Pulp and Paper Industry

• The pulp and paper industry is a large and essential sector globally
• This industry produces printing, writing, packaging, and specialty papers

Pulp and Paper Production

• The United States is the top global pulp producer with 47.02 million metric tons in 2023
• China produced 29.24 million metric tons
• Brazil produced 24.3 million metric tons
• Top pulp producing countries are abundant in forest resources

History of Pulp and Papermaking

• 3000 BCE: Papyrus was developed in Egypt
• 2nd Century BCE: Parchment was invented in Pergamum
• 105 CE: Ts'ai Lun documented papermaking in China
• 8th Century CE: Papermaking spread to the Islamic world
• 1151 CE: Water-powered stamping mill introduced in Spain
• 1264 CE: Fabriano, Italy became a major papermaking center
• 1690 CE: The first paper mill was established in the American colonies, Pennsylvania
• 1817 CE: The first paper machine was built in the U.S.
• 1844 CE: Wood pulp was introduced for papermaking
• 1915 CE Modern: TAPPI was founded for papermaking research

Local Pulp and Paper Companies in the Philippines

• SCG Paper: United Pulp and Paper Co., Inc. (UPPC) is located in Calumpit, Bulacan
• UPPC is the Philippines' leading manufacturer of high-quality industrial-grade paper for corrugated packaging
• Sterling Paper Group of Companies is located in Makati, Metro Manila
• Sterling Paper Group of Companies is a diversified conglomerate involved in school and office supplies, real estate, and agribusiness
• Pulp Specialties Philippines, Inc. (PSPI) is located in Albuera, Leyte
• In 2002, ISAROG Pulp & Paper Co., Inc. acquired PSPI's assets and operations
• PSPI developed specialty abaca pulp technology, along with kenaf, jute, sisal, and non-wood pulps
• Albay Agro-Industrial Development Corporation (ALINDECO) is located in Malinao, Albay
• ALINDECO is a leading manufacturer of abaca pulp sheets since January 24, 1974
• ALINDECO develops pulp grades to meet global market demands

Traditional Raw Materials - Cotton

• Cotton is widely used in papermaking for its softness, breathability, and durability
• Cotton linters are valuable for producing quality paper with a smooth texture and longevity
• Cotton-based paper is used for banknotes, archival documents, stationery, and artistic applications

Traditional Raw Materials - Linen Rag

• Linen is significant in papermaking for producing fine and durable paper
• Linen fibers are stronger and more resilient than cotton, making them resistant to aging and wear
• Linen-based paper is commonly used for important documents, banknotes, and artistic uses involving durability

Wood Fibers

• They are the dominant raw material in modern papermaking for availability and mass production suitability
• Paper properties depend on whether fibers come from hardwood or softwood trees

Hardwood (Deciduous Trees)

• Hardwood comes from trees like Oak, Maple, and Birch
• Hardwood fibers are shorter and thicker than softwood, producing smooth and opaque paper with excellent printability
• Hardwood pulp has more cellulose but less lignin, which makes processing and bleaching easier
• Hardwood is commonly used in printing and writing papers

Softwood (Coniferous Trees)

• Softwood is derived from trees of Pine, Spruce, and Fir
• Softwood fibers are longer and stronger than hardwood, enhancing paper's tensile strength
• Softwood pulp is brighter and more uniform, good for producing bright white paper
• Softwood is commonly used in packaging and high-strength papers

Other Non-Wood Alternatives - Abaca

• Abaca is a species of banana from the Philippines known for strong and water-resistant fibers
• Abaca fibers require minimal chemical treatment and retain durability in wet conditions
• Abaca is used for ropes and bags

Other Non-Wood Alternatives - Jute, seagrass, sisal

• Jute is a coarse fiber traditionally used in sacks and packaging
• Seagrass is an abundant aquatic plant with renewable fiber
• Sisal is known for its toughness and is often blended with wood pulp to improve paper strength/durability

Other Non-Wood Alternatives - Kenaf

• Kenaf is a fast-growing plant with high fiber content
• Kenaf fibers require less chemical processing while offering excellent tear resistance and printability

Composition of Wood - Cellulose

• Cellulose makes up 40–50% of wood's weight
• It is the primary component of wood fibers, providing the structural framework for strength/flexibility
• Cellulose is a polymer (C6H10O5) that can crystallize to form strong fibers

