AUTOMATIC CONTROL FOR GAS FRACTIONATION APPARATUS

A Pressure Swing Adsorption (PSA) appatus 100 uses controller 102 to make possible automatic and continuous modification of the air input flow in order to ensure that the produced nitrogen contains only a preselected range of an impurity which consists essentially of oxygen and to keep the output flow of nitrogen relatively high. The apparatus 100 has a valve 18a to control the flow of air through chambers 38 and 40 containing adsorbent. The controller 102 includes a converter 110 for operating valve actuator 18al. Flow detector means 106 senses the rate of flow of air through the chamber and imputiry detector 46 senses the level of oxygen impurity in the product nitrogen. A first comparator means 114 compares the output of the impurity detector 46 with a reference signal V ref 3 and generates a signal proportional to the difference therebetween. This signal is transmitted to a second comparator means 118 which compares it with the output from the flow detector means 104 to produce an output that is coupled to the input of the converter means 110. The converter means 110 is thereby cause to generate a signal that adjusts the position of the valve 18a.