Steam heat treatment

Samples of wood of various species were steam-treated at 150 °C, or oven-heated in air at 150°C, for various time periods and attack by the termite species C. formosanus or R. speratus determined (Doi etal., 1997, 1999). Steam heat treatment had the effect of encouraging attack upon the treated wood specimens, whereas dry heat treatment had little effect except for heat-treated Japanese larch with R. speratus. 

Doi, S., Kurimoto, Y., Takahashi, M. and Yoshimura, T. (1997). Effects of steaming heat treatment on the stimulation of termite feeding. International Research Group on Wood Preservation, Doc. No. IRGAVP 97-10212. 

Bamba, R. Matsui, R. Watabe, I. Effect of steam-heat treatment with/without divalent cations of the inactivation of lipopolysaccharides from several bacterial species. PDA J. Parenter. Sci. Technol. 1996, 50, 129-135. 

The Vepex process developed in Hungary (Table 9) involves disintegration of plant materials followed by double screw pressing to maximize juice production. Green chloroplastic protein is removed by direct steam-injection heat treatment at 82°C with the addition of flocculents and centrifugation. The white protein fraction is separated from the chlorophyU-free process juice by direct steam injection at 80°C, followed by centrifugation and drying (94). 

Other Continuous Processes. Various pasteurization heat treatments ate identified by names such as quick time, vacuum treatment (vacreator), modified tubular (Roswell), small-diameter tube (MaHotizer), and steam injection. The last three methods are ultrahigh temperature (UHT) processes (see Fig. 3). Higher treatment temperatures with shorter times, approaching two seconds, are preferred because the product has to be cooled quickly to prevent deleterious heat effects. 

Polyamides (nylons) are thermoplastic fibers that retain their form produced by heat treatment. They are usually given an alkaline scour and then heat-set. The heat-setting treatment is conducted at ca 10°C above the subsequent wet processiag steps this ensures good form retention after processiag. Woven fabrics are usually heat-set on a contact heat-setting machine and nylon tricot is generally heat-set on a tenter frame or ia steam chambers. 

Hot water and LP steam heating boilers generally accumulate some bottom sludge as a result of infrequent BD schedules. The sludge results either as reaction products of chemical treatments... 

NOTE Simple HW heating and LP steam boiler treatment apart, the term BW treatment is unfortunately often something of a misnomer. The practice is, in fact, generally recognized to be primarily concerned with adjustments to the boiler FW chemistry and the addition of polishing chemicals to compensate for deficiencies or potential problems associated with the FW rather than with the recirculating BW. 

When operators believe that their HW systems do not lose water through pump mechanical seals or other places. They also commonly state that their LP steam heating systems return 100% condensate, so that no additional corrosion protection precautions need be taken above or beyond the initial fill of chemical treatment and an occasional top-up dose. 

When chemical treatment for both HW heating and LP steam heating systems is generally some combination of a nitrite/borate/silicate/ molybdate formulation, usually with TTA/polymer or phosphate but having no specific oxygen-scavenging capability. 

In practice, however, it is often the case that for small LP steam heating boiler systems with a very high percentage of CR, and in those regions of countries where soft water is supplied, no water softener is provided or deemed necessary. Instead there is merely a reliance on internal chemical treatments (or sometimes magnetic devices or other types of gadget ). A good rule of thumb is ... 

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. 

The inherent heterogeneity of the material leads to variations in the responses of wood to thermal modification. The rate of transfer of heat into the interior of the wood is of paramount importance in order to ensure that there is a constant temperature throughout the sample. The thermal conductivity of dry wood is low and the heating method employed must ensure that the treatment is as even as possible. Heat transfer into the interior may be improved by the use of steam-heating. Heat transfer is a very significant factor in the treatment of timber of larger dimensions. 

ThermoWood is produced by a heat-treatment process in the presence of steam, and is thus a hygrothermal treatment. The steam acts as a blanket to limit the oxidative degradation of wood, and there are also additional reactions occurring as a result of the presence... 

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