Comparison of hot-water extraction and steam treatment for production of high purity-grade dissolving pulp from green bamboo

Abstract

The performance of hot-water extraction (HWE) and steam treatment (ST), followed by kraft pulping were compared for production of high puritygrade dissolving pulp from green bamboo. With the same prehydrolysis intensity (represented by the P-factor), the fractionation efficiency of HWE is far lower than that of ST. Because of lower removal of non-cellulosic components, the solid residue from HWE (even at approximately double the prehydrolysis intensity, P-factor = 1,379) required more active alkali (AA) during kraft pulping to obtain a cellulose purity equivalent to that achieved by the ST (Pfactor = 756)-kraft process. To reach equivalent hemicellulose removal, HWE required more severe intensity than ST. However, FTIR and SEM characterizations of solid residue confirmed that intensified HWE resulted in significant lignin condensation. Antagonistic effects of hemicellulose removal and lignin condensation extent on subsequent kraft pulping were therefore more apparent in HWE than that in ST. Under the same kraft pulping conditions, lignin condensation from a severely intensified HWE process (P-factor = 2,020) caused greater cellulose yield and viscosity loss than that found for ST. Finally, at a given residual pentosan or lignin content, the cellulose yields from all HWE-kraft pulps were about 3 % lower than those from ST-kraft pulps. Consequently, based on an optimally setup chlorine dioxide bleaching stage, a cellulosic pulp with alpha-cellulose content of 97.6 % and viscosity of 927 mL/g was successfully produced from a ST-kraft pulp (P-factor = 756, AA = 19 %).

Effect of hot-water extraction (HWE) severity on bleached pulp based biorefinery performance of eucalyptus during the HWE–Kraft–ECF bleaching process

“…After that lignin removal was slightly decreased. Under harsh extraction conditions, this is probably caused by the deposition of lignin or pseudo-lignin (Donohoe et al, 2008;Leschinsky et al, 2008;Luo et al, 2014;Sannigrahi et al, 2011;Selig et al, 2007).…”

“…Kraft pulps were bleached by the ECF bleaching sequence as described previously (Luo et al, 2014). D, Q and P denote chlorine dioxide bleaching, chelation treatment and hydrogen peroxide bleaching, respectively.…”

“…Interestingly, by conducting elemental chlorine free (ECF) bleaching, the differences in the resulting pulp yields and physical properties between un-and extracted samples were significantly reduced (Jahan and Rahman, 2012;Lei et al, 2010). However, the properties of bleached pulp would be poor if >60% of hemicelluloses in lignocelluloses were dissolved; this is thus undesirable in the production of paper-grade pulps but may be acceptable in dissolving-grade pulp production (Borrega et al, 2013;Luo et al, 2014).…”

Boosting Oxygen Delignification of Poplar Kraft Pulp by Xylanase Pretreatment

“…About 90% of the wood lignin can be removed through its depolymerisation and by the ionization of its fragments into alkaline liquor during the pulping process (Bajpai and Bajpai 1992). To produce fully bleached pulp, the remaining residual pulp lignin needs to be removed by bleaching, such as the commonly used oxidants chlorine and chlorine dioxide (Luo et al 2014). Effluents generated from bleach plants are significant contributors to waste water pollution of the pulping industry.…”

Improved Cellulose Yield in the Production of Dissolving Pulp from Bamboo Using Acetic Acid in Prehydrolysis

“…Unfortunately, to date there has been a scarcity of literature on dissolving pulp yield, despite its relation to the cost of the pulp. Too much emphasis has been placed on the performance of the products, the purity-grade dissolving pulp Luo et al 2014), and/or the structures of fiber (Testova et al 2014). Studies are required that simultaneously focus on how to improve the yield of dissolving pulp while retaining cellulose performance.…”