Save & prosper

Reduction in resin use - the second major production cost that manufacturers face - means a radical change to a company's financial resources, says Imal.

It says its more efficient approach to the amount of resin applied to the fibre has been accomplished with a system designed to inject resin at high pressure directly into the blow-line.

Meanwhile, it adds, increased production capacity has been achieved with the Imal Dynasteam®, designed to distribute steam over the two surfaces of the mat at the entrance to the continuous press, resulting in a more rapid cure of the core layer.

High pressure resination system

Sprayer nozzles with small orifices are needed to spray the resin at high pressure but the normal glue mix is full of crystals and impurities which can rapidly plug the nozzles, says Imal. To solve this problem, it designed and patented a system whose function is to pulverise the crystals in the line to produce a homogeneous glue mixture. The mixture is then filtered and pumped at around 150bar to the nozzles.

Imal says that how the reduction in resin addition rates is actually achieved, or rather how a better resin blend is obtained, may be illustrated with two simple examples:

1. The crystals that have been pulverised into hundreds of mini crystals spread much more easily over the micro-surface of the wood fibre and consequently only a portion of the resin crystals adhering to the fibre is sufficient.

2. The high pressure used creates an 'explosion' inside the blow-line, thus allowing a better distribution of the resin over the fibre.

Today's mainstream technologies are based on two theories: one relating to applying the resin at high pressure (the theory which Imal has adopted); and the other based on the application of the resin by means of steam nozzles.

Imal says its system can guarantee, as a minimum, the same performance, but it strongly opposes the use of steam in this application for one obvious reason: elevated cost of producing steam and hence elevated production costs.

If we take, for example, an MDF line with a daily production capacity of 35tph of fibre and where 14 steam nozzles have been mounted with overall consumption requirements of 2,300kg/hour, this means that approximately 2,000,000Kcal/hour will be required, says the company. Therefore, if one kilogram of biomass produces 2,000kcal, about 1,000kg/hour of biomass will be required to produce steam for the nozzles, costing around €300,000/year, it says.

Also there is the drawback that it is neither pleasant nor simple to work and run production with sprayer nozzles at 180C° and spare nozzles are expensive, adds Imal.

The technology company says that none of this happens with its application as there are no production costs and the nozzles are easy to handle during production because they are cold. Also, since the high pressure nozzles are just a few simple pipes, they are very cheap to purchase.

Imal says it is able to guarantee the same savings, but with significantly lower supply, installation and maintenance costs, saying that the cost of producing steam for sprayer nozzles is excessive.

The increase in capacity in Imal's system is achieved through the installation of the Dynasteam at the infeed to the continuous press, injecting steam into the mat to reduce the press factor.

The Dynasteam system

The unit is quickly and easily installed at the press infeed, mounted directly on the existing structure, without the need for any foundations, says Imal. It consists of two steam boxes, one above and one below the mat, which spray dry steam evenly over the two surfaces of the mat, without condensation forming. The system is said to accurately control the quantity of steam sprayed by means of two flow meters and two proportional valves, achieved by replacing the existing bottom feed belt with a special, perforated belt that allows the steam to travel through. The top unit comes with height regulation.

The unit looks like a small pre-press and sprays the desired quantity of steam onto the mat as it pre-compresses it. The company says that steam requirements are very low, ranging from approximately 300 to 600kg/hr, depending on plant size. If a more accurate calculation is needed, we are looking at standard steam requirements of 50/70g of steam per m2, per board surface. Energy costs as a result are claimed to decrease significantly, while on particleboard lines, the steam may be produced with the aid of a small heat exchanger, fuelled by the thermal oil from the press.

The results obtained with the DynaSteam application may be summed up briefly into nine main benefits, confirmed, Imal says, by its customers:

1. Increased production capacity. The saturated, dry, steam injected into the two surfaces superheats the mat so the core reaches 100°C well before the press frame where this temperature would normally be reached. Utilising a simple commercial instrument, Imal says it has found that, before installing the application on an MDF line, 100°C was reached at frame 46, while after installation this temperature was reached at frame 38. Therefore the operator increased the line speed so that the temperature was reached at the same frame as before, increasing speed, and hence production capacity, by 27%. In the case of particleboard lines, on the two lines in Italy where the application has been installed, more or less the same results were seen, with an average increase of 20 to 25%. Much better results have been achieved on an OSB line in Germany, where productivity has increased by over 30% due to the configuration of the strands and the ease with which the steam travels through the mat. In addition, the costs related to the increased capacity are those related to raw materials only (wood and resin) and a little additional power, without impacting on the fixed production costs, which have already been spread over standard plant production.

2. Some customers say they do not have the additional drying capacity, or wood preparation, to handle such an increase in production, but this does not mean that all the other production benefits the Dynasteam has to offer should be ignored, says Imal: at each production shut-down, for maintenance or whatever, the silos are full. Production with the Dynasteam can run at least 25% faster while the material is in excess. Furthermore, it is claimed it is possible to produce the same amount of m3/hour with all thicknesses.

3. It is a well-known fact that if you decide to change the type of resin you are using to reduce formaldehyde emission - to use E0 instead of E1 for example - the press factor decreases by about 18%. With the Dynasteam, this loss is easily regained to return to the same production speed when running the other resin, says Imal.

4. It also says it has noted that the wider the MDF line, the more likely the internal bond (IB) is to be lower in the centre than at the sides, since degassing is more problematic in the centre. With the Dynasteam, it has been noted that the IB is more homogeneous over the entire panel width.

5. The steam softens the two surfaces of the mat as it enters the press, making it easier to compress. A significant improvement in the density profile is immediately noted, compared to when steam is not used.

6. Imal says the steam also greatly reduces the pores on the two surfaces, resulting in a more compact surface. The results of the toluene test are much better and a significant reduction in lacquer consumption will be noted; Some customers report they have decreased lacquer consumption by up to 20%, thus lowering their costs.

7. Less formaldehyde is released with a tighter and more compact surface and customers who have installed Dynasteam report a reduction in board emission.

8. Since the mat is softer and easier to compress, the main drive motor tends to absorb less current. On an MDF line in Italy, absorption went from 240 to 200 amps, putting less strain on the chains, less wear on the steel belt, and reducing the amount of oil consumed. A reduction in pressure of 50- 60bar has also been noted on the hydraulic cylinders, claims the company.

9. If you try to decrease the speed of your existing line, consequently increasing cure time, you will see an increment in board property values, particularly the IB value.

So, Imal says, if you inject steam into the mat, but it is not possible to increase production capacity (insufficient material, drying capacity), and you maintain the same production speed, this will have the same effect as increasing board cure time because the temperature of 100°C is reached earlier. As a result, injecting steam into the mat at the same line speed will increase IB values and hence reduce the amount of resin used.