Factors affecting the bleachability of Eucalyptus camaldulensis kraft pulp | |
| Author | Zhao, Huaping |
| Call Number | AIT Thesis no.PP-04-07 |
| Subject(s) | Kraft paper Eucalyptus camaldulensis Wood-pulp--Bleaching |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. PP-04-07 |
| Abstract | Eucalyptus Camaldulensis wood chips were cooked at varied effective alkali charge and temperature. Cooking time at maximum cooking temperature was chosen as variable to get a range of kappa number (19.5-14.3). Effect of cooking conditions and kappa number on the bleachability in the ECF bleaching sequences - Q(PO)D1Q(PO) and DoEopD1 were examined. Effect of oxygen delignification in the sequence Q(PO)D1Q(PO) on the bleachability was identified. An acid stage was implemented prior to the Q(PO)D1Q(PO) sequence to characterize the effect of an A stage on the bleachability .. It shows that when EA was varied, a higher bleachability in both the Q(PO)D1Q(PO) and DoEopD1 sequence was seen for the lower EA, 20%. The bleachability in Q(PO)D1Q(PO) sequence was improved by decreasing the cooking temperature from 165°C to 155°C only at EA 20%. In the sequence D0EopD1 an increase of cooking temperature from 155°C to 165°C led to a better bleachability, also only at EA=20%. The optimal cooking conditions in the present study when considering total yield, viscosity and bleachability were EA=20%, T=155°C if subsequent bleaching sequence is the Q(PO)D1Q(PO) bleaching; and EA=20% for subsequence the DoEopD1sequence. High kappa number of unbleached pulp achieved better bleachability. Kappa number at 19.5 in the cook is recommended in both the Q(PO)D1Q(PO) and DoEopD1 sequences considering total yield, viscosity, strength and bulk properties. Effect of oxygen delignification on the bleachability and effect of acid stage on the bleachability was not conclusive in the Q(PO)D1Q(PO) sequence. If the evaluation method OXE/Kappa** (expressed as consumed OXE divided by the actual lignin content entering each bleaching stage) was used, higher delignification rate gave better bleachability for downstream pulp bleaching. However, increasing the delignification rate will suffer in pulp viscosity. The bleachability of the acid treated pulp deteriorated, with more acid applied to the pulp irrespective of the brightness above 90.5%ISO. Introduction of acid stage prior to the Q(PO)D1Q(PO) sequence had a greatly negative influence on the fully bleached pulp viscosity. Less acidic treatment provided a slightly less decreased pulp viscosity. The removal of HexA in Do stage in the sequence D0EopD1 was much more efficient than that in D1 stage in the sequence Q(PO)D1Q(PO), even with an A stage prior to the sequence Q(PO)D1Q(PO). The bleachability of Eucalyptus Camaldulensis kraft oxygen delignified pulp in the sequence DoEopD1 was greater in pulps with higher HexA content at the certain brightness. Higher HexA content in fully bleached pulps had higher viscosity and brightness in the pulps at the certain brightness in the sequence D0EopD 1. Strength properties were not much affected by cooking conditions in both the sequences Q(PO)D1Q(PO) and DoEopD1. It is acceptable only if the effect is unconditional 5-10% difference in this limit. Higher kappa number in the cook gave higher strength properties and lower bulk. Pulp without acid treatment had higher strength properties and lower bulk property. |
| Year | 2004 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. PP-04-07 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Pulp and Paper Technology (PP) |
| Chairperson(s) | Malinen, Raimo O. |
| Examination Committee(s) | Kolehmainen, Heikki; Lehtinen, Esa |
| Scholarship Donor(s) | Government of Finland;AIT Fellowship |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2004 |