Synthetic Mica Investigations: III, Precision-Controlled Electric Furnaces for Temperatures to 1500°C

Three furnaces using silicon carbide heating elements are described, including (1) a utility furnace for melting and testing, (2) a precisioncontrolled (± 1/2°C.) crystallization furnace, and (3) a rectangular crystallization furnace. Schematic drawings of the furnaces and a simplified wiring diagram for the heating elements are included. One composite controller is described from a functional viewpoint, with a block-diagram presentation. A complete circuit diagram of this controller also is incorporated. The use of saturable core reactors in regulating power to electric furnaces is advocated; reactors permit the control of electricity in a manner similar to adjustment of the flow of water by means of a valve.     

A HUMBLE TRIBUTE TO CHURCHILL-SENSEI

The performance of pitched blade turbines in a gas-liquid dispersion has been studied. The two-phase hydrodynamics, gassed power consumption and mass transfer properties have been examined using six blade open turbines with blade angles from 30 to 60 degrees to the horizontal, mounted for down flow.

There are two distinct regimes by which gas leaving the sparger reaches the impeller: at low gas rates this is indirect via the recirculation loops, while at higher gas flow rates the flow is direct.

The transition between these regimes is reflected in power consumption and mass transfer characteristics and is related to the formation of large cavities behind the blades. It was also concluded that, with respect to mass transfer efficiency, a pitched blade turbine is at least as good as a Rushton turbine.