Paper Recycling Technology Dr. Richard A. Venditti ppt

Recycled Fiber Definitionsz Recovery Rate RR „ how much paper is diverted from landfill z Utilization Rate UR „ fraction of recycled fibers contained in paper Consumed Paper of Tons Col

Paper Recycling Technology

Dr Richard A Venditti Dept of Wood and Paper Science

North Carolina State University

„ Unit Operations for Pulp and Paper

„ Paper Recycling (Distance)

z Director of Hands On Workshop for Pulp and Paper Basics, co-sponsored through TAPPI, on-campus and in-mill

z Technical services projects for over 20 companies

Dr Richard Venditti:

Research Projects in Paper Recycling

z The detection of adhesive contaminants, tracking through mills

z The changes in fibers upon recycling

z Automatic sorting of recovered papers

z Flotation deinking surfactants

z Agglomeration deinking

z Screening phenomena and pressure sensitive adhesives

z Deposition of adhesive contaminants

z Alternate recycling processes

„ Ultrasonic deinking

„ Supercritical carbon dioxide to extract wax from OCC

Flotation, Dispersion, Bleaching,

Course Activities

z Viewing of the Videos of Lectures

„ Base lectures by Venditti

„ Guest lectures from industry leaders

z Reading assignments from Recycled Fiber and Deinking, Book 7 of the Series: Papermaking Science and Technology

z Reading assignments: selected research papers

z Homeworks: 6 assignments

z Final Project: Literature Review and Research Proposal

Course Objectives

recycling science and technology

research topic in paper recycling

Critical Issues in Recycling:

=> poor quality material

getting more stringent

emerging countries

same time both of the above are being

satisfied

Recovered fiber, not

“Wastepaper”

Recovered Fiber, not

“Wastepaper”

z Learning objectives

the industry

recovered fiber

Global Paper and Board Demand

Overall Positive Growth

Slide by: Richard B Phillips, PhD

GDP Growth Major World Economies

China, Eastern Europe Dynamic Growth Regions

China

Eastern Europe

Source: RISI

Slide by: Richard B Phillips, PhD

Adjunct Professor WPS NCSU

Paper & Paperboard Consumption vs GDP

Increases with Wealth … Levels Off

Source: 2007 FAO Forest Resource Assessment

Slide by: Richard B Phillips, PhD

Adjunct Professor WPS NCSU

Asian Supply has Grown to Match Demand

Little Incentive for others to develop export strategy

Source: RISI

Slide by: Richard B Phillips, PhD

Adjunct Professor WPS NCSU

Use of Recovered Paper

Growing in China, Europe … flat in USA

Source: RISI

Slide by: Richard B Phillips, PhD

Adjunct Professor WPS NCSU

Use of Recovered fiber Flat in USA

Moving increasingly to Asia

Source: RISI

Slide by: Richard B Phillips, PhD

Adjunct Professor WPS NCSU

Recycled Fiber Definitions

z Secondary Fiber: fibers that have previously been used in a manufacturing process and have been

reclaimed as raw material for another process.

z Pre-consumer waste: any waste, printed or

unprinted, generated in the fabrication or

conversion of finished paper Before use by a

consumer as a final end product

z Post-consumer waste: Paper that has passed

through the end usage as a consumer product.

z Internal broke: off-specification paper that is

repulped and used at the same site, not considered secondary fiber.

Recycled Fiber Definitions

z Recovery Rate (RR)

„ how much paper is diverted from landfill

z Utilization Rate (UR)

„ fraction of recycled fibers contained in paper

Consumed Paper

of Tons

Collected Wastepaper

of

Tons

% 100

duced Paper Pro

of Tons

at Mills Consumed

Wastepaper of

Tons

% 100

Source: AF&PA, 2006 Recovered Paper Annual Statistics

Utilization of Recovered Paper in the US

Paper Recovered (000 tons)

Paper Landfilled (000 tons)

