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Wood Handling

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Wood may arrive at a pulp mill woodyard in the form of raw logs or as chips from a lumber mill. Some pulp mill operations have on-site sawmills (often called “woodrooms”) which produce both marketable lumber and stock for the pulp mill. Sawmilling is discussed in detail in the chapter Lumber. This article discusses those elements of wood preparation which are specific to pulp mill operations.

The wood preparation area of a pulp mill has several basic functions: to receive and meter the wood supply to the pulping process at the rate demanded by the mill; to prepare the wood so that it meets the mill’s feed specifications for species, cleanliness and dimensions; and to collect any material rejected by the previous operations and send it to final disposal. Wood is converted into chips or logs suitable for pulping in a series of steps which may include debarking, sawing, chipping and screening.

Logs are debarked because bark contains little fibre, has a high extractives content, is dark, and often carries large quantities of grit. Debarking can be done hydraulically with high-pressure water jets, or mechanically by rubbing logs against each other or with metal cutting tools. Hydraulic debarkers may be used in coastal areas; however, the effluent generated is difficult to treat and contributes to water pollution.

Debarked logs may be sawn into short lengths (1 to 6 metres) for stone groundwood pulping or chipped for refiner mechanical or chemical pulping methods. Chippers tend to produce chips with a considerable size range, but pulping requires chips of very specific dimensions to ensure constant flow through refiners and uniform cooking in digesters. Chips are therefore passed over a series of screens whose function is to separate chips on the basis of length or thickness. Oversized chips are rechipped, while undersized chips are either used as waste fuel or are metered back into the chip flow.

The requirements of the particular pulping process and chip conditions will dictate the duration of chip storage (figure 1; note the different types of chips available for pulping). Depending on fibre supply and mill demand, a mill will maintain a 2 to 6 week unscreened chip inventory, usually in large outdoor chip piles. Chips may degrade through auto-oxidation and hydrolysis reactions or fungal attack of the wood components. In order to avoid contamination, short-term inventories (hours to days) of screened chips are stored in chip silos or bins. Chips for sulphite pulping may be stored outside for several months to allow volatilization of extractives which may cause problems in subsequent operations. Chips used in kraft mills where turpentine and tall oil are recovered as commercial products typically proceed directly to pulping.

Figure 1. Chip storage area with front end loaders

PPI030F1

George Astrakianakis

 

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Contents

Preface
Part I. The Body
Part II. Health Care
Part III. Management & Policy
Part IV. Tools and Approaches
Part V. Psychosocial and Organizational Factors
Part VI. General Hazards
Part VII. The Environment
Part VIII. Accidents and Safety Management
Part IX. Chemicals
Part X. Industries Based on Biological Resources
Agriculture and Natural Resources Based Industries
Beverage Industry
Fishing
Food Industry
Forestry
Hunting
Livestock Rearing
Lumber
Paper and Pulp Industry
Major Sectors and Processes
Disease and Injury Patterns
Resources
Part XI. Industries Based on Natural Resources
Part XII. Chemical Industries
Part XIII. Manufacturing Industries
Part XIV. Textile and Apparel Industries
Part XV. Transport Industries
Part XVI. Construction
Part XVII. Services and Trade
Part XVIII. Guides

Paper and Pulp Industry Additional Resources

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Paper and Pulp Industry References

Canadian Pulp and Paper Association. 1995. Reference Tables 1995. Montreal, PQ: CPPA.

Food and Agriculture Organization (FAO) of the United Nations. 1995. Pulp and Paper Capacities, Survey 1994-1999. Rome: FAO.

Henneberger, PK, JR Ferris, and RR Monson. 1989. Mortality among pulp and paper workers in Berlin. Br J Ind Med 46:658-664.

International Agency on the Research of Cancer (IARC). 1980. Monographs on the Evaluation of Carcinogenic Risks to Humans: Wood, Leather and Some Associated Industries. Vol. 25. Lyon: IARC.

—.1987. Monographs on the Evaluation of Carcinogenic Risks to Humans, Overall Evaluations of Carcinogenicity: An Updating of IARC Monographs. Vol. 1-42 (supplement 7). Lyon: IARC.

—.1995. Monographs on the Evaluation of Carcinogenic Risks to Humans: Wood Dust and Formaldehyde. Vol. 62. Lyon: IARC.

International Labour Organization (ILO). 1992. Social and Labour Issues in the Pulp and Paper Industry. Geneva: ILO.

Jäppinen, P. 1987. Exposure to Compounds, Cancer Incidence and Mortality in the Finnish Pulp and Paper Industry. Thesis, Helsingfors, Finland.

Jäppinen, P and S Tola. 1990. Cardiovascular mortality among pulp mill workers. Br J Ind Med 47:259-261.

