Program for North American Mobility in Higher
Education
Introducing Process Integration for Environmental
Control in Engineering Curricula
Module 3: Environmental Challenges –
Pulp & Paper Industry
Caroline Gaudreault
Created at:
École Polytechnique de Montréal &
Texas A&M University, 2003
Purpose of Module 3
What is the purpose of this module?
This module is intended to overview the
environmental challenges of the pulp & paper
industry and, more specifically, the reduction of
environmental impacts related with the kraft
pulping process.
2
Structure of the Module 3
What is the structure of this module?
Module 3 is divided into 3 “tiers”, each with a specific goal:
•
Tier 1: Basic introduction
•
Tier 2: Case study applications
•
Tier 3: Open-ended problem
These tiers are intended to be completed in order. Students are
quizzed at various points, to measure their degree of
understanding, before proceeding.
Each tier contains a statement of intent at the beginning, and a quiz
at the end.
3
LEGEND
Go to the web site
Go to next subject
More information on the same subject
Look for the answer to the question
4
Tier I:
Background Information
Tier I: Statement of Intent
Tier I: Statement of Intent
The purpose of this module is to provides a
general overview of the concepts related to
minimum impact manufacturing in the Kraft
process, and an introduction to pertinent PI
tools.
Tier 1 also includes some selected readings, to
help the student acquire a deeper
understanding of this subject.
6
Tier I: Content
Tier I is broken into three sections:
1.1 Introduction to the kraft pulping process, its
related environmental impacts and related
regulations
1.2 Introduction to minimum impact
manufacturing
1.3 Related PI tools
At the end of Tier I, there is a short multipleanswer quiz
7
1.1 Introduction to the kraft pulping
process and its related environmental
impacts and related regulations
General Description of the Kraft Pulping
Process
 The kraft process is a form of chemical pulping. This
means that, in order to degrade and dissolve away
the lignin and keep most of the cellulose and
hemicellulose, the wood chips are cooked with
appropriate chemicals in an aqueous solution at
elevated temperature and pressure. The main
challenge is to form fibers that are practically intact.
 More specifically, the kraft process involves cooking
of the chips using a solution of sodium hydroxide
(NaOH) and sodium sulfide (Na2S)
 One major characteristic of the kraft process is that
the cooking chemicals are regenerated in a recovery
process that will be discussed later.
9
Advantages and Disadvantages of Kraft
Process
Advantages:
 High strength pulp
 Utilizes proven
technology for
chemical recovery
 Handles with a wide
variety of wood
species
 Tolerates bark in the
pulping process
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Disadvantages:
 Unbleached pulp is
characterized by a
dark brown color
 It is associated
malodorous gases
(organic sulfides)
Definitions and Nomenclature (1)
Pulp
White liquor:
Liquor containing the active cooking
chemicals (NaOH and Na2S) and used to
cook chips.
Cooking
&
Washing
Black liquor:
Residual liquor from cooking containing
the reaction products of lignin
solubilization. This liquor is concentrated
and burnt into a recovery furnace and
yields an inorganic smelt of Na2CO3.
Green liquor:
Liquor obtained by dissolving the latter
smelt. The green liquor is reacted with
CaO in order to convert the Na2CO3 in
NaOH and regenerate the white liquor.
Chips
BLACK LIQUOR
Alkali lignin
Hydrolysis salts
Sulphonation
products
Evaporation
&
Burning
WHITE LIQUOR
NAOH
NA2S
GREEN LIQUOR
Na2CO3
Na2S
The kraft sodium cycle
(Source:Smook, 1994)
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Causticizing
Definitions and Nomenclature (2)
TERM
DEFINITION
UNITS
Total Alkali
Total of all viable sodium alkali compounds i.e.
NaOH + Na2S + Na2CO3 + Na2SO4 + Na2S2O3 +
Na2SO3 (does not include NaCl)
g/L as Na2O
Total Titrable Alkali (TTA)
Total NaOH + Na2S + Na2CO3
g/L as Na2O
Active Alkali (AA)
Total NaOH + Na2S
g/L as Na2O
Effective Alkali (EA)
Total NaOH + ½ Na2S
g/L as Na2O
Activity
AA / TTA ratio
Causticity
NaOH / [NaOH + Na2CO3] ratio
% (on a Na2O basis)
Sulfidity
Na2S / AA (or TTA) ratio
% (on a Na2O basis)
Causticizing Efficiency
(White liquor)
Same as causticity. (However, the concentration of
NaOH in the green liquor should be subtracted so
that the value of NaOH represents only the portion
produced by the causticizing reaction.)
% (on a Na2O basis)
Residual Alkali (Black liquor)
Alkali concentration determined by titration
Reduction Efficiency
(Green liquor)
Na2S / (soda sulfur coumpounds) ratio (often
simplified as Na2S / [Na2S + Na2SO4 ] ratio)
%
g/L as Na2O
% (on a Na2O basis)
(Source:Smook, 1994)
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Sodium vs. Calcium Cycle
13
(Adapted from European Comission IPPC, 2001)
Wood Fibers
Pulp fibers are manufactured by chemically dissolving
those wood components (mainly lignin) that keep wood
cells together to form the original wood structure by
minimizing the damages to these components.
Chemical Components of Wood
Structure of cellulose
Wood
Lignin
21% Hardwoods
25% Softwoods
Carbohydrates
45%
Cellulose
Glucose
14
2-8%
Extractive
Terpenes
Resin acids (softwood)
Fatty acids
Phenols
Unsaponifiables
Hemicellulose
35% Hardwoods
25% Softwoods
Glucose
Mannose
Galactose
Xylose
Arabinnose
Source: Smook, 1994
Overview of the Kraft Process
Chips
Digester
White liquor
storage
White liquor
clarifier
Pulp to
bleaching
Grits
Strong black
liquor storage
15
Lime
Green liquor
storage
Weak black
liquor storage
Evaporators
Slaker
Green liquor
clarifier
Contaminated
condensates
Recovering
furnace
Smelt
Dissolving tank
Water
Lime mud
washer
Weak
Liquor
storage
Lime mud
thickener
Causticizers
Blow tank
Washers
Lime
mud
Lime kiln
Water
Dregs
Dregs
Dregs
washer
Weak liquor
storage
Source: Smook, 1994
Overview of the Kraft Process
Chips
Digester
Blow tank
Washers
Weak black
liquor storage
Evaporators
Strong black
liquor storage
16
Water
Lime
The wood is mechanically debarked
and cut
Lime mud
mud
White liquor prior
White
liquor that are screened
into
chips
the chemical
washer
clarifier
storage
treatment.
Lignin and some carbohydrate materialLime
aremud
Causticizers
dissolved from wood
chips during cooking
in
thickener
aqueous solution of alkaline, neutral or acidic
componentsGrits
at elevated temperature
and
Lime
Lime kiln
Slaker
Pulp
to
pressure.
bleaching
Chips
maintain their wood structure during
chemical pulping but
this
latter is so weak that it
Green
liquor
will break down to individual
fiber by modest
storage
Water
mechanical action.
Green liquor
clarifier
Contaminated
condensates
Recovering
furnace
Smelt
Dissolving tank
Dregs
Weak
Liquor
storage
Dregs
Dregs
washer
Weak liquor
storage
Source: Smook, 1994
Overview of the Kraft Process
Chips
Water
Lime
Spent
and
Lime dissolved
mud
mud
White
liquor inorganic
White liquor Washing:
washerfrom the
clarifier
storage
organic materials
are separated
Digester
Blow tank
Pulp
Washers
Bleaching
Weak black
liquor storage
Evaporators
Strong black
liquor storage
17
Contaminated
condensates
Recovering
furnace
pulp by multistage counter-current
Weak
washing system. Spent liquor
is sent toLiquor
Lime mud
Causticizers
storage
the regeneration system. thickener
Screening: Solid impurities contained in
Grits washed pulp (mainly
Lime incompletely
the
Lime kiln
Slaker
delignified wood and knots) are separated
by screening. The rejects are
Green liquor
reprocessed.
storage
Bleaching: Depending in the intended
Water
application, pulp can be bleached. Pulp
Dregs
Green liquor Dregs
Dregs
made by
the
kraft
process
is
darker
than
clarifier
washer
the original wood. Bleaching is the
purification
process that modify colored
Smelt
Weak liquor
substance
Dissolving
so tank
they either loose
their light
storage
absorption ability or they dissolve.
Source: Smook, 1994
Overview of the Kraft Process
Chips
White liquor
storage
Digester
White liquor
clarifier
Pulp
Bleaching
Grits
Strong black
liquor storage
18
Lime
Green liquor
storage
Weak black
liquor storage
Evaporators
Slaker
In order to be used asGreen
a fuel,
kraft liquor
liquor Dregs
Contaminated
must
be evaporated in aclarifier
multistage
condensates
evaporation system.
Recovering
furnace
Smelt
Dissolving tank
Water
Lime mud
washer
Weak
Liquor
storage
Lime mud
thickener
Causticizers
Blow tank
Washers
Lime
mud
Lime kiln
Water
Dregs
Dregs
washer
Weak liquor
storage
Source: Smook, 1994
Overview of the Kraft Process
Chips
White liquor
storage
Digester
White liquor
clarifier
Causticizers
Blow tank
Pulp
Washers
Bleaching
Weak black
liquor storage
Evaporators
Strong black
liquor storage
19
Contaminated
condensates
Recovering
furnace
Lime
mud
Water
Lime mud
washer
Weak
Liquor
storage
Lime mud
thickener
The
strong black liquor
is then burned in a
Grits
Lime
Lime kiln
Slaker
recovery furnace
where inorganic
substances are converted into
regenerable
Green substances.
liquor
storage
Sodium and
sulfur salts are converted
Water to
a smelt of Na2S and Na2CO3 and brought
Dregs
Green liquor Dregs
Dregs
to a dissolved
tank
clarifier
washer
Smelt
Dissolving tank
Weak liquor
storage
Source: Smook, 1994
Overview of the Kraft Process
Chips
White liquor
storage
Digester
White liquor
clarifier
Pulp
Bleaching
Grits
Green liquor
storage
Weak black
liquor storage
Evaporators
Strong black
liquor storage
20
Slaker
Water
Lime mud
washer
Weak
Liquor
storage
Lime mud
thickener
Causticizers
Blow tank
Washers
Lime
mud
Lime
Lime kiln
Water
The smelt is dissolved
liquor
Dregs washDregs
Green liquorin weak
clarifier plant.
washer
the recausticizing
Contaminated
from
condensates
Recovering
furnace
Smelt
Dissolving tank
Dregs
Weak liquor
storage
Source: Smook, 1994
Overview of the Kraft Process
Chips
White liquor
storage
Digester
White liquor
clarifier
Pulp
Source: Smook, 1994
21
Strong black
liquor storage
Slaker
Lime
liquor
The greenGreen
liquor
is
storage
clarified.
Weak black
liquor storage
Evaporators
Grits
Bleaching
Green liquor
clarifier
Contaminated
condensates
Recovering
furnace
Smelt
Dissolving tank
Water
Lime mud
washer
Weak
Liquor
storage
Lime mud
thickener
Causticizers
Blow tank
Washers
Lime
mud
Lime kiln
Water
Dregs
Dregs
Dregs
washer
Weak liquor
storage
Source: Smook, 1994
Overview of the Kraft Process
Chips
White liquor
storage
Digester
White liquor
clarifier
Pulp
Bleaching
Grits
Slaker
Water
Lime mud
washer
Lime mud
thickener
Causticizers
Blow tank
Washers
Lime
mud
Lime
Weak
Liquor
storage
Lime kiln
Theblack
green
Weak
liquor storage
liquor is causticized withGreen
reburned
lime to form white liquor:
liquor
storage
CaO and water are reacted in a slaker
to form CaOH, which
in turn
Water
reacts with Na2CO3 in the green liquor to form NaOH and CaCO3Dregs
.
Dregs
Green liquor
Dregs
Contaminated
Evaporators
The CaCO3, which
is
insoluble,
is
separated
by
filtering
and is
clarifier
washer
condensates
washed free from sodium salts.
Smelt
Recovering
Strong
black
It is then calcinated in a lime kilnDissolving
to CaOtank
and reused.Weak liquor
furnace
storage
liquor storage
The regenared white liquor is reused in cooking.
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Source: Smook, 1994
Pollutants in the P&P Industry
What is a pollutant?
A pollutant is “a substance that can alter the natural environment”
(Springer and al., 2000).
US EPA classification of pollutants








