Environmentally Friendly Production of Pulp and Paper E-Book

Pratima Bajpai

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 770

Veröffentlichungsjahr: 2011

Beschreibung

Implementing Cleaner Production in the pulp and paper industry

The large—and still growing—pulp and paper industry is a capital- and resource-intensive industry that contributes to many environmental problems, including global warming, human toxicity, ecotoxicity, photochemical oxidation, acidification, nutrification, and solid wastes. This important reference for professionals in the pulp and paper industry details how to improve manufacturing processes that not only cut down on the emission of pollutants but also increase productivity and decrease costs.

Environmentally Friendly Production of Pulp and Paper guides professionals in the pulp and paper industry to implement the internationally recognized process of Cleaner Production (CP). It provides updated information on CP measures in:

• Raw material storage and preparation

• Pulping processes (Kraft, Sulphite, and Mechanical)

• Bleaching, recovery, and papermaking

• Emission treatment and recycled fiber processing

In addition, the book includes a discussion on recent cleaner technologies and their implementation status and benefits in the pulp and paper industry.

Covering every aspect of pulping and papermaking essential to the subject of reducing pollution, this is a must-have for paper and bioprocess engineers, environmental engineers, and corporations in the forest products industry.

Leseprobe

Contents

Cover

Half Title Page

Title Page

Copyright

Preface

Chapter 1: Introduction

1.1 Superior Operating Procedures

1.2 Process Modifications

1.3 Process Redesign

1.4 Recycling

References

Chapter 2: Overview of Pulp and Papermaking Processes

2.1 Raw Material Preparation and Handling

2.2 Pulp Manufacturing

2.3 Pulp Washing and Screening

2.4 Pulp Bleaching

2.5 Stock Preparation

2.6 Papermaking

2.7 Chemical Recovery

References

Chapter 3: Environmental Issues of the Pulp and Paper Industry

3.1 Effluent Toxicity

3.2 Air Emissions

References

Chapter 4: Emissions from Pulp and Papermaking

4.1 Kraft Pulping

4.2 Sulfite Pulping

4.3 Mechanical Pulping

4.4 Recycled Fiber Processing

4.5 Papermaking

References

Chapter 5: Cleaner Production Measures in Pulp and Paper Processing

5.1 Kraft Pulping

5.2 Sulfite Pulping

5.3 Mechanical and Chemimechanical Pulping

5.4 Recycled Paper Processing

5.5 Papermaking

References

Chapter 6: Recent Developments in Cleaner Production

6.1 Use of Cooking Catalyst

6.2 Organo Solvent Pulping

6.3 Black Liquor Gasification

6.4 Removal of Chelating Agents

6.5 Energy-Efficient Thermomechanical Pulping Processes

6.6 Recovery of Boiler Ash and Carbon Dioxide Gas to Produce Recycled Mineral Fillers

6.7 Impulse Technology for Dewatering of Paper

6.8 Condebelt Process

6.9 Internal Heat Pumps

6.10 Total Site Integration Tools

6.11 Wastewater Treatment for Water Recovery and Reuse

6.12 Biotechnologies for Cleaner Paper Production

References

Glossary and Abbreviations

Subject Index

EnvironmentallyFriendly Productionof Pulp and Paper

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Published by John Wiley & Sons, Inc., Hoboken, New Jersey.

Published simultaneously in Canada.

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Library of Congress Cataloging-in-Publication Data

Bajpai, P. (Pratima)

  Environmentally-friendly production of pulp and paper / Pratima Bajpai.

    p.  cm.

  Includes index.

  ISBN 978-0-470-52810-5 (cloth)

