A decade or so ago discussions around kilning were often about how fast it could be achieved or whether in fact the product needed kilning at all. Today it is higher product quality and improved energy efficiency that are driving developments.
Swedish manufacturer Valutec has been in business for nearly a century and over that period customers’ requirements have continued to evolve.
“Ten years ago the emphasis was on capacity but in more recent times it has shifted to optimising the drying process to improve quality and reduce costs,” said CEO Robert Larsson.
In response, Valutec has simulation packages for both its batch and progressive kilns which are “very powerful” in helping it to design the dryers and optimise the drying process.
“It’s quite unique for us as a drying deliverer to do so much R&D work and to make our own simulation packages; it’s work that universities usually do,” he said. Since 2005 Valutec also has a patent on a system that allows the kiln to “listen” to the wood and to calculate the rate at which moisture is being removed and so decide the pace of the fans.
“The less water that comes from the wood, the lower the air speed and so the less electricity is consumed. This is used by a lot of our customers to optimise energy consumption,” said Mr Larsson.
R&D is an important element of Valutec’s work and the company has several other projects in the pipeline, including a system that calculates the moisture content without putting a probe into the wood.
German and Dutch manufacturer Bes Bollmann has also noted a trend towards greater automation.
“In the past you had a plant manager or drying manager who knew everything about wood drying,” said technical manager Henrie Dalhuisen. “Today there are fewer people on site so a more foolproof system is required; it’s much more automated and well controlled.”
As the focus on product quality and kiln optimisation has increased so too has demand for heat recovery systems.
“Five years ago 10% of kilns had heat recovery; now it’s 10% that don’t,” said Mr Dalhuisen. “First, the quality of the wood improves because you have a more constant climate, and second, the investment is not much greater and, with a wood-fired kiln, the payback will be one or two years.”
The rising demand for biomass and the resulting revenue also means sawmills want their fuel to go further.
“In the past, efficiency wasn’t that important because there was enough biomass and mills had to pay to get rid of it. Now they get money for it they want to save their biomass so kilns and boilers need to be more efficient,” said Mr Dalhuisen.
Kiln Services, the UK’s only manufacturer of commercial kilns, has also noticed a greater emphasis on energy efficiency.
“Nobody wants to use any more energy than they need to,” said managing director John Commons. “Since the introduction of the Renewable Heat Incentive we have installed a much lower percentage of projects with oil or gas as most of our customers produce biomass as a byproduct of their production.”
As the emphasis on renewable energy has grown, many property owners have installed log-burning stoves, creating demand for high-quality kiln-dried logs. In response Kiln Services has introduced a range of specialist log-drying kilns with capacities of 20-100m3.
Production flexibility is another increasingly requirement, which is where Valutec’s TC kiln comes in. The model has its roots in the company’s first continuous kiln introduced in 1928 but it’s been adapted for very large capacities, a wider range of material and greater flexibility.
This flexibility is provided by the TC’s ability to handle different material in each zone, each requiring a different moisture content. This in turn allows mills to be more flexible in their production.
“You only need to ensure you have sufficient material to fill the zone; you could put 16mm spruce in the first zone, 25mm pine in the next, then 22mm spruce, then 19mm. All can have different moisture contents and the control system takes care of the process through the whole kiln,” said Mr Larsson. “It’s a very flexible dryer which can be designed to fit the capacity need for a specific product, such as side boards, but it could accommodate a range of centre boards too.”
All zones operate for the same length of time no matter what product is loaded.
However, the TC doesn’t suit all requirements which is why Valutec offers a range of kilns including one and two zone progressive kilns and batch kilns.
“If you want to be super flexible with a large variety of moisture contents, drying everything from thin boards to thick materials then perhaps a batch kiln is a better solution,” said Mr Larsson. “If your only product was 2in glulam dried to 11% a two-zone progressive might be the most economical.”
Valutec is Europe’s largest kiln manufacturer. As well as facilities in Sweden it has offices in Finland and St Petersburg, and now it has formed a North American subsidiary – Valutec Wood Dryers Inc, which will have its headquarters in Vancouver, Canada.
