Лесотехнически Университет

Резюме

Аn approach for the calculation of the specific mass energy consumption  (in kWh.t^-1) needed for defrosting of the wood chips, which contain both frozen bound an free water, has been suggested. For the calculation of the  a software program has been prepared in MS Excel 2010. With the help of the program calculations have been carried out for the determination of  for oak, acacia, beech, and poplar frozen chips with moisture content in the range from u = 0.4 kg·kg^-1 to u = 1.0 kg·kg^-1 and with an initial temperature at the range from t₀ = –40 ^oC to t₀ = –1 ^oC. At temperature equal to –1 ^oC the defrosting process of the wood chips has been fully completed.

Резюме

The aim of this work was to highlight the importance of chip thickness and type of wood for pulp production under the conditions of modern displacement sulphate cooking CBC (Continuous Batch Cooking).

The main condition for optimal delignification process is the speed how the cooking chemicals come into contact with particular wooden fibres. This speed is given by chips quality – their dimensional, chemical and moisture uniformity.

The optimal thickness of well-impregnable sapwood chips 3–4 mm and recommended thickness for chips prepared from hard impregnable heartwood 2–3 mm are very important for impregnation phase of CBC cooking.

Different progress of impregnation of chips with thickness of 2–3 and 4–5 mm can be explained by different impregnation surface - the surface of fine chips was larger by 34.6%.

There are no significant differences between a conventional cooking of chips with different size of the monitored wood species. Influence of the chip thickness and the type of wood on monitored parameters (yield, kappa number, amount of undercooks and REA) in CBC cooking was more evident, because of very high dry matter value of used chips.

Regular impregnation and delignification of chips from hardwood mixture necessitate preparing of chips with thickness app. 3 mm from species with heartwood share greater than 50% (oak, black locust). The recommended ratio of sapwood and heartwood mixture is 4:1 (under realistic practice).

The suitable combination of above stated parameters allows the production of high quality pulp from non-uniform chips.