Brunner Hildebrand Presents “Green” Lumber Drying – Not Only for the Environment’s Sake

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Brunner Hildebrand”s Green-KilnR interconnection process allows recuperating heat more efficiently among the chambers. This technology focuses on reducing the energy consumption involved in the dry kilning process.

Changing Environmental Impact of Wood Products
Worldwide 150,000 lumber kilns are reportedly in use to dry lumber to adequate moisture contents. For almost 100 years, the conventional air-intake/exhaust drying process has been almost exclusively been used. This process has the disadvantage of high energy requirements with a low efficiency through continuously heating fresh incoming air.
Up to 50% of the used heating energy reportedly gets lost; in addition there are the unnecessary CO2 emissions. Lumber dry kilns are like houses in the winter with open windows and doors. Equipment manufacturers, research institutions, and kiln operators all need to be proactive. If possible, CO2 emissions should be reduced with no additional costs so everybody will benefit and participate in the effort.
In some countries laws demand that companies demonstrate the green-house emissions generated to manufacture any product (the carbon footprint). It is likely to be simply a matter of time before companies around the world will have to deal with the generation and reduction of CO2 emissions of their manufacturing processes.
Heating lumber dry kilns often uses fossil fuels (wood, gas, coke, etc). Each company is responsible to find the best way possible to reduce damaging emissions through the use of less energy with the same results with more efficient energy and environmental protection through higher investments.
Often people point out that wood heating emissions were cleaned out from the environment during the growth phase of the trees. Of course this does not include the energy CO2 emissions used to fell the trees, to transport them or saw them, even the energy to manufacture the boiler itself.
In addition, a climate change problem consists of generating more CO2 emissions than our planet can take. We have to either reduce the emissions or increase the CO2 lowering measures.
During the Cancun world climate conference in December 2010, they discussed some important issues. Should industrialized countries pay emerging countries to leave their forests untouched as reservoirs that can absorb CO2? Protection of the forests is an affordable option to compensate for the CO2 excess in our environment.
Wood waste or fiber are becoming a coveted fuel in many places. Large biomass plants use wood waste and any kind of wood fiber.
Worldwide the production of wood pellets has grown dramatically from around 16 million tons in 2010 to a projected 46 million tons in 2020.
The German corporation Viessmann plants poplar (cottonwood) to support power generation; it wants to be independent from external energy sources. Sadly, fast growing trees are often planted in areas where rain forests once grew. Sawmills often welcome this demand. Prices for waste wood have doubled in the last two years to around 100 EUR/ton with a tendency to increase further.
Wood is becoming too valuable to just burn. It needs to be processed into useful products and then burned as fiber later in its life cycle.