  1. Pulping–Environmental aspects.  2. Papermaking–Environmental aspects.

3. Sustainable engineering.  I. Title.

  TS1109.B24  2010

  676‵.042–dc22        2010005156

Printed in the United States of America

10  9  8  7  6  5  4  3  2

Preface

The pulp and paper industry is large and growing, reflecting the world's demand for paper. It is a capital- and resource-intensive industry that contributes to many environmental problems, including global warming, human toxicity, ecotoxicity, photochemical oxidation, acidification, nutrification, and solid wastes. Public concern is resulting in increased pressure on industry to focus on pollution prevention rather than on end-of-pipe cleanup. Industry is responding by modifying existing production processes or developing entirely new ones to achieve cleaner production (i.e., greater energy efficiency as well as reduced emissions of greenhouse gases and toxic substances). Many companies are beginning to find that cleaner production not only reduces environmental liabilities but also reduces costs and increases both productivity and competitiveness. Minimizing or eliminating the causes of wastes and emissions makes it easier to meet existing environmental regulations and reduces the environmental impact of the mill. Cleaner production is also attractive because of concerns about the lack of effectiveness of end-of-pipe solutions. Cleaner production and related approaches will be increasingly important in environmental management in the future. The introduction of cleaner production is an ongoing process. As resource prices and disposal costs continue to rise, new opportunities arise for pollution prevention and reductions in treatment costs. For this reason, cleaner production can be linked closely with environmental management systems. This book gives updated information on cleaner production measures in pulp and paper industry. Various chapters deal with cleaner production measures in raw material storage and preparation, in pulping processes (kraft, sulfite, and mechanical), in bleaching, recovery, papermaking, in emission treatment processes, and in recycled fiber processing. In addition, it includes a discussion on newer cleaner technologies and their implementation status and benefits in the pulp and paper industry.

Chapter 1

Introduction

“Cleaner production” is an international term for reducing environmental impacts from processes, products, and services by using better management strategies, methods, and tools. It is a global movement for improving business performance and a profitable, cleaner, and sustainable future. According to the United Nations Environment Programme (UNEP) definition of “cleaner production” and the one in most common use is, “Cleaner production is the continuous application of an integrated preventive strategy to processes, products and services, to increase ecoefficiency and to reduce risks to humans and the environment” (AIT, 1999). A number of related terms are also used, including pollution prevention, low- or no-waste technologies, waste minimization, waste and emission prevention, source reduction, ecoefficiency, and environmentally sound technology. All these terms basically refer to the same concept of integrating pollution reduction into the production process and even the design of the product.

The meaning of the term “cleaner production” varies from the perspective in which it is used. For production processes, cleaner production involves conserving raw materials and energy, eliminating the use of toxic substances as much as possible, and reducing the quantity as well as the toxicity of all emissions and wastes before they leave any given process. For products, it means reducing their environmental impacts during the entire life cycle, from raw material extraction to ultimate disposal. For services, it means incorporating environmental concerns when designing and delivering services (Fig. 1.1).

Figure 1.1 Cleaner production.

The adoption of cleaner production in the industry leads to multifold advantages to an operating industry. Cleaner production leads to better efficiency of production, which means more output of products per unit input of raw materials. This helps in improving the financial performance of the mill. The ultimate goal of cleaner production is to minimize the generation of emissions and waste that needs to be treated and the associated costs. Given the increasing cost of raw materials and the growing scarcity of good-quality water, no industry can afford to use these resources inefficiently. Cleaner production measures help in overcoming constraints posed by scarce or ever-increasing costly raw materials, water, and energy.

Cleaner production minimizes the amount and toxicity of waste and emissions and renders products that are more agreeable from an environmental standpoint. The direct effect is that the pollution load on the environment is decreased and environmental quality is improved. It focuses on minimizing resource use and avoiding the creation of pollutants, rather than trying to manage pollutants after they have been created. It involves rethinking products, processes, and services to move toward sustainable development. Sustainable development concerns essential human activities, and sustainable development goals are often expected to dramatically affect both individual and public choices to modify production and consumption patterns (OECD, 2002; World Bank, 1998). Sustainable development is of critical importance for all citizens; it engages choices that will affect essential aspects of our lifestyles, and, being typically crosscutting, it should take into consideration various conflicting interests.

Consumers, suppliers, governments, and the market at large are increasingly demanding environmental responsibility by the business community. Businesses ignoring this trend and rejecting the opportunity to improve their environmental performance may find themselves left behind in the highly competitive global marketplace. Cleaner production is set to become an integral part of the business strategies of enlightened companies that want to embrace the ongoing challenges of industry leadership and continuous improvement. Cleaner production can reduce operating costs, improve profitability and worker safety, and reduce the environmental impact of our business. Companies are frequently surprised at the cost reductions achievable through the adoption of cleaner production techniques. Frequently, minimal or no capital expenditure is required to achieve worthwhile gains, with fast payback periods. Waste handling and charges, raw material usage, and insurance premiums can often be cut, along with potential risks.

On a broader scale, cleaner production can help alleviate the serious and increasing problems of air and water pollution, ozone depletion, global warming, landscape degradation, solid and liquid wastes, resource depletion, acidification of the natural and built environment, visual pollution, and reduced biodiversity.