23
Oxygen-demanding substances
Disease-causing agents
Synthetic organic compounds
Plant nutrients
Inorganic chemical and mineral substances
Sediments
Radioactive substances
Thermal discharges
Environmental Impacts of the Kraft
Process
Wood preparation
Chips
To learn about major environmental impacts of the kraft
process: Click on the yellow then pink boxes!
White liquor
clarifier
White liquor
storage
Digester
Pulp
Bleaching
Grits
Source: Smook, 1994
24
Strong black
liquor storage
Lime
Green liquor
storage
Weak black
liquor storage
Evaporators
Slaker
Green liquor
clarifier
Contaminated
condensates
Recovering
furnace
Smelt
Dissolving tank
Water
Lime mud
washer
Lime mud
thickener
Causticizers
Blow tank
Washers
Lime
mud
Weak
Liquor
storage
Lime kiln
Water
Dregs
Dregs
washer
Weak liquor
storage
Dregs
Wood Preparation
Air Pollution:
Transportation of logs,
production, screening,
transportation and storage of
chips as well as debarking
activities can result in the
emission of particulate matters.
That are extremely difficult to
measure.
Water Pollution:
Water is used for 3
purposes: log
conveyance?, log washing
and wet debarking.
For more information
Another type of fugitive
emission associated with wood
preparation activities is gaseous
such as volatile organic
compounds (VOC).
25
Return to the
flowsheet
Pulp Production
Air Pollution:
Water Pollution:
The cooking process results in
formation and releases of VOC’s
and reduced components (TRS)
that are odorous.
Wood chips are cooked in
aqueous solution.
These compounds can exit the
digester either in gaseous or liquid
form. The gas are sent to
condensers to remove water and
other condensable compounds.
For more information
The non-condensable gas are
incinerated in order to eliminate the
odorous ones.
The remainder are condensed and
used to pre-heat the chips.
26
Return to the
flowsheet
Pulp Washing, Screening and
Deknotting
27
Air Pollution:
Water Pollution:
The pulp washing, screening
and deknotting do not result in
new pollutant but volatile
compounds contained in the
pulp can escape during those
operations.
Pulp is washed to remove
pulping chemicals and soluble
wood components and diluted
with water.
For more information
Return to the
flowsheet
Bleaching:
Oxygen Delignification (OD) – Air Pollution
In OD, steam, caustic (as oxidized white liquor),
and oxygen are added to the pulp in order to
reduce the lignin content before further
bleaching. VOC’s are present in the incoming
pulp, white liquor and washer shower water and
can be released.
CO2 and CO are formed in the reactor during
the delignification.
28
Bleaching – Air Pollution
Bleaching occurs in a multistep process involving the use of
chemicals that will oxidize and dissolve the lignin. Following this
process, the cellulose and the hemicellulose will be separated from
the undesirable material. This process also involves chemical
utilization.
Traditionally, chlorine was used in the first stage of bleaching but it
was replaced by ClO2 because of the possible formation of
unwanted chlorine compounds. Use of sodium hypochlorite in the
third stage has also mostly been discontinued because of concerns
related with chloroform and AOX formation.
Exhausts gases from bleaching will contain VOC’s, unreacted
bleaching chemical, and inadvertently formed compounds. Most
VOC’s are returned to the unbleached pulp slurry. It is also
possible that ClO2 and Cl are present in small amounts in the
bleach plant gases.
CO is mostly formed in the first stage of bleaching.
29
Bleaching – Water Pollution
Different chemicals are used in a multi-stage process to
bleach the pulp. Aqueous washing is performed
between stages to remove bleaching chemicals and any
dissolved wood components extracted during bleaching.
Water is also used to prepare bleaching chemical
solutions and in air emission control scrubbers.
Because waste water from bleaching usually has a high
content in content in chlorine, it is incompatible with
chemical recovery process and it is sent directly to the
wastewater treatment.
For more information
30
Return to the
flowsheet
Chemical Recovery:
Evaporation
Air Pollution:
Water Pollution:
Following the cooking, the spent
cooking liquor referred to as weak
black liquor. This liquor is composed
of around 85% water and 15% solids
that are a complex mixture of sulfur
and sodium containing organic and
inorganic compounds.
Water from weak black liquor is
evaporated and the
condensates from the
evaporators comprise the
excess water from liquor
concentration. These
condensates can be reused in
other processes but excess
condensates are discharged to
the wastewater treatment.
During the evaporation of water,
gaseous volatile compounds can be
formed. Also, because of the
presence of sodium sulfide in Kraft
cooking liquor, TRS compounds can
be released during the evaporation.
To avoid bad odors, these gas are sent
to combustion in order to oxidize the
TRS.
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Return to the
flowsheet
The condensates can contain
high level of TRS, methanol and
acetone.
For more information
Chemical Recovery:
Recovery Furnace – Air Pollution
When the liquor has a minimum of 60% solids, it is sent in the
recovery furnace where the organic compounds are burnt and the
inorganic compounds transformed in a molten smelt.
The recovery furnace is the recovery furnace is the predominant
source of TRS emissions.
Particulates such as sodium sulfate and sodium carbonate are also
emitted by the recovery furnace. Potassium compounds and other
metals can be present in smaller quantities.
Recovery furnaces also emit SO2, NOx, CO, volatile organic
compounds and other products from incomplete combustion.
There is also a potential for SO3, H2SO4, HCL and NH3 emissions.
There are possibilities for other chlorinated compounds emissions
but in very small quantities.
32
Return to the
flowsheet
Chemical Recovery:
Dissolving and Clarification – Air Pollution
Molten smelt drains from the furnace to a tank and the
smelt is broken up with steam. The smelt particles fall
into an agitated solution of weak wash. The mixture is
called green liquor that is pumped to the clarifier where
suspended solids are removed.
Most of the emissions from the dissolving tank are TRS
and particulate matter that are similar to the ones from
the recovery furnace.
VOC and NH3 can also be released.
33
Return to the
flowsheet
Chemical Recovery:
Lime Kiln
Air Pollution:
Water Pollution
Lime mud is calcinated to form
CaO and CO2 in the lime kiln.
Water is used to wash the solid
precipitates formed in the recovery
cycle. Washing recovers sodium
and sulfur containing from green
liquor dregs and lime mud. This
weak wash is reused to dissolve
recovery furnace and the excess is
sent to the wastewater treatment.
Most of the emissions from the
lime kiln are TRS and
particulate matter.
SO2 emissions are low because
of the alkaline atmosphere in
the lime kiln.
Lime kiln can also emit NOx, CO
and VOC from incomplete
combustion.
34
For more information
Return to the
flowsheet
Chemical Recovery:
Slaker – Air Pollution
CaO from the kiln and green liquor from the
dissolving tank are mixed together to give
NaOH, CaCO3. A large amount of steam that
must be ventiled is formed.
The steam contains a lot a particulate matter
that are mostly calcium and sodium carbonates
and sulfates.
NH3 can also be formed.
35
Return to the
flowsheet
Chemical Recovery
Other Causticizing Area Equipment
Air Pollution:
Other equipment associated with the processing of
green liquor (clarifiers, storage, surge tanks and dregs
washers), white liquor (causticizers tanks, clarifiers,
pressure filters and storage tanks), and lime mud (mix
tanks, dilution tanks, storage tanks, pressure filters and
pumps) can vent to the atmosphere.
However, gas flow rates such as VOC and NH3 from
this equipment are usually very small and
concentrations low.
36
Return to the
flowsheet
Representative Bleached Kraft Mill
Water Loads
 The highest volume
of discharges comes
from the paper mill.
 The largest BOD
loads occur at the
bleach plant.
 The paper mill
process the highest
amount of TSS.
Return to Lime Killn
Return to Evaporation
Return to Pulp Production
37
Return to Bleaching
Return to Pulp Washing
Return to Wood Preparation
(Source: Springer and al., 1997)
Most Impacting Environmental
Regulations
 Legislation is one of the drivers for implementing
environmental changes and it is also recognized as a
important factor to conserve an advantage over
competitors.
 Also, there is a consensus that legislations will be
more and more stringent over the next 25 years.
 For this reason, the regulations that have the most
significant impact on the pulp and paper industry will
be described in the following slides.
 The importance of legislation as well as of other
drivers for environmental change will be described in
tier II.
38
US EPA Clean Water Act
 The Clean Water Act launched in 1977
established the basic structure for regulating
discharges of pollutants into the waters of the
United States. By this, the USEPA has the
authority to implement pollution control
programs (e.g. setting wastewater standards
for industry).
 It aims at reducing direct pollutant discharges
into waterways, finance municipal wastewater
treatment facilities, and manage polluted
runoff using regulatory and non-regulatory
tools.
39
US EPA Cluster Rule
 The US EPA Cluster Rule integrates air and water regulations.
 It was first published in 1998 and was applying to bleached
paper grade kraft, soda and paper grade sulfite mills.
 Key features of the Cluster Rule are:








