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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
Read More
69 videos|121 docs

FAQs on PPT - Pulping and Bleaching - Chemical Technology - Chemical Engineering

1. What is pulping in chemical engineering?
Ans. Pulping is a process in chemical engineering that involves the separation of cellulose fibers from wood or other plant materials. This process is typically carried out by treating the raw material with chemicals, heat, and mechanical action to break down the lignin and hemicellulose components, leaving behind the cellulose fibers.
2. What is bleaching in chemical engineering?
Ans. Bleaching is a chemical engineering process used to remove color and impurities from pulped fibers. This process is essential in the production of white paper products. Bleaching agents such as chlorine dioxide or hydrogen peroxide are typically used to break down or remove the chromophores responsible for color in the fibers.
3. What are the key challenges in pulping and bleaching processes?
Ans. The key challenges in pulping and bleaching processes include controlling the efficiency of delignification, minimizing the formation of harmful byproducts, and reducing the environmental impact of chemical usage. Additionally, maintaining the strength and quality of the fibers while removing impurities is a crucial challenge in these processes.
4. How does pulping and bleaching impact the environment?
Ans. Pulping and bleaching processes can have significant environmental impacts due to the use of chemicals and the generation of harmful byproducts. The release of toxic substances into water bodies can result in water pollution, while the emission of volatile organic compounds (VOCs) and greenhouse gases can contribute to air pollution and climate change. Efforts are being made to develop more sustainable and environmentally friendly pulping and bleaching processes.
5. What are the alternatives to conventional pulping and bleaching methods?
Ans. Some alternatives to conventional pulping and bleaching methods include the use of chlorine-free bleaching agents, such as oxygen delignification or ozone bleaching. Additionally, the development of biorefinery concepts aims to utilize more sustainable feedstocks and minimize chemical usage in pulping and bleaching processes. Other alternatives include the use of enzymatic treatments and mechanical methods to reduce the need for harsh chemicals.
69 videos|121 docs
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