It is proved from the past records that there lies a great potential for reduction in the pollution levels in the pulp and paper mills. From the different demonstration projects, it is established that adoption to the cleaner production has not only reduced the pollution loads but also helped in generating revenues by controlling the waste going down the drain (Nath, 1997; Radka, 1994; Satyanarayana et al., 2004).

The main difference between pollution control and cleaner production is one of timing. Pollution control is an after-the-event, “react and treat” approach, whereas cleaner production reflects a proactive, “anticipate and prevent” philosophy. Prevention is always better than cure. This does not mean, however, that “end-of-pipe” technologies will never be required. By using a cleaner production philosophy to tackle pollution and waste problems, the dependence on “end-of-pipe” solutions may be reduced or, in some cases, eliminated altogether.

Investing in cleaner production to prevent pollution and reduce resource consumption is more cost-effective than continuing to rely on the increasingly expensive “end-of-pipe” solutions. When cleaner production and pollution control options are carefully evaluated and compared, the cleaner production options are often more cost-effective overall. The initial investment for cleaner production options and for installing pollution control technologies may be similar, but the ongoing costs of pollution control technologies will generally be greater than those of cleaner production. Furthermore, the cleaner production option will generate savings through reduced costs of raw materials, energy, waste treatment, and regulatory compliance.

The environmental benefits of cleaner production can be translated into market opportunities for “greener” products. Companies that factor environmental considerations into the design stage of a product will be well placed to benefit from the marketing advantages of any future ecolabeling schemes.

Increasing consumer awareness of environmental issues has brought about a need for the companies to demonstrate the environmental friendliness of their products and manufacturing processes, particularly in international markets. By adopting the cleaner production approach, many of the market requirements are met and a company’s ability to compete and get access to the “green market” increases.

Cleaner production not only improves the environment outside the mill but also improves working conditions. Keeping the mill clean and free of waste, spilled water, and chemicals not only reduces the likelihood of accidents but also motivates the workforce to control new leaks and material losses.

As public awareness of the need for environmental protection is growing each day, it becomes more and more important for the industry to respond and react to the questions and demands posed by the public. The environmental profile of a company is an increasingly important part of its overall reputation. Adopting cleaner production is a proactive, positive measure and can help the concerned company build confidence in the public regarding its environmental responsibility. Some reasons to invest in cleaner production are

Improvements to products and processesSavings on raw materials and energy, thus reducing production costsIncreased competitiveness through the use of new and improved technologiesReduced concerns over environmental legislationReduced liability associated with the treatment, storage, and disposal of hazardous wastesImproved health, safety, and morale of employeesImproved the company’s imageReduced costs of end-of-pipe solutions

Cleaner production depends only partly on new or alternative technologies. It can also be achieved through improved management techniques, different work practices, and many other “soft” approaches. Cleaner production is as much about attitudes, approaches, and management as it is about technology. Cleaner production approaches are widely and readily available, and methodologies exist for its application. While it is true that cleaner production technologies do not yet exist for all industrial processes and products, it is estimated that more than 70% of all current wastes and emissions from industrial processes can be prevented at source by the use of technically sound and economically profitable procedures (Baas et al., 1992).

Cleaner production can contribute to sustainable development. Cleaner production can reduce or eliminate the need to trade off environmental protection against economic growth, occupational safety against productivity, and consumer safety against competition in international markets. Setting goals across a range of sustainability issues leads to win–win situations that benefit everyone. Cleaner production is such a win–win strategy—it protects the environment, the consumer, and the worker. It also improves industrial efficiency, profitability, and competitiveness.

Cleaner production can be especially beneficial to developing countries and those undergoing economic transition by planning, design, and management practices that facilitate innovative approaches to the reuse, remanufacturing, and recycling of the limited amounts of waste that cannot be avoided (Gavrilescu, 2004).

Cleaner production involves initiating steps to reduce the intensity of pollution at various levels. This can be accomplished by reducing the generation of wastes at its source and reusing and recycling the resources. Pollution prevention is of environmental and economic significance because it makes judicious use of the existing resources such as chemicals and water and eliminates the recurring costs involved in waste treatment and disposal. Most companies across the globe have charted out pollution prevention programs suitable to their industry requirements. Recent R&D initiatives undertaken by various companies include formaldehyde-free products, organic biocides, biotechnology products such as microbes, enzymes, and natural pigments.

