Program for North American Mobility in Higher Education Introducing Process Integration for Environmental Control in Eng

1. Program for North American Mobility in Higher EducationIntroducing Process Integration for Environmental Control in Engineering Curricula Module 4: Environmental Challenges – Pulp & Paper Industry Caroline Gaudreault Created at: École Polytechnique de Montréal & Texas A&M University, 2003

2. Purpose of Module X 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.

3. Structure of the Module X What is the structure of this module? Module X 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.

4. LEGEND Go to the web site Go to next subject More information on the same subject Look for the answer to the question

5. Tier I:Background Information

6. 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.

7. 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 multiple- answer quiz

8. 1.1 Introduction to the kraft pulping process and its related environmental impacts and related regulations

9. 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.

10. Advantages: High strength pulp Utilizes proven technology for chemical recovery Handles with a wide variety of wood species Tolerates bark in the pulping process Disadvantages: Unbleached pulp is characterized by a dark brown color It is associated malodorous gases (organic sulfides) Advantages and Disadvantages of Kraft Process

11. Definitions and Nomenclature (1) Pulp Chips White liquor: Liquor containing the active cooking chemicals (NaOH and Na2S) and used to cook chips. 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. Cooking & Washing • BLACK LIQUOR • Alkali lignin • Hydrolysis salts • Sulphonation products • WHITE LIQUOR • NAOH • NA2S Evaporation & Burning Causticizing • GREEN LIQUOR • Na2CO3 • Na2S The kraft sodium cycle (Source:Smook, 1994)

12. Definitions and Nomenclature (2) (Source:Smook, 1994)

13. Sodium vs. Calcium Cycle (Adapted from European Comission IPPC, 2001)

14. 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 21% Hardwoods 25% Softwoods Lignin Extractive 2-8% Terpenes Resin acids (softwood) Fatty acids Phenols Unsaponifiables Carbohydrates 35% Hardwoods 25% Softwoods Hemicellulose Cellulose 45% Glucose Mannose Galactose Xylose Arabinnose Glucose Source: Smook, 1994

15. Overview of the Kraft Process Chips Water Lime mud Digester White liquor storage Lime mud washer White liquor clarifier Weak Liquor storage Lime mud thickener Causticizers Blow tank Grits Lime Washers Slaker Lime kiln Pulp to bleaching Green liquor storage Weak black liquor storage Water Dregs Dregs Dregs washer Green liquor clarifier Evaporators Contaminated condensates Smelt Dissolving tank Strong black liquor storage Recovering furnace Weak liquor storage Source: Smook, 1994

16. Overview of the Kraft Process Chips Water • The wood is mechanically debarked and cut into chips that are screened prior the chemical treatment. • Lignin and some carbohydrate material are dissolved from wood chips during cooking in aqueous solution of alkaline, neutral or acidic components at elevated temperature and pressure. • Chips maintain their wood structure during chemical pulping but this latter is so weak that it will break down to individual fiber by modest mechanical action. Lime mud Lime mud washer White liquor clarifier Digester White liquor storage Weak Liquor storage Lime mud thickener Causticizers Blow tank Grits Lime Washers Lime kiln Slaker Pulp to bleaching Green liquor storage Weak black liquor storage Water Dregs Dregs Dregs washer Green liquor clarifier Evaporators Contaminated condensates Smelt Dissolving tank Strong black liquor storage Recovering furnace Weak liquor storage Source: Smook, 1994

