Hot zone temperature

The composition of low-volatility two-component compounds in the Ga-Se system as controlled using chemical transport reactions has been studied (Zavrazhnov et al. 2003). For long-term heat treatment of a low-volatility phase in the presence of a transport agent, the annealed phase composition was found to be determined only by the temperature and the nature of the sample. In the case of a two-temperature anneal of gallium selenides with added iodine, the sample composition ranges are presented as a function of the cold and hot zones temperatures. A scheme of their experimental arrangement is shown in Fig. 6.14. 

The hot zone temperature can thus be determined from Eq. (17), knowing the hot and intermediate zone pressures, orifice areas and coefficients, and the temperature of the gas in the intermediate zone. 

Single-Bed, Nonisothermal Catalysts. In an attempt to circumvent the undesirable formation of hydrogen sulfide in the presence of water vapor, a nonisothermal reactor was constructed by placing 536 g of Jamaican red mud catalyst in a 2-cm diameter 96%-silica tube. The catalyst-filled tube was inserted into the bottom half of the furnace. This resulted in a 15-cm uniform temperature hot zone and a 25-cm zone with temperatures gradually decreasing to about 100 °C at the lower reactor exit. The inlet gas consisted of 17% water vapor, 5.8% carbon monoxide, and 3.0% sulfur dioxide, and 74.2% helium. Figure 5 shows the dependence of the exhaust gas analysis on the hot-zone temperature of the Jamaican red mud catalyst. No sulfur dioxide was removed at hot-zone temperatures lower than 240 °C. At 250 °C, some sulfur dioxide was removed, and small quantities of hydrogen sulfide were formed. Above 300°C, more than 80% of the sulfur dioxide and virtually all of the carbon monoxide... 

Series III. Hot Zone Temperature. Standard conditions included 150 amp, 8.5 moles hydrogen/min through the FCC, and sampling rate through the effluent hot zone at 2Vz min with variation of the hot zone temperature. Results are shown in Table III. It is evident that the hot zone temperature has a significant effect on the hydrocarbon composition of the effluent. 

Series IV. Hot Zone Surface Area. We noted the result of increased time of flow in the sampling rate shown above in Series II and assumed that 8.5 moles hydrogen/min through the FCC creates a steady state for carbon and hydrogen in the plasma at the arc crater (the sampling source), then the time of exposure to the hot zone wall of type 304 stainless steel was observed. This was accomplished at 150 amp, 8.5 moles hydrogen/min, and 800°C hot zone temperature, in two diameters of hot zone tubes, 11/16 and 9/16 inch—a cross-sectional area ratio of 4 1. To equate the sample residence times, the sample flow periods were adjusted to this ratio. Results are shown in Table IV. No acetylene was found in the 9/16-inch diameter samples while the small amounts in the 11/16-inch samples were consistent with the distribution for 20 and 30 sec checked with similar times observed in the earlier Series II above. 

Series VI. Effect of Hot Zone Surface Composition. We noted that the time-related suppression of methane and acetylene suggested a hot zone surface effect when stainless steel was used, so this material was replaced by several others, using 11/16-inch diameter tubes. Arc crater gas samples taken under otherwise identical conditions (viz., 150 amp, 8.5 moles hydrogen/min, hot zone temperature 800°C, parallel sampling flow rates) produced hydrocarbon compositions as shown in Figures 3-6. 

Fuel passing through certain hot zones of an aircraft can attain high temperatures moreover it is used to cool lubricants, hydraulic fluids, or air conditioning. It is therefore necessary to control the thermal stability of jet fuels, more particularly during supersonic flight where friction heat increases temperatures in the fuel tanks. 

Thermal Process. In the manufacture of phosphoric acid from elemental phosphoms, white (yellow) phosphoms is burned in excess air, the resulting phosphoms pentoxide is hydrated, heats of combustion and hydration are removed, and the phosphoric acid mist collected. Within limits, the concentration of the product acid is controlled by the quantity of water added and the cooling capabiUties. Various process schemes deal with the problems of high combustion-zone temperatures, the reactivity of hot phosphoms pentoxide, the corrosive nature of hot phosphoric acid, and the difficulty of collecting fine phosphoric acid mist. The principal process types (Fig. 3) include the wetted-waH, water-cooled, or air-cooled combustion chamber, depending on the method used to protect the combustion chamber wall. 

Thermal Reduction. Thermal reduction is usually accompHshed ki a high temperature countercurrent rotary kiln. "Hot zone," a region near the kiln spik, temperature is usually controlled at 1100—1200°C. The reaction rate has been shown to be only slighdy lower at 1050°C than at 1130°C (9). About 6% of the feed BaSO remains unreacted after 30 min at 1050°C. Reaction completion is approached ki less than 10 min at 1100°C (10). 

After the 20K step increase in feed temperature, not much change could be observed for two minutes. Then the last thermocouple started to increase from 560 to 1200 K level, and the hot zone widened. The forward migration rate of the hot zone was about 5 cm/min. After about six minutes, the oxygen content of the cycle gas became very low and temperature slowly started to decline. With this the experiment terminated. 

Quickly access for a victim airway, and ensure adequate respiration and pulse. If trauma is suspected, maintain cervical immobilization manually and apply cervical collar and a backboard if feasible. Victims should be kept warm and quiet as any activity subsequent to phosgene exposure may lead to death. If exposure levels are determined to be safe, decontamination should be conducted by personnel wearing a lower level of protection than that worn in the hot zone. If the exposure involved liquid phosgene, and the temperature is less than 47 degrees F., and the victim s clothing has been contaminated, remove and double-bag the clothing. 

The synthesis of compounds such as MPS3 (M = Mn, Cd) was performed (Villanueva et al. 2004) in a device consisting of a silica ampoule divided into a Dewar zone (hot zone) and a non-insulated part (cold zone) which can be operated inside domestic microwave ovens. This has been described as a rapid method which involves a heat concentration within the Dewar zone that allows the required temperature for the reaction to be reached. In the specific case a mixture of S, P, and the metal gives MPS3 compounds. The temperature gradient assures the vapour phase transport to the cold zone MPS3 crystals are deposited within a few minutes in this zone. 

A classical example of this process is given by the van Arkel method for the preparation (purification) of several metals. If impure Cr, for instance, is contained together with a small quantity of iodine in a vacuum tube maintained at a temperature at which chromium iodide volatilizes, and a hot zone is created by means of, say, a W filament heated by an electric current, the following reaction will be observed ... 

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