Composition of Wood - Hemicellulose

• Hemicellulose consists of 15–35% of the wood's weight
• It is a partly crystalline polymer acting as a matrix or binder, with shorter carbohydrate chains for flexibility and bonding

Composition of Wood - Lignin

• Lignin consists of 18-35% of the wood
• It is a complex polymer typically in an amorphous form that acts as the matrix or binding agent to hold cellulose fibers and adds strength/stiffness
• It is the component that must be removed during pulping/papermaking to prevent yellowing and brittleness

Composition of Wood - Extractives

• Extractives include resins, waxes, tannins, and oils
• They consist of 2-10% of the total weight of wood
• They are responsible for wood's odor, taste, color, and sometimes resistance to rot

Pulp and Paper Manufacturing - Wood Preparation

• This is the initial stage
• It involves converting raw logs into uniform wood chips suitable for pulping
• This stage includes debarking, chipping, screening, handling, and storage
• Wood preparation ensures efficient and high-quality pulping

Wood Preparation - Debarking

• It is a crucial step because bark is a contaminant
• Bark has low fiber and high extractive content that negatively affects pulp and increases chemical consumption

Types of Mechanical Debarkers

• Drum Debarkers: Logs tumble in a rotating steel drum to remove bark, common in large-scale operations
• Ream (Cambial Shear) Debarkers: A ring of knives peels bark off logs, preferred for high-quality pulp
• Rosserhead Debarkers: A rotating, toothed head grinds bark off, suitable for large-diameter logs
• Flail Debarkers: A rotating cylinder with hanging chains strips bark/removes limbs, used for debarking and delimbing

Wood Preparation - Chipping

• Debarked logs are processed into uniform-sized wood chips using mechanical chippers, which helps to maximize pulping efficiency

Types of Woodchippers

• Disk Chipper: A rotating disk with mounted knives cuts logs into chips, used in sawmills and pulp mills for uniform chip production
• Drum Chipper: A large cylindrical drum with knives slices logs into chips, common in large pulp mills for larger logs

Standard Wood Chip Sizes for Pulping

• Chemical Pulping (Softwoods): 25 mm long (±3 mm), 6-8 mm thick
• Mechanical Pulping (Softwood and Hardwood): 20 mm long (±2 mm), 6-8 mm thick

Wood Preparation - Screening

• Wood chips are screened to separate usable chips from fines and oversized pieces, ensuring chips are appropriately sized for pulping
• Acceptable chips are stored for pulping
• Fines are used in hog fuel boilers for energy production
• Oversized chips are reprocessed in chippers or slicers for size reduction

Pulping

• It is the process of breaking down fibrous materials like wood into a slurry of fibers for paper production
• This involves breaking the chemical bonds of the raw material through mechanical, chemical, or semi-chemical methods
• The primary goal is to extract fibrous cellulose while preserving hemicellulose to ensure a high yield
• Pulping methods are categorized based on how fibers are separated, influencing fiber quality, yield, and processing requirements

General Classification of Pulping Processes

• Mechanical: High yield (85-96%), lignin not removed, uses grinding or refining to separate fibers
• Semichemical: Intermediate yield (55-85%), combines chemical and mechanical methods to separate fibers
• Chemical: Low yield (45-50%), uses chemicals to dissolve lignin and separate fibers

Properties of Wood Used

• Mechanical: Uses non-resinous softwoods and some hardwoods. short, impure fibers with low strength that create high opacity, softness, a stable bulk and good print quality
• Semichemical: Uses mostly hardwoods, resulting in "intermediate" pulp properties and stiffness with moldability
• Chemical: Uses kraft, some hardwoods and non-resinous softwoods. This creates long, strong stable fibers

Mechanical Pulping

• Wood fibers are physically separated using grinding or refining, without significant chemical treatment
• Repeated compression/decompression weakens, fatigues, and separates fibers
• Mechanical pulping methods are classified by the refining process and whether pressure or steam is employed

Characteristics of Mechanical Pulping Processes

• Groundwood Pulping: Grinding using stones or discs separates fibers purely mechanically, leading to more fiber damage with lower energy consumption
• Thermomechanical Pulping: Similar action with groundwood pulping but pre-treats fibers with high temperature steam and has higher energy consumption

