PPT - Pulping and Bleaching Chemical Engineering Notes | EduRev

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Chemical Engineering : PPT - Pulping and Bleaching Chemical Engineering Notes | EduRev

 Page 1


Pulping
and
Bleaching
1
Pulping and Bleaching
Page 2


Pulping
and
Bleaching
1
Pulping and Bleaching
Pulping
and
Bleaching
PSE 476: Lecture 4 2
Introduction to Chemical Pulping
Agenda
 Raw material issues
 Digesters
 Packing the Digester
 Presteaming
 Heating
 Liquor Impregnation
 Typical Cooking Schedule
 Raw material issues
 Digesters
 Packing the Digester
 Presteaming
 Heating
 Liquor Impregnation
 Typical Cooking Schedule
Page 3


Pulping
and
Bleaching
1
Pulping and Bleaching
Pulping
and
Bleaching
PSE 476: Lecture 4 2
Introduction to Chemical Pulping
Agenda
 Raw material issues
 Digesters
 Packing the Digester
 Presteaming
 Heating
 Liquor Impregnation
 Typical Cooking Schedule
 Raw material issues
 Digesters
 Packing the Digester
 Presteaming
 Heating
 Liquor Impregnation
 Typical Cooking Schedule
Pulping
and
Bleaching
PSE 476: Lecture 4 3
Chemical Pulping Overview
Chip Quality Issues: Wood Species
 Softwoods (under kraft conditions)
» generally produces stronger pulp than hardwoods because
of longer fibers
- Lower yield than hardwoods because of higher lignin content
and more soluble hemicelluloses
 Hardwoods:
» Forms paper with good printing quality
» Smaller size produces smooth surface
 Softwoods (under kraft conditions)
» generally produces stronger pulp than hardwoods because
of longer fibers
- Lower yield than hardwoods because of higher lignin content
and more soluble hemicelluloses
 Hardwoods:
» Forms paper with good printing quality
» Smaller size produces smooth surface
Page 4


Pulping
and
Bleaching
1
Pulping and Bleaching
Pulping
and
Bleaching
PSE 476: Lecture 4 2
Introduction to Chemical Pulping
Agenda
 Raw material issues
 Digesters
 Packing the Digester
 Presteaming
 Heating
 Liquor Impregnation
 Typical Cooking Schedule
 Raw material issues
 Digesters
 Packing the Digester
 Presteaming
 Heating
 Liquor Impregnation
 Typical Cooking Schedule
Pulping
and
Bleaching
PSE 476: Lecture 4 3
Chemical Pulping Overview
Chip Quality Issues: Wood Species
 Softwoods (under kraft conditions)
» generally produces stronger pulp than hardwoods because
of longer fibers
- Lower yield than hardwoods because of higher lignin content
and more soluble hemicelluloses
 Hardwoods:
» Forms paper with good printing quality
» Smaller size produces smooth surface
 Softwoods (under kraft conditions)
» generally produces stronger pulp than hardwoods because
of longer fibers
- Lower yield than hardwoods because of higher lignin content
and more soluble hemicelluloses
 Hardwoods:
» Forms paper with good printing quality
» Smaller size produces smooth surface
Pulping
and
Bleaching
PSE 476: Lecture 4 4
Chemical Pulping Overview
Chip Quality: Chip Moisture
 Very low moisture content makes liquor
impregnation difficult
 It is very important to cooking parameters to know
the exact amount of wood mass in the digester as
well as the amount of water to be able to add the
correct amount of chemicals
 Chip moisture can affect pulp yield, kappa
number, and pulp quality
 Very low moisture content makes liquor
impregnation difficult
 It is very important to cooking parameters to know
the exact amount of wood mass in the digester as
well as the amount of water to be able to add the
correct amount of chemicals
 Chip moisture can affect pulp yield, kappa
number, and pulp quality
Page 5


Pulping
and
Bleaching
1
Pulping and Bleaching
Pulping
and
Bleaching
PSE 476: Lecture 4 2
Introduction to Chemical Pulping
Agenda
 Raw material issues
 Digesters
 Packing the Digester
 Presteaming
 Heating
 Liquor Impregnation
 Typical Cooking Schedule
 Raw material issues
 Digesters
 Packing the Digester
 Presteaming
 Heating
 Liquor Impregnation
 Typical Cooking Schedule
Pulping
and
Bleaching
PSE 476: Lecture 4 3
Chemical Pulping Overview
Chip Quality Issues: Wood Species
 Softwoods (under kraft conditions)
» generally produces stronger pulp than hardwoods because
of longer fibers
- Lower yield than hardwoods because of higher lignin content
and more soluble hemicelluloses
 Hardwoods:
» Forms paper with good printing quality
» Smaller size produces smooth surface
 Softwoods (under kraft conditions)
» generally produces stronger pulp than hardwoods because
of longer fibers
- Lower yield than hardwoods because of higher lignin content
and more soluble hemicelluloses
 Hardwoods:
» Forms paper with good printing quality
» Smaller size produces smooth surface
Pulping
and
Bleaching
PSE 476: Lecture 4 4
Chemical Pulping Overview
Chip Quality: Chip Moisture
 Very low moisture content makes liquor
impregnation difficult
 It is very important to cooking parameters to know
the exact amount of wood mass in the digester as
well as the amount of water to be able to add the
correct amount of chemicals
 Chip moisture can affect pulp yield, kappa
number, and pulp quality
 Very low moisture content makes liquor
impregnation difficult
 It is very important to cooking parameters to know
the exact amount of wood mass in the digester as
well as the amount of water to be able to add the
correct amount of chemicals
 Chip moisture can affect pulp yield, kappa
number, and pulp quality
Pulping
and
Bleaching
PSE 476: Lecture 4 5
Chemical Pulping Overview
Chip Quality Issues
 Chip Thickness
» If chips are too thick, liquor
cannot penetrate resulting in
an incomplete cook
- Formation of rejects
» If chip is cooked longer to
compensate, outside of
chips will be overcooked
lowering yield and pulp
strength
 Chip Thickness
» If chips are too thick, liquor
cannot penetrate resulting in
an incomplete cook
- Formation of rejects
» If chip is cooked longer to
compensate, outside of
chips will be overcooked
lowering yield and pulp
strength 0
5
10
15
20
33 34 36 40 42 43 46 48
Kappa Number
Screenings (%)
3mm
5mm
7mm
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