Pkging Material Recovered, 2006

Source: AF&PA, 2006 Recovered Paper Annual Statistics

Recovered Paper Statistical Highlights, 2005 Edition, AF&PA

Exports and Imports of Recovered Paper

Major Recovered Paper Grades

z Mixed Papers: mixed papers, low quality office

waste, magazines, catalogs, telephone directories, recycled boxboard cuttings, tissue paper

converting scraps if mainly composed of recycled fiber, mill wrappers, specialty grades, all other

grades not specified

z Newspapers: old newspapers, special news,

groundwood computer printout, coated

groundwood sections, publication blanks, mixed groundwood and flyleaf shavings

Major Recovered Paper Grades

z Corrugated: old corrugated containers, container cuttings, kraft paper and bags, old solid fiber

containers, kraft bag clippings, carrier stock and its clippings

z Pulp Substitutes and high grade deinking:

bleached chemical pulped office papers and CPO suitable for deinking, or as a pulp substitute if

unprinted, bleached sulfite and sulfate cuttings including tissue paper converting scrap if

predominantly composed of bleached chemical pulp fiber, coated book stock

Grades of Recovered Paper

z Double Sorted Corrugated

z New Double-Lined Kraft Corrugated Cuttings

z Used Brown Kraft

z Mixed Kraft Cuttings

z Carrier Stock

z New Colored Kraft

z Grocery Bag Scrap

z Kraft Multi-Wall Bag Scrap

z New Brown Kraft Envelope Cuttings

z Mixed Groundwood Shavings

z Telephone Directories

z White Blank News

z Groundwood Computer Printout

z Publication Blanks

z Flyleaf Shavings

z Coated Soft White Shavings

z Hard White Shavings

z Hard White Envelope Cuttings

z New Colored Envelope Cuttings

z Semi Bleached Cuttings

z Manila Tabulating Cards

z Sorted Office Paper

z Sorted Colored Ledger

z Manifold Colored Ledger

z Sorted White Ledger

z Manifold White Ledger

z Computer Printout

z Coated Book Stock

z Coated Groundwood Sections

z Printed Bleached Board Cuttings

z Misprinted Bleached Board

z Unprinted Bleached Board

z #1 Bleached Cup Stock

z #2 Printed Bleached Cup Stock

z Unprinted Bleached Plate Stock

z Printed Bleached Stock

Scrap Specifications Circular, Guidelines for ….Paper Stock…

By: Institute of Scrap Recycling Industries, Inc.

„ Any materials that may be damaging to the equipment

z News, De-ink Quality #7 Consists of sorted, fresh

newspapers, not sunburned, containing not more than the normal amount of rotogravure and colored sections

„ Prohibitive Materials None Permitted

„ Total Outhrows may not exceed ¼ of 1%

Scrap Specifications Circular, Guidelines for ….Paper Stock…

By: Institute of Scrap Recycling Industries, Inc.

Total Supply

Recovery of Paper and Paperboard (000 tons)

Source: AF&PA, 2006 Recovered Paper Annual Statistics

16.4 million t/yr

3.5 million 4.2 million

7.0 million

1.6 million

Source: AF&PA, 2006 Recovered Paper Annual Statistics

Recovered Paper Prices, $/ton

US Paper Spot Market Prices May 24, 2007 Corrugated Container 105

Recovered Paper Prices

Cost of DIP

z System

„ MOW to deinked, bleached pulp (DIP)

„ Flotation (2), washing, oxidative bleaching, complementary processes

„ Produce 200 ODTPD

„ Yield = 67%

z Total Capital Cost Installed= $42 MM

z $6 MM/yr depreciation for 7 years

z MOW Cost =$220/ton delivered

Cost of DIP: Variable Costs

$/ton

Cost of DIP: Fixed Costs

Fixed Costs $ Per Year $ / ton

Cost of DIP: ROI

Total Costs, $/ton produced 636

Total Costs per year, $ 44,532,716

Selling Price of ton DIP, $/ton 600

Paper Recycling Review

_ _

z Name 4 major categories of recovered paper

_ _

operations.