Semichemical Pulping

• This involves partial chemical treatment to remove part of the lignocellulose fiber-bonding material, followed by mechanical refining
• Wood chips are “cooked” using a pulping agent with different steps

Neutral Sulfite Semichemical (NSSC) Process

• A common semichemical pulping process developed in the 1940s to incorporate hardwoods into papermaking
• Wood chips are treated in a neutral solution of sodium sulfite buffered with sodium carbonate while maintaining a pH of 7-8
• Cooking occurs at lower temperatures than full chemical pulping to preserve fibers, later softened chips undergo mechanical refining
• The process creates partially digested pulp with improved strength

Chemical Pulping

• It is the most dominant pulping process removing lignin and enabling efficient separation of fibers

Advantages of Chemical Pulping

• Produces high-strength pulp
• Lignin removal yields stronger fibers
• Provides greater resistance to aging, therefore beneficial for records and archival documents
• Easier bleaching compared to mechanical pulp

Disadvantages of Chemical Pulping

• Lower yield
• Chemical pulping dissolves and removes up to 50% of the wood mass, including lignin and hemicellulose
• Releases harmful emissions and by-products
• Uses strong chemicals, which contaminate air and pollute

Kraft Pulping Process

• Kraft pulping is the dominant chemical pulping method, accounting for 98% of all chemical pulp production in the U.S. and 80% globally
• It is applicable to both softwoods and hardwoods
• It produces stronger fibers and has more efficient chemical recovery with less environmental impact

Kraft Pulping Process

• Wood chipped into uniform sizes is fed into a digester
• A large pressure vessel is where processes occur
• Digesters are cylindrical with a dome at the top and a cone at the bottom, ranging in size.
• It is composed of a feed system to send the woodchips through a large valve Preheating is often applied to improve chemical penetration.
• White Liquor injections occur, which is when wood chips are mixed with white liquor, a solution containing Sodium Hydroxide (NaOH) which is a strong base that completely dissociates in water to generate ions, initiating hydrolysis. Sodium Sulfide is added to attack C-C bonds in lignin with the presence of these ions to break easily

Kraft Pulping Parameters

• The pH is strongly alkaline at (12-14)
• Temperature 155-175 °C
• A cooking time of 30 minutes to 2 hours
• Pressure of 10 atm

Blow Tank for Pulp Discharge

• The digester undergoes rapid depressurization where the blow valve separates the fibers
• The loosened pulp is then discharged into a blow tank before washing to remove residual cooking chemicals

Sulfite Pulping

• It is the only acid process used in commercial pulping, but was replaced by the Kraft process due to limitations

Sulfite Pulping: Limitations

• It has limited compatibility with some wood species
• It is intolerant to bark
• It yields weaker pulp strength

Sulfite Pulping: Process

• Sulfur is the primary raw material used in the preparation of cooking liquor/acid
• Sulfur reacts with oxygen at high temperatures to form sulfur dioxide
• The sulfur dioxide formed helps produce sulfurous acid to break down lignin in wood
• The SO₂ gas produced is passed through a combustion chamber
• The gas is directed into a cooler to reduce its temperature
• A fan helps control the movement and pressure of the gas as it proceeds to the next stage
• Cooled, regulated SO₂ gas enters an absorption tower, dissolving in water in the presence of an alkaline base to form ions that are effective for lignin dissolution in wood

Sulfur Dioxide Absorption Pathways

• Once absorbed, SO2 follows three distinct pathways:

1. To low-pressure acid tank which acts as a buffer for the high pressure tank. 2.To scrubber in which excess and unreacted gas exits. 3.Recycling Process which involves in reusing the liquid

Sulfite Pulping Parameters

• The pH is acidic leaning to neutral at 1-5 dependent on the base used.
• Temperature is 130-160 °C
• The cooking time is 6 hours to 2 hours
• Pressure is 4-6 atm

Ether Bond Cleavage with Sulfite Pulping

• High temperatures allow for protonation of benzylic oxygen and release of alcohol fragments, creating the structure of lignin
• Lignin Sulfonation also occurs as an electrophilic attack
• This sulfonation increases lignin's water solubility
• After cooking, pulp and spent liquor are discharged into the blow tank allowing for the separation and the process with water

