sells pole buildings with steel or wood exteriors for just about any industrial application.
Lowell Thomas, owner of National Barn Co. NE said, “We offer customers a cost effective way to get the building they want.” Pole design construction helps reduce cost and increase the flexibility of the structures.
National Barn has been a Potomac customer in the past. Lowell said, “Potomac mills material that we use in our buildings. We are proud to partner with a third generation family business like Potomac.”
Cliff said that Potomac chose National Barn because it offered a cost effective solution and agreed to meet all the building code requirements that the company had for things such as hurricanes, snow loads and other concerns.
Cliff said, “It was a turnkey job. They had a good crew come on and did a good job.”
Looking to save money wherever possible, Potomac bought used farm silos to store its bio-fuel. Bio-fuel is fed into the McConnell burner via the Koger air handling system. Potomac was the first company to place variable frequency drives on the McConnell fuel feed system. This provides better control on lower speeds and makes it easier to adjust, according to Cliff.
Programmable logic controls (PLCs) take very accurate readings to keep the system running as efficiently as possible.
Switching from propane to biomass energy was not that difficult. Potomac installed its first Unitemp dry kiln in the 1970s and its second in 1997. As part of this new makeover, Potomac converted its second kiln over to wood fuel after the newest kiln was up and running on wood fuel. Cliff said, “We only shut the kiln down for one morning to hook the wood fuel burner into the side of the existing propane burner.”
The biggest thing to ensure a smooth transition was keeping all the duct work the same size and air flow capacity as the old system. Potomac shut down its original kiln and now has two identical 64-foot Unitemp kilns. The only difference is that the new kiln is set up so it can be converted over to run with the Pollard/3-Stage Drying process in the near future.
Cliff said, “Potomac has worked with Unitemp since the 1970s, when their staff installed our first kiln. Unitemp has always stood behind its kilns when it comes to components, service and parts. We felt it has always been a good relationship in the past.”
Unitemp Dry Kiln of Hope, Ark. has sold several hundred dry kilns all across the country. Jerry Stroud, owner of Unitemp, said his company offers a very hands-on approach; he is involved from sales to installation. Jerry recently took over as the new owner of Unitemp although he has been involved with the company since the 1970s. He remembered working on the first Potomac kiln installation back many years ago.
“We don’t have standard advertised models. We work with our customers to meet their specifications,” said Jerry.
Each Potomac kiln is capable of drying 120,000 bf. of lumber per charge. While updating the fuel system for the kilns, Potomac also decided to upgrade the controls and monitoring systems. Potomac chose the SmartTrac software by Signature Control Systems of Englewood, Colo. This decision worked out well because Signature recently bought Northern Milltech Inc. (NMI) to form SCS Forest Products Inc., and Potomac has the NMI inline moisture meter system at its planer mill. The combined company provides the industry’s only end-to-end line of integrated moisture measurement systems and related process optimization tools for sawmill, kiln and planer mills.
Cliff explained, “Signature’s SmartTrac looked to be the most user friendly product. It was in a price range that was reasonable. And the biggest selling point was that Signature’s kiln monitoring system interfaced with our NMI moisture measurement system. This allows you to track lumber after it comes out of the kiln and passes through heads to the planer mill.”
With over 300 installations around the world, SCS claims its technology can help improve yield. According to SCS, better moisture control combined with end-to-end data integration can result in a 4% or greater improvement in moisture grade.
Improved moisture control has emerged as a critical process improvement in the forest products industry as mills increasingly focus on profitability and yield. Adding NMI’s widely adopted sawmill and planer mill digital pulse moisture measurement technology to SCS’s in-kiln dielectric moisture measurement product line, offers the industry the first digitally integrated, end-to-end moisture measurement solution.
Cliff said, “You used to dry lumber by the seat of your pants. You used to dry lumber based on time and watching the dry bulb temperatures and looking for a wet bulb drop. Then companies started using drop across-the-load control methods. Now moisture meters have evolved to the point that the technology has become dependable while offering better results.”
Although there is a learning curve with the software, Cliff said the charts give you a good idea of what the kiln is doing. SmartTrac technicians can adjust the system remotely while providing technical support.
Cliff said, “It has taken us a couple of months to get everything calibrated so that you feel safe with it. We have gone from the stone age to the 21st century as far as drying techniques.”
He further explained, “Accuracy gives you efficiency. That means it requires less energy to dry. You are less likely to over dry or have wet lumber coming out since the data is more accurate.”
Plans for Future
Two years ago Potomac developed a four-phase plan to better utilize its biomass. The first phase was to install the new kiln and switch from propane to wood fuel. It has successfully done that and moved on to phase two, which will allow the company to sell its excess dry biomass to other markets. The third stage involves converting the new kiln to the recently developed triple-length, continuous lumber drying process.
Pioneered by Andy Pollard of Pollard Lumber Co. Inc. in Appling, Ga., the technology captures heat and circulates it to green lumber that is staged and ready to move into the drying chamber. Heat coming off dried lumber is captured and used to preheat the green lumber. Also, the moisture coming off the green lumber conditions the dry lumber. Additionally, excess steam can be produced from the kiln and harnessed into usable energy.
Rich said that Potomac installed its newest kiln with the ability to convert to the Pollard system when the market changes. Potomac prepared the site with wiring conduit, motor control capacity, electrical capacity and foundation. It can turn the single length kiln into a triple length process without having to modify the existing infrastructure.
Rich said, “At this point, the kilns we have are keeping up with production. When the market changes and we have the production capacity needs to justify it, we will probably convert the last kiln over to the continuous drying process.”
The fourth stage would catapult Potomac to the energy forefront. Potomac is considering newly developed turbine technology to generate electricity.
Bill said, “A significant percentage of biomass in the United States is left to rot in the forests. In Europe, logging sites look like they have been swept clean… My real dream is to generate power from the slash left in the forest.”
Potomac is actively looking at the technology and encourages other forest products companies to do the same. Bill believes it will take a massive industry-wide effort to really put wood energy on the map.
Bill said, “There is a critical need for critical mass. Without other people getting into this business, there is no real opportunity.”
