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MEMBER Wood Products;

0.00 $ (CAD)

MEMBER Forest Operations; Pulp, Paper and Bioproducts;

35.00 $ (CAD)

NON MEMBER

35.00 $ (CAD)

AssociateAssociates

35.00 $ (CAD)


Summary

Continuous drying is still in its relatively early stages and mills are currently dealing with process adjustments to obtain desired throughput and quality of the final product. Field measurement carried out in 2015-16 illustrated a number of opportunities for process optimization involving each of the three main stages of current continuous kilns. Simulations of industrial continuous drying at laboratory level performed in 2016-17 were successful and allowed the evaluation of each of the drying stages to be fully characterized (lumber temperatures, drying schedule conditions of dry and wet bulb temperatures). Thus, different drying schedules provided an excellent opportunity to examine the impact of schedule conditions on drying defects, drying rates and kiln residence times. The main objectives of the project for 2017-18 were to simulate continuous drying in laboratory conditions for different products, products mix, species and green sort groups. In addition, a detailed evaluation of potential technologies was carried out to explore the concept of dynamically adjusting speed (push rates), based on drying rates and moisture content. Piecewise regression was used to identify the optimum push rate and suggest design modifications of continuous kilns. This method proved to be efficient in identifying potential reductions in drying time for different sorts of sprue/pine (SP) lumber without compromising the quality of the final product. Simulations also allowed identifying the push rate of 2 feet/h to satisfactorily dry green hem-fir 2-inch lumber. Initial tests showed that mid-sort sub-alpine (moisture content below approximately 70%) could not be mixed with wet sort SP in a continuous kiln operating at push rate of 4.2 feet/hr because only 73% of the sub-alpine sort dried below 21%. Decreases in push rate will reduce the percentage of sub-alpine fir wets but will also increase the amount of over-dried lumber. Changes in kiln configuration may reduce the drying time but increase the percentage of over-dried lumber. The results indicated that additional laboratory tests are required to develop drying schedules and temperature profiles in the main drying zone of continuous kilns, drying times and final moisture content distribution.

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