17. Overview of the Kraft Process Chips Water Lime mud • Washing: Spent inorganic and dissolved organic materials are separated from the pulp by multistage counter-current washing system. Spent liquor is sent to the regeneration system. • Screening: Solid impurities contained in the washed pulp (mainly incompletely delignified wood and knots) are separated by screening. The rejects are reprocessed. • Bleaching: Depending in the intended application, pulp can be bleached. Pulp made by the kraft process is darker than the original wood. Bleaching is the purification process that modify colored substance so they either loose their light absorption ability or they dissolve. Lime mud washer White liquor clarifier Digester White liquor storage Weak Liquor storage Lime mud thickener Causticizers Blow tank Pulp Grits Lime Washers Lime kiln Slaker Bleaching Green liquor storage Weak black liquor storage Water Dregs Dregs Green liquor clarifier Evaporators Dregs washer Contaminated condensates Smelt Weak liquor storage Dissolving tank Strong black liquor storage Recovering furnace Source: Smook, 1994

18. Overview of the Kraft Process Chips Water Lime mud Digester White liquor storage Lime mud washer White liquor clarifier Weak Liquor storage Lime mud thickener Causticizers Blow tank Pulp Grits Lime Washers Slaker Lime kiln Bleaching Green liquor storage Weak black liquor storage Water In order to be used as a fuel, kraft liquor must be evaporated in a multistage evaporation system. Dregs Dregs Green liquor clarifier Evaporators Dregs washer Contaminated condensates Smelt Dissolving tank Strong black liquor storage Recovering furnace Weak liquor storage Source: Smook, 1994

19. Overview of the Kraft Process Chips Water Lime mud Digester White liquor storage Lime mud washer White liquor clarifier Weak Liquor storage Lime mud thickener Causticizers Blow tank • The strong black liquor is then burned in a recovery furnace where inorganic substances are converted into regenerable substances. • Sodium and sulfur salts are converted to a smelt of Na2S and Na2CO3 and brought to a dissolved tank Pulp Grits Lime Washers Lime kiln Slaker Bleaching Green liquor storage Weak black liquor storage Water Dregs Dregs Green liquor clarifier Evaporators Dregs washer Contaminated condensates Smelt Dissolving tank Strong black liquor storage Recovering furnace Weak liquor storage Source: Smook, 1994

20. Overview of the Kraft Process Chips Water Lime mud Digester White liquor storage Lime mud washer White liquor clarifier Weak Liquor storage Lime mud thickener Causticizers Blow tank Pulp Grits Lime Washers Slaker Lime kiln Bleaching Green liquor storage Weak black liquor storage Water The smelt is dissolved in weak wash liquor from the recausticizing plant. Dregs Dregs Green liquor clarifier Evaporators Dregs washer Contaminated condensates Smelt Dissolving tank Strong black liquor storage Recovering furnace Weak liquor storage Source: Smook, 1994

21. Overview of the Kraft Process Chips Water Lime mud Digester White liquor storage Lime mud washer White liquor clarifier Weak Liquor storage Lime mud thickener Causticizers Blow tank Pulp Grits Lime Washers Slaker Lime kiln Bleaching The green liquor is clarified. Green liquor storage Weak black liquor storage Water Dregs Dregs Evaporators Dregs washer Green liquor clarifier Contaminated condensates Source: Smook, 1994 Smelt Dissolving tank Strong black liquor storage Recovering furnace Weak liquor storage Source: Smook, 1994

22. Overview of the Kraft Process Chips Water Lime mud Digester White liquor storage Lime mud washer White liquor clarifier Weak Liquor storage Lime mud thickener Causticizers Blow tank Pulp Grits Lime Washers Slaker Lime kiln Bleaching • The green liquor is causticized with reburned lime to form white liquor: • CaO and water are reacted in a slaker to form CaOH, which in turn reacts with Na2CO3in the green liquor to form NaOH and CaCO3. • The CaCO3, which is insoluble, is separated by filtering and is washed free from sodium salts. • It is then calcinated in a lime kiln to CaO and reused. • The regenared white liquor is reused in cooking. Green liquor storage Weak black liquor storage Water Dregs Dregs Green liquor clarifier Evaporators Dregs washer Contaminated condensates Smelt Recovering furnace Weak liquor storage Dissolving tank Strong black liquor storage Source: Smook, 1994

