Heating Things Up

July 3, 2018 2:26 pm Published by 2 Comments

Last blog I touched on what happens in the planer. Since I started at the end of the process it only makes sense to go backwards. Before the wood goes through the planer, it must be dried in the kilns. The drying process of wood is crucial to every application of the finished product. It prevents premature decay, increases strength, and reduces weight for freight costs. But this can often be a double-edged sword; if the wood is dried too much it can twist and split making it a lower grade product than it could have been.

Over the last couple of weeks, I have been doing a study on the differences between the traditional batch kiln and the new Continuous Drying Kiln (CDK). While my findings are confidential, I can explain the differences between the two. Simply put, a batch kiln is like the oven you have at home. Put something in, close the door and wait. A CDK is like the oven in a pizza store. You put the raw pizza in one side and leave the door open, it comes out the other side fully cooked. However, unlike making pizzas, multiple textbooks have been written on the physics behind kilns and the relationship between water and wood.

In my undergraduate studies I dipped my toes into the world of kiln science. In order to evenly dry wood, at minimum, a kiln must be outfitted with on demand ventilation, reversible fans and a very powerful heating source. In state-of-the-art kilns like we have on site, every aspect is controllable and automated: how long and how often it vents, how fast it heats up, and how long It holds the temperature required by the schedule.

Kilns are powered by massive furnaces. Here in West Fraser Quesnel, all of our energy used in the kilns is generated from hog fuel that we produce. Hog fuel is composed of manufacturing residuals that cannot be viably sold, such as bark and sawdust. By doing so, we use very close to 100% of every log we process. Not having to burn fossil fuels is both economically and environmentally responsible. After all, what good is a green building material if the process of manufacturing it is unsustainable.

Besides the service applications of drying wood, there is another more ecological cause for drying wood: phytosanitation. For the same reason you can’t take plants across the border, you can’t take untreated wood across the border. Phytosanitation is the process in which all living organisms are totally eradicated in the wood. This prevents of the spread of invasive species when shipping the finished product all around the world. This heat treat program is controlled by the Canadian Food Inspection Agency and is inspected frequently to insure compliance.

I am looking forward to learning more about the role of drying in the modern sawmill as I expand on my study. Over the next 2 weeks I will be spending some time in the sawmill, looking at the first steps that the log goes through in the manufacturing process.

2 Comments

  • Reinaldo says:

    The truth is very interesting the drying of the wood for its use in the Forest Industry. I am also studying at the University the Forest Technical career. In the matter of Wood Technology we see everything about the industrialization of wood as: drying, impregnation to give different uses etc. Very interesting the forestry activity, the truth I would like to make an internship in this company.
    Congratulations greetings from Argentina.

  • Eileen says:

    This is an awesome read. Super informative!

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