Improvements in Pulp Properties by Alkali Pre-Extraction and Subsequent Kraft Pulping With Controlling H-Factor and Alkali Charge

Abstract

The objective of this study was to determine the processing conditions for obtaining improved pulp properties from the kraft pulping process with an alkali pre-extraction stage. Before the kraft pulping, a pre-extraction of hemicelluloses from mixed hardwood chips was performed with two different alkali concentrations (3% and 12% as Na 2 O) at 150 °C for 90 minutes. The kraft pulping of the pre-extracted chips was then conducted in two ways: with either the H-factor alone controlled or with both the Hfactor and the alkali charge controlled. When the chips were preextracted with the 3% alkali charge and with the kraft pulping controlled to an H-factor of 500, the yield and properties of the pulp were higher than those of the reference kraft pulp. The 12% alkali pre-extraction and kraft pulping resulted in a low yield of screened pulp. However, when the alkali charge and the H-factor were adjusted together, the pulp yield remained constant and the pulp properties improved in comparison to the reference pulp for both the 3 and 12% cases.

Chemical Pretreatments of Wood Chips Prior to Alkaline Pulping - A Review of Pretreatment Alternatives, Chemical Aspects of the Resulting Liquors, and Pulping Outcomes

“…When compared to hot-water and acidic pretreatment methods, mild alkaline pretreatments have advantages, as they generally maintain the yield and quality of the produced pulp and cause minor sugar degradation (Al-Dajani and Tschirner 2008;Chen et al 2012;Jun et al 2012;Sim et al 2012;Huang and Ragauskas 2013a,b). The difference between acidic and alkaline hydrolysis lies in the nature of the extracted carbohydrates (De Lopez et al 1996).…”

The Effect of H-Factor on Kappa Number and Viscosity in Continuous Digester

“…Several parameters including the H-Factor need to be considered to obtain high-quality pulp [4]. The H-Factor is one of the cooking variables that should be considered when processing wood chips in the digester unit due to its relationship with the strength of the pulp (viscosity) and the amount of lignin remaining in the chips (kappa number).…”

C-O Bond Hydrogenolysis of Aqueous Mixtures of Sugar Polyols and Sugars over ReOx-Rh/ZrO2 Catalyst: Application to an Hemicelluloses Extracted Liquor

“…The relatively low degree of polymerization and the branched side groups allow a large fraction of hemicelluloses to dissolve in aqueous solution. Various effective methods have been proposed for hemicelluloses extraction from wood chips prior to cooking, including the use of acids, water, and alkaline solutions [16][17][18][19][20][21][22][23][24][25][26][27]. Many applications for the extracted hemicelluloses have been developed [28].…”