Figure 1.2 shows the key initiatives taken by the pulp and paper industries to minimize pollution at various levels.

Figure 1.2 Key initiatives taken by the paper and pulp industries to reduce pollution.

1.1 Superior Operating Procedures

The industry can implement changes in various departments such as the personnel department, inventory, waste handling department, and housekeeping units to ensure proper handling and storage of the wastes and monitoring the wastes for spills and leakages. Some of these include utilization of best available techniques such as minimizing the production of wastes and recycling of resources, separate storage and transportation facilities for nonhazardous from hazardous waste to facilitate recovery, reuse of certain chemicals and minimize the disposal costs, and conservation of water by recycling water within the industry and using the recycled water. Regular inspection of the machineries such as valves, pumps, and seals to detect leaks and spillages and the utilization of non-halogenated solvents and nontoxic cleaners during the cleaning of the machinery are required to eliminate the contamination of other materials in contact with the machinery.

1.2 Process Modifications

The existing operations can be modified to make industries more efficient and cost-effective, for example, inclusion of spill pits inside the plant to capture the leaking processed water and reusing this water in the process. About 20% of water wasted in the paper mills is due to spills, leakages, and washdowns; evaporation of black liquor to obtain concentrated solids; and modification of the system to support the usage of recycled paper in the manufacturing process.

1.3 Process Redesign

The paper and pulp process can be modified and redesigned to accommodate the economic and environmental concerns. A few of the improved designs include dry barking of wood instead of wet to minimize the utilization of water and sludge production, wet air oxidation of wastewater sludge to obtain filler material, elimination of chlorine as a bleaching agent by using alternate bleaching agents such as ozone, and selection of additives that do not form dioxins and furans.

1.4 Recycling

The paper industry now utilizes certain amount of waste materials as raw materials, especially recycled fibers. Some of the key recycling procedures are utilization of filters or strainers to recycle secondary fibers, recycling, and reuse of water, and solvents used for cleaning operations can be recycled.

Tables 1.1 and 1.2 present the features of cleaner production technologies and management practices. Cleaner production technologies are related to make different changes in the process by addition of some equipment in the production processes. On the other hand, cleaner production management practices will talk of enhancing cleaner production by measures such as housekeeping and maintenance practices. The management practices will also encompass the production culture in the plant, which affects the production wastes (AIT, 1999; NPC, 1997; UNEP IE, 1996, 1997; Visvanathan et al., 1999).

Table 1.1 Cleaner Production Technologies

Table 1.2 Cleaner Production Management Practices

REFERENCES

AIT (1999). Cleaner production in the pulp and paper industry: technology fact sheets. Asian Institute of Technology, Pathumthani, Thailand, pp. 1–7.

Baas LW, Van Der Belt M, Huisingh D, and Neumann F (1992). Cleaner production: what some governments are doing and what all governments can do to promote sustainability. Eur Water Pollut Control, 2(1): 10–25.

Gavrilescu M (2004). Cleaner production as a tool for sustainable development. Environ Eng Manag J, 3(1): 45–70.

Nath S (1997). Cleaner production opportunities and environmental protection in pulp and paper industry, an overview. IPPTA Convention Issue, India, pp. 127–134.

National Productivity Council (1997). From waste to profits, waste minimization in agro-based pulp and paper industry. Technical Manual Series I, India.

OECD (2002). Working Together Towards Sustainable Development. OECD Publications Service, Paris.

Radka MK (1994). Cleaner production in the pulp and paper industry. IPPTA Convention Issue, India, pp. XIX–XXVI.

Satyanarayana CH, Das A, and Singh SK (2004). Cleaner production technology in pulp and paper industry. IPPTA Convention Issue, India, pp. 37–41.

United Nations Environment Programme Industry and Environment (UNEP IE) (1996). Environmental management in the pulp and paper industry. Technical Report No. 34, USA.

United Nations Environment Programme Industry and Environment (UNEP IE) (1997). Cleaner production at pulp and paper mills: a guidance manual.

Visvanathan C, Patankar M, and Svenningsen N (1999). Promotion of cleaner production in the pulp and paper industry: a technology fact sheets approach. Global Competitiveness through Cleaner Production, Scott JA and Pagan RJ (eds). Australian Cleaner Production Association Inc., pp. 557–563.

