Three zone furnace

After the initial hydrogenation studies were completed with WVGS 13407, all other liquefaction experiments were conducted in a larger, 3.8-liter bolted-closure autoclave fitted with an electrically driven magnetic stirrer arbitrarily set to provide mixmg at 1000 rpm. A temperature controller and power supply were connected to a three-zone furnace to control reaction temperature... 

A three-zone furnace (top to bottom are 31, 6", and 3", respectively) was used to maintain isothermal conditions along the reaction zone. Pressure was controlled by a back pressure regulator on the exit stream. A post reactor dropout trap was installed to condense the steam and hydrocarbon condensates. Downstream dry product flow rates were measured by a wet test meter. 

Substrate heating is required in CVD reactors. Since the films are grown under isothermal conditions, the substrate must be held at a constant growth temperature for an extended period of time. The achievement of this requirement is facilitated in two ways, and reactors are classified into two groups depending on how the substrate is heated. In a hot-wall design, the entire reactor is placed in a tube furnace and the substrate, the region of forced gas convention, and the walls of the reactor are maintained at the same temperature. Of course the ends of the reactor are cooler than the middle because of heat loss from the ends and the introduction of cold gas at the entrance of the reactor. To remedy this imbalance, a three-zone furnace, with independent feedback control for each zone, is usually employed. Substrates are loaded only in the portion of the reactor where the temperature can be accurately maintained. 

S. Boschert, P. Dold, K. W. Benz. Modelling of the temperature distribution in a three-zone resistance furnace influence of furnace configuration and ampoule position. J Cryst Growth 7S7 140, 1998. 

Preparation of Macrocrystalline Iron(III) Oxide. Assemble an apparatus for preparing hydrogen chloride. To dry the gas well, install a column with phosphorus(V) oxide in addition to two wash bottles with sulphuric acid. Spill amorphous iron(III) oxide into the middle part of a three-section quartz tube (Fig. 136). Put the latter into a two-zone furnace. To retain the temperature difference, wrap the unheated zone (the middle of the tube) with asbestos. 

Fig. 12. Production of synthesis gas in three-zone shaft reactor furnace (38).

Recommendation 3-6. A modified baseline process at Pueblo should include a four-zone (rather than three-zone) metal parts furnace with design provisions to ensure safe shutdown and restarting in the event of operational upsets, such as a loss of electrical power, combustion air supply, or exhaust gas capability. 

All experiments were carried out in a simple flow system. A schematic diagram of the apparatus is shown in Figure 1. The quartz reactor (10 mm i.d.) was heated in a three-zone electric furnace which gave a flat ( 2°C) temperature profile over about 45 cm. Reactor temperatures were measured by a thermocouple which could be moved in a sheath attached to the outside of the reactor. Initially, the sheath was placed inside the reactor, but the inside temperatures agreed so closely with the reactor wall temperatures that the inner thermocouple was removed to minimize catalytic effects. 

Fig. 14. Temperature profile in three-zone stabilization furnace ( standard screening conditions )...

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