New Hildebrand GreenKiln®
Worldwide 150,000 dry kilns generate about 40 million tons of CO2 each year. If they were running based on the new environmentally friendly drying process, operators would both save money and avoid the pollution equivalent to three million cars a year. The new Hildebrand GreenKiln® (interconnection of a set of kilns) saves 15-30% of the heating energy; one dry kiln avoids the pollution of about 20 cars a year.
The goals for the new green dry kiln generation are clear and demanding:
Environmentally friendly and economical but ideally without any additional investment or additional operational costs, thus environment protection free of charge – without an extension of drying time or a decrease in quality. To do this there are some known and proven measurements. No one is free; to some extent they require large additional costs:
• Reinforced insulation (roof, walls, gates, and floor). Will dry kilns soon have wall insulation thickness of 40 cm (approximately 16”)?
• External heat exchangers with large heating exchange surfaces on top of the roof.
• Heat pumps (condensation dry kiln): vacuum drying, direct heating, power heat cogeneration, block heating stations.
• The Brunner interconnection process.
Considering the competitive margins in lumber drying, real progress in “green drying” would require a considerable increase in profit margins. The most frequent innovations are those which aim to reduce operating costs, including robust, durable solutions with easy operation.
A critical reader will immediately ask, “15%-30% savings on heating energy without any additional cost? Green lumber drying with CO2 reduction? Relief of our environmental remorse and financial savings? All of these from the very first day? No drying time extension, no decrease in quality – yet enhancement?”
Brunner-Hildebrand offers some historical facts about the development of the idea of “interconnection of kilns.”
• First patent about “interconnection” was registered on 7/12/1984; many other patents followed. 25 years of experience in interconnected systems. However, the world did not talk about climate change until the Kyoto Treaty on 12/11/1997.
• In intake/exhaust air drying technology each individual kiln exchanges heating and saturated air for fresh air – a waste of energy.
• In the “interconnection process” (THES) exhaust air is not exhausted outside; rather it is transported to neighboring chambers. This saves energy and brings many other advantages.
• Hildebrand technology incorporates the experience of more than 15,000 lumber dry kilns into a sensational process – the termic coupling. Today there isn’t anything better than “interconnected drying.”
Over 20 years ago in 1987 the technical groundwork for the new “GreenKilns” was the patented “Brunner coupling process.” This process is characterized by a specially designed heating exchanger system integrated on top of the roof and equipped with a flap system within a double chamber duct.
Using single servomotor-driven flaps resulted in a) Chamber upper/lower duct and b) Double ducts for exterior air with selective connection to every single chamber or to the external air.
In addition to other advantages, this process achieves a better use of energy and humidity contained in the saturated air (climatic interconnection).
With GreenKilns valuable energy is not simply extruded out the exhausts vent – i.e. chimney. It stays in the system to everybody’s benefit.
One of the disadvantages for wide spread use was the high additional investment for ducts, flaps, servomotors, etc. and the resulting sensitivity of the hardware. And often there is the issue of using wood waste for heating energy. Is it a relatively free resource?
The time has come for using more powerful computer technology to help overcome increasing energy costs and climate problems. If no additional costs arise, and operational savings are possible day after day, the time to make these technology moves is here.
It is now possible with the new “GreenKilns” to set a trend and look forward. The following example deals with just three conventional dry kilns. Each interconnection assembly between two Hildebrand GreenKilns is responsible for a “green controlled climate.” It permanently generates a virtual duct for the air flow between the ceiling and roof. All of this saves energy.
The heat recovery (heat exchanger) unit with this new drying system is inside. External heat recovery units or heat exchangers (mounted on the roof) lose their efficiency over the years due to wood dust and other deposits such as resin.
The transversal fan runs sporadically. Through an adequate and coordinated change or interruption of rotating direction of recirculation fans from neighboring chambers, a pressure difference is created, allowing a flow and transportation of climatic conditions similar to the intake/exhaust air flaps. The transversal fans temporarily support the recirculation fans. The software can incorporate data obtained from sensoring probes and calculate conditions in the chambers together with the actual fan revolutions and enthalpies (energy content).
Through the interconnection results an ideal coupling of the system (Heat+humidity+air turbulence), including less spraying water with less heating and evaporation. It is even possible to spray with the humidity coming from the lumber, which brings 2%-5% savings on heating energy.
We can not accept any wasted energy or environmental pollution. With Hildebrand GreenKilns, valuable energy won’t blow away through the chimney; it will remain in the system to be properly used.
With this new dry kiln generation you won’t have additional costs in comparison with the conventional drying process; this means both systems cost exactly the same today.
When we dry wood with high moisture content, the energy to initially heat up is often as much as double that of the average heating process. Towards the end, the heating energy is just 5%-10% of that in the initial phase. In order to avoid extending drying times the heating capacity of a conventional kiln will be designed according to the need during the heating-up phase. This energy volume will be needed in only 1/10th of the drying time, which means for 90% of the time the heating capacity is over dimensioned. The THES process takes advantage of this fact.
In the interconected set of kilns, each single chamber uses not only its own heating capacity but also that of its neighboring ones. For this reason, they need less heating exchange surface, and fewer pipes and fans. Another strong factor that reduces costs is also avoiding the generation of “dead heat.”
All of this compensates the additional costs regarding the interconnection assembly and all additional hardware and software needed for the new process. The CO2 footprint for the used components remains all together well balanced.
The THES process improves the efficiency of the heating surface; consequently the boiler will be evenly used. It needs less capacity and at the same time increases its efficiency factor. Less CO2 goes to the environment, and the kiln operator also saves money.
A special case that saves a lot of money is the process of slow drying woods. In this case, only every other chamber or even a third of the chambers (within a large set of interconnected kilns) will get a heat exchanger. This means savings on heat exchangers’ surfaces, pipes, heating control systems, etc. Thanks to the heating coupling, the chambers without heating will get the energy form neighboring chambers.
Now many conventional dry kilns get additional heat exchangers on the roof. While this might be reasonable, it doesn’t achieve the heating values and advantages of a Hildebrand GreenKilns chamber.
The new process allows recuperating heat more effectively among chambers. In case of the before mentioned “brunner interconnect process”, even double ducts were installed on the roof; in contrast to that, the new Greenkilns use the existing space between roof and internal ceiling to reduce additional investments.
External heat exchangers cost more money and increase the total CO2 footprint. They demand more use of power in the existing fans in order to generate the air flow through them. Over time these fans reduce their effectiveness through deposits of resin and wood particles.
During the cooling phase the existing heat reservoir within the wood can not be used by the heat exchanges, and there is the problem with the existing dead heat.
Hildebrand indicates that for the first time it is possible to avoid dead heat without additional costs. The fresh and exhaust vents which work in synchrony in conventional drying systems are decoupled.
In today’s kilns dead heat results when air flow is heated after it exits the timber stack. Fresh ambient air is added. Behind the fans an already warm air flow exits the exhaust vents without going through the kiln system.
In conventional kiln systems, you can avoid the dead air problem only by placing the heat exchangers in the back and front apron; this means substantial investments due to double heating capacity, etc.
Hildebrand GreenKilns solve this problem by thermically coupling its kilns. This saves both energy and the environment. This heat savings cannot be achieved with external heat recovery units.
Only in very special cases “Greenkilns” get additional external heat exchangers. For instance, when the exhaust air is saturated with high humidity that can not be used in the process. Also in this case the THES offers an affordable solution, because only every other one or a third of the chambers would get an external heat exchanger, which can be commonly used.
All of this is managed by the software Merlin, which can adapt accordingly to the existing situation in each chamber and allocate the use of heat and the exchange of climatic conditions.
The new Hildebrand GreenKilns® provide an environmentally friendly solution with an affordable additional investment. Hildebrand has a financial comparison for four small chambers available.
Hildebrand GreenKilns eliminate “dead heat.” Flaps used in conventional kilns work in synchrony; with the THES they work independently. This decoupling avoids the generation of additional costs through heat loss or dead heat. The THES process connects climatic compatible chambers and eliminates dead heat. In addition to saving energy, the Hildebrand GreenKiln has heat savings of 2-5%, which is achieved without using external heat exchanges.
When cooling down to get to a feasible end wood temperature, the wood and chamber are built together as a sort of backing oven. GreenKilns makes use of this reservoir when external air flows through the stack before going to the neighboring chamber. In conventional dry kilns, the useful heat reservoir is wasted and never used. Even if you use external heat exchangers, this heat remains unused and the cooling period is unnecessarily prolonged.
Wood goes through a continuous process of changes based on accelerating phases and resting phases. According to the type of wood, wood thickness, and moisture content, the climatic conditions in the chamber experience changing intervals of increased temperature and relative humidity to create an equilibrium of moisture content. After that an interval of rest follows with a reduced heat supply and ventilation.
When two chambers are interconnected, the one in-between is put on rest by a software command in order for the wood to recover. This situation is the perfect configuration for the kiln set in order to save heat and power.