World Bank (1998).Pollution Prevention and Abatement Handbook, Section 2, USA.

Chapter 2

Overview of Pulp and Papermaking Processes

The pulp and paper industry is very diversified, using many types of raw materials to produce very different kinds of paper by different methods in mills of all sizes. Pulp and paper are manufactured from raw materials containing cellulose fibers, generally wood, recycled paper, and agricultural residues. In developing countries, about 60% of cellulose fibers originate from nonwood raw materials such as bagasse (sugarcane fibers), cereal straw, bamboo, reeds, esparto grass, jute, flax, and sisal (Gullichsen, 2000).

The paper manufacturing process has several stages: raw material preparation and handling, pulp manufacturing, pulp washing and screening, chemical recovery, bleaching, stock preparation, and papermaking (Fig. 2.1).

Figure 2.1 Pulp and papermaking processes.

Paper production is basically a two-step process in which a fibrous raw material is first converted into pulp, and then the pulp is converted into paper. The harvested wood is first processed so that the fibers are separated from the unusable fraction of the wood, the lignin. Pulp making can be done mechanically or chemically. The pulp is then bleached and further processed, depending on the type and grade of paper that is to be produced. In the paper factory, the pulp is dried and pressed to produce paper sheets. Postuse, an increasing fraction of paper and paper products is recycled. Nonrecycled paper is either landfilled or incinerated.

Pulp mills and paper mills may exist separately or as integrated operations. Figure 2.2 shows a simplified flow diagram of an integrated mill. Manufactured pulp is used as a source of cellulose for fiber manufacture and for conversion into paper or cardboard.

Figure 2.2 A simplified flow diagram of an integrated mill (chemical pulping, bleaching, and paper production). Based on Smook (1992b).

2.1 Raw Material Preparation and Handling

Pulp manufacturing starts with raw material preparation, which includes debarking (when wood is used as raw materials), chipping, chip screening, chip handling and storage, and other processes such as depithing (e.g., when bagasse is used as the raw material) (Biermann, 1996a; Gerald, 2006; Gullichsen, 2000).

Log debarking is necessary to ensure that the pulp is free of bark and dirt. Both mechanical and hydraulic bark removal methods are in common use. The barking drum is the most common form of mechanical debarking. Bark is removed from the logs by friction created from the rotating drum action as the logs rub against each other. In wet drumbarkers, water is added to the early solid steel portion of the drum to help loosen the bark. The remaining portion of the drum has slots to permit the removed bark to fall out while the log continues on through. In dry drumbarkers, the entire length of the drum has slots for bark removal. Dry drumbarkers are longer in length and rotate much faster than wet-type drumbarkers. The bark from dry drumbarking can be fired directly into bark-burning furnaces, while bark from a wet system must be collected in a water flume, dewatered and pressed before burning. Drumbarkers usually create about 4–5% wood waste and cause broomed ends on the logs that produce inferior wood chips for pulping. They are relatively low-cost devices but have high power consumption (Russel, 2006).

After debarking, the logs (or portions of logs) are reduced to chip fragments suitable for the subsequent pulping operations. Several designs of chippers are in use, the most common being the flywheel-type disk with a series of blades mounted radially along the face. The logs are usually fed to one side of the rotating disk at an optimum angle (about 45 degrees) through a vertical directing chute. The logs can also be fed horizontally to a disk mounted at the proper angle. Generally, the horizontal feed provides better control but is less suitable for scrap wood pieces. Off-size chips adversely affect the processing and quality of pulp.

Acceptable-size chips are usually isolated from fines and oversized pieces by passing the chips over multistage vibratory screens. The oversized chips are rejected to a conveyor, which carries them to a “rechipper.” The fines are usually burned with the bark (unless special pulping facilities are available).

Conventional screening segregates chips only on the basis of chip length. More recently, the greater importance of chip thickness has been recognized, and a few recently designed screens now segregate according to this parameter. Also, new design “rechippers” that slice the chip lengthwise to reduce thickness cause far less damage to the fibers than the old-style crushers.

Within mill areas, most chips are transported on belts or in pipes, using an airveying system. Chips are readily handled by air over distances of 300–400 m, but power consumption is high and chip damage can be significant. By contrast, a belt conveyor system has a much higher initial cost. Other systems such as chain and screw conveyors are also used to move chips, but usually for relatively short distances. Bucket elevators are used for vertical movement.