23. 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 • Oxygen-demanding substances • Disease-causing agents • Synthetic organic compounds • Plant nutrients • Inorganic chemical and mineral substances • Sediments • Radioactive substances • Thermal discharges

24. Environmental Impacts of the Kraft Process To learn about major environmental impacts of the kraft process: Click on the yellow then pink boxes! Wood preparation Chips Water Lime mud White liquor clarifier Digester White liquor storage Lime mud washer Weak Liquor storage Lime mud thickener Causticizers Blow tank Pulp Grits Lime Washers Lime kiln Slaker Bleaching Green liquor storage Weak black liquor storage Water Dregs Dregs Green liquor clarifier Evaporators Dregs washer Source: Smook, 1994 Contaminated condensates Smelt Dissolving tank Strong black liquor storage Recovering furnace Weak liquor storage

25. 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. Another type of fugitive emission associated with wood preparation activities is gaseous such as volatile organic compounds (VOC). Water Pollution: Water is used for 3 purposes: log conveyance?, log washing and wet debarking. Wood Preparation For more information Return to the flowsheet

26. Air Pollution: The cooking process results in formation and releases of VOC’s and reduced components (TRS) that are odorous. 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. The non-condensable gas are incinerated in order to eliminate the odorous ones. The remainder are condensed and used to pre-heat the chips. Water Pollution: Wood chips are cooked in aqueous solution. Pulp Production For more information Return to the flowsheet

27. Air 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. Water Pollution: Pulp is washed to remove pulping chemicals and soluble wood components and diluted with water. Pulp Washing, Screening and Deknotting For more information Return to the flowsheet

28. 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.

29. 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.

30. 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 Return to the flowsheet

31. Water Pollution: 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. The condensates can contain high level of TRS, methanol and acetone. Chemical Recovery:Evaporation Air 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. 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. For more information Return to the flowsheet

32. 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. Return to the flowsheet

33. 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. Return to the flowsheet

34. Air Pollution: Lime mud is calcinated to form CaO and CO2 in the lime kiln. 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. Water Pollution 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. Chemical Recovery:Lime Kiln For more information Return to the flowsheet

35. 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. Return to the flowsheet

36. Chemical RecoveryOther 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. Return to the flowsheet

37. 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 Bleaching Return to Pulp Washing Return to Pulp Production Return to Wood Preparation (Source: Springer and al., 1997)

38. 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.

39. 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.

40. 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: • 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.

41. 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: • Produce superior environmental results beyond those that would have been achieved under current and reasonably anticipated future regulations or policies; • 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; • Supported by stakeholders; • Achieve innovation/pollution prevention; • Produce lessons or data that are transferable to other facilities; • Demonstrate feasibility; • Establish accountability through agreed upon methods of monitoring, reporting, and evaluations; and • Avoid shifting the risk burden, i.e., do not create worker safety or environmental justice problems as a result of the experiment. In addition, projects must present economic opportunities and incorporate community planning.

42. 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.

43. 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: • 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.

44. 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.

45. 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.

46. 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.

47. References • ENVIRONNEMENT QUÉBEC. 2003. Le Programme de réduction des rejets industriels et l’attestation d’assainissement.http://www.menv.gouv.qc.ca/programmes/prri/index.htm(page consulted in 2004) • EUROPEAN COMISSION. Integrated Pollution Prevention and Control (IPPC) – 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).

48. 1.2 Introduction to minimum impact manufacturing (MIM)

49. Content • MIM concepts • Progressive water system closure and build-up of NPE’s • Zero discharge concepts • Tracking models for water, NPE’s, and targeted species • Kraft mill energy efficiency • Relation between minimum energy and minimum effluent • BAT concepts • Example of application of MIM concept

50. Content • MIM concepts • Zero discharge concepts • Progressive water system closure and build-up of NPE’s • Tracking models for water, NPE’s, and targeted species • Kraft mill energy efficiency • Relation between minimum energy and minimum effluent • BAT concepts • Example of application of MIM concept