Chips preheating

Wood chips are preheated in steam before passage through disc refiners. Heating is meant for softening the lignin portion of wood and to promote fiber separation. This pulp is stronger than that produced by the ground-wood process. 

Batch autohydrolysis was carried out in 300 ml pressure vessels in a preheated silicone bath, with due allowance for temperature equilibration to achieve as nearly as possible 195 C for 30 minutes. Chip moisture was adjusted to 50% for the batch autohydrolysis. 

Elevated temperatures up to 100°C have also been used with integrated HPLC chips that include both a column and an electrochemical detector [83]. This system used a resistive heater and a mobile phase preheater and was used to separate o-phthaldialdehyde amino acid derivatives. 

Note 1) held in place by a plug of glass wool supported by indentations in the tube, followed by 100 ml. of marble chips which serve as a vaporizer and preheater for the reactants. The reaction tube is supported in an electrically heated furnace (Note 2) extending from the inlet tube to the joint connecting the condenser. 

Florida Crushed Stone in Brookville, Florida, was feeding TDF into the preheater, but had to discontinue use because of plugging of the preheater (most likely due to oil condensate from the incomplete combustion of the tire chips). The company is in the process of installing a whole tire feeder with weight-belt, computer, variable rate belt, and triple gate chute to feed tires into the kiln.10... 

Figure 2. Hot-water extractability of wood chips as a function of saturated steam pressure used in the preheat segment of the digesting operation...

In the case of PGW, the casing surrounding the pulpstone is sealed and pressurized. This can be accomplished with steam, but most manufacturers now use air pressure. This pressure maintains higher temperatures in the grinding zone, and the yield of longer fiber pulp is increased. PRMP uses air or steam pressure applied to the refiner. The chips are unheated and untreated. TRMP is closely related to PRMP, the chips are preheated and refined at atmospheric pressure. 

A very facile dip acetylation procedure was developed for wood chips and fibers. The wood is dried at 105°C and then dipped in acetic anhydride for 1 min and drained. Then the sample is placed in a preheated (120°C) reactor for different lengths of time, depending on the degree of substitution of acetyl groups desired in the sample.29 The swelling of aspen flake-board made from such chemically modified flakes is dramatically reduced. For example, while unmodified flakeboard swelled by over 60 percent after immersion in water for 5 days, the modified material swelled by only about 8-22 percent, depending on the extent of chemical modification. 

The kinetic studies were done in a 1/2-inch pipe jacketed reactor with a 1/8-inch thermowell down the middle. The first 7 inches of the reactor was filled with quartz chips and used as a preheater. Ten grams of 10-20 mesh SK-500 was then mixed with twice its volume of quartz and placed on top of the preheat section. The feed was pre-mlxed In a pressurized tank and then pumped upflow through the reactor. The temperature was controlled by pumping Dow Therm through the jacket with heat being supplied externally. This resulted In the reactor being Isothermal. 

Almost all feedstocks of interest have such properties that they do not flow readily through cither pipes or shell of a conventional heat exchanger without distribution problems. Afler a number of alternatives had been considered it was concluded that the most adequate way of preheating is direct injection of hot water. In Fig. 3 this is done in vessel V where a stream of hot recycle water is mixed with the feed. A special way of contacting achieves efficient heat and mass transfer. It has been verified in our experiments that at 200-250°C biomass feedstocks of different origin, including wood chips, arc softened and form a pastc-like substance [7,8]. The... 

Preheat oven to 350°F. Place tortillas in a single layer on baking sheets, brush with a small amount of olive oil, and sprinkle with salt. Bake for 5 to 10 minutes, or until lightly browned. Break into chips and serve. 

The raw material, prepared as chip-sized particles, is delivered to a bin above the preheater, where atmospheric steam is injected to start the heating process. From the bottom of the presteaming bin the chips enter a screw feed that forms a tapered plug... 

The chips move down the preheater pressure vessel and are removed from the bottom by a scraper arm that breaks up the column of material, delivering it to a metering screw conveyor. The speed of this conveyor determines the production rate while delivering the preheated material to the refiner. 

In Situ Analysis in a Furnace Successful in situ measurement of coal pyrolysis have recently been made (24, 25)> In one application (24), small samples of coal were rapidly injected into a preheated zone which is traversed by the IR beam With this apparatus spectra have been obtained for gases at temperatures up to lOOO C In the second application a gas stream of predetermined composition is heated during transit through a bed of alumina chips maintained at furnace temperature The gas stream then enters a test section, maintained at the same temperature, where coal is introduced through a water cooled injector. After a variable residence time the reacting stream crosses the FT-IR beam and is quenched in a water cooled collector FT-IR spectra have been obtained at temperatures up to 1200 0 The input gas stream and effluent stream can also be analyzed by routing the stream through an infrared cell The spectra presented in Fig 22 were of the effluent gas in the external cell ... 

At time zero of the run, wood chips were fed to the preheated... 

Emerson Cuming Non-anhydride and 25 pm N/A Preheat substrate to Flip-chip devices... 

Emerson Cuming Snap-curable epoxy N/A N/A Preheat substrate to CSP, EGA, and flip-chip... 

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