Chemical Recovery

• Chemical recovery is crucial in chemical pulping for breaking down lignin and releasing cellulose fibers
• There is a recovery process that reduces waste, lowers costs, and improves sustainability

Kraft Chemical Recovery

• That helps make processes for kraft pulping and is used in more than 80% of all U.S. productions

Black Liquor Evaporation

• Weak black liquor is the spent cooking liquor that requires an evaporation system
• This evaporation system has 4 - 6 levels each running on increasingly lower pressure. In the first evaporator, steam heats the blank liquor, causing water to evaporate with vapors used for the next cycle.
• The black liquor becomes more concentrated, going to be 65 -75% solid. When there is higher energy there will be increased the higher concentrated

Black Liquor Combustion - Recovery Boiler

• This plays a central role in kraft chemical recovery for high -pressure steam to generate, and recaptures important pulping methods during the combustion. Sodium Sulfate needs to be reduced as it is a part of white liquir in cooking process

Slaking and Causticizing Reaction

• At this stage, sodium hydroxide, one of the key chemicals, is recovered to form slime.

Sulfite Chemical Recovery

• These are base alkaline for forming solutions used to help break down lignin, as well as varying with various handling methods

Bleaching

• Bleaching is a chemical process to whiten or brighten pulp

Factors that Affect the Degree of Bleaching

• Pulp type
• Wood species used
• End product requirement for ISO Brightness

Chemical Pulp Bleaching Stages

• It uses chlorine, sodium hydroxide, and oxygen
• Used for sulfite pulps
• Final goal of peroxide and ozone uses is to reach high brightnesses

Papermaking

• Papermaking is a process that transforms pulp into sheets of paper through mechanical and chemical operations

Fourdrinier Machine

• This papermaking machine has flat, horizontal wires than runs through dewatering devices

Stock Preparation

• Stock preparation ensures homogeneity, fiber modification, and the incorporation of necessary additives, which is composed of refining, additives blending in screening

Refining

• Modifies structure to improve bonding and strength, fibers to increase surface and improve uniformity

There are Multiple Additive Incorporations

• Functional additives enhance properties
• Controllable additives regulate papermaking

Control Additives

Additives that improve properties with added Clay, carbon, starch, and pigments

Improve Process Efficiency

• Retention, ensure and fillers stay in the sheet with sizing agents controlling water resistance
• Prevent bacterial growth

Metering and Blending

• This process regulates fiber proportions to ensure a consistent pulp

The Stage of Screening and Cleaning

• This process gets rid of unwanted particles such as dirt which could affect paper quality

Dewatering (Wet-End Operations)

• Excess water is gradually removed where the sheet takes shape as it determines structure

Dewatering is Composed of

• The fiber slurry, which is at a consistent solid measurement, spreads to ensure the sheet that is being made is unform
• A fiber sheet is formed and excess water is removed by compacting with pressure applied.

Drying (Dry-End Operations)

• The drying stage is important as moisture requirements
• This process section contains machines that evaporate water, and will use infrared dryers for moisture removal
• Calendering enhances heat and surface of the sheet

Finishing

• The sheet is large, manageable and rolled easily

Standard and Guidelines for Paper Product of Quality

• This process assesses regulatory bodies like ISO and TAPPI ensuring high quality
• There are several ISO guidelines for the DTI
• It is important to specify a grammage that has consistent weight which affects thickness

Different paper Products

• PNS ISO - This defines the method for whiteness of paper and board
• PNS ISO- Specificies tensile for tissue

Regulation for Paper Product Quality

• Substandard paper may be recycled, or disposed of through incineration, landfilling, or other waste management processes

Issues involving environmental Sustainability

• Air Pollution withemissions from power plants, that have pollutants
• Water pollution from wastewater in paper mills if not treated properly
• Deforestation reliance on wood fibres

How can you have company policies on Environmental Sustainability

• Have Sustainable sourcing opting for materials such as FSC certified
• Pollution Prevention to prevent and manage

Future trends and innovations

• New material for pulping for the increase in materials
• New research being conducted on stiffening agents in paper
• Better catalytic oxidation for delignification

Paper and Pulp News

• Award for Services to Paper industry, and kim winning award for sustainble help for new zealand pulp.