Студопедия
Случайная страница | ТОМ-1 | ТОМ-2 | ТОМ-3
АвтомобилиАстрономияБиологияГеографияДом и садДругие языкиДругоеИнформатика
ИсторияКультураЛитератураЛогикаМатематикаМедицинаМеталлургияМеханика
ОбразованиеОхрана трудаПедагогикаПолитикаПравоПсихологияРелигияРиторика
СоциологияСпортСтроительствоТехнологияТуризмФизикаФилософияФинансы
ХимияЧерчениеЭкологияЭкономикаЭлектроника

Fig. 8.5 Purification of hardwood sulfite pulps

Читайте также:
  1. Advanced a hypothesis that, for a given degree of delignification, sulfite pulps
  2. Alkaline Sulfite Pulping
  3. Alternative Sulfite Pulping Concepts
  4. Be transferred to paper-grade pulps. The papermaking properties of pulp are
  5. Beech Sulfite Beech Kraft Eucalyptus Kraft
  6. Bleaching to the activation with Mg(OH)2 is compensated by a final hydrosulfite
  7. Chemical pulps, in relation to various yields.

(HW-S) and eucalyptus prehydrolysis-kraft

Pulp (E-PHK) with cold aqueous NaOH solution

of varying strength [28]. HW-S:

unbleached, kappa number 6; (E/O) pretreated:

kappa 1.6. E-PHK: OZ pretreated,

kappa 0.6. CCE-treatment: 10%consistency,

C, 30 min.

0 20 40 60 80 100

90.0

O-Z treated E-PHK

R18 content [%]

NaOH concentration [g/l]

Fig. 8.6 Purification of eucalyptus prehydrolysis-kraft pulp (EPHK)

With cold aqueous NaOH solution of varying strength

[28]. E-PHK: OZ pretreated, kappa number 0.6. CCE-treatment:

10%consistency, 30 °C, 30 min.

Pulp Purification

Through alkaline treatment, depending on NaOH concentration, is further illustrated

In Fig. 8.7. The different levels of R18 content after cooking and subsequent

Oxygen delignification (O) of the eucalyptus PHK pulps have been adjusted by prehydrolysis

Intensity (P-factor). Even though xylan removal efficiency increases

With increasing initial hemicellulose content, the initial purity must exceed a certain

Level in order to achieve a sufficiently high purity without approaching a

Change in the supramolecular structure.

0 20 40 60 80 100

0.0

Initial R18 content:

96.6% 97.2% 97.6%

Xylan content [%]

NaOH concentration [g/l]

Fig. 8.7 Purification of eucalyptus prehydrolysis-

Kraft pulps (E-PHK) of three different initial

Purity levels with cold aqueous NaOH solution

of varying strength [28]. O-pretreated E-PHK

pulps: (a) R18 = 96.6%, kappa number 3.4; (b)

R18 = 97.4%, kappa number 2.5; (c)

R18 = 97.6%, kappa number = 2.2. CCE-treatment:

10%consistency, 30 °C, 30 min.

8.3.2

Time and Temperature

The influence of temperature on the performance of caustic extraction has been

Discussed in detail in Section 8.2. It is well established that lower temperatures

Cause a high degree of swelling, and this enhances the solubility of hemicelluloses.

The effect of temperature and retention time in the range 30–50 °C and 10–

60 min, respectively, while keeping the NaOH concentration constant at 70 g L–1,

Is illustrated in Fig. 8.8.

It can be seen that extraction time has no influence on the purification efficiency

In the range investigated. The retention time during alkalization is not a

critical parameter because swelling takes place almost instantaneously [4]. However,

the increase in temperature from 30 °C to 50 °C induces a decreased removal

of xylan content of 0.4% (from 1.5% to 1.9% in the residue). This temperature

Cold Caustic Extraction

0 20 40 60

0.0

C 40.C 50.C

Xylan content [%]

Time at Temperature [min]

Fig. 8.8 Influence of time and temperature during CCE treatment

Of eucalyptus prehydrolysis-kraft pulp (E-PHK) at a constant

NaOH concentration of 70 g L–1 [28]. E-PHK: OZ pretreated,

kappa 0.6. CCE-treatment: 10%consistency, 30 min,

70 g NaOH L–1.


Дата добавления: 2015-10-21; просмотров: 102 | Нарушение авторских прав


Читайте в этой же книге: Section 7.9 | Hemicelluloses), and the change of the molecular distribution to a narrow, | Temperatures. This explains why the alkali consumption does not correspond | The principal means of producing highly purified dissolving pulp. When applying | Concentrations, using X-ray diffraction. Ranby studied the appearance of cellulose | Appears to be alkali-resistant), the NaOH concentration must be increased from | This explains the different pattern of hemicelluloses removal as compared | During alkalization of a beech sulfite dissolving | Content is almost negligible. Therefore, the main objective of the alkali | Lattice planes is widened from the original 0.61 nm to more than 1.2 nm due |
<== предыдущая страница | следующая страница ==>
Washing. The pulp entering the CCE stage must be thoroughly washed and| Increase equally affects purification, as would a decrease in NaOH concentration

mybiblioteka.su - 2015-2024 год. (0.005 сек.)