40
Implementation within 3 years;
Bleach plant eflluent limitations for dioxin, chlorinated phenolics,
and chloroform;
AOX limitations;
Establishment of best management practices (BMP) for control of
spills of spent pulping liquor, turpentine and soap;
Encouragement of project XL;
No Change on BOD and TSS limits;
No limits on color, methylene chloride, or methy ethyl ketone;
No current COD limitations, but it changes in the future.
US EPA Project XL
Project XL stands for "eXcellence and Leadership” and is a US pilot program
that allows state and local governments, businesses and federal facilities to
develop with EPA innovative strategies to test better or more cost-effective
ways of achieving environmental and public health protection. Project XL has 8
selection criteria:
1. Produce superior environmental results beyond those that would have been
achieved under current and reasonably anticipated future regulations or policies;
2. Produce benefits such as cost savings, paperwork reduction, regulatory
flexibility or other types of flexibility that serve as an incentive to both project
sponsors and regulators;
3. Supported by stakeholders;
4. Achieve innovation/pollution prevention;
5. Produce lessons or data that are transferable to other facilities;
6. Demonstrate feasibility;
7. Establish accountability through agreed upon methods of monitoring, reporting,
and evaluations; and
8. Avoid shifting the risk burden, i.e., do not create worker safety or environmental
justice problems as a result of the experiment.
41
In addition, projects must present economic opportunities and incorporate community
planning.
Industrial Depollution Attestations
(Quebec)
Program for Industrial Waste Reduction:
The Program for waste reduction was launched in 1988.
Quebec Ministry of Environment has developed an
intervention strategy integrating all receiving medias.
The target industrials sectors were those whom
contaminant rejects, more specifically releases of toxic
substances had the largest impacts on local
environments.
Industrial Depollution Attestations:
The Industrial Depollution Attestation is the legal tool
that allows the ministry to operationalyze the Program
for Waste Reduction.
42
Industrial Depollution Attestations
(Quebec)
 The Industrial Depollution Attestation is a permit, renewable every
5 years, that establishes the environmental conditions under
which the industry must operate.
 The Industrial Depollution Attestation main components are:





Reject standards to respect;
Requirements related to rejects follow-up;
Other operation conditions as determined by the ministry;
Studies to perform;
Due dates and additional requirements.
 Targeted Sectors:




43
Pulp and Paper (is the only one to have completely implemented
the program to date);
Mines and Metallurgy;
Organic and Inorganic Chemistry;
Agri-food industry, wood transformation and textiles.
Integrated Pollution Prevention and
Control (IPPC) - Europe
What is the IPPC:
The IPPC is a European set of common rules on
permitting for industrial installations. The aims of the
IPPC Directive is to minimize pollution from various
point sources throughout the European Union. Permits,
based on the concept of Best Available Techniques (or
BAT), are necessary to certain industry to be able to
operate.
44
Kyoto Protocol and GHG Mitigations
Climate change is a problem which affects all countries. Many
human activities emit greenhouse gases (GHGs) to the atmosphere
( heating and cooling buildings, using energy,transportation,
industrial processes, etc.). When in contact with the sun radiations,
the GHGs act like a greenhouse's glass to block this heat from
escaping back to space increasing the earth temperature.
In1997, more than 160 countries met in Kyoto (Japan), and agreed
to targets to reduce GHG emissions. This agreement is called the
Kyoto Protocol. Canada's target is to reduce its GHG emissions to
6 percent below 1990 levels by the period between 2008 and 2012.
The Protocol will only become legally binding when it is ratified by
at least 55 countries, covering at least 55 per cent of the emissions
addressed by the Protocol. Neither USA or Mexico have ratified
the protocol. At this time (May 2004) the implementation is pending
ratification by either USA or Russia.
45
GHG Mitigations & Pulp and Paper
In 2003, the Forest Products Association
of Canada has sign an agreement with
the Canadian government concerning the
GHG emissions which includes a
commitment by the industry to reduce its
greenhouse gas (GHG) emissions
intensity by an average of 15 percent by
2008 to 2012, the first Kyoto commitment
period.
46
References

