Paper Manufacturing

Paper Manufacturing, a series of processes used for making paper and consisting of the following main production stages. -I. Preparation of semi-finished products (varying depending on the grade of paper being produced): a) processing of rags (for higher grades of paper); processes: disinfection and dusting of rags, manual sorting, cutting (manual or mechanical); subsequent dusting, cooking with lime milk under increased pressure, bleaching with chlorine lime, grinding in special roll mills; b) processing of wood into wood pulp; processes: debarking (manual or mechanical), sawing, mechanical sorting and separation, processing into sheets on pulp machines; c) processing of wood into cellulose: production of sulfur dioxide from sulfur or pyrite, preparation of bisulfite by passing sulfur dioxide through limestone in the presence of water (in special towers), cooking of wood chips with a bisulfite solution under specific pressure, discharge of cooked cellulose into receivers called strainers, manual unloading from strainers, mechanical cleaning and sorting; d) processing of paper waste: sorting, grinding on stone mills or in a waste beater.-II. These semi-finished products are then mixed in various proportions in commercial roll mills and processed, forming paper pulp. To the roll mills is also added separately prepared emulsion of rosin, alum, and dye.-III. From the commercial roll mills, the paper pulp goes to the paper machine, the 'self-dipper', where it is gradually dehydrated (on the wire), pressed and dried (on rolls and drums) and emerges in the form of a finished roll weighing up to 410 kg.-IV. In the finishing department, this paper is calendered and cut to the required formats.-V. In the packing room, it is sorted and packaged. When making cardboard, the drying department (in special long chambers) has particular professional-hygienic significance, where workers have to enter; in the production of parchment paper, the paper is passed through a 54% solution of H₂SO₄ and then gradually washed with water. Special mention should be made of the production of cellulose from straw; in the production of cellulose from wood by treatment with CaO, SO₂ is absent, but the caustic action of lime is noted. Sanitary-hygienic hazards of paper manufacturing. I. Dust.-1. Rag dust is found in rag sorting departments, manual and mechanical cutting, in dusting, in the rag opener, in the warehouse, when loading the rag digester. Properties: fibers, ranging from several microns to several millimeters in length, contain many inorganic particles; the possibility of various bacteria and spores is not excluded; tendency to settle, mainly, in the upper respiratory tract in solid and dense clots and crusts; insoluble in water. Effects-on the skin (eczema, scabies, ringworm, etc.), on the eyes (conjunctivitis, blepharitis), on the respiratory tract (rhinitis, pharyngitis, bronchitis and, as a secondary disease, emphysema of the lungs); possibility of infection, primarily by particularly persistent microorganisms and spores of anthrax and others. Preventive and health measures. Mechanization of production; preliminary disinfection and dusting of rags (which is extremely rarely done); proper local ventilation. - 2. Paper dust. In pure form, it is found mainly in the packing room, less in the finishing department. Properties: fibers are the same as in rag dust, but 2-10 times shorter; much fewer inorganic particles; infections are accidental (e.g., those that get into the dust from sick workers). Effects-mainly on the middle and deep respiratory tract (bronchitis, tuberculosis). Method of control-rational ventilation. Particular professional-hygienic significance is the dust when sorting paper waste and its grinding. Here, paper dust in terms of contamination and infection approaches rag dust; in addition, there are caustic and poisonous powders (in pharmaceutical packets, etc.). Means of control-establishment of strict standard requirements, 'conditions', when accepting raw materials and proper ventilation during work.-3. Iron pyrite dust-in the acid department when breaking, sifting and loading iron pyrite. Properties: fine, moderately sharp, hard, insoluble. Effects: on eyes and skin-irritating, on respiratory tract-injury, formation of pneumoconiosis. Method of control-mechanization of processes, proper ventilation.-4. Chlorine lime dust-in the chlorine department, especially when preparing the bleaching solution. Properties: very fine, caustic, eagerly combines with water, releasing free Cl. Effects: on the respiratory tract-suffocating cough, hemoptysis, acute and chronic catarrhs; on the eyes-conjunctivitis, blepharitis; on the skin-eczema, ulcers. Sanitary measures-mechanization and sealing of processes.-5. CaO dust-in the alkaline treatment of wood for cellulose production. Effects: similar to chlorine lime, but less pronounced. Control measures-analogous.-6. Rosin dust-when grinding and pounding rosin. Properties: fine, with pointed edges, brittle, easily soluble in water. Effects: irritation of the mucous membranes of the eyes and upper respiratory tract; bad taste in the mouth and loss of appetite. Means of control-mechanization and proper ventilation.- 7. Wood dust-in debarking, circular sawing, chopping of balance. Properties: organic, fairly large, sharp, moderately soft, slightly soluble (swelling from moisture). Effects: sometimes catarrhs of the upper respiratory tract, most often-eyestrain.- II. Gases. - 1. Sulfur dioxide (SO₂)-in the acid department, in the tower and cellulose cooking departments; less-in the strainers. The quantity of it in the room air depends on the design of furnaces and boilers, room conditions, ventilation, and mainly on the tightness of the equipment. Health measures: observance of basic sanitary-hygienic requirements regarding room volume, inflow of fresh air (exhaust ventilation is undesirable), tightness of equipment, rational design of boilers and furnaces. In case of sudden gas leakage, workers must be provided with respirators.-2. Chlorine is released when preparing chlorine lime and during its settling, as well as in the bleaching roll mills and less in strainers with bleaching material.-III. Caustic liquids: H₂SO₄-in the production of parchment paper (treatment of paper with a 54% solution of vitriol oil) and strong alkaline solutions in the alkaline method of obtaining cellulose. Effects mainly on the skin (burns). Requires appropriate special clothing and mechanization of processes.-IV. Meteorological hazards. - 1. Increased air humidity at high temperature: in the self-dipper department, at the wire section, humidity 80-90%, temperature 5-15° higher than the general factory temperature; in the rag digester when unloading rags, temperature up to 30-33°, relative humidity 59-65%.-2. Increased humidity at normal temperature: in the roll mill rooms (relative humidity 60-90%), in summer in closed strainers (relative humidity 90-92%).- 3. Increased humidity at temperatures below normal: in closed strainers (in winter), in pulp machine departments and others. These moments can be eliminated or reduced by rational ventilation and heating. Increased temperature with significant air dryness-in the cardboard drying chamber (in the chamber 70° and higher; the worker enters periodically for one-several minutes) and when drying sheets of high-grade paper (constant work, temperature 35-40°). These temperatures are required for the production process.-V. Accidents (injuries): a) most often at the self-dipper: entanglement in rolls when threading, adjusting, cleaning paper (necessarily while the machine is running); bruises when removing the press roll; b) in the finishing department (entanglement in rolls, injury from knives); c) in the forest yard and warehouse (bruises); d) during manual cutting (cuts); e) on stone mills and especially on the waste beater (when adjusting material while running, which is not allowed).-VI. A harmful effect of the paper factory on the surrounding area is noted: spoilage of air and plants by SO₂ emissions, spoilage of river water by waste waters discharged from the factory (fish die for several versts downstream, the water is unfit for drinking and even for washing).