Pitch control

Pitch control Pitched blade turbine Pit furnace Pi theorem Pitocin... 

Retention and drainage additives are vital to the use of recycled fibers. Papermakers consider recycled fibers to behave like virgin fines, while recycled fines behave like filler. Drainage on the paper machine can be impeded and first-pass retention reduced by the use of recycled fiber (9). Additionally, the negative impact of contaminants found in recycled fibers can be minimized by the appropriate use of dispersants and other pitch-control additives. 

The most widely used pitch control method is the addition of pitch dispersants, which can be either organic, ie, typically anionic polymers such as naphthalene sulfonates, ligninsulfonates, and polyacrylates (33,34), or inorganic, ie, typically clay or talc. The polymers maintain the pitch as a fine dispersion in the pulp, preventing agglomeration and potential deposition on the paper machine or the sheet. When talc, clay, or other adsorbent fillers are added to the furnish, moderate amounts of pitch can adsorb on these materials, producing a nontacky soHd that can be retained in the sheet. 

In the paper industry, PEO is widely used as a retention aid and pitch control agent in the newsprint industry (118—135). Typically, a phenol formaldehyde-type resin is added to the substrate before the addition of PEO. The chemical that is added before PEO has been referred to as an enhancer. Recent pubHcations on designing enhancers that work with PEO have resulted in expanding the use of PEO in flocculation of several substrates (128,129). 

In conventional chemical pulping systems, micronized talc is used for pitch control. The mechanism is not well understood, but talc does adsorb on the pitch and detackify it, preventing it from agglomerating and attaching on equipment. In de-inking talc is used both to enhance ink removal in conventional screening/centrifugation methods and as a carrier in flotation systems. 

Enzymes in Pulp and Paper Production. Enzyme-modified starch has been used for adhesives to strengthen paper base and for surface coating. Developments since the late 1980s of further uses of enzymes in papermaking include pitch control and bleach boosting, (see Paper Pulp). 

Pitch Control. Resinous constituents of wood cause problems in paper machines by sticking to the rollers and causing spots or holes in the paper the worst cases cause paper webs to mpture. Costly stoppages, wastages, and quaUty problems because of these resinous substances can be avoided by using Upases (84). 

Y. Itie and co-workers, Engymatic Pitch Control in Papermaking Systems, Papermakers Conference/TAPPI proceedings, 1990, p. 10. 

Hydraulic power supply This actuates brakes and also feeds the yawing and pitch control (if they are also hydraulically operated). 

Variable blade pitch control The impeller blade angle is varied when the fan is in operation, normally only for axial flow fans. 

Manual (for seasonal changes only) or automatic pitch control operated by air-motor on fan blades. 

Piston type aerosol system, 1 784 PIT (powder-in-tube) conductors, critical current density in, 23 833-834. See also PIT technique Pitch-based carbon fibers, 26 733-735 asbestos substitute, 3 314t compressive strength versus tensile modulus for, 26 742-743 Pitch-based fibers, 26 760 Pitch binders, 12 724-726 Pitchblende, 25 396-397 Pitch control, 10 304 Pitched blade turbine (PBT), 16 672 Pitches... 

Sources 1 D.H. Bennett, C.M. Falter and A.F. Campbell, Prediction of Effluent Characteristics, Use of Lime Treatments and Toxicity of the Proposed Ponderay Mill , Appendix in engineer s report on Effluent Characteristics for Washington State Department of Ecology, 1987. 2 D.F. Zinkel, Tall Oil Precursors of Loblolly Pine , Tappi, 1975, 58, 2, pp. 118-121. 3 R.W. Hemingway, P.J. Nelson and W.E. Hillis, Rapid Oxidation of the Fats and Resins in Pinus Radiata Chips for Pitch Control , Tappi, 1971, 54, 1, pp. 95-98. 4 D.O. Foster, D.F. Zinkel and A.H. Conner, Tall Oil Precursors of Douglas Fir , Tappi, 1980, 63, 12, pp. 103-105. 

Until recently, the use of enzymes in the paper and pulp industry was not cortsidered technically or economically feasible. Quite simply, suitable enzymes were not readily available, except for the limited use of enzymes to modify starch for paper coatings. However, research by scientific institutions and enzyme producers has led to the development of new enzymes that offer significant benefits for the industry, particrrlarly from the environmental point of view. Two examples of applications, in addition to the starch modification, made possible by new enzyme developments are given here bleach boosting and pitch control. 

Pitch control - [URANIUMAND URANIUMCOMPOUNDS] (Vol24) - [URANIUMAND URANIUMCOMPOUNDS] (Vol24) -m papermaking [PAPERMAKING ADDITIVES] (Vol 18)... 

Van Wyk ° used a similar geometry in developing plain spherical ceramic bearings for helicopter pitch control linkages. He tested several different composites of molybdenum disulphide in polyimide or metal, and these gave better performance... 

Use Water-softening, boiler-scale control, component of cleansers, laundry mixes, dishwashing compounds, pitch control in pulp industry, prevention of lime soap deposits in textile operations. 

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