Pulping processes thermomechanical

Few thermomechanical pulping processes existing today use the original Mason process now that more streamlined operations have evolved but all stem from Mason s development. 

Most virgin wood pulp used in fiberboard manufacture today is generated by thermomechanical pulping developed by William Mason in 1925 (2, 3). Few thermomechanical pulping processes existing today use the original Mason process now that more streamlined operations have evolved but all stem from Mason s development. 

Fibers for fiberboard are coarser and less refined chemically than those used for paper. Processes are used that bring about fiber separation with a minimum loss of chemical components and a maximum yield. The pulping processes used are generally the following mechanical, thermomechanical. 

The printing of newspapers is conducted at very high speeds, often reaching 3000 feet per miaute. AH three printing processes utilize similar quaHty newsptint which, essentiaHy, is made of groundwood or thermomechanical pulp. Presses are fed a continuous web of newsptint that unwiads from a feed roUer. Inks dry by absorption of Hquid iato the porosity of the substrate. Some evaporation of water ia a flexo pubHcation ink can accelerate the dryiag process. 

The TMP process is similar to the RMP process except that after chip washing, a steaming vessel is inserted to achieve the thermoplasticization of the lignin in the wood. The production of thermomechanical pulps increased dramatically after the introduction of this method in the early 1970s. Because these pulps can be substituted for conventional groundwood pulps in newsprint blends to give a stronger paper, lower quantities of the more expensive, lower yield chemical pulps are required. 

Commercial Masonite and Asplund boards and the asphalt-impregnated insulation board were sampled before any commercial heat treatment. The corresponding "thermomechanical" pulps had been produced by pressurized refining of steamed chips. The higher pre-steaming temperature used in the Masonite process resulted In a yield of about 85% as compared to a fiber yield of about 94% of the Asplund pulps, the remainder being dissolved. 

Aspen Wood Treated with Chemical-Thermomechanical Process. Aspen wood was pulverized into "chemithermomechanical pulp (CTMP) by a chemical-thermomechanical process 24), During this process, very little hemicellulose and lignin are removed. The CTMP was used without any... 

Until recently, the mechanism of the inhibition of light-induced yellowing was subject to speculation. However, solid state ESR and CIDEP have provided insight into the mode of inhibition by thiols (Wan, J.K.S., et al, J. Wood Chem. Technol., in press). Near-uv irradiation of unbleached and peroxide bleached thermomechanical pulp impregnated with thiols caused a rapid increase of the thiol radicals. The time resolved CIDEP spectrum, however, shows a symmetric broad band characteristic of the polarized phenoxy radical. This result suggests that thiols quench triplet generated phenoxy radicals in a secondary thermal process. 

There are many processes and variations of basic processes that can be used for making pulp from wood. The major processes are the kraft process (also known as the sulfate process), the groundwood and thermomechanical process, semichemical process, and the sulfite process. The kraft process remains dominant. 

Next, we consider an application related to the paper making process and study a water allocation problem for an integrated plant containing a thermomechanical pulping plant and a paper mill. For details of this problem with three objectives, see Hakanen et al. (2004). 

The upper part of Fig. 6.4 represents the thermomechanical pulping plant and the lower part represents the paper mill. The goal is to minimize the amount of fresh water taken into the process and also to minimize... 

S Robert, JP Lamothe, and C Daneault. Treatment of thermomechanical pulp from tamarack (Larix laricinia) by ozone and ozone-peroxide bleaching process Paper mechanical properties. J. Pulp Paper Sci. 17 168-172, 1991. 

Dried thermomechanical pulp (TMP) (mature loblolly pine, Pinus taeda) was obtained from the U.S. Department of Agriculture at Pineville, Mississippi. Steam pressures used during the TMP process were 4, 8, and 12 bar. Spruce (Picea glauca) chips were refined at 103 kPa, followed by atmospheric refining to 600 mL Canadian standard fi eeness (CSF). Spruce pulps were further refined to 70 mL CSF after enzyme treatments using a PFI mill to reduce the freeness. 

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