How Are Kiln-Dried Logs Made?

Drying freshly cut timber is important before using it in fireplaces or stoves. Green timber, which is freshly cut, usually has a high moisture content of over 60 percent. It should be noted that timbers, like a sponge, can absorb and release water. Different types of timbers can hold a different amounts of water; some can hold up to 200 percent.

While moisture or water is not bad for timbers because it contains the needed nutrients, high moisture is not good for firewood because it will have lots of environmental and health risks. Given this, the moisture content should be removed to a considerable level, usually below 20 percent, that will allow easy burning in fireplaces and stoves.

The process of removing the moisture content from green timber or freshly cut timber is called drying. There are two main methods of removing moisture in timbers: air drying and kiln drying methods. Kiln drying method is the technique used for making kiln dried logs.

How Are Kiln-Dried Logs Made?

Kiln dried logs are processed in a kiln specially built for removing moisture content from green timbers. The kiln enables the moisture in the freshly cut timbers to be removed down to less than 20 percent, which is the condition for effective burning. In the kiln, timbers get heated without affecting the fibers needed for burning. The excess moisture in the timbers evaporates during heating in the kiln.

Kiln drying allows timbers to dry from the inside out, and also enables the removal of impurities and insects from the timbers. The moisture content will also go down below 20 percent. These features improve the burning efficiency of the logs. Rather than stacking logs in the open air for 6 months to a year to draw out the moisture, kiln drying requires only 4–6 days to dry out the moisture from the timber and make the wood ready for burning.

After cutting and delimbing the timbers, the trunks will be debarked and grouped according to their sizes and moisture content. They will be placed into the kiln in batches and left there for 4 to 6 days to dry. The most common types of kilns usually used include conventional kilns and dehumidification kilns.

Conventional kilns have a heated chamber, usually fired by a gas boiler, with circulating fans that draw out the moisture content in the logs through the evaporation process. The excess moisture is discharged through the chimney. This type of kiln is not 100 percent effective, as the heat generated usually escapes through the chimney.

Dehumidification kilns are built to use heat pumps for generating and recycling heat in the kiln. This is the most effective kiln type for removing excess water vapor from logs. The heat pumps are powered by electricity to dehumidify the green logs in the kiln. When the kiln is heated through the heat from the heat pump, the moisture will be removed, and the logs will be removed and ready for use.

Takeaway

The above are the processes for making kiln dried logs. This process is considered better and faster than air drying, which takes about 4-6 months. Kiln drying also makes firewood always available for burning in fireplaces and stoves.

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Created on Dec 1st 2022 22:48. Viewed 99 times.

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