Timer, reflux ratio

Fig. 1-36. Reflux-ratio timer. Ri, 3-megohm potentiometer R , 250,000-ohm J-watt Ra, 1-megohm potentiometer Rt, 50,000-ohm -watt Ci, 4-mfd. paper, 400 volts Cl, 2-mfd. paper, 400 volts Ct, C<, 8-mfd. electrolytic, 250 volts Vt, Fa, 117L7/M7GT Ry 1, Ry 2, double-pole double-throw relays, 1,000— 4,000-ohm coil Pi, Pa, 115-volt pilot lights X, standard receptacle (output) Si, Sa, single-pole single-throw switches. (Courtesy of Dr. H. Fischer and Analytical Chemistry.)...

The timers functioning entirely on electronic principles allow take-off and reflux periods of 0.1 sec to 20 min. to be adjusted with an accuracy of 1% [56]. For an alteration of the reflux ratio they require a change to be made in both the take-off and reflux times. A number of electronic devices are commercially available most of which are provided with bubble-point control. The column head is set at infinite reflux ratio as soon as the pre-set temperature of the contact thermometer placed in the column head is reached. When the temperature falls below this threshold the preselected reflux ratio is automatically switched on again. As an example. Fig. 386... 

Reflux splitters. A reflux splitter (Fig. 19.5a) is an on/off solenoid-operated device actuated by a timer. The timer setting corresponds to a fixed reflux-distillate flow ratio. This setting is manipulated manually. The solenoid operates a slide gate that diverts all the liquid either to the column or to the product route. The solenoid operates at a high frequency so that neither reflux nor distillate flow is interrupted. 

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