Métodos alternativos para aproveitamentos das hemiceluloses da madeira de eucalipto na indústria de celulose kraft / Alternative methods for using eucalyptus wood hemicelluloses in the kraft cellulose industry

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The search for a better use of wood in the pulp industry has fuelled interest in a more rational use of its components, particularly hemicelluloses. This study investigates the impacts of alkaline leaching and self-hydrolysis of wood chips for hemicellulose removal, as well as re-adsorption into the fibers during kraft pulping of dissolved wood solids present in the black liquor on the performance of a line of eucalyptus fibers using the kraft pulping process and ECF (elemental chlorine free) bleaching. Alkaline leaching of the chips was inefficient in hemicelluloses removal (<40%), regardless of the time, temperature and NaOH concentration conditions employed. Cooking yield of the leached chips containing 39% less hemicelluloses was 7% lower than that of the chips with normal kappa number 16. Self-hydrolysis of the chips allowed the removal of up to 60% of hemicelluloses; however, the subsequent kraft cooking yield was very low, 6% lower than that of the normal chips, at this level of hemicellulose removal. Hemicelluloses loss sum in self-hydrolysis and kraft pulping was 13.4%. Kraft pulp derived from self-hydrolyzed chips had an efficiency of 75% in delignification with oxygen, compared with 43.6% of the reference-pulp, resulting in an ECF bleaching cost reduction in US$ 7.00 per ton of bleached pulp. Kraft process with the addition of 50% v/v of black liquor had an increase of 1.5% in the purified yield, of 0.5% in pentosan content and of 4.7 mmol/kg in HexAs content, in relation to the reference-cooking, with subsequent increase in total solids (3.4%) and organic solids (1.7%,) black liquor contents. The resulting kraft pulp presented a good performance in the pre delignification with oxygen, except for whiteness 1.2% ISO smaller. The use of black liquor in kraft cooking (50% v/v) negatively affected pulp bleachability, increasing the consumption of active chlorine in 3 kg/adt in order to obtain 92% ISO whiteness using the DHT(EP)D sequence. The physical-mechanical and optical properties of the pulps originated from the kraft cooking with the addition of black liquor were statistically similar to those of the reference-pulp.

ASSUNTO(S)

tecnologia e utilizacao de produtos florestais eucalyptus wood hemicelulose rendimento hemicellulose yield kraft pulping bleaching eucalipto polpação kraft branqueabilidade

ACESSO AO ARTIGO

Documentos Relacionados