“We see great opportunities to expand into the world market, especially since the interest in our new generation of continuous kilns continues to rise,” said Mr Larsson.
Valutec believes its technology has the edge on what is currently on offer in North America and that it will do well in Canada which has a climate similar to Scandinavia.
“Our equipment has to be able to work in tough conditions, which is why we work with stainless steel,” said Mr Larsson.
This summer Valutec is launching its third-generation feeding system which incorporates more than 50 separate improvements. It will be included as standard on all new kiln models.
The developments include a more robust and more protected guide track, electrically operated stop lugs for improved feeding safety and new feeding options for loading and unloading. The new feeding system also includes lateral movement of carts, adjustments to the existing traverse system, a more compact design and better protected driving stations for loading and unloading.
The new feeding system also means that TC kilns and wider continuous kilns are equipped with hydraulic feeding, a patent-protected solution that Valutec has developed.
In another new venture, last year Valutec launched the Kiln Operators Society, a forum for the industry to share knowledge and ideas. Mr Larsson said the concept was well received at the first meeting held in Sweden in December and further meetings are planned in Norway, Finland and Russia this year.
In recent years Kiln Services has introduced a control system of drying by weight, where the weight of the product automatically determines the end of the drying cycle.
“The moisture content of wood is expressed as a percentage of its dry weight density so to control the process by weight made complete sense,” said John Commons.
First the target weight is carefully assessed by drying one batch then assessing the moisture content and distribution through 10 or 20 samples of product. For example, the average weight of a euro pallet at 15% moisture could be 14.8kg or a willow cricket bat cleft at 12% could be 2.1kg, or a cubic metre of oak at 11% would be around 721kg.
The weigh bridge within the kiln can be designed for different products, for example complete packs of timber, 80 or so cricket bat clefts, or complete stacks of 25 pallets. The target weight for each product has to be assessed only once and then it is entered into the control system.
“This method has been particularly popular with pallet manufacturers, including Industrial Pallets and Intergrated Pallets in Northern Ireland as it ensures the products’ moisture content and final weight are as uniform as possible,” said Mr Commons.
“Instead of having just six or eight electrodes measuring electrical resistance between 35mm of wood we can now use hundreds of pieces of wood in a complete stack of pallets to control the process.”
The new system is also being used in other sectors, such as the cricket bat industry where the cleft has to be an exact weight after drying. Kiln Services recently installed a kiln with control by weight at Kippax Willow, doubling the cricket bat maker’s drying capacity to 2,000 clefts at one time. It has also reduced the drying time for the Yorkshire company.
“The new kiln halves the drying time. I get more timber in it and it dries it twice as quickly,” said owner and director Chris Kippax.
The company produces around 12,000 clefts a year which are air dried for three months. They have a 50% moisture content when they go in the kiln and the four-week drying process reduces it to 10%.
“Air drying dries slowly and removes some of the central moisture whereas kiln drying heats from the outside so you strike a balance between the two and get nice light clefts,” said Mr Kippax.
He hopes that the new kiln will enable Kippax Willow to produce a lighter bat and increase sales.
Bes Bollmann manufactures kilns for customers around the world and its clients range from sawmills and pallet manufacturers to furniture and coat hanger suppliers to IKEA, which produce around 60 million coat hangers a year.
In recent years it has been particularly active in South Africa and has also supplied 16 kilns to a customer in the Bolivian high-altitude city of La Paz.
“We built the kilns high in the mountains, 4,300m above sea level,” said Mr Dalhuisen.
It also recently supplied a boiler and kiln to Pontrilas Packaging and last year installed four high-speed kilns and a wood-fired boiler from sister company Kara Energy Systems at Murray Timber Group in Ireland.
While the timber industry and timber product manufacturers are the company’s main client base, it has also supplies kilns to other sectors, including Lamborghini. The luxury car manufacturer uses the kiln to achieve the right connection between the glued surfaces of aluminium and carbon fibre, heating to the required temperature and then holding it there.