ENVIRONNEMENT QUÉBEC. 2003. Le Programme de réduction des rejets

http://www.menv.gouv.qc.ca/programmes/prri/index.htm (page consulted in
2004)
EUROPEAN COMISSION. Integrated Pollution Prevention and Control (IPPC) –





47
industriels
et
l’attestation
d’assainissement.
Reference Document on Best Available Techniques in the Pulp and Paper
Industry. 2001, 475 p.
Gullichsen, J. Fogelholm, C-J. (eds). Papermaking Science and Technology,
Chemical Pulping, Book 6A. Tappi Press, Helsinki, Finland, 2000, 693 p.
SMOOK, G.A. Handbook for pulp & paper technologists. 2nd ed. Angus Wilde
Publications, Vancouver, Canada, 1992, 419 p.
SPRINGER, Allan M. (ed.) Industrial Environmental Control – Pulp and Paper
Industry. 3rd ed. Tappi Press, Atlanta, USA, 2000, 711 p.
USEPA. 2003. Project XL. http://www.epa.gov/ProjectXL/ (page consulted in
2004)
USEPA.
2003.
Industrial
Water
Pollution
Controls.
http://www.epa.gov/OST/pulppaper/cluster.html (page consulted in 2004).
1.2 Introduction to minimum impact
manufacturing (MIM)
Content
A. MIM concepts
B. Progressive water system closure and
build-up of NPE’s
C. Zero discharge concepts
D. Tracking models for water, NPE’s, and
targeted species
E. Kraft mill energy efficiency
F. Relation between minimum energy and
minimum effluent
G. BAT concepts
H. Example of application of MIM concept
49
Content
A. MIM concepts
B. Zero discharge concepts
C. Progressive water system closure and
build-up of NPE’s
D. Tracking models for water, NPE’s, and
targeted species
E. Kraft mill energy efficiency
F. Relation between minimum energy and
minimum effluent
G. BAT concepts
H. Example of application of MIM concept
50
Weyerhaeuser’s Vision of MIM
Minimum impact manufacturing (MIM) concept
has first been introduced by Weyerhaeuser:
“Using a Minimum Impact Manufacturing strategy,
Weyerhaeuser directs its efforts to manufacturing
quality products with minimal environmental impact and
maximum return to shareholders. The strategy works to
prevent pollution by continuously reducing process
byproducts and finding ways to capture, reuse or
recycle them.”
(Weyerhaeuser website, 2004)
51
Weyerhaeuser’s Vision of MIM
For a production facility MIM includes Weyerhaeuser's
commitment to strive to close the loop by further:
Optimizing raw materials used at the mill level
Reducing water usage
Minimizing fossil fuel for energy in manufacturing
Reducing/eliminating hazardous waste
Generating less solid waste
Reducing emissions to all media
Eliminating spills
Reusing and recycling from our mills the materials and residuals
that previously went to landfills
Collecting and recycling used waste paper for use as a raw
material
(Weyerhaeuser website, 2004)
52
Goals of MIM
Minimum Impact Manufacturing aims to:
 Eliminate process issues before they become
environmental problems.
 Address multiple environmental areas,
including air and water quality, solid and
hazardous waste minimization and more.
 Use science and economics to focus on
pollution prevention at the source rather than
end-of-pipe remedies.
(Weyerhaeuser website, 2004)
53
Environmental Hiearchy of Needs
Completion of the
Forest products cycle
Energy, odor, color,
biodiversity, etc.
Resource depletion
acute toxicity,
raw effluent,
etc.
54
Minimum
Impact
Subtle, Complex, Aesthetic
Chronic toxicity,
bioaccumulation,
etc.
Chronic and/or Long-Term Effects
Acute Impacts on the environment
Source: Erickson, Zacher and Decrease, 1996
Key Environmental Parameter
Related to MIM
55
Water
Air
 Water Usage
 Bleach Plant
Effluent Volume
 Final Effluent
Volume
 BOD
 COD
 TSS
 Effluent AOX
 Dioxin
 Color
 Chronic Toxicity
 Nutrients
Particulate
TRS
Methanol
Chloroform
Chlorine
Chlorine
Dioxide
CO/CO2
NOx
SO2
VOCs
Opacity
HAPS
Solid Waste
Solid Waste Generated
Solid Waste
Disposition:
- Landfill
- Recycled
- Energy
Reduction
Plans/Achievements
Hazardous Waste
Elimination
Other
Accidental Releases
 Non-Compliant Events
SARA 313 Releases
Energy Use/Energy
Exports
Aesthetics:
- Site Appearance
- Odor
- Noise
Improvement Projects
Chemical Management
Key Environmental
Accomplishments
Content
A. MIM concepts
B. Zero discharge concepts
C. Progressive water system closure and
build-up of NPE’s
D. Tracking models for water, NPE’s, and
targeted species
E. Kraft mill energy efficiency
F. Relation between minimum energy and
minimum effluent
G. BAT concepts
H. Example of application of MIM concept
56
Goal of Process Closure
The goal of process closure with respect
to effluent discharges is to minimize the
amount of waste generated. This can be
accomplished by:



Using more efficient processes;
Using processes that do not require water;
Recovering the waste materials.
(Source, NCASI, 2003)
57
Rapson-Reeve Process
 In 1967 Rapson proposed a bleached kraft pulp
manufacturing process that had the potential to
greatly reduce, if not eliminate, effluent discharges.
 The idea was based on a collection of technologies,
including incresed use of chlorine dioxide for
bleaching and a process for generating this chemical
that could be fully integrated with the chemical
requirements of the kraft pulping and bleaching
processes.
 The driver for this process was a cost effective
alternative to the biological effluent treatment.
 The process was implemented by the Great Lakes
Paper mill in Thunder Bay, but abandoned.
58
Rapson-Reeve Process
The original effluent-free mill concept was based on the
following ideas:





59
Replace 70-80% of the chlorine in the chlorination stage with
an equivalent amount of chlorine dioxide.
Use a new chlorine dioxide generating process.
Use countercurrent washing in bleach plant, using
wastewater from the wet end of the pulp dryer or paper
machine to minimize de volume of filtrate to be recovered.
Use a portion of the bleaching filtrate to wash the
unbleached filtrate, allowing the dissolved from bleaching to
be recovered via evaporation and burning.
Use the remainder of the bleaching filtrate to wash the lime
mud and green liquor dregs and to dissolve the smelt from
the recovery furnace.
Rapson Reeve Process
Effluent-free concept (Cont’d):



60
Treat the evaporator condensates with a small amount of
chlorine dioxide to oxidize the foul-smelling compounds and
use the oxidized condensates in place of fresh water on the
wet end of the pulp dryer or paper machine.
Remove the sodium chloride from the liquor cycle by
extracting it from the recovery furnace flue gas in the
electrostatic precipitator. A portion of the extract would be
used to generate chlorine dioxide for the bleach plant and
the remainder would be discarded.
Establish closed water systems for wood debarking, pulp
screening, and cleaning.
Main Problems in Making a Mill EffluentFree
 Non-process elements can accumulate.
 Pulp quality can be affected.
 About one quarter of the water pollution in bleached pulp mills
comes from spills and wash-up and are not well controlled.
 Calcium trap: when there is any acid stage in the bleaching
sequence (ozone), calcium carbonate will travel with the pulp in
neutral or alkaline stages, but dissolve in acid stages. If
countercurrent washing is used, the calcium will be precipitated into
the pulp in any previous alkaline stage and carried forward to be redissolved in acid stage.
 In order to obtain the appropriated displacement ratio and purge for
each stage, the flow of filtrate in and out must be precisely
balanced.
 In order to minimize the consumption of oxidizing agent in
subsequent stages throught incomplete washing, the concentration
of organic matter in each filtrate must be carefully controlled.
61
Process Closure Technologies
Definition:
Process closure technologies can be defined as
those which effect or enable the reduction of
waterborne wastes from pulp manufacturing
facilities. They serve to divert wood
components and other raw materials from liquid
waste streams by prevention, reuse, or
recovery.
These technologies were largely driven by the
desire to limit the discharge of chlorinated
organic compounds.
62
Zero Discharge Concept
 For a majority of pulp mills zero-effluent discharge is
impracticable.
 Currently, zero effluent operation appears to be
restricted to plants producing bleached chemical
thermal mechanical pulp and non-chlorine bleaching
agents.
 Since the bleach plant is the major source of
contaminated effluent in a kraft pulp mill, the closure
of these circuits is an essential prerequisite for
producing a zero-effluent kraft mill.
 This requires the simultaneous resolution of a
number of problems:

63
water balance, chemicals balance, corrosion, precipitation of
salts and removal of non-product substances.
Low Effluent Kraft Mill Examples
Newest Mills of America
The 3 newest mills of America were designed to
be highly economical and environmentally
performing using high capacity, single line
facilities, and employing modern technology for
pulp production and effluent treatment. None of
these mills practices recovery of bleaching
wastewaters but their effluent quality is among
the best in the world. These mills are:



64
Bahia Sul, Brazil;
Alabama Pine Pulp, USA;
Alberta-Pacific, Canada.
Low Effluent Kraft Mill Examples
Mill Practicing Recovery of Bleaching Filtrates
Linerboard mills:



65
AssiDomän Frövi, Swenden;
Kappa Kraftliner (formerly AssiDomän)
Piteå, Sweden;
SCA Munksund, Sweden.
Low Effluent Kraft Mill Examples
Mill Practicing Recovery of Bleaching Filtrates
Bleached papergrade kraft mills:










66
Blue Ridge Paper Products – Canton, North Carolina, U.S.A.
International Paper Company – Franklin, Virginia, U.S.A.
Aspa Bruk – Smurfit Munksjö, Sweden
M-Real Sverige AB – Husum, Sweden
SCA Pulp AB – Östrand, Sweden
Södra Cell – Mörrum, Sweden
Södra Cell – Värö Bruk, Sweden
Stora Enso – Skoghall, Sweden
Metsä-Botnia – Rauma, Finland
UPM-Kymmene Wisaforest – Pietarsaari, Finland
Content
A. MIM concepts
B. Zero discharge concepts
C. Progressive water system closure and
build-up of NPE’s
D. Tracking models for water, NPE’s, and
targeted species
E. Kraft mill energy efficiency
F. Relation between minimum energy and
minimum effluent
G. BAT concepts
H. Example of application of MIM concept
67
Progressive Water System Closure
Conventional methods to achieve water closure are simple and
include:










Using counter-current washing in pulping and bleaching operations;
Closing brownstock screen room;
Using dry debarking;
Using evaporator condensate for brownstock washing;
Recycling excess whitewater from paper machine to bleach plant;
Reusing stripped condensates from steam stripping of foul
condensates;
Using equipment and process that require less water;
Using cooling towers for vacuum pump seal water an non-contact
cooling water;
Using first bleach stage washer/filtrate to dilute brown high-density
stock;
Recycle/reuse secondary and/or tertiary treated effluent;
Applicating changes to pulping and bleaching practices will further
strive to the closure.
68
Non Process Elements (NPEs)
 NPEs are materials such as potassium (K),
phosphorus (P), manganese (Mn),
magnesium (Mg), iron (Fe), aluminium (Al),
silicon (Si), calcium (Ca), barium (Ba), and
chlorine (Cl) that enter the chemical pulping
process with the wood, water and chemicals.
 When we decrease fresh water consumption,
there is a potential for increasing the
concentration of some troublesome
substances and more specifically NPEs.
69
NPEs Consequences
 NPEs accumulate in the sodium and calcium cycle in
kraft process potentially causing the following
consequences:









70
Corrosion of the recovery boiler and other equipment;
Deposits on the boiler tubes that reduce heat transfer;
Scale in the digester, evaporators, and heat exchangers;
Blinding of white liquor and lime mud filters;
Reduced reburned lime reactivity;
Ring formation in the lime kiln;
Increased dust formation in the lime kiln;
Increased chemical consumption in bleaching;
Reduced effectiveness of ozone and peroxide bleaching.
NPEs Classification
There are to catogories of NPEs:
1. NPEs that form insoluble metal hydroxides
or carbonates and are removed from the
sodium cycle with the dregs and grits:
mostly Ca, Mg, Mn and Si.
2. NPEs that form soluble compounds in
alkaline solution: mostly Al, Cl, and K.
71
Build-up of NPEs
 In an « open » mill the presence of NPEs is not
importance since they are purged outside the system.
 When progressively closing mill, many outlets are not
available anymore. The consequence of this is the
build-up of NPEs.
 NPEs have a tendency to accumulate in eighter the
sodium or calcium cycle in the following way:
Sodium Cycle: K > Cl > Al > Fe > Si > Mn > Mg > Ca
Calcium Cycle: Mg > Al > Fe > Mn > Si > Na > K > S > Cl
 The most troublesome NPEs are K, Cl and Na. Na is
the most tricky because it is a process and nonprocess element at the same time.
72
Content
A. MIM concepts
B. Progressive water system closure and
build-up of NPE’s
C. Zero discharge concepts
D. Tracking models for water, NPE’s, and
targeted species
E. Kraft mill energy efficiency
F. Relation between minimum energy and
minimum effluent
G. BAT concepts
H. Example of application of MIM concept
73
Tracking Models for Water, NPE’s, and
Targeted Species
Path diagram equation:
It is a mass integration tool whose objective is to track
targeted species (e.g., NPEs and water) as they
propagate throughout the process and provides the
right level of details to be incorporated into a mass
integration analysis.
A typical form of the path equations is to describe outlet
flows and compositions from each critical unit as a
function of inlet flow, inlet compositions, and appropriate
design and operating parameters.
Steps for analysis will be described in the following
slides.
74
Main Characteristic of the Path Diagram
Equation
In order to optimize water allocation in a pulping process, two
important activities can be used together: mass integration and
process simulation. Mass integration techniques handle process
objectives, data, requirements and constraints. It will allow to fix
performance targets, solution strategies, and proposed changes to
the process.
P roc es s
Because of these changes,
the performance must be
reassessed using process
analysis or simulation. The
use of process simulation
enables the update of
flowrates and compositions
throughout the process
75
(Source: Lovelady, 2001)
O b jec tiv es , D a ta ,
a n d C o ns traints
P roc es s m o d ific ations ,
s truc tu ra l c ha ng es ,
P ro ce ss
In teg ra tion
P ro ce ss
S im ula tion
In p u t-o u tpu t
re la tion s,n e w
p ro ce ss
p e rfo rm a nc e
P e rfo rm an ce ta rg e ts,
S olu tio ns, S tra te gies ,
a n d Ins igh ts ,
Learn more about
simulation
Learn more about
Mass integration
1. Degrees of Freedom
NV = NS x NC
F= NV - NE = NC (NS - 1)
F: degrees of freedom
NV: number of variables
NE: number of equations
NC: number of targeted species
NS: number of outlet streams
Assumptions:
All inlets to a unit are known
and it is desired to determine
the outputs of the unit.
F must provided as additional
modeling equations,
assumptions, measurements, or
data in order to have an
appropriately specified
(determined) set of equations
that is solvable.
Outlet streams
Nstreams out
Inlet stream
(Fresh inputs or outlets from other units)
Unit U
76
2. Mixer-Splitter Model
The mixer-splitter model is a modeling technique
which relies on nominal data .
The nominal data are those for the plant prior to any
changes and can be obtained via simulation,
fundamental modeling, direct measurements, or
literature data.
There are various of the mixer splitter model:



Fixed split model;
Flow ratio model ;
Species ratio model.
Based on the knowledge of the process, choices can
be made for the selected model and streams/species.
Path equations can be developed for water and
targeted NPEs throughout the process.
77
Fixed Split Models
 The fixed split model adopts a certain split for
the flows of the various streams leaving the
unit.
 This model is useful in predicting flows out of
many units, particularly separators.
αF
F
78
Fixed Split
Model
(1-α)F
Flow Ratio Model
 The ratio model, relates certain streams or
components via fixed ratios.
 The flow ratio model assumes that inlet and
outlet flows of certain streams maintain a
certain ratio.
F
Flow Ratio
Model
G2 = G1 x F2
F1
79
G
Species Ratio Model
 The species ratio model is another form of the ratio
model.
 It assumes relationship between certain species
within the same stream via fixed ratios.
 This is particularly useful when one component can
be accurately tracked while another one cannot.
F
Flow Ratio
Model
B2 = A2 x (β/α )
80
Specy A = α
Specy B = β
Content
A. MIM concepts
B. Progressive water system closure and
build-up of NPE’s
C. Zero discharge concepts
D. Tracking models for water, NPE’s, and
targeted species
E. Kraft mill energy efficiency
F. Relation between minimum energy and
minimum effluent
G. BAT concepts
H. Example of application of MIM concept
81
Energy in Kraft Mill
 Kraft mills are usually partly energy
sufficient:



82
They generate power using sources such
as wood wastes and spent pulping liquor.
This is very important since CO2 emissions
from renewable sources are not included in
the greenhouse gases inventory
considered under the Kyoto protocol.
The emergence of new technologies will
allow the kraft mill to be essentially energysufficient in the future.
Kraft Mill Energy Efficiency
To maximize operating profit a mill requires the
following technologies:




83
Since black liquor is the largest source of energy in a kraft
mill, it is important to use it in an efficient way. A higher
solids content will result in more steam produced and less
heat going to recovery stack as water vapor.
Pulping yield must be increased using new cooking
technologies with reduced energy consumption.
Washing and screening must be runned at higher
consistencies and their performance must be increased in
order to reduce the water necessary to wash the pulp.
For improved steam economies and evaporation to high
solids levels with scaling, modern evaporators with heat
treatment can be used.
Kraft Mill Energy Efficiency
To maximize operating profit a mill requires the
following technologies:



New kiln technology with large precoat filters, flash dryers,
product coolers and better insulating brick will reduce lost of
heat.
Screening and conditioning of chips will reduce fines
generation and improve digester yield.
Others:




84
Economies of scale are important in terms of energy
consumption;
Using less water will generally reduce heating requirements;
Efficient mill layout will reduce friction loss associated with long
piping;
Etc.
Content
A. MIM concepts
B. Progressive water system closure and
build-up of NPE’s
C. Zero discharge concepts
D. Tracking models for water, NPE’s, and
targeted species
E. Kraft mill energy efficiency
F. Relation between minimum energy and
minimum effluent
G. BAT concepts
H. Example of application of MIM concept
85
Effect of Water Closure on Energy
 Effect of reducing water usage on energy
flows are strong and complex.
 This leads to complex process designs and
an increasing need for systematic and
system-oriented analysis of energy and water
use in the mills.
 On of the challenge is to deal with excess
heat that increases the temperature of
process streams and effluent.
 Process integration can be an useful tool to
understand this can of problems.
86
Content
A. MIM concepts
B. Progressive water system closure and
build-up of NPE’s
C. Zero discharge concepts
D. Tracking models for water, NPE’s, and
targeted species
E. Kraft mill energy efficiency
F. Relation between minimum energy and
minimum effluent
G. BAT concepts
H. Example of application of MIM concept
87
BAT Concept
(Source: European IPPC)
BAT: Best Available Technology economically achievable
Key characteristics of BATs:
 There is no single reference of best available techniques in pulp
and paper industry. In contrast, the list of techniques to consider in
the determination of BAT provides a lot of different options of an
overall BAT for given mills, which may be combined in different
ways.
 The BAT-concept is process-related because the environmental
impact is caused on this level i.e. by different manufacturing
processes as for instance cooking, bleaching, de-inking, coating etc.
The single processes, the raw materials used and the product
properties to be achieved determine the emission of a mill. That
means when approaching the pulp and paper industry different
types of raw materials used and processes involved have to be
distinguished.
88
BAT Concept
(Source: European IPPC)
Key characteristics of BATs (Cont’d):
 As pulp and paper products are highly diverse and utilized
processes even for one and the same product may vary greatly,
many factors of production technology must be taken into account
to guarantee a high level of environmental protection. For the pulp
and paper industry the best available techniques cannot be defined
solely by describing unit processes. Instead, the whole installations
must be examined and dealt with as entities. BAT in pulp and paper
industry is linked to the environmental performance of mills.
 There are different options for suitable combinations of processes
depending - besides other things - on the product properties to be
achieved. As a consequence, the process-oriented approach has to
be extended by a product-oriented concept i.e. the BAT approach
must be linked to the environmental performance of specific types of
mills where specific products are manufactured. Thus, in this
document best available techniques are presented for major mill
classes separately.
89
BAT - Remark
The following programs are based on BAT:
 USEPA Cluster Rules;
 European IPPC.
90
Content
A. MIM concepts
B. Progressive water system closure and
build-up of NPE’s
C. Zero discharge concepts
D. Tracking models for water, NPE’s, and
targeted species
E. Kraft mill energy efficiency
F. Relation between minimum energy and
minimum effluent
G. BAT concepts
H. Example of application of MIM concept
91
Application of MIM Concepts:
The Flint River Case Study
Description of the mill
 Flint River is a Kraft pulp mill located in Georgia,
USA.
 It is producing 320 000 tons per year of fluff pulp.
 Flint River Operations' environmental performance
has been recognized as superior within the bleached
Kraft pulping industry.
 Flint River was the first bleached Kraft pulp mill to
employ commercially viable advanced technologies
that minimize adverse impacts to the environment
such as oxygen delignification, 100% chlorine dioxide
substitution and bleaching and extensive water
conservation practices.
92
Application of MIM Concepts:
The Flint River Case Study
Weyerhaeuser Project XL:
Weyerhaeuser Company's pulp manufacturing facility in
Oglethorpe, Georgia, is striving to minimize the
environmental impact of its manufacturing processes on
the Flint River and surrounding environment by
pursuing a long-term vision of a Minimum
(environmental) Impact Mill. Weyerhaeuser Company is
taking immediate steps by decreasing water use and
meeting or exceeding all regulatory targets. EPA and
the State of Georgia have agreed to propose changes
in the rules to support minimum impact manufacturing.
The Final Project Agreement was signed on January
17, 1997.
93
Application of MIM Concepts:
The Flint River Case Study
MIM phases at Flint River
 MIM Phase I (1979-1980)

Original Facility Design





Oxygen Delignification
Extensive Water Recycle / Reuse
Chlorine/Chlorine Dioxide Bleaching
Air Emissions / Low Odor / BACT/ NSPS
Extensive Wastewater Treatment
 MIM Phase II (1981-1985)




94
River & Lake Environmental Studies
Holding Pond Addition / Delta Color Management
Process Reliability I (Rate/Surge)
Spill Containment & Liquor Best Management Practices
Application of MIM Concepts:
The Flint River Case Study
MIM phases at Flint River
 MIM Phase III (1986-1995)





Process Reliability II (Statistical Process Control)
Elimination Of Molecular Chlorine
Bleach Plant & Chemical Generator Collection
Emergency Response Team (Fire/Hazmat/EMT/Confined Space)
ISO 9000 Certification
 MIM Phase IV (1996-1997)




95
Isothermal Cooking
Odor Control System Upgrade
Energy Steam Reductions
ISO 14001 Environmental Management System (EMS)
Application of MIM Concepts:
The Flint River Case Study
MIM phases at Flint River
 MIM Phase V






Bleach Plant Effluent Reductions
Solid Waste Reductions
Timberland Resource Strategies
Water Use Reduction
Energy Conservation
Hazardous Air Pollutant (HAP) Emission Reductions
MIM Phase VI:

96
Life Cycle Inventory
References


EUROPEAN COMISSION. Integrated Pollution Prevention and Control
(IPPC) – Reference Document on Best Available Techniques in the Pulp and
Paper Industry. 2001, 475 p.
LOVELADY, EVA M. An Integrated Approach to the Optimization of Water
Usage and Discharge in Pulp and Paper Plants. Auburn University, USA,
2002, 185 p.





97
Minimum
Impact
Manufacturing.
1996
International
Environmental
Conference & Exhibits. 1996, p.623-628.
NCASI. Pulp Mill Process Closure: A Review of Global Technology
Developments and Mill Experiences in the 1990s. Technical Bulletin No. 860,
May 2003, 108 p.
PAPRICAN. Energy cost reduction in the pulp and paper industry. Pointe
Claire, QC, Canada : Pulp and Paper Research Institute of Canada, 1999.
USEPA.
Project
XL
–
Weyerhaeuser
Company.
http://www.epa.gov/projectxl/weyer/index.htm (page consulted in 2004).
WEYERHAEUSER.
2001.
Minimum
Impact
Manufacturing.
http://www.weyerhaeuser.com/environment/reducingpollution/minimumimpact
mfg.asp (page consulted in 2004)
1.3 Related PI Tools
Content
 Process Simulation
 Process Integration
 Mass Integration
 Energy Integration
 LCA
 Integrating these tools to address MIM
99
Content
 Process Simulation
 Mass Integration
 Energy Integration
 LCA
 Integrating these tools to address MIM
100
What is a Model? A Simulation?
 A model is an abstraction of a process
operation used to build, change, improve or
control that process.
 Models are useful for:





Equipment design, sizing, selection
Comparison of possible configurations
Evaluation of process performance against limits
(e.g. concentrations, effluent discharge rates, …)
Debottlenecking and optimization
Control strategy development and evaluation
 Simulation involves performing a series of
experiments with a process model.
101
Return to Path
Diagram Equation
Benefits of Simulation
 Better understanding of the process
 Consistent set of typical mill data
 Objective comparative evaluation of
options for ROI etc.
 Identification of bottlenecks, instabilities
etc.
 Perform many experiments cheaply
once model built
 Avoid implementing ineffective solutions
102
Return to Path
Diagram Equation
Models Are Only an Approximation of the
Reality
There is many type of
models:




103
Physical (e.g. mimic
panel) vs.
mathematical
Quantitative vs.
qualitative
First principles vs.
empirical
Steady state vs.
dynamic
Type and level of precision
of a model will depend on
many factors such as:





Phenomena represented
Level of detail and
granularity
Assumptions
Kind of input required
Functions performed


(constraint satisfaction?
optimization? …)
Nature of output generated
Return to Path
Diagram Equation
Content
 Process Simulation
 Process Integration
 Mass Integration
 Energy Integration
 LCA
 Integrating these tools to address MIM
104
Process Integration
Definitions:
 “Process integration is a holistic approach to
process design, retrofitting, and operation
which emphasizes the unity of the process.”
(El-Halwagi, 1997)
 “The holistic analysis of processes involving
the following elements:



105
Process data;
Systems and tools;
Process engineering principles and in dept
process sector knowledge.”(Stuart, 2002)
Content
 Process Simulation
 Process Integration
 Mass Integration
 Energy Integration
 LCA
 Integrating these tools to address MIM
106
Mass Integration
Definition:
“Systematic methodology that provides a fundamental
understanding of global flows of mass within the
process and employs this holistic understanding in
identifying performance targets and optimizing the
generation and routing of species throughout the
process” (El-Halwagi, 1997)
Pollution prevention is one of the most important
objectives of mass integration!
107
Return to Path
Diagram Equation
Principles of Mass Integration
 Mass integration is based on chemical engineering principles
combined with system analysis.
 Mass flow must be represented from a species viewpoint:




For each targeted species, there are sources (streams that carry
the substances) and sinks (reactors, heaters/coolers, etc.).
Streams living the sinks become sources.
The sinks can be generator of targeted species.
Each sink/generator can be manipulated through design or their
operations can be changed in order to affect the flow rate and
composition of what each sink/generator accepts as discharges.
 Sources are generally prepared for sinks through segregation
and separation via waste interception network.
 Effective pollution prevention can be reached by combination of
stream segragation, mixing, interception, recycle from sources
to sinks and sink/generator manipulations.
108
Return to Path
Diagram Equation
Segregation, Recycle, Interception
and Sink/Generator Manipulation
 Segregation: Avoiding the
mixing of the streams.
 Recycle: Utilization of pollutantladen stream (a source) in a
process unit (a sink).
 Interception: Utilization of
separation unit operation to
adjust the composition of the
pollution-laden streams to
make them acceptable for
sinks.
 Sink/Generator manipulation:
Design or operation of changes
that alter the flowrate or
composition of pollutant-laden
streams entering or leaving the
process units.
109
Sources
Return to Path
Diagram Equation
Mass and Energy-Separating
Segregated
Sinks/
Agents In
Sources
Generators
Sources
(back to
process)
1
2
Waste
Interception
Network
Nsink
Mass and Energy-Separating
Agents Out
(To Regeneration and Recycle)
Source: El-Halwagi, 1997
Content
 Process Simulation
 Process Integration
 Mass Integration
 Energy Integration
 LCA
 Integrating these tools to address MIM
110
Energy Integration
Definition:
“Systematic methodology that provides a fundamental
understanding of energy utilization within the process
and employs this understanding in identifying energy
targets and optimizing heat-recovery and energy-utility
systems” (El-Halwagi, 1997)
Energy integration tool:
Thermal-pinch techniques are based on thermodynamic
principles and are used, among others, to identify
minimum heating and cooling utility requirements.
111
Principles of Thermal Pinch
Reduction
of Utilities
Hot
Utility
Cold
Utility
Utility
costs
decrease
$
Internal
Exchanges
Trade-off
PROCESS
Costs related to
exchange area
increase
Trade-off
From 100% utilies… … toward 100% internal exchanges
112
Composite Curves
Definition:
Composite Curves consist of temperature-enthalpy (T-H) profiles of
heat availability in the process (the “hot composite curve”) and heat
demands in the process (the “cold composite curve”) together in a
graphical representation.
113
Grand Composite Curve
The grand composite curve is the tool that is used for
setting multiple utility targets.
T
Qh
Heat transfer
intra process
Pinch Point
Qc
114
H
Grand Composite Curve
Example of Application
T
HP
LP
Reduction of high pressure
steam (HP) by using a source
of energy of lower quality
(LP)
H
115
Heat Exchanger Network Design
Key Steps
Heat and Mass Balances
1.
Data Extraction
2. Analysis
 Targeting
 Process Modifications
 Utility Selection
PINCH
ANALYSIS
3.
4.
116
Design
Process
Simulation
Total Site
Analysis
Selection of Alternatives
5.
Project Detailling
Source: Linnhoff March,1998
Content
 Process Simulation
 Process Integration
 Mass Integration
 Energy Integration
 LCA
 Integrating these tools to address MIM
117
What is LCA
Definitions:
 A systematic set of procedures for compiling and examining the
inputs and outputs of materials and energy and the associated
environmental impacts directly attributable to the functioning of a
product or service system throughout its life cycle.” (Source: ISO
14040: Life cycle assessment – principles and framework, 1998)
 "Life Cycle Assessment is a process to evaluate the environmental
burdens associated with a product, process, or activity by
identifying and quantifying energy and materials used and wastes
released to the environment; to assess the impact of those energy
and materials used and releases to the environment; and to identify
and evaluate opportunities to affect environmental improvements.
The assessment includes the entire life cycle of the product,
process or activity, encompassing, extracting and processing raw
materials; manufacturing, transportation and distribution; use, reuse, maintenance; recycling, and final disposal". (Source: Guidelines
118
for Life-Cycle Assessment: A 'Code of Practice', SETAC, Brussels, 1993 )
Example
Life Cycle of Newspaper
Wood
Allocated out of the System
Aspen
Waste paper
Management
Forestry
Spruce
Steam
Generation
Hog fuel
Sawmill
Lumber
Allocated
out of the
system
Waste
paper
Chips
TMP
Electricity
Production
Municipal
Landfill
Fuel
Production
Air emissions
DIP
Chemical
Production
Wastewater
Papermaking
Water
Newsprint
Writing
Newspaper
Use phase
119
Solid wastes
Effluent
Treatment
Sludge
Treatment
Landfill
Industrial
Transportation
LCA Methodology
Applications:
Goal and
Scope
Definition
Interpretation
Invetory
Analysis
Impact
Assessment
For more information on each LCA methodology
steps, click on the corresponding box.
120
Development and
improvement of products
Strategic planning
Public policy
development
Marketing
Others
Other tools:
Technical
Economic
Market
Social
etc
Limitations
Goal and Scope Definition
The goal of an LCA study shall
unambiguously state the intended
application, the reasons for carrying out
the study and the intended audience, i.e.
to whom the results of the study are
intended to be communicated.
121
Goal and Scope Definition
The scope of the LCA consists in:







the functions of the product
system, or, in the case of
comparative studies, the
systems ;
the functional unit ;
the product system to be
studied ;
the product system
boundaries ;
allocation procedures ;
data requirements ;
assumptions ;
 types of impact and
methodology of impact
assessment, and
subsequent interpretation to
be used ;
 limitations ;
 initial data quality
requirements ;
 type of critical review, if any ;
 type and format of the report
required for the study.
Goal and
Scope
Definition
Interpretation
Invetory
Analysis
122
Impact
Assessment
Function
Definition:
Service supplied by a system of product or a process
unit.
Examples:
System
Possible
functions
123
Paper Recycling
Cogeneration
 Waste paper valorisation
 Electricity generation
 Deinked pulp production
 Steam production
 Etc.
 Etc.
Return to
the scope
Functional Unit
Definition:
« Quantified performance of a product system for use as a
reference unit in a life cycle assessment study »
Examples:
System
124
Paper Recycling
Cogeneration
Possible
functions
 Waste paper valorisation
 Deinked pulp production
 Etc.
 Electricity generation
 Steam production
 Etc.
Related
functional unit
 Recuperation of 1000 kg of
waste paper
 Production of 1 ton of
deinked pulp
 Etc.
 Generation of 1MW of
electricity
 Production of 300000 of
steam by hour at 125oC
and 0.3 MPa
 Etc.
Return to
the scope
Product System
Environment
Elementary flow
Unit process
A
Elementary flow
Intermediate flow
Elementary flow
Definition:
« Collection of
materially and
energetically connected
unit processes which
performs one or more
defined functions »
125
Unit process
B
Elementary flow
Intermediate flow
Elementary flow
Unit process
C
Elementary flow
Product flow
Environment
Return to
the scope
System Boundaries
Environment
System boundaries
Elementary flow
Unit process
A
Elementary flow
Intermediate flow
Elementary flow
Definition:
« Interface between a
product system and the
environment or other
product systems »
Unit process
B
Elementary flow
Intermediate flow
Elementary flow
Unit process
C
Elementary flow
Product flow
126
Environment
Return to
the scope
Allocation




