IE 21 LEC 25 Pulp and Paper Production Processes

Pulp

Crude fiber material for paper and chemicals.

Pulping

Process reducing wood to individual cellulose fibers.

Lignin

Non-fibrous constituent reducing paper quality.

Mechanical Pulp

Pulp made by grinding logs against abrasive stone.

Chemical Pulp

Pulp produced using chemical processes to dissolve lignin.

Soda Pulp

Chemical pulp made with caustic soda solution.

Sulfite Pulp

Pulp made using bisulfite solution under pressure.

Sulfate Pulp

Kraft pulp produced with caustic soda and sodium sulfide.

Semi-Chemical Pulp

Pulp with mild chemical treatment and mechanical disintegration.

Pulp Preparation

Steps to convert wood into usable pulp.

Pulp Washing

Washing pulp to remove chemicals and lignin.

Pulp Screening

Using a sieve to remove impurities from pulp.

Bleaching

Process to whiten pulp by removing lignin.

Mechanical Pulping Processes

Includes stone groundwood and pressurized groundwood methods.

Stone Groundwood Pulping

Tearing fibers apart using a rotating grindstone.

Pressurized Groundwood

Grinding at high pressure to improve pulp quality.

Chemical Pulping

Removes lignin, making fibers available for papermaking.

Soda Pulping Process

Uses sodium hydroxide to dissolve lignin in wood.

Pulping Processes

Mechanical, chemical, and semi-chemical methods of pulping.

Pulping Digestion

Converts wood chips into pulp using various methods.

Pulp Fiber Yield

Amount of usable pulp obtained from raw material.

Pulp Quality

Determined by strength, permanence, and print performance.

Pulping Energy Requirements

Mechanical processes require more electrical energy.

Pulp Products

Includes newsprint, magazines, and paper towels.

Pulping Equipment

Includes digesters and grinders for processing wood.

Pulping Chemicals

Used in chemical pulping to dissolve lignin.

Pulping Temperature

Elevated temperatures improve chemical pulping efficiency.

Pulping Pressure

Higher pressures enhance quality in pressurized pulping.

Soda Pulping

Green (fresh) liquor consisting of 10-15% NaOH, as the active reagent, and sodium carbonate, as the make-up, is pumped into the vessel. The vessel is pressurized (90-135 psi) and the contents boiled (150-170°C) for four to thirty hours, depending on the pulp and digestion vessel.

Soda Pulping Products

Used for the manufacture of high grade paper, book, magazine, and absorbent grades.

Sulfite Process

Wood chips are treated with a solution of a bisulfite, such as calcium, sodium, magnesium or ammonium, in an excess of sulfurous acid, under pressure and at an elevated temperature. The cooking operation is done in a digester.

Sulfite Process Products

Newsgrade, book or bond paper grade, chemical grade.

Sulfate (Kraft) Process

Uses the same soda liquor except for the introduction of sodium sulfide. Wood chips are fed into a digester, where they are cooked under slightly higher pressures and temperatures for shorter periods of time (4-6 hours).

Sulfate (Kraft) Process Cooking Liquor

The cooking liquor dissolves about 88-92% of the lignin from the pulp and supplies about 45-55% yield.

Kraft Pulp

Used where strength, wear and tear resistance and color are less important.

Kraft Process Products

High test board, brown paper bag, cement sacks, wrapping paper.

Semi-Chemical Process

A combination of the groundwood and chemical processes.

Neutral Sulfite Pulping

Process where the chips are digested using sodium sulfite which softens and partially breaks down the wood.

Neutral Sulfite Pulping pH

The pH of the cooking liquor approaches seven, thus giving the designation neutral.

Neutral Sulfite Pulping Products

The products of this process are generally used as starting materials for corrugated boards.

Paper

All kinds of matted or felted sheets of fiber formed on a fine wire screen from a water suspension.

Abrasive Kraft Paper

Use: Making sand paper used in roughening applications.

Art Paper

Normally, china clay (kaolin) coated on both sides of the paper. Uses: Brochures, calendars, magazine covers, magazine text, where high quality printing is required.

Bond Paper

This paper has good strength properties, good stiffness and good aesthetical look. Uses: Letterheads and for image building stationery.

Book Paper

A general term used to define a class of papers used by the book publishing industry; most commonly used for the book text paper but also for book cover paper.

Business Forms Paper

Paper made for the manufacture of business forms. Uses: Business forms and data processing such as computer printouts.

Carbon Paper

This thin paper could be either coated on one side or both sides with dry impressionable ink. Use: Mostly used where more than one copy is required simultaneously.

Carbonless Paper

Paper stock specially treated or coated to provide copies without the use of interleaved carbon. Uses: Application forms, computer stationery, time saving stationery.

Cardboard

A range of various boards such as pulp board, paste board, bristol board, ivory board, art board, chromo board in the form of a coherent sheet or web used for printing, packaging, decorating etc.

Chromo Paper

China clay (kaolin) coated on one side. Uses: Mainly used for self adhesive stickers, calendars, posters, labels and for applications where only one side has to be printed.

Copier Paper

Mainly used for copying. Used extensively in photocopiers, plain paper faxes, etc. and other office stationery. Thickness could range from 70 GSM onwards.

Electrical Insulating Papers

Use: Electrical insulation.

Fax Base Paper

It is first coated with photo conductive zinc oxide on which images are exposed. Use: Making fax images.

Fluorescent Paper

Uses: Labels, posters and decorative applications.

General Writing Paper (Notebook)

Paper used for notebooks should have excellent bulks because notebook should appear bulky, as otherwise it will be perceived as having less number of pages.

Glassine and Greaseproof Paper

These papers are characterized by very low porosity. Uses: Food packaging and other special wrapping applications.

MICR Cheque Paper

Magnetic Ink Character Recognition. Use: Making of cheques which are processed by computer.

Newsprint

Paper with strength and brightness for readability.

Sanitary Tissue

Absorbent paper made from rag pulp, 5-30 GSM.

Tea Bag Paper

Specialized paper for retail tea packaging.

Wall Paper

Decorative paper alternative to paint for walls.

Hydrapulper

Machine that disintegrates pulp in water.

Fibrillation

Process making fibers pliable for better bonding.

Disc Refiner

Machine with rotating discs for fiber refinement.

Jordan Refiner

Grooved cone that equalizes fiber length.

Blend Chest

Container where chemicals enhance paper properties.

Wet Strength

Paper's ability to maintain integrity when wet.

Opacity

Measure of how much light passes through paper.

Screening and Cleaning

Process removing impurities from pulp before paper.

Fourdrinier Machine

Oldest machine for continuous paper production.

Dandy Roll

Metal mesh roll that adds watermarks to paper.

Watermark

Translucent design visible when paper is backlit.

Headbox

Distributes pulp stock evenly to the former.

Press Section

Removes excess water using pressure rolls.

Dryer Section

Dries paper sheets to 60-70% moisture content.

Breaker Stack

Improves sheet smoothness between dryer sections.

Size Press

Applies sizing solution to seal paper surface.

Calender Stack

Compacts and smooths the paper sheet.

Reel

Winds continuous paper into large rolls.

Absorbency

Ability of paper to soak up liquids.

Tensile Strength

Resistance of paper to being pulled apart.

Controlled Combustion

Use of fillers to manage paper burning rate.

Mineral Fillers

Substances added to improve opacity and strength.

Insoluble Pigments

Coloring agents that do not dissolve in water.

Soluble Dyes

Coloring agents that dissolve in water.