Pulp and Paper

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  • Topic: Paper, Stainless steel, Kraft process
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  • Published : November 19, 2010
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APPENDIX W PULP AND PAPER

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APPENDIX W

PULP AND PAPER
MICHIEL P. H. BRONGERS1 AND AARON J. MIERZWA1
SUMMARY AND ANALYSIS OF RESULTS Corrosion Control and Prevention The $165 billion pulp, paper, and allied products industry supplies the United States with approximately 300 kg of paper per person per year. More than 300 pulp mills and more than 550 paper mills support its production. A typical pulp mill uses approximately 64 m3 of water per metric ton of pulp, and the combined pulp and paper manufacturers release approximately 100 thousand metric tons of toxic chemicals per year into the air, water, or land. The total annual corrosion costs for the pulp, paper, and paperboard industry, as determined as a fraction of the maintenance cost, is approximately $1.97 billion to $9.88 billion (average $5.928 billion per year). These estimates are between 1.2 percent and 6.0 percent of the total sales for the entire U.S. pulp and paper industry. The cost of corrosion for the pulp industry was only estimated at approximately $808.5 million per year. Paper production consists of a series of processes and can be roughly divided according to the five major manufacturing steps: (1) pulp production, (2) pulp processing and chemical recovery, (3) pulp bleaching, (4) stock preparation, and (5) paper manufacturing. Each manufacturing step has its own corrosion problems related to the size and quality of the wood fibers, the amount of and temperature of the process water, the concentration of the treatment chemicals, and the materials used for machinery construction. Examples of corrosion affecting production are: (1) corrosion products polluting the paper and (2) corrosion of rolls scarring the sheets of paper. Corrosion of components may also result in fractures or leaks in the machines, causing production loss and safety hazards.

Opportunities for Improvement and Barriers to Progress
Major changes in the paper-making process have occurred in the period from 1975 to 2000. Today’s digital world requires much-increased production of pulp and paper. Paper recycling and environmental issues concerning chemical releases have forced the pulp and paper industry to change their processes. The fierce competition within the pulp and paper industry has resulted in many company mergers, a smaller total number of pulp and paper mills, and significantly increased production capacity per mill. Furthermore, factories are no longer allowed to "run a river through their plant" and dump the processed water back into the environment without cleaning it first. There is a clear trend of decreasing the amount of process water, recycling and reusing the water in closed-loop systems, and cleaning the water before releasing. This results in a more corrosive process environment. Paper mills in the United States are traditionally constructed of a combination of carbon steels and stainless steels. In general, production systems run cleaner if all machinery in contact with the process stream would be constructed of corrosion-resistant alloys, which effectively reduce the general corrosion rate. Although stainless steel can be susceptible to other forms of corrosion, such as stress corrosion cracking of weld heat-affected zones, the use of stainless steel reduces the formation of thick corrosion scales and significant wall loss can be prevented.

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CC Technologies Laboratories, Inc., Dublin, Ohio.

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Appendix W – Pulp and Paper

An important barrier to immediate implementation of a complete change from carbon steel to stainless steel is the value of this investment. To resolve this, companies gradually exchange their equipment, when processupgrades are made. Pulp and paper mills are factories that involve a series of consecutive pieces of equipment, each with a different useful service life. At the end of the service life, when production is severely affected by the age of the equipment, equipment is completely replaced. The...
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