127
Most industrial processes comprise more that one output
product, and raw material inputs include intermediate products.
These processes are multifunctional.
In LCA terms, this means that the product system under
system provides more functions than the one related to the
functional unit. A decision will have to be taken in order to
decide how to split flows and environmental intervention
between these functions. This is allocation: “partitioning the
input or output flows of a unit process to the product system
under study”
The allocation procedures must respect the mass conservation
rules.
The production of by-products as well as the open loop
recycling are two common situations implicating allocation.
By-Products
Definition:
A by-product can be defined as an output which is
neither the primary product neither a waste.
Example:
Suppose you have a system with primary function to
produce paper. In this system, you have a unit process
which is wood sawing and which results in two
products, chips and lumber. Only chips will be used in
the wood manufacturing, lumber will be sent out of the
system and use in another one. So, in the system
which has as main funtion to produce paper, lumber is a
by-product.
128
Open vs. Close-Loop Recycling
Close-loop recycling:
Raw Material
The product is reused in the
same product system to produce
the same product.

Production
Recycling
Use
No allocation required!
Disposal
Close-loop recycling:
Recycling of one product from on
system to another.

129
Allocation of environmental
impacts and credits of recycling
will have to be allocated between
both system.
Return to
the scope
Raw Material
(product 1)
Raw Material
(product 2)
Production
(product 1)
Production
(product 2)
Recycling
Use
(produit 1)
Use
(produit 2)
Disposal
(product 1)
Disposal
(product 2)
Inventory Analysis
Definition:
“Phase of life
cycle assessment
involving the
compilation and
quantification of
inputs and
outputs, for a
given product
system
throughout its life
cycle”
Goal and
Scope
Definition
Interpretation
130
(Source: ISO 14041)
Invetory
Analysis
Impact
Assessment
Life Cycle Impact Assessment
Definition:
“Phase of life cycle assessment aimed at understanding and
evaluating the magnitude and significance of the potential
environmental impacts of a product system”
(Source: ISO 14042)
131
From Inventory to Impact
Assessment
Impact
Inventory
Production
Processes
Energy
Production
Waste
Disposal &
Management
Transport
Emissions:
CFC
Pb
Cd
HAP
COV
DDT
CO2
SO2
NOX
P
Dust
Etc.
Resource Depletion
Resource
Depletion
Global Warming
Ozone Depletion
Ecotoxicology
Human Health
Smog
Acidification
Eutrophication
Etc…
Mortality and
Diceases
Agregated Indicator
Resource Depletion
Ecosystem
Depletion
Aesthical
Value
Solid Wastes
Solid
Wastes
Problem Approach
“Midpoint”
Damage Approach
“Endpoint”
Solid wastes
132
PRECISION
Goal and
Scope
Definition
Interpretation
Invetory
Analysis
Impact
Assessment
Interpretation
Definition:
“Phase of life cycle assessment in which the findings of either the
inventory analysis or the impact assessment, or both, are combined
consistent with the defined goal and scope in order to reach
conclusions and recommendations”
LCA FRAMEWORK
INTERPRÉTATION
GOAL &
SCOPE
LCI
LCIA
1. Significant points
identification
2. Verification by:
- Completeness check
- Sensibility check
- Coherence check
- Others
Conclusions
Recommendations
Reports
Goal and
Scope
Definition
Interpretation
Invetory
Analysis
133
(Source: ISO 14043)
Applications
Impact
Assessment
LCA Main Limitations




Site-specific impact are not well considered
Steady-state approach
Linear modeling
Based on a number of technical assumptions
and value choices for instance:




Impact categories
Characterization models
System boundaries
Weighting of impacts
 Availability and reliability of data and models
134
Content
 Process Simulation
 Process Integration
 Mass Integration
 Energy Integration
 LCA
 Integrating these tools to address MIM
135
In Summary
 Minimum Impact Manufacturing aims at minimizing:



Resource consumption
Energy consumption
Environmental impact (soil, air and water emissions)
 Simulation are useful to better understand the
process
 Mass integration is a tool to reduce resource
consumption and reject in the environment
 Energy integration is a tool that allows for a better
utilization of the energy
 LCA allows for a holistic evaluation of environmental
impacts over the product chain
136
Integration of Tools to Address MIM
 MIM is a multi-objective problem involving the best
trade-offs between:





Minimum resource consumption;
Minimum energy consumption;
Minimum air emissions;
Minimum water emissions;
Minimum solid wastes.
 This is also submitted to a lot of complicated
constraints:




137
Process constraints ;
Technology constraints;
Life cycle interactions;
Costs.
 For these reasons, integration of PI tools to address
MIM is not obvious.
References
 El-Halwagi, Mahmoud M. Pollution Prevention through Process
Integration, Academic Press, San Diego, USA, 1997, 318 p.
 ISO 1997. Management environnemental – Analyse du cycle de vie
Principes et cadres. CAN/CSA-ISO 14040:1997
 ISO 1998. Management environnemental – Analyse du cycle de vie –
Définition de l’objectif et du champ de l’étude et analyse de
l’inventaire. CAN/CSA-ISO 14041:1998
 ISO 2000. Management environnemental – Analyse du cycle de vie –
Analyse de l’impact du cycle de vie. CAN/CSA-ISO 14042:2000
 ISO 2000. Management environnemental – Analyse du cycle de vie
– Interprétation du cycle de vie. CAN/CSA-ISO 14043:2000
 Linnhoff March. 1998.
Introduction to Pinch Technology.
http://www.linnhoffmarch.com/pdfs/PinchIntro.pdf (page consulted in
2004)
138
QUIZ
Question 1
What is one of the main characteristics of
kraft processes?
a)
b)
c)
d)
140
The mechanical pulp
The necessity to bleach the pulp
The chemical recovery system
Its low water consumption
Question 2
Which of the following unit processes
generates the most sulfur compound
emissions?
a)
b)
c)
d)
141
Oxygen delignification
Bleaching
Pulping (digester)
Recovery furnace
Question 3
Toward which of the following elements is
MIM oriented?
a)
b)
c)
d)
e)
142
Reducing air emissions
Reducing solid wastes
Maximising shareholder value
a and b
a, b and c
Question 4
Which of these technical problem can be
associated to process closure?
a) Accumulation of undesirable elements
in the recovery system
b) Higher cost of utility
c) Higher energy consumption
d) Need of more pulping chemicals
143
Question 5
Which of these tracking model will you
use if one component can be accurately
tracked while another one cannot
a)
b)
c)
d)
144
Fixed split model
Flow ratio model
Species ratio model
Degree of freedom equation
Question 6
Which of these is not a characteristic of
BAT?
a)
b)
c)
d)
145
They must be economically achievable
They must be process unit oriented
They must be process oriented
They must be product oriented
Question 7
Which of the following will not decrease
Kraft mill energy consumption
a)
b)
c)
d)
146
Water consumption reduction
Chips screening
Less piping
Changing ECF bleaching for TCF
bleaching
Question 8
Which of the following trade-offs is the
most communly associated with energy
integration?
a) Reducing energy while increasing water
consumption
b) Capital vs. operating costs
c) Energy vs. chemical costs
d) Time horizon vs. energy savings
147
Question 9
Which of the following correspond to
segregation in mass integration?
a) Avoiding the mixing of the streams.
b) Utilization of pollutant-laden stream (a source)
in a process unit (a sink).
c) Utilization of separation unit operation to
adjust the composition of the pollution-laden
streams to make them acceptable for sinks.
d) Design or operation of changes that alter the
flowrate or composition of pollutant-laden
streams entering or leaving the process units.
148
Question 10
Which of the following can be described
as a functional unit?
a) The production of kraft pulp
b) The production of kraft pulp during 10
hours
c) The production of 1 admt kraft pulp
d) b and c
149