Jäppinen, P, T Hakulinen, E Pukkala, S Tola, and K Kurppa. 1987. Cancer incidence of workers in the Finnish pulp and paper industry. Scand J Work Environ Health 13:197-202.

Johnson, CC, JF Annegers, RF Frankowski, MR Spitz, and PA Buffler. 1987. Childhood nervous system tumors—An evaluation of the association with paternal occupational exposure to hydrocarbons. Am J Epidemiol 126:605-613.

Kuijten, R, GR Bunin, and CC Nass. 1992. Parental occupation and childhood astrocytoma: Results of a case-control study. Cancer Res 52:782-786.

Kwa, SL and IJ Fine. 1980. The association between parental occupation and childhood malignancy. J Occup Med 22:792-794.

Malker, HSR, JK McLaughlin, BK Malker, NJ Stone, JA Weiner, JLE Ericsson, and WJ Blot. 1985. Occupational risks for pleural mesothelioma in Sweden, 1961-1979. J Natl Cancer Inst 74:61-66.

—. 1986. Biliary tract cancer and occupation in Sweden. Br J Ind Med 43:257-262.

Milham, SJ. 1976. Neoplasias in the wood and pulp industry. Ann NY Acad Sci 271:294-300.

Milham, SJ and P Demers. 1984. Mortality among pulp and paper workers. J Occup Med 26:844-846.

Milham, SJ and J Hesser. 1967. Hodgkin’s disease in woodworkers. Lancet 2:136-137.

Nasca, P, MS Baptiste, PA MacCubbin, BB Metzger, K Carton, P Greenwald, and VW Armbrustmacher. 1988. An epidemiologic case-control study of central nervous system tumors in children and parental occupational exposures. Am J Epidemiol 128:1256-1265.

Persson, B, M Fredriksson, K Olsen, B Boeryd, and O Axelson. 1993. Some occupational exposures as risk factors for malignant melanomas. Cancer 72:1773-1778.

Pickle, L and M Gottlieb. 1980. Pancreatic cancer mortality in Louisiana. Am J Public Health 70:256-259.
Pulp and Paper International (PPI). 1995. Vol. 37. Brussels: Miller Freeman.

Robinson, C, J Waxweiller, and D Fowler. 1986. Mortality among production workers in pulp and paper mills. Scand J Work Environ Health 12:552-560.


Schwartz, B. 1988. A proportionate mortality ratio analysis of pulp and paper mill workers in New Hampshire. Br J Ind Med 45:234-238.

Siemiatycki, J, L Richardson, M Gérin, M Goldberg, R Dewar, M Désy, S Campell, and S Wacholder. 1986. Association between several sites of cancer and nine organic dusts: Results from an hypothesis-generating case control study in Montreal, 1979-1983. Am J Epidemiol 123:235-249.

Skalpe, IO. 1964. Long-term effects of sulfur dioxide exposure in pulp mills. Br J Ind Med 21:69-73.

Solet, D, R Zoloth, C Sullivan, J Jewett, and DM Michaels. 1989. Patterns of mortality in pulp and paper workers. J Occup Med 31:627-630.

Torén, K, S Hagberg, and H Westberg. 1996. Health effects of working in pulp and paper mills: Exposure, obstructive airways diseases, hypersensitivity reactions, and cardiovascular diseases. Am J Ind Med 29:111-122.

Torén, K, B Järvholm, and U Morgan. 1989. Mortality from asthma and chronic obstructive pulmonary diseases among workers in a soft paper mill: A case referent study. Br J Ind Med 46:192-195.

Torén, K, B Persson, and G Wingren. 1996. Health effects of working in pulp and paper mills: Malignant diseases. Am J Ind Med 29:123-130.

Torén, K, G. Sällsten, and B Järvholm. 1991. Mortality from asthma, chronic obstructive pulmonary disease, respiratory system cancer among paper mill workers: A case referent study. Am J Ind Med 19:729-737.

US Department of Commerce. 1983. Pulp and Paper Mills. (PB 83-115766). Washington, DC: US Department of Commerce.

—.1993. Selected Occupational Fatalities Related to Pulp Paper and Paperboard Mills as Found in Reports of OSHA Fatality/Catastrophe Investigations. (PB93-213502). Washington, DC: US Department of Commerce.

Weidenmüller, R. 1984. Papermaking, the Art and Craft of Handmade Paper. San Diego, CA: Thorfinn International Marketing Consultants Inc.

Wingren, G, H Kling, and O Axelson. 1985. Gastric cancer among paper mill workers. J Occup Med 27:715.

Wingren, G, B Persson, K Torén, and O Axelson. 1991. Mortality patterns among pulp and paper mill workers in Sweden: A case-referent study. Am J Ind Med 20:769-774.

Workers’ Compensation Board of British Columbia. 1995. Personal communication.