„ A Is about 100% for all systems

„ B Ranges from 20-80% depending on the system

„ C Ranges from 60-94% depending on the system

„ D Is 50% for all systems

Common Contaminants in

Waste Paper

Common Contaminants in Wastepaper

z Large Junk

„ metals: nuts, screws, foil, cans

„ plastics: films, bags, envelopes

„ dirt

„ cloth, yard waste, leather, etc.,

z Inks & toners

z Stickies

z Coatings

z Fillers

z Papermaking additives

Inks & Toners

Type Component Drying System Ink Resin Film Particle Size

Absorption into Web

Weak 1-15 Letterpress

Early Newsprint Newsprint and

Offset

Pirgment + Soft Resin &

Mineral Oil

Penetration of Vehicle into Web + Resin Oxidation

+Hard Resin &

Solvent

Solvent Evaporation

Hard Film 2-250 Magazines,

Water Resistant Film

N/A Newsprint

inserts, Corrugated

UV Cured Pigment

+Monomer

UV Photopolymeri zation

Non swelling, Non saponif.

Hard Film

50-100 High Speed

Coated Papers Specialty Various

Pgiments and Rosins

Heat set or Other

Hard, Coherent Films

40+ Xerography

Laser Printers Electronic Forms

z Currently the most challenging problem in paper recycling

z Stickies: contaminants in pulp that have the potential to deposit on solid surfaces

z Typically organic materials:

„ Man made stickies: adhesives, coatings…

„ Natural stickies: pitch, resins

z May deposit on papermachine wires, press felts, dryer fabrics, calendar rolls and cause significant down-time on machine

z Are hard to remove in recycling due to often having a

neutral density, and an ability to flow and change shape

Coatings as a Contaminant

polymeric binders

„ Coating binders can behave as stickies,

sometimes termed white pitch

„ Coating fillers are washed out of the pulp and

lower the overall yield of the recycling process

„ Wax can cause recycled paper to be weak and

slippery

„ Wax can deposit on machinery

Fillers as a Contaminant

the overall yield of the recycling process

„ Common fillers:

– clay – CaCO3 – TiO2

products such as tissue paper

z Wet strength additives cause the paper to be

unpulpable in many cases, making the entire paper product unusable and thus, a contaminant

Contaminant Removal

Contaminant Size vs Removal Efficiency

Recovered fiber, not

“Wastepaper”: Review-Quiz

recycled overall is about 50%

„

„

„

„

similar in shape, strength, density, etc.,

Effect of Recycling on Fiber

Properties

Effect of Recycling on Fiber

Properties

z Learning objectives

chemically pulped fiber

mechanically pulped (lignin containing) fibers

Effects of Recycling on Chemical Pulps

Effect of Chemical Pulping

Fiber wall structure as in the tree Chemical pulping removes

lignin from cell wall

Hornification: Irreversible

A Wet kraft fiber before drying

B 30% consistency (Irreversible processes begin to occur)

C 30-75% consistency

D >75% consistency

Hornification: Irreversible

Never Dried

Fiber

Fiber SwollenWith Water

Dried CollapsedFiber - Hornified

Effects of Recycling on Chemical Pulps

Effect of Recycling on Chemical Pulps

z Chemically pulped fibers that have never been dried:

„ can be mechanically treated (refining) to increase the flexibility

z The flexible never dried fibers are able to conform in the paper sheet which increases the fiber bonded area making strong

paper

z When dried, the fibers become rigid, termed hornification

Effect of Recycling on Chemical Pulps

z Previously dried fibers, upon exposure to water, do not swell and

do not become flexible

z These rigid fibers break upon refining: causing fines

z When paper is made, the rigid fibers do not conform in the paper sheet and the resulting low fiber bonded area produces a weak sheet