“It’s similar to pallet treatment,” said Mr Dalhuisen.
Bes Bollmann kilns are also used in the wind farm industry as the subsea cables required for offshore facilities are heat treated before installation.
Each of these sectors, and different companies within the timber industry, have their own requirements and Bes Bollmann prides itself on meeting those needs.
“We always look at what the best solution is for the company. Rather than selling a kiln, we’re selling a solution, from logistics on site to the end product,” said Mr Dalhuisen.
Valutec bolsters bollsta
When SCA decided to expand capacity at its Bollsta sawmill with a new boiler, an upgrade of the saw line and increased drying capacity, Valutec won the contract to supply the progressive kiln and six batch kilns.
SCA boosted the mill’s annual capacity from 450,000m3 to 525,000m3 and Valutec’s TC progressive kiln dries more than 100,000m3 a year.
It was decided that the new kilning capacity should focus on drying 25mm pine side boards to an 18% moisture content.
The solution was a progressive kiln with cross-circulation and 10 drying zones were installed to meet the required capacity.
The control system keeps track of each package, allowing different dimensions to be loaded between the zones which increases flexibility and reduces the planning required.
Last year Valutec supplied and installed an FB progressive kiln at Crown Timber’s sawmill in Hamina in Finland.
The mill, which Crown Timber acquired in October 2013, produces specific lengths of spruce timber.
The kiln, equipped with pressure frames and a heat recovery system, increased the mill’s drying capacity from 110,000m3 to 150,000m3
M&M Timber increases capacity
M&M Timber has boosted its kilning capacity by a third to meet increasing demand for its landscaping inground contact timber.
At its site near Kidderminster, the company recently installed a third 60m3 capacity kiln ready for the busy spring and summer seasons.
“We’re seriously developing our landscaping and play offer and a key part of that are inground contact timbers,” said sales director Fraser Hall. “We’re also seeing growing demand for a 30-year life for our products, such as the Unilog retaining wall system. We need to kiln dry the pine, to reduce the moisture content, before the pressure treatment process to achieve full sapwood penetration and required preservative loadings.”
The extra capacity will also ensure that M&M continues to meet just-in-time demand while maintaining product quality.
Each of the three kilns has a 60m3 capacity, providing roughly two artic loads of roundwood per kiln.
“We could be shipping 6-10 artic loads of finished product every day so we’re constantly trying to bring lead times down. It’s all about having the confidence that when those markets become available we have the capacity, which in turn gives our customers added confidence,” said Mr Hall.
The new kiln, which sits alongside M&M’s two existing kilns, was supplied by Kiln Services.
When Forest Garden bought M&M in January 2014 the Kidderminster site had just one kiln but the new owner identified drying as a growth area and soon installed the second chamber.
“When we took over, some kilning was outsourced so it made sense to bring it inhouse, but in the last two years we’ve grown the business and now we need extra capacity,” said Mark Dayson, Forest Garden’s engineering and products director.
Mr Hall added that the third kiln not only provided more capacity but was also an indication of Forest’s continued intentions to invest in M&M.
About 60-70% of the site’s output is now kiln dried and one particular growth area – longlife deer fencing for solar farms – will keep the kilns busy.
“Many solar perimeter fences require a correctly treated product that is nonstandard, with a robust replacement warranty that is traceable. The volumes are quite substantial so even with the third kiln, the demand in this sector means we’ll be running three kilns full-time,” said Mr Hall.
M&M has also changed its fuel from diesel to biomass. The switch will reduce fuel costs, it will also provide income through the Renewable Heat Incentive.
Some of its co-products are contracted to AW Jenkinson so a proportion of the kilns’ fuel comes from Forest Garden’s fence panel and shed manufacturing site about 10 miles away in Hartlebury. The investment at M&M has included a shredder for this material.
“We run a transport system between the two sites so we utilise this to transfer the waste,” said Mr Hall.
The biomass unit has the capacity for a fourth kiln if extra drying capacity is required in future.