Large Fans
In addition to the air volume per hour, the uniformity of flow distribution and the speed of the air over the surface of the wood are decisive for the drying result. These influence the material-exchange between the wood and air (moisture-absorption, turbulence). The air speed is determined by the volume of air and the flow power generated by the fans. Because of this, the fans should be larger – 1000 mm in diameter instead of the existing standard of 800 mm. This means 200 mm higher kilns, which cost more, but this is compensated for by needed fewer fans. Although larger fan motors have to be used, less consumption of power is possible using frequency converters. Transversal fans equipped with frequency converters used in Hildebrand GreenKilns provide the necessary turbulence on the wood’s surface together with changing speeds along the stack’s width.
If you reduce fan revolutions by 20%, a power consumption reduction of 50% is achieved. This means you still have 80% of air volume and speed. The ventilator is 25% larger and can generate up to 100% more volume than the existing ones.

Fast Hardware and More Intelligent Software
Ten or even 100 single kilns can be controlled using state-of-the-art computer technology, allowing the control of every single chamber using the same control procedure. When the drying parameters are interconnected, there is an infinite number of possible combinations. The Fox control has been limited to only 15 chambers in a kiln set.
The complexity of the task demands a powerful computer technology along with proven software – Brunner’s Fox control system with incorporated computer and touchscreen. An operator can use a radio-waves-based netwook for wireless data transfer, monitoring and operating. That way he can obtain any drying process data from anywhere within the site. It is also possible to log in via the internet.
The connection is encrypted via a virtual private network, which offers higher security standards against misuse and is much better than modem-based or ISDN-based solutions. Other options via Smart phone or tablets are possible.
The Fox and the special software Merlin deliver informative graphs in 3D technology for parameters like heat, moisture content, and airflow among the chambers.

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Future Perspectives
Consumers are looking for responsible environment protection. Governments demand more and more from larger companies about their actions and how they influence the climate. Lumber dry kiln operations need more peace of mind on environmental issues without jeopardizing their profitability. They need climate change neutral solutions which can lead them to a transparent, positive CO2 footprint. Their decision to invest in favor of a green, environmentally-friendly technology needs to be “cost-neutral” like GreenKilns.
Since April 2010, in the UK and Sweden, small and middle-sized companies must participate in an emissions-grading-market. In France and Japan the CO2 footprint has to be printed on all products next to the use-by-date. Society is working to develop ambitious climate-protection goals in addition to the development of alternative renewable energy resources. Financial support and government funds are likely to increase.
Last, but not least, all of us need to support effective initiatives that contribute to the reduction of CO2 emissions in wood drying. So, we should support new developments like the one presented here in order to banish from earth lumber dry kilns with unacceptable efficiency factors.
The preceding Advertorial material was submitted by Brunner Hildebrand.