Flexible Fibers Stiff fibers

Effect of Recycling on Mechanical Pulps

Effects of Recycling on Mechanical Pulps

Effect of Recycling on Mechanical Pulps

z Wood containing pulps from mechanical pulping processes have lignin (a three-dimensional crosslinked polymer) which makes

fiber walls stiff and deters water swelling

z The stiff, somewhat round cross section fibers make paper with low fiber bonded area and weak fiber bonds

z Therefore, the strength of never dried mechanical pulps is

generally lower than of never dried chemical pulps

z Recycling may improve properties of mechanical pulps by

flatening and flexiblizing the fibers

z “Different behavior than chemical pulps on recycling”

Effects of Recycled Fibers on the

Papermaking Process

z Lower freeness: decrease machine

speeds or add drainage aid

z Lower paper strength: more sheet breaks

z Low efficiency of chemical additives (fines and anionic trash)

z Increased deposits

z Decreased cleanliness

Paper Strength vs Number of Times Recycled

(Howard and Bichard, 1st Res Forum on Recycling, Oct 1991, CPPA)

Effect of Recycling on Fiber

Properties: Review Quiz

z True or False: A pulp produced for

newsprint using a CTMP process should have almost equal or better strength

properties after recycling

Paper Recycling Operations

An Example: OCC Recycling

Paper Recycling Operations

An Example: OCC Recycling

z Learning objectives

OCC recycle mill

sub-operation works

Why is contaminant removal so difficult?

z No single separation device can remove all of the

different types of contaminants

z Thus, recycling processes consist of many

sub-operations that complement each other

Major Recycling Steps

z Dispersion and Kneading

z Bleaching - used to produce printing or tissue

z Water Treatment

z Solid Waste Handling

Example: An OCC Recycling Process

z In the next section, we will take a look at the operations in an OCC recycling process

sub-z The process has the following operations:

Pulping of Recovered Paper

Pulping of recovered paper

Definition

Pulper : A device whose main objective is to convert recovered paper into a slurry of well separated fibers and other waste paper

components.

Pulping of recovered paper

The pulping operation is the first and probably the most critical operation in paper recycling.

Proper pulping is a requirement if unit operations

downstream (cleaning, screening, flotation… ) are

to be effective.

Incorrect pulping conditions can irreversibly damage fibers making them inappropriate for papermaking uses

Main Function : Disperse recovered paper into separated fibers.

Several sub-objectives that are also important :

1 Detach contaminants from fibers.

2 Mix paper with water and chemicals at the correct ratios

3 Maintain contaminants as large as possible to aid subsequent removal processes.

4 Avoid damage to the fibers (fiber cutting).

5 Removal of large debris from system.

Basic Pulping Categories : Batch vs Continuos Pulping

and chemicals are all charged at the beginning of the process and are removed all at once at the end

of the process The batch process is repeated

water and chemicals are continuously added to the pulper and at the same time, the pulped product is also being continuously removed

Basic Pulping Categories : Low vs High Consistency

Low Consistency Pulping: Typically

from 3-6 % K Produces a relatively

easily pumpable fluid The fluid is

“pourable”.

High Consistency Pulping: Typically

from 8 - 18 % K Produces a thick,

slurry that will not flow under the

influence of gravity alone.

Consistency (solids) 100 * solids wt

General Parts of a Pulper

z 1 Wastepaper feed method (conveyor).

Forces in a Pulper

These are caused when

the fast moving rotor

impacts material in the

relatively slower body of

pulp stock around it

z Faster rotor speeds

cause more intense

mechanical forces in the

pulper

Pulper Forces

z Hydraulic Forces :

z These are caused by the

motion of fluid that is caused by

the spinning rotor (not by the

direct impact of the rotors)

z When two adjacent portions of

a fluid are moving in different

directions ( or at different

speeds) a shear force is

present An example in the

picture would be at point A

A

Forces in a Pulper

z Mechanical shearing forces that

occurs between the moving

rotor and a static extraction

plate near the rotor.

z The rotor forces fiber bundles

between the rotor and extraction

plate Intense hydraulic forces

act to cut the fiber bundles and

fibers This can cause

significant damage to fibers.

z Used only for low % K pulping

because the pulp must be

screenable.